2
J. N. BALL AND BRIDGET I. BAKEX
(Green and Maxwell, 1959; Green, 1966). Thus the gland is a composite
organ, and it has many different endocrine functions.
The adenohypophysis is the site of synthesis, storage, and release into
the blood of several different peptide hormones; and the greater part of
pituitary histophysiology is concerned with the allocation of each of these
hormones to the type of pituitary cell that secretes it. The adenohypophysis is divided into the pars distalis, site of secretion of most adenohypophysial hormones, and the pars intermedia. The neurohypophysis
in fishes is rather simpler than in land vertebrates ( Wingstrand, 1 W a )
and consists essentially of a hypophysial stalk, suspending the gland from
the ventral region of the diencephalon (hypothalamus) and containing
an extension of the third ventricle (infundibular recess), and at the distal
end of the stalk an enlargement, the neurohypophysial lobe or core,
which forms the middle of the gland (Figs. 1 and 2). The stalk contains
the axonal fibers of neurosecretory cells, the cell bodies being located in
the hypothalamus. The neurohypophysial core consists largely of the endings of these fibers interspersed with cells termed “pituicytes.” The neurohypophysis seems to be in general a storage-release center for materials
which are actually synthesized in the hypothalamus and then transported
to the neurohypophysial core along the neurosecretory axons (Section
11, C). In many fishes, the neurohypophysial stalk is virtually absent, the
pituitary then being pressed close to the ventral surface of the hypothalamus, while in a few teleosts (e.g., Lophim) the neurohypophysial stalk
is extremely long ( Wingstrand, 1966a).
B. Adenohypophysial Histophysiology and Cytophysiology
Purves (1966) has usefully divided the cytological criteria used in the
study of the adenohypophysis into two groups. The first category consists
of features that are indicators of the specific nature of the functions of
individual cell types such as granule size, staining reactions and chemical
nature, cell morphology, and reactions to specific physiological alterations; these features are the data of special cytology, which is particularly
concerned with allocation of function to each cell type. The second category includes those features which are indicators of the functional state
of the cell, indicating high or low rates of metabolic or secretory activity
such as nuclear size, nucleolar size, amount of cytoplasmic RNA, state of
the Golgi apparatus, and accumulation or loss of secretory granules.
These features constitute the field of general cytology. In the study of
fishes, as in other vertebrate groups, workers on the pituitary have been
concerned with both kinds of criteria. However, more than in the highly
worked field of mammalian pituitary histophysiology, most investigations
J. N. BALL AND BRIDGET I. BAKEX
(Green and Maxwell, 1959; Green, 1966). Thus the gland is a composite
organ, and it has many different endocrine functions.
The adenohypophysis is the site of synthesis, storage, and release into
the blood of several different peptide hormones; and the greater part of
pituitary histophysiology is concerned with the allocation of each of these
hormones to the type of pituitary cell that secretes it. The adenohypophysis is divided into the pars distalis, site of secretion of most adenohypophysial hormones, and the pars intermedia. The neurohypophysis
in fishes is rather simpler than in land vertebrates ( Wingstrand, 1 W a )
and consists essentially of a hypophysial stalk, suspending the gland from
the ventral region of the diencephalon (hypothalamus) and containing
an extension of the third ventricle (infundibular recess), and at the distal
end of the stalk an enlargement, the neurohypophysial lobe or core,
which forms the middle of the gland (Figs. 1 and 2). The stalk contains
the axonal fibers of neurosecretory cells, the cell bodies being located in
the hypothalamus. The neurohypophysial core consists largely of the endings of these fibers interspersed with cells termed “pituicytes.” The neurohypophysis seems to be in general a storage-release center for materials
which are actually synthesized in the hypothalamus and then transported
to the neurohypophysial core along the neurosecretory axons (Section
11, C). In many fishes, the neurohypophysial stalk is virtually absent, the
pituitary then being pressed close to the ventral surface of the hypothalamus, while in a few teleosts (e.g., Lophim) the neurohypophysial stalk
is extremely long ( Wingstrand, 1966a).
B. Adenohypophysial Histophysiology and Cytophysiology
Purves (1966) has usefully divided the cytological criteria used in the
study of the adenohypophysis into two groups. The first category consists
of features that are indicators of the specific nature of the functions of
individual cell types such as granule size, staining reactions and chemical
nature, cell morphology, and reactions to specific physiological alterations; these features are the data of special cytology, which is particularly
concerned with allocation of function to each cell type. The second category includes those features which are indicators of the functional state
of the cell, indicating high or low rates of metabolic or secretory activity
such as nuclear size, nucleolar size, amount of cytoplasmic RNA, state of
the Golgi apparatus, and accumulation or loss of secretory granules.
These features constitute the field of general cytology. In the study of
fishes, as in other vertebrate groups, workers on the pituitary have been
concerned with both kinds of criteria. However, more than in the highly
worked field of mammalian pituitary histophysiology, most investigations