106 



The technique depended on the fact that when a cell has its full enzynrie 

 content, it never expresses more than about 5 percent of it .... that is, if you 

 assay the intact cell you get l/20th of what you obtain on assay of a cell lysate. 

 Now let us consider, say 100 cells that are being induced to form enzymes. 

 Suppose that the enzyme-forming capacity is discontinuously distributed through- 

 out the population, so that, for example, 10 cells make enzymes extremely rap- 

 idly in the first 10 minutes and another 10 cells begin making enzyme in the next 

 10 minutes, and so on. If you examine the ratio of activity of the lysed cells to 

 the intact-cell in the early course of the induction, you should find the expected 

 20-fold increase. If on the other hand, all the cells are acting alike and form- 

 ing enzyme uniformly, the ratio will start out as 1 : 1 and then gradually climb to 

 the 20:1 characteristic of full enzyme content. The results obtained agreed with 

 the last statement. 



Thus, if you could find a biochemical activity easily assayed that be- 

 haved cryptically in this fashion, and that was lost as a result of irradiation, you 

 might be able to determine whether the loss is uniformly occurring among all 

 the cells of your population or is discontinuously distributed. 



DUBOIS: Going back to Dr. Potter s point, I too feel, that all of these 

 things may have a common denominator because the changes that I have dis- 

 cussed, and probably a number of others, are similar insofar as their onset, 

 duration, etc. , are concerned. If we consider changes occurring in the spleen 

 after 400 r, i.e. , the inhibition of citric acid synthesis, the increase in phos- 

 phatases, and the decrease in ATP, they all follow the same pattern. The de- 

 crease in endogenous respiration does also. I have purposely avoided talking 

 about nucleotides because of Dr. Carter's discussion tomorrow, but there are 

 some interesting relationships between nucleotide changes and those that I have 

 reported. 



KAPLAN: Hydrocortisone is a very powerful lympholytic agent, par- 

 ticularly on the thymus. It will wipe out the lymphocytic population of the thy- 

 mus just as effectively as a good-sized dose of X-rays. 



One way in which one might get at this question, I think, is to see 

 whether there is an increased activity of some of these enzymes in the cell popu- 

 lation left after treatment with hydrocortisone where radiation is eliminated as a 

 factor. If such an increase occurs, then I think it would be fair to say that the 

 cells that are not destroyed by these two agents have as their inherent level of 

 activity one that is appreciably higher than that of the population before the lym- 

 phocytes are taken out of it. Perhaps a comparative experiment with hydrocort- 

 isone might be a useful way to approach this. 



JONES: I should like to ask this question for information. It seems to 

 me that with most of the substrates used by Dr. DuBois there was some depres- 

 sion of respiration. Two interpretations of this could be possible: (1) That this 

 would then reflect a possible change in enzymatic functional reserve that was fai 

 greater than the shift in the steady state concentration of the cells tested has re- 

 vealed, just as Dr. Spiegelman suggested a moment ago and (2) Shouldn't we ex- 

 plore the matter of total cell damage as being a summation of many little frag- 

 ments of change? 



DUBOIS: In this case, a very small depression could be a reflection of 

 a change in one enzyme system because the whole cycle is operating in the oxida- 

 tions described. The dose used was very high, and we have other data with lower 

 doses that show no effect. With exposures lower than the LD50 range and with 



r 



