Yasui L S
Northern Illinois University, Department of Biological Sciences, DeKalb 60115.
Int J Radiat Biol. 1992 Nov;62(5):613-8. doi: 10.1080/09553009214552531.
The survival of parental Chinese hamster ovary (CHO) K1 cells and the DNA double strand break (DSB) repair deficient mutant, xrs-5 was determined after accumulation of 125I decays. Both CHO and xrs-5 cells were extremely sensitive to accumulated 125I decays. The D0 values for CHO and xrs-5 cells were 40 and approximately 7 decays per cell, respectively. The difference in cell survival between CHO and xrs-5 cells was not due to differences in overall 125IUdR incorporation, differences in labelling index (LI) or differences in plating efficiency (PE). Relative biological effectiveness (RBE) values calculated relative to 137Cs gamma radiation survival values (D0 and D10) were higher in xrs-5 cells compared with CHO cells. Although both CHO and xrs-5 cells have high RBE values that correspond to a high sensitivity of CHO and xrs-5 cells to 125I decay. The higher RBE observed for xrs-5 cells in combination with the known repair defect in xrs-5 cells support the idea that unrepaired DNA double strand breaks are lethal to the cell.
在积累了125I衰变后，测定了亲本中国仓鼠卵巢（CHO）K1细胞和DNA双链断裂（DSB）修复缺陷型突变体xrs - 5的存活率。CHO细胞和xrs - 5细胞对积累的125I衰变都极为敏感。CHO细胞和xrs - 5细胞的D0值分别为每细胞40次和大约7次衰变。CHO细胞和xrs - 5细胞之间细胞存活率的差异并非由于总体125IUdR掺入量的差异、标记指数（LI）的差异或接种效率（PE）的差异。相对于137Csγ射线存活值（D0和D10）计算的相对生物效能（RBE）值，xrs - 5细胞比CHO细胞更高。尽管CHO细胞和xrs - 5细胞都具有较高的RBE值，这对应于CHO细胞和xrs - 5细胞对125I衰变的高敏感性。在xrs - 5细胞中观察到的较高RBE值，再加上已知xrs - 5细胞中的修复缺陷，支持了未修复的DNA双链断裂对细胞具有致死性这一观点。
