Studies on chromosome aberrations in the eggs of mice fertilized in vitro after irradiation. II. Chromosome aberrations induced in mature oocytes and fertilized eggs at the pronuclear stage following X-irradiation.
Cytological analysis of the first-cleavage metaphase of eggs exposed to X-rays at the mature oocyte stage or the pronuclear stage 4 h after fertilization was performed using the in vitro fertilization technique. The frequency of chromosome aberrations in irradiated mature oocytes increased exponentially with dose, the dose-response relationship being best fitted to the linear-quadratic model. On the other hand, in eggs irradiated at the early pronuclear stage, the frequency increased linearly with dose and the dose-response relationship was best fitted to the linear model. The aberrations were mainly chromosome-type (mature oocytes: 86.0% and pronuclear stage: 88.5%) and the majority were fragments in both cases. Eggs in the early pronuclear stage were markedly more radiation-sensitive than mature oocytes. A comparison of the present results with the previous ones (Matsuda et al., 1985b) showed that the sensitivities to induction of chromosome aberrations were in the order: egg at early pronuclear stage (highest) greater than mature oocyte greater than mature sperm.
D000818:Animals; D002869:Chromosome Aberrations; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005307:Fertilization in Vitro; D051379:Mice; D009154:Mutation / Q000528:radiation effects*; D009865:Oocytes / Q000528:radiation effects*; D014965:X-Rays; D015053:Zygote / Q000528:radiation effects*