CELL-SURVIVAL CHARACTERISTICS OF INTESTINAL STEM-CELLS AND CRYPTS OF GAMMA-IRRADIATED MICE

Ninety-one female Swiss Webster mice which survived to 4 days after whole-body irradiation (137Cs-γ rays, 102 rad/min) were sacrificed for assay of the number of surviving crypts. [3H]Thymidine was injected 45 min prior to sacrifice and crypt survival determined from 3H counts per crypt, 3H counts per milligram of dry intestine, and the dry weight of the whole intestine after single doses of 960 to 1924 rad or split doses (4-hr interval) of 1155 + 385 to 962 rad. For the two highest doses in each series, for which crypts were very sparse, the 3H-counting procedure was replaced by a visual count in a specimen large enough to be weighed. The results were analyzed using for comparison various mathematical models. The best fit was obtained with nonlinear regression using a multitarget-with-two-components model. The parameters of this curve are D0, 109 rad; n (cell extrapolation number), 55; and A (stem cells per crypt), 31. The results are compared with those obtained by other workers.