780 ADVEXTUKES IX RADIOISOTOPE RESEARCH 



The total sarcoma activity as a percentage of the plasma activity plus 

 the sarcoma activity was: 



(a) 25.4; 



(b) 25.8. 



and per gm sarcoma tissue 



(a) 4..91; 



(b) 4.30. 



The addition of colchicine therefore does not affect the formation of 

 nucleic acid. A negative result was also obtained on adding diethylstil- 

 boestrol (addition of 3 mgm of a sample prepared by Dr. E. Adler). 



Formation of Nucleic Acid without Additives 



In one experiment in which 5.38 gm of sarcoma sections was shaken 

 with 25 cm^ of blood the percentage ratio of the activity of 1 mgm of 

 nucleic acid P to that of 1 mgm of free P was 0.033. 



Metabolism of Nucleic Acid in Liver Sections 



The determination of the metabolism of nucleic acid in liver slices 

 lies outside the scope of this investigation. Yet a determination of this 

 kind has been performed as a sort of purity check. The amount of labelled 

 nucleic acid formed in the liver in a period of 2 hr amounts to only 

 about 0.1 per cent of the total amount of nucleic acid present. A consi- 

 derably smaller value must be expected in liver slices. A weight of 

 10.6 gm of liver slices was shaken for 4 hr with 24 cm^ of plasma, which 

 contained 15 /^c of ^^p^ at 37° C and the percentage ratio of the specific 

 activity of the nucleic acid P and of the free tissue P was then determined. 

 This was found to be 0.0085. The percentage ratio of the nucleic acid P 

 and of the plasma P was 0.0021. These figures show that the formation 

 of new molecules of nucleic acid in the liver sections is lower by a factor 

 of 10, or more, than in the liver. These data provide further evidence 

 that the purification of our nucleic acid from phosphorus-containing 

 impurities is efficient. 



AMOUNT OF NUCLEIC ACID DECOMPOSED PER HOUR IN SARCOMA 



SECTIONS 



In order to obtain information on the rate at which nucleic acid decom- 

 poses in sarcoma sections, a determination of the nucleic acid content 

 has been made immediately after killing a rat. Some toluene was added 

 to another part of the sarcoma and, after keeping the tissue for 24 hr 



