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At least 685 records · Page 38Linked to original sources
PubMed1982

Development of the ovarian surface and associated germ cells in the human fetus. A correlated study by scanning and transmission electron microscopy.

The ovarian surface and associated germ cells have been studied in human fetuses from 12 weeks of age until near term, using light, TEM and SEM techniques. The surface epithelium and related cords proliferate extensively, especially at midterm. The cords of the ovarian cortex appear to be linked with ingrowths from the surface epithelium, and both structures have a common basal lamina. Germ cells are always interspersed among the somatic cells of the surface epithelium and associated cords. These results indicate that both the proliferating cords and surface epithelium may contribute to the formation of early follicles. Furthermore, the occurrence, of elements having some of the features of primitive steroidogenic cells in the regions of cord-surface epithelium continuity, suggests that both structures (surface epithelium and cords) contribute somatic cells, which in addition to becoming granulosa cells, might also contribute to the provision of primitive interstitial cells. Gonocytes tend to migrate through the developing ovarian tissue towards the surface where they become extruded into the peritoneal cavity. This phenomenon might contribute to the reduction in the number of germ cells at birth and parallels the atretic processes within the ovary.

Cell Membrane↗
PubMed1978

Scanning and transmission electron microscopy of the subfornical organ of the grass frog (Rana pipiens).

The ventricular surface of the subfornical organ of the frog is made up of ependymal cells with numerous apical microvilli, occasional cytoplasmic protrusions and many vacuoles projecting into the lumen of the third ventricle. Between these cells dendrites of cerebrospinal fluid-contacting neurons reach the ventricle to terminate in bulbous enlargements. In addition, flask-shaped encephalo-chromaffin cells, containing granulated vesicles and aggregates of filaments in their cytoplasm, project into the cerebrospinal fluid. Surrounding the centrally located capillaries are enlarged dendrites and axons of heterogeneous morphology, some of which appear to originate within the subfornical organ, intermingled with dendrites and axons of normal structure. The glial cells in this region, especially the microglial cells, often contain large lipofuscin inclusions, suggestive of degeneration and subsequent phagocytosis of some of the enlarged dendrites and axons. The normally scarce neurosecretory peptidergic axons become more evident and form typical Herring bodies in stalk-transected animals. Neuronal perikarya of varying morphology are predominantly located peripheral to the region of enlarged dendrites and axons. Supraependymal macrophages are particularly numerous on the subfornical organ.

Animals↗
PubMed1977

Scanning electron microscopy of dissociated pancreatic acinar cell surfaces.

The pancreatic acinar cell surfaces have been studied by SEM with a dissection of 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.

Animals↗
PubMed1980

A study of scanning (SEM) and transmission (TEM) electron microscopy of the glomerular capillaries in developing rat kidney.

Kidneys of 2 to 10 day-old rats of Wistar and Sprague-Dawley strains were fixed with glutaraldehyde by retrograde vascular perfusion and then prepared for observation in TEM and SEM. In addition methacrylate casts of differentiating glomerular capillaries were examined by SEM. Although the glomerular vascular pattern differs from one glomerulus to another, its differentiation proceeds according to the following general plan. First the glomerular capillary splits longitudinally, finally to form 3 to 5 lobules consisting of a capillary network, sustained centrally by the mesangium. In the present study the differentiation of glomerular capillaries is described in five successive arbitrarily selected stages. At Stage I a capilllary loop penetrates between the lower limb and the middle segment of the S-shaped body, the rudimentary nephron. At Stage II the capillary undergoes a first subdivision, establishing the primitive lobulation of the glomerulus. At Stage III the vascular and urinary poles differentiate. At Stage IV the glomerulus assumes the aspect of a spherical body, and the capillaries in each lobule undergo subdivision. In Stage V the glomerular vascular pattern approaches its adult appearance, although the maturation processes continue for an extended period of time. Hence in the 10 day-old rat the best-differentiated glomeruli are half the size of adult glomeruli, and their capillary loops are proportionally less well-developed. The capillaries of adjacent lobules may communicate with each other, but a direct vascular shunt between the afferent and efferent vessels cannot be demonstrated.

Animals↗
PubMed1990

Different phenotypes of cultured microvessel endothelial cells obtained from bovine corpus luteum. Study by light microscopy and by scanning electron microscopy (SEM).

Morphological heterogeneity has not been documented for cultured endothelial cells isolated from the microvascular bed of any organ. As the corpus luteum depends on a rich microvascularization, endothelial cells were dislodged from developing corpora lutea by mechanical dissection followed either by collagenase digestion or by no digestion. Cell separation was carried out by Percoll density centrifugation. Although the yield of intact cells was higher with collagenase treatment than without, successful endothelial cell cultures were only established when cells remained untreated. Viewed by light microscopy after an average lag phase of 10 days, five different phenotypes of endothelial cells were found under similar simple culture conditions: isomorphic epithelioid, polymorphic epithelioid, spindle-shaped, round, and phase-dense phenotypes. Monolayers appeared within 2-4 weeks. After an additional period of 2-4 weeks, tubular forms with a specific pattern were noted for types 1-3, the so-called pseudotubular forms for type 4, and none for type 5. Cell types differed in their cytochemical and immunocytochemical responses. Examined by SEM, type 1 displayed a more conspicuous surface anatomy than type 2. Types 3-5 demonstrated striking cell processes that were characteristic of each type. Tubular forms of types 1 and 2 showed cell borders and a marked increase in surface specializations, whereas tubular forms of type 3 lacked detectable cell borders in the absence of a striking surface anatomy. Pseudotubular forms of type 4 developed no particular spatial organization. Thus, for the first time, morphological evidence is provided that different endothelial cell types are obtained from diverse segments of the microvascular bed.

Acid Phosphatase↗
PubMed1981

Scanning and transmission electron microscopy of cloned rat astrocytoma cells treated with dibutyryl cyclic AMP in vitro.

Two cloned rat astrocytoma cell lines, 36 B-10 and 40 A-2, maintained in vitro were treated with 1 mM dibutyryl cyclic AMP. This treatment induced arborization of cellular processes and rounding-up of cell bodies in both cell lines and was associated with increased microvillous development in 40 A-2. There were not detectable concomitant changes in either (a) the quantity or organization of microtubules or 80-100 nm microfilaments, or (b) the intensity of glial fibrillary acidic protein indirect immunofluorescence staining.

Animals↗
PubMed1981

The combination of scanning and transmission electron microscopy techniques in pathology of the organ of Corti in guinea pigs.

The pathology of the organ of Corti in guinea pigs is studied by means of SEM and TEM. It was the purpose of this study to examine the surface of an experimentally altered organ of Corti by means of SEM screening method). As it was our main interest to find out the localization of acoustic stimulation regarding the tonotopicity on the surface of the organ of Corti, we always examined the whole cochlear by means of SEM first. In acoustic experiments we used long-time pure-tone stimulation beyond the directly damaging sound pressure level, as well as white noise or shots for experimental damage of hair cells and supporting cells. Specimens of particular interest underwent a special procedure for a supplementary TEM examination. A prolonged and modified technique of embedding the specimens in Epon 812 permitted us to obtain supplementary data from TEM without major artifacts in the fine structure of the cells.

Acoustic Stimulation↗