46 I. LESLIE 



In view of discrepancies between the results of Nowinski and Yushok 

 and those of other authors for DNA in chick embryonic nuclei, it should 

 be mentioned that good agreement has been obtained for determinations 

 of DNA made on replicate roller tubes of chick heart explants by the 

 Schmidt and Thannhauser procedure and the microbiological assay for 

 deoxyribosides of Hoff-J0rgensen.-^^ 



Patterson and her colleagues,^^^ in their studies on salivary glands of 

 Drosophila melanogaster, report that females of genotypes XX and XXY 

 have significantly higher amounts of PNA per gland and PNA per cell 

 than males of genotypes XO and XF, but that there are no significant 

 differences within the male and female pairs. The Y chromosome in this 

 case has no measurable effect on the amounts of nucleic acids in the sali- 

 vary gland cells. 



In the regenerating mouse liver,^'^ the restoration of DNA was com- 

 pleted after 8 days, but only 60% of the original number of nuclei were 

 present. While the ratio of DNA/protein was remarkable constant over 

 28 days' regeneration, the PNA/protein was greater than normal values 

 as long as protein synthesis was proceeding. Einhorn et alP'^ have studied 

 the action of cortisone on regenerating liver, and confirm previous findings 

 by Roberts et al}^^ In both normal and regenerating liver, cortisone treat- 

 ment produced decreased cellularity and inhibited the restoration of DNA 

 to a greater extent than PNA. 



It is not possible to summarize adequately the detailed account given 

 by Laird^'* of the proportions of PNA, DNA, and protein found in the 

 different intracellular fractions of a number of normal and malignant 

 tissues from rat, mouse, and man. Using the Schneider method, she has 

 found higher values for the DNA per average nucleus than previously 

 reported. Distinctly different patterns of intracellular distribution were 

 apparent amongst the various tissues; in particular, there were smaller 

 amounts of cytoplasmic particulate fractions in adrenal, thymus, and all 

 tumors than in liver, kidney, pancreas, and submaxillary gland: in tumor 

 mitochondria the PNA/protein ratio was, however, higher than in any of 

 the normal tissues. All the tumors examined were closely similar in the 

 proportion and composition of their intracellular fractions. Albert and 

 Johnson^^^ confirm that the lower PNA-P content of the cytoplasmic 



"* E. Hoff-J0rgensen and I. Leslie, unpublished results. 



"* E. K. Patterson, Helga M. Lang, M. E. Dackerman, and J. Schultz, Exptl. Cell 



Research Q, 181 (1954). 

 "« K. K. Tsuboi, H. O. Yokoyama, R. E. Stowell, and M. E. Wilson, Arch. Biochem. 



and Biophijs. 48, 275 (1954). 

 2" S. L. Einhorn, E. Hirschberg, and A. Gellhorn, J. Gen. Phijsiol. 37, 559 (1954). 

 "8 A. K. Laird, Exptl. Cell Research 6, 30 (1954). 

 "9 S. Albert and R. M. Johnson, Cancer Research 14, 271 (1954). 



