Cellularity and Deoxyribonucleic Acid Synthesis in Bone Marrow after Total- and Partial-Body Irradiation

Abstract

Rats were exposed to 600 r, and the cellularity, cytology, and ability to synthesize DNA by using H/sup 3/-thymidine and autoradiography were studied in the erythroid precursors over the first 24 hours after exposure. The loss of red cell precursors was early and profound, most marked in the younger forms. The number of cells capable of being labeled during DNA synthesis in all maturation compartments decreased considerably more rapidly than did the total number of similsr cells, or the number of similar cells not in DNA synthesis. Some of the marked effect on DNA-synthesizing ability was due to an inhibition or to a decreased rate of the actual process of DNA synthesis as indicated by reduced grain counts. However, some was probably due to normal movement of cells out of the DNA synthesis phase, with failure of replacement due to cell death and/or delay of cells entering DNA synthesis. Effects of the exposure on the number of mitotic figures and on cytology are described. A slight and transient effect in shielded bone marrow on the number oi labeled cells, the grain count, and the number of mitotic figures was observed. (auth)