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PubMed1978

[Ultrastructural characteristics of the specialized ependyma of the 3d cerebral ventricle in rats].

The ultrastructure of the specialized ependyma of the third cerebrals ventricle was studied in males of albino Wistar rats, 160--180 g of weight. The ependyma lining the inferolateral walls (alpha-tanycytes) was found to differ ultrastructurally from that of the floor of the third ventricle or of the median eminence (beta-tanycytes). These differences are assumed to reflect a specific functional differentiation of the different types of tanycytes. Various types of microvesicles and a system of peculiar membranous cavities are described in the alpha-and beta-tanycytes. These structures are supposed to be associated with the transport and secretory function of tanycytes.

Animals↗

PubMed1978

The fine structure of ependyma in the hypothalamus of the hamster (Cricetus cricetus).

The ciliated ependyma of the hypothalamus of the hanster (Cricetus cricetus) consists of a sheet of cells, the luminal surface of which is reflected over cilia and numerous microvilli. The lateral portions of the plasmalemma of contiguous cells are fused at some sites to from junctions of five layers, the zonula occludens. These fusions occur usually in continuity with other intercellular junctions, the zonula adhaerens. In the apical regions of the ependyma these fusions are almost spiralled. The nucleus is regularly oval and lying close to the basal plasmalemma. The cytoplasm contains a finely granular matrix, filamentous components close to the junctions. The endoplasmic reticulum is sparse. The Golgicomplex is confined to the supranuclear cytoplasm, and mitochondria, are more numerous in the apical than in the basal regions of ependymal cells; the mitochondria are generally rounded and have transverse cristae and granules. The apical regions of the cytoplasm contain the basal bodies of cilia; they form non-striated rootlets and the rootlet filaments tend to diverge, ending in a granular zone.

Animals↗

PubMed1980

Effects of cytochalasin B on the ependyma.

In order to analyse whether or not surface morphology and intracellular skeleton are interdependent, Cytochalasin B (CB), an agent which interferes with microfilaments, was introduced ino the brain ventricular system of adult rats. Following intraventricular application of CB for different periods of time (up to 6h) the animals were sacrificed and the ventricular wall examined with both transmission and scanning electron microscopes. The first signs of cellular alteration after short periods of CB application were an increase in the number of microfilaments within the cytoplasm and the appearance of a multitude of small knobs on the surface of the cilia of the cuboidal ependymal cells, whereas the tanycytes exhibited extensive blebbing at their apical poles. When the duration of CB perfusion was lengthened, entire ciliated cells became rounded up and were loosened from the epithelium, especially in the transition zone of the third ventricle where the ependyma is composed of both tanycytes and ciliated cells. The significance of the CB-induced changes in the ependyma are discussed in relation to the ependymal surface modifications seen under physiological and other experimental conditions.

Animals↗

PubMed1981

Histological study of the ependyma of the hypothalamic third ventricle in the water snake Natrix maura (L).

The ependyma of the hypothalamic third ventricle of Natrix maura (L) has been investigated by light microscopy employing Nissl and Golgi stains. Electron microscopy was also used. Brains were fixed by intraventricular perfusion and embedded in paraffin, celloidin and Spurr resin. Light-microscopically the ependyma appears as a simple layer epithelium with round or enlarged nuclei. It sometimes shows basal processes extending into the subependymal tissue. These processes can be clearly seen in Richardson stained semithin sections. They often contact the subependymal capillaries. Electronmicroscopically, tanycytes contacting capillaries show numerous microvilli and few cilia as well as pinocytotic vesicles at their apical surfaces. There are zonulae adherentes and probably gap junctions as well as digitations and desmosomes. In the apical cytoplasm there are mainly mitochondria, endoplasmic reticulum and Golgi apparatus. Near the nuclei and specially in the basal process there are many microtubules. The tanycytes contact the capillaries by an end foot containing mitochondria and pinocytotic vesicles, which are also observed in the endothelian cytoplasm. These structures lead us to think, like several other authors, that the tanycytes of Natrix maura (L) may serve as a linkage between CSF and the capillaries and that they possess the morphological features which are necessary to effect intracellular transportation.

Animals↗

PubMed1993

Immunohistochemical studies on choroidal epithelial cyst and neuroepithelial cyst: in comparison with normal choroid plexus and ependyma.

Immunohistochemical evaluations with antibodies against S-100 protein, glial fibrillary acidic protein, cytokeratin and prealbumin were applied to 2 intracranial cysts of choroidal epithelial and neuroepithelial origin, and to the normal choroid plexus and ependyma. All specimens showed various immunoreactivities with the 4 antigens: especially, prealbumin-positive cells were detected in normal choroid plexus, part of normal ependyma, and part of choroidal epithelial cyst. The epithelium of neuroepithelial cysts presumably has multipotentials in cellular differentiation.

Brain Diseases↗

PubMed1977

[The ependyma of the lateral ventricle in Acanthodactylus pardalis (Reptilia, Lacertidae)].

Within the lateral ventricles of the brain of Acanthodactylus pardalis, different zones of ependymal cells are recognizable through their fluctuating changes from one into the other. The frontal pole of the hemisphere shows a rather homogeneous ependyma whose cells are laying together. Cell fibers are not visible. Farther caudally, the ventricular wall is subject to some alterations; there are more long-shaped cell nuclei. The ventricular sulci are areas of different ependymal structures. The sulcus terminalis represents a zone of dense-laying cells, whose nuclei possess in several regions more round or more elongated forms. An apical cytoplasmatic border and cilia are often clearly built out. The sulcus lateralis and the sulcus septo-archipallialis have a dense cell layer. The region below the medial cortex, near the sulcus septo-archipallialis, shows tanycytes with long basal fibers. The ependyma of the dorsal striatum shows dorsally as well as laterally, at the ventricle, areas with loosely arranged cells. The orientation of the cell nuclei to the ventricular surface is variable, especially at the ventricular wall of the septum and the opposite side of the striatum, where cell nuclei are to be found whose axis lays no more vertical but parallel to the ventricular surface.

Animals↗

PubMed1963

THE FINE STRUCTURE OF EPENDYMA IN THE BRAIN OF THE RAT.

The ciliated ependyma of the rat brain consists of a sheet of epithelial cells, the luminal surface of which is reflected over ciliary shafts and numerous evaginations of irregular dimensions. The relatively straight lateral portions of the plasmalemma of contiguous cells are fused at discrete sites to form five-layered junctions or zonulae occludentes which obliterate the intercellular space. These fusions occur usually at some distance below the free surface either independently or in continuity with a second intercellular junction, the zonula adhaerens. The luminal junction is usually formed by a zonula adhaerens or, occasionally, by a zonula occludens. The finely granular and filamentous cytoplasm contains supranuclear dense bodies, some of which are probably lysosomes and dense whorls of perinuclear filaments which send fascicles toward the lateral plasmalemma. The apical regions of the cytoplasm contain the basal body complexes of neighboring cilia. These complexes include a striated basal foot and short, non-striated rootlets emanating from the wall of each basal body. The rootlets end in a zone of granules about the proximal region of the basal body, adjacent to which may lie a striated mass of variable shape. All components of the basal body complex of adjacent cilia are independent of each other.

Brain↗

PubMed1978

Early postnatal development of ependyma in the third ventricle of male and female rats.

Ependyma in the third ventricle of developing male and female rats (0, 5, and 10 days postpartum) were compared with those of sexually mature male rats by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). No sexual dimorphism appeared in the developmental group. At all ages the dorsolateral ventricular wall was composed of ciliated ependymal cells, while ependymal cells of the ventrolateral wall exhibited apical microvilli and bleb-like irregularities. While SEM revealed similarities in apical morphology between ependymal cells adult and developing animals, TEM revealed marked differences between these cells. Many ciliated ependymal cells in developing animals resembled those of the adult while other neonatal cell profiles suggested ciliogenesis. Adult male rats exhibited two distinct tanycyte populations. One population, characterized by elaborate intercellular interdigitations and basal processes containing predominantly fine filaments, occurred adjacent to the ventromedial nucleus (VMN). The second population, characterized by less extensive intercellular interdigitations and basal processes containing, primarily microtubules, lined the roof of the lateral recess adjacent to the arcuate nucleus. Many tanycytes at the level of the arcuate nucleus in developing rats resembled closely those of the adult. In contrast, developing ependymal cells at the level of the VMN differed differed from their adult counterparts in that they exhibited little intercellular interdigitation and projected basal processes characterized by an internal framework of microtubules. Similarities in cytology between developing and adult tanycytes of the arcuate region suggest that the adult function of this population may be operative in the early postnatal period. In contrast, the differing cytology between adult and developing tanycytes of the VMN region suggests that the function of these cells is age-dependent.

Animals↗

PubMed1979

The morphology of extrachoroidal ependyma overlying gray and white matter in the rabbit lateral ventricle.

A morphologic investigation of ependyma over gray matter (caudate nucleus) and over periventricular white matter (tapetum) of the rabbit lateral ventricle was undertaken prior to evaluation of morphological changes which occur with experimental hydrocephalus. Ependymal cells over the caudate nucleus are cuboidal and heavily ciliated. Numerous microvilli cover the cell surface. The lateral margins are straight and interdigitations between adjacent ependymal cells are absent. Ependymal cells over white matter are squamous. Nonciliated as well as ciliated cells contribute to the epithelial lining. Microvilli are present at the cell surface but tend to aggregate near the cellular borders. The lateral margins are convoluted and complex interdigitations are present between adjacent cells. Morphologic differences between ependymal cells over the caudate nucleus and those over periventricular white matter may help to explain the differential response to hydrocephalus observed in these two regions of the lateral ventricle.

Animals↗

PubMed1983

Serotonin axons of the ependyma and circumventricular organs in the forebrain of the guinea pig. An immunohistochemical study.

The distribution of supraependymal nerve fibers (SEF) containing serotonin (5-HT) was investigated immunohistochemically in the forebrain of the guinea pig. The highest densities of immunoreactive axons were found in the pars centralis and the inferior horn of the lateral ventricle and also in the superior part of the third ventricle. Because of the special development of the choroid plexus in these ventricular regions, it is suggested that 5-HT SEF might be involved in the regulation of the composition of the cerebrospinal fluid. The ependyma lining the circumventricular organs located in the forebrain, was not observed to receive a significant 5-HT-SEF innervation. In the pituitary gland, a loose but constant network of 5-HT axons, resembling those which course in the anterobasal hypothalamus, arcuate nucleus and internal layer of the median eminence, was observed in the neural lobe. In the epiphysis, immunoreactive 5-HT was detected in all pinealocytes (the entire cell was filled with reaction product) and in fibers running between them.

Animals↗

PubMed1996

Dorsal border periaqueductal gray neurons project to the area directly adjacent to the central canal ependyma of the C4-T8 spinal cord in the cat.

In a previous study horseradish peroxidase (HRP) injections in the upper thoracic and cervical spinal cord revealed some faintly labeled small neurons at the dorsal border of the periaqueductal gray (PAG). The present light microscopic and electronmicroscopic tracing study describes the precise location of these dorsal border PAG-spinal neurons and their terminal organization. Wheat germ agglutinin-conjugated HRP (WGA-HRP) injections into cervical and upper thoracic spinal segments resulted in several hundreds of small retrogradely labeled neurons at the dorsal border of the ipsilateral caudal PAG. These neurons were not found after injections in more caudal segments. WGA-HRP injections in the dorsal border PAG region surprisingly resulted in anterogradely labeled fibers terminating in the area dorsally and laterally adjoining the central canal ependyma of the C4-T8 spinal cord. No anterogradely labeled fibers were found more caudal in the spinal cord. The labeled fibers found in the upper cervical cord were not located in the area immediately adjoining the ependymal layer of the central canal, but in the lateral part of laminae VI, VII and VIII and in area X bilaterally. Electronmicroscopic results of one case show that the dorsal border PAG-spinal neurons terminate in the neuropil of the subependymal area and in the vicinity of the basal membranes of capillaries located laterally to the central canal. The terminal profiles contain electron-lucent and densecored vesicles, suggesting a heterogeneity of possible transmitters. A striking observation was the lack of synaptic contacts, suggesting nonsynaptic release from the profiles. The function of the dorsal border PAG-spinal projection is unknown, but considering the termination pattern of the dorsal border PAG neurons on the capillaries the intriguing similarity between this projection system and the hypothalamohypophysial system is discussed.

Animals↗

PubMed1994

Ependyma: phylogenetic evolution of glial fibrillary acidic protein (GFAP) and vimentin expression in vertebrate spinal cord.

The phylogenetic evolution was studied of both glial fibrillary acidic protein (GFAP) and vimentin expression in the ependyma of the adult vertebrate spinal cord. Eleven species from different vertebrate groups were examined using different fixatives and fixation procedures to demonstrate any differences in immunoreactivity. GFAP expression in the ependymal cells showed a clear inverse relation with phylogenetic evolution because it was more elevated in lower than in higher vertebrates. GFAP positive cells can be ependymocytes and tanycytes, although depending on their structural characteristics and distribution, the scarce GFAP positive ependymal cells in higher vertebrates may be tanycytes. Ependymal vimentin expression showed a species-dependent pattern instead of a phylogenetic pattern of expression. Vimentin positive ependymal cells were only found in fish and rats; in fish, they were tanycytes and were quite scarce, with only one or two cells per section being immunostained. However, in the rat spinal cord, all the ependymocytes showed positive immunostaining for vimentin. The importance of the immunohistochemical procedure, the cellular nature of GFAP positive ependymal cells and the relationship between tanycytes and ependymocytes are discussed, as well as GFAP and vimentin expression.

Animals↗

PubMed1975

Secretory phenomena at the ependyma of the IIIrd ventricle of the embryonic rat.

On the basis of previous observations of the third ventricle, the brains of rat embryos in the 17 to 21 gestation days were examined by light- and electron microscope as well as histochemically. Following results were obtained: 1. Between the 18th and 20th gestation days supraependymal secretion spherules and intraventricular secretion masses were observed in the rostral part of the third ventricular lumen. The intraventricular structures are not demonstrable with neurosecretory stains; they are PAS-negative and do not stain with periodic-acid-bisulfite-aldehydethionine. All histochemical reactions performed were negative. 2. The morphological finding in the same frontal plane is not uniform. Dorso-ventral difference exist between one ependymal region which lies caudal to the subfornical organ and an area in the same plane which is situated further ventrally near the entrance to the foramina Monroi (Fig. 1 a). In the superior portion, the supraependymal structures are spherical or bottle-shaped formations and are easily definable. In the lower ventricular portion densely situated ependymal protrusions are seen which become sperical only in the ventricular lumen. 3. In both instances (the spherical and flask-shaped protrusions of the superior portion and the strongly shaped protrusions of the lower portion of the third ventricle) cytoplasmic protuberances containing more or less dense, fine-grain ground plasma and a differentiated number of polyribosomes can be seen. Using the Richardson stain, chromophobe protrusions are seen to possess a diffuse ground plasma and only a few ribosomes, while chromophile protrusions have a dense ground plasma and numerous polyribosomes rosettes. Only rarely are single vesicles observed in the protrusions. 4. The ependyma cells contain densely packed, rough-walled endoplasmic reticulum whose cisterns are irregularly dilated and filled with electron-dense material; they also contain many ribosomes and dictyosomes. The organelles are accumulated mainly in the apical cell portions. A terminal web spans the cell surface and attaches to the zonulae adhaerentes, preventing the flow of cell organelles into the organelle-free secretory protrusions. 5. The functional implication of the ependymal secretion, which appears in the third ventricle for a few days only, during embryonic development, is still unknown and is the goal of subsequent examinations.

Animals↗

PubMed1976

Distribution and properties of an adenosine triphosphatase in the tanycyte ependyma of the IIIrd ventricle of the rat.

The distribution, histochemical properties and ultrastructural localization of adenosine triphosphate (ATP) hydrolyzing enzymes in the tanycyte ependyma of the third ventricle have been studied in female Wistar rats. Using a calcium-cobalt procedure and a lead capture technique, splitting of ATP could be demonstrated in perikarya and processes of tanycytes in the region of the ventromedial nucleus. The reaction showed no dependence on magnesium or sodium ions, did not occur with other monodi-, and tri-phosphates as substrates, and was inhibited by p-chlormercuribenzoate (PCMB) and sodium fluoride, but not by ouabain. With the calcium-cobalt method the highest intensity of reaction was found at pH 9.4, whereas the lead method gave optimal results at pH 6--8. At the ultrastructural level, the reaction product was found at the outer surface of the plasma membranes of tanycytes and reached its highest concentrations in the region of the region of the apical microvilli; From the findings it is concluded that splitting of ATP in tanycytes is due to a true ATPase. The enzyme might be involved in an active transport of substances by tanycytes.

Adenosine Triphosphatases↗

PubMed1988

Histochemistry of proteases in ependyma, choroid plexus and leptomeninges.

Aminopeptidase M (APM), aminopeptidase A (APA), dipeptidyl peptidase IV (DPP IV) and gamma-glutamyl transferase (GGT) were demonstrated histochemically in cryostat sections of the rat brain to show the reaction pattern of ependyma, choroid plexus and leptomeninges. GGT was only demonstrable in the cell membranes of ependymal cells and in the leptomeninges; however, APA, APM and DAP IV showed a variable degree of activity in the capillary endothelium of the choroid plexus as well as in the leptomeninges. On the basis of these results, it is postulated that peptides in the cerebrospinal fluid can be cleaved extraventricularly by the enzymes demonstrated in the leptomeninges.

Animals↗

PubMed1979

Pathological alterations of ependyma and choroid plexus after experimental cerebral infection of mice with Sendai virus.

The effects of intracerebral inoculation of Sendai virus into young adult mice were investigated by immunofluorescence, light, and electron microscopy. Immunofluorescence of virus-specific antigens was maximal on the third day after inoculation, revealing infection of leptomeninges, ependyma, and choroid plexus. Histologically, meningitis, ependymitis, and choroiditis occurred between the second and third days. The choroiditis was associated with formation of vacuoles within the cytoplasm of epithelial cells. The vacuoles reached diameters up to 50 micrometer. The ubiquitous vacuolization of plexus epithelia resulted in a honeycomb-like pattern. Opaque viral inclusions were visible within the cytoplasm of choroidal and ependymal epithelium as well as in mononuclear inflammatory cells. On electron microscopy, they were composed of intracytoplasmic nucleocapsid accumulations. Viria lay free between microvilli of plexus epithelial cells, and budding virus structures were observed at cellular surfaces. Occasionally, complete viria occurred in the cytoplasm of plexus epithelial cells and were surrounded by a unit membrane from which they appeared to arise by budding. The formation of this small cavity can be interpreted as the first stage of vacuole formation.

Animals↗

PubMed1982

Pineal innervation of the third ventricular ependyma in the teleost, Puntius sophore (Ham.).

In the teleost Puntius sophore a well defined pineal tract intersects the posterior commissure at right angles and enters the ependymal layer in the roof of the third ventricle. In the ependymal layer it gives out varying number of branches which are in morphological contact with the component cells. Few branches apparently project into the third ventricles also. Further, EM studies would confirm the site of their constituent axonal endings. Such a direct pineal pathway projecting into the ependyma and third ventricle may be of great functional importance.

Animals↗

PubMed1999

Use of a heterologous monoclonal antibody for cloning and detection of glial fibrillary acidic protein in the bovine ventricular ependyma.

From protozoans to vertebrates, ciliated cells are characterized by well-developed cytoskeletal structures. An outstanding example is the epiplasm, a thick, submembranous skeleton that serves to anchor basal bodies and other cell surface-related organelles in ciliated protozoans. An epiplasm-like cytoskeleton has not yet been observed in metazoan ciliated cells. In a previous study, we reported on MAb E501, a monoclonal antibody raised against epiplasmin-C, the major membrane skeletal protein in the ciliate Tetrahymena pyriformis. It was shown that MAb E501 cross-reacts with glial fibrillary acidic protein (GFAP), the class III intermediate filament protein found in astrocytes and other related glial elements. Here we used a post-embedding immunogold-staining method to localize MAb E501 cross-reactive antigens in ciliated cells from the ventricular ependyma in bovine embryos. When ependymocytes were treated with MAb E501, the ciliated region of the cell cortex was devoid of significant labeling. Instead, a gold particle deposit was evident around the nucleus, with only conventional ependymocytes being immunostained. Similar results were obtained by utilizing a rabbit antiserum against GFAP, revealing glial filaments and indicating an astroglial lineage of conventional bovine ependymocytes. In contrast, secretory ependymocytes of the subcommissural organ (SCO) were not stained by either of the two antibodies. Using MAb E501 as a heterologous probe, we cloned bovine GFAP cDNA. In situ hybridization experiments failed to detect GFAP transcripts in SCO ependymocytes, confirming the abscence of immunoreactivity in these cells.

Amino Acid Sequence↗