大鼠第三脑室室管膜NADPH-d阳性伸展细胞的形态与分布

应用 Ｎ Ａ Ｄ Ｐ Ｈｄ 组织化学方法研究了大鼠第三脑室视前区室管膜的伸展细胞⒚结果表明：１）第三脑室视前区室管膜存在 Ｎ Ａ Ｄ Ｐ Ｈｄ 阳性的伸展细胞,其基突伸向视前区并与神经元或毛细血管相接触;２） Ｎ Ａ Ｄ Ｐ Ｈｄ 阳性的伸展细胞在第三脑室侧壁常见、室底少见、室顶未发现其存在;３） Ｎ Ａ Ｄ Ｐ Ｈｄ 阳性的伸展细胞的形态与分布,在雌、雄大鼠间不存在明显的性别差异⒚尽管 Ｎ Ａ Ｄ Ｐ Ｈｄ 阳性的伸展细胞的生理功能不十分清楚,但本研究为伸展细胞作为脑脑脊液环路的一部分,介导下丘脑对脑脊液中化学变化的感受提供了形态学依据,并提示一氧化氮可能参与了这一过程⒚     

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.

     

Ependymoneuronal specializations between LHRH fibers and cells of the cerebroventricular system

Summary Light-and electron-microscopic immunocytochemistry (LM-ICC and EM-ICC) were used to visualize luteinizing hormone-releasing hormone (LHRH) in fibres associated with ventricular ependyma and tanycytes of the median eminence. LM-ICC suggests that LHRH fibers appear to enter the third ventricle. However, with EM-ICC, LHRH fibers are in fact found within ependymal canaliculi formed by adjacent ependymal cells. The canaliculi contain other myelinated and unmyelinated axons in addition to immunoreactive LHRH fibers. Thin slips of ependymal and tanycyte processes project into the canaliculi and enclose axons to varying degrees. At the median eminence many LHRH fibers bend sharply downwards from their ventricular course and travel with tanycytic processes towards their common destination — the perivascular space of the hypophysial-portal vascular system. Here, EM-ICC reveals that LHRH fibers closely contact basal processes of tanycytes. Lateral processes from tanycytes form glioplasmic sheaths which surround some individual LHRH fibers. A few LHRH terminals contact the perivascular space directly but more often are separated from the perivascular space by intervening glia. It is hypothesized that: (1) glia of this region responds to the physiological state of the animal and may determine the degree of LHRH secretion by varying the extent of glial investment of LHRH terminals; and (2) may play a role during development by providing direction and support for LHRH fibers similar to that described for radial and other glial cells.     

A histoenzymological study of the saccus vasculosus of the freshwater teleost, Clarias batrachus (L.).

The saccus vasculosus (SV) of C. batrachus is comparatively small and situated latero-dorsal to the pituitary in between the lobi inferiores. It is in open communication with the third ventricle and is made up of coronet and supporting glial cells with interspersed liquor contacting neurons. These cellular constituents are arranged in one to three layers which are not thrown into folds. The PAS positive nature of the apical part of some coronet cells and their continuation with the PAS and AF positive material present in the lumen strongly suggest their secretory role. The coronet cells exhibited strong NADH diaphorase, NADPH diaphorase, cytochrome oxidase and MAO activity. AChE activity was comparatively weak. These enzyme histochemical studies show that SV has a dual function of transport and secretion. The strong MAO activity suggests the probable aminergic control of this organ.     

Light and electron microscopic studies of the ventricular wall

Summary Electron microscopic data confirm the results gained with rapid Golgi preparations of adult rodent brains that tanycytes occur in clusters along the lateral wall of the third ventricle. The cytoplasmic matrix of these cells is considerably denser than that of typical ependymal cells. They have filaments and microtubules throughout their cytoplasm along with mitochondria and polysomes. At the surface is a compact group of microvilli which suggest that tanycytes might selectively absorb material from the ventricle.The tanycytes are segregated from neuropil by other tanycyte processes, by neighboring ependymal cells and by astrocytes. Yet there are gaps in this sheath. At these points tanycytes either abut upon or surround nonglial components of the neural fabric.Their cytological features and relations with the neuropil suggest that tanycytes selectively absorb material from the ventricle and release it along the basal process, primarily affecting those segments of neurons immediately adjacent to the tanycyte.Supported by: NINDS Grants 5 R01 NS 09001-02 NEUA, 5T01 NB 5309, and GM 00958, and by the Eleanor Roosevelt Cancer Foundation Research Institute.Acknowledgements: This work was initiated in the Anatomy Department of the Harvard Medical School with facilities provided by Prof. S. L. Palay (U.S. Public Health Service Grant No. NB 05591). Dr. R. B. Wuerker kindly and patiently provided the instruction and orientation to electron microscopy. The major portion of the study was completed in the Neurology Department of the University of Utah with the extremely competent, challenging assistance of Dee Lerdahl, Nina Belgarian, Keith Johnson and Lynn Kendricks.     

Vascular and leptomeningeal projections of the subcommissural organ in reptiles. Lectin-histochemical, immunocytochemical, and ultrastructural studies

In the snake, Natrix maura, and the turtle, Mauremys caspica, the basal processes of the ependymal cells of the subcommissural organ project toward the local blood vessels and the leptomeninges. These processes and their endings were studied using aldehyde-fuchsin (AF), periodic-acid Schiff (PAS), periodic-acid silver-methenamine (PA-SM), concanavalin A (ConA), wheat germ agglutinin (WGA), immunoperoxidase staining (employing an antiserum against bovine Reissner's fiber; AFRU), and conventional transmission electron microscopy. For the purposes of comparison, the ventricular cell pole was also analyzed. The secretory material located in the ventricular cell pole and that present in ependymal endings had only a few staining properties in common, i.e., affinity for AF, ConA, and AFRU at a dilution of 1:1000. On the other hand, PAS, PA-SM, WGA, and AFRU at a dilution of 1:200,000 stained the apical (ventricular) secretory material but not the secretory material of the ependymal processes. The histochemical features of the secretory material located in the terminals of ependymal processes, as well as the presence at these sites of numerous rough-endoplasmic-reticulum cisternae and secretory granules, suggest that secretory material may be synthesized in these terminals. The probable fate of this material, i.e., release to the perivascular and leptomeningeal spaces or transport to the ventricular cell pole, is discussed.     

Fine structure of neurons of the arcuate nucleus and median eminence of the hypothalamus of the golden hamster following immobilization

Summary The fine structure of arcuate neurons of the arcuate nucleus, the ependymal tanycytes and the contact zone of the median eminence was examined following immobilization, an acute stress which significantly activated the hypothalamo-pituitary-adrenal (HPA) axis. Arcuate neurons of immobilized adult male hamsters displayed morphological indications of heightened activity; the number of lysosomes and dense core vesicles (80–120 nm) was increased. A markedly greater number of dense core vesicles was present in axon terminals of the contact zone of the mid-central median eminence and the ventral proximal stalk.Tanycytes of the median eminence exhibited an augmented number of electron dense bodies in both perikarya and end processes. These results indicate that the arcuate neurons, the axons of the contact zone, and the ependymal tanycytes of the hamster medial basal hypothalamus (MBH) may be involved in the response to immobilization.This work was supported by Program Project Grant #NS-11642     

Ultrastruktur der Liquorkontaktneurone des Rückenmarkes von Reptilien

Zusammenfassung Im Rückenmark der Reptilien kommen zwischen und unter den Ependymzellen des Zentralkanals bipolare Nervenzellen vor. Ihre Dendriten dringen in den Liquor cerebrospinalis ein und bilden dort charakteristische Nervenendigungen, die sich in lange, fingerförmige Fortsätze verzweigen. Letztere enthalten orientierte Filamente. In den Nervenendigungen findet man ebenfalls Filamente, multivesikuläre Körper und ferner Basalkörper, von denen Zilien und lange Zilienwurzeln ausgehen. Die Dendriten der Neurone sind durch desmosomenartige Strukturen mit den apikalen Abschnitten der benachbarten Ependymzellen verbunden und enthalten zahlreiche Mitochondrien und Golgi-Felder. Im Perikaryon der Neurone findet man ebenfalls ausgedehnte Golgi-Areale, ferner ein mit Ribosomen besetztes endoplasmatisches Retikulum, Mitochondrien, multivesikuläre Körper und granulierte Vesikel (Durchmesser um 870 Å). Der Neurit der Nervenzellen verläuft ependymofugal, in ihm kommen lange Mitochondrien und Neurotubuli vor. Auf den Dendriten, der Basis des distalen Fortsatzes, und den Perikaryen der Neurone können Synapsen beobachtet werden, deren präsynaptischer Bereich synaptische Vesikel, Mitochondrien und einige granulierte Bläschen (Durchmesser um 800 Å) aufweist. In einer Schnittebene dringen 5–6 Nervenendigungen in etwa gleicher Entfernung voneinander in den Zentralkanal ein.Unterhalb der intraependymalen Liquorkontaktneurone findet man eine weitere Nervenzellart, deren Zytoplasma heller ist und größere (Durchmesser um 1250 Å), den neurosekretorischen Elementargranula ähnliche Granula enthält. Die Ependymzellen des Zentralkanals besitzen zahlreiche Mikrovilli. Die Liquorkontakt-Nervenendigungen können mit dem Reissnerschen Faden in direktem Kontakt stehen. Die Hypothese wird diskutiert, daß die spinalen Liquorkontaktneurone — ähnlich denen der bisher beschriebenen Liquorkontaktgebiete — Rezeptoren sind, bei deren Funktion auch der Reissnersche Faden eine Rolle spielen kann.

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Ultrastructure of the liquor contacting neurons of the spinal cord of reptiles

Summary In the spinal cord of reptiles, nerve cells are situated between and below the ependymal cells of the central canal. These neurons are bipolar; their dendrites protrude into the cerebrospinal fluid of the central canal where they build up characteristic nerve endings. These terminals ramify into long, finger-like processes containing oriented filaments. In the terminals, filaments, too, can be found besides of multivesicular and basal bodies, the latter giving rise to long rootlet fibres and cilia. The dendrite of the neurons is connected with the apical part of the neighbouring ependymal cells by desmosome-like structures, and it contains numerous mitochondria and Golgi areas. In the perikarya, enlarged Golgi areas, rough endoplasmic reticulum, mitochondria, multivesicular bodies and dense-core vesicles (diameter about 870 Å) are found. The neurite of the nerve cells that passes ependymofugally, contains long mitochondria and neurotubules. On the dendrite, the basis of the distal cell process and the perikarya of the neurons, synapses can be observed; their presynaptic cytoplasm contains synaptic vesicles, mitochondria and some dense-core vesicles (diameter about 800 Å). In one section, 5 to 6 nerve terminals protrude into the central canal in about equal distance from each other.Below these liquor contacting neurons situated intraependymally and described above, there is another type of nerve cells which cytoplasm is more electron lucent and contains larger (diameter about 1,250 Å) granules resembling neurosecretory granules. The ependymal cells of the central canal possess numerous microvilli. The liquor contacting nerve terminals may sometimes contact the Reissner's fibre directly. It is suggested that the spinal liquor contacting neurons — similarly to those of the liquor contacting territories described up to now — are receptors. In their function, also the Reissner's fibre may play a role.

     

Vascular and leptomeningeal projections of the subcommissural organ in reptiles

Summary In the snake, Natrix maura, and the turtle, Mauremys caspica, the basal processes of the ependymal cells of the subcommissural organ project toward the local blood vessels and the leptomeninges. These processes and their endings were studied using aldehyde-fuchsin (AF), periodicacid Schiff (PAS), periodic-acid silver-methenamine (PASM), concanavalin A (ConA), wheat germ agglutinin (WGA), immunoperoxidase staining (employing an antiserum against bovine Reissner's fiber; AFRU), and conventional transmission electron microscopy. For the purposes of comparison, the ventricular cell pole was also analyzed. The secretory material located in the ventricular cell pole and that present in ependymal endings had only a few staining properties in common, i.e., affinity for AF, ConA, and AFRU at a dilution of 1:1000. On the other hand, PAS, PA-SM, WGA, and AFRU at a dilution of 1:200 000 stained the apical (ventricular) secretory material but not the secretory material of the ependymal processes. The histochemical features of the secretory material located in the terminals of ependymal processes, as well as the presence at these sites of numerous rough-endoplasmic-reticulum cisternae and secretory granules, suggest that secretory material may by synthesized in these terminals. The probable fate of this material, i.e., release to the perivascular and leptomeningeal spaces or transport to the ventricular cell pole, is discussed.This work was partially supported by grants from the Stiftung Volkswagenwork, Federal Republic of Germany (1/38259), from the Dirección de Investigaciones, Universidad Austral de Chile (S-85-39), and from Fondo Nacional de Desarrollo Científico y Tecnológico, Chile (6027; all to E.M.R.)     

Elevated expression of glucose transporter-1 in hypothalamic ependymal cells not involved in the formation of the brain-cerebrospinal fluid barrier

Glucose transporters play an essential role in the acquisition of glucose by the brain. Elevated expression of glucose transporter-1 has been detected in endothelial cells of the blood-brain barrier and in choroid plexus cells of the blood-cerebrospinal fluid barrier. On the other hand, there is a paucity of information on the expression of glucose transporters in the ependymal cells that line the walls of the cerebral ventricles. The tanycytes are specialized ependymal cells localized in circumventricular organs such as the median eminence that can be segregated into at least three types, alpha, beta1 and beta2. The beta2 tanycytes form tight junctions and participate in the formation of the cerebrospinal fluid-median eminence barrier. Using immunocytochemistry and in situ hybridization, we analyzed the expression of hexose transporters in rat and mouse hypothalamic tanycytes. In both species, immunocytochemical analysis revealed elevated expression of glucose transporter-1 in alpha and beta1 tanycytes. Intense anti-glucose transporter-1 staining was observed in cell processes located throughout the arcuate nucleus, in the end-feet reaching the lateral sulcus of the infundibular region, and in cell processes contacting the hypothalamic capillaries. On the other hand, there was very low expression of glucose transporter-1 in beta2 tanycytes involved in barrier function. In contrast with the results of the cytochemical analysis, in situ hybridization revealed that tanycytes alpha, beta1, and beta2 express similar levels of glucose transporter-1 mRNA. Further analysis using anti-glial fibrillary acidic protein antibodies to identify areas rich in astrocytes revealed that astrocytes were absent from areas containing alpha and beta1 tanycytes, but were abundant in regions containing the barrier-forming beta2 tanycytes. Overall, our data reveal a lack of correlation between participation in barrier function and expression of glucose transporter-1 in hypothalamic tanycytes. Given the virtual absence of astrocytes in areas rich in alpha and beta1 tanycytes, we speculate whether the tanycytes might have astrocyte-like functions and participate in the metabolic coupling between glia and neurons in the hypothalamic area.     

Ultrastructure of the area postrema of the monkey, Macaca fascicularis

The area postrema of the monkey, Macaca fascicularis, were a pair of oval organs at the caudal end of the floor of fourth ventricle. Their ependymal lining was covered by well-developed microvilli with occasional overlying supraependymal cells. Two types of lining cells were present: pyramidad- and flattened cells. The pyramidal cell showed a long extending basal process resting on the underlying blood vessels. In transmission electron microscopy, the organ showed numerous fenestrated sinusoids characterized by a distinct perivascular space containing mast cells, macrophages and collagen fibrils. The parenchyma of the organ was composed of neurons and glial elements. Only one type of neuron ranging from 9.5 to 15 microns could be distinguished. The neurons contained an indented nucleus surrounded by organelle rich cytoplasm. The soma of the neuron was enclosed by glial element resembling astrocyte. The glial processes terminated on the blood vessel where they were "tunnelled" by a variable number of nerve fibres some of which gained a direct access to the external basal lamina of the perivascular space. Synapses in the neuropil predominantly of the axodendritic variety were observed. Axon terminals containing round agranular vesicles were seen to make synaptic contacts with the neuronal soma. No structural changes were observed in the area postrema following bilateral cervical vagotomy. However, degenerating axon terminals were observed in the subpostremal zone 7, 14 and 21 days after vagotomy suggesting a direct afferent projection into this region.     

Liquorkontaktneurone im Nucleus paraventricularis

Zusammenfassung Der neurosekretorische Nucleus paraventricularis von Reptilien wurde licht- und elektronenmikroskopisch untersucht. Zellen dieses Kernes bilden ventrikuläre Fortsätze, welche mit knöpfchenförmigen Endigungen — Liquorkontaktnervenendigungen — in das Lumen des 3. Ventrikels vordringen. — Der Nucleus paraventricularis der Sumpfschildkröte (Emys orbicularis) besteht aus einer proximalen, am Ependym liegenden Zelllage und einer distalen Nervenzellgruppe. Zwischen den Zellreihen sind synaptische Zonen vorhanden.Elektronenmikroskopisch weisen die knöpfchenförmigen, mit dem Liquor in Kontakt stehenden Nervenendigungen Elemente des endoplasmatischen Retikulums, freie Ribosomen und eine wechselnde Anzahl von Mitochondrien auf. Die Endigungen enthalten neurosekretorische Elementargranula (Durchmesser 1300–1800 Å) und sind mit atypischen Zilien versehen, zu denen meist zwei Basalkörperchen mit langen Zilienwurzeln gehören. Die Liquorkontakt-Endigungen sind mit den benachbarten Ependymzellen und mitunter untereinander durch Desmosomen verbunden. — Im Lumen des 3. Ventrikels treten auch dünne, Katecholamingranula enthaltende Axone auf, die mit den den Liquor erreichenden Nervenendigungen des Nucleus paraventricularis Synapsen bilden. Synapsen werden außerdem auf den ventrikulären und peripheren Fortsätzen und an den neurosekretorischen Perikaryen beschrieben. In den synaptischen Zonen findet man axodendritische Synapsen, deren Dendrit neurosekretorische Elementargranula enthält. — Die morphologische Ähnlichkeit zwischen neurosekretorischen Liquorkontakt-Nervenendigungen und denen des Liquorkontakt-Neuronensystems wird hervorgehoben. An Hand der Ergebnisse wird die Bedeutung und Funktion der neurosekretorischen, mit dem Liquor in Kontakt tretenden Nervenendigungen im Rahmen des Informationsaustausches zwischen Liquor cerebrospinalis und dem neuroendokrinen System diskutiert.

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Liquor contacting neurons in the paraventricular nucleus

Summary The neurosecretory paraventricular nucleus of reptilia was studied light and electron microscopically. Nerve cells of this nucleus form ventricular processes which as club-like endings — liquor contacting nerve endings — protrude into the lumen of the 3rd ventricle. — The paraventricular nucleus of the turtle, Emys orbicularis, is built up of a proximal neuronal layer situated close to the ependyma, and of a distal group of neurons. Synaptic zones can be found between the cell rows.As demonstrated electronmicroscopically, the club-shaped liquor contacting nerve endings show elements of the endoplasmic reticulum, free ribosomes and mitochondria in various amounts. The terminals contain neurosecretory elementary granules (diameter about 1,300–1,800 Å) and bear atypical cilia supplied mostly with two basal bodies and long rootlet fibres. The liquor contacting nerve endings are connected by desmosomes with the neighbouring ependymal cells and sometimes with one another. — In the lumen of the 3rd ventricle, also small axons containing catecholamine granules, can be found. These neurites form synapses with the liquor contacting nerve terminals of the paraventricular nucleus. Furthermore, synapses situated on the ventricular and peripheral nerve processes and on the neurosecretory perikarya, are described. In the synaptic zones, axodendritic synapses occur; the dendrite contains neurosecretory elementary granules. — The morphological similarity between neurosecretory liquor contacting nerve terminals and those of the liquor contacting neuronal system is stressed. On the basis of the results, the significance and function of the neurosecretory liquor contacting terminals is discussed in connection with the exchange of informations between cerebrospinal fluid and the neuroendocrine system.

     

A golgi study on tanycytes and liquor-contacting cells in the posterior hypothalamus of the newt

Summary Golgi methods were employed to study neurons and ependymal tanycytes in the posterior hypothalamus of the newt. The tanycytes send a few coarse, spiny or barbed processes towards the pia mater. In the periventricular grey, the neurohistological methods show common neurons, ranging from a multipolar to a plumed organization, and abundant liquor-contacting cells. These cells, possibly neurons, give rise to a process that reaches the cerebro-spinal fluid, and terminates in a spindle-shaped swelling, with a thin thread at its tip. In other cells, the intraventricular endings are bulbous or finger-like. The occurrence of: (1) branches of the liquor-contacting process, running parallel to the infundibular surface; (2) infundibular processes which end at the base or between the ependymal cell bodies; and (3) axons coursing in the same position, all indicates that the subependymal layer is a site for complex intercellular relationships. The significance of liquor-contacting cells and tanycytes is discussed, in view of the possibility that they may represent part of a system for hypothalamic regulation in response to changes in the CSF.     

Ultrastructure of the subfornical organ of the chicken (Gallus domesticus)

Summary The SFO of the chicken is divided in half by a large central blood sinus; ventrally it is covered by a thin layer of ependyma (including tanycytes, dendrites, and axons) which connects the two lateral halves and protrudes as a midsagittal crest into the lumen of the third ventricle. The ependyma consists predominantly of tanycytes with long basal processes which terminate upon perivascular spaces. These cells have an extensive Golgi apparatus and abundant lysosomes; their cellular apices containing polyribosomes and a few vesicles frequently protrude into the ventricle. In addition to astrocytes, oligodendrocytes, and microglial cells, there is another glial cell population that is distinguished by the presence of parallel stacks or spherical to ovoid conglomerates of rough ER and their unique location, i.e., limited to areas ventral and ventral-lateral to the large blood sinus. Two types of neurons are present: neurons in which there is a paucity of granulated vesicles and occasional vacuoles in both the cytoplasm and nuclei, the second type of neuron elaborates many granulated vesicles. Numerous puncta adhaerentia are observed between adjacent neuronal perikarya and between glial processes and neuronal perikarya.Diverse axon types are found within the chicken SFO. Axo-dendritic and axo-somatic axon terminals and presynaptic axon dilations contain assorted combinations of electron-lucent and granulated vesicles of different maximal diameters. Based on the morphology of these axons, cholinergic, peptidergic, and serotoninergic fibers are described. There are two additional groups of axons whose classification awaits further investigation.The chicken SFO differs from the mammalian SFO in several respects: it possesses an ependyma with secretory and/or absorptive tanycytes predominating; it is divided midsagittally by a central blood sinus; its lateral and dorsal limits are nebulous; a previously undescribed peculiar type of glial cell is found in a limited portion of the organ; supraependymal neurons are lacking.Dedicated to Prof. H. Grau at the occasion of his 80th birthdayWe gratefully acknowledge the technical help of Susan Woroch and secretarial assistance of Diana Hapes and Debbie Harrison     

Hypothalamo-neurohypophysial neurosecretory system and its vasculature in the freshwater catfish Mystus vittatus (Bloch)

The architectural pattern of the hypothalamo-neurohypophysial (HN) system of M. vittatus basically resembles that of other catfishes described earlier (Sathyanesan 1969 a, b). Some of the neurons of the nucleus preopticus of the hypophysectomised fish exhibit degeneration, whereas the viable ones were degranulated. The neurosecretory tract (NT) is in close association with the ependymal lining, both in the third ventricle and infundibular recess extending into the neurohypophysis. The pituicytes of the neurohypophysis are in close association with the NT which is of functional significance. In this species the NT entering the pituitary could be demonstrated with aldehyde fuchsin (AF), Palmgren's silver impregnation technique, alkaline and acid phosphatase and ascorbic acid tests. At least some among them may constitute separate tracts and their origin needs to be confirmed. As all those tracts pass through the infundibular base they come in direct contact among themselves as well as with the nucleus lateralis tuberis (NLT) neurons which lie on their pathway. In M. vittatus, in addition to the presence of neuro-adeno interface vasculature which is the median eminence (ME) equivalent of the teleosts, there is morphological evidence for the presence of a ME of tetrapodan type. The presence of strong alkaline and acid phosphatase and ascorbic acid activity in both the sites further supports the above view. However, additional ultrastructural evidence is needed to prove the functional status of the extra-hypophysial ME.     

Tanycyte absorption affected by the hypothalamic deafferentation in Japanese quail,Coturnix coturnix japonica

In Japanese quail, Coturnix coturnix japonica the tanycytes of the median eminence absorbed peroxidase injected into the third ventricle. The number of tanycytes showing peroxidase reaction was greater in the posterior median eminence than in the anterior median eminence. Following hypothalamic deafferentation, the tanycyte absorption was augmented both in the posterior and anterior median eminence. These findings suggest that axons of some neurons, which have inhibitory action on the tanycyte absorption, were transected by deafferentation resulting in augmentation of tanycyte absorption. A considerable number of ependymal cells lining the upper portion of the third ventricle and those of the pars nervosa also absorbed peroxidase. In birds with a deafferented hypothalamus, photostimulated ovarian growth was completely inhibited.     

Localization of immunoreactive prolactin in ependyma and circumventricular organs of rat brain

Summary Immunoreactive prolactin (IMP) has been localized in the male rat brain using the soluble peroxidase-anti-peroxidase (PAP) technique. In normal untreated animals, reaction product was seen in choroid plexus (CP) and in ependymal cells of the ventricular lining with heaviest concentrations of positively staining cells in the 3rd ventricle near the subcommisural organ (SCO), in the lateral ventricles near the subfornical organ (SFO), and in the 4th ventricle near the area postrema (AP). IMP was also present in numerous ependymal cells resembling tanycytes in the cerebral aqueduct, central canal of the spinal cord at the level of the AP, the organum vasculosum of the lamina terminalis (OVLT) and the floor of the infundibular recess. Immunoreactive cells resembling neurons were localized within the substance of the AP, SCO, and OVLT. IMP was also present in fibers of the zona externa of the median eminence and infundibular stalk; a few cells of the pars tuberalis contained reaction product. Hypophysectomized rats and bromocriptine-treated rats exhibited a similar staining pattern except that bromocriptine treatment eliminated IMP from most CP cells. Hypophysectomy, bromocriptine or estrogen treatment enhanced staining for IMP in cells of the pars tuberalis; estrogen treatment or hypophysectomy produced an increase in the number and distribution of immunoreactive cells as well as increased density of reaction product in cells of the medial habenular nucleus. The functional relevance of prolactin in these locations in the brain, the possible routes of transport of prolactin from the pituitary gland to the central nervous system, and the strong suggestion of extra-pituitary sites of synthesis of a prolactin-like hormone are discussed.     

Antibodies obtained by xenotransplantation of organ-cultured median eminence specifically recognize hypothalamic tanycytes

Tanycytes are specialized ependymal cells lining the infundibular recess of the third ventricle of the cerebrum. Early and recent investigations involve tanycytes in the mechanism of gonadotropin-releasing hormone (GnRH) release to the portal blood. The present investigation was performed to obtain a specific immunological marker of tanycytes and to identify the compound(s) responsible for this labeling. After 30 days of organ culture, explants of bovine median eminence formed spherical structures mostly constituted by tanycytes. These tanycyte spheres were xenotransplanted to rats, and the antibodies raised by the host animals against the transplanted living tanycytes were used for immunochemical studies of the bovine and rat median eminence. This antiserum immunoreacted with two compounds of 60 kDa and 85 kDa present in extracts of bovine and rat median eminence. The individual immunoblotting analysis of rat medial basal hypothalami showed a decrease in the amount of the 85-kDa compound in castrated rats as compared to control rats processed at oestrus and dioestrus. The antiserum, labeled as anti-P85, when used for immunostaining of sections throughout the rat central nervous system, immunoreacted specifically with the hypothalamic tanycytes. Within tanycytes, P-85 immunoreactivity was exclusively present in the basal processes. It is suggested that the 85-kDa and 60-kDa compounds correspond to two novel proteins selectively expressed by tanycytes. The possibility that they are secretory proteins involved in GnRH release is discussed. Anti-P85 appears to be the first specific marker of hypothalamic tanycytes.     

A Golgi study on the cerebrospinal fluid (CSF)-contacting neurons in the paraventricular nucleus of the Pekin duck

The present investigation based on classical neurohistological techniques (Nissl-staining, Golgi-impregnation) was focussed on the cytoarchitecture of the periventricular layer of the paraventricular nucleus in the Pekin duck. This region is endowed with intraependymal neurons, the perikarya of which are mostly covered by a thin ependymal lamella. Several of the intraependymal neurons were shown to give rise to dendrites extending into the third ventricle. An additional population of nerve cells located in the deeper layers of the periventricular region also gained direct access to the cerebrospinal fluid by means of long dendrites terminating with a bulbous-like swelling in the third ventricle. This cerebrospinal fluid (CSF)-contacting dendrite branched off several times in a rectangular fashion to give rise to collaterals running in the subependymal or periventricular layers. The axons of these CSF-contacting neurons were followed into the magnocellular portion of the paraventricular nucleus. Small bipolar nerve cells with processes parallel to the surface of the third ventricle occupied a subependymal position. The isodendritic magnocellular neurons of the paraventricular nucleus emitted dendritic processes that reached the basal pole of the ependymal cells. The complex arrangement of the periventricular layer of the paraventricular nucleus might provide the structural basis for the mechanisms of cerebral osmoreception defined by means of physiological parameters.     

Accessibility of low‐molecular‐mass molecules to the median eminence and arcuate hypothalamic nucleus of adult mouse

Blood‐derived molecules are able to access to the median eminence (ME) and arcuate hypothalamic nucleus (Arc) due to the lack of the blood–brain barrier. In the present study, we examined the accessibility of low‐molecular‐mass (LMM) molecules into parenchyma in the ME and Arc of adult mice by administration of Dextran 3000 (Dex3k), Dex10k, Evans blue (EB) and fluorescein isothiocyanate (FITC). In the external zone of the ME, the fluorescence of Dex3k, EB and FITC tracers generated an intensity gradient from fenestrated capillary, but that of Dex10k was detected only between the inner and outer basement membrane of pericapillary space. The fluorescence of FITC in the external zone of the ME was closely associated with axonal terminals and surrounded by cellular processes of tanycytes‐like cells and astrocytes. In the ependymal/internal zone of the ME and Arc, the fluorescence of all LMM tracers was seen at tanycytes‐like cells and neurons. The fluorescence of EB and FITC in these regions was not detected when brains were fixed during or before the administration of tracers. The inhomogeneity of accessibility for fluorescent tracers depended on routes for tracer administration. Thus, the present study indicates that the accessibility of LMM blood‐derived molecules to parenchyma depends on fenestration of the capillary in the external zone of the ME and active transport of ependymal cells in the ependymal/internal zone of the ME and Arc. Copyright © 2013 John Wiley & Sons, Ltd.