[Effect of dentin mineralization in the rachitic rat. Fluorescence microscopy and scanning electron microscopy studies].
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Animals↗
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Results for “Microscopy, Electron”
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A study of the carious lesion utilizing radiography, polarized light microscopy, and scanning electron microscopy.
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Dental Caries↗
Co-ordinated electron microscopy and X-ray studies of glycerinated insect flight muscle. II. Electron microscopy and image reconstruction of muscle fibres fixed in rigor, in ATP and in AMPPNP.
This paper presents electron microscopy, supported by optical diffraction and filtering of images from 100 nm and 25 nm sections, to complement the companion report of X-ray diffraction monitoring (immediately preceding this article) performed on the same insect flight muscle specimens during fixation, dehydration and embedding. Glycerinated Lethocerus fibre bundles initially fixed in rigor, in ATP relaxing buffer, or in 1 mM AMPPNP at 2 degrees C, gave thin-section images from each state whose optical transforms match the distinctive X-ray diffraction patterns from the embedded samples. For rigor and relaxed states, this extends and confirms a long-known correlation between X-ray patterns and EM image regularities. For the AMPPNP state, such correlation is here fully developed for the first time, and involves a new and distinctive EM image pattern of the crossbridge array, clearly different from a previously reported structure in AMPPNP-treated muscles that appears identical to fixed relaxed muscle. We found this latter artifact of 'AMPPNP-relaxed structure' in many fibres from our best AMPPNP specimen, but could identify other fibres which retained the distinctive AMPPNP structure, known to be dominant in this specimen from the X-ray pattern. The true AMPPNP structure shows features of both the ATP-relaxed and rigor crossbridge patterns, not as separate patches, but hybridized uniformly along each filament and throughout each affected sarcomere and fibre. It presents a 14.5 nm repeat of striping and lateral projections along thick filaments, together with variously angled crossbridge attachments to actin that form a 38.7 nm repeat of diffuse chevrons or deltoids replacing the more clearly delinated rigor double chevrons. The associated optical transform has the typical AMPPNP features, that is, it has in common with rigor a strong 19.3 nm layer line and strong second to fourth row line sampling on the 38.7 nm layer line, it has in common with relaxed patterns a strong 14.5 nm meridional and layer line, but it uniquely shows no intensity at the first row line on the 38.7 nm layer line (the 10.3 X-ray reflection), where rigor and relaxed transforms always show high intensity. The processing artifacts which intensify the 10.3 reflection, and produce the weak 19.3 nm layer line (a gain of intensity for ATP but a loss for the AMPPNP state), throughout ATP specimens and in those analogue-treated fibres showing AMPPNP-relaxed structure, might indicate trapping and accumulation of minority populations within the native equilibrium distribution of crossbridge conformations in each nucleotide state.
Adenosine Triphosphate↗
Microcirculation of the pancreas: a correlative study of intravital microscopy with scanning electron microscopy of vascular corrosion casts.
The microcirculation of the pancreas in anesthetized rats was examined by intravital microscopy. Scanning electron microscopic observation of vascular corrosion casts of the same parts of the pancreas as viewed light microscopically in vivo, allowed detailed analysis of microcirculation in particular vessels. Blood vessels with flowing blood cells were clearly observed under incident ultraviolet illumination following systemic injection of an intravascular fluorescent tracer. The islets of Langerhans were easily identified by their brighter appearance than the exocrine portions under incident ultraviolet illumination. Blood leaving the islets passed through the insulo-acinar portal vessels into the capillary network around the acini. The periductular plexus received blood from the periacinar capillary network via either venules or capillaries as well as directly from the inter- or intralobular arteries. The periductular plexus also received blood from the islets located close to the ductules. The results obtained show blood in the pancreas flowing in a manner in which it carries insular secretions in high concentrations through short and direct vascular routes from the islets to the pancreatic exocrine tissues, including their duct system.
Animals↗
Wide-field electron microscopy. A rapid method for the study of histologic material that provides a bridge between light and electron microscopy.
Wide fields of tissue can be rapidly examined by electron microscopy by use of Formvar films for the support of ultrathin sections on slot grids. The intervention of the grid bars of conventional mesh grids is avoided, and a continuous micrograph of the specimen at scanning magnifications can be obtained. Enough material is sublimed from the section and the supporting film by deliberate exposure to the electron beam to permit one to obtain an image with good contrast. This method of examination, which takes in all about two hours, permits examination of an extensive area of tissue in relation both to its topography at low magnifications and to its ultrastructural detail, and accordingly adds to electron microscopy a dimension characteristic of the lower powers of the light microscope. It offers the histopathologist the option of using micrographs taken during the scanning survey of a tissue to detect regions that can be readily re-examined at high magnification in the same ultrathin section.
Animals↗
Vascular interrelationships of near-term mink placenta: light microscopy combined with scanning electron microscopy of corrosion casts.
The microvasculature of the near-term zonary placenta of the mink has been studied using light microscopy and scanning electron microscopy of corrosion casts, prepared from maternal and fetal vessel systems, respectively. The zonary area, most important for placental exchange, includes a characteristic labyrinth. The labyrinth is composed of lobules oriented in a maternal-fetal direction. One maternal stem artery serves as the central axis of a lobule, and about six pairs of fetal stem arteries and stem veins of the chorionic primary villi mark the periphery of the lobule. Viewed from the fetal side of the labyrinth, this lobular structure presents a roughly hexagonal pattern, with the central maternal stem artery and radially oriented arteriolar branches giving the lobule the shape of a star. These arterioles frequently form bridges to neighboring lobular systems; however, the majority continue into the feto-maternally oriented three-dimensional network of maternal capillary sinusoids, which converge on the outlets of the maternal stem veins on the maternal side of the labyrinth. Maternal main crypts are delimited by the rays of the star-shaped lobules containing chorionic primary villi. The latter penetrate into maternal crypts from the fetal side, and are characterized by their axial arterial and venous stem vessels. Fetal secondary villi are arranged at different levels from these stem vessels. The secondary villi are characterized by arterioles and venules branching in pairs from the stem vessels and supply the tributary capillary complexes of terminal villi. The lobular structure of the placental labyrinth provides a three-dimensional framework of vessels where maternal capillary sinusoids and fetal capillaries meet in a one-way cross-current arrangement. The blood flow conditions and the peculiarities of the mink placenta interhemal membrane are compared to those of other carnivores and discussed with respect to the efficiency of the endotheliochorial placenta.
Animals↗
Diagnostic electron microscopy of faeces. I. The viral flora of the faeces as seen by electron microscopy.
A method is described for examining viruses in faeces by direct electron microscopy using negative staining. The particles found in a group of patients with gastroenteritis and a group with other conditions are compared. Small particles in the range of sizes covering parvoviruses and enteroviruses were found about as frequently in each group. Many of these were probably bacteriophages. Many bacteriophages with tails of various sizes and lengths were found. Adenoviruses were found in five of eight patients from whom they were isolated. Reovirus- (or orbivirus-) like particles were found associated with some gastroenteritis patients.
Adenoviridae↗
Dendritic cell/lymphocyte clustering: morphologic analysis by transmission electron microscopy and distribution of gold-labeled MHC class II antigens by high-resolution scanning electron microscopy.
Dendritic cells (DCs) are potent antigen-presenting cells for a variety of immune responses; however, their mechanism of action has not been established. It is known that DCs can cluster with one another and with other cell types during in vitro immune responses, and clustering may be essential for the activation of resting lymphocytes. In this study, ultrastructural examination of clusters that form during extended culture of enriched rat splenic DCs (approximately 70% DCs) is reported. DCs were readily distinguished from other cell types, which included lymphocytes and macrophages. DCs displayed characteristic veils and/or dendritic processes that intertwined with processes of other cells within the cluster, or extended from the cluster periphery. Occasional DCs contained large vacuoles lined with small vesicles. A paramount feature of DCs is their constitutive expression of high levels of surface major histocompatibility complex class II antigens. The surface distribution of class II antigens on clustering DCs was examined using 10 nm immunogold labeling techniques and high-resolution scanning electron microscopy. DCs were readily distinguished by morphologic criteria, and examination of various surface membrane regions revealed a differential distribution of class II antigens. Gold label was frequently distributed in linear arrays and clusters, suggesting a cytoskeletal role in the recycling/redistribution of Class II antigens. These morphologic findings further an understanding of basic DC biology and their mechanism of action as antigen-presenting cells.
Animals↗
The structure of the H(+)-ATP synthase from chloroplasts and its subcomplexes as revealed by electron microscopy.
The electron microscopic data available on CF(0)F(1) and its subcomplexes, CF(0), CF(1), subunit III complex are collected and the CF(1) data are compared with the high resolution structure of MF(1). The data are based on electron microscopic investigation of negatively stained isolated CF(1), CF(0)F(1) and subunit III complex. In addition, two-dimensional crystals of CF(0)F(1) and CF(0)F(1) reconstituted liposomes were investigated by cryo-electron microscopy. Progress in the interpretation of electron microscopic data from biological samples has been made with the introduction of image analysis. Multi-reference alignment and classification of images have led to the differentiation between different conformational states and to the detection of a second stalk. Recently, the calculation of three-dimensional maps from the class averages led to the understanding of the spatial organisation of the enzyme. Such three-dimensional maps give evidence of the existence of a third connection between the F(0) part and F(1) part.
Chloroplasts↗
Scanning electron microscopy of the wall of the third ventricle of the brain of Rana temporia. II. Electron microscopy of the ventricular surface of the pars ventralis of the tuber cinereum.
Scanning electrom microscopy of the ventricular surface of the pars ventralis of the tuber cinereum of the frog Rana temporaria shows that it can be divided in (1) a dorsolateral area, characterized by the presence of very numerous large, solid, bulbous protrusions (2) a medial area, where the large bulbous structures are completely absent and which is diffusely covered with very numerous cilia, (3) a transiotional area located between the two other regions. The large bulbs, shown by scanning electron microscopy, correspond with the end-bulbs of thick ventricular dendrites of nerve cells revealed by transmission electron microscopy. At least many of these intra-ventricular bulbs are dendritic endings of peptidergic neurosecretory neurons, which have been tentatively identified as adenohypophysiotropic neuro-hormone producing neurons (Derickx et al., 1972, 1973a, 1973b). The structural features of the dendritic endings plead in favour of a possible receptive role.
Animals↗
Transmission electron microscopy and immunocytochemical studies of yeast: analysis of HMG-CoA reductase overproduction by electron microscopy.
The results and anecdotes presented here are intended only as a general guide to other would-be immunocytochemists, because other proteins will undoubtedly respond at least somewhat differently than does HMG-CoA reductase. Nevertheless, based on these experiences, we offer the following suggestions: 1. Antiserum of high specificity should be raised and affinity-purified. Using this antiserum, immunofluorescence microscopy should be attempted before resorting to electron microscopic localization. In the absence of immunolocalization at the light-microscope level, it may be a waste of time to pursue the problem to higher levels of resolution. 2. Cells should be prefixed in 1% formaldehyde-1% glutaraldehyde. Direct fixation of the growing culture and use of phosphate buffer are recommended. The prefixed sample can then be divided into two or three aliquots. One aliquot should receive no postfixation (for optimal immunoreactivity), while the others can be postfixed in osmium-potassium ferricyanide (for possible immunolocalization) or permanganate (for ultrastructural analysis). Because of its ease of use, Spurr's resin should be tried initially. If immunocytochemistry is successful, no further preparations are necessary. If unsuccessful, LR White resin is recommended, but the sample must be treated to remove the cell wall. Electron microscopy and immunocytochemistry offer views into the molecular arrangement of individual cells, a view not easily obtained by other means. It is satisfying and often enlightening to be able to see the extremes as well as the average. In studies of the organization of karmellae, for example, ultrastructural analysis easily revealed the asymmetric segregation pattern, while immunoblots and cell fractionation could not even demonstrate the existence of this membrane organization. The richness of the information available to those who can avert reductionist tendencies, even for a short time, is remarkable.
Histocytochemistry↗
Characteristics of human chondrocytes, osteoblasts and fibroblasts seeded onto a type I/III collagen sponge under different culture conditions. A light, scanning and transmission electron microscopy study.
Hyaline cartilage has only a limited capacity of regeneration, thus, lesions of articular cartilage can lead to early osteoarthrosis. Current concepts in conservative orthopedic therapy do not always lead to satisfying results. As one new attempt to facilitate cartilage repair, autologous transplantation of articular chondrocytes is investigated in different assays. This study was designed to create a resistible and stable cell-matrix-biocomposite with viable and biosynthetically active human chondrocytes, osteoblasts or fibroblasts. This biocomposite might serve as an implant to treat deep osteochondral defects in the knee. We collected cartilage, spongiosa and skin probes from healthy patients undergoing hip-surgery and enzymatically liberated the chondrocytes, seeded them into culture flasks and cultured them until confluent. The spongiosa and the skin samples were also placed in culture flasks and cells cultured until confluent. After 4-6 weeks, cells were trypsinized and grown on a type I/III collagen matrix (Chondrogide, Geistlich Biomaterials, Wolhusen, Switzerland) for 7 days in standard Petri dishes and in a special perfusion chamber culture system. As controls, cells were seeded onto plastic surfaces. Then scaffolds were fixed and embedded for light microscopy and electron microscopy by routine methods. Light microscopically, chondrocytes grown on the surface of the scaffold form clusters or a dense layer of sometimes rather fibroblast-like and sometimes roundish, chondrocyte-like cells. Only a few cells grow deeper into the matrix. In transmission electron microscopy, the cells have a rather chondrocyte-like morphology which emphasizes the matrix-induced redifferentiation after dedifferentiation of chondrocytes in monolayer-culture in culture flasks. Chondrocytes on plastic surfaces have a spinocellular aspect with little signs of differentiation. Grown on Chondrogide, cells are more roundish and adhere firmly to the collagen fibrils of the scaffold. Osteoblasts grown on the collagen scaffold and examined by light microscopy form a thin cell-layer on the surface of the matrix with a reticular layer of dendritic cells underneath this sheet. Transmission electron micrographs show spinocellular and flat cells on the collagen fibrils. Scanning electron micrographs show large dendritic osteoblasts on plastic and a confluent layer of flattened, dendritic cells on the collagen scaffold. Fibroblasts form a thick multi-layer of typical spinocellular cells on the collagen matrix. Fibroblasts grown on plastic surfaces and examined by scanning electron microscopy also show a dense layer of fibroblast-like cells. For all three different types of cells no morphological differences could be seen when comparing cultivation in the perfusion culture system to cultivation in standard Petri dishes, although mechanical stress is believed to induce differentiation of chondrocytes. Especially the observed partially differentiated chondrocyte-matrix biocomposite might serve as an implant to treat deep cartilage defects, whereas osteoblasts and fibroblasts seem to be less suited.
Aged↗
Observations of the microcirculatory bed in rat mesocecum using differential interference constrast microscopy in vivo and electron microscopy.
The microvascular bed of the rat mesocecum has been examined in vivo using differential interference (Nomarski) optics and subsequently by electron microscopy. The preferential channel, from terminal arteriole to collecting venule, has been examined. In the terminal arteriolar segment the endothelial layer is covered by a continuous layer of smooth muscle cells which, in turn, are surrounded by adventitia. In the metarteriolar segment the periendothelial cells still resemble smooth muscle cells but the tunica media is discontinuous. In the distal segment periendothelial cells are more scattered and have the appearance of pericytes. There appears to be a continuous transition of the periendothelial cell layer from terminal arteriole to distal segment. Nerve endings were seeen in both the terminal arteriolar and metarteriolar segments. During contraction smooth muscle cells, oriented circumferentially, shorten and thicken. Endothelial cells appear anchored by myoendothelial junctions. Endothelial cells have filaments which show increased banding during vasoconstriction, suggesting that such cells may contract. Capillary offshoots leave the preferential channel, usually at right angles. Smooth muscle cells are oriented to form a sphincter and there are many myoendothelial junctions at the branch point. Within a short distance the capillary branch loses its periendothelial coat.
Animals↗
Scanning and transmission electron microscopy of the normal rabbit aortic endothelium after controlled perfusion fixation.
Light microscopy, scanning electron microscopy, and transmission electron microscopy were employed on the anterior wall of the rabbit thoracic aorta with the particular purpose to study endothelial marginal flaps and the structure of stomata under physiological conditions at 100 mm Hg. Intra-aortic pressure monitoring was performed during the whole period of perfusion (2h), restricting pressure variations to a maximum of +/- 5 mm Hg in order to preserve endothelial architecture. We found the endothelial surface uniformly smooth. Marginal flaps of the endothelial cells were mutually overlapping, often forming multiple layers. Underlying flaps might protrude to the lumen between neighbouring flaps as flat mushrooms. Flaps of adjacent cells might diverge for short distances to decover an underlying endothelial cell. Downstream flaps of the cells might be overlapped at their base by flaps of adjacent cells, the extremity of the flap thus appearing as a disc separated from the cell. The small discs and troughs thus formed are considered equivalent to the so-called stomata.
Animals↗
[23d meeting of the German Society for Electron Microscopy including the 20th colloquium of the Study Groups for Electron Microscopy Direct Imaging and Analysis of Surfaces. Bremen, 13-19 September 1987. Abstracts].
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Animals↗
Electron microscopy of the epiphyseal cartilage plate. A critical review of electron microscopy observations on enchondral ossification.
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Animals↗
Analyses of phosphorylase kinase by transmission and scanning transmission electron microscopy.
Under conventional electron microscopy negatively stained phosphorylase kinase exhibits a bilobal structure resembling two bridged opposing parentheses. In this predominant particle orientation, usually only one bridge is observed; however, in many particles two bridges can be seen. Scanning transmission electron microscopy of unstained phosphorylase kinase shows very similar structures, with a particle mass equivalent to that of the hexadecameric holoenzyme. Partial digestion of the enzyme with chymotrypsin, which preferentially hydrolyzes the alpha-subunits, causes no significant changes in the structure; however, when both the alpha and beta subunits are degraded by trypsin, single lobed particles appear, i.e. the connecting bridges are missing. Mass analysis of scanning transmission electron microscopy images of trypsinized enzyme indicates that the protease does, in fact, split the particle into halves. Transmission electron microscopy of an alpha gamma delta complex isolated after incubation of the holoenzyme with LiBr shows only small particles approximately one-fourth the size of the holoenzyme. Thus, integrity of the beta subunit may be necessary in order for the two lobes of phosphorylase kinase to be bridged. These data also indicate that the subunits are arranged as a bridged dimer of octamers 2 (alpha 2 beta 2 gamma 2 delta 2).
Animals↗
Further observations on cerebellar climbing fibers. A study by means of light microscopy, confocal laser scanning microscopy and scanning and transmission electron microscopy.
The intracortical pathways of climbing fibers were traced in several vertebrate cerebella using light microscopy, confocal laser scanning microscopy, scanning and transmission electron microscopy. They were identified as fine fibers up to 1(micron thick, with a characteristic crossing-over bifurcation pattern. Climbing fiber collaterals were tridimensionally visualized forming thin climbing fiber glomeruli in the granular layer. Confocal laser scanning microscopy revealed three types of collateral processes at the interface between granular and Purkinje cell layers. Scanning electron microscopy showed climbing fiber retrograde collaterals in the molecular layer. Asymmetric synaptic contacts of climbing fibers with Purkinje dendritic spines and stellate neuron dendrites were characterized by transmission electron microscopy. Correlative microscopy allowed us to obtain the basic three-dimensional morphological features of climbing fibers in several vertebrates and to show with more accuracy a higher degree of lateral collateralization of these fibers within the cerebellar cortex. The correlative microscopy approach provides new views in the cerebellar cortex information processing.
Adolescent↗