MVSc

A cytogenetic investigation on the effect of long-term
..
background radiation on cattle was carried out in this study.
It involved the analysis of sister chromatid exchanges (SCEs)
which was the most sensitive and quickest mammalian system to
find out the effect of mutagens on genetic material.



The


technique


standardized


for


sister


chromatid



differentiation (SCD) involved culturing of lymphocytes in
RPMI-1640 medium and incorporation of 5-bromo-2-deoxy uridine
(BrdU) at 20th hour of incubation. The cells were harvested
at the end of 70th hour and the thionine stained~slides were
exposed to UV light for one hour at a distance of one foot



from the UV source.
analysed for SCE.


Metaphase spreads showing SCD were



Cattle reared in the four coastal wards of Chavara
Panchayat (Kovilthottam, Cherusseribhagam, Kolangarabhagam and



Kari thura) were taken as experimental group.


Cattle from



University Livestock Farm (ULF) , Mannuthy, which has no
reports of background radiation, formed the control group.
The mean SCE frequency per cell was found to be 1.536 ±
0.249 and 3.368 ± 0.273 for control and experimental groups,

respectively. The range and number of SCEs/cell/generation
for control animals were 0 to 5 and 0.768, respectively. In
the experimental group it was 0 to 9 and 1.684. Thus an
increase of 119.27 per cent in SCE frequency was recorded in
high background radiation area when compared to that of
control.
The mean SCE frequencies for cattle of Kovilthottam,
Cherusseribhagam, Kolangarabhagam and Karithura were 4 ±
0.966, 2.563 ± 0.584, 3.206 ± .411 and 3.389 ± 0.504,
respectively and the SCE ranges were 0 to 7, 0 to 6, 0 to 7
and 0 to 9. There was no significant difference in SCE
frequency among the four wards. The difference between SCE
frequencies of Kovilthottam, Kolangarabhagam and Karithura to
that of control was significant. This could be due to the
effect of high background radiation on DNA and chromosomes.
However, difference in SCE frequency between Cherusseribhagam
and control was not significant. This could be due to non-
homogenous distribution of monazite deposits in the coastal
belt.
Though the increase in SCE frequencies in Karithura,
Kolangarabhagam and Kovilthottam were statistically
significant, cattle reared in this area did not reveal any
deviation in physiological and phenotypic performance.
Thus this study indicates that SCE frequenc,y for cattle
reared in Chavara panchayat with high background radiation



was significantly higher than that of control group. This
discloses the occurrence of chromosomal damage in this area
though these cattle performed normally. This may be because
of the repair mechanism or balanced by exchange mechanism
during active replication of chromosomes.