الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
 |  | from | 178 |  |  |
| | | from | 178 | | |
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.