7. THE ULTIMOBRANCHIAL GLANDS
385
thelial cells are evident. Both contain small, membrane-enclosed granules
which may be seen in both apical and basal portions of the cells. One cell
type has a dark homogeneous appearing nucleus and numerous mitochondria in the cytoplasm. The other cell type has a relatively pale
nucleus and few mitochondria and fewer granules. In Fig. 4, one of the
dark cells appears to be discharging granules and cytoplasmic material
into the follicle. It is not possible at this time to tell whether these
represent two conditions of the same functional cells, or separate functions; however, they do appear to be involved in internal secretion.
2. TELEOSTS
Krawarik (1936) has described the location and microscopic appearance of the ultimobranchial glands in a number of bony fishes found in
Germany. The gland is bilateral or midline, and is located in the transverse septum between the abdominal cavity and sinus venosus just ventral
to the esophagus. In the rainbow trout, Salmo gairdneri, it can be seen on
the septum as a band of white tissue. The appearance under the light
microscope, as seen in Fig. 5, shows cords of polygonal cells superficially
resembling the parathyroid tissue in higher vertebrates. There are no
follicles, but the gland tissue tends to spread diffusely in the septum.
Marked hypertrophy of the gland was observed by Rasquin and Rosenbloom (1954) in eyed forms of Astyanar mexicanus when maintained in
darkness.
III. CALCITONIN
Calcitonin-the second calcium-regulating hormonewas discovered
less than a decade ago (Copp et al., 1962) and its association with the
ultimobranchial gland was not recognized until 1967 (Copp et al., 1967a,b;
Pearse and Carvalheira, 1967; Tauber, 1967). During this same year,
there were three international conferences dealing with this newly discovered hormone (Pechet, 1967; Taylor, 1968; Talmage and BBlanger,
1968). There have been a number of excellent reviews on this subject
( Anast, 1966; Copp, 1967, 1968a,b, 1969a; Foster, 1968; MacIntyre, 1967;
Munson and Hirsch, 1966).
In this chapter, the original name “Calcitonin” will be used rather than
the alternative term “Thyrocalcitonin,” since it seems more appropriate
for a hormone of ultimobranchial origin. Calcitonin has also been designated as the generic name for the hormone by the World Health Organi-
385
thelial cells are evident. Both contain small, membrane-enclosed granules
which may be seen in both apical and basal portions of the cells. One cell
type has a dark homogeneous appearing nucleus and numerous mitochondria in the cytoplasm. The other cell type has a relatively pale
nucleus and few mitochondria and fewer granules. In Fig. 4, one of the
dark cells appears to be discharging granules and cytoplasmic material
into the follicle. It is not possible at this time to tell whether these
represent two conditions of the same functional cells, or separate functions; however, they do appear to be involved in internal secretion.
2. TELEOSTS
Krawarik (1936) has described the location and microscopic appearance of the ultimobranchial glands in a number of bony fishes found in
Germany. The gland is bilateral or midline, and is located in the transverse septum between the abdominal cavity and sinus venosus just ventral
to the esophagus. In the rainbow trout, Salmo gairdneri, it can be seen on
the septum as a band of white tissue. The appearance under the light
microscope, as seen in Fig. 5, shows cords of polygonal cells superficially
resembling the parathyroid tissue in higher vertebrates. There are no
follicles, but the gland tissue tends to spread diffusely in the septum.
Marked hypertrophy of the gland was observed by Rasquin and Rosenbloom (1954) in eyed forms of Astyanar mexicanus when maintained in
darkness.
III. CALCITONIN
Calcitonin-the second calcium-regulating hormonewas discovered
less than a decade ago (Copp et al., 1962) and its association with the
ultimobranchial gland was not recognized until 1967 (Copp et al., 1967a,b;
Pearse and Carvalheira, 1967; Tauber, 1967). During this same year,
there were three international conferences dealing with this newly discovered hormone (Pechet, 1967; Taylor, 1968; Talmage and BBlanger,
1968). There have been a number of excellent reviews on this subject
( Anast, 1966; Copp, 1967, 1968a,b, 1969a; Foster, 1968; MacIntyre, 1967;
Munson and Hirsch, 1966).
In this chapter, the original name “Calcitonin” will be used rather than
the alternative term “Thyrocalcitonin,” since it seems more appropriate
for a hormone of ultimobranchial origin. Calcitonin has also been designated as the generic name for the hormone by the World Health Organi-