Tanycyte and vascular patterns in the basal hypothalamus of Coturnix quail with reference to their possible neuroendocrine significance

Summary A well developed system of ependymal glial cells with long basilar processes stretching to the surface of the brain (tanycytes, Horstmann, 1954) has been described in the basal hypothalamus of Coturnix quail. The tanycytes both in the median eminence and the ventro-lateral hypothalamus form a link between the third ventricle and the hypophysial circulation. The processes of the ventro-lateral tanycytes terminate in the region of the infundibular sulcus in apposition to a loose network of vessels which are continuous with the primary plexus of the hypophysial portal system.Within the median eminence, the subependymal capillary network connects the vasculature of the contra-lateral sides of hypothalamus. There are no direct connections with the hypophysial portal vessels.With the aid of the light and electron microscope the ventricular ependyma was divided into a dorsal typical region and two glandular regions (ventro-lateral and ventral). Each region contains different forms of tanycyte. One of the two forms of tanycyte (designated type 3) associated with the ventro-lateral glandular ependyma has no contact with the third ventricle.Ultrastructural studies on the glandular ependyma failed to show any obvious differences between castrated, oestrogen or testosterone implanted, and sexually mature or immature quail.The possibility that the tanycyte-vascular system may have a neuroendocrine role is discussed.I am indebted to Professor A. Oksche, Dept. of Anatomy, University of Giessen for providing research facilities and to The Royal Society for additional financial support.     

Cytoarchitectonic pattern of the hypothalamus in the turtle,Lissemys punctata granosa

Summary In the hypothalamus of the turtle, Lissemys punctata granosa, two magnocellular and 23 parvocellular neuronal complexes can be distinguished. The magnocellular complexes include the nucleus supraopticus and the nucleus paraventricularis; paraventricular neurons are partly arranged in rows parallel to the third ventricle. Most infundibular parvocellular nuclei display neurons disposed in rows parallel to the ventricular surface. In the preoptic region, the prominent parvocellular neuronal complexes encompass the nucleus periventricularis anterior, lateral preoptic area, the nucleus of the anterior commissure and the nucleus suprachiasmaticus. The prominent nucleus periventricularis posterior extends caudad and shows neurons arranged in vertical rows parallel to the third ventricle. Other parvocellular nuclei of the rostral hypothalamus are composed of clustered subunits. The nucleus arcuatus is a fairly large nuclear entity extending from the level marked dorsally by the nucleus paraventricularis to the area occupied by the nucleus of the paraventricular organ. A well-developed ventromedial nucleus is located ventrolateral to the paraventricular organ. The prominent paraventricular organ consists of tightly arranged neurons, some of which possess apical projections into the third ventricle; it is surrounded by the nucleus of the paraventricular organ. Nucleus hypothalamicus medialis et lateralis, nucleus hypothalamicus posterior and the nuclei recessus infundibuli are further nuclear units of the tuberal region. The caudal end of the hypothalamus is marked by the nucleus mamillaris; its neurons are scattered among the fibers of the retroinfundibular commissure. The median eminence is well developed and shows a large medial and two lateral protrusions into the infundibular recess.     

The distribution of nuclear progesterone receptor in the hypothalamus and forebrain of the domestic hen

Summary Cell nuclei containing progesterone receptor were identified immunohistochemically in the hypothalamus and forebrain of the domestic hen using an antiserum to the steroid binding B subunit (110 kDa) of chicken oviduct progesterone receptor and the avidin-biotin complex procedure. Cell nuclei containing progesterone receptor were widely distributed in the anterior, medial and basal hypothalamus with the highest density occurring in the lamina terminalis and the preoptic area. Abundant, though less intensely reacting progesterone receptor was present in cell nuclei in the tuberal infundibular area and in the internal zone of the median eminence. A large group of cell nuclei containing progesterone receptor occurred in the dorsal anterior hypothalamus between the anterior commissure and the lateral ventricle. This group of nuclei extended anteriorly into the telencephalon. A small number of cell nuclei containing progesterone receptor was also found in the ventral telencephalon in the region of the nucleus accumbens.     

Effect of differential photostimulation on induction of Fos-like immune-reactivity in the MBH region of Indian weaver bird

This study investigated the neuronal activation (c-fos) in the mediobasal hypothalamus (MBH) of the Indian weaver bird, after exposure to a single long-day. Wild-caught photosensitive birds were exposed to the short-days (LD 8L:16D). After four days of short-days photoperiod, the LD cycle was programmed such that the light illumination was continuous after zeitgeber time (ZT) 8. Birds were perfused on the same day at ZT 4 or ZT 20. Brains were processed for the immunohistochemistry of c-fos (Fos) in the MBH. We found a significant higher activation of Fos in neurons within the ventral tuberal division (containing infundibular nucleus) of the MBH, in group that received 20-h light than that received 4-h light on first long-day. But in the dorsal tuberal division, there was no noticeable difference in Fos-lir activation on after 4-h and 24-h light exposure. The results suggest that the ventral tuberal division of mediobasal hypothalamus is principally involved in detecting the photoperiodic information from the external environment, and hence, suggested as the key neural center, involved in the photoperiodic mechanism in Indian weaver bird.     

Cerebrospinal fluid contacting neurons in the reduced brain ventricular system of the atlantic hagfish,Myxine glutinosa

Cerebrospinal fluid (CSF)-contacting neurons are sensory-type cells sending ciliated dendritic process into the CSF. Some of the prosencephalic CSF-contacting neurons of higher vertebrates were postulated to be chemoreceptors detecting the chemical composition of the CSF, other cells may percieve light as "deep encephalic photoreceptors". In our earlier works, CSF-contacting neurons of the mechanoreceptor-type were described around the central canal of the hagfish spinal cord. It was supposed that perceiving the flow of the CSF they are involved in vasoregulatory mechanisms of the nervous tissue. In the present work, we examined the brain ventricular system of the Atlantic hagfish with special reference to the presence and fine structure of CSF-contacting neurons. Myxinoids have an ontogenetically reduced brain ventricular system. In the adult hagfish (Myxine glutinosa) the lumen of the lateral ventricle is closed, the third ventricle has a preoptic-, infundibular and subhabenular part that are not connected to each other. The choroid plexus is absent. The infundibular part of the third ventricle has a medial hypophyseal recess and, more caudally, a paired lateral recess. We found CSF-contacting neurons in the lower part of the third ventricle, in the preoptic and infundibular recess as well as in the lateral infundibular recesses. No CSF-contacting neurons were found in the cerebral aqueduct connecting the subhabenular recess to the fourth ventricle. There is a pineal recess and a well-developed subcommissural organ at the rostral end of the aqueduct. Extending from the caudal part of the fourth ventricle in the medulla to the caudal end of the spinal cord, the central canal has a dorsal and ventral part. Dendrites of CSF-contacting neurons are protruding into the ventral lumen. Corroborating the supposed choroid plexus-like function of the wall of the dorsal central canal, segmental vessels reach a thin area on both sides of the ependymal lining. The perikarya of the CSF-contacting neurons found in the brain ventricles are mainly bipolar and contain granular vesicles of various size. The bulb-like terminal of their ventricular dendrites bears several stereocilia and contains basal bodies as well as mitochondria. Basal bodies emit cilia of the 9+0-type. Cilia may arise from the basal body and accessory basal body as well. The axons run ependymofugally and enter--partially cross--the periventricular synaptic zones. No neurohemal terminals similar to those formed by spinal CSF-contacting neurons of higher vertebrates have been found in the hagfish. We suppose that CSF-contacting neurons transform CSF-mediated non-synaptic information taken up by their ventricular dendrites to synaptic one. A light-sensitive role for some (preoptic?) groups of CSF-contacting neurons cannot be excluded.     

Studies on the subcommissural organ of Salmo gairdneri

The light microscopic analysis of serial sections of the subcommissural organ (SCO) of the rainbow trout (Salmo gairdneri) shows that the form of the groove-like (in cross section) organ varies over its total length. Its rostral origin is a tunnel-like structure anterior to the orifice of the hollow pineal stalk. The SCO forms the dorsal wall of the brain. Caudally the SCO is increasingly displaced from the surface of the brain by the fibers of the posterior commissure; the organ ends in a tabular area beyond the latter. The orifice of the pineal stalk is surrounded by the ependyma of the SCO that invaginates like a funnel and joins with the ependyma of the pineal stalk after a considerable narrowing. The rudimentary parapineal organ is located on the left side of the brain and is connected with the left habenular ganglion through the parapineal tract. It contacts the third ventricle with a short channel within the ependyma of the SCO. The histological organization of the ependymal and hypendymal cells of the SCO is typical of teleosts. Secretory material is located basally and apically in relation to the nucleus, but there is no indication of a basal secretory release. Basal ependymal processes terminate with broadened endings at the membrana limitans externa. The apical product is discharged into the third ventricle, where it aggregates into the thread-like structure of Reissner's fibre. The SCO cells have no direct contact with cerebral or meningeal blood vessels.     

The development of a hypothalamic monoaminergic system for the regulation of the pars intermedia activity in Xenopus laevis

Summary In Xenopus laevis the development of hypothalamic monoaminergic cells was studied in relation to adaptation to background colour. The first melanophores appear at stage 33/34 (normal table of Nieuwkoop and Faber, 1956), gradually increasing in number. The melanine granules are dispersed throughout the cell, irrespective of the background colour. The dispersion apparently is caused by MSH released by the developing pars intermedia cells. Between stage 39 and stage 41, larvae placed on a white background changed colour from black to white due to aggregation of the melanine granules within the melanophores. With Falck's method for demonstrating monoamines, a small number of fluorescent cells was observed in the hypothalamus simultaneously with the first background-dependent colour change. These cells were arranged in a paired nucleus, bordering the third ventricle. Initially, the nucleus extends from 50 microns behind the optic chiasma to the lateral dilatations of the third ventricle; 8–10 hours later, similar cells were also found at the lateral dilatations and in the dorso-lateral part of the infundibular lobe. The cells have apical processes protruding in the ventricular lumen. Fluorescent axons, originating from the cells, were occasionally observed. Considering the above-mentioned results in combination with the electron microscopical data of Nyholm (1972), it is concluded that the MSH producing cells are under monoaminergic nervous control from the beginning of background colour adaptation.This paper was presented at the Fourth Joint Meeting of the Dutch and British Societies for Endocrinology (Terlou et al., 1973).The authors wish to thank Prof. Dr. P.G.W.J. van Oordt for his stimulating interest and helpful suggestions. The photographs were made by Mr. H. van Kooten and his co-workers.     

Morphology and distribution of tanycytes in the third ventricle of the adult rat. A study using semithin methacrylate sections

Light microscopy and semithin methacrylate sections were used to study the tanycytic projections and morphology in the floor of the third ventricle of the rat. The tanycytic cell soma was located in the ependyma. The luminal surface showed minute protrusions into the ventricular space and their basal processes projected across the width of the parenchyma of the infundibular region. During their course, tanycytic processes made contact with capillaries in the parenchyma and pial surface, suggesting that they might be involved in uptake and/or delivery mechanisms between the cerebrospinal fluid, hypothalamic cells and blood vessels.     

Light and electron microscopical investigations on the tanycyte differentiation during the perinatal period in the rat

Summary The differentiation of tanycytes was studied light and electron microscopically during the perinatal period in rats, the time when functional connections between hypothalamus and hypophysis are established. The 3rd ventricle is slit-like between 16 and 18 days of the prenatal period. Its wall is formed by intensively proliferating matrix cells with apical processes, ovoid perikarya and a basal process. The ventral region of the 3rd ventricle becomes funnel-shaped on the 20th day of the prenatal period. As the cells differentiate, the apical process becomes shorter and broader. Moreover, on day 20 of prenatal life cells without apical processes appear. Their number increases during the postnatal period. The concentration of endoplasmic reticulum, mitochondria, polysomes, lipid droplets, dense bodies (lysosomes), lamellated and multivesicular bodies increases. Initially the cells are similar but from the 3rd day of postnatal life differentiation occurs in different regions of the infundibular recess. After the 5th day, there are no marked changes in the structure and distribution of these cells.K. Chandrasekhar wishes to thank the Indian National Science Academy and USSR Academy of Sciences for the award of a fellowship during the tenure of which this work was completed     

Ultrastructural changes in the median eminence of the rat following deafferentation of the basal hypothalamus

Summary This report concerns a light and electron microscopic investigation of the median eminence and dorsal infundibular stem of the rat following surgical isolation (deafferentation). Using a modification of the Halász technique, the basal hypothalamus, including the arcuate nucleus and median eminence were surgically isolated from surrounding structures. Special attention was directed to the contact (external) zone of the median eminence and rostral infundibulum where tuberohypophyseal axons as well as ependymal cell processes abut upon the abluminal basement membrane of the portal perivascular space. The results of this study to date suggest that 9, 20, and 40 days following surgical isolation, there is a distinct increase in the population of tuberohypophyseal dense core vesicles. It is suggested that deafferentation abolishes inhibitory and excitatory input that serves to modify the cellular dynamics of tuberohypophyseal neurosecretory elements. Comments are also made on the presence of cistern-like structures in the lateral median eminence; the presence of vesicle-like inclusions in terminal ependymal processes is discussed in relationship to the role that ependyma may play in linking the third ventricle with the adenohypophysis.This research was supported by USPHS Grants NB 08171 and AM 10002. The authors are indebted to the excellent technical assistance provided by G. Krobisch Dudley. Further, the authors wish to express their thanks to Dr. Adolph Weindl for his valuable advice and criticism, and to Matilde Holzwarth for her helpful assistance.     

An immunohistochemical study of the GnRH neuron morphology and topography in the adult female rabbit hypothalamus

The morphology and distribution of immunoreactive (GnRH) neural elements in the hypothalamus of the adult nulliparous female rabbit were examined. Approximately 1,000 GnRH cells (range 890-1136) were counted in the right half of the hypothalamus. Two distinct GnRH cell types were observed: GnRH cells with rough or spiny contours accounted for 64% of the total immunoreactive cells, and smooth-contoured cells represented 34% of the total. The majority of immunoreactive neural elements were found in the anterior hypothalamus. GnRH cells and processes were located primarily in the ventral and medial anterior hypothalamus forming an inverted V pattern. Processes were followed from the medial preoptic area and suprachiasmatic nucleus to the infundibular stem. Extrahypothalamic projections of GnRH cells were observed. Immunoreactive fibers were also found to contact the ependymal lining of the third ventricle. It is concluded that two morphologically distinct GnRH cell types exist and have a broad distribution in the rabbit hypothalamus. The functional significance of these cell types requires further study.     

Distribution of aromatase-immunoreactive cells in the mouse forebrain

Summary The distribution of aromatase-immunoreactive cells was studied by immunocytochemistry in the mouse forebrain using a purified polyclonal antibody raised against human placental aromatase. Labeled perikarya were found in the dorso-lateral parts of the medial and tuberal hypothalamus. Positive cells filled an area extending between the subincertal nucleus in the dorsal part, the ventromedial hypothalamic nucleus in the ventral part, and the internal capsule and the magnocellular nucleus of the lateral hypothalamus in the lateral part. The same distribution was seen in the two strains of mice that were studied (Jackson and Swiss), and the number of immunoreactive perikarya did not seem to be affected by castration or testosterone treatment. No immunoreactivity could be detected in the medial regions of the preoptic area and hypothalamus; these were expected to contain the enzyme based on assays of aromatase activity performed in rats and on indirect autoradiographic evidence in mice. Our data raise questions concerning the distribution of aromatase in the brain and the mode of action of the centrally produced estrogens.     

Distribution of aromatase-immunoreactive cells in the forebrain of zebra finches (Taeniopygia guttata): Implications for the neural action of steroids and nuclear definition in the avian hypothalamus

Cells immunoreactive for the enzyme aromatase were localized in the forebrain of male zebra finches with the use of an immunocytochemistry procedure. Two polyclonal antibodies, one directed against human placental aromatase and the other directed against quail recombinant aromatase, revealed a heterogeneous distribution of the enzyme in the telencephalon, diencephalon, and mesencephalon. Staining was enhanced in some birds by the administration of the nonsteroidal aromatase inhibitor, R76713 (racemic Vorozole) prior to the perfusion of the birds as previously described in Japanese quail. Large numbers of cells immunoreactive for aromatase were found in nuclei in the preoptic region and in the tuberal hypothalamus. A nucleus was identified in the preoptic region based on the high density of aromatase immunoreactive cells within its boundaries that appears to be homologous to the preoptic medial nucleus (POM) described previously in Japanese quail. In several birds alternate sections were stained for immunoreactive vasotocin, a marker of the paraventricular nucleus (PVN). This information facilitated the clear separation of the POM in zebra finches from nuclei that are adjacent to the POM in the preoptic area-hypothalamus, such as the PVN and the ventromedial nucleus of the hypothalamus. Positively staining cells were also detected widely throughout the telencephalon. Cells were discerned in the medial parts of the ventral hyperstriatum and neostriatum near the lateral ventricle and in dorsal and medial parts of the hippocampus. They were most abundant in the caudal neostriatum where they clustered in the dorsomedial neostriatum, and as a band of cells coursing along the dorsal edge of the lamina archistriatalis dorsalis. They were also present in high numbers in the ventrolateral aspect of the neostriatum and in the nucleus taeniae. None of the telencephalic vocal control nuclei had appreciable numbers of cells immunoreactive for aromatase within their boundaries, with the possible exception of a group of cells that may correspond to the medial part of the magnocellular nucleus of the neostriatum. The distribution of immunoreactive aromatase cells in the zebra finch brain is in excellent agreement with the distribution of cells expressing the mRNA for aromatase recently described in the finch telencephalon. This widespread telencephalic distribution of cells immunoreactive for aromatase has not been described in non-songbird species such as the Japanese quail, the ring dove, and the domestic fowl. © 1996 John Wiley & Sons, Inc.     

Ultrastructural signs of the absorption of substances by the ependyma of the III ventricle in rats in the perinatal period]

The distribution of pinocytic vesicles, relief of apical surface and intercellular contacts were studied by means of electron microscope in ependyma of ventral region of III ventricle during perinatal period in rats. Morphological evidence was obtained for the fact that substances are absorbed by ependyma via pinocytic vesicles from the liquor beginning at least from the 16th day of prenatal development. During the postnatal period the intensity of absorption in the ventrolateral region of infundibulum of III ventricle and along the periphery of its extended part is higher than in the ventral region. At the same time the number of evaginations of the apical surface increases, especially in the ventrolateral region of infundibulum and along the periphery of its extended part. As a result, numerous depressions are formed on the ependyma surface, thus creating favourable conditions for the absorption of substances, circulating in the liquor. Changes in the apical surface configuration is provided by a special system of filaments. The apical parts of cells during perinatal period are girdled by a zone of specialized contacts, including cleft contacts, zones of adhesion and zones of closure. The latter, as known, limit markedly the penetration of substances.     

Vergleichende neurohistologische Studien am Nucleus infundibularis einiger australischer Vögel

Zusammenfassung Das Zwischenhirn-Hypophysensystem von zwei australischen Finken,Taeniopygia guttata castanotis undPoephila acuticauda, sowie von zwei kleinen Strandläufern,Calidris acuminata undCalidris ruficollis, wurde neurohistologisch untersucht.BeiCalidris acuminata finden sich im caudalen basalen Abschnitt des Infundibulums paraldehydfuchsin-positive Neurone, deren Fortsätze auf die Eminentia mediana posterior ausgerichtet sind. Diese Zellen liegen oft direkt unter dem Ependym des Recessus infundibuli. BeiCalidris ruficollis wurden keine Gomori-positiven Tuberneurone beobachtet. In Nissl-Präparaten zeigt der rostrale Abschnitt des Infundibularkerns vonCalidris acuminata undCalidris ruficollis die typische Dreischichtung in Basiskern, sowie eine erste und zweite dorsale Auflagerung. Im mittleren und caudalen Abschnitt ändert er sein Aussehen: Die Neurone sind dort in starken Lamellen um den Recessus infundibuli angeordnet. Ihre einzelnen Lagen werden von charakteristischen, unterschiedlich großen multipolaren Ganglienzellen aufgebaut. Trotz dieser eigentümlichen Strukturanordnung bleibt die Dreischichtung des Infundibularkerns erhalten. Die kleinen Neurone sind im basalen Teil des Nucleus infundibularis reihenförmig angeordnet, während die mittleren und großen Neurone dorsal Lamellen bilden.Der Infundibularkern vonTaeniopygia guttata castanotis besteht aus dem basalen Grundkern und einer ersten und zweiten dorsalen Auflagerung. Auffällig ist die strukturarme erste dorsale Auflagerung; hier findet man nur wenige mittelgroße Neurone. Der Nucleus infundibularis vonPoephila acuticauda zeigt ebenfalls drei schalenartig übereinander gelegene Abteilungen, die jedoch relativ weit nach dorsal verlagert sind.Diese Ergebnisse zeigen die anatomische Variabilität des Infundibularkerns bei verschiedenen Vogelarten.

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Comparative neurohistological studies of the infundibular nucleus in some Australian birds

Summary The hypothalamo-hypophysial systems of two Australian finches,Taeniopygia guttata castanotis andPoephila acuticauda, and two species of waders,Calidris acuminata andCalidris ruficollis, were studied with neurohistological methods.Paraldehyde fuchsin-positive tuberal neurons were observed in the caudo-basal portion of the infundibulum inCalidris acuminata. The axons of these cells are directed towards the posterior median eminence. Frequently the Gomori-positive tuberal cells are located near the ependyma of the infundibular recess. However, no Gomori-positive tuberal neurons were observed inCalidris ruficollis. InCalidris acuminata andCalidris ruficollis the rostral division of the infundibular nucleus showed in Nissl preparations the typical three layers: (1) a three-laminar basal nuclear portion, and (2, 3) two dorsal layers. The structure of the medial and caudal part of the infundibular nucleus is different from that of its rostral part: the medial and lateral neurons have a lamellar arrangement around the infundibular recess. The size of the larger multipolar ganglion cells varies from one layer of the infundibular nucleus to the other. In spite of this, the characteristic three layers of the infundibular nucleus were always recognizable. The smaller neurons of the infundibular nucleus are arranged in basal rows, while the medium- and large-sized neurons form the dorsal lamellae.The infundibular nucleus ofTaeniopygia guttata castanotis consists of the basal nucleus and two dorsal layers. The first dorsal layer has only medium-sized neurons. The infundibular nucleus ofPoephila acuticauda has a similar structural pattern, but its three layers protrude further dorsally.These results point out clearly the anatomical variability of the infundibular nucleus in different avian species.

Herrn Prof. D. S. Farner, Seattle, danke ich für die großzügige Überlassung des Hirnmaterials. [This investigation was supported in part by grants (G-3416, GB-1380, and GB4433) from the National Science Foundation to Professor Donald S. Farner, Department of Zoology, University of Washington, Seattle. The advice and assistance of Dr. D. L. Serventy and Miss C. A. Nicholls, Division of Wildlife Research, C.S.I.R.O., and of the Department of Zoology (Prof. H. Waring), University of Western Australia, are gratefully acknowledged]. — Die histologische Aufarbeitung des Materials erfolgte mit Unterstüzung durch die Deutsche Forschungsgemeinschaft. — Für Beratung, Diskussion und Kritik bin ich den Herren Professoren D. S. Farner, Seattle, und K. Immelmann, Braunschweig, zu großem Dank verpflichtet.     

Neurosecretory processes projecting from the preoptic nucleus into the third ventricle of Zoarces viviparus L.

Summary The cellular processes loaded with neurosecretory elementary granules penetrate the ependyma and project into the third ventricle at the level of preoptic nucleus of Zoarces viviparus L. These cellular processes seem to be arising from the neurosecretory cells. At this zone, not all but some of the ependymal cells have a cilium. In this paper the possible function of these neurosecretory processes and the ciliated ependymal cells are discussed.This work was aided by a Grant from NATO and the Deutsche Forschungsgemeinschaft.     

Scanning electron microscopy of the third ventricle of sheep

Summary Scanning electron microscopy of the third ventricle of sheep demonstrates areas of ciliated ependymal cells at the dorsal and middle third. The cilia of the dorsal portion of the ventricle have biconcave discs that are attached to each cilium by a slender stalk. The lower third and floor of the ventricular wall, as well as the pineal recess, are largely covered by ependymal cells that possess numerous microvilli with only a few isolated cilia scattered along cell surfaces. The infundibular recess is papillated with apical blebs of the ependymal cells that project into the lumen of the recess. Measurements of these surface elements indicate an average diameter of 0.28 for cilia, 0.10 for microvilli and 0.50 for the apical blebs of the infundibular recess. The functional significance of the regional differences in surface structures is discussed in relation to cerebrospinal fluid movement, ependymoabsorption and ependymosecretion.Supported by U.S.P.H.S. Grant NS 08171.Career Development Awardee KO4 GM 70001.     

Immunoreactive material resembling ovine prolactin in perikarya and nerve terminals of the rat hypothalamus

Summary The presence of prolactin (PRL)-like material is demonstrated in the brain of rats with the aid of anti-ovine PRL (oPRL) IgG as primary antibody in the unlabeled antibody-enzyme method. Immunoreactive deposits are visualized as an intraneuronal constituent with a widespread distribution in the hypothalamus and neural lobe of the pituitary. Dense networks of reactive nerve terminals derived from two prominent fibre tracts, a ventral (VHT) and a dorsal hypothalamo-neurohypophysial tract (DHT) are seen. The VHT is confined to the median eminence and pars oralis tuberis, the DHT to the pars caudalis tuberis. Both fibre tracts pass through the infundibular stalk into the neural lobe. The origin of the immunoreactive nerve terminals can be elucidated only to some extent. The VHT gives off beaded fibres entering the ependymal and glandular layer of the median eminence. Immunoreactive perikarya are observed in the supraoptic nucleus, the paraventricular nucleus, the anterior hypothalamic nucleus, the anterior commissural nucleus, the preoptic nucleus and the interstitial nucleus of the stria terminalis. A few of the immunoreactive perikarya are observed in close connection with brain vessels and the ependymal cells of the third ventricle. The results indicate that the anti-oPRL has a unique region specificity implying that only a segment of the mammalian PRL molecule is present in these nuclei of the brain. Fragments of PRL may function as neuromodulators or neurotransmitters in the rat brain.We are indebted to Dr. Mogens Hammer, Rigshospitalet, Copenhagen for the gift of Arg-VP and anti-VP, and to NIAMDD for the gift of ovine PRL, ratPRL, anti-rPRL, anti-hPRL and bovineSTH     

Morphology and distribution of type II supraependymal cells in the third ventricle of the guinea pig.

The distribution and morphology of phagocytic (Type II) supraependymal cells residing within the third ventricle of the guinea pig were investigated by scanning electron microscopy. Type II supraependymal cells were restricted to nonciliated regions of the ventricle. They were most numerous on the choroid plexus, abundant within the infundibular recess and were present on the ventricular floor in the region of the median eminence. Morphologically, they were characterized by a soma from which pseudopodia-like processes extended to the subjacent ependyma. Type II cells varied in configuration according to their location. Those residing on the choroid plexus typically had irregular somas and possessed processes that generally terminated in finger-like extensions. In contrast, cells on the ventricular floor and within the infundibular recess were stellate and possessed processes that terminated in fan-like cytoplasmic expansion. There were no differences noted in the frequency, distribution or morphology of Type II supraependymal cells in male and female animals. Furthermore, cell frequency did not appear to vary in relation to the estrous cycle. The data suggest that the pleomorphism exhibited by Type II supraependymal cells may reflect adaptations to diverse environmental conditions present within different regions of the third ventricle.     

The hypothalamic neurosecretory system of the marine teleost fish, Mugil auratus risso.

The hypothalamic neurosecretory system of the marinefish, Mugil auratus, consists of two nuclei, viz., the nucleus praeopticus and the nucleus laterlis tuberis. Both are paired, and while those of the nucleus praeopticus are vertically arranged as L-shaped bodies, their strand-like counterparts in the nucleus lateralis tuberis extend in an antero-posterior direction. The two constituent bodies of the nucleus praeopticus lie on both sides of the third cerebral ventricle. Each is differentiated into a dorsal pars magnocellularis and a ventral pars parvocellularis. A nervous tract, the hypothalamo-hypophysial tract, extends posteriorly from each body, but it is not until after they penetrate the pituitary gland that they fuse into one structure, the neurohypophysis. Many neurosecretory granules accumulate in the neurohypophysis adjacent to the meta-adenohypophysial region, and fewer scattered granules of varying sizes are also present along the hypothalamo-hypophysial tracts. Inner to these hypothalamo-hypophysial tracts extend the two bodies of the nucleus lateralis tuberis along the infundibular region. Axons from this nucleus extend sideways, and as they merge with those adjacently disposed of the hypothalamo-hypophysial tracts, they enter the pituitary gland as a unified structure.