The pattern of regenerating optic axons following various surgical manipulations in the goldfish brain has been studied using ('3)H proline radioauthography. The results demonstrate that in most cases severed optic axons regenerate preferentially into degenerating axonal pathways. It is therefore suggested that the degenerating axonal debris and the concomitant glial proliferation in a degenerating pathway, in some way, influences the entry of regenerating optic axons into the path. However, in view of the exceptional cases in which regenerating optic fibers either failed to grow into a degenerating pathway, or grew into pathways which apparently did not degenerate, it is further suggested that the influence of the degenerating pathways on the regenerating optic axons is neither 'compelling' nor 'restrictive'. Similarly, although the results also demonstrate that denervated optic terminal zones may influence the choice of pathways by regenerating axons and that the proximity of a pathway to the regenerating optic axons may do so as well, such influences are also neither 'compelling' nor 'restrictive'. Taken together, the data presented here indicate that the guidance of regenerating optic axons is probably influenced by a combination of these factors.

Patterns of proliferation and changes in total cell number in the optic nerve, tract and tectum of goldfish have been examined following optic nerve crush or optic enucleation, using bromodeoxyuridine to label the proliferating cells. In general, an increase in proliferation and total cell number in all parts of the visual system was observed peaking between 7 and 14 days and resolving itself to normal or near normal levels by 32 days postoperative. Enucleation resulted in elevated proliferation values as compared to animals with an optic nerve crush, at least one early timepoint in each part of the visual system, but overall, there is little to suggest that axons are exerting a major effect on the cellular response. Finally, a seasonal effect on the proliferative response of non-neuronal cells and axonal regrowth has been demonstrated. Fish acclimatized under autumn-like conditions showed a faster initiation of the non-neuronal cell response and an enhanced rate of axonal regrowth when compared to fish acclimatized under spring-like conditions. It is believed that photoperiod plays a major role in the seasonal effects observed with temperature playing only a minor one.

This study aims at providing a new technique for the isolation and culture of goldfish microglial cells. So far no protocol has been designed for the growth of these cells in vitro, despite the growing interest in the remarkable capacity of goldfish central nervous system (CNS) for regenerating severed axons. This newly developed technique has little or no similarity to those used in the isolation of mammalian microglia, and is distinguished by its simple setup and its fast yield for microglial cells. In addition, a virtually pure population of microglia was generated when plated on untreated plastic dishes, eliminating further need for purification. This technique may thus provide a starting point for future characterization of the microglial cells in vitro, which may eventually help toward building a better understanding of the function and biology of these cells. A preliminary morphological characterization of the cells has also been conducted, in addition to groundwork experiments on the phagocytic activity of these cells in vitro, using myelin to stimulate phagocytosis. These assays were oriented toward providing a comparison to the mammalian cultures of microglia, and so far, displayed several similarities in morphologies and phagocytosis.

No description available.

The generation of macrophages requires the coordinated responses to stimulatory and inhibitory signals that cell receive from their environment. While the up-regulation of macrophage production and survival is essential to fortify the immune system, their down-regulation is also vital to prevent macrophage related diseases and malignancy. Previous studies in goldfish showed that primary kidney macrophages release endogenous growth inducing factors into proliferative phase supernatant, which up-regulate their proliferation and survival. In this thesis, the effect of senescence phase supernatant (collected from goldfish primary kidney macrophage cultures) on goldfish primary kidney macrophages proliferation, survival and its impact on the ability of macrophages to tolerate H2O2 was analyzed. The results showed that the senescence phase supernatant down-regulated the proliferation and survival, and decreased the chemical tolerance of the cells. This indicated that the goldfish primary kidney macrophages promote targeted control of their proliferation and survival by secreting endogenous growth inhibitory factors in the senescence phase supernatant. / Physiology, Cell and Development Biology

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 109-144).

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 89-106).

Thesis (M. Phil.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 77-85).

Thesis (M.Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 109-144) Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.