92 



PATT: We are, I think, quite a few molecules and minutes away from 

 what you probably mean by primary mechanism. 



BARRON: If you irradiate protein the effect is different. 



PLATZMAN: The initial chemical effects cannot be qualitatively dif- 

 ferent at different doses. 



BARRON: As a matter of fact, they are different. 



PLATZMAN: I am referring to the primary effects. 



BARRON: The chemical effect after irradiation is qualitatively differ- 

 ent according to the intensity of the radiation. 



PLATZMAN: Not the primary effects. What you refer to arises from 

 the kinetics. 



PATT: What is primary? 



PLATZMAN: The first thing that happens after irradiation. 



JONES: You have been making a model perhaps too remote for us to 

 observe it. Let us look for things that we can measure. 



PLATZMAN: I only hope that no one imagines that there' is any differ- 

 ence whatever in the qualitative initial effects. 



KAPLAN: One important objection is that if you talk about observing 

 the effect of sublethal doses, the first thing you have to be sure of is that your 

 observation is an effect. I think this is really primary. At the risk of repeti- 

 tion it gets back to the question of cell population. In Figure 1, DuBois shows . 

 heart, kidney, and brain. He is dealing with relatively homogeneous radiore- 

 sistant tissues there, and the cellular elements other than parenchyma that are 

 present are negligible. There is some supporting tissue but not much. On the 

 other hand, the spleen is really at least two different kinds of tissue. Even in 

 the thymus, although it looks like it is all lymphocytes, if you abolish the lym- 

 phocytes you see that there are a lot of other cells. 



The real question is: have you demonstrated any alteration in the cit- 

 rate metabolism of those cells of the thymus or spleen that are left after the ex- 

 posure that you have given? I don't see that you have any evidence for such an 

 effect. If you are dealing with 2, 3 or 4 different cell populations, each of which 

 metabolizes citrate normally at a different rate, and then by irradiation abolish 

 one of the cell populations, then you will seem to get an effect on citrate metab- 

 olism. Therefore, I think we have to back up and make sure that there has been 

 any real effect. 



DUBOIS: That is right and it is in line with the whole idea that I am 

 trying to develop this afternoon. The first thing that we have to do is to look for 

 effects in the irradiated tissue and discard from further consideration, the tis- 

 sues and enzyme systems in which no changes are found. Then we have to as- 

 certain whether the observed effects represent actual changes in metabolism of 

 the irradiated tissue or are a reflection of the condition of the entire organ. The 

 pathological and biochemical changes in tissues such as the spleen might be the 

 result of radiation injury to some other portion of the body and thus secondary 

 in nature. 



