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Results for “Microscopy, Electron”

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At least 577 records · Page 32Linked to original sources

PubMed1996

A novel method for viewing heavy metal stained and embedded biological tissue by field emission scanning electron microscopy.

Backscattered electron (BSE) imaging was used to display heavy metal stained biological structures of various embedded specimens. Samples were fixed, stained and embedded in resin blocks as with preparation for the transmission electron microscope (TEM). Blocks were trimmed to center the specimens in a trapezoidal face of up to 5 mm2 and their sides painted with conductive silver paint leaving the face uncovered. Blocks were sputter coated with 6-8 nm of silver, chromium or aluminum, with aluminum providing the best specimen contrast in BSE mode. Samples were examined in a field emission scanning electron microscope operated at a high emission current of 50 microA. Both the fixation protocol and microscope operating parameters were optimized to maximize the number of BSE available from the smallest probe. An accelerating voltage of 10 keV was found optimal for resolution and contrast. The technique allowed the direct visualization of embedded samples at resolutions beyond light microscopy with good contrast, without cutting sections, and avoiding grid bars obscuring areas of interest. The two dimensional images provided averaged information on the internal structures of the specimens in relation to the predicted emission depth of the BSE. The technique could be used for rapid diagnostics in pathological examinations, or for routine preselection of areas of interest within a sample face before final trimming for ultrathin sectioning for higher resolution TEM study.

Animals↗

PubMed1979

A study of arterial prostheses by scanning electron microscopy.

Scanning electron micrographs were taken of ten different vascular prostheses. The micrographs showed that some prostheses were damaged and some had traces of chemicals on their surface. The application of standard vascular clamps damaged most grafts and some showed remarkable changes on resterilization.

Arteries↗

PubMed1975

Detection of adenovirus in patient specimens by indirect immune electron microscopy.

Immune electron microscopic procedures for the detection of adenovirus type 7 directly in throat swab specimens from patients are described. Nineteen of 25 throat swab samples, known to be positive for adenovirus type 7 by isolation of virus from tissue culture, were shown to contain aggregates of adenovirions coated with antibody. Sensitivity tests of the immune electron microscopic method showed that as few as 16 to 32 tissue culture infective doses of virus could be detected by the direct immune electron microscopic technique. It was also demonstrated that aggregation of virus-antibody complexes could be further enhanced by use of anti-immunoglobulin G sera (indirect immune electron microscopic procedures). These results demonstrate that examination of patient specimen by immune electron microscopic procedures is a feasible and rapid method for adenovirus detection and suggest that it could be applied as a routine laboratory procedure for the diagnosis of other virus infections.

Adenoviridae↗

PubMed1986

Rat macrophage activity against Toxoplasma gondii studied by electron microscopy.

An electron microscope model was used to study the effect of rat peritoneal macrophages on Toxoplasma gondii. 10(7) tachyzoites were injected i.p. in 30 days-old rats. After 1, 2, 4, 8 and 24 h peritoneal exudate was withdrawn and infected phagocytic cells were prepared for electronic microscope studies. Toxoplasma organisms inside of rat macrophages showed remarkable lesions such as vacuolization and organisms were totally lysed inside of macrophages of more than 8 h infection rats. The results confirm at molecular level, the importance of rat macrophages in the natural adaptation of this rodent to T. gondii.

Animals↗

PubMed1971

Endothelial projections as revealed by scanning electron microscopy.

Scanning electron micrographs of the endothelium of the pulmonary artery reveal that the entire surface is covered by a meshwork of irregular projections which vastly increase the surface area. The size and density of the projections suggest that they may function to direct an eddying flow of plasma along the endothelial surface.

Animals↗

PubMed1981

The relation of keratinization to bacterial colonization on the baboon tongue as demonstrated by scanning electron microscopy.

Scanning electron microscopic observations of the baboon tongue demonstrating specificity of microbial distribution as related to epithelial keratinization are presented. The number of bacteria inhabiting a surface was related to the degree of keratinization. Orthokeratotic dorsal tongue surfaces were most heavily colonized by bacteria. The parakeratotic and non-keratinized surfaces were less heavily populated, with non-keratinized areas showing the fewest numbers of bacteria.

Animals↗

PubMed1992

Recent studies of surface dynamic processes by reflection electron microscopy.

Reflection electron microscope studies of surface dynamic processes are reviewed and illustrated with recent new observations. They include: surface electromigration and current dependent structures of Si surfaces; surface etching by oxidation of Si surface; and growth of two dimensional alloyed adsorbate by co-deposition of metals on Si surface. The observations revealed details of the surface dynamic processes, which are difficult to obtain with other surface analysis techniques.

Adsorption↗

PubMed1987

Overall morphology of basement membrane of rat seminiferous tubule as revealed by scanning electron microscopy.

Scanning electron microscopic observation of the basal surface of the basement membrane of the rat seminiferous tubule has revealed that the basement membrane appears to be like a tiled floor, and formation of meshwork structure of collagen fibrils is evident in some exfoliated areas of basement membrane. This meshwork structure is considered to ensure fluid regulation from the intertubular medium toward the lumen of the seminiferous tubules.

Animals↗

PubMedDate not supplied

Endothelial cell ischemic injury: protective effect of heparin or aspirin assessed by scanning electron microscopy.

Scanning electron microscopic observations of the luminal surface of the rabbit common carotid artery subjected to occlusion for 30 minutes or two hours revealed crater-like and balloon-like defects in the endothelial surface. The frequency of occurrence of these abnormalities was significantly decreased by pretreatment with heparin or aspirin in doses considered to have antiplatelet aggregating activity.

Animals↗

PubMed2001

Ribosomal dynamics explored by cryo-electron microscopy.

Cryo-electron microscopy has furnished direct evidence for conformational changes of the ribosome as it proceeds, in a cyclic manner, through different functional states. Strategies to explore the ribosome dynamics include trapping of particular functionally meaningful states by chemical, genetic, or physical means. The new atomic information obtained by X-ray crystallography should make it possible to track conformational changes observed by cryo-electron microscopy to changes of the underlying structural framework of the ribosome.

Cryoelectron Microscopy↗

PubMed2004

Viruses and the development of quantitative biological electron microscopy.

The electron microscope has become an important tool for determining the structure of biological materials of all kinds. Many technical advances in specimen preparation and in sophisticated methods of image analysis, initially based on optical systems but latterly on computer processing, have contributed to the development of the subject. Viruses of various kinds have often provided a convenient and appropriate test specimen. This paper describes the major technical advances and shows how viruses have had an important role in most of the developments.

Bacteriophage T4↗

PubMed1982

Double staining by vaporized osmium tetroxide-hydrazine hydrate of biological specimens for non-coated scanning electron microscopy.

Sufficient electron conductivity was obtained in biological specimens following double staining with vaporized osmium tetroxide and hydrazine hydrate for non-gold coated scanning electron microscopic observations. No charging was noted at 25 kV acceleration voltage in rat kidney, liver or other specimens. The foot processes of the glomerular podocytes and micropores of the glomerular endothelium as well as the intracellular endoplasmic reticulum of liver cells were particularly well visualized without the addition of evaporated metal. Repeating this vapor phase osmication method produced even higher contrast at high magnifications compared to the single vaporized osmication method.

Animals↗

PubMed1976

An investigation of the binding sites of proteins S8, L23 and L24 on the ribosomal RNAs of Escherichia coli by electron microscopy.

An electron microscopic method was used to investigate the binding regions of proteins S8 on 16S RNA, and proteins L23 and L24 on 23S RNA. Regions of the RNA that were not stabilised by the protein were completely denatured in 80% dimethyl-sulfoxide. The lengths of these denatured RNA regions were compared with that of the whole denatured RNA. Conclusions are drawn concerning the approximate location of the three proteins and these results are correlated with both RNA structural data and RNA sequence data on the RNA binding regions of the proteins.

Bacterial Proteins↗

PubMed1978

In vitro crosslinking of DNA by 8-methoxypsoralen visualized by electron microscopy.

By electron microscopic visualisation of totally denatured DNA, we have detected photochemically induced 8-methoxypsoralen crosslinks in vitro after irradiation at 360 nm. The amount of crosslinks was expressed as the percentage of DNA length which was kept in double-stranded appearance by closely situated crosslinks. This percentage correlated well with irradiation time, irradiation intensity, and the concentration of 8-methoxypsoralen. These parameters have also been correlated with the mean size and the size distribution of non-crosslinked regions of DNA, so called bubbles. For a comparison with another psoralen type, we have carried out a similar set of experiments using 4,5,8-trimethylpsoralen.

Coumarins↗

PubMed1992

[Synaptonemal complexes of human spermatocytes and foetal oocytes observed by electron microscopy].

The electron microscopical studies on the synaptonemal complexes (SC) of Chinese spermatocytes and foetal oocytes have been made and used to construct SC karyotype with a modified surface micro-spreading technique. We also confirm the SC formation between the short arms of the X chromosome and Y chromosome as well as secondary association between the distal tips of Xq and Yq at pachytene. Moreover, attentions are paid to the morphology of the XY pairs and five pairing type of XY pairs. In our preparations, a rare triploid spermatocyte was observed and triple pairing was described. Some possible significances of the triple pairing of triploid spermatocyte in relation to the human chromosomal abnormalities have been supposed.

Female↗

PubMed1999

Immunoglobulin structure and function as revealed by electron microscopy.

Electron-microscopic (EM) analysis preceded crystallographic analysis [1,2] of Igs by over a decade and was for a time the only direct way of analyzing their 3-D molecular structure. Once the X-ray structures were deduced, the role of EM gradually shifted from gross structural analysis to the addressing of more sophisticated structural and functional questions. EM remains a vital adjunct to the many physicochemical, biochemical, and serological tools brought to bear on these remarkable molecules as we try to relate form to function. In this review I will highlight some of the many contributions that have been made possible by virtue of being able to 'see' Ig molecules and immune complexes.

Animals↗

PubMed1986

Transmission and scanning electron microscopy of peripheral nerves.

Electron microscopy of peripheral nerve tissue by SEM and TEM facilitates a better understanding of the complex nerve architecture described by early light microscopists. Details of axonal morphology and the Schwann cell/myelin sheath complex in healthy and diseased nerves have been described in the literature. The techniques of tissue harvesting and processing and the observed appearance of peripheral nerves by electron microscopy should be useful to clinicians and researchers involved in peripheral nerve surgery and research.

Animals↗

PubMed1986

[Ultrastructure of the terminal vessels in squamous cell carcinoma of the human external ear. A transmission electron microscopy study].

Electron microscopic findings of vascular fine structure of the squamous cell carcinoma of the human auricle are reported. According to morphological criteria, the tissue was divided into three areas: non-infiltrated zone, transitional zone and centre of the tumor. In the non-infiltrated zone the vessels reveal the pattern of normal vessels of the skin. In the transitional zone endothelial cells bearing all signs of newly formed vessels can be detected as well as endothelial cells that show structural characteristics of severe cellular damage. In the tumour centre itself vessels are found with fenestrations and even true endothelial gaps. Interstitially located RBCs imitate the former outline of the vascular lumen. The observations are discussed and compared with the relevant literature.

Aged↗