Influence of gestational age at exposure on the prenatal effects of gamma-radiation.
The abdominal region of pregnant Swiss albino mice was exposed to single dose of 0.5 Gy gamma-radiation at gestation days from 1.5 to 17.5 days post-coitus (p.c). The animals were sacrificed on day 18 p.c. and foetuses were examined for resorption and embryonic death, foetal death, growth retardation, small head, low brain weight, micro-phthalmia and any other gross morphological abnormalities. The period of maximum sensitivity for each effect varied. The only demonstrable effect of irradiation during the pre-implantation period was an increase in prenatal mortality. Resorptions were maximal after exposure between days 2 and 4 p.c. The pre-implantation irradiated embryos which survived did not show any major foetal abnormalities. These results confirm earlier mouse studies using higher doses of X-rays. Small head, low brain weight and microphthalmia were prominent after exposure during the late organogenesis period, especially between days 9 and 13 p.c. But no other externally visible anomalies were detected. These findings demonstrate that mouse organogenesis is very sensitive to radiation-induced retardation of development, even at doses < 1 Gy. One exencephaly, one cleft palate and two cases of open eyelids were observed in the foetuses exposed on days 14.5 and 15.5 p.c.; the number of these cases was too small to indicate a causal relationship with exposure.
Devi
P U
PU
Department of Radiobiology, Kasturba Medical College, Manipal, India.
Baskar
R
R
D000016:Abnormalities, Radiation-Induced; D000818:Animals; D001921:Brain / Q000528:radiation effects; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D005720:Gamma Rays; D005865:Gestational Age; D008297:Male; D051379:Mice; D008850:Microphthalmos / Q000209:etiology; D009929:Organ Size / Q000528:radiation effects; D011247:Pregnancy