2. THE NEUROHYPOPHYSIS
119
marinus ammocoete, Oztan and Gorbman, 196Ob). Occasionally, these
ependymal cells appear to sink into the pars nervosa, where they have
been described as pituicytes (Green and Maxwell, 1959). Although a few
neurosecretory fibers associate with the ependyma, it is clear that most
terminate in swollen accumulations of neurosecretion, like Herring bodies,
and these are grouped around blood vessels (Gorbman and Bern, 1964;
Petromyzon marinus ammocoete, Oztan and Gorbman, 1960b). Although
the ventral surface of the pars nervosa interdigitates with the pars intermedia to give a serrated appearance, there is no evidence that any neurosecretory axons penetrate the intermedia tissue ( Petromyzon marinus,
Tilney, 1937; P. fluviatilis, Dodd and Kerr, 1963). The border between the
two regions is marked by thin connective tissue, which is liberally supplied
by a reticulum of capillaries (Petromyzon marinus, Lampetra planeri;
Gorbman, 1965). This reticulum is filled and drained by blood vessels
which are independent of those concerned with the rostra1 regions of the
adenohypophysis. Since there is no observable portal system in the lamprey
pituitary, and these vessels both supply the pars nervosa and penetrate
the pars intermedia, they are a potential vascular link between the two
regions of the pituitary (Green and Maxwell, 1959; W. H. Sawyer, 1961;
Gorbman, 1965). It may be significant that van der Kamer and Schreurs
(1959) have noted that these vessels enlarge during the metamorphosis
of the ammocoete larva of Lampetra planeri. However, these same blood
vessels also empty into the general circulation of the head (Gorbman,
1965), so that they form a potential route by which neurohypophysial
peptides could reach all parts of the body.
B. The Nature of the Neurohypophysial Principles of the Cyclostomes
1. MYXINIFORMES
There is little knowledge of the principles present in the hagfish. This
is because of the disappointingly low activities found in the glands, together with the difCiculties of obtaining these deep-water animals. Such
studies as exist are confined to one species, Myxine glutinosa. Herring’s
remarkable early work (1913) reported the presence of a vasopressor
principle in this species. It was almost half a century before Adam (1961)
observed a frog water-balance effect when extracts from Myxine were
tested on Bufo viridis. In 1964, Follett and Heller were able to detect
oxytocic and natriferic activity in an extract of 150 glands, but they failed
to find a vasopressor effect (1964a). The total oxytocic activity obtained
amounted to only 74 mu, and since no more than one quarter of this
showed the lability to sodium thioglycollate treatment typical of neurohypophysial principles, they deduced that the hagfish pituitary contained
119
marinus ammocoete, Oztan and Gorbman, 196Ob). Occasionally, these
ependymal cells appear to sink into the pars nervosa, where they have
been described as pituicytes (Green and Maxwell, 1959). Although a few
neurosecretory fibers associate with the ependyma, it is clear that most
terminate in swollen accumulations of neurosecretion, like Herring bodies,
and these are grouped around blood vessels (Gorbman and Bern, 1964;
Petromyzon marinus ammocoete, Oztan and Gorbman, 1960b). Although
the ventral surface of the pars nervosa interdigitates with the pars intermedia to give a serrated appearance, there is no evidence that any neurosecretory axons penetrate the intermedia tissue ( Petromyzon marinus,
Tilney, 1937; P. fluviatilis, Dodd and Kerr, 1963). The border between the
two regions is marked by thin connective tissue, which is liberally supplied
by a reticulum of capillaries (Petromyzon marinus, Lampetra planeri;
Gorbman, 1965). This reticulum is filled and drained by blood vessels
which are independent of those concerned with the rostra1 regions of the
adenohypophysis. Since there is no observable portal system in the lamprey
pituitary, and these vessels both supply the pars nervosa and penetrate
the pars intermedia, they are a potential vascular link between the two
regions of the pituitary (Green and Maxwell, 1959; W. H. Sawyer, 1961;
Gorbman, 1965). It may be significant that van der Kamer and Schreurs
(1959) have noted that these vessels enlarge during the metamorphosis
of the ammocoete larva of Lampetra planeri. However, these same blood
vessels also empty into the general circulation of the head (Gorbman,
1965), so that they form a potential route by which neurohypophysial
peptides could reach all parts of the body.
B. The Nature of the Neurohypophysial Principles of the Cyclostomes
1. MYXINIFORMES
There is little knowledge of the principles present in the hagfish. This
is because of the disappointingly low activities found in the glands, together with the difCiculties of obtaining these deep-water animals. Such
studies as exist are confined to one species, Myxine glutinosa. Herring’s
remarkable early work (1913) reported the presence of a vasopressor
principle in this species. It was almost half a century before Adam (1961)
observed a frog water-balance effect when extracts from Myxine were
tested on Bufo viridis. In 1964, Follett and Heller were able to detect
oxytocic and natriferic activity in an extract of 150 glands, but they failed
to find a vasopressor effect (1964a). The total oxytocic activity obtained
amounted to only 74 mu, and since no more than one quarter of this
showed the lability to sodium thioglycollate treatment typical of neurohypophysial principles, they deduced that the hagfish pituitary contained