title: Decrease in the ability of CFU-s in shielded marrow to be recruited into cell cycle after multiple irradiations: experimental results and computer simulations.
abstract: Nine doses of 1.5 Gy given to mice with one shielded leg result in very similar perturbations in shielded marrow (CFU-s kinetics whatever the source of radiation (X or gamma rays). At the time of the ninth irradiation, the size of the shielded CFU-s compartment is reduced to 75% of control level. After 15 min it decreases to 47% and, 1 day later, remains below the pre-ninth irradiation level (62% of control level) in spite of two significant peaks of CFU-s in DNA synthesis, at 1 and 8 hr after the ninth irradiation. For acceptable fitting to experimental data, computer simulations make it necessary to assume that a fraction of shielded marrow CFU-s is not capable of entering the cell cycle after the treatment. This is not explainable by defects in the stimulators of CFU-s proliferation secreted by shielded haemopoietic tissue because their production and their efficacy are demonstrated to be normal after the nine exposures. The incomplete recovery of the shielded CFU-s pool from proliferating CFU-s can be attributed to a loss in CFU-s by differentiation at birth.
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000528:radiation effects*; D001854:Bone Marrow Cells; D002453:Cell Cycle / Q000528:radiation effects*; D003037:Cobalt Radioisotopes; D003115:Colony-Stimulating Factors / Q000378:metabolism; D003201:Computers; D004247:DNA / Q000096:biosynthesis; D005260:Female; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000528:radiation effects*; D007399:Interphase / Q000528:radiation effects; D007700:Kinetics; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D011835:Radiation Protection
chemical_list: D003037:Cobalt Radioisotopes; D003115:Colony-Stimulating Factors; D004247:DNA