Scanning electron microscopy of the human cerebral ventricular system

Summary Scanning electron microscopy was used to assess the ultrastructural differences exhibited by the varigated ependymal lining of the near-term human fetal 4th ventricle. The central portion of the fourth ventricular floor, including the median sulcus is punctuated by numerous clumps of cilia. The density of cilia here is not as great as that described for other regions of the human cerebral ventricular system; accordingly, underlying substructure can be noted. There are distinct differences between ependymas that line the floor of the fourth ventricle with those of the adjacent area postrema. The latter region possesses not cilia, but instead exhibits a dense knap of microvilli. The ultra-architecture of the choroid plexus is relatively similar to that of other circumventricular organs with the exception that it possesses small isolated groups of cilia as well as microvilli. These findings are discussed with respect to the dynamics of local CSF movement and flow, ependymoabsorption and ependymosecretionSupported by U.S.P.H.S. Grant NS 08171.Career Development Awardee GM K04 70001.     

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     

Fenestration of the epithelium lining the roof of the fourth cerebral ventricle in amphibia

Summary Scanning electron microscopy of the caudal end of the roof of the fourth cerebral ventricle in four amphibian species shows that numerous pores occur between the ependymal cells. These pores have diameters ranging from 5–100 m; they permit bulk flow of cerebrospinal fluid out of the ventricular system into the subarachnoid space.     

The third ventricle of monkeys

Summary Surface features of the ependymal lining of the third ventricle in mature male and female monkeys have been investigated with scanning electron microscopy (SEM). Broad aspects of third ventricular morphology from three species of monkey are similar regardless of sex. The lateral walls are heavily ciliated whereas the ventral floor and most ventral parts of the lateral walls are not. Clumps of cilia on the lateral walls are so dense that underlying surface details are usually obscured. There is a transition zone between the ciliated lateral wall and nonciliated ventral floor. The floor and lower part of the lateral walls of the third ventricle exhibit a characteristic polygonal pattern upon which surface specializations such as microvilli, blebs and polymorphous membrane protrusions are superimposed. Ependyma of the choroid plexus of the third ventricle also display membrane specializations. Supraependymal cells are more visible in nonciliated regions.Supported by USPHS Grants RR-05432, GM-16598 and HD-10010 from the National Institutes of Health and GSRF 171 funds from the University of Washington Graduate School. Portions of this work have been reported previously in abstract form in Anat. Rec. 175, 294 (1973) (before the 86th annual session of the American Association of Anatomists, New York, N.Y., April, 1973)     

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 microscopy of human cerebellar cortex

Summary Scanning electron microscopy and cryofracture technique were applied to study neuronal architecture and synaptic connections of the human cerebellum. Samples were processed according to the technique of Humphreys et al. (1975) with minor modifications. The granule cells exhibit unbranched filiform axons and coniform dendritic processes. The latter show typical claw-like endings making gearing type synaptic contacts with mossy fiber rosettes. The unattached mossy rosettes appear as solid club-like structures. Some fractographs show individual granule cells, Golgi neurons and glomerular islands. The climbing fibers and their Scheibel's collaterals were also characterized. In the Purkinje layer the surface fracture was produced at the level of the Bergmann glial cells, which are selectively removed, allowing us to visualize the rough surface of Purkinje cells and the supra- and infraganglionic plexuses of basket cell axons which appeared as entangled threads. In the molecular layer the three-dimensional configuration of the Purkinje secondary and tertiary dendritic branches was obtained. The filiform parallel fibers make cruciform synaptic contacts with the Purkinje dendritic spines. The appearance of stellate neuronal somata closely resembled that of the granule cells. The subpial terminals of Bergmann fibers appeared attached to the exterior of the folia forming the rough surfaced external glial limiting membrane.     

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 microscopy of echinoid podia

Summary Tube feet of the sea urchin Strongylocentrotus franciscanus were studied with the scanning electron microscope (SEM). By use of fractured preparations it was possible to obtain views of all components of the layered tube-foot wall.The outer epithelium was found to bear tufts of cilia possibly belonging to sensory cells. The nerve plexus was clearly revealed as being composed of bundles of varicose axons. The basal lamina, which covers the outer and inner surfaces of the connective tissue layer, was found to be a mechanically resistant and elastic membrane. The connective tissue appears as dense bundles of (collagen) fibers. The luminal epithelium (coelothelium) is a single layer of flagellated collar cells.There is no indication that the muscle fibers, which insert on the inner basal lamina of the connective tissue layer are innervated by axons from the basiepithelial nerve plexus.The results agree with previous conclusions concerning tube-foot structure based on transmission electron microscopy, and provide additional information, particularly with regard to the outer and inner epithelia.This investigation was supported by the Sonderforschungsbereich 138 of the Deutsche Forschungsgemeinschaft. The work was carried out at the Friday Harbor Laboratories of the University of Washington. The authors are indebted to the Director, Professor A.O.D. Willows for use of the facilities, and to Drs. Christopher Reed and Tom Schroeder for invaluable instruction and assistance     

Scanning electron microscopy of bone cells in culture

Summary Embryonic and young rat bone cells have been grown in culture and examined in the scanning electron microscope (SEM). Compared with cells fixed in situ and taken directly from the animal, the cultured osteoblastic cells were smoother, flatter and more extensive and showed tighter intercellular contacts. Some matrix is formed in culture and undergoes at least partial mineralization as judged by the accumulation of Ca and P measured by energy dispersive x-ray analysis. Findings concerning the morphology of the collagen arrangement were indecisive. Some superficial cells, free of surrounding matrix, resembled osteocytes in normal in vivo bone. This may indicate that a proportion of the extracellular matrix produced by the cultured cells failed to polymerise into recognizable bone matrix, and that osteocytic morphology is not dependent upon the physical characteristics of the bone matrix.     

Scanning electron microscopy of peripheral blood leukocytes of the chicken

Summary Polymorphonuclear leukocytes, e.g., neutrophilic granulocytes, were enriched from heparinized blood by a Ficoll-step-gradient centrifugation procedure. Scanning electron microscopy (SEM) revealed a surface morphology of narrow ridge-like profiles and small ruffles with occasional microprocesses. Mononuclear leukocytes were isolated by centrifugation over a Ficoll-Metrizoat gradient. The lymphocytes showed varying numbers of microvilli of different length, size and shape. B lymphocytes, characterized by their capability of sheep red blood cell (SRBC)-rosette formation, displayed a similar surface morphology. Completely smooth lymphocytes, described in the literature as T lymphocytes, could not be detected, although many lymphocytes with few microprocesses were observed. Thus, SEM is not a useful tool for distinguishing between B and T lymphocytes in the peripheral blood of chickens. Monocytes were characterized by prominent membrane-like ruffles, but in some cases they closely resembled granulocytes. An influence of the various separation media on the surface morphology of the isolated cells could not be detected when compared with cells isolated by the buffy-coat method.     

Scanning electron microscopy of the cleft of the rat pituitary

Summary Scanning electron microscopy of the lining of the pituitary cleft was carried out in normal, lactating, castrated, adrenalectomized, and cyproterone-treated adult rats. Four cell types could be differentiated in the posterior wall in control and experimental animals: (1) cells with a smooth surface, (2) cells with microvilli located at the cellular borders, (3) ciliated cells, and (4) cells with evenly distributed microvilli. The anterior wall showed mainly cells with few microvilli located at their margins, and clusters of ciliated cells. In normal, and more frequently in experimental animals, the anterior wall showed shriveled cells, and variously sized cavities. Colloid appeared either as a network of finely granular material or as compact bodies adhering to the epithelial surface. These observations suggest that a compact component of the colloid is derived at least in part from degraded cells.Fellow of the Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET), Argentina. The author owes many thanks to Professor I. Nouzeillez and Dr. J.C. Cavicchia for their assistance in translating this paper     

Scanning electron microscopy of fused mouse placentas and associated uterine bed

Summary The decidual surface of two fused placentas and the associated uterine bed were examined by scanning electron microscopy. The compact decidua basalis fits into a uterine depression filled with coarse fibers which is surrounded by a smooth area that gradually becomes folded. Placental fusion due to twinning or crowding is discussed.Financial support was provided by an NIH Biomedical Research Support Grant 5 S07-RR05794-02 and by the Department of Anatomy, Wright State University. Technical assistance of Robert Principato is gratefully acknowledged     

Scanning electron microscopy preparation protocol for differentiated stem cells

The lack of an established protocol for scanning electron microscopy (SEM) studies on stem cells differentiating into adipogenic lineage led us to develop a protocol for the preparation of differentiated adult bone marrow-derived mesenchymal stem cells (BMSC) for SEM. This protocol describes the procedure to maintain and preserve the structural organization of cellular components following differentiation, for morphological and physical characterization. The fixation of the differentiated cells was followed by dehydration using methanol, and vacuum desiccation before microscopy. The use of longer chain alcohols as dehydrating agents was avoided in our method to reduce the dissolution of lipid deposits in cells, thus allowing the maintenance of their structural integrity. The time period for the processing of samples was reduced by avoiding the osmium tetroxide postfixation and critical point drying. Thus, this protocol helps in determining the potential, fate, and degree of stem cell differentiation. This may be useful for SEM analysis of differentiated cells, especially those grown on various scaffolds.     

Scanning electron microscopy of dissociated pancreatic acinar cell surfaces

Summary The pancreatic acinar cell surfaces have been studied by SEM with a dissection technique and correlated with results obtained by TEM. The SEM results demonstrate characteristic arrangement of microplicae which in some areas are densely packed.In many areas, the microplicae are distributed in such a manner that they create zones with typical geometrical shapes and show a relatively smooth surface.These smooth areas may coincide, as indicated by correlated TEM results, with the limits of intimate contact between adjacent acinar cells which, in turn, represent part of the junctional complex. Another aspect revealed by these SEM preparations concerns the presence of groups of densely packed microplicae, arranged in regular rows and distributed along some grooves and/or infoldings of the cellular surface. On the basis of SEM and TEM information, it is likely that these structures correspond to intercellular (and possibly, in some cases, intracellular) canaliculi which topographically form a kind of extensive microlabyrinthine arrangement running along all the cell sides.One final point revealed by fractured samples concerns the finding of spherical zymogen droplets within the vesicles of the Golgi complex. Because in many scanning images these vesicles appear connected by small openings, it is suggested that they may represent a system of intercommunicating chambers (vacuoles) through which the zymogen droplets can be continuously accumulated and discharged into the acinar lumen.     

Scanning electron microscopy of isolated peripheral nerve fibres

Summary The surface morphology of normal myelinated nerve fibres prepared in different ways for scanning electron microscopy has been studied and compared with the surface features of similar fibres undergoing retrograde changes. Nodes of Ranvier, paranodal specializations, artefactual fractures of the myelin, and the endoneurial collagen sheaths are described. A regular pattern of elevations, usually with a pitted or depressed surface seen on normal myelinated fibres after certain preparative procedures are thought to be artefacts produced during preparation and to be related to the neurokeratin network.Alterations in the surface structure of fibres central to long-standing nerve transections include irregular protuberances, serial surface corrugations and large swellings, all associated with demyelination. Fibres that have undergone retrograde degeneration consist of endoneurial tubes with focal swellings occupied by macrophages or myelin debris, together with fine unmyelinated and small myelinated regenerating axons. Strict centrifugal progression of myelination of regenerating axons was not observed.We thank Mr. R. A. Willis for his collaboration and for taking the SEM photographs of normal nerve fibres, and the Cambridge Scientific Instrument Co. Ltd. for permission to reproduce the SEM photographs of experimental nerve fibres. We also thank Dr. A. Boyde for access to his SEM and for helpful comments on interpretation of the scanning electron micrographs, Prof. J. Z. Young, Dr. P. K. Thomas, and Dr. R. H. M. King for discussion, and Messrs. P. Reynolds and D. Gunn for photography.A grant from the Muscular Dystrophy Group of Great Britain is gratefully acknowledged.     

Scanning electron microscopy and microspectrophotometry of the photoreceptors of ictalurid catfishes

The retinal photoreceptors from larval channel catfish (Ictalurus punctatus) were studied using single cell, in situ microspectrophotometry. Rods appear at 5 days after hatch; cones are present from day one. The rods contain a visual pigment which absorbs light maximally at 540 nm. The cones contain either a green sensitive visual pigment with peak absorbance at 535 nm or a red sensitive visual pigment with peak absorbance at 608 nm. All pigments are based on vitamin A₂. Visual pigment complement does not change with age, as photoreceptors from adultI. punctatus, I. catus andI. melas contain visual pigments virtually identical to those of the larvalI. punctatus. Regardless of age, no visual pigment with peak absorbance in the short wavelength region of the spectrum was ever observed. Scanning electron microscopy of adultI. punctatus retinas showed large rods with long, cylindrical outer segments and smaller cones with short, tapered outer segments. The myoids of both rods and cones are extensable. The rods, embedded in a granular tapetal material, comprise from 50 to 60% of the photoreceptors. Only single cones are present. The data are consistent with the idea that the ictalurid catfishes spend their entire lives in an environment deficient in blue light.     

Scanning electron microscopy of olfactory rosette in sea trout

Summary Scanning electron microscopy has been employed to study the central axis and laminae of the olfactory rosette in adult sea trout (Salmo trutta trutta L.) caught in the River Umeälven when they were homing from sea.—Both flat sides of the primary laminae are secondarily folded all over their surface. In one organ there are about 200 secondary laminae usually arranged in longitudinal, parallel ridges crossing the surface of the primary laminae. Initially they are covered with sensory epithelium, but as the folds grow they become covered with an increasing area of indifferent ciliar epithelium with bushes of cilia separated by microvilli cells and goblet cells. Parts of the central axis and primary laminae have a nonciliar indifferent epithelium. The sensory epithelium has irregularly arranged cilia. Like those of the indifferent epithelium they have uniform thickness and granulated surface. The function of laminae, secretion and cilia is discussed.The author wish to acknowledge the technical facilities and assistance in the use of the scanning electron microscope to Jeolco Stockholm office. This research was supported by grants 2389-10, 2389-11 and 2389-13 from the Swedish Natural Science Research Council.     

Scanning electron microscopy of the renal corpuscle of the mesonephros in the lamprey,entosphenus japonicus martens

Summary The renal corpuscle of the lamprey mesonephros was studied under the scanning electron microscope.Bowman's capsules with individual spaces are chockshaped sacs closely packed together along a medial artery. The lateral walls of the capsules are apposed to those of neighbouring capsules.Glomerular capillaries from the medial artery extend radially between the apposed walls of neighbouring Bowman's capsules. Bulgings of capillaries into the capsular space are associated with mesangial folds of the capsular epithelium.The transitional zone of the visceral layer with podocytes and the parietal layer of squamous epithelium is bounded by linearly arranged rod-shaped epithelial cells. Apertures of the urinary tubule are lined by cells equipped with a fascicle of cilia.     

Scanning electron microscopy of vascular architecture in the gastric mucosa of the golden hamster

Summary The three-dimensional architectures and the regional differences of the vascular system in the mucosa of the hamster stomach were revealed by scanning electron microscopy of corrosion casts. In the forestomach, the vascular network spreads two-dimensionally in a thin lamina propria. In the corpus and the antrum, the capillaries in the thick lamina propria are well developed, extending three-dimensionally along the gastric pits and glands. In the corpus, the submucosal arteries enter the lamina propria to become ascending capillaries, which project toward the top of the lamina propria and anastomose to create a capillary network beneath the mucosal epithelium. A subepithelial capillary is much wider in diameter than an ascending capillary and is, therefore, a sinusoid capillary. Subepithelial capillaries join descending venules, which are less numerous than the ascending capillaries. Near the gastric lumen, the capillaries in the corpus can be classified into two types: arched type in the cephalic (upper) region and honeycomb type in the caudal (lower) region. In the antrum, the submucosal arterial plexus is less well developed than that in the corpus. The mucosal aspect of the corrosion cast shows many clumps, formed by a unit of capillary network. Functional significances of different vascular architectures in the gastric mucosa of the forestomach, corpus, and antrum are discussed.This study was supported in part by grants from the Research Fund of the Ministry of Education, Science, and Culture, Japan     

Scanning electron microscopy of experimental adiaspiromycosis

Adiaspiromycotic granulomas of mice experimentally inoculated with fungusEmmonsia crescens Emmons et Jellison 1960 were examined by scanning electron microscopy. Their morphology, surface structures, and germinating adiaspores isolated from granulomas are described.