4
J. N. BALL AND BRIDGET I. BAKER
eels caught on their migration to the sea, the endoplasmic reticulum was
more prominent and the secretory granules more concentrated, suggesting
greater activity ( Knowles and Vollrath, 1966b,d). The presumptive TSH
cells of Zoarces uiuiparus, in contrast, contained large granules (&am
about 400 mp), with foamlike cisternae in the endoplasmic reticulum;
in some cases, smaller granules of varied size (120-160 mg) could be
found in these cisternae (Oztan, 1966a). The trout TSH cells displayed
a well-developed endoplasmic reticulum, with numerous smooth-walled
cisternae. The secretory granules varied greatly in size, from 100 to 800
mp ( Follenius, 1963a).
Nearly every student of the teleost pituitary has described basophils
in the pars distalis, usually in the proximal region, but in some species in
the rostra1 region also; however, most workers have not distinguished
TSH cells from gonadotrops either tinctorially or functionally.
Euidence for the Secretion of TSH by the S Cells. The most detailed
investigation of pituitary-thyroid relationships in teleosts is that of
Olivereau on the eel. Massive doses of radioiodine resulted in partial or
total destruction of the thyroid in male silver eels. The animals were
sacrificed at different times after the radioiodine treatment, up to 7
months, and even at 1 month after radiothyroidectomy, the 6 cells were
degranulated and hypertrophied, and displayed mitotic activity. The cells
enlarged, losing their angular outline and the cytoplasm became foamy
and vacuolated, and the nucleus and nucleolus hypertrophied (Figs. 19
and 20) (Olivereau, 1963a). Although the T and E cells were slightly affected in this experiment (Sections 11, B, 1 and 11, B, 2), the reactions of
the S cells were so strong and characteristic that there can be little doubt
of their thyrotropic function; this marked degranulation of these cells in
the radiothyroidectomized male eel is paralleled by a fall of nearly 80%
in the TSH content of the pituitary of radiothyroidectomized female eels
(Y. A. Fontaine, 1957). The complement of radiothyroidectomy was the
treatment of immature male eels with thyroxine, which produced marked
histological signs of involution in the thyroid gland, accompanied by inactivation changes in the S cells, which shrank and lost their granulation,
finally becoming small inactive chromophobic cells with small nuclei and
nucleoli (Olivereau, 1962a). As in the case of the radiothyroidectomy
experiment, collateral effects on the T cells and E cells were observed
(Olivereau, 1969a,b), but the pronounced changes in the 6 cells marked
them as the thyrotrops.
In the trout, Salmo gairdneri, iodine deficiency stimulated the thyroid
gland and led to an increase in the number of S cells and in the size of
their nucleoli; subtotal radiothyroidectomy resulted in strongly hypertrophied S cells, with enlarged nuclei and nucleoli and loss of glyco-
J. N. BALL AND BRIDGET I. BAKER
eels caught on their migration to the sea, the endoplasmic reticulum was
more prominent and the secretory granules more concentrated, suggesting
greater activity ( Knowles and Vollrath, 1966b,d). The presumptive TSH
cells of Zoarces uiuiparus, in contrast, contained large granules (&am
about 400 mp), with foamlike cisternae in the endoplasmic reticulum;
in some cases, smaller granules of varied size (120-160 mg) could be
found in these cisternae (Oztan, 1966a). The trout TSH cells displayed
a well-developed endoplasmic reticulum, with numerous smooth-walled
cisternae. The secretory granules varied greatly in size, from 100 to 800
mp ( Follenius, 1963a).
Nearly every student of the teleost pituitary has described basophils
in the pars distalis, usually in the proximal region, but in some species in
the rostra1 region also; however, most workers have not distinguished
TSH cells from gonadotrops either tinctorially or functionally.
Euidence for the Secretion of TSH by the S Cells. The most detailed
investigation of pituitary-thyroid relationships in teleosts is that of
Olivereau on the eel. Massive doses of radioiodine resulted in partial or
total destruction of the thyroid in male silver eels. The animals were
sacrificed at different times after the radioiodine treatment, up to 7
months, and even at 1 month after radiothyroidectomy, the 6 cells were
degranulated and hypertrophied, and displayed mitotic activity. The cells
enlarged, losing their angular outline and the cytoplasm became foamy
and vacuolated, and the nucleus and nucleolus hypertrophied (Figs. 19
and 20) (Olivereau, 1963a). Although the T and E cells were slightly affected in this experiment (Sections 11, B, 1 and 11, B, 2), the reactions of
the S cells were so strong and characteristic that there can be little doubt
of their thyrotropic function; this marked degranulation of these cells in
the radiothyroidectomized male eel is paralleled by a fall of nearly 80%
in the TSH content of the pituitary of radiothyroidectomized female eels
(Y. A. Fontaine, 1957). The complement of radiothyroidectomy was the
treatment of immature male eels with thyroxine, which produced marked
histological signs of involution in the thyroid gland, accompanied by inactivation changes in the S cells, which shrank and lost their granulation,
finally becoming small inactive chromophobic cells with small nuclei and
nucleoli (Olivereau, 1962a). As in the case of the radiothyroidectomy
experiment, collateral effects on the T cells and E cells were observed
(Olivereau, 1969a,b), but the pronounced changes in the 6 cells marked
them as the thyrotrops.
In the trout, Salmo gairdneri, iodine deficiency stimulated the thyroid
gland and led to an increase in the number of S cells and in the size of
their nucleoli; subtotal radiothyroidectomy resulted in strongly hypertrophied S cells, with enlarged nuclei and nucleoli and loss of glyco-