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Teratogenic effect of fission neutron and tritium water on rat embryo
Abstract:
The method employed was to give a single whole body exposure of Cf-252 at various doses to pregnant rats on day 8 or 9 of pregnancy, performing microscopic autopsy of the fetuses at the terminal stage of pregnancy, and examining the external and internal organ anomalies. For comparison, an experiment was also made by irradiating pregnant rats with various doses of Co-60 standard gamma-rays at the same dose rate (1 rad/min.). As a result, relative biological effects (RBE) of 2.3-2.7 was obtained from the straight line that was given by modifying by the method of least squares the curves of the frequency of anomalous fetuses in total implants and survived embryos irradiated from 20 to 120 rad by Cf-252 and from 80 to 220 rad by Co-60 on day 8 of pregnancy. Further, the anomalies of Cf-252 and Co-60 irradiated cases were alike in their types of malformations. Using fetal LD50 as an index, 2.4 was obtained as the RBE of cases irradiated on day 8 of pregnancy and 3.1 as that of cases irradiated on day 9. The teratogenic effects of HTO on rat embryos were also examined and the results obtained were compared with those of tritium simulator (Cs-137 gamma-rays) for determining the RBE for the incidence of malformations. Six groups of pregnant rats were injected intraperitoneally with HTO containing 25, 50, 75, 100, 125 or 150 mCi HTO/300g B.W. on day 9 of pregnancy. To obtain accurate RBE values of HTO in rats, six groups of pregnant rats were exposed to Cs-137 gamma-rays by tritium simulator on days 9-18 of pregnancy at exponentially decreasing doses in accordance with body tritium concentration. The rats were sacrificed on day 18 and the offsprings were examined for external and internal malformations. Malformations were seen at the highest incidence of 100% of the survived embryos and 81.3% of total implants in the group given 100 mCi (accumulated doses were about 451 rad) of HTO on day 9 of pregnancy. Tritium simulator accumulated doses of Cs-137 gamma-rays irradiation at 680 rad induced 98.4% malformation in survived embryos and 71.7% of the total implants on day 9 of pregnancy. Both radiations (HTO and Cs-137 gamma-rays) induced similar anomalies of the cardiovascular system in rat embryos.(ABSTRACT TRUNCATED AT 400 WORDS)