Survival Time in Germfree Mice after Lethal Whole Body X-irradiation.

The survival time of germfree Swiss-Webster mice to whole-body X-irradia tion in the range of 500 to 35,000 R was compared to that of conventional Swiss Webster mice. The relationship between the survival time and X-ray dose administered to germfree and conventional mice shows three different straight line segments and cne curved segment, each with distinctive dose response characteristics on a log log scale. No essential difference can be recognized on the dose-response rela tions between germfree and conventional mice. However, the mean survival time of germfree mice in the X-ray dose range which causes "hemopoietic death" is 12.5 days as compared to 11.2 days for conventional mice, a difference of 1.3 days. The mean survival time of germfree mice in the so-called "gut death" range is 7.2 days as compared to 3.4 days of conventional mice, more than twice the difference. In general, the survival time of germfree mice in the zone of death caused by damage to the cell renewal system was much longer than that of conventional mice. However, the survival time of germfree mice in the so called "brain death" X-ray dose range (over 17,500 R) is reversed and is shorter than that of conventional mice.