BIOCHIMIE KT RADIOBIOLOGIE DU NOYAU CELLULAIRE 171 



ekreka: My first impression is tliat tlicrc are two iiKM-liaiiisms operating: RNA 

 synthesis may jiroeeed in the microsomes or in tlH> nucleoli. But wo failed to 

 differentiate them. We tried, but thd not succeed hi fin( hng a difference between 

 the corresjionding nucIeoU and microsome fractions. They were difficult to 

 differentiate. 



makcovich: RNA is Hrst synthesized in the nucleus and then it comes out into 

 the cytoplasm? 



ERRERA : The transfer of RNA from nucleus into cytoplasm was demonstrated 

 by experiments with short and long term incubation of the cells. 



We believe that RNA is synthesized in the nucleus and that this is conunon 

 to all dividing cells. It is the accepted view on the matter until new data appear. 



gray: I should very nnich like to know^ the methods for specific inhibition. It 

 seems to me you have made it clear enough that radiation damage to the chromo- 

 somes is dependent in some measure on total phosphorylation. It would be very 

 interesting to study whether it is cytoplasmic or nuclear phosphorylation. Can 

 they be differentiated? In what way is inhibition of phosphorylation connected 

 with mitochondria? 



ERRERA : Inhibition of phosphorylation in the nuclei proceeds without affecting 

 the mitrochondria. PhosjDhorylation in the nucleus and cytoplasm can be in- 

 hibited separately. 



passynsky: Is it possible to regard the post-irradiation loss of Na+ and K+ ions 

 as a result of damage to the nuclear membrane? Wliat is the absolute quantity 

 of Na+ and K+ ions which leaked out from the nucleus following exposure, and 

 what is its quantitative relationship to the ionization value of the medium? 



ERRERA : Little is Imown about this. It is possible that basic proteins are capable 

 of binding positive ions. In the case of Na+ about 80 per cent is lost upon exposure 

 to 50 r, whereas in the case of K+ there is no loss of ions up to doses of 30 r. When 

 this dose is exceeded, the loss proceeds very rapidly; at 100 r the loss of this ion 

 is almost complete. 



passynsky: If this constitutes damage, I should like to draw attention to the 

 possibility of using impedance measurement techniques to study it. 



ERRERA: I have no experience in this field. 



PASSYNSKY : As far as I know, the loss of ions may be caused by a damage to the 

 membrane or changes of the absorption. It is a problem which may be studied 

 by means of the impedance technique. If the membrane is damaged, several 

 centres of damage may be discovered. 



ERRERA: To elucidate this question, electron microscope pictures should be 

 available, otherwise it would be difficult to get the answer. I have never taken 

 electron micrographs of such nuclei. My belief is that the membrane is severely 

 damaged, but I am not sure of that. For final confirmation good electron 

 micrographs are necessary. 



BACQ: In the first experiment you cited you irradiated intact cells and studied 

 synthesis of the RNA and proteins by means of autoradiography. In other 

 experiments it was isolated nuclei you studied? 



