X-irradiation of pregnant Mongolian gerbils.

Abstract

AbstractFemale Mongolian gerbils were x‐irradiated at various doses from 200r to 1200r on day 2 (fertilized eggs at 2‐cell stage) or day 9 (embryos at the early primitive streak stage) after mating and examined on day 18. No significant differences in numbers of corpora lutea were observed between controls and females irradiated at 200–800r on day 2 or day 9, although irradiation at 1200r on day 2 caused regression of all corpora lutea. Preimplantation loss as determined by the proportion of eggs that failed to implant in the pregnant females, was significantly increased only in the females irradiated at 1200r on day 2 (100% loss) as compared with control animals. The mean numbers of fetuses were significantly reduced in the females irradiated on day 2 at 400r (3.00 ± .71) and at 800r (1.2 ± .37), or on day 9 at 400r (3.0 ± 1.14) or at 800r (0) as compared with controls (5.4 ± .51). The embryonic loss after but not before implantation was significantly increased in all irradiated animals except those irradiated at 200r on day 9. When mated females irradiated at 400r or 800r on day 2 were examined on day 12, 15 or 16 of pregnancy, the mean diameter of implantation sites was significantly smaller in the females irradiated at 800r on day 2 (5.4 ± 0.53 mm) than those in the control females (9.3 ± 0.17 mm). No gross abnormalities of fetuses were observed in the control animals, only two abnormal out of 21 fetuses were found in females irradiated on day 2, but various abnormalities, such as retarded development, cleft palate, spina bifida, acephaly or amorphous fetuses were observed in 20 out of 45 fetuses from females irradiated at 200–400r on day 9. Histological examination of ovaries revealed that all pregnant females had fully developed corpora lutea while the ovaries of females without implantation sites following irradiation contained regressing corpora lutea, and in some cases newly formed corpora lutea. The number and morphology of chromosomes of embryos from females irradiated at 400r or 800r were examined, but no differences were found as compared with embryos of control animals.It appears that whereas x‐irradiation of the 2‐cell gerbil eggs increased the mortality of implanted embryos, irradiation of the early primitive streak stage caused embryonic death as well as developmental abnormalities. Chromosomal abnormalities of fetuses however were not observed.