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At least 379 records · Page 21Linked to original sources
PubMed1981

Topographic examination of sister chromatid differential staining by Nomarski interference microscopy and scanning electron microscopy.

BrdU-substituted Chinese hamster chromosomes were treated with a hog Na2HPO4 solution and stained with Giemsa to produce sister chromatid differential staining (SCD). The process of SCD was examined with the Nomarski differential interference microscope and the scanning electron microscope. After the Na2HPO4 treatment alone, unifilarly BrdU-substituted (TB) chromatids appeared somewhat more severely collapsed than the bifilarly substituted (BB) chromatids. Subsequent Giemsa staining, however, brought about pronounced piling up of the Giemsa dye on the TB-chromatids but not on the BB-ones, causing highly distinct differential Giemsa staining as well as a marked differentiation in surface topography between the sister chromatids. Removal of the Giemsa dye from the differentially Giemsa stained chromosomes resulted in a disappearance of such a pronounced topographic differentiation.

Animals↗
PubMed1983

The mineral content of human enamel studied by polarizing microscopy, microradiography and scanning electron microscopy.

The total observed birefringence and mineral content of the outer 300 micron of longitudinal sections of sound buccal premolar enamel were measured and three-dimensional contour maps were made. Using similar contour maps of calcium, carbonate and magnesium content from the literature, it seemed possible to explain the differences between the contour maps of total observed birefringence and mineral content. Scanning electron micrographs provided information about the orientation of the prisms. The cervical part of the enamel had a high intrinsic birefringence which may explain the difference between mineral content and total observed birefringence. This high intrinsic birefringence may be caused by a high carbonate content in cervical enamel.

Bicuspid↗
PubMed1980

Light microscopy, scanning electron microscopy, and microprobe analysis of bone response to zinc and nonzinc amalgam implants.

Freshly mixed, unset zinc-free and zinc-containing analgam was implanted in the right tibia of 32 rats. Half of the specimens were examined by the light microscope and the other half by the scanning electron microscope and x-ray microprobe analysis. It was found that amalgam is well tolerated by the rat osseous tissue, and there were no histologic reaction differences between zinc and zinc free amalgam. The surfaces of the implants were covered by an organic film at 3 weeks and with bone at later intervals. Very little corrosion products containing sulfur were observed on the amalgam surface at all intervals. Bone adjacent to the amalgam contained tin and sulfur irrespective of the presence of zinc in the alloy, indicating outward migration of specific components of the alloy.

Animals↗
PubMed1994

Atomic force microscopy and scanning tunnelling microscopy: refining techniques for studying biomolecules.

The scanning tunnelling microscope and the atomic force microscope offer the prospect of real-time, nanometre-scale imaging of biomolecules and biosurfaces under physiological environments. Much effort is therefore being made to establish these techniques as routine biophysical tools. The considerable recent progress that has been made in biotechnological applications is reviewed, highlighting specific examples of the applications of this new and exciting method of analysis.

Biological Products↗
PubMed1992

Scanning force microscopy and cryo-electron microscopy of tobacco mosaic virus as a test specimen.

In this study, tobacco mosaic virus (TMV) provides a resolution criterion for specimen preparation methods as well as for imaging parameters of the scanning force microscope (SFM). We present scanning force microscopic images of the virus embedded in 0.5% buffered phosphotungstic acid solution adsorbed on a freshly cleaved mica surface, and imaged under atmospheric conditions. Individual TMV particles were clearly identified with a characteristic shape of long rods of about 300 nm long and 60-70 nm in apparent width due to the geometric parameters of the tip. The structure of the virus was compared with cryo-electron microscopic data of vitrified suspensions observed to a resolution of 1.15 nm. Uncoated TMV particles were also deposited on evaporated titanium thin films and imaged by SFM.

Cryopreservation↗
PubMed2004

Purification of the recombinant hepatitis B virus core antigen (rHBcAg) produced in the yeast Saccharomyces cerevisiae and comparative observation of its particles by transmission electron microscopy (TEM) and atomic force microscopy (AFM).

Hepatitis B virus core antigen (HBcAg) gene (C gene) was expressed in Saccharomyces cerevisiae and the products (rHBcAg or core particles) were purified from a crude lysate of the yeast by three steps: Sephrose CL-4B chromatography, Sucrose step-gradient ultracentrifugation and CsCl-isopycnic ultracentrifugation. It has been observed that HBcAg was synthesized in yeast cells as a particle consisting of polypeptides with a molecular weight of 21.5 kDa (p21.5). Results of ELISA test and density analysis of CsCl-isopycnic ultracentrifugation indicated that the purified products (rHBcAg particles) with HBcAg antigenicity mainly located at the densities of 1.27 and 1.40 g ml(-1), respectively. Observation and analysis of the purified rHBcAg products by TEM indicated that rHBcAg peptides could mainly self-assemble into two size classes of core particles. The larger particles were approximately 30.1 nm and the smaller were approximately 21.5 nm in mean diameter. Further observation and analysis of the same rHBcAg (core) particles by AFM also indicated that rHBcAg (core) particles were similar to the native HBcAg (core) particles from infected human hepatocytes and mainly composed of two size classes of partides core. The larger particles were approximately 31.3 nm and the smaller were approximately 22.5 nm in mean diameter which was similar to the results obtained by TEM. All results from both TEM and AFM suggested that core particles (capsids) produced in S. cerevisiae possessed dimorphism.

Genes, Viral↗
PubMed1999

Reflection interference contrast microscopy combined with scanning force microscopy verifies the nature of protein-ligand interaction force measurements.

The integration of a stand-alone scanning force microscope (SFM) scanner with a reflection interference contrast microscope (RICM) makes it possible to measure directly the separation distance between the SFM probe and the sample surface. The SFM-RICM combination, when applied to the force measurements between ligand-derivatized SFM probe and a protein receptor-derivatized surface, showed that the anomalous force discontinuities often observed for such interacting pairs were indeed a real behavior characteristic of a particular experimental configuration. Apart from small discrepancies due to transient damping, commercially available cantilevers did behave in an ideal mechanical fashion, thus indicating that protein-ligand unbinding events were occurring at distances much larger than their maximum extended length. This external verification of separation distance requires a closer examination of the physical events occurring upon detachment of the surfaces. An alternative interpretation of such force measurements is proposed here in which the protein and/or ligand immobilization chemistry is called into question.

Biophysical Phenomena↗
PubMed1993

Intestinal lesions in experimental phocine distemper: light microscopy, immunohistochemistry and electron microscopy.

The involvement of the intestinal mucosa and of the gut-associated lymphoid tissue in phocine distemper was studied in six severely diseased harbour seals 11 to 16 days after experimental infection. Five seals exhibited a mild or moderate enteritis in the small or large intestine. In all the seals, a moderate to severe depletion of submucosal lymphoid follicles was found. Likewise, antigen of phocine distemper virus (PDV) was demonstrated immunohistochemically in the intestinal wall of all the seals. Most antigen was found in the submucosal lymphoid follicles, followed by the crypt epithelium and follicle-associated epithelium (FAE). Ultrastructurally, intracytoplasmic tubular structures were detected in the FAE and interpreted as morbilliviral nucleocapsids. The results indicate a direct cytopathogenic effect of PDV on intestinal lymphoid and epithelial cells and suggest an important role of the intestinal tract in phocine distemper and, by analogy, in other morbillivirus infections as a regular site of virus replication, virus shedding and immunosuppression.

Animals↗