Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Microtomy”

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 415 records · Page 23Linked to original sources
PubMed1993

Epstein-Barr virus and gastric cancer: data and unanswered questions.

Sixty-five unselected cases of gastric cancer have been analysed for EBV DNA by polymerase chain reaction, in situ hybridization and immunohistochemistry for CD21 antigen expression. Four cases were found EBV-positive by PCR, while ISH yielded positive results in 3 of these cases, demonstrating EBV in the nuclei of cancerous cells. CD21 antigen was expressed in cancerous cells in all 3 ISH-positive cases. All the EBV-positive cancers of the present series were poorly to moderately differentiated adenocarcinomas with prominent lymphoid infiltration. These results are discussed also on the basis of the literature.

Adenocarcinoma↗
PubMed1983

Immunocytochemical localization of the gap junction 26 K protein in mouse liver plasma membranes.

Specific binding sites for anti-26 K antibodies directed against the liver gap junction protein (26 K) were localized by immunoelectron microscopy in gap junction plaques purified from hepatic plasma membranes. Using immunofluorescence microscopy we found discrete fluorescent spots on plasma membranes in cross sections of liver tissues after incubation with anti-26 K antibodies. This is consistent with the notion of specific binding to gap junction plaques. Quantitative binding of anti-26 K antibodies was indirectly measured by the protein A-gold technique. We found that urea/detergent-treated, purified gap junction plaques bind 30-fold more anti-26 K antibodies than preimmune serum. Anti-26 K antibodies also bind specifically to native gap junction plaques within hepatic plasma membranes although only about one fifth as efficiently as to purified plaques. Possibly the anti-26 K antibodies raised after injection of SDS-denatured 26 K protein into rabbits recognize the cytoplasmic face of urea/detergent-treated plaques better than that of native plaques. Some, if not most, of the vesicular structures in preparations of purified plaques appear to be derived from split gap junction plaques and are probably sheets of gap junction hemichannels. In some vesicles the former cytoplasmic face of the hemichannels is turned outside, other vesicles have the former cell surface turned outside. The anti-26 K antibodies do not recognize any 26 K protein on the sheets of partially split gap junction plaques, on the heterogeneous vesicular structures, or on non-junctional areas of hepatic plasma membranes. These results suggest that the conformation of the 26 K protein in plaques must be different from that of the 26 K protein in earlier biosynthetic steps of plaque assembly.

Animals↗
PubMed1994

Targeted expression of a dominant negative FGF receptor blocks branching morphogenesis and epithelial differentiation of the mouse lung.

Mouse lung development begins when two lung buds sprout from the epithelium of the embryonic gut. Patterning of the airways is then accomplished by the outgrowth and repetitive branching of the two lung buds, a process called branching morphogenesis. One of the four fibroblast growth factor (FGF) receptor genes, FGFR2, is expressed in the epithelium of a number of embryonic organs including the lung buds. To block the function of FGFR2 during branching morphogenesis of the lung without affecting its function in other embryonic tissues, the human surfactant protein C promoter was used to target expression of a dominant negative FGFR2 exclusively to lung bud epithelium in transgenic mice. Newborn mice expressing the transgene were completely normal except that instead of normally developed lungs they had two undifferentiated epithelial tubes that extended from the bifurcation of the trachea down to the diaphragm, a defect that resulted in perinatal death. Thus, the dominant negative FGF receptor completely blocked airway branching and epithelial differentiation, without prohibiting outgrowth, establishing a specific role for FGFs in branching morphogenesis of the mammalian lung.

Animals↗
PubMed1980

Haversian osteons: longitudinal variation of internal structure.

Previous studies have suggested that one general type of osteon exists, rather than the three types previously classified as light, intermediate, and dark. A method is presented that permits rapid, quantitative measurement of the percent transmission of osteons seen in thin section between crossed polarizers. In studies of osteon segments from human cortical bone, cut either 200 or 5 micrometers in length, a continuous variation of transmission is seen, both for the populations as a whole and for serial sections. These variations cannot be ascribed to angulation between the direction of observation and the axis of the osteonal segment. No correlation can be observed between the angle of the segment axis and the percent transmission. It is suggested that the collagen fiber orientation in osteonal segments must be considered to be continuous, as judged by scattering of polarized light.

Collagen↗
PubMed2003

Atomic force microscopy and nanoindentation characterization of human lamellar bone prepared by microtome sectioning and mechanical polishing technique.

Surface topography, microstructure, and micromechanical properties of human lamellar bone were characterized by atomic force microscopy and nanoindentation. The lamellar bone surfaces were prepared by two different methods: microtome sectioning and mechanical polishing. The lamellar bone surfaces prepared by mechanical polishing revealed that thin lamellae formed depressions approximately 200 nm deep, whereas the surfaces prepared by microtome sectioning were flat. Atomic force microscopy surface topographic images at higher magnification showed differences between thick and thin lamellae in polished samples, but these differences were less pronounced in microtomed samples. Roughness measurements confirmed that there was a significant difference between thick (21.0 nm) and thin lamellae (8.3 nm) in polished samples (p < 0.001). The difference in surface roughness between thick (13.9 nm) and thin lamellae (12.7 nm) in microtomed sample was statistically insignificant (p = 0.74). Higher elastic modulus values were observed for thick lamella in microtomed samples compared with that of thin lamellae, whereas measured elastic modulus differences between thick and thin lamellae in polished samples were found to be statistically insignificant.

Biomechanical Phenomena↗
PubMed1986

The solid, calcium-phosphate mineral phases in embryonic chick bone characterized by high-voltage electron diffraction.

The solid mineral phases of calcium-phosphate (Ca-P) in the long bones from embryonic chicks between the ages of 9 and 13 days have been examined by high voltage (1.0 MV) electron microscopy and electron microdiffraction. The study was undertaken to identify the chemical and crystallographic nature of the inorganic mineral phase(s) prepared under conditions which significantly reduce artifacts of specimen preparation and microscopic examination of the tissues. Electron microdiffraction patterns of solid mineral phase particles in the osteoid matrices of the subperiosteal region of tibiae were principally those of poorly crystalline hydroxyapatite. In rare instances (less than 1% of the estimated volume of the mineral phase present in the zone of early mineralization), relatively large single crystals were observed within clusters of hydroxyapatite. From calculations of both interplanar spacings and measurements of angular displacement of diffraction reflections from single crystal microdiffraction patterns, two distinct phases other than hydroxyapatite were identified: brushite and beta-tricalcium phosphate. A third phase, resembling an apatite, remains unidentified. The results suggest that very small amounts of nonapatitic phases of Ca-P exist in chicken bone tissue. No temporal relationship could be established between the nonapatitic and apatitic phases. There is at present no evidence from this study to support the concept that nonapatitic phases are precursors of a final apatitic phase in bone.

Animals↗
PubMed1996

Dual-energy X-ray absorptiometry for histologic bone sections.

In fundamental osteoporosis research precise and accurate assessment of the mineral quantity in histological bone sections is of particular importance when studying the local effects of implants releasing bone modulating agents. A potentially useful technique to estimate the bone mineral density (BMD) is dual-energy X-ray absorptiometry (DXA). A highly collimated (0.13 mm) Hologic 2000 with a line spacing and point resolution of 0.13 mm was used. The mineral content was measured in regions of 3.1 mm(2). A ceramic hydroxyapatite (CHA) phantom was developed as a reference standard. The phantom was made of a single-phase hydroxyapatite starting powder by compressing and sintering at 1000 degrees Celsius. The true density was 3.14 + or - 0.001 g/cm(3). The calcium/phosphorus ratio was close to the theoretical one of 1.67. The mean precision error expressed as the coefficient of variation (CV) of the mineral density (MD) measurements of the phantoms with thicknesses of 1, 2, and 3 mm was 0.2%. Embedded undecalcified alveolar bone sections of dogs (0.0015-1 mm in thickness) were scanned simultaneously with a phantom 1 mm in thickness. The precision error (CV) of the BMD measurements calculated by DXA for sections > or = 0.1 mm and with a BMD > or = 0.14 g/cm(2) was 0.81%. There was a linear relationship between the BMD calculated by DXA and the estimated BMD in the histological bone sections by means of the true density of the phantom. It is concluded that DXA using a standard CHA phantom is a precise and accurate method to measure MD changes as small as 1% in histological bone areas of 3.1 mm(2) provided that the loss or gain in BMD is > or = 0.14 g/cm(2).

Absorptiometry, Photon↗
PubMed1992

A new monoclonal antibody for detection of EGF-receptors in western blots and paraffin-embedded tissue sections.

The prognostic significance of the epidermal growth factor receptor status (EGF-R-status) for certain human tumors requires the development of antibodies useful for clinical application. We used purified receptor preparations to generate monoclonal antibodies immunoreactive with the EGF-R purified from placenta membranes and A431 tumors. Four of the hybridomas contained antibodies (R2, R3, R5, and R9) which recognized both antigens. Antibody R3 was shown to display the following properties: it binds with a KD value of about 10(-9)-10(-10) M to the receptor, a half maximal inhibition of EGF-binding is achieved at 5 x 10(-8) M, and in Western blots of cell membranes R3 specifically detects the EGF-R at 0.1 micrograms/ml. R3 inhibits EGF-dependent clonogenic growth of NRK cells and completely blocks EGF stimulated autophosphorylation of the receptor. Moreover, R3 also detects EGF-R in paraffin-embedded tissue sections taken from human salivary gland, term placenta, and adult skin and mammary carcinomas. Thus, R3 can be used in retrospective diagnostic clinical studies and might help to develop new immunotherapeutic intervention.

Animals↗
PubMed1995

Criteria for consistent and high sensitivity of DNA in situ hybridization on paraffin sections: optimal proteolytic enzyme digestion.

It is technically challenging for the detection of target DNA in low abundancy, such as viral DNA sequences in latently infected cells by nonisotopic in situ hybridization (ISH). Consistent result is even more difficult to achieve on routine paraffin sections. Proteolytic enzyme digestion is most critical for both consistency and sensitivity of the technique. We here have investigated the effect of enzyme digestion on cell morphology, protein and DNA reduction, and hybridization efficiency. The results demonstrated that enzyme digestion improves efficiency of ISH through a process involving partial DNA purification on sections. There is a clear relationship between proteolytic enzyme digestion, morphology changes, and hybridization efficiency. Although detection of DNA sequences in abundance can be achieved within a relatively wide range of digestion levels, maximum hybridization efficiency was always related to the cells, which showed morphology of nuclear swollen, weak homogeneous chromatin staining with hematoxylin and loss of visible nuclear membrane. Detection of viral DNA in low copy number critically depends on the creation of the morphologic changes by enzyme digestion. The morphological changes would therefore serve as important criteria for optimal digestion, result interpretation, and comparison.

Anal Canal↗
PubMed1982

Intracellular localization of certain membrane glycoproteins in mouse T-lymphoma cells using immunoferritin staining of ultrathin frozen sections.

Comparative studies on the cellular morphology of culturd mouse T-lymphoma cells (with particular emphasis on organelles and membrane-associated materials) were conducted using both frozen thin sections and epon thin sections. Due to the fact that the frozen thin sectioning technique allows antigenicity to be retained and also permits good accessibility of the external macromolecular reagents to the interior of the cell, we have been able to explore the intracellular localization of some membrane glycoproteins such as Con A-binding sites and viral membrane glycoprotein, gp 69/71. Our data indicate that most of the membranous cellular structures (e.g., rough endoplasmic reticulum, vesicles, Golgi and nuclear envelope) contain the Con A-specific sugars, mannose, and glucose. In addition, we have found that intracellular gp 69/71 molecules exist in an aggregated form at the terminal region of cisternae of rough endoplasmic reticulum and in vesicles of two size ranges (0.1 to 0.15 microns and 0.3 to 0.4 microns) as well as in the cytoplasm close to the plasma membrane. These findings have not only confirmed some of the previous biochemical data but have also provided new information concerning the biochemical nature of intracellular membrane components and the possible biosynthetic fate of membrane precursor molecules.

Animals↗
PubMed2002

Method for preparing thin sections of untreated equine hoof horn for electron microscopic examination.

The preparation of hard tissues such as the equine hoof horn for electron microscopic examination is very difficult. In particular the penetration of fixatives and chemicals used during fixation and embedding is a problem. The objective of this study was to find and implement an alternative method enabling the preparation of high-quality thin sections of hoof horn and other hard tissue, which maintains the hard tissue ultrastructure and can be used for immuno-labeling. Compared to commonly used fixation and embedding techniques, the preparation of thin sections from untreated material method saves time and material and provides equivalent ultrastructural information. Furthermore, thin sections from untreated material are significantly larger and more homogeneous, more resistant to the electron ray, as well as more suitable for sectioning. The electron microscopical pictures obtained allow a comparison to previous test results achieved with fixed and embedded material. Using the preparation of thin sections from untreated material method, fixation and embedding artifacts are avoided, providing a clearer interpretation of the electron microscopical findings. Considerable advantages are achieved by using immunohistochemical techniques with untreated horn specimens because fixation invariably decreases antigenicity.

Animals↗
PubMed2002

Increasing membrane contrast by means of imidazole-osmium post-fixation as exemplified by skeletal muscle fiber.

Until now, the interpretation of findings derived from investigations on membrane structures (T tubules, sarcoplasmic reticulum, the Golgi apparatus) in thick sections of mammalian muscle tissue has been limited in TEM due to the lack of sharp resolution of the membrane contours. This article shows how the imidazol-osmium post-fixation of tissue blocks can be used to achieve well-contrasted, sharply defined membrane contours. Therefore, unstained sections from imidazol-osmium post-fixed tissue can be examined immediately. But protein structures (e.g., ribosomes) remain uncontrasted with this technique. If needed, it is possible to visualize the protein structures by conventional section staining with uranyl acetate and lead citrate. This method is suitable for both ultrathin and thick sections (>150 nm).

Animals↗
PubMed1987

New cryoultramicrotome with a feedback-advance system.

Cryoultramicrotomy is gaining in significance and use as technical improvements are made. In comparison with epoxy resin procedures, cryopreparations are more rapid; there is only a negligible loss of material and thus antigenicity is well preserved. The present work contains some newly developed details for the exact determination of the advancement of the sample in the direction of the knife in a microtome. It is a software-controlled ultramicrotome advance drive system with feedback regulation as well as repeatedly patented devices for advancement sensors.

Cold Temperature↗
PubMed1988

EELS log-ratio technique for specimen-thickness measurement in the TEM.

We discuss measurement of the local thickness t of a transmission microscope specimen from the log-ratio formula t = lambda ln (It/I0) where It and I0 are the total and zero-loss areas under the electron-energy loss spectrum. We have measured the total inelastic mean free path lambda in 11 materials of varying atomic number Z and have parameterized the results in the form lambda = 106F (E0/Em)/ln (2 beta E0/Em) where F = (1 + E0/1,022)/(1 + E0/511)2, the incident energy E0 is in keV, the spectrum collection semiangle beta is in mrad, and Em = 7.6Z0.36. This formulation should allow absolute thickness to be determined to an accuracy of +/- 20% in most inorganic specimens.

Mathematics↗
PubMed1988

A study of section wrinkling on single-hole coated grids using TEM and SEM.

To prevent section wrinkles usually encountered with the use of coated single-hole grids, a simple method was developed. Formvar film resting on a platform with holes (3.5 mm diameter) was heated with a slide warmer (60-65 degrees C). The bottom of a glass petri dish was inverted over the platform to keep the ambient air at the desired temperature. Sections were picked up from the boat of the diamond knife with a single-hole grid and deposited at the orifice of the platform and allowed to dry. The grids were then carefully pushed through the orifice of the platform with the blunt head of a nail (3 mm diameter).

Animals↗