Originally published in Ark. Kemi. 19A, No. 13 (1945). 



74. THE INDIRECT EFFECT OF X-RAYS 

 ON THE JENSEN-SARCOMA 



L. Ahlstrom, H. Euler and G. Hevesy 



From the Institute for Research in Organic Chemistry, Stockholm 



Several observations have been made that besides the direct effect 

 of X-rays there is also an indirect effect which is able to influence the 

 division of cells. Kok and Vorlaender(^) observed, for example, an 

 indirect effect in the "unirradiated" skin of the mouse, in addition to 

 the direct radiation effect. This "indirect" effect is fundamentally similar 

 to the direct one, yet a more or less important graded difference can be 

 recognized which always points to weakening. 



In another communication Kok stated that he had similar good results 

 with a 25 per cent dosage delivered to the whole body of the animal 

 as with optimum local irradiation. 



Russ, Chambers and ScoTT<2)had already found, a long time ago, 

 that Jensen-sarcoma transferred by inoculation into rats grew more 

 slowly in those which had been repeatedly exposed to small doses of 

 irradiation than in the unirradiated controls. These authors have shown^^) 

 more recently that the inoculated Jensen-sarcomas grow better in a 

 normal tissue than in tissue whose surroundings have been irradiated. 

 These experiments have been continued in recent years^^). Russ and 

 Scott compare the growth of sarcomas of approximately the same size 

 from two rats of the same age. In one case, only the sarcoma was irra- 

 diated, while the whole of the body was protected by lead sheet from the 

 effect of radiation. In the other case, they irradiated only the surroundings 

 of the sarcoma, while the sarcoma itself and the remainder of the body 

 were protected by means of lead. 



Some time ago we showed, with the help of radioactive phosphorus as a 

 tracer^s), that the rate of synthesis of desoxyribose nucleic acid molecules 



(^) Kok and K. Vorlaender, Strahlentherapie 14, 497 (1923); Fr. Kok, Ibid 

 18, 90 (1924). 



(^) W. Russ, Chambers and G. M. Scott, Proc. Boy. Soc. B 92 (1921). 



<^)S. Russ and G. M. Scott, Brit. J. Radiol. 32, 289 (1927). 



<*)Cf. Medical uses of radium, Brit. Soc. Radiol. N. S. 14, 9 (1942). 



(^) H. Euler and G. Hevesy, Kgl. Danske Vidensk. Selskab. Biol. Medd. 17, 



8 (1942); Ark. Kern. 17, No. 30 (1944). 



