28
J. N. BALL AND BRIDGET I. BAKER
1963). Tritiated acetate and labeled amino acids were rapidly accumulated by the a! cells of goldfish, evidence of intense protein synthesis
( Deminatti, 1962a,b, 1964a). Mugil a granules are precipitated by weak
(2.5%) trichloroacetic acid, in contrast to the 7 granules which precipitate
only with a stronger (7.5%) solution ( Leray, 1966) ; and Follenius ( 1967)
found that the a cells were selectively labeled following intraperitoneal
injections of ~ , ~ - n ~ r a d r e n a l i n e - ~ H
in Gusterosteus. The significance of this
finding is uncertain at present.
a Cells have been recognized by nearly all workers on the teleost
pituitary, and a resume of all their accounts would be unnecessary.
Certain ultrastructural observations are important. In AnguilZu, Knowles
and Vollrath (1966b) observed that the (Y cells appeared to be filled with
spherical or slightly oval membrane-bound vesicles, about 400 mp in
diameter. No clear indications of endoplasmic reticulum or Golgi apparatus could be found, and there were few mitochondria. Follenius
( 1963a ) described ultrastructural variations which he thought might
indicate a cycle of activity in the a cells of Perca. Cells rich in endoplasmic reticulum were poor in secretory granules, and vice versa; in cells
that were primarily storing their secretory products, the endoplasmic
reticulum was reduced to a few cysts, often perinuclear in position.
Follenius described granules of secretion forming in the Golgi region
(cf. mammals, Racadot et al., 1965; Hopkins and Baker on eel 7 cells,
Section 11, B, l ) , and also extrusion of these granules from the cell
surface in a process reminiscent of that described by Weiss for the
teleostean 7 cell (Section 11, B, 1). Follenius emphasized that the a cells
present greater variations in activity than the 7 cells, but he did not study
the responses of the 7 cells to changes in salinity.
Evidence for the Secretion of Growth Hormone by the (Y Cells. A few
years ago, Olivereau (1963a,b) summarized the evidence that the teleostean a cell secretes growth hormone. As she said, there was then no direct
proof of this ascription, although the similarity of the (Y cells to the
somatotrops of mammals made it probable (see Herlant, 1964, 1965;
Purves, 1966). In teleosts, the a cells are more numerous in salmon during
the period of rapid growth in the smolt stage (M. Fontaine and Olivereau,
1949; Olivereau, 1954) and were also very active in Oncorhynchus captured at sea during the adult period of rapid growth (Olivereau and
Ridgeway, 1962). The greater abundance and activity of these cells in
the female eel may relate to the greater size attained by the female in
freshwater (Olivereau, 1967a), and the generally larger size of the female
may similarly explain the sexual dimorphism of the a cells in Poeciliu
(Olivereau and Ball, 1964).
More recently, with the experimental evidence that has been derived
J. N. BALL AND BRIDGET I. BAKER
1963). Tritiated acetate and labeled amino acids were rapidly accumulated by the a! cells of goldfish, evidence of intense protein synthesis
( Deminatti, 1962a,b, 1964a). Mugil a granules are precipitated by weak
(2.5%) trichloroacetic acid, in contrast to the 7 granules which precipitate
only with a stronger (7.5%) solution ( Leray, 1966) ; and Follenius ( 1967)
found that the a cells were selectively labeled following intraperitoneal
injections of ~ , ~ - n ~ r a d r e n a l i n e - ~ H
in Gusterosteus. The significance of this
finding is uncertain at present.
a Cells have been recognized by nearly all workers on the teleost
pituitary, and a resume of all their accounts would be unnecessary.
Certain ultrastructural observations are important. In AnguilZu, Knowles
and Vollrath (1966b) observed that the (Y cells appeared to be filled with
spherical or slightly oval membrane-bound vesicles, about 400 mp in
diameter. No clear indications of endoplasmic reticulum or Golgi apparatus could be found, and there were few mitochondria. Follenius
( 1963a ) described ultrastructural variations which he thought might
indicate a cycle of activity in the a cells of Perca. Cells rich in endoplasmic reticulum were poor in secretory granules, and vice versa; in cells
that were primarily storing their secretory products, the endoplasmic
reticulum was reduced to a few cysts, often perinuclear in position.
Follenius described granules of secretion forming in the Golgi region
(cf. mammals, Racadot et al., 1965; Hopkins and Baker on eel 7 cells,
Section 11, B, l ) , and also extrusion of these granules from the cell
surface in a process reminiscent of that described by Weiss for the
teleostean 7 cell (Section 11, B, 1). Follenius emphasized that the a cells
present greater variations in activity than the 7 cells, but he did not study
the responses of the 7 cells to changes in salinity.
Evidence for the Secretion of Growth Hormone by the (Y Cells. A few
years ago, Olivereau (1963a,b) summarized the evidence that the teleostean a cell secretes growth hormone. As she said, there was then no direct
proof of this ascription, although the similarity of the (Y cells to the
somatotrops of mammals made it probable (see Herlant, 1964, 1965;
Purves, 1966). In teleosts, the a cells are more numerous in salmon during
the period of rapid growth in the smolt stage (M. Fontaine and Olivereau,
1949; Olivereau, 1954) and were also very active in Oncorhynchus captured at sea during the adult period of rapid growth (Olivereau and
Ridgeway, 1962). The greater abundance and activity of these cells in
the female eel may relate to the greater size attained by the female in
freshwater (Olivereau, 1967a), and the generally larger size of the female
may similarly explain the sexual dimorphism of the a cells in Poeciliu
(Olivereau and Ball, 1964).
More recently, with the experimental evidence that has been derived