Changes in the Natural Radioresistance of the Mouse after Hypoxia of Several Days' Duration: The Post-hypoxic Behaviour of Stem Cells

Summary

The bone-marrow contribution to the post-hypoxic changes in the radiosensitivity in mice has been studied, using the endogenous and exogenous spleen-colony methods. After ten days of hypoxia the number of bone-marrow colony-forming units had decreased to about 60 per cent. It begins to rise on the second post-hypoxic day, reaching normal values on the third day and overshooting between the fourth and the sixth days. The lowest number of endogenous spleen colonies was detected when the radiation was given on the second post-hypoxic day. On the other hand, the repopulation in the bone-marrow seems to be improved after sublethal irradiation between the first and third post-hypoxic days. The dissociation between the behaviour of the CFUs and the changes in animal radiosensitivity is discussed.