1. THE PITUITARY GLAND
61
NPO (Follenius, 1963b, 1965a,b). Several kinds of Type A fibers have
been described differing in the size of their granules, their destination
within the pituitary, and in their response to experimentation (see chapter
by Perks, this volume).
Within the pituitary of Anguilla and Conger, the Type A fibers mostly
terminate in or close to the pars intermedia, or on extravascular channels
between the endocrine cells, or make direct contact with the pituicytes, or
occasionally with the pars intermedia cells. A Type A3 fiber has been
distinguished in the eel pars distalis and appears to be distinct from the
A l and A2 fibers found in the neurohypophysial core close to the pars
intermedia (Knowles and Vollrath, 1966a,b). The Type A3 fibers in the
pars distalis of the eel, like the more numerous Type B fibers in this
region, terminate on extravascular channels, very close to the intrinsic
endocrine cells (Fig. 23).
Light microscope accounts of changes in the neurosecretory material
in the neurohypophysis nearly all relate to the (presumptive) Type A
fibers in the distal neurohypophysial core, close to the pars intermedia.
The amount of stainable material in this region commonly alters in
response to osmotic stimuli. In many teleosts, transfer to a hypertonic
medium results in loss of this material, both from the neurohypophysis
Fig. 23. Diagram to illustrate the relationship between a neurosecretory fiber
terminal ( N ) , intrinsic endocrine cells (EC), and a blood capillary ( C ) in the proximal pars distalis of the eel; extravascular space (EVC). Modified from Knowles and
Vollrath (1966b).
61
NPO (Follenius, 1963b, 1965a,b). Several kinds of Type A fibers have
been described differing in the size of their granules, their destination
within the pituitary, and in their response to experimentation (see chapter
by Perks, this volume).
Within the pituitary of Anguilla and Conger, the Type A fibers mostly
terminate in or close to the pars intermedia, or on extravascular channels
between the endocrine cells, or make direct contact with the pituicytes, or
occasionally with the pars intermedia cells. A Type A3 fiber has been
distinguished in the eel pars distalis and appears to be distinct from the
A l and A2 fibers found in the neurohypophysial core close to the pars
intermedia (Knowles and Vollrath, 1966a,b). The Type A3 fibers in the
pars distalis of the eel, like the more numerous Type B fibers in this
region, terminate on extravascular channels, very close to the intrinsic
endocrine cells (Fig. 23).
Light microscope accounts of changes in the neurosecretory material
in the neurohypophysis nearly all relate to the (presumptive) Type A
fibers in the distal neurohypophysial core, close to the pars intermedia.
The amount of stainable material in this region commonly alters in
response to osmotic stimuli. In many teleosts, transfer to a hypertonic
medium results in loss of this material, both from the neurohypophysis
Fig. 23. Diagram to illustrate the relationship between a neurosecretory fiber
terminal ( N ) , intrinsic endocrine cells (EC), and a blood capillary ( C ) in the proximal pars distalis of the eel; extravascular space (EVC). Modified from Knowles and
Vollrath (1966b).