122
A. M. PERKS
which was similar to that of arginine vasotocin. Although, milk-ejection
effects and antidiuretic activity were detected at Rf values between 0.5
and 0.8-the approximate position of oxytocinlike peptides-Follett and
Heller did not consider that this was evidence for the presence of an
oxytocinlike principle. However, their findings suggest that there should
be some caution before the possibility of an oxytocinlike peptide is eliminated from cyclostome physiology. Most work has been done on adult
animals during their spawning migration, and W. H. Sawyer (1961) has
pointed out that oxytocinlike peptides might exist during other stages of
the life cycle. The histological studies of van der Kamer and Schreurs
(1959) have shown that neurosecretory material is remarkably dense in
parts of the neurohypophysis during the ammocoete stage, but parallel
pharmacological studies are lacking.
There have been no chemical studies of the structure of any cyclostome principal. Nevertheless, all present evidence indicates that the
cyclostome pituitary contains an overwhelming preponderance of arginine
vasotocin and that some cyclostomes may well be unique in possessing a
single neurohypophysial principle in their pituitaries.
C. The Actions of Neurohypophysial Principles in Cyclostomes
1. MYXIN~ORMES
Studies of the actions of neurohypophysial principles in the hagfish
are few and brief. It is possible that the peptides influence salt and water
metabolism. Chester Jones et al. (1962), working with Myxine glutimsa,
determined the effects of neurohypophysial principles on hagfish whose
body fluids had been diluted or concentrated by immersion in diluted or
concentrated seawater. Hagfish pituitary extracts, equivalent to 10 glands,
or possibly 1.3 mU of oxytocic activity (calculated from the data of
Follett and Heller, l W a ) , were injected daily for 4 days into hagfish
adapted to diluted (70%) seawater. The treatment resulted in a rise in
the serum sodium level. A mammalian oxytocin-vasopressin preparation
(Pituitrin) was injected at high dose levels (loo0 m u ) , daily for 5 days,
into hagfish adapted to concentrated (165%) seawater. This treatment
resulted in a fall in serum sodium level. It is dangerous to generalize from
such scanty data, but it seems possible that neurohypophysial peptides
tended to return body sodium levels toward the natural value for normal
seawater, presumably by affecting sodium fluxes. Although the hagfish is
incapable of maintaining its internal environment in the face of external
A. M. PERKS
which was similar to that of arginine vasotocin. Although, milk-ejection
effects and antidiuretic activity were detected at Rf values between 0.5
and 0.8-the approximate position of oxytocinlike peptides-Follett and
Heller did not consider that this was evidence for the presence of an
oxytocinlike principle. However, their findings suggest that there should
be some caution before the possibility of an oxytocinlike peptide is eliminated from cyclostome physiology. Most work has been done on adult
animals during their spawning migration, and W. H. Sawyer (1961) has
pointed out that oxytocinlike peptides might exist during other stages of
the life cycle. The histological studies of van der Kamer and Schreurs
(1959) have shown that neurosecretory material is remarkably dense in
parts of the neurohypophysis during the ammocoete stage, but parallel
pharmacological studies are lacking.
There have been no chemical studies of the structure of any cyclostome principal. Nevertheless, all present evidence indicates that the
cyclostome pituitary contains an overwhelming preponderance of arginine
vasotocin and that some cyclostomes may well be unique in possessing a
single neurohypophysial principle in their pituitaries.
C. The Actions of Neurohypophysial Principles in Cyclostomes
1. MYXIN~ORMES
Studies of the actions of neurohypophysial principles in the hagfish
are few and brief. It is possible that the peptides influence salt and water
metabolism. Chester Jones et al. (1962), working with Myxine glutimsa,
determined the effects of neurohypophysial principles on hagfish whose
body fluids had been diluted or concentrated by immersion in diluted or
concentrated seawater. Hagfish pituitary extracts, equivalent to 10 glands,
or possibly 1.3 mU of oxytocic activity (calculated from the data of
Follett and Heller, l W a ) , were injected daily for 4 days into hagfish
adapted to diluted (70%) seawater. The treatment resulted in a rise in
the serum sodium level. A mammalian oxytocin-vasopressin preparation
(Pituitrin) was injected at high dose levels (loo0 m u ) , daily for 5 days,
into hagfish adapted to concentrated (165%) seawater. This treatment
resulted in a fall in serum sodium level. It is dangerous to generalize from
such scanty data, but it seems possible that neurohypophysial peptides
tended to return body sodium levels toward the natural value for normal
seawater, presumably by affecting sodium fluxes. Although the hagfish is
incapable of maintaining its internal environment in the face of external