50 



BENNETT: All of your values are for compounds in solution. In the 

 solid form, some compounds, e.g., choline; appear to be particularly suscepti- 

 ble to irradiation. G values of the order of 500 are obtained from self-irradia- 

 tion of choline with carbon- 14. Dr. Lemmon has presented the data in several 

 papers (12-14). 



He has also investigated the effect of structural changes in the choline 

 molecule on the G value. For instance, with choline, if an analogue is made 

 that contains the 3-hydroxy propyl group instead of the 2-hydroxy ethyl group, 

 the G value drops by a factor of 10. • 



BARRON: Is the choline oxidized? 



BENNETT: It goes to acetaldehyde and trimethylamine. As far as can 

 be determined, these are the only main products. The acetaldehyde has not 

 been determined quantitatively, but when experiments are done with methyl la- 

 beled choline, then trimethylamine is the only radioactive compound that is ob- 

 tained. The G value depends upon the type of irradiation. In other words, if the 

 irradiation is done with cobalt-60 as the source, the G value is around 180, and 

 if the irradiation is done with high energy electrons, the G value is around 20. 

 Experiments are in progress to determine the sensitivity of different compounds 

 and the effect of structural changes. These preparations are dry and they are 

 irradiated in the absence of oxygen, in other words, evacuated systems. 



POLLARD: It is obviously a reaction that goes from molecule to 

 molecule. It is a lot of fun to start putting things between the molecules. 



BENNETT: For instance, this is choline chloride. If you change the 

 system to choline iodide, which is in a sense putting in something different, the 

 G value goes down considerably -- by a factor of about 10. The G value for 

 choline chloride in the 2-to-4 Mev. bombardment is around 20, and for the io- 

 dide appears to be of the order of 2. There are some experimental difficulties 

 in accurately determining the G value. If one goes, for example, to a choline 

 analogue where there is chlorine in place of the -OH, the G value is also quite 

 low, so that there are profound effects with changes of structure. 



POLLARD: Did you try to irradiate this at liquid air temperatures? 



BENNETT: No. Choline was chosen for these studies because of a 

 number of compounds that we had prepared with carbon- 14 and stored, it ap- 

 peared to be the most sensitive. For instance, adenine was relatively insensi- 

 tive, as were most of the amino acids. Many compounds can be tried, and un- 

 doubtedly we will try more of them. 



PATT: I believe that your group has studied radiation effects on co- 

 enzyme A in tissue. 



BENNETT: I would say that the effect appears to be small. In an 

 earlier report it was stated that there was considerable effect, but there now ap- 

 pears to be little effect of X irradiation on coenzyme A or DPN (15). 



DUBOIS: I would agree with that conclusion on the basis of experi- 

 ments that we have done. In our experiments, sulfanilamide acetylation was 

 studied in irradiated rats. We gave a dose of 100 mg. per kg. per day of sul- 

 fanilamide. This normally results in excretion of about 50 percent of the inject- 

 ed dose in the acetylated form and the rest in the free form. By determining 

 daily urinary excretion of acetylsulfanilamide throughout the survival time after 



