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Sprague-Dawley rats were exposed to vinyl chloride to determine the earliest sequential biochemical changes occurring with liver injury before anglosarcoma development. Activity of glucose-6-phosphatase, a key gluconeogenic enzyme in the liver microsomal fraction, decreased 25% with respect to controls after 70 h of exposure. Glucose-6-phosphate dehydrogenase activity increased twofold after more than 100 h of exposure. Nonprotein sulfhydryl levels (glutathione and/or cysteine) showed a slight but progressive elevation, whereas glutathione reductase activity increased 50-60% during exposure to vinyl chloride.NADPH-cytochrome c reductase and mixed function oxidase were unchanged in the same microsomal fraction. There markers of liver mitochondrial, cytosol, and microsomal function. No significant histological changes were found on light microscopic examination during this exposure period. However, with electron microscopy, dilation of rough endoplasmic reticulum was seen in the animals exposed for more than 137 h. These enzymatic changes are considered to reflect early hepatocellular adaptation to vinyl chloride exposure with very mild or limited hepatocellular injury in its earliest stage.

Public Reporting Burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Final Report for "The Structural Analysis and Bioengineering of Thermostable Pyrococcus furiosus Prolidase for Optimization of Organophosphorus Nerve Agent Detoxification"Report Title ABSTRACTThe aims of this project were to structurally study and bioengineer thermostable prolidase from Pyrococcus furiosus to enable its use for oganophosphorus nerve agent detoxification. Prolidase contains one dinuclear Co metal-center/monomer and has optimal activity at 100°C, exhibiting no activity in the absence of Co2+ or at temperatures <50°C. Requirement for metal ions is characteristic of all organophosphorus nerve agent hydrolases and results from these enzymes containing dinuclear metal-centers with one tight-binding metal atom and a second loose-binding metal atom. One primary objective of this study was to determine which of the metal sites is integral and which is labile, information that will be used to bioengineer prolidases. Another objective was to produce P. furiosus prolidase mutants that have increased catalytic activity over a lower range of temperatures using random mutation and a low-temperature selection method. Three mutant prolidases targeting metal-binding amino acids have been successfully produced and biochemical analysis has demonstrated that the Co1 metal-binding site is the high-affinity site and the Co2 site, the low-affinity site. Conditions for selection of mutant prolidases with increased activity at lower temperatures have been determined and mutant prolidases (G39E and E236V) isolated that have higher activity than wild type at 37 °C.