24 I. LESLIE 



of PNA or DNA over a 14-day growth period. However, they obtained no 

 net increase in DNA over their zero time vakie. 



VI. Dietary Factors Influencing Nucleic Acid Content 



The loss of liver tissue, which occurs in rats during a fast or on a protein- 

 deficient diet, involves a decrease in cell volume,''^ the loss of cytoplasmic 

 granules'^" and pentose,"^ but little or no change in the DNA content or 

 cell number. This conclusion has been established by various studies on the 

 effect of dietary deficiency on tissue nucleic acids (Table VIII). 



Among the earlier observations, Campbell and Kosterlitz^^^ reported a 

 fall in PNA-P concentration per unit weight of rat liver without a corres- 

 ponding decrease in DNA-P concentration after one week on a protein-free 

 diet; later they reported that they found no change in the DNA-P per liver 

 in rats on high or low fat diets, whether choline was present or not.^^^ Pre- 

 viously, Davidson^ had found that, although liver weight decreased by 11 % 

 and PNA-P content by 20%, the total DNA-P per liver remained un- 

 changed after 2 days of fasting. According to Thomson et al.,^* the DNA-P 

 content of rat liver and the average amount of DNA-P per nucleus are not 

 significantly altered by a 72-hr. fast, a high fat diet for 35 days, a protein- 

 free diet up to 15 days, or a thiamine-deficient diet for 21 days. By contrast, 

 the average cell mass (liver weight/total DNA-P content) decreases by 

 about 35 %, and the average cell content of phospholipid, PN, and PNA-P 

 by between 20 and 30 % during fasting or protein deficiency. 



Mandel and his collaborators extended their earlier observations to the 

 study of the effects of prolonged protein deficiency (50 to 70 days' duration) 

 on the nucleic acid content of various rat tissues (Table VII refs. 48, 60). 

 In most of the tissues (brain, kidney, liver, cardiac, and skeletal muscle) the 

 DNA-P content and (by implication or by actual nuclear counts) the cell 

 number remained unaltered or only slightly increased. Only in the rat 

 spleen was there a considerable reduction (55 %) in the DNA-P content 

 and in the total number of nuclei.^" The accompanying loss of PNA and 



'3^ R. M. Campbell and H. W. Kosterlitz, /. Physiol. 106, 12P (1947). 



»35 R. M. Campbell and H. W. Kosterlitz, Science 115, 84 (1952). 



"6 (a) E. Muntwyler, S. Seifter, and D. M. Harkness, J. Biol. Chem. 184, 181 (1950); 



(b) S. Seifter, E. Muntwyler, and D. M. Harkness, Proc. Soc. Exptl. Biol. Med. 75, 



46 (1950). 

 '" G. C. Villela, Rev. brasil biol. 12, 321 (1952). 

 138 M. Fukuda and A. Sibatani, Expenentia 9, 28 (1953). 

 '39 H. W. Kosterlitz and I. D. Cramb, J. Physiol. 102, 18P (1943). 

 1^0 H. W. Kosterlitz, Nature 154, 207 (1944). 

 1" J. Brachet, R. Jeener, M. Rosseelt, and L. Thonet, Bull. soc. chim. biol. 28, 460 



(1946). 

 i« R. M. Campbell and H. W. Kosterlitz, Biochim. el Biophys. Ada 8, 664 (1952). 



