306
AUGUST EPPLE
is a strong tendency to split the compact pancreas, which results in partial
topographic separation of exocrine and endocrine tissue in a number of
species.
( 4 ) The islet tissue of all gnathostomes contains A, B, and D cells,
suggesting the existence of glucagon, insulin, and a further, still unknown
hormone. The holocephalians have large numbers of peculiar X cells with
cytological signs of secretory activity. Further cell types occur, but these
are very likely immature forms or intergrade stages of other islet cells.
( 5 ) Glucagon, presumably a new acquisition of the gnathostomes,
seems to be immunologically and biologically rather species specific.
( 6 ) The insulins of the vertebrates differ greatly in their immunological and at least in some of their physiological effects from the “insulin“
of the invertebrates. The insulin of Myxine differs structurally, immunologically, and biologically from the insulins of the gnathostomes. The
insulins of the “higher” fishes show structural, immunological, and biological variations; in several teleosts two different insulins were found.
( 7 ) The islet tissue of the Brockmann bodies of several teleosts has
been used for extractions and in vitro studies of hormones, enzymes, and
zinc.
( a ) It appears that insulin synthesis takes place in the microsome
fraction and that insulin is subsequently transferred to the
granules.
( b ) Both Embden-Meyerhof and pentose shunt pathways of glucose
metabolism are effective in the endocrine tissue of the teleosts.
( c ) The key enzymes of carbohydrate metabolism have been shown
to be present in islet tissue.
( d ) The islet tissue of the teleosts has a high zinc content; in Cottw
scorpius, the zinc is localized in the B and/or D cells.
( 8 ) The zinc content of the cyclostome islet varies. It is very low in
Myxine glutinosu, which is possibly correlated with the structure of the
insulin of this species.
(9) Cautery of the islets in Petromyzon was followed by hyperglycemia; surgical removal of the islet tissue in Myxine had no effect on
the blood sugar level. Pancreatectomy increases the blood sugar in
elasmobranchs; this can be alleviated by hypophysectomy. Islectectomy
in teleosts causes hyperglycemia, glucosuria, and increase of liver lipids.
The effect of islectectomy, however, seems to depend on the nutritional
state of the animals. Studies on a greater variety of teleosts are desirable.
(10) It is possible to destroy the B cells in cyclostomes, chondrichthyans, and teleosts by alloxan. However, the degree of destruction varies
greatly, and some investigators report damage in other tissues.
(11) After injection of cobaltous chloride there is a concentration of
AUGUST EPPLE
is a strong tendency to split the compact pancreas, which results in partial
topographic separation of exocrine and endocrine tissue in a number of
species.
( 4 ) The islet tissue of all gnathostomes contains A, B, and D cells,
suggesting the existence of glucagon, insulin, and a further, still unknown
hormone. The holocephalians have large numbers of peculiar X cells with
cytological signs of secretory activity. Further cell types occur, but these
are very likely immature forms or intergrade stages of other islet cells.
( 5 ) Glucagon, presumably a new acquisition of the gnathostomes,
seems to be immunologically and biologically rather species specific.
( 6 ) The insulins of the vertebrates differ greatly in their immunological and at least in some of their physiological effects from the “insulin“
of the invertebrates. The insulin of Myxine differs structurally, immunologically, and biologically from the insulins of the gnathostomes. The
insulins of the “higher” fishes show structural, immunological, and biological variations; in several teleosts two different insulins were found.
( 7 ) The islet tissue of the Brockmann bodies of several teleosts has
been used for extractions and in vitro studies of hormones, enzymes, and
zinc.
( a ) It appears that insulin synthesis takes place in the microsome
fraction and that insulin is subsequently transferred to the
granules.
( b ) Both Embden-Meyerhof and pentose shunt pathways of glucose
metabolism are effective in the endocrine tissue of the teleosts.
( c ) The key enzymes of carbohydrate metabolism have been shown
to be present in islet tissue.
( d ) The islet tissue of the teleosts has a high zinc content; in Cottw
scorpius, the zinc is localized in the B and/or D cells.
( 8 ) The zinc content of the cyclostome islet varies. It is very low in
Myxine glutinosu, which is possibly correlated with the structure of the
insulin of this species.
(9) Cautery of the islets in Petromyzon was followed by hyperglycemia; surgical removal of the islet tissue in Myxine had no effect on
the blood sugar level. Pancreatectomy increases the blood sugar in
elasmobranchs; this can be alleviated by hypophysectomy. Islectectomy
in teleosts causes hyperglycemia, glucosuria, and increase of liver lipids.
The effect of islectectomy, however, seems to depend on the nutritional
state of the animals. Studies on a greater variety of teleosts are desirable.
(10) It is possible to destroy the B cells in cyclostomes, chondrichthyans, and teleosts by alloxan. However, the degree of destruction varies
greatly, and some investigators report damage in other tissues.
(11) After injection of cobaltous chloride there is a concentration of