present. The cell types can be divided into two major groups, acidophils and basophils, dep ending upon reactiv ity of their constituent granules with acidic or basic
dyes. HYMER and MCSHAN (1963) have separ ated the basophilic and acidophilic
granules of the adenohypophysis by ultrafiltration, the acidophil material
sedimenting more rapidly. The basophil granules were found to contain
glycoprotein hormones, FSH, LH, and TSH, while the acidophilic granules
contained prolactin and growth hormone. Corticotrophin was contained in the
small-particle fraction. The further identification of the cell types with particular
hormones, is based on observed histological changes associated with altered endocrine conditions, such as thyroidectomy or gonadectomy, and correlation of this
with the hormone content of the gland. Analogous types of cells have been identified in all the major vertebrate groups. These have the gener ic suffix 'troph' so
that the cells secreting th yrotrophic hormone are called thyrotrophs and so on .
The precise chemical structure of an adenohypophysial hormone from the nonmammalian vertebrates has not yet been described, presumably reflecting the difficult y of the procedures involved and human preference for the mammals. However, the considerable divergency in biological activity of the non-mammalian and
mammalian hormones suggests that such knowledge may be particularly interesting with respect to the relationship of the structure and biological activity of
such molecules.
P) Neurohypophysis. The hormones of the neurohypophysis are polypeptides with
a molecular weight of about 1000. Like the adenohypophysial hormones, there
are differences in structure among the various vertebrate species. This is combined
with a certain conservatism, as illustrated by vasotocin, which, with its distinct amino acid sequence, is represented in all the major non-mammalian groups.
The precise structures of the releasing and inhibiting factors found in the median
eminence have not been determined, but it is known that they are polypeptides
with a relatively low molecular weight. Amino acid analysis of corticotrophic releasing factors (CRF) suggests that they have similarities to both vasopressin and
MSH (SCHALLY, SAFFRAN, and ZIMMERMAN, 1958; SCHALLY and G UILL EMIN
1963), and that this accounts for the early difficulties in distinguishing, and separating the activities of these peptides. The polypeptides of the neurohypophysial
regions thus have a cross-over in their biological activities , that sometimes makes
it difficult to relate each precisely to a distinct physiological action.
The structures of the mammalian neurohypophysial hormones, arginine-vasopressin (lysine-vasopressin in the pig family) and oxytocin were determined by
Du VIGNEAUD and his collaborators in 1953 (Du VIGNEAUD et al., 1953a and
1953b) and they were subsequently made by chemical synthesis. Structural analogues of these hormones were also synthesized, and one of these, arginine-vasotocin, was subsequently shown to be identical with the amphibian 'water balance
principle', which was pharmacologically identified in lower vertebrates by HELLER
18 years previously (HELLER, 1941; PICKERING and HELLER, 1959; SAWYER, MUNSICK, and VAN DYKE, 1959). This created the interesting precedent of a hormone
being synthesized in the laboratory before it was known to exist in nature. The
neurohypophysial peptides consist of a ring of five amino acids joined by a disulphide bridge, contributed by two half-cystine residues, to which is attached a
54
dyes. HYMER and MCSHAN (1963) have separ ated the basophilic and acidophilic
granules of the adenohypophysis by ultrafiltration, the acidophil material
sedimenting more rapidly. The basophil granules were found to contain
glycoprotein hormones, FSH, LH, and TSH, while the acidophilic granules
contained prolactin and growth hormone. Corticotrophin was contained in the
small-particle fraction. The further identification of the cell types with particular
hormones, is based on observed histological changes associated with altered endocrine conditions, such as thyroidectomy or gonadectomy, and correlation of this
with the hormone content of the gland. Analogous types of cells have been identified in all the major vertebrate groups. These have the gener ic suffix 'troph' so
that the cells secreting th yrotrophic hormone are called thyrotrophs and so on .
The precise chemical structure of an adenohypophysial hormone from the nonmammalian vertebrates has not yet been described, presumably reflecting the difficult y of the procedures involved and human preference for the mammals. However, the considerable divergency in biological activity of the non-mammalian and
mammalian hormones suggests that such knowledge may be particularly interesting with respect to the relationship of the structure and biological activity of
such molecules.
P) Neurohypophysis. The hormones of the neurohypophysis are polypeptides with
a molecular weight of about 1000. Like the adenohypophysial hormones, there
are differences in structure among the various vertebrate species. This is combined
with a certain conservatism, as illustrated by vasotocin, which, with its distinct amino acid sequence, is represented in all the major non-mammalian groups.
The precise structures of the releasing and inhibiting factors found in the median
eminence have not been determined, but it is known that they are polypeptides
with a relatively low molecular weight. Amino acid analysis of corticotrophic releasing factors (CRF) suggests that they have similarities to both vasopressin and
MSH (SCHALLY, SAFFRAN, and ZIMMERMAN, 1958; SCHALLY and G UILL EMIN
1963), and that this accounts for the early difficulties in distinguishing, and separating the activities of these peptides. The polypeptides of the neurohypophysial
regions thus have a cross-over in their biological activities , that sometimes makes
it difficult to relate each precisely to a distinct physiological action.
The structures of the mammalian neurohypophysial hormones, arginine-vasopressin (lysine-vasopressin in the pig family) and oxytocin were determined by
Du VIGNEAUD and his collaborators in 1953 (Du VIGNEAUD et al., 1953a and
1953b) and they were subsequently made by chemical synthesis. Structural analogues of these hormones were also synthesized, and one of these, arginine-vasotocin, was subsequently shown to be identical with the amphibian 'water balance
principle', which was pharmacologically identified in lower vertebrates by HELLER
18 years previously (HELLER, 1941; PICKERING and HELLER, 1959; SAWYER, MUNSICK, and VAN DYKE, 1959). This created the interesting precedent of a hormone
being synthesized in the laboratory before it was known to exist in nature. The
neurohypophysial peptides consist of a ring of five amino acids joined by a disulphide bridge, contributed by two half-cystine residues, to which is attached a
54