Patterns of embryonic mortality in mice after exposure to 137cs gamma irradiation

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Virginia Polytechnic Institute and State University

A series of experiments were designed to test the effects of ¹³⁷cs irradiation on the viability of mouse embryos irradiated in vitro and subsequently transferred to recipient females or cultured in vitro.

The first experiment was designed to evaluate the viability of embryos after combinations of whole body irradiation to the recipient (0, 100 and 200 R) and in vitro irradiation to the embryo (0, 100 and 200 R). Nine treatment combinations were possible. Controls, in which neither recipient or embryo were irradiated, resulted in 41.3% viable fetuses 14 days after irradiation and transfer. Controls were significantly different from all other treatments (P < 0.01). Embryo irradiation at 200 R resulted in 8.8, 4.8 and 12.1% viable fetuses when the recipients received 0, 100 and 200 R, respectively. Embryo irradiation at 100 R resulted in 15.6, 21.4 and 17.7% viable fetuses when the recipient received 0, 100 and 200 R. Irradiation of the recipient at 100 and 200 R, while the embryo was unirradiated, resulted in 18.4 and 25.3% viable fetuses. Irradiation of the embryo had a significant effect (P < 0.05) on the percentage of the fetuses alive 14 days after transfer. Irradiation of the recipient and the dam embryo interaction were not significant in terms of inducing embryonic mortality. There was no significant difference in resorption percentage between the nine treatments.

The second experiment was designed to measure the day of death of embryos placed into each of three treatments. The treatments consisted of controls, recipients receiving 200 R and embryos 0 R, and recipients receiving 0 R and embryos 200 R. Recipients were autopsied on days 4 through 10 following transfer. There was no significant difference between treatments, or on days of autopsy between or within treatments. The two treatments involving irradiation were combined and the days of autopsy grouped into 4 and 5, 6 and 7 and 8, 9 and 10 and compared with controls. Viability and resorptions were significantly different (P < 0.05) on days 8, 9 and 10 in the irradiated embryos when compared with controls.

The third experiment was designed to measure the response of mouse blastocysts irradiated at 0, 100 and 200 Rand cultured in vitro. Irradiation at 100 and 200 R significantly increased degeneration of embryos (P 0.01) and decreased hatching ability (P < 0.01). Embryos were examined using the differential interference contrast microscope at 24, 48 and 72 hours after receiving 0, 100 or 200 R. No consistent morphological changes due to irradiation were observed.