Ijiri K, Potten C S
Radioisotope Center, University of Tokyo, Japan.
Int J Radiat Biol. 1990 Jul;58(1):165-75. doi: 10.1080/09553009014551521.
Apoptosis is a mode of cell death involving nuclear pycnosis, cytoplasmic condensation and karyorrhexis. Changes in the number of apoptotic cells at various times (3-12 h) after a single dose of either 0.5 or 9.0 Gy given at 09.00, 21.00 or 03.00 h were studied in histological sections of small intestinal crypts of mice. The incidences of apoptosis were examined 3 or 6 h after irradiation at different times of day with different doses of gamma-rays ranging from 0.15 to 9.0 Gy. Survival curves were constructed from the dose-incidence curves for apoptosis, using the number of apoptotic cells after high doses (NM) as the maximum cell population size. The mean lethal doses (Do) for the dose range 0-0.5 Gy were calculated for each time of day. A circadian rhythm in both Do and NM values was detected, indicating that both the number and sensitivity of radiation-induced apoptosis were changing throughout the day. A possible explanation based on the cell-cycle states of the target cell population for apoptosis (presumably functional stem cells) was drawn. Most of the target cells were assumed to be in an extended G1 phase. Around 21.00 h a transition from G1 to S phase takes place in some of these cells (approximately seven or eight cells per whole crypt). The S phase then lasts till around 06.00 h. They may be at G2 and M around 06.00-09.00 h, and then they re-enter G1. The circadian rhythm for the number and sensitivity of the cells susceptible to apoptosis obtained in the present report agrees well with this pattern of cell-cycle phases of target cells.
细胞凋亡是一种细胞死亡方式，涉及核固缩、细胞质浓缩和核碎裂。研究了在09:00、21:00或03:00给予小鼠单次剂量0.5或9.0 Gy后不同时间（3 - 12小时）小肠隐窝组织切片中凋亡细胞数量的变化。在一天不同时间用0.15至9.0 Gy不同剂量的γ射线照射后3或6小时检查凋亡发生率。使用高剂量后凋亡细胞数量（NM）作为最大细胞群体大小，从凋亡的剂量 - 发生率曲线构建存活曲线。计算了一天中每个时间0 - 0.5 Gy剂量范围内的平均致死剂量（Do）。检测到Do和NM值均存在昼夜节律，表明辐射诱导的凋亡细胞数量和敏感性在一天中都在变化。基于凋亡靶细胞群体（可能是功能性干细胞）的细胞周期状态给出了一种可能的解释。大多数靶细胞被认为处于延长的G1期。在21:00左右，其中一些细胞（每个完整隐窝约七八个细胞）从G1期过渡到S期。然后S期持续到06:00左右。它们可能在06:00 - 09:00处于G2和M期，然后重新进入G1期。本报告中获得的易发生凋亡细胞数量和敏感性的昼夜节律与靶细胞的这种细胞周期阶段模式非常吻合。
