HYPOPHYSEAL MORPHOLOGY 



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granule fraction in sucrose solution homog- 

 enates of pars intermedia tissue, because it 

 sediments with the microsomal fraction on 

 centrifugation (Jeener and Brachet, cited 

 by Herlant, 1952a). In this respect it be- 

 haves like the hormones secreted by baso- 

 phil cells in the pars anterior. 



Evidence of specific secretion from pars 

 intermedia tissue is provided by the inter- 

 esting studies of Allen (1930) and Etkin 

 (1941) in transplantation experiments in 

 tadpoles. Their results indicate that sever- 

 ance of the stalk connection with the hypo- 

 thalamus removes an inhibiting influence 

 from the pars intermedia cells, and that the 

 resultant hypertrophy and hyperplasia is 

 accompanied by oversecretion of intermedin 

 which produces a permanent blackening of 

 the animals. Etkin (1958) found that the 

 capacity of the pars intermedia to differ- 

 entiate and secrete was not prevented by 

 transplantation of the epithelial primor- 

 dium of the pituitary to the tail bud of the 

 wood frog where it developed away from 

 any neural tissue. It was, however, in con- 

 tact with the neural epithelium before trans- 

 plantation and before Rathke's pouch had 

 begun to form. Copeland (1943) observed in 

 Triturus viridescens that the differentiation 

 of the pars intermedia occurs immediately 

 before the first metamorphosis, and at this 

 time the characteristic pigmentation of the 

 red eft stage begins to appear. 



The pars intermedia, unlike the pars ner- 

 vosa, does not undergo degeneration after 

 stalk section in mammals (Rasmussen and 

 Gardner, 1940; Brooks, 1938; Stutinsky, 

 Bonvallet and Dell, 1950; Barrnett and 

 Greep, 1951). Indeed, a hypertrophy of the 

 pars intermedia is usually observed with 

 signs of cellular activation. Fisher (1937) 

 demonstrated that intermedin is still present 

 in the cat hypophysis after the pars nervosa 

 has degenerated after stalk section. 



The intensity of specific staining of pars 

 intermedia cells varies with the species. 

 This variation is the result of variation in 

 the cjuantity of specific granulation. The 

 granulation when present appears to contain 

 glycoprotein, because it gives a positive PAS 

 reaction and is stainable by aldehyde-fuch- 

 sin without prior oxidation. The glycopro- 

 tein character of the intermedia cell granu- 

 lation has been demonstrated in the bat by 

 Herlant (1956a) and in the frog by Ortman 

 (1954, 1956c). In both species the granules 

 are stained by aldehyde-fuchsin. I have ob- 

 served the same staining reactions in the 

 granules of intermedia cells in the cat, dog, 

 sheep, deer, and rat (Fig. 3.16). In the rat 

 the glycoprotein reaction and the aldehyde- 

 fuchsin staining are negative after extrac- 

 tion by perfusion with saline saturated with 

 ether or by immersion in a neutral buffer 

 after acetone treatment. Intermedia cells 

 are, therefore, typical basophil cells contain- 



PI 



HC 



PA 



cells by aldehyde-fuchsiu (AF). The colloid of the hypophyseal cleft is not stained. PX, pars 

 nervosa; PI, pars intermedia; HC, hypophyseal cleft; PA, pars anterior. Formol sublimate 

 fixation, AF X 43. 



Fig. 3.17 (light). Section of the rat hypophysis showing the alteration of the staining prop- 

 erties of the pars intermedia by fixation in Helly's fluid. Except for a few coarse granules of 

 unknown nature, the pars intermedia cells are almost unstained in comparison with Figure 

 3.16. Key to lettering as in Figure 3.16. Helly, AF, X 150. 



