PhD

An experimental study was carried out to delineate the
pathological effects of ochratoxin in goats. A comparative assessment of
ochratoxin production by A. ochraceus and A. sulphureus on what and
rice under static and shake cultures was also made. A. ochraceus was
found to be a better toxin producing strain in both substrates under
static and shake cultures systems and wheat was a better substrate
than rice.
Toxicity studies were conducted in Sannen – Malabari cross-bred
goats of 1 to 3 months age. Purified ochratoxin produced in the
laboratory was administered by oral, intra-peritoneal and intravenous
routes. The different dose levels adopted were 2.5 mg/kg body weight, 1
mg/kg body weight and 0.5 mg/kg body weight. The synergistic effect of
ochratoxin and aflatoxin in goats was studied by adminstering the
crystalline toxins simultaneously (Makor Chemicals, Israel) by
itraperitoneal route. The parameters of study were: clinical signs,
haematological and biochemical alterations, pathological changes in
urine, and macroscopic, microscopic and ultra-structural alterations in
organs.
Varying degree of clinocopathological changes were noticed in the
test animals. The animals became weak and listless and in general
there was reduction of total erythrocyte count, PCV, haemoglobin and
lymphocyte count. Serum protein level was lowered while BUN and
creatinine and blood coagulation time were high. There was rise in
ALP, SGOT and SGPT in some of the test animals. The changes and
degree of variation depended on the dose, total quantity and rate of
administration of the toxin and duration of the experiment. More
severe alterations were noticed when ochratoxin and aflatoxin were
administered simultaneously. Important changes in the urine were
lowering of pH, albuminurea and presence of epithelial cells and casts.
Pathological changes varied in severity in different organs and
were observed in the following descending order: kidney, liver,
intestines, stomach, lymph nodes, spleen, thymus, genital organs,
endocrines. In the kidneys, the order of intensity of pathological
alterations was: proximal convoluted tubules, Henle’s loop, distal
convoluted tubule, glomeruli, collecting tubules. Retrogressive changes
of different degree and necrosis of the lining epithelial cells of tubules
and endothelium and epithelium of glomeruli were the important
lesions. Changes in glomeruli and Bowman’s capsule noticed in the
higher dose group included shrinkage of glomeruli and presence of
proteinaceous material in the capsular space. Eosinophilic granular
casts and PAS positive bodies were present in the lumen of tubules. The
necrobiotic renal changes were more intense when orchatoxin and
aflatoxin were administered simultaneously. Hepatic lesions were
mainly fatty infiltration, necrosis of hepatocytes and haemorrhage. The
changes were most severe in combined toxicity. Mallory bodies and
mild biliary hyperplasia were noticed in a few sections. Necrosis and
subsequent depletion of lymphocytes wee the lesions in lymph nodes,
spleen and thymus in some test animals. Degenerative changes were
also noticed in testis, ovary, pituitary, adrenals and pancreas in
experimental groups. In the combined toxicity group the pathological
effect was more intense.
At the ultra-structural level, the hepatcytes as well as the
epithelial cells in the kidney showed severe changes. The cell organelles
were either completely damaged or showed partial configurational
alterations. Mitochondria showed changed in the density of matrix as
well as disorientation and destruction of the limiting membranes and
cristae. Cytolysosomes incorporating damaged cell organelles were
abundant. Disaggregation of ribosomes and fragmentation of ER were
noticed. In the glomerulus, there was destruction of the basement
membrane and disruption of the regular arrangement of the foot
processes of podocytes. In the cytoplasm of hepatocytes, Mallory bodies
and lipid droplets were present. Varying degree of nuclear changes like
clumping, condensation and disappearance of chromatin and
fragmentation of nucleolus and nuclear membrane were observed.
Changes occurred in the tight junctions of epithelial cells of bile ducts.
Pathological alterations were more pronounced when ochratoxin
was administered by the pwerenteral route. Oral administration of
toxin also effected structural alterations which indicated that some
fraction of ochratoxin escaped degradation in the rumen. From this
study it became evident that aflatoxin potentiated the effect of
ochratoxin.
The structural damage to the cells might be due to the inhibition
of oxidative enzymes which is reflected by the extensive ultra-
structural alteration observed in the mitochondria and RER.
Biochemical changes like high BUN and creatinine were evidently due
to necrobiotic changes in the kidney. Interference in the synthesis of
proteins due to damage of hepatic cells and escape of protein molecules
due to alteration in the podocyte foot processes and basement
membranes may account for the reduced serum protein levels. The
nature of organellar destruction and configurational changes in the
cells indicate the toxic potency of the mycotoxin on the biological
system.