HEMATOLOGIC EFFECTS OF RADIATION 



1065 



of histologic preparations, the production of erythrocytes was maintained 

 within essentially normal limits. The failure of a mid-lethal dose (800 r) 

 to produce further anemia under these conditions or to interfere materi- 

 ally with recovery is probably dependent on the multiplication of the 

 surviving primitive erythroblast precursors or on the functional survival 

 of even more primitive cells such as reticular cells. That this phenom- 

 enon was not due to a specific effect of the phenylhydrazine itself on the 

 cells of the marrow is indicated by the fact that phlebotomy before 

 irradiation afforded similar protection. Schack and MacDuffee (1949) 

 have corroborated these findings using the technique of exposing mice to a 



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PHENYLHYDRAZINE 

 ADMINISTRATION 



2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 

 TIME AFTER X RAY, days 



o o PHENYLHYDRAZINE AND 800 r OF TOTAL-BODY X IRRADIATION 



o o 800 r OF TOTAL" BODY X IRRADIATION ONLY 



• • CONTROL © @ PHENYLHYDRAZINE 



Fig. 16-16. Effect of a single dose of 800 r of total-body roentgen irradiation on the 

 erythrocyte values in the peripheral blood of normal rabbits and rabbits with a 

 phenylhydrazine-induced anemia. {Originally published in Science, 107: 249, 1948.) 



low oxygen tension (simulated high altitude of 15,000 ft) and thus induc- 

 ing erythroblastic hyperplasia prior to irradiation. Bethard, Skirmont, 

 and Jacobson (1950) have demonstrated that, during the period of 

 maximum erythroblastic hyperplasia induced by cobalt, radiophosphorus 

 produces lesser inhibition of erythropoiesis than in normal rats (Fig. 

 16-18). More recently, Valentine and Pearce (1952) have compared the 

 regenerative capacity of erythroid tissue in irradiated and nonirradiated 

 cats. Immediately prior to irradiation (200 r, whole body) the cats were 

 bled sufficiently to reduce the peripheral erythrocyte count by 40 per cent. 

 It was found that recovery from the anemia induced by hemorrhage 

 immediately prior to irradiation was only slightly less rapid than in the 

 control nonirradiated cats. Exposure to low oxygen tension after irradia- 

 tion had no effect on recovery of hematopoiesis after 400 or 500 r according 

 to Smith, Dooley, and Thompson (1948). 



