DISCUSSION 215 



from an experimental embryo. If the embryos are allowed to metabolize at 

 room temperature, those that receive 25,000 r undergo a negative growth. The 

 negative growth is less pronounced with higher doses, so that with 200,000 r there 

 is no morphological change. Cytologically every nucleus becomes pycnotic 

 after doses of from 25,000 to 200,000 r. The respiration, however, of embryos 

 that receive 25,000 r is approximately 50 per cent higher than those of the 

 control, whereas the respiration of those that receive 200,000 r gradually di- 

 minishes. 



This indicates that to bring about a change after irradiation in a cell two 

 processes, namely anabolism and catabolism, must be considered. With lower 

 doses only the anabolic processes are injured, whereas with higher doses anabolic 

 and catabolic processes are injured. After irradiation, if experimental eggs are 

 placed in an icebox for as long as 6 months and then observed after removal 

 from the icebox, no damage is seen. However, if these eggs are maintained at 

 a metabolic temperature, the injury shows up as if they were taken from the 

 x-ray machine and left at room temperature. 



Low-Beer: 



I wonder whether Hevesy compared the uptake of P'^ in Jensen sarcoma with 

 the oxygen consumption after x-ray irradiation. Some years ago Reiss and I 

 found that, when Jensen sarcoma in vivo was exposed to approximately 600 r of 

 0.7 mm Cu, HVL x-rays, the oxygen consumption decreased by a factor of 4 when 

 measurements were made 24-48 hr after irradiation. 



As to the use of P^^ as a metabolic indicator of radiosensitivity, I might 

 mention that uptake of P^^ is decreased six- to eight-fold in human breast cancer 

 after a tissue dose of approximately 4000 r (1.0 mm Cu HVL) without dis- 

 cernible microscopic changes of the cells when tissue sections are compared before 

 and 4 weeks after irradiation. I should mention that a decrease of P^^ uptake 

 occurs also in some instances after the administration of estrogens and in some 

 lymphoma group tumors after administration of HN2. Thus the effect ap- 

 parently is general metabolic inhibition. 



