Thesis (M.S.)--University of North Carolina at Wilmington, 2003.

No description available.

Thesis (Ph. D.)--Oregon Graduate Institute of Science and Technology, 1990.

Thesis (Ph.D.)--University of Western Australia, 2004.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 57-62).

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves 135-137).

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 79-90.

Thesis (Ph. D.)--Drexel University, 2007. / Includes abstract and vita. Includes bibliographical references (leaves 101-108).

M.Sc. (Biochemistry) / Dry eye disease (DED) and keratoconus (KC) continue to affect the quality of life of many South Africans (and elsewhere) and in the case of KC often leads to blindness. It is estimated that DED affects 14% to 33% of the population worldwide, while 1 in 2000 of the worlds population is affected by KC. However, details of the etiology of these diseases and their biochemical ‘fingerprint’ remain uncertain. In this study, emphasis was placed on the investigation of immunological proteins in the precorneal tear film of DED and KC subjects and meibomian lipids in these individuals. Tear fluid and meibum were collected from control, DED and KC volunteers. Control subjects were non-contact lens wearers and free from ocular diseases, whereas DED subjects were diagnosed by means of an ocular surface disease index (OSDI) questionnaire. DED subjects were divided into two groups: ‘moderate DED’ and ‘severe DED’ based on OSDI. KC subjects were diagnosed by the use of a slit-lamp biomicroscopy exam. Enzymelinked immunosorbent assays were performed to quantitate secretory immunoglobulin A (sIgA), tumour necrosis factor-alpha (TNF-á) and matrix metalloproteinase-1 (MMP-1) in the collected tear fluid. Meibum was analysed with proton nuclear magnetic resonance (1H-NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR). Multivariate data analyses (PCA) were used to extract interpretable information from the multidimensional data generated from the aforementioned techniques and used to build a broad picture of the general lipidomic differences between DED, KC and healthy subjects. Tear levels of sIgA and MMP-1 were significantly decreased in patients with KC compared to control. In contrast, the tears of severe DED subjects were characterised by higher levels of TNF-á and lower levels of sIgA. In subjects with moderate DED, TNF-á levels were significantly elevated. The results of this study re-emphasize that KC and DED individuals are associated with differential expression of specific tear proteins and support the view that the severity of DED is reflected in the levels of immunological proteins present in basal tears. Differences in the chemical composition of meibum from subjects with severe DED and KC compared to control were observed, more specifically in the aliphatic region of 1H-NMR spectra and C-C rocking region of FTIR spectra. The results therefore point towards the saturated components of fatty acids (and their chemical environments) as key targets for future investigations to elucidate compositional differences between DED, KC and healthy meibum.

This dissertation represents an attempt to understand the mechanism of the action of pesticides derived from chlorinated phenols (pentachlorophenol, pentachlorobenzenethiol, and 2,4,5-trichlorophenol) in lipid membranes; specifically, the kinetics of pesticide induced hydrogen ion transfer in lecithin-cholesterol membranes and its relationship to uncoupling activity in energy transducing membranes. Information on pesticide induced charge transport in membranes was obtained from the measurements of steady state and transient membrane conductance and membrane potentials as a function of the composition of the aqueous phase surrounding the membrane and of membrane composition. In addition, a systematic theoretical study of a series of membrane transport models was performed in order to elucidate the various aspects of membrane transport kinetics and to make predictions relevant to the interpretation of experimental results. Based on the theoretical results, two kinetic schemes of membrane transport were proposed to explain the experimental results; one for pentachlorophenol and 2,4,5-trichlorophenol, and another for pentachlorobenzenthiol. The schemes differ in the proposed mechanism of charge transfer across membrane water interface. Some conclusions regarding the rate limiting step in the charge transport process are drawn. Measurements of membrane surface potentials based on the microelectrophoretic method reveal that the density of ionized pentachlorophenol at the membrane surface can be predicted from the Langmuir adsorption model, provided that electrostatic repulsion between pentachlorophenol ions adsorbed at the membrane and free ions in the aqueous phase is taken into account. The fact that the adsorption of positively charged tetraphenylarsonium ions and negatively charged salicylate ions modify the membrane charge transport induced by 2,4,5-trichlorophenol, can be explained by electrostatic arguments. The 2,4,5-trichlorophenol, can be explained by electrostatic arguments. The ability of pentachlorobenzenethiol and of chlorinated phenols to induce proton transport in membranes is regarded as the origin for both the membrane electrical conductivity and their toxic action in energy transducing membranes. We have found similarities between the pH dependence of pentachlorobenzenethiol induced membrane conductance and the pH dependence of the pentachlorobenzenethiol uncoupling activity found in mitochondria, as reported in the literature. We have also found that the level of pentachlorophenol concentration at which the membrane conductance increases above the background level corresponds to the onset of reduction of carbon uptake by algae.