778 ADVENTURES IN RADIOISOTOPE RESEARCH 



(a), 23.0; 

 (b), 33.5. 



and calculated per gm of tissue: 



(a), 4.6; 

 (b), 4.4. 



Approximately 0.1 per cent of the nucleic acid present was therefore 

 synthesized during the experiment, and the addition of NaF reduced 

 the amount synthesized to about one-fifth of this value. In 1 gm of tissue 

 there was more than 4 per cent of the activity present at the end of the 

 experiment in the plasma plus sarcoma section system. 



A significant amount of activity also penetrated into the blood cor- 

 puscles, but this is not of interest in connexion with the above dis- 

 cussion. 



Formation of Nucleic Acid in the Presence and Absence of Monoiodo- 

 Acetic Acid 



In experiments (a) and (b), 4.31 and 3.72 gm of tissue, respectively, 

 were immersed in 16.2 cm^ of blood; 5 cm^ of physiological saline solution 

 containing ^-P was added to the blood in experiment (a), while in experi- 

 ment (b) 2 cm^ of physiological saline solution and 3 cm^ of an aqueous 

 solution, which contained 10 mgm of sodium iodoacetate adjusted to pH 

 7.4 by addition of NaOH, were added to the blood. The activity of 1 mgm 

 of nucleic acid P as a percentage of the activity of 1 mgm of free sarcoma 

 P was found to be: 



(a) 0.0338; 



(b) 0.00076. 



Formation of Nucleic Acid with and without Addition of Oestrone 



In experiments (a) and (b), respectively, 3.3 and 3.9 gm of tissue section 

 were immersed in 16.5 cm^ of blood to which active sodium phosphate 

 (2 mgm P in physiological saline) had been added; 2 mgm of oestrone dissol- 

 ved in 0.1 cm^ of alcohol was added to the experimental solution (b); 

 0.1 cm^ of alcohol, without oestrone, was added to solution (a). The acti- 

 vity of 1 mgm of nucleic acid P, expressed as a percentage of the activity 

 of 1 mgm of free sarcoma P, was found to be: 



(a) without oestrone, 0.097; 



(b) with oestrone, 0.074. 



The percentage of the activity of the whole tissue present in the 

 plasma plus sarcoma tissue at the end of the experiment was: 



