Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Microscopy, Electron”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed2004

Phan3D: design of biological phantoms in 3D electron microscopy.

Three-Dimensional Electron Microscopy (3DEM) has turned out to be a major player in structural proteomics. In 3DEM, tens of thousands of EM images from a macromolecule at different views are combined to derive its structure by means of a 3D reconstruction algorithm. However, for an optimal reconstruction, the most suitable algorithm has to be used and its parameters have to be tuned for the macromolecule under study and the experimental conditions found. The use of phantoms is central to objective comparison of reconstruction algorithms and optimization of their parameters. Phan3D is a tool intended to provide a fully visual and interactive environment that facilitates the design of phantoms resembling biological specimens in 3DEM. Phan3D has been developed as an alternative to the tedious, error-prone and old-fashioned phantom design that is based on hand-written text description files.

Computer Graphics↗
PubMed1986

Early dentinogenesis in mice: von Korff fibres and their possible significance. A preliminary study by light and electron microscopy.

By light and electron microscopy we have confirmed the collagenous nature of von Korff fibres in early dentinogenesis in mice. Each fibre array begins as an argyrophil 'stem' lying between the outermost cells of the dental papilla, with finer divisions passing into the papilla. With the appearance of odontoblasts, a cone-like 'spray' of nonargyrophil fibres in continuity with the stem spreads peripherally between these cells to the dental epithelial basement membrane. After the sprays become immured in dentine matrix, the stems are removed. Later, new stems appear. Sprays are restricted to enamel-bearing parts of teeth. The possible nature and functions of von Korff fibres are discussed.

Animals↗
PubMed1981

Improved contrast in cytochemistry of dehydrogenases by scanning transmission electron microscopy.

A scanning transmission electron microscope (STEM) was used to examine ultrathin sections of rabbit white skeletal muscle. Lactic dehydrogenase (LDH) activity was localized in the tissue using the tetra-nitro blue tetrazolium (TNBT) method. For most specimens postfixation was omitted in order to avoid reoxidation and solubilization of the formazan by osmium tetroxide. The STEM image revealed sufficient contrast of the intracellular structures and apparently electron-dense reaction product in the sarcoplasmic reticulum and mitochondria. Substantially less contrast was obtained when the same areas were observed by conventional transmission electron microscopy (CTEM). In material postfixed with osmium tetroxide, although the tissue contrast was improved, the TNBT reaction product was focally leached out, exhibiting lower contrast than in unosmicated sections. These results indicate that the fine structural visualization of dehydrogenases with TNBT, the STEM technique as used in the present study is superior to that obtained by CTEM.

Animals↗
PubMed1990

Three-dimensional organization of extracellular matrix in elastic cartilage as viewed by quick freeze, deep etch electron microscopy.

Freeze-etch electron microscopy was used to reexamine the ultrastructure of extracellular matrix in elastic cartilage. This revealed that extremely delicate, approximately 4 nm diameter fibrils join end-to-end and sometimes side-to-side to form a tightly woven mesh that extends continuously from the cell membrane throughout the intercellular space. Within this meshwork were found large, irregularly contoured and densely packed elastin fibers as well as long, thin (20 nm) fibers with the appearance of type II collagen. By comparison, type I collagen fibers found in the skin surrounding the cartilage appeared much thicker (30 nm) and displayed the usual periodic banding pattern. Freeze-etching the latter fibers displayed a helicoidal arrangement of subfibrils within. In both cartilage and type I collagen-rich extracellular matrix, some of the approximately 4 nm filaments in the matrix could be seen to contact collagen fibers orthogonally, apparently connecting adjacent fibers at regular intervals. The organization of these fine filaments and others composing the matrix has several features that suggest a different organization for cartilage than currently thought. Specifically, the distance between branch or contact points of fibrils in the matrix is seldom more than 35 nm, substantially less than the length of one extended proteoglycan monomer. This suggests that other proteoglycans, or other unidentified components of the matrix, bind along the proteoglycan core protein at intermediate binding sites in order to form a finely partitioned structure.

Animals↗
PubMed1987

Vascular casting and scanning electron microscopy in diabetes.

Scanning electron microscopic (SEM) studies of the vascular casts of human eyes removed at autopsy from subjects with a long-standing history of Diabetes Type I were performed. Changes in the choroidal vasculature include: Venal focal dilations and narrowings, increased tortuosity, hypercellularity, increased formation of vascular loops and microaneurysms in choriocapillaries and formation of sinus-like structures between choroidal lobules. This study strongly supports earlier light microscopic and transmission electron microscopy observations on changes in the choroid. The retinal vascular changes shown by SEM are microaneurysm formation, drop-out of capillaries and neovascularization. Changes in the choroid, especially in diabetic choriocapillaries can be suspected to be a supporting factor in diabetic retinopathy by a decrease of oxygenation of the outer layers of the retina.

Capillaries↗
PubMed1989

Localization of functional centers on the prokaryotic ribosome: immuno-electron microscopy approach.

Immuno-electron microscopy studies on the morphology of the Escherichia coli ribosome and the topography of its functional centers are summarized. A three-dimensional model of the ribosome with indications of the mRNA-binding site, the peptidyl-transferase center, the EF-Tu and EF-G-binding sites and the tRNA-binding sites in given. Thus, the mutual arrangement of the centers corresponding to the main functional activities of the ribosome during the process of translation is presented.

Binding Sites↗
PubMed1987

Small-cell pediatric tumors: histology, immunohistochemistry, and electron microscopy.

Histology, immunohistochemistry, and electron microscopy give an account on what is known of the correlation between histologic appearance and prognosis in this important group of tumors. Ultrastructural and immunohistochemical findings are presented that frequently are useful in establishing a diagnosis, but also serve to elucidate the histogenesis of some tumors, especially those that lack characteristic features.

Child↗
PubMed1988

Electron microscopy of nucleic acid.

Electron microscopy (EM) of nucleic acids was first described by Kleinschmidt and Zahn 1959 (1). By complexing duplex DNA with basic proteins and spreading the complexed DNA onto the surface of an aquous phase it was possible to obtain well stretched DNA molecules that could be examined by EM. Addition of formamide to DNA spreading solution as well as to hypophase prevented single-stranded DNA and RNA from forming secondary structures thus providing conditions for analysis of these molecules. EM studies have provided information about molecular weight, molecular configuration and homogeneity/heterogeneity of the DNA preparations examined. Furthermore, intramolecular heterogeneity in base sequence could be analyzed by partial denaturation of duplex DNA. By partial denaturation mapping information of the orientation of DNA molecules was obtained. Sequence homology between two DNA molecules were studied by heteroduplex analyses where the two DNAs to be studied were denatured to full strand separation followed by reassociation. This method has been widely used to analyze DNA mutations, and to discover sequence homologies within a DNA molecule or between two DNA molecules. Heteroduplex analyses between DNA and RNA (R-loop formation) provided information about distribution of ribosomal RNA genes and gave the first information of eukaryotic post transcriptional processing of mRNA. Also the various modes for DNA replication and transcription were studied by EM. It is possible to study duplex DNA not complexed by basic proteins by EM. The DNA is then adsorbed to an activated carbon film and rotary shadowed with finely grained metals to enhance the contrast. Using this method it was possible to study binding of proteins to DNA. This method was also used in the study of chromatin structure where it provided information of the size and distribution of nucleosomes as well as packaging of DNA in chromatin fibres. The complicated nature of DNA strand exchange and repair reactions was studied by in-vitro systems where EM analysis was used in the description of the presynoptic filament and structure of the joined molecules. Furthermore, EM provided the first direct evidence for the existence of the paranemic joint, where the DNA strands are joined without Watson-Crick base-pairing.

Animals↗
PubMedDate not supplied

[Possibility of detecting the matrix protein of the influenza virus in intact and disrupted virions by immunoenzyme analysis and immune electron microscopy].

ELISA and immune electron microscopy were used to study possible causes of the detection of antigenic reactivity of influenza virus matrix protein in purified virus suspension directly adsorbed on polystyrene. No interaction of antibody to M protein with the surface of virus and subvirus particles was observed. The process of virus sorption on polystyrene for a long period was shown not to lead to disruption of intact virus particles, and the detection of the internal matrix protein in preparations of purified influenza virus was due only to the presence of partially or completely destroyed virions in the viral suspension.

Absorption↗
PubMed1983

The microtrabecular lattice and its relationships to other organelles in prokaryotes and eukaryotes--high resolution scanning electron microscopy.

High resolution scanning electron microscopy demonstrated the microtrabecular lattice in bacteria, fungi, plant and animal cells. It is attached to ribosomes and plasma membranes generally, but to other organelles and the nuclear envelope in eukaryotes. The eukaryotic organelle surface substructure is described. Differentiation of real structure from artifacts of fixation, critical point drying and sputter-coating, is discussed.

Animals↗
PubMed1988

The use of electron microscopy for the diagnosis of cancer in bronchial biopsies.

To investigate whether electron microscopic examination of bronchial biopsy specimens was of any additional value in the diagnosis of lung cancer, we examined 235 consecutive biopsy specimens embedded in Epon. Semithin sections were used to establish a light microscopic diagnosis, and the results were compared with those of electron microscopy. Ninety-six biopsies contained tumor. In 13 instances, the light microscopic diagnosis had to be revised after electron microscopic examination. Another 5 biopsies contained tissue suspected to be tumor; in 1 biopsy this possibility could be ruled out. Three biopsies contained tumor suspected of being small cell cancer, and this diagnosis was confirmed by electron microscopy. Electron microscopy was helpful in 17 of 106 biopsies. Histopathologic examination of surgically resected material from 18 patients confirmed the electron microscopic results of biopsies. We conclude that electron microscopy of bronchial biopsy specimens gives important additional information for accurate diagnosis. For practical purposes, however, specimens should be embedded in Epon or glycol-methacrylate for light microscopy. Developments in immunohistologic techniques will change choices of histologic techniques.

Adenocarcinoma↗
PubMed1985

Scanning electron microscopy, x-ray diffraction, and electron microprobe analysis of calcific deposits on intrauterine contraceptive devices.

Deposits found intrauterine contraceptive devices (IUDs) were studied by scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray microanalysis. All seven devices, including five plastic and two copper IUDs, were coated with a crust containing cellular, acellular, and fibrillar material. The cellular material was composed of erythrocytes, leukocytes, cells of epithelial origin, sperm, and bacteria. Some of the bacteria were filamentous, with acute-angle branching. The fibrillar material appeared to be fibrin. Most of the acellular material was amorphous; calcite was identified by x-ray diffraction, and x-ray microanalysis showed only calcium. Some of the acellular material, particularly that on the IUD side of the crust, was organized in spherulitic crystals and was identified as calcium phosphate by x-ray microanalysis. The crust was joined to the IUD surface by a layer of fibrillar and amorphous material. It is suggested that the initial event in the formation of calcific deposits on IUD surfaces is the deposition of an amorphous and fibrillar layer. Various types of cells present in the endometrial environment adhere to this layer and then calcify. Thus, the deposition of calcific material on the IUDs is a calcification phenomenon, not unlike the formation of plaque on teeth. Hum Pathol 16:732-738, 1985.

Calcium↗
PubMed2002

Comparative study of a block copolymer morphology by transmission electron microscopy and scanning force microscopy.

Using transmission electron microscopy (TEM) and scanning force microscopy (SFM) together, it was possible to verify important structural features of a nanostructured bulk material such as the kp-morphology in an ABC triblock copolymer. By applying suitable imaging techniques during the SFM measurements it was possible to determine the morphology without additional manipulation steps in between. In comparison, TEM investigations on this type of material usually require selective staining procedures prior to the measurement. Also electron beam damage is often encountered during TEM measurements especially if components such as poly(methacrylates) are present. In contrast, SFM measurements can be assumed not to significantly change the phase dimensions of the components.

Journal Article↗
PubMed2000

Structure of cytomatrix and nuclear matrix revealed by embedment-free electron microscopy.

Embedment-free electron microscopy (EFEM) is a new method which allows the visualisation of cytoskeleton in whole-mounted cells. In this study we employed EFEM to investigate the structure of cellular scaffolds in glioma C6 cell line. The cells were extracted with Triton X-100 that dissolves phospholipids in the membranes and removes most of cytoplasmic soluble proteins. The DNA and nuclear histones were removed with DNase I and high-salt buffer, respectively. The remaining cellular frameworks were temporary embedded in diethylene glycol distearate (DGD), sectioned and observed in transmission and scanning electron microscope after the removal of DGD. The predominant structure was the extensive meshwork of 10-20 nm filaments in the cytoplasm (cytomatrix) and 15-30 nm filaments in the nucleus (nuclear matrix). The 5 nm filaments, presumably corresponding to the actin filaments, were present in the cytomatrix, but not in the nuclear matrix. Moreover, the ultrathin (3 nm) filaments, connecting other cytoskeletal components were detected. Those are possibly identical with the previously described plectin filaments. For the first time we report the occurrence of ultrathin filaments in the nuclear matrix. Thus, in a addition to the well known cytoskeletal components (microtubules, intermediate filaments, actin microfilaments) EFEM showed a new type of filaments (the ultrathin filaments) in the cytomatrix and nuclear matrix. Further immunocytochemical studies are needed to determine the biochemical identity of the filaments observed in EFEM.

Animals↗
PubMed1975

Scanning electron microscopy of the nephrotic kidney.

Scanning electron microscopy (SEMy), supplemented with light microscopy and transmission electron microscopy, was used to study aminonucleoside nephrosis in rats. The visceral epithelium undergoes dramatic restructing in response to aminonucleoside nephrosis. Due in part to an accumulation of intracellular vacuoles, kidney podocytes swell in size. Podocyte major processes lose their many pedicles and slit pores and form close junctions (80 A) with adjacent podocytes. Although no prominant pores opening into the urinary space are found in the visceral epithelium, there is evidence that podocyte vacuoles may rupture and thereby release protein into the urinary space. Many parietal cells also increase in size, accumulate intracellular vacuoles and come into very cose proximity to the visceral epithelium. Casts of PAS-positive, electron-dense material fill the lumina of many uriniferous tubules. Although most proximal tubules exhibit an extensive loss of brush border, no significant changes in other kidney microprojections or cilia were noted. Transmission electron and light microscopy of nephrotic kidneys reveal considerable changes in proximal and distal tubules including a reduction in mitochondria, in cell height, in electron density of the cytoplasmic matrix, in lateral and basal plasmalemma infolds, enlarged euchromatic nuclei, dilated lumens, and accumulation of PAS-positive cytoplasmic granules. SEMy of kidney needle biopsies from patients with proteinuria reveal that SEMy is useful for evaluating glomerular changes in man.

Animals↗
PubMed1969

Application of electron diffraction to biological electron microscopy.

Three methods by which electron diffraction may be applied to problems in electron microscopy are discussed from a fundamental point of view, and experimental applications with biological specimens are demonstrated for each case. It is shown that wide-angle electron diffraction provides valuable information for evaluating specimen damage that can occur either during specimen preparation or while in the electron beam. Dark-field electron microscopy can be used both to enhance the image contrast and to provide highly restricted and therefore highly specific information about the object. Low-angle electron diffraction provides quantitative information about the object structure in the range from 20 A to approximately 1000 A. Lowangle electron diffraction also demonstrates the important role of Fourier contrast with biological specimens, which are usually characterized by structural features with dimensions of 20 A or larger.

Electrons↗
PubMed2005

Characterization of chiral mesoporous materials by transmission electron microscopy.

By using transmission electron microscopy (TEM), the chirality of novel mesoporous materials has been studied. In addition, a computer simulation that uses a simple structural model was employed. The existence of chiral channels inside a tubelike material was confirmed by the observation of fringes along the length of the tubes. The chiral pitch of the channels was measured from the intermittent period, the chirality (right- or left-handed) was determined from the tilt direction of a tube compared with the direction of incident electrons and the curvature direction of the curved intermitted fringes as viewed in the TEM images.

Absorption↗
PubMed2000

A Comparative Study of Enzymatically and Photochemically Polymerized Artificial Lignin Supramolecular Structures Using Environmental Scanning Electron Microscopy.

Environmental scanning electron microscopy images of the self-assembled structures of enzymatically (DHP) and photochemically polymerized (PCP) artificial lignin are herein presented. Differences in the structural organization between DHP and PCP polymer at the supramolecular level were reported. Based on topological information, we proposed a hypothesis about possible new physiological roles of lignin in live plant cells and the ecological significance of possible in-vivo photochemical lignin polymerization. Copyright 2000 Academic Press.

Journal Article↗