bluuebunny/crossref_metadata_2025_split huggingface dataset:
Motile microtubles in foraminifera: Correlative video-enhanced contrast light and transmission electron microscopy
Authors: Travis J.L. , Bowser S.S. 
Published: June 2020

Analog and digital contrast-enhanced video light microscopy have provided exciting new views of subcellular architecture and dynamics. One such example is recent work on the motility of the pseudopodia of Allogromia and other foraminifera. Because of the unsurpassed clarity with which their cytoplasmic microtubules can be visualized, these organisms have been used extensively as model systems in which to study microtubule- associated cell motility in vivo. We have employed correlative electron microscopy to further resolve the subcellular processes imaged by the video microscope. Our studies indicate that the bidirectional axial and lateral movements of cytoplasmic microtubules drives the formation and movement of the pseudopodia. Furthermore, organelle and cell surface transport occur exclusively along the motile microtubules.The exceptional visibility of foraminiferan microtubules in vivo is due to the fact that when the organisms are plated on cationized substrates, the normally cylindrical pseudopodia spread along the substrate and become highly flattened (generally to a thickness of ≤ 0.5μm).
high-resolution cryomicroscopy of porin (OmpF)
Authors: Sass H.J. , Massalski A. , Beckmann E. , Büldt G. , Dorset D. , Heel M.v. , Rosenbusch J.P. , Zeitler E. , Zemlin F. 
Published: June 2020

Porin (OmpF) is one of the major outer membrane proteins of Escherichia coli /1/. This integral membrane protein functions as a molecular sieve for hydrophilic molecules with an exclusion limit of around 600 dalton /2/.For our investigation, purified porin was reconstituted in di-myristoyllecithin vesicles, where it formed 2D-lattices. The crystallinity was considerably improved by subsequent treatment with phospholipase. Electron microscopy was done on the “Suleika”, a cryo-electron microscope which permits low-dose imaging under “cryo-protection” conditions (4K) /3/. The embedding medium was glucose, which allows the visualisation of integral membrane proteins at high resolution /4/. Under these conditions, we obtained several electron micrographs showing optical diffraction of up to 0.8nm resolution. Image prossessing was performed by using the correlation averaging method to overcome the imperfections of the porin lattice. Only about 80% of the lattice shows well defined cross-correlation peaks which are marked in Figure 1. Dislocations along the lattice lines are clearly discernable. The averaged image of the porin trimer (Fig. 2 ) was built up from unit cells corresponding to positions with correlation peaks above the noise level.
Herpesvirus Nucleocapsids Imaged in the Frozen-Hydrated State
Authors: Booy F. P. , Newcomb W. W. , Brown J. C. , Steven A. C. 
Published: June 2020

Herpesviruses are an extensive family of double-stranded DNA-containing animal viruses. The typical herpes-virion consists of a loosely-fitting envelope derived from the nuclear membrane of the host cell, within which a proteinaceous "tegument" layer encloses an icosahedral nucleocapsid. The capsid is a thick-walled shell of triangulation class T=16, whose major constituent is a protein of monomer mass ∽ 155kDa. Hexamers of this protein occupy the hexavalent sites of the icosahedral surface lattice. The nucleocapsid also contains several minor proteins and the linear genome of 80-150 MDaDespite investigations extending over more than 20 years, many basic questions concerning the HSV nucleocapsid structure remain unanswered; e.g. where are the minor proteins located? and what is the structure and chemical identity of the vertex capsomers? Moreover, although several models have been proposed for the packing of DNA inside the capsid, further, more detailed, evidence is needed to settle this issue. Conventional electron microscopic approaches having been constrained by difficulties in preserving and conveying the native structures of intact nucleocapsids, we have started to explore the potentialities of cryo-electron microscopy for this system.
Fourier Analysis of Digital STEM Images in the Study of Transparency in Human Cornea And Sclera
Authors: Vaezy S . 
Published: June 2020

The structure of transparent human cornea is similar to that of the opaque human sclera, and they both consist of collagen fibers embedded in a mucopolysaccharide matrix.[1] This similarity in structure and composition, in contrast to a large difference in turbidity, presents an important question regarding the basis of transparency in the cornea.In general, a transparent structure permits most of the incident light to be transmitted, whereas an opaque structure scatters it. Scattering of an incident light wave occurs when the spatial fluctuations in the index of the refraction of the medium have dimensions close to the wavelength of visible light.[2] To analyze spatial fluctuations in cornea and sclera we have developed techniques based on Fourier analysis of digital STEM images.Fourier analysis allows direct quantitative measurements of the fluctuations in any signal. The signal is resolved into its constituent sinusoids or Fourier components. Amplitude, and frequency of each component are quantitatively obtained using the Fourier Transform (FT).
Image Contrast in the SEM from 1 to 30 keV
Authors: Joy David C 
Published: June 2020

The image produced by the SEM is not an intrinsic property of the object viewed but is also a function of the electron-optical conditions used to generate the image as well as of the chemical and geometric characteristics of the specimen itself. The image is therefore not a simple representation of the specimen, but must be interpreted to yield the desired information. A general purpose method for image interpretation is to perform a detailed contrast simulation for the specified object and to then examine the influence of various factors such the beam energy or signal mode on the form of the image so as to deduce the rules which relate the form of the image to the form of the specimen.In the computations shown here a Monte Carlo simulation is used to model the interaction of the incident beam. The generation of the secondary electron signal is incorporated using the method proposed by Salow, and the escape probability of these secondary electrons is computed using a simple exponential approximation.
High-Resolution SEM of Colloidal Gold Labels
Authors: Albrecht Ralph M. , Simmons Scott R. , Prudent James R. , Erickson Chris M. 
Published: June 2020

Colloidal gold, conjugated to a number of biologically active molecules, including ligand and antibody, provides a useful label for light microscopy and electron microscopy. This stems, in part, from its color, density, and regular spherical shape although the ability to make the particles in a number of defined sizes, the ease of conjugation to biological material, and the retention of activity of bound molecules are also important factors.Although nearly all sizes of colloidal gold particles, from 2.0 nm on up, can be identified in transmission or high voltage transmission electron microscopy, it has generally been the larger sized particles, 15 nm and up, that have proved useful for scanning electron microscopic studies. This is due principally to the resolution limits of conventional SEMs and the need to employ backscattered electron imaging, BEI, to unambiguously define the gold labels.
Contrast and Resolution in the ESEM
Authors: Danilatos G. D. 
Published: June 2020

The basic theory of contrast arid resolution for the SEM is applicable to the environmental scanning electron microscope (ESEM) except that it must be extended to include the effects of the gaseous environment on the beam-specimen—signals system. The resolution depends on the detection mode and the associated beam specimen interaction volume, provided there is enough contrast for a particular feature to become visible. The ultimate resolution (resolving power) is limited by the precise electron beam profile as it propagates through the gas. This has been examined in a previous presentation here and the overall topic has been surveyed in detail elsewhere.There are two different situations under which the resolving power is considered: (i) When the electron skirt (scattered electrons) is comparable with the original spot size (unscattered electrons). This can happen in the case of a very broad beam, where the scattered electrons fall in the neighborhood of the original spot and cannot be easily distinguished from the unscattered ones.
Ultrastructure of Ligament Extracellular Matrix After Chondroitinase ABC Digestion
Authors: Bray D. F. , Frank C. 
Published: June 2020

The cationic stain ruthenium hexammine trichloride (RHT) has been utilized as a connective tissue stain primarily due to its ability to stabilize and stain anionically-charged glycosaminoglycans (GAGs). A major drawback of this procedure however is that the increased preservation and visibility of the GAGs obscures other RHT-stained constituents of the “ground substance”. In order to more readily visualize these non-GAG ground substance components ligament tissue was pre-treated with chondroitinase ABC, an enzyme that removes most, if not all of the GAGs present.Segments of the midsubstance of medial collateral ligaments (MCL) of mature New Zealand white rabbits were excised and incubated 1 hat 37°C in chondroitinase ABC (1 U/ml in 0.25M Tris, 0.18M NaCl, 5mM benzamidine HC1, 0. 1. 6-amino-n-caproic acid, pH 8.0) followed by fixation in Na-cacodylate (0.1M, pH 7.4) buffered glutaraldehyde (2.5%) containing RHT (lmg/ml) for 2.5 h. Post-fixation for 1 h in cacodylate-buffered osmium tetroxide (1%) plus RHT (lmg/ml) preceded ethanol dehydration and embedding in Spurr's resin.
Deformation of Yeast Plasma Membrane by Ethidium Bromide
Authors: Keyhani E. 
Published: June 2020

The mutagenic effect of ethidium bromide on the mitochondrial DNA is well established. Using thin section electron microscopy, it was shown that when yeast cells were grown in the presence of ethidium bromide, besides alterations in the mitochondria, the plasma membrane also showed alterations consisting of 75 to 110 nm-deep pits. Furthermore, ethidium bromide induced an increase in the length and number of endoplasmic reticulum and in the number of intracytoplasmic vesicles.Freeze-fracture, by splitting the hydrophobic region of the membrane, allows the visualization of the surface view of the membrane, and consequently, any alteration induced by ethidium bromide on the membrane can be better examined by this method than by the thin section method.Yeast cells, Candida utilis. were grown in the presence of 35 μM ethidium bromide. Cells were harvested and freeze-fractured according to the procedure previously described.
Occurrence of abundant autophagosomes in bird hepatocytes
Authors: Keyhani E. 
Published: June 2020

Autophagy is a process by which the cytoplasm of the cell segregates and degrades endogenous macromolecules and organelles. Autophagy plays an important role in the degradation of intracellular components during physiological cell functioning. This paper describes the morphology of bird hepatocytes with reference to abundant formation of autophagosomes.Six house sparrows were purchased from a local dealer, and, on examination, all were apparently healthy, did not show any sign of starvation or disease. Their liver was removed after cervical dislocation and was doubly fixed with glutaraldehyde-osmium, and processed with conventional methods.The hepatocytes were generally polyhedral, sometimes slightly oval. The nuclei were round, slightly eccentric and contained one or two prominent nucleoli. Nuclear chromatin exhibited the normal structure and organization of hetero- and euchromatin. The cytoplasm showed abundant mitochondria round and elliptic. No intramitochondrial vacuolization and swelling were seen and cristae exhibited the normal structure described for liver cells. The Golgi apparatus was poorly developed.
Trophoblast ultrastructure in murine interspecies pregnancy
Authors: Crepeau M. , Yamashiro S. , Bast T. , Croy B.A. 
Published: June 2020

Mus caroli blastocysts transferred to the uterus of pseudopregnant Mus musculus implant but do not survive past midgestation. Blastocyst microsurgery has been used to show that trophoblast is the tissue responsible for pregnancy failure but the nature of the failure remains undefined. Therefore a histological study, was undertaken to compare development of M. caroli embryos in M. musculus and M. caroli uteri at a time point just prior to development of grossly observable lesions.Seven transferred M. caroli embryos and six transferred M. musculus embryos were recovered from three M. musculus recipients on day 8.5 of gestation. Four M. caroli embryos recovered from a M. caroli uterus on day 7.5 of gestation were used as stage-matched controls. For light microscopy, 2 μm thick, glycol methacrylate embedded (3), sections of implantation sites were stained with H & E or periodic acid-Schiff (PAS). For electron microscopy, small pieces of the tissues were fixed and processed routinely.
Electron microscopic study of respiratory syncitial (RS) virus: A new approach
Authors: Alain R. , Bélanger F. , Berthiaume L. , Trudel M. 
Published: June 2020

The respiratory syncytial (RS) virus is included in the Paramyxoviridae family, genus Pneumovirus. In the present study, three strains were compared: human (HRS), bovine (BRS) and caprine (CRS). The ultrastructure of HRS virus has been previously described according to conventional methods of negative staining and ultrathin sectioning (Berthiaume et al., 1974). Recently, bridges between BRS particles in ultrathin sections were noted (Bélanger et al., 1988). Bridges were also observed with CRS (unpublished results). We were interested in studying, by negative staining, what produced these bridges and why they were present on BRS and CRS particles and not on HRS.Human, bovine and caprine RS virus were propagated in ovine kidney (OK) cells. After 5 to 7 days post-infection, when viral titers were at a maximum, supernatants were collected. They were separated in two parts: the first aliquot was used without treatment immediately after collection; the second aliquot was immediately fixed with glutaraldehyde (final concentration of 0,5% (v/v)) and after ten minutes fixation, samples were prepared for electron microscopy.
Quantitative changes of organelles in early cirrhosis of rat
Authors: Ryoo J. W. , Buschmann R. J. 
Published: June 2020

Cirrhosis involves major architectural changes in the liver. The changes are appreciated histologically as regenerative nodules and septa, but they do not reflect directly the structural/functional changes which must occur at the subcellular level. In order to test for these subcellular changes, we chose to carry out a morphometric analysis of two organelle systems that are most likely to be affected in liver cirrhosis.Early cirrhosis was produced by CC14 inhalation along with phenobarbital continuously in the drinking water (CCl4+PB). Two groups of control rats were used. One group was given neither the CCI4 nor the phenobarbital (CONT); the other group was given just the phenobarbital (PB). After 8 wk the rat livers were fixed by perfusion, The left lobe was isolated, weighed, and its volume determined. Tissue was prepared for electron microscopy. Micrographs of random areas of hepatocyte cytoplasm (36000x), hepatocyte mitochondria (90000x), and Ito cell cytoplasm (54000x).
Ultrastructural observations in two cases of acute pyelonephritis
Authors: Caughey R.C. , Kelly C.E. 
Published: June 2020

In two histologically diagnosed cases of acute pyelonephritis, several ultrastructural features were observed. The transmission electron microscope (TEM) highlights the bacterial adhesion, inflammatory process, phagocytosis and lysosomal release characteristic of pyelonephritis.The renal biopsies from both patients were fixed in 2.5% glutaraldehyde, rinsed with Millonig&#x0027;s buffer, and post fixed with 1% osmium tetroxide. They were then en bloc stained with 0.5% uranyl acetate, rinsed with Walpole&#x0027;s buffer, dehydrated with a graded series of ethanols and embedded with Epon 812 epoxy resin. Ultramicrotomy thin sections were stained with uranyl acetate and lead citrate and scanned using a JEOL - JEM100C.Using the TEM, bacteria are seen in tubular epithelial cells, phagocytized to the basement membrane, within cells of the tubular lumen, and within the polymorphonuclear leukocytes (polys). Bacteria may also be seen phagocytizing within cells in the tubular lumen. The inflammatory response of polys is seen in the tubular lumen and interstitium, and attached and within the tubular basement membrane.
A web-like network of type vi collagen in human skin is revealed by immuno-electron microscopy
Authors: Keene Douglas R. , Glanville Robert W. , Engvall Eva 
Published: June 2020

A mouse monoclonal antibody (5C6) prepared against human type VI collagen (1) has been used in this study to immunolocalize type VI collagen in human skin. The enbloc method used involves exposing whole tissue pieces to primary antibody and 5 nm gold conjugated secondary antibody before fixation, and has been described in detail elsewhere (2).Biopsies were taken from individuals ranging in age from neonate to 65 years old. By immuno-electron microscopy, type VI collagen is found to be distributed as a fine branching network closely associated with (but not attached to) banded collagen fibrils containing types I and III collagen (Fig. 1). It appears to enwrap fibers, to weave between individual fibrils within a fiber, and to span the distance separating fibers, creating a “web-like network” which entraps fibers within deep papillary and reticular dermal layers (Fig. 2). Relative to that in the dermal matrix, the concentration of type VI collagen is higher around endothelial basement membranes limiting the outer boundaries of nerves, capillaries, and fat cells (Fig. 3).
Demonstration of somatomedin c/insulin-like growth factor I (SM-C/IFG-I) and growth hormone (GH) bindings on chick embryo tissues
Authors: Wang J. J. , Teng C. S. 
Published: June 2020

The presence of SM-C/IGF-I has been described on chick embryo tissues. The binding of endogenous GH on Mullerian ducts (Mds) has been detected previously. Recently, the presence of SM/IGF and SM/IGF receptors were identified in 9-12 day-old mouse embryos. These evidences indicate that SM-C/IGF-I and GH are involved in embryonic development.Antiserum against porcine GH and anti-SM-C/IGF-I antibody were used as primary antibodies for immunocytochemical labelling probes by the avidin-biotin complex (ABC)-gold technique. There is no or very weak cross reactions between these two antibodies by ELISA. Chick embryos and Mds were fixed in 2.5% glutaraldehyde for 30 minutes. Washes with phosphate buffer were administered between each of the following incubations: 1. 2% bovine serum albumin, 2. Primary antibody (1/200 dilution), 3. Biotinated secondary antibody (1/100), 4. Avidin conjugated with gold particles (1/50). The 10-day Mds were double labelled with SM-C/IGF-I-gold and then with MIS-peroxidase (MIS-PO) as described before.
Thick-sectioning characteristics of vitreous carbon microtome knives
Authors: Disharoon D. R. , Wickham M. G. , Myrick J. J. 
Published: June 2020

Since the introduction of vitreous carbon microtome knives progress has been made on improving the quality of the cutting edge. It has been found that long uniform edges produced by mechanical lapping are superior to cleaved edges. Knife edges of 12.5mm to 25mm with 45° cutting angles have been produced, mounted for ultramicrotomes in aluminum boats (Fig. 1) and alpha tested under routine microtomy conditions. In tests at independent laboratories, the 25mm, 45° knives were found to produce routine l-2μm thick sections of a variety of materials embedded in a range of media.Vitreous carbon was commercially obtained in square sheets, 76mm X 76mm X 3mm, cut and processed for polishing by standard machine grinding. Uniform edges with 45° cutting angels were produced by lapidary procedures incorporating the sequential use of fine polishing grits.
Preparation and staining of hard seed tissue for backscatter imaging
Authors: Paul R. N. , Egley G. H. 
Published: June 2020

Hard seed coat material is extremely difficult to prepare for observation at the EM level. Seed coat segments are usually removed for embedding and sectioning, which results in loss of tissue juxtaposition. Observation and monitoring reactions of the intact seed coat under experimental procedures such as tracking dye penetration into seeds make seed coat dissection unfeasible. Efforts to apply analytical EM methods such as STEM/EDS analysis, are restricted by the limiting effect of section thickness on X-ray signal. We investigated the ultrastructure of dry seeds by treating them with various metallic staining solutions and observing the trimmed block faces with the SEM in backscatter mode. Good structural information was obtained as well as visualization of a specific tissue layer that accumulates lead.Intact seeds were incubated in several aqueous solutions including: 2% w/v uranyl acetate; 1% w/v OsO4; 2% ferrous chloride (Followed by 5% potassium ferricyanide to form an insoluble precipitate) ; and various lead solutions including Reynolds lead citrate.
New replica method with plasma polymerized film by glow discharge
Authors: Tanaka A. , Yamaguchi M. , Hirano T. 
Published: June 2020

The plasma polymerization replica method and its apparatus have been devised by Tanaka (1-3). We have published several reports on its application: surface replicas of biological and inorganic specimens, replicas of freeze-fractured tissues and metal-extraction replicas with immunocytochemical markers.The apparatus for plasma polymerization consists of a high voltage power supply, a vacuum chamber containing a hydrocarbon gas (naphthalene, methane, ethylene), and electrodes of an anode disk and a cathode of the specimen base. The surface replication by plasma polymerization in negative glow phase on the cathode was carried out by gassing at 0.05-0.1 Torr and glow discharging at 1.5-3 kV D.C. Ionized hydrocarbon molecules diffused into complex surface configurations and deposited as a three-dimensionally polymerized film of 1050 nm in thickness.The resulting film on the complex surface had uniform thickness and showed no granular texture. Since the film was chemically inert, resistant to heat and mecanically strong, it could be treated with almost any organic or inorganic solvents.
Scanning tunneling microscopy of biomacromolecules
Authors: Stemmer A. , Engel A. , Häring R. , Reichelt R. , Aebi U. 
Published: June 2020

Since its invention in the early 1980s the scanning tunneling microscope (STM) has rapidly evolved into a well established tool in solid state physics for surface structure analysis at atomic resolution. Recently a growing interest in the STM for investigating biological matter has been expressed, since surface ‘topographs’ of biomacromolecules can be recorded at ambient pressure or possibly in buffer solutions, thereby eliminating structural alterations induced by specimen dehydration such as required for electron microscopy (EM).As simple as a STM may look, it provides a wealth of information ranging from mere surface topography and local variations in the tunnel-barrier height to local spectroscopy of electronic states and elasticity. On the other hand the physics involved in imaging biological specimens such as protein or DNA, membranes, or fatty acid monolayers, which are generally known to be poor conductors, is not quite understood yet. To cope with insulators the atomic force microscope (AFM), a relative of the STM, provides a means to obtain topographs and elasticity data.