الفهرس | Only 14 pages are availabe for public view |
Abstract Polyvinyl alcohol (synonyms, vinyl alcohol polymer, PVA, ethenolhomopolymer) is a water-soluble synthetic resin, prepared by the polymerization of vinyl acetate, followed by partial or complete catalysed hydrolysis. In this study , the effect of thermal degradation products of PVA was studied in Clarias gariepinius. The half lethal concentration of thermally decomposed PVA was 1.1 g/l. Fish were categorized into 4 groups : the first act as control , the second exposed to 1/2 half lethal concentration for 1 w ( short term intoxicated group) , while the third and the fourth exposed to 1/5 and 1/10 half lethal concentration for 6 w( long term intoxicated groups). The PVA exposed fish showed nervous manifestations, , abnormal swimming behaviour in the form of erratic swimming and/or circling was also noticed beside abnormal skin disclouration in few cases and darkness in the others. The postmortem findings revealed, congestion and haemorrhages in all internal organs in addition to pale anaemic gills. Mortality rate was 50 % in short term PVA exposed group while was about 40 % and 30 % in fish groups exposed to 1/5 and 1/10 half lethal concentration of PVA during long term exposure. Biochemical investigations declared that there was significant increase in lipid peroxidation product ( malondialdehyde) , glutathione-s-transferase, catalase and superoxide dismutase ,alpha fetoprotein, tumor necrosis factor and interleukin-6 in both short and long term PVA intoxicated fish while there was a significant increase in reduced glutathione during short term exposure and significant decrease during long term exposure. Results of proteinogram showed that there was a significant hyporoteinaemia, hypogloblinaemia and hypoalbuniaemia in both short and long term PVA intoxicated fish in addition to a significant decrease in total immunoglobulins in PVA intoxicated fish. It was concluded from Abstract and Introduction 2 this study that although PVA is a safe widely used product , the thermal degradation products of PVA had several toxic effects in fish . These toxic effects could be attributed to that the PVA, after thermal treatment, can form chromophoricpolyene structure, as well as carbonyl and hydroxyl groups. |