HIGH ENERGY IRRADIATION: BIOELECTRIC EFFECTS 



285 



and dependent on the quantity of dose absorbed. The inhibition of neural 

 activity resulting from irradiation was not reversible. 



Radioactive Studies 



The influence of alpha particle irradiation on sodium ion permeability of 

 sciatic nerve can be presented here only as a brief, preliminary report. Nerve 

 sheaths were left intact in order to prevent volume changes. 



Long life Na^^ was used as a radioactive tracer in Ringer's solution ( 1 )u.c 

 per ml of Na-^). The proximal ends of isolated nerves were ligated with 3 

 mil tantalum wire to allow manipulation of the nerves. To determine the 

 time course for the penetration of radioactive sodium, the nerve was im- 

 mersed in "hot" Ringer's solution, and the activity accumulated during this 

 soaking period was estimated by removing the nerve from the Na-^ Ringer's 

 solution to a 4 ml vial of nonlabeled Ringer's. A scintillation spectrometer 

 registered the radioactivity of the sample, and the nerve was restored to the 

 Na^" Ringer's solution for additional radioactive tracer uptake. The Na^^ 

 which diffused from the nerve during the counting time could subsequently 

 be estimated by recounting the vial of contaminated Ringer's solution. 



Results revealed that nerves given less than 150 krad of alpha particle irra- 

 diation did not differ significantly from their nonirradiated controls in the 

 kinetics of sodium penetration. In the dose range 150-200 krad, the rate of 

 Na-^ uptake for irradiated ner\es was increased to only a small extent over 

 controls (Fig. 8) . 



7x10^ 



80 



Minutes 



160 



Fig. 8. The time course for the entry of radioactive tracer sodium into sciatic 

 nerve exposed to a 150 krad dose of 910 Mev alpha particles and its pair control. 

 The experimental temperature was 21°C±1.5°C. 



