SummaryThe repopulation of the spermatogonial epithelium in mice after whole-body exposure to 1 MeV fast neutrons was compared for doses from 320 to 400 rads, either single or divided into two fractions 1 to 31 days apart. Repopulation was measured after 11 weeks by determining the percentage of seminiferous tubuli showing signs of spermatogenesis. Dose-fractionation decreased the repopulation more than single exposure, but to a varying degree depending on the length of the interval. Repopulation is lowest for the 1-day interval, indicating a synchronized entry of the spermatogenetic stem cells surviving the first fraction into a very radiosensitive phase of their cycle within 24 hours. For intervals of 12 to 17 days, repopulation shows a maximum resulting either from an increased number of stem cells or from a decreased radiosensitivity at the time of the second exposure.
No takes yet. Share an insight, caveat, or question.
Kramer et al. (1974) studied this question.
Synapse has enriched 2 closely related papers on similar clinical questions. Consider them for comparative context: