ON THE MECHANISM OF INHH^ITION OF CELL 

 DIVISION INDUCED BY IONIZING RADIATION 



A. V. LEBEDINSKY, V. M. MASTRYUKOVA AND A. D. STRZHTZHOVSKY 



Academy of Medical Sciences of the U.S.S.R., Moscoiv, U.S.S.E. 



SUMMARY 



The inhibition of mitotic activity lies at the very basis of the radiation effect 

 on physiological regeneration. 



The inlnbition of this activity may result from : 



(i) radiation damage to the synthesis of the products that are necessary for 

 cell division: 



(ii) damage to the mitotic apparatus with the blocking of mitosis even in tlie 

 case where there is a sufficient quantity of tlie products necessary for cell division. 



The biochemical disturbances are reversible, the genetic disturbances are 

 irreversible. The cells with the damaged genetic apparatus give rise to patho- 

 logical mitoses and perish during the first generation. On the basis of these 

 assumptions a formula was elaborated for determining the index of normal 

 mitosis as the function of time and irradiation dose. Besides the intracellular 

 processes mentioned the mitotic activity of cells in an organism is influenced also 

 by extracellular processes. 



The report presents experimental data concerning the influence of nervous, 

 hormonal and cytolytic factors on mitotic activity in irradiated organisms. 

 The necessity to modify the eciuation is suggested so that both intracellular and 

 extracellular factors may be taken into account. 



One of the most important problems for our imderstaiiding of the 

 living organism is the process of physiological regeneration. The normal 

 realization of this function is based upon periodically repeated mitotic 

 activity in the cells. 



One of the most characteristic effects of radiation upon biological 

 objects is the inhibition of the processes of physiological regeneration. 

 The inhiljition of mitotic activity lies at the very basis of this phenom- 

 enon, which has attracted considerable investigations. Their signifi- 

 cance is not only in the fact that they enable us to study several general 

 laws concerned with cell reactions in response to the radiation effect 

 but also in the evidence that the experimental results obtained enal)le 

 us to penetrate deeply into the very essence of the phenomenon of 

 mitotic activity. 



The most general form of the reaction arising in response to radiation 



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