32 I. LESLIE 



81 % and the PNA by 28 %, thus decreasmg the PNA/DNA ratio.^^ Treat- 

 ment of mice carrying the transplantable sarcoma 180 with aminopterin 

 reduced the PNA and DXA concentrations and increased the PNA/DNA 

 ratio in the tumor tissue."* 



VIII. Hormonal Influences 



The changes in nucleic acid content after administration of various hor- 

 mones are summarized in Table X, and those following the surgical removal 

 of glands are summarized in Table XI. 



After the daily injection of 20 mg. cortisone acetate for 7 days, rabbits 

 were found to have hypertrophied livers, in which the amounts of protein 

 and PNA relative to DNA were greatly increased (Table X^^). Similar re- 

 sults were reported independently by Lowe et al. (Table X^^). The decrease 

 found in PNA concentration per unit weight indicates that other cell con- 

 stitutents (e.g., lipids) are building up to a greater extent than PNA. In 

 such circumstances, the basophilia of the cytoplasm will decrease, but it 

 does not follow that PNA synthesis is reduced by cortisone, as the authors 

 suggest.®^ 



That fat accumulation is largely responsible for the lower PNA and DNA 

 concentrations is shown by the changes in composition of mouse liver dur- 

 ing cortisone treatment.^** Other experiments of Roberts et al}^^ on mice 

 with regenerating livers suggested that "DNA fails to regenerate quickly 

 in livers of cortisone-treated mice." 



Inhibition of growth was also obtained on injection of 1.25 mg. cortisone 

 acetate into the chorioallantoic membrane of the 8-day chick embryo. ^^' 

 However, in this case, the cortisone lowered the PNA/DNA ratio and de- 

 creased the protein content of the cells. Leslie'^'* added cortisone to the 

 growth-promoting medium of cultures of embryonic chick heart explants 

 and found slight increases in the total DNA-P synthesis and in the PNA/ 

 DNA ratio. When cortisone and growth hormone were combined, the total 

 synthesis of PNA and DNA rose as much as 75 % above normal over 6 days. 

 Growth hormone applied alone slightly inhibited cell multiplication. 



According to Gerarde and Jones^^^ the nucleic acid concentrations did not 



'68 K. B. Roberts, H.W. Florey, and W. K. Joklik, Quart. J. Exptl. Phtjsiol. 37, 239 



(1952). 

 '" C. CavaUero, A. Di Marco, L. Fuoco, and G. Sala, Proc. Soc. Exptl. Biol. Med. 81, 



619 (1952). 

 "0 W. E. J. Phillips, R. H. Common, and W. A. Maw, Can. J. Zool. 30, 201 (1952). 

 '" R. M. Campbell, I. R. Innes, and H. W. Kosterlitz, J. Endocrinol. 9, 52 (1953). 

 •" M. A. Telfer, Arch. Biochem. and Biophys. 44, 111 (1953). 

 '" I. Leslie and J. N. Davidson, Biochem. J. 49, Proc. xli (1951). 

 »'^ I. Leslie, Biochem. J. 52, Proc. xxi (1952). 

 •" H. W. Gerarde and M. Jones, J. Biol. Chem. 201, 553 (1953). 



