Effects of ionizing radiation on the early development of Oryzias eggs.

須 山 一 兵*),江 藤 久 美**),:丸 山隆 司***),加 藤 義 雄****),市 川 竜 資*):放 射 線 医 学 総 合 研 究 所,環 境 衛 生 研 究 部*),放射線医学総合研究所,生 物 研 究 部**),放射線医学総合研究所,物 理 研 究部***),放射線医学総合研究所,養 成 訓 練 部****),千 葉市 穴 川4丁 目9番1号 〒260 Continuous irradiation/Fish embryo/Chromosome aberration 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/1) and in 90Sr-90Y (0-1 ,000 ƒÊCi/1), 2) irradiated continuously with ƒÁ-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 26•Ž. The frequencies of chromosome bridges increased significantly when the eggs were treated with solutions of concentrations higher than 0.5 Ci/1 (>19 rad) for HTO and 100 ƒÊCi/1(>58 rad) for 90Sr-90Y, or were irradiated with ƒÁ-rays of 78 rad or more, or were given single doses more than 100R of X-rays. Comparing the continuous irradiation experiments, it is considered that ƒÀ-rays from tritium are more effective than the other radiations in inducing chromosome aberrations. Hatch ability 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 360R.