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At least 1,171 records · Page 65Linked to original sources
PubMed1991

Three-dimensional structure of myosin subfragment-1 from electron microscopy of sectioned crystals.

Image analysis of electron micrographs of thin-sectioned myosin subfragment-1 (S1) crystals has been used to determine the structure of the myosin head at approximately 25-A resolution. Previous work established that the unit cell of type I crystals of myosin S1 contains eight molecules arranged with orthorhombic space group symmetry P212121 and provided preliminary information on the size and shape of the myosin head (Winkelmann, D. A., H. Mekeel, and I. Rayment. 1985. J. Mol. Biol. 181:487-501). We have applied a systematic method of data collection by electron microscopy to reconstruct the three-dimensional (3D) structure of the S1 crystal lattice. Electron micrographs of thin sections were recorded at angles of up to 50 degrees by tilting the sections about the two orthogonal unit cell axes in sections cut perpendicular to the three major crystallographic axes. The data from six separate tilt series were merged to form a complete data set for 3D reconstruction. This approach has yielded an electron density map of the unit cell of the S1 crystals of sufficient detail. to delineate the molecular envelope of the myosin head. Myosin S1 has a tadpole-shaped molecular envelope that is very similar in appearance to the pear-shaped myosin heads observed by electron microscopy of rotary-shadowed and negatively stained myosin. The molecule is divided into essentially three morphological domains: a large domain on one end of the molecule corresponding to approximately 60% of the total molecular volume, a smaller central domain of approximately 30% of the volume that is separated from the larger domain by a cleft on one side of the molecule, and the smallest domain corresponding to a thin tail-like region containing approximately 10% of the volume. This molecular organization supports models of force generation by myosin which invoke conformational mobility at interdomain junctions within the head.

Actomyosin↗
PubMed1984

Scanning and transmission electron microscopy of normal chicken tracheal epithelia.

The ultrastructure of normal chicken tracheal epithelia was studied by scanning and transmission electron microscopy. Scanning electron microscopy revealed only two cell types on the surface of the tracheal epithelium; ciliated and nonciliated with microvilli. Three cell types were observed with the transmission electron microscope: ciliated, goblet, and basal cells. The ciliated cells were the most numerous.

Animals↗
PubMed1980

Morphological changes of mouse spermatozoa in uterus as revealed by scanning and transmission electron microscopy.

Submicroscopic alterations occurring in mouse spermatozoa during their sojourn into the female reproductive tract--as revealed by Scanning Electron Microscopy and Transmission Electron Microscopy using ruthenium red as marked for glycosaminoglycans--are described in the present investigation. The results show that the surface of the plasma membrane covering the acrosomal region of the spermatozoa found in the uterus--at different intervals of time after copulation (between 10 minutes up to 20 hrs)--are provided with an increasing number of granules and small vesicles. Some of the surface structures appear gradually leading to perforation of discrete areas of plasma membrane in regions corresponding to acrosomal areas covering the head of spermatozoa. Similarly ruthenium red preparations, show a significant decrease of glycosaminoglycans and their sialic acid moieties, which specifically precede further vesiculation and perforation of the sperm plasma membrane covering the same acrosomal regions.

Acrosome↗
PubMed1980

[Synovial vascularization and inflammation. I. Morphologic study using light and electron microscopy].

The authors studied using light and electron microscopy, 40 cases of sub-acute inflammatory synovitis (including 24 cases of rheumatoid synovitis) and 10 normal synovia. In light microscopy, the study dealt with images of capillary congestion, endothelial hyperplasis and capillary obliterations. In electron microscopy the morphology of the capillaries, the images of plasmic exsudation, images of extravascular cell migration and vascular obliteration by the endothelial cells, were studied in comparison with the inflammatory synovitis and the normal synovia. Inflammatory synovitis are characterized by the frequency of extracapillary cell migrations without there being any other pathological change of the microvessels that can be attributed to inflammation.

Capillaries↗
PubMed1975

High resolution scanning electron microscopy at the subcellular level.

Recently developed scanning electron microscopes provide sufficient resolution to allow useful observation of subcellular biological objects. Preparation methods for such objects need not be limited to the traditional coating and mounting procedures. Many methods developed for transmission electron microscopy are immediately adaptable to scanning electron microscopy. We show that a number of techniques are available to the microscopist which yield adequate contrast and high resolution. As examples we show skeletal muscle myofibrils dispersed to reveal thick filaments, uncoated on a thin carbon film; a tropomyosin tactoid, negatively stained with uranyl acetate; oncornavirus, conventionally coated; and T4 bacteriophage on an aluminium substrate.

Animals↗
PubMed1983

Value of electron microscopy in cytologic diagnosis of fine-needle biopsy.

Fine-needle biopsy in 14 consecutive patients with suspected malignancies were evaluated by routine cytology and electron microscopy. A protocol is described in which material from fine-needle biopsy can be held in glutaraldehyde and later processed for electron microscopy if necessary. Adequate tissue for electron microscopy was obtained in 12 of 14 cases. Specific classification of the tumor cells in these cases was achieved through electron microscopy. In six cases electron microscopy provided a more certain diagnosis than cytology alone. In two cases electron microscopy had significant impact on diagnosis and clinical management. The opportunity to examine tissues with electron microscopy increased the utility and specificity of the fine-needle technique without adding to patient discomfort or the cost of a second procedure.

Abdominal Neoplasms↗
PubMed1981

Rapid detection of viruses in biopsy or autopsy specimens by the pseudoreplica method of electron microscopy.

A rapid pseudoreplica method of electron microscopy (EM) was used to detect viruses in brain tissues obtained from 57 patients suspected of having herpes simplex encephalitis (HSE). Herpesvirus particles were demonstrated in 18 of the 20 (90%) specimens from which herpes simplex virus was isolated in tissue culture. The procedure takes less than 2 hours, as compared to the time (greater than or equal to 2 days) usually required for virus isolation or standard thin-section electron microscopy. Although the immunofluorescence test has comparable rapidity, it was found to be less sensitive and to yield occasionally false-positive reactions. Our findings indicate that, until a brain biopsy can be replaced by less invasive procedures, examination of brain tissue by the pseudoreplica method offers a rapid diagnosis of a herpesvirus encephalitis. Furthermore, the demonstration of viruses in brain, lung and liver specimens obtained by biopsy or at autopsy suggests that this electron-microscopic method would be advantageous for detecting viruses in tissue samples, particularly in the case of viruses which may not be readily demonstrable by conventional methods.

Adult↗
PubMed1964

CORRECTION OF POLYRIBOSOME DISTRIBUTIONS AS OBSERVED IN CELL SECTIONS BY ELECTRON MICROSCOPY.

Clusters of ribosomes observed by electron microscopy in thin sections of rabbit reticulocytes are of the same order of size as the section thickness of 600 A. Many of the observed clusters must therefore have been transected by the section surfaces and observed as clusters containing fewer ribosomes. A probability method of correcting for this effect is given. Comparison of the results with grid observations of ribosome distributions indicates sufficiently good agreement for application to cell section observations.

Animals↗
PubMed2006

The comparative roles of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumours.

Electron microscopy has contributed to the diagnosis of soft tissue tumours for four decades, and immunohistochemistry for two. Because of its relative ease of use and interpretation, the latter technique has become extensively and routinely applied to identify lines of differentiation in benign soft tissue tumours and in sarcomas. The use of electron microscopy has declined but retains a role because few antibodies are wholly specific or fully sensitive, some tumours are polyphenotypic or divergent in differentiation, and others have no specific antigens. Immunohistochemistry is superior in diagnosis of smooth muscle tumours, small round cell tumours, sarcomas with epithelioid morphology, and most synovial sarcomas. Electron microscopy is of particular value for peripheral nerve sheath tumours, marker-negative synovial sarcomas, pleomorphic sarcomas and mesotheliomas. As with all adjunctive techniques, immunohistochemistry and electron microscopy should be used in a complementary fashion according to the nature of the diagnostic problem.

Diagnosis, Differential↗
PubMed1977

The sporulation process in Thermomonospora fusca as revealed by scanning and transmission electron microscopy.

The sporulation process in the thermophilic actinomycete Thermomonospora fusca was observed by scanning and transmission electron microscopy. As shown by scanning electron microscopy, spores were produced primarily on aerial hyphae and first appeared as bud-like enlargements at the tips of short multibranched sporophores. Young spores were oval to spherical in shape with a smooth surface. As they matured spores enlarged and developed a rough and globular covering, which was quite fragile and easily detached from the spore. This outer layer, as observed by transmission electron microscopy, was thought equivalent to the sheath of other Thermomonospora species. In cross section, mature spores exhibited a thick spore coat underneath the outer globular layer. This spore coat was usually observed as a single layer, but some spores produced a bilayered coat. No multilayered spore coat or spore cortex was observed in the heat-sensitive spores of T. fusca. They were, therefore, shown to be aleuriospores (microcondia), and not endospores.

Cell Wall↗
PubMed1988

Critical underfocus in low-magnification electron microscopy: rationale and practice.

Focus in transmission electron microscopy, especially at low-to-moderate powers, is usually achieved by an empirical, though largely hap-hazard, process of defocusing the objective below what is known to be perfect focus as defined by the absence of Fresnel diffraction fringes at the edges of holes. In this article we provide a precise, empirical method of focus, whose rationale resides in the less-than-perfect image transfer from the image space of the objective to the negative, i.e., the modulation transfer function. In practice, "perfect focus," as defined above, is established with a beam deflector ("wobbler"), to which underfocus is then applied routinely by reference to a table. Such "critical underfocus" values have to be calibrated, as described here, for each microscope and depend on all factors that influence contrast, that is, accelerating voltage, condenser defocus and coherence of illumination, focal length of the objective, aperture sizes, combination of intermediate and projection lenses, and the properties of the photographic emulsion.

Emulsions↗