The aim of this study is to preliminary characterise XvLOB, a LOB domain containing gene, which has been isolated from a dehydration stress library in X. viscosa. In this study the gene was isolated and cloned, the DNA and amino acid sequences were analysed by in silico analysis, the recombinant XvLOB protein expressed, subcellular localisation examined and both the transcript and protein expression levels in response to dehydration was investigated.

Includes bibliographical references (leaves 44-54). / Genes that are upregulated in the early response to stress are not well understood. ERD15 (early-responsive to dehydration) in Arabidopsis and its homologues in various other plants have been shown to be upregulated within I hr post-exposure to dehydration and high salinity stress treatments. There is however limited literature on the functionality of ERD15. A cDNA showing homology to ERD15 was isolated from a library generated by low temperature stress treatment of Xerophyta viscosa and was subsequently named XvERD15.

Includes abstract. / Includes bibliographical references (leaves 139-148). / The devastating effect the HIV pandemic has had on the human population in the last twenty five years has highlighted the great need to develop a prophylactic HIV vaccine. The manufacture of a vaccine has proven difficult though, with a number of successful designs in animal models having little success in humans. In view of this, there has been a need for novel vaccine approaches that are able to elicit effective cellular and humoral immune responses, both of which are believed to be important in the eradication of the virus. One such approach is the use of HIV-1 Gag VLPs as vaccine candidates. In this study, the production of two chimaeric (Gag VLP vaccine candidates (GagRT and GagTN) was optimized in insect cells, and their ability to enhance a murine immune response in a DNA prime-VLP boost vaccine strategy was evaluated.

Includes bibliographical references. / It has been 30 years since HIV was first discovered, yet the molecular mechanisms whereby the virus mediates its pathogenic effects have not yet been completely elucidated. The glucocorticoid receptor (GR) is a ligand-activated host transcription factor, which mediates anti-inflammatory effects in response to stimulation with glucocorticoids (GC). One of the HIV-1 accessory proteins, Vpr, is highly immunosuppressive and contributes to suppression of the immune system thereby creating an environment favourable for viral proliferation. Vpr has been previously reported to act as a GR co-activator on glucocorticoid response element (GRE) containing promoters. Thus, the GR appears likely to play a role in HIV-1 pathogenesis. Contraceptive usage is also likely to affect HIV-1 pathogenesis as some hormonal contraceptives can bind to and activate the GR. Progesterone (P4) regulates the female reproductive system and the synthetic progestins medroxyprogesterone acetate (MPA) and norethisterone acetate (NET-A) are extensively used as injectable contraceptives. MPA has been shown to act as a partial or full GR agonist and recent evidence indicates that injectable MPA increases HIV-1 acquisition and transmission. The molecular mechanisms of this remain unclear, but may involve decreasing the thickness of the vaginal epithelium as well as actions via the GR that affect gene expression in the cervo-vaginal environment and/or elsewhere. This study aims to investigate the actions of GC's, P4, MPA and NET-A via the GR in the absence and presence of Vpr protein towards gaining some insight into the potential interplay between the host GR, contraceptive use, HIV-1 pathogenesis, and the mechanisms thereof.

[T]he purpose of this study was to describe the distribution of morning- or evening-preferring individuals (measured using the Horne-Östberg morningness-eveningness personality questionnaire) and PER3 VNTR polymorphism (from genomic DNA products extracted from human buccal cell samples amplified and digested with NcoI) within male Caucasian, trained cyclists (CYC, n=138), Ironman triathletes (IM, n=301) and an active, but non-competitive control population of Caucasian males (CON, n=120). In addition, performance was assessed in trained cyclists strongly preferring mornings or evenings at various times of day.

Includes abstract. Includes bibliographical references.

Includes bibliographical references. / This thesis reports the development of Single-Strand Conformation Polymorphism (SSCP) technique to assess sequence level variation within the Major Histocompatibility Complex (MHC) DRB1 gene in four South African buffalo populations. MHC gene products are involved in the immune response, and so variation within these genes provides information on the immunological fitness of the population under study. The aims of this study were: (i) to develop the SSCP technique; (ii) to investigate the level of genetic variation at the peptide binding region (PBR) of the DRB1 gene in four South African buffalo populations. (iii) This data was then compared to data generated previously in a study on the same populations using microsatellite DNA, (iv) the statistical comparisons were used to assess the appropriateness of SSCP data for population genetic analysis. Levels of heterozygosity, allelic diversity and population differentiation were quantified using MHC DRB1 gene. The amplified region (Exon 2 of the DRB1 gene) showed high levels of variability, with 77 alleles found in the 84 individuals examined using SSCP analyses.

Includes bibliographical references. / Farmed abalone is a reliable and good quality source of abalone. Cryptococcus species SS1 was isolated from the gut of the South African abalone, Haliotis midae, and has been identified as a potential probiotic for farmed abalone. The implementation of strain SS1 as a probiotic for aquacultured abalone required the design of a fermentation system to produce hjgh concentrations of the yeast strain in order to supply the probiotic to commercial abalone producers. The aim of this project was to assist in the recommendation of a commercial fermentation process that is economically feasible for the production of strain SS1. This involved evaluation of all the main factors that will contribute to the cost of the fermentation; i.e. cultivation medium, fermentation space and time, and productivity.

Includes bibliographical references. / The cell wall is a dynamic and elastic structure that provides osmotic and physical protection to the yeast cell (l). As such, it forms the immediate site of contact between the yeast cell and its environment (2), and is essential for maintaining cell integrity and shape. Cell growth and development demand that the cell wall is not rigid and unchangeable as the cell needs to adjust the wall composition and structure during growth and development stages such as morphogenesis, flocculation, cell-cell recognition and pathogenicity, and in response to changes in environmental conditions (l, 2, 3, 4).

Dominant white, a mutation of the I gene, leads to amelanosis and is common to many commercial breeds of fowl, including Pile Games, White Plymouth Rocks and White Leghorns. Despite much investigation on the cellular mechanisms of Dominant white, its mode of action is still poorly understood. The aim of this study is to elucidate the molecular basis of amelanosis in WPR X PG chickens by addressing the following two questions: are melanocytes present in the skin regions and feather follicles in normal numbers of 8- to 13-day white chick embryos? If melanocytes are present in normal numbers, are they unable to synthesise pigment because of a defect in melanocyte differentiation? Two approaches were used to answer the first question. MelEM, a monoclonal antibody, shown to react specifically to quail melanocytes, was found to be unsuitable for localisation of chicken melanocytes. Secondly, in situ hybridisation with tyrosinase and tyrosinase related protein-2 (TYRP2) probes was carried out to quantitate the number of melanocytes at different stages of development. The results indicate that tyrosinase - and TYRP2 -expressing melanocytes are present in 10-day white chick skin and feather buds in normal, if not greater numbers than in the control (Black Australorp) breed. This suggests that amelanosis is not due the failure of migratory melanoblasts to reach the developing feathers, nor is it due to the selective elimination of melanocytes during migration. The results further showed that with increasing developmental age (12- and 13-days), there is a decline in the number of tyrosinase - and TYRP2-expressing melanocytes in the white chick breed in comparison to the black breed. This suggests that white skin melanocytes either downregulate tyrosinase and TYRP2 gene expression yet remain viable, or they undergo cell death. At 17-days, the results showed an absence of gene expression in both the black and white follicles due to the normal process of feather development. Thus, although WPR x PG melanocytes are present in normal numbers in 10-day skin and feather follicles, they never melanise. To address this issue, black and white neural crest cells were cultured in conditions resembling their respective skin environments. Firstly, black neural crest cells grown in defined medium with either black or white skin extract were able to synthesise melanin. This suggests that white skin contains the appropriate signals necessary to induce melanogenesis of black melanocytes. This in turn suggests that the white melanocyte itself is intrinsically defective. To test this, white chick neural crest cells were grown in defined medium in the presence of black or white skin extract. The results showed that white cells were able to respond to signals in extracts of skin from both breeds and became melanised, suggesting that white melanocytes are not intrinsically defective. Due to the intricate nature of this study and subsequent experimental limitations encountered, these contradictory results could not be completely resolved. However, a testable model in which the I gene is postulated to encode c-kit is presented.