Teses / dissertações: "Dioxins Metabolism"

1

Furness, Sebastian George Barton. "Novel mechanisms for activation of the dioxin (Aryl-hydrocarbon) receptor /". Title page, table of contents and summary only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phf988.pdf.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

2

Högberg, Pi. "Disruption of vitamin A metabolism by dioxin /". Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-608-1/.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

3

Shinkyo, Raku. "Structure-function analysis of mammalian cytochromes P450 involved in metabolism of dioxins". Kyoto University, 2006. http://hdl.handle.net/2433/144094.

Texto completo da fonte

Resumo:

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第12357号
農博第1538号
新制||農||923(附属図書館)
学位論文||H18||N4115(農学部図書室)
24193
UT51-2006-J349
京都大学大学院農学研究科食品生物科学専攻
(主査)教授井上國世, 教授吉川正明, 教授村田幸作
学位規則第4条第1項該当

Estilos ABNT, Harvard, Vancouver, APA, etc.

4

Hu, Keke. "Structure-activity relationships for the metabolism of polychlorinated dibenzo-p-dioxins and related compounds". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ35799.pdf.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

5

Murtomaa-Hautala, M. (Mari). "Species-specific effects of dioxin exposure on xenobiotic metabolism and hard tissue in voles". Doctoral thesis, Oulun yliopisto, 2012. http://urn.fi/urn:isbn:9789514297830.

Texto completo da fonte

Resumo:

Abstract The evaluation of the effects and levels of contaminants in wildlife is an essential part of assessing risks for chemical exposure in the environment. Although the circumstances are not as controlled as in laboratory, wildlife studies offer the concept of environmental exposure in its entirety, with all the natural variation. In the present study, two wild vole species, bank vole (Myodes glareolus) and field vole (Microtus agrestis), were used in assessing environmental levels of dioxins. The effects of dioxin exposure on tooth and bone development were studied in order to determine whether they could be used as biomarkers for environmental exposure. Xenobiotic metabolism activity after dioxin exposure – both natural and experimental – was studied by quantifying selected cytochrome P-450 (CYP) enzymes. The results confirmed the fact that dioxins are ubiquitous in the environment, also in areas far from contaminant sources and human activity. The development of the third molar in bank vole was found to be a sensitive biomarker for dioxin exposure. The two vole species under study do not respond similarly to environmental concentrations of dioxins; there were significant differences in body burdens and activity levels of xenobiotic metabolizing enzymes
Tiivistelmä Haitallisten kemikaalien tason ja vaikutusten arviointi ympäristössä on olennainen osa kemikaalien riskin arviointia. Vaikka laboratoriossa olosuhteita kontrolloidaan ja tutkimukseen vaikuttava variaatio on paremmin hallittavissa, luonnonvaraisten lajien tutkiminen luo kokonaisvaltaisen ja todenmukaisen kuvan ympäristön kemikaalialtistuksesta kaikkine todellisine vaihteluineen. Tässä väitöskirjassa tarkastellaan kahden luonnonvaraisen pikkunisäkkään, metsämyyrän (Myodes glareolus) ja peltomyyrän (Microtus agrestis), käyttöä ympäristön kemikaalitason arvioinnissa. Pääpaino on dioksiinien kaltaisissa yhdisteissä. Työssä tutkitaan yhdisteiden kertymistä myyriin kahdessa ympäristössä: voimakkaasti dioksiineilla saastuneella maa-alueella sekä kaukana ihmistoiminnasta sijaitsevassa erämaassa. Herkiksi tiedettyjä vasteita – hampaiden ja luiden kehitystä – käytetään dioksiinialtistuksen indikaattoreina. Vierasainemetaboliasta vastaavien entsyymien (sytokromi P450 eli CYP) aktiivisuutta kartoitetaan molemmilla myyrälajeilla, jotta saadaan tietoa entsyymien indusoinnista luonnonvaraisilla myyrillä yleensä ja selvitetään havaittuja lajien välisiä eroja dioksiinivasteissa. Tulokset vahvistavat, että dioksiinit ovat laajalle levinneitä yhdisteitä, joita löytyy paitsi läheltä päästölähdettä myös kaukana ihmistoiminnasta olevilta alueilta. Metsämyyrällä kolmannen poskihampaan kehitys osoittautuu herkäksi dioksiinialtistuksen biomarkkeriksi. Samasta elinympäristöstä huolimatta tutkituista myyrälajeista mitatut dioksiinipitoisuudet eroavat huomattavasti toisistaan, samoin kuin vierasainemetaboliasta vastaavien entsyymien aktiivisuus ja niiden induktio TCDD-altistuksen jälkeen

Estilos ABNT, Harvard, Vancouver, APA, etc.

6

Labaronne, Emmanuel. "Impacts métaboliques d'un mélange faiblement dosé de polluants alimentaires dans un modèle murin : effets dépendants de l'âge, du sexe et du contexte nutritionnel". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1204/document.

Texto completo da fonte

Resumo:

Plusieurs travaux suggèrent l'implication des polluants de l'environnement dans l'épidémie d'obésité et l'incidence du diabète. Cependant, l'impact cumulé de cette myriade de polluants auxquels l'homme est exposé à faibles doses pendant toute sa vie n'a pas été totalement appréhendé.Au laboratoire, nous utilisons un modèle souris d'exposition chronique (toute la vie) à un mélange de polluants (TCDD, PCB153, DEHP et BPA) via leur ajout à une alimentation obésogène ou standard. Les doses des polluants sont ajustées de sorte à ce que l'exposition soit de l'ordre de la Dose Journalière Tolérable, supposée sans effet chez l'homme, pour chacun des 4 polluants.Nos résultats montrent que dans un contexte d'obésité induite par le régime et à l'âge adulte, l'exposition au mélange de polluants altère le métabolisme hépatique du cholestérol chez les mâles et aggrave l'intolérance au glucose chez les femelles. L'analyse du profil métabolique de femelles immatures nourries avec le régime obésogène indique que les effets des polluants sont liés au contexte hormonal et à l'activité oestrogéno-mimétique des polluants. Enfin, en condition de régime standard, nous observons une dyslipidémie chez les femelles adultes exposées au mélange, possiblement en lien avec la dérégulation génique dans le foie de plusieurs voies métaboliques dont le rythme circadien et le métabolisme du cholestérol. En revanche, les polluants n'ont pas d'effet obésogène.En conclusion, nos travaux démontrent que les polluants en mélange exercent un impact métabolique adverse chez la souris à des doses supposées sans effet individuellement, et ces effets sont dépendants du sexe de l'âge et du contexte alimentaire
Pollutants are suspected to contribute to the etiology of obesity and related metabolic disorders but the current risk assessment does not take into account the cocktail effect resulting from the large amount of chemicals to which humans are exposed.We fed mice with high fat or standard diet with or without a mixture of food pollutants, either persistent pollutants (TCDD, PCB153) or short-lived pollutants (DEHP, BPA). Doses are adjusted resulting in mice exposure at the Tolerable Daily Intake dose range for each pollutant. Mice are chronically exposed from preconception to adult life.We demonstrated that a mixture of 4 pollutants triggers in the adult male offspring (12 weeks) an alteration of hepatic cholesterol metabolism. In females, there was a marked deterioration of glucose tolerance, which may be related to decreased hepatic estrogen signaling. The analyze of 7 week-old female mice, when they exhibit early signs of obesity and immature estrogen levels, shown that pollutant exposure alleviated HFSD-induced glucose intolerance, suggesting apparent biphasic effects of pollutants along with hormonal context. Then we compared hepatic signature of gene expressions from exposed non-obese or non exposed obese females and we highlight 4 main pathways that were targeted by both treatments and appeared to be affected by different but overlapping mechanisms. Plus, we showed that pollutants can markedly alter the circadian clock in the liver.Altogether, we emphasize that, pollutants presented in a mixture, have adverse metabolic effects at doses where they are supposed to be without any individual effect, and these effects depend on the gender, age and dietary context

Estilos ABNT, Harvard, Vancouver, APA, etc.

7

Arnoldsson, Kristina. "Polybrominated dibenzo-p-dioxins : Natural formation mechanisms and biota retention, maternal transfer, and effects". Doctoral thesis, Umeå universitet, Kemiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-50887.

Texto completo da fonte

Resumo:

Polybrominated dibenzo-p-dioxins (PBDD) and dibenzofurans (PBDF) are a group of compounds of emerging interest as potential environmental stressors. Their structures as well as toxic responses are similar to the highly characterized toxicants polychlorinated dibenzo-p-dioxins. High levels of PBDDs have been found in algae, shellfish, and fish, also from remote areas in theBaltic Sea. This thesis presents studies on PBDD behavior in fish and offspring, and natural formation of PBDDs from naturally abundant phenolic precursors. The uptake, elimination, and maternal transfer of mono- to tetraBDD/Fs were investigated in an exposure study reported in Paper I. The effects of PBDDs in fish were examined in a dose-response study (Paper II). It was shown that fish can assimilate PBDD/Fs from their feed, although non-laterally substituted congeners were rapidly eliminated. Laterally substituted congeners were retained as was congeners without vicinal hydrogens to some extent. PBDD/Fs were transferred to eggs, and congeners that were rapidly eliminated in fish showed a higher transfer ratio to eggs. Exposure to the laterally substituted 2,3,7,8-TeBDD had significant effects on the health, gene expression and several reproduction end-points of zebrafish, even at the lowest dose applied. The geographical and temporal variations of PBDD in biota samples from the Baltic Seasuggest biogenic rather than anthropogenic origin. In Paper III, bromoperoxidase-mediated coupling of 2,4,6-tribromophenol yielded several PBDD congeners, some formed after rearrangement. The overall yield was low, but significantly higher at low temperature, and the product profile obtained was similar to congener profiles found in biota from the Swedish West Coast. In Paper IV, photochemically induced cyclization of hydroxylated polybrominated diphenyl ethers under natural conditions produced PBDDs at percentage yield. Rearranged products were not detected, and some abundant congeners do not seem to be formed this way. However, the product profile obtained was similar to congener profiles found in biota from the Baltic Proper. Since the PBDD congeners found in biota have a high turn-over in fish, the exposure must be high and continuous to yield the PBDD levels measured in wild fish. Thus, PBDDs must presumably be formed by common precursors in general processes, such as via enzymatic oxidations, UV-initiated reactions or a combination of both. The presented pathways for formation of PBDDs are both likely sensitive to changes in climatic conditions.

Estilos ABNT, Harvard, Vancouver, APA, etc.

8

Rosenzweig, Ella. "Exploring the role and the function of Aryl Hydrocarbon Receptor (AhR) and Aryl Hydrocarbon Nuclear Translocator (ARNT) in T cells". Thesis, University of Dundee, 2012. https://discovery.dundee.ac.uk/en/studentTheses/1d8657f4-b7b1-4508-a93f-76f21fa8d605.

Texto completo da fonte

Resumo:

The Aryl Hydrocarbon Receptor (AhR) and the Aryl Hydrocarbon Nuclear Translocator (ARNT) play a role in mediating transcriptional responses to environmental pollutants, including the highly toxic compound 2,3,7,8-tetrachlorodibenzo -p-dioxin (TCDD) but also endogenous physiological ligands. More recent studies have also indicated that the AhR plays a role in the immune system notably in effector Th17 cells where it seems to be critical for the production of the IL-22 cytokine. It is known that AhR ligands such as dioxins can suppress CD8 T cell mediated antiviral immune responses but it is not known whether this reflects a direct role of the AhR in CD8 T cells.Accordingly, one objective of the present study was to explore AhR and ARNT expression in CD8 T cells. The initial strategy was to probe AhR and ARNT expression by western blot analysis. A second approach was to develop a mouse model that would fate mark single lymphocytes that have activated AhR signaling pathways. A third strategy was to examine the impact of deletion of AhR and ARNT on CD8 T-cell function.The data show that AhR and ARNT expression in CD8 T cells is limited to immune activated effector cells and these transcription factors are not expressed in naïve CD8 T cells. There are only low levels of AhR complexes in conventional CD8 positive cytotoxic T cells. To investigate AhR function at the single cell level we developed a mouse model to fate mark cells that have activated AhR signaling. In this model a mouse expressing Cre recombinase ‘knocked in’ to the CYP1A locus (CYP1A1Cre+/-) was backcrossed to the R26REYFP reporter mouse. In R26REYFP mice, a gene encoding EYFP is knocked into the ubiquitously expressed Rosa26 locus preceded by a loxP flanked stop sequence. CYP1A1 expression is controlled by AhR/ARNT complexes and the concept of our model was that cells that express AhR and ARNT complexes and are triggered with AhR ligands will express Cre recombinase and delete the loxP flanked stop sequence in the R26REYFP reporter locus and hence begin to express YFP.In vitro experiments demonstrated the validity of this AhR reporter model. The in vitro data reveal that expression of functional AhR/ARNT complexes occurs during Th17 and Tc17 cell differentiation but only a very low frequency of cytotoxic T cells activates the AhR. In vivo data found no evidence for AhR activation during T cell development in the thymus but show strong evidence for activation of AhR/ARNT signaling in innate lymphocytes in the gut. The ARNT transcription factor is highly expressed in cytotoxic T cells. These cells do not express functional AhR complexes, yet we considered that ARNT might play a role in CD8 T cell biology because of its ability to dimerise with the transcription factor Hif-1a. Our studies of T cells lacking ARNT expression revealed that in CD4 T cells the ARNT transcription factor regulates IL-17 and IL-22 production. In CD8 T cells we discovered that Hif-1a/ARNT signaling controls glycolysis in immune activated cells by sustaining expression of glucose transporters and multiple rate limiting glycolytic enzymes. ARNT was not required for CD8 T cell proliferation but was required for immune activated CD8 T cells to normally differentiate to express perforin and granzymes and to acquire the migratory program of effector T cells. Importantly, we discovered that Hif-1a/ARNT signaling is regulated by mTOR (mammalian target of rapamycin) thus revealing a fundamental mechanism linking nutrient sensing and transcriptional control of CD8 T-cell differentiation.

Estilos ABNT, Harvard, Vancouver, APA, etc.

9

Leblanc, Alix. "Effets d’un mélange de polluants organiques persistants sur le métabolisme hépatique". Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05P629/document.

Texto completo da fonte

Resumo:

Des études épidémiologiques ont montré que l’exposition à certains xénobiotiques est associée à une augmentation de la prévalence des maladies métaboliques. L’Homme est exposé à des mélanges de xénobiotiques de manière chronique et inévitable. Nous avons étudié les effets de l’interaction de deux xénobiotiques sur le métabolisme du foie, organe majeur de détoxification de l’organisme. Nous avons choisi deux perturbateurs endocriniens et polluants organiques persistants, qui activent des voies de signalisation différentes: la 2, 3, 7, 8 tétrachlorodibenzo-p-dioxine (TCDD), agissant via le récepteur aux hydrocarbures aromatiques (AhR), et l’α-endosulfan, un pesticide organochloré, qui peut agir via la voie du récepteur aux oestrogènes (ER) ou du récepteur X aux pregnanes (PXR). Notre objectif est de déterminer l’effet du mélange de ces polluants par rapport à chaque polluant isolé sur la régulation de certaines voies du métabolisme hépatique in vitro dans la lignée hépatocytaire humaine, HepaRG. Dans une première publication, une étude du transcriptome de cellules HepaRG différenciées a été effectuée. Ces cellules ont été exposées pendant 30 heures à 25nM de TCDD, 10μM d’α-endosulfan, ou au mélange. Nous avons observé que le mélange inhibe fortement l’expression de certains gènes impliqués dans le métabolisme glucidique et dans celui des alcools. Dans une seconde étude, nous avons donc étudié le mécanisme d’action du mélange sur le métabolisme glucidique. L’expression de deux gènes de la néoglucogenèse hépatique, le transporteur de glucose 2 (Glut2) et la glucose 6 phosphatase (G6Pc), est réduite de plus de 80% par le mélange. L’expression d’autres gènes du métabolisme glucidique (pyruvate kinase, glycogène synthase, glycogène phosphorylase, pyruvate déhydrogénase 2) est aussi diminuée, suggérant que le mélange peut affecter ce métabolisme de manière significative. De plus, la production de glucose diminue de 80% avec le mélange dans des conditions néoglucogéniques. En condition glycolytique, l’oxydation du glucose en CO2 diminue de 30% après 72 heures d’exposition au mélange. Un traitement à plus long terme (8 jours) avec des doses plus faibles des polluants (0.2 à 5nM de TCDD, 3μM d’α-endosulfan) diminue aussi l’expression de la G6Pc et de Glut2. Nous avons montré que la TCDD active bien la voie du AhR, et que le ER est impliqué dans l’action de l’α-endosulfan. Dans la troisième partie de cette thèse, nous avons étudié la régulation de plusieurs enzymes impliquées dans le métabolisme de l’alcool (alcool déshydrogénases, ADHs, cytochrome P450 2E1, CYP2E1) après l’activation du AhR. Les agonistes du AhR entrainent la diminution de l’expression des ARNm des ADH1, 4, 6 et du CYP2E1 et des protéines correspondantes. Nous avons montré que cette régulation utilise la voie génomique du AhR. De plus, cet effet est également observé après traitement de 8 jours par de faibles doses de TCDD. L’exposition chronique de l’Homme à de faibles doses de xénobiotiques en mélange pourrait affecter le métabolisme glucidique hépatique et contribuer, en partie, au développement du syndrome métabolique
Epidemiological studies have shown that exposure to certain xenobiotics is associated with an increased prevalence of metabolic diseases. Humans are exposed to mixtures of xenobiotics in a chronic and inevitable way. We studied the effects of the interaction of two xenobiotics on metabolism in the liver, the major organ for detoxification in the body. We chose two endocrine disruptors and persistent organic pollutants which activate different signaling pathways: 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), which uses the AhR (Aryl hydrocarbon receptor) pathway, and α-endosulfan, an organochlorine pesticide, which acts via the PXR (pregnane X receptor) and/or the ER (estrogen receptor) pathway. Our aim was to determine the effects of this pollutant mixture, as compared to each pollutant alone, on the regulation in vitro of some hepatic metabolism pathways in the human hepatic cell line, HepaRG. In the first publication, a transcriptomic study of differentiated HepaRG cells was performed. The cells were exposed for 30h to 25nM TCDD, to 10 µM α-endosulfan or to the mixture. We observed that the mixture strongly inhibited the expression of some genes involved in the metabolism of glucose and alcohol. In the second study, we studied the mechanism of action of the mixture of pollutants on the metabolism of glucose. The expression of two genes involved in hepatic gluconeogenesis, glucose transporter 2 (GLUT2) and glucose-6-phosphatase (G6Pc), were reduced 80% by the mixture. The expression of other glucose metabolism genes (pyruvate kinase, glycogen synthase, glycogen phosphorylase, pyruvate dehydrogenase 2) also was decreased suggesting that the mixture might impact markedly carbohydrate metabolism. Furthermore, glucose production decreased 40% with the mixture under gluconeogenic conditions. Under glycolytic conditions, the oxidation of glucose into CO2 decreased 30% after 72h of exposure of the cells to the mixture. Long-term treatment (8 days) with lower doses (0.2 to 5 nM TCDD, 3 µM α-endosulfan) similarly decreased G6Pc and GLUT2 expression. We showed that TCDD activated the AhR pathway, and that ER was partly involved in the α-endosulfan effect. In the third part of this thesis, we studied the regulation of several enzymes involved in the metabolism of alcohol (alcohol dehydrogenase, ADH, cytochrome P450 2E1, CYP2E1) after activation of AhR. AhR agonists led to a decrease in the amounts of mRNAs for ADH1, 4, 6 and CYP2E1 and the corresponding proteins. We showed that this regulation uses the AhR genomic pathway. Furthermore, this effect was also observed after 8 days of treatment with lower doses of TCDD. Chronic exposure of individuals to low doses of xenobiotics in mixtures might significantly affect hepatic carbohydrate metabolism and be a contributing factor for the development of the metabolic syndrome

Estilos ABNT, Harvard, Vancouver, APA, etc.

10

Gadupudi, Gopi Srinivas. "PCB126-induced metabolic disruption: effects on liver metabolism and adipocyte development". Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2208.

Texto completo da fonte

Resumo:

Recently, persistent organic pollutants such as polychlorinated biphenyls (PCBs) were classified as “metabolic disruptors” for their suspected roles is altering metabolic and energy homeostasis through bioaccumulation in liver and adipose tissues. Among PCBs, a specific congener, 3,3',4,4',5-pentachlorobiphenyl (PCB126), is a potent arylhydrocarbon receptor (AhR) agonist and elicits toxicity similar to the classic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). PCB126 levels found in human blood are particularly associated with diabetes and nonalcoholic fatty liver disease (NAFLD) in humans, however the mechanisms are unclear. We hypothesized that the accumulation of PCB126 disrupts carbohydrate and lipid metabolism by altering the functions of liver and adipose tissues. Hence, our objective was to characterize PCB126 induced-metabolic disruption and the underlying molecular mechanisms that cause toxicity. Separate animal studies were performed using a rat model to understand the time- and dose-dependent effects after PCB126 administration. The chronology of PCB126 toxicity showed early decreases in serum glucose level at 9 h, worsened in a time-dependent way until the end of the study at 12 d. Lipid accumulation and the liver pathology also worsened over time between 3 d and 12 d post administration. These observed effects in the liver were also found to be dose-dependent. The decrease in serum glucose was a result of a decrease in the transcript levels of gluconeogenic and glycogenolytic enzymes, necessary for hepatic glucose production and hence the maintenance of steady glucose levels in the blood. Phosphoenolpyruvate carboxykinase (PEPCK-C), the rate limiting enzyme of gluconeogenesis, was found to be significantly decreased upon exposure to PCB126. The expression levels of peroxisome proliferator-activated receptor alpha (Pparα) and some of its targets involved in fatty acid oxidation were also found to be time and dose-dependently decreased upon exposure to PCB126. In an attempt to understand the molecular targets that may cause these dual effects on both gluconeogenic and fatty acid oxidation, we found that PCB126 significantly decreases phosphorylation of the cAMP response element-binding protein (CREB). CREB is a nuclear transcription factor that is activated in the liver through phosphorylation; to switch-on the transcription of enzymes that catalyze gluconeogenesis and fatty acid oxidation, in order to meet energy demands, especially during fasting. Further, to understand the toxicity of PCB126 on adipose tissue, a human pre-adipocyte model that can be differentiated into mature adipocytes was used. In these studies, we found that exposure of preadipocytes to PCB126 resulted in a significant reduction in their ability to differentiate into adipocytes. This results in decreased lipid accumulation in the adipocyte. Reduction in the differentiation by PCB126 was associated with down regulation in transcript levels of a key adipocyte transcription factor, PPARγ and its transcriptional targets necessary for adipogenesis and adipocyte function. These inhibitory effects of PCB126 on the regulation of PPARγ and the initiation of adipogenesis were mediated through activation of AhR. Overall, this work shows that PCB126 disrupts nutrient homeostasis through its effects on the function of target tissues; liver and adipose. PCB126 significantly alters the nutrient homeostasis through its effects on gluconeogenesis and fatty-acid oxidation necessary for glucose and energy regulation during fasting. In addition, PCB126 interrupts the storage functions of adipose tissue by inhibiting adipogenesis and thus disrupts lipid storage and distribution

Estilos ABNT, Harvard, Vancouver, APA, etc.

11

Farmer, Ryan Michael. "Coordination of Carbon Dioxide and Nitrogen Metabolism in Rhodobacter sphaeroides". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365519943.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

12

Negri, Víctor Augusti 1986. "Estudo do metabolismo de CO2 em Propionibacterium acidipropionici visando o aumento no rendimento da produção de ácido propiônico". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316757.

Texto completo da fonte

Resumo:

Orientador: Gonçalo Amarante Guimarães Pereira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-25T04:53:49Z (GMT). No. of bitstreams: 1 Negri_VictorAugusti_M.pdf: 12106388 bytes, checksum: d15b4a2052af5e412ac086681ebf3a4b (MD5) Previous issue date: 2014
Resumo: Propionibacterium acidipropionici é uma bactéria gram-positiva que apresenta a capacidade de produzir ácido propiônico em sua via fermentativa, composto de grande importância na indústria petroquímica e alimentícia. Tendo-se em vista que esse ácido é hoje obtido através de derivados do petróleo, P. acidipropionici vem sendo apontada como uma potencial plataforma industrial na produção de ácido propiônico. Uma das características que enfatizam a sua utilização está a sua capacidade em fixar CO2 e direcioná-lo para a produção de ácido propiônico. Entretanto, pouco se sabe sobre esse fenômeno em propionibactérias. O presente trabalho teve como objetivo caracterizar e estudar o metabolismo de assimilação de CO2 em P. acidipropionici, visando avaliar a relevância do mesmo na fermentação desta bactéria. Através da análise do genoma e resultados prévios de expressão global foram identificados potenciais genes envolvidos tanto na assimilação de CO2 quanto na produção de ácido propiônico, destacando-se a enzima piruvato carboxilase como uma importante candidata envolvida na fixação de CO2. Dados de expressão dessa enzima indicaram que a mesma tem sua expressão aumentada quando a bactéria é cultivada em glicerol como fonte de carbono, condição em que há uma maior produção de ácido propiônico. Outros genes que se destacaram foram os genes do metabolismo de biotina, cofator importante em enzimas fixadoras de dióxido de carbono. Foi descrito que os genes envolvidos na sua síntese estão ausentes em seu genoma e que os genes envolvidos em sua assimilação se mostraram diferencialmente expressos ao fim das fermentações em glicerol e glicose, indicando uma possível carência metabólica dessa vitamina. Adicionalmente, foi reportado que a assimilação de CO2 pode ocorrer em diferentes fontes de carbono, podendo apresentar até 25% de ácido propiônico e até 32% do ácido succínico, contendo pelo menos um carbono proveniente do CO2. Tais dados revelaram que a assimilação de CO2 é provavelmente um fenômeno recorrente e relevante em P. acidipropionici, o que reforça essa bactéria como uma promissora plataforma industrial. Por fim, experimentos realizados em biorreator indicaram que ambientes com alta disponibilidade de CO2 podem levar a um aumento expressivo da produção de ácido succínico, intermediário da via do ácido propiônico e também um importante produto de interesse da indústria química
Abstract: Propionibacterium acidipropionici is a gram-positive bacterium that has the ability to produce propionic acid through its fermentative pathway, a highly important compound in petrochemical and food industry. In view that nowadays this acid is obtained through petroleum derivatives, P. acidipropionici is being appointed as an important candidate as an industrial platform in propionic acid production. One of the characteristics that emphasize its use is the ability to fix CO2 and direct the assimilated carbon to the production of propionic acid. Little is known about this phenomenon in propionibacteria, however it¿s occurrence is described when the bacterium is cultivated in glycerol as its only carbon source. The present work had as objective to characterize and study the CO2 assimilation mechanism in P. acidipropionici, aiming to evaluate how relevant this mechanism is in its fermentative metabolism. Through genome analysis, genes and pathways potentially involved in this process were identified. The analysis highlights the enzyme pyruvate carboxylase, a propionic acid cycle¿s acting enzyme and little distributed in Propionibacteria, and the genes involved in biotin¿s metabolism, a vitamin that acts as an important cofactor in CO2 fixation reactions in bacteria. The biotin production pathway is not complete in P. acidipropionici, being observable in this project that in fact there is a deficiency in its growth in the absence of the same. Seeking trancriptional clues of the phenomenon and having glycerol as carbon source, a global gene expression analysis of the fermentation of P. acidipropionici was performed in glycerol, glucose and sugarcane juice in different points of bacterial growth (RNASeq). Interestingly, the most differentially expressed enzyme of the fermentative pathway in glycerol is the enzyme pyruvate carboxylase. The biotin related pathways are also differentially expressed at the final stages of the bacterium¿s fermentation, what can be related to a requirement of this vitamin at these stages. The supplementation of this vitamin was performed at the three studied carbon sources. However, no difference in growth or acids production was found. Aiming to explore in which situations the CO2 fixation happens, fermentations with six different carbon sources supplemented with carbon-13 containing sodium bicarbonate were performed. It was evaluated from this experiment that the CO2 assimilation occurs in all studied carbon sources, and that about 1/4 of the propionic acid total has a carbon that comes from the diluted bicarbonate. The generated data reveals that the phenomenon is relevant in P. acidipropionici. Lastly, the effect of sodium bicarbonate supplementation in P. acidipropionici fermentations having glycerol as carbon source was studied. As a result, an expressive increase in the production of succinic acid was observed, another fermentation final product in propionibacteria. Such phenomenon, therefore, could also be more explored for the production of this second acid, equally important in the industrial point of view
Mestrado
Genetica de Microorganismos
Mestre em Genética e Biologia Molecular

Estilos ABNT, Harvard, Vancouver, APA, etc.

13

Makley, Meghan Katherine. "NMR analyses show TCDD elicits differences in hepatic metabolism in female C57BL/6 mice and Sprague-Dawley rats". Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1230048333.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

14

Sun, Mingwei. "REGULATION OF CIRCADIAN CLOCKS AND METABOLISM BY SYNTHETIC AHR AGONIST BETA-NAPHTHOFLAVONE IN MICE". OpenSIUC, 2016. https://opensiuc.lib.siu.edu/dissertations/1253.

Texto completo da fonte

Resumo:

The circadian clock system is essential for mammals to adapt to environmental conditions such as light-dark cycles and to manage the optimal timing for cyclical physiological processes, including sleep-wakefulness, fasting-feeding and multiple aspects of metabolism. The circadian timing system is arranged in hierarchical fashion, with the master clock in the suprachiasmatic nucleus (SCN) of the hypothalamus, acting as the pace-maker and maintaining synchrony among clocks found in every organ system throughout the body. The core molecular clock consists of two interconnected transcriptional-translational feedback loops comprising core clock components: Brain and Muscle Arnt-Like protein1 (BMAL1), Circadian Locomoter Output Cycles Kaput (CLOCK), Period (PER), Cryptochrome (CRY), Nuclear Receptor family1 D1 (REV-ERB) and Retinoic acid-related Orphan Receptor (ROR). Circadian clock disruptions, through environmental changes to light-dark cycles or through genetic modification of core clock genes cause metabolic disturbances. Aryl hydrocarbon receptor (AhR), also known as the dioxin receptor, mediates systemic metabolism and toxicity of a range of environmental contaminants. Epidemiological studies have established a positive correlation between exposure to dioxins and other synthetic organic chemicals and metabolic diseases such as diabetes and dyslipidemia. Animal research have supported these findings by showing that AhR activation has detrimental effects on glucose and lipid homeostasis. Mechanisms for AhR-mediated metabolic dysfunction remain unknown. Coincidently, both AhR and many core clock components, for example BMAL1 and CLOCK, belong to the basic helix-loop-helix/Per-Arnt-Sim (bHLH-PAS) domain family. Previous studies have linked AhR signaling to circadian rhythm. Importantly, activation of the AhR can impair transcriptional activity of the CLOCK: BMAL1 heterodimer in cultured cells. However, because the AhR is differentially expressed among the body’s tissues, its activation may have distinctive, tissue-specific effects on the hierarchical circadian clock oscillators in vivo, which have not been investigated. Therefore, this dissertation is designed to examine the short-term and long-term effects of AhR activation on circadian clocks and downstream clock-regulated metabolic pathways. Specifically, this dissertation is aimed to explore how acute and chronic activation of AhR affects rhythmic aspects of behavior, as well as clock-controlled glucose and lipid metabolism. In the acute AhR activation model, a single dose of the synthetic AhR agonist, β-Naphthoflavone (BNF), was administered to C57Bl/6J wild type mice. Circadian behavior was monitored before and after acute AhR activation. Circadian expression of core clock genes, as well as key metabolic genes in the liver, skeletal muscle and adipose tissue were examined. Compared to the vehicle group, BNF-treated mice displayed a transient loss of behavioral rhythmicity and delayed activity onset, which suggest that acute activation of AhR acts directly on the central clock, the suprachiasmatic nucleus of the hypothalamus. In contrast, circadian oscillations of core clock genes were not eliminated in the peripheral tissues (liver, skeletal muscle and adipose tissue), but changes were observed in their rhythmic amplitude or phase. Rhythms of key enzymes related to glucose and lipid metabolic pathways in the liver and adipose were decreased while those in the skeletal muscle were increased. These results indicate that acute AhR activation affects the central clock and peripheral clock differently. Moreover, acute AhR activation significantly dampened the rhythm of genes involved in lipogenesis, lipolysis and lipid storage. In the chronic AhR activation model, C57Bl6/J mice were exposed to BNF for a month to explore whether long-term AhR activation can cause bigger disruption of circadian clocks and lead to metabolic dysfunction in vivo. Unexpectedly, general circadian behavior was maintained although after each dose of BNF there was a consistent, transient loss of behavioral rhythmicity and significant phase delay (about 30 minutes) in BNF-treated mice. Liver and skeletal muscle clocks were not significantly altered after 4 doses of BNF, and the in-phase oscillations of core clock genes in liver and skeletal muscle suggested a functional SCN as well as the two peripheral clocks. However, the adipose clock was significantly disrupted. Altered clock-regulated rhythms in lipid metabolism genes are associated with impaired lipid storage functions in white adipose tissues and deregulated plasma lipids in BNF-treated mice. The results of acute and chronic AhR activation support a significant interaction of AhR with the circadian clock system. Although future studies are needed to elucidate how AhR signaling specifically interacts with the clock in different cell types, the current research establishes a model for studying the crosstalk between AhR and circadian rhythm and provides new perspectives into the mechanisms of metabolic diseases correlated with exposure to synthetic organic chemicals.

Estilos ABNT, Harvard, Vancouver, APA, etc.

15

Stanton, Rebecca (Beckye) Joy. "Effects of TCDD (2,3,7,8-tetrachlorodibenzo-[rho]-dioxin) and estrogen on fatty acid metabolism in chickens (Gallus domesticus) /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

16

Giuntoli, Alberto. "Increased carbon dioxide concentration affects photoinhibition of photosynthesis in wheat and grapevine in the field". Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327070.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

17

Souza, Amanda Pereira de. "A cana-de-açucar e as mudanças climaticas : efeitos de uma atmosfera enriquecida em 'CO IND. 2' sobre o crescimento, desenvolvimento e metabolismo de carboidratos de Saccharum ssp". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/317739.

Texto completo da fonte

Resumo:

Orientadores: Marcos Silveira Buckeridge, Marilia Gaspar
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-09T03:07:16Z (GMT). No. of bitstreams: 1 Souza_AmandaPereirade_M.pdf: 752519 bytes, checksum: 0abdf68fd1d19b70a0af931741ccf052 (MD5) Previous issue date: 2007
Resumo: Desde o início da Revolução Industrial as concentrações de CO2 atmosférico aumentaram em cerca de 30% e estimativas apontam que esta concentração poderá atingir aproximadamente 720 ppm até a metade deste século. Estudos sobre o efeito do alto CO2 no desenvolvimento de diversas espécies vegetais já foram realizados, porém poucos com espécies de gramíneas tropicais do tipo C4, como é o caso da cana-de-açúcar. Considerando a importância econômica da cana e seu potencial na obtenção de biocombustíveis é importante saber como esta cultura irá responder ao aumento previsto na concentração de CO2 atmosférico. Sendo assim, o objetivo deste trabalho foi estudar o efeito do aumento do CO2 atmosférico sobre o crescimento, desenvolvimento e metabolismo de carboidratos da cana-de-açúcar visando avaliar o potencial de seqüestro de carbono e o impacto das mudanças climáticas sobre a produtividade. Parâmetros fisiológicos, bioquímicos e moleculares foram analisados em plantas cultivadas em câmaras de topo aberto durante 50 semanas com atmosfera de CO2 ambiente (~370 ppm) e elevada (~720 ppm). Os principais resultados obtidos indicam incremento em altura, na taxa fotossintética e em biomassa de colmo e folhas das plantas cultivadas sob elevado CO2. Ao final das 50 semanas foi detectado no colmo das plantas crescidas em tais condições, um aumento no teor de sacarose, de fibras e no conteúdo de celulose. A análise do perfil de transcritos de folhas após 9 e 22 semanas de cultivo usando microarranjos revelou expressão diferencial de 37 genes, sendo que 14 foram reprimidos e 23 foram induzidos e correspondem principalmente a genes de fotossíntese e desenvolvimento. Nossos resultados indicam que a cultura da cana-de-açúcar tem capacidade para seqüestro de carbono e potencial para aumento na produtividade em condições de alta concentração de CO2
Abstract: Since the beginning of the Industrial Revolution, the concentrations of CO2 in the atmosphere increased about 30% and the current forecasts point out that this concentration will reach approximately 720 ppm until the middle of this century. Studies about the effect of CO2 on the development of several plant species have been performed. However, few studies have been performed with tropical grass species having photosynthesis C4, as is the case of sugar cane. Due to the economic importance of sugar cane and its high potential to obtain biofuel, it is important to known how this crop will respond to the forecasted increase in the CO2 concentration in the atmosphere. Therefore, the goal of this work was to study the effects of increased CO2 concentration on growth, development and carbohydrate metabolism of sugar cane aiming the evaluation of the potential of this specie for carbon sequestration and the impact of the global climatic change on its productivity. Physiological, biochemical and molecular features of these plants have been analyzed during 50 weeks of growth in Open-Top-Chambers (OTCs) with ambient (~370 ppm) and elevated (~720 ppm) CO2 concentrations. After 50 weeks of growth under these conditions, we observed an increase of sucrose content, fiber an also in cellulose contents in stems of plants grown under elevated CO2. The microarray analysis of the transcriptome of leaves was obtained after 9 and 22 weeks and revealed differential expression of 37 genes. Fourteen genes were repressed and 23 induced by elevated CO2. The latter correspond mainly to the processes of photosynthesis and development. Our results indicate that the sugar cane crop has a high potential for carbon sequestration and increase of productivity under elevated CO2 concentrations
Mestrado
Biologia Celular
Mestre em Biologia Celular e Estrutural

Estilos ABNT, Harvard, Vancouver, APA, etc.

18

Bui, Peter Hoang. "Functional characterization of the novel dioxin-inducible P450, CYP2S1, and its role in metabolism of carcinogens and eicosanoids". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1973844961&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

19

Lin, Shuhai. "Mass spectrometry-based metabolomics delineates biochemical changes in 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity, high-fructose diet effect, Alzheimer's disease and viral infection". HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1248.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

20

Bostner, Albin. "Carbon dioxide dynamics in agricultural streams : Investigation of two streams draining catchments dominated by agricultural land". Thesis, Uppsala universitet, Luft-, vatten- och landskapslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-421345.

Texto completo da fonte

Resumo:

In recent years, streams draining agricultural land has been suggested to exhibit high carbon dioxide (CO2) concentrations when compared to streams draining other land-types. The transport of carbon from land to ocean is mainly occurring through the chain of inland waters, and with agricultural land today representing 40% of all continental area many of these inland waters are influenced by agricultural land. The aim of this study was to improve the understanding of CO2 dynamics and its control in agricultural streams. Continuous data was collected from two catchments of different scales, near the city of Uppsala, Sweden. Both catchments are typical low-land catchments largely dominated by agricultural land. The measured CO2 concentrations were analyzed to find temporal variations and differences in dynamics between the catchments. The interplay between CO2 and parameters such as dissolved oxygen, discharge and conductivity were analyzed to determine the main drivers for CO2 dynamics. The findings show supersaturation of CO2 concentration during the full length of the measurement periods, with mean CO2 concentrations higher than what have been observed in streams draining other land-type catchments. Diel CO2 cycles were found throughout most of the measurement periods, where manual measurements were conducted to confirm these findings. The diel CO2 patterns were suggested to be heavily dependent on in-situ metabolic control while hydrological factors, such as sufficient discharge, seemed to be needed to produce a good diel CO2 signal. CO2 build-up is suggested to occur in the catchment soil and, when flushed out after rain events, result in an increasing CO2 concentration. This might be one important driver for the high levels in CO2 concentration found in the streams during summer and autumn. Analysis of the catchment areas suggest the percentage of agricultural land and the size of the catchment areas had an impact on hydrology, both for sufficient water flow to exist but also for the CO2 response after rain events. More research is encouraged, where more parameters should be investigated, such as groundwater inputs and carbonate precipitation.
Bäckar som dränerar åkermark har under de senaste åren blivit mer uppmärksammade på grund av nya studier som visat att dessa bäckar tenderar att ha högre CO2-koncentration än bäckar som dränerar andra marktyper. Idag utgör cirka 40% av all kontinentalyta åkermark, då den huvudsakliga transporten av kol från land till hav sker genom sammankopplade vattendrag är därav en förståelse av åkermarkers dränering till bäckar av stor betydelse. Syftet med studien var att förbättra förståelsen av CO2-dynamiken och dess påverkan på bäckar i jordbruksdominerade avrinningsområden. Kontinuerlig data samlades in, samt erhölls från tidigare mätningar, från två avrinningsområden med olika storlekar och markfördelningar nära Uppsala. Båda avrinningsområdena var typiska låglands- avrinningsområden som dominerades av åkermark. Data för CO2-koncentration analyserades för att hitta kort- och långsiktiga variationer i CO2-dynamiken samt undersöka hur denna dynamik skiljer sig mellan avrinningsområden med olika storlek och markfördelning. Samspelet mellan CO2 och parametrar såsom vattenlösligt syre, vattenföring och konduktivitet analyserades för att hitta drivkrafter bakom CO2-dynamiken. Resultatet visar att de undersökta bäckarna var övermättade med CO2 under hela mätperioden, samt att medelkoncentrationerna som uppmättes var högre än vad som observerats i bäckar som dränerar andra landtyper. En dygnsvariation av CO2 observerades under större delar av mätperioderna, manuella prover utfördes för att stärka denna data. Den observerade dygnscykeln av CO2-koncentrationen konstaterades korrelera med den in-situ metaboliska kontrollen medan hydrologiska faktorer, såsom ett tillräckligt högt vattenflöde, visade sig var viktigt för att en CO2-dygnscykel ska existera. De mycket höga toppar av CO2-koncentration som observerats under mätningarna tros bero på ackumulering av CO2 i avrinningsområdenas marker, vilket under nederbörd utarmas och transporteras till bäcken. Vid jämförelse av de två avrinningsområdena föreslogs den procentuella andelen åkermark och storleken av avrinningsområdet ha en stor påverkan på hydrologin, både för att ett tillräckligt vattenflöde ska existera men också för CO2-responsen vid större nederbördsmängder. Mer forskning behövs där fler parametrar börs ta i beaktning, till exempel in-situ karbonutfällning och inflöde av CO2 via grundvatten, för att få en bättre bild över åkermarkens påverkan på CO2-dynamik i bäckar.

Estilos ABNT, Harvard, Vancouver, APA, etc.

21

Cai, Yanling. "Titanium Dioxide Photocatalysis in Biomaterials Applications". Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160634.

Texto completo da fonte

Resumo:

Despite extensive preventative efforts, the problem of controlling infections associated with biomedical materials persists. Bacteria tend to colonize on biocompatible materials and form biofilms; thus, novel biomaterials with antibacterial properties are of great interest. In this thesis, titanium dioxide (TiO2)-associated photocatalysis under ultraviolet (UV) irradiation was investigated as a strategy for developing bioactivity and antibacterial properties on biomaterials. Although much of the work was specifically directed towards dental materials, the results presented are applicable to a wide range of biomaterial applications. Most of the experimental work in the thesis was based on a resin-TiO2 nanocomposite that was prepared by adding 20 wt% TiO2 nanoparticles to a resin-based polymer material. Tests showed that the addition of the nanoparticles endowed the adhesive material with photocatalytic activity without affecting the functional bonding strength. Subsequent studies indicated a number of additional beneficial properties associated with the nanocomposite that appear promising for biomaterial applications. For example, irradiation with UV light induced bioactivity on the otherwise non-bioactive nanocomposite; this was indicated by hydroxyapatite formation on the surface following soaking in Dulbecco’s phosphate-buffered saline. Under UV irradiation, the resin-TiO2 nanocomposite provided effective antibacterial action against both planktonic and biofilm bacteria. UV irradiation of the nanocomposite also provided a prolonged antibacterial effect that continued after removal of the UV light source. UV treatment also reduced bacterial adhesion to the resin-TiO2 surface. The mechanisms involved in the antibacterial effects of TiO2 photocatalysis were studied by investigating the specific contributions of the photocatalytic reaction products (the reactive oxygen species) and their disinfection kinetics. Methods of improving the viability analysis of bacteria subjected to photocatalysis were also developed.

Estilos ABNT, Harvard, Vancouver, APA, etc.

22

Minnaar, Martha Maria. "Constraints on photosynthesis and antioxidant metabolism in winter and summer crops induced by sulphur dioxide fumigation / Martha Maria Minnaar". Thesis, North-West University, 2012. http://hdl.handle.net/10394/9522.

Texto completo da fonte

Resumo:

Recently, major advances have been made in developed countries elucidating the effects of air pollutants on crop plants. In contrast, similar studies on the effects of elevated SO2 concentrations on crops in developing countries such as South Africa are far less advanced. In South Africa, fossil fuel combustion is the main source of energy for most of the country. The tremendous increase in population size and consequental increase in energy demand has lead to considerable increases in fossil fuel burning. This phenomenon has lead to increases in tropospheric air pollutants such as SO2, NO2 and the secondary pollutant, O3. These increases, combined with climatic variations are subject of much concern in agricultural sectors. Fortunately, through many research studies done in European and other developed countries, threshold values have been established for selected crops in an attempt to mitigate the damage done by SO2 and other air pollutants. However, it is with due care that we apply these legislatory thresholds since the environmental conditions in the Southern hemisphere differs greatly from that of the Northern hemisphere. The main aims of this study was firstly to determine the physiological and biochemical basis of SO2 induced inhibition in the C3 and C4 crops, Brassica napus and Zea mays, respectively, and secondly, to study their response with special reference to photosynthesis. The combination of different SO2 levels and induced drought was also investigated. It was hypothesised that SO2 will impair the photosynthetic capacity of both Brassica napus and Zea mays test plants, but that with the addition of drought as co-stress, partial stomatal closure would lead to a mitigation of the SO2-effect on the photosynthetitc apparatus of the mentioned crops. Most of the research that has been done on air pollutants was short term studies, focused on generating dose-response data only over a few weeks of growth. Short term exposures do not answer questions on how initial constraints on photosynthesis could affect crops at a later stage, i.e. how and if these inhibitions affect the yield. In the present study, crops were grown for an entire growth season, from germination until harvest in open-top chambers (OTCs) in an attempt to link early photochemical inhibition to the reduction in yield. OTCs are internationally accepted as the best method to assess the effect of pollutant dosage on crops. Two crops, Brassica napus (C3) and Zea mays (C4) were cultivated and subjected to SO2 enriched air (50,100 and 200 ppb) for eight hours/day, seven days a week. Control plants only received carbon filtered (CF) air. An additional drought treatment was induced in half of the plants of each SO2 treatment. Experiments specifically focussed on the detrimental effect of SO2 on the photosynthetic capacity of the test plants. The photosynthetic capacity was evaluated using chlorophyll a fluorescence induction and photosynthetic gas exchange measurements in parallel, on a weekly basis. Analysis of the OJIP transients provided a number of parameters estimating the energy fluxes and ratios through photosystem II and the intersystem electron transport chain. Gas exchange parameters were deduced from CO2 response curves (A:Ci curves). The ability of the antioxidant metabolism to detoxify reactive oxygen species (ROS) was determined by measuring the POD activity and comparing it to the H2O2 content for Zea mays leaves over a period of nine weeks. Ultimately the cumulative effect of SO2 on the yield was evaluated by determining the shoot mass of Brassica napus and the cob mass of Zea mays. Elevated SO2 concentrations resulted in the partial destruction of chlorophyll pigments, leading to the formation of yellow chlorotic regions in both Brassica napus and Zea mays leaves. These visual effects appeared long after first changes occurred in photosystem II function or photosynthetic gas exchange. In addition to the visual damage, results revealed that elevated SO2 concentrations lead to an impaired photosynthetic capacity in both Brassica napus and Zea mays plants, especially concerning PSII function. The decline in photosynthetic capacity was mainly due to a loss in stomatal functionality, indicated as a reduction in the stomatal conductance for both Brassica napus and Zea mays plants. This was true for well watered and drought stressed treatments in both C3 and C4 crops. The reduced photosynthetic capacity was due to stomatal limitation and to a greater extent, biochemical (mesophyll) limitation. Mespohyll limitation was evident by the decrease in Rubisco activity (Brassica napus: C3) and PEPc activity (Zea mays: C4), in well watered and drought stress treatments. The inability to effectively regenerate ribulosebisphosphate (Brassica napus: C3) and phosphoenolpyruvate (Zea mays: C4) in well watered and drought stressed plants was another mesophyll limitation that contributed to the decline in photosynthesis. By in depth analysis of the chlorophyll a fluorescence transients according to the JIP test, the sites of inhibition in the photosynthetic electron transport chain were elucidated. The changes in the fluorescence transients revealed that the inhibition of the primary processes of photochemistry was mainly due to uncoupling of the oxygen evolving complex in well watered Zea mays and drought stressed Brassica napus plants and to the inhibition of the reduction of end electron acceptors beyond PSI in well watered and drought stressed Brassica napus plants and drought stressed Zea mays test plants. In Zea mays the source of the inhibition of the primary photochemistry through the decline in the reduction of end electron acceptors, was further investigated by in depth analysis of the I-P phase of the OJIP fluorescent transients, i.e. a segment only through photosystem I (PC→RE). The inhibition in well watered and drought stressed treatments were found, not only to be a result of the reduced pool size of electron acceptors, but was also due to a decline in the rate at which end electron acceptors were being reduced. These constraints on the functioning of the photosynthetic electron transport chain were reflected by the inhibition of CO2 assimilation rate, the decline in Rubisco activity (C3 plants) and PEPc anctivity (C4 plants), and decline in the regeneration rate of ribulosebisphosphate (C3 plants) and phosphoenolpyruvate (C4 plants) both due to the decreasing production of reduction equivalents in the light phase. This means that although the fluorescence transients are measured within one second in the dark adapted state, they provide a reliable measure of the whole photosynthetic electron transport chain. SO2 affected both the stomatal function and photosynthetic capacities of Zea mays and Brassica napus. The SO2-related stomatal closure resulted in a decrease in CO2 influx into the leaf and thus a decline in CO2 assimilation. This phenomenon was corroborated by the large decrease in water use efficience in Zea mays and Brassica napus. A marked SO2-concentration dependent decline in the shoot biomass in well watered and drought stressed Brassica napus was evident. Similarly, a reduction in yield occurred in Zea mays test plants, namely reductions in cob mass, in both well watered and drought stressed treatments. The data of the current investigation presented clearly indicate that marked impairment of photosynthesis and yield reduction in the crops, Zea mays and Brassica napus, occured at SO2 concentrations of 50 ppb.These findings proved the first hypothesis of this study to by true in that SO2 adversely affects the photosythetic capacity of crop plants. In Zea mays, more energy was expended towards growth than detoxification of sulphur metabolites. Due to this fact, Zea mays plants still grew to a considerable length with less energy available for cob formation. An increase in H2O2 content due to elevated SO2 concentrations, lead to the degradation of chlorophyll molecules and inhibition of the photosystems which consequentially inhibited the photosynthetic capacity of well watered and drought stressed Zea mays plants. The effectiveness of the antioxidant metabolism to remove H2O2 from mesophyll cells was displayed by the overall decrease in H2O2 content for WW and DS treatments after 9 weeks fumigation. This was achieved by the increased scavenging enzyme activity (increased POD activity) that effectively removed the ROS from the mesophyll cells. Ultimately the data showed that the C3 plant, Brassica napus, was more adversely affected by elevated SO2 concentrations, reducing the photosynthetic assimilation rate greatly. Drought stress however, ameliorated the damaging effect of SO2 on the photosystems to some extent, proving the second hypothesis true for Brassica napus plants. Zea mays plants however showed greater sensitivity towards elevated SO2 concentrations with the addition of drought as a costressor, while amelioration of the inhibitory effect through stomatal closure, proved not to be effective. These findings proved that the second hypothesis was thus only partially proven to be true, and only at low SO2 concentrations for Zea mays crop plants. Within natural environments there may be a magnitude of biotic and abiotic stresses being inposed on crops. The work done in this study is thus of great value to the agricultural sector in early determination of how multiple stressors (SO2 and drought in this case) might affect yield. Management plans can be implemented accordingly. This fact emphasises the magnitude of the relevance and the importance of multiple stress-response studies done on crops, such as the present.
Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

Estilos ABNT, Harvard, Vancouver, APA, etc.

23

Dougherty, Edward J. "Analysis of the role of bHLH/PAS proteins in aryl hydrocarbon receptor signaling". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002441.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

24

Pereira, Adriano José. "Gradientes de oxigênio, glicose, dióxido de carbono e lactato em diferentes compartimentos vasculares". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/5/5152/tde-27102011-160323/.

Texto completo da fonte

Resumo:

INTRODUÇÃO: Apesar do amplo uso da medida da saturação central de oxigênio como meta terapêutica em pacientes de terapia intensiva, diferenças absolutas em relação à saturação venosa mista existem. As causas desses gradientes, bem como o comportamento das mesmas ao longo do tempo nas doenças graves não foram completamente esclarecidas. Considerando que a maioria das intervenções atualmente empregadas para reverter desequilíbrios de oxigenação tecidual presentes nos pacientes graves é direcionada, direta ou indiretamente, ao coração; a situação particular de elevada taxa de extração de oxigênio basal do miocárdio e a ausência de ferramentas de monitorização do impacto miocárdico dessas intervenções, o presente estudo, diante da possibilidade teórica da participação do efluente do seio coronário nessas diferenças centrais para pulmonares, não só para a saturação de oxigênio (SO2), analisou o comportamento da SO2, pressão parcial de dióxido de carbono (PCO2), lactato e glicose, em diferentes modelos de hipóxia e compartimentos vasculares, com ênfase na avaliação do metabolismo miocárdico e seu impacto nos gradientes centrais para pulmonares. MÉTODOS: 37 porcos, machos, com peso em torno de 35 Kg, sedados e ventilados mecanicamente, foram estudados após indução de quatro diferentes tipos de injúria hipóxica (hipóxia anêmica, estagnante, hipóxica e sepse), sendo 8 animais por grupo e mais 5 controles. Além de variáveis hemodinâmicas e de oxigenação, SO2, PCO2, lactato e glicose foram medidos, em diferentes momentos, em 9 compartimentos vasculares distintos, incluindo o seio coronário (artéria femoral, veia cava inferior e superior, átrio direito, ventrículo direito, artéria pulmonar, veia suprahepática direita e veia porta). PRINCIPAIS RESULTADOS: As concentrações de O2, lactato e glicose no efluente do seio coronário apresentaram padrões distintos entre os grupos: troca de substrato energético de lactato por glicose nos grupos hipóxia hipóxica e anêmica, aumento no consumo de ambos os substratos na sepse e ausência de tendência clara no grupo da hipóxia estagnante. Os gradientes de PCO2 entre seio coronário e artéria femoral mantiveram-se estáveis com tendência de alargamento tardio em todos os modelos. Na análise dos demais gradientes regionais, o seio coronário apresentou a menor SO2 do organismo, as menores concentrações de lactato, os maiores níveis de PCO2, e esses padrões variaram ao longo do tempo. Mesma tendência evolutiva foi percebida entre os gradientes centrais para pulmonares de O2, lactato, CO2 e glicose e a medida desses mesmos parâmetros no seio coronário. CONCLUSÕES: As concentrações de O2, lactato e glicose no efluente do seio coronário estão relacionadas ao tipo de injúria e não apenas à disponibilidade de substrato energético. Padrões de gravidade, comuns às fases tardias de todos os grupos, puderam ser identificados: qualquer redução da SO2 coronariana; incremento do metabolismo de glicose; produção de lactato pelo miocárdio e surgimento de igualdade ou inferioridade dos níveis da PCO2 coronariana em relação aos valores dos demais compartimentos vasculares do organismo (independentemente da trajetória). A tendência dos gradientes de PCO2 transmiocárdicos seguiu a do débito cardíaco e, certamente, deve refletir fluxo coronariano. A análise dos gradientes regionais se mostrou capaz de permitir a avaliação de contextos orgânicos regionais específicos, como na avaliação do metabolismo hepático, na qual foi possível demonstrar que na hipóxia, a produção de glicose hepática é mantida até o óbito, diferentemente do padrão descrito para a sepse. Por fim, com a análise dos dados do grupo sepse, foi possível demonstrar que: a) assim como os gradientes centrais para pulmonares de SO2 e lactato já foram descritos, gradientes de glicose e PCO2 também existem; b) o seio coronário participa, significativamente, na formação desses gradientes de lactato, CO2 e glicose
INTRODUCTION: Despite of the widespread use of the central venous oxygen saturation measurement as a therapeutic goal in critically ill patients, absolute differences between this measurement and the mixed venous oxygen exist. Causes of these differences, as well the behavior of these gradients in critical illness, are not completely understood. Considering current therapeutic interventions aimed to reverse tissue oxygenation impairment are mediated by increases in cardiac output; the particular scenario in which the heart is not physiologically able to further increase oxygen extraction and the absence of tools to monitoring the myocardium impact of those interventions, the present study, facing the theoretical possibility of the coronary sinus effluent participation in those central to mixed venous differences, has analyzed the oxygen saturation (SO2), carbon dioxide partial pressure (PCO2), lactate and glucose concentrations behaviors over time, in different models of tissue hypoxia and in different vascular sites. Emphasis on the myocardial energetic metabolism and its impact over central to mixed venous gradients was placed. METHODS: 37 pigs, males, weighting about 35 Kg, sedated and mechanically ventilated, were studied after induction of four different hypoxic injury models (sepsis, and anemic, stagnant, hypoxic hypoxia), eight for group and five controls. In addition to hemodynamic and oxygen variables, SO2, PCO2, lactate and glucose were measured in different phases, in 9 distinct vascular sites, including coronary sinus (femoral artery, inferior and superior vena cava, right atria, right ventricle, pulmonary artery, right suprahepatic vein and portal vein). MAIN RESULTS: Concentrations of O2, lactate and glucose in the coronary sinus effluent presented distinctive patterns among groups: shift from lactate to glucose consumption in hypoxic hypoxia and anemic hypoxia groups, increase in both glucose and lactate consumption in sepsis and absence of clear trend in stagnant hypoxia group. PCO2 gradients from systemic artery to coronary sinus presented late enlargement trend in all groups. In the regional gradients analysis comparisons, coronary sinus presented the lowest SO2, the lowest lactate concentrations, the highest PCO2 levels, and these patterns changed over time. Similar evolution trends were observed between central to mixed venous O2, PCO2, lactate and glucose gradients and the same parameters measured in coronary sinus. CONCLUSIONS: Different concentrations of O2, PCO2, lactate and glucose in coronary sinus are related to the type of hypoxic injury and not only to energetic substrate availability. Severity-related patterns, common to all groups in late phases, were identified: any reduction of coronary SO2, shift to glucose consumption, net lactate myocardial production and equality or inferiority of PCO2 levels related to other vascular compartments (independently of trend). Trends in transmyocardial PCO2 gradients followed cardiac output ones and, certainly, should mirror coronary blood flow. Regional gradients analysis showed suitable to explore specific regional metabolic settings, as in the described example of liver metabolism, in which production of glucose were maintained in all phases by this organ in hypoxic hypoxia groups, differently from the impaired production described in literature for sepsis. At last, data from sepsis group have showed: a) as to the previously known central to mixed venous SO2 and lactate gradients, PCO2 and glucose gradients also exist; b) coronary sinus has participated significantly in formation of central to mixed venous lactate, PCO2 and glucose gradients

Estilos ABNT, Harvard, Vancouver, APA, etc.

25

Nunes, Ana Rita Silva Martins. "O2/CO2-sensitive cyclic AMP-signalling pathway in peripheral chemoreceptors". Doctoral thesis, Faculdade de Ciências Médicas. UNL, 2013. http://hdl.handle.net/10362/9153.

Texto completo da fonte

Resumo:

RESUMO: O corpo carotídeo (CB) é um pequeno órgão sensível a variações na PaO2, PaCO2 e pH. As células tipo I (células glómicas) do corpo carotídeo, as unidades sensoriais deste órgão, libertam neurotransmissores em resposta às variações dos gases arteriais. Estes neurotransmissores atuam quer em recetores pré-sinápticos, localizados nas células tipo I, quer em recetores póssinápticos, localizados nas terminações do nervo do seio carotídeo, ou em ambos. A activação dos recetores pré-sinápticos modula a atividade do corpo carotídeo, enquanto que, a activação dos recetores pós-sinápticos, de carater excitatório, desencadeia um aumento da frequência de descarga das fibras do CSN, com subsequente despolarização dos neurónios do gânglio petroso, e posterior despolarização de um grupo específico de neurónios do centro respiratório central, desencadeando, como resposta final, hiperventilação. Estes recetores pré- e pós-sinápticos podem ser classificados em ionotrópicos ou metabotrópicos, estando os últimos acoplados a adenilatos ciclases transmembranares (tmAC). O mecanismo exato pelo qual as variações dos gases arteriais são detetadas pelo CB não se encontra ainda completamente elucidado, mas tem sido sugerido que alterações nos níveis de cAMP estejam associadas ao mecanismo de deteção de variações de O2 e CO2. Os níveis de cAMP podem ser regulados através da sua via de síntese, mediada por dois tipos de adenilatos ciclases: tmAC sensível aos eurotransmissores e adenilato ciclase solúvel (sAC)sensível a variações de HCO3/CO2, e pela sua via de degradação mediada por fosfodiesterases. A via de degradação do cAMP pode ser manipulada farmacologicamente, funcionando enquanto alvo terapêutico para o tratamento de patologias do foro respiratório (e.g. asma, hipertensão pulmonar, doença pulmonar obstructiva crónica e apneia do sono), que induzem um aumento da actividade do CB.O trabalho descrito nesta dissertação partiu da hipótese de que a actividade do CB é manipulada por fármacos, que interferem com a via de sinalização do cAMP, tendo sido nosso objectivo geral, investigar o papel do cAMP na quimiotransdução do CB de rato, e determinar se a actividade dos enzimas responsáveis pela via de sinalização do cAMP é ou não regulada por variações de O2/CO2. Assim, a relevância deste trabalho é a de estudar e identificar possíveis alvos moleculares (sAC, isoformas de tmAC e PDE) com potencial para serem usados no tratamento de patologias relacionadas com o controlo respiratório. A primeira parte do presente trabalho, centrou-se na caracterização farmacológica da PDE4 no CB e em tecidos não quimiorecetores (e.g. gânglio cervical superior e artérias carótidas), e na observação do efeito de hipóxia aguda na acumulação dos níveis de cAMP, induzidos pelos inibidores de PDE, nestes tecidos. A quantificação de cAMP foi efectuada por técnica imunoenzimática (EIA), tendo sido elaboradas curvas de dose-resposta para os efeitos de inibidores, não específicos (IBMX) e específicos para a PDE2 e PDE4 (EHNA, Rolipram e Ro 20-1724), nos níveis de cAMP acumulados, em situações de normóxia (20%O2/5%CO2) e hipóxia (5%O2/5%CO2). A caracterização das PDE no gânglio cervical superior foi aprofundada, utilizando-se a técnica de transferência de energia de ressonância por fluorescência (FRET) em culturas primárias de neurónios, na presença de inibidores não específicos (IBMX) e específicos para a PDE3 e PDE4 (milrinone e rolipram, respetivamente). Foram igualmente estudadas, através de RT-qPCR, as alterações na expressão de PDE3A-B e PDE4A-D, no gânglio cervical superior, em resposta a diferentes percentagens de oxigénio. Na segunda parte do trabalho investigou-se a via de síntese do cAMP no CB em resposta a variações na concentração de HCO3/CO2. Em concreto, o protocolo experimental centrou-se na caracterização da sAC, dado que a sua actividade é regulada por variações de HCO3/CO2. A caracterização da expressão e regulação da sAC, em resposta a variações de HCO3/CO2 ,foi efectuada no CB e em tecidos não quimioreceptores periféricos (e.g. gânglio cervical superior, petroso e nodoso) por qRT-PCR. A actividade deste enzima foi caracterizada indirectamente através da quantificação dos níveis de cAMP (quantificação por EIA), induzidos por diferentes concentrações de HCO3/CO2, na presença de MDL-12,33-A, um inibidore da tmAC. A expressão das isoformas da tmAC no CB e gânglio petroso foi determinada por RT-qPCR. Adicionalmente, estudámos a contribuição relativa da tmAC e sAC no mecanismo de sensibilidade ao CO2 no CB. Para o efeito foram estudadas as alterações: 1) nos níveis de cAMP (quantificado por EIA) na presença de diferentes concentrações de HCO3/CO2 e ao longo do tempo (5-30 min); 2) na ativação da proteína cinase A (PKA, FRET baseado em sensores) em células tipo I do CB; e 3) na frequência de descarga do CSN (registos) na presença e ausência de ativadores e inibidores da sAC,tmAC e PKA. Por último, foi caracterizada a expressão e actividade da sAC nos quimioreceptors centrais (locus ceruleus, rafe e medula ventro-lateral) através de técnicas de RT-qPCR e EIA. A expressão das isoformas da tmAC foi aprofundada no locus coeruleus através de RT-qPCR. Por fim, comparámos a contribuição da tmAC e sAC nos níveis de cAMP no locus coeruleus em condições de normocapnia e hipercapnia.O nosso trabalho teve os seguintes resultados principais: 1) PDE4 está funcional no corpo carotídeo, artérias carótidas e gânglio cervical superior de rato, embora a PDE2 só se encontre funcional neste último; 2) Os efeitos dos inibidores de PDE nos níveis de acumulação de cAMP foram exacerbados em situações de hipóxia aguda no CB e artérias carótidas, mas foram atenuados no gânglio cervical superior; 3) No gânglio cervical superior, diferentes tipos de células apresentaram uma caracterização específica de PDEs, sugerindo uma subpopulação de células neste gânglio com funções fisiológicas distintas; 4) Embora todas as isoformas de PDE4 e PDE3 estivessem presentes no gânglio, a PDE3a, PDE4b e a PDE4d foram as isoformas mais expressas. Por outro lado, incubações de gânglio cervical superior, em diferentes percentagens de oxigénio, não alteraram (não regularam) significativamente a expressão das diferentes isoformas de PDE neste órgão; 5) a sAC encontra-se expressa e funcional no CB e nos quimiorecetores centrais estudados (locus coeruleus, rafe e medula ventrolateral). A sAC apresenta maior expressão no CB comparativamente aos restantes orgãos estudados, exceptuando os testículos, orgão controlo. Variações de HCO3/CO2 de 0/0 para 24/5 aumentaram os níveis de cAMP no CB e quimiorecetores centrais, tendo sido o aumento mais significativo observado no CB. Concentrações acima dos 24mM HCO3/5%CO2 não induziram alterações nos níveis de cAMP, sugerindo que a actividade da sAC se encontra saturada em condições fisiológicas (normocapnia) e que este enzima não desempenha qualquer papel na deteção de situações de hipercapnia; 6) No CB, a expressão das isoformas tmAC1, tmAC4, tmAC6 e tmAC9 é mais elevada comparativamente à expressão da sAC; 7) Utilizamos diferentes inibidores da tmAC (MDL 12-330A, 500μM, 2’5’-ddADO, 30-300μM, SQ 22536, 200μM) e da sAC (KH7, 10-100μM) para estudar a contribuição relativa destes enzimas na acumulação do cAMP no CB. Tanto a tmAC como a sAC contribuem para a acumulação dos níveis de cAMP em condições de hipercapnia. Contudo, existe um maior efeito destes inibidores nas condições de 12 mM HCO3/2.5%CO2 do que em condições de normocapnia e hipercapnia, sugerindo um papel relevante destes enzimas na atividade do CB em situações de hipocapnia; 8) Não se observaram variações nos níveis de cAMP em resposta a diferentes concentrações de HCO3/CO2 ao longo do tempo (5-30 min). O efeito inibitório induzido por ddADO e KH7 foi sobreponível após 5 ou 30 minutos de incubação em todas as concentrações de HCO3/CO2 estudadas; 9) Por último, verificou-se um aumento na frequência da descarga do nervo do seio carotídeo entre as condições de normocapnia e hipercapnia acídica. Ao contrário do KH7 (10μM), o 2’5’-ddADO reduziu significativamente a frequência de descarga do nervo, quer em condições de normocapnia quer de hipercapnia acídica. Contudo, não se verificou aumento na frequência de descarga do nervo entre normocapnia e hipercapnia isohídrica, sugerindo que a sensibilidade à hipercapnia no CB é mediada por variações de pH. Em conclusão, os resultados decorrentes deste trabalho permitiram demonstrar que, embora os enzimas que medeiam a via de sinalização do cAMP possam ser bons alvos terapêuticos em condições particulares, a sua actividade não é específica para o CB. Os resultados sugerem ainda que o cAMP não é um mediador específico da transdução à hipercapnia neste orgão. Contudo, os nossos resultados demonstraram que os níveis de cAMP são mais elevados em condições fisiológicas, o que sugere que o cAMP possa ter uma função homeostática neste orgão. Por último, o presente trabalho demonstrou que os aumentos de cAMP descritos por outros em condições de hipercapnia, não são observáveis quando o pH se encontra controlado. ------------------ ABSTRACT: The work presented in this dissertation was aimed to establish how specific is cAMP-signaling pathways in the CB mainly in different CO2 conditions and how O2 concentrations alter/drives the manipulation of cAMP signaling in the CB. The experimental studies included in this thesis sought to investigate the role of cAMP in the rat CB chemotransduction mechanisms and to determine whether the enzymes that participate in cAMP signal transduction in the CB are regulated by O2/CO2. We characterized the enzymes involved in the cAMP-signaling pathway in the CB (sAC, tmAC, PDE) under different O2/CO2 conditions. Our results demonstrated that many of these enzymes are involved in CO2/O2 sensing and while they may be useful in treating conditions with alterations in CO2/O2 sensing,they will not be specific to chemoreception within the CB: 1) PDE4 is ubiquitously expressed in CB and non-chemoreceptor related tissues and their affinity to inhibitors change with O2 tensions in both CB and carotid arteries, and 2) sAC and tmAC are expressed in peripheral and central chemo- and non-chemoreceptor tissues and their effect on cAMP levels do not change between normocapnic and isohydric hypercapnic conditions. Our results provide evidence against a specific role of cAMP as a mediator for O2 and CO2 chemotransduction in the rat CB and emphasized the role of pH in CO2 sensitivity of the CB. Furthermore, our results demonstrate that cAMP levels are maintained higher under physiological conditions, supporting recent finding from our lab, which all together suggests that cAMP has a homeostatic function in this organ.

Estilos ABNT, Harvard, Vancouver, APA, etc.

26

George, Mary. "Urea and Non-Protein Nitrogen Metabolism in Infants : With Special Reference to the Sudden Infant Death Syndrome (SIDS)". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5141-1/.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

27

Robertson, Jane Isabella. "The coulometric determination of total inorganic carbon in seawater and the study of the inter-relationship between the planktonic metabolism of carbon dioxide and oxygen". Thesis, Bangor University, 1989. https://research.bangor.ac.uk/portal/en/theses/the-coulometric-determination-of-total-inorganic-carbon-in-seawater-and-the-study-of-the-interrelationship-between-the-planktonic-metabolism-of-carbon-dioxide-and-oxygen(bb8e93ac-5197-474e-a930-021d1b5358f4).html.

Texto completo da fonte

Resumo:

A microprocessor- controlled coulometric system for measuring total inorganic carbon in seawater samples was refined. A precision of 0.5 micromoles/kg (one standard error) from a single sample was routinely achieved in the laboratory. This was reduced to 1.0 micromoles/kg at sea due to an increase in the instrument blank. The system has proved to be a robust and reliable method, well suited for routine plankton productivity measurements and oceanic mapping. The coulometric technique was used in conjunction with an automated Winkler oxygen method to make in vitro and in situ observations of planktonic photosynthetic ana respiratory quotients. In common wi th earlier published observations, a wide range of quotients were obtained. A detailed consideration of analytical and sampling errors led to the conclusion that the quotients could mostly be explained by the stoichiometry of conventional biochemical products and reactants. In situ observations were carried out within mesoCosms:-Tn one field study, particular attention was paid to the correction of data for physical mixing within the mesocosm and exchange with the atmosphere. A dye diffusion study coupled wi th continuous temperature profiles led to the the conclusion tha t the circulation wi thin these bags is complex and cannot be described by use of a one-dimensional vertical diffusion model. The total inorganic carbon measurements determined from vertical CTD profiles during the 1987 RV Challenger cruise were compared to similar stations sampled during the Transient Tracers in the Ocean Programme (1981). Although the TTO measurements were calculated from a potentiometric titra tion there was no evidence for major errors of accuracy.

Estilos ABNT, Harvard, Vancouver, APA, etc.

28

Matarese, Dawn Marie. "Impacts of Rhizosphere CO₂ on Root Phosphoenolpyruvate Carboxylase Activity, Root Respiration Rate and Rhizodeposition in Populus spp". PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/345.

Texto completo da fonte

Resumo:

Roots live in and have evolved in a high carbon dioxide (CO₂) environment, yet relatively little research has been conducted on the impacts of soil dissolved inorganic carbon (DIC) on root metabolism. In this thesis, I explore the impacts of root-zone DIC on whole plant biomass accumulation, water use efficiency, and above-ground gas exchange. In addition, I explore the impacts of root-zone DIC on root processes: root PEP-Carboxylase activity, root respiration rate and root exudation of Krebs cycle organic acids. Root-zone DIC did not impact biomass accumulation, leaf gas exchange parameters or water use efficiency under the growth conditions examined. Root-zone DIC did increase root PEP-Carboxylase activity, but decreased root respiration (both CO₂ production and O₂ consumption) and decreased organic acid exudation rates. Increase in measurement CO₂ partial pressure was found to cause an instantaneous decrease in root CO₂ production, and I provide evidence that changes in root metabolism (CO₂ uptake by roots) are part of the cause of this phenomenon. A hypothesized relationship between root respiration rate and Krebs cycle organic acid exudation was not supported by my data. I conclude that root-zone DIC has important impacts on critical functions of root metabolism, and should be considered as an important abiotic factor much in the same way atmospheric CO₂ is for leaves and whole plant biology.

Estilos ABNT, Harvard, Vancouver, APA, etc.

29

Hoytema, Nanne van [Verfasser], Christian [Akademischer Betreuer] Wild e Michael [Akademischer Betreuer] Friedrich. "The importance of carbon dioxide and dinitrogen fixation for seasonal coral reef metabolism: from organism to ecosystem functioning / Nanne van Hoytema. Gutachter: Christian Wild ; Michael Friedrich. Betreuer: Christian Wild". Bremen : Staats- und Universitätsbibliothek Bremen, 2015. http://d-nb.info/107635842X/34.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

30

Samuelsson, Catrin. "Mineralization rates of organic matter in freshwater sediments when different electron acceptors dominate". Thesis, Linköping University, Department of Thematic Studies, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2417.

Texto completo da fonte

Resumo:

Microbial decomposition of organic matter in aquatic environments plays an important role in natural fluxes of methane and carbon dioxide because the gases are end-products in microbial energy metabolism of organic matter. Microbial metabolism depends on the use of electron donors and electron acceptors in redox reactions that generate energy for growth and maintenance. Energy yields can be used to envisage specific patterns of microbial redox reactions and these predictions depend on the hypothesis that, in a specified environment, the metabolic reaction that yields most energy will dominate over any competing reactions. The energy yield hypothesis indicates a sequential order in electron acceptor use by microbes and also make it tempting to conclude that degradation rate of organic matter is different depending on available electron acceptors. The main purpose of this thesis was to study how the presences of different electron acceptors in freshwater sediments influence organic matter decomposition. Mineralization rates of organic matter under six different conditions regarding the electron acceptor availability were investigated in a river sediment sample from Stångån, Sweden, by measuring carbon dioxide and methane production using gas chromatography. This was done during a fixed time period, in vials containing a mixture of water, sediment, buffer solution and a dominating electron acceptor. Six different metabolic processes; aerobic respiration, denitrification, manganese reduction, iron reduction, sulphate reduction and methanogenesis were included. The overall result indicates similar mineralization rates in both oxic and anoxic treatments. The result also indicates that methane formation was present in the iron reduction and methanogenesis treatments and not evident in the oxic treatments. Sulphate reduction, denitrification and manganese reduction seems to inhibit methanogenesis, but the result also indicates that no significant total mineralization was apparent when NO3- and Mn(IV) were the dominating electron acceptors. The similarities between oxic and anoxic mineralization rates indicates that organic matter degradation rates are not dependent on available electron acceptors and that degradation rates of organic matter are independent of the thermodynamically based energy yield.

Estilos ABNT, Harvard, Vancouver, APA, etc.

31

Schmidt, Carsten. "Entwicklung einer Analysenmethode zur sensitiven Bestimmung von Retinoiden in biologischen Matrizes sowie ihre Anwendung in der Untersuchung des Einflusses von 2,3,7,8-Tetrachlordibenzo-p-dioxin auf den Vitamin-A-Metabolismus". [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966355873.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

32

Jayawardena, Dileepa M. "Effects of Elevated Carbon Dioxide Plus Chronic Warming on Plant Nitrogen Relations and Leaf Hyponasty". University of Toledo / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1588865503446332.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

33

Golly, Francis. "Metabolisme des phospholipides dans les neurones de poulet en culture primaire : modifications induites par la cdp-choline". Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13149.

Texto completo da fonte

Resumo:

Lors de lesions nerveuses par retrait de co::(2), l'etude du metabolisme des lipides a montre qu'un traitement a la cdp-choline ne modifie pas la distribution et la synthese des phospholipides et des acides gras mais provoque par contre une diminution de la liberation d'acides gras. La cdp-choline diminue l'activite phospholiposique a1 au niveau des membranes et protege donc celles-ci de la degradation

Estilos ABNT, Harvard, Vancouver, APA, etc.

34

Mayeux, Bruno. "Ecologie microbienne et métabolisme associé : étude de l'eau interstitielle et de la roche argileuse du Callovo-Oxfordien dans le Laboratoire de Recherche Souterrain de l’Andra (Meuse/Haute-Marne)". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4783/document.

Texto completo da fonte

Resumo:

Dans le cadre des recherches de l'ANDRA sur le confinement en couche géologique profonde de déchets radioactifs, une étude microbiologique a été menée sur l'eau interstitielle et l'argile du Callovo-Oxfordien (–490m, 165 millions d'années). Deux types d'études ont été menés, culturale et moléculaire.Malgré différentes tentatives d'extractions, et comme pour les études antérieures effectuées, aucun ADN n'a pu être extrait au cours de ce travail. Par contre, une approche culturale a permis de mettre en évidence la présence d'une microflore peu dense mais viable et métaboliquement assez variée : neuf espèces aérobies dont quatre facultatives et deux anaérobies strictes, de différents types métaboliques : sulfato-réducteur, réducteur de Fe(III), fermentaire et oxydation complète des substrats en CO2. Au vu des disponibilités in-situ en sources de carbone (SC) et d'énergie nécessaires à la croissance bactérienne, la production d'acétate et autres acides gras volatils ainsi que la production d'hydrogène pourraient potentiellement être actifs dans le Cox. L'étude des produits du métabolisme a permis d'identifier plusieurs agents biotiques (dont H2S) ayant potentiellement une activité biocorrosive. Par ce travail il apparait fondamental que la composante biologique soit prise en compte dans la conception du stockage, afin notamment d'éviter ou de limiter tout apport de matière organique exogène à la formation argileuse. Cette prise en compte biologique apparait cruciale pour tenter de restreindre le réseau trophique bactérien à ces conditions initiales, celles qui sont potentiellement présentes sur le site de stockage, qui concernent les seules SC et d'énergie autochtones
In the framework of research of ANDRA about reversible deep geological radioactive waste, a microbiological study was conducted on pore water and Callovo-Oxfordian clay layer (-490m and 165 million years). Two types of studies were conducted, a cultural approach and a molecular approach.Despite various attempts of extraction, and as for the previous, no DNA could be extracted in this work. However, the cultural approach has highlighted the presence of a sparse microflora but viable and metabolically quite varied: nine aerobes species including four facultative anaerobes and two strictly anaerobes. They represent different metabolic types: sulfate-reducing, iron-reducing, fermentative and complete oxidation of substrates into CO2. In view of the availability of in-situ sources of carbon and energy required for bacterial growth, the production of acetate and other volatile fatty acids as well as hydrogen production could potentially be active in the clay layer of Cox and open to varied bacterial growth.The study of metabolic products has also identified several biotic agents (including hydrogen sulfide) having a potentially biocorrosive activity. Through this work it appears that the biological component is to be taken into account in the design of radioactive waste storage, in particular to avoid or minimize any contribution of exogenous organic matter in the clay formation.This biological consideration appears crucial to attempt to restrict bacterial trophic network on these initial conditions, that is to say those that are potentially present on the storage site, that concern solely autochthonous carbon and energy sources

Estilos ABNT, Harvard, Vancouver, APA, etc.

35

Chu, Sophie Ning-Shin. "Capturing dynamics of inorganic carbon fluxes from diurnal to decadal timescales". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108900.

Texto completo da fonte

Resumo:

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The marine carbon cycle plays an important role in regulating Earth's climate. The vastness of the open ocean and the large variability in the coastal ocean provide obstacles to accurately quantify storage and transport of inorganic carbon within marine ecosystems and between marine and other earth systems. Thus far, the open ocean has been the only true net sink of anthropogenic carbon dioxide (Canthro) emissions. However, ocean storage of Canthro is not uniformly distributed. Changes in water chemistry in the Northeast Pacific were quantified to estimate the amount of Canthro stored in this region over the last decade. This additional Canthro was found to cause acidification and aragonite saturation horizon shoaling at rates towards the higher end of those found in Pacific and Atlantic Ocean basins, making the Northeast Pacific one of the most sensitive regions to the invasion of anthropogenic carbon dioxide. Due to large variability in biogeochemical signals in coastal oceans, it is challenging to accurately assess carbon fluxes across different boundaries, such as tidal exchange between coastal wetlands and coastal oceans. Coastal salt marshes have been suggested to be a large net CO₂ sink, thus designated as a type of "blue carbon." However, accurate and dynamic estimates of carbon fluxes to and from tidal marshes are still premature, particularly carbon fluxes from marshes to the coastal ocean via tidal exchange, often referred to as marsh lateral fluxes. In this thesis, lateral total alkalinity (TA) and dissolved inorganic carbon (DIC) export fluxes were realistically quantified using high frequency time-series, in situ data. High-resolution fluxes permitted a closer look at how marsh generated TA and DIC are being exported over diurnal, spring-neap, and seasonal scales. I investigated the best way to capture variability of marsh exports via traditional bottle sampling and assessed uncertainties associated with different sampling strategies. Marsh TA and DIC exports significantly modified buffering capacity of coastal waters. This work contains the first realistic estimate of TA exports from a tidal salt marsh. Accurate estimates of DIC and TA fluxes indicate the significance of salt marshes to the coastal carbon and alkalinity budgets.
by Sophie Ning-Shin Chu.
Ph. D.

Estilos ABNT, Harvard, Vancouver, APA, etc.

36

Moriya, Henrique Takachi. "Avaliação de transdutores para análise metabólica humana". Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-05102017-091731/.

Texto completo da fonte

Resumo:

A calorimetria indireta para análise do metabolismo humano tem se mostrado um método não invasivo de crescente importância no estudo mais preciso das respostas metabólicas e cardio-respiratórias. Entretanto, o alto custo dos equipamentos aliado à falta de conhecimento das técnicas tem impedido a disseminação do uso de analisadores metabólicos no Brasil. Este trabalho foi desenvolvido com o intuito de oferecer uma visão global dos procedimentos de calorimetria indireta aplicados à avaliação do metabolismo humano sob a abordagem de Engenharia Biomédica. Foram avaliados três transdutores tipicamente utilizados em equipamentos de calorimetria indireta para análise metabólica humana: um transdutor eletroquímico de oxigênio, um transdutor de dióxido de carbono por radiação infravermelha e um transdutor de fluxo em volume tipo turbina. O transdutor de oxigênio mostrou-se bastante confiável, mas com um tempo de resposta bastante elevado para aplicações em análises de respiração a respiração. A principal deficiência do transdutor de dióxido de carbono está no fato de sua configuração proporcionar um aumento significativo na resistência à respiração do indivíduo. Verificou-se que o transdutor de fluxo em volume apresenta um melhor comportamento para um fluxo em torno de 20 litros/minuto. Apesar das limitações apresentadas pelos transdutores, os resultados dos ensaios foram úteis e representativos para a compreensão do funcionamento de um analisador metabólico humano porcalorimetria indireta, evidenciando quais deficiências devem ser sanadas em pesquisas futuras e os cuidados a serem considerados na implantação do laboratório para análise metabólica/respiratória sendo instalado no Laboratório de Engenharia Biomédica da Escola Politécnica da Universidade de São Paulo.
The indirect calorimetry for analysis of the human metabolism has been a no invasive method of increasing importance in the study of metabolic and cardiorespiratory responses. However, the high cost of the equipment ally to the lack of knowledge of the techniques have been obstacles to the use of metabolic analysers in Brazil. This research was developed with the intention to offer a global vision of the applied procedures of indirect calorimetry to the evaluation of the human metabolism under the prism of the Biomedical Engineering. Three transducers typically used in equipment of indirect calorimetry for metabolic analysis had been evaluated: an electrochemical transducer of oxygen, a carbon dioxide transducer by infrared absorption and a turbine flowmeter. The oxygen transducer revealed sufficiently trustworthy, but a too high response time for applications in breath by breath analyses. The main deficiency of the transducer of carbon dioxide is to provide a significant increase in the flow resistance. It was verified that the flowmeter presents one better behavior for a stream around 20 litres/minute. Despite the limitations presented for the transducers, the results of the assays had been useful and representative for the understanding of the functioning of a human metabolic analyser for indirect calorimetry, evidencing which points have to be improved in future researches and to be considered in the implantation of the laboratory for metabolic and respiratory analysis being installed in the Laboratório de Engenharia Biomédica da Escola Politécnica da Universidade de São Paulo.

Estilos ABNT, Harvard, Vancouver, APA, etc.

37

Lees, Michael (Michael James). "Characterising the mechanism of activation of the bHLH/PAS Dioxin Receptor". 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phl4873.pdf.

Texto completo da fonte

Resumo:

"October 10, 2002" Includes bibliographical references (leaves 104-114) Examines the regulation of the receptor in terms of cellular localisation and ligand activation and investigates the contribution that molecular chaperones play in this process

Estilos ABNT, Harvard, Vancouver, APA, etc.

38

Lees, Michael James. "Characterising the mechanism of activation of the bHLH/PAS Dioxin Receptor / by Michael Lees". 2002. http://hdl.handle.net/2440/21908.

Texto completo da fonte

Resumo:

"October 10, 2002"
Includes bibliographical references (leaves 104-114)
ix, 114 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Examines the regulation of the receptor in terms of cellular localisation and ligand activation and investigates the contribution that molecular chaperones play in this process
Thesis (Ph.D.)--University of Adelaide, Dept. of Molecular Biosciences, 2003

Estilos ABNT, Harvard, Vancouver, APA, etc.

39

Furness, Sebastian George Barton. "Novel mechanisms for activation of the dioxin (Aryl-hydrocarbon) receptor / Sebastian George Barton Furness". Thesis, 2003. http://hdl.handle.net/2440/22026.

Texto completo da fonte

Resumo:

"December 2003"
Includes bibliographical references (p. 83-93)
93 p. : ill. (chiefly col.), plates ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, School of Molecular and Biomedical Science, Discipline of Biochemistry, 2004

Estilos ABNT, Harvard, Vancouver, APA, etc.

40

胡志謙. "The Influence of Sulfur Dioxide on the Metabolism in Cinnamomum caphora and Casuarina equisetifolia". Thesis, 1991. http://ndltd.ncl.edu.tw/handle/23925473248073405845.

Texto completo da fonte

Resumo:

碩士
國立臺灣大學
森林學研究所
79
Sulfur dioxide is a poisonous , stimulant, and colorless gas, and it is about 2.21 times as heavy as air. It is one of the gases that do extremely serious pollution and harm to trees. The main parts to which sulfur dioxide make harm are leaves. After keep the concentration of sulfur dioxide at O.5ppm for one week and 1ppm for one week in two sealed boxes, each of one-year-old Cinnamomum camphora and Casuarina eauisetifolia are seperately put in, the changes on the amount of fats, of total Sugars, of reducing sugars, and of α-amino acids of leaf blades are clearly showed. Meanwhile, through this experiment, the change, under the influence of sulfur dioxide, on the activation of the two enzymes, which are phosphorylase and transketolase and related to the metabolism of saccharides of plants, is examined and tested. All of the results of this experiment as follows: I. the amount of fats of per gram leaf: After Cinnamomum camphora and Casurina equisetifolia are treated, the amount of fats of each of then is less than the controls. There are no significant variances when they are under 0.5 ppm; however, the variances are significant when they are under 1 ppm. Ⅱ. the amount of total sugars and reducing sugars of per gram leaf: After Cinnamomum camphora and Casuarina equisetifolia are treated, the amount of total sugars and of reducing sugars of each of them is less than the controls. The variances are significant when they are under 0.5ppm or under 1 ppm. Ⅲ. the aaount of α-amino acid per gram leaf: After they are treated, the average amount of α-aminoacid of Cinnamomum camphora is more than the control. The variances under 0.5 ppm or under 1ppm are significant. However, the average amount of α-amino acid of Casuarina eguisetifolia is less than the control. There is no significant variance under 0.5 ppm; however, there is 5% variance when it is under 1 ppm. Ⅳ. phosporylase Under 0.5 ppm or under 1 ppm, the activation of phosporylase of Cinnamomum camphora and Casuarina equisetifolia fail to be examined and tested.

Estilos ABNT, Harvard, Vancouver, APA, etc.

41

Feng, Cheng-yu, e 馮成宇. "Influence of benzo[a]pyrene and 2.3.7.8-tetrachlorodibenzo-p-dioxin (TCDD) on estrogens metabolism in human lung cells". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/07918152783549714427.

Texto completo da fonte

Resumo:

碩士
中山醫學大學
醫學分子毒理學研究所
93
Dioxins and benzo[a]pyrenes (B[a]P), commonly present in the environment, are respectively classified as human and animal carcinogens. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most potent carcinogenic dioxin. Previously we reported that TCDD and B[a]P increased cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1) gene expression in human adenocarcinoma cell lines H1355. It has been demonstrated that CYP1A1 and CYP1B1 respectively catalyzed 2- and 4-hydroxylation of estrogens. However, we found that TCDD increased the accumulation of methoxyestradiols (MeOE2), which induced intracellular oxidative stress. The effects of B[a]P on estrogen metabolism were still unclear. The objective of this study was to compare effects of TCDD and B[a]P on estrogen metabolism and homeostasis. H1355 cells and an immortalized cell lines BEAS-2B were treated with 1 nM TCDD or 10 M B[a]P, in the presence of 100 nM E2 for 24 hr. Concentrations of estrogens and their metabolites in the conditioned medium were determined with LC/MS/MS. We found that TCDD significantly increased the accumulation of 2-MeOE2 and 4-MeOE2 in H1355 and BEAS-2B cells. But B[a]P significantly reduced the accumulation of 2MeOE2 and 4-MeOE2 in H1355 cells, and that of 4-MeOE2 in BEAS-2B cells. Simultaneously, B[a]P increased the accumuation of 2-OHE2 and 4-OHE2 in H1355 cells, but not in BEAS-2B cells. It has been reported that OHE2s mainly were converted into MeOE2s by catechol-O-methyl transferase (COMT). Using the real-time RT-PCR assay, we found that TCDD and B[a]P induced CYP1A1 and CYP1B1 expression in both H1355 and BEAS-2B cells, but had no significant effects on COMT mRNA levels. Utilizing GC/MS to measure COMT enzyme activity, we observed a slight reduction in COMT activity by B[a]P, but not by TCDD. It is well known that TCDD and B[a]P are agonists of aryl hydrocarbon receptor (AhR). 3,4-Mimethoxyflavone, an AhR antagonist, failed to prevent B[a]P—induced reduction of COMT activity. It suggested that B[a]P-induced COMT reduction was not AhR-dependent. There are three major natural estrogens: estrone (E1), E2 and estriol (E3). The order of estrogenic efficacy are E2>E1>E3. We showed that B[a]P significantly increased E1 and E2 levels, but reduced E3 level in the medium of H1355 cells. In contrast, TCDD significantly reduced E1 level in the medium of H135 cells. In BEAS-2B cells, B[a]P only significantly increased E1 levels and TCDD failed to change estrogens levels. In summary, our present study showed that B[a]P not only shifted estrogens homeostasis to more potent estrogens, but also increased the accumulation of carcinogenic OHE2s in lung cancer cell lines H1355. The unbalance in estrogens homeostasis and metabolism may contribute to the development of B[a]P-associated female lung carcinogenesis.

Estilos ABNT, Harvard, Vancouver, APA, etc.

42

Dunn, Tracy Joseph. "The regulation of genes that encode enzymes involved in xenobiotic metabolism rat cytosolic aldehyde dehydrogenases induced by phenobarbital and dioxin /". 1988. http://catalog.hathitrust.org/api/volumes/oclc/19581962.html.

Texto completo da fonte

Resumo:

Thesis (Ph. D.)--University of Wisconsin--Madison, 1988.
Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Estilos ABNT, Harvard, Vancouver, APA, etc.

43

Osman, I. F., A. Baumgartner, E. Cemeli, J. N. Fletcher e D. Anderson. "Genotoxicity and cytotoxicity of zinc oxide and titanium dioxide in HEp-2 cells". 2010. http://hdl.handle.net/10454/6119.

Texto completo da fonte

Resumo:

AIMS: The rapidly growing industrial and medical use of nanomaterials, especially zinc oxide and titanium dioxide, has led to growing concerns about their toxicity. Accordingly, the intrinsic genotoxic and cytotoxic potential of these nanoparticles have been evaluated. MATERIALS & METHODS: Using a HEp-2 cell line, cytotoxicity was tested along with mitochondrial activity and neutral red uptake assays. The genotoxic potential was determined using the Comet and the cytokinesis-blocked micronucleus assays. In addition, tyrosine phosphorylation events were investigated. RESULTS & CONCLUSION: We found concentration- and time-dependent cytotoxicity and an increase in DNA and cytogenetic damage with increasing nanoparticle concentrations. Mainly for zinc oxide, genotoxicity was clearly associated with an increase in tyrosine phosphorylation. Our results suggest that both types of nanoparticles can be genotoxic over a range of concentrations without being cytotoxic.

Estilos ABNT, Harvard, Vancouver, APA, etc.

44

許素華. "Influence of lower brain stem cardiovascular intergate area on blood oxygen and carbon dioxide and metabolism in cats". Thesis, 1992. http://ndltd.ncl.edu.tw/handle/47060715121919462401.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

45

Williams, Cristopher A. "Characterization of the changes in cholesterol metabolism, steroidogenesis, and extracellular matrix properties induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured bovine adrenocortical cells". 1990. http://catalog.hathitrust.org/api/volumes/oclc/22355610.html.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

46

"Engineering Cyanobacteria to Convert Carbon Dioxide to Building Blocks for Renewable Plastics". Doctoral diss., 2014. http://hdl.handle.net/2286/R.I.25052.

Texto completo da fonte

Resumo:

abstract: The production of monomer compounds for synthesizing plastics has to date been largely restricted to the petroleum-based chemical industry and sugar-based microbial fermentation, limiting its sustainability and economic feasibility. Cyanobacteria have, however, become attractive microbial factories to produce renewable fuels and chemicals directly from sunlight and CO2. To explore the feasibility of photosynthetic production of (S)- and (R)-3-hydroxybutyrate (3HB), building-block monomers for synthesizing the biodegradable plastics polyhydroxyalkanoates and precursors to fine chemicals, synthetic metabolic pathways have been constructed, characterized and optimized in the cyanobacterium Synechocystis sp. PCC 6803 (hereafter Synechocystis 6803). Both types of 3HB molecules were produced and readily secreted from Synechocystis cells without over-expression of transporters. Additional inactivation of the competing PHB biosynthesis pathway further promoted the 3HB production. Analysis of the intracellular acetyl-CoA and anion concentrations in the culture media indicated that the phosphate consumption during the photoautotrophic growth and the concomitant elevated acetyl-CoA pool acted as a key driving force for 3HB biosynthesis in Synechocystis. Fine-tuning of the gene expression levels via strategies, including tuning gene copy numbers, promoter engineering and ribosome binding site optimization, proved critical to mitigating metabolic bottlenecks and thus improving the 3HB production. One of the engineered Synechocystis strains, namely R168, was able to produce (R)-3HB to a cumulative titer of ~1600 mg/L, with a peak daily productivity of ~200 mg/L, using light and CO2 as the sole energy and carbon sources, respectively. Additionally, in order to establish a high-efficiency transformation protocol in cyanobacterium Synechocystis 6803, methyltransferase-encoding genes were cloned and expressed to pre-methylate the exogenous DNA before Synechocystis transformation. Eventually, the transformation efficiency was increased by two orders of magnitude in Synechocystis. This research has demonstrated the use of cyanobacteria as cell factories to produce 3HB directly from light and CO2, and developed new synthetic biology tools for cyanobacteria.
Dissertation/Thesis
Ph.D. Biological Design 2014

Estilos ABNT, Harvard, Vancouver, APA, etc.

47

Jílková, Veronika. "Lesní mravenci rodu Formica jako významní ekosystémoví inženýři". Doctoral thesis, 2015. http://www.nusl.cz/ntk/nusl-352953.

Texto completo da fonte

Resumo:

This thesis consists of one chapter accepted for publication in a book and four papers published in international journals with impact factors. All of the contributions deal with the role of wood ants in energy and nutrient fluxes in forest ecosystems. Wood ant nests are known as hot spots of carbon dioxide (CO2) production and are also thought to affect methane (CH4) flux. Stable high temperatures are maintained in ant nests even in cold environments. This study is focused on quantification of CO2 and CH4 flux in wood ant nests, contribution of ants and microbes to CO2 production, properties of nest material that affect CO2 production and the role of ants and microbes in the maintenance of nest temperature. The research was conducted in temperate and boreal forests inhabited by wood ants (Formica s. str.). Gas fluxes were measured either by an infrared gas analyser or a static chamber technique. Ants and nest materials were also incubated in a laboratory. Material properties potentially influencing CO2 flux, such as moisture, nutrient content or temperature were determined. According to the results, CH4 oxidation was lower in wood ant nests than in the surrounding forest soil suggesting that some characteristics of ant nests hinder CH4 oxidation or promote CH4 production. Wood ant nests clearly are hot...

Estilos ABNT, Harvard, Vancouver, APA, etc.

48

Kiser, Matthew R. "Development of a System for Real-Time Measurements of Metabolite Transport in Plants Using Short-Lived Positron-Emitting Radiotracers". Diss., 2008. http://hdl.handle.net/10161/708.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

49

Hendrickson, Luke. "Chilling and grapevine photosynthesis : an investigation into the carbon metabolism and photoprotection of leaves in the field and laboratory". Phd thesis, 2003. http://hdl.handle.net/1885/146165.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

50

Iwasaki, Kenji. "Algal bioproducts : investigating the effect of light quality on metabolite production by photosynthetic diatoms". Thesis, 2019. http://hdl.handle.net/10453/137125.

Texto completo da fonte

Resumo:

University of Technology Sydney. Faculty of Science.
In Australia, between 2016 and 2017, aquaculture products made up 44% of Australian seafood product in value, reaching over $1.35 billion in production value. One of the top five profitable Australian aquaculture products during this period were edible oysters which is worth more than $112 million in production value. Oysters are fed with live microalgae (including diatoms) during the larval, juvenile and adult stages of growth, as are other shellfish, some crustaceans, shrimps/prawns and fish. The rearing of oysters and other aquaculture products rely on the constant production of live diatoms as feed. Diatom production in Australian hatcheries are commonly recognised as the major bottleneck in oyster production, estimated to be on average, 30-40% of hatchery operational cost. In order to meet the increasing production demand diatom production must be improved, while making it economically feasible and environmentally sustainable. In this thesis, 𝘊𝘩𝘢𝘦𝘵𝘰𝘤𝘦𝘳𝘰𝘴 𝘮𝘶𝘦𝘭𝘭𝘦𝘳𝘪, a common feed for oysters, was studied for their responses to a variety of environmental growth conditions including light. To achieve this, laboratory scale photobioreactors were used to continuously monitor environmental factors to record biological responses of 𝘊. 𝘮𝘶𝘦𝘭𝘭𝘦𝘳𝘪 to different environmental conditions including light wavelengths. A brief introduction to diatom physiology and its application to aquaculture will be provided in Chapter one. The second chapter assessed the two key environmental limitations in diatom cultivation in aquaculture facilities, light and CO₂. An empirical process model was developed to analyse the importance of light configuration to maximise light availability. High CO₂ availability coupled with high light availability significantly increased growth rates and maximum cell density. The third chapter then assessed the growth, metabolic content and cost efficiency of different colour LEDs (blue, green, red and white) based on the findings in Chapter 2. Blue light was found to be the most cost efficient in biomass and metabolite production, requiring less than half the Watt hours of other LEDs. In the fourth chapter, the wavelength of the growth light was shifted to assess its feasibility to modify metabolic content, as well as its effects on growth, photosynthesis and digestibility. The final chapter discussed the key findings of the thesis and the future research prospects. Several important avenues were identified to improve diatom production in aquaculture, such as improving light availability to increase the efficiency of CO₂ usage, blue LEDs to improve cost efficiency of biomass production and the utilization of wavelength shifting to manipulate diatom metabolite content.

Estilos ABNT, Harvard, Vancouver, APA, etc.

Teses / dissertações sobre o tema "Dioxins Metabolism"

Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos