50 A. G. PASSYNSKY 



as proteins, nucleic acids, lipids, corresponding proteins, etc. Despite 

 the significance of this work, it should be noted that in essence they did 

 not take into consideration the specificity of cell structures and the 

 complicated heterogeneity of the internal structure of the protoplasm. 

 Primary mechanisms of action of radiation were often analysed as if 

 the cells were just a homogenous solution of various substances but in 

 fact it is the complexity of the intracellular structure that underlies the 

 qualitative peculiarities in the action of radiation on the living cell in 

 comparison with its action on isolated cell substances and separates 

 true radiobiology from radiation chemistry of complex molecules. 



Current theories of radiobiological action associate the effect of the 

 action of radiations with the damage of either nuclear structures 

 (chromosomes), or microscopic cytoj^lasmic structures (mitochondria 

 microsomes, etc). Chromosomes being unique cell structures, the first 

 group of theories makes it possible to explain the death of cells with a 

 "target" volume of molecular size, and the genetic effect of radiation, 

 but it does not allow for physiological changes in cells after radiation 

 and for many other radiobiological phenomena. 



Considerable dependence of the number of chromosomal aberrations 

 on the dose intensity, temperature and kind of irradiation, as well as 

 many instances of their deviations from the exponential, show that 

 they themselves may be of a secondary character (Bacq and Alexander, 

 1956). The second group of theories (Bacq and Alexander, 1956) 

 attributes a major role to the damage of structurally-conjugated 

 enzymic systems in mitochondria, microsomes, etc. These theories are 

 also of certain interest ; they encounter difficulty, however, in the fact 

 of the multiplicity of mitochondria and microsomes in the cell. A sharp 

 increase of radioresistance in polyploid cells, the chromosome number 

 of which is only two to four times that of the normal, shows that in the 

 presence of scores or hundreds of parallel functioning structures it is 

 in fact very difficult to explain the high sensitivity of cells to the action 

 of radiations by the damage of several molecules in one of these struc- 

 tures. One of the attempts to take into consideration the influence of 

 intracellular structure in the light of the theory of open systems is the 

 elucidation of the possibility of destroying the stationary state in the 

 cells through essential change in diffusion parameters of the cell brought 

 about, however, by damaging a small number of molecules. 



It is evident that the cause of such an effect cannot consist in the 

 destruction of observed structures formed by thick polymolecular 

 membranes or films, since the destruction of several molecules in them 

 would not essentially change their coefficient of permeability. It would 

 seem that breaks in the structure of thin monomolecular or bimolecular 



