CELL GROWTH AND MULTIPLICATION 



157 



TABLE 3 



DNA CONTENT PER NUCLEUS IN BEEF TISSUES 



After Vendrely, 1955 



of a species. Haploid cells show half the amount (Table 3; Vendrely, 1955). 

 This has been established by chemical analysis (Schmidt-Tannhauser and 

 Schneider methods), as well as UV spectrophotometry and quantitative photom- 

 etry in visible light (Feulgen preparations). In contrast to the RNA content of 

 the cell which shows considerable variation with functional factors (type of tissue, 

 nutrition, hormones, mitotic activity, etc.), the DNA content of the nucleus is a 

 species-specific constant, remaining unaltered by such factors. This constancy of 

 DNA content even applies to many tumor cells (in spite of pyknosis, etc. of 

 nuclei), and appears to change only with mitosis in dividing cells and the poly- 

 ploidy appearing in many malignancies. Because of the constancy of DNA per 

 nucleus, DNA content can be used as a measure of the number and multiplication 

 of cells within an organ. Data on DNA and RNA content of normal and tumor cells 

 are surveyed, from own observations and survey of literature, by Sandritter (1958). 



Duplication of DNA and chromatin preceding mitosis takes place during 

 interphase and prior to the visible stages of mitosis, in a stage suitably denominated 

 as antephase. This is shown by the methods mentioned as well as the turnover of 

 DNA determined by introduction of 32P (Stevens, Daoust and Leblond, 1953a; 

 Daoust, F. D. Bertalanffy and Leblond, 1954). 



While somatic cells of an organ in general show the same size of the nucleus 

 due to the same diploid chromosome set and DNA content, in many organs 

 nuclear series are found (Jacobj, 1925; Wermel et al., 1932-35; Helweg-Larsen, 

 1952; Fankhauser, 1954; Linzbach, 1955). 



In many tissues nuclear volumes appear as multiples of a unit. Hence, in 

 graphical representations a simple binomial distribution is found in tissues con- 

 taining only one nuclear class, while in organs with several nuclear classes a 

 curve with several peaks is found, the maxima showing a ratio i : 2 : 4 . . . 

 For example, the nuclei of all (36) observed organs in man, the guinea pig and 

 the rabbit are distributed among nine classes, their volumina showing a ratio 

 I : 2 : 4 : 8 : 16 : 32 : 64 : 128 : 256. Erythroblast nuclei belong to the smallest 

 class, those of spinal ganglia to the largest (Jacobj, 1935; Freerksen, 1933; 

 Korner, 1937; and others). 



The increase of nuclear volume is paralleled by a corresponding multiplication 

 of DNA content (Fig. 3). On the other hand, in pituitary dwarf mice (with a 

 hereditary lack of eosinophilic cells in the hypophysis and corresponding lack of 

 somatotropin, cf. p. 220), the nuclear series are absent but do appear after 



Literature p. 253 



