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Ionizing Radiation 

 and Cellular Metabolism 



GEORGE HEVESY 



Institute for Research in Organic Chemistry 



University of Stockholm 



Stockholm, Sweden 



It has been known for many years that ionizing radiation interferes 

 only to a minor extent with respiration and glycolysis, whereas it 

 markedly influences mitotic processes. Though developments have 

 shown that the first-mentioned effects are far from being negligible, the 

 most conspicuous effect still remains the action of ionizing radiation on 

 cell division, which will be considered first. Radiation causes a drop 

 in the rate of mitosis, followed by an attempt at recovery accompanied 

 by the appearance of degenerate cells. For example, 5 min after ex- 

 posure of cultures of avian fibroblasts to a total of 1000 r UX beta 

 radiation, the mitotic figures were found to be reduced from 100 to 87; 

 after 30 min to 15. After 9 hr, however, mitosis was increased (1). 

 When leukocytes from patients with chronic myeloid leukemia were ex- 

 posed to x-rays in tissue cultures, mitosis was temporarily inhibited by a 

 dose of 100 r, and apparently permanently inhibited by 1000 r (95). 



Irradiation may influence the rate of mitosis not only of cells in an 

 advanced stage of the mitotic cycle, but also of those in an early or the 

 earliest period of interphase. 



Since in the mitotic process the cell nuclei are primarily involved, 

 irradiation can be expected to influence the cell nucleus. This was shown 

 to be the case in numerous investigations. For example, Henshaw (2) 

 found that, when nucleated and enucleated egg fragments of Arbacia 

 were x-rayed and then fertilized with normal sperm, delayed and ab- 

 normal development was found only in nucleated egg fragments. 



Of the nuclear constituents, desoxyribonucleoproteins, having a molec- 

 ular weight of about 1 million and comprising a large part of the nuclear 

 material, may be the most important. Ionizing radiation, possibly 

 through the intermediary of active radicals produced in the tissue water 

 or other tissue constituents, interferes with the synthesis assembly of 



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