S-Phase Cell Distribution In The Small Intestine Irradiated at Different Times Of The Day: II. Recovery Phase

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Abstract
Modifications occurring during recovery in the small intestine of animals exposed to the same radiation dose given at different times of the day were evaluated. S-phase cell distribution along the crypts and invertase activity were evaluated to ascertain the functional capacity of epithelial cells. In animals killed between 5 and 6 days after exposure, S-phase cell distribution and functional conditions tended towards normality although recovery was not complete. Labelled cells occurred also at villus junctions, demonstrating limitation in size of the differentiating compartment. This was confirmed by reduced activity of the brush border enzymes. Animals irradiated at the end of the dark period recovered more quickly and efficiently. In this group, labelled cell distribution was almost the same as in the controls starting from 120 h, and invertase activity was also closer to the controls than in any other group.