NUCLEOLINUS 



241 



NUCLEONUCLEOLAR RATIO 



by dividing the nucleic acid nitrogen 

 by the total coagulable nitrogen less 

 nucleic acid nitrogen. 



Nucleolinus is a term introduced by Haeckel 

 to indicate a deeply staining granule 

 within a nucleolus. For details see 

 Champy, C.and Carleton, H.M., Quart. 

 J. Micr. Sci., 1921, 65, 589-610. 



Nucleolus (L. dim. of nucleus) is a body 

 within a nucleus. There are at least 

 three sorts. 



1. Plasmosomes. These can be de- 

 fined as roughly spherical bodies, which 

 can easily be seen in the nuclei of some 

 living cells without the aid of any stains, 

 which stain after appropriate fixation, 

 namely, with plasma or "acid" stains 

 like eosin, (hence the name) and which 

 do not directly contribute material 

 to the formation of chromosomes. 



Plasmosomes are not to be confused 

 with cytoplasmic granules called plas- 

 mosomes by Arnold many years ago or 

 with plastosomes, a term given by 

 Meves to mitochondria and now fortu- 

 nately being discarded. They can be 

 referred to as acidophilic or oxyphilic 

 nucleoli, but sometimes they are tinged 

 quite strongly with basic dyes. They 

 are of dense consistency, easily^ shifted 

 by centrifugal action and are in some 

 cases more resistant to the digestive 

 action of pepsin and hydrochloric acid 

 than karyosomes. 



2. Karyosomes, are by contrast in- 

 tensely basophilic and do contribute 

 material to the making of chromosomes 

 during mitosis. But they are resistant 

 to peptic hydrochloric acid digestion. 

 Wilson (E. B., Heredity, New York: 

 Macmillan 1925, p. 93) recognizes 3 

 types, net-knots, chromosome-nucleoli 

 andkaryospheres. There is doubt about 

 the existence in vivo of the net-knots in 

 the same shape, size and position as 

 observed in stained sections. 



3. Amphinucleoli (G. amphi on both 

 sides) are nucleoli consisting of both 

 plasmosome and karyosome material. 

 Often the acidophilic substance acts as 

 a kind of core and the basophilic sub- 

 stance is close to it or appears to be 

 plastered on its surface. The latter may 

 not occur in the same form in the living 

 nucleus. 



The fixation which shows, when the 

 sections are stained, the highest degree 

 of nucleolar detail is not necessarily 

 the best (see remarks about Nuclei,). 

 The Linin network, net-knots and 

 basophilic material marginated on plas- 

 mosomes may result in part from the 

 coagulating action of the fixative on 

 material originally distributed diffusely 

 in the nucleoplasm. Nucleoli which 

 look bubbly, or are surrounded by halos, 



are to be regarded with suspicion. 

 Fixation in Acetic-Gsmic-Bichromate 



and in other fluids containing osmic 

 acid is indicated but they penetrate 

 poorly. Staining by almost any tech- 

 nique which gives a good color contrast 

 between acidophilic and basophilic 

 materials is satisfactory. The classical 

 stain is with safranin and light green. 

 Eosin and methylene blue, hematoxylin 

 and eosin are recommended, likewise all 

 methods advised for Nuclear Inclusions 

 caused by viruses. 



Usually no difficulty is experienced 

 in the identification of nucleoli. How- 

 ever with the plasmosomes there may 

 be some question. In the first place 

 nuclear inclusions type B (Cowdry 

 E. v.. Arch. Path., 1934, 18, 527-542) 

 look something like plasmosomes. For 

 example, the nuclear inclusions in Borna 

 disease are acidophilic and may be of 

 the same size as plasmosomes ; but, they 

 like others of type B are strongly 

 acidophilic, are seldom tinged with 

 basic stains and are generally surrounded 

 by halos of unstained nucleoplasm. 

 Moreover they are not present in normal 

 animals. 



Secondly cells are sometimes encoun- 

 tered in which there is an increase in 

 acidophilic nuclear material often ac- 

 companied by nuclear hypertrophy. 

 The material may occur in the form 

 of dense spherules or of masses which 

 are bluntly angular and without halos. 

 Colored illustrations of liver cell nuclei 

 are given by Cowdry, E. V. and Kitchen, 

 S. F., Am. J. Hyg., 1930, 11, 227-299, 

 figs. 43 and 44. These bodies may be 

 true nucleoli which have undergone 

 hypertrophy or they may be simply 

 accumulations in the nuclei of aci- 

 dophilic material. The only sure way 

 to tell would be to ascertain whether 

 they comport themselves like true 

 plasmosomes during mitosis but the 

 cells involved have not been seen in 

 division. In other conditions (^lioma- 

 tous tumors, etc.) cells are found whose 

 nuclei are enlarged and possess roughly 

 spherical, vacuole-like masses of granu- 

 lar acidophilic material. The granules 

 have the appearance of coagula produced 

 by the fixative in a rather thin fluid 

 medium. There is no halo. Such 

 bodies are probably not altered plas- 

 mosomes. Their density is much less. 



Differential staining. Nucleoli are 

 colored brown after fixation in equal 

 parts of 1% aq. chromic acid and 10% 

 formalin and staining of chromosomes 

 by Feulgen Reaction (Bhaduri, P. N., 

 J. Roy. Micr. Sci., 1938, 58, 120-124). 

 Nucleonucleolar Ratio recommended as an 

 aid in the grading of malignancy with 



