The effect of anoxia on the response of haemopoietic colony-forming units in different proliferative states to rays or D-T neutrons.

Abstract

Abstract The spleen colony assay technique was used to measure the oxygen enhancement ratio (OER) for the stem cells in mouse bone marrow, irradiated with γ rays or a collimated 14 MeV neutron beam. The reduction in OER with neutrons compared with low LET radiation, found in most biological systems studied, was also observed in the present experiments. However, a difference was found between the γ-ray OER for steady-state marrow (1·77 ± 0·12) and that for regenerating marrow (2·51 ± 0·08), which resulted in a larger gain factor for the latter (1·87 ± 0·13) than the former (1·37±0·17). The differences are considered to result from radiation effects on the complex processes involved in the differentiation and proliferation of these cells, rather than from differences in oxygen tension. The implications of the results for radiotherapy are discussed.