Changes in cellularity and/or weight of mouse hemopoietic tissues as a measure of acute radiation effects.

Simultaneous determinations of the spleen weight loss, and thymus and femoral bone marrow cell depletion of approx. 45 h after whole-body irradiation of mice have been demonstrated to be a simple, rapid, sensitive and economical way of quantitating radiation damage to the hemopoietic system. Within the dose range of 45 to 300 rad of 250 kV X-rays, for all three end-points the logarithm of the radiation effect has been found to be proportional to the logarithm of dose, with the extrapolated common threshold dose of 29 +/- 3 rad, and 50% decrease relative to control values following 330 (extrapolated), 54, and 109 rad in case of the spleen weight, and thymus and bone marrow cellularities, respectively.