l.\|LRV AM) Rl.CONKRV IN M-l'IROX-IRRADIA TKl) ANIMALS 



body weight) showed the same 1\ jk- of dose reduction we had previously 

 reported'*. 



The three treatments were therefore combined, cysteine being injected 

 intraperitoneally into mice before neutron exposure; these irradiated animals 

 were then given 0-2 c.c. of bone-marrow cells from other CF No. 1 female 

 mice into a tail vein within a few hours after irradiation. The bone marrow 

 technique was the same as that described aljovc. The mice were also 



?5 100 



90 



80 



70- 



I 60- 

 o 



E 



<K 50 



> 



E 



AO - 



30- 



20 - 



10- 



8 12 16 20 

 Days after irradiation 



2A 



28 



Figure 6. Comparative mortality, in the acute 30-day 

 period following single exposure, between neutron- 

 irradiated control mice and neutron-irradiated mice 

 treated with a combination of cysteine (before ex- 

 posure) and bone-marrow cells and streptomycin 

 (after exposure). 



injected daily with a dose of 0-5 c.c. streptomycin, given subcutaneously, 

 for a ten-day period after exposure. 



Other neutron-irradiated mice received an injection of water as a pre- 

 irradiation control for the cysteine. These animals also received 0-2 c.c. 

 Tyrode's solution (the bone marrow vehicle) and daily injections of 0-5 c.c. 

 saline solution instead of streptomycin. This group constituted the neutron- 

 irradiated, 'nontrcated' controls. 



The data from this experiment are summarized in Figure 6. It is clear that 

 we are dealing with so-called supralethal doses of fission neutrons : only one 

 of the control mice survived the exposure. In contrast, only one of the 32 

 mice treated with the triple technique died within the acute 30-day period. 

 It is interesting to point out that both in the experimental and in the control 



228 



