Acute radiation injury of mice and the influence of sudden time shift.

The daily light-dark regimen for two groups of mice was advanced by 8 hr. A third group remained in unchanged lighting conditions. At seven different times within the following day subgroups of the time-shifted mice as well as of the group with unchanged time schedule were exposed to whole-body X irradiation. Mortality, body weight, and temperature of each animal were registered for 30 days following exposure and were regarded as indicators of radiation response. Radioresistance was found to be highest after two-thirds of the daily light span, confirming earlier reports by other authors. Well-defined effects of time shift and a corresponding shift of the maximum of radioresistance could be demonstrated. With the individual body weight as an independent variable, mathematical formulas for survival prognosis could be established.