Effects of ionizing radiation on the early development of Oryzias eggs

The chromosome aberrations (chromosome bridges) were observed at the blastula stage of Oryzias eggs treated in the following three manners, 1) incubated in HTO (0 - 10 Ci/l) and in 90Sr-90Y (0 - 1,000 μCi/l), 2) irradiated continuously with γ-rays (0 - 74 rad/h), 3) given single doses of X-rays (0 - 500 R), All the treatments were initiated immediately after fertilization (at the one-cell stage). and the continuous irradiation time was eight hours at 260C. The frequencies of chromosome bridges increased significantly when the eggs were treated with solutions of concentrations higher than 0.5 Ci/l (>19 rad) for HTO and 100 μCi/l (>58 rad) for 90Sr-90Y, or were irradiated with γ-rays of 78 rad or more, or were given single doses more than 100 R of X-rays. Comparing the continuous irradiation experiments, it is considered that β-rays from tritium are more effective than the other radiations in inducing chromosome aberrations. Hatchability of Oryzias eggs irradiated with X-rays at the one-cell stage was checked and the dose required for 50% killing of embryos was estimated at 360 R. (author)