bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopy analysis of grain boundaries in a crept oxide dispersion strengthened alloy
Authors: Koo J. Y. , Smith P. , Petkovic-Luton R.
Published: June 2020

The evolution of grain boundary microstructures has been characterized of a Fe-base oxide dispersion strengthened (0DS) alloy crept at stress substantially less than the threshold stress for dislocation creep. The alloy used for the present study was 0DS MA 956 (Fe-20Cr-5Al-0.5Ti-0.5 Y2O3) with a coarse-elongated grain structure. A bicrystal creep sample with the grain boundary inclined about 45° to the applied stress axis was cut from the coarse grained polycrystall ine bar. Creep test was performed at 1100°C with the stress of 21 MPa. The test was interrupted after 18,000 hours for microstructural investigation. The samples for TEM examination were obtained by cutting a thin slice from the gauge section parallel to the stress axis, followed by grinding, jet polishing, and etching and ion milling (when needed) the 3 mm disc containing a segment of the grain boundary. Microstructural analysis was carried out using Philips 400 TEM/STEM equipped with FEG.
Molybdenum solubility differences in MC phases formed in titanium and niobium modified austenitic stainless steels determined using AEM
Authors: Maziasz P. J.
Published: June 2020

Molybdenum is added to improve elevated temperature strength and corrosion resistance for type 316 compared to type 304 stainless steel. Strong carbide forming elements, like titanium and niobium, are also added to these steels to improve creep strength and reduce stress corrosion cracking, as well as to improve resistance to irradiation induced swelling and helium embrittlement. This work shows that fairly pure TiC and NbC form in Ti- and Nb- stabilized versions of type 304 stainless steel (types 321 and 347, respectively); however, the Ti-rich MC dissolves Mo considerably whereas the NbC remains compositionally quite pure when these phases form in Ti- and Nb- modified type 316 stainless steels, respectively.
Microcrystallography and chemical microanalysis of polycrystalline Nb3Sn superconductors
Authors: Taftϕ J. , Sabatini R. L. , Suenaga M.
Published: June 2020

Polycrystalline Nb3Sn is a superconductor with a high superconducting temperature, 18 K. The material can withstand a high magnetic field which makes it especially useful in strong superconducting magnets for magnetically confined fusion reactors and high energy particle accelerators. Several metallurgical factors influence the superconducting properties of Nb3Sn, e.g. grain size, compositional inhomogenities and small amounts of alloying elements. We have used a 100 keV analytical electron microscope (AEM) to detect the characteristic x rays (EDS) in order to study spatial composition variations, and to locate alloying elements in the crystal unit cell using ALCHEMI (Atom Location by Channeling Enhanced Microanalysis).
Bend contours and KM zone-axis patterns maps from aluminum
Authors: Silva E. , Riquelme J.
Published: June 2020

Zone axis patterns maps from pure Aluminum have been obtained using two kinds of crystallographic contrast technique in TEM: bend contours (BCP) and Kossel-Mollenstedt (KMP) patterns. Observations of zone axis patterns on the BCP map enable to carry out orientations determination accurately and directly in the image plane. Both kinds of map were assembled from a large number of micrographs taken at 100 kV on Philips EM 300 microscopes using double-tilt specimens holder to set up suitable regions in various orientations. BCP were obtained with conventional objective lens whereas for KMP convergent beam illumination was required.
Overview of industrial machine vision
Authors: Mandeville Jon R.
Published: June 2020

One hardly needs to emphasize the importance of visual sensing and interpretation in our everyday lives and the severe limitations and handicaps imposed on the blind. The importance of human vision has motivated an intense interest in and significant research on artificial vision systems over the last 20 years. The relatively new, fast growing discipline of “machine (or computer) vision” is an outgrowth of this research.

Machine vision is computation on images to produce useful, meaningful descriptions of a visual environment. A machine vision system may be used either as a symbiotic enhancement to human vision or as the perceptual component of an autonomous, goal-driven computational system capable of cognitive processing.
Plasmon energy and chemical composition of amorphous SiX C1-X:H
Authors: Sabatini R. L. , Taftϕ J. , Kampas F. J. , Rajeswaran G.
Published: June 2020

Using a TEM equipped with an electron energy loss spectrometer (EELS) the plasmon energy, Ep of a material can easily be determined for specimens of thickness up to a few thousand Å. This coincides with the film thicknesses encountered in thin film technology, e.g., amorphous solar cells. Ep is to the first approximation proportional to the square root of the valence electron density, and is thus sensitive to the chemical composition and the density of a material. Ep measurements using EELS have therefore the potential of being a convenient way of characterizing a material, as has been demonstrated for hydrogenated metals, and this could be particularly useful for amorphous materials where characterization techniques such as x-ray and electron diffraction are of limited value.
Microstructural development of protective A12O3 scales
Authors: Smialek James L.
Published: June 2020

The most severe demands of a jet turbine engine in terms of high temperature (1000-1100°C) oxidation of superalloys have been successfully met with the use of NiCrAlY or NiAl types of coating materials. The success of these coatings is due to their ability to form an adherent slow-growing scale of α-Al2O3. The growth mechanism of these scales is generally accepted to be short-circuit grain boundary diffusion of oxygen resulting in an inward growing scale. Oxide-metal adherence is ultimately due to a fine dispersion of oxygen active elements (Y, Zr, Hf, Th, etc.) in the coating, whose effect appears to be intricately involved with subtle changes in scale growth processes. The present paper documents the scale microstructures developed on NiCrAl alloys, and emphasizes features relevant to growth mechanisms.
Localization of adenylation site on glutamine synthetase ofE. coliby immunoelectron microscopy and image averaging
Authors: Wagenknecht T. , Bronstein G. , Frank J. , Frink R. , Eisenberg D. , Glitz D.
Published: June 2020

The glutamine synthetase (GS) from E. coli is a donut-shaped molecule comprising 12 identical subunits arranged in two opposing hexameric layers (dihedral D6 symmetry). In one mode of regulating enzymatic activity, each of the subunits is subject to adenylation at a specific tyrosine residue. A previous study used the technique of immunoelectron microscopy to map the position of adenylation on the surface of the molecule. We describe here a refinement of the analysis be means of computerized single particle averaging methods.

Electron micrographs were digitized with a .78 nm sampling distance and images of GS in the six-fold orientation were selected and brought into mutual alignment by correlation methods. The images were divided into two classes depending on whether or not an antibody was visible at the periphery of the molecule. Selected examples of control and antibody-labeled molecules are shown in Fig. la,b respectively.
Ultrastructural study of a granular cell tumor from forearm
Authors: Sun C.N. , Shaefer R.
Published: June 2020

Granular cell tumors are frequently reported in different body locations. Some authors believed it to be a neoplasm derived from skeletal muscle and others propose the origin of these lesions are from fibroblasts, histocytes, mesenchymal cell, neuron or Schwann cells. So far the tumor cells origin is still controversial. The purpose of this report is to present a case showing the cellular fine structures and to propose a possible origin of the tumor cells.

A tumor mass (5 x 3 cm) from the left forearm of a 49 year old white male was removed, cut into small pieces (about 1 mm3), immediately fixed in 4 percent glutaraldehyde in phosphate buffer for 2 hours, and then post fixed in 1 percent buffered osmium tetroxide for 1 hour. After dehydration, tissues were embedded in Epon 812.
Ultrastructural studies on fish microsporidians
Authors: Morrison C.M. , Sprague V. , Hoffman G.L. , Marryatt V. , Gray B.
Published: June 2020

During our studies of fish microsporidia, we have been lucky enough to encounter the three genera which occur most commonly in fish; Glugea, Loma and Pleistophora. All form whitish nodules containing vegetative and spore-forming stages of the parasite. In Glugea and Loma these stages are contained within a hypertrophied host cell. In Glugea most of the vegetative stages are at the periphery of the nodule, and groups of 16 spores form in sporophorous vesicles limited by thin membranes. In Loma vegetative and spore-forming stages are mixed in the nodules, and only 1-2 spores are found in each sporophorous vesicle. In Pleistophora the stages are again mixed, with large groups of spores forming in sporophorous vesicles each surrounded by a thick pansporoblast membrane which persists in squash preparations, so that the spores appear to be in “packets”. The nodules are often surrounded by host fibroblasts, and are sometimes invaded by macrophages.
Reversal of cardiomyopathy resulting from prenatal exposure to ethanol
Authors: Uphoff C. , Nyquist-Battie C.
Published: June 2020

Fetal Alcohol Syndrone (FAS) is a syndrome with characteristic abnormalities resulting from prenatal exposure to ethanol. In many children with FAS syndrome gross pathological changes in the heart are seen with septal defects the most prevalent abnormality recorded. Few studies in animal models have been performed on the effects of ethanol on heart development. In our laboratory, it has been observed that prenatal ethanol exposure of Swiss albino mice results in abnormal cardiac muscle ultrastructure when mice were examined at birth and compared to pairfed and normal controls. Fig. 1 is an example of the changes that are seen in the ethanol-exposed animals. These changes include enlarged mitochondria with loss of inner mitochondrial membrane integrity and loss of myofibrils. Morphometric analysis substantiated the presence of these alterations from normal cardiac ultrastructure. The present work was undertaken to determine if the pathological changes seen in the newborn mice prenatally exposed to ethanol could be reversed with age and abstinence.
Ultrastructure of the soil fungus, Geomyces pannorus
Authors: Traquair J. A. , Kokko E. G.
Published: June 2020

With the advent of improved dehydration techniques, scanning electron microscopy has become routine in anatomical studies of fungi. Fine structure of hyphae and spore surfaces has been illustrated for many hyphomycetes, and yet, the ultrastructure of the ubiquitous soil fungus, Geomyces pannorus (Link) Sigler & Carmichael has been neglected. This presentation shows that scanning and transmission electron microscopical data must be correlated in resolving septal structure and conidial release in G. pannorus.

Although it is reported to be cellulolytic but not keratinolytic, G. pannorus is found on human skin, animals, birds, mushrooms, dung, roots, and frozen meat in addition to various organic soils. In fact, it readily adapts to growth at low temperatures.
Copper-Beryllium Microstructures
Authors: Tanner Lee E. , Laughlin David E.
Published: June 2020

Recently, the late R. Shiromizu carried out studies to establish the limits of metastability in the Cu-Be system. Con-currently, we engaged in parallel research, but with a broader emphasis on the microstructures concomitant with quenching, aging and reversion. A complete report covering 0.16 to 2.1 wt.% Be will be published elsewhere; certain unique structures are presented below.

Alloys of >0.8 wt.% Be quenched from the α (f.c.c.) region exhibit weak {110} tweed strain contrast. Direct lattice imaging did not detect discrete particles in this condition, whereas rather high densities of {100} G.P. Zone plates in regular stairstep array were revealed after aging at temperatures well below the G.P.Z. solvus.
Electron Microscopy of the Domain Structure in Ferromagnetic Metallic Glasses
Authors: Leamy H. J. , Ferris S. D. , Joy D. C. , Chen H. S.
Published: June 2020

The formation of glassy (amorphous) metallic alloys by rapid quenching from the liquid state was discovered in 1960 (1), and subsequent work revealed that certain metallic glasses are ferromagnetic (2). Recently, transition metal based alloys, which possess Curie temperatures as high as 700°K and saturation magnetizations up to 15,000 Gauss, have been shown to be both mechanically very hard and magnetically quite soft (3). We have applied the SEM technique of Fathers et al. (4) as well as electron transmission Lorentz microscopy to a study of roller quenched (5) metallic glass ribbons of composition: TM0.75P.16X.06A1.03, where TM denotes Fe, Co, Ni, or an alloy of these and X denotes either B, C or Si (6).
The Effect of Deformation Twins on the Microhardness in a Two-Phase Alloy Steel
Authors: Staudhammer K.P. , Murr L.E.
Published: June 2020

The close correlation of strength properties with twin density in 304 stainless steel and manganese steel, has suggested indirectly that twin boundaries act as significant hardening mechanisms by acting as dislocation barriers. The presence of twins can be regarded as a grain-size refinement which can be viewed in terms of the Hall-Petch relation as producing an increase in the flow stress.

In the present study, 60 mil thick sheets of Uniloy 326, having a residual grain size of 1 to 2 μ were explosively shock loaded. The shock loading was performed in sandwich assemblies containing 304 and 316 stainless steels as reference materials utilizing techniques previously described.
Microstructures of Ti-1.5 w/o Ni Alloys with Mo and A1 Additions
Authors: Fraker Anna C.
Published: June 2020

Small amounts of nickel are added to titanium to improve the crevice corrosion resistance but this results in an alloy which has sheet fabrication difficulties and is subject to the formation of large Ti2Ni precipitates. These large precipitates can serve as local corrosion sites; but in a smaller more widely dispersed form, they can have a beneficial effect on crevice corrosion resistance. The purpose of the present work is to show that the addition of a small amount of Mo to the Ti-1.5Ni alloy reduces the Ti2Ni precipitate size and produces a more elongated grained microstructure. It has recently been reported that small additions of Mo to Ti-0.8 to lw/o Ni alloys produce good crevice corrosion resistance and improved fabrication properties.
An Analytical Scanning Transmission Electron Microscope
Authors: von Harrach H. , Lyman C.E. , Walker A.R. , Joy D.C. , Booker G.R.
Published: June 2020

A scanning transmission electron microscope (STEM) with a field emission gun has been developed for quantitative microanalysis. The high brightness source combined with X-ray analysis, electron diffraction and electron energy loss analysis provides a technique of microanalysis from regions of thin specimens as small as a few hundred angstroms.

The electron optical lay-out of this microscope is shown in Figure 1. A triode field-emission gun is mounted in a U HV chamber with mu-metal walls for screening. The gun which can be operated at up to 100kV provides a virtual source; the position of this source is largely independent of the ratio of the acceleration voltage to extraction voltage.
A Jeolco 200A Cartridge with Specimen Heating, Tilting, and Power Provisions
Authors: Anderson R. M. , Howard J. K. , Fullam P.
Published: June 2020

The transmission electron microscopic study of thin metal film interconnections on electronic integrated circuits requires a sophisticated in-situ capability. Electromigration, particularly, cannot be investigated solely by viewing static heat-treated or electrically stressed specimens ex-situ. The key to the early electromigration studies by Blech, and others, was the in-situ observation of material movement in anelectrical-powering-stage equipped TEM. Blech's approach was insensitive to structure effects because of an absence of heating capability; he therefore relied on joule heating and temperature gradient effects.
Liquid Helium Cryostat for the Imaging System of a High Resolution Electron Microscope
Authors: Musinski D. L. , Wang S. T. , Siegel B. M.
Published: June 2020

The specimen environment for high resolution microscopy of biomolecular materials is critical. To obtain the optimum conditions we maintain the specimen in an ultra high vacuum (10-10 Torr) and at liquid helium temperatures to minimize contamination and hopefully radiation damage. To meet these specifications, the imaging system composed of the cryostat shown in the schematic drawing was developed and constructed. Besides assuring that the basic design does not limit the desired resolution, our cryostat offers the maximum in engineering flexibility so alternate lens configurations or even extensive design modifications are relatively easy to accomplish.
A Study of Shock-Induced Point Defect Concentrations in Molybdenum by Transmission Electron and Field-Ion Microscopy
Authors: Morales Albert A. , Murr L. E. , Inal O. T.
Published: June 2020

The passage of a shock wave through a metal is particularly conducive to the production of point defects in the form of vacancies behind the shock front. Vacancies in the metal can be considered a form of relief for the high stresses associated with the shock wave. The amount of data covering the effect of high strain rates on lattice defects (vacancies) is small. Although previous research work has supported the existence of vacancies in shock loaded metals, vacancies have not actually been observed, nor have the concentrations of vacancies or vacancy clusters been studied quantitatively in relation to shock deformation.

In the present investigation, annealed molybdenum wires (3 mil diameter)(1250°C for 10 min. in high vacuum) and molybdenum foils (1 mil thick)(1250°C for 15 hrs. in high vacuum) were prepared and placed in sandwich assemblies for shock loading.
Imaging of Amorphous Objects by Tilted Beam Bright Field Illumination
Authors: Goldfarb W. , Krakow W. , Ast D. , Siegel B.
Published: June 2020

Bright field tilted beam illumination is commonly used to demonstrate the resolution of a transmission electron microscope by forming lattice fringes.

The unscattered and diffracted beams are symmetrically positioned on either side of the optic axis so that the spherical, defocus and chromatic abberations will cancel. The cancellation of chromatic aberration is particularly important. However, the balancing of aberration occurs not only for the one diffraction direction across the axis from the unscattered beam but for an entire hollow cone of scattering vectors centered on the microscope axis and passing through the unscattered beam. This hollow cone projects as a circle in the back focal plane (BFP) of the microscope with zero net aberrations for one sideband of the scattering. Because the image amplitude is squared to form the image intensity, the single ring of cancelled aberrations in the BFP corresponds to a symmetrical pair of rings in the spatial power spectra of the micrograph. These ring pairs show up strongly in the experimental diffractograms, Figures 1, 3 and 4.
Computer-Aided Indexing and Simulation of Transmission Electron Diffraction Patterns
Authors: Rao Prakash , Goehner R. P.
Published: June 2020

The process of indexing electron diffraction patterns is well established and reasonably straightforward. However, in the more complicated crystal systems (e.g. hexagonal, rhombohedral, orthorhombic and monoclinic), indexing and orientation determination is not always simple. In order to considerably ease the tedium of routinely indexing such electron diffraction patterns, automation of the procedure has been carried out in our laboratory by the use of two computer programs written in conversational Fortran.

Simplified flow diagrams of the two programs are shown in Figure 1. The first program (Figure 1a) indexes diffraction spots whose x and y coordinates are obtained from an experimental pattern and supplied, along with crystal structure, lattice constants, space group restrictions, camera constant, and the position and angle errors allowable.
The Wet Replication Technique
Authors: Parsons Donald F. , Basu Samarendra
Published: June 2020

This report explains the physical aspects of the wet replication technique using a differentially pumped hydration chamber. These relate to the flow of evaporating gases through saturated water vapor, to selecting an evaporant material andfinally, to the shape replicating ability of the technique.

Fig. 1 explains how the present method of wet replication differs in principle from conventional replication in high vacuum. In conventional dry replication, the replica material is evaporated on top of the specimen at normal incidence. This may either preceed or follow angular shadowing by a heavy metal. In the present method the wet specimen inside the hydration chamber is first replicated by SiO vapor at normal incidence from the bottom, and then shadowed with pt-c at 30°-35° angle as shown on the right on Fig. 1, for dry replication.
Characterization of Ion Migration in MOS Systems by Internal Interface Imaging
Authors: Bottoms W.R. , Guterman D. , Roitman P.
Published: June 2020

Sodium ions are endemic to MOS systems and they become mobile at elevated temperature. These ions may be drifted, under applied bias, to either interface where they form a dipole layer which effectively lowers the work function at the interface. A method for providing high spatial resolution for the imaging of internal lateral nonuniformities in MOS structures in the scanning electron microscope has been described. This method, based on the electron beam induced current (EBIC) mode of the SEM, is capable of providing spatial resolution on the order of 1000 Å for a structure at an internal interface beneath oxides of thickness on the order of 5000 Å. The contrast for this imaging method is provided by any physical process which alters current collected in an external circuit as the electron beam scans across the sample. These processes can be divided into four general categories: surface emission, barrier height modulation at either interface, variations in the fields across the oxide, and variations in the materials parameters of the oxide, metallization, or semiconductor region of the sample.
Cathodoluminescence-Mode Scanning Electron Microscopy of GaAs Alloys and Diodes
Authors: Levin E. R. , Ettenberg M.
Published: June 2020

Cathodoluminescence (CL)-mode scanning electron microscopy studies were made on n-type GaAs substrate crystals, and on liquid (LPE)- and vapor-phase-epitaxial (VPE) GaAs. The observations were carried out in a Stereoscan S4-10 equipped with a separate CL detector and signal processing channel. Broad-band detection was employed, with the CL radiation from the specimen focused directly onto a photomultiplier (RCA type 7102) with S-l spectral response. The CL was excited by 30 kV electrons, with beam currents typically about 10 nanoamperes.

Figure 1 shows a low dislocation-density (˜103/cm2) substrate crystal. The CL image contains only heavy horizontal striations, which may be attributed to varying concentrations of dopant formed during growth, and a few contrast effects related to surface features (cf., emissive-mode (SE) image).The high dislocation-density (˜105/cm2) GaAs substrate in Figure 2 shows in addition a distribution of discrete dark spots and short line segments, identified as emerging dislocations: Dislocation etching of the specimen revealed a distribution and density of dislocations comparable to the CL-image dark spots.
Asbestos Background Levels in Three Filter Media Used for Environmental Monitoring
Authors: Chatfield E. J.
Published: June 2020

Monitoring of the environment for asbestiform minerals has recently been of major interest, and analysis methods for the samples have been variable in reliability. Because of the difficulty in preparing suitable standards, acceptable criteria for reproducibility in asbestos analytical techniques have been that results on the same sample should agree within a factor of two or three. Various analytical techniques have been reported, but most of these rely on complete dissolution or oxidation of the filter medium used for collection and preparation of a transmission electron microscope sample. One technique reported uses ultrasonic treatment of the membrane in distilled water to remove fibers, after which the filter is discarded. Unfortunately, there is then no record of how many fibers remained attached and were discarded along with the filter membrane.
Computer Reconstruction of the Cellular Architecture of the Daphnia Magna Optic Ganglion
Authors: Macagno E. R. , Levinthal C.
Published: June 2020

The optic ganglion of Daphnia Magna, a small crustacean that reproduces parthenogenetically contains about three hundred neurons: 110 neurons in the Lamina or anterior region and about 190 neurons in the Medulla or posterior region. The ganglion lies in the midplane of the organism and shows a high degree of left-right symmetry in its structures. The Lamina neurons form the first projection of the visual output from 176 retinula cells in the compound eye. In order to answer questions about structural invariance under constant genetic background, we have begun to reconstruct in detail the morphology and synaptic connectivity of various neurons in this ganglion from electron micrographs of serial sections (1). The ganglion is sectioned in a dorso-ventra1 direction so as to minimize the cross-sectional area photographed in each section. This area is about 60 μm x 120 μm, and hence most of the ganglion fit in a single 70 mm micrograph at the lowest magnification (685x) available on our Zeiss EM9-S.
Three-Dimensional Structure Reconstruction by High Voltage Electron Microscopy of Biological Specimens
Authors: Peachey Lee D.
Published: June 2020

A major advantage of the high voltage electron microscope (HVEM, accelerating voltage 1000 kV) is its ability to produce high quality images of slices of enbedded biological tissue or whole mounts of cells 1 μm or greater in thickness. Several workers have been trying to exploit this feature in studies of cell structures using the HVEM facility at the University of Colorado. When the right combination of thickness and contrast has been obtained, the resulting micrographs can be quite remarkable both for the quantity of information they contain and for the directness and clarity with which the three-dimensional information can be seen.

For purposes of discussion, one can group the kinds of biological specimens and HVEM approaches to their study into three classes. First there are isolated cells or cell parts that can be fixed, mounted directly on support films, dried by the critical point or other appropriate method, and examined immediately without embedding or other treatment.
Observations on the Nucleus of “Stripped” He La Cells
Authors: Watson John H. L. , Swedo John L. , Page Robert H.
Published: June 2020

A new specimen preparation technique, called “stripping”, has been applied to normal, monolayer cultures of HeLa cells grown on coverslips to reveal a new view of nuclei, their surface and internal structure, and of other organelles in situ by scanning electron microscopy (SEM). Stripping, which is described fully in reference, is a simple procedure at present in developmental stage, performed at ambient temperature on cells and other biological structures critical point dried (CPD) in CO2. The mitotic state of individual cells in CPD cell cultures is determined in advance by light microscopy, and pertinent fields are recorded in phase contrast prior to their vacuum metal-coating and subsequent stripping. The outer surface of the same cell is studied by SEM, and is then stripped and studied again for a direct view of its internal structures. Micrographs will be shown of the chromosomal substance in the region of the metaphase plate, of the regions of the midbody and separating nuclei of cells in telephase, and of whole nuclei in stripped interphase cells.
Autophagy Involves the Golgi Complex in a Two Step Process
Authors: Locke M. , Sykes A.K.
Published: June 2020

The role of the Golgi complex as a distributing center for membranes and their contents has been studied by observing the origin of the membranes and lytic enzymes involved in autophagy. Friend's hot osmium staining method implicates the outer region of the Golgi complex as the source of the isolation membranes that sequester organelles in preparation for their destruction in autophagic vacuoles. The localization of acid phosphatase suggests that the inner secretory region of the Golgi complex is the source of the lytic enzymes carried to autophagic vacuoles by primary lysosomes.

In addition to packaging material for secretory vesicles to make blood proteins, the Golgi complex (GC) has two separate roles in the organelle destruction which takes place when insect fat body cells change their activities during metamorphosis from the larva to the pupa. The process by which organelles are sequestered from the rest of the cell is temporally and spatially distinct from the addition of lytic enzymes.
Cytomegalovirus in Wild Mice
Authors: Rongey R. , Officer J.E. , Estes J.D. , Coffey G. , Gardner M.B.
Published: June 2020

The inadvertant dissemination of otherwise latent or chronic herpes virus, especially cytomegalovirus (CMV), is an important consideration in humans given immunosuppressive treatment for renal or cardiac transplantation. It is desirable to have an animal model of chronic CMV infection that does not require experimental virus inoculation. Laboratory mice are unsuitable in this regard since they have a low prevalence (2-3%) of naturally occurring chronic CMV infection. However, chronic CMV infection with shedding of virus in saliva is apparently ubiquitous in wild mice (Mus musculus), suggesting that feral mice might be an appropriate model for studying the effects of immunosuppression upon natural CMV infection. We have found that wild mice immunosuppressed with antithymocytic sera (ATS) show a high incidence of disseminated virulent CMV infection.

We confirmed the presence of chronic indolent subclinical CMV infection in high prevalence in healthy wild mice.
Studies of Epstein-Barr Virus Antigens Using Immunoperoxidase and Immunofluorescence Techniques
Authors: Stephens R. , Traul K. , Woolf D. , Gaudreau P.
Published: June 2020

A number of antigens have been found associated with persistent EBV infections of lymphoblastoid cells. Identification and localization of these antigens were principally by immunofluorescence (IF) techniques using sera from patients with nasopharyngeal carcinoma (NPC), Burkitt lymphoma (BL), and infectious mononucleosis (IM). Our study was mainly with three of the EBV related antigens, a) virus capsid antigen (VCA), b) membrane antigen (MA), and c) early antigens (EA) using immunoperoxidase (IP) techniques with electron microscopy (EM) to elucidate the sites of reactivity with EBV and EBV infected cells.

Prior to labeling with horseradish peroxidase (HRP), sera from NPC, IM, and BL cases were characterized for various reactivities by the indirect IF technique. Modifications of the direct IP procedure described by Shabo and the indirect IP procedure of Leduc were made to enhance penetration of the cells and preservation of antigen reactivity.
Stereo Electron Microscopy of Freeze-Fractured Cells Reveals the Three-Dimensional Continuity of Tobacco Mosaic Virus Crystals
Authors: Steere Russell L. , Erbe Eric F.
Published: June 2020

The large hexagonal crystals which develop in cells of some plants infected with tobacco mosaic virus (TMV) have been shown to consist of ordered arrays of TMV virions. The virions of one layer are parallel to each other but usually tilted with respect to adjacent layers within the crystal to form a "herringbone" pattern if cut or fractured in a certain plane. The hexagonal outline of crystals containing numerous layers leads one to suspect that these are true three-dimensional crystals with a specific orientation of virions, not only within each layer but also between adjacent layers.

Recent improvements in freeze-fracture techniques made it practical to reinvestigate these crystals. Epidermal strips from tobacco plants systemically infected with the common strain of TMV were placed in a gradient consisting of 0 to 25% sucrose and 0 to 25% glycerol in 0.2 M phosphate buffer of pH 7.
Skin Vascular Ultrastructure During Thermal Injury, Hypertrophic Scarring and its Resolution
Authors: Kischer C. W.
Published: June 2020

The usual result of deep thermal injury of the skin in children is hypertrophic scarring. The dynamics of revascularization have been implicated as integral to development and resolution of hypertrophic scarring. Thus, special attention is being directed toward examining vessels at different stages after injury.

In vessels from normal skin endothelial cells do not contain many organelles; Golgi membranes are sometimes observed, a few mitochondria and occasional profiles of rough endoplasmic reticulum. Pinocytic vesicles are present on both tissue and blood side of the endothelial cells and in the perivascular satellite cells. Infrequently multivesicular bodies are observed. A thin basement membrane underlies endothelial cells and their satellites (Fig. 1).

In the post-injury granulation tissue pinocytic vesicles and multivesicular bodies are seldom seen. The endothelial cells contain a marked increase in rough endoplasmic reticulum, often dilated, and intracytoplasmic filaments (Fig. 2).
Ultrastructural Features of Normal and Diseased Hair Revealed by Ion Beam Etching and Freeze Fracture
Authors: Spector M. , Brown A. C.
Published: June 2020

Ion beam etching and freeze fracture techniques were utilized in conjunction with scanning electron microscopy to study the ultrastructure of normal and diseased human hair. Topographical differences in the cuticular scale of normal and diseased hair were demonstrated in previous scanning electron microscope studies. In the present study, ion beam etching and freeze fracture techniques were utilized to reveal subsurface ultrastructural features of the cuticle and cortex.

Samples of normal and diseased hair including monilethrix, pili torti, pili annulati, and hidrotic ectodermal dysplasia were cut from areas near the base of the hair. In preparation for ion beam etching, untreated hairs were mounted on conducting tape on a conducting silicon substrate. The hairs were ion beam etched by an 18 ky argon ion beam (5μA ion current) from an ETEC ion beam etching device. The ion beam was oriented perpendicular to the substrate. The specimen remained stationary in the beam for exposures of 6 to 8 minutes.
The Role of Mitochondria in the Genesis of Neuroaxonal Dystrophy in the Brains of Aging Mice
Authors: Johnson J.E.
Published: June 2020

Although neuroaxonal dystrophy (NAD) has been examined by light and electron microscopy for years, the nature of the components in the dystrophic axons is not well understood. The present report examines nucleus gracilis and cuneatus (the dorsal column nuclei) in the brain stem of aging mice.

Mice (C57BL/6J) were sacrificed by aldehyde perfusion at ages ranging from 3 months to 23 months. Several brain areas and parts of other organs were processed for electron microscopy.

At 3 months of age, very little evidence of NAD can be discerned by light microscopy. At the EM level, a few axons are found to contain dystrophic material. By 23 months of age, the entire nucleus gracilis is filled with dystrophic axons. Much less NAD is seen in nucleus cuneatus by comparison. The most recurrent pattern of NAD is an enlarged profile, in the center of which is a mass of reticulated material (reticulated portion; or RP).
Formation of Centrioles in Some Endocrine Adenomas
Authors: Horvath E. , Kovacs K.
Published: June 2020

Centrioles, known to play a fundamental role in mitotic division, are regarded as representing self-replicating organelles. They occur with varying frequency in different normal cells and exhibit uniform appearances showing no signs indicative of duplication such as budding or division. In order to obtain a deeper insight into centriole formation and evolution, cases of parathyroid and pituitary adenomas with a high centriole population were investigated by electron microscopy.

The material used for the present study consisted of 4 chief cell adenomas of the parathyroid gland, 7 sparsely granulated pituitary growth hormone cell adenomas and 1 mixed cell pituitary adenoma composed of sparsely granulated growth hormone cells and prolactin cells. These adenomas were selected from a large number of cases (26 parathyroid adenomas and 49 pituitary adenomas). All specimens were obtained by surgery from various patients with hyperparathyroidism or acromegaly. Small pieces of tissue were fixed immediately after removal in 2.5 per cent glutaraldehyde in Sorensen's buffer, postfixed in 1 per cent osmium tetroxide in Millonig's buffer, dehydrated in graded ethanol and embedded in Epon 812.
A Low Power S.E.M. Study of Normal and Colitic Human Large Bowel
Authors: Riddell R.H. , Eisenstat L. , Golomb H. , Brynes R. , Levin B.
Published: June 2020

There have been few studies of the human colon using SEM. A further study was prompted by the repeated finding of a regular surface pattern in histological sections taken in the longitudinal, but rarely the transverse plane, from resection specimens of non-colitic large bowel. The commonest situation was in resections for carcinoma where it was frequently seen in the mucosa away from the tumour. The pattern consists of a series of primary crypts into which several crypts open separated by low ridges containing 5-7 secondary crypts opening onto the surface, and this gives the luminal surface a scalloped appearance.(Fig.1). Furthermore it was noted that these changes were rarely seen in ulcerative colitis, a disease characterized by repeated ulceration and regeneration, unless the regenerative features were so mild that no atrophy was apparent. To investigate this further, mucosa was taken in a longitudinal plane from normal appearing mucosa away from carcinomas and also from resections for ulerative colitis.
Effects of Asbestos Fibers on Mammalian Cells in Culture
Authors: Barry Brenda E. , Fisher Harold W.
Published: June 2020

In previous reports from this laboratory, we examined the correlation of the toxic effects of several organic pesticides, herbicides and trace metals on the plating efficiency to the ultrastructural changes found in the treated cells in culture. Since there has been a long-term interest in the effects of exposure of humans and experimental animals to asbestos, the current study was undertaken to determine if ultrastructural changes would also be found in mammalian cells grown in vitro after exposure to asbestos. In a series of preliminary experiments, suitable fractionation by low-speed differential centrifugation and concentrations of amphibole asbestos were found in which there was at least 70% to 90% viability depending on the cell type. The viability of the cells incubated in the presence of the asbestos was determined both by growth curves established from direct cell counts and from staining with trypan blue which does not penetrate viable cells.
Ultrastructural Evaluation of Bone, Parathyroid and Ultimobranchial Glands in Lizards with Nutritional Osteodystrophy
Authors: Anderson M. P. , Capen C. C.
Published: June 2020

Lizards in captivity are commonly afflicted with an osteodystrophy related to dietary imbalances in calcium, phosphorus and vitamin D. Young green iguanas (Iguana iguana) were fed beef heart based diets either low (0.2%) in calcium (experimental group) or adequate (2.7%) in calcium (control group). Both diets were unsupplemented with vitamin D and contained 1.1% P, 82% protein and 14% fat on a dry weight basis. Beginning with the sixth month iguanas of the experimental group developed progressive hypocalcemia (8.0 to 3.2 mg/100 ml plasma) resulting in secondary hyperparathyroidism. Progressive osteoporosis, detected radiographically,with osteomalacia was apparent from the seventh month until termination of the experiment at 9 months.

Parathyroid chief cells of iguanas in the experimental group were primarily in the active stage of the secretory cycle. Lamellar and circular aggregations of rough endoplasmic reticulum were extensive and Golgi apparatuses were prominent (Fig. 1). Mitochondria often were displaced peripherally in chief cells by the large arrays of endoplasmic reticulum.
Ultracytochemical Localization of Potassium-Dependent NPPase in Rat Choroid Plexus
Authors: Davis D. A. , Milhorat T. H. , Hammock M. K.
Published: June 2020

From a morphological standpoint, the choroid plexus epithelium appears ideally suited for the task of transporting fluid and electrolytes. However, until recently, a suitable method for demonstrating enzyme systems associated with these functions has been unavailable. In 1972, Ernst reported a technique for specifically localizing Na-K-ATPase. This technique was used in the following study on rat choroid plexus.

The choroid plexuses from the lateral ventricles of adult male Wistar rats were fixed intraventricularly with 3% depolymerized paraformaldehyde in 0.1M cacodylate buffer at pH 7.3-7.4. The tissue was excised and placed in a vial where pre-fixation continued for 90 minutes at room temperature. Subsequently, choroid plexus tissue was incubated according to the method of Ernst. Control experiments consisted of: 1) omitting either potassium or magnesium from the incubation medium; 2) omitting the substrate p-nitrophenyl phosphate (NPP) from the incubation medium; and 3) adding lOmM ouabain to the incubation medium.
Cytochemical Specializations on the Luminal Surface of Blood Vessels in the Developing Rat Central Nervous System
Authors: Hannah R. S. , Rosenquist T. H.
Published: June 2020

Developing blood vessels in the rat central nervous system exhibit several unusual luminal features. Hannah (1975) used high voltage electron microscopy to demonstrate numerous ridges of endothelium, some near junctional complexes. The ridges produced troughs (which may appear as depressions) in the endothelial surface. In some areas ridges extended over the troughs, removing them from direct contact with the luminal surface. At no time were the troughs observed to penetrate the basal laminae. Fingerlike projections also extended into the lumina.

To determine whether any chemical specializations accompanied the unusual morphological features of the luminal surface, we added 0.1% Alcian blue (Behnke and Zelander, 1970) to the 3% glutaraldehyde perfusate (cacodylate buffer, pH 7.4). After Alcian blue had reacted with the luminal glycocalyces, the dye was dissociated with MgCl2 via critical electrolyte concentration method of Scott and Dorling (1965). When these methods are applied together, it is possible to differentiate mucopolysaccharides (glycosaminoglycans or GAG) with the electron microscope.
High Resolution Cytochemical Demonstration of Electrical Charges in Synaptosome Surface Coat
Authors: Feria-Velasco Alfredo , Sánchez Salvador , Magdaleno Víctor
Published: June 2020

Electrophoretic mobility studies in synaptosomes from rodent brain have shown that approximately a third of their mobility towards to the cathode is conferred by sialic acid exposed to neuraminidase. On the other hand, it is known from biochemical works that sialic acid is one of the carbohydrate residues present in glycoproteins and gangliosides at the nervous tissue elements.

The present work deals with the identification and distribution pattern of electrical charges at the synaptosome surface by means of cytochemical techniques for electron microscopy and correlative biochemical methods.

Synaptosome fraction was obtained from mice brain homogenates in 0.32M sucrose according to a previously described method (3). After glutaraldehyde fixation, the samples were stained with dialyzed colloidal iron solutions, at pH 1.8 [(+)Fe] or 4.0 [(-) Fe] respectively (4), postfixed in osmium tetroxide and further processed for electron microscopy. With (+)Fe, homogeneous fine electrondense deposits were seen at the synaptosome surface (Fig. 1).
Epithelialization of the Anterior Chamber: An Ultrastructural Study
Authors: Nopanitaya Waykin , Purnell William D. , McPherson Samuel D.
Published: June 2020

Epithelial downgrowth is a serious late complication of perforating wounds of the anterior segment of the eye, whether they are accidental or secondary to operation. Both post-traumatic and post-operative epithelialization typically develops because of delayed or faulty coadaptation of wound edges at the corneoscleral junction. Reverse corneal grafts and direct implantation of corneal and conjunctival tissue have also been reported to induce epithelialization of the anterior chamber. An experimental model of so-called epithelialization of the rabbit's anterior chamber has been successfully developed in this laboratory. This model provided an easily reproducible method of wounding which caused epithelialization analogous to the clinical occurrence. There have been no attempts to study the ultrastructure of the cells which grew downward into the anterior chamber following corneal suturing. The present investigation is undertaken to observe and to identify the ultrastructural features of these downgrowing cells which subsequently developed in an experimental model of epithelialization.
Ultrastructural Changes in Hamster Retina Following Injection of 5-Hydroxy-Tryptophan
Authors: Taylor R. , Gerodetti M. , Blystone R.V. , Smith P.
Published: June 2020

It has been proposed that 5-hydroxy-tryptamine (5-HT) may function either as a neural transmitter or as a neural regulator within the central nervous system. Upon administration of adequate amounts of 5-hydroxy-tryptophan, the level of 5-HT within the central nervous system is significantly increased. 5-hydroxy-tryptophan is actively transported from the blood into the central nervous system where it is decarboxylated to form a mobile pool of 5-HT which is presumably stored and concentrated within the synaptic vesicles of the nerve endings.

Hamsters were administered 100-150 mg/kg of body weight injections of 5 hydroxy-tryptophan. Within 15 to 30 minutes post injection, the hamsters began experiencing massive tremors and loss of coordination but were observed entering a more tranquil state after an hour and a half. At two hours post injection, the hamsters were sacrificed by cervical dislocation, the eyes removed, and retinal tissue obtained.
Scanning Electron Microscopy of the Normal Rabbit Hepatocyte
Authors: Nopanitaya Waykin , Grisham Joe W.
Published: June 2020

Current interest in the ultrastructure of the liver arises partly from demonstrations that scanning electron microscopy is very useful for studying surfaces and interrelationships of intrahepatic structures in both normal and pathological situations. In recent years, the development of the scanning electron microscope and techniques of tissue preparation has provided a three-dimensional method for examination of the features of intrahepatic ultrastructure. Only reports on the rat liver were available. However, SEM observations on the liver from other species are currently in progress in our laboratories. In this report, the SEM observations on the rabbit hepatocyte and the relevant technique for preparing hepatic tissues are described.

Healthy, adult New Zealand rabbits were anesthetized by either intravenous or intraperitoneal injection of pentobarbital. Both abdominal and thoracic walls of anesthetized animals were opened. A small incision was made in the inferior vena cava at the level just below the renal veins, immediately followed by intracardiac perfusion of chilled 0.9% saline for 5 minutes.