Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Beverly A. Weeks-Perkins


Cell-mediated lysis of cultured tumor target cells by nonspecific cytotoxic cells (NCC) was examined in the oyster toadfish (Opsanus tau), an estuarine teleost. NCC activity was evaluated in cells taken from the head kidney, peripheral blood, spleen and peritoneal cavity. NCC activity was a property of plastic nonadherent cells which lacked phagocytic activity, indicating that in terms of their functional capacity, the cells which mediate nonspecific cytoxic immune responses in oyster toadfish do not appear to be monocytes or macrophages. However, light and electron microscopic examination of these cells revealed that morphologically, they resemble monocytes and macrophages. A new technique to assess in vitro phagocytic function of fish macrophages is described. This assay involves the spectrophotometric measurement of congo red-stained yeast cells that have been phagocytized by macrophages. The assay is simple, rapid and reproducible. Furthermore, it is less subjective than previously described methods that employ microscopic examination of cells. Using this technique with oyster toadfish, phagocytosis of yeast cells was found to increase with time, reaching a maximum between 60 and 90 minutes (as determined by absorbance at 510 nm). Sampling sites selected for this field investigation had a sediment-bound polycyclic aromatic hydrocarbon (PAH) concentration gradient of 55 ppb to 96,000 ppb total PAH. Results of this study suggest that varying levels of PAH contamination did not lead to significant between-site differences in terms of simple ability of oyster toadfish macrophages to phagocytize foreign particles. This technique has been used in studies designed to characterize the functioning of oyster toadfish NCC and in toxicological investigations comparing the effects of PAH and NCC and macrophage function in oyster toadfish. Studies were undertaken to determine the effect of the chemical carcinogen 7,12-dimethylbenz (a) anthracene (DMBA) on the function of oyster toadfish peritoneal nonspecific cytotoxic cells (NCC) and macrophages. The functioning of these two cell populations was assessed in terms of their ability to lyse cultured tumor target cells and to phagocytize yeast cells, respectively. In a time-course study, the effects of DMBA on NCC activity were found to be highly persistent. Following a single intraperitoneal injection of 10 mg/kg, NCC activity was again virtually eliminated, and did not recover throughout the 28 days of the exposure study. (Abstract shortened by UMI.).



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