Immunocytochemical identification of melanin-concentrating hormone in the brain and pituitary gland of the teleost fishes Oncorhynchus keta and Salmo gairdneri

Summary Melanin-concentrating hormone (MCH) has been purified from the chum salmon pituitary. Its complete amino acid sequence has recently been established. To identify the precise site of origin of MCH, immunostaining was performed in the brain and pituitary gland of the chum salmon and the rainbow trout using a highly sensitive and specific antiserum raised against synthetic MCH. In these two salmonid species immunoreactivity for MCH was detected in neurons and neuronal processes in the pars lateralis of the nucleus lateralis tuberis (NLT) in the basal hypothalamus. Numerous positive-staining processes of these MCH-neurons project to the pituitary gland, extending into neurohypophysial tissues within the pars intermedia and, to a lesser extent, into the pars distalis. No pituitary cells showed cross-reactivity. These results suggest that MCH is biosynthesized in the neurons of the NLT/pars lateralis and released in the neurohypophysis. On the other hand, prominent but less numerous MCH-positive processes could be traced to the pretectal area in which projection of both optic and pineal fibers has been detected using tracers. This observation suggests that the synthesis and/or release of MCH might be under the influence of either of these photosensory neurons. Moreover, the existence of an extrahypothalamic projection from MCH-positive neurons suggests that, in addition to melanin-concentration, MCH might be involved in other neuronal functions, perhaps serving as neuromodulator in the brain.     

Nucleus praeopticus and nucleus lateralis tuberis of Salmo salar and Salmo gairdneri: Structure and relationship to the hypophysis

Summary The nucleus praeopticus (NPO) is located on both sides of the preoptic recess and is composed of a pars parvocellularis and a pars magnocellularis. Only in the rainbow trout does the pars magnocellularis consist of separately located medium-sized cells and very large cells. Cytologically, three cell types can be distinguished: 1) unipolar cells ending in the cerebrospinal fluid (CSF), 2) bipolar cells also ending in the CSF and forming an axon, and 3) multipolar cells which generally do not have a direct connection with the ventricle.Axons originate from the cell bodies forming the paired preopticohypophysial tract that runs along the border of the diencephalon and the optic tract. A considerable number of NPO fibers leading to the hypophysis makes close contact with the cell bodies of the pars lateralis of the nucleus lateralis tuberis, indicating a functional relationship. Most NPO fibers terminate in the caudal part of the neurohypophysis, around blood capillaries and at the basal lamina of the pars intermedia. Far fewer fibers appear to terminate near the boundary of the neurohypophysis and the rostral and proximal pars distalis.The nucleus lateralis tuberis (NLT) is located in the caudal hypothalamus, beginning at the rostral end of the horizontal commissure and extending caudally beyond the hypophysial stalk. It consists of the partes rostralis, medialis, lateralis and ventrolateralis. In both species the p. rostralis contains small subependymal neurons and some larger ones. Only in the p. medialis of the Atlantic salmon are large cells present. In both species the most prominent part is the p. lateralis, which consists solely of large cells. Cells situated between the p. medialis and the p. lateralis are grouped in the p. ventrolateralis. It was impossible to trace the axons originating in the NLT, since the cyto- and axoplasm could not be stained specifically.The structure of the NPO and NLT in the two salmonid species is compared with that of other teleosts.     

Localization of somatostatin mRNAs in the brain and pancreas of rainbow trout (Oncorhynchus mykiss)

Rainbow trout possess three distinct mRNAs, each encoding a separate precursor: PPSS I, which contains a 14-amino acid sequence at its C-terminus (somatostatin-14) that is highly conserved among vertebrates, as well as two others, PPSS II' and PPSS II", both containing [Tyr(7), Gly(10)]-somatostatin-14 at their C-terminus. In this study, we used RNA template-specific PCR and in situ hybridization to determine the distribution and cellular localization of PPSS mRNAs in the brain and Brockmann body of rainbow trout. PPSS I, PPSS II' and PPSS II" were expressed in the Brockmann body and pituitary; the expression of PPSS mRNAs in the brain was region specific. PPSS I mRNA was expressed in the Brockmann body predominantly by cells other than those that expressed PPSS IIs; however, there were several instances where PPSS I and PPSS IIs were co-expressed within the same cell. Of the PPSS II-expressing cells, many were observed to express both PPSS II' and PPSS II" mRNA; however, some cells expressed only PPSS II' mRNA, while other cells expressed only PPSS II" mRNA. In the brain, PPSS I mRNA was expressed in the optic tectum (OT) and in many hypothalamic nuclei, including the nucleus rotundus (NR), nucleus anterioris hypothalami (NAH), nucleus anterior tuberis (NAT), nucleus lateral tuberis (NLT), as well as in the pituitary (adenohypophysis). PPSS II" mRNA was present in the same regions as PPSS I mRNA; however, PPSS II' mRNA was present primarily in OT, NAT, NLT and adenohypohysis. These results indicate that PPSS mRNAs are expressed differently by different cells, suggesting that cell-specific mechanisms are involved with the control of PPSS expression and that particular biological responses may be associated with a specific SS isoform.     

Immunocytochemical localization and ontogenic development of melanin-concentrating hormone in the brain of a pleuronectiform fish,the barfin flounder

Melanin-concentrating hormone (MCH) was first discovered in the pituitary of chum salmon because of its role in the regulation of skin pallor. Later, it was found that MCH could also play a role as a central neurotransmitter or neuromodulator in the brain. However, knowledge of the function of MCH in fish has been restricted to certain fish species. Therefore, in the present study, the immunocytochemical localization and ontogenic development of MCH in the brain of a pleuronectiform fish, the barfin flounder Verasper moseri, were examined to obtain a better understanding of this hormone. In adult barfin flounder, MCH-immunoreactive (ir) neuronal somata were most prevalent in the magnocellular neurons of the nucleus tuberis lateralis (NLT), which project to the pituitary. In the pituitary, MCH-ir fibers were distributed in the neurohypophysial tissues within the pars intermedia and, to a lesser extent, into the pars distalis. MCH-ir neuronal somata were also present in dorsally projecting parvocellular neurons, located more posteriorly in the area above the lateral ventricular recess (LVR). LVR-MCH neurons did not seem to project to the pituitary. In the brain, MCH-ir fibers were detected not only in the hypothalamus but also in areas such as the optic tectum and thalamus. MCH-ir neuronal somata and fibers were not detected on the day of hatching. MCH-ir neuronal somata and fibers were first detected in the hypothalamus and the pituitary, respectively, 7 days after hatching. Subsequently, MCH-ir neuronal somata were observed in the NLT and in the area above the LVR 14 days after hatching. The distribution of MCH-ir neuronal somata and fibers showed a pattern similar to that in the adult fish 35-42 days after hatching. These results indicate that MCH neurons were located in the NLT and in the area above the LVR and that NLT-MCH neurons project to the pituitary. MCH neurons were first detected 7 days after hatching, suggesting that MCH plays some physiological role in the early development of barfin flounder.     

Gene expression and intracellular localization of somatolactin in the pituitary of rainbow trout

The gene expression and intracellular localization of somatolactin (SL), a putative pituitary hormone structurally related to both growth hormone and prolactin, were investigated in the pituitary of rainbow trout, Oncorhynchus mykiss. Using an in situ hybridization technique, we demonstrated the gene expression of the SL molecule in cells bordering the neurohypophysial tissue in the pars intermedia. These cells were identified immunocytochemically as SL-cells on the adjacent section. Electron-microscopic immunocytochemistry by means of the protein A-gold technique, also revealed that the SL-immunoreactivity was located mostly on the secretory granules in SL-cells. Our findings clearly indicate that SL is biosynthesized and stored in the granules in these cells.     

Identification of luteinizing hormone-releasing hormone (LH-RH) in the brain and pituitary gland of a fish by immunocytochemistry.

For the first time immunoreactive luteinizing hormone-releasing hormone (LH-RH) is demonstrated in both the brain and pituitary gland of a teleost (Xiphophorus maculatus) using an immunoperoxidase procedure. It is specifically localized in the perikarya and their axons of the ventral telencephalon and nucleus lateralis tuberis and within and between the gonadotrops and within some cells of the pars intermedia. These immunoreactions are extinguished when antiserum to LH-RH is preincubated with LH-RH antigen but not with neurohypophysial hormones.     

Hypophysiotropic neurons in the goldfish hypothalamus demonstrated by retrograde transport of horseradish peroxidase

Summary The horseradish-peroxidase (HRP) technique was used to visualize the cell bodies of axons projecting to the goldfish pituitary. Following intravenous injections of HRP, HRP reaction products were observed in axons of the rostral pars distalis, proximal pars distalis, neurointermediate lobe, pituitary stalk and in axons coursing from the pituitary into the hypothalamus. HRP-labelled cells in the brain were localized in two regions only — the nucleus preopticus (NPO) pars magnocellularis and pars parvocellularis, and the nucleus lateralis tuberis (NLT) of the hypothalamus. These observations suggest that the NPO and NLT are the source of the neurosecretory innervation of the goldfish pituitary.     

Aminergic Innervation of the Cranial and Caudal Neurosecretory Systems in the Teleost Gillichthys mirabilis

Abstract Numerous fluorescent varicosities surround most of the caudal neurosecretory neurons and also regularly occur among pars intermedia cells of the adenohypophysis in the teleost, Gillichthys mirabilis. The color of the varicosities, as well as their responses to pharmacological treatments, is diagnostic of catecholaminergic neurons and processes. No fluorescence characteristic of monamines is found in the rostral pars distalis, in the proximal pars distalis or in the cells of the nucleus lateralis tuberis (NLT), although fluorescent varicosities are found within the ventral hypothalamus in the vicinity of the NLT. Bilateral clusters of fluorescent cell bodies are located in the ventral hypothalamus (posterior to the NLT); some of these cells border the neurohypophysis. Fluorescent tracts from these cell clusters extend to a pair of elongate nuclei of nonfluorescent neurons which are surrounded by fluorescent varicosities. Alteration of osmotic conditions did not effect the fluorescence, except for the caudal neurosecretory cells of fish exposed to fresh water for long periods. Adrenergic nervous input thus seems to be an important component of both the cranial and caudal neurosecretory systems.     

Galanin-like immunoreactivity in the brain and pituitary of the "four-eyed" fish, Anableps anableps

The distribution of galanin (GAL)-like immunoreactivity was investigated in the brain and pituitary of the "four-eyed" fish, Anableps anableps. GAL-immunoreactive (GAL-ir) perikarya were located in the area ventralis telencephali pars supracommissuralis, nucleus preopticus periventricularis, nucleus preopticus pars parvocellularis, nucleus preopticus pars magnocellularis, nucleus lateralis tuberis ventralis, nucleus lateralis tuberis lateralis, and nucleus lateralis tuberis posterior. A few scattered, GAL-ir neurons were also observed in or adjacent to the nucleus recessus lateralis, nucleus recessus posterioris and lobus facialis (VII). GAL-ir fiber networks were widespread in the brain, with a comparatively higher density in the ventral telencephalic, preoptic and infundibular regions. The neurohypophysis showed GAL-ir innervation and there were GAL-ir cells in the adenohypophysis. The presence of GAL-ir cells in the hypothalamus and in the pituitary is an important asset for the supposed role of GAL-like peptide in neuroendocrine regulation of brain and pituitary functions.     

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.     

The nucleus preopticus and the nucleus lateralis tuberis in the roach,Leuciscus rutilus

Summary The hypothalamus of the teleost fish Leuciscus rutilus was investigated with the Falck-Hillarp technique. The nucleus preopticus (NPO) and the nucleus lateralis tuberis (NLT) contain no fluorescent, i.e. catecholaminergic cells. Green fluorescent fibers probably originating from the paraventricular organ and/or the preoptic recess organ, are intermingled with the cells.The electron microscopical study was based on the three fixatives glutaraldehyde-osmium tetroxide, osmium tetroxide and potassium permanganate. In the NPO two cell types are recognized, characterized mainly by dense core vesicles (dcv) with measured diameter of 130 nm and 170 nm across respectively. The endoplasmic reticulum in the former cell type generally has large dark inclusions measuring from 175 to 375 nm across, which are also found in the neurite. In the NLT, four different cell types are identified, some of which are subject to considerable variations. The rostral and the medial parts of the nucleus include a large cell type (I) with dcv of diameter 170 nm. The medial part also has a small cell type (II) with dcv of 80 nm. The lateral part is characterized by two cell types (III, IV). Cell type III occurs in three forms with dcv of about 140 nm. The fourth cell type (IV) is rare and contains irregularly formed granules, the most circular ones measuring about 130 nm and the most elongated ones 110 nm×210 nm. The ventrolateral part contains the same cell types (except for type II) as those found in the lateral and medial parts.The morphological differentiation of the NLT as well as its different cell types strongly indicates its functional diversity.After permanganate fixation the secretory granules of the different cell types in the NPO and the NLT appear as empty vesicles. This method also reveals that the cell types of the two nuclei have dcv of about 90 nm. The possible monoaminergic content and the role of these dcv are discussed.Supported by grants from the Swedish Natural Science Research Council (No 2502-1-7).I should like to express my gratitude to Doctor Gunnar Fridberg for initiating this work and for many stimulating discussions.     

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.     

Cellular localization of somatolactin in the pars intermedia of some teleost fishes

Summary We report here on the cellular localization in the fish pituitary of somatolactin (SL), a putative new pituitary hormone related to growth hormone and prolactin, which has been recently identified in the piscine pituitary gland. Immunocytochemical staining, using anti-cod SL serum, revealed that in the cod pituitary gland, SL is produced by cells in the intermediate lobe, bordering the neural tissue. These cells, staining weakly with periodic-acid-Schiff (PAS), are distinct from the melanocyte stimulating hormone (MSH) cells which, as in all teleosts, are PAS-negative. SL-immunoreactivity was observed in the same location in all other teleost species examined: flounder, rainbow trout, killifish, molly, catfish and eel. In most fish the SL-immunoreactive cells are either strongly or weakly PAS-positive but in rainbow trout are chromophobic, indicating that the SL protein can probably exist in glycosylated and non-glycosylated forms. Thus, in demonstrating the cellular localization of SL, this study provides the first identification of the enigmatic, second cell-type of the fish pars intermedia.     

Liquorkontaktneurone im Nucleus lateralis tuberis von Fischen

Zusammenfassung Der Nucleus lateralis tuberis (NLT) von Fischen wurde licht- und elektronenmikroskopisch untersucht. Beim Karpfen senden die ventromedialen Zellen des Kernes Fortsätze in das Lumen des 3. Ventrikels, wo sie auffallend große, knopfförmige, aus einer inneren und äußeren Zone bestehende Liquorkontakt-Nervenendigungen bilden. Zwischen den Zellen des NLT liegen bedeutend kleinere Neurone, deren kleine, freie, dense-core Vesikel enthaltende, zilientragende Nervenendigungen den Liquor cerebrospinalis erreichen.Die äußeren Zonen der Liquorkontakt-Nervenendigungen des NLT besitzen ein außerordentlich gut entwickeltes endoplasmatisches Retikulum, dessen flache, mit Ribosomen besetzte Cisternen sich parallel zur Oberfläche der Endigung ausdehnen. In der inneren Zone des Endkolbens können neben verstreuten endoplasmatischen Cisternen Golgi-Felder und zahlreiche Mitochondrien beobachtet werden. Die Endigung enthält neurosekretorische Elementargranula (Durchmesser 1,300—1,900 Å) in wechselnder Menge und einzelne Neurotubuli.Im Lumen des 3. Ventrikels treten ferner Katecholamingranula-haltige Neuriten auf, die mit den Liquorkontaktendigungen des NLT mehrfach Synapsen bilden. Der präsynaptische Bereich ist durch synaptische (400–550 Å) und granulierte Vesikel (600–800 Å) charakterisiert. Ähnliche Synapsen werden auf den neurosekretorischen Perikaryen und ihren Fortsätzen beschrieben. In den ausgedehnten Golgi-Feldern der Perikaryen des NLT findet man Zeichen einer Sekretbildung. Aufgrund der morphologischen Daten wird der kammernahe Teil des NLT als ein Gebiet des Liquorkontakt-Neuronensystems angesehen. Die mutmaßliche Bedeutung der Liquorkontakt-Nervenendigungen wird diskutiert.

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Liquor contacting neurons in the nucleus lateralis tuberis of fishes

Summary The nucleus lateralis tuberis (NLT) of fishes was studied light- and electron microscopically. In the carp, the ventromedial cells of the nucleus send processes into the lumen of the 3rd ventricle where they form strikingly large, club-shaped liquor contacting nerve endings built up of an inner and outer zone. Smaller neurons situated between the cells of the NLT, form small, ciliated, free, dense-core vesicles containing nerve endings in the cerebrospinal fluid.The outer zone of the liquor contacting terminals of the NLT contains an extraordinarily well developed endoplasmic reticulum which flat, rough cisternae run parallel to the surface of the terminal. In the inner zone of the nerve ending, Golgi areas and numerous mitochondria can be observed besides of scattered endoplasmic cisternae. The terminal contains neurosecretory granules (1,300–1,900 Å) of various amounts, and some neurotubules.Furthermore, in the lumen of the 3rd ventricle, there occur neurites containing catecholamine granules. These axons form repeatedly synapses with the liquor contacting terminals of the NLT. The presynaptic cytoplasm is characterized by synaptic (400–550 Å) and densecore vesicles (600–800 Å). Similar synapses occur on the neurosecretory perikarya and their processes. The extensive Golgi region of the perikarya of the NLT shows equivalents of secretory activity. On the basis of the morphological data, the part of the NLT situated near the ventricle is considered as to belong to the liquor contacting neuronal system. The presumable significance of the liquor contacting nerve endings of the NLT is discussed.

     

Nucleus tuberis lateralis in the human brain. A pigmentarchitectonic study]

In the present article the shape of the nucleus tuberis lateralis and a hitherto unknown cell group in the human hypothalamus is described. Neurolipofuscin is selectively stained with aldehyde-fuchsin. This method enables the exact determination of the three dimensional shape of a griseum by using slices more than 500 mum thick. Differences in the distribution and amount of pigment within different types of nerve cells provide a basis for cellular demarcation and subdivision (pigmentarchitectonics). The intensely stained nucleus tuberis lateralis can be seen as consisting of a main lateral and a medial group. There are elevan cell groups which constantly occur. The individual range of their shapes causes a great variation in the shape of the lateral tuberal nucleus. It also has portions in the medial field of the hypothalamus: a pars suprafornicalis and 'mediale Streuzellen' ('medial scatter-cells'). Rostrally it extends almost to the chiasma with scattered irregularly occurring groups of cells. The amount of intracellular lipofuscin depends on the respective cell group and the age of the brain. By the age of 12 years the nucleus is already more intensely pigmented than the surrounding grisea. There is an indication of a tendency towards an aggregation of the cell groups with age. Connections between pigmentation and the phylogeny are discussed. Ventrally the nucleus tuberis lateralis is bounded by a hitherto undescribed heteromorphous cell group. It is clearly delimited and can be divided into a longish pars lateralis and a spherical pars medialis. Both parts consist of small as well as medium-sized cells which accumulate diffusely distributed granula of lipofuscin in adult brains. The name 'nucleus paratuberalis' is suggested for this griseum.     

Immunocytochemistry of somatotrophs,gonadotrophs, prolactin and adrenocorticotropin cells in larval sea bream (Sparus auratus) pituitaries

Summary The chronological appearance of endocrine cells in the pituitary of sea-bream (Sparus auratus) larvae was studied using antisera against salmon prolactin, trout growth hormone, salmon gonadotropin and N-terminal human adrenocorticotropin. The larval pituitary (1–12 days after hatching) was oval in shape and was composed of a dense mass of cells with few neurohypophysial fibres. By 60 days after hatching it began to resemble the adult and was divisible into a distinct rostral pars distalis containing prolactin and adrenocorticotropin cells; a proximal pars distalis containing somatotrophs and gonadotrophs and a pars intermedia. Cells immunoreactive with antisera against growth hormone were observed immediately after hatching (2 days post-fertilization). Weakly staining prolactin cells were observed 2 days later in the region corresponding to the rostral pars distalis. Cells immunoreactive with anti-gonadotropin and anti-adrenocorticotropin sera were observed in the pituitary 6 and 8 days after hatching, respectively. All the cell-types studied were immunoreactive from the time they were first identified until the final samples 90 days after hatching.     

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.     

Proopiomelanocortin (POMC)-related peptides in the brain of the rainbow trout, Salmo gairdneri

We have investigated the presence of ACTH, -MSH and β-endorphin, three peptides which derive from the multifunctional precursor protein proopiomelanocortin (POMC) in the brain of the rainbow trout Salmo gairdneri. Using both the indirect immunofluorescence and peroxidase-antiperoxidase techniques, a discrete group of positive cells was identified in the hypothalamus, within the anterior part of the nucleus lateralis tuberis. -MSH-containing neurons represented the most abundant immunoreactive subpopulation. Coexistence of -MSH, ACTH and β-endorphin was observed in the lateral part of the nucleus. ACTH- and β-endorphin-containing cells were mainly distributed in the rostral and caudal regions of the nucleus. In the medial portion of the nucleus lateralis tuberis, numerous cells were only stained for -MSH. Moderate to dense plexuses of immunoreactive fibers were observed in the ventral thalamus and the floor of the hypothalamus. Some of these fibers projected towards the pituitary. The concentrations of ACTH, -MSH and β-endorphin-like immunoreactivities were measured in microdissected brain regions by means of specific radioimmunoassays. Diencephalon, mesencephalon and medulla oblongata extracts gave dilution curves which were parallel to standard curves. The highest concentrations of POMC-derived peptides were found in the diencephalon (-MSH: 4.28±0.43 ng/mg prot.; ACTH: 1.08±0.09 ng/mg prot.; β-endorphin: 1.02±0.1 ng/mg prot.), while lower concentrations were detected in the mesencephalon, medulla oblongata and telencephalon. The present results demonstrate that various peptides derived from POMC coexist within the same cell bodies of the fish hypothalamus. Taken together, these data suggest that expression and processing of POMC in the fish brain is similar to that occurring in pituitary melanotrophs.     

Demonstration of gonadotropic cells in the adenohypophysis (pars distalis and pars tuberalis) of the monkey Macacus irus. Immunofluorescence study using human anti-beta-FSH and ovine anti-beta-LH antibodies

Indirect immunofluorescence technique with anti-beta FSH and anti-beta oLH antisera has allowed us to detect "gonadotropic cells" in the pars distalis and in the pars tuberalis of the adenohypophysis of the monkey Macacus irus. In the pars distalis, 85-90 % of the "gonadotropic cells" react simultaneously with these two antisera ; 10-15 % of these cells react only either with anti-beta hFSH or anti-beta oLH antisera. The gonadotropic cells are dispersed in the whole pars distalis, amid the other cellular types ; indeed, in the female, there is a "gonadotropic zone" in the median zone of the lateral lobes of the gland. In the pars tuberalis, we have observed "gonadotropic cells" which react only with anti-beta oLH antiserum. These results are compared with observations of some authors.