12
J. N. BALL AND BRIDGET I. BAKER
platy (Xiphophorus muculutus), the 7 granules are revealed by the
electron microscope as membrane-bound osmophilic vesicles, between 200
and 300 mp diam (Follenius and Porte, 1960, 1961c; Weiss, 1965), and
Weiss ( 1965) has described ultrastructural appearances that suggest that
the 7 granules in the platy are probably released from buds projecting
from the cell surface, by a process in which the granule membrane fuses
with the cell membrane and the granule escapes through the resulting
opening; this resembles one of the modes of granule extrusion described
in higher vertebrates (see Benoit and Da Lage, 1963).
At the light microscope level, 7 granules appear to vary in size even
within individual cells, and commonly vary between individuals and
species; in Poecilia lutipinna, when the granules are rather sparse they
appear to be distinct and large, but if they are densely packed they seem
smaller, while in the eel and trout the granules are usually coarse and
distinct no matter what their density. Here, and in other places in this
review, we should emphasize that granule size, even if determined with
the electron microscope, is not an exact criterion of cell type in comparisons between species ( cf. Herlant, 1963, 1965). Fluorescent antibody
to ovine prolactin located specifically on the 7 granules in Fundulus
heteroclitus ( Emmart et al., 1966; Emmart and Mossakowski, 1967), confirming that the granules themselves do contain fish prolactin.
Histochemically the prolactin cells have been shown to contain SH/SS
groups in the eel (Olivereau, 1962a, 1963a), Mugi2 (Leray, l966), and
Xiphophorus (Sage, 1968); but as in other species they do not react with
Alcian blue even after oxidation, indicating that they are not particularly
rich in cysteine (see Olivereau, 1963a,b; Olivereau and Ball, 1964; &tan,
1966a). Nevertheless, Mugil prolactin cells will incorporate cy~teine-~~S
(Leray, 1963). In goldfish in freshwater these cells displayed intense
incorporation of a~etate-~H, indicating intense protein synthesis ( Deminatti, 1964a). The 7 granules in fresh Mugil glands were precipitated only
by 7.51% or stronger trichloroacetic acid, in contrast to the a: granules
(growth hormone cells) which were precipitated by 2.5% TCA (Leray,
1966). In ultrastructural studies of eel prolactin cells, acid phosphatase
was shown to be distributed in particles in the apical cytoplasm, and also
within the Golgi region and in some of the developing 7 granules, possibly
concerned in the destruction of excess secretory material (Hopkins and
Baker, 1968) as suggested for the lysosomelike bodies in the gonadotrops
(Section 11, B, 4 ) .
Evidence for the Secretion of Fish Proluctin by the 7 Cells. As early as
1960, Olivereau and Herlant pointed to the similarity in staining properties of the teleostean 7 cell and the prolactin cell of mammals. However,
too little was known at that time about the physiological role of prolactin
J. N. BALL AND BRIDGET I. BAKER
platy (Xiphophorus muculutus), the 7 granules are revealed by the
electron microscope as membrane-bound osmophilic vesicles, between 200
and 300 mp diam (Follenius and Porte, 1960, 1961c; Weiss, 1965), and
Weiss ( 1965) has described ultrastructural appearances that suggest that
the 7 granules in the platy are probably released from buds projecting
from the cell surface, by a process in which the granule membrane fuses
with the cell membrane and the granule escapes through the resulting
opening; this resembles one of the modes of granule extrusion described
in higher vertebrates (see Benoit and Da Lage, 1963).
At the light microscope level, 7 granules appear to vary in size even
within individual cells, and commonly vary between individuals and
species; in Poecilia lutipinna, when the granules are rather sparse they
appear to be distinct and large, but if they are densely packed they seem
smaller, while in the eel and trout the granules are usually coarse and
distinct no matter what their density. Here, and in other places in this
review, we should emphasize that granule size, even if determined with
the electron microscope, is not an exact criterion of cell type in comparisons between species ( cf. Herlant, 1963, 1965). Fluorescent antibody
to ovine prolactin located specifically on the 7 granules in Fundulus
heteroclitus ( Emmart et al., 1966; Emmart and Mossakowski, 1967), confirming that the granules themselves do contain fish prolactin.
Histochemically the prolactin cells have been shown to contain SH/SS
groups in the eel (Olivereau, 1962a, 1963a), Mugi2 (Leray, l966), and
Xiphophorus (Sage, 1968); but as in other species they do not react with
Alcian blue even after oxidation, indicating that they are not particularly
rich in cysteine (see Olivereau, 1963a,b; Olivereau and Ball, 1964; &tan,
1966a). Nevertheless, Mugil prolactin cells will incorporate cy~teine-~~S
(Leray, 1963). In goldfish in freshwater these cells displayed intense
incorporation of a~etate-~H, indicating intense protein synthesis ( Deminatti, 1964a). The 7 granules in fresh Mugil glands were precipitated only
by 7.51% or stronger trichloroacetic acid, in contrast to the a: granules
(growth hormone cells) which were precipitated by 2.5% TCA (Leray,
1966). In ultrastructural studies of eel prolactin cells, acid phosphatase
was shown to be distributed in particles in the apical cytoplasm, and also
within the Golgi region and in some of the developing 7 granules, possibly
concerned in the destruction of excess secretory material (Hopkins and
Baker, 1968) as suggested for the lysosomelike bodies in the gonadotrops
(Section 11, B, 4 ) .
Evidence for the Secretion of Fish Proluctin by the 7 Cells. As early as
1960, Olivereau and Herlant pointed to the similarity in staining properties of the teleostean 7 cell and the prolactin cell of mammals. However,
too little was known at that time about the physiological role of prolactin