CELL DAMAGE IN THE MAMMALIAN RADIATION SYNDROME 255 



shown that local irradiation of tho dioncc^i-halon, i.e. hypothalamic region, with 

 small doses brings about typical "radial ion sickness^' in the bone-marrow. 



I would like to know how you excluded the influence of the hypothalamus on 

 haematopoiesis in the case of total body irradiation and whether there have been 

 qualitative and quantitative differences in the cell degeneration process following 

 local irradiation of the limb. 



GRAYEVSKY : As I have said already Dr. Barakina has foimd that cell destruction 

 occm-s only in directly irradiated areas; there was no destruction in the 

 screened areas. We failed to establish qualitative and quantitative differences 

 in the cell destruction process occurring in the haematopoietic organs following 

 total body and local irradiation. During the repair stage the difference was that 

 followhig local irradiation regeneration proceeded more rapidly. This is accoimted 

 for by the preservation in the body of intact haematopoietic elements. 



TOBIAS: I did not quite understand what protective substance was used in the 

 case of catalase. Can you not give more detailed information about the degree of 

 the protective action of this substance when aqueous solutions of catalase 

 were irradiated? 



GRAYEVSKY: In the experiments to which you refer we have studied the radia- 

 tion effects on the catalase both in solution and in the unicellular organism {P. 

 caudatum). Irradiation of the catalase solution with 10,000 r brought about 

 destruction of this enzyme, whereas in the cell the enzyme was not inactivated 

 even when doses of the order of 100.000 r were used. 



ALEXANDER: Have you any observations on a spontaneous restoration of the 

 lesions in the liver cells? 



Have you data that would make it possible to conclude how much time is 

 required for the repair of the destroyed chromosomes in liver cells? 



GRAYEVSKY : Dr. Shapiro studied this problem on rat liver cells. He has shown 

 that the number of cells with anaphase bridges and acentric chromosome frag- 

 ments remains the same irrespective of the time after exposure (1, 2 or 4 months) 

 when the hepatectomy was performed. Hence it follows that in resting cells 

 there is a persistent chromosome damage induced by radiation. 



He has also shown with mouse corneal epithelimn that the cells with chromo- 

 some damage perish in the first to third generation. 



