708 



ADVENTURES IN RADIOISOTOPE RESEARCH 



Percentage of injected P^^ present in 1 mgm 



The intrinsically decreased metabolism of nucleic acid in necrotic tissue is re- 

 duced Still further by the action of the X-rays. 



Table 10. — Comparison of the Mean Values of Nucleic Acid Formation and 

 OF Phosphate Permeability in Fresh and Necrotic Tissue 



Activity of 1 mgm of nucleic acid phosphorus 

 as a percentage of the activity of the 

 free sarcoma P 



Katio of the activity of 1 mgm of free P of | 

 the necrotic and fresh sarcoma tissues / 



Unirradiated 

 Irradiated with 

 2000 r 



Unirradiated 

 Irradiated 



Fresh tissue 



2.05 



0.65 



Necrotic 

 tissue 



1.12 

 0.16 



0.66 

 0.76 



Amount of Nucleic Acid Newly Formed in the Sarcoma Tissue in the 

 Course of 2 hr 



We found (Table 8) that two hours after subcutaneous injection of 

 the radioactive phosphate, the activity of the nucleic acid phosphorus 

 amounts to 2 per cent of the activity of the free sarcoma phosphorus. 

 If the activity of the free sarcoma phosphorus were the same during 

 the experimental period as at the end of the experim.ent, it would be 

 possible to conclude from the above data that nucleic acid molecules 

 constituting 2 per cent of the total nucleic acid present in the sarcoma, 

 i. e. on the average 0.18 mgm/g of tissue for sarcomas weighing less than 

 40 gm (see Table 12), had been formed during the 2 hr experimental period. 

 The activity of the sarcoma P, however, changes in the course of the 

 experiment. If we assume, for example, that it increases linearly with 



