Call number: LD2668 .T4 1951 H38 / Master of Science

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M.Sc. (Zoology) / Please refer to full text to view abstract

Four commonly occurring genera of ticks in South Africa were tested for their capacity to acquire and transmit Borrelia burgdoiferi, the causative agent of Lyme disease. Attempts were made to infect rabbits with a culture of B. burgdoiferi, and tick transmission experiments were carried out using the rabbits as the host of infection. Only one rabbit was successfully infected. Histological changes associated with a B. burgdoiferi infection were noted in this rabbit, but no spirochaetes were isolated. All other host animals failed to become infected with the B. burgdoiferi. As a consequence transmission experiments with the local ticks failed. Serological surveys conducted on rodents, horses and cattle using immunofluorescent and haemagglutination tests indicated that there is evidence that Borrelia species occur widely and that there is a possibility of B. burgdoiferi occurring in South Africa. Studies conducted on ticks from suspected endemic areas revealed the presence, in Ixodes bakeri only, of a spirochaete-like organism that reacted with monoclonal antibody H5332. Shortcomings of the study are highlighted and proposals are presented to address the problem of identifying specific B. burgdoiferi infections.

Liposomes have important potential as drug delivery vehicles. However, in order to realize this potential, much basic research is required to elucidate the interactions experienced by liposomes in vivo. In this thesis two aspects of these interactions are investigated: the influence of vesicle size and lipid composition on the biodistribution observed in vivo; and the interaction of liposomes with plasma proteins. In order to determine the in vivo behavior of liposomal systems, a new vesicle marker is synthesized (¹²⁵I-tyraminyl-inulin, ¹²⁵ITI) and tested in vivo. It is shown that this probe satisfies the necessary criteria for an accurate marker of liposome behavior, and is superior to probes used by other workers in terms of accuracy, convenience, high specific activity, low tissue quenching and cost. The use of ¹²⁵ITI as a vesicle marker allows accurate measurements to be made with lower doses of liposomes than previously employed. The influence of vesicle size, composition, and dose on the blood residency times, leakage and tissue distributions of vesicles was therefore investigated at these lower doses, employing a cannulation procedure to monitor vesicles. It is demonstrated that the clearance of vesicles from the circulation exhibits biphasic kinetics. The relative number of vesicles cleared during the early phase (halflife <20 min) is decreased by increasing the vesicle dose or decreasing the size. The behavior of small vesicles produced by extrusion is also investigated, and the in vivo behavior of these systems is shown to be equivalent to conventional sonicated systems. The second part of this thesis investigates the binding of plasma proteins to vesicles in vitro. It is shown that vesicles bind a large number of plasma components and that the binding is strongly dependent on the surface charge of the vesicle. Some of the proteins have been tentatively identified with 2-D electrophoresis and several were positively identified via immuno- autoradiography. A hypothesis is advanced regarding the role of plasma proteins in the fate of liposomes in vivo. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Master of Engineering

Vector control is fundamental to the suppression and/or eradication of many endemic and epidemic diseases affecting man. The discovery and widespread application of insecticides in vector control programs focused early attention on studies revealing ecological and behavioral characteristics of arthropod vectors. As a consequence of this emphasis, few attempts were made to investigate arthropod cytogenetics. However, recent recognition of the deleterious effects of highly persistent insecticides on the environment and the development of insecticide resistance by vectors of human disease have established the importance of cytogenetics as a base on which programs for control of vector populations may be built (Wrigth and Pal, 1967).

PhD, Faculty of Science, University of the Witwatersrand, 1999

No description available.

No description available.