Alkaline phosphatase activity of the IVth ventricular choroidal epithelium of rats during embryonic and neonatal development

The cytochemical localization of alkaline phosphatase (AlPase) activity in the developing IVth ventricular choroidal epithelium was investigated in embryonic and neonatal rats. During the initial development of the choroidal primodium the flattened and/or cuboidal epithelial cells of the ventricular roof were changed to columnar cells with well-developed microvilli and apical tight junctions. When compared to AlPase activity on the lateral plasma membranes of the surrounding ependymal cells, these columnar cells of the choroidal primodium revealed activity on the lateral and luminal plasma membranes, but no activity was found on the basal surface of these cells. On the other hand, the epithelial cells in the neonatal choroid plexus showed a continuous morphological alteration from columnar cells with short microvilli to mature cuboidal cells with numerous long microvilli. AlPase activity in immature columnar cells was observed on all plasma membranes, except for the apical junctional area of the lateral surface. With maturing of the choroidal epithelial cells, the activity appeared to be eliminated from the lateral and luminal plasma membranes of the cuboidal cells, and mature choroidal epithelial cells showed activity on the basal surface only. These findings suggest that AlPase may play an important role in the membrane activity of epithelial cells differentiating between the primitive epithelial cells of the ventricular roof and the mature choroidal epithelial cells.     

The ependyma of goat. II. Ependymal lining of the lateral ventricles, mesencephalic canal, and fourth ventricle: scanning electron microscopic study

The ependymal surface of the lateral cerebral ventricle, mesencephalic canal, and IVth ventricle of 13 male and female goats were studied by means of scanning electron microscopy. The lateral cerebral ventricle was covered mostly with thin cilia that might have club-like terminations on nucleus caudatus, the wide "naked" places with bleb-like protrusions occurred in the transition to cornu temporale during anestrous cycle. The ependymal surface of mesencephalic canal of female goats during anestrus was covered with abundant spherical protrusions. No other changes that could be related to the sexual differences were found.     

Concanavalin A binding sites on the luminal surface of ependymal cells of third ventricle

Summary Detection of the Concanavalin A binding sites within the luminal surface of ependymal cells of the third ventricle has been accomplished using perfusion techniques as a way of exposing the cells to reaction solutions. Parameters for this procedure were established. It was found that electron dense reaction products form a layer ranging from 25–40 nm in thickness on the luminal surface of investigated cells. The microvilli exhibited a slightly thiner layer, the reaction products formed small patches on cilia.     

Bovine Reissner’s fiber (RF) and the central canal of the spinal cord: an immunocytochemical study using a set of monoclonal antibodies against the RF-glycoproteins

The subcommissural organ secretes N-linked complex-type glycoproteins into the cerebrospinal fluid. These glycoproteins condense to form Reissner’s fiber (RF), which extends along the fourth ventricle and central canal of the spinal cord. A set of three monoclonal antibodies (Mabs 3E6, 3B1, and 2A5) has been obtained using these glycoproteins as immunogens. Competitive and sandwich enzyme-linked immunoassay methods have demonstrated that the three monoclonal antibodies are directed against different epitopes, and that there is no competition among them for their binding to glycoproteins of RF. Mab 3E6 displays immunoblotting properties that are similar to those of a polyclonal antibody against the pool of glycoproteins from RF, but that are different from those of Mabs 3B1 and 2A5. All three antibodies immunostain the bovine subcommissural organ and RF. A population of ependymal cells is stained by the polyclonal antibody, and Mabs 2A5 and 3E6, but not by Mab 3B1. The material present in a population of ependymal cells of the central canal, and the glycoproteins secreted by the subcommissural organ thus probably have partial chemical identity. Some evidence suggests that the immunoreactive ependymal cells are secretory cells. The luminal surface of the central canal is coated by a thin layer of material with immunocytochemical characteristics different from those of the ependymal cells; such a coat may correspond to material released from RF. Received: 19 December 1995 / Accepted: 30 April 1996     

Distribution of intraventricularly injected horseradish peroxidase in cerebrospinal fluid compartments of the rat spinal cord

Summary The circulation of the cerebrospinal fluid along the central canal and its access to the parenchyma of the spinal cord of the rat have been analyzed by injection of horseradish peroxidase (HRP) into the lateral ventricle. Peroxidase was found throughout the central canal 13 min after injection, suggesting a rapid circulation of cerebrospinal fluid along the central canal of the rat spinal cord. It was cleared from the central canal within 2 h, in contrast with the situation in the brain tissue, where it remained in the periventricular areas for 4 h. In the central canal, HRP bound to Reissner's fiber and the luminal surface of the ependymal cells; it penetrated through the intercellular space of the ependymal lining, reached the subependymal neuropil, the basement membrane of local capillaries, and appeared in the lumen of endothelial pinocytotic vesicles. Furthermore, it accumulated in the labyrinths of the basement membrane contacting the basolateral aspect of the ependymal cells. In ependymocytes, HRP was found in single pinocytotic vesicles. The blood vessels supplying the spinal cord were classified into two types. Type-A vessels penetrated the spinal cord laterally and dorsally and displayed the tracer along their external wall as far as the gray matter. Type-B vessels intruded into the spinal cord from the medial ventral sulcus and occupied the anterior commissure of the gray matter, approaching the central canal. They represented the only vessels marked by HRP along their course through the gray matter. HRP spread from the wall of type-B vessels, labeling the labyrinths, the intercellular space of the ependymal lining, and the lumen of the central canal. This suggests a communication between the central canal and the outer cerebrospinal fluid space, at the level of the medial ventral sulcus, via the intercellular spaces, the perivascular basement membrane and its labyrinthine extensions.     

The ventricular surface of the area postrema and the adjacent area subpostrema in the rabbit brain]

The ependymal surface of the area postrema (rabitt) was examined by scanning and transmission electron microscopy. The flattened ependymal cells show few microvilli. Towards the central canal, the ependymal cells change gradually to a columnar shape; the number of microvilli increases concomitantly. The area postrema ependymal cell surface mostly bears a single cilia. In contrast, a region immediately adjacent to the area postrema, which has been named area subpostrema (Gwyn and Wolstencroft 1968), shows cilia arranged in bunches. These cilia are regularly covered with colloid -- like droplets. A period-acid-bisulfit-aldehydthionine method (Specht 1970) permits to identify these droplets with glyproteids.it has been suggested that the droplets might derive from the area subpostrema ependymal cells. Above the ependymal surface of the area postrema, a great number of fine unmyelinated neuronal processes and thicker processes are observed. Some of them show bulb-like endings. These terminals contain small vesicles, dense cored vesicles (400...800 A), and mitochondria which are mostly characterized by a single central prismatic tubule. The plasmalemma of some bulbs is in a synaptic contact with the apical plasmalemma of the ependyma, while other bulbs see to end freely in the ventricle. Some neuronal processes penetrate between ependymal cells of the area postrema into the ventricular lumen.     

Ependyma and supraependymal structures in some areas of the fourth ventricle in the rat

The ependyma was investigated in five areas of the rat ventricle system by means of both light and electron microscopy. The columnar, cuboidal and flattened types of the ependymal cells were mainly seen. All of them were seen in the fourth ventricle, while in the aqueductus cerebri and in the central canal the flattened type of the cell was lacking. An unusual variation as to the form of the ependymal cells was found on the roof of the fourth ventricle. Three groups of intraventricular structures were found in all investigated parts of the ventricle system: supraependymal globular structures containing irregularly arranged cristae, supraependymal protrusions appearing as homogeneous contents, and nerve profiles including nerve endings and nerve axons. The morphological characteristics of the ependyma and intraventricular profiles in the fourth ventricle allow to suppose a certain role of these structures in the exchange of various materials between the CSF, ependyma and neuropile.     

新生鼠中枢神经系统内Nestin蛋白免疫阳性的组织分布

为了观察Nestin在新生SD大鼠中枢神经系统中的分布,探讨神经干细胞在新生鼠的分布.采用免疫荧光法,显示含神经干细胞特征性的标志物Nestin的阳性结构在新生SD大鼠中枢神经系统中的分布.结果表明在新生SD大鼠中枢神经系统中,Nestin在前脑、脑干和小脑的各个部位均有表达,阳性结构多为纤细的纤维状突起,分布密集,标记强度多为中等强度,分布相对比较均匀.在脊髓实质的Nestin免疫阳性产物明显减少,分布稀疏,染色也较浅,中央管Nestin免疫染色阳性的室管膜细胞很少,但在脊髓中央管的背侧(延髓见于腹侧和背侧)可见到“喷泉”状免疫强阳性纤维束垂直伸展,直达软膜.由此可得出结论:新生SD大鼠中枢神经系统的广泛脑区均存在大量的神经干细胞,而脊髓的神经干细胞数目较少,提示神经干细胞在生后从神经系统的尾端开始逐渐减少.     

Spinal cord central canal of the German shepherd dog: Morphological,histological, and ultrastructural considerations

This study deals with some macroscopical, microscopical, and ultrastructural aspects of the spinal cord central canal of the German shepherd dog. The caudal end of the spinal cord is constituted by the conus medullaris, which may extend to the first sacral vertebra, the terminal ventricle, and the filum terminale. The latter structure is considered as internum (second to third sacral vertebrae) or externum (fifth caudal vertebra), according to its relation to the dura mater. Occasionally, there is a second anchorage which is close to the level of the sixth caudal vertebra. The central canal is surrounded by a ciliated ependymal epithelium, which differs depending upon the levels. The most caudal part of the filum terminale bears a columnar ciliated ependymal epithelium surrounded by two layers of glia and pia mater, which separate the central canal from the subarachnoid space. Microfil injections show a communication between the cavity and the subarachnoid space, as the plastic is able to pass through the ependymal epithelium. At the level of the terminal ventricle there are real separations of the ependymal epithelium, which seem to connect the lumen of the spinal canal with the subarachnoid space. These structures probably constitute one of the drainage pathways of the cerebrospinal fluid. The diameter of the central canal is related to the age of the animal. However, even in very old animals the spinal cord central canal reaches the tip of the filum terminale and remains patent until death. At the ultrastructural level the ependymal cells present villi, located on cytoplasmic projections, cilia, dense mitochondria, and oval nuclei. © 1995 Wiley-Liss, Inc.     

Experimental protein malnutrition as a causative factor in the histological and histochemical disruption of the ependymal cells of the third ventricla and cervical central canal of squirrel monkeys.

The histologic disturbances of the cuboidal and columnar ependymal cells of the neonates under the extrinsic influence of maternal protein deprivation during most of the gestation period have been demonstrated in the central canal of the cervical spinal cord and III ventricle of the squirrel monkey brain. The control animals whose mothers were maintained on high protein diets showed an unbroken ependymal layer with an intact glial fiber layer and the subependymal cell plate. Taking birth-weight as an indication of the degree of malnutrition, maximum disruption of the ependymal layer was observed in those animals born around 80 g birth-weight. In the latter, most of the ependymal cells lost their characteristic arrangement and columnar shapes. The ependymal cells of the manourished animals show a marked reduction of oxidative enzyme content and relatively active glycogen metabolism as compared to the healthy controls. The significance of these changes has been discussed in the light of parallels in the embryological development and, to some extent, functions between the orinary neurons, ependymal cells of the choroid plexus, other ependymal cells and the glial cells. In this context, the changes observed in the present studies under the effect of protein malnutrition must be taken as part of overall changes experienced by various kinds of cells comprising the nervous system.     

Akhirin regulates the proliferation and differentiation of neural stem cells in intact and injured mouse spinal cord

Although the central nervous system is considered a comparatively static tissue with limited cell turnover, cells with stem cell properties have been isolated from most neural tissues. The spinal cord ependymal cells show neural stem cell potential in vitro and in vivo in injured spinal cord. However, very little is known regarding the ependymal niche in the mouse spinal cord. We previously reported that a secreted factor, chick Akhirin, is expressed in the ciliary marginal zone of the eye, where it works as a heterophilic cell‐adhesion molecule. Here, we describe a new crucial function for mouse Akhirin (M‐AKH) in regulating the proliferation and differentiation of progenitors in the mouse spinal cord. During embryonic spinal cord development, M‐AKH is transiently expressed in the central canal ependymal cells, which possess latent neural stem cell properties. Targeted inactivation of the AKH gene in mice causes a reduction in the size of the spinal cord and decreases BrdU incorporation in the spinal cord. Remarkably, the expression patterns of ependymal niche molecules in AKH knockout (AKH?/?) mice are different from those of AKH+/+, both in vitro and in vivo. Furthermore, we provide evidence that AKH expression in the central canal is rapidly upregulated in the injured spinal cord. Taken together, these results indicate that M‐AKH plays a crucial role in mouse spinal cord formation by regulating the ependymal niche in the central canal. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 75: 494–504, 2015     

Comparative scanning and transmission electron microscopy studies of the ependyma of the central canal in the spinal cord of primates. I. Electron optical image of the ependyma in the central canal of the spinal cord of the callithrix monkey (Callithrix jacchus, Linné 1758)

The ependyma lining the central canal of the spinal cord of adult males and females monkey, Callithrix jacchus, was examined by scanning and transmission electron microscopy. The cross section of the lumen of the central canal are round, oval, or triangular. Light and dark ependymal cells, depending on the density of the cytoplasm, were found. The light ependymal cells are fewer than the dark cells. The ependyma cytoplasm contained numerous mitochondria, filamentous structures, one or more well-developed Golgi-complexes, vesicles of the smooth endoplasmic reticulum, ribosomes, lysosomes, multivesicular bodies, profiles of the rough endoplasmic reticulum, large osmophilic bodies, and microtubules. The nuclei of the ependyma cells usually have a simple, regular round or oval shape. They occupy a relatively large portion of the cell volume and lie in the central or mediobasal position. Some of the nuclei show deep invaginations into the karyoplasm. Most of the mitochondria occupy mainly the supranuclear portion of the apical cytoplasm. There are of the crista-typ. Ribosomes occur free in the cytoplasm, but some attached to the profiles of the rough endoplasmic reticulum or being arranged as polysomes. The filamentous structures are generally prominent cytoplasmic components and are distributed at the apical, lateral, or basal region of the ependymocytes. They are grouped into bundles and arranged in parallel arrays. Some of these bundles reach the plasmamembrane at the free lumina of the central canal, others take contact to the filamentous structures of the zonulae adherentes of the junctional complex below the free surface. The granular endoplasmic reticulum shows specializations. There profiles surrounding granular substances and widely distributed granulations in connection with the nuclear envelope. The functional significance of the deposition of these granulations is still unknown. The luminal surface of the ependymocytes bears many microvilli and cilia. The cilia are regularly arranged in cranio-caudal direction. Each cilium has the typical (9 + 2)-subfibres. The intercellular space at the surface of the ependymal layer shows a single zonula adherens or zonulae adherentes in the row. Tight junctions and gap junctions were not found in the material examined. Cell processes of liquor contacting neurons between adjacent ependyma cells, protruding into the lumen of the central canal, could be observed. The termination of these neurons contains accumulations of mitochondria in the central part, large amounts of vesicles, and small dense bodies. They have short microvilli and some stereocilia at the free surface.(ABSTRACT TRUNCATED AT 400 WORDS)     

Development and differentiation of the brain ventricular system in tadpoles of Xenopus laeris (Daudin) (Amphibia, Anura)

The development and the differentiation of the ventricular system of the brain of tadpoles of the South African Clawed Toad, Xenopus laevis (Daudin), is studied by light microscopy (stages 45 to 66) and scanning and transmission electron microscopy (stages 50 to 66). Special interest is paid to the ependymal structures of the foramen of Monroe, the ventricles of the diencephalon, the mesencephalon, and the rhombencephalon, and to the ependymal of the central canal and the choroid plexus of the third and fourth ventricle. At early developmental stages the lower two thirds of the ventricles are dominated by blebs, cytoplasmatic protrusions of the ependymal cells. During the development they become reduced and replaced by cilia. The number of cilia and microvilli increases strongly towards the end of the metamorphosis. The surface structures demonstrated by scanning electron microscopy are discussed in respect to morphology and physiology.     

Scanning electron microscopy of the wall of the third ventricle in the brain of Rana temporaria. Part IV.

Summary The surface specializations of the wall of the third cerebral ventricle of Rana temporaria were investigated with the scanning electron microscope. These specializations can be divided into three types: cilia, large bulbous protrusions, and microvillus-like protrusions.Most parts of the ventricular surface are densely ciliated. In contrast, other regions are either scantily ciliated or devoid of cilia. Four areas of the ventricular surface are studded with numerous large bulbous protrusions. These large protrusions can be divided into two types: One type consists of intraventricular end bulbs of dendrites of secretory neurons. The other type is represented by large cytoplasmic extensions of ependymal cells.In the third ventricle of Rana, microvillus-like surface specializations of ependymal cells are ubiquitous structures. Generally, filiform protrusions of varying length are the predominant type. The microvillus-like specializations are transient structures, the number of which varies according to different physiological states of the ependymal cells.This investigation was supported by a grant from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk Onderzoek     

Scanning electron microscopic analysis of the linings of the fourth ventricle in the domestic fowl

Summary Surface features of the ependymal linings of the fourth ventricle in the fowl were analyzed employing the scanning electron microscope (SEM). On the floor of the median sulcus, each ependymal cell has a solitary cilium, whereas on both sides of the sulcus, cilia are so densely distributed that the details of the underlying cell surface are usually obscured. On the roof of the fourth ventricle, except for the surface of the ciliated groove where numerous cilia are present, the ependymal cells are polygonal in shape, and the center of each cell possesses an aggregate of ten to twenty cilia. Cell surfaces of the choroid tela are entirely covered with delicate microvilli and possess clumped cilia. The ependymal cell surfaces of the area postrema are dome-like in shape. Each ependymal cell has a solitary cilium and shows a smooth surface free of microvilli.This work was supported by a Scientific Research Grant, No. 144017, from the Ministry of Education of Japan to Professor M. Yasuda     

Ependymal Cell Differentiation and GLUT1 Expression is a Synchronous Process in the Ventricular Wall

Ependymal cells appear to be totally differentiated during the first 3 weeks in the mouse brain. Early during postnatal development ependymal cells differentiate and undergo metabolic activation, which is accompanied by increased glucose uptake. We propose that ependymal cells induce an overexpression of the glucose transporter, GLUT1, during the first 2 weeks after delivery in order to maintain the early metabolic activation. During the first postnatal day, GLUT1 is strongly induced in the upper region of the third ventricle and in the ventral area of the rostral cerebral aqueduct. During the next 4 days, GLUT1 is expressed in all differentiated ependymal cells of the third ventricle and in hypothalamic tanycytes. At the end of the first week, ependymal cell differentiation and GLUT1 overexpression is concentrated in the latero-ventral area of the aqueduct. We propose that ependymal cell differentiation and GLUT1 overexpression is a synchronous process in the ventricular wall.     

Ventriculomegaly associated with ependymal gliosis and declines in barrier integrity in the aging human and mouse brain

Age‐associated ventriculomegaly is typically attributed to neurodegeneration; however, additional factors might initiate or contribute to progressive ventricular expansion. By directly linking postmortem human MRI sequences with histological features of periventricular tissue, we show that substantial lateral ventricle surface gliosis is associated with ventriculomegaly. To examine whether loss of ependymal cell coverage resulting in ventricle surface glial scarring can lead directly to ventricle enlargement independent of any other injury or degenerative loss, we modeled in mice the glial scarring found along the lateral ventricle surface in aged humans. Neuraminidase, which cleaves glycosidic linkages of apical adherens junction proteins, was administered intracerebroventricularly to denude areas of ependymal cells. Substantial ependymal cell loss resulted in reactive gliosis rather than stem cell‐mediated regenerative repair of the ventricle lining, and the gliotic regions showed morphologic and phenotypic characteristics similar to those found in aged humans. Increased levels of aquaporin‐4, indicative of edema, observed in regions of periventricular gliosis in human tissue were also replicated in our mouse model. 3D modeling together with volume measurements revealed that mice with ventricle surface scarring developed expanded ventricles, independent of neurodegeneration. Through a comprehensive, comparative analysis of the lateral ventricles and associated periventricular tissue in aged humans and mouse, followed by modeling of surface gliosis in mice, we have demonstrated a direct link between lateral ventricle surface gliosis and ventricle enlargement. These studies highlight the importance of maintaining an intact ependymal cell lining throughout aging.     

Fine structure and its functional properties of the ependymal cell in the frog median eminence

Summary Intercellular canaliculi surrounded by several ependymal cells, having numerous microvilli and a few cilia on the apical surface, are present throughout the frog median eminence. The intercellular canaliculi penetrate deeply near the portal vessel from the third ventricle. They are separated from the pericapillary space only by the thin cytoplasm of the ependymal cell.The cytoplasmic protrusions containing a large number of clear vesicles are often found at the apical surface of ependymal cells facing the third ventricle or the lumen of intercellular canaliculus. The ependymal cell shows well developed Golgi apparatus and well developed rough endoplasmic reticulum in its cytoplasm. Dense granules of about 1200–1500 A diameter suggesting secretory materials are found in small number near the Golgi apparatus and abundantly in the ependymal process lying around the portal vessel.Synaptic contacts between the ependymal cell and two different types of the nerve endings, monoaminergic and peptidergic, are frequently observed. A few small flasklike caveolae suggesting micropinocytosis are found in the post-synaptic membrane as well as in the lateral and basal plasma membranes of the ependymal cell. The author consideres that the ependymal cell in this region has secretory and transport (absorption) activities.     

Fine structure of the rhombencephalic tela of the bullfrog,Rana catesbeiana

Summary The posterior rhombencephalic tela choroidea of the bullfrog was examined by electron microscopy. This membrane, the pia-ependymal roof of the caudal hindbrain, contains a large central region characterized by cuboidal ependymal cells which surround sizable microscopic apertures — the interependymal pores.Ultrastructurally ependymal cells of this area are characterized by infrequent apical microvilli and cilia. They contain irregularly shaped nuclei and few cytoplasmic organelles that are largely apical in position. The most striking feature is an abundance of cytoplasmic filaments forming an extensive cytoskeleton. Laterally these cells are joined by numerous elaborate desmosomes. The majority of the ependymal cells have a basal lamina consisting of single, double, or triple laminae lying parallel to the basal plasma membrane.Several unusual specializations are seen at the margins of the interependymal pores. The ependymal cells have lateral cytoplasmic processes that form the actual border of each pore. These processes originate from the apical surface of the cell and partially enclose an elaborate network of basal lamina associated with the interependymal pores.These findings demonstrate microscopic apertures in the roof of the fourth ventricle in the bullfrog that are associated with an unusual form of supportive ependyma.     

A scanning electron microscopic survey of the brain ventricular system of the female armadillo

Summary The scanning electron microscope was used to survey the brain ventricular system of the female armadillo (Dasypus novemcinctus) with emphasis on the third ventricle. The walls of the lateral ventricles, aqueduct, and fourth ventricle are covered by long cilia. In the lateral ventricle, the cilia are arranged in groups; but in the aqueduct and fourth ventricle, they are evenly placed over the cellular surfaces. The ependymal cells of the third ventricle are densely ciliated except for the organum vasculosum and infundibular recess. The non-ciliated luminal surface of these areas has a pebblestone appearance punctuated by numerous microvilli and two types of supraependymal cells.Supported by Edward G. Schlieder Foundation GrantThe authors would like to thank Jacqueline Skaggs for her secretarial assistance and Garbis Kerimian for his photographic work