bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine Structure of the Intestine of Dirofilaria Immitis
Authors: Lee Chin-Chiu , Miller Joseph H.
Published: June 2020

Carhonell and Apitz (1959) described the presence of pigment granules in the intestinal cells of Ascaris lumbricoides. They regarded these granules as intermediate products of metabolism. A careful examination of the ultrastructure of the intestine of Ancylostoma caninum revealed the presence of similar granules, and their relationship to host hemoglobin has been indicated (Lee, 1968). Another blood-feeding nematode, Dirofilaria immitis, was examined to study further intestinal granules. The intestine of adult female worms of D. immitis from naturally infected dogs was fixed with glutaraldehyde and postosmicated. Dehydration in an ethanol series proceeded embedment with Araldite 502. Sections from the anterior, middle, and posterior portions of the intestine were stained with lead hydroxide, and viewed in a Hitachi HU-11A microscope.
A New Multicolored Staining Procedure for One-Micron Sections of Epoxy Embedments
Authors: Ghidoni J. J. , Campbell M. M. , Adams J. G. , Thomas H. , Ramos E. E.
Published: June 2020

Adequately stained one-micron sections of epoxy embedments offer a convenient means of selecting appropriate blocks for electron microscopic study. In most instances extensive light microscopic study of an experimental model is prerequisite to intelligent electron microscopic study of tissues from the model and these preparations are an aid in making the cytologic and histologic transitions from light microscopy to electron microscopy. This communication presents a staining procedure which evolved empirically in our laboratory and has enhanced the utility of the one-micron section. The procedure is now used routinely for staining one-micron sections of tissue embedded in a Maraglas-D.E.R. 732-DDSA mixture.

The following procedure is carried out in Coplin jars set in 50°C water baths. More rapid staining can be obtained with more concentrated stain solutions used at higher temperatures; however, reproducibility is virtually lost.

5 min. in 2% Periodic acid at room temperature.

Rinse in water.

5 min. in 0.15% Basic Fuchsin in 50% ETOH at 50°C.

Rinse in water.

5 min. in methylene blue-azure II at 50°C.

Rinse in water and dry.

Coverslip.
Correspondence of Etch Pits and Dislocations in Silicon
Authors: Anderson L. J. , Barrett C. R. , Taylor T. A.
Published: June 2020

Etch pitting techniques have been extensively used to study both dislocation arrangements and densities in covalently bonded materials. In these investigations it is generally assumed that a one-to-one correspondence exists between etch pits and dislocations. In the course of the present work, which involved a study of dislocation arrangements in deformed silicon single crystals, it was observed that more than one dislocation can be associated with a single etch pit.

Silicon single crystals, oriented for single slip, were deformed in compression at temperatures near 900°C. Typical dislocation arrangements are illustrated in Figures 1 and 2. Figure 1 is an optical micrograph showing the etch pit arrangement on the (211) face (the operative slip plane is normal to this face and the slip direction is parallel to this face). This sample was etched with the standard Sirtl etchant for 60 seconds. The etch pits are generally well defined and their density can be readily measured. Figure 2 is a transmission electron micrograph showing the arrangement of dislocations in the (111) slip plane. The dislocations often occur as elongated loops or dipoles and multipoles.
Charged Particle Irradiation of Thin Metal Films
Authors: Merkle K. L.
Published: June 2020

Two of the main problems in the radiation damage in metals are the mechanisms of formation and the identification of defects that are produced due to the displacement of atoms from their regular lattice sites.

We are concerned here with the class of those defects that can be observed by transmission electron microscopy of thin films. At present this includes those clusters of vacancies and interstitials that are larger than about 10Å in diameter and smaller than the film thickness (≈1000 Å).

Thin expitaxially grown single-crystalline metal films have the advantage that the specimens can be observed before and after irradiation without being disturbed other than by the irradiation. Films of different orientations offer the possibility to study the anisotropy of the defects themselves as well as the anisotropies of the production of defects by a collimated beam of charged particles. Most important however is the use of thin films in the study of the energy dependence in irradiations with heavy charged particles in order to minimize the energy loss in the foil.
Development of High Resolution Electron Microscope, JEM-100B
Authors: Watanabe M. , Yanaka T. , Yamamoto M. , Suzuki S. , Nagahama Y. , Fujisawa U.
Published: June 2020

The JEM-100B electron microscope has been developed with a view to the possibility of obtaining an ultimate resolving power at a beam accelerating voltage of 100kev. Prom the very nature of the instrument, the stability is fully ensured from a mechanical and electrical point of view. In the electron optical system, since highly excited lenses are utilized, image formation under the lowest aberration condition are ensured. The image forming system is of the 4-stage type which greatly expands the range of application not only in microscopic studies but also in the study of electron diffraction. Furthermore, with a view to simplifying instrument operation, various problems have been solved this enabling the instrument to be fully automated. The JEM-100B exhibits the following features.

Objective Lens: At the present stage of development, fo=1.6mm. However, so as to be able to incorporate a lens (T. Yanaka et al, 1967) possessing an extremely small spherical aberration coefficient in the future, lens excitation has been made sufficiently high (8kA) and the movable aperture control knob and the specimen device have been designed accordingly.
A New Hot Stage for the Philips EM 200 and Its Calibration
Authors: Sprys J. W. , Gallagher P. C. J.
Published: June 2020

A hot stage for use in metallurgical investigations with the electron microscope should have several, if not all, of the following characteristics.

The specimen temperature should be measurable with accuracy over the full range of operation of the stage.

The stage should allow a large tilt angle for diffraction and contrast work.

The stage should not restrict expansion of the sample during temperature cycling thus avoiding alteration to the sample's defect structure from the presence of thermal stress.

The heater and sample should approach equilibrium rapidly after any change in temperature, with a minimum of drift during the change, and a high degree of stability at temperature.

The stage should permit study of as much of the thinned specimen area as is possible compatible with adequate thermal coupling to the furnace.
Preparation of Electron Transparent Metal-Matrix Composites
Authors: Pinnel M. R. , Lawley A.
Published: June 2020

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.

The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.
Etched Sodium Chloride Surfaces
Authors: Rosauer E. A. , Lingscheit J. N.
Published: June 2020

Treatment of a freshly-cleaved NaC1 surface with a solution containing 3 g HgCl2 per liter absolute ethanol results in typical inverted-pyramidal etch pits at the emergence points of dislocations. The pit sides are parallel to the [100] directions. There seems to be general agreement that crystal material at a dislocation emergence point has a higher dissolution rate than material at some distance from the emergence point. The role of the HgCl —the inhibitor—is not precisely understood; however, the literature suggests that the inhibitor is sorbed at certain sites near the emergence point and controls the rate of lateral and vertical dissolution. Since dissolution is the reverse of growth, removal of crystal material is thought to be on a monatomic scale.

In this study freshly-cleaved NaCl surfaces were treated for various periods of time (1-30 sec) with ACS absolute methanol and with absolute methanol containing various concentrations of NH4Cl (1-20 g/1). Freshly-cleaved NaCl crystals were held with tweezers and swirled in the etchant for the designated time period.
An Electron Gun Scanning Microscope
Authors: Crewe A. V. , Johnson D. , Isaacson M.
Published: June 2020

A simple scanning electron microscope has been built using a field emission electron gun. The gun is used alone, without the aid of auxiliary lenses, and is theoretically capable of producing a 100 Å probe with a beam current of 10-10 A. Such a beam current allows scan times of the order of a few seconds.

A schematic drawing of the microscope is shown in Fig. 2. The field emission voltage is applied to the first anode which controls the emission current. An accelerating voltage is applied to the second anode, and the field between the anodes focuses the electrons to form an image of the tip at the specimen. The angular spread of the beam is limited by an aperture on the second anode.
Computer-Controlled Scanning Electron Microscopy
Authors: MacDonald N. C.
Published: June 2020

In order to utilize more fully the potential of scanning electron microscopy, digital computers may be used to reduce, to correct, and to analyze micrographs. Toward this goal, a scanning electron microscope (SEM) has been connected to an IBM 1800 computer system. The computer not only processes the video information, but also generates the raster for the SEM. Digital signals generated by the computer are amplified and fed directly to the scan coils of the SEM and the monitor cathode-ray-tube (CRT). In this manner, a block of points, a raster, is produced on the specimen and the CRT. For each point in the raster generated by the computer, a sample of the video signal corresponding to the output of an appropriate detector (e.g., a secondary electron detector, light detector, etc.) is transmitted to the computer and subsequently stored in the computer memory. A certain amount of processing of the signals may be performed before the signals are sent to the computer. Subsequent processing of the signals such as corrections to the signal level may be programmed into the computer before the signal is stored. The process of generating a raster, of processing the signals, and of storing the signals in the memory results in a stored picture.
Voltage Contrast in Scanning Electron Microscopy
Authors: Kimoto S. , Hashimoto H. , Mase K.
Published: June 2020

In the study of such micro electronic devices as a transistor and an integrated circuit by using a scanning electron microscope the contrast of a secondary electron image reveals potential distribution on the surface of a specimen. The intensity of secondary electrons collected by a detector depends on the potential of the specimen surface because the yield of the secondary electrons is restricted by the surface potential and the trajectory of the secondary electrons from the specimen to the detector is disturbed by the field which is produced by the potential applied to the specimen. The relation between the contrast and the potential of the specimen surface varies according to instruments.

A simple specimen was used in order to obtain the relation. Two copper blocks with flat surfaces were arranged with a narrow gap of about 50 μ. One of them is electrically grounded and the other is variously biased. The intensity of the secondary electrons emitted from each block of the specimen was measured at the output of a photomultiplier of the detector.
Precipitation in Al + 4% Cu Epitaxial Films
Authors: Herd S. , Mader S. M.
Published: June 2020

Single crystal films in (001) orientation, about 1500 Å thick, were produced by R-F sputtering of Al + 4 wt % Cu onto cleaved KCl at 150°C substrate temperature. The as-deposited films contained numerous θ-CuAl2 particles (C16 structure) about 0.1μ in size. They were transferred onto Mo screens, solution treated and rapidly cooled (within about ½ min) so as to retain a homogeneous solid solution. Subsequently, the films were aged in vacuum at various temperatures in order to induce precipitation and to compare structures and morphologies of precipitate particles in Al-Cu films with those found in age hardened bulk material.

Aging for 3 weeks at 60°C or 48 hrs at 100°C did not produce any detectable change in high resolution micrographs or diffraction patterns. In this range Guinier-Preston zones (GP) form in quenched bulk material. The absence of GP in the present experiments in this aging range is perhaps due to the cooling rate employed, which might be more equivalent to an aged and reverted bulk material than to a quenched one.
Morphology of Amorphous Polymers
Authors: Lambert S.L. , Yeh G.S.Y.
Published: June 2020

Our general concept of the amorphous morphology of polymers is that of a structureless mass of coiled and intercoiled molecules. However, replica studies of freeze-fractured rubbers, amorphous polystyrene and polymethyl methacrylate and ion-etched glassy polycarbonate often suggest the presence of nodular structures (100-1000 Å) of unknown origin. Recently a nodular ball-like structure of the order of 100 Å was also observed in thin films of amorphous polyethylene terephthalate, its appearance being due to polymer molecules tending to back fold and arranging themselves more or less parallel to one another.

We have extended these studies to several other polymers including amorphous and crystallizable polystyrene and polymethyl metha-crylate, trans- and cis-polyisoprene, polyphenylene oxide, etc. and have observed similar ball-like structures (Figs. 1 and 2). The size of these structures may vary from polymer to polymer (30-100 Å), however for a given polymer no substantial size variation has been observed with respect to preparation conditions, e.g., temperature, solvent and molecular weight.
Techniques to Study Devitrification in Glass Systems Using Electron Microscopy and Diffraction
Authors: Tufts Charles F.
Published: June 2020

Adequate description of crystalline states in glass systems should include information about geometry, structure and perfection of crystals less than 1000Å in size. Such information can be obtained by analyzing thin sections (<2000Å thick) using transmission electron diffraction-contrast microscopy (TEDCM) and selected area electron diffraction (SAED). If surfaces can be prepared that represent bulk character, reflection electron diffraction (RED) should be employed as a supplementary tool. Preparation of thin glass sections and surfaces by chemical methods usually introduces serious artifacts. The techniques described here use surfaces produced by fracture in inert gas and are applicable to the study of various glasses and ceramics.

The specimen is fractured in a dry box containing an inert gas such as nitrogen or argon with dew point lower than -50°C. The specimen is protected at all times by the gas when not under vacuum. After fracture, the specimen is moved to an electron diffraction camera filled with flowing inert gas until evacuated for analysis.
Electron Microscopy of Precious Opal
Authors: Amaral Eugene J. , Rau Robert C.
Published: June 2020

Replica and transmission electron microscopy have been used to study the microstructure of precious opal. This mineral is an amorphous silica which is often prized as a gemstone because of its vivid display of iridescent colors when viewed in visible light. For the present study, specimens were examined in fractured, polished, and etched conditions.

As shown in the figures, precious opal consists of many tiny silica spheres, of essentially uniform diameter, that have been deposited in an orderly array before silica cementation. Regularly spaced interstitial voids resulting from the ordered packing serve as a three dimensional diffraction grating for visible light, thus giving rise to the characteristic play of colors. The separation of the voids is controlled by sphere diameter, and determines the maximum wavelength of visible light diffracted. Thus specimens consisting of larger spheres diffract higher order colors (longer wavelengths) than specimens consisting of smaller spheres. For example, the specimen shown in Fig. 1 contained spheres of approximately 2700 Å diameter and diffracted all visible colors up through red, while the specimen shown in Fig. 2 contained spheres of approximately 2000 Å diameter and diffracted only blues and greens.
Ruthenium red-osmium bridging with TCH: new technique to stain biological specimens for light and TEM and to coat them for SEM
Authors: Giammara B. , Hanker J.
Published: June 2020

The demonstration and coating of glycomacromolecular surface coat components of biological specimens (1) with ruthenium red (RR, Fig. 1) is improved by treating with osmium tetroxide (2) probably due to its attachment to glycolipids. Since 1966 studies have shown how bridging osmium to osmium with thiocarbohydrazide (TCH, Fig. 2) can result in improvement in contrast of biological specimens (3,4) for light and electron microscopy. Since 1973 this bridging procedure has widely been applied (5,6) to obtain a conductive coating for biological specimens for SEM eliminating the need for sputter coating. Improvement in conductance of uncoated specimens for EM has also been obtained (6) by bridging osmium with p-phenylenediamine hydrochloride (PPD). The improvement in conductance of RR coated biological specimens for SEM by OsO4treatment without TCH (2) required repeated application of the reagent solutions and did not result in sufficient staining of the glycomacromolecules and glycolipids for the light microscopic selection of areas for electron microscopic study.
In vivo confocal imaging of the eye using tandem scanning confocal microscopy (TSCM)
Authors: Jester J. V. , Cavanagh H. D. , Lemp M. A.
Published: June 2020

New developments in optical microscopy involving confocal imaging are now becoming available which dramatically increase resolution, contrast and depth of focus by optically sectioning through structures. The transparency of the anterior ocular structures, cornea and lens, make microscopic visualization and optical sectioning of the living intact eye an interesting possibility. Of the confocal microscopes available, the Tandem Scanning Reflected Light Microscope (referred to here as the Tandem Scanning Confocal Microscope), developed by Professors Petran and Hadravsky at Charles University in Pilzen, Czechoslovakia, permits real-time image acquisition and analysis facilitating in vivo studies of ocular structures.

Currently, TSCM imaging is most successful for the cornea. The corneal epithelium, stroma, and endothelium have been studied in vivo and photographed in situ. Confocal scanning images of the superficial epithelium, similar to those obtained by scanning electron microscopy, show both light and dark surface epithelial cells.
Ruthenium red and alcian blue effects on outer structures of methanotrophic bacteria
Authors: Fassel T.A. , Schaller M.J. , Remsen C.C.
Published: June 2020

Methane, a contributor to the “greenhouse effect”, is oxidized in the natural environment by methanotrophic bacteria. As part of a comprehensive research effort, we have been examining the ultrastructure of methanotrophs. These microorganisms have complex outer cell wall structures similar to those frequently found in other chemol itho- trophic bacteria. (1,2)

In our work, we have focused on the “type” strains of Methylomonas albus BG8 and Methylosinus trichosporium OB3b. Between Spurr and LR White embedding resins, we found a difference 1n the preservation of an outer cup layer of BG8 external to the peripheral membranes. Cells from the same sample embedded in Spurr consistently lacked this feature (FIG. 1). This effect was overcome by an en bloc ruthenium red (RR) protocol that resulted in successful retention of the cup layer in Spurr resin (FIG. 2). For OB3b cells, the en bloc RR protocol resulted in an exterior bead feature distinguishable in thin section (FIG. 4) that previously was seen only by SEM.
The use of thick sections with transmission electron microscopy in combination with scanning electron microscopy to study the attachment of Neisseria gonorrhoeae to vero cells infected with Chlamydia trachomatis
Authors: Pontrefract R. D. , Ng C. W. , Ashton E. E. , Bergeron G.
Published: June 2020

Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) are well known pathogens associated with sexually transmitted disease. Clinical studies have shown that these organisms are frequently found together, and it has been suggested that gonorrhoeae be used as a marker for chlamydial infections. The reason for the high rates of co-infection is not known. However, in vitro studies (Ng et al. manuscript in preparation) have shown that the adsorption of NG to Vero cells pre-infected with CT is increased at least twenty times compared with that obtained with non-infected cells. In order to determine the areas of attachment and the fine structure of the attachment sites of the gonococci to the CT infected Vero cells, both transmission electron microscopy (TEM) using thick (0.25-0.5μm) sections and scanning electron microscopy (SEM) were used.

To prepare samples for TEM, Vero (African green monkey kidney) cells were grown in T-flasks for 48h in M199 + 10% fetal calf serum at 37C in an atmosphere containing 5% CO2.
GACH-prepared specimens for sem and confocal reflected light microscopy
Authors: Crang R. E. , Thompson B.
Published: June 2020

Biological specimens prepared for SEM are difficult to observe in detail by means of light microscopy. Conventional epi-illuminescence produces relatively poor images with reflected light due to poor contrast and multiple scattering of the light (1). However, we have found that mammalian tissue culture cells prepared for SEM by means of the co-polymerized glutaraldehyde-carbohydrazide (GACH) technique (2), can be alternately observed by means of SEM and reflected light microscopy if the light optical instrument is a confocal tandem scanning microscope (TSM). The images produced with TSM show resolution comparable to that of the SEM at magnifications ≤ 1,000 X. Furthermore, due to the extremely small depth of focus containing high contrast and brightness, optical sections can be produced which bear detail similar to that in conventional TEM observations.

Fibroblasts and myotobes, from newborn rat hindlimb muscles were grown in Eagle's minimum essential medium with 10% fetal calf serum on collagen- coated glass cover slips for a period of 7 d (3).
Optical studies on the development of the focal contact
Authors: Izzard C.S.
Published: June 2020

The focal contact is a localized region of relatively strong adhesion formed between cultured fibroblasts and planar substrates. The contact can be visualized and its formation followed in the live cell by the use of high illuminating-numerical-aperture interference reflection microscopy (IRM). The focal contact is the site into which stress fibers, or bundles of microfilaments, insert at the plasma membrane via a patch of amorphous material, the adhesion plaque. Through the use of immunochemical staining, a number of proteins have been shown to be concentrated at the focal contact/adhesion plaque complex. However, little is known about the sequence of events at the structural and protein levels that result in formation of the focal contact/adhesion plaque complex. We demonstrated previously that the focal contact forms rapidly as a stable adhesion beneath the motile lamellipodium at the cell margin. Parallel IRM and differential interference contrast (DIC)observations further showed that the contact forms specifically beneath a rib-like structure in the lamellipodium, which therefore functions as a precursor of the focal contact.
Analysis of the Mechanism of Microtubule Dynamic Instability Using a UV Microbeam to Sever Elongating Microtubules
Authors: Walker R.A , Inoue S. , Salmon E.D.
Published: June 2020

Microtubules polymerized in vitro from tubulin purified free of microtubule-associated proteins exhibit dynamic instability (1,2,3). Free microtubule ends exist in persistent phases of elongation or rapid shortening with infrequent, but, abrupt transitions between these phases. The abrupt transition from elongation to rapid shortening is termed catastrophe and the abrupt transition from rapid shortening to elongation is termed rescue. A microtubule is an asymmetrical structure. The plus end grows faster than the minus end. The frequency of catastrophe of the plus end is somewhat greater than the minus end, while the frequency of rescue of the plus end in much lower than for the minus end (4).

The mechanism of catastrophe is controversial, but for both the plus and minus microtubule ends, catastrophe is thought to be dependent on GTP hydrolysis. Microtubule elongation occurs by the association of tubulin-GTP subunits to the growing end. Sometime after incorporation into an elongating microtubule end, the GTP is hydrolyzed to GDP, yielding a core of tubulin-GDP capped by tubulin-GTP (“GTP-cap”).
Localization of Surfactant Phospholipids in the Peritoneal Mesothelium
Authors: Lloyd J. K. , Dobbie J. W. , Hauck W. N. , Manning K. A.
Published: June 2020

The peritoneum consists of a monocellular layer of mesothelium supported by fibrous connective tissue of variable thickness. This tissue covers the walls of the abdominal cavity (parietal) and the surfaces of the abdominal organs, omentum and mesentery (visceral). A recent study has shown that the mesothelium synthesizes phosphatidylcholine which is the principle constituent of pulumonary surfactant phospholipids (1). Pulmonary surfactant is synthesized by Type II pneumocytes and stored in cytoplasmic structures called lamellar bodies. Tannic acid fixation has been shown to enhance preservation of these lamellar bodies (2). In the present study, samples of peritoneum from mice were prepared by tannic acid fixation and examined.

CF1 mice were injected intraperitoneally with 1% tannic acid in a 2% glutaraldehyde solution (Sorensen's phosphate buffer). Tissues from the parietal peritoneum (anterior abdominal wall) and mesentery were removed and placed in the tannic acid/glutaraldehyde solution for 24 hours at 4°C. Tissues were post-fixed in 1% osmium tetroxide and embedded in Spurr.
Lung Parenchymal Response to Amosite Asbestos and Cigarette Smoke Exposure
Authors: Gray L. D. , Brady D. E. , Ford Joan O.
Published: June 2020

Asbestos exposure in humans has been associated with a variety of debilitating and potentially fatal conditions including lung fibrosis, mesothelioma and lung cancer. Persons who have been exposed to asbestos and who also smoke cigarettes are at far greater risk of developing lung cancer than individuals who either smoke or are exposed to asbestos alone. The mechanisms of this synergistic effect are poorly understood at present and it is important that they be studied because many (if not most) individuals who occupationally work with asbestos also smoke cigarettes.

The purpose of the present study was to investigate the parenchymal reaction to asbestos and smoke exposure in an animal model and to clarify the roles of epithelial cells and phagocytes in the ensuing pathologic response.

Male Hartley outbred guinea pigs approximately 700 g each were divided into groups of 8 animals as follows. One group was exposed to 4 cigarettes per day, 5 days per week for a total of 8 weeks.
The Orientation of Sickle Hemoglobin Fibers Within Bundles as Determined by Correspondence Analysis
Authors: Lee T. E. , Carragher B. , Watowich S. J. , McDade W. A. , Josephs R.
Published: June 2020

Sickle cell anemia results from the polymerization of deoxygenated sickle hemoglobin (HbS) into long helical fibers. In red blood cells, and in vitro, fibers aggregate and align to form bundles which eventually crystallize. The fiber bundles distort the red cells and have been implicated in the catalysis of the polymerization reaction. Although the structure of the HbS fiber has been extensively investigated, the packing of fibers in bundles and the fiber rearrangements which accompany crystallization are poorly understood, even though these phenomena are of interest at both a clinical and a basic level. We have used correspondence analysis to establish that during crystallization fibers separate into rows of particles oriented in opposite directions.

Axial projections in opposite directions down the HbS fiber are different and are related by mirror symmetry. Thus they can be used to determine the particle orientation in or out of the plane of projection. Figure 1 shows these projections for models of an HbS fiber.
3-D Structure of Negatively Stained Chromatin Fibers
Authors: Woodcock C.L. , McEwen B.F
Published: June 2020

In the eukaryotic nucleus, DNA is packaged into nucleosomes, and the nucleo- some chain folded into '30nm' chromatin fibers. A number of different model structures have been proposed for the arrangement of nucleosome within the fiber1 and most of these are based on helical symmetry. Indications of helical order have been observed over short regions of fiber but the structure is too disordered to allow reconstruction by Fourier methods. We have used tomography, an approach developed for asymmetric specimens, to prepare 3D reconstructions of chromatin fibers.

Nuclei from Necturus maculosus erythrocytes were briefly digested with micrococcal nuclease, and the released chromatin fibers fixed with 0.1% gluta- raldehyde, and stained with 1.5% sodium phosphotungstate pH 7.0 containing 0.015. glucose. Tilt series were taken at 5° intervals from +70° to -70° using a Philips 420 EM at 100KV and 30,000x magnification. Straight regions of fiber showing indications of internal order were digitized with a pixel size of l.lnm, reconstruction carried out as described, and the final 3D data sets filtered to a resolution of 3.5nm.
Electron Beam Profile in the ESEM
Authors: Danilatos G. D.
Published: June 2020

The examination of specimens in the presence of gas in the environmental scanning electron microscope (ESEM) requires the electron beam to pass through a minimum (optimum) 1ayer of gas before it strikes the specimen. The electron scattering by the gas molecules results in a modification of the original beam profile. Some conclusions from a study on these profiles are presented here but more details can be found elsewhere.

When an electron beam travels a distance L through a gas with n particles per unit volume, the average number of collisions per electron m= σ⊤nL, where σ⊤ is the characteristic total collision cross section for the gas. The electron beam collision process is described by the Poisson distribution P (x) =mx e-m/X!, where P(x) is the probability that an electron undergoes x number of collisions (X=0, 1 ,2. . . ) . Thus, when m=1 , about 37% of electrons undergo no collisions, 37% undergo a single collision, 18% two collisions, 6%. three collisions etc.
Backscattered Electron Imaging of GaAs/AlGaAs Super Lattice Structures with an Ultra-High- Resolution SEM
Authors: Ogura Kazumichi , Kersker Michael M.
Published: June 2020

Backscattered electron (BE) images of GaAs/AlGaAs super lattice structures were observed with an ultra high resolution (UHR) SEM JSM-890 with an ultra high sensitivity BE detector. Three different types of super lattice structures of GaAs/AlGaAs were examined. Each GaAs/AlGaAs wafer was cleaved by a razor after it was heated for approximately 1 minute and its crosssectional plane was observed.

First, a multi-layer structure of GaAs (100nm)/AlGaAs (lOOnm) where A1 content was successively changed from 0.4 to 0.03 was observed. Figures 1 (a) and (b) are BE images taken at an accelerating voltage of 15kV with an electron beam current of 20pA. Figure 1 (c) is a sketch of this multi-layer structure corresponding to the BE images. The various layers are clearly observed. The differences in A1 content between A1 0.35 Ga 0.65 As, A1 0.4 Ga 0.6 As, and A1 0.31 Ga 0.69 As were clearly observed in the contrast of the BE image.
High-Resolution, Low-Voltage SEM of Cell Wall Regeneration of Yeast Shizosaccharomyces Pombe Protoplasts
Authors: Osumi M. , Yamada N. , Nagatani T.
Published: June 2020

Even though many early workers had suggested the use of lower voltages to increase topographic contrast and to reduce specimen charging and beam damage, we did not usually operate in the conventional scanning electron microscope at low voltage because of the poor resolution, especially of bioligical specimens. However, the development of the “in-lens” field emission scanning electron microscope (FESEM) has led to marked inprovement in resolution, especially in the range of 1-5 kV, within the past year. The probe size has been cumulated to be 0.7nm in diameter at 30kV and about 3nm at 1kV. We have been trying to develop techniques to use this in-lens FESEM at low voltage (LVSEM) for direct observation of totally uncoated biological specimens and have developed the LVSEM method for the biological field.
Application of Low-Voltage SEM in the Analysis of Complex Intracellular Structures
Authors: Ris H.
Published: June 2020

In 1986 the Madison IMR acquired a Hitachi S-900 LVSEM and I became interested in exploring whether it could help in the analysis of threedimensional structures where thin and thick sections had failed. The question was not whether cytoplasmic structures known from TEM were visible by SEM, but whether LVSEM could provide unique information that was not supplied by other means. In a study of intracellular transport of pigment granules in xanthophores of the goldfish, HVEM pictures of the thin edge of cells had shown that the carotenoid granules were attached to intermediate filaments (IF). But it was impossible to see this relationship in the interior of cells either in whole mounts or in thick sections. To see internal structure with SEM, the cell has to be cracked open without causing distortions. We found two simple methods that gave useful results: 1.Dry-cleaving.
Low-Voltage Scanning Electron Microscopy Investigation of Polymers
Authors: Berry V. K.
Published: June 2020

The morphological characterization of any polymer blend plays an important part in the development of a new blend system because the properties of blends are dictated by phase morphology which is dependent upon the chemistry and the processing conditions. Light microscopy, scanning electron microscopy and transmission electron microscopy are the most commonly used microscopical techniques for morphological characterization. Transmission electron microscopy techniques provide the best resolution (≈ 0.3 nm) but are limited in the size of sample area and require elaborate sample preparation procedures. Surface charging and beam damage problems have been some of the drawbacks of conventional scanning electron microscopy with non-conducting materials like polymers.

The use of low accelerating voltage scanning electron microscopy (LVSEM) in the characterization of polymers and other non-conducting materials is beginning to be recognized.
Ligand-Induced Clustering of the LDL Receptor in the Absence of Coated Pits
Authors: Anderson Richard G. W. , Donzell William C. , Larkin Janet M.
Published: June 2020

A remarkable feature of the LDL receptor in human fibroblasts is that in the absence of ligand there is a preferential clustering of the receptor over clathrin-coated pits. The physiologic significance of this distribution was made apparent when it was discovered that certain mutations localized to the cytoplasmic tail of the LDL receptor resulted in the receptor being randomly distributed on the cell surface and unable to efficiently internalize LDL. These results raise the questions of what determinants in the coated pit are responsible for receptor clustering and whether the receptor is able to cluster in the absence of coated pits. Although the answer to the first question is still not known, we've been able to address the second question by utilizing a method for removing the coated pits in situ. This method depends upon the observation that when human fibroblasts are depleted of intracellular K+, coated pits disappear from the cell surface.
High-Vacuum Evaporation and a Cryostage to Observe Fractured Yeast
Authors: Wergin William P. , Erbe Eric F. , Vigil Eugene L.
Published: June 2020

Investigators have long realized the potential advantages of using a low temperature (LT) stage to examine fresh, frozen specimens in a scanning electron microscope (SEM). However, long working distances (W.D.), thick sputter coatings and surface contamination have prevented LTSEM from achieving results comparable to those from TEM freeze etch. To improve results, we recently modified techniques that involve a Hitachi S570 SEM, an Emscope SP2000 Sputter Cryo System and a Denton freeze etch unit. Because investigators have frequently utilized the fractured E face of the plasmalemma of yeast, this tissue was selected as a standard for comparison in the present study.

In place of a standard specimen holder, a modified rivet was used to achieve a shorter W.D. (1 to -2 mm) and to gain access to the upper detector. However, the additional height afforded by the rivet, precluded use of the standard shroud on the Emscope specimen transfer device. Consequently, the sample became heavily contaminated (Fig. 1). A removable shroud was devised and used to reduce contamination (Fig. 2), but the specimen lacked clean fractured edges. This result suggested that low vacuum sputter coating was also limiting resolution.
Effects of Heat Shock on Nucleolar Organization in Tobacco Cells
Authors: Yen Y. H. , Chen Y. R.
Published: June 2020

In the previous study, supraoptimal and lethal temperatures affected on the structure of cell organelles in root meristematic cells of soybean were reported(l). In the present study, nucleolar organization in cultured cells responsing to heat shock will be invastigated.

Suspension culture cells of tobacco(Nicotiana tobaccumW 38) growing in MS medium containing 1 ppm 2,4-D and 1 ppm kinetin were divided into several groupes and incubated as follow: 1), 28°C(2h); 2), 38°C(2h); 3), 42°C(2h); 4), 45°C(2h); 5), actino- mycin D(2 ug/ml, 3h). After incubation, cells were collected, fixed in 3% glutaraldehyde, post-fixed in 1% osmic tetraoxide, dehydrated in ethanol series and embedded in Spurr's resin. Thin sections were collected on formvar-supported grids and stained with uranyl acetate and lead citrate. Silver-staining adopted the method of Medina et al.(2) and sample were prefixed in 3% glutaraldehyde, post-fixed in Carnoy's solution, and then impregnated with silver by 2-step method.
Application of Polyethylene Glycol (PEG) Embedding and Rotary-Replication Techniques to the Study of Photoreceptor Synaptic Ribbon Ultrastructure
Authors: Dickson D. Howard , WhitefieLd Stephan C. , Morrison Christine A.
Published: June 2020

Synaptic ribbons (SRs) are electron-dense, LameLLar specializations found in the retina, inner ear and pineal. Although it has been suggested that SRs may have a functional role in the maintenance of synaptic terminal shape or in orienting synaptic vesicles to the presynaptic membrane neither hes been confirmed. Their intimate association with synaptic vesicles has however supported the Latter hypothesis. Controversy also exists with respect to diurnal rhythmicity of these organelles. Recently, a major advance in our knowledge of SR structure was achieved through the application of freeze-slamming and freeze-substitution techniques. However, the cost and complexity of these techniques, together with the Limitations imposed by freezing rate and ice-crystal damage has Led us to explore the use of the PEG-embedding technique to further our study of SRs in retina and pineal.

Chick retinas were prepared following the technique of Kondo. Tissues were fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer containing 0.5% tannic acid at pH 7.4 for 2 hr, washed in buffer and postfixed in 1% OsO4 for 1 hr.
Biological Control of Postharvest Diseases of Fruit: Inhibition Of Botrytis Rot On Apple by an Antagonistic Yeast
Authors: Wisniewski M. , Wilson C. , Chalutz E. , Hershberger W.
Published: June 2020

As an alternative to fungicides, biological control of postharvest diseases of fruit has recently met with good success with peaches and apples and is an area of great potential. In contrast to previous study, we were particularly interested in finding antagonists that did not produce antibiotics as part of their mode of action. After extensive screening, several yeast and bacteria were identified that exhibited biocontrol of a number of postharvest disease organisms. In particular, the yeast, Debaryomyces hansenii, indicated great potential as a biocontrol agent without exhibiting antibiotic production as a mode of action. It has been recently shown to effectively control decay on citrus caused by Penicillium digitatum, Penicilliim italicum and Geotrichum candidum. The present report is the first to document the use of D. hansenii to control postharvest decay of apples by Botrytis cinerea and present possible inodes of action.

To test for biocontrol activity, apples (cv Golden Delicious) ware wounded with a 4 nm cork borer to a depth of 5 mm.
Microscopy studies of Tilletia controversa teliospore development in wheat ovaries and in culture
Authors: Hess W. M. , Trione E. J.
Published: June 2020

Teliospore formation begins in wheat ovaries when they are about 0.5 mm diam. Tilletia controversa hyphal cells initially invade host cells intercellularly. During development a narrow band of sporogenous hyphal cells develop into reticulated teliospores without hyphal attachments. The host tissue is utilized in the formation of mature teliospores. Eventually a thin layer of host tissue surrounds the mature teliospores. In contrast, when the teliospores form in medium hyphal tips appear to enlarge into developing teliospores. Light microscopy, SEM, and thin sections with TEM were used to determine whether teliospores formed from enlarged hyphal tips or from sporogenous cells which fragment from hyphae.

Teliospores were obtained from USDA ARS experimental plots at Logan, UT. Wheat plants were inoculated and grown in a greenhouse. Tissues were fixed for 1 h or longer in 2% glutaraldehyde, 3% acrolein, 0.1 M Na-cacodylate buffer, pH 7.3; rinsed several times in the same buffer; postfixed in 1% OsO4 in 0.1 M Na-cacodylate buffer, pH, 7.3 for 2 h in an ice bath; and rinsed in 0.1 M Na-cacodylate buffer prior to dehydration in a graded ethanol series.
The distribution of calcium and magnesium in developing tobacco leaves as measured by low-temperature X-ray microanalysis
Authors: Echlin Patrick
Published: June 2020

The processes of leaf maturation and senescence are linked closely to the redirection of ions and organic nutrients between leaves and other part of the plant. It is known from work on whole leaves, that Ca2+ and Mg2+ play an important role in leaf development, although no studies have been made of changes at the cell and tissue level. This present study follows the cellular changes in Ca2+ and Mg2+ in the epidermal and photosynthetic tissues by X-ray microanalysis of frozen hydrated leaves.

Full details of sample preparation, instrumentation, and the basis of the quantitative procedures have been reported elsewhere. Flat, frozen hydrated fracture faces of upper and lower epidermis; palisade and spongy mesophyll cells were analysed for Ca2+ and Mg2+. Data was collected from each of the four cell types in 20 different leaves at each of the following five stages of growth. Juvenile (10 weeks from seed); Mature (13 weeks), Ripe (16 weeks), Senescent (19 weeks) and Old (21 weeks). Cells containing obvious calcium oxalate crystals were avoided.
High-voltage electron microscopy of maxillary gland of spirochete-infected brine shrimp: lesion of efferent tubule
Authors: Tyson G. E. , Song M. J.
Published: June 2020

Natural populations of the brine shrimp, Artemia, may possess spirochete- infected animals in low numbers. The ultrastructure of Artemia's spirochete has been described by conventional transmission electron microscopy. In infected shrimp, spirochetal cells were abundant in the blood and also occurred intra- and extracellularly in the three organs examined, i.e. the maxillary gland (segmental excretory organ), the integument, and certain muscles The efferent-tubule region of the maxillary gland possessed a distinctive lesion comprised of a group of spirochetes, together with numerous small vesicles, situated in a cave-like indentation of the base of the tubule epithelium. in some instances the basal lamina at a lesion site was clearly discontinuous. High-voltage electron microscopy has now been used to study lesions of the efferent tubule, with the aim of understanding better their three-dimensional structure.

Tissue from one maxillary gland of an infected, adult, female brine shrimp was used for HVEM study.
Indirect immunogold labeling of methanol dehydrogenase in a methanotrophic and a methylotrophic bacterium
Authors: Fassel T.A. , Buchholz L.A. , Lidstrom M.E. , Schaller M.J. , Remsen C.C.
Published: June 2020

Methanol dehydrogenase (MDH), is used by methanotrophic and methylotrophic bacteria to oxidize methanol to formaldehyde. (1) The enzyme is thought to exist both in a soluble form and in association with membrane. (2) Antisera prepared againstMethylomonas albusBG8 MDH andMethylobacteriumsp. strain AM1 MDH was used in an indirect Immunogold procedure to demonstrate localization of MDH. Following a modification of the method of De Mey (3), thin sections were incubated with primary antibody before exposure to gold-labeled secondary antibody.

BG8, an obligate methanotroph, grows on methane and converts it to methanol. Methanol is then further oxidized by MDH to formaldehyde. A distinguishing feature of BG8 are extensive Intracytoplasmlc membranes (ICM) that form bundles or vesicular stacks located away from the peripheral membranes and extending into the cytoplasm (Fig. 1). (4) It is theorized that MDH is associated with ICM.