bluuebunny/crossref_metadata_2025 huggingface dataset:
The Microstructure of Nickel Oxide Scales
Authors: Tinker M. T. , Hobbs L. W.
Published: June 2020

There is considerable technological interest in oxidation of nickel because of the importance of nickel-base superalloys in high-temperature oxidizing environments. NiO scales on nickel grow classically, by outward diffusion of nickel through the scale, and are among the most studied of oxidation systems. We report here the first extensive characterization by transmission electron microscopy of nickel oxide scales formed on bulk nickel substrates and sectioned both parallel and transversely to the Ni/NiO interface.

Electrochemically-polished nickel sheet of 99.995% purity was oxidized at 1273 K in 0.1 MPa oxygen partial pressure for times between 5 s and 25 h. Parallel sections were produced using a combination of electropolishing of the nickel substrate and ion-beam thinning of the scale to any desired depth in the scale. Transverse sections were prepared by encasing stacked strips of oxidized nickel sheet in epoxy resin, sectioning transversely and ion-beam thinning until thin area spanning one or more interfaces was obtained.
Lattice Imaging of Heteroepitaxial Silicon on Sapphire
Authors: Ponce Fernando A.
Published: June 2020

The silicon-on-sapphire technology has produced electronic devices with high switching speeds and low power consumption. These features are mainly due to the insulating nature of the substrate and the consequent reduction in parasitic capacitances. TEM observations of the crystalline structure of the silicon layer reveal the presence of large densities of twins and stacking faults, which are thought to have an adverse effect on the overall electrical characteristics of the devices and it is, therefore, desirable to understand their nature and origin.

In this work the lattice structure of the silicon-sapphire junction has been imaged by high resolution TEM. The silicon layer was deposited at 960°C by chemical vapor deposition of silane in H2, at a rate of 1.4 μm/min on a (1102) sapphire substrate surface. The silicon was grown with its [001] direction perpendicular to the substrate plane to a thickness of 0.65 μm. Specimens were prepared in cross section with argon-ion bombardment as the final thinning step. TEM observations were performed with a Philips EM400 microscope equipped with a high resolution stage (spherical aberration coefficient of 1.1 mm) and a LaB6 filament, at an operating voltage of 120 kV.
Analysis of Grain Boundary Precipitation in 7475 Al Alloys Using High Resolution and Analytical Electron Microscopy
Authors: Koo J. Y. , Park B. K.
Published: June 2020

High resolution electron microscopy has considerably enhanced our understanding of phase transformation behaviors by providing details which supersede the resolution capabilities of other experimental techniques. This paper presents the analysis of grain boundary precipitation in 7475 alloy utilizing the lattice fringe imaging technique in conjunction with microdiffraction and X-ray microanalysis.

The commercial 7475 alloy was solution heat treated at 900°F for 1-1/2 hr. and subsequently quenched to room temperature. The specimens were then given double aging treatments, 6 hrs. at 150°C plus 2 hrs. at 80°C. Thin foils were examined using a Philips 400 TEM equipped with FEG, twin lens, and energy dispersive X-ray unit. Figure 1 is the lattice fringe image showing a grain boundary precipitate (∼300Å dia.) growing into two neighboring PFZ across the boundary. Also shown in the micrograph is another precipitate (arrowed) nucleated at the junction between the grain boundary and the bigger particle. Energy dispersive X-ray spectra from the particles (dotted), partially shown in Figures 2 and 3 in comparison with those of matrix (bars), indicate that the major elements present are A1 and Mg (not shown), and Cr in the bigger particle, and A1 and Mg (not shown), Zn and Cu in the small precipitate.
Analytical Treatment of the Breakdown of Friedels Law. Application to Crystal Polarity Determination in Semiconductors with Sphalerite Structure
Authors: J. Taftø
Published: June 2020

In a recent paper a simple method for determination of the direction of the polarity of noncentrosymmetric crystals was presented. The method was based on qualitative considerations. To test the validity of this method a three beam case where Friedels law does not apply is solved analytically. Based on the Bloch wave treatment (see e.g. ) we consider the situation shown in fig. la with Ug = Uh-g = U-h = V exp(iω) and both reflections at the Bragg position. The group of the dispersion matrix is C3 (or 3) and according to group character tables e.g. the coefficients of the Bloch waves are:

By inserting these eigenvectors into the dispersion matrix we get the eigen-values:
Ion Beam Induced Interfacial Reactions in Molybdenum Thin Films on Silicon
Authors: Chen L. J. , Hung L. S. , Mayer J. W.
Published: June 2020

When an energetic ion penetrates through an interface between a thin film (of species A) and a substrate (of species B), ion induced atomic mixing may result in an intermixed region (which contains A and B) near the interface. Most ion beam mixing experiments have been directed toward metal-silicon systems, silicide phases are generally obtained, and they are the same as those formed by thermal treatment.

Recent emergence of silicide compound as contact material in silicon microelectronic devices is mainly due to the superiority of the silicide-silicon interface in terms of uniformity and thermal stability. It is of great interest to understand the kinetics of the interfacial reactions to provide insights into the nature of ion beam-solid interactions as well as to explore its practical applications in device technology.

About 500 Å thick molybdenum was chemical vapor deposited in hydrogen ambient on (001) n-type silicon wafer with substrate temperature maintained at 650-700°C. Samples were supplied by D. M. Brown of General Electric Research & Development Laboratory, Schenectady, NY.
TEM In-Situ Epitaxy on Recrystallized Sapphire Substrates
Authors: Anton R. , Poppa H. , Heinemann K.
Published: June 2020

The suitability of freshly recrystallized clean and well ordered alumina films for meaningful and reproducible in-situ studies of the nucleation, growth, and epitaxy of vapor-deposited materials was investigated, using Au, Ag, Fe, Pd, Mo, and W as deposit materials.

A typical example of the dependence of the number density of nuclei on the substrate surface conditions is shown in Fig. 1. The highest density was found, as expected, in the polycrystalline substrate area (lower right); a lower particle number density, along with decoration of surface relief structures, was noted in the sapphire grain (upper right) near the boundary with the polycrystalline film; and the density is lowest on a (0001)-oriented α-Al2O3, grain which is also close to the center of the recrystallized area. This substrate region probably was hottest during the in-situ recrystallization process and is, therefore, low in defects and free of contaminants; gold deposited at 750°C was found to be nearly perfectly epitaxial, exhibiting good crystal lographic habits.
Efficient Algorithms for Computer Diffraction Pattern Analysis
Authors: Warren J. B.
Published: June 2020

The increasing availability of position-sensitive radiation detectors has facilitated the automated analysis of electron diffraction patterns with computers. One problem that lends itself to solution by these methods is the computation of the electron beam-sample orientation from Kikuchi patterns. A precise orientation is required for a wide variety of problems including the determination of grain boundary misorientations, precipitate-matrix relationships and the computer simulation of crystal defect images. In all of these investigations the beam-sample relationship is required for several sample orientations and computational labor can be excessive unless some form of automated analysis is employed.

If a position-sensitive detector composed of two arrays of elements is placed at the electron microscope phosphor screen position, the orientation can be determined directly from the diffraction pattern. As shown in Fig. 2, a rectangular detector array would detect many Kikuchi lines and the algorithm used to interpret data must be able to determine which Kikuchi line pairs are suitable for use in computation, choose the proper (hkl) lattice plane associated with the Kikuchi line pair, and finally index the chosen line pairs in a consistent manner.
A Color Coded STEM/SEM Image Storage System
Authors: Kokubo Y. , Hardy W. H. , Dance J. , Jones K.
Published: June 2020

A color coded digital image processing is accomplished by using JEM100CX TEM SCAN and ORTEC’s LSI-11 computer based multi-channel analyzer (EEDS-II-System III) for image analysis and display. Color coding of the recorded image enables enhanced visualization of the image using mathematical techniques such as compression, gray scale expansion, gamma-processing, filtering, etc., without subjecting the sample to further electron beam irradiation once images have been stored in the memory.

The powerful combination between a scanning electron microscope and computer is starting to be widely used 1) - 4) for the purpose of image processing and particle analysis. Especially, in scanning electron microscopy it is possible to get all information resulting from the interactions between the electron beam and specimen materials, by using different detectors for signals such as secondary electron, backscattered electrons, elastic scattered electrons, inelastic scattered electrons, un-scattered electrons, X-rays, etc., each of which contains specific information arising from their physical origin, study of a wide range of effects becomes possible.
Minimal Exposure, Rotary Hollow-Cone Illumination and Focus Wobble Added to The Deflection System of an HVEM
Authors: Pawley James B.
Published: June 2020

Radiation damage places the fundamental limitation on the retrieval of structural information from co-valently bonded material by electron microscopy. Our interest here is simply to describe a system developed for the HVEM which will reduce to a practical minimum the amount of radiation to which the sample must be exposed in order to make a micrograph. Several methods have been described to accomplish this end in the 100 kV microscope. They usually involve pre-focusing on one area of the sample and then misaligning the column mechanically or by electromagnetic deflection in order to image a nearby part of the sample which remains unirradiated until just before the exposure of the micrograph. The only HVEM minimal exposure system seems to be the shutter fitted above the sample on the Cambridge 600 kV HREM.

As the angular deviation caused by off axis displacement of the imaged area is inversely proportional to objective lens focal length, the degradation of imaging quality caused by such a displacement will be relatively less in the HVEM because of its longer focal length (EM-7 with side entry stage f=8.5mm).
Thermomechanical Treatment of a 4340 Ni-Cr-Mo Alloy Steel
Authors: Jahn M.T. , Yang J.C. , Wan C.M.
Published: June 2020

4340 Ni-Cr-Mo alloy steel is widely used due to its good combination of strength and toughness. The mechanical property of 4340 steel can be improved by various thermal treatments. The influence of thermomechanical treatment (TMT) has been studied in a low carbon Ni-Cr-Mo steel having chemical composition closed to 4340 steel. TMT of 4340 steel is rarely examined up to now. In this study we obtain good improvement on the mechanical property of 4340 steel by TMT. The mechanism is explained in terms of TEM microstructures

4340 (0.39C-1.81Ni-0.93Cr-0.26Mo) steel was austenitized at 950°C for 30 minutes. The TMTed specimen (T) was obtained by forging the specimen continuously as the temperature of the specimen was decreasing from 950°C to 600°C followed by oil quenching to room temperature. The thickness reduction ratio by forging is 40%. The conventional specimen (C) was obtained by quenching the specimen directly into room temperature oil after austenitized at 950°C for 30 minutes. All quenched specimens (T and C) were then tempered at 450, 500, 550, 600 or 650°C for four hours respectively.
Magnetic Domain Observation of an Amorphous Fe-Si-B Ribbon by Means of a High Voltage Scanning Electron Microscope
Authors: Tsuno K. , Harada Y. , Sato T.
Published: June 2020

Magnetic domains of ferromagnetic amorphous ribbon have been observed using Bitter powder method. However, the domains of amorphous ribbon are very complicated and the surface of ribbon is not flat, so that clear domain image has not been obtained. It has been desired to observe more clear image in order to analyze the domain structure of this zero magnetocrystalline anisotropy material. So, we tried to observe magnetic domains by means of a back-scattered electron mode of high voltage scanning electron microscope (HVSEM).

HVSEM method has several advantages compared with the ordinary methods for observing domains: (1) high contrast (0.9, 1.5 and 5% at 50, 100 and 200 kV) (2) high penetration depth of electrons (0.2, 1.5 and 8 μm at 50, 100 and 200 kV). However, image resolution of previous HVSEM was quite low (maximum magnification was less than 100x), because the objective lens cannot be excited for avoiding the application of magnetic field on the specimen.
Imaging of Magnetic Steel Filaments with an HB-5 STEM
Authors: Chan I. Y. T. , Wilsdorf H. G. F.
Published: June 2020

The tensile strength of polycrystalline steel filaments 0.2-0.6 cm long with diameters between 1 μm and 20μm can be as high as 8 GPa. When compared to steels of similar composition (α-Fe with 1.5 w/o C, 0.8 w/o O) obtained by solidification, they exhibit an exceptional microstructure due to their production by chemical vapor deposition in the presence of a strong magnetic field. Regardless of the diameter, the grain size is between 10 nm and 30 nm. TEM, field ion microscopy, electron and x-ray diffraction studies have shown that within the grains a microdispersion of iron oxides, iron carbides, and carbon exists. Also, it was found in a recent investigation that the boundaries between grains are not sharp and planar but consist of regions about 2 nm wide. The following research was aimed at clarifying the grain boundary structure.
Phase Contrast Imaging of Styrene/Isoprene Block Copolymers
Authors: Handlin Dale L.
Published: June 2020

SAXS shows that in polystyrene (PS)/polyisoprene (PI) block copolymers with lamellar morphologies there is a sufficient electron density difference for x-ray scattering [1]. It has been accepted, however, that this difference is insufficient for TEM imaging by amplitude contrast. Therefore, contrast has been produced by staining the PI phase with OsO4 [2]. Staining changes the mechanical and chemical structure of the PI phase perhaps altering the phase separation and the domain interfaces (figure 1).

Mean inner potential calculations, however, show potentials of 8.29V for PS and 7.57V for PI. This indicates that for a simple specimen geometry (e.g. lamellar) with sharp phase interfaces oriented parallel to the incident beam, a film 500Å thick will provide a phase change (Δψ) of 0.3 radians at 100 KV. This phase change is sufficient for imaging under defocus conditions and contains information about the interface region between the domains. The phase change may be increased by using lower voltage (50% increase at 40 KV).
Microdiffraction Study of Short Range Ordering in LiFeO2
Authors: Chan I.Y.T. , Cowley J. M.
Published: June 2020

Typical selected area electron diffraction patterns from materials with short range ordering reveal diffuse intensities outside the fundamental Bragg reflections of the average structure. Such information allows one to construct three dimensional surfaces in the reciprocal space where the diffuse intensity lies. De Ridder et al have proposed clustering models through a geometrical analysis of these surfaces. The short range ordering state is then described by interconnecting these clusters. Alternatively, it may be described in terms of microdomains of different superstructures. However, these SAD patterns originated from areas much larger than the proposed size of the microdomains, hence, the structural information of individual domains were obscured. With the aid of the optical system of the HB5 STEM at Arizona State University, microdiffraction patterns from small areas (≲20Å) are routinely obtained.
Electron Microscope Provided with a Six-Stage Image Forming Lens System
Authors: Arai Y. , Ishida Y. , Watabe T. , Harada Y.
Published: June 2020

The image forming lens system of an electron microscope used for medical and biological applications has to meet the following requirements: (1) minimum off-axis aberration and distortion, (2) eliminated image rotation and focus deviation over wide magnification range, and (3) a wide field of view at low magnification. We have developed a new type of electron microscope which has a six-stage image forming lens system to satisfy the above requirements.

The present paper describes the features of the electron microscope and also gives some application data for biological fields obtained with this instrument. The electron optical system is designed to provide a wide magnification range of 50x to l,000,000x by using a high resolution side entry goniometer with tilting facility of ±25°. Fig.l shows typical ray diagrams formed by the six-stage image forming system. The system consists of a dual objective (objective lens; OL and objective mini-lens; OM), triple intermediate lens (IL1, IL2 and IL3) and single projector lens (PL).
Low Cost 210K Gain Transmission Electron Microscope Image (TEMI) Intensifier
Authors: Rosemeier R.G. , Taylor M.E. , Wylie A.G.
Published: June 2020

There are a number of factors that limit transmission electron microscope (TEM) characterization. For example, when it is necessary to statistically assess large numbers of samples quickly, conventional time consuming film recording is not a plausible solution. In the case of many electron beam sensitive biological, polymeric, and fiber materials, great care must be taken to avoid both specimen damage or structure change by using minimum electron beam current densities. On the other hand, for mineral specimens, which are in general difficult to thin, maximum electron beam currents may not be high enough to produce anything but faint TEM images. As a result, a low cost portable TEM image (TEMI) intensifier was developed that allows both direct viewing of faint electron diffraction phenomenon as well as conventional TEM viewing. Figure 1 shows the portable high gain TEMI intensifier.
Electron-Acoustic Microscopy of Polycrystalline Metals and Alloys
Authors: Cargill S.
Published: June 2020

Electron-acoustic microscopy is a mode of ultrasonic imaging in scanning electron microscopy for which image contrast arises primarily from spatial variations in the elastic and thermal properties of a specimen, e.g., its resistance to bending, resistance to heat flow, and volume expansion on heating. Electron-acoustic (EA) microscopy differs from conventional scanning electron microscopy in that the electron beam is chopped at kHz or MHz rates, and a piezoelectric transducer bonded to the specimen is used to detect ultrasonic signals which are generated thermoelastically within the specimen. A scanned, magnified image of the specimen is formed using the rectified output of this transducer, in place of the usual secondary or back scattered electron signal. This technique provides near-surface and subsurface information which is not accessible in other modes of SEM imaging. The experiments described here were performed with a Cambridge Stereoscan S4-10 SEM in which the electron beam was chopped electrostatically by deflector plates located below the second condenser lens.
Epizootic Hemorrhagic Disease Virus Infection in Salivary Glands ofCulicoides Variipennis
Authors: Foster Neil M. , Jones Robert H.
Published: June 2020

Epizootic hemorrhagic disease virus (EHDV) is transmitted to ruminants by the biting gnatculicoides variipennis. In cultured cells, EHDV replicated in cytoplasmic matrixes; filaments and macrotubules were observed in the cytoplasm and in association with viroplasms. This report describes EHDV infection ofC. variipennissalivary gland cells.

Normal colony female flies were infected either by intrathoracic inoculation of EHDV propagated in BHK-21 cell cultures (CC) or orally on EHDV-infected CC fluids mixed 1:9 with normal sheep blood. EHDV-exposed flies and noninfected controls were maintained alternately on water and a 10% sugar solution until salivary glands were removed at 9 (inoculated flies) and 19 (orally exposed flies) days for processing and viewing in thin section.

Viroplasms were observed in the cytoplasm often in intimate association with progeny virions and macrotubules (Fig. 1). Macrotubules and progeny virions also were found free in the cytoplasm away from viroplasms (Fig. 2). Macrotubules were found in bundles in ordered array whether in association with viroplasms or free in the cytoplasm.
Studies on the Fungal Pathogen of Dutch Elm Disease
Authors: Mazzone H.M. , Wray G. , Zerillo R.
Published: June 2020

The fungal pathogen of the Dutch elm disease (DED), Ceratocystis ulmi (Buisman) C. Moreau, has eluded effective control since its introduction in the United States more than sixty years ago. Our studies on DED include establishing biological control agents against C. ulmi. In this report we describe the inhibitory action of the antibiotic polymyxin B on the causal agent of DED.

In screening a number of antibiotics against C. ulmi, we observed that filter paper discs containing 300 units (U) of polymyxin B (Difco Laboratories) per disc, produced zones of inhibition to the fungus grown on potato dextrose agar or Sabouraud agar plates (100mm x 15mm), Fig. 1a. Total inhibition of fungal growth on a plate occurred when agar overlays containing fungus and antibiotic (polymyxin B sulfate, ICN Pharmaceuticals, Inc.) were poured on the underlying agar growth medium. The agar overlays consisted of the following: 4.5 ml of 0.7% agar, 0.5 ml of fungus (control plate); 4.0 ml of 0.7% agar, 0.5 ml of fungus, 0.5 ml of polymyxin B sulfate (77,700 U). Fig. 1, b and c, compares a control plate and polymyxin plate after seven days.
Polymorphism of Actin Paracrystals
Authors: Fowler W.E. , Aebi U.
Published: June 2020

In the muscle sarcomere and in certain specialized non-muscle cells actin filaments are organized in bundles or paracrystalline arrays. Structural studies of these naturally occurring filament arrays have been limited to about 3nm resolution, mainly due to inherent disorder of the specimen and/or difficulties with the preparation of these arrays for EM. Skeletal muscle G-actin can be induced to form synthetic filament paracrystals upon addition of non-physiological concentrations of Mg++ (e.g. 50mM) . The structural resolution obtained with these synthetic paracrystals has been of the same order (about 3nm) as that encountered with the naturally occurring filament arrays. Using a new method of induction, we have obtained synthetic paracrystals with two non-muscle actins which reveal structural detail to almost 2nm resolution (Figs. 1,2,3). While the same types of paracrystals were observed with Physarum and Acanthamoeba actin, skeletal muscle actin displayed a different polymorphism under identical conditions.
Ultrastructural Changes in Tumor Cells During Human Peripheral Blood Monocyte-Mediated Cytotoxicity
Authors: Muse K. E. , Fischer D. G. , Koren H. S.
Published: June 2020

Mononuclear phagocytes, a pluripotential cell line, manifest an array of basic extracellular functions. Among these physiological regulatory functions is the expression of spontaneous cytolytic potential against tumor cell targets.

The limited observations on human cells, almost exclusively blood monocytes, initially reported limited or a lack of tumoricidal activity in the absence of antibody. More recently, freshly obtained monocytes have been reported to spontaneously impair the biability of tumor target cells in vitro (Harowitz et al., 1979; Montavani et al., 1979; Hammerstrom, 1979). Although the mechanism by which effector cells express cytotoxicity is poorly understood, discrete steps can be distinguished in the process of cell mediated cytotoxicity: recognition and binding of effector to target cells,a lethal-hit stage, and subsequent lysis of the target cell. Other important parameters in monocyte-mediated cytotoxicity include, activated state of the monocyte, effector cell concentrations, and target cell suseptibility. However, limited information is available with regard to the ultrastructural changes accompanying monocyte-mediated cytotoxicity.
Fine Structure of Type IV Glycogenosis
Authors: Simons P.K.
Published: June 2020

Glycogenosis is defined as any condition in which the tissue concentration of glycogen is increased. There are currently ten recognized variants of glycogenosis that are heritable inborn errors of metabolism. The specific enzymatic defect in each of the variants is known or at least suspected. In all cases, the enzymatic defect prevents the proper metabolism or formation of the glycogen molecule. The clinical and histologic differences between the types of glycogenosis is important to a proper diagnosis after the presence of such a condition is realized. This study was initiated to examine the ultrastructure of the rare Type IV Glycogenosis (Amylopectinosis) of which there is very little morphologic characterization in the literature.

Liver tissue was obtained by needle biopsy from a 12-month-old Oriental female who was originally admitted to the hospital after observation of poor development, loss of appetite, and hepatomegaly. The majority of the tissue was fixed for light microscopy in neutral buffered formalin and processed using routine and special staining procedures (reticulin, trichrome, iron, copper, PAS, PAS-diastase and PAS-pectinase.
SEM Evaluation of Fluoride Pretreatment Effects on Acid-Etching of Caries-Like Enamel Lesions In Vitro
Authors: John Hicks M.
Published: June 2020

Acid-etching of enamel surfaces has been performed routinely to bond adhesive resin materials to sound dental enamel as a caries-preventive measure. The effect of fluoride pretreatment on acid-etching of enamel has been reported to produce inconsistent and unsatisfactory etching patterns. The failure to obtain an adequate etch has been postulated to be due to fluoride precipitation products deposited on the enamel surface. The purpose of this study was to evaluate the effects of fluoride pretreatment on acid-etching of carieslike lesions of human dental enamel.

Caries-like lesions of enamel were created in vitro on human molar and premolar teeth. The teeth were divided into two fluoride treatment groups. The specimens were exposed for 4 minutes to either a 2% Sodium Fluoride (NaF) solution or a 10% Stannous Fluoride (SnF2) solution. The specimens were then washed in deionized-distilled water. Each tooth was sectioned into four test regions. This was carried out to compare the effects of various time exposures (0 to 2 minutes) and differing concentrations (10 to 60% w/w) of phosphoric acid (H3PO4) on etching of caries-like lesions. Standard preparation techniques for SEM were performed on the specimens.
Myofibrillogenesis and Heart Induction in Cardiac Mutant Axolotls
Authors: Lemanski Larry F.
Published: June 2020

Mutant genes have been used in the past as research ‘tools’ for better understanding selected biological phenomena and for solving certain biological problems. It is particularly exciting when these mutations affect specific major organs of vertebrates. One such naturally-occurring recessive mutant gene, designated c for ‘cardiac lethal’ was discovered recently in the Mexican axolotl, Ambystoma mexicanum. Homozygous embryos (c/c) exhibit a lack of heart Function even though initial development of the organ seems normal. Cardiac lethal mutant (c/c) embryos are obtained by mating heterozygous adults (+/c x +/c) and can first be distinguished from their normal (+/+ or +/c) siblings at stage 35 (one week postfertilization) when the normals develop vigorously contracting hearts. Mutant embryos at this stage appear grossly normal, but their hearts fail to contract and cardiovascular circulation is not established. In spite of their nonfunctional hearts, mutant embryos survive through stage 41 (about 20 days beyond the heart-beat stage) and during this time display normal swimming movements indicating that skeletal muscle is not affected by the mutation.
Localization of Alpha Bungarotoxin Binding Sites in the Rat Carotid Body Using Horseradish Peroxidase-Conjugated Toxin
Authors: Chen I-Li , Mascorro Joe A. , Lumsden Patricia W. , Yates Robert D.
Published: June 2020

In a previous communication, we reported binding of 125I-alpha bungarotoxin (αBgt) to certain parenchymal cells in the rat carotid body. However, the exact cell types exhibiting the binding sites were not definitively identified. During the present study, horseradish peroxidase (HRP)-conjugated αBgt was used in order to obtain a precise location of αBgt-acetylcholine (ACh) receptor sites in the carotid body. αBgt was conjugated to HRP by a two-step technique, and its specificity to ACh receptors was tested histochemically by utilizing frozen sections of the mouse diaphragm. Carotid bodies from adult rats, with or without preincubation in 10-3M d-tubocurarine (d-Tc), were incubated in approximately 700 nM αBgt-HRP for one hour at 37°C. The tissue was washed, fixed in glutaraldehyde, reacted with a diaminobenzidine-hydrogen peroxide mixture, postosmicated and embedded in Epon 812.

Semithin sections revealed that the conjugate penetrated throughout the carotid body and became localized in all groups of parenchymal cells. Preincubation in 10-3M d-Tc completely abolished the labelings.
Dedifferentiation of the Axolemma Associated with Demyelination
Authors: Rosenbluth J. , Sumner A. , Saida T.
Published: June 2020

Freeze-fracture analysis of myelinated nerve fibers has shown that the axolemma has a highly differentiated structure. The node is characterized by a high concentration of intramembranous particles, primarily in the E fracture face, which may represent the sodium channels known to be concentrated there, and the paranodal axolemma is characterized by a distinctive paracrystalline pattern that corresponds to the intercellular junction formed with the terminal “loops” of myelin lamellae. Studies of myelin formation in normal animals and of myelin-deficient mutant animals indicate that the development of these axolemmal specializations is profoundly influenced by the associated myelinforming cells. The present study considers whether or not nodal or paranodal specializations that have already formed persist after demyelination.

In order to investigate this question, specimens of peripheral nerves were examined following exposure to an antiserum to galactocerebroside (GC), which is known to cause a predictable series of changes leading to demyelination. Freeze-fracture replicas of rat spinal roots exposed to anti-GC serum in situ for six hours showed marked changes in the paranodal axolemma.
The Role of the Golgi Apparatus in Mammalian Cell Secretion
Authors: Fleischer Becca
Published: June 2020

A major function of the Golgi apparatus of mammalian cells is the transport and modification of secretory products of the cell. These include proteins, glycoproteins, glycolipids, and lipoproteins. Our approach to understanding the role of the Golgi apparatus has been to isolate fractions rich in Golgi apparatus from mammalian tissues and to determine directly what secretory products and enzymic activities are present in these fractions compared to other purified cell components such as plasma membranes, mitochondria, nuclei, and endoplasmic reticulum. In order to accomplish this, we developed methods for this isolation of Golgi apparatus from liver, since methods for the isolation of the other organelles of this tissue were already well developed and liver is the sole source of most of the proteins and glycoproteins secreted into serum. We then applied these techniques with appropriate modification to isolate Golgi apparatus and other purified cell organelles from kidney, which we believe was a better source for study of the biosynthesis of glycolipids.
Studies on the Galactose-Specific Recognition System of Mammalian Liver
Authors: Hubbard A. L. , Wall D. A. , Zeitlin P. L. , Hong S. W.
Published: June 2020

The rapid removal of circulating desialylated glycoproteins from the blood plasma of mammals is well-documented, occurs exclusively in the liver and is mediated by a carbohydrate recognition system present only in hepatocytes. After binding to a plasma membrane receptor that recognizes galactose, glucose or N-acetylgalactosamine residues on their oligosaccharide chains, ligands are rapidly internalized, transported within membrane-bound structures to lysosomes and subsequently degraded. The fate of the receptor is less clear, although it is reutilized. Our recent experiments have addressed three questions: 1) What is the detailed intracellular pathway taken by asialo-glycoproteins (ASGP's)? 2) Where on the hepatocyte cell surface are ASGP's bound? and 3) What is the intracellular distribution of the ASGP receptor?

Two electron microscopic tracers have been used to investigate the internalization of ASGP's by hepatocytes: asialoorosomucoid covalently coupled to horseradish peroxidase (ASOR-HRP); and lactosaminated ferritin (Lac-Fer), a ferritin molecule to which 90-110 lactose molecules have been attached via their glucose moieties.
Structural Changes in Cerebellar Cortex Induced by Intrauterine Growth Retardation in the Rat
Authors: Feria-Velasco Alfredo , Tapia-Arizmendi Guadalupe
Published: June 2020

Intrauterine growth retardation (IUGR), both in human and experimental animals, can be produced by two types of factors : intrinsic and extrinsic. Intrinsic growth failure may result from congenital and/or genetic alterations. Two main categories of extrinsic growth failure have been described: a) produced by interfering with placental blood flow to fetuses; and b) produced by maternal dietary restriction. In both types, alterations of neurological functions are observed, mainly related to learning and memory.In various models of IUGR, the cerebellum is more affected than the other structures of the central nervous system,according to biochemical studies carried out by different authors.

For the present work, IUGR was produced in Sprague Dawley rats according to Wigglesworth's method by ligation of one uterine artery at the 15th gestational day. The products and placentas were obtained by cæsarean section at the 21st gestational day to be weighed and studied with the light and electron microscope. The data here presented correspond to the ultrastructural study of cerebellar cortex of neonates perfused intravascularly with 2.5% buffered-glutaraldehyde, postfixed with buffered osmium tetroxide and processed for transmission electron microscopy.
Ultrastructure of Human Placenta: Effects of Maternal Drinking
Authors: Amankwah K.S. , Weberg A.D. , Kaufmann R.C.
Published: June 2020

The effects of maternal alcohol consumption upon the fetus during gestation have been well documented in the literature. The data in such studies are primarily based on gross morphological evaluations of the fetus and the placenta. The placenta is an organ specially formed during gestation to exchange metabolites between mother and fetus. Although it functions by selectively transporting certain materials from the maternal blood, it is freely permeable to other substances such as alcohol. In this investigation, we have studied the effects of maternal alcohol consumption on the ultrastructure of the human placenta by TEM and SEM.

Placentae from four women who admitted to consuming copious amounts of alcoholic beverages and four controls were used in this study. Villous tissue from centrally located cotyledons of freshly delivered placentae were fixed in 3% gluteraldehyde in 0.1M cacodylate buffer pH 7.3.Samples for SEM were processed by OTOTO3 technic, dehydrated and critical point dried with CO2. Samples for TEM were post-fixed in Osmium ferro- cyanide (1:1 mixture of 1.5% aqueous OsO4 and 2.5% K4Fe(CN)6).
Morphologic Changes in the Egg of the Polychaete Worm Mercierella Enigmatica after Fertilization
Authors: Humphreys Walter J.
Published: June 2020

Comparative ultrastructural studies of changes in the morphologies of invertebrate eggs that occur after fertilization may shed light on the evolution of the fertilization process and the incorporation of mechanisms that may serve to insure monospermy as well as to provide protective envelopes for the developing embryo. This report describes changes that occur in the egg of Mercierella enigmatica as noted 35 minutes after fertilization.

Eggs or sperm were shed spontaneously when the worms were pulled from their tubes and placed in individual watch glasses containing sea water. The unfertilized eggs were fixed for 1 hour in 2.5% glutaraldehyde in 0.1M cacody- late buffer at pH 7.5. The eggs were rinsed in sea water and post fixed for 1 hour in 1% osmium tetroxide buffered with 0.1M phosphate buffer at pH 7.5. Other eggs were fertilized by the addition of sea water containing sperm and fixed as above after 35 minutes. Eggs were embedded in Epon and compared by TEM. Embedments of the unfertilized eggs and fertilized eggs were fractured and coated with vacuum evaporated gold for SEM.
Rotary Beveling for In Situ Thin-Section Microscopy of Cell Cultures
Authors: Handley Dean A. , Alexander Jack T. , Chien Shu
Published: June 2020

In situ preparation of cell cultures for ultrastructural investigations is a convenient method by which fixation, dehydration and embedment are carried out in the culture petri dish. The in situ method offers the advantage of preserving the native orientation of cell-cell interactions, junctional regions and overlapping configurations. In order to section after embedment, the petri dish is usually separated from the polymerized resin by either differential cryo-contraction or solvation in organic fluids. The remaining resin block must be re-embedded before sectioning. Although removal of the petri dish may not disrupt the native cellular geometry, it does sacrifice what is now recognized as an important characteristic of cell growth: cell-substratum molecular interactions. To preserve the topographic cell-substratum relationship, we developed a simple method of tapered rotary beveling to reduce the petri dish thickness to a dimension suitable for direct thin sectioning.
Activated Pectin Stained with Heavy Metals
Authors: Smith Craig A. , Hanker Jacob S. , Malcolm Brown R.
Published: June 2020

Pectin was visualized in carrot tissue culture with a stain utilizing hydroxylamine and iron. Actively growing cells were fixed in glutaraldehyde or paraformaldehyde. The pectin was activated by an alkaline hydroxylamine treatment. When the so formed pectic hydroxamic acids were reacted with ferric chloride, a reddish-brown color was visible en masse, but the cells were not sufficiently stained for either light or electron microscopy.

We hoped to intensify the stain by bridging iron to osmium. Since one Fe (III) complexes three gallocyanins, we tested this dye as a bridge in an attempt to amplify the staining. Thiocarbohydrazide (TCH) was tested as an alternate bridge. After excess iron was washed out, the cells were treated with either 1% gallocyanin for one hour, or 0.5% TCH for one minute. After excess bridge was removed by a second wash, a portion of each treatment was placed in 1% osmium tetroxide for one hour.
The Extent of Platinum-Carbon Electron Beam Gun Degassing Before Replication Can Change the Size and Frequency of Replicated Small Particles
Authors: Ruben George C.
Published: June 2020

The freeze-fracture of cellular membranes generally reveals particles of different sizes distributed on a membrane fracture face. These views of the membrane are generally characterized by the frequency of particles per area and a particle shadow width distribution with its mean. It is generally assumed that these particle size and frequency parameters can be influenced by the replica film thickness and the shadowing angle. It is not known whether the extent of Pt-C electron beam gun degassing prior to the replication step can change the shadow width distribution means of spherical gold particles, and their percent representation following replication.

Two experiments were performed in a Balzer's model 360M freezing microtome (10-6 torr) in which the EKV 552 Pt-C electron beam gun was degassed for 19 sec. (film I) and for 120 sec. (film II) at a current setting of 5 on the EVM 052 control unit. The gold ball calibration grids (2) were cooled to -96°C and covered with the knife arm (-196°C) during degassing.
Regulation and Localization of Calmodulin in Eucaryotic Cells
Authors: Means A.R. , Chafouleas J.G. , Bolton W. , Boyd A.E. , Lagace L. , Rowle D. , Guerriero V.
Published: June 2020

Calmodulin (Cam) regulates cyclic nucleotide and glycogen metabolism, protein phosphorylation, Ca2+flux, cell motility and division. CaM also affects the state of microtubule (MT) polymerization by promoting the disassembly of these structures in a Ca2+-dependant manner. In mitotic cells, we have established an inverse relationship between the number of polymerized MTs and the concentration of CaM. These data suggested that selective elevation of CaM in a cell should result in a decrease in the number of polymerized MTs. Many malignant cells have been reported to exhibit a diminished cytoplasmic microtubule complex (CMTC). When CaM levels were quantitated by radioimmunoassay (RIA), it was found that transformed cells always contained 2-3 times more CaM than their nontransformed counterparts. This elevation was found regardless of whether the cells were transformed by oncogenic viruses, chemical carcinogens or hormones. Studies in two companion cell lines, Swiss mouse 3T3 and 3T3 cells transformed by SV-40 (SV3T3) as well as normal rat kidney (NRK) and NRK transformed by Rous sarcoma virus (RSV), have shown that the increase in CaM occurs at the level of synthesis and not degradation.
Correlation of Ultrastructural, Morphometric and Biochemical Changes in Rats after Treatment with the Hypolipidemic Drugs Clofibrate and Probucol
Authors: Visscher G. E. , Robison R. L. , Engstrom R. G.
Published: June 2020

It was our goal to evaluate the reliability and reproducibility of semi-automated morphometric techniques in the analysis of structural changes observed during drug safety assessment. Studies are presented to correlate the ultrastructural, morphometric and biochemical effects that the two hypolipidemic agents, clofibrate and probucol, produce in rats.

Charles River CD Sprague-Dawley derived male rats (200-225 g body wt.) were used for the three studies performed. In studies I and II, clofibrate was administered as a dietary admixture to approximate a dosage of 300 mg/kg/day for six days. In study III, clofibrate and probucol were given as dietary admixtures to approximate dosages of 300 and 250 mg/kg/day respectively for fourteen days. Processing of hepatic specimens for electron microscopy included fixation in 1.3% sym-collidine buffered osmium tetroxide, ethanol dehydration and Epon embedment. Thin sections (600Å) were stained with uranyl acetate and lead citrate. Survey and photography was performed in the manner according to Weibel. Final prints (14,400x) were analyzed with a Zeiss MOP for morphometric quantitation.
Characteristic Lesions in Mouse Retina Irradiated with Accelerated Iron Particles
Authors: Malachowski M.J. , Philpott D.E. , Corbett R.L. , Tobias C.A.
Published: June 2020

During the Apollo flights to the moon the astronauts reported light flash sensations after dark adaption. The cause of these “flashes” is due to the passage of heavy energetic cosmic-ray particles (HZE) through the retina. The rate of energy transfer of the HZE particle in tissue along the path of the particle is proportional to the square of the atomic number and approximately inversely proportional to the kinetic energy. Thus, a single iron particle (Z=26) transfers 676 times more energy than a proton of the same velocity. A critical question concerning the potential hazards of HZE particles is whether or not an individual particle can inflict serious damage to a series of ceils.

A program is underway to determine the radiation hazards of HZE particles using the Bevalac, a heavy-ion accelerator at LBL. Our earlier work with helium, carbon, neon, and argon particles, and exposure of rats to HZE particles in space flight demonstrated some deleterious biological effects.
Purkinje Cell Morphology Under Experimental and Natural Rabies Infection in Different Species
Authors: Hernández-Jáuregui P. , González-Angulo A. , Hernández-Baumgarten E.
Published: June 2020

Purkinje neurons frequently showed rabies inclusion bodies in natural rabies infection thus providing elements for an accurate diagnosis of rabies. After studying several sections of cerebellar cortex of experimentally infected mice with fixed rabies virus, no viral inclusion bodies were found. Degenerative changes in Purkinje cells however were commonly found as mayor evidence of cell damage or infection. (Fig. 1,2) The fact that no viral inclusions (Negri bodies) were present in Purkinje neurons of experimentally infected animals and instead there were definite degenerative changes prompted us to study the ultrastructure of these cells in an attempt to find an explanation of this peculiar reactions.

Experimentally infected animals; 20 mice were infected in the brain using the Mazatan and V319 fixed rabies strains isolated from infected Desmodus rotundus vats. Five dogs were innoculated in the maseteric muscles using a salivary gland suspension previously obtained from natural rabid dogs. The cerebellar cortex of these animals were fixed by vascular perfusion and conventionally studied for transmission electron microscopy.
Feeding and Digestion in Allogromia (Foraminifera)
Authors: Bowser S. S. , Koury S. T. , McGee-Russell S. M.
Published: June 2020

Foraminifera (“forams”) are important to micropaleontology as stratigraphic indicators and within this context the literature is extensive. Comparatively, biological studies are few. The striking bidirectional cytoplasmic streaming in the reticulopo-dial network (RPN) of some forams has been of primary interest. Only recently has their potential as a model system for other aspects of cellular transport been recognized. The naked foraminiferan Allogromia sp. (N.F.Lee), is particularly well suited for such studies. We have found that by plating these forams on coverslips treated with protamine sulfate (1.5 mg/ml) the flexible theca flattens, thus exposing the cell body contents and complex patterns of cytoplasmic streaming to the light microscope (LM). Our aim is to take advantage of the ease with which correlative LM and EM techniques can now be applied to the study of function and transport of components in both the cell body (CB) and RPN.