HEMATOLOGIC EFFECTS OF RADIATION 



10G9 



of hematopoietic dysfunction. In the studies that are discussed in the 

 following sections, a close parallelism between survival and hemato- 

 poietic regeneration is obvious, but it must be borne in mind that this cor- 

 relation may be more apparent than real and that failure of tissues other 

 than the blood-forming tissue may be critical. More precise methods of 

 study of other organ systems and of the dependence of organ systems on 

 one another may be necessary before the factors contributing to death or 

 survival of irradiated animals can be clearly separated. 



Lead Shielding of the Exteriorized Spleen and Other Parts of Body. Lead 

 shielding of the surgically exteriorized spleen (average weight 0.1 g) of 



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TIME AFTER X RAY, days 

 CONTROLS O O OPERATED CONTROLS 



1300 r WITH SPLEEN SHIELDING 

 AND DISTAL VESSEL NOT CUT 

 600 r WITH SPLEEN EXTERIORIZED 

 AND DISTAL VESSEL CUT 



Fig. 16-19. Comparative effect of 600 r of total-body roentgen irradiation (spleen 

 exteriorized and distal vessel cut) and of 1300 r with lead shielding of the exteriorized 

 spleen (distal vessel not cut) on the erythrocyte values of CFi female mice. 



adult mice during exposure to 1025 r of total-body X irradiation markedly 

 enhances survival (Table 16-5). After exposures up to 1300 r. no anemia 

 and only a transient leukopenia and thrombocytopenia appear in spleen- 

 shielded mice, whereas a severe pancytopenia follows exposure to 600 r 

 without spleen shielding (Figs. 16-19, 16-20). Recovery of hemato- 

 poietic tissue in mice exposed to 1025 r with spleen shielding occurs by 8 

 days, but no hematopoietic recovery is noted during this interval in 

 unshielded mice, Fig. 16-21 (Jacobson, Simmons, Marks, et at., 1950). 

 Recovery of the lymphatic tissue in the wall of the gastrointestinal tract 

 in spleen-shielded mice parallels recovery of the hematopoietic tissue 

 elsewhere. These observations led to the theory that the mechanism of 

 recovery from radiation injury under these conditions was on a humoral 

 basis and that the factor (or factors) responsible was produced by the 



