GENERAL DISCUSSION 345 



doses, the regulating action of llie iiiitochoiub-la- in the synthesis of 

 fats and sterols is noticeably ini|)aired, as a result of A\hich a sharp 

 increase in the synthesis of fats and sterols occurs. 



I Mould like to emphasize that the radiosensitivity of this system 

 (the interactions between the mitochondria and the endoplasmic 

 reticulum) is almost the same as the sensitivity of oxidative phos- 

 phorylation and the metabolism of DNA. Thus, for example, in yeast 

 a marked increase in the biosynthesis of ergosterol takes place after 

 irradiation of the cells with a dose of 5 kr ; at the same dose a reduction 

 in the DNA metabolism is noted. All the remaining metabolic processes 

 are much more radio -resistant. 



More remarkable is the fact that the formation of sterols in irradiated 

 cells, which continue to metabolize, increases. This is an extremely 

 common reaction to irradiation, observable l)oth in micro-organisms 

 and in the cells of higher organisms. 



MOUTON : I think that, in examining the damage caused by irradiation, 

 we have somewhat neglected the fact that there are natural conditions, 

 unrelated to radiation damage to the cell, where processes of meta- 

 bolic damage may be produced which are also observed in radiation 

 damage. 



For example, the jsost mortem autolysis of cells which has been 

 investigated in my laboratory is accompanied by a reduction of pH 

 which evidently leads to the ra^iid destruction of the nuclear membrane 

 and then to the activation of jDroteolytic enzymes. 



With this in mind we have at the present time undertaken investi- 

 gations which have as their purpose to compare autolytic and radio- 

 lytic lesions in mice, which are nurtured in aseptic conditions. 



We would welcome the study of this question for other objects 

 belonging to other biological systems (a study that could confirm or 

 reject our hypothesis), that the damage to the structure by radiation can 

 arise as a result of a rapid alteration of a metabolic process, which 

 is similar to the normal glycolytic process observable in the natural 

 death and physiological autolysis of the cell. 



kuzin: It seems to me advantageous at the end of our discussion to 

 attempt to compare the diverse points of view expressed here and to 

 present, as it were, schematically the most probable course of events 

 arising in the irradiated cell. In 1958 I gave such a scheme and I will 

 permit myself today to draw your attention to this, introducing into 

 this scheme greater refinements on the basis of later investigations, 

 because, as it seems to me, it very closely reflects our conceptions. 



