Ultrastructure of the Non-granulated Hypophysial Cells in the Teleost Pseudocrenilabrus philander (Hemihaplochromis philander), with Particular Reference to Cytological Changes in Culture

Abstract In the intact gland, non-granulated cells are most numerous in the rostral pars distalis; they are characterized by a lack of typical secretory granules, a ribosome-rich cytoplasm and long cytoplasmic processes. The latter extend between the granulated cells and often form a layer beneath the capsule and at the zone of contact between adenohypophysis and neurohypophysis. Study of cultured hypophysial tissue provides unequivocal evidence for the phagocytosis of cytoplasm of granulated cells by non-granulated cells. In short-term cultures (1.5 h), non-granulated cells envelop small portions of granulated cell cytoplasm and their processes extend into intercellular spaces and contact tissue fragments located there. In longer term cultures (6—120 h), large areas of cytoplasm belonging to presumptive prolactin and somatotropic cells are engulfed by non-granulated cells; these phagosomes undergo progressive breakdown to form residual bodies. It is suggested that an accumulation of cellular debris and/or stale secretory material may be important factors promoting phagocytic activity in cultured non-granulated cells.     

Comparative ultrastructural studies on the prolactin cells in the pituitary of nine-spined sticklebacks,Pungitius pungitius L., with and without adenohypophyseal cysts

Summary The ultrastructure of the prolactin cells in nine-spined sticklebacks (Pungitius pungitius L.) with and without large pituitary cysts was compared. Prolactin cells from animals with cysts were less active as regards hormone synthesis and release than those from animals without cysts. Rough endoplasmic reticulum, mitochondria, Golgi apparatus and exocytotic figures were all more prominent in animals without cysts. Lysosomes and mature secretory granules were more plentiful in animals with cysts. The correlation between inactive prolactin cells and pituitary cysts argues against the hypothesis that cysts store prolactin released by holocrine secretion. It is more likely that the origin of cysts from degenerating cells signals extreme inactivity in the rostral pars distalis.     

Occurrence of colloid-containing follicles and ciliated cysts in the hypophysial pars tuberalis from guinea pigs of various ages

Colloid-containing follicles and ciliated cysts in the hypophysial pars tuberalis of guinea pigs at various ages ranging from 5 days to 36 months were examined by periodic acid-Schiff (PAS) reaction, immunohistochemistry, and electron microscopy. The follicles storing PAS-positive colloid were encountered in the pars tuberalis of all guinea pigs examined, although only a few were present in young animals. The follicles gradually increased in number with age. The largest number of follicles was found in the senile male group: 141.3 +/- 11.9, about 10 times the number in the 5-day-old male group. The follicles were scattered throughout the entire length of the pars tuberalis. Follicles with enlarged luminal cavities were concentrated in the ventral caudal region surrounding the infundibular stem and merges with the pars distalis. Three different types of follicles were found by electron microscopy: 1) those surrounded by nongranulated follicular cells that may correspond to the stellate-follicular cells in the pars distalis, 2) those surrounded by specific cells that were packed with vesicular inclusions, and 3) those surrounded by granulated cells that may be gonadotropes. In the follicles lined by non-granulated follicular cells, long, prominent microvilli and cytoplasmic processes protruding into the lumen and invaginations of colloid were often observed at the apical cell region. The follicles lined by the specific cells having numerous vesicles were localized only in the ventral caudal portion. The vesicles ranged from 200 to 700 nm in diameter, and the outer surface of their limiting membrane was partly studded with ribosomes. Gonadotropes immunoreactive to the luteinizing hormone (LH) and follicle-stimulating hormone (FSH) antisera were distributed in the guinea pig pars tuberalis. As well as the typical follicles described above, the follicles composed solely of granulated cells showed microvilli protruding into the cavities and junctional complexes at the apical lateral surface. They stored heterogeneous materials in the lumina. Some secretory granules gave the appearance of being discharged into the lumen. Ciliated cysts were frequently observed in the pars tuberalis; their incidence was 71.7%. The ciliated cysts were much larger than colloid-containing follicles. Cystic cavities were only partly filled with heterogeneous materials showing colloid-like, flocculent, and granular features.     

Pituitary cytology of the chimaeroid fish Hydrolagus colliei (Lay and Bennett).

The pituitary of Hydrolagus colliei is divided into the adenohypophysis, neurohypophysis and an oral Rachendachhypophyse. The adenohypophysis is further divided into rostral and proximal pars distalis and neurointermediate lobe. The neurohypophysis is restricted to the pars intermedia only. The rostral pars distalis is composed of acidophils, chromophobes, lightly PAS+ cells and amphiphils. The amphiphils were stained with Heidenhain's iron haematoxylin and lead haematoxylin also. The proximal pars distalis is formed of cyanophils where the granules are AF and PAS positive, acidophils, chromophobes and H.Pb+ cells. The pars intermedia has perviascular amphiphils which are H.Pb+, lightly PAS+ cells and chromophobes. Few AF+ cells were also identified. All the component parts of the adenohypophysis have follicular cavities which are probably developed from the hypophysial cavity, which is well seen in the young specimen as a single cavity extending antero-posteriorly throughout the adenohypophysis.     

An immunohistochemical study of adenohypophyseal cells in the viviparous reptile Chalcides chalcides

The morphology of the hypophysis and the immunocharacteristics of the adenohypophyseal cells in the viviparous reptile Chalcides chalcides were studied by light microscopy, using conventional staining methods and an indirect antibody technique (ABC method), respectively. The general morphology of the C. chalcides hypophysis was comparable to that of other reptiles, showing three main regions: the pars distalis, the pars intermedia and the pars nervosa. The gland appeared as an elongated body in a cephalic-caudal direction and was almost completely enclosed in the sella turcica. For this reason, the hypophysis was studied in toto with the brain in decalcified specimens. The pars distalis accounted for most of the whole organ. The pars intermedia surrounded the pars nervosa as a goblet. The pars tuberalis was lacking.The immunohistochemical identification of the adenohypophyseal cells was performed using rabbit antisera against mammalian/synthetic hypophyseal hormones. Prolactin cells were clustered in small cellular cordons in the rostral pars distalis and in the medial pars distalis in both male and female specimens. Somatotropic cells were found in the caudal pars distalis. Corticotropic cells were observed in the medio-rostral pars distalis, as well as in the pars intermedia, where melanotropic cells were also present. Melanotropic cells were confined to the pars intermedia. Gonadotropic cells were mostly distributed in the ventral and lateral portions of the pars distalis, where they were found isolated or in small clusters. Thyrotropic cells were detected in the pars distalis with a distribution similar to that of the gonadotropic cells; however, atypically, they were also found in the pars intermedia. Therefore, the cytological characteristics of the adenohypophyseal cells appeared mostly conserved.     

The hypothalamo-hypophysial vascular relationship in Indian fresh-water goby, Glossogobius giuris (Ham.).920u.

The hypothalamo-hypophysial vascular relationship and intra-hypophysial vasculatisation have been described in order to understand the regulatory mechanism of hypothalamic control over the functions of the pituitary gland. In Glossogobius giuris, the disposition of the blood vessels in the head region is on typical teleostean pattern with certain modifications. The nucleus preopticus is supplied through the nucleus preopticus artery, a small blood vessel arising from the anterior branch of the posterior cerebral artery, whereas the pituitary gland receives blood through a pair of hypophysial arteries. The blood from the pituitary is drained off by the pituitary veins whch pour their blood into the supra-orbital sinus. The anterior cerebral vein after taking the blood from anterior part of the brain including the hypothalamus and the nucleus preopticus joins with the supra-orbital sinus. The hypothalamo-hypophysial portal system is absent in this fish. The saccus vasculosus receives blood from the posterior cerebral artery through a small blood vessel and is collected by a prominent saccus vasculosus vein which pours blood into the supra-orbital sinus before it joins the infra-orbital sinus to form the heat vein. There seems to be no physological connection between the saccus vasculosus and pituitary gland. The highly vascularised neurohypophysis interdigitate with the pars intermedia and extends upto the proximal pars distalis. The blood vessels are restricted to the neurohypophysial extensions only. However, in the rostral pars distalis the blood vessels are present but the neurohypophysis does not extend to this part. The blood capillaries enter the rostral pars distalis from the capillary network on the surface of pituitary gland along with the connected tissue covering of the pituitary. The neurohypophysis shows a greater vascularisation in comparison to that of the other glandular part of the pituitary gland. In the present study of Glossogobius giuris, though an extensive ramification of neurohypophysis occurs with the pars intermedia and the proximal pars distalis, the neurosecretory axons do not innervate the endocrine cells of the pituitary gland and the blood vessels are found restricted to the neurohypophysial extensions except that of the rostral pars distalis. The neuro-vascular way of hypothalamic control over the functions of the pituitary gland seems to be justified as the neurosecretory fibres have been found associated with the blood vessels.     

Immunohistochemically detected ontogeny of prolactin and growth hormone cells in the African catfish Clarias gariepinus

The chronological appearance of selected endocrine cells in the pituitary of African catfish Clarias gariepinus (Burchell, 1822) was studied morphologically, histologically and immunohistochemically by using antisera raised against catfish growth hormone (cgGH) and recombinant tilapia prolactin I (tPRL). cgGH- and tPRL-like immunoreactive cells were visible from day 1 post fertilisation (hatching) throughout the juvenile and the adult stage. From 1 to 90 days after hatching, the larval pituitary is oval in shape with a distinctly shaped rostral pars distalis, proximal pars distalis and pars intermedia. From day 120 onwards allometric growth of the rostral and proximal pars distalis extended the prolactin and growth hormone cells anteriorily and posteriorily, respectively. Size and activity of the prolactin and growth hormone cells, measured by the ratio of cell surface to nuclear surface remained constant until day 40 and showed a growth spurt thereafter. Growth hormone content, measured with a catfish-specific radio-immunoassay from hatching until 60 h post hatching, increased exponentially between 30 and 60 h.     

Immunohistochemical Localization of Growth Hormone and Prolactin in the Pituitary Gland of Acipenser güldenstaedti Brandt (Chondrostei)

Abstract Prolactin (LTH) and growth hormone (GH) containing cells in A. güldenstaedti have been localized by means of anti-ovine prolactin and anti-bovine growth hormone respectively, coupled indirectly to peroxidase, and localized histochemically with hydrogen peroxide as substrate and 3,3′-diaminobenzidine as capturing agent. The distribution of the anti-prolactin positive cells has been demonstrated and correlated histologically with the acidophilic cells both in the rostral and proximal pars distalis. This cell type is elongated and arranged in follicles in the rostral pars distalis; in the proximal pars distalis they are smaller and oval, without any special orientation. Neither of the other cell types which are scattered among these acidophils contain prolactin. The anti-bovine growth hormone positive cells are evenly distributed in the proximal pars distalis above the hypophysial cleft, and some are also found in the pars intermedia. The anti-GH positive cells have been correlated histologically with the amphiphilic cells in the proximal pars distalis. These cells are arranged in cell cords in close contact with the secondary capillary plexus, near its origin from the primary capillary plexus covering the median eminence.     

The Cell Types in the Adenohypophysis of the Marine Teleost Crenilabrus melops

Sagittal sections from pituitaries of winter and spring fish were stained with a number of methods including alcian blue-PAS-orange G, Herlant's tetrachrome, Luxol fast blue-PAS-orange G and lead haematoxylin. By these methods seven different endocrine cell types were readily demonstrated in the adenohypophysis. In the rostral pars distalis (RPD), there were conspicuous vacuoles (intra- and possibly extracellular) in the prolactin cell zone of all animals. The ACTH cells in the RPD were very numerous. In the proximal pars distalis (PPD), the growth hormone cells were arranged in coiling bands that were predominantly dorsal and juxtaposed to neurohypophysis. Two types of basophils were readily distinguished: both were predominantly ventral in the proximal pars distalis, though the type I basophil also formed a constant group in the dorsal region of the pituitary, between the PPD and the RPD. The pars intermedia contained two cell types — a lead haematoxylin-positive cell and a PAS-positive cell. The pituitary morphology is compared with that of other teleosts.     

Immunocytochemical analysis of somatotrophs and mammotrophs in the pars distalis of postnatal dwarf (dw) mutant mice

Summary The postnatal differentiation of somatotrophs and mammotrophs in the pars distalis of normal and dwarf (dw/dw) mice was analyzed by means of immunocytochemistry at the electron-microscopic level. Thin sections of Araldite-embedded pituitaries from postnatal mice ranging in age from 2 days to 3–4 months were exposed to antigrowth hormone serum (anti-GH) or to anti-prolactin serum (anti-PRL) and were processed immunocytochemically by means of the colloidal-gold technique. In the normal adult pars distalis, somatotrophs reacted strongly with antiGH, and mammotrophs showed a positive anti-PRL reaction. In the dwarf adult, the granulated cells were unreactive with either anti-GH or anti-PRL. However, at 6 days postnatally, some cells in the dwarf pars distalis showed a positive reaction with anti-GH, though the reaction was not as strong as in the 6-day normal pars distalis. The 6-day dwarf was only faintly reactive with anti-PRL, and by 14 days the dwarf was unreactive with anti-GH as well as anti-PRL, in contrast to the strong positive reactivity to these two antisera in the normal 14-day pars distalis.Supported by USPHS grant HD12308     

The pituitary gland of the coelacanth fish Latimeria chalumnae Smith: General structure and adenohypophysial cell types

The pituitary gland of Latimeria chalumnae is situated rostroventral to the telencephalon. The hollow pituitary stalk is bent forward and is ventrally connected to a saccus-vasculosus-like organ, rostrally to a neurointermediate lobe. The infundibular lumen protrudes far into the neurohypophysial lobules. The elongated principal part (pars cerebralis) of the pars distalis is partly embedded in a dorsal depression of the pars intermedia and caudally invaded by the neurohypophysis. It may be divided into rostral and proximal pars distalis and includes a ramified hypophysial cleft, which continues rostrally as a duct with adjacent islets of pars distalis tissue (parts of a pars buccalis). The adenohypophysis consists of cell cords and follicles. Eight tinctorial cell types can be distinguished: in the rostral islets: large basophils with acidophil globules, in the rostral pars distalis: small basophils, large basophils with amphiphil characters and erythrosin-, orange G-positive acidophils; in the proximal pars distalis: orange G-positive acidophils and small and large basophils, having similar staining properties; in the pars intermedia: one amphiphil cell type.     

Vascularization of the pars distalis of the hypophysis in the toad,Bufo bufo (L.) (Amphibia,Anura)

Summary The vascularization of the pars distalis of the hypophysis of the toad, Bufo bufo (L.), was studied by the traditional method of injecting a mixture of India-ink and gelatine into the circulatory system of the head via the arteria carotis communis. Further, methyl-methacrylate corrosion casts of the brains were made; the hypothalamo-adenohypophysial region of these corrosion casts was studied with the scanning electron microscope. The results showed that the portal vessels which arise from the median eminence do not supply distinct areas in the pars distalis as is supposed by the point-to-point-hypothesis. The portal vessels enter the ventro-median region of the pars distalis and branch off into a three-dimensional network of the secondary capillary plexus of the pars distalis. The plexus is made up mostly by four- to six-sided meshes. This angioarchitecture guarantees an optimal supply of the glandular cells of the pars distalis with nutritional factors and releasing hormones, on the one hand, and facilitates the removal of the hormones which are released by these cells, on the other hand. The venous drainage of the pars distalis is exerted mainly by two large veins, which bilaterally leave the dorso-lateral region (venous pole) of the pars distalis and by a few small veins, which drain into the wide, sinus-like vessel, which curves around the dorso-caudal region of the pars distalis and joins bilaterally the vena hypophysea transversa.This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung (Projekt Nr. 2183/N 39) and by the Stiftungs- und Förderungsgesellschaft der Paris-Lodron-Universität SalzburgThe authors wish to thank Mag. Ursula Albrecht for excellent technical assistance and Mr. Gerhard Sulzer for photographic work     

Vascularization of the pituitary of the Australian lungfish and Neoceratodus forsteri

The vascularization of the brain and the pituitary region of the Australian lungfish, Neoceratodus forsteri is described from serial section reconstruction. The distal lobe has no direct arterial blood supply and receives blood solely from a pituitary portal system basically similar to that of other sarcopterygians. The primary capillary plexus of the median eminence receives its arterial blood from the infundibular arteries, which on their way distribute some small branches to the prechiasmatic region. The primary plexus also receives capillaries from the adjacent pial hypothalamic plexus. The primary capillary plexus of the median eminence comprises a rostral 'uncovered' and caudal 'covered' part which are not sharply delineated. Distinct portal vessels connect the 'uncovered' rostral part of the primary plexus with the secondary capillary plexus supplying the rostral subdivision of the pars distalis. The 'covered' caudal part of the primary plexus merges into the proximal subdivision of the pars distalis, apparently without formation of distinct portal vessels. The primary plexus has some connections with the plexus intermedius via a hypophysial stem capillary plexus. The plexus intermedius has a substantial arterial supply and gives off capillaries to the parenchyma of the pars intermedia. The adenohypophysis is drained into an unpaired hypophysial vein. The significance of the vascular pathways is discussed from comparative, functional, and evolutionary viewpoints.     

Immunocytochemical identification of prolactin cells in the pituitary gland of tilapia larvae (Oreochromis mossambicus: Teleostei)

Summary Using an antiserum to highly purified chum salmon prolactin, prolactin cells were identified in the putative rostral pars distalis of newly hatched tilapia larvae (Oreochromis mossambicus) by the immunogold method for the electron microscope. In the putative rostral pars distalis, some cells had another kind of secretory granule which was much less numerous, much smaller in size, and without immunoreactivity to salmon prolactin antiserum. Controls incubated with salmon prolactin-preabsorbed antiserum or normal serum showed no immunoreactive cells, confirming the specificity of the antiserum. The possible role of prolactin in the osmoregulation of tilapia larvae is discussed.     

Ultrastructural features of the developing hypothalamo-hypophysial axis in the rat

Summary Nerve fibres containing granular vesicles first appear in the median eminence of the rat on the 16th foetal day while secretory granules in the cells of the adenohypophysis are not present till the 17th foetal day. These observations suggest that the differentiation and early activity of pars distalis cells may depend on substances elaborated at nerve terminals in the median eminence. Although the loops of the primary plexus of portal vessels do not develop until the 4th postnatal day, substances released by nerve fibres in the neurohypophysis could reach the pars distalis through vessels already present at the 15th foetal day in the mesenchyme between the diencephalon and the adenohypophysis. This view is supported by the fact that the earliest cells to exhibit ultrastructural evidence of secretory activity are in the rostral pole of the pars distalis, the first region of the gland to become vascularized. The earliest granules to appear in the cells of the pars distalis correspond to those which are considered to contain mucoprotein hormones; somatotrophin type granules were seen only in postnatal tissues.The finding that, in the median eminence, the development of granular vesicles precedes that of agranular vesicles is discussed with reference to the times at which neurosecretory materials and monoamines become detectable in the region.We should like to thank Miss Ann Pearson, Mr. D. Burns, and Mr. J. Nailon for their technical assistance, and Mr. J. Simmons, F.R.P.S., for his help in the preparation of illustrations. This work was supported by grants from the National Health and Medical Research Council of Australia.     

Ultrastructure of the adenohypophysis in the teleost Poecilia latipinna

Summary In the sailfin molly, Poecilia latipinna, seven morphological endocrine celltypes could be distinguished with the electron microscope. Each of these was identified with one of the seven cell-types distinguished with the light microscope, to most of which endocrine functions have previously been allocated. Corticotrophs and prolactin cells form the rostral pars distalis, and the proximal pars distalis consists of an outer layer of gonadotrophs and an inner zone containing growth hormone cells and thyrotrophs. The pars intermedia contains two cell-types, of uncertain function. Stellate cells (interstitial cells) occur throughout the adenohypophysis, but are most numerous and prominent in the rostral pars distalis. The inner proximal pars distalis contains a cell-type not previously distinguished in this species with the light microscope, the Z-cell, which could be aminergic.The ultrastructural features of each cell-type are described in detail, and discussed in comparisons with the homologous cells described in other teleosts. There is good agreement for different teleosts in the ultrastructural details of each cell type.We thank Mr. L. Ethridge, Mr. M. P. Hancock, Mr. D. Hollingworth and Mr. W. Thomson for technical assistance, and Mr. D. Taylor of the Nuffield Institute of the Zoological Society of London for permission to use the Nuffield Institute electron microscope. We are grateful to Dr. Harry Grier, who collected and embedded glands from P. latipinna in its natural fresh-water habitat in Florida, U.S.A. T. Batten is in receipt of an S.R.C. Research Studentship.     

An immunocytochemical study of the pituitary gland of the white seabream (Diplodus sargus)

The adenohypophysis of the white seabream (Diplodus sargus) was studied using histochemical and immunocytochemical techniques. The adenohypophysis was composed of rostral pars distalis, proximal pars distalis and pars intermedia. Prolactin (anti-chum salmon prolactin positive) and adrenocorticotropic (anti-human ACTH positive) cells were found in the rostral pars distalis. Prolactin cells were organized into follicles, while ACTH cells were arranged in cords around neurohypophyseal tissue branches that penetrated the rostral pars distalis. In the proximal pars distalis, somatotropic (anti-chum salmon and anti-gilthead seabream growth hormone positive), gonadotropic (anti-chum salmon -gonadotrophin II and anti-carp -gonadotrophin II positive, but anti-chum salmon -gonadotrophin I negative) and thyrotropic (anti-human -thyrotropin positive) cells were observed. Growth hormone cells were restricted to the dorsal and ventral part of the proximal pars distalis. They were clustered or surrounded the neurohypophyseal branches. Only one type of gonadotrophin cell was identified and they were clustered or isolated in the proximal pars distalis. Scattered groups of thyrotropin cells were located throughout the proximal pars distalis. In the pars intermedia somatolactin (anti-chum salmon and anti-gilthead seabream somatolactin positive) and melanotropic (anti--melanotropic hormone positive) cells were localized. In addition, gonadotrophin cells surrounded the pars intermedia or distributed evenly between somatolactin and melanotropic hormone cells. Somatolactin cells were periodic acid-Schiff negative and surrounded the neurohypophyseal branches intermingled with melanotropic cells. These cells were also immunoreactive to anti-human ACTH antiserum.     

An electron microscopic study of stellate cells and cavities in the pars distalis of frog pituitary

Stellate cells in the pars distalis of adult Rana ridibunda were observed electron microscopically under normal and experimental conditions (TRH injection). The stellate cells have lengthy processes extending into the intercellular spaces between the secretory cells and scanty cytoplasm surrounding the nucleus. Occasional desmosomes link stellate cells to adjacent secretory cells. In the pars distalis of animals injected with thyrotropic-releasing hormone (TRH), the stellate cells form large cavities (2-6 mum) filled with heterogeneous material. Their cytoplasm contains well-developed Golgi complexes and some lysosomes; these are the principal morphological alterations as compared to those observed in control animals. It is suggested that stellate cells could play an active role in addition to providing a structural framework for the pars distalis.     

The pituitary of Aphanius dispar (Rüppell) from hypersaline marshes and freshwater

Summary An ultrastructural study of the rostral pars distalis of the pituitary of Aphanius dispar specimens taken from freshwater or hypersaline marshes revealed significant structural differences which indicate higher activity of the prolactin cells in the hypotonic medium. Prolactin cells from freshwater specimens had larger secretory granules, a higher amount of endoplasmic reticulum, and expanded intercellular spaces with many secretory lakes. These cells contained an unusual cytoplasmic structure, consisting of twisted canals with vesicular lumina, connected to the endoplasmic reticulum of the cell. This structure is about 1–2 m in diameter.Stellate cells are characterized by extracellular spacing junctions which are particularly noticeable at the confluence of the interstellate cell canaliculi and the pericapillary space.Abbreviations FW freshwater - HS hypersaline - NS neurosecretory - PCB paracrystalline body - PNH proximal neurohypophysis - RPD rostral pars distalis - SG secretory granule - SW seawater This paper is dedicated with affectionate respect to Professor Berta Scharrer on the occasion of her 70th birthdayThe assistance of Cynthia Bellon in editing this paper is gratefully acknowledged