INJURY AM) RKC:()VKRV I.N NEUTRON-IRRADIATED ANIMALS 



Tvrodc's solution, by means of a hypodermic needle. For every irradiated 

 mouse which received a bone-marrow injection, one donor mouse was 

 sacrificed, and each bone-marrow injection contained the equivalent of the 

 cellular contents from two femurs. 



The results of this experiment are illustrated in Figure 2. It is clear from 

 the cumulative mortality indicated for the y-irradiated mice that the single 

 intravenous injection of bone-marrow cells gave definite protection. All of 

 the 34 irradiated controls died within 10 days after exposure. In contrast, 

 only 15 of the 35 mice (43 per cent) which received bone-marrow cells died 

 during the 30-day period following irradiation. The protective action of 

 these cells following irradiation with fission neutrons is much less evident. 

 For seven or eight days after exposure, no protection by the marrow cells is 

 seen. However, there is evidence of marrow protection in the neutron- 

 irradiated mice after the first week and the 30-day lethality is decreased. 



It seems probable that bone-marrow cells failed to protect neutron- 

 irradiated mice during the first week after exposure because these animals 

 were dying as a result of intestinal damage against which the bone-marrow 

 cells were ineffective. In contrast, X- or y-irradiated mice are well pro- 

 tected by bone-marrow cells because their haematopoietic systems are 

 stimulated to prevent death from the usual 'haematological syndrome'. 



The Synergistic Action of Intravenous Bone-Marrow Cells and Streptomycin 

 in Protecting Neutron-Irradiated Alice 



Since it has been demonstrated that an antibiotic such as streptomycin can 

 protect neutron-irradiated mice for at least 10 days after exposure" it seemed 

 possible that a combination of marrow cells and streptomycin might result 

 in better protection than either agent alone. It was thought that the anti- 

 biotic would keep some of the irradiated mice alive beyond the period of 

 the intestinal syndrome, and that the bone-marrow cells could then assume 

 their protective role in helping to prevent the later deaths associated with 

 the destruction of the blood-forming elements. 



Approximately 130 CF No. 1 female mice were irradiated with 350 rad 

 of fission neutrons at the CP-5 research reactor. The reactor was operated 

 at 2000 kW, twice the power of the first experiment, so that the second 

 exposure was carried out in 46 min, at a dose rate of 7 • 5 rad min. 



The irradiated mice were divided into four equal groups as follows : 



Group I (32 mice) received a single intravenous injection of bone-marrow 

 cells (0-2 c.c. in Tyrode's solution) within a few hours after exposure. 



Group II (32 mice) received a single intravenous injection of bone-marrow 

 cells and, in addition, received daily subcutaneous injections of strepto- 

 mycin (5 mg in 0-5 c.c. physiological saline) for the first 12 days after 

 irradiation. 



Group III (32 mice) received a single intravenous injection of Tyrode's 

 solution (0-2 c.c.) and daily streptomycin injections, as above. 



Group IV (30 mice) received a single intravenous injection of Tyrode's 

 solution plus daily subcutaneous injections of 0-5 c.c. physiological 

 saline solution. 



A fifth group of 32 mice served as unin-adiated controls. 



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