718 EFFECT OF X-EAYS ON NUCLEIC ACID IN JENSEN-SAECOMA 



formed in the course of the experiment. X-ray dosages of 2000 r units 

 do not, therefore, prevent the almost complete renewal of the molecules 

 of hydrolysable acid-soluble phosphorus compounds in the sarcoma. 

 The metabolism of the acid-soluble phosphorus compounds is closely 

 related to the oxidation and reduction processes taking place in the 

 cells, and it is well known that these latter processes are quite insensitive 

 towards the action of X-rays. ^^^ 



Enzyme Activity in Irradiated Jensen- Sarcomas 



An effect of X-rays on the enzymes taking part in the processes of 

 degradation and synthesis of the acid-soluble phosphorus compounds 

 was not to be expected, having regard to the insensitivity of these pro- 

 cesses to X-rays, as mentioned in the last section. 



Experiments in which the effectiveness of the catalase isolated from 

 the sarcoma 1 hr after irradiation with 3000 r was studied, showed that 

 this effectiveness had not suffered as a result of irradiation of the sarcoma. 

 While the catalase activity of the muscle of normal rats has been found 

 to be 0.0252, the muscle catalase of the irradiated rats showed a value 

 of 0.0385.^2) 



The effect of nuclease, obtained from sarcoma irradiated with 3000 r, 

 on desoxyribonucleic acid used as substrate did not in any way fall 

 short of the effectiveness of the nuclease obtained from unirradiated 

 sarcoma. Whereas the former decomposed 66 per cent of the desoxyribo- 

 nucleic acid in the course of 4 hr, the corresponding value for the unirra- 

 diated sarcoma amounted to 46 per cent. 



From the chemical point of view^ the cell division is a consequence 

 of the very intensive synthetic process which takes place in the nuclei 

 of the cells. Interference with these synthetic processes can stop the cell 

 division. Interference by means of the action of irradiation can take 

 place either by more rapid destruction of the molecules indispensable 

 in the synthesis than the rate at which they are formed, or by the form- 

 ation of noxious products, as a result of the effect of radiation, which 

 enter into the chemical processes occurring in the cell nuclei or in certain 

 parts of these nuclei and thus inhibit the normal course of these processes 

 and their sequel, cell division. Among the effects of X-rays there is, 

 for example, splitting of high polymer molecules, as is known from the 



1 Whereas four-fifths of the sarcomas have been prevented from growing 

 after transplantation, by irradiation with 1800 r, the oxygen consumption of these 

 sarcomas was not different from that of the control sample (W. Keil, Arch, 

 exp. Pathol, 167, 338 (1932). 



2 These experiments are described in more detail elsewhere. 



