Dardalhon M, Nohturfft A, Meniel V, Averbeck D
Institut Curie-Biologie, CNRS URA 1292, Paris, France.
Int J Radiat Biol. 1994 Mar;65(3):307-14. doi: 10.1080/09553009414550361.
We investigated the effects of gamma-ray exposures at high dose-rate (HDR, 23.2 Gy/min) and low dose-rate (LDR, 0.47 Gy/min) on survival and the induction of DNA double-strand breaks (dsb) in a diploid wild-type (D7) and the repair-deficient mutant strain rad52/rad52 of Saccharomyces cerevisiae. Analysis by pulsed-field gel electrophoresis (PFGE) using a contour homogeneous electric field apparatus revealed that, at HDR, in the range 0-400 Gy, dsb are induced as a linear function of gamma-ray dose. Liquid holding recovery in non-nutrient medium (LHR) for 48 h of wild-type cells treated at HDR, significantly increased survival and reduced the yield of dsb. Such changes did not occur in rad52/rad52 cells defective in the repair of dsb. Thus, in gamma-irradiated wild-type cells, an efficient repair of dsb is taking place during LHR. Treatments of wild-type cells at LDR resulted in higher survival and an approximately two-fold lower yield of dsb than at HDR. Such a dose-rate effect was absent in rad52/rad52 cells suggesting that, in wild-type cells during LDR exposures, significant amounts of dsb can be repaired. This repair could be very much accentuated by 48-h LHR of wild-type cells treated at LDR. The relationship observed between gamma-ray survival and dsb repair clearly indicates that increases in survival of wild-type cells, during LDR as compared with HDR exposures and after LHR, are strongly related to the repair of dsb.
我们研究了高剂量率（HDR，23.2 Gy/分钟）和低剂量率（LDR，0.47 Gy/分钟）的γ射线照射对酿酒酵母二倍体野生型（D7）和修复缺陷突变株rad52/rad52的存活及DNA双链断裂（dsb）诱导的影响。使用轮廓均匀电场装置通过脉冲场凝胶电泳（PFGE）分析表明，在HDR条件下，在0 - 400 Gy范围内，dsb的诱导与γ射线剂量呈线性函数关系。在HDR处理的野生型细胞在无营养培养基中进行48小时的液体保持恢复（LHR），显著提高了存活率并降低了dsb的产量。在dsb修复存在缺陷的rad52/rad52细胞中未发生此类变化。因此，在γ射线照射的野生型细胞中，LHR期间发生了dsb的有效修复。在LDR条件下处理野生型细胞，与HDR相比，存活率更高，dsb产量降低约两倍。rad52/rad52细胞中不存在这种剂量率效应，这表明在LDR照射期间的野生型细胞中，大量dsb可以被修复。在LDR处理的野生型细胞进行48小时LHR后，这种修复作用会大大增强。γ射线存活与dsb修复之间观察到的关系清楚地表明，与HDR照射相比，在LDR期间以及LHR之后，野生型细胞存活率的提高与dsb的修复密切相关。
