Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 198-219). / Also available by subscription via World Wide Web / xvii, 219 leaves, bound ill., some col. 29 cm

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.

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.

No description available.

Stratospheric ozone plays an important role in absorbing ultraviolet radiation. The well-known depletion of the ozone layer has raised several concerns in terms of an expected increase in surface ultraviolet radiation. South Africa, situated in the southern mid-latitude regions, has experienced a general downward trend in total column ozone since 1979, As a result of this negative trend in total column ozone, the ultraviolet flux at the earth's surface is expected to increase. Excessive exposure to ultraviolet radiation is known to have acute and chronic effects on human health, including erythema and skin cancer. Numerous studies have acknowledged a relationship between childhood ultraviolet radiation exposure and the risk of contracting skin cancer, namely malignant melanoma, during adulthood. The aim of this study is to investigate the ultraviolet radiation dose and exposure of children and adolescents in Durban, South Africa. Polysulphone film badges were used to quantify the daily erythemal ultraviolet radiation dose of 30 individuals of varying ages and skin types, engaged in different activities, over a one-week period during summer. The results highlight the diversity of childrens' and adolescents' behavioural patterns, with behaviour being found to play an important role in determining an individual's ultraviolet radiation dose. The mean daily erythemal ultraviolet radiation dose of the children and adolescents was 1.03 MED units with a median of 0.57 MED units and a 95% range of 0.22 - 7.22 MED units. The most striking finding was that the median value was below the critical value of 1 MED unit. An explanation for the unexpectedly low erythemal ultraviolet radiation doses recorded in this study was sought in the prevailing climatic conditions. Ambient erythemal ultraviolet radiation levels recorded during the study period were high, ranging between 20.57 - 30.60 MED units. However, high temperatures (>27°C), coupled with high humidity values, may have encouraged the children and adolescents to avoid direct sunlight and find shade while outdoors. The daily erythemal ultraviolet radiation doses of the children and adolescents were also compared to the ambient erythemal ultraviolet radiation levels received on a horizontal surface by a YES UVB-l pyranometer located at the University of Natal (Durban). Children and adolescents in Durban received approximately 4.58% of the total daily ambient erythemal ultraviolet radiation incident upon a horizontal surface. This was found to be similar to a study (5 - 6%) conducted by Diffey et al. (1996) in England, as well as a study (4 - 8%) by Gies et al. (1998) in Brisbane, Australia. The personal ultraviolet radiation exposure journals of the children and adolescents were used to determine the timing of exposures, duration of exposures and nature of outdoor activities and these were then related to their daily ultraviolet radiation doses. Of all the factors considered, the nature of an individual's activity was found to have the strongest influence in determining their ultraviolet radiation dose. An activity model was derived in order to investigate the effect of activity on ultraviolet radiation dose, where three activity factors, namely swimming, walking and tennis, were calculated for a South African context and compared with those from previous international studies. It was found that the activity factors derived in this study were similar to Holman et al. (1983) and Herlihy et al. (1994) and may be used in an activity model to estimate individual erythemal ultraviolet radiation dose for a particular activity. The value of this innovative activity model lies in its ability to predict individual ultraviolet radiation dose and this may help to emphasise the importance of responsible outdoor behaviour. A mannequin was used to quantify the anatomical distribution of erythemal ultraviolet radiation under clear sky and overcast conditions. It was found that the vertex of the head and shoulders received the highest erythemal ultraviolet radiation doses under both conditions. This was then related to the erythemal ultraviolet radiation doses of the children and adolescents as recorded by the polysulphone film badges in order to identify anatomic sites susceptible to high erythemal ultraviolet radiation doses. Behaviour alternatives and ultraviolet radiation protective mechanisms were discussed and recommendations made for children and adolescents residing in Durban. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

No description available.

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

No description available.

Activity curves for Dipodomys ordii were developed from data obtained from a study utilizing an electrically monitored trapping grid. The curves for non-perturbated populations showed an initial post-dusk peak, followed by increasing activity and a large pre-dawn peak; but after ten dominant animals had been removed, the largest activity peak was post-dusk. Differences in activity patterns were not found among sex, age or reproductive classes. Rising ambient temperatures, falling barometric pressures, winds over 3.2 km/hr and the absence of the moon depressed capture numbers; while increasing humidity (relative and absolute), decreasing soil temperatures at 20 and 40 cm below ground level, rising barometric pressures, winds under 3.2 km/hr and clear periods with moonlight increased capture numbers; but only cloudy periods significantly altered the shape of the curves. Low statistical correlation indicated that other independent environmental variables, in addition to those considered, determined the observed activity patterns. Visual observations did not differ significantly from trap results.

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.