252
AUBREY GORBMAN
jected dose in 4 days (Tong et al., 1961) in Eptatretus stouti or 3.4% in
6 days (Waterman and Gorbman, 1963) in Myrine g2utinosu. Tong et al.
( 1961 ) found that radioiodine-labeled thyroxine was eventually detectable, but only 2% of the accumulated thyroidal radioiodine was in this
form after 4 days. Furthermore, no radiothyroxine was found in the blood
until 4 days after injection of the 1311. Waterman and Gorbman (1963)
observed that the lumen of the hagfish thyroid follicle does not contain
the characteristic thyroglobulin-containing “colloid” material seen in all
other vertebrates. Instead, there are numerous colloidlike droplets within
the lining epithelium of the follicles. This is of particular interest since
Waterman and Gorbman (1963) and Tong et al. (1961) made radioautographs of tissue sections of l3l1-injected hagfish thyroid and located
all of the radioiodoprotein in the cells and none in the colloid, as in other
vertebrates.
In the lamprey larval endostyle, Gorbman and Creaser (1942), using
radioautography found that radioiodine localizes in only certain of the
cell types lining the cylinders, and Leloup and Berg (1954) and Leloup
(1955) reported that radioiodine metabolized in the endostyle is in part
converted to thyroxine. Clements-Merlini ( 1W2) found that radioiodine
metabolism in the endostyle can be stimulated by pituitary hormones.
These findings have been confirmed by others, and further, Clements and
Gorbman (1955) found a protease in the endostyle that resembles the one
found in thyroid tissue. The iodoprotein of Petromyzon adult thyroid
tissue, labeled with lZ5I has been analyzed by Aloj et al. (1967) by density gradient ultracentrifugation and fractions at 5, 12, and 17 S were
obtained. Aloj et al. consider these fractions to be similar to the elementary units and polymerized molecules characteristic of other vertebrate
thyroglobulins. With so much interest in the thyroidlike properties of the
endostyle it is difficult to underst: ad why there has been almost no study
of the adult lamprey thyroid.
Elasmobranch thyroid function has received relatively little study, but
it appears to be typical (Gorbman et al., 1952; Leloup, 1952; Berg et al.,
1959; Leloup and Fontaine, 1960). In Scyliorhinus, for example, maximum
thyroidal uptakes in excess of 20% of an injected dose of tracer lSi1 can
be measured at about 17 hr after injection (Gorbman et al., 1952). The
proportion of labeled organic iodine that is found in the form of thyroxine
continues to increase gradually for at least 4 days or more. Detailed study
of the dynamics of thyroxinogenesis, of the enzymic activities aiding the
process, or of the character of the thyroid protein has not been done.
Teleost thyroid function, as might be expected, has received the most
attention, and also as might be expected, the goldfish and several salmonids have been most studied. One obvious reason for this is that
AUBREY GORBMAN
jected dose in 4 days (Tong et al., 1961) in Eptatretus stouti or 3.4% in
6 days (Waterman and Gorbman, 1963) in Myrine g2utinosu. Tong et al.
( 1961 ) found that radioiodine-labeled thyroxine was eventually detectable, but only 2% of the accumulated thyroidal radioiodine was in this
form after 4 days. Furthermore, no radiothyroxine was found in the blood
until 4 days after injection of the 1311. Waterman and Gorbman (1963)
observed that the lumen of the hagfish thyroid follicle does not contain
the characteristic thyroglobulin-containing “colloid” material seen in all
other vertebrates. Instead, there are numerous colloidlike droplets within
the lining epithelium of the follicles. This is of particular interest since
Waterman and Gorbman (1963) and Tong et al. (1961) made radioautographs of tissue sections of l3l1-injected hagfish thyroid and located
all of the radioiodoprotein in the cells and none in the colloid, as in other
vertebrates.
In the lamprey larval endostyle, Gorbman and Creaser (1942), using
radioautography found that radioiodine localizes in only certain of the
cell types lining the cylinders, and Leloup and Berg (1954) and Leloup
(1955) reported that radioiodine metabolized in the endostyle is in part
converted to thyroxine. Clements-Merlini ( 1W2) found that radioiodine
metabolism in the endostyle can be stimulated by pituitary hormones.
These findings have been confirmed by others, and further, Clements and
Gorbman (1955) found a protease in the endostyle that resembles the one
found in thyroid tissue. The iodoprotein of Petromyzon adult thyroid
tissue, labeled with lZ5I has been analyzed by Aloj et al. (1967) by density gradient ultracentrifugation and fractions at 5, 12, and 17 S were
obtained. Aloj et al. consider these fractions to be similar to the elementary units and polymerized molecules characteristic of other vertebrate
thyroglobulins. With so much interest in the thyroidlike properties of the
endostyle it is difficult to underst: ad why there has been almost no study
of the adult lamprey thyroid.
Elasmobranch thyroid function has received relatively little study, but
it appears to be typical (Gorbman et al., 1952; Leloup, 1952; Berg et al.,
1959; Leloup and Fontaine, 1960). In Scyliorhinus, for example, maximum
thyroidal uptakes in excess of 20% of an injected dose of tracer lSi1 can
be measured at about 17 hr after injection (Gorbman et al., 1952). The
proportion of labeled organic iodine that is found in the form of thyroxine
continues to increase gradually for at least 4 days or more. Detailed study
of the dynamics of thyroxinogenesis, of the enzymic activities aiding the
process, or of the character of the thyroid protein has not been done.
Teleost thyroid function, as might be expected, has received the most
attention, and also as might be expected, the goldfish and several salmonids have been most studied. One obvious reason for this is that