NUCLEI 



239 NUCLEIC ACID-DYE INTRACTIONS 



virus action are usually acidophilic, 

 that formalin used alone is contraindi- 

 cated as a fixative. 



On the morphological side it is known 

 that nuclei stained in sections after 

 fixation in the usual ways show a di- 

 versity, or heterogenic! ty, of internal 

 structure which cannot be observed by 

 the most careful examination of the 

 nuclei of living cells. In thelatteronly 

 the nucleolus can generally be distin- 

 guished. The so-called linin network, 

 and small irregular particles staining 

 with acid and basic dyes, are not ob- 

 served. These probably result from the 

 coagulating action of the fixative upon 

 materials present in solution or fairly 

 uniformly distributed in the nucleo- 

 plasm. Stained sections of tissues fixed 

 in fluids containing fair amounts of 

 osmic acid (Altmann's Mixture and 

 Bensley's Acetic-Osmic-Bichromate) 

 exhibit, on the contrary, nuclei with 

 quite homogeneous looking nucleoplasm, 

 containing nucleoli, which portray the 

 condition in vivo more accurately. 

 Colored illustrations of the nuclei of 

 liver cells containing inclusions after 

 osmic and non-osraic fixation (Figs. 47 

 and 20) are provided by Cowdry, E. V. 

 and Kitchen, S. F., Am. J. Hyg., 1930, 

 11, 227-299. This does not mean, 

 however, that the ground substance is 

 always optically homogeneous in vivo. 



The shrinkage of nuclei when exam- 

 ined in stained sections is generally 

 more than 10% of their size in vivo. 

 In post-mortem autolysis, particularly 

 of the kidney, one of the first nu- 

 clear modifications is shrinkage. The 

 shrunken nuclei may stain intensely 

 with both basic and acid dyes. The 

 acidophilic material in them may even 

 appear to be increased; for it is more 

 concentrated, owing to decrease in 

 volume (oxychromatic degeneration). 

 They are also more spherical and less 

 oval in shape. In early stages this 

 modification can easily be identified 

 by its occurrence in some tubules and 

 not in others. A comparable hyper- 

 chromatism of nuclei at the edge of a 

 section accompanied by a flattening of 

 them may indicate that a surface film 

 of tissue was permitted to dry before 

 fixation. 



Among the stains Iron Hematoxylin 

 is a favourite because of its sharpness 

 and permanence. Phloxin-Methylene 

 Blue is also recommended. If one de- 

 sires to reverse the colors and get red 

 nuclei and green cytoplasm Safranin 

 Light Green is suggested. The 

 Safranin-Gentian Violet-Orange G 

 technique gives several beautiful color 

 tones. Recently the Feulgen reaction 



by which Thymonucleic Acid can be 



demonstrated has become very popular 

 as the most sharply discriminating 

 nuclear stain. Microchemical studies 

 are now possible which a few years ago 

 were undreamed of. The method of 

 Microincineration reveals some of the 

 mineral constituents (Scott, G. H., 

 Proc. Soc. Exp. Biol. & Med., 1935, 

 32, 1428-1429). 



The collection of nuclei in bulk for 

 chemical analysis is now feasible (see 

 Centrifugation). Thus nuclei of liver 

 cells can be separated from cytoplasms 

 by centrifugation after treatment with 

 dilute citric acid. Normal liver nuclei 

 do not accumulate P32 while tumor 

 nuclei and regenerating nuclei do 

 (Marshak, A., Federation Proceedings, 

 Baltimore, 1942, 1, (2) 57). A method 

 for separating nuclei from rest of thy- 

 mus is described by Williamson, M.B 

 and Gulick, A., J. Cell. & Comp. Phys- 

 iol., 1942, 20, 116-118. The authors 

 analysed the mass of nuclei for calcium, 

 magnesium and phosphorus. Another 

 method for separating from cytoplasm 

 (Crossmon, G., Science, 1937, 85, 250) 

 is to place drop 5% aq. citric acid in 

 center of a slide smeared with Mayer's 

 Albumin Glycerin. Add piece fresh 

 muscle. This slowly becomes trans- 

 parent and infiltrated. The cloudiness 

 of the citric acid is caused by released 

 nuclei. Remove muscle and allow fluid 

 containing nuclei to dry completely. 

 Hold nuclei in place by treating with 

 95% ethyl alcohol. Wash in tap water, 

 then in aq. dest., stain with A-Iayer's 

 Hemalum, blue in tap water, counter- 

 stain in eosin, dehydrate, clear and 

 mount. 



For a technique to demonstrate sex 

 differences in neuroglial and nerve 

 cell nuclei consult Barr, M. L. (Exp. 

 Cell Res., 1951, 2, 288-290). See Argin- 

 ase and Diaminoacridines for visual- 

 ization of nuclei in vivo by their fluores- 

 cence. 



Nucleic Acids, see Ribonucleic, Thymo- 

 nucleic and Desoxyribonucleic. Micro- 

 spectrophotometry. 



Nucleic Acid-Dye Interactions — Written by 

 Edward L. Kuff, Dept. of Anatomj'^, 

 Washington University, St. Louis 10, 

 Missouri. October 18, 1951— Pure 

 nucleic acids are not known to react 

 with acid dyes. The staining of nuclei 

 with acid dyes which can be made to 

 occur in tissue sections is due pre- 

 sumably to interaction of the dye with 

 protein constituents of the nuclei, 

 although this phenomenon has not been 

 adequately studied. 



Nucleic acids of both cytoplasmic and 

 nuclear origin react strongly with a 



