1038 



RADIATION BIOLOGY 



Determination of the erythrocytes of the peripheral blood and their 

 hemoglobin content by standard techniques is a rather crude means of 

 measuring the effect of irradiation, especially during the first two weeks 

 after exposure to X-ray dosages in the LD 5 o range or above. Even after 

 exposure to dosages well above the lethal range it is common experience 

 to find that no significant reduction in the erythrocyte, hemoglobin, or 

 hematocrit values occurs prior to the sixth day. Since, after exposure to 

 a dosage of this magnitude, destruction of the bone marrow occurs rapidly 

 (within the first 24 hours) and thus delivery of erythrocytes ceases, a 

 steady decline of these hematologic values would be expected to begin 



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X 



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6 8 10 12 20 



TIME AFTER X RAY, days 



-•CONTROL 



O -O OPERATED CONTROLS 



A A 600 r WITH SPLEEN EXTERIORIZED 



® ©1025 r WITH SPLEEN EXTERIORIZED 



Fig. 16-5. Comparative effect of 600 and 1025 r of total-body roentgen irradiation on 

 the erythrocyte values of CFi female mice. 



simultaneously with exposure and continue until such time as regenera- 

 tion and delivery of erythrocytes equaled or exceeded these effete cells. 

 As suggested by Furth et al. (1951) and Jacobson, Simmons, Marks, et al. 

 (1950), the destruction of hematopoietic tissue and thus the cessation of 

 erythropoiesis that occurs in dogs, rabbits, rats, pigs, guinea pigs, and 

 mice after exposure to dosages in the LD 50 range may be sufficient to 

 account for the anemia observed. However, the degree and rapidity 

 with which anemia develops above the LD 5 o range suggests that addi- 

 tional factors are involved. The speed and severity with which anemia 

 appears in mice exposed to 1025 r as compared with that following 600 r 

 exemplifies this problem (Fig. 16-5). Histopathologic investigations 

 show that erythropoiesis ceases within 24 hours after either level of 

 exposure. The anemia would be expected to be qualitatively the same 



