Changeable aspects of radiation-induced chromosome aberrations during early development of the zygote

为了了解辐射诱导的染色体畸变（CAs）在胚胎发育过程中的变化，我们对γ辐照（2,4 Gy）精子的小鼠胚胎进行了细胞遗传学和胚胎学研究。建立了一种非常成功的小鼠1- 4细胞胚胎染色体制备方法。辐照组和对照组共1170个受精卵进行核型分析。具有结构染色体畸变（SCAs）的受精卵表现出明显的剂量依赖性，在4 Gy组中达到36%。未发现非整倍体的剂量依赖性增加。2 .最主要的类型是染色体断裂/片段（60%），其次是双中心染色体（25%）。对396个2细胞胚胎进行了核型分析。SCAs胚胎的发生率与单细胞胚胎几乎相同，但其中约90%转化为嵌合型SCA。在辐照组中，sca衍生的非整倍体的发生率也显著高。对537个4细胞胚进行了核型分析。绝大多数SCA胚为嵌合型。非整倍体的发生率下降，表明它们再次转化为镶嵌型。约50%至60%的SCA胚胎进入囊胚期，没有发育停滞或延迟。对85个活胚胎（10 ~ 11日龄）的2240个体细胞进行染色体分析。所有胚胎均未发现染色体异常。辐照组胚胎着床后死亡发生率明显高于辐照组，死亡胚胎几乎都处于退化状态。这些结果表明，CA胚的选择主要发生在着床后。16 ~ 17日龄胎儿未见胚胎死亡或发育异常增加（对52例孕妇的调查），支持上述建议。

To understand changeable aspects of radiation-induced chromosome aberrations (CAs) during the embryonic development, mouse pie-implantation and post-implantation embryos derived from gamma-irradiated (2,4 Gy) spermatozoa were studied cytogenetically and embryologically.1.Ahighly successful method for chmmosome preparation of mouse 1-cell to 4-cell embryos was established.2.A total number of 1,170 zygotes were karyotyped in irradiated and control groups. The zygotes with structural chromosome aberrations (SCAs) showed a clear dose-dependent increase, reaching 36% in the 4 Gy group. No dose-dependent increase of aneuploidy was found. The most predominant type of CA was chromosome breaks/fragments (60%) which was followed by dicentric chromosomes (25%).3.A total number of 396 2-cell embryos were karyotyped. The incidence of embryos with SCAs was nearly the same as that in 1-cell embryos, but about 90% of them converted into mosaic-type SCA. The incidence of SCA-derived aneuploidy was also significantly high in the irradiated groups.4.A total number of 537 4-cell embryos were karyotyped. A great majority of the embryos with SCA were of mosaic-type. The incidence of aneuploidy became decreased, suggesting that they converted again into mosaic type.5.About 50 to 60% of embryos with SCA reached to blastocyst stage, showing no developmental arrest or delay.6.Chromosome analysis was carried out with 2,240 somatic cells obtained from 85 live embryos (10〜11-day old). None of embryos was found to be chromosomally abnormal. The incidence of post-implantation death was significantly high in the irradiated groups, almost all the dead embryos were being in the state of degenerated conceptus. These suggest that selection of the embryos with CA mainly takes place immediately after implantation.7.No increase of embryonic death or developmental anomalies was observed in 16〜17-day-old fetuses (survey of 52 pregnant females), supporting the above-mentioned suggestion.