BIOCHEMICAL MECHANISM OF CELL DIVISION DISTURBANCE 235 



Protassova's papers, data may be found pointing to a considerable disturbance 

 of the tjTosine niotabolism in the irradiated animals. In the animal body other 

 enzymatic systems may be present, but the process of their activation and the 

 formation of the quinone-like tyrosine oxidation products may bo similar to 

 those observed in plants. 



paribok: Did you observe in your interesting investigations chromosomal 

 aberrations induced by substances extracted from the irradiated leaves, that is to 

 say, was there any genetic damage other than mitotic inhibition? 



KUZiN : This is a question we are very interested in and at present data are being 

 accumulated which we hope will enable us to answer this question with some 

 degree of certainty. 



passynsky: You have reported very interesting data. Are not disturbances in 

 tyrosine metabolism particularly important? It seems highly probable, as you 

 have pointed out, that melanine formation plays some role here. We, in ovir work 

 with Dr. Budnitskaia and Dr. Virovets, have observed considerable activation of 

 polyphenol-oxidases following irradiation. An increase in oxidation processes 

 takes place, caused probably not by changes in enzymatic activity but by 

 changes occurring in intracellular membranes. Any explanation of radiobiological 

 effects should start from an initial damage to a few molecules only. If we say that 

 the level of the oxidation-reduction processes is changing, these changes should be 

 caused by some preceding changes due to damage to a few molecules. The fact 

 is that the activation of such enzymes as polyphenoloxidase or peroxidase is 

 probably due to the damage to cellular membranes demonstrated experimentally. 



POLLARD : Did you test these substances on bacteria? 



KtJZiN : At present we have only tested the enzymatic oxidation products of the 

 tyrosine on bacteria. 



