Induction of external abnormalities in offspring of male mice irradiated with ²⁵²Cf neutron

To assess the genetic effects of fission neutron, the induction of external malformations was studied in F₁ fetuses after F₀ male mice were irradiated. Male mice of the ICR: MCH strain were irradiated with ²⁵²Cf neutron at doses of 0.238, 0.475 and 1.9 Gy. They were mated withnon-irradiated female mice at 71-120 days after the irradiation. Pregnant females were autopsied on day 18 of gestation and their fetuses were examined for deaths and external abnormalities. No increases of pre- and post-implantation losses were noted at any dose. External abnormalities were observed at rates of 1.40% in the 0.238 Gy, 2.23% in the 0.475 Gy, 3.36% in the 0.95 Gy and 3.26% in the 1.9 Gy groups; the rate in the control group was 1.65%. The dose-response curve was linear up to 0.95 Gy, and then flattened out; the induction rate of external abnormalities was 2.7 × 10^-4/gamete/cGy based on the linear regression. These results indicated that fission neutron effectively induces external abnormalities in F₁ fetuses after spermatogonial irradiation.