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Singh, Rahul. "Electrochemical and Partial Oxidation of CH4." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1208025200.
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Cehic, Eldina. "An annual evaluation of CH4 oxidation in a freshwater lake." Thesis, Linköpings universitet, Tema Miljöförändring, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165902.
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Freshwater lakes constrain its methane (CH4) emissions through CH4 oxidation. CH4 includes three carbon (C) isotopes; the stable isotopes 12C,13C and the unstable and more uncommon isotope 14C. Methanotrophs (i.e. methane oxidizing bacteria) oxidize the lighter isotope more rapidly. Changes in relative isotopic composition can therefore be used to calculate how much CH4 is oxidized in a system. This study investigates an annual CH4 oxidation in a freshwater lake. Water samples and bubbles of CH4 gas were collected once a month, from March to November, in lake Gundlebosjön. The CH4 gas was separated from the water samples with a headspace extraction technique. The concentration and isotopic composition of CH4 was analyzed in a cavity ring down spectrometer. The isotopic data was used in two mathematical models, based on open-steady state and closed systems. It was found that the stable isotope method to estimate CH4 oxidation was only useful during periods when clear concentration and isotope differences could be observed in the water column. CH4 oxidation could only be estimated in the water column in August, and in the surface layer in June and July.Utsläppen av metan (CH4) från sötvattensjöar begränsas genom CH4 oxidation. Det är två stabila kolisotoper som dominerar i CH4; 12C och 13C. Den ostabila kolisotopen 14C finns även i CH4, men den är mer ovanlig i naturen. Metantrofer (metanoxiderande bakterier) oxiderar den lättare kolisotopen snabbare. Förändringar i isotopsammansättningen kan användas för att beräkna hur mycket CH4 som oxideras i ett system. Denna studie undersöker en årlig CH4 oxidation i en sötvattensjö. Vattenprover och bubblor av CH4-gas samlades en gång i månaden, från mars till november, i Gundlebosjön. CH4 gasen separerades från vattenproverna med en ”headspace extraction” teknik. Koncentration och isotopsammansättningen av CH4 analyserades i en ”cavity ring down spectrometer”. Isotopdata användes i två matematiska modeller, baserade på öppet-stabilt tillstånd och stängt system. Den stabila isotopmetoden för att uppskatta CH4 oxidation var endast användbar under perioder då tydliga skillnader i koncentrationen och isotopsammansättningen kunde observeras i vattenpelaren. CH4 oxidation kunde endast uppskattas i vattenpelaren i augusti, och i vattenpelarens ytskikt i juni och juli.
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Han, Jinyi. "Kinetic and Morphological Studies of Pd Oxidation in O2-CH4 mixtures." Digital WPI, 2004. https://digitalcommons.wpi.edu/etd-dissertations/219.
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The oxidation of Pd single crystals: Pd(111), Pd(100) and Pd(110) was studied using Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Low Electron Energy Diffraction (LEED) and Scanning Tunneling Microscopy (STM) as they were subjected to O2 in the pressure range between 1 and 150 Torr at temperatures 600-900 K. The oxygen species formed during oxidation, the oxygen uptake dependence on the sample history, the Pd single crystal surface morphology transformations, and the catalytic methane combustion over Pd single crystals were investigated in detail. The Pd single crystal oxidation proceeded through a three-step mechanism. Namely, (1) oxygen dissociatively adsorbed on Pd surface, forming chemisorbed oxygen and then surface oxide; (2) atomic oxygen diffused through a thin surface oxide layer into Pd metal, forming near surface and bulk oxygen; (3) bulk PdO formed when a critical oxygen concentration was reached in the near surface region. The diffusion of oxygen through thin surface oxide layer into Pd metal decreased in the order: Pd(110)>Pd(100)>Pd(111). The oxygen diffusion coefficient was estimated to be around 10-16 cm2 s-1 at 600 K, with an activation energy of 80 kJ mol-1. Once bulk PdO was formed, the diffusion of oxygen through the bulk oxide layer was the rate-determining step for the palladium oxidation. The diffusion coefficient was equal to 10-18 cm2 s-1 at 600 K and the activation energy was approximately 120 kJ mol-1. The oxygen diffusion through thin surface oxide layer and bulk PdO followed the Mott-Cabrera parabolic diffusion law. The oxygen uptake on Pd single crystals depended on the sample history. The uptake amount increased with the population of the bulk oxygen species, which was achieved by high oxygen exposure at elevated temperatures, for example in 1 Torr O2 at above 820 K. Ar+ sputtering or annealing in vacuum at 1300 K depleted the bulk oxygen. The Pd single crystal surface morphology was determined by the oxidation conditions: O2 pressure, treatment temperature and exposure time. When bulk PdO was formed, the single crystal surface was covered with semi-spherical agglomerates 2-4 nm in size, which tended to aggregate to form a“cauliflower-like" superstructure. The single crystal surface area during oxidation, determined by integrating the STM image, experienced three major expansions in consistent with a three-step oxidation mechanism. The surface area on the oxidized single crystals increased in the order: Pd(110)
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Rismanchian, Azadeh. "Electrochemical and Photocatalytic Oxidation of Hydrocarbons." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415799133.
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Zinner, Christopher. "METHANE AND DIMETHYL ETHER OXIDATION AT ELEVATED TEMPERATURES AND PRESSURE." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3457.
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Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy release from the mixture is occurring in the time between the arrival of the incident shock wave and the ignition event. An adjustment scheme for temperature and pressure was devised to account for this energy release and its effect on the ignition of the mixture. Two separate ignition delay correlations were developed for these pressure- and temperature-adjusted data. These correlations estimate ignition delay from known temperature, pressure, and species mole fractions of methane, dimethyl ether, and air (0.21 O2 + 0.79 N2). The first correlation was developed for ignition delay occurring at temperatures greater than or equal to 1175 K and pressures ranging from 0.8 to 35.3 atm. The second correlation was developed for ignition delay occurring at temperatures less than or equal to 1175 K and pressures ranging from 18.5 to 40.0 atm. Overall good agreement was found to exist between the two correlations and the data of these experiments. Findings of these experiments also include that with pressures at or below ten atm, increased concentrations of dimethyl ether will consistently produce faster ignition times. At pressures greater than ten atmospheres it is possible for fuel rich mixtures with lower concentrations of dimethyl ether to give the fastest ignition times. This work represents the most thorough shock tube investigation for oxidation of methane with high concentration levels of dimethyl ether at gas turbine engine relevant temperatures and pressures. The findings of this study should serve as a validation for detailed chemical kinetics mechanisms.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering MSME
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Brauneder, Kerstin M. "Geochemistry of Forest Rings in Northern Ontario: Identification of Ring Edge Processes in Peat and Soil." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23205.
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Forest rings are large features common in Ontario’s boreal forests that comprise circular topographic depressions in carbonate mineral soil that are filled with peat. This thesis documents differences in peat and soil chemistry along transects across the “Bean” and “Thorn North” rings, which are centered on accumulations of CH4 and H2S, respectively. Within the mineral soil, ring edges are characterized by strong negative anomalies in pH, ORP and carbonate, as well as positive anomalies of Al, Fe and Mn in the results of aqua regia and hydroxylamine-hydrochloride digestions. Within the peat, positive carbonate and pH anomalies are recorded. This antithetic relationship suggests vertical migration of carbonate species from clay to peat. An inverse relationship exists between ORP, versus redox inferred from aqua regia. Strong ORP lows occur where oxidized products show highest concentrations. This is interpreted to reflect the proliferation of autotrophic organisms occupying the strong redox gradient at the ring edge.
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Herrera, Delgado Karla [Verfasser], and O. [Akademischer Betreuer] Deutschmann. "Surface Reaction Kinetics for Oxidation and Reforming of H2, CO, and CH4 over Nickel-based Catalysts / Karla Herrera Delgado. Betreuer: O. Deutschmann." Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1056955864/34.
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Preuss, Inken-Marie [Verfasser], and Eva-Maria [Akademischer Betreuer] Pfeiffer. "In-situ Studies of Microbial CH4 Oxidation Efficiency in Arctic Wetland Soils– Application of Stable Carbon Isotopes / Inken-Marie Preuss. Betreuer: Eva-Maria Pfeiffer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1038789451/34.
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Guérin, Frédéric. "Emission de gaz à effet de serre (CO2,CH4) par une retenue de barrage hydroélectrique en zone tropicale (Petit-saut, Guyane française) : expérimentation et modélisation." Toulouse 3, 2006. https://tel.archives-ouvertes.fr/tel-00079947.
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Les émissions de dioxyde de carbone (CO2) et de méthane (CH4) et le cycle du carbone dans la retenue de barrage de Petit-Saut et la rivière Sinnamary (Guyane Française) ont été étudiés dans le but de développer un modèle couplé hydrodynamique-biogéochimie. Le développement de ce modèle a nécessité l'étude de trois processus contrôlant ces émissions : (i) la production de CO2 et de CH4 lors de la dégradation de la matière organique (MO) des sols et de végétaux, (ii) l'oxydation aérobie du CH4 dans la colonne d'eau du barrage et (iii) les processus d'échange gazeux à l'interface air-eau. Sur 10 ans, les émissions atmosphériques se sont avérées très significatives, notamment les trois premières années ayant suivies la mise en eau, puis décroissent au cours du temps. Tandis que 50% des émissions de CO2 ont lieu à la surface du lac, les émissions de CH4 sont principalement localisées en aval des turbines. Les émissions atmosphériques résultent de la dégradation de la MO (sol et biomasse issus de la forêt tropicale) immergée lors de la mise en eau et leur diminution au cours du temps découle de l'épuisement du stock de MO. Au terme de 10 ans, 20% du stock de carbone a été minéralisé et émis vers l'atmosphère sous forme de CO2 et de CH4. L'oxydation aérobie du CH4 transforme plus de 95% du CH4 diffusant depuis l'hypolimnion en CO2 dans la colonne d'eau du lac et 40% du CH4 entrant dans la rivière à l'aval. A l'échelle du barrage ce processus est responsable de l'oxydation de 90% du CH4 produit et de 30% des émissions totales de CO2. Le CH4 et le CO2 qui atteignent les eaux de surface du barrage sont émis vers l'atmosphère par flux diffusifs. L'étude de ce processus de transfert gazeux à l'interface air-eau montre que, en milieu tropical, les flux diffusifs sont accélérés par les fortes températures et les phénomènes pluvieux. Le modèle est basé sur le modèle hydrodynamique SYMPHONIE 2D et les modules biogéochimiques développés dans le cadre de cette étude à partir des données cinétiques des processus étudiés. Les profils verticaux simulés de température, d'oxygène, de CO2 et de CH4 sont bien reproduits. Ce modèle pose les bases d'un outil opérationnel de modélisation pour la retenue de Petit Saut ainsi que pour d'autres réservoirs en milieu tropicalThe emissions of carbon dioxide (CO2) and methane (CH4) and the carbon cycle in the Petit-Saut reservoir and in the Sinnamary River (French Guiana) were studied with an aim of developing a coupled physical/biogeochemical model. The development of this model required the study of three processes controlling these emissions: (i) CO2 and CH4 production during the mineralization in anoxic condition of organic matter (OM) from soils and plants, (ii) aerobic CH4 oxidation in the water column of the lake and (iii) the processes involved in gas exchange at the air-water interface. Over 10 years, atmospheric emissions were shown to be very significant, in particular the first three years having followed the reservoir impoundment and then decreased with time. While 50% of the CO2 emissions take place at the surface of the lake, the emissions of CH4 are mainly localized downstream from the turbines. The atmospheric emissions result from the degradation of OM (soil and biomass originating from the tropical forest) flooded during impoundment and their reduction with time rises from the exhaustion of the OM stock. 10 years after impoundement, 20% of the carbon stock were mineralized and emitted to the atmosphere in the form of CO2 and of CH4. Aerobic CH4 oxidation transforms more than 95% of the CH4 diffusing upward from the hypolimnion into CO2 in the water column of the lake and 40% of the CH4 entering the river downstream of the dam. In the whole Petit Saut system, this process is responsible for the oxidation of 90% of the produced CH4 and 30% of the total CO2 emissions. The CH4 and CO2 which reach the water surface of the reservoir and of the river downstream of the dam are emitted to the atmosphere by diffusive flux. The study of this process of gas transfer to the interface air-water shows that, in tropical environment, diffusive fluxes are enhanced by the elevated temperatures and the rainy phenomena. The model is based on the hydrodynamic model SYMPHONY 2D and the biogeochemical model developed during this study starting from the kinetic data of the studied processes. The simulated vertical profiles of temperature, oxygen, CO2 and CH4 are well reproduced. This model poses the bases of an operational tool of modeling for the Petit-Saut reservoir like for other reservoirs in tropical environments
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Fairbrass, Danielle L. "Engineering oxidative stress resistance in CHO cell factories." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/16227/.
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Oxidative stress is a phenomenon created by an imbalance in the amount of Reactive Oxygen Species (ROS) created within a cell, and the ability of its defence mechanisms to effectively deal with ROS. Oxidative stress is extremely deleterious to the cell, and is known to cause damage to DNA, proteins and lipids (Turrens, 2003). Mitochondria are the cell’s predominant producer of ROS (Murphy, 2009), but it has also been shown that increased protein folding in the Endoplasmic Reticulum (ER) results in an increase in ROS levels (Malhotra, 2008), an issue particularly pertinent as developers move towards hard-to-express proteins. As well as many enzymes dedicated to the eradication of ROS, such as caspases, peroxidases and superoxide dismutases (SODs) the cell maintains a glutathione pool to buffer the increase of ROS (Lu, 2009). Design of Experiment models were designed and implemented using the growth, productivity and ROS content data from batch experiments in order to design anti-oxidant supplementation strategies. Two rounds of fed-batch screening were performed and a feeding strategy identified that improved the growth and ROS burden of three cell lines producing the same recombinant MAb product. A directed evolution strategy was employed to engineer oxidative stress resistant host cell lines through chronic exposure to Hydrogen Peroxide. Following transfection with a recombinant MAb product, the novel engineered cell line consistently outperformed the original cell line in terms of growth and ROS content, in both transient and stable transfection processes. Doubling time of stably transfected evolved cell line was reduced to 23 hours, a substantial time frame reduction. A link between ROS level reduction and improvement in cell line performance was demonstrated, with further investigation needed to unpick the mechanistic underpinnings of the oxidative stress resistance as well as to attempt to address the imbalance of improvements in growth compared to productivity.
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Ribaldo, Perola Del Bianco. "O cha verde (Camellia sinensis) atenua a nefropatia atraves da redução da expressão da subunidade NOX-4 da ND(P)H oxidase no diabetes mellitus experimental." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/312554.
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Orientador: Jose B. Lopes de FariaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas
Made available in DSpace on 2018-08-12T08:15:20Z (GMT). No. of bitstreams: 1 Ribaldo_PerolaDelBianco_M.pdf: 920213 bytes, checksum: e99a6b84c11f7c94edce6679b6c82c1d (MD5) Previous issue date: 2008
Resumo: Introdução e Objetivos: Ha. muito se sabe que a hiperglicemia e a hipertensão arterial são fenômenos promotores de estresse oxidativo no tecido renal. O estresse oxidativo, por sua vez, contribui fortemente com a doença renal do diabetes, especialmente pela geração de oxidantes via NAD(P)H oxidase. Em contrapartida, inúmeros pesquisadores tem sugerido que o chá verde (Camellia sinensis) possa reduzir o estresse oxidativo. Desta forma, como objetivos deste estudo, testamos se a administração de chá verde a ratos espontaneamente hipertensos (SHR) diabéticos ameniza o dano renal, verificando ainda se os efeitos se fazem por redução do estresse oxidativo. Métodos: Ratos SHR com 12 semanas de idade foram tornados diabéticos por injeção de estreptozotocina (50 MG/kg) e os grupos controle receberam somente o veiculo (tampão citrato de sódio pH 4.5). Animais diabéticos (SD) (glicemia > 270 MG/dl) e controle (SC) foram randomicamente divididos para receber chá verde (CV) ou água (A) como fonte única de líquidos, totalizando 8 a 10 animais por grupo, sendo eles SCA (SHR controle recebendo água), SCC (SHR controle recebendo chá verde), SDA (SHR diabético recebendo água) e SDC (SHR diabético recebendo chá verde). Peso, glicemia, pressão arterial sistólica (PAS) e albuminuria foram determinados a cada 4 das 12 semanas de acompanhamento. Resultados: Durante as 12 semanas de estudo, as glicemias foram significativamente maiores (p<0.001) nos animais SDA do que nos controles SCA e SCC , não sendo alteradas pela administração de CV. As PAS não foram afetadas pelo diabetes ou pelo tratamento com CV. A albuminuria dos animais não diabéticos SCA e SCC foram semelhantes, aumentando significativamente (p=0.048) nos SDA e reduzindo no tratamento com o CV (SDC) de forma significativa (p=0.048). A atividade da NAD(P)H oxidase, determinada por quimiluminescência foi significativamente maior (p=) no grupo SDA comparado ao SCA. O tratamento com CV reduziu de forma significativa (p=0.01) na ausência e presença do diabetes. A expressão da subunidade NOX-4 da NAD(P)H oxidase, determinada por Western Blot, aumentou de forma significativa (p=0.04) no grupo SDA em relação aos grupos não diabéticos SCA e SCC. Porem, em ratos diabéticos tratados com CV (SDC) esta expressão reduziu significativamente (p=0.04) chegando aos níveis do controle. A nitro tirosina, um marcador de modificação de proteína induzida pelo estresse oxidativo/nitros ativo avaliada por Western Blot, foi significativamente (p=0.04) maior no SDA do que no SCA e SCC, sendo no entanto significativamente reduzida (p=0.04) no grupo SDC . A expressão renal de colágeno IV determinada por Western Blot foi significativamente aumentada (p=0.008) nos ratos SDA comparados aos SCA e SCC. NA presença do diabetes, a administração de CV reduziu de forma significativa (p=0.013) esta variável. Conclusão: Em ratos hipertensos e diabéticos, o chá verde restabeleceu o equilíbrio redox, reduzindo marcadores de nefropatia sem alterar glicemia e pressão arterial. Desta forma, o consumo de chá verde pode ser benéfico a pacientes diabéticos e hipertensos.
Abstract:It has been suggested that green tea (GT) has beneficial properties in the treatment or prevention of human disease. The major biological mechanisms of action of GT are being attributed to its antioxidant properties. Several lines of evidence suggest that oxidative stress contributes to the pathogenesis of diabetic nephropathy. The effect of GT on diabetic nephropathy is unclear. We tested the hypothesis that GT prevents diabetes and hypertension-related renal oxidative stress and attenuates renal injury. Spontaneously hypertensive rats (SHR) with streptozotocin-induced diabetes and control SHR were treated daily with tap water or fresh GT extract. After 12 weeks, the systolic blood pressure was unchanged by diabetes or GT. However, there was a decrease in body weight and a significant (p<0.0001) increase in blood glucose level in diabetic SHR. These parameters were unaffected by GT therapy. GT prevented the increase in 8-hydroxy-2'- deoxyguanosine, an indicator of renal oxidative stress-induced DNA, and nitrotyrosine, an indicator of oxidative stress-induced protein modification, that were significantly (p<0.01) elevated in diabetic SHR. Likewise, GT attenuated(p=0.048) ADPH oxidase-dependent superoxide generation and the expression of renal ortex NOX-4, a subunit of NADPH oxidase, that were elevated (p=0.013) in diabetic HR. Treatment with GT significantly (p=0.048) reduced the indices of renal injury, lbuminuria and renal expression of collagen IV in diabetic SHR. GT reestablished he redox state and reduced the indicators of nephropathy without altering blood lucose and blood pressure levels in diabetic SHR. These findingssuggest that the onsumption of GT may ameliorate nephropathy in diabetic hypertensive patients.
Mestrado
Ciencias Basicas
Mestre em Clinica Medica
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Bach, Griera Jordi. "Estudi in vitro del paper del dany oxidatiu com a mecanisme d’acció en la carcinogènesi associada a l’arsènic." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/321106.
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L’arsènic inorgànic es presenta com un carcinogen molt ben establert en humans. Milions de persones es troben exposades arreu del món, fonamentalment a través de l’aigua de consum contaminada per aquest compost. Encara que existeixen múltiples mecanismes d’acció pels quals l’arsènic pot exercir els seus efectes carcinògens, la generació de dany oxidatiu en el DNA a partir de les espècies reactives d'oxigen derivades de la seva biotransformació es presenta com un dels mecanismes importants a l’hora d’explicar l’aparició dels fenòmens tumorals associats amb la seva exposició.
En aquest context, l’objectiu principal d’aquesta Tesi ha estat demostrar la connexió existent entre la presència de dany oxidatiu i la carcinogènesi associada a una exposició amb arsènic inorgànic. Per arribar a aquest objectiu s’ha implementat una estratègia innovadora de treball en el qual s’emulen les condicions d’exposició ambiental a les que es troben exposades les poblacions humanes. Concretament, aquesta estratègia es basa a desenvolupar un model d’exposició crònica in vitro a dosis subtòxiques d’arsènic inorgànic. A més, s’ha utilitzat un model cel·lular particular constituït per dues línies cel·lulars isogèniques de fibroblasts embrionaris de ratolí (MEF), una de les quals és deficient en la reparació de lesions oxidants del DNA que requereixen el mecanisme BER, exhibint un genotip knockout pel gen Ogg1, un dels gens principals de l’esmentada ruta de reparació del DNA.
Al llarg d’aquest període d’exposició crònica a dosis de 0,5, 1 i 2 µM d’arsenit sòdic, es van avaluar diferents paràmetres en ambdues línies cel·lulars, els valors dels quals van ser comparats amb els corresponents controls temporals. Dits paràmetres mesuren els nivells acumulats de dany oxidatiu (8-OH-dG), la capacitat de reparar el dany en el DNA, l’estudi de possibles mecanismes d’adaptació i, finalment, l’adquisició d’un fenotip tumoral in vitro en ambdues línies cel·lulars al llarg d’un procés d’exposició arsenit sòdic del voltant 40 setmanes.
Els resultats obtinguts donen suport a la hipòtesi reflectida en l’objectiu principal. Així, les línies cel·lulars Ogg1 deficients (MEF Ogg1 -/-) crònicament exposades a l’arsènic mostren una acumulació progressiva de dany oxidatiu en el DNA, mentre que l’increment d’aquest dany no es detecta en la línia salvatge. Paral·lelament, l’eficiència dels mecanismes de reparació del dany induït en el DNA es veu afectada en ambdues línies cel·lulars, manifestant-se així l’activitat cocarcinògena de l’arsènic. Pel que fa referència a l’adquisició del fenotip tumoral, trobem que l’arsènic és capaç d’induir un fenotip tumoral de manera primerenca en la línia deficient, el que indicaria que el dany oxidatiu en el DNA juga un paper fonamental en la carcinogènesi associada a l’exposició. Així, les cèl·lules Ogg1 -/- manifesten un fenotip tumoral al cap de 30 setmanes d’exposició, caracteritzat per canvis morfològics, un increment en proliferació cel·lular, el descontrol en estat de diferenciació, l’ increment en la secreció de metal·loproteïnases de la matriu extracel·lular, l’adquisició de la capacitat de créixer independent d’ancoratge, i la capacitat de promoure el creixement tumoral i la invasió.
A manera de conclusió, aquesta Tesi demostra, principalment i per primera vegada, que el fons genètic referent al gen OGG1 i la inducció de 8-OH-dG són factors rellevant en el procés de carcinogènesi associada a l’arsènic. Indirectament, el treball posa de manifest el risc associat dels individus amb polimorfismes al gen OGG1, fent-los més susceptibles a l’aparició dels efectes genotòxics i carcinògens derivats de l’exposició.Inorganic arsenic is presented as a very well established human carcinogen. Millions of people around the world are exposed to this compound mainly through contaminated drinking water. Although there are multiple mechanisms of action by which arsenic may exercise their carcinogenic effects, the generation of oxidative DNA damage from reactive oxygen species derived from its biotransformation is presented as one of the most important mechanisms explaining the associated cancer phenomena. In this context, the main objective of this thesis was to demonstrate the connection between the presence of oxidative damage and carcinogenesis, linked to inorganic arsenic exposure. In order to reach this objective, we have implemented an innovative strategy plan which emulated environmental conditions in which human populations are exposed. Specifically, this strategy is based on developing an in vitro model of chronic exposure to subtoxic inorganic arsenic doses. In addition, we used a particular cell model comprising two isogenic cell lines from mouse embryonic fibroblasts (MEF), being one of them deficient in the repair of oxidative DNA lesions that require the BER mechanism, showing a knockout genotype for Ogg1, one of the major genes of this DNA repair pathway. Throughout this period, cells were exposed to 0.5, 1 and 2 µM of sodium arsenite for 40 weeks. Different parameters were evaluated in both cell lines, the values of which were compared with the corresponding time-matched controls. These parameters were the accumulated levels of oxidative damage (8-OH-dG), the ability of repairing DNA damage, the mechanisms of adaptation and, finally, the acquisition of an in vitro tumor phenotype. Results supported the main hypothesis. Thus, Ogg1 deficient cell lines chronically exposed to arsenic showed a progressive accumulation of oxidative DNA damage, whereas that increase was not detected in its wildtype counterparts. Moreover, the efficiency of DNA repair mechanisms in repairing the induced damage was affected in both cell lines, manifesting the arsenic co-carcinogen activity. Taking into account the acquisition of the tumor phenotype, we found that arsenic can induce an early tumor phenotype in the deficient Ogg1 cell line, indicating that oxidative DNA damage plays a role in carcinogenesis associated with the exposure. Thus, Ogg1 - /- cells expressed a tumor phenotype after 30 weeks of exposure, characterized by morphological changes, an increase in cell proliferation, the lack of a correct differentiation status, the increase in secretion of extracellular matrix metalloproteinases, the acquirsition of the ability to grow independent of anchor, and the acquisition of the ability to promote tumor growth and invasion. In conclusion, this thesis shows for the first time that the genetic background of the reference gene OGG1 and the induction of 8-OH-dG are key factors in the arsenic-associated carcinogenesis. Indirectly, the work highlights the associated risk of individuals carrying OGG1 gene polymorphisms, as they are expected to be more susceptible to the genotoxic and carcinogenic effects of the exposure.
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Baek, Naerin. "Effects of Natural Antioxidants on Lipid Oxidation of Menhaden Oil." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/19214.
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Preventing oxidative deterioration of fish oil is a significant challenge for the food industry. Natural antioxidants are widely incorporated into foods and oils to prevent oxidation and extend shelf life. The goal of the study is to investigate the activity of novel antioxidants in menhaden oil and to develop optimum formulations containing mixed tocopherols to control oxidation of menhaden oil. Alpha tocopherol, gamma tocopherol, and delta tocopherol in menhaden oil were found at 0.18mg/g, 0.37mg/g, and 0.14mg/g, respectively, using HPLC analysis. Teng Cha extract effectively delayed oxidation of menhaden oil (MO) when stored at 40°C for eight days by measuring primary oxidation products and secondary oxidation products. The combinations of Teng Cha extract and rosemary extract and combinations of ascorbyl palmitate, citric acid, Teng Cha extract and rosemary extract more effectively improved stability of MO containing mixed tocopherols than Teng Cha extract alone at 40°C storage for eight days by measuring primary oxidation products and secondary oxidation products. From this study, Teng Cha extract can be used as a potential natural antioxidant in food industry, especially in combinations with rosemary extract and tocopherols, extending shelf life of menhaden oil.Master of Science in Life Sciences
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Zanchi, Mariane Magalhães. "Papel protetor da infusão do chá verde sobre o dano induzido pela ciclofosfamida no sistema reprodutor de camundongos." Universidade Federal do Pampa, 2014. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/312.
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MARIANE MAGALHÃES ZANCHI.pdf: 1185149 bytes, checksum: 5b02afd42e868819a353f05a3e1fb99a (MD5)Made available in DSpace on 2016-04-18T17:36:59Z (GMT). No. of bitstreams: 1 MARIANE MAGALHÃES ZANCHI.pdf: 1185149 bytes, checksum: 5b02afd42e868819a353f05a3e1fb99a (MD5) Previous issue date: 2014-07-26
A ciclofosfamida (CF) é um agente antineoplásico e imunossupressor, usada no tratamento de diversos tipos de tumores e em algumas doenças auto-imunes. A CF é considerada um pró-fármaco, portanto, precisa sofrer biotransformação hepática para formar seus metabólitos ativos, como a mostarda fosforamida e a acroleína. Seu metabólito terapêutico, a mostarda fosforamida, é responsável pelo efeito citotóxico na célula tumoral, enquanto a acroleína é conhecida por apresentar um efeito tóxico secundário, por aumentar a produção de espécies reativas ao oxigênio, causando estresse oxidativo. Esse, por sua vez, poderia estar diretamente relacionado com a redução da fertilidade causada por esta droga. Diante disso, compostos naturais com atividade antioxidante poderiam ser uma alternativa ao dano causado pela CF. O chá verde, obtido da planta Camellia sinensis, tem ação antioxidante e scavenger de radicais livres, devido ao alto conteúdo de polifenóis. O presente estudo avalia o papel protetor da infusão do chá verde sobre o dano oxidativo no sistema reprodutor de camundongos machos, e a sua relação com a fertilidade, após uma administração aguda de CF. Os camundongos foram pré-tratados por gavagem com veículo ou chá verde diariamente, por 14 dias, na dose de 250 mg/kg. A CF foi administrada via intraperitoneal no 14o dia, 1 hora após a administração do chá, na dose de 100 mg/kg. Os camundongos foram eutanasiados 24 horas após a administração da CF, e os testículos e epidídimos foram retirados para posteriores análises bioquímicas e avaliação espermática. O conteúdo de catequinas, principais constituintes do chá verde foi avaliada por HPLC. Epigalocatequina galato (EGCG) está presente em alta concentração na nossa infusão (1340,2 μg/mL), seguido por epicatequina (EC-500,95 μg/mL) e epicatequina galato (ECG-302,84 μg/mL). CF causou estresse oxidativo no sistema reprodutor dos animais, evidenciado neste trabalho por danificar tanto lipídios, como proteínas e DNA. A CF causou um aumento na peroxidação lipídica (níveis de MDA), dano de DNA (ensaio cometa) e atividade da enzima superóxido dismutase (SOD), enquanto diminuiu a atividade da glutationa peroxidase (GPx), glutationa-S-transferase (GST) e 17β–hidroxiesteróide desidrogenase (17β–HSD) em ambos os tecido testados. A atividade da enzima catalase (CAT) e a quantificação de proteína carbonil foram alteradas somente em testículo, mas não em epidídimo. Em relação à avaliação espermática, CF reduziu significativamente apenas a concentração de espermatozóides, comparado ao controle. O pré-tratamento com a infusão do chá verde reduziu significativamente a produção de MDA, carbonilação de proteína, dano de DNA e restaurou a atividade da GPx e GST. Em epidídimo, o chá verde também aumentou a concentração espermática e restaurou a atividade da enzima 17β–HSD. Pode-se concluir que a infusão do chá verde melhora o dano induzido pela CF, no sistema reprodutor de camundongos, e este efeito poderia ser atribuído ao alto conteúdo de catequinas presentes no chá e à sua atividade antioxidante.
Cyclophosphamide (CP) is an antineoplastic and immunosuppressive agent used to treat various types of tumors and in some autoimmune diseases. CP is considered a prodrug, therefore, must undergo hepatic biotransformation to form its active metabolites, such as phosphoramide mustard and acrolein. Its therapeutic metabolite, phosphoramide mustard, is responsible for the cytotoxic effect on tumor cells, while acrolein is known to provide a secondary toxic effect by increasing the reactive oxygen species production, causing oxidative stress. This might be directly related to the fertility reduction caused by this drug. Therefore, natural compounds with antioxidant activity could be an alternative to the damage caused by CP. Green tea, obtained from the plant Camellia sinensis, has antioxidant and free radical scavenging effect, due to the high content of polyphenols. The present study evaluates the protective role of the green tea infusion on oxidative damage on male mice reproductive system, and their relationship to fertility after an acute administration of CP. The mice were pre-treated by gavage with vehicle or green tea daily for 14 days at dose of 250 mg/kg. CP was administered intraperitoneally on day 14, 1 hour after administration of tea at dose of 100 mg/kg. Mice were euthanized 24 hours after the administration of the CP and testes and epididymis were removed for further biochemical analysis and sperm assessment. The content of catechins, the main constituents of green tea were evaluated by HPLC. Epigallocatechin gallate (EGCG) is present in high concentrations in our infusion (1340.2 μg/ml), followed by epicatechin (EC-500.95 μg/ml) and epicatechin gallate (ECG-302.84 μg/mL). CP caused oxidative stress in the reproductive system of animals, evidenced in this work by damaging not only lipids, but also proteins and DNA. CP increased lipid peroxidation (MDA), DNA damage (comet assay) and superoxide dismutase (SOD) activity, while decreased glutathione peroxidase (GPx), glutathione-S-transferase (GST) and 17β-hydroxysteroid dehydrogenase (17β-HSD) activity in both tissues tested. Catalase (CAT) activity and quantification of protein carbonyl were altered only in testes but not in the epididymis. Regarding sperm evaluation, CF significantly decreased only sperm concentration, compared to the control group. Pre-treatment with green tea infusion significantly reduced MDA production, protein carbonylation, DNA damage and restored GPx and GST activity. In epididymis, green tea also increased sperm concentration and restored 17 β-HSD activity. Green tea infusion improves the damage induced by CP in the reproductive system of mice, and this effect is attributed to the high content of catechins in tea and its antioxidant activity.
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Kim, Jong Min. "Electrochemical Promotion of Gold Nanoparticles Supported on Yttria-Stabilized Zirconia." Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20435.
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The feasibility of highly dispersed gold nanocatalyst supported on yttria-stabilized zirconia (YSZ) for the model reactions of C2H4 and CO oxidation is demonstrated for the first time. Gold nanoparticles are synthesized on YSZ powder by chemical reduction of the precursor salt in the mixture of ethanol, water and polyvinylpyrrolidone (PVP). Resulting metal loading of the catalysts are 1 wt.% with average particle sizes ranging from 6 to 9 nm. Results of CO and C2H4 oxidation display catalytic activity at 65 0C and 25 0C for CO and C2H4 oxidation, respectively. The catalytic properties of the catalysts are different due to their average particle size. Electrochemical Promotion of Catalysis (EPOC) of C2H4 oxidation is demonstrated. Application of constant potential difference between two electrodes in the bipolar electrochemical cell led to increase in C2H4 conversion. A proposed mechanism explains the bipolar EPOC phenomenon through formation of O2- flux across the electrochemical cell, resulting in the change of Work Function of gold nanoparticles placed in between the electrodes and is electronically isolated.
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Wang, Jin. "A mechanistic study of the preferential photo-oxidation of the 5-CH3 substituent of thymine and thymidine mediated by NH4(VO(O2)2(5-NO2phen))." HKBU Institutional Repository, 2009. http://repository.hkbu.edu.hk/etd_ra/1056.
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Modesto, Pamela Nayara. "Influência do extrato do chá verde (Camellia sinensis) no metabolismo energético cardíaco de ratos expostos a doxorrubicina." Botucatu, 2019. http://hdl.handle.net/11449/181755.
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Orientador: Paula Schimidt Azevedo GaiollaResumo: INTRODUÇÃO: A doxorrubicina (DOX) é um medicamento muito eficaz no tratamento de vários tipos de câncer, mas seu uso em larga escala tem causado preocupação devido à cardiotoxicidade causada pela droga. Não se sabe exatamente quais mecanismos estão envolvidos, mas acredita-se nos papeis centrais da ligação da DOX com a topoisomerase 2-β (Top2-β), que é uma enzima que protege a célula da citotoxicidade e destruição; da interação DOX-ferro gerando espécies reativas de oxigênio; além de disfunção mitocondrial, seguida por muitas outras vias secundárias ativadas por essas primárias, como inflamação e fatores da matriz extracelular (MEC). Por outro lado, o chá verde, uma bebida muito popular em todo o mundo, tem efeitos antioxidantes e antitumorais. MÉTODOS: Foram utilizados 60 ratos Wistar machos. Estes animais foram divididos grupos: C=20 (controle) que recebeu ração padrão e administração intraperitoneal de salina, CV=20 (controle + chá verde) que receberam ração adicionada de extrato de chá verde e administração intraperitoneal de solução salina, D=20 (doxorrubicina) que recebeu ração padrão e administração intraperitoneal de doxorrubicina e DCV=20 (doxorrubicina + chá verde) que receberam ração adicionada de extrato de chá verde e administração intraperitoneal de doxorrubicina. A ração foi oferecida por 35 dias e no 33º dia a infusão de doxorrubicina ou soro fisiológico foi realizada na mesma proporção (20 mg / kg em dose única) e os animais foram eutanasiados 48 horas após a... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: INTRODUCTION: doxorubicin (dox) is a very effective drug in the treatment of several types of cancer, but it plays an important role in cardiotoxicity. The mechanisms of DOX-induced cardiotoxicity include: binding to Top2-β, an enzyme that protects cells from citotoxicity and destruction; interaction with iron and altering intracellular and mitochondrial antioxidants enzymes activities, followed by many other secondary pathways activated by these primary, for example inflammation, estracellular matrix ( ECM) factors and others. On the other hand, green tea, a very popular beverage all over the world, has antioxidants and antitumor properties. METHODS: Sixty male Wistar rats were used. These animals were divided into groups: C = 20 (control) that received standard chow and intraperitoneal administration of saline, GT = 20 (control + green tea) receiving added chow of green tea extract and intraperitoneal administration of saline solution, D = 20 (doxorubicin) who received standard chow and intraperitoneal administration of doxorubicin and DGT = 20 (doxorubicin + green tea) who received added ration of green tea extract and intraperitoneal administration of doxorubicin. The feed was offered for 35 days and on the 33rd day the infusion of doxorubicin or saline was performed in the same proportion (20 mg / kg in a single dose) and the animals were euthanized 48 hours after the injection of the drug. The rats were submitted to echocardiogram to evaluate the cardiac morphology and ... (Complete abstract click electronic access below)
Doutor
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Panza, Vilma Simões Pereira. "Efeito do consumo de chá mate (Ilex paraguariensis) em marcadores do dano muscular, da inflamação e do estresse oxidativo após o exercício excêntrico." reponame:Repositório Institucional da UFSC, 2016. https://repositorio.ufsc.br/xmlui/handle/123456789/167730.
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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Nutrição, Florianópolis, 2016.Made available in DSpace on 2016-09-20T04:14:50Z (GMT). No. of bitstreams: 1 339573.pdf: 9639865 bytes, checksum: 7e3a334e066742f6776fb267f53abaae (MD5) Previous issue date: 2016
O exercício excêntrico pode resultar em dano muscular, déficit na força muscular e respostas inflamatórias/oxidativas. Certos alimentos ricos em fitoquímicos podem melhorar as alterações funcionais/metabólicas induzidas pelo exercício excêntrico. Nesse sentido, o chá mate (Ilex paraguariensis) rico em compostos fenólicos e saponinas possui um potencial interessante, devido às suas propriedades antioxidantes/anti-inflamatórias. No presente estudo, foram investigados os efeitos do consumo de chá mate em marcadores do dano muscular, do estresse oxidativo e da inflamação após uma sessão de exercícios excêntricos. Em desenho cruzado e randomizado, homens saudáveis (N=20) consumiram chá mate ou água (controle), três vezes/dia, por 11 dias. No 8° dia, os indivíduos realizaram três séries de 20 ações excêntricas máximas unilaterais com os músculos flexores do cotovelo. Os picos de torque isométrico, concêntrico e excêntrico foram medidos antes (PRÉ) e 0, 24, 48 e 72 h após o exercício excêntrico. Amostras sanguíneas foram obtidas no PRÉ e 24, 48 e 72 h após o exercício excêntrico. Foram quantificados: creatina quinase e aldolase no soro; compostos fenólicos totais no plasma; glutationa reduzida (GSH) e glutationa oxidada (GSSG) no sangue total e hidroperóxidos lipídicos e carbonilas protéicas no plasma; leucócitos no sangue; interleucina (IL)- 1b, IL-6, fator de necrose tumoral-a (TNF-a) e proteína C-reativa de alta sensibilidade (PCR-as) no soro; e expressão das proteínas CD11b e p47phox em neutrófilos. Em ambos os grupos, os valores dos picos de torque isométricos, concêntricos e excêntricos permaneceram abaixo do PRÉ, durante 72 h pós-exercício excêntrico (P<0,05). Entretanto, em 24 h, os picos de torque isométrico e concêntrico foram maiores no chá mate (P<0,05). A atividade da creatina quinase elevou acima do PRÉ em 72 h (P<0,05), em ambos os grupos. O chá mate diminuiu os valores da aldolase no PRÉ e em 24 h (P<0,05). A concentração de fenóis totais foi maior no chá mate no PRÉ e em 24 e 72 h (P<0,05). No controle, a concentração de GSH diminuiu em 72 h (P<0,05) e foi menor que no chá mate no PRÉ e em 48 e 72 h (P<0,05). O exercício excêntrico não modificou a concentração de GSSG, porém, a razão GSH/GSSG em 72 h foi maior no chá mate (P<0,05). A concentração de hidroperóxido lipídicos não foi alterada pelo exercício excêntrico; enquanto que a de carbonilas protéicas aumentou em 72 h no controle (P<0,05). O exercício excêntrico não alterou os valores de leucócitos, IL-6, TNF-a, PCR-as, CD11b e p47phox. Entretanto, o chá mate preveniu o aumento nos valores de IL-1b em 24 h (P<0,05) e diminuiu a concentração de IL- 6 em 24 a 72 h (P<0,05) e de TNF-a em 24 h (P<0,05). Além disso, o chá mate atenuou a concentração de PCR-as entre o PRÉ e 72 h (P<0,05) e a expressão da p47phox no pré-esforço (P=0,05). Conclui-se que o chá mate acelerou a recuperação na força muscular 24 h após o exercício excêntrico. Além disso, o chá mate modulou favoravelmente as respostas ao exercício excêntrico relativo aos marcadores bioquímicos do dano muscular, do estresse oxidativo e da inflamação, e melhorou os perfis sistêmicos de antioxidantes e mediadores inflamatórios no pré-esforço.
Abstract : Eccentric exercise may result in muscle damage, deficit in muscle strength and inflammatory/oxidative responses. Certain foods rich in phytochemicals can improve the functional/metabolic changes induced by eccentric exercise. In this sense, mate tea (Ilex paraguariensis) - which is rich in phenolic compounds and saponins - has an interesting potential due to its antioxidant/anti-inflammatory properties. In this study, we investigated the effects of mate tea consumption on muscle damage, oxidative stress, and inflammation markers after an acute bout of eccentric exercise. In a randomized crossover design, 20 healthy men were assigned to drink either mate tea or water (control), three times/day for 11 days. On the 8th day, subjects performed three sets of 20 maximal eccentric elbow flexion exercises. Isometric, concentric, and eccentric peak torques were measured before (PRE) and and at 0, 24, 48, and 72 h after eccentric exercise. Blood samples were obtained before and at 24, 48, and 72 h after eccentric exercise and were analyzed for: serum creatine kinase and aldolase in serum; total phenolic compounds in plasma; reduced glutathione (GSH) and oxidized glutathione (GSSG) in whole blood and lipid hydroperoxide and protein carbonyls in plasma; blood leukocytes; interleukin (IL)-1b, IL-6, tumor necrosis factor-a (TNF-a), and high-sensitivity C-reactive protein (hs-CRP) in serum; and CD11b and p47phox expression in neutrophils. In both groups, isometric, concentric, and eccentric peak torques remained below PRE values throughout 72 h after eccentric exercise (P <0.05). However, at 24 h, isometric and concentric peak torques were higher (P<0.05) in the mate tea than in the control group. Creatine kinase activity was higher at 72 h than PRE in both groups. Aldolase activity was lower in mate tea than in control at PRE and 24 h after eccentric exercise (P<0.05). Phenolic compounds levels were higher in mate tea than in control group at PRE and 24 and 72 h after eccentric exercise (P<0.05). In control, the GSH concentration was decreased at 72 h after eccentric exercise (P<0.05) and was smaller than in mate tea at PRE and 48 and 72 h after eccentric exercise (p <0.05). GSSG level was unchanged in either group overtime. The GSH/GSSG ratio was higher in mate tea than in control at 72 h after eccentric exercise (P<0.05). Lipid hydroperoxide concentration was not altered by the eccentric exercise; while protein carbonyls levels increased at 72 h after eccentric exercise in control (P <0.05). Leukocyte counts, IL-1b, IL-6, TNF-a, hs-PCR, CD11b, and p47phox were unnaffected in either groups overtime. In the control group, IL-1b was higher at 24 h than at PRE (P<0.05). IL-6 were lower in mate tea than in control from 24 to 72 h (p<0.05). TNF-a was lower in mate tea than in control at 24 h after eccentric exercise (P<0.05). In the mate group, hs-CRP was decreased at 72 h compared with PRE (P<0.05). p47phox expression was lower in mate tea than in control before eccentric exercise (P=0.05). It is concluded that mate tea supplementation hastened muscle strength recovery over 24 h after eccentric exercise. Furthermore, mate intake favorably modulated muscle damage, oxidative stress, and inflammation biochemical markers responses to eccentric exercise and improved pre-exercise profiles of antioxidants and systemic inflammatory mediators.
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Tomás, Gonçalo David Cabral. "Male fertility and type 2 diabetes mellitus: effect of white tea." Master's thesis, Universidade da Beira Interior, 2013. http://hdl.handle.net/10400.6/1348.
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Diabetes mellitus (DM) is one of the major public health problems and its increase
incidence is closely related with a decrease in birth rates. Male infertility related with type 2
DM (T2DM) has been linked to reactive oxygen species (ROS) overproduction and increased
testicular oxidative stress (OS). Tea is one of the most widely consumed beverages and its
antihyperglycemic and antioxidant potential has been reported. Herein, we hypothesized that
White Tea (WTEA) consumption by T2DM rats could prevent testicular OS preserving sperm
quality. For that purpose, we used a neonatal STZ-induced diabetic rat model. At one month
of age, water was substituted by WTEA during two months and testicular antioxidant
potential and OS were evaluated, as well as sperm parameters in normal and T2DM rats
drinking water or WTEA.
WTEA consumption improved glucose tolerance and insulin sensitivity in T2DM rats.
WTEA consumption restored protein oxidation and lipid peroxidation to normal levels.
Testicular antioxidant potential was increased by WTEA consumption in T2DM, while
testicular OS was decreased. Nevertheless, glutathione content and redox state was not
altered. After WTEA consumption by T2DM rats, sperm concentration was improved while
sperm motility, viability and the abnormal spermatozoa reached normal values evidencing
that epididymal sperm quality was restored. Overall, our results show that WTEA consumption
causes an important improvement in sperm parameters and thus in male T2DM reproductive
function, due to a significant decrease in testes ROS production. WTEA consumption can be a
natural, economical and good strategy to counteract the deleterious effects of T2DM in male
reproductive function.A diabetes mellitus é um dos principais problemas de saúde pública e seu aumento de incidência está intimamente relacionado com a diminuição das taxas de natalidade. A infertilidade masculina relacionada com a diabetes tipo 2 tem sido associada ao aumento de produção de espécies reactivas de oxigénio e ao aumento do stress oxidativo testicular. O chá é uma das bebidas mais consumidas no mundo e o seu potencial anti hiperglicémico e antioxidante tem sido descrito em diversos estudos. Com este trabalho pretende-se investigar se o consumo de chá branco por ratos diabéticos tipo 2 pode prevenir o stress oxidativo testicular e assim preservar a qualidade espermática. Para essa finalidade, utilizou-se um modelo de rato diabético tipo 2 induzido por streptozotocina. Em animais com um mês de idade, a água foi substituída por chá branco durante dois meses e após esse período o potencial antioxidante e o stress oxidativo nos testículos foi avaliado, bem como os parâmetros espermáticos em ratos normais e em ratos diabéticos tipo 2 que consumiram água ou chá branco. O consumo de chá branco melhorou a tolerância à glucose e a sensibilidade à insulina em ratos diabéticos tipo 2. Restaurou ainda os níveis de oxidação proteica e de peroxidação lipídica para níveis presentes em ratos controlo. O potencial antioxidante testicular foi aumentado pelo consumo de chá branco em ratos diabéticos tipo 2, enquanto o stress oxidativo testicular foi diminuído. No entanto, o teor de glutationa e o seu estado redox não foram alterados. Após o consumo de chá branco por ratos diabéticos tipo 2, a concentração espermática foi aumentada, enquanto a motilidade, a viabilidade e o número de espermatozóides anormais atingiram valores normais, evidenciando que a qualidade dos espermatozóides epididimais foi restaurada. No geral, estes resultados mostram que o consumo de chá branco provoca uma melhoria acentuada nos parâmetros espermáticos e, portanto, na função reprodutora masculina em diabetes tipo 2, devido a uma diminuição significativa na produção de espécies reactivas de oxigénio nos testículos. O consumo de chá branco pode ser uma estratégia natural e económica para neutralizar os efeitos deletérios da diabetes tipo 2 na função reprodutiva masculina.
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Tuli, Leepika. "Proteome Profiling of Saccharomyces cerevisae stress response to Cumene Hydroperoxide (CHP)." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28620.
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Oxidative stress, described as the state of disturbed intracellular redox balance, has been associated with several human conditions including ageing, apoptosis, cancer, autoimmune and neuro-degenerative diseases. Stress studies have shown that reactive oxygen species (ROS) and reactive nitrogen species (RNS) along with its intermediates can attack essential cell targets such as: DNA, proteins, lipids and carbohydrates, leaving behind dysfunctional biologic molecules. In effect, a cellâ s primary response is to involve several defense mechanisms that are under a complex and intricate regulatory control to repair any damages that may have occurred. Although several stress studies have been conducted in the past that have approached this biologically complex process step by step, application of a Systems Biology towards a comprehensive understanding is still emerging.
The current objective of this project is to identify proteins that change in response to cumene hydroperxoide (CHP) treatment and in parallel make an attempt to uncover events and processes that are a part of CHP-induced oxidative stress response. From a systems biology viewpoint, the Yeast Oxidative Stress project will monitor response at three different levels: transcriptomics, proteomics and metabolomics, with dynamic changes being measured from 3 to 120 min after CHP addition. Data collected from the different levels will be integrated to accomplish a holistic viewpoint of stress response in the given system and to develop mathematical tools for modeling biochemical networks.
Saccharomyces cerevisiae was chosen as a model, based on its availability of a completely mapped genome sequence with a collection of null mutants that was relevant to our fundamental research of stress response mechanism. Yeast, a simple unicellular eukaryote has been extensively used for applied studies and has proven to be indispensable for stress research. Information derived from this project can reveal response mechanisms used by higher eukaryotes, especially if via analogous signaling cascades that are comparable between organisms.
Current research investigates an optimal workflow for generating 2D gel based protein expression data and identifying proteins that are induced by cumene hydroperoxide treatment. A non-targeted protein profiling followed by a 2-way ANOVA analysis provided a list of proteins that differ significantly between treatments. Protein identification provided relevant information on which proteins are affected by CHP induced stress response, including posttranslational modifications of peroxiredoxins. Redox active protein, Ahp1, was regulated post-translationally with sulfonic acid modification observed for its active Cys(62) residue.Ph. D.
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Flôres, Maíra Frigo. "Efeitos do exercício físico e da suplementação com chá-verde sobre características bioquímicas e comportamentais associadas ao envelhecimento." Universidade Federal do Pampa, 2013. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/308.
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Maíra Frigo Flores.pdf: 606784 bytes, checksum: 320f5eb7c4c92844adfadf846bcd39d7 (MD5)Made available in DSpace on 2016-04-08T19:23:35Z (GMT). No. of bitstreams: 1 Maíra Frigo Flores.pdf: 606784 bytes, checksum: 320f5eb7c4c92844adfadf846bcd39d7 (MD5) Previous issue date: 2013-11-08
O envelhecimento causa rejuízos cognitivos e de memória que têm sido relacionados com o estresse oxidativo (EO). Descobrir formas de atenuar o EO é importante para minimizar perdas cognitivas. O exercício físico e as catequinas constituintes do chá verde são potenciais antioxidantes que podem auxiliar na proteção das funções cognitivas e de memória. Ao passo que evidências sugerem papel neuroprotetor do exercício, efeitos do chá verde durante o envelhecimento como estratégia para combater o EO ainda são bastante incipientes. Essa pesquisa verificou os efeitos do exercício físico e da suplementação com o chá verde sobre aspectos bioquímicos e comportamentais associados ao envelhecimento. Ratos Wistar com 9 meses de idade foram divididos em grupos, sendo eles: controle, exercício, chá verde, exercício e chá verde, além de um grupo controle jovem. As intervenções foram feitas por três meses, constando de exercício aeróbico e ingestão de chá verde de maneira isolada, e realização de exercício aeróbico com concomitante ingesta de chá verde. Em conclusão, o chá verde não evitou déficits cognitivos no envelhecimento, mas diminuiu as espécies reativas aumentando as defesas antioxidantes. O exercício melhorou diversos parâmetros bioquímicos e comportamentais. A falta de efeito do chá verde na cognição pode estar relacionada com as características da intervenção, ao passo que a diminuição nas espécies reativas sugere um papel de proteção do chá verde mesmo em um período curto de suplementação.
Aging is associated with cognitive and mnemonic deficits frequently reported as related to the oxidative stress (OS). There is continuous interest to minimize effects of OS in order to avoid cognitive deficits. Physical exercise and catechines from green tea are potential antioxidants helping to protect cognitive and memory functions. While there are evidences supporting the neuroprotective role of physical exercise, the effects of green tea supplementation during aging as strategy to combat OS still are quiet incipient. In this study the effects of physical exercise and green tea supplementation on biochemical and behavioral characteristics associated with aging were addressed. Wistar rats 9 months aged were organized in groups as follow: young control group; aged control group; exercise aged group; green tea supplementation aged group; exercise and green tea supplementation aged group. Interventions lasted 3 months composed by aerobic exercise and green tea, combined or not. Green tea was not effective in avoid cognitive deficits associated with aging, but significantly decreases ROS activity with significant improve in antioxidants defenses. Physical exercise improved all parameter in both biochemical and behavioral testing. The lack of effects of green tea on cognition may rely on the duration of the intervention, while decrease in the ROS suggests its effect role even during a short supplementation period.
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Bachmann, Christoph [Verfasser]. "Kinetic, electrochemical and spectroscopic investigation of the oxidation of CO and C2H4 on YSZ-supported metal model electrodes / Christoph Bachmann." Gießen : Universitätsbibliothek, 2015. http://d-nb.info/1074355172/34.
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Menezes, Jefferson Rosa de. "Estratégias para prevenção de déficits cognitivos associados à deprivação maternal." Universidade Federal do Pampa, 2017. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/1554.
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A deprivação maternal é um potente estressor na fase inicial da vida de mamíferos, ocasionando diversos déficits cognitivos que se mantêm na vida adulta. Dentre os mecanismos envolvidos nestes déficits estão o desiquilíbrio oxidativo e as alterações em determinadas proteínas, como o fator neurotrófico derivado do cérebro (do inglês Brain-Derived Neurotrophic Factor, BDNF). Estes eventos podem ocorrer em diferentes regiões do no cérebro, entre elas o hipocampo, principal região responsável pela formação e consolidação das memórias. Esta dissertação investigou os efeitos de diferentes estratégias neuroprotetoras (exercício físico, suplementação com chá verde, e, enriquecimento ambiental) nos déficits de memória advindos da deprivação maternal. Para avaliar a função mnemônica, foi utilizado um modelo animal de DM (em ratos Wistar) e os testes de reconhecimento de objetos, esquiva inibitória e labirinto aquático de Morris. Para avaliar o balanço redox hipocampal quantificamos espécies reativas de oxigênio (EROs), espécies reativas ao ácido tiobarbitúrico (TBARS), níveis de glutationa (GSH) e capacidade antioxidante total (FRAP), além disso, determinamos a atividade da enzima acetilcolinesterase e a quantificamos os níveis de BDNF. Nossos resultados demonstram que o exercício físico e o chá verde são estratégias antioxidantes eficazes de neuroproteção em um modelo de DM. Também demonstram que o enriquecimento ambiental é capaz de reverter os efeitos deletérios oriundos da DM por meio do incremento dos níveis de BDNF. Estes resultados revelam a possibilidade da utilização dessas intervenções como estratégia de neuroproteção.
Maternal deprivation is a potent stressor in the early life of mammalian, leading to several cognitive deficits that remain until adulthood. Among the mechanisms involved in these deficits are the oxidative imbalance and the alterations in some proteins, such as Brain-Derived Neurotrophic Factor (BDNF), events that can occur in different brain regions, as the hippocampus, the main region responsible for the memory formation and consolidation. This master thesis investigated the effects of different neuroprotective strategies (physical exercise, green tea supplementation, and environmental enrichment) on memory deficits related to maternal deprivation (MD). To evaluate the mnemonic function was used an animal model of MD (using Wistar rats) and the object recognition, inhibitory avoidance and Morris water maze memory tests. To evaluate hippocampal redox balance we quantified the reactive oxygen species (ROS), the thiobarbituric acid reactive species (TBARS), the glutathione levels (GSH) and the total antioxidant capacity (FRAP), as well as determine the acetylcholinesterase activity and the BDNF levels. Our results show that physical exercise and green tea are effective neuroprotective antioxidant strategies in a MD model. They also demonstrate that environmental enrichment is capable to reverse the deleterious effects of MD by increasing BDNF levels. These results reveal the possibility of using these interventions as a neuroprotection strategy.
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Panza, Vilma Simões Pereira. "Efeito do consumo de chá verde no estresse oxidativo em praticantes de exercício resistido." Florianópolis, SC, 2007. http://repositorio.ufsc.br/xmlui/handle/123456789/90316.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde. Programa de Pós-graduação em NutriçãoMade available in DSpace on 2012-10-23T08:30:55Z (GMT). No. of bitstreams: 1 244890.pdf: 694164 bytes, checksum: e8bd74bd82b7f6395fed8f98188e7838 (MD5)
O interesse nos efeitos do consumo de antioxidantes fenólicos dietéticos no estresse oxidativo induzido pelo exercício tem sido foco de pesquisas recentes. Não há relatos quanto à influência da ingestão de alimentos ricos em compostos fenólicos no estresse oxidativo associado ao exercício resistido. Este estudo investigou os efeitos do consumo de chá verde, por, aproximadamente, oito dias (2 g de erva em 200 mL de água, 3 vezes/dia), em marcadores do estresse oxidativo e de danos teciduais, em homens jovens (n=14) submetidos a um protocolo de exercício resistido. Amostras sangüíneas foram obtidas antes e após (1 e 15 min) a execução de um exercício submáximo em supino reto (4 séries; 10 a 4 repetições; 75 a 90% de 1RM), sem (controle) ou com a intervenção com chá verde (CV). Foi avaliado: i) capacidade antioxidante total - (FRAP), glutationa reduzida (GSH), hidroperóxidos lipídicos e substâncias reativas ao ácido tiobarbitúrico (TBARS); ii) creatina quinase (CK), transaminase (AST) e lactato desidrogenase (LD) e; iii) marcadores do metabolismo das purinas (hipoxantina, xantina oxidase (XO) e ácido úrico). Na condição controle, o exercício não afetou as concentrações plasmáticas de hidroperóxidos lipídicos, TBARS e FRAP, mas diminuiu os valores de GSH (p<0,05). O exercício aumentou a concentração das enzimas citosólicas circulantes CK e AST (p<0,05), mas não modificou a atividade da LD. A execução do exercício também aumentou a atividade da XO (p<0,05), porém não alterou os valores da hipoxantina e do ácido úrico. O chá verde diminuiu os valores pós-esforço de hidroperóxidos lipídicos (p<0,001) e aumentou a concentração de GSH (p<0,001) e a capacidade antioxidante do plasma (p<0,05), sendo que os valores de TBARS permaneceram inalterados; e inibiu a elevação das enzimas CK e AST promovida pelo exercício. Além disso, a ingestão de chá verde diminuiu a concentração de hipoxantina e de ácido úrico, antes e após o exercício, e inibiu a elevação da atividade da XO induzida pelo exercício (p<0,05). A avaliação do consumo alimentar demonstrou que os participantes possuem uma dieta desequilibrada, particularmente em relação a vitamina E e carotenóides. Os resultados do estudo sugerem que o consumo regular de chá verde melhora os mecanismos de defesa antioxidante em praticantes de exercício resistido, conforme avaliado pelos marcadores plasmáticos. Além disso, o chá verde pode reduzir a manifestação de danos teciduais induzidos pelo esforço, possivelmente por meio da neutralização da ação danosa de radicais livres. Em suma, sugere-se que alimentos e bebidas ricos em polifenóis, como, por exemplo, o chá verde, podem oferecer proteção contra o dano oxidativo induzido por exercícios, e que a orientação alimentar para esportistas deva ser enfatizada.
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Modesto, Pamela Nayara [UNESP]. "Influência do extrato de chá verde na remodelação cardíaca induzida por administração de doxorrubicina." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132032.
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000851622.pdf: 961386 bytes, checksum: bf132ab8813673411d4b6dbc521e732b (MD5)A doxorrubicina (DOX) é um medicamento amplamente utilizado como agente quimioterápico, tendo eficácia no tratamento de inúmeros tipos de cânceres. Entretanto, o uso desse medicamento pode proporcionar efeitos indesejáveis, como a cardiotoxidade. Diferentes mecanismos têm sido propostos para a cardiotoxicidade induzida pela doxorrubicina, como o estresse oxidativo, inflamação e alterações da matriz extracelular, levando ao processo de remodelação cardíaca. Chá verde (Camellia sinensis), uma das bebidas mais populares em todo o mundo, tem demonstrado uma relação positiva entre o seu consumo habitual e a proteção contra doenças cardiovasculares e contra alguns tipos de neoplasias. Isso se deve as propriedades antioxidantes, antiinflamatórias, antiapoptóticas encontradas nas catequinas, presentes no chá verde. Portanto, é possível que o mesmo atenue os afeitos cardiotóxicos da doxorrubicina, retardando o processo de remodelação cardíaca. O objetivo do presente estudo foi avaliar se o extrato de chá verde atenua a remodelação cardíaca induzida pela doxorrubicina, por meio da avaliação de variáveis bioquímicas, celulares, intersticiais e variáveis morfofuncionais cardíacas. Para isso, foram utilizados ratos Wistar machos com peso de 300 á 350 gramas. Esses animais foram divididos em 4 grupos: CP (controle) que receberam ração padrão e administração intraperitoneal de solução salina, CCV (controle + chá verde) que receberam ração adicionada de extrato de chá verde e administração intraperitoneal de solução salina, DX (doxorrubicina) que receberam ração padrão e administração intraperitoneal de doxorrubicina e DX-CV (doxorrubicina + chá verde) que receberam ração adicionada de extrato de chá verde e administração intraperitoneal de doxorrubicina. A ração foi ofertada por 35 dias e no 33◦ dia foi feita a infusão de doxorrubicina ou de solução salina foram na mesma proporção...
Doxorubicin (DOX) is a widely used drug as a chemotherapeutic agent having efficacy in the treatment of numerous cancers. However, use of this drug may provide undesirable effects such as cardiotoxicity. Various mechanisms have been proposed for doxorubicin cardiotoxicity, such as oxidative stress, inflammation and alterations in the extracellular matrix, leading to cardiac remodeling. Green tea (Camellia sinensis), the most popular drinks in the world, has demonstrated a positive relationship between regular consumption and protection against cardiovascular disease and some types of cancer. This is the antioxidant, anti-inflammatory, antiapoptotic found in catechins present in green tea. It is therefore possible that it mitigates the cardiotoxic fond of doxorubicin, slowing the process of cardiac remodeling. The aim of this study was to evaluate whether the green tea extract attenuates cardiac remodeling induced by doxorubicin, through the evaluation of biochemical variables, cell phones, and interstitial cardiac morphofunctional variables. For this, was used male Wistar rats weighing 250 to 300 grams. These animals were divided into 4 groups: CP (control) received standard chow and intraperitoneal administration of saline, CCV (control + green tea) receiving feed added green tea extract and intraperitoneal administration of saline, DX (Doxorubicin) who received standard chow and intraperitoneal administration of doxorubicin and DX-CV (doxorubicin + green tea) fed diets with added green tea extract and intraperitoneal administration of doxorubicin. The feed was supplied for 35 days and on day 33◦ doxorubicin or infusion of saline solution were carried out in the same ratio (20 mg / kg single dose) and the animals were euthanized 48 hours after drug injection. The rats were subjected to the echocardiography before and 48 hours after injection of doxorubicin. Was conducted evaluation of oxidative stress by spectrophotometry ...
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Altermann, Caroline Dalla Colletta. "Efeitos do tratamento com chá verde (camellia sinensis) no dano oxidativo e déficit de memória induzido pelo acidente vascular cerebral (AVC) isquêmico e pelo AVC hemorrágico em ratos." Universidade Federal do Pampa, 2016. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/318.
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CAROLINE DALLA COLLETTA ALTERMANN.pdf: 1566326 bytes, checksum: 5dc99f1d9fd7e1cb15d604b2290150a0 (MD5)Made available in DSpace on 2016-04-18T19:58:51Z (GMT). No. of bitstreams: 1 CAROLINE DALLA COLLETTA ALTERMANN.pdf: 1566326 bytes, checksum: 5dc99f1d9fd7e1cb15d604b2290150a0 (MD5) Previous issue date: 2016-03-15
O Acidente Vascular Cerebral (AVC) é classificado em dois tipos: Isquêmico e Hemorrágico. Dentre as sequelas decorrentes do AVC destacam-se as alterações funcionais, prejuízo cognitivo e perda de memória. Além disso, sabe-se que em uma situação como o AVC ocorre o desbalanço do estado redox e, como resultado final, o dano neuronal. Atualmente buscam-se intervenções para promover a neuroproteção através de compostos naturais que possam interferir nos mecanismos bioquímicos visando à redução dos danos. O objetivo este estudo foi investigar o efeito da suplementação com chá verde (Camellia Sinensis) sobre o dano oxidativo e déficit de memória de reconhecimento de objetos (RO) induzidos por dois modelos experimentais de AVC, isquêmico (isquemia-reperfusão transitória; IR) e hemorrágico (hemorragia intracerebral, HIC), em ratos. Para isso 80 ratos machos da raça Wistar foram submetidos à cirurgia de indução da IR ou HIC ou Sham, e divididos em oito grupos: Sham IR, Sham IR e chá verde, AVC Isquêmico, AVC Isquêmico e chá verde, Sham HIC, Sham HIC e chá verde, AVC Hemorrágico, AVC Hemorrágico e chá verde. A suplementação com chá foi realizada por 10 dias antes da cirurgia e mantida por 7 dias após, na dose diária de 400 mg/kg. Após a indução do AVC/Sham os animais foram submetidos a tarefas de memória de reconhecimento para avaliar memória curta e longa duração. Além disso, análises em hipocampo para mensuração de parâmetros relacionados ao estresse oxidativo através da determinação dos níveis de Espécies Reativas de Oxigênio (EROs), detecção de substâncias reativas ao ácido tiobarbitúrico (TBARS); e para a avaliação da capacidade antioxidante através do método de determinação de transferência de elétrons – FRAP, foram realizadas. Os resultados do RO foram analisados através do Teste t de uma amostra (média teórica 50%), e os resultados bioquímicos através do teste t de Student ou ANOVA de uma via com post hoc de Dunn. Ambos os tipos de AVC causaram déficit de memória de curta e longa duração no teste de RO, de forma que os animais não reconheceram o novo objeto após o AVC. Por outro lado, os animais que receberam chá verde previamente ao AVC, assim como os animais dos grupos Sham, gastaram significativamente mais de 50% do tempo total de exploração explorando o novo objeto. Os dois subtipos de AVC induziram um aumento nos níveis de EROs, o AVC hemorrágico causou lipoperoxidação hipocampal e o AVC isquêmico diminuiu a capacidade antioxidante total, o que relacionamos os consequentes déficits mnemônicos observados. A suplementação com chá verde, por sua vez, demonstrou efeito neuroprotetor e preveniu o dano celular causado pelos modelos de AVC; o chá foi eficiente em evitar o aumento de EROs nos dois modelos, e peroxidação lipídica no grupo AVC Hemorrágico, além manter a capacidade antioxidante total em ambos. Estes resultados comprovam que o AVC provoca déficit de memória de reconhecimento de curta e longa duração e dano oxidativo hipocampal, e que a suplementação de chá verde pode proteger contra tais danos.
The stroke is classified in two types: Ischemic and Hemorrhagic. Among the consequences resulting from the stroke there are the functional changes, cognitive deficit and memory impairment. Furthermore, it is known that in a situation such as stroke is followed by disbalance of the redox state and, as a final result, neuronal damage. Currently, interventions to promote neuroprotection through natural compounds that may interfere in biochemical mechanisms aiming the reduction of damage are sought. The aim of this study was to investigate the effect of supplementation with green tea (Camellia sinensis) on oxidative damage and object recognition memory (OR) deficit induced by two experimental models of stroke: ischemic (ischemia-reperfusion, IR) and hemorrhagic (intracerebral hemorrhage, ICH), in rats. To this, 80 Wistar male rats divided into 8 groups according the stroke type induced were used (n=10/group): Sham IR, Sham IR and green tea, IR, IR and green tea, Sham ICH, Sham ICH and green tea, ICH, ICH and green tea. Supplementation with green tea was initiated 10 days before the stroke surgery and continued for 7 days after in a dose of 400 mg/kg per day. After all, the rats were subjected to object recognition task (OR) to assess short (STM) and long term memory (LTM). Additionally, hippocampus were used to measure parameters related to oxidative stress by determining the reactive species of oxygen levels (ROS), detection of reactive substances to thiobarbituric acid (TBARS) and the evaluation of the antioxidant capacity by the method of electron transfer determination - FRAP. OR results were analyses using one-sample t-test (theoretical mean 50%) and biochemical parameters using Student's t-test or one-way ANOVA followed by Dunn’s post hoc. Both types of stroke caused STM and LTM in OR test, so, the animals did not recognize the new object after stroke. On the other hand, animals that received green tea previous to stroke, and the animals of the sham group, spent significantly more than 50% of the total exploration time exploring the new object. The two types of stroke induced an increase in the levels of ROS, hemorrhagic stroke caused hippocampal lipid peroxidation and ischemic stroke caused the decrease of the total antioxidant capacity, which is related to the consequent mnemonic deficits observed. Supplementation with green tea showed neuroprotective effect and prevent cell damage caused by stroke models; the green tea was effective in preventing the increase of ROS in both models, and lipid peroxidation in hemorrhagic stroke group, besides keeping the total antioxidant capacity in both. These results show that stroke causes short and long term memory deficits and hippocampal oxidative damage, and that the green tea suplementation can protect against such damage. Keywords: memory, oxidative stress, green tea, neuroprotection, stroke
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Molina, Nathalia. "Avaliação de parâmetros oxidativos e funcionais em linfócitos de ratos obesos suplementados cronicamente com extrato de chá verde." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/42/42136/tde-13082014-170430/.
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O chá verde (CV) é um fitoterápico produzido a partir da planta Camellia sinensis e apresenta propriedades antioxidantes, anti-inflamatórias, anticancerígenas e antiobesidade. Foi realizado um estudo para investigar se o CV seria capaz de modular alguns parâmetros funcionais de linfócitos de animais induzidos à obesidade por dieta hipercalórica. Os grupos suplementados receberam 500 mg/kg de CV durante 22 dias seguida da dieta hipercalórica por mais 44 dias acompanhada também do tratamento com o CV. O tratamento com o CV reduziu a proliferação celular, a atividade das enzimas metabólicas hexoquinase e glicose-6-fosfato desidrogenase, aumentou a atividade de enzimas antioxidantes, diminuiu a produção de espécies reativas de oxigênio, a produção de citocinas pró- inflamatórias (IL-6, IL-1β, TNF-α) e restaurou os índices de IL-10 que se encontrava diminuído no grupo obeso. Os efeitos observados pelo CV podem proporcionar um ambiente mais adequado para o bom funcionamento celular, diminuindo a produção de mediadores inflamatórios que estão presente na obesidade.Green tea (GT) is a phytochemical produced from Camellia sinensis and it has anti-inflammatory, anti-cancer, anti-obesity and antioxidant properties. This study was conducted to investigate whether the GT was able to modulate some lymphocyte functional parameters of obesity - induced animals by hypercaloric diet. Supplemented groups received 500 mg/kg GT for 22 days followed by hypercaloric diet for additional 44 days, together with the GT treatment. Treatment with GT reduced the cell proliferation capacity, the activity of metabolic enzymes hexokinase and glucose-6-phosphate dehydrogenase, increased the activity of antioxidant enzymes, decreased the production of reactive oxygen species, production of proinflammatory cytokines (IL-6, IL-1β, TNF-α) and restored the levels of IL-10 which was reduced by obesity. The GT effects can provide a more suitable environment for proper lymphocyte function, also reducing production of inflammatory mediators in obesity.
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Teixeira, Nelson Augusto Ferreira. "Effect of white tea consumption on the heart of type 2 diabetic rats." Master's thesis, Universidade da Beira Interior, 2013. http://hdl.handle.net/10400.6/1624.
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According to the World Health Organization (WHO), diabetes mellitus (DM) is the ninth leading cause of death worldwide, and 80% of those deaths are due to cardiovascular disease. The heart functions as a pump with a continuous need for energy and therefore is very susceptible to metabolic and/or oxidative alterations. It is well known that DM induces important metabolic alterations that result in increased oxidative stress (OS). Many medicinal plants are used worldwide to counteract the deleterious effects of DM. Although it is a fact that some harmful characteristics of DM are indeed ameliorated, the mechanisms by which medicinal plants improve the body response to this disease remain unknown. In the last few years, scientific studies concerning the effect of tea consumption, one of the most consumed beverages in the world, significantly increased. There are several works reporting that tea consumption may improve heart function in diabetic individuals. However, much of these studies are focused in green tea (GT) and most of the mechanisms of tea action remain unknown. Herein, we hypothesized that the consumption of the less studied tea, the white tea (WTEA), improves the heart functioning of diabetic individuals. To test our hypothesis, we used a STZ-induced Type 2 diabetes (T2D) rat model. The animals were divided in 3 groups: control, STZ-induced T2D (STZ) and WTEA drinking STZ-induced T2D rats (STZ+WTEA). Before sacrifice, the animals were subjected to a glucose tolerance and insulin sensitivity tests. Heart lipid peroxidation and protein oxidation were determined. Glucose, lactate, alanine and acetate contents in the hearts were quantified. mRNA expression levels of glucose transporter-1 (GLUT1), lactate dehydrogenase (LDH) and monocarboxylate transporter 4 (MCT4) were also determined, as well as LDH activity, in the heart.
Our results show that WTEA consumption restored insulin sensitivity and glucose tolerance in STZ-induced T2D rats. Besides, WTEA consumption restored lipid peroxidation to control values and decreased protein oxidation in hearts from STZ-induced T2D rats. Finally, STZ-induced T2D rats presented an impaired glycolysis that appears to be ameliorated by WTEA consumption. In these processes, regulation of GLUT1 and LDH activity proved to be essential in the protective effect shown by WTEA consumption.
More studies are needed to confirm the beneficial effects of WTEA consumption but our results provide clear evidence that WTEA ingestion can be a good, safe and inexpensive strategy to decrease the deleterious effects of T2D to the heart.De acordo com a Organização Mundial de Saúde (WHO), a diabetes mellitus (DM) é a nona causa de morte a nível mundial e cerca de 80% destas mortes são devido a doenças cardiovasculares. O coração funciona como uma bomba e tem uma necessidade contínua de energia, sendo muito susceptível a alterações metabólicas e/ou oxidativas. É bem conhecido que a DM é responsável por alterações metabólicas importantes que resultam num aumento de stress oxidativo (OS). Muitas plantas medicinais são usadas por todo o mundo para contrariar os efeitos deletérios da DM. De facto, alguns efeitos prejudiciais da DM são prevenidos pelo uso dessas plantas, mas os mecanismos pelos quais essa prevenção ocorre, permanecem desconhecidos. Nos últimos anos tem-se assistido a um aumento significativo de estudos científicos baseados no consumo de chá, uma das bebidas mais consumidas no mundo. Existem vários estudos que demonstram que o consumo de chá pode melhorar a função cardíaca de indivíduos diabéticos. No entanto, a maioria destes estudos está focada no chá verde (GT) e os mecanismos de acção do chá permanecem desconhecidos. Neste trabalho colocámos a hipótese de que o consumo de chá branco (WTEA), que é o chá menos estudado, poderia melhorar o funcionamento do coração de ratos diabéticos. Para testar a nossa hipótese usámos um modelo de rato para a diabetes tipo 2 (T2D). Os animais foram divididos em 3 grupos: grupo controlo, grupo T2D induzido por estreptozotocina (STZ) e grupo T2D induzido por STZ ao qual foi administrado chá branco (STZ+WTEA). Antes do sacrifício, os animais foram sujeitos aos testes de tolerância à glucose e resistência à insulina. Após recolha do tecido cardíaco, os níveis de peroxidação lipídica e de oxidação proteica foram determinados. O conteúdo de glicose, lactato, alanina e acetato nos corações foi quantificado. Os níveis de mRNA do transportador de glicose 1 (GLUT1), lactato desidrogenase (LDH) e transportador de monocarboxilatos 4 (MCT4) foram igualmente determinados, assim como a actividade da LDH. Os resultados obtidos demonstram que o consumo regular de WTEA permitiu a recuperação da sensitividade à insulina e da tolerância à glicose nos ratos T2D. Além disso, preveniu a peroxidação lipídica e diminuiu a oxidação proteica nos corações de ratos T2D. Esses ratos apresentaram distúrbios severos no processo glicolítico que foram normalizados pelo consumo de WTEA. Para isso contribuiu um efeito importante na regulação da expressão do GLUT1 e na actividade da LDH. Mais estudos são necessários para confirmar os efeitos benéficos do consumo regular de WTEA mas os nossos resultados demonstram que a ingestão de chá branco pode ser uma boa estratégia para diminuir os efeitos nefastos da T2D na função cardíaca.
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Epaminondas, Poliana Sousa. "Avaliação do potencial antioxidante de extratos vegetais, isolados ou associados sinergicamente a antioxidantes sintéticos, aplicados ao óleo de linhaça." Universidade Federal da Paraíba, 2013. http://tede.biblioteca.ufpb.br:8080/handle/tede/4057.
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Previous issue date: 2013-09-30Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Faced with the need to find new natural sources, able to replace partially or totally artificial antioxidants, reducing the phenomenon of oxidation and ensuring increased shelf life of edible oils, we sought to investigate the behavior of natural extracts of garlic, green tea and ginger on linseed oil, for their ability to protect against lipid oxidation. For this, the ethanol and methanol/ acetonic extracts of garlic (EEGL and MAEGL), green tea (EEGT and MAEGT) and ginger (EEGG and MAEGG), respectively, were initially compared for total phenolic content (TPC), by Folin-Ciocalteau method, as the antioxidant capacity, by Radical-Scavenging Activity of the DPPH (RSA-DPPH), by Ferric Reducing Antioxidant Power (FRAP) and by β-carotene/ linoleic acid system method, and the thermal stability, by Thermogravimetry/ Differential Thermal Analysis (TG/ DTA). The thermal and oxidative stability of the linseed oil added with ethanolic extracts, singly or with synthetic compounds tert-butylhydroquinone (TBHQ) and butylated hydroxytoluene (BHT), were evaluated, respectively, by Thermogravimetry/ Differential Thermal Analysis (TG/ DTA) and accelerated oxidation tests, such as accelerated storage test in oven, Pressurized Differential Scanning Calorimetry (P-DSC), PetroOxy and Rancimat. The extracts showed the following descending order of TPC: EEGT (483.45 ± 15.23 mg GAE.g-1) ~ MAEGT (469.28 ± 17.84 mg GAE.g -1) > EEGG (235.49 ± 1.34 mg GAE.g-1) > MAEGG (60.36 ± 1.90 mg GAE.g-1) > EEGL (10.55 ± 0.76 mg GAE.g-1) > MAEGL (3.01 ± 0.15 mg GAE.g mg-1 dry matter ). For the tests to determine the antioxidant capacity, green tea extracts showed higher RSA-DPPH and FRAP, compared to other samples. The extracts showed the following decreasing order of thermal stability : EEGT (111 ºC) ~ MAEGT (110 ºC) > EEGL (104 ºC) > EEGG (96 ºC) > MAEGL (68 ºC) > MAEGG (63 ºC). Despite the low response TPC and small compared to RSA-DPPH and FRAP, the ethanol extract of garlic showed considerable ability to inhibit lipid peroxidation, by β-caroteno/ácido linoleic system, and high thermal stability, attributed to organosulfur compounds. Considering the oxidative stability tests of samples of additived oil, it was found that the ethanolic extract of garlic, alone or synergistically associated with the BHT or TBHQ, protected the linseed oil in a manner similar to or even higher than synthetic antioxidants alone, by P-DSC and PetroOxy assays, keeping it in good condition overall until the 8th day accelerated storage in an oven at 60 ºC. Extracts of green tea and ginger offered protection to linseed oil until the 4th day of storage accelerated when combined synergistically to TBHQ, also demonstrating good oxidative stability by P-DSC, PetroOxy and Rancimat techniques. The results suggest the feasibility of using green tea and ginger extracts as partial substitutes (LOGT / TBHQ (50/50) and LOGG / TBHQ (50/50)) and garlic extract as total substitute (LOGL 100) of synthetic antioxidants, being alternative natural sources of antioxidants for application to the edible oil industry.
Diante da necessidade de descobrir novas fontes naturais, capazes de substituir os antioxidantes artificiais parcial ou totalmente, atenuando o fenômeno da oxidação e garantindo o aumento da vida de prateleira de óleos comestíveis, buscou-se investigar o comportamento de extratos naturais de alho, chá verde e gengibre sobre o óleo de linhaça, quanto à capacidade de proteção contra a oxidação lipídica. Para isso, os extratos etanólicos e metanol/ acetônicos de alho (EEGL e MAEGL), chá verde (EEGT e MAEGT) e gengibre (EEGG e MAEGG), respectivamente, foram inicialmente comparados quanto ao conteúdo de fenólicos totais (TPC), pelo método de Folin-Ciocalteau, quanto à capacidade antioxidante, pelos métodos de sequestro do radical DPPH (RSA-DPPH), do poder de redução do ferro (FRAP) e do sistema β-caroteno/ácido linoleico, e quanto à estabilidade térmica, por meio de Termogravimetria/ Análise Térmica Diferencial (TG/ DTA). As estabilidades térmica e oxidativa do óleo de linhaça adicionado dos extratos etanólicos isolados ou associados aos compostos sintéticos terc-butil-hidroquinona (TBHQ) e butil-hidroxitolueno (BHT) foram avaliadas, respectivamente, por meio das técnicas TG/ DTA e de ensaios de oxidação acelerada, como Calorimetria Exploratória Diferencial Pressurizada (P-DSC), PetroOxy, Rancimat e teste de estocagem acelerada em estufa. Os extratos avaliados apresentaram a seguinte ordem decrescente de TPC: EEGT (483.45 ± 15.23 mg GAE.g-1) ~ MAEGT (469.28 ± 17.84 mg GAE.g-1) > EEGG (235.49 ± 1.34 mg GAE.g-1) > MAEGG (60.36 ± 1.90 mg GAE.g-1) > EEGL (10.55 ± 0.76 mg GAE.g-1) > MAEGL (3.01 ± 0.15 mg GAE.g-1 extrato seco). Para os ensaios de determinação da capacidade antioxidante, os extratos de chá verde apresentaram maior RSA-DPPH e FRAP, em relação às demais amostras. Os extratos apresentaram a seguinte ordem decrescente de estabilidade térmica: EEGT (111 ºC) ~ MAEGT (110 ºC) > EEGL (104 ºC) > EEGG (96 ºC) > MAEGL (68 ºC) > MAEGG (63 ºC). Apesar do baixo TPC e da pequena resposta frente a RSA-DPPH e FRAP, o extrato etanólico de alho apresentou considerável capacidade de inibição da peroxidação lipídica, pelo sistema β-caroteno/ácido linoleico, e alta estabilidade térmica, atribuídos aos compostos organossulfurados. Considerando os ensaios de estabilidade oxidativa das amostras de óleo aditivado, verificou-se que o extrato etanólico de alho, isolado ou sinergicamente associado ao TBHQ ou ao BHT, protegeu o óleo de linhaça de forma similar ou até superior aos antioxidantes sintéticos isolados, diante dos ensaios de P-DSC e PetroOxy, mantendo-o em bom estado de conservação geral até o 8º dia de armazenamento acelerado em estufa a 60 ºC. Os extratos de chá verde e gengibre ofereceram proteção ao óleo de linhaça até o 4º dia de estocagem acelerada, quando associados sinergicamente ao TBHQ, demonstrando ainda boa estabilidade oxidativa diante das técnicas P-DSC, PetroOxy e Rancimat. Os resultados sugerem a viabilidade de utilização dos extratos de chá verde e gengibre como substitutos parciais (LOGT/ TBHQ (50/50) e LOGG/ TBHQ (50/50)) e o extrato de alho como substituto total (LOGL 100) de antioxidantes sintéticos, sendo fontes alternativas naturais de antioxidantes para a aplicação na indústria de óleos comestíveis.
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Ye, Liyun. "Antioxidant Activity of Ampelopsis Grossedentata Crude Extract and its Major Component Dihydromyricetin." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76833.
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Oxidation limits the shelf life of many food products. Adding antioxidants to foods is the most common way to solve this problem. Reports on safety issues of synthetic food additives have raised consumer interest in "all natural" foods, without added antioxidants or with synthetic replaced with natural antioxidants. The natural antioxidants now in use are much more expensive and less potent than the synthetic antioxidants. Thus, effective and economical natural antioxidants are of great interest to researchers. Teng Cha is a type of herbal tea found in China that has reported high levels of antioxidants. Antioxidant activity of Teng Cha extract and its major component dihydromyricetin has been reported, but no studies have provided clear evidence for the antioxidant effectiveness of Tech Cha extracts. The goal of this study was to measure the antioxidant activity of Teng Cha extract and dihydromyricetin (DHM), a major component of Tech Cha extract. The DPPH assay was conducted and antioxidant activities of the crude extract and dihydromyricetin were evaluated in soybean oil based on the peroxide value, anisidine value, Totox value, headspace volatiles and headspace oxygen. Antioxidant effectiveness was also evaluated in a cooked beef model system. DHM was more potent than BHA in preventing soybean oil oxidation. The crude extract was not as effective as BHA and DHM, possibly because it contained transition metals. In cooked beef, DHM and the crude extract showed lower activity than BHA, possibly due to their low solubility. Overall, Teng Cha extract and DHM are potential natural food antioxidants for future applications.Master of Science in Life Sciences
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Carvalho, Michelle Garcêz de. "Influência do processamento, de antioxidantes e da estocagem sobre a estabilidade oxidativa lipídica do ovo." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/9/9131/tde-25062013-105834/.
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O ovo é consumido in natura ou processado, e usado como matéria-prima em diversos produtos. A pasteurização e a atomização são os principais processamentos aplicados ao ovo. Diferentes condições de processamento, embalagem e estocagem podem afetar a estabilidade oxidativa lipídica e reduzir a proteção antioxidante natural do ovo. O uso de embalagens onde não haja contato do ovo com a luz e oxigênio, estocagem em temperaturas baixas e uso de antioxidantes podem prevenir a oxidação lipídica. Atualmente, os antioxidantes sintéticos são cada vez mais substituídos por antioxidantes naturais ou feita uma associação entre eles. O alecrim (Rosmarinus officinalis L.) e o chá verde (Camelia sinensis L) constam entre os vegetais com grande potencial antioxidante. Com base no exposto, os objetivos do trabalho foram: a) Padronizar o método do fosfomolibdênio para avaliação da capacidade antioxidante total da fração lipídica (CATL) do ovo; b) Investigar o efeito da pasteurização e da atomização do ovo no que se refere à capacidade antioxidante e à estabilidade oxidativa da fração lipídica do ovo; c) Avaliar a estabilidade oxidativa de ácidos graxos e a capacidade antioxidante do ovo integral pasteurizado atomizado, estocado a 5ºC, por 90 dias; d) Verificar por meio de teste de concentração de antioxidantes, a estabilidade oxidativa lipídica do ovo integral pasteurizado atomizado adicionado da mistura de extrato de alecrim, extrato de chá verde e BHA (butilato de hidroxianisol); e) Otimizar a concentração da mistura de extrato de alecrim, extrato de chá verde e BHA a ser adicionada ao ovo líquido integral pasteurizado, posteriormente atomizado, pelo modelo matemático proposto pela metodologia de superfície de resposta; f) Investigar o efeito da mistura otimizada de extrato de alecrim, extrato de chá verde e BHA na estabilidade oxidativa lipídica do ovo integral pasteurizado atomizado, estocado sob as temperaturas de 5°C e 25ºC, por 90 dias. O método do fosfomolidênio para medir a CATL do ovo apresentou adequação analítica, indicada pela equação de regressão (y = 13,705x + 0,0808), coeficiente de determinação (R2 = 0,9931), limite de detecção (0,005mg α-tocoferol/ mL), limite de quantificação (0,017mg α-tocoferol/ mL), coeficiente de correlação (r = 0,9965), sendo que a precisão não indicou dispersão ao redor da média. A CATL diminuiu com o progresso do processamento e o inverso foi observado quanto aos lipídios, 7-CETO (7-cetocolesterol) e TBARS (substâncias reativas ao ácido tiobarbitúrico). O ovo integral pasteurizado atomizado (OIPA) mantido sob condições de estocagem consideradas ideais permaneceu estável em relação à hidratação, a CATL e as TBARS. Pelo teste de concentração de antioxidantes, foram ensaiadas dez misturas (alecrim, chá verde e BHA) no OIPA e refletiu na sua estabilidade oxidativa lipídica, verificada pelas TBARS, CATL, CT-F (capacidade redutora pelo reativo de Folin - Ciocalteau), AGL (ácidos graxos livres) e AS-233 (substâncias absorvidas a 233 nm). Os resultados mostraram que a metodologia de superfície de resposta (RSM) foi adequada para descrever a formação dos AGL e AS-233 no OIPA, podendo serem usadas para fins preditivos. A otimização da mistura de antioxidantes baseou-se no modelo matemático obtido com as AS-233, onde foi proposto como sistema antioxidante 150ppm de BHA, 600ppm de alecrim e 300ppm de chá verde. As condições de estocagem adotadas e a adição dos antioxidantes foram efetivas para manter estável o OIPA, sendo mais efetivo quando estocado a 5°C. Concluíu-se que o método do fosfomolibdênio apresentou adequação analítica. A pasteurização não afetou os parâmetros analisados (lipídios, TBARS, CATL e 7-CETO), mas a atomização provocou diminuição significativa da CATL, e elevação dos lipídios, TBARS e 7-CETO. Foi mantida a hidratação e a estabilidade oxidativa do OIPA estocado por 90 dias a 5°C, indicando que as condições de embalagem e estocagem foram efetivas. Pelo modelo matemático proposto pela RSM foi constatado que apenas os AGL e AS-233 podem ser usados para fins preditivos, optando-se pela otimização da concentração da mistura de antioxidantes, usando apenas o modelo matemático obtido nas AS-233. Com a presença ou não de antioxidantes, o OIPA estocado a 5°C, ao longo dos 90 dias, apresentou-se mais estável quanto à hidratação e à oxidação lipídica.Egg is consumed in natura or processed and is used as raw material in various food products. The pasteurization and spray-drying processes are the main processing applied to the egg. Different processing conditions, packaging and storage can affect the lipid oxidative stability and may reduce the natural antioxidant protection of this product. The use of packages in which the egg has no contact with light and oxygen, storage at low temperatures, and the use of antioxidants can prevent lipid oxidation. Currently, synthetic antioxidants have been increasingly replaced by natural antioxidants or an association between synthetic and natural antioxidants is adopted by food companies. Rosemary (Rosmarinus officinalis L.) and green tea (Camellia sinensis L) are among the vegetables that present the highest antioxidant potential. Based on the above-mentioned considerations, the objectives of this research were: a) To standardize the method of phosphomolybdenum to evaluate the total antioxidant capacity of lipid fraction (CATL) egg; b)To investigate the effect of pasteurization and spray-drying on the antioxidant capacity and oxidative stability of the lipid fraction of egg; c) To assess the oxidative stability of fatty acids and the antioxidant capacity of whole egg subjected to pasteurization followed by spray-drying, stored at 5ºC for 90 days, d) To evaluate the by testing the concentration of antioxidants, oxidative stability of the lipid fraction of egg subjected to pasteurization and spray drying, added with a mixture of rosemary and green tea extracts and BHA (butylated hydroxyanisole); e) To optimize the concentration of the mixture composed of rosemary and green tea extracts and BHA to be added to pasteurized liquid egg (and further subjected to spray-drying) by using Response Surface Methodology; f) To investigate the effect of the addition of this optimized mixture of antioxidants on of the lipid fraction of spray-dried egg, stored at temperatures of 5 and 25°C for 90 days. The phosphomolybdenum method CATL of egg presented analytical suitability once it presented a high coefficient of determination (R2 = 0,9931), a regression equation expressed as y = 13.705 + 0.0808 x, a limit of detection of 0.005 mg α- tocopherol/mL, a limit of quantitation of 0.017 mg α-tocopherol/mL, a significant and high correlation coefficient (r = 0.9965), and the accuracy did not indicate dispersion around the mean. The CATL decreased with the progress of processing and the reverse was observed for the lipids, 7-CETO (7-ketocholesterol) and TBARS (thiobarbituric acid reactive substances). The pasteurized spray-dried egg (OIPA), which was kept under ideal storage conditions, remained stable in relation to moisture content, CATL and TBARS. In order to test the concentration of antioxidants to be added to OIPA, a total of 10 mixtures (rosemary, green tea and BHA) were assayed. The addition of antioxidants resulted in a higher oxidative stability of the lipid fraction as measured by TBARS, CATL, CT-F (reduction capacity by using the Folin-Ciocalteau reagent), AGL (free fat acids) and AS-233 (substances that absorb at 233 nm). The results showed that the response surface methodology (RSM) was adequate to describe the development of free fat acids and AS-233 in OIPA, and the RSM model proposed for AS-233 can be used for prediction purposes. The optimization of the antioxidant mixture based on the mathematical model proposed for AS-233 indicated that the mixture of 150ppm of BHA, 600ppm of rosemary extract and 300ppm of green tea extract was the best combination of antioxidants. The adopted storage conditions and the addition of antioxidants to OIPA were effective to maintain the response variables stable, and the stability was higher when OIPA was stored at 5°C. It was concluded that the method of phosphomolybdenum suitability presented analytically. The pasteurization did not affect the analyzed parameters (lipids, TBARS, CATL and 7-CETO), but the spray-drying caused a significant decrease CATL, and an increase in lipids, TBARS and 7-CETO. The hydration and the oxidative stability of OIPA remained stable for 90 days at 5°C, indicating that the packaging and storage conditions were effective. The RSM models proposed for free fat acids and AS-233 could be used for predictive purposes; however, the optimization procedure was performed taken into account only the AS-233 model. The OIPA stored at 5°C for 90 days, with or without the addition of the antioxidant mixture, was more stable in relation to hydration and lipid oxidation.
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Vahlas, Zoï. "Régulation métabolique de l'infection des cellules T CD4 par VIH-1 : vers de nouvelles cibles thérapeutiques." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTT009.
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La susceptibilité des lymphocytes T CD4 (LT) à l'infection par VIH-1 est régulée par le métabolisme du glucose et de la glutamine. Cependant, les contributions relatives de ces nutriments à l'infection étaient peu connues lorsque j’ai débuté ma thèse. Au cours de mes travaux, j'ai identifié la glutaminolyse comme une voie majeure alimentant la phosphorylation oxydative (OXPHOS) dans les sous-populations de LT activés naïves et mémoires, et j'ai découvert que l'induction de ce réseau métabolique est nécessaire pour une infection optimale par VIH-1. J’ai constaté qu’en condition limitante en glutamine, l’α-kétoglutarate (α-KG), un intermédiaire du cycle TCA (TriCarboxylic Acid) issu de la glutaminolyse, constitue un facteur clé de l'infection des LT CD4 par VIH-1. L'ajout d’α-KG exogène induit une augmentation rapide du ratio OXPHOS/glycolyse et rend les LT naïfs et mémoires plus susceptibles à l’infection. Par ailleurs, l’inhibition du flux glycolytique du pyruvate vers le lactate induit une augmentation de l'OXPHOS et de l'infection des LT CD4 par VIH-1. En accord avec ces données, les LT CD4 infectés présentent une augmentation de la biomasse et de l'activité mitochondriale en comparaison à leurs homologues non infectés. Ces données identifient l'équilibre OXPHOS/glycolyse aérobie comme un élément clé de l'infection des LT par VIH-1.Afin de mieux appréhender les voies métaboliques régulant l'infection des LT par VIH-1, j'ai développé une approche complémentaire basée sur l’utilisation de shRNA ciblant spécifiquement les transporteurs de nutriments GLUT1, ASCT2 et CAT1, permettant notamment le transport du glucose, glutamine et arginine dans la cellule, respectivement. Ainsi, j’ai observé une diminution de la survie d’environ 80% des cellules shRNA+, témoignant ainsi de l’importance de ces transporteurs lors de l’activation de ces cellules. Cependant, la permissivité des LT CD4 à l’infection par VIH-1 est impactée différemment par la diminution de l’expression des transporteurs de nutriments. Conformément aux données présentées ci-dessus, l’inhibition de GLUT1 n'a pas eu d'impact significatif sur l'infection par VIH-1, tandis que l’inhibition de CAT1 a réduit de manière significative l’OXPHOS ainsi que l'infection par VIH-1 (de 35 %). Il est toutefois surprenant de constater que l’inhibition d’ASCT2 entraîne une augmentation de l'infection de 20 %. Cela était associé à une persistance significativement plus élevée des cellules T naïves dont l’expression d’ASCT2 était inhibée, par rapport aux LT mémoires. Ces données mettent ainsi en évidence l’importance relative de ces 3 transporteurs de nutriments dans la survie des LT naïfs par rapport aux LT mémoires et démontrent leur impact spécifique sur la permissivité de ces populations à l'infection par VIH-1.En conclusion, en utilisant deux approches complémentaires, mes travaux de thèse révèlent l'impact critique de l'état énergétique d'une cellule T CD4 sur sa susceptibilité à l'infection par VIH-1. Mes données mettent en évidence l'importance du métabolisme mitochondrial, avec un environnement riche en intermédiaires du cycle du TCA comme l’α-KG, dans la régulation de la sensibilité des LT à l'infection par VIH-1. En outre, l'expression des transporteurs de nutriments impacte différentiellement la sensibilité des LT naïfs et mémoires à l'infection par VIH-1. Ces études offrent donc de nouvelles perspectives utilisant le métabolisme pour le développement de stratégies thérapeutiques ciblées contre l'infection par VIH-1The susceptibility of CD4 T cells to HIV-1 infection is regulated by glucose and glutamine metabolism, but the relative contributions of these nutrients to infection are not known. During my PhD, I identified glutaminolysis as a major pathway fueling oxidative phosphorylation (OXPHOS) in activated naïve as well as memory CD4 cell subsets, and found that induction of this metabolic network is required for optimal HIV-1 infection. Moreover, we determined that under conditions of attenuated glutaminolysis, the α-ketoglutarate (αKG) TCA (tricarboxylic acid) cycle intermediate is a rate-limiting step in infection; exogenous α-KG directly increased OXPHOS and rendered both naïve and memory CD4 T cells significantly more sensitive to infection. Furthermore, blocking the glycolytic flux of pyruvate to lactate resulted in an increased OXPHOS and a significantly augmented level of HIV-1 infection. In agreement with these data, infected CD4 T cells exhibited increased mitochondrial biomass and respiration as compared to their non-infected counterparts. These data identify the OXPHOS/ aerobic glycolysis balance as a major regulator of HIV-1 infection in CD4 T lymphocytes.In order to gain more insight into the metabolic pathways regulating HIV-1 infection in CD4 T cells, we developed a complementary approach to target upstream processes, specifically altering glucose (GLUT1), glutamine (ASCT2), and arginine (CAT1) transporter expression by lentiviral-mediated delivery of specific shRNAs. Testifying to the importance of these transporters, CD4 T cells with downregulated expression of either GLUT1, ASCT2 or CAT1 were negatively selected, resulting in a loss of approximately 80% of shRNA-transduced cells within 14 days. Notably, the permissivity of CD4 T cells to HIV-1 infection was differentially impacted by inhibition of specific nutrient transporters. Consistent with the data presented above, knockdown of GLUT1 did not significantly impact HIV-1 infection whereas knockdown of CAT1 significantly decreased both OXPHOS as well as HIV-1 infection (by 35%). Surprisingly though, ASCT2 knockdown resulted in a significantly augmented infection, by approximately 20%. Mechanistically, we found that this was associated with a markedly higher persistence of naïve, as compared to memory, T cells with downregulated ASCT2 levels. These data highlight differences in the relative importance of distinct nutrient transporters in the survival of naïve vs memory CD4 T cell subsets and demonstrate their specific impact on the sensitivity of these populations to HIV-1 infection.In conclusion, using two complementary approaches, my PhD research has revealed the critical impact of a CD4 T cell’s energetic state on its susceptibility to HIV-1 infection. My data identify the importance of mitochondrial metabolism, with an environment rich in TCA cycle intermediates such as α-KG, in regulating the susceptibility of CD4 T cells to HIV-1 infection. Furthermore, I find that nutrient transporter expression differentially impacts the sensitivity of naïve and memory CD4 T cells to HIV-1 infection. These studies therefore provide new prospects for the development of targeted metabolic therapeutic strategies against HIV-1 infection
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Neto, Renato Motta. "Lippia Aff. Gracilis, Lippia Gracilis e L-Glutamina e suas aÃÃes antibacteriana, antioxidante e imunomoduladora em modelos de ratos diabÃticos." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1095.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorO efeito antibacteriano de Ãleos essenciais extraÃdos de folhas das espÃcies de Lippia aff. gracilis e Lippia gracilis frente a cepa de Staphylococcus aureus isolada de Ãlcera de paciente com pà diabÃtico foi avaliado mediante experimentaÃÃo in vitro e in vivo, utilizando-se o modelo experimental de ratos diabÃticos aloxano induzidos. Cento e doze ratos machos Wistar diabÃticos com peso mÃdio de 180g foram distribuÃdos ao acaso em dois experimentos. Cada experimento foi dividido em dois procedimentos que avaliaram a atividade antibacteriana de soluÃÃes dos Ãleos essenciais a 5%, em dois diferentes procedimentos: um no ato da administraÃÃo do inÃculo bacteriano e outro apÃs vinte e quatro horas de administraÃÃo. A administraÃÃo tanto do inÃculo 108ufc/ml quanto da suspensÃo dos Ãleos foi por via subcutÃnea no membro pÃlvico dos ratos diabÃticos. CinqÃenta e seis ratos Wistar foram utilizados para cada experimento, no qual os mesmos foram distribuÃdos ao acaso em 8 (oito) diferentes grupos: 4 grupos por experimento, apresentando 7 ratos por grupo (G1-Branco; G2-Controle negativo; G3-Controle positivo; G4-Teste). Foi verificado que no procedimento 1(S.aureus sem Lippia aff gracilis 108  698 versus S.aureus com Lippia aff gracilis 293,1  79,07; S.aureus sem Lippia gracilis 108  873 versus S.aureus com Lippia gracilis 302  57,2) e no procedimento 2 (S.aureus sem Lippia aff gracilis 108  313 versus S.aureus com Lippia aff gracilis 13,28  4,03; S.aureus sem Lippia gracilis 108  818 versus S.aureus com Lippia gracilis 13,14  4,27); houve reduÃÃo na contagem bacteriana tanto para Lippia aff. gracilis quanto para Lippia gracilis. Quando comparados os grupos G4 com G3, observou-se que esta suspensÃo a 5% nÃo apresentou efeito prÃ-inflamatÃrio. Para a validaÃÃo destes resultados, foram utilizados os testes Mann-Whitney e Bartletts &Newman-Keuls (MÃdia  - E.P.M) com nÃvel de significÃncia de (p<0,05). Ainda neste estudo foi avaliado a aÃÃo antioxidante e imunomoduladora da L-glutamina em modelos de ratos Wistar diabÃticos quando administrada por gavagem a uma concentraÃÃo de 0,7g/kg em um perÃodo de 30 dias. Quarenta ratos Wistar machos foram distribuÃdos ao acaso em 5 grupos (GI-nÃo diabÃtico; GII-diabÃtico; GIII-diabÃtico com salina; GIV-diabÃtico com L-glutamina; GV-diabÃtico com ProteÃna do Soro do Leite). Passado este perÃodo, foram determinadas as concentraÃÃes de substÃncias reativas ao Ãcido tiobarbitÃrico (TBARS) e glutationa reduzida (GSH) no soro e nos tecidos hepÃticos, pancreÃticos, mÃsculo esquelÃtico, rins e tecido adiposo. Para as comparaÃÃes entre o grupo tratado com L-glutamina com os demais, utilizou-se a anÃlise de variÃncia (ANOVA-teste Tukey). As comparaÃÃes entre grupos foram feitas utilizando-se o teste t de Student. Valores de p<0,05 foram considerados significantes. A suplementaÃÃo com L-glutamina induziu ao aumento nas concentraÃÃes de GSH (MÃdia  E.P.M) e reduÃÃo significante nas concentraÃÃes de TBARS (MÃdia  E.P.M), quando comparadas com o grupo controle, nos espÃcimes analisados. A aÃÃo imunomoduladora foi avaliada atravÃs da quantificaÃÃo de linfÃcitos CD4+ e CD8+ em sangue total. Vinte e quatro ratos Wistar machos diabÃticos foram distribuÃdos igualmente em 3 grupos (G1-diabÃtico com salina; G2-diabÃtico com L-glutamina; G3- diabÃtico com ProteÃna do Soro do Leite). Observou-se um aumento significante nas populaÃÃes de linfÃcitos CD4+ (MÃdia  E.P.M) com reduÃÃo nas populaÃÃes de linfÃcitos CD8+ (MÃdia  -E.P.M) do grupo G2 quando comparado com o grupo controle, ressaltando a importÃncia da L-glutamina como imunonutriente
The antibacterial effect of essential oils extracted from leaves of the species of Lippia aff. gracilis and Lippia gracilis against strains of Staphylococcus aureus isolated from patients with diabetic foot ulcers were evaluated in vitro and in vivo experimetation utilizing an experimental model of alloxan-induced diabetic rats. One hundred and twelve male diabetic Wistar rats with mean weight of 180g were distributed by chance into two experiments. Each experiment was divided in two procedures with evaluation of antibacterial activity of essential oils at 5% solutions; one procedure in the act of administration of bacterial inoculums and the other one 24 hours later. 108 CFU (Colony Forming Unit) /mL, as well as oils suspension inoculated in the subcutaneous tissue of the pelvic member of diabetic rats. Lower than 5% concentration of administered solution presented antibacterial effect in the in vitro experiment. Fifty-six Wistar rats were utilized in each experiment, randomly distributed in 08 different groups: 04 groups per experiment, each group with 07 rats (G1-White; G2-Negative Control; G3- Positive control; G4-Test). There was decrease in CFU/mL in procedure 1 (S.aureus without Lippia aff gracilis 108  698 versus S.aureus with Lippia aff gracilis 293,1  9,07; S.aureus without Lippia gracilis 108  873 versus S.aureus with Lippia gracilis 302Â57,2), which evaluated antibacterial effect of oils concomitantly with the administration of inocula as well as in procedure 2 (S.aureus without Lippia aff gracilis 108  313 versus S.aureus with Lippia aff gracilis 13,28  4,03; S.aureus without Lippia gracilis 108  818 versus S.aureus with Lippia gracilis 13,14  4,27) , which evaluated antibacterial effect of oils 24 hours after the administration of the inoculum . When comparing group G4 with G3, it was observed that 5% solution presented no pro-inflammatory effect, for analysis of these results, the tests of Mann-Whitney and Bartletts & Newman-Keuls (X  S.E.M) with level of significance (p<0,05) were used. Part of this study evaluated the antioxidant and immunomodulating effect of L-glutamine in models of Wistar diabetic rats when administered by gavages at a 0,7g/kg during 30 days. Fourty Wistar male rats were randomly distributed in 5 groups (GI- non diabetic; GII-diabetic; GIII-diabetic with saline; GIV- diabetic with L-glutamine; GV- diabetic with Whey Protein). After 30 days concentrations of TBARS and GSH in serum and in hepatic, pancreatic, skeletal muscles, kidneys and fat tissues were determined. For comparisons between the group treated with L-glutamine with the others, the ANOVA â Tukey test was utilized and the comparisons between groups were done using Studentâs t test. Values of p<0.05 were considered significant. The supplementation with L-glutamine induced an increase in the concentrations of GSH (MeanS.E.M) and significant reduction in the TBARS (mean  S.E.M) concentrations, when compared to the control group, in the analyzed specimens. The immunomodulating effect was evaluated by quantification of CD4+ and CD8+ lymphocytes in total blood. Twenty-four Wistar male diabetic rats were distributed equally in 3 groups (G1-diabetic with saline; G2-diabetic with L-glutamine; G3- diabetic with Whey Protein). It was seen a significant increase of CD4+ (mean  S.E.M) lymphocytes with reduction of CD8+ (mean  S.E.M) lymphocytes in group G2 when compared to the control group, showing the importance of L-glutamine as an immunonutrient
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Arçari, Demétrius Paiva. "Efeitos biológicos do consumo de chá-mate (ilex paraguariensis) frente à obesidade em camundongos." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/6/6138/tde-02032009-094433/.
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RESUMO Introdução: Atualmente a obesidade tem atingido proporções epidêmicas, evidências científicas mostram uma forte associação entre a obesidade e o maior risco para o desenvolvimento de diversas doenças tais como: doenças cardíacas, diabetes tipo II (mellitus), hipertensão e resistência à insulina. Bebidas à base de erva-mate (Ilex paraguariensis) têm importantes atividades biológicas, principalmente pelo alto teor de compostos polifenólicos existentes, que são reconhecidos por sua atividade antioxidante. Além dos compostos polifenólicos como flavonóides (quercetina e rutina) e ácidos fenólicos (ácido clorogênico e ácido cefeico), a erva-mate também é rica em cafeína e saponinas. Estudos recentes, com modelos animais e humanos demonstram inúmeros benefícios após o consumo de erva-mate, dentre estes, destaca-se sua atividade antioxidante, proteção ao DNA contra o dano induzido, atividade quimioprotetora celular, efeito na redução do LDL-colesterol, efeitos na motilidade intestinal, efeito vasodilatador, inibição da glicação e efeito termogênico. Objetivo: Avaliar os efeitos anti-obesidade do consumo de chá-mate em camundongos submetidos a uma dieta hiperlipídica. Métodos: Foram utilizados camundongos Swiss (n=62), eutróficos, machos, divididos aleatoriamente em diferentes grupos de acordo com a dieta utilizada (padrão ou hiperlipídica) e a intervenção escolhida (água ou chá-mate), por dezesseis semanas. Após a intervenção, as análises bioquímicas foram determinadas empregando-se o sistema Cobas-Mira e o quadro glicêmico foi determinado utilizando-se um glicosímetro seguido do ITT (teste de tolerância à insulina), a ação quimioprotetora ao DNA foi realizado pelo ensaio cometa; a expressão gênica das enzimas antioxidantes foi avaliada por PCR em tempo real. Para a significância dos dados foi utilizado análise de variância (ANOVA), seguido por Bonferronis post hoc teste para comparações múltiplas. Resultados: A intervenção com chá-mate nos camundongos submetidos à dieta hiperlipídica foi capaz de melhorar os seguintes parâmetros avaliados: peso corpóreo, glicemia, resposta à insulina, colesterol, triacilglicerol e LDL-colesterol. O nível de danos ao DNA foi significativamente reduzido nos camundongos obesos tratados com chá-mate em todas as doses avaliadas, porém o consumo de chá-mate não modificou a expressão das enzimas antioxidantes avaliadas (SOD, GPx e Cat) independentemente da dose utilizada. Conclusão: O presente estudo demonstra que o consumo do chá-mate pode influenciar de maneira positiva alguns biomarcadores relacionados com a obesidade induzida por dieta hiperlipídica em camundongos.Introduction: Obesity has reached epidemic proportions, and there is a lot of evidence supporting the association of obesity with health conditions such as cardiovascular disease, diabetes, hypertension, and insulin resistance. Yerba Maté (Ilex paraguariensis) beverages have been reported to present biological activities attributed, mainly, to the it high polyphenol content, long known as antioxidants. In addition to the polyphenols such as flavonoids (quercetin and rutin) and phenolic acids (chlorogenic and caffeic acids), yerba maté is also rich in caffeine and saponins. Recently published evidences with animals and humans, has shown some beneficial effects related to the consumption of yerba maté, which include antioxidant activity, protecting effect on DNA against induced damage, chemopreventive activities, choleretic and intestinal effects, vasodilatation effects, inhibition of glycation and atherosclerosis and thermogenic effects. Objective: We evaluated the anti-obesity effects of yerba maté in a high-fat diet in mice. Methods: Sixty-two Swiss mice, were randomly assigned in different groups according to the diet and the intervention (mate-tea or water), for sixteen weeks. After intervention, the biochemical analysis was performed with Cobas-Mira system, the insulin test tolerance was determined by means of KITT, antioxidant activity were tested using Comet Assay and gene expression of antioxidant enzymes were evaluated by PCR real time . Statistical analysis was done using one-way ANOVA followed by unpaired Bonferroni. Results: Mate-tea intervention decreased in obese animals the following biochemical parameters: weight, glucose blood level, response to insulin, cholesterol, triglycerides and LDL-cholesterol. The DNA damage levels were significantly lower in obese animals treated with mate tea in all doses, but mate tea didnt affect the gene expression of antioxidant enzymes (SOD, GPx e Cat). Conclusion: In conclusion, this study reports that mate-tea may beneficial influence some biochemical markers related to high-fat diet induced obesity in mice.
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Aye-Baratier, Mélanie. "La génotoxicité des quantum dots et le rôle du stress oxydant : implications sur l'environnement et la santé humaine." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5050.
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Les quantum dots (QDs) sont des cristaux semi-conducteurs de dimensions nanométriques. Ils peuvent être employés comme des marqueurs photosensibles du métabolisme cellulaire et peuvent être utiles dans différents domaines notamment en médecine mais il s’est rapidement avéré nécessaire de démontrer leur innocuité avant leur utilisation à grande échelle et leur diffusion dans l’environnement. Nous proposons un projet de thèse de doctorat sur le thème : La génotoxicité des quantum dots et le rôle du stress oxydant, implications sur l’environnement et la santé humaine. Il s’organise suivant trois axes: L’étude in vitro des propriétés génotoxiques et mutagènes des QDs Les QDs induisent des lésions primaires de l’ADN sur cellules CHO-K1 par le test des comètes qui sont associées à un stress oxydant. Ils sont plus actifs après irradiation par le spectre solaire. Ils induisent des mutations chromosomiques. L’étude in vivo des propriétés génotoxiques et mutagènes des QDs Les QDs induisent une augmentation significative des lésions de l'ADN chez le rat qui varie selon l’organe considéré (foie, rein, poumon, cerveau et testicule). Ils induisent une augmentation significative et une réponse dose-dépendante des micronoyaux indiquant nettement leur pouvoir clastogène/aneugène. Aucune variation significative des variables biochimiques mesurées n’est apparue. La mise en évidence de leurs effets sur l’environnement L'exposition aux QDs et au CdCl2 a entraîné une augmentation significative des lésions de l'ADN chez E. fetida et N. diversicolorQuantum dots (QDs) are semiconductor nanocrystals which can be employed as sensitive biomarkers of cellular metabolism and thus show their usefulness in various fields, including medicine and it soon became necessary to prove their safety before their widespread use and their distribution in the environment. The thesis project targeted on: Genotoxicity of quantum dots and the role of oxidative stress implications for the environment and human health. This study was organized in three main parts The in vitro study of the genotoxic and mutagenic properties of QDs QDs induced primary DNA lesions in CHO-K1 cells using the comet assay and were associated with oxidative stress. We demonstrated that the QDs were more active after irradiation by the solar spectrum. We showed the ability of QDs to induce chromosomal mutations. The main mechanism was probably that of the production of free radicals. The in vivo study of the genotoxic and mutagenic properties of QDs The comet assay shows that QDs induced an overall significant increase in DNA lesions of different organs (liver, kidneys, lungs, brain and testes). However, each organ had a specific susceptibility. QDs induced a significant increase in a dose-dependent manner of micronuclei. These results clearly indicated the in vivo clastogenic / aneugenic properties of QDs. No significant variation in the measured biochemical variables. The evidence of their effects on the environment Evaluation of genotoxicity was performed on coelomocytes of E. fetida and N. diversicolor resulting in a significant increase in DNA damage
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Thorslund, Sara. "Microfluidics in Surface Modified PDMS : Towards Miniaturized Diagnostic Tools." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7270.
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Lin, Chien-Hao, and 林建豪. "Computational Studies For The Mechanisms of CH4 Dissociation and oxidation on Pt/graphene oxide Surface." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/49535554392786749185.
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碩士國立臺灣師範大學
化學系
102
Based on density functional theory (DFT) calculation, the synthesis of methanol from the methane oxidation has been investigated on the graphene oxide nanosheets supporting two platinum atoms (Pt2-graphene oxide). According to previous literature, the platinum atoms could increase the adsorption energies of hydrocarbon species, and facilitate C-H bond scission to form the methanol. In our calculation, two CH4 molecule could be adsorbed on each Pt atom of the Pt2-graphene oxide surface, and the calculated possible mechanism of the methane oxidation reaction includes two parts; before and after the oxygen molecule adding to the system. First section involves the following three sequential steps: (I) dehydrogenation of one methane to the surface oxide to form methyl-Pt(1) and hydroxyl (Ea = 0.34 eV), (II) dehydrogenation of the other methane to Pt atom to form methyl and H-Pt(2) (Ea = 0.51 eV), and then (III) the coupling of the hydroxyl and the methyl to produce the methanol (Ea = 0.20 eV); Then,methanol could be desorbed from Pt2-graphene oxide catalyst. The second section contains two successive steps after adding oxygen molecule: the initial step is the scission of O-O bond and formation of hydroxyl group with the H atom on Pt(2) atom (Ea = 0.34 eV), and then, the hydroxyl would couple with methyl-Pt(1) to produce the other methanol (Ea = 1.25 eV). At last, we could gain two methanol and return to the original graphene oxide . Key point: Platinum atom 、Graphene-oxide 、methane 、 DFT
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Yu, Shi, and Gan-Moog Chow. "Synthesis and Characterization of Magnetic Nanoparticles with High Magnetization and Good Oxidation Resistibility." 2004. http://hdl.handle.net/1721.1/7499.
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Magnetic nanoparticles attract increasing attention because of their current and potential biomedical applications, such as, magnetically targeted and controlled drug delivery, magnetic hyperthermia and magnetic extraction. Increased magnetization can lead to improved performance in targeting and retention in drug delivery and a higher efficiency in biomaterials extraction. We reported an approach to synthesize iron contained magnetic nanoparticles with high magnetization and good oxidation resistibility by pyrolysis of iron pentacarbonyl (Fe(CO)[subscript 5]) in methane (CH[subscript 4]). Using the high reactivity of Fe nanoparticles, decomposition of CH[subscript 4] on the Fe nanoparticles leads to the formation of nanocrystalline iron carbides at a temperature below 260°C. Structural investigation indicated that the as-synthesized nanoparticles contained crystalline bcc Fe, iron carbides and spinel iron oxide. The Mössbauer and DSC results testified that the as-synthesized nanoparticle contained three crystalline iron carbide phases, which converted to Fe[subscript 3]C after a heat treatment. Surface analysis suggested that the as-synthesized and subsequently heated iron-iron carbide particles were coated by iron oxide, which originated from oxidization of surface Fe atoms. The heat-treated nanoparticles exhibited a magnetization of 160 emu/g, which is two times of that of currently used spinel iron oxide nanoparticles. After heating in an acidic solution with a pH value of 5 at 60°C for 20 h, the nanoparticles retained 90 percentage of the magnetization.Singapore-MIT Alliance (SMA)
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Τριανταφυλλόπουλος, Νικόλαος. "Μελέτη των ροφημένων ειδών άνθρακα κατά την ισορροπία της διασπαστικής ρόφησης του CH4 σε κεραμοδιμεταλλικούς ηλεκτροκαταλύτες βασισμένους στο νικέλιο." 2006. http://nemertes.lis.upatras.gr/jspui/handle/10889/299.
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Στην παρούσα διδακτορική διατριβή έγινε η μελέτη της φύσης των επιφανειακών ειδών άνθρακα που δημιουργούνται στην επιφάνεια κεραμομεταλλικών υλικών βασισμένα στο Ni-YSZ κατά την θερμοδυναμική ισορροπία της διασπαστικής ρόφησης του μεθανίου. Κύριος στόχος της μελέτης ήταν να διερευνηθεί η επίδραση της παρουσίας ενός δεύτερου μετάλλου στο Ni-YSZ, όσον αφορά τον σχηματισμό και/ή την αναστολή του ανενεργού άνθρακα. Η επικάλυψη της επιφάνειας του Ni με μικρή ποσότητα Au (≤1%at σε σχέση με το Ni) επηρέασε σημαντικά την κινητική της διασπαστικής ρόφησης του CH4 και την ενέργεια δεσμού των ροφημένων ειδών CHx στην επιφάνεια του Ni. Ο σχηματισμός γραφιτικού άνθρακα παρεμποδίστηκε, ενώ η επιφανειακή δραστικότητα για την υδρογόνωση των CHx προς CH4 ήταν χαμηλότερη από ότι στον Ni-YSZ. Αυτό έχει ως αποτέλεσμα την υψηλότερη σταθερότητα και την επιμήκυνση του χρόνου ζωής των CHx πάνω στην επιφάνεια του NiAu/YSZ πριν την διάσπαση τους προς επιφανειακά καρβιδικά είδη. Με βάση τις πειραματικές μετρήσεις, προτάθηκε κινητικό μοντέλο για την περιγραφή της μερικής οξείδωσης του μεθανίου για την παραγωγή αερίου σύνθεσης. Οι αντιδράσεις οξείδωσης περιλαμβάνουν την οξείδωση των ειδών CHx προς CHxO και την επακόλουθη διασπασή τους σε υψηλές θερμοκρασίες (700 Κ) προς CO και H2, ενώ τα καρβιδικά είδη οξειδώνονται εκλεκτικά προς CO2 από χαμηλότερες θερμοκρασίες (500 Κ). Από αυτή την άποψη, η εκλεκτικότητα ως προς το αέριο σύνθεσης εξαρτάται από δύο παράγοντες: (i) τον χρόνο ζωής και την επιφανειακή συγκέντρωση των ειδών CHx, και (ii) τη θερμοκρασία διάσπασης των ειδών CHxO. Ως γενικό συμπέρασμα, ο ηλεκτροκαταλύτης Ni(1%at Au)/YSZ αναμένεται να έχει υψηλή αντοχή στην εναπόθεση άνθρακα όπως και εκλεκτικότητα για την μερική οξείδωση του CH4 προς αέριο σύνθεσης.In order to investigate the possibility of the direct introduction of CH4 into a SOFC, the dissociative adsorption of CH4 and the nature of the various carbon adspecies on Ni-based cermets were studied in the present thesis by means of thermodynamic equilibrium measurements and temperature programming methods. The aim of this study was mainly to elucidate the effect of a second metal addition on Ni-YSZ, regarding the formation and/or inhibition of inactive carbon. The decoration of the Ni surface with very small quantity of Au (≤1at% with respect to Ni) affected significantly both the kinetics of CH4 dissociative adsorption and the binding strength of the adsorbed CHx species on the Ni surface. The formation of graphitic carbon was significantly inhibited, while the surface reactivity towards the hydrogenation of CHx species into CH4 was lower than on the unmodified Ni/YSZ surface. This resulted in the higher stability and elongation of the CHx species life time on the NiAu/YSZ surface prior to their decomposition into surface carbidic species. Based on the experimental results and discussion, a kinetic model is proposed for the description of the partial oxidation of methane towards the production of synthesis gas. The oxidation reactions involve both the oxidation of CHx species into CHxO and its subsequent decomposition at elevated temperatures (700 K) into CO and H2, while carbidic species are selectively oxidized into CO2 at temperatures as low as 500 K. In this respect, the selectivity towards synthesis gas depends on two factors: (i) the lifetime and surface concentration of CHx species, and (ii) the decomposition temperature of the CHxO species. As a conclusion, the Ni(1%at Au with respect to Ni)/YSZ catalyst is expected to be highly carbon tolerant and selective catalyst/electrode for the CH4 partial oxidation reaction for the production of synthesis gas.
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liu, shiuann-bang, and 劉炫邦. "Oxidative Decomposition of (CH3)2S2 and CH4 over Al2O3-supported Mixed-Metal-Oxide Catalysts --Effect of Acid Treatment aand Reaction Kinetics." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/91106752085143735467.
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Domingues, Neuza Luisa da Silva. "In vitro and in vivo studies of proatherogenic effects induced by end-products of cholesteryl esters oxidation." Doctoral thesis, 2018. http://hdl.handle.net/10362/34210.
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ABSTRACT:Atherosclerosis is a chronic inflammatory disease and the major worldwide cause of human
death. It is initiated by the constitutive uptake of modified low density lipoproteins trapped
in the arterial intima by monocyte-derived macrophages, leading to the formation of foam
cells. The oxidation levels and the quantity of lipid loading in macrophages influence their
inflammatory phenotype and function. With time, atherosclerotic macrophages become
dysfunctional and a clear trigger for this process relies on lysosomal malfunction. Eventually
this process leads to apoptotic cells and toxic lipid accumulation in arterial intima, culminating
in the formation of an irreversible advanced atheroma. Thus, the establishment of
a correlation between the composition of lipid species and the irreversibility/instability of
atherosclerotic lesions can contribute to the development of powerful tools for the diagnosis
and treatment of the cardiovascular disease burden. The main objective of this work was
the study of cholesteryl hemiesters (ChE), an oxidized product of cholesteryl esters, as an
atherogenic compound. Here, using the shotgun lipidomics technique, we showed that these
lipids are increased in the plasma of cardiovascular disease patients. We subsequently evaluated
the in vitro and in vivo atherogenic relevance of these oxidized lipids. Monocytes and
macrophages exposed to ChE presented an unusual inflammatory profile, presenting both
pro- and anti-inflammatory markers. ChE-loaded macrophages revealed endocytic trafficking
delays and dysfunctional enlarged lysosomes. The sub cellular location of the observed enlarged
stressed lysosomes was more peripheral than lysosomes from control macrophages.
Furthermore, these lysosomes from ChE-loaded macrophages displayed an increase in their
exocytic capacity. In addition, macrophages stimulated with ChE revealed a metabolic shift,
which, as with the inflammatory response, was dependent on toll-like receptor 4 signaling.
These foamy macrophages also presented an increased proliferative capacity as compared to
the control macrophages. Finally, using zebrafish larvae, several of the in vitro atherogenic
properties of ChE were confirmed in vivo, namely lipid accumulation, inflammation and
macrophage lysosomal dysfunction. Altogether, the work presented here contributes to the
identification of new etiologic compounds in human atherosclerotic lesions and advances
our mechanistic understanding of the alterations observed in atherosclerotic macrophages.RESUMO: A aterosclerose é uma doença inflamatória crónica e a principal causa de morte no mundo inteiro. Caracteriza-se pela internalização contínua de lipoproteínas de baixa densidade, que sofreram modificações por macrófagos derivados de monócitos, levando à formação de “células espumosas”. O nível de oxidação lipídica e a quantidade de lípido internalizada pelos macrófagos influencia o seu fenótipo e a sua função inflamatória. Com o tempo, os macrófagos presentes na lesão tornam-se disfuncionais e um dos principais responsáveis por este processo é o mau funcionamento dos lisossomas. Eventualmente, esta disfunção lisossomal leva à formação de células apoptóticas e à acumulação de lípidos tóxicos na íntima arterial, culminando na formação de um ateroma de estado avançado e irreversível. Deste modo, o estabelecimento de uma correlação entre a composição das espécies lipídicas e a irreversibilidade/instabilidade da lesão pode contribuir para o desenvolvimento de ferramentas fundamentais no diagnóstico e tratamento de doenças cardiovasculares. O objetivo principal deste trabalho foi o estudo de hemiesteres de colesterol (ChE), produtos resultantes da oxidação de ésteres de colesterol, como compostos aterogénicos. Neste trabalho, através da utilização da técnica de lipidómica “shotgun”, demonstramos que os ChE estão aumentados no plasma de pacientes com doenças cardiovasculares. De seguida, avaliamos a relevância aterogénica destes lípidos oxidados, através de estudos in vitro e in vivo. Monócitos e macrófagos expostos a ChE apresentaram um perfil inflamatório incomum, exibindo marcadores pró- e anti-inflamatórios. Os macrófagos carregados de ChE revelaram atrasos no tráfego endocítico e um aumento do tamanho dos seus lisossomas, assim como uma perda da sua função. Observou-se, também, uma alteração da localização dos lisossomas stressados nas células tratadas com ChE, verificando-se uma distribuição mais periférica, enquanto as células controlo apresentam uma distribuição mais homogénea dos lisossomas. Estes lisossomas de macrófagos carregados com ChE demonstraram um aumento adicional da sua capacidade exocítica. Além disso, os macrófagos estimulados com ChE revelaram uma alteração metabólica, que juntamente com a resposta inflamatória, foi dependente da sinalização através do receptor “toll like receptor-4”. Os macrófagos “espumosos” apresentaram, ainda, um aumento da capacidade proliferativa em relação aos macrófagos controlo. Finalmente, usando larvas de peixe-zebra, várias propriedades aterogénicas dos ChE observadas in vitro foram confirmadas in vivo, nomeadamente, a acumulação de lípidos, a propriedade inflamatória e a disfunção lisossomal em macrófagos. Em suma, o trabalho aqui apresentado contribui para a identificação de novos compostos etiológicos nas lesões de aterosclerose humana e contribui para o avanço da nossa compreensão mecanística das alterações celulares nos macrófagos das lesões.
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Mirrahimi, Arash. "Glycemic Index, Oxidized LDL, and CHD Risk." Thesis, 2012. http://hdl.handle.net/1807/35523.
Full textAbstract:
The aim was to determine whether the dietary glycemic index (GI) related to coronary heart disease (CHD) risk and whether oxidized LDL could explain this relation. Nine prospective cohorts of GI or glycemic load (GL) associations were pooled in a meta-analysis and showed an increased risk of CHD for high GI (near significant at RR=1.13, 95%CI; 1.00-1.26) and GL diets (significant at RR=1.40, 95%CI; 1.17-1.68), both with significant evidence of heterogeneity (P<0.07). Sera from 151 type 2 diabetics who completed a 6-month trial of a low GI diet demonstrated no treatment difference in measures of oxidative damage. However, when data from both treatments were pooled, oxidized LDL as a marker of CHD risk inversely related to low GI carbohydrate intake. We conclude that GI and GL relate to CHD and oxidative damage to LDL may explain part of this association.
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Jong, Huang，Guay, and 黃貴中. "Investigations on the oxidation kinetics and thermal stability of C54-TiSi2, NiSi2 and CoSi2 on Si substrate." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/32456334304539890743.
Full text
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CHEN, WEI-LUN, and 陳緯綸. "Simultaneous oxidation/reduction catalytic ability Au-Fe3O4@Chl nanocatalyst for rapid detection of nitro-polycyclic aromatic hydrocarbons under Raman spectroscopy." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/2ujw5j.
Full textAbstract:
碩士國立屏東大學
應用化學系碩士班
107
This study proposes a new type of nanogold (reduction catalyst)-nano iron oxide (oxidation catalyst)-chlorophyll (photooxidation property) three-in-one catalyst, which is expected to reduce high activity nitro group to low toxicity through the composition of nano gold. Amine-based, nano-iron oxide rface modification chlor -ophyll can provide nucleation sites, control nano-gold growth in the size of Fe3O4@ Chl, catalyze the double bond oxidation of phenol and polycyclic aromatic hydrocar- bons through nano-iron oxide, thereby destroying the benzene ring Structure, process can be combined with solar light to induce chlorophyll to produce singlet oxygen act- ivee substances, thereby increasing the benzene epoxidation efficiency. The whole process of pollutant decomposition can be monitored by nano-gold, supplemented by SERS technology to monitor phenol, polycyclic matic hydrocarbons, nitrate The de- gradation of the functional groups such as the base confirms the residual amount of environmental pollutants, and the ultimate goal is to develop in the direction of susta- inable chemical, and to make a contribution to the global environmental protection.
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Veiga, Anette Sousa da. "Influence of bioactive compounds present in white tea in Sertoli Cells oxidative and metabolic profiles." Master's thesis, 2019. http://hdl.handle.net/10400.6/10170.
Full textAbstract:
The tea is the second most popular drink in the world and is prepared by infusing of the
leaves and/or the buds of the specie Camellia sinensis (L.). Tea is divided in four types: green,
black, oolong and white. From those, the white tea (WTEA) remains as the less studied though
previous reports from our team showed that it may have more biological activity when
compared to the popular green tea. Based on the processing, WTEA can be classified as: Bai
Hao Yin Zhen (BHYZ), Bai Mu Dan (BMD), Gong Mei (GM) and Shou Mei (SM). These WTEA differ
in quality, flavor and performance being that BMD and BHYZ are the most consumed types
grades on the Asian continent. Energy metabolism is a key for spermatogenesis, the process of
spermatozoa production. Anaerobic glycolysis and oxidative phosphorylation, which takes place
in the mitochondria, are the main metabolic pathways involved in ATP production. However,
during those processes, several cellular sources produce significant amounts of reactive oxygen
species (ROS). ROS overproduction results in oxidative stress (OS), which is related with several
problems that may end up in male subfertility or infertility. Herein we proposed to study how
WTEA aqueous extracts of subtypes BMD and BHYZ may influence the nutritional support of
spermatogenesis. Firstly, we exposed the cells responsible for that function, human Sertoli cells
(hSC), to increasing concentrations of WTEA extracts subtypes BMD and BHYZ (in mg/mL: 0.05;
0.5 and 5) to evaluate cytotoxicity by measuring metabolic activity (MTT assay) and growth
(SRB assay). Only the exposure to 5 mg/mL of WTEA extract subtype BMD induced cytotoxicity
to hSC. Therefore, we selected to expose hSC to 0.5 mg/mL of WTEA extracts subtypes BMD
and BHYZ during 24h. Media and cells were collected for metabolism study using 1H-NMR,
complemented with LDH activity and mRNA and protein quantification of metabolism-related
enzymes and transporters. We also determined protein carbonylation and DNA mitochondrial
copy number in hSC. Our data shows that both WTEA extract subtypes BMD and BHYZ increase
glycolysis-related membrane transporters in hSC, while also decreasing LDH activity and
mitochondrial complex V expression, which further indicates an adaptative mechanism. Protein
carbonylation was also decreased after exposure to WTEA extract of both subtypes. Overall,
these results illustrate that WTEA extract modulates metabolic and oxidative profile of hSC,
which appears to have a positive effect to the nutritional support of spermatogenesis. In
addition, WTEA extract subtype BMD decreased oxidative stress which was followed by
decreased mitochondrial DNA copy number and increased mitochondrial complex II activity.
Overall, our data suggests that WTEA BMD may be more effective to counteract deleterious
effects induced by metabolic diseases that alter the nutritional support of spermatogenesis.
Nevertheless, more studies will be needed to support this hypothesis.O chá é a segunda bebida mais consumida em todo o mundo, sendo preparada a partir de infusão das folhas e /ou dos rebentos da espécie Camellia Sinensis (L.). Existem quatro tipos de chá: verde, preto, oolong e branco. Destes, o chá branco (WTEA) permanece o menos estudado embora estudos anteriores do nosso grupo tenham demonstrado que poderá ter uma maior atividade biológica quando comparado com o popular chá verde. Com base no processamento, o WTEA pode ser classificado como: Bai Hao Yin Zhen (BHYZ), Bai Mu Dan (BMD), Gong Mei (GM) e Shou Mei (SM). Estes subtipos de WTEA diferem em qualidade, sabor e atuação sendo que BMD e BHYZ são os subtipos mais consumidos no continente asiático. O metabolismo energético é a chave para a espermatogénese, o processo de produção de espermatozoides. A glicólise anaeróbia e a fosforilação oxidativa, que ocorre nas mitocôndrias, são as principais vias metabólicas envolvidas na produção de ATP. Contudo, durante esses processos, várias fontes celulares produzem quantidades significativas de espécies reativas de oxigénio (ROS). A superprodução de ROS causa um stress oxidativo (OS), que está relacionado com vários problemas que podem resultar na subfertilidade ou infertilidade masculina. Neste trabalho, propomos estudar como os extratos aquosos de WTEA dos subtipos BMD e BHYZ podem influenciar o suporte nutricional da espermatogénese. Primeiramente, expusemos as células responsáveis por essa função, células de Sertoli humanas (hSC), a concentrações crescentes de extratos WTEA subtipos BMD e BHYZ (em mg/mL: 0.05; 0.5 e 5) para avaliar a citotoxicidade através da medição da atividade metabólica (MTT assay) e de crescimento celular (SRB assay). Apenas a exposição a 5 mg/mL de extrato de WTEA subtipo BMD induziu citotoxicidade nas hSC. Por isso, selecionamos expor as hSC a 0.5 mg/mL de extratos WTEA subtipos BMD e BHYZ durante 24h. Meios e células foram recolhidos para estudo do metabolismo recorrendo à 1HNMR, complementado com estudos da atividade da lactato desidrogenase (LDH), mRNA e quantificação de proteínas e enzimas relacionadas ao metabolismo. Também determinamos a carbonilação proteica e o número de cópias de DNA mitocondrial nas hSC. Os nossos resultados mostram que ambos os subtipos de extrato WTEA, BMD e BHYZ aumentam os transportadores membranares relacionados à glicólise em hSC, enquanto também diminuem a atividade da LDH e expressão do complexo mitocondrial V, o que indica um mecanismo adaptativo. A carbonilação proteica também diminuiu após exposição ao extrato de WTEA de ambos os subtipos. Globalmente, estes resultados ilustram que o extrato de WTEA modula o perfil metabólico e oxidativo das hSC, o que parece ter um efeito positivo no apoio nutricional da espermatogénese. Além disso, o extrato de WTEA subtipo BMD diminuiu o OS que foi seguido pela diminuição do número de cópias de DNA mitocondrial e aumento da atividade do complexo mitocondrial II. Em geral, os nossos dados sugerem que o subtipo BMD do WTEA pode ser mais eficaz para combater os efeitos prejudiciais causados por doenças metabólicas que alteram o suporte nutricional da espermatogênese. No entanto, mais estudos serão necessários para apoiar esta hipótese.
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Huang, Chien Chih, and 黃建誌. "1.Decomposition Reaction of Pd(CH=CHR)(Br)(PPh3)2;2.Oxidative Ad- dition of Tetraaryl Phosphonium Salt to Pd(0)." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/72063703511091146830.
Full textAbstract:
碩士國立清華大學
化學學系
82
PdI(Ar)(PPh3)2的苯環交換反應,在一般的有機溶劑中都會發生.那如果Ar 取代基換為烯基時,是否會有同樣的情況發生呢?當我們把PdBr(CH=CH )(PPh3)2溶在CDCl3作交換反應追蹤時,卻得到化合物Pd(0)-olefin com- ,結構鑑定是利用單晶X-ray繞射方法.一般Pd(0)-olefin complex 不b ,這是因為Pd的游離能較高,回饋鍵較弱.鹵化烯基三苯基鏻在常溫下與Pd( PPh3)4反應可得Pd(0)-olefin com- plex.在溶劑為THF,溫度為攝氏60度, 卻會有氧化還原加成反應的發生.以其整個步驟來看,這似乎是達成烯基苯 環交換反應的分解步驟.第一步驟先形成鏻鹽,第二步驟再氧化加成至Pd金 屬中心.我做了一些四芳香基鏻鹽氧化加成至Pd上,嘗試著解釋苯環交換的 反應可能途徑.我們提出二可能性的反應途徑來解釋PdI(Ar)(PPh3)2的苯 環交換反應。途徑一：PdI(Ar)(PPh3)2在溶劑中及PPh3存在下產生 tetraaryl phosph- onium salt及Pd(PPh3)2，但是四芳香基鏻鹽似乎沒 有離開Pd的配位圈，馬W又氧化加成回去，得到苯環交換反應的產物，如 果碘化四芳香基鏻有離開開Pd金屬的配位圈，便會在溶液中沈澱出來，便 較不容易再氧化加成回去了。途徑二：PdI(Ar)(PPh3)2在溶劑中先有一分 子的PPh3游離出來，產生中間體，而後經由一個分子內的重排反應使的芳 香基轉移到磷上，苯環轉移到Pd上，再與一分子的PPh3重新結合完成交換 反應。
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Shih-Chueh and 陳世爵. "Effect of Tai Chi Exercise on Body Weight, Metabolic Profiles, Oxidative Stress Indicators and Life Quality in Obese Type 2 Diabetic Patients." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/66075842340584098429.
Full textAbstract:
博士中山醫學大學
醫學研究所
98
Objective: This study aimed to validate the effects of a simplified, gentle form of Tai Chi Chuan in obese type 2 diabetic patients.Design: Randomized, controlled trial. Setting: Department of Metabolism and Endocrinology at Cheng Ching Hospital, Taichung, Taiwan.Subjects: Hospital-based obese type 2 diabetic patients (aged 40-70, BMI 30-35 kgw/m2) were randomly selected and grouped into Tai Chi exercise and conventional exercise groups. Interventions: After receiving instruction in Tai Chi, the Tai Chi group and the conventional exercise group practiced three times a week, including one practice session lasting up to 1 hour, for 12 weeks. Outcome measures: Hemoglobin A1C, serum lipid profile, serum malondialdehyde, and C-reactive protein were measured. Physical parameters of body weight and body mass index were also measured. Diet and medications of participants were monitored carefully as biochemical and physical conditions were analyzed. Results: After 12 weeks, hemoglobin A1C values of the experimental group did not decrease (8.9±2.7%: 8.3±2.2%, P=0.064). Body weight (83.9±4.2 : 82.4±3.2, P=0.022 )and body mass index (33.5±4.8: 31.3±4.2, P=0.038) and serum lipids, including triglyceride (214±47 mg/dL: 171±34 mg/dL, P=0.012) and high density lipoprotein cholesterol (38±16 mg/dL: 45±18 mg/dL, P=0.023) showed significant improvements. Serum malondialdehyde tended to decrease from baseline (2.66±0.78 μmol/L: 2.31±0.55 μmol/L, P=0.035), and C-reactive protein also decreased (0.39±0.19 mg/dL: 0.22±0.15 mg/dL, P=0.014). No improvements were seen in BMI, lipid and oxidative stress profiles in the conventional exercise group. The life quality scores showed some improvements of physiological functions (1.56±0.17 : 1.62±0.20, P=0.038 ) and consensuses of health (1.39±0.35:1.57±0.52,P=0.033)in Tai Chi group. There were also some improvements of consensuses of health(1.39±0.35:1.57±0.52, P=0.033) in the conventional exercise group. Conclusion: Tai Chi exercise practiced by obese diabetic patients is efficient and safe when supervised by professionals and helps to improve parameters such as body mass index, lipid profiles, C-reactive protein, oxidative stress indicators such as malondialdehyde and life quality. Periodic monitoring of blood glucose, blood pressure; heart rate, breathing, physical fitness and symptoms of discomfort of patients who exercise helps to prevent injury. Simple, gentle “Tai Chi exercise” can be applied as regular daily exercise for type 2 diabetic patients even when obese.
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Martins, Cristiana Sofia de Figueiredo. "Filme ativo com extrato de chá verde na preservação de alimentos suscetíveis à oxidação lipídica." Master's thesis, 2018. http://hdl.handle.net/10316/84599.
Full textAbstract:
Dissertação de Mestrado em Segurança Alimentar apresentada à Faculdade de FarmáciaNos últimos anos, as exigências dos consumidores e da indústria têm vindo a alterar-se e as embalagens convencionais, caracterizadas por não interagirem com o seu conteúdo e ser provenientes de fontes não renováveis, não permitiram acompanhar as necessidades do mercado. Assim, surgiram as embalagens ativas, que interagem deliberadamente com o seu conteúdo, encontrando-se legisladas na União Europeia (Regulamento (CE) n.º 1935/2004 e Regulamento (CE) n.º 450/2009). Estas embalagens podem retardar ou mesmo inibir processos de deterioração dos alimentos, tais como a oxidação lipídica, ou o crescimento de microrganismos patogénicos, permitindo aumentar o tempo de vida útil dos alimentos.Na sua grande maioria, as embalagens convencionais são fabricadas a partir de materiais não biodegradáveis que, para além de representarem um grave problema ambiental, podem interagir de forma não intencional com a matriz alimentar que protegem, passando para os alimentos compostos potencialmente tóxicos para a Saúde Humana. Este fenómeno de transferência de massa é denominado migração. Quando aplicado às embalagens ativas emissoras é um processo desejado, já que se trata de substâncias destinadas a prolongar a vida útil do alimento.Uma das reações mais relevantes, relacionadas com a degradação dos alimentos, é a oxidação lipídica, que leva a uma alteração nutritiva e sensorial e diminui o prazo de validade dos produtos embalados. Assim, a indústria alimentar tem um grande interesse na prevenção de fenómenos de oxidação e esta é minimizada através da adição de antioxidantes sintéticos ou naturais ao alimento. Os antioxidantes naturais são uma alternativa segura aos antioxidantes sintéticos, pelo que o seu uso tem aumentado na conservação de alimentos. No presente trabalho, o extrato de chá verde foi escolhido para ser incorporado numa embalagem alimentar, uma vez que a sua eficácia como antioxidante é largamente reconhecida na literatura.O presente trabalho teve como objetivo principal avaliar a eficácia de uma nova embalagem alimentar ativa biodegradável, baseada em ácido polilático (PLA), com capacidade antioxidante através da incorporação de extrato de chá verde em diferentes concentrações, 1% e 2%, a fim de evitar a oxidação lipídica de alimentos com alto teor lipídico.No âmbito deste trabalho foi, também, estudada a atividade antimicrobiana da embalagem ativa e do extrato de chá verde incorporado na embalagem.Inicialmente, foi avaliada e comparada a capacidade antioxidante de três extratos de chá verde preparados em laboratório com um extrato de chá verde comercial. A capacidade antioxidante foi avaliada pelo sistema de inibição do radical DPPH e pelo teste do branqueamento do β-caroteno. Além disso, foram determinados, também, o conteúdo em fenólicos totais e em flavonoides totais. O extrato de chá verde comercial apresentou maior capacidade antioxidante e conteúdo superior em compostos fenólicos totais.Relativamente à atividade antimicrobiana, o extrato de chá verde demonstrou capacidade inibitória sobre as estirpes S. aureus, B. cereus, L. monocytogenes e E. faecalis, no entanto, quando incorporado no filme de PLA, nas concentrações 1% e 2%, não apresentou atividade antimicrobiana em relação aos microrganismos testados. Posteriormente, foi avaliada a eficácia de um filme de PLA com o extrato de chá verde comercial incorporado em diferentes concentrações, 1% e 2%, na inibição da oxidação lipídica de um alimento modelo. O alimento escolhido foi o salmão fumado devido ao elevado teor de ácidos gordos polinsaturados presentes na sua composição, suscetíveis à oxidação lipídica. As fatias de salmão fumado foram embaladas com os filmes ativos (PLA/Chá Verde 1% e PLA/Chá Verde 2%) e o filme controlo (sem extrato) durante 7, 15, 30, 45 e 60 dias, à temperatura de 5 ᵒC, protegidas da luz. O estado de oxidação lipídica das fatias de salmão fumado foi avaliado através de quatro métodos: o índice de peróxidos, a determinação do valor da p-anisidina, o ensaio de TBARS - Substâncias Reativas ao Ácido Tiobarbitúrico e a determinação do hexanal.Os resultados demostraram que a incorporação de extrato de chá verde, em filmes PLA, protegeu o salmão fumado da oxidação lipídica, nos diferentes tempos de armazenamento testados. No entanto, devem ser realizados estudos adicionais a fim de compreender melhor o mecanismo de ação do extrato de chá verde, pois os resultados sugeriram um efeito pró-oxidante do filme PLA/Chá Verde 2%, após os 60 dias de armazenamento.
In recent years, consumers and industry demands have been changing and conventional packaging, characterized by absence of interaction with its content, could not accomplish the emerging market needs. However, active packaging, characterized by actively interacting with its content, emerged and is legislated in the European Union (Commission Regulation (EU) no. 1935/2004 and Commission Regulation (EU) no. 450/2009). These packages may delay or inhibit the deterioration processes of foods, such as lipid oxidation, or the growth of pathogenic microorganisms, allowing to extend food shelf life.In its vast majority, conventional packages are manufactured from non-biodegradable materials which, in addition to represent a serious environmental concern, they may interact unintentionally with the food matrix they protect, transferring potentially toxic compounds to Human Health to foods. This mass transfer phenomenon is called migration. When applied to the releasing active packaging can be a desired process, since the substances are intended to extend food shelf life.There are several reactions that can cause food degradation. Lipid oxidation is one of the most relevant and it is capable of causing nutritional and sensory alterations, leading to shelf-life reduction. Therefore, the prevention of oxidation reactions is of great interest for the food industry. The addition of natural or synthetic antioxidants is used to counteract lipid oxidation of foodstuffs. Natural antioxidants are a safe alternative to synthetic antioxidants and its use in food preservation has been increasing. In the present work, green tea extracts (Camellia sinensis L.) were chosen to be incorporated in active films since its effectiveness as an antioxidant is extensively reported in the literature.The main objective of the present work was to evaluate the efficacy of a new biodegradable active food packaging, based on PLA, with antioxidant capacity through the incorporation of green tea extract in two different concentrations, 1% and 2%, in order to prevent lipid oxidation of foods with high lipid content.In this work the antimicrobial activity of the active packaging and of the green tea extract incorporated in the package was also studied.Initially, the antioxidant capacity of three of green tea extracts prepared in the laboratory was evaluated and compared with the one of an commercial green tea extract. The antioxidant capacity was evaluated by DPPH• radical scavenging method and β-carotene bleaching method. Moreover, the total phenolics content and total flavonoids content were also determined. The commercial green tea extract presented greater antioxidant capacity, reflected in higher values of Trolox Equivalent, smallest EC50 and premium content in total phenolic compounds.Regarding the antimicrobial activity, the green tea extract inhibited the strains, S. aureus, B. cereus, L. monocytogenes and E. faecalis, however, when incorporated in the film of PLA, at concentrations of 1% and 2% did not show antimicrobial activity in relation to the tested microorganisms.Afterwards, the effectiveness of a film of PLA with commercial green tea extract was evaluated incorporating two different concentrations, 1% and 2%, in the inhibition of lipid oxidation of a food model. The food chosen to be packaged with the active film was smoked salmon, due to the high content of polyunsaturated fatty acids present in its composition, susceptible to lipid oxidation. Slices of smoked salmon were packaged with the active films (PLA/Green Tea 1% and PLA/Green Tea 2%) and the control film (without extract) for 7, 15, 30, 45 and 60 days at a temperature of 5 ᵒC, protected from light. The lipid oxidation status of the smoked salmon slices was evaluated by four methods: peroxide value, p-anisidine value, TBARS test and monitoring of hexanal.The results showed that the incorporation of GTE in the PLA films protects the smoked salmon from lipid oxidation in the different storage times tested. However, additional studies should be performed to better understand the GTE mechanism of action as the results suggest a pro-oxidant effect of PLA/GTE 2% after 60 days of storage.
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Silveira, Ana Carolina Lourenço. "Antioxidant properties of white tea in (pre)diabetic rats." Master's thesis, 2018. http://hdl.handle.net/10400.6/9770.
Full textAbstract:
Diabetes Mellitus (DM) is one of the most prevalent metabolic diseases in the western world and results from failure of insulin secretion and/or action. This hormone, produced in pancreatic ß cells allows cells to capture glucose to meet their energy needs. When insulin is absent or when its function is not normal the cells do not absorb glucose that remains in the bloodstream causing hyperglycaemia. DM is associated with excessive formation of free radicals and when endogenous antioxidant defenses are not present in sufficient amounts to neutralize them cause cell damage. DM is associated with excessive free radical formation and when endogenous antioxidant defenses are not present in sufficient amounts to neutralize them, they cause cell damage. DM is still associated with aging and with age progression there is a tendency for several complications to arise in different organs. One of the complications that occurs later is respiratory failure resulting from physiological and structural changes in lung tissue and decreasing alveolar gas exchange. Prediabetes (PrDM) is a condition in which some, but not all, of the criteria for DM are verified and represent a high risk for the development of DM and whose prevalence has been increasing significantly in recent decades. It is therefore essential to find therapeutic alternatives in the fight against the negative effects of this pathology and its progression to DM.
White tea is rich in polyphenols and methylxanthines, which is why it has a high antidiabetic and antioxidant potential. This study intends to evaluate for the first time the effects of PrDM in the lung and to verify if the regular consumption of white tea contributes to the improvement of the antioxidant capacity of the lung tissue of PrDM rats. A Wistar rat model with PrDM induced with a low dose of streptozotocin was used in which one of the groups consumption of water was replaced by white tea. After two months the lung tissue was collected and the antioxidant potential, the activities of seceral enzymes involved in the endogenous antioxidant defenses and some oxidative parameters, such as protein oxidation (nitration and carbonylation), lipid peroxidation and damage in the deoxyribonucleic acid. In this study, PrDM was found to decrease the activity of the superoxide dismutase and glutathione peroxidase. In addition, it increased levels of protein nitration and lipid peroxidation and decreased histone H2A levels of this tissue. That is, with the decrease in the activity of antioxidant enzymes of the lung occurred an increase in the oxidative damage of its cells. Our results demonstrate that regular consumption of white tea restored the total antioxidant capacity of lung tissue, decreased levels of protein nitration and lipid peroxidation, and increased levels of histone H2A from this tissue. These results show for the first time that regular consumption of white tea improves the antioxidant capacity of the lung tissue of PrDM rats, suggesting that it may be a natural and economical alternative to treat the deleterious effects of PrDM in the lung and avoid progression to DM.A Diabetes Mellitus (DM) é uma das doenças metabólicas mais prevalentes no mundo ocidental e resulta de uma falha na secreção e/ou ação da insulina. Esta hormona, produzida nas células ß pancreáticas permite que as células captem glucose para suprir as suas necessidades energéticas. Quando a insulina está ausente ou quando a sua função não é normal as células não absorvem glucose que permanece na corrente sanguínea causando hiperglicémia. A DM está associada à formação excessiva de radicais livres e, quando as defesas antioxidantes endógenas não estão presentes em quantidade suficiente para neutraliza-los causam danos celulares. A DM está ainda associada ao envelhecimento e com a progressão da idade há uma tendência para surgirem várias complicações em diferentes orgãos. Uma das complicações que ocorre mais tardiamente é a insuficiência respiratória que resulta das alterações fisiológicas e estruturais do tecido pulmonar e que diminuem as trocas gasosas alveolares. A pré-diabetes (PrDM) é um estado em que alguns, mas não todos os critérios para a DM são verificados sendo que representa um elevado risco para o desenvolvimento da DM. A sua prevalência tem vindo a aumentar significativamente nas últimas décadas. É por isso essencial encontrar alternativas terapêuticas no combate aos efeitos negativos desta patologia e à sua progressão para DM. O chá branco é rico em polifenóis e metilxantinas, motivo pelo qual apresenta um elevado potencial antidiabético e antioxidante. Este estudo pretende avaliar, pela primeira vez, os efeitos da PrDM no pulmão e verificar se o consumo regular de chá branco contribui para a melhoria da capacidade antioxidante total do tecido pulmonar de ratos PrDM. Para isso usou-se um modelo de rato Wistar com PrDM induzida com uma dose baixa de estreptozotocina em que num dos grupos o consumo de água foi substituído por chá branco. Após dois meses recolheu-se o tecido pulmonar e avaliou-se o potencial antioxidante, as atividades de várias enzimas envolvidas nas defesas antioxidantes endógenas e alguns parâmetros oxidativos, como a oxidação de proteínas (nitração e carbonilação), a peroxidação lipídica e os danos no ácido desoxirribonucleico. Neste estudo, verificou-se que a PrDM diminuiu a atividade da supéroxido dismutase e da glutationa peroxidase. Além disso, aumentou os níveis de nitração proteica e de peroxidação lipídica e diminuiu os níveis de histonas H2A deste tecido. Ou seja, com a diminuição da atividade das enzimas antioxidantes do pulmão ocorreu um aumento nos danos oxidativos das suas células. Os nossos resultados demonstram que o consumo regular de chá branco repôs a capacidade antioxidante total do tecido pulmonar, diminuiu os níveis de nitração de proteínas e de peroxidação lipídica e aumentou os níveis de histonas H2A deste tecido. Estes resultados mostram, pela primeira vez, que o consumo regular de chá branco melhora a capacidade antioxidante total do tecido pulmonar de ratos PrDM, sugerindo que pode ser uma alternativa terapêutica natural e económica para fazer face aos efeitos deletérios da PrDM no pulmão e evitar a progressão para DM.
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Pors, Klaus, Paul M. Loadman, Steven D. Shnyder, Mark H. Sutherland, Helen M. Sheldrake, M. Guino, K. Kiakos, J. A. Hartley, M. Searcey, and Laurence H. Patterson. "Modification of the duocarmycin pharmacophore enables CYP1A1 targeting for biological activity." 2011. http://hdl.handle.net/10454/6138.
Full textAbstract:
The identification of an agent that is selectively activated by a cytochrome P450 (CYP) has the potential for tissue specific dose intensification as a means of significantly improving its therapeutic value. Towards this goal, we disclose evidence for the pathway of activation of a duocarmycin analogue, ICT2700, which targets CYP1A1 for biological activity.