bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of some mechanical properties of embedding resins with their behaviour in microtomy
Authors: Acetarin Jean‐Dominique , Carlemalm Eric , Kellenberger Eduard , Villiger Werner 
Published: February 2005

AbstractThe technology of ultramicrotomy is now well established, but the properties of the resin that determine the different forces needed to generate a section have been neglected, although this process could introduce artefacts in the thin sections. We have investigated the principal resin dependent factors involved in the sectioning process and determined the related mechanical properties. Tensile experiments have given the best correlation with the sectioning quality of the resin: the elastic (Young's) modulus value (depending on polymer structure or hardening mode), the presence of a short plastic flow for a controlled fracture and enough flexibility to minimize shearing, and internal cracks, appear to be the main characteristic parameters. The ultrathin section seems to be generated by a process close to cleavage, favoured by the relative hardness of the embedding media, while machining and “true” sectioning requires softer resins.Consequently, the rupture follows the path of least resistance in the specimen‐resin composite, providing sections with a surface relief. Embedded biological material copolymerizes with polycondensed matrix (epoxy resins), and, by reducing the heterogeneity, gives smoother sections. Embedments hardened by radical polymerization provide a rougher relief, since almost no copolymerization occurs, offering to the microtome a heterogeneous block with two constituents of very different mechanical properties. The surface relief seems to be an important factor in labelling, staining, and imaging, and more attention has to be paid for some improvements of the quality of the information provided by electron microscopy.
The study of 3‐dimensional structure at the node of ranvier and specimen contrast enhancement techniques
Authors: Ellisman Mark H. , Deerinck Thomas J. , Anderson Karen L. 
Published: February 2005

AbstractIn determining what to write about for this volume to honor Keith Porter, we thought about our projects and considered which ones Keith had either stimulated or otherwise influenced with his technological wizardry or intuition about cell structure and function. Perhaps, not surprisingly, we found something of Keith in everything we are working on. We therefore chose a topic that we presently are very interested in, and that we hope he will enjoy reading about and following in the years to come.
Dynamic aspects of the interaction between microtubules and actin filaments
Authors: Euteneuer Ursula , Cooper Mark C. , Pryzwansky Katherine B. , Schliwa Manfred 
Published: February 2005

AbstractThis paper summarizes observations on the motility and behavior of microtubule asters in polymorphonuclear leukocytes under a variety of experimental conditions. These observations suggest that the location and organization of microtubules is influenced, at least in part, by the activity of the cortical actin network. Aster motility may therefore serve as an indicator of the interaction between the centrosomal microtubules and the cell cortex, and it is speculated that this interaction is of importance for leukocyte translocation.
Three‐dimensional reconstructions from serial micrographs using the IBM PC
Authors: Young Stephen J. , Royer Suzanne M. , Groves Philip M. , Kinnamon John C. 
Published: February 2005

AbstractWe have prepared software for producing three‐dimensional reconstructions from serial micrographs using an IBM PC or compatible. The software can be configured for a variety of graphics board and digitizing tablet combinations.Data is entered into the program by digitizing contours directly from micrographs. The program can handle up to 2,000 contours per data file, of up to 255 object types. Morphometric information such as line length, perimeter, and area are generated for each contour. The reconstruction program aligns the plane information from each section and displays the final reconstruction on a high resolution (640 × 400 pixels) color monitor. Object types can be differentiated by line width, line color, and fill color. Hidden line processing and conditional fill routines make it possible to produce reconstructions with either a solid or semi‐transparent appearance. Reconstructions can be generated quite rapidly from any viewing angle in the X, Y, and Z axes. The program has proven valuable for the elucidation of the three‐dimensional nature of biological structures.
Immunolocalization of Alpha‐Actinin in Adult Chicken Skeletal Muscles
Authors: Zimmer Danna B. , Goldstein Margaret A. 
Published: February 2005

AbstractImmunoelectron microscopy techniques were used to localize alpha‐actinin within the Z lattice of adult skeletal muscles. Analysis of electron micrographs by direct visualization demonstrated that anti‐alpha‐actinin Fab fragments bound throughout the Z lattice. A low‐resolution scanning densitometry technique was developed to quantitate the visual increase in the density of the Z lattice. These techniques did not allow determination of the particular component of the Z lattice, amorphous matrix, axial filaments, or cross‐connecting filaments with which the antibody was associated. Therefore, additional techniques, including direct measurement of filament diameters and optical diffraction, were utilized in determining which components of the Z lattice bound anti‐alpha‐actinin Fab fragments. These analyses suggest that the antibody binding is distributed evenly throughout the lattice, along the filaments, and between them and is confined to the region of double overlap of the ends of the thin filaments.
Preparation of neural tissues and sensory structures for electron microscopy
Authors: Song Jindan 
Published: February 2005

AbstractThis paper describes the preparation of specimens of neural tissues and sensory structures for electron microscopy. A solution of 2% paraformaldehyde and 2.5% glutaraldehyde was used as fixative. The fixative entered the spinal cord of the rhesus monkey through the aorta abdominalis and emptied into the internal ear of the guinea pig via the arteria vertebralis by the vascular perfusion method. After perfusion, the spinal cord and internal ear were removed from the columna vertebralis and temporal bone, respectively. The tissues were postfixed in 1% OsO4. If a desired direction of the section was required, directional embedding was applied. The application of vascular perfusion fixation, excising tissues on orientation, and embedding specimens in a certain direction makes it possible to obtain the desired tissue section and intact cellular ultrastucture.
Ultrastructural study of the morphogenesis of herpes simplex virus type 2 in organ cultured human uterine cervix and the interactions between virus and host cell
Authors: Lee Kun , Bao Jiaju , Wang Jiedong , Zhao Weiming , Liu Shide , Si Jingyi , Wang Yanyun , Zhang Wei , Jiang Jingwu 
Published: February 2005

AbstractTo determine the pathogenesis of herpes cervicitis and the relationship between herpes simplex virus type 2 (HSV‐2) and the carcinogenesis of human uterine cervix, the ultrastructural changes of 15 cases of long‐term organ cultures of human uterine cervix infected with HSV‐2 were studied. In order to demonstrate the morphogenesis of the virus and the interactions between virus and host cells, EM autoradiography was performed. After viral inoculation, the course of viral DNA replication, and the processes of maturation of virus were examined. Pathological alterations of infected nuclei‐including two kinds of granular matrix aggregations, proliferative changes in nuclei and nuclear envelope, multi‐lobular nucleated giant cell formation, intranuclear microtubules, and some evidence of replication of HSV‐2 in cytoplasm‐were observed. Because of the similarity of the pathologic alterations and the course and duration of infection in the clinic cases and our experimental subjects, this system appears to be a good model to investigate the pathogenesis of herpes cervicitis and the relationship between human cervical cancer and HSV‐2, other viruses, or other co‐carcinogens.
Effect of antibodies against gap junction protein on gap junction formation in early amphibian embryogenesis
Authors: Zeng (Mi‐Pai Tseng) Mibai 
Published: February 2005

AbstractBy electron microscopic observations of freeze‐etching replicas, the gap junctions of ectoderm cells of early gastrulae of Xenopus leavis, injected with antibodies against gap‐junction protein at an earlier stage, were compared with those of normal gastrulae. Most of the gap junctions found in the antibody‐injected series were of very small size and consisted of fewer than 40 connexons, while those of the normal gastrulae usually have gap junctions with over 100 connexons. It was concluded that the normal assembly of intramembranous particles to form gap junctions was attenuated by microinjection of the antibodies.
Distribution of lead in renal proximal convoluted tubules of lead‐poisoned rats
Authors: Zhong Cisheng , Ling Yiping , Wu Zhengquan , Zhu Shiya , Hu Rongfang 
Published: February 2005

AbstractIntranuclear inclusions have been found in epithelial cells of renal proximal convoluted tubules (RPCT) in lead poisoned animals. It has been suggested previously that the inclusions contained lead. The present report gives evidence to the contrary. Samples of renal cortex were taken from adult rats fed laboratory chow containing 2% lead acetate for 1 month. Under the electron microscope (EM), intranuclear inclusions were observed in epithelial cells of RPCT. They were round or ovoid, and not delineated by a membrane. They consisted of two parts: Peripheral and central. Lysosomes increased in number, and many myelin figures appeared in the cytoplasm. In the lumen of the tubules, high electron‐dense concretions were found. By x‐ray microranalysis, neither the central part nor the peripheral part of the intranuclear inclusions produced a lead peak in the spectrum. Lysosomes and the cytoplasmic matrix also showed no lead peak. However, when the electron beam was focused on the concretion in the lumen of the RPCT, the Lα peak of lead (10.551 keV) and Kα peak of calcium (3.691 keV) were evident. From these findings it is suggested that intranuclear inclusions in the cells of RPCT are not lead deposits. Rather, it is the concretions found in the lumen of tubule that contain lead.
Ultrastructural and cytochemical characteristics of megakaryoblastic leukemic cells
Authors: Tang Xueming , Chu Shaoyou , Zhang Huixin 
Published: February 2005

AbstractTransmission electron microscopy, scanning electron microscopy, and ultrastructural cytochemistry were utilized to study megakaryoblastic cells from four patients suffering from megakaryoblastic leukemia. The results show that megakaryoblastic leukemic cells have a unique ultrastructural appearance, surface architecture, and cytochemical activity. The cells are positive for platelet peroxidase cytochemical reaction, which is localized in the perinuclear space and endoplastic reticulum, but not in the Golgi apparatus and cytoplasmic granules. They have a rather smooth surface and display blebs or tuberculi which are different from those in other types of leukemic cells as seen under the scanning electron microscope. The megakaryoblastic leukemic cells also show a special appearance under the transmission electron microscope, such as a cytoplasm which contains numerous small mitochondria, mostly concentrated in one pole of the cell. These ultrastructural and cytochemical characteristics of the megakaryoblastic leukemic cells revealed by the combined techniques are very useful in the diagnosis of megakaryoblastic leukemia.
Use of sputter coating to prepare whole mounts of cytoskeletons for transmission and high‐resolution scanning and scanning transmission electron microscopy
Authors: Bell Paul B. , Lindroth Margaretha , Fredriksson Bengt‐Arne 
Published: February 2005

AbstractThis paper describes the use of sputter coating to prepare detergent‐extracted cytoskeletons for observation by scanning (SEM), scanning transmission (STEM), inverted contrast STEM, and transmission (TEM) electron microscopy. Sputtered coats of 1–2 nm of platinum or tungsten provide both an adequate secondary electron signal for SEM and good contrast for STEM and TEM. At the same time, the grain size of the coating is sufficiently fine to be just at (platinum) or below (tungsten) the limit of resolution for SEM and STEM. In TEM, the granular structure of platinum coats is resolved, and platinum decoration artifacts are observed on the surface of structures. The platinum is deposited as small islands with a periodic distribution that may reveal information about the underlying molecular structure. This method produces samples that are similar in appearance to replicas prepared by low‐angle rotary shadowing with platinum and carbon. However, the sputter‐coating method is easier to use; more widely available to investigators; and compatible with SEM, STEM, and TEM. It may also be combined with immunogold and other labeling methods. While TEM provides the highest resolution images of sputter‐coated cytoskeletons, it also damages the specimens owing to heating in the beam. In SEM and STEM cytoskeletons are stable and the resolution is adequate to resolve individual microfilaments. The best single method for visualizing cytoskeletons is inverted contrast STEM, which images both the metal‐coated cytoskeletal structures and electron‐dense material within the nucleus and cytoplasm as white against a dark background. STEM and TEM were both suitable for visualizing colloidal gold particles in immunolabeled samples.
Electron diffraction identification of structure types of martensite in Cu‐Zn‐Al alloys
Authors: Wang Renhui , Zhao Yuechao , Gui Jianian 
Published: February 2005

AbstractElectron diffraction technique for identifying structure types of martensite in β‐Hume‐Rothery alloys is described. It includes determination of the stacking sequence of the martensite of the basal planes, differentiation of the long‐range ordering in martensite inherited from its parent phase (A2 type disordered; B2 type ordered; and DO3, or Heusler, type ordered), and distinguishing between normal‐type and modified‐type martensite. In addition to the 18R1‐type martensite, 12R, 6R, and 2H martensites were found in quenched Cu‐Zn‐Al alloys using this technique.
Comparison of TEM and APFIM in microstructural characterization and interpretation: An overview
Authors: Burke M. G. , Miller M. K. 
Published: February 2005

AbstractA comparison of transmission electron microscopy (TEM) and atom probe field‐ion microscopy (APFIM) is presented with respect to the interpretation of complex microstructures, phase identification, determination of crystallographic order, and analysis of interfaces. The capabilities, spatial resolutions, and limitations of each technique are discussed with examples taken from combined analytical electron microscopy (AEM) and APFIM studies. Both techniques are extremely powerful for routine characterization of a wide range of materials, although care must be exercised in experimentation and interpretation. The combined use of TEM and APFIM is synergistic and extends their individual capabilities from the macro scale to the atomic level.
A study of section wrinkling on single‐hole coated grids using TEM and SEM
Authors: Abad Andre 
Published: February 2005

AbstractTo 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°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).
Defect structure of superconducting YBa2Cu3O7−δ
Authors: Van Tendeloo G. , Amelinckx S. 
Published: February 2005

AbstractThe superconducting material Y1Ba2Cu3O7−δ has been investigated by electron microscopy. Special attention has been paid to the defects occurring in the material. Twinning on (110) or (110) planes is intrinsically related to the orthorhombicity, and when cooled slowly the twin bands are pseudoperiodic with an average width of ˜ 50 nm. The orthorhombic‐tetragonal transition is reversible and diffusion controlled. Under particular conditions and in slightly reduced material a 2a0 X b0 superstructure resulting from vacancy ordering is formed. When kept in air under powder form the material seems to be unstable. Planar defects along (001) accompany the degeneration of the material.
A procedure for making phosphor viewing screens for the transmission electron microscope
Authors: King Murray Vernon 
Published: February 2005

AbstractA technique is described for preparing uniform, durable phosphor layers for viewing screens suitable for the transmission electron microscope; a settling procedure is used. The example described here is for a high‐voltage instrument, but with adjustment of the coating density, the technique should be equally suitable for screen preparation for transmission electron microscopes that operate at lower acceleration voltages.
Critical underfocus in low‐magnification electron microscopy: Rationale and practice
Authors: Fahrenbach Wolf H. , Luft John H. 
Published: February 2005

AbstractFocus in transmission electron microscopy, especially at low‐to‐moderate powers, is usually achieved by an empirical, though largely haphazard, 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.
Progress in quantitative X‐ray microanalysis of frozen‐hydrated bulk biological samples
Authors: Marshall A. T. 
Published: February 2005

AbstractThe analysis of bulk frozen‐hydrated biological samples has developed now to a level where practical application of the technique is possible. Provided the sample is carefully coated with a conductive metal, the development of a space charge capable of causing a significant distortion of the electron diffusion volume does not seem to occur, and analytical resolution can be conveniently held to approximately 2 μm (both depth and lateral resolution). Two valid quantitative methods are available, and two methods of determining dry weight fractions are also available. An area where further research could lead to improvement in analysis of frozen‐hydrated bulk samples is in the investigation of fracturing methods. If fracture planes that were flat and reproducible could be easily obtained, some of the difficulties of analysing frozen‐hydrated bulk samples would be considerably reduced.
X‐ray microanalysis of freeze‐dried and frozen‐hydrated cryosections
Authors: Zierold Karl 
Published: February 2005

AbstractThe elemental composition and the ultrastructure of biological cells were studied by scanning transmission electron microscopy (STEM) combined with energy dispersive X‐ray microanalysis. The preparation technique involves cryofixation, cryoultramicrotomy, cryotransfer, and freeze‐drying of samples. Freeze‐dried cryosections 100‐nm thick appeared to be appropriate for measuring the distribution of diffusible elements and water in different compartments of the cells. The lateral analytical resolution was less than 50 nm, depending on ice crystal damage and section thickness. The detection limit was in the range of 10 mmol/kg dry weight for all elements with an atomic number higher than 12; for sodium and magnesium the detection limits were about 30 and 20 mmol/kg dry weight, respectively.The darkfield intensity in STEM is linearly related to the mass thickness. Thus, it becomes possible to measure the water content in intracellular compartments by using the darkfield signal of the dry mass remaining after freeze‐drying. By combining the X‐ray microanalytical data expressed as dry weight concentrations with the measurements of the water content, physiologically more meaningful wet weight concentrations of elements were determined.In comparison to freeze‐dried cryosections frozen‐hydrated sections showed poor contrast and were very sensitive against radiation damage, resulting in mass loss. The high electron exposure required for recording X‐ray spectra made reproducible microanalysis of ultrathin (about 100‐nm thick) frozen‐hydrated sections impossible. The mass loss could be reduced by carbon coating; however, the improvement achieved thus far is still insufficient for applications in X‐ray microanalysis. Therefore, at present only bulk specimens or at least 1‐μm thick sections can be used for X‐ray microanalysis of frozen‐hydrated biological samples.
Cytochemical applications of X‐ray microanalysis
Authors: Sumner A. T. 
Published: February 2005

AbstractX‐ray microanalysis (XRMA) has been applied to a wide variety of cytochemical problems, but the most valuable applications have been to the validation of cytochemical methods (by the qualitative or quantitative analysis of reaction products), and to the simultaneous localization of more than one substance, which cannot easily be achieved by using alternative methods. The latter applications involve stoichiometric studies (the quantitative relationships between reaction products and substrates), and distribution studies. Ultrastructural cytochemistry with XRMA is limited by the need to use high‐brightness electron sources. Apart from the limited availability of such sources, they may cause unacceptable damage to the specimen.Preparation methods for cytochemistry using XRMA are reviewed; in principle these do not differ from those used for other cytochemical applications, but it is important not to introduce extraneous elements (from fixative, buffer, or embedding medium) into the specimen, where the additional X‐ray peaks may interfere with the analysis.Quantification in XRMA of cytochemical preparations poses special problems, because the addition of the reaction product to the specimen alters the yield of continuum X rays, used for assessing the mass of the specimen, and also dilutes endogenous elements. However, measurement of ratios between characteristic elemental peaks is a useful method in X‐ray microanalytical cytochemistry, and it is concluded that one of the most important attributes of XRMA for cytochemical purposes is the ease with which the substances of interest can be measured.