NUCLEIC ACIDS IN CHROMOSOMES AND MITOTIC DIVISION 195 



tion (see also Sect. II.2.a). The spread of values obtained from interphase 

 nuclei in dividing cells was in marked contrast to the sharply defined classes 

 found in differentiated, nongrowing tissue. Klein et aZ.^^^'-* however, found 

 no significant difference in the statistical distribution of the total ultravio- 

 let absorption at 265 m^ in individual isolated nuclei from certain diploid 

 ascites tumors compared with nongrowing lymphocyte and histiocyte 

 nuclei. The doubUng of the chromosomal DNA in this material thus seems 

 to proceed during a relatively short period immediately before or after 

 mitotic division. It may be that this behavior is peculiar to tumor cells. It 

 should be mentioned that in this tumor material good agreement was ob- 

 tained between macrochemical estimations of DNA-phosphorus, ultra- 

 violet absorption values, and also the degree of ploidy.^^^ •^^'^ 



Interesting suggestions concerning the mechanism of distribution of 

 nucleic acids during mitotic division have been made by Jacobson and 

 Webb, ^^^'^^2 using the ordinary May-Griinwald and Giemsa stains in com- 

 bination with digestion by ribo- and deoxyribonucleases. The prophase and 

 telophase chromosomes stained red in contrast to the blue-black staining 

 of the metaphase chromosomes. The authors concluded that DNA-proteins 

 were present in the chromosomes of the interphase nucleus and in the 

 division chromosomes. PNA-proteins, on the other hand, were present in 

 the chromosomes only from the end of prophase, through meta- and ana- 

 phase, up to early telophase. During the anaphase movement, PNA-pro- 

 teins appeared to be shed from the chromosomes into the space between the 

 two groups of chromosomes. In spite of painstaking experiments to show 

 the specificity of the May-Griinwald and Giemsa stain, these conclusions 

 seem not fully convincing. As mentioned in Section 1 1. 2. 6 previous studies 

 have shown the reactions between dyes and the intracellular structures to 

 be a complicated matter of adsorption, salt linkages, etc. Moreover, the 

 results of analyses of interphase chromosomes (Sect. II. 1) make it im- 

 probable that these structures are devoid of PNA. It seems probable that 

 Jacobson and Webb are dealing with effects of interaction between quanti- 

 tative changes of DNA, PNA, and proteins, the magnitudes of which 

 cannot be evaluated from the staining properties. All these findings need 



" F. Schrader and C. Leuchtenberger, Proc. Natl. Acad. Sci. 35, 464 (1949). 

 ^^ J. Pasteels and L. Lison, Arch. hiol. {Liege) 61, 445 (1950). 

 " A. H. Sparrow, M. J. Moses and R. Steele, Brit. J. Radiol. 25, 182 (1952). 

 " H. Swift, Intern. Rev. Cytol. 2, 1 (1953). 



" G. Klein and G. Moberger, Report from Gustaf V. Research Foundation, Stock- 

 holm, 1953. 

 " G. Klein, Eva Klein, and Elin Klein, Cancer Research 12, 484 (1952). 

 " C. Leuchtenberger, G. Klein, and E. Klein, Cancer Research 12, 480 (1952). 

 '<" T. Hauschka and A. Levan, Exptl. Cell Research 4, 457 (1953). 

 '' W. Jacobson and M. Webb, J. Physiol. 112, 2P (1950). 

 32 W. Jacobson and M. Webb, Exptl. Cell Research 3, 163 (1952). 



