1. THE PITUITARY GLAND
65
An isolated report suggests some relationship between the neurohypophysis and the thyroid, although this is difficult to interpret in
physiological terms : Injections of TSH, or thyroxine, encouraged the
movement of neurosecretory material in Salmo from the NPO to the
neurohypophysial core ( Arvy et al., 1957).
New fields for investigation are indicated by the observations that
electrical stimulation of the olfactory tract of goldfish caused depletion of
stainable material from the NPO and its axons (Jasinski et al., 1966); and
by the report of wide diurnal variations in the amount of A F + v e
material in the goldfish NPO, variations that do not seem to be regular
(rhythmic), although generally the cells stain more deeply during the
day than at night (Sathyanesan, 1966). In the light of this last finding,
some of the earlier work may need reconsideration, since investigators
have not usually paid attention to the possibility of diurnal changes in the
neuroh y po ph ysis.
There have been few observations on the Type A neurosecretory
material among the cells of the pars distalis, where the function of the
fibers is presumably the control of adenohypophysial activity. Knowles
and Vollrath (1966b,c) described Type A3 fibers in the rostral and
proximal pars distalis of eel and found that the number of these fibers,
and the amount of stainable material, was greater in the silver eel than
in younger animals. They suggested that this might be correlated in some
way with the greater activity of the TSH cells and gonadotrops in the
silver stage. In mature seawater eels, these authors (1966d) observed a
decrease in the A F + ve material and in Type A3 granules (140 mp
diam) in the proximal pars distalis, but fibers with smaller granules (100
mp) were now found in this region. The signifkance of these changes is
not known, and Knowles and Vollrath did not identify the fibers with
100 mp granules as being distinct from the Type A3 fibers of the river eel.
2. “NONSTAINABLE” FIBERS, PROBABLY KNOWLES’ TYPE B
The nonstainable fibers probably originate from the nucleus lateralis
tuberis (NLT) of the hypothalamus ( Samuelsson and Fridberg, 1964;
Honma and Tamura, 1965b; Knowles and Vollrath, 1 W b ) and do not
stain with the classic neurosecretion stains, although they have been
described as A F + ve by some workers (Rasquin and Stoll, 1957; Oztan,
1963; Honma and Tamura, 1965b). They can be stained with acid dyes
such as azocarmine, eosin, light green, phloxin, and also with PAS Aniline
blue or silver impregnation; similar staining reactions are seen in the cells
of the NLT (Stahl and Leray, 1962; Samuelsson and Fridberg, 1964;
Honma and Tamura, 1965b). Their pathway within the pituitary has
65
An isolated report suggests some relationship between the neurohypophysis and the thyroid, although this is difficult to interpret in
physiological terms : Injections of TSH, or thyroxine, encouraged the
movement of neurosecretory material in Salmo from the NPO to the
neurohypophysial core ( Arvy et al., 1957).
New fields for investigation are indicated by the observations that
electrical stimulation of the olfactory tract of goldfish caused depletion of
stainable material from the NPO and its axons (Jasinski et al., 1966); and
by the report of wide diurnal variations in the amount of A F + v e
material in the goldfish NPO, variations that do not seem to be regular
(rhythmic), although generally the cells stain more deeply during the
day than at night (Sathyanesan, 1966). In the light of this last finding,
some of the earlier work may need reconsideration, since investigators
have not usually paid attention to the possibility of diurnal changes in the
neuroh y po ph ysis.
There have been few observations on the Type A neurosecretory
material among the cells of the pars distalis, where the function of the
fibers is presumably the control of adenohypophysial activity. Knowles
and Vollrath (1966b,c) described Type A3 fibers in the rostral and
proximal pars distalis of eel and found that the number of these fibers,
and the amount of stainable material, was greater in the silver eel than
in younger animals. They suggested that this might be correlated in some
way with the greater activity of the TSH cells and gonadotrops in the
silver stage. In mature seawater eels, these authors (1966d) observed a
decrease in the A F + ve material and in Type A3 granules (140 mp
diam) in the proximal pars distalis, but fibers with smaller granules (100
mp) were now found in this region. The signifkance of these changes is
not known, and Knowles and Vollrath did not identify the fibers with
100 mp granules as being distinct from the Type A3 fibers of the river eel.
2. “NONSTAINABLE” FIBERS, PROBABLY KNOWLES’ TYPE B
The nonstainable fibers probably originate from the nucleus lateralis
tuberis (NLT) of the hypothalamus ( Samuelsson and Fridberg, 1964;
Honma and Tamura, 1965b; Knowles and Vollrath, 1 W b ) and do not
stain with the classic neurosecretion stains, although they have been
described as A F + ve by some workers (Rasquin and Stoll, 1957; Oztan,
1963; Honma and Tamura, 1965b). They can be stained with acid dyes
such as azocarmine, eosin, light green, phloxin, and also with PAS Aniline
blue or silver impregnation; similar staining reactions are seen in the cells
of the NLT (Stahl and Leray, 1962; Samuelsson and Fridberg, 1964;
Honma and Tamura, 1965b). Their pathway within the pituitary has