1. THE PJTUITARY GLAND
43
Fortunately, the visual distinction between TSH cells and gonadotrops
depends not only on such tenuous tinctorial reactions, but also on marked
topographical separation of the two cell-types. Reference has already
been made (Section 11, A, 3) to the fact that the TSH cells lie in the
rostral pars distalis, as in the eel, or in the proximal pars distalis, as in
Poecilia. Even in the latter type, when both TSH cells and gonadotrops
occur in the proximal pars distalis, there is usually a spatial separation
between them, the TSH cells lying dorsally (e.g., Poeciliu and other
cyprinodonts) or antero-dorsally (cichlids and Mugil), while the gonadotrops tend to lie in the ventral region, sometimes forming a virtual
gonadotropic zone as in Poecilia. However, this special separation may
not always be clear ( e.g., Astyanax).
In the immature male eel, the TSH cells are small angular elements,
lying in the rostral pars distalis between the follicles of 9 cells, and sometimes infiltrating into the follicle walls, with very fine secretory granules
staining with Ox-AB, Aniline blue, thionine, PAS, and A F (Olivereau,
1963a). In immature female eels, the TSH cells are similar, but here they
tend to form large cell cords between the follicles in the middle of the
rostral region ( Olivereau, 1967a).
In Poecilia the thyrotrops lie in the finger-like inner prolongations of
the proximal pars distalis into the neurohypophysis, mixed with the more
numerous a cells (see Figs. 2, 5, and 6). They are generally rounded or
angular cells, more or less square in section, with a large rounded nucleus
and a rather coarse granulation, positive to PAS, OxAB, AF, and Aniline
blue.
In all teleosts in which the thyrotrops have been identified, they
display the typical staining reactions of basophils. Surprisingly little
information seems to be available specifically about the histochemistry
of the cells. In immature Mugil, the thyrotrops incorporate labeled
cysteine (Leray, 1963), and they also incorporate 35S0,Na, in Poeciliu
sphenops, although more weakly than the gonadotrops (Deminatti,
196413). Correspondingly the TSH cells of the guppy contain SS and SH
groups (Sage, 1967), although Olivereau ( 1962a) could find no evidence
of these groups in the thyrotrops of the eel. Certain cells in the rostral
pars distalis of the goldfish, identified by Olivereau (1962b) as TSH cells,
rapidly incorporated gl~cose-~H, probably an indication of their synthesis
of mucopolysaccharides and glycoproteins ( Deminatti, 1966). Otherwise,
one must infer the histochemistry of the TSH cells from consideration of
their general staining reactions, as done by Olivereau and Fontaine
( 1966) for the eel gonadotrops ( see Section 11, B, 4).
The TSH cells of the juvenile river eel are revealed by the electron
microscope as containing small vesicles or secretory granules (ca. 140 mp
diam), and a diffuse endoplasmic reticulum with wide cisternae; in silver
43
Fortunately, the visual distinction between TSH cells and gonadotrops
depends not only on such tenuous tinctorial reactions, but also on marked
topographical separation of the two cell-types. Reference has already
been made (Section 11, A, 3) to the fact that the TSH cells lie in the
rostral pars distalis, as in the eel, or in the proximal pars distalis, as in
Poecilia. Even in the latter type, when both TSH cells and gonadotrops
occur in the proximal pars distalis, there is usually a spatial separation
between them, the TSH cells lying dorsally (e.g., Poeciliu and other
cyprinodonts) or antero-dorsally (cichlids and Mugil), while the gonadotrops tend to lie in the ventral region, sometimes forming a virtual
gonadotropic zone as in Poecilia. However, this special separation may
not always be clear ( e.g., Astyanax).
In the immature male eel, the TSH cells are small angular elements,
lying in the rostral pars distalis between the follicles of 9 cells, and sometimes infiltrating into the follicle walls, with very fine secretory granules
staining with Ox-AB, Aniline blue, thionine, PAS, and A F (Olivereau,
1963a). In immature female eels, the TSH cells are similar, but here they
tend to form large cell cords between the follicles in the middle of the
rostral region ( Olivereau, 1967a).
In Poecilia the thyrotrops lie in the finger-like inner prolongations of
the proximal pars distalis into the neurohypophysis, mixed with the more
numerous a cells (see Figs. 2, 5, and 6). They are generally rounded or
angular cells, more or less square in section, with a large rounded nucleus
and a rather coarse granulation, positive to PAS, OxAB, AF, and Aniline
blue.
In all teleosts in which the thyrotrops have been identified, they
display the typical staining reactions of basophils. Surprisingly little
information seems to be available specifically about the histochemistry
of the cells. In immature Mugil, the thyrotrops incorporate labeled
cysteine (Leray, 1963), and they also incorporate 35S0,Na, in Poeciliu
sphenops, although more weakly than the gonadotrops (Deminatti,
196413). Correspondingly the TSH cells of the guppy contain SS and SH
groups (Sage, 1967), although Olivereau ( 1962a) could find no evidence
of these groups in the thyrotrops of the eel. Certain cells in the rostral
pars distalis of the goldfish, identified by Olivereau (1962b) as TSH cells,
rapidly incorporated gl~cose-~H, probably an indication of their synthesis
of mucopolysaccharides and glycoproteins ( Deminatti, 1966). Otherwise,
one must infer the histochemistry of the TSH cells from consideration of
their general staining reactions, as done by Olivereau and Fontaine
( 1966) for the eel gonadotrops ( see Section 11, B, 4).
The TSH cells of the juvenile river eel are revealed by the electron
microscope as containing small vesicles or secretory granules (ca. 140 mp
diam), and a diffuse endoplasmic reticulum with wide cisternae; in silver