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     

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     

Fine structure of the ependymal cells in the area postrema of the domestic fowl

Summary The ultrastructure of the ependymal cells in the area postrema of the domestic fowl was studied by scanning and transmission electron microscopy. The ependymal surface of the area postrema is covered with many furrows and ridges. These ridges consist of ependymal cells aggregated in a fan-like shape. The ependymal cell lacks clustered cilia, microvilli are few, and a long basal process extends through the parenchymal layer of the area postrema. Within the cytoplasm as well as in the basal process, a spherical body with a diameter ranging from 1.5 to 2 gmm is occasionally observed.This work was supported by a Scientific Research Grant, No. 144017, from the Ministry of Education of Japan to Professor M. YasudaThe authors are grateful to Drs. T. Fujioka and T. Watanabe for their valuable advice     

Scanning electron microscopy of the third ventricle of sheep

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

Ependymal specializations

Summary The ependymal cells of the toad subcommissural organ produce pale and dense secretory granules. Both types of granules are mainly concentrated in the apical cytoplasm and in the perinuclear region. Pale and dense granules are synthesized by and packed in the rough endoplasmic reticulum, bypassing the step of the Golgi apparatus. The apical cytoplasm of some subcommissural ependymal cells protrudes into the ventricle. All the cells project a few cilia and numerous slender, long microvilli into the ventricular lumen.Contacting the cilia and the microvilli there is a filamentous material identical to that observed in the fibre of Reissner at the aqueduct of Sylvius. In addition to filaments, the fibre of Reissner contains vacuolar formations. The fibre is surrounded by numerous ependymal cilia, some of which are embedded in the filamentous material of the fibre.The presence of numerous microvilli projected into the ventricle and the large number of vesicles scattered in the supranuclear cytoplasm seem to indicate that the subcommissural organ may have absorption functions. The fact that the intercellular space of the ependymal layer of the subcommissural organ is not separated from the ventricular lumen by tight junctions but by zonulae adhaerentes could indicate that the cerebrospinal fluid penetrates these intercellular spaces bathing all sides of the ependymal cells. The presence in the ependymal cells of vesicles opening into the intercellular space would be in agreement with the latter possibility.There are some ultrastructural differences between the ependymal cells of the cephalic end of the subcommissural organ and those of the caudal end. A critical analysis of Reissner's fibre formation is made.This investigation was partially supported by a Grant of the Wellcome Trust Foundation.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina. The author wishes to thank the valuable help of Mr. P. Heap.     

The ependyma of the ventriculus mesencephali in the rat

The ventriculus mesencephali in the rat proceeds in the colliculi posterior region from the mesencephalic aqueduct in the dorsal direction. The ependymal lining is formed by flat, cuboid and cylindrical cells. The cylindrical cells, which occur in all parts of the ventriculus mesencephali, are the most numerous. The cuboid cells are localized mainly in the anterior part, the flat ones in the posterior part of the ventriculus mesencephali. Some cuboid and cylindrical cells have short basal processes. Among the ependymal cells, there are cells with long basal processes. The ependyma is at sites interrupted by flocks of ependymal cells. On the cell surface, there area cilia, microvilli and protoplasmic extrusions. The cell nuclei are spherical to oval. Supraependymally, there are homogeneous globules and intraventricular fibres. The histological variability of ependymal cells may point to the active participation of these cells in functional processes, even within such a small part of the ventricle system as the ventriculus mesencephali.     

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.     

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.     

In Vivo Expression of the PTB-deleted Odin Mutant Results in Hydrocephalus

Odin has been implicated in the downstream signaling pathway of receptor tyrosine kinases, such as the epidermal growth factor and Eph receptors. However, the physiologically relevant function of Odin needs to be further determined. In this study, we used Odin heterozygous mice to analyze the Odin expression pattern; the targeted allele contained a β-geo gene trap vector inserted into the 14th intron of the Odin gene. Interestingly, we found that Odin was exclusively expressed in ependymal cells along the brain ventricles. In particular, Odin was highly expressed in the subcommissural organ, a small ependymal glandular tissue. However, we did not observe any morphological abnormalities in the brain ventricles or ependymal cells of Odin null-mutant mice. We also generated BAC transgenic mice that expressed the PTB-deleted Odin (dPTB) after a floxed GFP-STOP cassette was excised by tissue-specific Cre expression. Strikingly, Odin-dPTB expression played a causative role in the development of the hydrocephalic phenotype, primarily in the midbrain. In addition, Odin-dPTB expression disrupted proper development of the subcommissural organ and interfered with ependymal cell maturation in the cerebral aqueduct. Taken together, our findings strongly suggest that Odin plays a role in the differentiation of ependymal cells during early postnatal brain development.     

Immunohistochemical study of localization of gamma-glutamyl transpeptidase in the rat brain

Gamma-glutamyl transpeptidase (gamma-GTP) is a membrane-bound enzyme which is known to play a crucial role in active transport of amino acids across membrane barriers. We prepared a monoclonal antibody recognizing specifically rat gamma-GTP and investigated localization of the enzyme in the rat brain by immunohistochemistry with this antibody. The antigen was localized on the ependyma, epithelia of the choroid plexus and microvessels. More precise localization of gamma-GTP was examined with immuno-electron microscopy. The antigen was recognized on the microvilli and cilia of the ependymal cells, microvilli of the choroid epithelial cells and luminal membranes of the vascular endothelial cells.     

Surface morphology and functions of pharyngeal structures in the larval lamprey Petromyzon marinus

To gain insight into the multiple functions of a complex biological structure, the morphology of the pharynx of the larva (ammocoete) of the lamprey Petromyzon marinus was investigated with scanning electron microscopy and histochemistry (PAS and Alcian blue). Features studied include the gills, the parabranchial chambers external to the gills, intrapharyngeal ciliary tracts, the ridged pharyngeal roof, the floor, and the intrapharyngeal taste buds. Significant findings are: (1) All (nonciliated) cells lining these structures are covered with microvilli or microridges. The pattern and packing density of these membrane features vary among different pharyngeal structures. The lumenar membranes of pharyngeal lining cells overlie a mucous prosecretion in the apical cytoplasm, suggesting that the microvilli/ridges on these membranes function to anchor mucus. (2) Patterns of microvilli/ridges on the gill respiratory lamellae differ among ammocoetes of different species. (3) Pharyngeal osmo-regulatory cells (“chloride cells”) could not be identified on the basis of the microvillus/ridge pattern. (4) Two types of ciliary tracts are present within the pharynx. One has tall (x = 13 μm) and densely packed cilia, whereas the other has shorter (x = 7 μm) and less densely packed ones. Because mucus covers both types of tracts their function appears to involve the transport of mucus. (5) Food particles were found on the lateral surfaces of the gill filaments and on the surfaces of the parabranchial chambers. It appears that goblet cells in the epithelia of these regions secrete mucus in which the particles are trapped.     

Fine structure of ependymal cysts in and around the area postrema of the rat

Summary Peculiar cells forming cysts were observed in the area postrema and sometimes also in the choroid plexus and the tela chorioidea near the area postrema, and were studied in detail by electron microscopy. The cytological features of the cyst cell and its junctional relationship to neighboring cells imply that cyst cells are derived from ependymal and choroid epithelial cells. The cyst cells usually contact directly the perivascular spaces of postremal, choroidal or pial capillaries, where the cytoplasm is often considerably attenuated. The cystic lumen is commonly filled with a flocculent material. The limiting membrane of the cystic lumen, which frequently bears cilia and microvilli, has the same thickness as the surface cell membrane. In many cases, the cyst is surrounded by the cytoplasm of a single cell. In some cases, however, two cells participate in the formation of the cyst, although one is only a slender process and joined by a zonula occludens with the main cyst cell. Horseradish peroxidase (HRP) injected into the cerebrospinal fluid (CSF) space failed to enter the cystic lumen. A possible significance of the cyst in relation to the CSF and blood circulation was considered.     

Ependyma and ependymal protrusions of the lateral ventricles of the rabbit brain

Summary The ependymal lining of the lateral ventricles of the rabbit brain was studied by means of scanning (SEM) and transmission electron microscopy (TEM). There exist cells devoid of cilia in the anterior horn over the region of the caudate nucleus, in the inferior horn over the hippocampus and on the opposite side over cortical regions. On the surface of some of these ependymal cells, accumulations of cytoplasmic folds and globules can be found. They bulge at different height over the ependymal cells. Clots of these cell particles are tied off from the cell, coming to lie as globules either on or between the cilia of the ependyma. TEM reveals that these tissue protrusions are cell debris consisting of different sized vesicles, cell organelles, tubuli and filaments. They originate from the ependymal layer but may reach down to subependymal cells. Multivesicular protrusions into the ventricular lumen are also observed. Possible causes of these protrusions are discussed; they are likely to be related to the age of the animals.On the ependyma of the caudate nucleus cilia, microvilli, microblebs and supraependymal neuronal cell processes are distributed unevenly over the surface. Within regions where cilia predominate there are cells which are tightly covered with microvilli. A certain direction of the course of the supraependymal neuronal fibers could not be found.The author is pleased to acknowledge useful discussions with Prof. Dr. med. E. van der Zypen. This study was partly supported by the Stanley Thomas Johnson Foundation     

The surface fine structure of the walls of cerebral ventricles and of choroid plexus in cat

Summary The surface of ependymal cells bordering the brain ventricles, and that of the epithelial cells of choroid plexuses of the cat have been investigated by means of the scanning electron microscope. The ventricle walls are entirely covered with very long and numerous cilia and no regional differences have been observed regarding their number and disposition. Among the ciliated cells dome-shaped structures are present, possibly containing nervous elements. The ependymal cells of the third ventricle floor are mainly non ciliated but the surface thereof shows numerous small microvilli. Numerous round formations are present among these cells, their nature being difficult to interpret. Also present on the floor are small cells of triangular shape with long and tortuous protrusions, tentatively identified as small neurons. The choroid plexuses have a typical sinuous structure of long tortuous villi rich in cavities and convolutions. Details of the epithelial cells covering the plexus and their surface organization are also reported.Part of these results were presented to the Septième Congrès International de Microscopie Electronique, Grenoble 1970.     

The collicular recess organ: Evidence for structural and secretory specialization of the ventricular lining in the collicular recess

Summary The collicular recess organ and adjacent portions of the collicular recess were studied by light microscopy, scanning electron microscopy and transmission electron microscopy. In the collicular recess, the ventricular wall contains folds and is well vascularized. The adluminal ependymal cells generally bear kinocilia and microvilli on their ventricular surface. Among the cilia, many secretory droplets, some axons, and few supraependymal cells are seen. Various stages of apocrine ependymosecretion are observed. In addition to tanycytes, coelocytes are found scattered throughout the ependymal lining of the collicular recess. Coelocytes, characterized by lumina containing cilia and a few microvilli, are accumulated in ependymal and hypependymal positions of the collicular recess organ at the roof of the collicular recess.Supported by PHS grants NS 09914 and T32 CA09156. We thank Dean Wyrick and John McNeill, Jr., for their technical assistanceNRSA Postdoctoral Trainee     

Surface specializations of the olfactory epithelium of rainbow trout, Salmo gairdneri

Receptors for olfactory stimulus molecules appear to be located at the surface of olfactory receptor cells. The ultrastructure of the distal region of rainbow trout (Salmo gairdneri) olfactory epithelium was examined by transmission electron microscopy. On the sensory olfactory epithelium, which occurs in the depressions of secondary folds of the lamellae of the rosettes, five cell types were present. Type I cells have a knob-like apical projection which is unique in this species because it frequently contains cilia axonemes within its cytoplasm in addition to being surrounded by cilia. Type II cells bear many cilia oriented unidirectionally on a wide, flat surface. Type III cells have microvilli on a constricted apical surface and centrioles in the subapical cytoplasm. Type IV cells contain a rod-like apical projection filled with a bundle of filaments, and type V cells are supporting cells. Cilia on the sensory epithelium contain the 9 + 2 microtubule fiber pattern. Dynein arms are clearly present on the outer doublet fibers, which suggests that the cilia in the olfactory region are motile. Their presence in olfactory cilia of vertebrates has been controversial. The cilia membrane in this species is unusual in often showing outfoldings, within which are included small, irregular vesicles or channels. In addition, cilia on type II cells frequently contain dense-staining bodies closely apposed to the membranes, along with a densely stained crown at the cilia tip. Previous biochemical evidence indicates that odorant receptors are associated with the cilia.     

Surface fine structure of the globiferous pedicellariae of the regular echinoid,Psammechinus miliaris gmelin

The globiferous pedicellariae of Psammechinus miliaris are described. Two fixation methods giving minimal distortion and rapid tissue hardening were adapted for soft tissue preparation for scanning electron microscopy. The pedicellarial valves are covered by a microvillous epithelium. The outer valve epithelial microvilli overlying red spherulocytes in the epidermis are characterized by a filament matrix radiating out from each microvillus. These microvilli may function in epidermal absorption of organic solutes. The inner valve microvilli are more densely packed and the filament matrix is absent. Ciliation is confined to the inner valve surface where the cilia are concentrated to form a distal sensory pad and sensory hillock. Behavioural evidence suggests a chemo- and mechanosensory role for the inner valve surface.     

p73 is required for ependymal cell maturation and neurogenic SVZ cytoarchitecture

The adult subventricular zone (SVZ) is a highly organized microenvironment established during the first postnatal days when radial glia cells begin to transform into type B‐cells and ependymal cells, all of which will form regenerative units, pinwheels, along the lateral wall of the lateral ventricle. Here, we identify p73, a p53 homologue, as a critical factor controlling both cell‐type specification and structural organization of the developing mouse SVZ. We describe that p73 deficiency halts the transition of the radial glia into ependymal cells, leading to the emergence of immature cells with abnormal identities in the ventricle and resulting in loss of the ventricular integrity. p73‐deficient ependymal cells have noticeably impaired ciliogenesis and they fail to organize into pinwheels, disrupting SVZ niche structure and function. Therefore, p73 is essential for appropriate ependymal cell maturation and the establishment of the neurogenic niche architecture. Accordingly, lack of p73 results in impaired neurogenesis. Moreover, p73 is required for translational planar cell polarity establishment, since p73 deficiency results in profound defects in cilia organization in individual cells and in intercellular patch orientation. Thus, our data reveal a completely new function of p73, independent of p53, in the neurogenic architecture of the SVZ of rodent brain and in the establishment of ependymal planar cell polarity with important implications in neurogenesis. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 730–747, 2016     

Conversion of Blebs to Microvilli: Cell Surface Reorganisation After Trypsin

The blebbed surface morphology produced by trypsinisation of Chinese hamster ovary cells is subsequently reorganized to a microvillous topography, even in the continued presence of trypsin. Scanning and transmission electron microscope (SEM and TEM) observations of this transition showed the initial formation of a 'crown' of densely clustered microvilli at one pole of the cell. At the periphery of this region the blebs coalesced to form ridges which subsequently extended over the entire cell surface. Long, and occasionally branched microvilli were generated from the ridges. Large numbers of membrane associated vesicles were also characteristic of these areas of surface reorganisation.     

The ultrastructural organization and the alkaline phosphatase activity of the epithelial surface of the bovine fallopian tube

Summary The epithelial surface of the bovine Fallopian tube has been studied with respect to its ultrastructure and alkaline phosphatase activity. The ciliated cells were found to be provided with cilia and microvilli. The cilia were placed in rows and were most frequent in the central area of each cell surface. The basal corpuscles were provided with indistinct rootlets. The microvilli occurred between the cilia, but showed the reverse distribution, being most frequent towards the periphery of the cell surface. As a rule a marked alkaline phosphatase activity could be revealed on the ciliated cell surface, presumably associated with the microvilli.The secretory cells were bulging over the surface of the ciliated cells. Theywere provided with irregular protrusions, which were as a rule long and slender during the follicular phase but shorter and bulkier during the luteal phase. No alkaline phosphatase activity was detected.This investigation was supported by a grant from the foundation Thérèse och Johan Anderssons Minne.