Abstract

The presence of polychlonnated biphenyls (PCBs) in our environment continues to pose a threat to aquatic animal health. The environmental stability and lipophilic nature of PCBs has led to global contamination and bioaccumulation within the food chain. PCBs have been found in almost every natural medium including water, air, soil, animal and human tissues.⁷ Recent studies have shown PCBs to be potential neurotoxic agents.^3,4,6,8,9 The goal of this project was to develop a marine invertebrate model to study possible developmental deficits in the embryonic nervous system related to PCB exposure. The study was designed to compare the neuronal development of molluscan embryos treated with PCBs to embryos with no PCB exposure using in vitro fertilization, immunocytochemistry, and confocal microscopy.

Briefly, adult surf clams (Spisula solidissma) were collected from Nantucket Massachusetts and gametes collected by gonadal excision. In vitro fertilization was performed in artificial sea water,¹² and fertilization events were observed and recorded. Aroclors 1254, a predominant mixture of PCBs in the environment,⁵ was added to embryos following fertilization and was removed by washing prior to mobilization. PCB concentrations ranged from 1 to 500 ppm, representing environmentally relevant doses in New Bedford Harbor, an EPA Superfund site. Embryos were cultured and then fixed at 48 and 72 hours post-fertilization. To study serotonergic neuronal development embryos were incubated with either rabbit anti-serotonin IgG or normal rabbit IgG (control) followed by a secondary FITC labeled antibody. To study dopaminergic neuronal development embryos were incubated with either mouse anti-tyrosine hydroxylase IgG or normal mouse IgG (control) followed by a secondary FITC labeled antibody. Confocal necroscopy was used to quantitate serotonergic and dopaminergic neuronal expression witlun both PCB exposed and unexposed embryos. Preliminary results showed a decrease in number of serotonergic and dopaminergic cell bodies at 72 hours post-fertilization as a result of exposure to 500 ppm PCB. Data will continue to be collected to assess statistical relevance of the variation in nerve cell body numbers between PCB treated and untreated embryos.

A marine invertebrate model was developed to study the toxic effects of PCBs and other environmental pollutants on the embryonic development of the nervous system using serotonin and dopamine as neuronal cell markers. The applications of this model in environmental toxicology research are profound, including detection of mechanistic changes due to low levels of contaminants in the aquatic environment. Furthermore, the applications of the model are not limited to study of the nervous system. With the incorporation of additional cell markers into the experimental design, we will be able to study the effect of PCBs on the development of both endocrine and immune systems. In by providing a means of identifying the physiological mechanisms of pollutant toxicology, we win address the short and long term consequences of environmental contamination on aquatic wildlife.

Acknowledgements

This research is funded in part by a grant from the Sweet Water Foundation and a NIH Short-Tenn Training Grant (T3 5DKO7635). The authors would like to thank Lewellys Barker, Mark Martindale, Roxanna Smolowitz, Joan King, Louie Kerr, and Bob Brown for their expertise and assistance on this project.

References

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