HYPOPHYSEAL MORPHOLOGY 



227 



cies of vertebrates with results which are 

 always concordant with this concept of the 

 function of hypothalamic neurosecretion. 

 The subject has been reviewed by Bargmann 

 (1954), Scharrer and Scharrer (1954), 

 Palay (1953), Hild (1956), and Sloper 

 (1957). It is now generally accepted that 

 the neurohypophyseal hormones have their 

 origin in the neurosecretory cells of the 

 hypotholamus. 



B. THE CHEMICAL NATURE OF THE STAINABLE 

 NEUROSECRETORY MATERIAL 



Specific histochemical tests indicate that 

 the neurosecretion in the hypothalamus and 

 neurohypophysis is a protein with a high 

 cystine content (Barrnett, 1954; Adams and 

 Sloper, 1955). The test used by Adams and 

 Sloper, performic acid oxidation followed by 

 Alcian blue, depends on the oxidation of the 

 sulfur groups of cystine to sulfonic acid 

 groups by performic acid and subsecjuent 

 binding of the basic dye Alcian blue by the 

 strong acid groups so formed. Dawson's 

 (1953) method depends on the same prin- 

 ciples but involves the use of permanganate 

 for the oxidation and aldehyde-fuchsin as 

 a basic dye. It is probable that Gomori's 

 (1941) chrome alum-hematoxylin method 

 also demonstrates sulfonic acid groups 

 formed by permanganate oxidation of cys- 

 tine, because it as well as Dawson's method 

 stains the insulin-containing granules of 

 pancreatic islet ^-cells. There is little doubt 

 that the secretion is a complex of the 

 normally active octapeptides with the van 

 Dyke protein which is demonstrated by 

 these staining methods (Smith, 1951 ; Sloper, 

 1957). The amount of material stained is 

 much greater than the content of specific 

 octapeptides and corresponds with estimates 

 of the amount of van Dyke protein present 

 (Albers and Brightman, 1959). The stain- 

 able material is not a glyco-lipo-protein 

 complex as suggested by Schiebler (1952) 

 because tests for lipid and carbohydrate are 

 weak, variable in different species, and often 

 negative (Sloper, 1955; Howe and Pearse, 

 1956). 



It is often stated that the stainable com- 

 ponent of neurosecretion is an inert carrier 

 substance which can be totally extracted 

 from the tissue by organic solvents leaving 



the hormone activity behind. This is not 

 correct. As Sloper (1955) demonstrated, nei- 

 ther the stainable material nor the hormone 

 activity can be extracted by organic sol- 

 vents, but both remain water soluble after 

 treatment with organic solvents and neither 

 can be demonstrated by staining unless a 

 chemical fixation is used before exposure of 

 the tissue to water. It would appear that 

 about 10 per cent of the cystine content of 

 the van Dyke protein octapeptide complex 

 is in the octapeptide component and that 

 the octapeptides, if they are retained by 

 fixation, contribute to depth of staining of 

 the neurosecretory material by the staining 

 methods now in use. 



C. THE PHYSICAL FORM OF NEUROSECRETION 



IN THE neurohypophysis: THE 



SECRETORY GRANULE 



Electron microscopy is required to reveal 

 the form in which neurosecretion occurs in 

 the mammalian neurohypophysis. Electron 

 microscopic studies of the mammalian neu- 

 rohypophysis have been published by Green 

 and van Breemen (1955), Palay (1955, 

 1957) and Bargmann and Knoop (1957). 



The relationships of the various struc- 

 tures in the felted mass of nerve fibers and 

 cytoplasmic processes of pituicytes in the 

 pars nervosa are especially difficult to vis- 

 ualize and this difficulty is responsible for 

 some differences in the interpretation of the 

 structure by the different authors. Our pri- 

 mary interest is with the form in which 

 neurosecretory substance occurs. There is 

 general agreement that it is visible in elec- 

 tron micrographs as numerous spherical 

 bodies 100 to 180 m/x. in diameter. These 

 l)odies have the typical structure of secre- 

 tory granules as seen in the exocrine cells 

 of the pancreas or the endocrine cells of the 

 adenohypophysis. A dense limiting mem- 

 brane is visible enclosing a homogeneous 

 content. Identification of the granules with 

 the stainable neurosecretion follows from 

 the appearance of the Herring bodies. These 

 bodies in the rat appear to be simple dilata- 

 tions of the axones and do not have the end 

 bulb structure described by Bucy (19301 

 and Bodian (1951) for the Herring bodies 

 in other mammals. In these bulbous struc- 

 tures in the rat the secretory granules ai'e 



