5. THE ENDOCRINE PANCREAS
287
It was impossible to demonstrate gastrin within the Brockmann bodies
( Osborne et al., 1963; Blair et al., 1968).
In conclusion, there is a fundamental difference in pancreas structure
and islet histophysiology between cyclostomes and gnathostomes. Pancreas morphology and islet structure of all higher vertebrates can be
derived from a primitive gnathostome type of the pancreas as exemplified
by some elasmobranchs.
There is no reason to assume that insulin is absent in any species. A
cells and glucagon appear to be absent in the cyclostomes, but A cells
could be demonstrated in all species of higher fishes. However, so far
glucagon (or glucagonlike activity) has been extracted only from a few
teleosts. D cells were demonstrated in all gnathostomes which were
studied by appropriate techniques.
E. Variations in Structure and in Biological and Immunological
Activities of the Islet Hormones in Fishes
1. INSULIN
While the structures of the invertebrate “insulins” are still unknown,
the available data on their biological and immunological activities indicate
that they differ greatly from the vertebrate insulins (Falkmer and Wilson,
1967).
In fishes, we sometimes find an enormous discrepancy between the
biological and the immunological activity of insulin (cf. S . Wilson, 1966;
Falkmer and Wilson, 1967; Falkmer, 1969). In the light of their evolution
this is not surprising, and we also have to bear in mind that even two
mammals, the guinea pig and the nutria (both rodents) have insulins
structurally very different from each other and from the other heretofore
known mammalian insulins (J. K. Davidson et al., 1968a).
a. Cycbstomata. In both biological and immunological activity, the
insulin of the hagfish, Myxine glutinosa, differs greatly from the insulins
of the higher vertebrates. With the double antibody method, the activity
is about 0.1% that of bovine insulin. In the fat pad assay with the rat it has
an activity of about 7% bovine preparations (Weitzel et al., 1967). Forty
mU of anti-ox-insulin serum and 20 mU of anti-codfish-insulin serum from
guinea pigs are necessary to neutralize 1 mU of hagfish insulin ( S . Wilson,
1966). According to Falkmer and Matty (1966a) and Falkmer and
Wilson ( 1967), ox and codfish insulin are much less effective in producing
hypoglycemia in the hagfish than crude hagfish preparations (see also
287
It was impossible to demonstrate gastrin within the Brockmann bodies
( Osborne et al., 1963; Blair et al., 1968).
In conclusion, there is a fundamental difference in pancreas structure
and islet histophysiology between cyclostomes and gnathostomes. Pancreas morphology and islet structure of all higher vertebrates can be
derived from a primitive gnathostome type of the pancreas as exemplified
by some elasmobranchs.
There is no reason to assume that insulin is absent in any species. A
cells and glucagon appear to be absent in the cyclostomes, but A cells
could be demonstrated in all species of higher fishes. However, so far
glucagon (or glucagonlike activity) has been extracted only from a few
teleosts. D cells were demonstrated in all gnathostomes which were
studied by appropriate techniques.
E. Variations in Structure and in Biological and Immunological
Activities of the Islet Hormones in Fishes
1. INSULIN
While the structures of the invertebrate “insulins” are still unknown,
the available data on their biological and immunological activities indicate
that they differ greatly from the vertebrate insulins (Falkmer and Wilson,
1967).
In fishes, we sometimes find an enormous discrepancy between the
biological and the immunological activity of insulin (cf. S . Wilson, 1966;
Falkmer and Wilson, 1967; Falkmer, 1969). In the light of their evolution
this is not surprising, and we also have to bear in mind that even two
mammals, the guinea pig and the nutria (both rodents) have insulins
structurally very different from each other and from the other heretofore
known mammalian insulins (J. K. Davidson et al., 1968a).
a. Cycbstomata. In both biological and immunological activity, the
insulin of the hagfish, Myxine glutinosa, differs greatly from the insulins
of the higher vertebrates. With the double antibody method, the activity
is about 0.1% that of bovine insulin. In the fat pad assay with the rat it has
an activity of about 7% bovine preparations (Weitzel et al., 1967). Forty
mU of anti-ox-insulin serum and 20 mU of anti-codfish-insulin serum from
guinea pigs are necessary to neutralize 1 mU of hagfish insulin ( S . Wilson,
1966). According to Falkmer and Matty (1966a) and Falkmer and
Wilson ( 1967), ox and codfish insulin are much less effective in producing
hypoglycemia in the hagfish than crude hagfish preparations (see also