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Dissertations / Theses on the topic 'Ultraviolet radiation Physiological effect'

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Published: 4 June 2021
Last updated: 20 February 2023

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1

Welsh, Belinda M. "Retinoid augmentation of ultraviolet radiation induced melanogenesis." Thesis, The University of Sydney, 1997. https://hdl.handle.net/2123/27563.

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The capacity of human skin to increase it's pigmentation in response to sunlight is an important protective mechanism employed by the body against the potential harmful effects of excess ultraviolet radiation These include the development of skin cancer and premature aging of the skin. Intense scientific research, particularly over the past two decades, has led to a greater understanding of the biology of the pigment producing cells in the skin, melanocytes, and their secretory product, melanin. Melanocyte function in the skin depends on a delicate and complex interaction with the surrounding skin cells, systemic hormones and external stimuli, especially ultraviolet radiation from the sun.
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2

Yam, Cheuk-sing, and 任卓昇. "The impact of ultraviolet light on cataract: a systematic review." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45174969.

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3

Ladin, Loren Guerrero 1959. "Effect of ultraviolet light on reproduction in Hydra littoralis." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277085.

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The "DNA Damage Hypothesis" pertaining to the evolution of sex was tested using Hydra littoralis. DNA damage was produced by irradiating whole live hydra with ultraviolet light. A curve of uv light dosage vs. survival was constructed. Estimations of threshold fluence and LD50 were made from the survival curve. In four separate experiments, using various combinations of environmental temperatures, uv doses, and number of doses, frequencies of asexual and sexual reproduction were observed and compared. The hydra that received uv treatments did not show an increase in the consequent amount of sexual reproduction, and actually showed a decrease. An increase in the amount of sexual reproduction following DNA damage is predicted by the DNA damage hypothesis, therefore these results do not support this theory. The data was also used to make contradictory observations regarding the "stress hypothesis" for the occurrence of sexual reproduction in hydra.
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4

Howell, Anne C. "Effects of antioxidant vitamin treatment on UV-irradiated cells." Virtual Press, 1995. http://liblink.bsu.edu/uhtbin/catkey/941360.

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Ultraviolet (UV) radiation damages both eukaryotic and prokaryotic cells by causing the formation of free radicals which damage cell membranes and DNA. Antioxidant vitamins have been shown to protect cells from UV-induced damage by scavenging free radicals. The protection of skin and its normal flora is necessary for the health of individuals in resisting diseases caused by microorganisms and delaying the long-term damage caused by UV radiation.This research investigated the effects of the antioxidants vitamin A and ascorbic acid, as well as UV-irradiation on both prokaryotic (Staphylococcus epidermidis) cells and eukaryotic (human fibroblast skin) cells. This information is important in determining the effects of vitamin treatment on skin and its normal flora.Results indicate that ascorbic acid is rapidly (within six hours) degraded after being dissolved in water or medium. Treatment of cells with ascorbic acid must take into account this rapid degradation. S.epidermidis cells were protected from UV-induced damage by treatment with ascorbic acid but were more sensitive to UV-irradiation when treated with vitamin A. Human fibroblast cells treated with ascorbic acid did not exhibit morphological changes when compared to untreated cells.
Department of Biology
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5

Vishvakarman, Devasenapathy. "Occupational exposure to ultraviolet radiation in Central Queensland." Thesis, Queensland University of Technology, 1999.

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6

Kovach, Matthew James. "Adaptive Advantages of Carotenoid Pigments in Alpine and Subalpine Copepod Responses to Polycyclic Aromatic Hydrocarbon Induced Phototoxicity." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc28444/.

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Alpine zooplankton are exposed to a variety of stressors in their natural environment including ultraviolet radiation. Physiological coping mechanisms such as the accumulation of photoprotective compounds provide these zooplankton protection from many of these stressors. Elevated levels of carotenoid compounds such as astaxanthin have been shown to help zooplankton survive longer when exposed to ultraviolet radiation presumably due to the strong antioxidant properties of carotenoid compounds. This antioxidant capacity is important because it may ameliorate natural and anthropogenic stressor-induced oxidative stress. While previous researchers have shown carotenoid compounds impart increased resistance to ultraviolet radiation in populations of zooplankton, little work has focused on the toxicological implications of PAH induced phototoxicity on zooplankton containing high levels of carotenoid compounds. This thesis discusses research studying the role that carotenoid compounds play in reducing PAH induced phototoxicity. By sampling different lakes at elevations ranging from 9,500' to 12,700' in the front range of the Colorado Rocky Mountains, copepod populations containing different levels of carotenoid compounds were obtained. These populations were then challenged with fluoranthene and ultraviolet radiation. Results discussed include differences in survival and levels of lipid peroxidation among populations exhibiting different levels of carotenoid compounds, and the toxicological and ecological implications of these results.
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7

Meldrum, Lennox R. "Estimate of lifetime UV exposure for selected workers in South East Queensland." Thesis, Queensland University of Technology, 1998.

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8

Zhang, Zixin. "UVR transmission through clothing fabrics." Thesis, Queensland University of Technology, 1994. https://eprints.qut.edu.au/37170/1/37170_Zhang_1994.pdf.

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A new fabric transmission measuring system (FTMS) utilising a solar UV simulator and a broad band radiometer, has been designed and developed for fast assessment of the protection levels of clothing fabrics against the biological damage caused by sunlight. The radiometer has a spectral response similar to the erythema action spectrum for human skin. The advantages of the FTMS are simplicity, reliability, low cost and, most importantly, time-efficiency. It has a capacity to process sixty-five clothing samples in about twenty-five minutes. The FTMS was calibrated against a spectroradiometer. The error of the results obtained by the FTMS is estimated within ±8%. The FTMS was employed to study the effects of the parameters and conditions of clothing fabrics on the result of the erythema effective transmittance, i.e. the transmittance of irradiance weighted with the erythema action spectrum for human skin. It was observed that weave structure of clothing fabrics could change the transmittance by up to 11.2 times even though all other factors such as the colour and the dryness condition were maintained at constant. The variations of transmittance with various colours were up to about 200% for polyester(65%)/cotton(35%) samples, and 600% for cotton samples in the studies. A variation as high as about 20 times in transmittance was recorded by stretching lycra clothing fabrics. Wetness of clothing fabrics could change the erythema effective transmittance in either directions, i.e. increase and decrease, depending on the types of clothing fabrics. An increase of transmittance of about 3.1 times and a decrease of about 70% due to the wetness conditions were observed. A model was proposed to correlate the UV transmittance and the characteristics of clothing fabrics. The model was preliminarily tested and a correlation coefficient of 0.902 for the UV transmittance measured with the FTMS and the UV transmittance calculated by the model was obtained. The UV transmission through clothing fabrics is not only determined by the uncovered area of clothing fabrics, but also by the UVR scattering of clothing fabrics. Taking into account of the effects of UVR scattering by clothing fabrics would improve the results.
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9

Ho, Wing-kwok, and 何永國. "Solar ultraviolet radiation: monitoring, dosimetry and protection." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31222675.

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10

Allman, Amy Jane. "Effects of UV radiation on Marfan syndrome cells in culture." Virtual Press, 1993. http://liblink.bsu.edu/uhtbin/catkey/879841.

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Ultraviolet radiation causes an alteration in DNA by modifying neighboring thymine bases resulting in the formation of a dimer. These dimers block the processes of transcription and translation and ultimately no protein is synthesized and the cell dies. However, DNA repair mechanisms correct this damage by excising the dimer from the DNA strand and inserting replacement bases which are joined to the original strand by DNA ligase. This allows transcription to resume and ultimately protein synthesis to take place.This research focused on determining the DNA damage and subsequent repair levels in a connective tissue disorder, namely Marfan syndrome. This information is important in understanding the clinical expression and management of life threatening conditions in Marfan syndrome individuals.Preliminary results indicate that at 20-25J/m2 UV dose (254nm) Marfan syndrome skin cells show a mean reduced survival value of 12% compared to normal human skin cells. Gel electrophoresis indicates a reduced DNA repair level 24h post UV irradiation for Marfan syndrome skin cells compared to normal human skin cells. These results suggest Marfan syndrome skin cells have reduced survival and DNA repair levels compared to normal human skin cells.
Department of Biology
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11

Verma, Meera Mary. "On the effect of UV-irradiation on DNA replication in Escherichia coli." Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phv522.pdf.

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12

Schoen, David Jay 1962. "The effects of retinoids and carotenoids on the in vitro function of human monocytes treated with ultraviolet light." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276640.

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Human peripheral blood monocytes provide a model for the in vivo exposure to, and immune functional damage caused by chronic UVB exposure at the skin surface. Retinoids and carotenoids are known immune function enhancers; they can also prevent cellular toxic product formation caused by UVB exposure. Application of these compounds in vitro may prevent functional damage to monocytes. Monocytes were exposed in vitro to UVB, then assayed for cytotoxic, phagocytic, and antigen presenting abilities. Phagocytic activity was protected from UVB damage by exposure to these compounds; cytotoxic activity was not altered by UVB exposure, but increased by retinoid or carotenoid exposure. Antigen presentation was not affected by either the UVB or these compounds. Protection of phagocytic function was not due to release of activating monokines or prostaglandins. Instead, the cell membrane antioxidant properties of these retinoids or carotenoids were the factors that protected the monocyte from phagocytic damage caused by UVB exposure.
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13

Cobb, Jennifer L. "Validation of a Sun-Exposure Questionnaire for Adolescent Girls." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/CobbJL2001.pdf.

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14

Wilcox, Stephany Vanessa. "Molecular diagnostic approach to determine the degree of photoaging of the skin." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96779.

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Thesis (MScMedSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Context: Excessive exposure to ultraviolet radiation (UV) results in the risk of acquiring long-term harmful effects such as photoaging, which is characterised by deep wrinkles, roughness, dyspigmentation and an increased loss in elasticity. As a result, the detection of photoaging at an early stage is crucial to improving morbidity, whilst preventing the advancement of skin cancer. Aim: The aim of the study was to develop and to validate a diagnostic real-time PCR method in order to establish the gene expression profiles of potential biomarkers in the skin so as to quantify the degree of photoaging: this was conducted by retrieving total RNA from cells adherent to tape strips from sun exposed and non-exposed skin areas. Materials and methods: Twenty healthy volunteers consisting of seven males and thirteen females aged 25 to 67 years were included in this study. Tape stripping was performed using pre-cut D-Squame® 22 mm adhesive discs. Samples were collected on the right medial thigh area 20 cm above the patella and 2 cm below the lateral canthus of the right eye. Total RNA was extracted and relative standard curve method of gene expression was performed. TGF-β, MMP 9, TNF-α and IL-6 mRNA transcripts were selected as representative cytokines to determine the relative fold-change in sun exposed and non-exposed areas of the skin so as to determine extent of photoaging. Results: Repeatability and reproducibility was determined by the coefficient of variation (CV) was within an acceptable range. Thirty five percent (n=7) samples displayed down-regulatory effects for TGF-β. Down regulation of MMP 9 was observed within 30% (n=6) of samples, while 15% (n=3) showed marked up regulation. Only two samples showed measurable levels of TNF-α in the assay, of which one showed significant up regulation. Furthermore, we were unable to detect any IL-6 expression in any of the samples prepared. Conclusion: we have shown that epidermal cytokines can be retrieved from tape stripped samples and can be quantified via real-time PCR. However, the choices of cytokine biomarkers reveal that they are as important as the concentration of starting material. In this study cytokines such as IL-6 is not as informative in determining the extent of photoaging without high doses of ultraviolet radiation before sample collection as opposed to the other explored cytokines.
AFRIKAANSE OPSOMMING: Konteks: Oormatige blootstelling aan ultraviolet (UV) bestraling kan tot ‘n risiko van skadelike en lantermynse nagevolge lei wat gekenmerk word deur foto-veroudering. Dit sluit in diep plooie, growwe vel en ‘n toenemende verlies in elastisiteit. Die ontdekking van foto-veroudering op ‘n vroeë stadium is van kardinale belang vir die verbetering van morbiditeit en die voorkoming van velkanker bevordering. Doelstelling: Die doel van hierdie studie was om ‘n diagnostiese polimerase kettings reaksie (PKR) metode te ontwikkel om geen uitdrukkings profiele van potensiële bio-merkers te vestig in die vel, om so die graad van foto-veroudering in areas van vel wat blootgestel word aan die son en beskermde van die son te bepaal deur totale RNS te versamel van kleeflintskyfies. Materiale en metodes: Twintig gesonde vrywilligers (sewe mans en dertien vroue), tussen die ouderdom van 25 en 67 jaar, was ingesluit in hiedie studie. Vel monsters was versamel deur gebruik te maak van Dsquame® 22 mm kleeflintskyfies 20 cm bokant die patella van die regterkanste mediale heup en 2 cm onder die regter oog. Totale RNS was geisoleer en die relatiewe vlak van geen uitdrukking was bepaal deur gebruik te maak van die kurwe model. Die boodskapper ribonukleiosier transkripsies van die sitokiene TGF- β, MMP 9, TNF-α en IL-6 was gekies as verteenwoordigers van foto-veroudering om die relatiewe verandering van foto-veroudering in die vel te bepaal. Resultate: Validering metodes was aanvaarbaar. ‘n Afwaarts reguleringseffek in TGF-β en MMP 9 merker uitdrukking is gevind in vyf en dertig persent (n=7) en dertig persent (n=6) van monsters, onderskuidelik. In vyftien persent (n=3) van monsters is ‘n opwaarts reguleringseffek in die laasgenoemde gevind. Slegs twee monsters het meetbare vlakke van TNF-α getoon in die eksperiment, waarvan slegs een ‘n noemenswaardige opwaartse regulering getoon het. IL-6 uitdrukking is nie gevind in enige van die monsters. Gevolgtrekkings: Hierdie studie het bepaal dat sitokiene van die vel geisoleer van kleeflint monsters en gekwantifiseer deer relatiewe PKR uitdrukking bepaal kan word. Die keuse van bio-merkers is egter net so belangrik as konsentrasie bepaling van die monsters. Die IL-6 sitokien, in vergelyking met ander, is slegs informaliet tydens hoë ultraviolet bestraling aan die vel blootgestel is.
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15

Saul, Alison Nicole. "Psycho-physiological stress and its effects on ultraviolet light induced inflammation, DNA damage, and skin carcinogenesis." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1172850801.

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16

McGlade, Jacqueline Patricia. "Suppression of the asthmatic phenotype in mice by UVB irradiation." University of Western Australia. School of Paediatrics and Child Health, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0086.

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Background: Exposure of skin to UVB radiation (290-320 nm) modulates the immune system, with most studies showing a suppression of Th1-driven immune responses. Investigations into the effects of UVB exposure on allergic respiratory responses have been limited. This study investigated the systemic effects of UVB on Th2-associated immune responses using two different murine models of allergic respiratory inflammation. The mechanism of immune regulation was also examined. Methods and Results: Two murine models of asthma were used: the papain model and the ovalbumin (OVA) model using papain and OVA, respectively, as the allergens. In the papain model, C57BL/6, histamine receptor-1 knockout (H1RKO) and histamine receptor-2 knockout (H2RKO) mice were exposed to a single 4 kJ/m2 dose of UVB (twice a minimal oedemal dose) on shaved dorsal skin three days prior to intranasal sensitisation with papain, a cysteine protease homologue of the house dust mite (Dermatophagoides pteronyssinus) allergen Der p 1. Sensitisation and boost each consisted of five daily intranasal doses of 1 µg papain whilst the challenge consisted of three daily intranasal doses of 100 µg papain. Asthmatic symptoms were assessed 24 h after the final challenge dose. H1RKO mice demonstrated enhanced papain-specific inflammatory responses in the lung-draining lymph nodes (LDLNs) whilst the responses of H2RKO mice closely mimicked those of C57BL/6 mice. UVB irradiation three days before sensitisation reduced in vitro papain-specific proliferation of LDLN cells from C57BL/6 and H1RKO mice but not H2RKO mice 24 h after challenge. The regulatory effect of UVB was transferred by adoptive transfer of 5 x 106 unfractionated LDLN cells from UVB-irradiated, papain-sensitised and -challenged C57BL/6 and H1RKO donor mice into naïve recipients of the corresponding strain that were ii subsequently sensitised and challenged with papain. Additionally, UVB exposure suppressed papain-induced IL-5 and IL-10 production in vitro by LDLN cells from H1RKO mice but not from C57BL/6 mice or H2RKO mice. The results of this study demonstrate systemic immunomodulation of responses to intranasally delivered antigen by UVB irradiation and the induction of regulatory cells in the LDLN following UVB exposure. Furthermore, these results implicate a role for the H2R in UVB-induced suppression of antigen-specific responses in the draining lymph nodes.
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17

Wright, Caradee Yael, and n/a. "UVR exposure of NZ schoolchildren." University of Otago. Dunedin School of Medicine, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070817.093312.

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Excess exposure to solar ultraviolet radiation (UVR) is the only readily modifiable skin cancer risk factor, and childhood exposure is implicated in melanoma aetiology. To assist the design and evaluation of child sun protection interventions in the school and community context, this first comprehensive study used electronic monitors to record time-stamped, second-by-second UVR exposure of 325 children (from 28 randomly selected New Zealand primary schools) who kept a diary record of concurrent activities and sun-protective practices and completed a sun-related knowledge, attitudes and usual behaviours questionnaire. School principals and Health promoters (HPs) were interviewed about school and community sun protection efforts. Using the Haddon matrix and Ottawa Charter of Health Promotion to guide research, four potential domains of influence were identified: the physical and social environments, protective products, and host (child). Two key outcomes identified were child UVR exposure and sun-protective practices. A path model was developed where potential influences on these outcomes included school, community, host factors (demographics, skin type, sun-related attitudes, and sun-related knowledge), and pattern of concurrent outdoor activity. Seven specific hypotheses were defined to investigate the effects of host, school and community factors on UVR exposure, sun-protective practices, and sun-related knowledge, attitudes and behaviours. To test for the effects of host factors, day of the week and activity on UVR exposure and sun-protective practices, linear mixed models containing these factors and interactions between Year level-sex, activity-Year level and activity-sex, accounting for clustering within schools and allowing for repeated measures, were applied. Logistic regression with a random school effect was used to assess differences in scored student questionnaire items. Structural equation modelling was implemented to consider associations between sun-related knowledge, attitudes and behaviours, and other explanatory factors for variations in UVR exposure and sun-protective practices. Three of the seven specific hypotheses were supported. There were statistically significant differences in UVR exposure by sex, skin type, day of the week and activity, and sex-activity and Year level-activity interactions. Passive pursuits were associated with the highest UVR exposure rates compared to outdoor active, travel and unclassified pursuits. There were statistically significant differences in sun-protective practices by sex, ethnicity and skin type, and sex-activity and Year level-activity interactions. Girls tended to have higher sun protection scores than boys, but were more likely to sunbathe and use sunscreen. Children identifying with Pacific Island ethnicities had higher scores than children with other ethnicities, and children with Fitzpatrick skin types I and II had higher scores than children with skin types III, IV and V. School and community factors were not associated with UVR exposure, sun-protective practices, sun-related knowledge, attitudes and behaviours, but school and HPs� scores were relatively high, reflecting the significant time and effort spent promoting youth sun protection. Trends for Year level indicated that whereas child sun-related knowledge increased with Year level, attitudes and behaviours supportive of sun protection declined. When considering sun-related knowledge, attitudes and behaviours simultaneously, knowledge was only significantly associated with behaviours when mediated by attitudes. The study findings have implications for child sun protection interventions.
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18

Ruscas, Ligia Ioana. "Effets antiinflammatoires des lymphocytes irradiés par les rayons UV: induction d'IL-1Ra et d'IL-10 par les monocytes macrophages." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211036.

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Par leur capacité de moduler la réponse immune, les rayons ultraviolets (UV) ont trouvé des applications dans le traitement de diverses maladies immunes. Leurs mécanismes d’action sont encore incomplètement définis. L’un d’entre eux comporte l’induction de cytokines immunosuppressives et antiinflammatoires. Ce processus peut être provoqué par la phagocytose de corps apoptotiques, l’apoptose constituant une des lésions cellulaires élémentaires provoquée par les UV. Le but de notre travail a été de préciser les cytokines impliquées dans la réponse aux UV, de définir certains mécanismes de leur production et de la potentialiser par des agents pharmacologiques.

Notre étude a comporté deux parties: (1) l’une in vivo chez des malades souffrant de GVH chronique résistante aux traitements conventionnels et traités par photochémothérapie extracorporelle, procédure dans laquelle les leucocytes du malades, prélevés par leucaphérèse puis traités par un psoralène et par UVA lui sont finalement réinjectés; (2) l’autre in vitro où des PBMC de volontaires sains ont été irradiés avec 10J/m2 de rayons UVC qui ne nécessitent pas de photosensibilisation par psoralène. Deux cytokines, l’IL-10 et l’IL-1Ra ont été évaluées par RT-PCR dans un système de coculture autologue entre PBMC et PBL rendus apoptotiques par irradiation. L’évolution du processus apoptotique déclenché par les UV a été mesurée par cytomètrie de flux. Celui-ci concernait essentiellement les lymphocytes, les monocytes/macrophages révélant une résistance relative à l’apoptose, il était progressif, culminant entre la 24ème et la 48ème heures. Lors des cocultures entre PBMC et PBL irradiés, un accroissement très significatif du nombre de copies d’ARNm, concernant les deux cytokines étudiées, l’IL-10 et l’IL-1Ra était observé. L’induction d’IL-1Ra était dépendante de l’IL-10. Une préactivation par du LPS était nécessaire pour la révélation du phénomène.

Ensuite, nous avons évalué l’implication sur la synthèse de cytokines du processus de phagocytose de lymphocytes rendus apoptotiques par irradiation UV et divers moyens pharmacologiques pour la potentialiser. La préincubation du matériel irradié pendant une nuit (16h) à 37° dans le but d’accroître la proportion de cellules en voie d’apoptose avant mise en contact avec les PBMC a permis d’obtenir un accroissement très marqué sans nécessiter de LPS, portant essentiellement sur la production d’IL-1Ra tant sur l’ARNm que la protéine secrétée; l’induction d’IL-10 était cette fois négligeable. L’implication de la phagocytose dans le processus a été démontrée par deux agents bloquants (a) l’anticorps monoclonal anti-CD36 (corécepteur avec l’intégrine &61537;V&61538;3 de la thrombospondine) activant la production d’IL-1Ra et mimant par ce fait le processus phagocytaire et (b) la cytochalasine E la bloquant.

Nous avons testé diverses substances pharmacologiques dont l’action activatrice de l’IL-1Ra est connue, en l’occurrence les immunoglobulines G à usage IV (IgIV) et le GM-CSF. L’adjonction d’IgIV (1mg/ml) ou GM-CSF (10 ng/ml) une heure après le début de la coculture exerce sur la sécrétion d’IL-1Ra un effet additif avec les UV. Selon la concentration utilisée, les IgIV peuvent agir par deux mécanismes. Outre l’effet d’activation macrophagique lié au récepteur Fc, nous avons démontré à haute concentration un mécanisme nouveau, du à la présence dans les IgIV d’anticorps naturels antiFas induisant l’apoptose des lymphocytes. Une incubation de 16h des lymphocytes avec 25 mg/ml d’IgIV avant mise en culture provoque outre une apoptose importante une augmentation significative de l’IL-1Ra. Dans ce cas, le processus est indépendant du fragment Fc, la fraction F(ab’)2 gardant la capacité d’induire l’apoptose et de provoquer la production d’IL-1Ra.

En conclusion, nous avons mis en évidence un mécanisme nouveau d’induction d’IL-1Ra, non décrit auparavant et défini diverses modalités qui pourraient accroître sa production:

- L’incubation de 16h du matériel irradié permet d’orienter le système en accroissant la production de l’IL-1Ra sans que la production de l’IL-10 soit modifiée et sans nécessiter de LPS. Nous attribuons cet effet à l’accroissement du processus apoptotique qui en résulte.

- Nous avons potentialisé la production d’IL-1Ra par deux agents pharmacologiques, le GM-CSF et les IgIV. Les mécanismes d’action des IgIV dépendent de la concentration utilisée.

1. Aux concentrations de l’ordre de 1mg/ml, les IgIV exercent, avec les UV un effet additif sur l’induction d’IL-1Ra par une action dépendant du fragment Fc.

2. Aux concentrations élevées de 25mg/ml, un effet apoptotique attribuable à l’action d’anticorps anti-Fas agonistes est observé. Une préincubation de 16h de lymphocytes avec cette concentration d’ IgIV avant mise en culture avec les PBMC autologues provoque outre l’apoptose importante des lymphocytes un accroissement significatif de la production d’IL-1Ra. Le processus est indépendant du fragment Fc, la fraction F(ab’)2 gardant la capacité d’induire l’apoptose et la production d’IL-1Ra. \
Doctorat en sciences biomédicales
info:eu-repo/semantics/nonPublished

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19

Mizdrak, Jasminka. "Human lens chemistry: UV filters and age-related nuclear cataract." Australia : Macquarie University, 2007. http://hdl.handle.net/1959.14/16855.

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"A thesis submitted in partial fulfillment of the requirements for the award of the degree of Doctor of Philosophy".
Thesis (PhD) -- Macquarie University, Division of Environmental and Life Sciences, Dept. of Chemistry and Biomolecular Sciences, 2007.
Bibliography: p. 243-277.
Introduction -- A convenient synthesis of 30HKG -- Facile synthesis of the UV filter compounds 30HKyn and AHBG -- Synthesis, identification and quantification of novel human lens metabolites -- Modification of bovine lens protein with UV filters and related metabolites -- Effect of UV light on UV filter-treated lens proteins -- Conclusions and future directions.
The kynurenine-based UV filters are unstable under physiological conditions and undergo side chain deamination, resulting in α,β-unsaturated carbonyl compounds. These compounds can react with free or protein bound nucleophiles in the lens via Michael addition. The key sites of the UV filters kynurenine (Kyn) and 3-hydroxykynurenine (3OHKyn) modification in human lenses include cysteine (Cys), and to a lesser extent, lysine (Lys) and histidine (His) residues. Recent in vivo studies have revealed that 3-hydroxykynurenine-O-β-D-glucoside (3OHKG) binds to Cys residues of lens crystallins in older normal human lenses. As a result of this binding, human lens proteins become progressively modified by UV filters in an age-dependent manner, contributing to changes that occur with the development of age-related nuclear (ARN) cataract. Upon exposure to UV light, free UV filters are poor photosensitisers, however the role of protein-bound species is less clear. It has been recently demonstrated that Kyn, when bound to lens proteins, becomes more susceptible to photo-oxidation by UV light. Therefore, the investigation of 3OHKG binding to lens proteins, and the effect of UV light on proteins modified with 3OHKG and 3OHKyn, were major aims of this study. As a result of the role of these compounds as UV filters and their possible involvement in ARN cataract formation, it is crucial to understand the nature, concentration and modes of action of the UV filters and their metabolites present in the human lenses. Therefore, an additional aim was to investigate human lenses for the presence of novel kynurenine-based human lens metabolites and examine their reactivity.--As 3OHKG is not commercially available, to conduct protein binding studies, an initial aim of this study was to synthesise 3OHKG (Chapter 2). Through the expansion and optimisation of a literature procedure, 3OHKG was successfully synthesised using commercially available and inexpensive reagents, and applying green chemistry principles, where toxic and corrosive reagents were replaced with benign reagents and solvent-free and microwave chemistry was used. A detailed investigation of different reaction conditions was also conducted, resulting in either the improvement of reaction yields or reaction time compared to the literature method. Applying the same synthetic strategy, and using key precursors from the synthesis of 3OHKG, the UV filters 3OHKyn and 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid-O-β-D-glucoside (AHBG), were also successfully synthesised (Chapter 3).
Chapter 4 describes the investigation of both normal and cataractous human lenses in an attempt to identify novel human lens metabolites derived from deaminated Kyn and 3OHKyn (Chapter 4, Part A). Initially, 4-(2-aminophenyl)-4-oxobutanoic acid (AHA), glutathionyl-kynurenine (GSH-Kyn), kynurenine yellow (Kyn yellow), 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid (AHB), glutathionyl-3-hydroxykynurenine (GSH-3OHKyn) and 3-hydroxykynurenine yellow (3OHKyn yellow) were synthesised and human lenses were examined for their presence. AHA and AHB were synthesised from similar precursors to those used in the synthesis of 3OHKG, while the GSH adducts and yellow compounds were synthesised from Kyn and 3OHKyn via base induced deamination. Following isolation and structural elucidation, AHA, AHB and GSH-Kyn were confirmed as novel human lens metabolites. They were quantified in low pmol/mg lens (dry mass) levels in normal and cataractous lenses of all ages, while GSH-3OHKyn, Kyn yellow and 3OHKyn yellow were not detected. In contrast to AHA, the lens metabolites AHB, GSH-Kyn and GSH-3OHKyn were found to be unstable at physiological pH. The spectral properties of these compounds suggest that they may act as UV filters. --Chapter 4 (Part B) also describes the identification and characterisation of a novel human lens UV filter, cysteinyl-3-hydroxykynurenine -O-β-D-glucoside (Cys-3OHKG). An authentic standard was synthesised via Michael addition of cysteine to deaminated 3OHKG. Cys-3OHKG was detected in low pmol/mg lens (dry mass) levels in normal lenses only after the 5th decade of life and was absent in cataractous lenses. Cys-3OHKG showed rapid decomposition at physiological pH.
Chapter 5 describes the identification and quantification of amino acids involved in covalent binding of 3OHKG to lens proteins. Model studies with bovine lens proteins and 3OHKG at pH 7.2 and 9.5 were undertaken. The amino acid adducts were identified via total synthesis and spectral analysis, and subsequently quantified upon acid hydrolysis of the modified lens proteins. Under both pH conditions, 3OHKG was found to react with lens proteins predominantly via Cys residues with low levels of binding also detected at Lys residues. Comparative studies with Kyn (pH 9.5) and 3OHKyn (pH 7.2 and 9.5) resulted in modified lens proteins at Cys residues, with only minor modification at Lys residues at pH 9.5. The extent of modification was found to be significantly higher at pH 9.5 in all cases. His adducts were not identified. 3OHKG-, Kyn- and 3OHKyn-modified lens proteins were found to be coloured and fluorescent, resembling those of aged and ARN cataractous lenses. In contrast, AHB and AHA, which can not form α,β-unsaturated carbonyl compounds, resulted in non-covalent modification of lens proteins. AHB may contribute to lens colouration and fluorescence as further reactions of this material yielded species that have similar characteristics to those identified from 3OHKyn modification. These species are postulated to arise via auto-oxidation of the o-aminophenol moiety present in both 3OHKyn and AHB.--In Chapter 6, the potential roles of 3OHKG and 3OHKyn, and the related species AHA and AHB, in generating reactive oxygen species and protein damage following illumination with UV light was examined. The UV filter compounds were examined in both their free and protein-bound forms. Kyn-modified proteins were used as a positive control. Exposure of these compounds to UV light (λ 305-385 nm) has been shown to generate H2O2 and protein-bound peroxides in a time-dependent manner, with shorter wavelengths generating more peroxides. The yields of peroxides were observed to be highly dependent on the nature of the UV filter compound and whether these species were free or protein bound, with much higher levels being detected with the bound species. Thus, protein-bound 3OHKyn yielded higher levels of peroxide than 3OHKG, with these levels, in turn, higher than for the free UV filter compounds. AHB-treated lens proteins resulted in formation of low but statistically significant levels of peroxides, while AHA-treated lens proteins resulted in insignificant peroxide formation. The consequences of these photochemical reactions have been examined by quantifying protein-bound tyrosine oxidation products (3,4-dihydroxyphenylalanine [DOPA], di-tyrosine [di-Tyr]) and protein cross-linking. 3OHKG-modified proteins gave elevated levels of di-Tyr, but not DOPA, whereas 3OHKyn-modified protein gave the inverse. DOPA formation was observed to be independent of illumination and most likely arose via o-aminophenol auto-oxidation. AHB- and AHA-treated lens proteins resulted in statistically insignificant di-Tyr formation, while a light independent increase in DOPA was observed for both samples. Both reducible (disulfide) and non-reducible cross-links were detected in modified proteins following illumination. These linkages were present at lower levels in modified, but non-illuminated proteins, and absent from unmodified protein samples.
This work has provided an optimised synthetic procedure for 3OHKG and other lens metabolites (Chapters 2 and 3). Four novel lens metabolites have been identified and quantified in normal and cataractous human lenses (Chapter 4). Subsequent experiments, described in Chapter 5, identified the major covalent binding sites of 3OHKG to lens proteins, while AHA and AHB showed non-covalent binding. Further work described in Chapter 6 showed that protein-bound 3OHKG, Kyn and 3OHKyn were better photosensitisers of oxidative damage than in their unbound state. Together, this research has provided strong evidence that post-translational modifications of lens proteins by kynurenine-based metabolites and their interaction with UV light appear, at least in part, responsible for the age-dependent colouration of human lenses and an elevated level of oxidative stress in older lenses. These processes may contribute to the progression of ARN cataract.
Mode of access: World Wide Web.
xxxix, 308 p. ill. (some col.)
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20

Kaplan, Jefferson Coker. "Effect of UV irradiation on properties of hot pressed aluminum nitride." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19480.

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Li, Dongyun. "The effect of UV-laser radiation on lenses and lens proteins." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/27271.

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Aguilar, Lara Karla. "Effect of ultraviolet/visible radiation processing on the quality of fruit juices." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/405804.

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Aquest treball va estudiar la irradiació ultraviolada-visible (UV-Vis) com una alternativa per a la pasteurització de sucs. Els resultats van mostrar que la irradiació ultraviolada no produeix hidroximetilfurfural i es capaç de degradar-lo. Es va proposar un mecanisme de foto-degradació i es van usar diferents models cinètics per descriure la reacció. La foto-degradació de la vitamina C va ser insignificant usant una làmpada d’emissió múltiple. A més, el processament d’UV-Vis va ser efectiu inactivant els enzims polifenoloxidasa i peroxidasa; a major temperatura major inactivació. Mentrestant, la majoria dels paràmetres fisicoquímics van ser pràcticament inalterats i la quantitat inicial de pigments es va reduir. Per tant, el processament d’UV-Vis combinat amb lleu escalfament és una alternativa viable per a la pasteurització de sucs.
Este trabajo estudió la irradiación ultravioleta-visible (UV-Vis) como una alternativa para la pasteurización de zumos. Los resultados demostraron que la irradiación ultravioleta no produce hidroximetilfurfural y es capaz de degradarlo. Se propuso un mecanismo de foto-degradación y se usaron diferentes modelos cinéticos para describir la reacción. Por el contrario, la foto-degradación de la vitamina C fue insignificante usando una lámpara de emisión múltiple. Además, el procesamiento UV-Vis fue efectivo inactivando las enzimas polifenoloxidasa y peroxidasa en zumos; a mayor temperatura, mayor inactivación. Mientras tanto, la mayoría de los parámetros fisicoquímicos fueron prácticamente inalterados y la cantidad inicial de pigmentos fue reducida. Por lo tanto, el procesamiento UV-Vis combinado con un calentamiento suave representa una alternativa viable para la pasteurización de zumos.
This work studied the ultraviolet-visible (UV-Vis) irradiation as an alternative for fruit juice pasteurisation. The results showed that ultraviolet irradiation does not produce hydroxymethylfurfural and is capable of degrade it. A mechanism of photo-degradation was proposed and different kinetic models were used to describe the reaction. On the contrary, the photo-degradation of vitamin C was insignificant using a multi-wavelength emitting lamp. Moreover, the UV-Vis processing was effective inactivating the enzymes polyphenoloxidase and peroxidase in fruit juices. The higher the temperature the higher the inactivation. Meanwhile, most physicochemical parameters were practically unaltered and the initial quantity of pigments was reduced. Therefore, the UV-Vis processing combined with a mild-heating represents a viable alternative for fruit juice pasteurisation.
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23

Malallah, Yousef Abdalaziz. "A study of the effect of ultraviolet radiation on normal human skin." Thesis, University of Dundee, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364698.

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Parisi, A. "A new method using a dosimetric technique to evaluate ultraviolet spectra and doses for application to plants." Thesis, Queensland University of Technology, 1996.

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Rafferty, Teresa S. "The effect of selenium on ultraviolet-B radiation-induced damage to the skin." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/22570.

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Selenium (Se) is a trace element found in many food sources, it is incorporated into specific selenoproteins. These include glutathione peroxidase and thioredoxin reductase which have strong antioxidant functions. In mice Se supplementation can reduce the number of skin tumours formed after UV irradiation. The purpose of the present thesis research was to characterise these protective mechanisms. To assess the effect of Se supplementation on UV irradiation of the skin, human skin cells were grown in vitro and supplemented with Se. Selenoprotein profiles were characterised by 75Se labelling. It was shown that primary human fibroblasts, melanocytes and keratinocytes all express unique patterns of selenoproteins. Se reduced the amount of cell death induced by ultraviolet- B radiation(UVB), it also reduced apoptotic cell death. Following keratinocytes Se reduced the induction of mRNA for IL-8, IL-6 and TNFa, but not the protein. In mouse keratinocytes the levels of mRNA for TNFa and IL-10 were reduced and IL-10 protein level was reduced. The effect of Se on the UV induction of DNA damage was assessed by the comet assay. The formation and rate of repair of cyclobutane dimer sites was not affected by Se. However the formation of oxidative damage was reduced. P53 protein is also induced following UVB irradiation, Se did not affect the abundance of the protein, but it did reduce the activity of P53 as measured by reporter assay. Se also reduced the production of lipid peroxides in keratinocytes following UVB. Mouse studies were also carried out where mice were fed different levels of Se for six weeks, then exposed to MED UVB. It was found that the number of Langerhan cells was higher in the Se replete animals and remained higher even after UVB treatment.
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Coombs, Anne-Marie. "A study of near-ultraviolet radiation induced oxidative damage in Escherichia coli." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380929.

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Johnson, William H. "Lost life expectancy rate survey meter." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16408.

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Matallana, Surget Sabine-Astrid Biotechnology &amp Biomolecular Sciences Faculty of Science UNSW. "Physiological and molecular responses of the marine oligotrophic ultramicrobacterium Sphingopyxis Alaskensis rb2256 to visible light and ultraviolet radiation." Awarded By:University of New South Wales. Biotechnology & Biomolecular Sciences, 2009. http://handle.unsw.edu.au/1959.4/43251.

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Ultraviolet radiation reaching the Earth’s surface (UVR, 280-400 nm) may penetrate deep into the clear oligotrophic waters influencing a large part of the euphotic layer. Marine heterotrophic bacteria at the surface of the oceans are especially sensitive to the damaging solar radiation due to their haploid genome with little or no functional redundancy and lack of protective pigmentation. In a context of climate change and ozone depletion, it is clearly important to understand the physiology and underlying molecular UVR responses of abundant marine bacteria species. We chose the marine ultramicrobacterium Sphingopyxis alaskensis as a reference species to study the impact of solar radiation due to its numerical abundance in oligotrophic waters and its photoresistance, previously reported. For this purpose, we focused on the formation of the two major UVB-induced DNA photoproducts (CPDs and 6-4PPs) as well as the differential protein expression under solar radiation. We first demonstrated that the GC content of prokaryotic genome had a major effect on the formation of UVB-induced photoproducts, quantified by HPLC-MS/MS. Due to its high GC content, S. alaskensis presented a favoured formation of highly mutagenic cytosine-containing photoproducts and therefore would be more susceptible to UVinduced mutagenesis. By comparing S. alaskensis to another marine bacterium Photobacterium angustum, we observed for the latter strain a remarkable resistance to high UVB doses associated with a decrease in the rate of formation of CPDs explained by a non-conventional activity of photolyase. We also demonstrated that DNA damage in S. alaskensis was markedly modulated by growth temperature and time spent in stationary phase. In order to assess the effects that environmental UV-R had on regulatory networks and pathways of S. alaskensis, and determine how the cell’s physiology was affected, a quantitative proteomics investigation was performed. Changes in proteome were analyzed, with the recent and powerful mass spectrometry based approach using iTRAQ methodology. Approximately, one third of the proteome of S. alaskensis was identified, with 119 statistically and significantly differentially abundant proteins. Cellular processes, pathways and interaction networks were determined and gave us unique insight into the biology of UV response and adaptation of S. alaskensis.
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Matallana, Surget Sabine. "Physiological and molecular responses of the marine oligotrophic ultramicrobacterium Sphingopyxis alaskensis RB2256 to visible light and ultraviolet radiation." Paris 6, 2009. http://www.theses.fr/2009PA066080.

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Les rayonnements ultraviolets (UVR) pénétrent en profondeur dans les eaux claires oligotrophes affectant une large part de la couche euphotique. Les bactérie hétérotrophes marines jouent un rôle fondamental dans la reminéralisation de la matière organique dissoute et sont spécialement sensibles aux UVR à la surface des océans. Dans un contexte de changement climatique et réduction de la couche d'ozone, il est fondamental de mieux comprendre la physiologie et la réponse de bactéries marines abondantes, exposées aux UVR. Nous avons choisi comme modèle d'étude, la bactérie Sphingopyxis alaskensis, numériquement abondante dans les eaux oligotrophes et précédemment décrite comme photorésistante. Nous avons démontré que les dommages ADN sont fortement modulés par le GC%, la température de croissance et temps passé en phase stationnaire. Les modifications du protéome ont été également analysées par technique iTRAQ et des processus cellulaires originaux ont été caractérisés en réponse aux UVR.
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Davis, Christopher John. "Neuropharmacological investigations into the mechanisms of emesis caused by cytotoxic drugs and radiation." Thesis, University of Oxford, 1988. https://ora.ox.ac.uk/objects/uuid:b9afefde-a43e-415e-8754-ed2a8eaac620.

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31

Waiser, Marley J. "The effect of solar radiation on the microbial ecology and biogeochemistry of prairie wetlands." Thesis, Edinburgh Napier University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343410.

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MacKenzie, Joanna Leigh. "The effects of ultraviolet-B radiation on mutational parameters in Arabidopsis thaliana /." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82283.

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This project was designed to investigate the impact of natural levels of ultraviolet-B radiation on the genomic mutation rate in Arabidopsis thaliana. UV-B radiation is a known mutagen, but plants may have evolved mechanisms to cope with any genomic damage induced by routine exposure to this radiation. In an attempt to determine whether the genomic mutation rate in a plant species is elevated in the presence of UV-B, two eleven generation mutation accumulation studies were preformed. One study incorporated levels of UV-B similar to that encountered on a clear mid-summer's day, while the other was performed in the absence of this mutagen. Mutation rate estimates, obtained primarily from maximum likelihood analysis of phenotypic data, were not significantly greater than zero, both in the presence and absence of UV-B. No evidence was found to support the notion that the genomic mutation rate is increased by exposure to natural levels of UV-B.
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Fatnasare, Ike S. "A study of the effect of water-pick up of UV curable offset ink on its curing time and its end use properties /." Online version of thesis, 1993. http://hdl.handle.net/1850/11169.

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Smith, Andrew E. "The effect of enhanced ultraviolet-B radiation on the photosynthetic metabolism of terrestrial Antarctic plants." Thesis, Anglia Ruskin University, 2009. https://arro.anglia.ac.uk/id/eprint/581959/1/Andrew%20Edwin%20Smith%20thesis.pdf.

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The potential effect of increased UV-B radiation on photosynthetic activity and related processes in a range of terrestrial Antarctic plant species was investigated; from a chlorophyte alga to a vascular plant (Deschampsia antartica). The relative contribution of the UV-B waveband to photosystem II (PSII) damage was used to construct an action spectrum for those species found to be sensitive to UV-B exposure. Investigation involved non-invasive measurements of photosynthesis using chlorophyll-a fluorescence emission coupled with polarographic measurement of oxygen and infra-red gas analysis of carbon dioxide. Compounds associated with UV-B protection were extracted, and analysed using high performance liquid chromatography. Different species exhibited differing sensitivity to UV-B exposure. Reduction in the efficiency of the light independent stage of photosynthesis and decrease in leaf length were found in D. antarctica. A decline in the potential activity of PSII (dark-adapted chlorophyll-a fluorescence) was found in some cryptogams, but no concurrent decrease in gas exchange parameters. Shorter wavelengths of UV-B were shown to be more effective in depression of PSII efficiency. The first action spectrum for terrestrial Antarctic plants would predict a higher weighted UV-B exposure under ambient ozone, but would expect less damage under stratospheric ozone depletion than the commonly used plant action spectrum. Some of the plants investigated contained increased amounts of UV absorbing flavonoids following UV-B exposure. The morphological changes found in D. antarctica should lower photosynthetic productivity, but are dependent on developmental stage. The action spectrum produced herein would still forecast increased damage to PSII due to early spring ozone depletion, but not as great as previously predicted. Moreover, current levels of UV-B radiation may be more damaging to some species than previously thought based on other plant action spectra.
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Smith, Andrew E. "The effect of enhanced ultraviolet-B radiation on the photosynthetic metabolism of terrestrial Antarctic plants." Thesis, Anglia Ruskin University, 2009. http://arro.anglia.ac.uk/581959/.

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The potential effect of increased UV-B radiation on photosynthetic activity and related processes in a range of terrestrial Antarctic plant species was investigated; from a chlorophyte alga to a vascular plant (Deschampsia antartica). The relative contribution of the UV-B waveband to photosystem II (PSII) damage was used to construct an action spectrum for those species found to be sensitive to UV-B exposure. Investigation involved non-invasive measurements of photosynthesis using chlorophyll-a fluorescence emission coupled with polarographic measurement of oxygen and infra-red gas analysis of carbon dioxide. Compounds associated with UV-B protection were extracted, and analysed using high performance liquid chromatography. Different species exhibited differing sensitivity to UV-B exposure. Reduction in the efficiency of the light independent stage of photosynthesis and decrease in leaf length were found in D. antarctica. A decline in the potential activity of PSII (dark-adapted chlorophyll-a fluorescence) was found in some cryptogams, but no concurrent decrease in gas exchange parameters. Shorter wavelengths of UV-B were shown to be more effective in depression of PSII efficiency. The first action spectrum for terrestrial Antarctic plants would predict a higher weighted UV-B exposure under ambient ozone, but would expect less damage under stratospheric ozone depletion than the commonly used plant action spectrum. Some of the plants investigated contained increased amounts of UV absorbing flavonoids following UV-B exposure. The morphological changes found in D. antarctica should lower photosynthetic productivity, but are dependent on developmental stage. The action spectrum produced herein would still forecast increased damage to PSII due to early spring ozone depletion, but not as great as previously predicted. Moreover, current levels of UV-B radiation may be more damaging to some species than previously thought based on other plant action spectra.
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36

Dev, Kumar Govindaraj. "Effect of Ozone and Ultraviolet Irradiation Treatments on Listeria monocytogenes Populations in Chill Brines." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35954.

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The efficacy of ozone and ultraviolet light, used in combination, to inactivate Listeria monocytogenes in fresh (9% NaCl, 91.86% transmittance at 254 nm) and spent chill brines (20.5% NaCl, 0.01% transmittance at 254 nm) was determined. Preliminary studies were conducted to optimize parameters for the ozonation of â freshâ and â spentâ brines. These include diffuser design, comparison of kit to standard methods to measure residual ozone, studying the effect of ozone on uridine absorbance and determining presence of residual listericidal activity post ozonation. An ozone diffuser was designed using 3/16 inch PVC tubing for the ozonation of brines. The sparger was designed to facilitate better diffusion and its efficiency was tested. The modified sparger diffused 1.44 ppm of ozone after 30 minutes of ozonation and the solution had an excess of 1 ppm in 10 minutes of ozonating fresh brine solution (200ml). Population levels of L. monocytogenes were determined at various time intervals post-ozonation (0, 10, 20, 60 min) to determine the presence of residual listericidal activity. The population post ozonation (0 minutes) was 5.31 Log CFU/ml and was 5.08 Log CFU/ml after a 60 minute interval. Therefore, residual antimicrobial effect was weak. Accuracy of the Vacu-vial Ozone analysis kit was evaluated by comparing the performance of the kit to the standard indigo colorimetric method for measuring residual ozone. The kit was inaccurate in determining residual ozone levels of spent brines and 1% peptone water. Uridine was evaluated as a UV actinometric tool for brine solutions that were ozonated before UV treatment. The absorbance of uridine (A262) decreased after ozonation from 0.1329 to 0.0512 for standard 10 minutes UV exposure duration. Absorbance of uridine was influenced by ozone indicating that the presence of ozone may hamper UV fluence determination accuracy in ozone-treated solutions. Upon completion of diffuser design and ozone/UV analysis studies, the effect of ozone-UV combination on L. monocytogenes in fresh and spent brines was evaluated. Ozonation, when applied for 5 minutes, caused a 5.29 mean Log reduction while 5 minutes of UV exposure resulted in a 1.09 mean Log reduction of L. monocytogenes cells in fresh brines. Ten minutes of ozonation led to a 7.44 mean Log reduction and 10 minutes of UV radiation caused a 1.95 mean Log reduction of Listeria in fresh brine. Spent brines required 60 minutes of ozonation for a 4.97 mean Log reduction in L. monocytogenes counts, while 45 minutes resulted in a 4.04 mean Log reduction. Ten minutes of UV exposure of the spent brines resulted in 0.30 mean Log reduction in Listeria cells. A combination of 60 minutes ozonation and 10 minute UV exposure resulted in an excess of 5 log reduction in cell counts. Ozonation did not cause a sufficient increase in the transmittance of the spent brine to aid UV penetration but resulted in apparent color change as indicated by change in L*a*b* values. Ozonation for sufficient time had considerable listericidal activity in fresh brines and spent brines and when combined with UV treatment, is effective reducing L. monocytogenes to undetectable levels in fresh brines.
Master of Science in Life Sciences
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37

Wong, H. M. "Probing the interactions between iron nutrition, salinity and ultraviolet-B radiation on the physiological responses of wheat (Triticum aestivum L.)." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1327.

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When plants are exposed to multiple environmental stress factors, one form of stress can affect the response to another stress. This study used seedlings of a new cultivar of wheat(Triticum aestivum L. cv. 1862), grown under factorial combinations of two levels of ultraviolet-B (UV-B)radiation, two salinity regimes and two levels of iron treatment in chelator-buffered nutrient solutions in a growth chamber. A number of morphological and physiological measurements were made. The accumulation of chlorophyll, UVabsorbing compounds and proline in shoots, as well as phytosiderophores (PSs) in root exudates were measured. Feed value measurements included crude protein, water-soluble carbohydrates, acid detergent fibre and Fe in shoots and roots. After 21 days of stress exposure, results showed that Fe deficiency and NaCl stress generally decreased plant growth and function as well as nutritive value, but increased plant biochemical protection traits such as proline accumulation (16.3 fold under salinity stress) and release of PSs (2.4 fold under Fe deficiency). Interestingly, UV-B radiation affected belowground parameters, inducing a 47% reduction in PS release, together with decreasing root DM by 9% and Fe concentration in roots by 7%. When Fe deficiency and NaCl stress were combined, the results showed a decrease in PS release by 3.5 fold compared to unstressed plants. UV-B radiation synergistically increased UV-absorbing compound levels in combination with Fe deficiency, compared to plants grown under optimal Fe levels. This stress combination also resulted in a cumulative effect by decreasing Fe concentration in shoots and roots. However, salt stress did not interact with UV-B radiation for any of the traits measured. In addition, some three-way interactions were noted, with the Fe x NaCl x UV-B stress combination slightly decreasing PS release and resulting in a cumulative effect by decreasing Fe concentration in roots. In conclusion, this study found that aboveground stress factors such as UV-B can affect important aspects of belowground plant function, and that Fe deficiency can interact with UV-B and salinity stress in modifying plant responses to either stress alone.
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Fris, Miroslav. "The effect of single and repeated ultraviolet radiation on the anterior segment of the rabbit eye." Doctoral thesis, Norwegian University of Science and Technology, Department of Neuroscience, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2110.

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Over the last two decades, depletion of stratospheric ozone has increased the flux of ultraviolet radiation (UVR) at the surface of the earth and the cumulative effect of UVR has become an important aspect of UV-induced eye damage. Epidemiological studies generally assess the chronic, low dose UVR exposure conditions while the laboratory animal experiments usually examine the acute response to high dose exposures. Thus, the study conditions are dissimilar and we are not free to assume that the two variant experimental settings necessarily trigger the same damage or repair mechanism. In order to correlate the results obtained from both experimental settings, laboratory studies of repeated UVR exposures under specific experimental design need to be conducted. The purpose of the present study was to focus on the comparison of the effects of single and repeated UVR-B exposures of the same overall doses on the metabolic profile of the anterior segment of the rabbit eye.

Rabbit eyes were exposed to single (312 nm, 3.12 J/cm2) or repeated (312 nm, 3 x 1.04 J/cm2) UVB irradiations and corneal, aqueous humour and lenticular samples were analysed by NMR spectroscopy. Special grouping patterns among the tissue samples and the relative percentage changes in particular metabolite concentrations were evaluated using advanced statistical methods (Principal component analysis, One-way ANOVA, Independent sample t-test).

The metabolic profiles of UVB irradiated and control samples were significantly different. Especially, alterations in the concentrations of antioxidants (ascorbate, GSH), compounds related to sugar metabolism (glucose, lactate), osmolytes (taurine, hypo-taurine, myoinositol, scylloinositol), choline-containing compounds (choline, phosphocholine) and amino acids were observed. A substantiall additivity of the repeated UVR-B exposures was revealed.

For the first time, a comparison of the effect of a single and repeated UVR exposure of the same overall dose on the metabolic profile of rabbit eye was conducted and described. This study reveals the cumulative effect of repeated UVB irradiation on the anterior segment of the rabbit eye and shows that even a 48 hours interval between subsequent UVR-B exposures is not sufficient for the healing process to restore normal metabolic status in the anterior segment of the rabbit eye.

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39

Borke, Michael Faison. "Modification of x-ray tissue doses with strong magnetic fields." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/17905.

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Ilnytskyy, Yaroslav, and University of Lethbridge Faculty of Arts and Science. "Non-targeted effects of ionizing radiation in vivo : epigenetic aspects / Yaroslav Ilinytskyy." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biomolecular Sciences, [c2010], 2010. http://hdl.handle.net/10133/2630.

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The classical paradigm of radiation biology is based on the notion that ionizing particle has to traverse a nucleus of a living cell in order to damage genetic material either directly or via production of short living free radicals. After DNA damage is introduced it can be either safely repaired and the cell can continue divisions unaltered; or it can result in a failure to repair and cells death; or finally, upon misrepair, the cell would be carrying genetic alteration that could result in cancer or developmental abnormality. Therefore modern risk estimations are based on the notion that nucleus is the true target of radiation effects and those are essentially stochastic with linear dependence on the dose. During the last two decades or so, a different idea was developed based on the observation that irradiated cells can communicate radiation induced stress signals to their unaffected neighbors and themselves become reprogrammed to maintained abnormal radiation-induced phenotype across multiple cellular divisions. Even more astonishingly this phenotype maybe transmitted by irradiated germ cells to unexposed progeny. Here we suggest that these non-targeted effects are maintained by epigenetic mechanisms and examine epigenetic underpinnings of bystander and transgenerational effects in vivo.
xi, 190 leaves ; 28 cm
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Parker, Nicole Renee. "The role of kynurenine and UV light in lens protein modification." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060720.111305/index.html.

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Thesis (Ph.D.)--University of Wollongong, 2005.
Typescript. EMBARGOED - This thesis is subject to a 12 month embargo (07/03/06 to 07/03/07) and may only be viewed and copied with the permission of the author. For further information please Contact the Archivist. Includes bibliographical references: leaf 236-266.
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陳木華 and Mok-wah Chan. "Exposures to artificial sources of ionising radiation in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31208496.

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Mwanza, Patrick. "Determination of the effects of sunlight and UV irradiation on the structure, viability and reapplication frequency of the biopesticide cryptophlebia leucotreta granulovirus in the protection against false codling moth infestation of citrus crops." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/6346.

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Cryptophlebia leucotreta granulovirus (CrleGV-SA) is a baculovirus specifically pathogenic to the citrus pest false codling moth, Thaumatotibia leucotreta. CrleGV- SA is formulated as a commercial biopesticide, Cryptogran® (River Bioscience, South Africa). The virus has a stable, proteinaceous crystalline occlusion body (OB) that protects the nucleocapsid. The major limitation to the use of baculoviruses is their susceptibility to the ultraviolet (UV) component of sunlight, which rapidly and greatly reduces their efficacy as biopesticides. The UVA and UVB components are the most destructive to biological organisms. To date no publication has reported the effect of UV on the structure and virulence of CrleGV, or the effectiveness of the OB as a UV protectant. In this study the effect of UV irradiation on the structure and infectivity of pure CrleGV-SA and Cryptogran® was investigated using scanning electron microscopy (SEM), Raman spectroscopy, qPCR, and bioassays. The project included laboratory and field studies. In the laboratory, CrleGV-SA and Cryptogran® were exposed to either UVA or UVB for periods of 24 hours to 7 days before analysis. In the field, Cryptogran® was applied to trees in a citrus orchard with young fruit. The fruit were collected from 24 hours to 28 days after application and bioassays conducted to assess the effect of sunlight over time on virus structure and efficacy when applied to the northern or southern sides of the trees. No surface morphological changes to the virus were detected using SEM. However, small compositional changes were detected by Raman spectroscopy. qPCR and bioassays demonstrated that UV irradiation damaged the viral DNA, greatly reducing the infectivity of pure CrleGV-SA and Cryptogran®. Exposure to UVB reduced the virulence of the virus more than UVA. The field studies revealed that the activity of CrleGV-SA decreased more on the northern side of the trees than on the southern side.
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Kuffner, Ilsa Boysen. "The Effects of Ultraviolet Radiation on Reef Corals and the Sun-Screening Role of Mycosporine-like Amino Acids." Thesis, University of Hawai'i, Honolulu, 1999. http://hdl.handle.net/10125/15319.

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Shallow-dwelling scleractinian corals live in high irradiance environments where they are exposed to large fluxes of ultraviolet radiation (UVR, 280 - 400 nm). A suite of UV-aborbing compounds, know as mycosporine-like amino acids, is found within the tissues of coral-algal symbioses and may perform a sun-screening role. The seasonal variation in MAA concentration was investigated for two corals in Kaneohe Bay, Hawai'i, Porites compressa and Montipora verrucosa. Regressions of MAA concentration and the amount of UVR measured prior to collection date were not significant for total MAA concentration of either species. However, individual MAAs, shinorine in P. compressa and palythene in M. verrucosa, did show significant correlation with UVR. The effects of UVR and water motion on Porites compressa were investigated in a flume and in the field. Exposure to ambient UVR was the most important factor tested in determining the concentration of MAAs in the tissues of P. compressa. Water motion also positively affected the concentration of MAAs, but only in the presence of UVR. When UVR was screened from the corals' environment, the tissue concentration of MAAs slowly decreased over time (approximately 2.5 to 5% per week) regardless of water motion. The effect of UVR on coral planulae was investigated in field experiments with Pocillopora damicornis. Larvae were taken from four different source adults: those from <0.5 m, those from 3 m, those incubated in the absence of UVR for two months, and those incubated in ambient UVR for two months. Deep larvae and larvae from adults incubated in the absence of UVR had roughly half the amount ofMAAs found in the shallow larvae and the larvae from adults in ambient UVR. Origin of larvae was not a significant factor in determining larval survival or recruitment success. UVR, however, was important in determining recruitment rate. Larvae were less likely to recruit to the settlement tile in the presence of ambient UVR than in treatments where the UVR was screened out.
Thesis (Ph. D.)--University of Hawaii at Manoa, 1999. Includes bibliographical references (leaves 151-164).
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Anouti, Abdel Rahman Jamil. "THE INFLUENCE OF WAVELENGTH SELECTIVE GREENHOUSE FILMS ON ENERGY CONSUMPTION AND PRODUCTION OF FLORICULTURAL CROPS." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275442.

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Huang, Bingsheng, and 黃炳升. "Radiation dose and cancer risk of cardiac CT scan and PET-CT scan." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B41757993.

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Khan, Shanchita R. "Effect of sunlight exposure on 25-Hydroxyvitamin D concentration." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/115121/2/Shanchita%20Khan%20Thesis.pdf.

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Sunlight generates vitamin D, but there is scant human data from randomised trials on which to base health policy advice about how much sun exposure is necessary to change 25(OH)D concentrations. This thesis studies the effect of solar ultraviolet (UV) radiation exposure on 25(OH)D concentration in a randomised controlled trial. The intervention group received nine standard erythemal dose of UV radiation over three weeks which caused a 2.5 nmol/L higher increase than that in the control group, although this was not statistically significant. This study identifies key issues to be considered in the design of a larger trial.
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Park, Young C. (Young Chul) 1960. "A Study of Some Biological Effects of Non-Ionizing Electromagnetic Radiation." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278105/.

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The experimental studies of this work were done using a microwave cavity spectrometer, Escherichia coli (E-coli) bacteria, and other peripheral equipment. The experiment consists of two steps. First, a general survey of frequencies from 8 GHz to 12 GHz was made. Second, a detailed experiment for specific frequencies selected from the first survey were further studied. Interesting frequency dependent results, such as unusually higher growing or killing rates of E-coli at some frequencies, were found. It is also concluded that some results are genetic, that is, the 2nd, and 3rd subcultures showed the same growing status as the 1st cultures.
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Nabasenja, Caroline. "Radiation doses for barium meals and barium enemas in the Western Cape South Africa." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1560.

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Thesis submitted in fulfilment of the requirements for the award of the degree of Master of Technology Radiography (Diagnostic) in the Faculty of Health and Wellness Sciences at the Cape Peninsula University of Technology 2009
Since their discovery in 1895, the use of x-rays is continuously evolving in medicine making the diagnosis of injuries and diseases more practicable. It is therefore not surprising that x-rays contribute 90% of the radiation dose to the population from manmade sources (DWP, 1992). Moreover, these radiation doses are associated with both fatal and non-fatal cancer risk that is detrimental to adults between 20 to 60 years (Wall, 1996). Radiation dose to individuals therefore needs to be actively monitored in order to minimise such risk. Barium contrast examinations were characterised as one of the radiological examinations that contributed enormously to the collective dose to the patients in the radiology department (DWP, 1992). Determining the diagnostic reference levels of such examinations would reduce the over-exposure of individuals to ionising radiation. Currently in South Africa (SA), there are no diagnostic dose reference levels for barium meal (BaM) and barium enema (BaE) examinations. This study therefore investigated the radiation doses delivered to patients referred for BaM and BaE, obtained potential regional reference doses for these examinations, compared the radiation doses obtained with those from similar dosimetry studies and investigated sources of dose variation among the study sites. A total of 25 BaM and 30 BaE patients in the age range 18 to 85 years, weighing 50 kg to 90 kg, at 3 hospitals in the Western Cape, SA were investigated. The radiation dose to the patients was measured using Dose Area Product (DAP) meters that were permanently fitted onto fixed fluoroscopy units at these 3 hospitals. The third quartile DAP values were 20.1 Gycm2 and 36.5 Gycm2 for BaM and BaE respectively. The median DAP values were 13.6 Gycm2 and 27.8 Gycm2 for BaM and BaE respectively. The median values were recommended as the potential Diagnostic Reference Levels for BaM and BaE as they are less affected by outlying values of under or over- weight (Yakoumakis, Tsalafoutas, Sandilos, Koulentianos et al, 1999). The weights of the patients, fluoroscopy time, the number of images obtained, the use of digital or conventional fluoroscopy equipment and the level of training of the radiologists were the factors considered for dose variation among the 3 hospitals.
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Zerabruk, MA. "Repair of sub-lethal damage following single and split-dose irradiation using 60co-gamma and p(66)Be neutrons." Thesis, Cape Peninsula University of Technology, 2005. http://hdl.handle.net/20.500.11838/1504.

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Thesis (MTech Biomedical Technology)--Cape Peninsula University of Cape Town, 2005
In clinical radiotherapy, experiments are performed to determine optimal conditions of the radiation prior to radiotherapy. These experiments focus on the relative biological effectivness(RBE) determination and are predominantly applied in high linear energy transfer (LET) radiations i.e. fast neutrons, as the RBE values for such radiations vary greatly. In general, the RBE of a certain radiation relative to a given reference radiation flCo gamma) varies widely with the energy, dose, dose rate, fractionation, type of tissue and end-point used. Experience with neutron therapy at iThemba LABS has shown that treatment with more fractions and lower doses per fraction may be beneficial for some patients. To calculate the iso-effective treatment dose needed, an appropriate alp ratio for early effects is needed. In this study, the repair of mouse jejunum was measured for split-dose irradiations to determine if a suitable alP ratio for neutrons could be estimated using the known value for gamma rays and the applicable RBE.. Crypt stem cell survival was measured 3.5 days after split-dose exposures to p(66)/Be neutrons and 6OCo gamma rays. Dose response curves for both treatment modalities and for both acute and fractionated exposures were constructed by counting crypts of Leiberkhiin at the base of the villi in haematoxylin and Eosin-stained sections of mouse jejunum. Using a RBE value of 1.64 and an alP ratio of 7Gy noted for tbe fractionated photon exposures, an alP ratio of 11.5 IV could be estimated for neutrons.
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