bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reflection electron energy‐loss spectroscopy and imaging for surface studies in transmission electron microscopes
Authors: Wang Z. L. , Bentley J. 
Published: February 2005

AbstractA review is given on the techniques and applications of high‐energy reflection electron energy‐loss spectroscopy (REELS) and reflection electron microscopy (REM) for surface studies in scanning transmission electron microscopes (STEM) and conventional transmission electron microscopes (TEM). A diffraction method is introduced to identify a surface orientation in the geometry of REM. The surface dielectric response theory is presented and applied for studying α‐alumina surfaces. Domains of the α‐alumina (012) surface initially terminated with oxygen can be reduced by an intense electron beam to produce Al metal; the resistance to beam damage of surface domains initially terminated with Al+3 ions is attributed to the screening effect of adsorbed oxygen. Surface energy‐loss near‐edge structure (ELNES), extended energy‐loss fine structure (EXELFS), and microanalysis using REELS are illustrated based on the studies of TiO2 and MgO. Effects of surface resonances (or channeling) on the REELS signal‐to‐background ratio are described. The REELS detection of a monolayer of oxygen adsorption on diamond (111) surfaces is reported.It is shown that phase contrast REM image content can be significantly increased with the use of a field emission gun (FEG). Phase contrast effects close to the core of a screw dislocation are discussed and the associated Fresnel fringes around a surface step are observed. Finally, an in situ REM experiment is described for studying atomic desorption and diffusion processes on α‐alumina surfaces at temperatures of 1,300—1,400°C.
Observation of double line contrast in surface imaging
Authors: Yao Nan , Cowley John M. 
Published: February 2005

AbstractThe double line contrast of a single‐atom height step observed in surface imaging for a single crystal in reflection electron microscopy is studied under a variety of experimental conditions. It is suggested that this abnormal contrast is directly associated with the dynamical electron diffraction process. The behavior of the double line contrast is closely related to the order of the Bragg reflected beam, and can be observed mostly under one of the two commonly cited resonance conditions. This phenomenon clearly reveals the differences in the surface imaging for various resonance conditions.
Preparation and characterization of MgO surfaces by reflection electron microscopy
Authors: Crozier P. A. , Gajdardziska‐Josifovska M. , Cowley J. M. 
Published: February 2005

AbstractWe have employed several different methods to prepare (100) and (111) surfaces of MgO crystals. (100) surfaces prepared by simple cleaving give good reflection high energy electron diffraction (RHEED) patterns and surfaces with a high density of coarse steps. Chemical polishing of this surface results in a roughening of the topography whilst annealing in oxygen considerably smoothens the surfaces although they appear to be contaminated. Under certain conditions we find that the MgO crystals will cleave along the (111) plane. Both cleaved and mechanically polished (111) surfaces are atomically flat and reconstructed after oxygen annealing.
Scanning electron microscopy of negatively stained catalase on a silicon wafer
Authors: Furuno Taiji , Ulmer Kevin M. , Sasabe Hiroyuki 
Published: February 2005

AbstractA high‐resolution scanning electron microscope capable of 7 Å spatial resolution at 30‐kV accelerating voltage was used to observe negatively stained protein molecules. Thin platelet crystals, densely packed monolayers, and low‐density deposits of beef liver catalase were prepared on the surface of silicon wafers and negatively stained with phosphotungstic acid. The tetrameric structure of the catalase molecule was observed for the first time by scanning electron microscopy on the surface of the smooth silicon wafer.
A combined pseudoreplica‐immunochemical technique for research and diagnostic Virology
Authors: Fritz Blayne , Moore Kenneth , Naides Stanley J. 
Published: February 2005

AbstractPseudoreplica and immunochemical techniques were combined in a single protocol for identification of virus in research and clinical specimens. Stock preparations of vesicular stomatitis virus (VSV), cytomegalovirus (CMV), and herpes simplex virus (HSV) were used to develop the technique. Traditional pseudoreplicas of viral stock solutions were prepared but not negatively stained. The virus was then immunolabeled in two stages. Virus‐specific polyclonal antisera were used in the first stage; colloidal gold congugated antibodies were used as indicator antibody in the second stage. After immunolabeling, the grids were negatigvely stained. As a demonstration of the clinical usefulness of this approach, it was employed to antenatally identify human parvovirus B19 particles in ascites from a 22 week gestational fetus with nonimmune hydrops fetalis. The combined pseudoreplica‐immunochemical approach offers several advantages over both the pseudoreplica and immunochemical methods when used in isolation. Advantages include relative purification of samples, concentration of virus, morphological preservation, and enhanced diagnostic specificity.
Ultrastructure of the mammalian pinealocyte under natural and experimental conditions: Quantitative aspects
Authors: Karasek Michal 
Published: February 2005

AbstractThis review briefly summarizes data accumulated on the quantitative aspects of the ultrastructure of the mammalian pinealocyte. Quantitative changes have been demonstrated under natural and experimental conditions in pinealocyte cell organelles in various species. Special attention is paid to two cytoplasmic components most frequently studied by means of quantitative electron microscopy, namely, dense‐core vesicles and “synaptic” ribbons.
The thickness determination of organic crystals under low dose conditions using electron energy loss spectroscopy
Authors: Rez Peter , Chiu Wah , Weiss J. K. , Brink J. 
Published: February 2005

AbstractIn the 3‐dimensional (3‐D) reconstruction of protein crystals with variable thicknesses the electron images and diffraction patterns can only be merged if the crystal thickness is known. Measurement of the thickness using the ratio of the number of inelastically scattered electrons to the number of electrons in the zero loss peak can be accomplished with parallel electron energy loss spectrometry (PEELS). A theoretical analysis of the accuracy of the technique on paraffin crystals of different thicknesses is presented. Our experimental studies with paraffin crystals show the feasibility of measuring a single layer of 47 Å with good accuracy under low dose and low temperature conditions. A simple experimental apparatus is proposed to obtain thicknesses from small regions of unstained protein crystals prior to collecting the 3‐D data sets from the unexposed area of the same crystal.
Computer‐assisted morphometry: Point, intersection, and profile counting and three‐dimensional reconstruction
Authors: Hyde Dallas M. , Magliano David J. , Reus Edward , Tyler Nancy K. , Nichols Steve , Tyler Walter S. 
Published: February 2005

AbstractThe use of computers in morphometry can involve (1) automated image analysis, semiautomated image analysis and point, intersection, intercept and profile counts of two‐dimensional images on tissue sections with mathematical extrapolation to the third dimension, (2) direct measurement of volumes, surfaces, lengths, and curvature using x,y,z coordinates of serial sectioned images, or (3) stereologic techniques and serial sections which is a combination of 1 and 2 above. Automated and semiautomated image analysis are generally restricted to specimens that are characterized by differential contrast such as interalveolar septa in the lung or histochemically stained mucous granules in pulmonary epithelium. Point, intersection, and profile counts using hand‐held, notebook PCs, portable PCs, or standard PCs and MS‐DOS—based application programs are extremely efficient, precise, affordable, and convenient methods of quantitating average values of a population. When morphometric measurements of individual structures are required, computer‐assisted three‐dimensional reconstruction using x,y,z coordinates of the surface outline from serial sections is a tedious yet precise method. We describe a computer program that efficiently estimates mean caliper diameter, volume, and surface area with less than five percent error with five sections per structure. We also describe a program that does digital image subtraction on serial sections, superimposes digitally generated test systems on biological images, and accumulates point, intersection, and profile counts using a Macintosh II series computer. © 1992 Wiley‐Liss, Inc.
Application of automatic image analysis for quantitative morphological studies of peroxisomes in rat liver in conjunction with cytochemical staining with 3‐3′‐diaminobenzidine and immunocytochemistry
Authors: Beier Konstantin , Fahimi H. Dariush 
Published: February 2005

AbstractWe describe the application of automatic image analysis for quantitative morphological studies of peroxisomes in rat liver. For automatic detection by light and electron microscopy peroxisomes must be stained with the alkaline DAB procedure for catalase. There is a good agreement between the results obtained by conventional morphometric techniques and by automatic image analysis of DAB‐stained electron microscopic preparations. Moreover, the image analyzer may be used in conjunction with a light microscope for evaluation of semithin sections (1–0.25 μm), provided the section thickness factor is taken into consideration. This latter approach has proven highly efficient in estimation of peroxisome proliferation. The limitations of this method and the relevance of volume density as a reliable morphometric parameter for evaluation of peroxisome proliferation are discussed. In the second part of this study we present the application of image analysis for quantitation of alterations of individual peroxisomal enzyme proteins after treatment with bezafibrate in immunogold stained ultrathin sections. There is good agreement between the results of quantitative immunocytochemistry and Western (immuno) blot analysis of highly purified peroxisomal fractions. In our experience quantitative immunoelectron microscopy provides a versatile, highly sensitive, and efficient method for detection of modulations of various proteins in peroxisomes. Finally the limitations and prospects of quantitative immunocytochemistry for investigation of peroxisomal proteins are discussed. © 1992 Wiley‐Liss, Inc.
Computer assisted data collection for stereology: Rationale and description of point counting stereology (PCS) software
Authors: Pentcheff N. Dean , Bolender Robert P. 
Published: February 2005

AbstractThe paper describes microcomputer software for point counting stereology. Stereology includes a collection of statistical methods that quantify the images of light and transmission electron microscopy. The methods use test grids placed over images to collect raw data, which includes counts of points, intersections, transections, and profiles. In turn, the counts are included in stereological equations that give estimates of compartmental volumes, surfaces, lengths, or numbers. These parameters describe the composition of a structure in three‐dimensional space. The PCS (point counting stereology) System Software III serves as a data collection, storage, and management tool. Users set up point counting protocols without programming, enter data by pressing predefined function (MS‐DOS) or alphabetic keys (UNIX), store data in files, select files for analysis, and calculate results as stereological densities. The latest version of the PCS software includes a new user interface and is designed as a research “front end” that can feed data either into the calculation tools of a stereology tutorial (Bolender, 1992, this issue) or into the analysis routines of quantitative morphology databases (Bolender and Bluhm, 1992). © 1992 Wiley‐Liss, Inc.
From egg to pole cells: Ultrastructural aspects of early cleavage and germ cell determination in insects
Authors: Zissler Dieter 
Published: February 2005

AbstractInsect eggs are giant and very complex cells covered by an extremely resistant shell. Both the egg cell and surrounding eggshell express anteroposterior and ventrodorsal polarity. The molecular and cytoplasmic organization of both axes originates during oogenesis and leads to the production of an ooplasmic system which consists of euplasm and deutoplasm (yolk) and contains a nucleus as well as extranuclear determinants of maternal origin. Both are part of the store of information for early embryogenesis. In addition, the deutoplasm serves as raw material and early nutrient supply for building the embryo.
The insect egg cell, which is arrested in the first maturation division when released from the ovary during oviposition, will be activated by different stimuli among different species to complete meiosis and start embryogenesis. The zygote nucleus undergoes a number of synchronous mitotic divisions leading to cleavage energids which initially form a syncytial blastoderm and subsequently the cellular blastoderm. In many insects, prior to blastoderm formation, polar granules (or oosome material) are incorporated in a single cell or a small number of cells which bud off at the posterior pole. These so called pole cells give rise to the primordial germ cells. Therefore, polar granules or the oosome material mark the germ line, and while structural counterparts of determinants of body pattern formation have so far not been found, the polar granules or oosome serve as an autonomous ooplasmic determinant for the pole or germ cells. Anteroposterior body polarity can arise independent of the germ plasm. © 1992 Wiley‐Liss, Inc.
Preservation and visualization of molecular structure in detergent‐extracted whole mounts of cultured cells
Authors: Lindroth Margaretha , Bell Paul B. , Fredriksson Bengt‐Arne , Liu Xiao‐Dong 
Published: February 2005

AbstractToday's electron microscopes have a resolution sufficient to resolve supramolecular structures. However, the methods used to prepare biological samples for electron microscopy often limit our ability to achieve the resolution that is theoretically possible. We use whole mounts of detergent‐extracted cells grown on Formvar‐coated gold grids as a model system to evaluate various steps in the preparation of biological samples for high resolution scanning electron microscopy (SEM)Factors that are important in determining the structure and composition of detergent‐extracted cells include the nature of the detergent and the composition of the extraction vehicle. Chelation of calcium is extremely important to stabilize and preserve the cytoskeletal filaments. We have also demonstrated both morphologically and by gel electrophoresis that treatment of cells with bifunctional protein crosslinkers before or during extraction with detergent can significantly enhance the preservation of both proteins and supramolecular structures.The methods used to dry samples are a major determinant of the quality of structural preservation. For cytoskeletons freeze‐drying (FD) is superior to critical point‐drying (CPD), one reason being that CPD samples have to be dehydrated, thereby causing more shrinkage as compared to FD samples. The high pressures to which samples are exposed during CPD may also cause increased shrinkage, and water contamination during CPD causes severe structural damage. We have obtained the best structural preservation of detergent‐extracted and fixed cells by manually plunging them into liquid propane and drying over night in a freeze‐drayer.The factor that most limits achievement of high resolution in SEM is the metal coat, which has to be very thin, uniform, and free of grain in order not to hide structures or to create artifactual ones. We have found that sputter‐coating with 1–3 nm of tungsten (W) or niobium )Nb( gives extremely fine‐grained films as well as satisfactory emission of secondary electrons. These samples can also be examined at high resolution by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The best preservation and visualization of supramolecular structures have been obtained using cryosputtering, in which the samples are freeze‐dried and then sputter‐coated within the freeze‐dryer while still frozen. © 1992 Wiley‐Liss, Inc.
Sample preparation for electron microscopy of internal cell structure
Authors: Haggis Geoffrey H. 
Published: February 2005

AbstractMethods are reviewed for examination of internal cell structure by high‐resolution scanning electron microscopy and compared with the rapid‐freeze deep‐etch replica technique used in transmission electron microscopy. Rapid freezing of fresh material, followed by freezefracture, provides a theoretically attractive approach in ultrastructure studies, but the high protein and solute content of most cells prevents a deep three‐dimensional view for material frozen without some form of extraction. After discussion of other methods it is concluded that the most useful general approach, at least for cultured cells, is to first permeabilize or break open the cells in a medium which preserves the structure under study in a functional state as, for example, the movement of chromosomes along the division spindle, or transport of proteins within the Golgi region. After permeabilization, with attendant partial extraction, the preparation can be fixed, then viewed by either deep‐etch replication, or by high‐resolution scanning electron microscopy, with structure of interest revealed in deep view. © 1992 Wiley‐Liss, Inc.
Cortical ultrastructure and chemoreception in ciliated protists (ciliophora)
Authors: Hufnagel Linda A. 
Published: February 2005

AbstractThe ciliated protists (ciliates) offer a unique opportunity to explore the relationship between chemoreception and cell structure. Ciliates resemble chemosensory neurons in their responses to stimuli and presence of cilia. Ciliates have highly patterned surfaces that should permit precise localization of chemoreceptors in relation to effector organelles. Furthermore, ciliates are easy to grow and to manipulate genetically; they can also be readily studied biochemically and by electrophysiological techniques. This review contains a comparative description of the ultrastructural features of the ciliate cell surface relevant to chemoreception, examines the structural features of putative chemoreceptive cilia, and provides a summary of the electron microscopic information available so far bearing on chemoreceptive aspects of swimming, feeding, excretion, endocytosis, and sexual responses of ciliates. The electron microscopic identification and localization of specific chemoreceptive macromolecules and organelles at the molecular level have not yet been achieved in ciliates. These await the development of specific probes for chemoreceptor and transduction macromolecules. Nevertheless, the electron microscope has provided a wealth of information about the surface features of clliates where chemoreception is believed to take place. Such morphological information will prove essential to a complete understanding of reception and transduction at the molecular level. In the ciliates, major questions to be answered relate to the apportionment of chemoreceptive functions between the cilia and cell soma, the global distribution of receptors in relation to the anterior‐posterior, dorsal‐ventral, and left‐right axes of the cell, and the relationship of receptors to ultrastructural components of the cell coat, cell membrane, and cytoskeleton. © 1992 Wiley‐Liss, Inc.
Ultrastructural neurobiology of the olfactory mucosa of the brown trout, Salmo trutta
Authors: Moran David Taylor , Rowley J. Carter , Aiken George R. , Jafek Bruce W. 
Published: February 2005

AbstractThis paper describes four investigations of the olfactory mucosa of the brown trout: 1) the ultrastructure of the olfactory mucosa as revealed by scanning (SEM), conventional transmission (TEM), and high voltage (HVEM) electron microscopy; 2) light and electron‐microscopic investigations of retrograde transport of the tracer macromolecule horseradish peroxidase (HRP) when applied to the cut olfactory nerve; 3) SEM and TEM investigations of the effects of olfactory nerve transection on cell populations within the olfactory epithelium; and 4) ultrastructural investigations of reversible degeneration of olfactery receptors caused by elevated copper concentrations. The trout lofactory epithelium contains five cell types: ciliated epithelial cells, ciliated olfactory receptor cells, microvillar olfactory receptor cells, supporting cells, and basal cells. The ciliated and microvillar olfactory receptor cells and a small number of basal cells are backfilled by HRP when the tracer is applied to the cut olfactory nerve. When the olfactory nerve is cut, both ciliated and microvillar olfactory receptor cells degenerate within 2 days and are morphologically intact again within 8 days. When wild trout are taken from their native stream and placed in tanks with elevated copper concentrations, ciliated and microvillar cells degenerate. Replacement of these trout into their stream of origin is followed by morphologic restoration of both types of olfactory receptor cells. Ciliated and microvillar receptor cells are primary sensory bipolar neurons whose dendrites make contact with the environment; their axons travel directly to the brain. Consequently, substances can be transported directly from the environment into the brain via these “naked neurons.” Since fish cannot escape from the water in which they swim, and since that water may occasionally contain brain‐toxic substances, the ability to close off—and later reopen—this anatomic gateway to the brain would confer a tremendous selective advantage upon animals that evolved the “brain‐sparing” capacity to do so. Consequently, the unique regenerative powers of vertebrate olfactory receptor neurons may have their evolutionary origin in fishes. © 1992 Wiley‐Liss, Inc.
Olfactory epithelium in young adult and aging rats as seen with high‐resolution scanning electron microscopy
Authors: Nagurok Tomonori , Iwashita Kazuto 
Published: February 2005

AbstractThe present study uses mainly scanning electron microscopy to demonstrate the three‐dimensional internal cell structures of rat olfactory epithelial cells. The aldehyde‐prefixed osmium‐DMSO‐osmium (AODO) method devised by Tanaka and Mitsushima (1984) was applied to the present study to disclose intracellular structures such as endoplasmic reticulum, mitochondria, Golgi apparatus, and lysosomes. The spatial distribution pattern of these structures in olfactory and supporting cells is discussed, paying special attention to the formation of lipofuscin‐like granules present in aged rats. © 1992 Wiley‐Liss, Inc.