The rostral pars distalis of the pituitary gland of the freshwater and marine alewife (Alosa pseudoharengus)

Summary In the alewife the orohypophyseal duct, a remnant of Rathke's pouch, persists in adults as a tube passing from the rostral pars distalis to the pharyngeal region. Its lumen is not open to the buccal cavity. The prolactin cells are situated around the bifurcations of this duct in the rostral pars distalis. Contents from prolactin cells, such as granules, nuclei, mitochondria and Golgi structures were found in these bifurcations. These contents were indistinguishable from those of intact prolactin cells. Evidence of actual release into the duct was often noted. At the presumptive point of release, the cells lining the lumen separate and the contents, probably of an entire prolactin cell, are extruded. The cilia usually found at the point of extrusion arise from prolactin cells. The prolactin cells of freshwater fish were more heavily granulated than those from a marine environment. Prolactin cells of fish entering freshwater streams were not heavily granulated but showed evidence of increased activity. Granule size was not affected by salinity. The ACTH cells are arranged in bands along branches of the neurohypophysis in the rostral pars distalis. No differences in ACTH cells from fish of different salinities were noted.We would like to thank Mr. D. D. Zumwalt of the John G. Shedd Aquarium in Chicago, Dr. E. D. Warner, Mr. R. L. Flayter, Dr. J. G. Stanley of the University of Wisconsin, Milwaukee, Mr. L. Wells of the U. S. Fish and Wildlife Service, Great Lakes Fisheries Laboratory, Ann Arbor, and Mr. L. N. Flagg of the Department of Sea and Shore Fisheries, Augusta, Maine, for their assistance in obtaining the fish used in this study. Dr. T. N. Tahmisian and Mr. G. T. Chubb of Argonne National Laboratories, and Dr. L. M. Srivastava and Dr. V. Bourne of Simon Fraser University, Canada, kindly made electron microscope facilities available. Finally, we wish to thank Mr. W. Goossens and Mr. D. J. DeJong for valuable assistance. This project was supported by a grant from the National Marine Fisheries Service.     

The goldfish pituitary

Summary In the goldfish, Carassius auratus, morphological and functional aspects of the pituitary gland were studied at the ultrastructural level and six cell types could be distinguished in the pars distalis. Acidophilic cells of the rostral pars distalis were identified as prolactin cells, the chromophobic cells of the rostral pars distalis as ACTH cells, the non-globular basophilic cells of the rostral and the proximal pars distalis as TSH cells, the globular basophils of the proximal pars distalis as gonadotropic cells and the acidophils of the proximal pars distalis as somatotrophs.Besides some of the well established criteria of morphological and functional identification of different cell types, two new approaches have been used in the present study. One was to express the electron density of secretory granules objectively by means of a photometric method. It was found that both types of acidophilic cells which produce the proteohormones prolactin and somatotropin respectively, had granules with the highest electron densities. The basophilic cells producing the glycoproteins gonadotropin and TSH respectively, possessed granules of intermediate electron density whereas the chromophobic cells storing the peptide hormone ACTH had granules of lowest densities. The second new approach was the administration of the synthetic mammalian releasing hormones LH-RP and TRF, which helped in identifying gonadotropic and thyrotropic cells respectively. In the goldfish there is evidence for the presence of only one type of gonadotropic cell.Supported by a grant of the Science Research Council of Great Britain to Professor Sir Francis Knowles, F.R.S. The electron microscope used was provided by the Medical Research Council of Great Britain. The integrating photometer IPM2 was kindly on loan from Messrs. Carl Zeiss, Oberkochen, Germany. For technical advice we are greatly indebted to Mr. P. K. Kaul, B. E., M.I. Struct. E., C. Eng.     

Immunocytochemical identification and ontogeny of adenohypophyseal cells in a cave fish,Phreatichthys andruzzii (Cypriniformes: Cyprinidae)

The morphogenesis of the pituitary gland and the chronological appearance of adenohypophyseal cells were investigated for the first time in the Somalian cave fish Phreatichthys andruzzii by immunocytochemistry. The adult adenohypophysis contained: a rostral pars distalis, with prolactin (PRL) cells arranged in follicles and adrenocorticotropic (ACTH) cells, a proximal pars distalis with somatotropic (GH), β‐thyrotropic (TSH), β‐gonadotropic type I (FSH) and type II (LH) cells and a pars intermedia with α‐somatolactin (SL), α‐melanotropic (MSH) and β‐endorphin (END) cells. All regions were deeply penetrated by neurohypophyseal branches. At hatching (24 h post‐fertilization) the pituitary was an oval cell mass, close to the ventral margin of diencephalon. The first immunoreactive cells appeared as follows: PRL at 0·5 days after hatching (dah), GH and SL at 1·5 dah, END at 2 dah, TSH, ACTH and MSH at 2·5 dah, FSH at 28 dah and LH at 90 dah. The neurohypophysis appeared at 5 dah and branched extensively inside the adenohypophysis at 130 dah, but there was no boundary between rostral pars distalis and proximal pars distalis at this stage. The potential indices of prolactin and growth hormone production increased until 28 and 60 dah, respectively. The potential index of growth hormone production correlated positively with total length. Activity of PRL and GH cells, measured as ratio of cell area to nucleus area, was significantly higher in juveniles than in larvae.     

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.     

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.     

Histology of the pituitary gland of the grey mullet, Mugil cephalus L.

The present communication deals with a histological study of the pituitary gland of the teleost fish Mugil cephalus , found in the estuarine waters of Cochin area. Six different cell types were identified in the pituitary gland on the basis of their grouping, distribution and staining properties. The prolactin and the TSH cells (thyroid stimulating hormone producing cells or thyrotrops) were identified in the rostral pars distalis and the ACTH cells (adrenocorticotropic hormone producing cells or corticotrops) in the interphase between the neurohypophysis and the rostral pars distalis. The STH cells (somatotropic hormone producing cells or somatotrops) and the gonadotropic cells were distinguished in the proximal pars distalis and the MSH cells (melanin stimulating hormone producing cells or melanotrops) in the pars intermedia.     

The influence of social rank on adenohypophysial cell activity in Salmo irideus

Summary In nine cell types of the adenohypophysis in untreated adult rainbow trout, histologically different activity phases, seasonal changes in activity, and the relation between certain cell types and the interrenal gland, thyroid or gonads were investigated by light and, occasionally, by electron microscopy. Special attention was given to the effect of social rank on the synthetic activity in adenohypophysial cells of trout kept in small groups in which a social hierarchy with one (light) dominant and several (dark) submissives is established.Cell types in the rostral pars distalis were azocarminophil (I) or amphiphil (II). Proximal pars distalis cell types were slightly basophil (IV), orangeophil (V), strongly basophil (VI) or chromophobe (VII). In the pars intermedia, cell types were amphiphil (VIII) or very slightly basophil (IX). Type III was a non-secretory supporting (?) cell.Histologically different activity phases abounded in type IV cells, which mainly occurred in the proximal pars distalis but were also found dispersed in the rostral pars distalis, the pars intermedia and the neurohypophysis.Influences of social rank were pronounced in type IV cells. Phases with a high synthetic activity were exclusively found in submissive animals, phases with a low synthetic activity occurred in dominants. As a positive relation existed between type IV cell activity and the social rank dependent activity of the interrenal gland, it was suggested that type IV cells produce ACTH.In (dominant) male trout treated with DOCG or ACTH, colloid-containing type IV cell phases, reflecting accumulation of the secretory product, were found. This supported the earlier suggestion that ACTH in the trout is produced in the basophil type IV cells and not, as reported in the literature, in cells comparable to type II.The author is greatly indebted to Miss M.C. Wentzel, Miss I. Stulen, Mr. J. Veening and Dr. J.G. van Rhijn for their help with histological techniques, interrenal cell measurements and statistical aspects     

Structure of the nongranulated cells in the hypophyseal rostral pars distalis of cyclostomes and actinopterygians

Summary The structure of the nongranulated cells in the sea lamprey adenohypophysis and similar cells of the rostral pars distalis in a number of actinopterygian fishes was examined with the aim of determining the role(s) of these cells in pituitary function.A number of possible roles are proposed for the nongranulated cells. In salmonids and Amia calva the cells may be involved in the active movement of material into or from the follicle lumina. The structure of the nongranulated cells in in vitro cultured and in in vivo transplanted trout rostral pars distalis also suggests a phagocytotic role for these cells. In teleosts with a non-follicular rostral pars distalis the nongranulated cells appear to play roles in the release of granules from the prolactin cells and in the subsequent dispersal of the hormone (and/or carrier substance) into the peripheral circulation.We wish to thank Dr. B.I. Baker who performed the trout pituitary in vitro cultures and Professor M. Hyder who was closely involved with the collection of the Tilapia specimens. We also wish to thank Mr. R. Lindsay and Mrs. L. Lin for their technical assistance and Drs. F.W.H. Beamish and R. Sonstegard for their help in supplying some of the animals used in this study. —The work was supported in part by a grant-in-aid of research from the National Research Council of Canada to J.F.L. and in part by a negotiated NRC grant. The paper is number 138 in the physiology of migration series.     

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 neurohypophysis of the teleost Poecilia latipinna in relation to neural control of the adenohypophysial cells

Summary The structure of the neurohypophysis of Poecilia latipinna (green molly, sailfin molly) was studied with the electron microscope. Profile diameters of neurosecretory granules in the non-myelinated neurohypophysial nerve fibres were measured and mathematically corrected for error due to section thickness. Six different types of nerve fibres could be distinguished by statistical classification of their granules and by other ultrastructural features. One fibre-type (type B) contained granules with a mean diameter of 85 nm, and the other five types (types Ala, Alb, A2, A3 and A4) all contained granules with mean diameters greater than 100 nm. Synaptic contacts were observed between type B fibres and all the adenohypophysial cell-types, although in the case of the ACTH cells the synapses were separated from the cell membrane by a continuous double basement membrane. Type A fibres were observed to contact the cells of the proximal pars distalis and pars intermedia, but did not form synapses. However, synapses occurred between type A fibres and pituicytes, and between type A fibres and the pericapillary basement membrane in the interior of the neurohypophysis. The possible roles of the different types of nerve fibres in controlling the adenohypophysial cells are discussed in the context of evidence from other teleosts.We thank Mr. W.A. Thomson and Mr. D.I. Hollingworth for technical assistance, and Dr. D.I.C. Pearson (Department of Physics, University of Nancy, Nancy, France) for advice on mathematical analysis and computer programs. The work was carried out during the tenure of an S.R.C. Research Studentship by T.F.C.B.     

乌脑龟垂体显微及其腺垂体超微结构的研究

乌龟脑垂体由柄形神经垂体和椭圆形腺垂体两部分组成,神经垂体位于腺垂体后部上方呈背腹型排列。神经垂体中神经叶不发达,腺垂体分为远侧部和中间部,特殊空泡结构成为垂体门脉系统的特征。远侧部细胞分为嗜酸性细胞、嗜碱性细胞和嫌色细胞3种。通过透射电镜观察,腺垂体远侧部主要有5种分泌激素细胞：即生长激素（GH）分泌细胞、催乳激素（PRL）分泌细胞、促甲状腺激素（TSH）分泌细胞、促肾上腺皮质激素（ACTH）分泌细胞、促性腺激素（GTH）分泌细胞和非分泌类型滤泡．星形细胞（Fs）。生长激素分泌细胞核大、分泌颗粒少的特征成为乌龟与其他动物最大的区别,可能与乌龟具有生长慢、寿命长的生物学特性有关。     

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.     

乌龟脑垂体显微及其腺垂体超微结构的研究

乌龟脑垂体由柄形神经垂体和椭圆形腺垂体两部分组成,神经垂体位于腺垂体后部上方呈背腹型排列。神经垂体中神经叶不发达,腺垂体分为远侧部和中间部,特殊空泡结构成为垂体门脉系统的特征。远侧部细胞分为嗜酸性细胞、嗜碱性细胞和嫌色细胞3种。通过透射电镜观察,腺垂体远侧部主要有5种分泌激素细胞:即生长激素(GH)分泌细胞、催乳激素(PRL)分泌细胞、促甲状腺激素(TSH)分泌细胞、促肾上腺皮质激素(ACTH)分泌细胞、促性腺激素(GTH)分泌细胞和非分泌类型滤泡-星形细胞(FS)。生长激素分泌细胞核大、分泌颗粒少的特征成为乌龟与其他动物最大的区别,可能与乌龟具有生长慢、寿命长的生物学特性有关。       

Structure of the adenohypophysis in juvenile harp seal,Pagophilus groenlandicus

Summary A study was made of the morphology of the adenohypophysis in immature harp seals and the fine structure of cellular components of the pars tuberalis, pars intermedia and pars distalis was described.The pars intermedia composed 8–15% of the hypophysis and contained colloid filled vesicles similar to those found in the other mammalian species.The pars distalis cells were grouped into more or less well defined regions, thus facilitating the correlation of cellular identification from both light and electron micrographs. Five chromophilic cell types were tentatively identified, one acidophil (putative somatotroph), four basophils (3 putative gonadotrophs and one cell type with the characteristics of both corticotrophs and thyrotrophs) and non-granulated stellate cells. The absence of a positive prolactin cell identification was thought to be due to the immaturity of the seals used in the study.The mercury exposure experiment was supported by a contract grant from the Halifax Laboratory of Fisheries and Marine Service. Drs. Uthe and Freeman of that laboratory also carried out the methyl mercury analyses. We recognize the support in maintaining the seals provided by Mrs. C. Rae, Mrs. H. Pedersen, Mr. S. Tessaro and Dr. J. M. Terhune. We also wish to thank Mrs. L. Lin for her technical assistance. Further financial support was provided through operating and development grants. The paper is number 134 in the physiology of migration series     

The Pituitary Gland of the Roach Leuciscus rutilus

Three different endocrine cell types were identified by electron microscopy in the rostral pars distalis (RPD) of the roach, Leuciscus rutilus. The cells which are characterized by the morphology and sizes of their secretory granules are assumed to secrete prolactin, ACTH and TSH. Prolactin cells occur in two forms which could be separated on account of the sizes of their granules. Intra-peritoneal injections of reserpine had a strong and persistent effect 24 hours after the treatment. The prolactin cells with small granules reacted with a marked release of secretion. The border of the RPD is composed of a so-called double basement membrane in contact with the perivascular spaces and forms extensive ramifications into the rostral neurohypophysis (RNH). Nerve fibers of different categories terminate at the border and its network in the RNH. Substances released from these terminals may influence the endocrine cells of the RPD. The ACTH cells and the prolactin cells are innervated by axons with granules less than 100 nm. The nomenclature of type ‘A’ fibers and ‘B’ fibers is discussed because it was difficult to make a reliable discrimination of the fibers and their nature by the sizes of their granules. However, four types of nerve fibers were distinguished in connection with the RPD although the presence of more types was indicated. In all four types the size variations of the granules are great and overlapping. The average sizes of the granules in these fibers are 157, 114, 119 and 81 nm. The origin of the nerve fibers innervating the RPD is discussed. All morphological data indicate a complex hypothalamic control of the RPD of the roach.     

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.     

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.     

Ultrastructure of the pituitary gland (pars distalis) in sockeye salmon (Oncorhynchus nerka) during gonad maturation

Summary The fine structure of the various hormone-producing cell types (with the exclusion of the prolactin cells) in the pituitary gland (pars distalis) of migratory sockeye salmon is described. All fish were in an advanced stage of sexual maturation. In the proximal pars distalis five cell types were distinguished: growth hormone cells, ACTH cells, gonadotrops, vesicular cells, and chromophobe cells. Gonadotrops were also found throughout the rostral pars distalis. A conspicuous feature of the gonadotrops was the presence of two kinds of secretory inclusions: small electron-dense granules (200–375 m) and large, relatively electron-translucent globules (400–2 000 m). The large vesicular cells, so called because of their conspicuous vesicular endoplasmic reticulum, were numerous and often appeared to contain some small granules. It is argued that they may represent a second type of gonadotropic cell, which, in earlier stages of gonad development, contains many granules but becomes largely degranulated near the time of reproduction when the other gonadotrops (globular gonadotrops) abound. The chromophobes, which were smaller and far less abundant than the vesicular cells, also appeared to contain small granules (120–280 m). They are probably thyrotrops.The assistance of Mr. S. Killick, of the International Pacific Salmon Fisheries Commission, who helped in the collection of salmon, is gratefully acknowledged.     

The utility of antisera to different synthetic adrenocorticotrophins (ACTH) and melanotrophins (MSH) for immunocytochemical staining of the dog pituitary gland

Using the immunoperoxidase technique and specific antisera to synthetic ACTH beta (1-24), ACTH beta (17-39) and bMSHbeta1, selective immunocytochemical staining was localized in a distinctive cell type in the pars distalis and pars tuberalis of the dog pituitary gland. Except for a rare cell, the pars distalis and pars tuberalis did not stain with an anti-bMSH alpha serum. In the pars intermedia immunoreactive cells containing ACTH beta(1-24), ACTHbetap(17-39), bMSHbeta and/or bMSH alpha were observed. The specificity and validity of the antisera were demonstrated by elimination of their immunostaining capacity after prior absorption with their respective antigens, while absorption with other antigens failed to decrease staining intensity. The cytoplasm of the ACTH/MSH cells showed a positive reaction to periodic-acid-Schiff and assumed a pale aniline blue colour, whilst the granules were stained with carmoisine L and acid alizarine blue. These ACTH/MSH cells were further differentiated from other functional cell types of the pars distalis on the basis of their typical cytological features, intraglandular distribution and by immunochemical double staining. It is concluded that ACTH and MSH beta were present and most probably produced by the corticomelanotrophs of the pars distalis and pars tuberalis. In addition to corticomelanotrophs analogous to those of the pars distalis and pars tuberalis, the pars intermedia showed many cells which contain MSH alpha alone or together with MSH beta and/or ACTH.     

Immunocytochemical characterization of adenohypophyseal cells in the greater weever fish (Trachinus draco)

The adenohypophysis of the greater weever fish (Trachinus draco) was studied using histochemical and immunocytochemical methods. The adenohypophysis comprised the rostral pars distalis (RPD), the proximal pars distalis (PPD), and the pars intermedia (PI). Neurohypophysis showed a patent hypophyseal stalk which was divided into several branches intermingled with the adenohypophysis. Salmon prolactin (PRL)-immunoreactive (ir) cells, arranged in follicles, resided in the RPD and the most rostral part of the ventral PPD. Human adrenocorticotropin (ACTH)-ir cells were located in the RPD between PRL-ir cells and the neurohypophyseal processes. Salmon and seabream somatotropin (GH)-ir cells were located in both the dorsal and the ventral PPD. Some GH-ir cells were seen in surrounding and in contact with neurohypophyseal branches, whereas other isolated or clustered GH-ir cells were embedded in adenohypophyseal cells of the PPD. In addition, isolated or clustered GH-ir cells were also detected in the tissue of the PPD covering the most rostral part of PI. Only one class of salmon and carp gonadotropin (GTH)-ir cells was detected. Isolated or clustered GTH-ir cells resided in both the dorsal and the ventral PPD and were seen surrounding the PI and in the tissue of the PPD covering the most rostral part of PI. In addition, a few scattered GTH-ir cells were observed in the ventral RPD. Scattered groups of thyrotropin (TSH)-ir cells were present in the anteroventral PPD. Salmon and seabream somatolactin (SL)-ir and bovine melanotropin (MSH)-ir cells were intermingled surrounding the neurohypophyseal tissue. SL-ir cells were negative to periodic acid-Schiff technique. MSH-ir cells showed a very weak immunoreactivity to anti-human ACTH((1-24)) serum. In addition to the PI location, few isolated or clustered SL- and MSH-ir cells were observed in the dorsal PPD.