304 General Discussion 



Now going back to Dr. Anderson's work, which is being extended 

 by Mr. Fisher, of course the original work at Oak Ridge was initiated 

 on the effects on the nucleic acids on the basis of the experiments we 

 had done many years ago in co-operation with Drs. Greenstein and 

 Taylor at the National Cancer Institute and National Institute of 

 Health, when we found that 10-20,000 or 50,000 rontgen were 

 necessary to depolymerize sodium thymonucleate, and it might 

 interest you that the background for the work on the nucleic acids at 

 Oak Ridge was this finding. But it was quickly found out by Dr. 

 Carter and later on by Dr. Cohn that the materials we were working 

 with were either very impure compounds or isolations of mixed 

 materials with which experiments could not be repeated from time to 

 time, and it was finally decided at that time to go more thoroughly 

 into the whole problem of nucleic acids, first of isolation and then 

 structure of the nucleic acids, and we are just starting again to study 

 the effects of radiation on these mixtures or compounds if we can get 

 them pure enough. I think that there are many possibilities, even 

 with the impure mixtures, to follow what radiation will do in them; 

 concentrating entirely on first getting the purest possible compound 

 may not tell us this story. I feel that even these crude extracts may 

 give us more information than the very pure compounds which we 

 finally will have to study; these crude mixtures may tell us much 

 more of what is happening inside the cell. I think Dr. Anderson 

 picked the easiest tissues to handle, as Prof, de Hevesy pointed out. 

 But he plans to go ahead on other tissues too and see if he gets the 

 same type of result. 



de Hevesy: Errera needed 5,000 r, Anderson only 50. Errera 

 worked with nucleated red corpuscles of the hen, in which no DNA 

 turnover takes place. So it is not impossible that the tremendous 

 dose difference, 50-5,000 r, is not only due to Anderson's improved 

 technique but the fact that Anderson picked out a very radiosensi- 

 tive system while Errera worked with a very radioresistant one. 



Alexander: I think this difference between Errera and Anderson is 

 largely one of concentrations. One can add as much water as one 

 likes to these nucleoprotein gels and when dilute they show dilution 

 effect typical of indirect action in a very pronounced manner. 

 Before concluding that one system is more sensitive than another we 

 must take concentration into account. Errera 's concentration was 

 governed by the physiology of the cell and was quite high. In the 

 test-tube one can handle it at much lower concentrations, and one 

 of the reasons why Anderson could detect such small doses must 

 have been that he worked at concentrations which were much lower 

 than those of Errera. 



Butler: With regard to de Hevesy's point about the other tissues, 



