1. THE PITUITARY GLAND
33
eel Type 2 cells tend to be smaller than the Type 1 cells, but with larger
nuclei (Olivereau, 1967a). At the electron microscope level, two kinds
of gonadotrops have been separated in the eel, with granules of about
130 and 190 mp diam (Knowles and Vollrath, 1966b), probably corresponding to the light microscope categories of Olivereau. Ox-AB-PASOG distinguishes two gonadotrops in the goldfish, as in the eel and
salmon (Olivereau, 1962b). Two types are also discernible in Mugil
auratus ( Olivereau, 1968) : In this fish, one kind of gonadotrop is situated
medially in the gland and is colored a clear blue-green after Aliz B, and
also stains with PbH. After spawning this cell becomes vacuolated. The
second gonadotrop is placed more laterally in the gland, stains purple
with Aliz B, is negative to PbH, and rarely becomes vacuolated. Different
techniques applied to another mullet, M . cephalus also separated two
gonadotrops : with the aldehyde thionine-PAS-naphthol yellow method
(AT-PAS), one type lying at the periphery of the cell cords of the
proximal pars distalis stains brick red, while the other type lies in the
center of the cord and stains dark violet (Leray and Carlon, 1963). The
peripheral cells are also AB + ve, the central cells PAS + ve after OxAB-PAS-OG (Leray, 1966). In studying the precipitation of pituitary
secretory granules by trichloroacetic acid (TCA), Leray ( 1966) found
that while the acidophil granules were precipitated by lower concentrations of TCA (Section 11, B, 1 and 11, B, 3), the central gonadotrops were
not precipitated until the TCA concentration was raised to l a , and the
granules of the peripheral gonadotrops were only precipitated at higher
concentrations, up to 15%; thus, the two gonadotrops in Mugil cephulus
may be distinguished by their situation, staining reactions, and by the
precipitation of their granules by TCA. The AT-PAS method also separates two gonadotrops in Mugil capito (Abraham et al., 1967). Electron
microscope studies indicate two types in the viviparous Zoarces (Oztan,
1966a). One type has granules 60-160 mp diam, which tend to accumulate at one pole of the cell; and the endoplasmic reticulum consists of
vacuolar cisternae; this cell becomes highly activated after parturition, in
relation to ovarian follicular development. The second gonadotrop has
granules 80-240 mp diam, an endoplasmic reticulum with cisternae as
dilated sacs or tubules, and is numerous and active during pregnancy.
At the ultrastructural level, Knowles and Vollrath (196613) have given
further details about the gonadotrops of the eel. The type with larger
(190 mp) granules may be an LH cell, and it persists with little change
in seawater eels in which gonadal development was assumed to have
started. However, the other type of gonadotrops, possibly an FSH cell,
with granules of 130 mp diam, apparently changes considerably as the
eel becomes sexually mature; and Knowles and Vollrath (1966d) reported
that they could identify typical FSH cells and, in addition, cells probably
33
eel Type 2 cells tend to be smaller than the Type 1 cells, but with larger
nuclei (Olivereau, 1967a). At the electron microscope level, two kinds
of gonadotrops have been separated in the eel, with granules of about
130 and 190 mp diam (Knowles and Vollrath, 1966b), probably corresponding to the light microscope categories of Olivereau. Ox-AB-PASOG distinguishes two gonadotrops in the goldfish, as in the eel and
salmon (Olivereau, 1962b). Two types are also discernible in Mugil
auratus ( Olivereau, 1968) : In this fish, one kind of gonadotrop is situated
medially in the gland and is colored a clear blue-green after Aliz B, and
also stains with PbH. After spawning this cell becomes vacuolated. The
second gonadotrop is placed more laterally in the gland, stains purple
with Aliz B, is negative to PbH, and rarely becomes vacuolated. Different
techniques applied to another mullet, M . cephalus also separated two
gonadotrops : with the aldehyde thionine-PAS-naphthol yellow method
(AT-PAS), one type lying at the periphery of the cell cords of the
proximal pars distalis stains brick red, while the other type lies in the
center of the cord and stains dark violet (Leray and Carlon, 1963). The
peripheral cells are also AB + ve, the central cells PAS + ve after OxAB-PAS-OG (Leray, 1966). In studying the precipitation of pituitary
secretory granules by trichloroacetic acid (TCA), Leray ( 1966) found
that while the acidophil granules were precipitated by lower concentrations of TCA (Section 11, B, 1 and 11, B, 3), the central gonadotrops were
not precipitated until the TCA concentration was raised to l a , and the
granules of the peripheral gonadotrops were only precipitated at higher
concentrations, up to 15%; thus, the two gonadotrops in Mugil cephulus
may be distinguished by their situation, staining reactions, and by the
precipitation of their granules by TCA. The AT-PAS method also separates two gonadotrops in Mugil capito (Abraham et al., 1967). Electron
microscope studies indicate two types in the viviparous Zoarces (Oztan,
1966a). One type has granules 60-160 mp diam, which tend to accumulate at one pole of the cell; and the endoplasmic reticulum consists of
vacuolar cisternae; this cell becomes highly activated after parturition, in
relation to ovarian follicular development. The second gonadotrop has
granules 80-240 mp diam, an endoplasmic reticulum with cisternae as
dilated sacs or tubules, and is numerous and active during pregnancy.
At the ultrastructural level, Knowles and Vollrath (196613) have given
further details about the gonadotrops of the eel. The type with larger
(190 mp) granules may be an LH cell, and it persists with little change
in seawater eels in which gonadal development was assumed to have
started. However, the other type of gonadotrops, possibly an FSH cell,
with granules of 130 mp diam, apparently changes considerably as the
eel becomes sexually mature; and Knowles and Vollrath (1966d) reported
that they could identify typical FSH cells and, in addition, cells probably