59 



is a paper (13) which perhaps bears on this point, showing inhibition of oxidative 

 phosphorylation in mitochondria from irradiated animals. But certainly the 

 kind of correlation that Dr. Potter is talking about is not made. 



BENNETT: I am not clear about this protein turnover. These are non- 

 dividing E. coli cells, are they not? 



SHERMAN: That is right. 



BENNETT: What were the experiments of Monod? Were they not with 

 non-dividing E. coli that shows no protein turnover? 



MAZIA: Monod could find no evidence of protein turnover in growing 

 E. coli. 



BENNETT: If the proteins are not being degraded and re-formed in 

 the cells, it would rule out an explanation such as you have offered. 



SHERMAN: If this is so, then some other repair or some other factor 

 is interfered with. 



BENNETT: Not the protein parameter or the enzyme parameter ? 



MAZIA: As I understand it, Monod claims that enzyme is extremely 

 stable in E. coli. If the cells are under non-growing conditions, the enzyme 

 stays put and if they are under growing conditions, the enzyme is diluted out. 

 On the time scale within which he is working, the enzyme molecule would seem 

 to be immortal. 



SHERMAN: I would like now to discuss some experiments on yeast by 

 Bair and Stannard (10), Yeast cells irradiated in potassium phosphate with 

 90, 000 r of 250-KV X-rays had a significantly larger Q 2 than nonirradiated 



CO2 

 controls. Those receiving the same exposure but suspended in triethylamine- 

 succinate- tartrate buffer at pH 4. 5 showed marked inhibition of anaerobic COt 

 production. 



The role of electrolytes in the metabolism of irradiated yeast was in- 

 vestigated by treating the cells with a cation exchange resin (Dowex-50). The in- 

 fluence of potassium on fermentation (14) and the early work of Nadson and Zol- 

 kevic (15) led Bair and Stannard to suspect that depletion of cellular potassium 

 might expose radiation damage to catabolic processes. 



Yeast cells were suspended in Dowex-50 (50-100 mesh) that had been 

 converted to the triethylamine form. The resin exchanged triethylamine for the 

 cations of the yeast suspension. This treatment did not reduce the number of 

 cells that were able to decolorize methylene blue. Treatment of yeast with 

 Dowex-50 after irradiation resulted in a larger inhibition of respiration and fer- 

 mentation than treatment before irradiation. Glucose uptake by irradiated cells 

 did not differ markedly from that of nonirradiated cells. The inhibition of respi- 

 ration and fermentation was due to the inability of the yeast to utilize the sub- 

 strate. 



Dowex-50 can remove the potassium or sodium or other cations that 

 happen to be in the medium. Spectrographic analysis of Dowex-50 treated yeast 

 indicated that the level of intracellular potassium and sodium was unaltered (10). 

 However, treatment of irradiated cells with Dowex-50 resulted in a reduction of 



