Sequential expression of Efhc1/myoclonin1 in choroid plexus and ependymal cell cilia

EFHC1 is a gene mutated in patients with idiopathic epilepsies, and encodes the myoclonin1 protein. We here report the distribution of myoclonin1 in mouse. Immunohistochemical analyses revealed that the myoclonin1 first appeared at the roof of hindbrain at embryonic day 10 (E10), and moved on to choroid plexus at E14. At E18, it moved to ventricle walls and disappeared from choroid plexus. From neonatal to adult stages, myoclonin1 was concentrated in the cilia of ependymal cells at ventricle walls. At adult stages, myoclonin1 expression was also observed at tracheal epithelial cilia in lung and at sperm flagella in testis. Specificities of these immunohistochemical signals were verified by using Efhc1-deficient mice as negative controls. Results of Efhc1 mRNA in situ hybridization were also consistent with the immunohistochemical observations. Our findings raise "choroid plexusopathy" or "ciliopathy" as intriguing candidate cascades for the molecular pathology of epilepsies caused by the EFHC1 mutations.

Distribution of nestin and other stem cell-related molecules in developing and diseased human spinal cord

In mammalian spinal cords, no neurogenesis has been observed after initial development. However developed mammalian spinal cords seemingly contain neural stem cells (NSC), which can give rise to neurons and glial cells when they are placed in appropriate environments. The purpose of the present paper was to investigate the developing, developed, and diseased human spinal cord to see which cell types have an immunophenotype similar to NSC. In 12 specimens from preterm neonates and term infants up to 14 months old, nestin was expressed in cells that extended fibrous processes and were located around the midline in the ependymal layer. In all the preterm neonates, Musashi-1 and glial fibrillary acidic protein (GFAP) were also expressed in this subpopulation, whereas Lewis X was detected in a less restricted subpopulation. Nestin expression by these cells was not detected in most adult spinal cords, but was observed in three spinal cords from 13 amyotrophic lateral sclerosis patients and eight of 14 spinal cords involved by the tumor. The present observations suggest that during gestation a subpopulation of cells in the ependymal layer remains undifferentiated as potential NSC/neural progenitor cells, and becomes unidentifiable in early infancy. These cells, however, appear in response to disease conditions, especially tumor involvement.

Fetal MRI demonstrates glioependymal cyst in a case of sonographic unilateral ventriculomegaly

We report a fetus of 28 weeks' gestation in which ultrasonography demonstrated unilateral ventriculomegaly and microcephaly. Fetal MRI demonstrated a simple, left paramedian occipital cyst with rarefaction of the corpus callosum and thinning of the adjacent cortical mantle. Ischaemia was suggested as the underlying pathogenesis, but autopsy after termination of pregnancy revealed a glioependymal cyst. This case highlights consideration of the rare diagnosis of glioependymal cyst when a cystic lesion associated with cerebral malformations, particularly dysgenesis of the corpus callosum, is demonstrated and fetal MRI suggests an ischaemic origin.

Early Embryonic Development of the Camel Lumbar Spinal Cord Segment

The lumbar spinal cord segment of the one-humped camel (Camelus dromedarius) embryos at 2.4- to 28-cm crown vertebral rump length (CVRL) was examined. Major changes are occurring in the organization of the lumbar spinal cord segment at this early developmental period. At first, the spinal cord is flattened from side to side but with increase in gestational age it becomes flattened dorsoventrally. The size and shape of the lumen changes in indifferent stage of development. These changes may be in relation to the decrease of ependymal layer and increase of the mantel layer during the developmental stages. The lumen of the spinal cord is a wide spindle in shape at 2.4-cm CVRL, diamond in shape at 5.5-cm CVRL and narrow oval in shape at 28-cm CVRL. It occupies about the whole, half and one-seventh of the total height of the spinal cord at 2.4-, 5.5- and 28-cm CVRL, respectively. At the 2.4-2.7 CVRL, the spinal cord is formed of six plates: roof, floor, two alar and two basal plates. The present investigation indicates that the distribution of the ependymal, mantle and marginal layers differs in the various developmental stages of the camel embryos. The majority of the cross section of the spinal cord consists at first of ependymal and mantle layers, and a thin outer rim of the marginal layer. With the advancement of age, the ependymal layer diminishes in size, while the mantle and marginal layers increase in size forming the future grey and white matters, respectively.

Olig2-positive progenitors in the embryonic spinal cord give rise not only to motoneurons and oligodendrocytes, but also to a subset of astrocytes and ependymal cells

Motoneurons and oligodendrocytes in the embryonic spinal cord are produced from a restricted domain of the ventral ventricular zone, termed the pMN domain. The pMN domain is the site of expression of two basic helix-loop-helix transcription factors, Olig1 and Olig2, which are essential for motoneuron and oligodendrocyte development. Previous lineage-tracing experiments using Olig1-Cre and Olig2-GFP mice suggested that motoneurons and oligodendrocytes, but not astrocytes, are produced from the pMN domain. However, important questions remain, including the fate of neuroepithelial cells in the pMN domain, and specifically whether motoneurons and oligodendrocytes are the only types of cells produced in the pMN domain. We performed lineage-tracing experiments using a tamoxifen-inducible Cre-recombinase inserted into the Olig2 locus. We demonstrated that motoneurons and oligodendrocyte progenitors are derived from the Olig2+ progenitors in the pMN domain, and also found that a subset of astrocytes at the ventral surface of the spinal cord and ependymal cells at the ventricular surface are also produced from the pMN domain. These findings demonstrate that motoneurons and oligodendrocytes are not the only cell types originating from this domain.

Lectin binding in the ependymal cells of the cephalic portion of the nervous system in the chick embryo

The content, distribution and changes of the glycoconjugates oligosaccharides in the ependymal cells of the cephalic portion of the nervous system, in the chick embryo from 5 days of incubation till hatching and in the 3 days old chicken, were investigated. For this purpose a battery of six HRP-conjugated lectins were used (WGA, SBA, UEA I, LTA, PNA, ConA). Enzyme and chemical treatments were performed on some sections prior to staining with HRP-lectins. Our findings showed a large amount of all the investigated sugar residues at the apical portion of the ependymal cells, for the whole considered period of incubation and in the 3 days old chicken. This could indicate that also the immature ependymal cells (spongiobasts) begin to play a tipical role of the mature cells. The presence of cytoplasmic sopranuclear granules, containing D-glucosamine, D-galactose-(beta --> 3)-N-acetil-D-galactosamine and sialic acid in the early stages of incubation, might represent a secretion by the ependymal cells to integrate a not yet fully functioning secretion by the choroid plexuses. At the ciglia a large amount of oligosaccharides were detected in the second part of the period of incubation and in 3 days old chicken. These oligosaccharides could be involved in determining and mantaining the movement of the ciglia to facilitate the flow of the CSF.

Upregulated and prolonged differentiation potential of the ependymal cells lining the ventriculus terminalis in human fetuses

The ventriculus terminalis (VT) is a dilated cavity within the conus medullaris of the spinal cord. Although the VT was discovered in the mid-nineteenth century, little is known about its characteristics during development in human fetuses. Ependymal cells lining the cavities within the CNS retain high differentiation potential, and are believed to be responsible for the postnatal neurogenesis. To evaluate the differentiation capacity of the ependymal cells lining the VT during development, we examined glial fibrillary acidic protein (GFAP) and proliferating cell nuclear antigen (PCNA) expression in the spinal cord of 18-24-week-old human fetuses. GFAP is a marker for the degree of ependymal cell differentiation in the human fetus, and PCNA is a well-known marker for cell division. Morphological characteristics of the VT were also examined. At the lower portion of the conus medullaris, the central canal abruptly expands dorsally to become the VT. Then the VT widens bilaterally while its anteroposterior diameter reduces gradually in a caudal direction. Finally, the VT becomes a narrow, transverse slit at the level of the lowermost conus medullaris. Compared with those lining the central canal, more numerous ependymal cells lining the VT showed more intensive GFAP and PCNA expression throughout all gestational ages examined. This suggests that, in the developing human spinal cord, ependymal cells lining the VT retain their differentiation potential, including a higher proliferative capacity, until a later stage of development than those lining the central canal.

Adult ependymal cells are postmitotic and are derived from radial glial cells during embryogenesis

Ependymal cells on the walls of brain ventricles play essential roles in the transport of CSF and in brain homeostasis. It has been suggested that ependymal cells also function as stem cells. However, the proliferative capacity of mature ependymal cells remains controversial, and the developmental origin of these cells is not known. Using confocal or electron microscopy (EM) of adult mice that received bromodeoxyuridine (BrdU) or [3H]thymidine for several weeks, we found no evidence that ependymal cells proliferate. In contrast, ependymal cells were labeled by BrdU administration during embryonic development. The majority of them are born between embryonic day 14 (E14) and E16. Interestingly, we found that the maturation of ependymal cells and the formation of cilia occur significantly later, during the first postnatal week. We analyzed the early postnatal ventricular zone at the EM and found a subpopulation of radial glia in various stages of transformation into ependymal cells. These cells often had deuterosomes. To directly test whether radial glia give rise to ependymal cells, we used a Cre-lox recombination strategy to genetically tag radial glia in the neonatal brain and follow their progeny. We found that some radial glia in the lateral ventricular wall transform to give rise to mature ependymal cells. This work identifies the time of birth and early stages in the maturation of ependymal cells and demonstrates that these cells are derived from radial glia. Our results indicate that ependymal cells are born in the embryonic and early postnatal brain and that they do not divide after differentiation. The postmitotic nature of ependymal cells strongly suggests that these cells do not function as neural stem cells in the adult.

Ependymal Denudation and Alterations of the Subventricular Zone Occur in Human Fetuses With a Moderate Communicating Hydrocephalus

In mutant rodents, ependymal denudation occurs early in fetal life, preceding the onset of a communicating hydrocephalus, and is a key event in the etiology of this disease. The present investigation was designed to obtain evidence whether or not ependymal denudation occurs in 16- to 40-week-old human fetuses developing a communicating hydrocephalus (n = 8) as compared to fetuses of similar ages with no neuropathologic alterations (n = 15). Sections through the walls of the cerebral aqueduct and lateral ventricles were processed for lectin binding and immunocytochemistry using antibodies against ependyma, astroglia, neuroblasts, and macrophages markers. Anticaveolin was used as a functional marker of the fetal ependyma. The structural and functional molecular markers are differentially expressed throughout the differentiation of the human fetal ependyma. Denudation of the ependyma of the aqueduct and lateral ventricles occurred in all fetuses developing a communicating hydrocephalus, including the youngest ones studied. The denuded surface area increased in parallel with the fetus age. The possibility is advanced that in many or most cases of human fetal hydrocephalus there is a common defect at the ependymal cell lineage leading to ependymal detachment. Evidence was obtained that in hydrocephalic human fetuses a process to repair the denuded areas takes place during the fetal life. In hydrocephalic fetuses, detachment of the ependyma of the lateral ventricles resulted in the (i) loss of the germinal ependymal zone, (ii) disorganization of the subventricular zone and, (iii) abnormal migration of neuroblasts into the ventricular cavity. Thus, detachment of the ependymal layer in hydrocephalic fetuses would not only be associated with the pathogenesis of hydrocephalus but also to abnormal neurogenesis.

[Where have the neuronal stem cells of the subependymal zone gone in human beings?]

Stem cells are characterized by their ability for self-renewal (allowing them to be present throughout the entire life of the organism) and their ability to give rise to differentiated cells belong to one or more lineages. The strict definition of these cells is however still a matter of debate. There is new experimental evidence (including in human beings) that stem cells are present within the brain and may give rise to neurons. Ependymal cells have been proposed to play such a role. In fact, subependymal cells expressing GFAP would be more likely candidates. Such cells are observed in the brain of human beings. They are able to differentiate into neurons in vitro but such potential appears to be repressed in vivo.

Anatomic analysis of blood vessels in germinal matrix, cerebral cortex, and white matter in developing infants

The germinal matrix (GM) located in the thick subependymal cell layer of the thalamostriate groove is a major site of cerebral hemorrhage in premature infants. Comparing the morphology of vasculature among GM, gray and white matter of the brain may help in understanding the pathogenesis of GM hemorrhage and also of periventricular leukomalacia. The objective of the present study was to determine the morphology of blood vessels in the GM, gray matter, and white matter and to examine maturational changes in the morphology of these vessels as a function of gestational age. We measured vessel density, percentage of blood vessel area, mean surface area, length, breadth, perimeter, radius, and shape of blood vessels in coronal sections of the GM, gray matter, and white matter in postmortem human brain samples for 17 fetuses and premature infants of gestational age 16-40 wk and 2 adults. We performed immunohistochemical staining using anti-laminin primary antibody, confocal microscopy to acquire images, and analysis using Metamorph version 6.1. Vessel density and the percentage of blood vessel area increased as a function of gestational age in the GM, gray matter, and white matter (p < 0.001 each). The blood vessel density and the percentage of blood vessel area were largest in the GM followed by gray matter and then white matter in all of the gestational age categories (p < 0.001 for all comparisons). Increased vascularity of the GM compared with gray and white matter may play a role in GM hemorrhage, whereas a relatively low vascularity of white matter may increase the propensity for the occurrence of periventricular leukomalacia in premature infants

Molecular mapping of the origin of postnatal spinal cord ependymal cells: evidence that adult ependymal cells are derived from Nkx6.1+ ventral neural progenitor cells

Recent studies have suggested that the ependymal cells lining the central canal of postnatal spinal cord possess certain properties of neural stem cells. However, the embryonic origin and developmental potential of the postnatal spinal cord ependymal cells remain to be defined. In this report, we investigated the developmental origin of postnatal spinal ependymal cells by studying the dynamic expression of several neural progenitor genes that are initially expressed in distinct domains of neuroepithelium in young embryos. At later stages of development, as the ventricular zone of the embryonic spinal cord is reduced, expression of Nkx6.1 progenitor gene is constantly detected in ependymal cells throughout chick and mouse development. Expression of other neural progenitor genes that lie either dorsal or ventral to the Nkx6.1+ domain is gradually decreased and eventually disappeared. These results suggest that the remaining neuroepithelial cells at later stages of animal life are derived from the Nkx6.1+ ventral neuroepithelial cells. Expression of Nkx6.1 in the remaining neuroepithelium is closely associated with, and regulated by, Shh expression in the floor plate. In addition, we suggested that the Nkx6.1+ ependymal cells in adult mouse spinal cords may retain the proliferative property of neural stem cells.

Chronic hypoxia up-regulates fibroblast growth factor ligands in the perinatal brain and induces fibroblast growth factor-responsive radial glial cells in the sub-ependymal zone

A number of signaling molecules have been implicated in the acute response to hypoxia/ischemia in the adult brain. In contrast, the reaction to chronic hypoxemia is largely unexplored. We used a protocol of chronic hypoxia in rat pups during the first three postnatal weeks, encompassing the period of cellular plasticity in the cerebral cortex. We find that the levels of fibroblast growth factor 1 (FGF1) and FGF2, two members of the FGF family, increase after 2 weeks of chronic hypoxia. In contrast, members of the neurotrophin family are unaffected. FGF2 is normally expressed in the nucleus of mature, glial fibrillary acidic protein (GFAP)-containing astrocytes. Under hypoxia, most FGF2-containing cells do not express detectable levels of GFAP, suggesting that chronic low O(2) induces their transformation into more immature glial phenotypes. Remarkably, hypoxia promotes the appearance of radial glia throughout the sub-ventricular and ependymal zones. Most of these cells express vimentin and brain lipid binding protein. A subset of these radial glial cells expresses FGF receptor 1, and are in close contact with FGF2-positive cells in the sub-ventricular zone. Thus, FGF receptor signaling in radial glia may foster cell genesis after chronic hypoxic damage. From the results of this study we suggest that after the chronic exposure to low levels of oxygen during development, the expression of radial glia increases in the forebrain periventricular region. We envision that astroglia, which are the direct descendants of radial glia, are reverting back to immature glial cells. Alternatively, hypoxia hinders the normal maturation of radial glia into GFAP-expressing astrocytes. Interestingly, hypoxia increases the levels of expression of FGF2, a factor that is essential for neuronal development. Furthermore, chronic hypoxia up-regulated FGF2's major receptor in the periventricular region. Because radial glia have been suggested to play a key role in neurogenesis and cell migration, our data suggests that hypoxia-induced FGF signaling in radial glia may represent part of a conserved program capable of regenerating neurons in the brain after injury.

NudC associates with Lis1 and the dynein motor at the leading pole of neurons

NUDC is a highly conserved protein important for nuclear migration and viability in Aspergillus nidulans. Mammalian NudC interacts with Lis1, a neuronal migration protein important during neocorticogenesis, suggesting a conserved mechanism of nuclear movement in A. nidulans and neuronal migration in the developing mammalian brain (S. M. Morris et al., 1998). To further investigate this possibility, we show for the first time that NudC, Lis1, and cytoplasmic dynein intermediate chain (CDIC) colocalize at the microtubule organizing center (MTOC) around the nucleus in a polarized manner facing the leading pole of cerebellar granule cells with a migratory morphology. In neurons with stationary morphology, NudC is distributed throughout the soma and colocalizes with CDIC and tubulin in neurites as well as at the MTOC. At the subcellular level, NudC, CDIC, and p150 dynactin colocalize to the interphase microtubule array and the MTOC in fibroblasts. The observed colocalization is confirmed biochemically by coimmunoprecipitation of NudC with CDIC and cytoplasmic dynein heavy chain (CDHC) from mouse brain extracts. Consistent with its expression in individual neurons, a high level of NudC is detected in regions of the embryonic neocortex undergoing extensive neurogenesis as well as neuronal migration. These data suggest a biochemical and functional interaction of NudC with Lis1 and the dynein motor complex during neuronal migration in vivo.

Multiple sites of L-histidine decarboxylase expression in mouse suggest novel developmental functions for histamine

Histamine mediates many types of physiologic signals in multicellular organisms. To clarify the developmental role of histamine, we have examined the developmental expression of L-histidine decarboxylase (HDC) mRNA and the production of histamine during mouse development. The predominant expression of HDC in mouse development was seen in mast cells. The HDC expression was evident from embryonal day 13 (Ed13) until birth, and the mast cells were seen in most peripheral tissues. Several novel sites with a prominent HDC mRNA expression were revealed. In the brain, the choroid plexus showed HDC expression at Ed14 and the raphe neurons at Ed15. Close to the parturition, at Ed19, the neurons in the tuberomammillary (TM) area and the ventricular neuroepithelia also displayed a clear HDC mRNA expression and histamine immunoreactivity (HA-ir). From Ed14 until birth, the olfactory and nasopharyngeal epithelia showed an intense HDC mRNA expression and HA-ir. In the olfactory epithelia, the olfactory receptor neurons (ORN) were shown to have very prominent histamine immunoreactivity. The bipolar nerve cells in the epithelium extended both to the epithelial surface and into the subepithelial layers to be collected into thick nerve bundles extending caudally toward the olfactory bulbs. Also, in the nasopharynx, an extensive subepithelial network of histamine-immunoreactive nerve fibers were seen. Furthermore, in the peripheral tissues, the degenerating mesonephros (Ed14) and the convoluted tubules in the developing kidneys (Ed15) showed HDC expression, as did the prostate gland (Ed15). In adult mouse brain, the HDC expression resembled the neuronal pattern observed in rat brain. The expression was restricted to the TM area in the ventral hypothalamus, with the main expression in the five TM subgroups called E1-E5. A distinct mouse HDC mRNA expression was also seen in the ependymal wall of the third ventricle, which has not been reported in the rat. The tissue- and cell-specific expression patterns of HDC and histamine presented in this work indicate that histamine could have cell guidance or regulatory roles in development.

Localisation of the SRY-related HMG box protein, SOX9, in rodent brain

Human mutations in the transcription factor gene, SOX9, cause campomelic dysplasia (CD), a severe dwarfism associated with brain abnormalities including dilation of lateral ventricles, hypoplasia of the corpus callosum and cerebellum defects. To improve our understanding of how SOX9 contributes to the molecular genetic pathway of brain development we sought to investigate the distribution of SOX9 protein in rat and mouse brain. The regions of SOX9 expression identified in this study correlated with the sites of reported brain abnormalities in CD patients. SOX9 immunoreactivity was observed in nuclei of scattered cells throughout the brain, in the ependymal layer and cells of the choroid plexus. In the forebrain most SOX9-immunoreactive nuclei co-localised with the glial astrocyte marker S-100. In the cerebellum, SOX9 was observed mostly in cells surrounding Purkinje cells, which were identified, by electron microscopy, as Golgi epithelial cells, also known as Bergmann glia. Using SOX9 antibody as a marker for the precursors of Bergmann glia, we traced their origin during mouse development. At embryonic day (E)14.5 and E16.5, SOX9 immunoreactivity was present mainly in the primordial choroid plexus, and ventricular zone. By E18.5, SOX9 was observed in the granular cell and Purkinje cell layers but no labelling was detectable in the external granular layer. These results suggest that SOX9 immunoreactivity is a marker for Bergmann cells during development and favour the proposed origin of the secondary glial scaffold arising from Bergmann cells derived exclusively from the ventricular zone.

Fucosylated glycans in the periventricular structures and the cerebrospinal fluid of the fetal rat forebrain. An autoradiographic and lectin binding histiotopic study

Our autoradiographic 3H-fucose incorporation study of the brains of 20-day-old rat fetuses showed that the synthesis of fucosylated glycans is significantly higher in the ventricular germinative zone of the forebrain hemisphere than in the more superficial layers, including the cortical plate. Intense incorporation of 3H-fucose also occurred in the choroid plexus, both its epithelial and stromal component, in the primordial ependymal lining of the lateral ventricles, meninges and capillaries of the forebrain parenchyma. In the lateral ventricles, densely labeled microprecipitates of the cerebrospinal fluid (CSF) were occasionally observed. The histiotopic differences in 3H-fucose labeling were absent, or were much less expressed, in the autoradiograms prepared from unfixed cryostat sections containing mainly unincorporated isotope. This indicates that the blood-mediated supply of 3H-fucose to the studied brain compartments was essentially equal and our incorporation data reflect actual differences in the rate of fucosylation within the forebrain hemispheres. The cytochemical lectin-binding assay, carried out with Ulex europaeus and Lotus tetragonolobus agglutinins, showed that regions with a higher rate of 3H-fucose incorporation were also richer in fucose-bearing glycoconjugates. The study revealed that the periventricular regions and the CSF of fetal rat forebrain form a fucosylated glycan-enriched complex, which represents a new chemoarchitectonic feature that may be of importance for maintaining the germinative properties of the ventricular neuroepithelium and the growth of the hemispheric ventricles.

Subcommissural organ/Reissner's fiber complex: characterization of SCO-spondin, a glycoprotein with potent activity on neurite outgrowth

In the developing vertebrate nervous system, several proteins of the thrombospondin superfamily act on axonal pathfinding. By successive screening of a SCO-cDNA library, we have characterized a new member of this superfamily, which we call SCO-spondin. This extracellular matrix glycoprotein of 4,560 amino acids is expressed and secreted early in development by the subcommissural organ (SCO), an ependymal differentiation located in the roof of the Sylvian aqueduct. Furthermore, SCO-spondin makes part of Reissner's fiber (RF), a thread-like structure present in the central canal of the spinal cord. This novel protein shows a unique arrangement of several conserved domains, including 26 thrombospondin type 1 repeats (TSR), nine low-density lipoprotein receptor (LDLr) type A domains, two epidermal growth factor (EGF)-like domains, and N- and C-terminal von Willebrand factor (vWF) cysteine-rich domains, all of which are potent sites of protein-protein interaction. Regarding the huge number of TSR, the putative function of SCO-spondin on axonal guidance is discussed in comparison with other developmental molecules of the CNS exhibiting TSR. To correlate SCO-spondin molecular feature and function, we tested the effect of oligopeptides, whose sequences include highly conserved amino acids of the consensus domains on a neuroblastoma cell line B 104. One of these peptides (WSGWSSCSRSCG) markedly increased neurite outgrowth of B 104 cells and this effect was dose dependent. Thus, SCO-spondin is a favorable substrate for neurite outgrowth and may participate in the posterior commissure formation and spinal cord differentiation during ontogenesis of the central nervous system.

Ependymal cells and astrocytes generate neurons

Recent studies have showed that the ependymal cells and subventricular zone astrocytes are neurosphere-initiating cells and are neural stem cells. They give rise to neurons and glial cells in response to injury and utilization of endogenous stem cells in the treatment of nervous system diseases is important strategy in neurogenesis.

Extensive glycosylation changes revealed by lectin histochemistry in morphologically normal prenatal tissues of the mouse mutant undulated (un/un)

Recently we observed that in human embryos and fetuses with a variety of malformations, not only malformed tissues, but also several non-malformed tissues displayed alterations in the glycosylation pattern. It was the aim of this work to investigate this more or less inexplicable phenomenon under experimental conditions. To this end, we studied a well known mouse model, the mouse mutant undulated, which has an exactly defined genetic defect (substitution in the pax-1 gene) leading to a localized malformation in the vertebral column. The glycosylation pattern was studied using lectin histochemistry. Distribution of binding sites for the lectins RCA I, Con A, SNA, SBA, PNA, LTA and WGA was studied during the organogenesis stages (i.e., days 11-18). It was striking that in mutants, changes in the glycosylation pattern were found not only in the malformed organ (i.e., vertebral anlage), but also in other embryonic tissues, which showed normal morphology. This suggests that the altered glycosylation seems to be a part of genetically determined phenomena throughout the entire organism. Our results show that a defect in a gene with a very restricted expression can cause universal changes in the glycosylation pattern during development.

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.

Periventricular nodular heterotopia and childhood absence epilepsy

A young female presented with an epileptic syndrome resembling childhood absence epilepsy, a normal neurologic examination, generalized 3-Hz spike-and-wave discharges, and clinical absences. Her seizures responded to treatment with valproic acid. Other abnormalities in her electroencephalogram prompted neuroimaging studies, which demonstrated periventricular nodular heterotopia. Review of published reports confirmed this presentation to be atypical of this developmental lesion. The authors describe their patient and discuss this unexpected association and the relevant reports briefly.

Supraependymal cells and fibers during the early stages of chick rhombencephalic development

Supraependymal cellular elements are a constant feature in the adult cerebroventricular system. However, there has been no analysis of their distribution and morphology during the embryonic stages of the chick brain. The ultrastructural features of the rhombencephalic luminal surface of chick embryos ranging from stage 10 to 22 were studied with both scanning and transmission electron microscopy. In addition, immunocytochemistry and confocal laser microscopy were used to examine the presence of 68 kD neurofilaments in supraependymal elements. The ultrastructural observations revealed significant morphological differences in the apical cell surface between the cells at rhombomere boundaries and those in the rhombomere bodies. These differences support the idea that the boundary and the body of rhombomeres contain two morphologically distinct cell types. Supraependymal (SE) cells and SE fibers were present in the rhombencephalon of all embryos studied from stage 12 to 22. The cells were bipolar spindle-shaped. The SE fibers showed a characteristic spatial pattern within the rhombencephalon, following a straight course parallel to the rhombomere boundaries. The SE fibers showed varicosities and their endings contained small vesicles. Both SE cells and SE fibers were positive for 68 kD neurofilaments. Their morphology and reactivity for neurofilaments indicate a neuronal function. The constant presence of SE cells and SE fibers on the surface of the developing rhombencephalon, their special pattern and close relationship with the neural tube fluid (NTF) suggest that these supraependymal elements may be involved in a neuronal signalling pathway between different parts of the same rhombomere and also in chemical communication and integration within the ventricular system, linking distant parts of the developing central nervous system by means of NTF.

Dorsal spinal cord neuroepithelium generates astrocytes but not oligodendrocytes

There is evidence that oligodendrocytes in the spinal cord are derived from a restricted part of the ventricular zone near the floor plate. An alternative view is that oligodendrocytes are generated from all parts of the ventricular zone. We reinvestigated glial origins by constructing chick-quail chimeras in which dorsal or ventral segments of the embryonic chick neural tube were replaced with equivalent segments of quail neural tube. Ventral grafts gave rise to both oligodendrocytes and astrocytes. In contrast, dorsal grafts produced astrocytes but not oligodendrocytes. In mixed cultures of ventral and dorsal cells, only ventral cells generated oligodendrocytes, whereas both ventral and dorsal cells generated astrocytes. Therefore, oligodendrocytes are derived specifically from ventral neuroepithelium, and astrocytes from both dorsal and ventral.

Ependymal development, proliferation, and functions: a review

A survey of the literature shows that proliferation of ependyma occurs largely during the embryonic and early postnatal periods of development in most species. Differentiation of these cells proceeds along particular regional and temporal gradients as does the expression of various cytoskeletal (vimentin, cytokeratins, glial fibrillary acidic protein) and secretory proteins (S-100). Turnover declines significantly postnatally, and only low levels of residual activity persist into adulthood under normal conditions. Although the reported response of ependyma to injury is somewhat equivocal, only limited regenerative capacity appears to exist and to varying degrees in different regions of the neuraxis. Proliferation has been most often observed in response to spinal cord injury. Indeed, the ependyma plays a significant role in the initiation and maintenance of the regenerative processes in the spinal cord of inframammalian vertebrates. In the human, however, ependyma appears never to regenerate at any age nor re-express cytoskeletal proteins characteristic of immature cells. The functions of ependyma including tanycytes, a specialized form of ependymal cell that persists into adulthood within circumscribed regions of the nervous system, are still largely speculative. Fetal unlike mature ependyma is believed to be secretory and is believed to play a role in neurogenesis, neuronal differentiation/axonal guidance, transport, and support. In the adult brain, mature ependyma is not merely an inert lining but may regulate the transport of ions, small molecules, and water between the cerebrospinal fluid and neuropil and serve an important barrier function that protects neural tissue from potentially harmful substances by mechanisms that are still incompletely understood.

Histochemistry and immunocytochemistry of the developing ependyma and choroid plexus

The adult human ependyma expresses no intermediate filament proteins or secretory proteins; the fetal ependyma shows strong immunocytochemical (ICC) expression of vimentin, glial fibrillary acidic protein (GFAP), cytokeratins (CKs) of high molecular weight, glycoproteins, and S-100beta protein. Each has a precise and specific spatial distribution within the developing ependyma and a predictable time of appearance and regression in each region of the ventricular system. Several are coexpressed, but some appear earlier or persist longer than others. Secretory proteins of ependymal cells are important in several developmental processes such as the guidance of axonal growth cones. GFAP is not expressed in the floor plate ependyma at any stage of development, unlike vimentin and CK. The choroid plexus epithelium is a specialized ependyma, with an ICC profile that differs from the surface ependyma: vimentin, CK, and S-100beta protein continue to be expressed throughout fetal and adult life, but GFAP is not expressed. Certain cerebral malformations are associated with specific ICC abnormalities: ependymal S-100beta protein continues to be immunoreactive in disorders of neuroblast migration; ependymal vimentin is focally upregulated in Chiari malformations and congenital aqueductal stenosis. Other mammalian and nonmammalian species have characteristic profiles of ependymal immunoreactivity to the same proteins expressed in humans but exhibit interspecific differences.

Fetal ependyma in sheep and goat. A scanning electron microscopy study

Morphology of the surface of apical membranes of ependymal cells has been studied in the whole ventricular system of the brain in goat and sheep fetuses using a scanning electron microscope. The surface structure of the ependymal lining surface in fetuses of small ruminants is very similar to that in adult animals. Supraependymal cells were found only in the lower part of the third cerebral ventricle in goat fetuses, but not in sheep fetuses. In small ruminants the ependymal surface is already regionally differentiated within the end of the first half of prenatal development. Fetal ependyma of goats and sheep, unlike the adult ependyma, is characterized by a high secretory activity, which is independent of sex or age of fetuses.

Neuroepithelial and ependymal changes in HTX rats with congenital hydrocephalus: an ultrastructural and immunohistochemical study

To investigate the pathogenesis of congenital hydrocephalus the brains of HTX rats aged between 16 days and 4 weeks and the brains of normal Wistar rats of the same ages were examined. In the fetal HTX rat brains, the lateral ventricles were symmetrically dilated from 20 days of gestation. The neuroepithelium bordering the ventricles showed thinning with cellular disarrangement and deformity. Similar neuroepithelial abnormalities were also found in the lateral ventricles of the HTX rat brain with no macroscopic signs of hydrocephalus at 20 days of gestation. The neuroepithelium showed flattening of the cells, widening of the intercellular spaces, formation of microvilli on the detached lateral cell surfaces, and frequent macrophage infiltration. On the other hand, the neuroepithelial cells of the third ventricle and the aqueduct were affected less severely or showed no significant abnormalities. Immunohistochemically, most of the neuroepithelium and ependyma of the lateral ventricles were positive for vimentin in both prenatal and postnatal hydrocephalic HTX rats, while a small number or none of those in normal control rats were positive. These morphological changes suggested that preferential involvement of the lateral ventricular neuroepithelium might be closely associated with the pathogenesis of congenital hydrocephalus in HTX rats.

Immunohistochemical study of microtubule-associated protein 5 (MAP5) expression in the developing human brain

The expression of microtubule-associated protein 5 (MAP5) in the developing human brain was studied by means of an immunohistochemical method. In the cerebellum, MAP5 immunoreactivity appeared in the molecular layer and subcortical white matter from the early fetal age of 13 gestational weeks (GW), and temporally increased in the outer halves of the molecular layer and subcortical white matter at 36 GW to 2 months of age and 20 to 22 GW, respectively. In the cerebrum, it already appeared in the molecular layer and subcortical white matter from 13 GW, and was marked at 20 to 26 GW and 24 to 32 GW, respectively. Cortical pyramidal neurons gradually became immunoreactive from 28 GW to adolescence. Ependymal cilia were markedly positive in ventricular wall in all ages. In Western blot analyses, MAP5 showed two separate molecular weight bands. In the fetal period 320 kDa protein was prominent, but 300 kDa protein could be detected only at 11 years of age. Thus MAP5 was markedly expressed in growing axon in the fetal period and may be essential for the elongation and maturation as well as the function maintenance of axons and dendrites in developing human brain.

Specific potentialities of embryonic rat serotonergic neurons to innervate different periventricular targets in the adult brain

During the development of the central nervous system, neurons are directed by both genetic and environmental factors to differentiate and form connections with their targets. We took advantage of the abundant homogeneous serotonergic innervations of the ependyma forming the supra- and subependymal plexuses to investigate possible commitment of embryonic neurons to innervate specific targets during axogenesis in the rat. The origin of the supraependymal innervation was determined by retrograde transport of cholera toxin (CT) from the ventricles. The supraependymal plexuses of the fourth ventricle mainly originated from neurons in the dorsocaudal region of the raphe dorsalis (DRN), while the rostral DRN and raphe centralis (CRN) contained perikarya projecting into the third ventricle. This suggested the existence, along the rostrocaudal axis of the raphe, of different neuronal subsets able to form distinct supraependymal plexuses in the third or fourth ventricle. To determine whether serotonergic neurons were committed to innervate specific areas of the ependyma, different embryonic metencephalic segments (rostral, median, or caudal) from 14-day-old rat embryos were independently grafted into the third or fourth ventricle of an adult brain in which the serotonergic neurons had been previously destroyed. The distinctive patterns of re-innervation specific to each of grafted segments indicate that subsets of embryonic serotonergic neurons are indeed committed to innervate certain restricted ependymal areas of the adult brain, presumably in response to different neurotropic and/or neurotrophic cues.

Developmental changes of epidermal growth factor-like immunoreactivity in the human fetal brain

We investigated the immunohistochemical localization of epidermal growth factor (EGF) in the developing human brain from 6 weeks of gestation to 3 months postpartum. EGF-like immunoreactivity varied in its localization and intensity according to the stage of development. At 10 - 20 weeks of gestation, EGF-like immunoreactivity appeared in proliferating and migrating cells in the cerebrum, disappeared thereafter, and appeared again in cortical neurons after 27 weeks of gestation. Astrocytes also showed EGF-like immunoreactivity from 27 weeks of gestation. These results suggest developmental regulation of EGF expression in the human brain, suggesting its physiological role in both neuronal and glial cells.

Development of ependyma in neural transplants

Under in situ conditions, the innermost (juxtaventricular) neuroepithelial layer of the embryonic brain wall develops into ependyma. No development of ependyma was usually observed, however, in transplanted embryonic brain wall. In our telencephalic transplants, however, cysts lined by epithelium resembling ependyma were observed, although only sporadically. We supposed that occasional foldings of the transplanted telencephalic wall enclosed the aforementioned cysts and so induced the formation of ependyma. This hypothesis was supported by the observation that ependyma developed frequently in a model system in which the telencephalic wall was folded artificially prior to transplantation.

Long-term survival of dopaminergic neurones in free-floating roller tube cultures of human fetal ventral mesencephalon

Transplantation of human fetal ventral mesencephalon (VM) to Parkinsonian patients has shown beneficial effects in several clinical trials. However, further improvements in the transplantation technique are needed. Delayed surgery, i.e., the in vitro maintenance of the tissue prior to transplantation would present several advantages. The roller tube technique as initially described by Gähwiler (1981) was modified in several aspects for the long-term maintenance of dopaminergic neurones of human fetal VM. Tissue cultures were maintained free-floating in the medium for up to 42 days. The human fetal material was obtained from legal induced suction abortions. The embryonic age ranged from 5 to 12 weeks post-conception. Identification of VM was possible in 43% of the cases. Neurones in cultures were demonstrated by means of immunohistochemistry for tyrosine hydroxylase (TH) and gamma-amino butyric acid (GABA), by electron microscopy and by hybridisation histochemistry using a TH-mRNA-sensitive probe. A high variability in the number of TH-positive cells in individual cultures derived from the same embryo was observed. In 20 microns frozen sections of such tissue cultures the mean +/- SEM of TH-positive cells was 6.5 +/- 1.2/0.1 mm2 (n = 79; range: 0-73). The technique described insures the growth of long-term cultures of human fetal VM.

Differentiation of ependymal surface of lateral ventricles in fetus and newborn rabbits: observations by SEM

The ultrastructural modifications that occur on the ependymal surface of the lateral ventricles of prenatal rabbit brains at 25, 27, 29 days of pregnancy, of term fetuses (30-31 days) and of 5, 10, 15 day old newborn rabbits, were studied by a SEM. On the ependymal surface the cilia, usually associated in tufts and the microvilli, variable in size and number, that surround them, show a rate of development correlated to the age. The results show the early differentiation of the surface features commensurated with early cerebrospinal fluid (CSF) functioning.

Role of human fetal ependyma

Fetal ependyma is an active secretory structure for the programming of developmental events, including the arrest of neuronogenesis, the guidance of axonal growth cones, motor neuron differentiation, and probably also the maintenance and transformation of radial glial cells that guide migratory neuroblasts. The floor plate, induced by the notochord, is the first part of the neuroepithelium to differentiate. It establishes polarity and growth gradients of the neural tube and has immunohistochemical features that differ from all other regions of the ependyma. The dorsal and ventral median septa, formed by floor and roof plate ependymal processes, prevent aberrant decussations of developing long tracts, but permit the passage of commissural axons. Fetal ependyma synthesizes several intermediate filament proteins absent from mature ependymal cells, although some are also expressed in undifferentiated neuroepithelial cells. Fetal ependyma also produces diffusible molecules, such as neural cell adhesion molecule, proteoglycans, nerve growth factor, and S-100 protein, all in specific temporal and spatial distributions. Maturation of the ependyma is not complete until the postnatal period. An abnormal fetal ependyma may play a primary role in the pathogenesis of some cerebral malformations, such as lissencephaly/pachygyria and holoprosencephaly.

Regional differentiation of the human fetal ependyma: immunocytochemical markers

The development of the ependyma from 6 weeks (wk) gestation to term was studied in 26 human fetuses and infants for immunocytochemical differentiation using antibodies against vimentin, several cytokeratins, glial fibrillary acidic protein (GFAP) and S-100 protein. Acridine orange-RNA fluorescence was uniform in all differentiated ependymal cells. Marked differences were demonstrated among various anticytokeratin antibodies. Vimentin was demonstrated in undifferentiated cells, particularly during mitosis, and persisted as the ependyma matured. It was strong in floor plate cells and processes forming the ventral median septum. Vimentin and cytokeratin CK-904 coexisted with other immunoreactive proteins but disappeared in a caudorostral gradient with maturation. At 8 wk gestation, GFAP was detected in roof plate cells and their processes forming the dorsal median septum. S-100 protein appeared as early as 6 wk and had a more restricted regional distribution than GFAP at all ages. It was strong in the basal plate ependyma of the spinal cord in young fetuses. The temporal and spatial distributions of the immunoreactive proteins studied correlate with evidence that fetal ependymal cells synthesize compounds that attract or repel axonal growth cones to prevent axons from entering the ventricles or deviating from programmed projection pathways. An additional role may be to induce the transformation of radial glial cells in the subventricular zone.

Monoclonal antibodies as probes for the analysis of the secretory ependymal differentiation in the subcommissural organ of the chick embryo

Monoclonal antibodies directed against components of the subcommissural organ (SCO) of the chick embryo were produced by immunizing mice with SCO homogenate. In three series of production, 788 hybridomas were screened by immunofluorescence microscopy. Four hybridoma cell lines producing antibodies that specifically recognize both SCO cells and Reissner's fiber (RF) were selected and cloned. Using these immunological probes, the ontogenetic development of the SCO and RF was investigated in the chick embryo. Immunoreactive material could be detected in the SCO anlage from stage 17 on and RF was first observed in the central canal of the thoracal part of the spinal cord in 10-day-old embryos. Monoclonal antibodies can be useful as markers for analyzing molecular mechanisms involved in the specific function of these ependymal cells.

Developmental expression of glial markers in ependymocytes of the rat subcommissural organ: role of the environment

The rat subcommissural organ (SCO), principally composed of modified ependymocytes (a type of glial cell), is a suitable model for the in vivo study of glial differentiation. An immunohistochemical study of the ontogenesis of rat SCO-ependymocytes from embryonic day 13 to postnatal day 10 shows that these cells express transitory glial fibrillary acidic protein (GFAP) from embryonic day 19 until postnatal day 3. However, S100 protein (S100) is never expressed in the SCO-cells, contrasting with the ventricle-lining cells of the third ventricle, which contain S100 as early as embryonic day 17. Environmental factors could be responsible for the repression of GFAP and S100 in adult rats, because GFAP and S100 are observed in ependymocytes of SCO 3 months after being grafted from newborn rat into the fourth ventricle of an adult rat. Neuronal factors might be involved in the control of the expression of S100, since after the destruction of serotonin innervation by neurotoxin at birth, S100 can be observed in some SCO-ependymocytes of adult rats. On the other hand, GFAP expression is apparently not affected by serotonin denervation, suggesting the existence of several factors involved in the differentiation of SCO-cells.

A morphometric study on the development of the lateral ventricle choroid plexus, choroid plexus capillaries and ventricular ependyma in the rat

Morphometric changes in the rat lateral ventricle choroid plexus epithelium and endothelium and in the ventricular ependyma were studied between 16 days gestation and 30 days after birth, using stereological techniques. The epithelial apical surface density increased from 0.6 to 3.3 microns 2/microns 3 and the mitochondrial volume fraction from 3.2 to 7.6% during this period. The endothelial fenestrations increased from 0.05 to 0.39 micron-1. These changes may be related to postnatal increases in choroid plexus function. Morphological changes in basolateral surface density, cell height and nucleus and glycogen volume fraction have also been measured. The development of the lateral ventricle choroid plexus was qualitatively similar to the fourth ventricle plexus reported previously, but small quantitative differences occurred. The ventricular ependyma also showed a significant increase in mitochondrial volume fraction after birth, though to a lesser extent than the plexus epithelium. The total apical surface area of the choroid plexuses was estimated at 75 cm2 for 30-day-old rats. This figure, which takes into account the apical microvilli, is much greater than previous estimates and is similar to the surface area of the cerebral capillaries (155 cm2), and suggests that the choroid plexuses may play a more important role in the regulation of the brain microenvironment than previously thought.

The development of ependyma in the human fetal brain: an immunohistological and electron microscopic study

The stratified inner layer of the embryonic fetal brain, the ventricular zone (VZ), contains glial fibrillary acidic protein (GFAP)-positive cell bodies of radial glia. The adult cerebral ventricle is lined by a single layer of cuboidal, ciliated common ependymal cells which are, immunohistologically, GFAP negative. In late gestation, the ventricular lining is formed by tanycytes, ependymal cells with short, intensely GFAP-positive basal fibres. The development of ependyma was examined, morphologically and immunohistologically, in human fetal brain from between 11 weeks gestation to 6 months post-term to determine the relationship between the radial glia cell, tanycyte and common ependymal cell. This study was not able to show whether tanycytes were formed from radial glia or were formed from a previously uncommitted population of VZ cells. The study did show, however, that tanycytes probably mature into common ependymal cells following acquisition of cilia and loss of basal fibres. Electron microscopic data indicate that tanycytes have features suggestive of a secretory and/or transport function.

Fetal antigen retained by mature neurons and ependyma studied with a monoclonal antibody (6B9)

A mouse monoclonal antibody (MAb 6B9, isotype IgM) was raised against autopsy tissue samples from the central nervous system (CNS) of multiple sclerosis (MS) patients. By immunofluorescence microscopy, MAb 6B9 intensely stains most or all cells in fetal rats. However, MAb 6B9 differentially stains various cell types in adult rats. Neurons, ependymal cells, and adrenal chromaffin cells are stained intensely, whereas astrocytes and oligodendrocytes are not stained. The 6B9-reactive antigen (6B9 antigen) is sensitive to periodic acid, but insensitive to treatment with protease, RNase, or hyaluronidase. Results from immunofluorescence microscopy on semithin sections and cultured neuroblastoma cells indicate that 6B9 antigen is intracellular. This is supported by immunoelectron microscopy, where labeling for 6B9 antigen appears in the cytoplasm distinct from any identifiable organelle. Further studies on 6B9 antigen should reveal its chemical nature as well as the significance of developmental changes in its distribution.

Presence and development of ependymal cells in primary tissue cultures derived from embryonic rat cerebral cortex

Using indirect immunohistochemistry, a secondary antibody was detected in a commercial preparation of antiserum against vasoactive intestinal polypeptide. The secondary antibody selectively stained ependymal cells during the first 3 weeks in vitro in cultures of dissociated cerebral cortical tissue from rat. This staining provided a convenient mechanism for investigating the development and properties of these cells in cultures. The overall level of immunofluorescent staining during the initial 3-week time period appeared to directly reflect the proliferation and development of ependymal cells. Fluorescent staining was initially detected in cells which appeared to correspond to matrix cells or progenitor cells from the ependyma. These cells underwent rapid cell division, as evidenced by distinct morphological stages, to yield daughter cells which were the precursors of mature ependymal cells. Three different morphological classes of mature ependymal cells were observed in the cortical cultures. These classes corresponded to the cuboidal, tanycyte and secretory ependymal cell types described in vivo. Direct counting of stained cells showed that these morphological classes were represented in the cultures in roughly the same proportions seen in vivo (cuboidal 75%, tanycyte 19% and secretory 6%). The temporal aspects of ependyma development permitted the staining of developmental stages corresponding to the various morphological classes or types. The morphological sequence of development of the cuboidal cell and tanycyte from the precursor cell or matrix cell--daughter cell was determined. These two cell types displayed marked differences in their developmental sequence. The developmental sequence of the secretory cell could not be resolved; however, what appeared to be multiple morphological subtypes of this cell class were encountered.(ABSTRACT TRUNCATED AT 250 WORDS)

Fourth ventricular floor in human embryos: scanning electron microscopic observations

The ultrastructural surface features of the normal fourth ventricular floor of seven human embryos ranging from Carnegie stage 14 to stage 19 (crown-rump length: 7.6-16.2 mm) were examined by using scanning electron microscopy (SEM). Low-power SEM views showed the median sulcus, sulcus limitans, and neuromeres, transient structures characteristic of the earlier embryonic period. High-power SEM observation revealed supraependymal cells (SE cells) and supraependymal fibers (SE fibers) which exhibited a characteristic localization, as well as generalized surface-membrane modifications such as microvilli and cilia. SE cells could be classified into two major groups. The type 1 SE cells seem to possess neuronal functions, as deduced from morphological similarities to their counterparts in adults and the specialized distribution closely related to neuromeres. The type 2 SE cell morphologically resembled the phagocytic SE cell described in related literature. SE fibers ran a course either rostrocaudally in the median sulcus or mediolaterally on the neuromeres, most frequently near the interneuromeric cleft; they made contact with type 1 SE cells and ependymal surface modifications and then penetrated the ependymal layer.

Neural tube defects. Some remarks on the possible role of glycosaminoglycans in the genesis of the dysraphic state, the anomaly in the configuration of the posterior cranial fossa, and hydrocephalus

Recent developments in the field of experimentally induced neural tube defects (NTD) indicate that specific substances, namely the glycosaminoglycans (GAGs) may play a role in the genesis of spinal malformations. The authors report the results obtained by evaluating the GAGs in rat fetuses with NTD, secondary to the administration of Trypan Blue during pregnancy. A characteristic decrease in GAGs formation in the spinal and cranial structures as well as in the subependymal regions of the brain was found in the malformed fetuses. The authors hypothesize that this anomaly in GAGs formation is responsible for both the NTD and the associated malformations, namely hydrocephalus and hypoplasia of the posterior cranial fossa.

Ependymal lining of infundibular recess in perinatal rats: relationships with portal capillaries and permeability

Structure and permeability of the ependymal lining the infundibular recess were studied in perinatal rats with silver impregnation, electron microscopy, radioautography, and tracer techniques. According to our data basal processes of ependymal cells reach the primary portal plexus linking the 3rd ventricle and the hypophysial portal system all through the perinatal period. After birth, some of the processes penetrate into the perivascular space of the primary portal plexus and abut there on the endothelium of capillaries. Ependymal cells of fetuses and neonates are joined by specialized junctions (tight junctions, gap junctions and zonulae adhaerentes). Intraventricularly injected ionic lanthanum crosses the ependymal lining of fetuses both trans- and extra-cellularly everywhere in the infundibular recess. By postnatal day 9 only the rostral portion of the recess remains readily permeable. Caudally, extracellular leakage becomes highly restricted, apparently due to the appearance of circumferential tight junctions. Finally, [3H]dopamine seems to penetrate through the ependymal lining in the same way as ionic lanthanum entering the portal capillaries. These findings suggest that the adenohypophysiotropic neurohormones can penetrate from the cerebrospinal fluid into the portal circulation from the very beginning of the establishment of the hypothalamo-hypophysial functional relationships during ontogenesis.

Peanut agglutinin receptor is a marker of myelin in rat brain. Developmental changes in its distribution

Peanut agglutinin receptor, which is a glycoconjugate with terminal Gal(beta 1-3)GalNAc residues, was found to be a specific biochemical marker of the myelin in rat brain. The localization of peanut agglutinin receptor in rat brain was studied by use of fluorescein-conjugated peanut agglutinin. In adult rat brain, receptors were found only on myelin. In contrast, the receptors in fetal brain were not found in the white matter, but only in the ependyma. Peanut agglutinin receptors were extracted from adult and fetal rat brains with 2% Triton X-100, subjected to electrophoresis on 10% sodium dodecyl sulfate-polyacrylamide gel, blotted onto nitrocellulose filters, and detected by their reaction with peroxidase-conjugated peanut agglutinin. A major receptor of Mr 130,000 and a minor one of Mr 200,000 were found in both adult and fetal rat brains.