Changes in cellularity, CFU-S number and chromosome aberrations in bone marrow and blood of rats after neutron and continuous gamma irradiation.

Changes in the hematopoietic bone marrow of rats were observed after single wholebody neutron dose of 2 Gy and combined single neutron (2 Gy) and continuous gamma (6 Gy, daily dose rate of 0.5742 Gy) irradiation. Neutron irradiation significantly reduces the number of karyocytes in the bone marrow including CFU-S and induces the extensive cytogenetic damage. The following continuous gamma irradiation does not intensify the primary damage, but maintains the CFU-S and cellularity values at a decreased level for the whole time of irradiation. Recovery of the damage begins only after the termination of continuous irradiation; its course is similar to that after single neutron irradiation. The influence of combined effect of neutrons and gamma rays is nevertheless manifested in later periods after the irradiation by reduction in the total CFU-S number in the bone marrow.