170 



HYPOPHYSIS AND GONADOTROPHIC HORMONES 



the enzymes which would produce these ef- 

 fects are not, with present technicjues, de- 

 monstrable by staining reactions. It is there- 

 fore not possible at present to stain different 

 cell types in the pituitary, if by this phrase 

 we mean the demonstration of differences 

 in the cytoplasmic make-up of cells with 

 different secretory functions. Differences in 

 staining, which are observed with more or 

 less ease, are due to the staining reactions 

 of the products of hormone synthesis within 

 the cell ; they do not demonstrate differences 

 in the synthesizing mechanisms directly. 

 One consequence of this is that specific cell 

 types are only differentiated w^hen there 

 is, within their cytoplasm, an adequate 

 amount of their specific product in the 

 form of granules. 



Specific staining of granules requires 

 methods which stain granules while leaving 

 other cytoplasmic components unstained. 

 Simple basic dyes such as methylene blue 

 are not useful for this purpose. The baso- 

 philia of the basophil granules is weak, the 

 binding power is weaker than that of ribo- 

 nucleic acid. The capacity for dye absorp- 

 tion is great at high pH, so that cells with 

 heavy accumulations of basophil granules 

 appear densely stained, and it is this density 

 of staining in densely granulated cells, 

 rather than any exceptional strength of 

 binding, that justifies the use of the term 

 basophil for a certain class of cells in the 

 adenohypophysis (Peterson and Weiss, 

 1955). Simple acid dyes do stain certain 

 secretory granules specifically and find a 

 use as counterstains to other procedures. 



Modern methods of staining allow clear- 

 cut differentiations of specific granules by 

 methods that do not depend on the distinc- 

 tion between acidophilia and basophilia. 



The results of histochemical procedures 

 may be expected to show a more consistent 

 relation to function than the results of 

 empiric staining methods. The McManus 

 (194G» periodic-acid Schiff (PAS) reaction, 

 which under certain conditions is specific 

 for i)rotein-carbohydrate complexes in sec- 

 tions of animal tissues, allows a partition 

 of the granules into two classes, which may 

 have a consistent functional significance. 

 An intense red or magenta color produced 

 by this procedure in certain granules indi- 

 cates that they contain glycoprotein. These 



glycoprotein-containing granules are baso- 

 phil granules, showing the same character- 

 istic basophilia wherever they occur in all 

 cells of all species. Their staining reactions 

 to acid dyes are, however, variable. The 

 PAS reaction can be combined with counter- 

 stains which demonstrate the granules com- 

 posed of simple proteins. The latter gran- 

 ules are acidophil granules. 



Inasmuch as both the acidophil class and 

 basophil class are composite, additional 

 methods must be applied to effect a further 

 separation of each class. Methods of gen- 

 eral usefulness for this purpose are: (1 1 

 Staining by a mixture of acid dyes in such 

 methods as Heidenhain's azan or Cross- 

 mon's (1937) modification of Mallory's 

 stain. Granules may be stained orange, red, 

 or blue, or a purple color from a mixture 

 of red and blue dye. The coloration in each 

 case depends on acidophilia; it has no rela- 

 tion to basophilia. The varying colors de- 

 pend on variations in the strength and the 

 quality of the acidophilia. Acidophil gran- 

 ules, like other strongly acidophilic struc- 

 tures, are stained either orange or red. 

 Basophil granules may be orange, red, pur- 

 ple, or blue. (2) The use of elastic tissue 

 stains such as kresofuchsin, resorcin-fuchsin, 

 or Gomori's (1950) aldehyde-fuchsin, of 

 which only the latter is in present-day use 

 as a stain for hypophyseal granules. With 

 these stains it is possible to stain some baso- 

 phil (glycoprotein) granules while leaving 

 others unstained. 



By combining the results of the above 

 methods of staining, at least 10 distinctly 

 different staining reactions have been ob- 

 served in specific granulation in the adeno- 

 hypophyses of vertebrates. To date, how- 

 ever, no more than 4, or possibly 5, distinct 

 staining reactions have been observed in 

 the pars anterior of any one species. There 

 is no possibility, therefore, of any constant 

 relationship between staining and function. 



Before progressing to the subject of cell 

 classes and cell types, the problem 

 presented by the existence of cytoplasmic 

 ribonucleic acid should be discussed. Ribo- 

 nucleic acid occurs in the cytoplasm of aci- 

 dophils and basophils. It is a component of 

 the Palade granules (Palade, 1955) which 

 are described in the section on electron 

 microscopy of the adenohypophysis. These 



