Nagasawa H, Robertson J B, Arundel C S, Little J B
Radiat Res. 1984 Mar;97(3):537-45.
When mouse C3H 10T1/2 cells were allowed to reach the density-inhibited plateau phase of growth, 0-3% of the cells were in the S phase as determined by pulse-labeling indices and about 90% of cells were in the G1 phase as determined by flow microfluorometry (FMF). Density-inhibited cultures were exposed to moderate doses of X ray: immediately after X irradiation the cultures were trypsinized and the cells were subcultured at low density in fresh medium. FMF profiles and pulse and continuous-labeling indices were studied. It was determined by pulse-labeling indices that the cell population which was released from the plateau-phase cultures remained in the G1 phase longer than the duration of the normal G1 phase in exponentially growing cells. When plateau-phase cultures were irradiated with 400 rad before subculture, the cells moved into the S phase approximately 4 hr later than did nonirradiated cells. Despite the G1/S delay, both irradiated and nonirradiated cell populations showed a similar rate of progression through the S phase. As determined by cumulative labeling indices, the fraction of cells which remained in G1 up to 120 hr post-subculture (G1 block) increased linearly with X-ray doses. There was no measurable X-ray-induced G1 delay or G1 block in cells irradiated after subculture at the G1/S border during semi-synchronous growth.
当小鼠C3H 10T1/2细胞生长至密度抑制的平台期时，通过脉冲标记指数测定，0-3%的细胞处于S期，通过流式细胞荧光术（FMF）测定，约90%的细胞处于G1期。将处于密度抑制状态的培养物暴露于中等剂量的X射线：X射线照射后立即用胰蛋白酶消化培养物，并将细胞以低密度接种于新鲜培养基中进行传代培养。研究了FMF图谱以及脉冲标记和连续标记指数。通过脉冲标记指数确定，从平台期培养物中释放的细胞群体在G1期停留的时间比指数生长细胞正常G1期的持续时间更长。当在传代培养前用400拉德的X射线照射处于平台期的培养物时，细胞进入S期的时间比未照射的细胞大约晚4小时。尽管存在G1/S延迟，但照射组和未照射组的细胞群体在S期的进展速率相似。通过累积标记指数确定，在传代培养后长达120小时仍处于G1期（G1期阻滞）的细胞比例随X射线剂量呈线性增加。在半同步生长期间，处于G1/S边界传代培养后照射的细胞中，未检测到X射线诱导的G1延迟或G1期阻滞。
