ASSESSMENT OF THE ROLE OF AFLATOXIN IN THE AETIOLOGY OF CARCINOMA OF THE MUCOSA OF THE ETHMOID
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Date
1995
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES Mannuthy - Thrissur
Abstract
The present investigations were planned to assess the
role of aflatoxin B, (APE.) and/or virus in the aetiology of
ethmoid carcinoma using pig as a model in yivQ and bovine
ethmoid mucosa culture in vitro.
Thirty-two, Large White Yorkshire piglings of
two-three months age were procured from the University Pig
Breeding farm, Mannuthy and divided at random into four groups
of eight each.
The pigs in group I and group II were administered
aflatoxin B^ (0.070 mg/kg b.wt/inoculum by intravenous route
at weekly interval for six months) and/or ethmoid tumour
extract (2 ml/pig/inoculum, intranasally, at fortnight
interval for three months) . The pigs in group III were
administered ethmoid tumour extract alone, while the pigs in
group IV were kept as negative controls.
During the period of observation of 18 months all the
pigs of different groups given AFB, and/or ethmoid tumour
extract appeared healthy and no clinical manifestation of the
carcinoma of the mucosa of ethmoid was observed. However,
there was appreciable reduction in the weight and mild degree
of depression.
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In the AFBj^ treated pigs, sacrificed at 9, 12, 15 and
18 months of investigation, the ethmoid mucosa had greyish
white, soft and oedematous appearance along with scattered
small pale elevations at necropsy. Histologically, the
ethmoid mucosa exhibited hyperaemia, varying degree of
mononuclear cell infiltration and fatty degeneration in the
initial stages. In the later stages, there was proliferation
of mucous glands showing acinar, tubular or papillary
arrangements. Occasionally papillary projection of the surface
epithelium and focal squamous metaplasia were also observed.
Ultrastructural features of the cells of the ethmoid mucosa
consisted of both productive and degenerative changes. The
cells had sparse cytoplasmic organelles. The poor cytoplasmic
contents and irregular nucleus with nucleolar margination were
the other electron microscopic features observed in the
ethmoid mucosa of AFB^ treated pigs.
AFB^ in the range of 43.12-139.43 ppb could be
detected in the blood of 52.37 per cent of the ethmoid tumour
bearing cattle analysed in the present study.
The blood samples from the AFB^ treated pigs were
positive for AFB^ (40-160 ppb) upto 10 days after the
withdrawal of treatment whereas AFM^ could be detected in
blood sample of one pig only upto 3 days after the treatment.
The ethmoid mucosa analysed after 3 months and at subsequent
specified intervals was consistently negative for AFB and
AFM
By concerted efforts cells of the mucosa of the
ethmoid were established ^ vitro. AFB^^ treatment of long
term epithelial cultures initiated from the primary culture of
bovine ethmoid mucosa origin resulted in morphological
transformation accompanied by increased growth in soft agar
and cytochemical positivity of gamma-glutamyl transpeptidase.
This confirmed the tumourigenicity of AFB^. The
xenotransplantation of these iji vitro transformed epithelial
cells in mice was not successful.
Electron microscopic studies of the cells of the
carcinoma of the ethmoid mucosa in spontaneous cases of cattle
revealed varying ultrastructural features. The neoplasticoells
were either well differentiated secretory structures or
undifferentiated ones. Desmosomes and tight junctions were
seen between the epithelial cells. Endoplasmic reticulum and
mitochondria varied in their contents and degree of
disorganization. Nucleus was highly pleomorphic and
predominantly euchromatinic.
The retroviral like particles were demonstrated
intracellularly and occasionally in extracellular spaces in
the neoplastic cells of 7 tumour bearing cattle. Similar
particles were also seen in the cell free ethmoid tumour
extract in three of 21 tissues examined.
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