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M.Sc. / This study was initiated after a clear need to test and establish a more userfriendly fish species for use in routine laboratory bioassays was identified. This led to a literature review of current toxicity testing species of fish being used, internationally as well as nationally, and identifying which species could possibly be the most suited for use in South African laboratories. From this literature review, it was evident that much emphasis is placed on the practicability of the chosen fish species, and the fact that it can easily be bred within the laboratory, as well as the particular fish specie’s general sensitivity to various toxicants over a wide range of concentrations. The objective of this study is therefore to profile various species of fish to determine which species would be most suited to routine toxicity testing under South African laboratory conditions. This will be done through assimilation of available literature as well as personal communications with people with various expertise and experience in working with the particular fish species. This choice will then be based on the ability of the particular species of fish to ‘balance’ amenability to laboratory conditions with general sensitivity to toxicants. Various indigenous as well as exotic species were therefore selected and tested for suitability for routine testing. Exotic species included Poecilia reticulata and Danio rerio, while the indigenous species tested were Barbus trimaculatus, Barbus argenteus, Tilapia sparrmanii, Oreochromis mossambicus and Pseudocrenilabrus philander philander. Breeding experiments were conducted with all of the abovementioned species and, based on these results; recommendations are made as to which species of fish showed the highest degree of amenability to maintenance within the laboratory.

Indiana University-Purdue University Indianapolis (IUPUI) / Bone growth can be impaired due to disease, such as osteoporosis. Currently, intermittent parathyroid hormone (PTH) treatment is the only approved therapy in the United States for anabolic bone growth in osteoporosis patients. The anabolic effects of PTH treatment are due, at least in part, to modulation of the Wnt/β-catenin pathway. Activation of the Wnt/ β-catenin pathway using a small molecule inhibitor of GSK3β was previously shown to increase markers of bone formation in vitro. Our study utilized a zebrafish model system to study Wnt activated fin regeneration and bone growth. Wnt signaling is the first genetically identified step in fin regeneration, and bony rays are the main structure in zebrafish fins. Thus, zebrafish fin regeneration may be a useful model to study Wnt signaling mediated bone growth. Fin regeneration experiments were conducted using various concentrations of a GSK3β inhibitor compound, LSN 2105786, for different treatment periods and regenerative outgrowth was measured at 4 and 7 days post amputation. Experiments revealed continuous low concentration (4-5 nM) treatment to be most effective at increasing regeneration. Higher concentrations inhibited fin growth, perhaps by excessive stimulation of differentiation programs. In situ hybridization experiments were performed to examine effects of GSK3β inhibitor on Wnt responsive gene expression. Experiments showed temporal and spatial changes on individual gene markers following GSK3β inhibitor treatment. Additionally, confocal microscopy and immunofluorescence labeling data indicated that the Wnt signaling intracellular signal transducer, β-catenin, accumulates throughout GSK3β inhibitor treated tissues. Finally, experiments revealed increased cell proliferation in fin regenerates following LSN 2105786 treatment. Together, these data indicate that bone growth in zebrafish fin regeneration is improved by activating Wnt signaling. Zebrafish Wnt signaling experiments provide a good model to study bone growth and bone repair mechanisms, and may provide an efficient drug discovery platform.