302
AUGUST EPPLE
trated in the central islet region of this species. Repeated injections of
CoCl, destroyed the B cells and perhaps also the D cells, while A and
agranular ( C ) cells were unaffected (Falkmer, 1965b). Alterations in
the A cells after application of CoC1, may be secondary effect to changes
in the blood sugar ( Falkmer et al., 1964a,b).
Block et al. (1964) used the toadfish to analyze glycemic changes
induced by methylglyoxal bis ( guanylhydrazone ) , a chemotherapeutic
agent against human leukemia and solid tumors which also causes profound hypoglycemia. Low doses caused hypoglycemia; high doses caused
hyperglycemia and A-cell degranulation. The authors suggest that the
drug induces hepatic glycogenolysis and increases glucose uptake in the
peripheral tissues of the toadfish.
5. EFFECTS OF HORMONE INJECTIONS AND HYPOPHYSECXOMY
ON ISLET TISSUE
In lampreys ( Petromyzon planeri and Petromynon fluuiati2is) , insulin
injections sometimes led to B-cell stimulation ( degranulation and nuclear
enlargement) and sometimes to B-cell atrophy. There was no clear effect
on the second type of granular islet cell ( Ermisch, 1966,1967). In Myxine
glutinosu, injections of thyrotropin, corticotropin, prolactin, thyroxine,
adrenalin, glucagon, or insulin evoked no histological changes in the islet
tissue; also, hypophysectomy did not affect the islet tissue (Falkmer and
Matty, 1966a). Butler (1940) reports an enlargement of the islets in the
goldfish, Carassius auratus, after injection with a pituitary brei of the
same species. No cytological changes could be observed in the pancreatic
islets of Fundulus heteroclitus following removal of the pituitary or after
treatment with mammalian growth hormone ( Pickford, 1953; Pickford
and Atz, 1957). In Cottus scorpius, injections of adrenalin, porcine growth
hormone, glucagon, and insulin had no effect on the islet histology, while
hydrocortisone led to occasional B-cell damage (Falkmer, 1961; Falkmer
and Matty, 1966b). Hypophysectomy did not influence the islet histology
in this species (Falkmer and Matty, 196613). Khanna and Mehrotra
(1969b) observed shrinkage of B cells in Clarias batrachus after insulin
injection. In the eel, Anguilla anguilla, thyroxine injections decreased the
number of islets ( Palayer, 1962).
C. Effects of Exogenous Islet Hormones in Fishes
1. INSULIN
a. Blood Sugar. Most authors have observed that exogenous insulin
has a hypoglycemic action in fishes and that excessive doses of insulin lead
AUGUST EPPLE
trated in the central islet region of this species. Repeated injections of
CoCl, destroyed the B cells and perhaps also the D cells, while A and
agranular ( C ) cells were unaffected (Falkmer, 1965b). Alterations in
the A cells after application of CoC1, may be secondary effect to changes
in the blood sugar ( Falkmer et al., 1964a,b).
Block et al. (1964) used the toadfish to analyze glycemic changes
induced by methylglyoxal bis ( guanylhydrazone ) , a chemotherapeutic
agent against human leukemia and solid tumors which also causes profound hypoglycemia. Low doses caused hypoglycemia; high doses caused
hyperglycemia and A-cell degranulation. The authors suggest that the
drug induces hepatic glycogenolysis and increases glucose uptake in the
peripheral tissues of the toadfish.
5. EFFECTS OF HORMONE INJECTIONS AND HYPOPHYSECXOMY
ON ISLET TISSUE
In lampreys ( Petromyzon planeri and Petromynon fluuiati2is) , insulin
injections sometimes led to B-cell stimulation ( degranulation and nuclear
enlargement) and sometimes to B-cell atrophy. There was no clear effect
on the second type of granular islet cell ( Ermisch, 1966,1967). In Myxine
glutinosu, injections of thyrotropin, corticotropin, prolactin, thyroxine,
adrenalin, glucagon, or insulin evoked no histological changes in the islet
tissue; also, hypophysectomy did not affect the islet tissue (Falkmer and
Matty, 1966a). Butler (1940) reports an enlargement of the islets in the
goldfish, Carassius auratus, after injection with a pituitary brei of the
same species. No cytological changes could be observed in the pancreatic
islets of Fundulus heteroclitus following removal of the pituitary or after
treatment with mammalian growth hormone ( Pickford, 1953; Pickford
and Atz, 1957). In Cottus scorpius, injections of adrenalin, porcine growth
hormone, glucagon, and insulin had no effect on the islet histology, while
hydrocortisone led to occasional B-cell damage (Falkmer, 1961; Falkmer
and Matty, 1966b). Hypophysectomy did not influence the islet histology
in this species (Falkmer and Matty, 196613). Khanna and Mehrotra
(1969b) observed shrinkage of B cells in Clarias batrachus after insulin
injection. In the eel, Anguilla anguilla, thyroxine injections decreased the
number of islets ( Palayer, 1962).
C. Effects of Exogenous Islet Hormones in Fishes
1. INSULIN
a. Blood Sugar. Most authors have observed that exogenous insulin
has a hypoglycemic action in fishes and that excessive doses of insulin lead