165 albino rats of different ages (immature, adult and senile) were
utilized to test the effect of Malathion ingestion on the visual cortex. The
animals were divided into four groups according to the age (one day, 3 weeks,
3 months and 18 months) and each group was subdivided into subgroups
comprising controls and experimentals. One hemisphere was used to prepare
paraffin sections to study the general arrangement of the cortical layers in
different age groups (Hx & E), to test the integrity of Nissl granules (toluidine
blue), to detect myelin sheaths (Heidenhain's modification of Kultschitsky's
method), to detect the neurofibrils (Glees' silver stain) as well as to estimate
the diameters of the granular cells, the surface areas of the pyramidal, lozenge
and flattened cells, the thickness of the cortical layers and to quantitate the
results in control and experimental subgroups to make the statistical
comparison (Student-t test). The other hemisphere was used to prepare frozen
sections to detect the activity of non-specific esterase, choline esterase and
adenosine triphosphatase enzymes.
The results showed that Malathion caused shrinkage of cells in all age
groups with a decrease in the thickness of layers only in animals of the young
groups. In addition, degeneration of neurofibrils and chromatolysis were
observed in all treated groups.
Histochemical observations showed a decrease in the activity of nonspecific
esterase and choline esterase enzymes, thus contributing for the
blockage of cholinergic transmission, which results from the accumulation of
acetylcholine. On the other hand, Malathion administration led to increased
ATP-ase reactivity possibly as a compensatory mechanism to increase the
metabolic efficiency of the affected cells |
