Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Cataract formation in the Elizabeth River (ER) has been reported since 1986. Previous studies have concentrated on describing cataract as a function of exposure to polluted sediments, especially polycyclic aromatic hydrocarbons (PAH). These studies, however, have not examined what processes might be involved in fish cataractogenesis. The overall objective of this research was to identify important processes associated with the early development of cataract in feral fish populations. Field studies were used to systematically examine cataract development. Cataract in sciaenids was not associated with previously described cataractogenic factors, but could be linked to contaminated sediments of the ER. Cataract was highly prevalent, first appeared at the visible center of the lens, varied in the degree opacification (&<&10-100%), could be classified into stages of development (stage 1-4), and inhibited lens growth. Furthermore, data showed that a positive association existed between bottom water temperatures (&\sp\circ&C) and cataract prevalence. Biochemical comparison of lenses revealed that the water content, cholesterol level, and free fatty acid composition were significantly elevated, total esters reduced, while no significant changes occurred in the protein composition of lenses with early cataract development. These data suggest that altered plasma membrane permeability might be involved in opacification. Investigations of cataract in fish at the cellular level have not been studied due to the absence of a reliable in vitro model. Protocols were established for the primary culture, successful passage (45 subcultures), and the long-term maintenance (54 months) of spot lens epithelial cells. Cells exhibited certain morphological characteristics, crystallin-protein composition, and chromosome complement indicative of epithelial cell differentiation and cell-line transformation. In vitro experiments indicated that both DNA and RNA indices were positively associated with cataract development in spot lenses. Results suggested that high molecular weight PAH may play a role in interfering with the mitotic cycle of epithelial cells. These results suggest that lens epithelial cells are disturbed and may be involved in the initial steps of cataractogenesis. In conclusion, results demonstrate that cataract development is associated with high levels of contamination found in the ER. Altered membrane permeability and epithelial cell function may play a key role in cataract initiation.
© The Author
Williams, Christopher D., "Investigations into cataract formation in sciaenid fish species from the Elizabeth River, Chesapeake Bay, Virginia" (1994). Dissertations, Theses, and Masters Projects. Paper 1539616904.