Effects of 1000 R whole-body X-irradiation on DNA synthesis and mitosis in the duodenal crypts of the BCF1 mouse

Summary Effects of 1000 R, whole-body X-irradiation on the proliferative cells of the mouse duodenal crypts, in the four phases of the generation cycle; namely, the DNA synthesis phase, S; the pre-mitotic gap, G ₂; the division phase or mitosis, M; and the pre-synthesis gap, G ₁. As pointed out by Whitmore and Till (1964) G₁ and G₂ are characterized only by the fact that no DNA synthesis is taking place in these phases.In the intestinal crypts of BCF₁ mice, a 1000 R whole-body X-ray exposure blocks cells in G₂ for approximately 18 hours, and reduces the number of cells in S to less than 1/2 that observed in control animals during the first 12 hours after exposure. Cells synthesizing DNA, and undergoing division, remain few in number for more than 48 hours. Between 48 and 72 hours a compensatory reaction begins, and the number of cells in M and S increases from 28 at 48 hours to 150 at 72 hours and reaches a mean value of 482 at 96 hours.Work supported under the auspices of the US Atomic Energy Commission.