Candidate: Marla Ann Fisher

Date: Friday, March 12, 2004 1:30 pm - 3:30 pm
2722 Wood

Abstract: Polychlorinated biphenyls (PCBs) are a class of synthetic halogenated aromatic hydrocarbons that are widely used in industry and manufacturing. Due to their resistance to degradation and highly lipophilic nature, PCBs persist in the environment and bioaccumulate in organisms, adversely affecting a variety of health endpoints. I first tested for observable health effects of PCBs in a laboratory model aquatic animal, Xenopus laevis, exposed to PCBs dissolved in dimethylsulphoxide (DMSO) carrier-medium from day 5 through day 9 postfertilization. Exposure to acute, high concentrations of the PCB mixture Aroclor 1254 (10, 50 and 100 ppm) caused statistically significant reductions in survival and body size. In addition, I observed several histological indicators of health effects, including aberrant tail tip, myotomal, and melanocyte morphologies.
I next tested for potential health effects of PCBs in carp (Cyprinus carpio) from the Kalamazoo River Superfund site (MI, USA). Carp are found throughout the Kalamazoo River and feed benthically in heavily PCB-contaminated sediment. I utilized real time RT-PCR to examine mRNA expression levels of multiple genes in hepatopancreas of carp from both juvenile carp exposed to PCBs in the laboratory and from carp caught from PCB contaminated and upstream control sites in the Kalamazoo River. Significantly elevated levels of cytochrome P4501A1 (CYP1A1) mRNA was found in PCB contaminated Kalamazoo River carp (t-test, t=0.0302) and in carp fed PCBs in the laboratory (ANOVA, p=0.0012). However, no significant changes were found in bioindicator oxidative stress genes (gamma-glutamyl cystein synthetase and magnesium superoxide dismutase) and metabolic genes (phosphoenolpyruvate carboxykinase and nucleolin) examined.
I further examined hepatopancras histopathology and ultrastructure in Kalamazoo River carp. I found that carp from PCB contaminated sites have an increased total area (ANOVA, p=0.0263) and number per area (ANOVA, p=0.0453) of macrophage aggregates in hepatopancreas than carp from control sites. Ultrastructural images show an increase in activated phagolysosomes and phospholipid inclusions in macrophage aggregates, suggesting alterations in lipid metabolism. This research indicates that carp are responding to PCB exposure, and that chronically exposed field carp show changes in liver cell disposition that may contribute to health effects.

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