抄録
We have reported that pre-irradiation with a small dose (0.3-0.5 Gy) induces radio-resistance observed as an increased survival rate from bone marrow death in ICR and C57BL/6 mice. This was also observed in splenectomized C57BL/6 mice, and the lifespan of pre-irradiated group after observation of bone-marrow death rate was significantly longer than that of non-pre-irradiated control group. In this study, lifespan of intact (without splenectomy) mice was examined. The 30-day survival rates of pre-irradiated and non-preirradiated control animals were 96% (48/50) and 58% (29/50), respectively. Increment of the survival rate was significant (Fisher's exact probability=0.0000035). Lifespan of the survived 48 (pre-irradiated) and 29 (control) animals were observed. The average survival time (and its standard error) was 347.3 (29.8) days for pre-irradiated group and 378.9 (40.9) days for control group. The difference of the lifespan was not significant both in generalized Wilcoxon's rank sum test (p=0.55) and log rank test (p=0.32). [J Radiat Res 44:389 (2003)]
