356 GENERAL DISCUSSION 



of the protein. I will alloy myself to put forward certain general 

 considerations as to the reasons why the metal-containing enzymes 

 can be held to be substances of special radiosensitivity. Among such 

 reasons is this, that the variable valency metal-containing enzymes, 

 under the action of iDenetrating radiation, are easily subjected to 

 oxidation, as a result of which a break in the bond between the haem 

 and the jirotein may occur. Metals, in comparison with non-metallic 

 substances entering into the composition of the cell, are capable, 

 to a considerable extent, of absorbing the energy of the penetrating 

 radiation and the absorbed radiation dose will be larger by several 

 orders than in other organic compounds. It is also known that the 

 metal-containing enzyme systems are concentrated in the structured 

 inclusion bodies of cells and in connection with this they can be re- 

 garded as substances existing in cells in a more or less solid state. 

 Investigations in the field of radiation chemistry have shown that as 

 the concentration of the dissolved substances increases, there begins 

 more and more to emerge a direct action of the penetrating radiation. 

 In these conditions, the oxidation and reduction reactions are frequently 

 accompanied by the destruction of organic substances. In this contri- 

 bution I want to draw the attention of radiobiologists to the pressing 

 problem of the need to study adequately the state of the metal - 

 containing substances in the cell of an ir]-adiated organism. 



stoyanova: The method of the gas micro-chamber, developed as a 

 result of the study of the interaction of electrons with biological 

 preparations, allowed us to produce m the electron microscope condi- 

 tions for the observation of wet biological objects and living micro- 

 organisms, such that the latter remain capable of life. This provides us 

 with the possibility of studying the dynamics of changes in the bio- 

 logical preparations under the action of various factors, including 

 (since an electron beam is a source of ionizing radiation) ionizing 

 radiation. 



The maintenance by micro-organisms of their life potential is proved 

 by the fact that those processes which took place prior to the moment 

 of irradiation are continued in the cells. They continue to divide, grow 

 and interact with each other. 



The investigation of the action of ionizing radiations was carried out 

 on living bacteria B. mycoides and B. mese7itericus. Under direct obs- 

 ervation in an electron microscope, the bacteria were examined from 

 the beginning in their initial condition and then after the reaction. It 

 was discovered that for radiation doses of up to 10^ r for the first 

 5 to 10 sec no marked morphological variations are observed, and 



