HOWARD H. VOGKL, JR., BONN L. JORDAN AND SAMUEL LESHER 



groups, all the mortality in the acute period took place within 10-12 days 

 after exposure. 



Further experiments have been carried out recently at still higher doses 

 of fission neutrons : we have been able to protect neutron-irradiated mice 

 which have received doses as high as 400 rad. 



In Figure 7 the body weight data are illustrated for the various groups of 

 mice. It is clear that there is a sharp decline in body weight for at least four 

 days following exposure, but in the treated animals there is a definite 

 recovery as shown by the average body weights, usually beginning between 

 the sixth and seventh days after exposure. This is evidence, we believe, that 



27 



ai 



O 



CD 



26 h 

 25 



2Ah 

 23 

 22 - 

 21 - 

 20 



o— -o Unirradiated controls (8) 



x^x Neutron irradiated mice treated with cysteine, bone marrow cells, 



and streptomycin (32) ^ ^. 



^-••Neutron irradiated mice injected with water, Tyrode's ^' 



solution, and physiological saline (32) ^_o ,^^ 



2 A 6 8 10 12 K 16 18 20 

 Day of Irradiation 



Time, days 



Figure 7. Body weight comparisons between unirradiated control mice, 

 neutron-irradiated controls, and neutron-irradiated mice 'protected' with 

 combined cysteine, bone-marrow cells, and streptomycin techniques. The 

 numbers below the lines indicate the number of mice alive at that particular 



day. 



the administered bone-marrow cells have been transplanted successfully into 

 the host's blood-forming system and are stimulating haematopoietic recovery. 

 If one looks at the cumulative mortality curve for untreated neutron- 

 irradiated mice {Figure 6), it is evident that at this time, one week after 

 exposure, more than 80 per cent of the mice are dead. This is undoubtedly 

 the reason that bone-marrow cells alone are not very effective in mice 

 exposed to lethal doses of fission neutrons. The antibiotic streptomycin helps 

 to protect the mice from fatal bacteraemia and septicaemia during the 

 10-day period following exposure '^•^. By this time the bone marrow, in- 

 effective against the intestinal syndrome, has taken over its protection of the 

 mouse haematological system. The cysteine helps the entire protective 

 process by reducing the total effective radiation dose by approximately 

 10 per cent. 



16 229 



