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既往研究发现，高传能线密度（ Ｌ Ｅ Ｔ）辐射可引起正常人细胞遗传不稳定，但低 Ｌ Ｅ Ｔ 照射是否也有此现象尚不清楚。作者探讨了 ６ Ｇｙ Ｘ 射线照射后幸存的正常人胚细胞克隆株的迟发再生死亡和有丝分裂期细胞染色体形成情况。从照射组和对照组培养细胞中分离出 １８ 个原始克隆株进行第二代克隆生长。 Ｘ 射线照射后幸存细胞组有 ６ 个原始克隆株生存，显著地低于对照组的克隆率（ Ｐ＜ ０．００１），对照组和照射组的平均克隆率分别为 １６４％ 和 ７２％ 。照射组克隆率在第三代克隆形成时仍然表现出降低，表明 Ｘ 射线照射正常人类细胞后克隆率持续降低的遗传可超过 ４０ 代。照射后幸存的克隆株中有 ５ 个经常出现多样巨大细胞，而对照组的克隆株中则很少出现。在进一步分析体外亚克隆形成过程中细胞分裂后期染色体情况时发现，４ 个接受６ Ｇｙ Ｘ 射线照射后幸存细胞株染色体桥的形成明显增高（ Ｐ＜ ０．００１），且微核形成明显增加。结果表明，低 Ｌ Ｅ Ｔ 照射可引起正常人胚胎细胞遗传不稳定，并且 Ｘ 射线照射后幸存细胞的后代断裂染色体末端错位接合增加。
Previous studies have found that high energy density (L E T) radiation can cause normal human cells genetic instability, but whether low L E T irradiation is also the phenomenon is not clear. The authors investigated the delayed death of normal human embryonic cell clones surviving 6 Gy X-ray irradiation and the chromosomal formation of mitotic cells. Eighteen original clones were isolated from irradiated and control cells for second generation clonal growth. The survival of 6 surviving cell groups after X-ray irradiation was significantly lower than that of the control group (P <0.001). The average clonality rates of control group and irradiation group were 16.4% and 77%, respectively 2%. The cloning efficiency in the irradiated group still showed a decrease when the third generation clone was formed, indicating that the inheritance of the clonal rate decreased continuously after X-ray irradiation on normal human cells can exceed 40 generations. Five of the surviving clones that emerged after irradiation had diverse, large cells often found in the cloned colonies of the control group. Further analysis of the chromosomal status during the late stage of cell division during in vitro subcloning revealed that the formation of chromosome bridges in the surviving cell lines was significantly increased (P <0.001) and the formation of micronuclei was significantly increased after irradiated with 6 Gy X-rays. The results show that low L E T irradiation can cause normal human embryonic cells to be genetically unstable, and the displacement of the surviving cells after X-ray irradiation breaks up the end of the chromosome mismatch junction.