GENERAL DISCUSSION 357 



certain processes are continued which were takhig place in the cells 

 prior to the moment of irradiation. With doses of lO"? to lO^ r for the first 

 few seconds marked morphological injuries occur, the membrane 

 and flagellae are noticeably destroyed and the iirotoplast is altered. 



When investigating the action of ionizing radiation on collagen 

 in the electron microscope in a moistened state, we managed to observe 

 how, under the action of ionizing radiation, a breakdown occurs in 

 certain interconnections in the collagen fibrils. 



FRANK : The present section of the discussion has attracted the greatest 

 attention. This is quite natural since during the last years the previously 

 unknown submicroscopical cell structure was discovered and "super- 

 molecular morphology"' began to develop. For this reason it is of 

 considerable interest to discuss the problem of the damaging effect not 

 only from the point of view of the initial effect on different substances 

 but also on this highly differentiated supermolecular organization. 



Therefore one must agree with Dr. Alexander who paid attention 

 to the possible primary role of damage to membrane organization 

 (therefore function also) and probably to multi-membrane systems. 

 Really, damage to such membrane molecular organization can have 

 much more consequence than the inactivation of single, separately 

 studied, biologically important molecules, particularly enzymes. 



One must also agree with the point of view of Prof. A. M. Kuzin, 

 who paid attention to the fact that the function of such membranous 

 or multi-membranous systems can be damaged even by single cross- 

 linkages, and also by the change in the activity of enzymes, not as of 

 single molecules but as of the components of branched surface structures. 

 I believe that everybody will agree with the fact, that when we transfer 

 our interests from damage to substances to damage to cell organization 

 we by no means oppose the one by the other. Here, in fact, a different 

 interpretation of the acceleration mechanisms of primary lesions is 

 given. The essence of this matter is not that chemically important 

 molecules are inactivated, thus weakening one of the links in metabo- 

 lism but, in fact, that single molecules which are the components of 

 functional structural systems are inactivated, or the bonds between 

 them are damaged. Here the inactivation of single molecules or 

 damage to chemical bonds disturbs the function of the system in a 

 similar way as, if we may use a rough analogy, one broken tooth only 

 in a single gear-wheel can lead to the arrest of the whole mechanism. 



Besides that we must note that structural disorganization 

 (nobody has mentioned this directly during the discussion) influences 

 primarily all the cellular mechanisms of autoregulation. Probably, 



