bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Interaction of Protamine by Dark Field Electron Microscopy
Authors: Bazett-Jones D.P. , Ottensmeyer F.P. 
Published: June 2020

It has been shown for some time that it is possible to obtain images of small unstained proteins, with a resolution of approximately 5Å using dark field electron microscopy (1,2). Applying this technique, we have observed a uniformity in size and shape of the 2-dimensional images of pure specimens of fish protamines (salmon, herring (clupeine, Y-l) and rainbow trout (Salmo irideus)). On the basis of these images, a model for the 3-dimensional structure of the fish protamines has been proposed (2).The known amino acid sequences of fish protamines show stretches of positively charged arginines, separated by regions of neutral amino acids (3). The proposed model for protamine structure (2) consists of an irregular, right-handed helix with the segments of adjacent arginines forming the loops of the coil.
Evidence for a Unique Intercellular Communication in the Thymic Cortical Capillaries of the Mouse
Authors: DAVENPORT WM. D. 
Published: June 2020

Thymic tissue from 24-56 day old mice was examined with respect to the ultrastructure of the endothelial cell junctions of the cortical capillaries. These junctions have been described as being desmosomes, desmosome-like, or tight junctions. Data obtained from the present study suggest that these junctions are unique.The morphologically mature thymic cortical capillary (TCC) endothelial cell junction in the present study is considered to be a pentalaminar structure consisting of: (1) a cytoplasmic density, 800-1500 Å in length and 200-500 Å in width, against the inner leaflet of the unit membrane of the endothelial cell process; (2) a space or area of decreased density adjacent to the outer leaflet of the unit membrane of the same endothelial cell process;
The Effect of Viewing Angle on the Appearance of Trilaminar Structures of Desmosomes
Authors: Neal Richard J. , Paulson Joy L. 
Published: June 2020

Examination of desmosomes in the spinous region of the epidermis of human skin reveals that the trilaminar structure, usually associated with desmosomes, is not always observed. Desmosomes were examined utilizing serial sectioning and tilting techniques to determine if the trilaminar structure is consistant throughout the desmosome. Concomitantly, information concerning the size and shape of the spinous layer desmosomes was obtained from examination of serial sections that completely transversed many desmosomes.Figures 1 and 2 are from a serial section series and demonstrate that the trilaminar structure of desmosomes (Dl and D2) can be observed in one section (figure 1) and not observed in an adjacent section (figure 2). Figure 3 thru Figure 6 are micrographs of the same section seen in Figure 2. These micrographs show the effect on the appearance of desmosomes Dl and D2 when they have been tilted about their longitudinal axes 5, 10, 20, and 30 degrees, respectively.
Effect of Thyroxine and Estrogens on Collagen Synthesis in Rats: A Transmission and Scanning Electron Microscopy Study
Authors: Lupulescu A. , Habowsky J.E. , Milkintas J. , Birmingham D. 
Published: June 2020

Recent light and electron microscopic studies showed that corticosteroids and testosterone induced changes in the structure of fibroblasts and collagen synthesis. Our previous investigations demonstrate that also calcitonin significantly interferes with collagen synthesis and fibroblast growth in wounded rabbits.Conflicting findings were reported by using biochemical and light microscopic studies following estrogens and thyroxine administration. This report concerns some investigations with regard to the role of estradiol and thyroxine on collagen synthesis in rats.Adult male rats were used in these experiments. They were divided in three groups of 10 rats each. A) Thyroxine-treated rats: each rat received intramuscularly (im) 100 μg thyroxine (Synthroid), every other day, for one month. B) Estrogen-treated rats: each rat received 500 μg estradiol dipropionate, every other day, for one month. C) Controls, received only the diluent.
Electron Microscopic Analysis of Myonecrosis Induced by a Pure Component Isolated From Rattlesnake Venom
Authors: Ownby Charlotte L. , Cameron David , T. Tu Anthony 
Published: June 2020

In the United States the major health problem resulting from snakebite poisoning is local tissue damage, i.e. hemorrhage and myonecrosis. Since commercial antivenin does not usually prevent such damage to tissue, a more effective treatment of snakebite-induced myonecrosis is needed. To aid in the development of such a treatment the pathogenesis of myonecrosis induced by a pure component of rattlesnake venom was studied at the electron microscopic level.The pure component, a small (4,300 mol. wt.), basic (isoelectric point of 9.6) protein, was isolated from crude prairie rattlesnake (Crotalus viridis viridis) venom by gel filtration (Sephadex G-50) followed by cation exchange chromatography (Sephadex C-25), and shown to be pure by electrophoresis. Selection of the myotoxic component was based on light microscopic observations of injected mouse muscle.
Scanning Electron Microscopy of Chondrocytes from Fracture Callus Cartilage
Authors: Jafri A.M. , Ketenjian A.Y. , Arsenis C. 
Published: June 2020

There is little information available in the literature on scanning electron microscopy of cartilage tissue. Most of the available information deals with articular cartilage (1,2). More specifically, there are no studies reported on the scanning electron microscopy of differentiating callus cartilage. This preliminary report is part of our studies on the differentiation and eventual calcification of rabbit callus cartilage.Closed fractures were produced in the tibias of white rabbits by acute angulation. Seven days after fracture, the callus was dissected into homogenous cartilage sections corresponding to the fibrous, hypertrophic and calcified cartilage types of the epiphyseal plate (3). The cartilage specimens were dehydrated by ascending acetone series or freeze-dried. Some acetone dried specimens were freeze-dried while others were critical point dried. All specimens were mounted on Cambridge specimen stubs and coated with carbon and gold.
Fine Structure of the Elastic Fibers and the Elastin Crystalloids by Means of Tannic Acid Fixation Method
Authors: Mizuhira V. , Futaesaku Y. , Nakamura H. 
Published: June 2020

It is well known that the elastic fibers do not stain well with conventional electron fixation and staining methods. However some investigators have tried to demonstrate elastic fibers as a stained structure under the electron microscope. Greenlee et al.(1966) and Ouintarelli et al.(1973) reported a phosphotaungstic acid staining method for elastic fibers; Albert (1970 & 1971) reported his results using a metalic tetraphenylprophine staining method.In the contrast to these staining methods for elastic fibers, Mizuhira et al (1971,'72, ‘75) have succeeded in demonstrating elastic fibers very clearly using an improved fixation method for proteins with glutaraldehyde containing tannic acid, followed by the osmium tetraoxide method.This new fixation method is very simple. Aorta, ear cartilage, intestine or skin are fixed with 2.5 % glutaraldehyde, containing 0.5 % to 4 % tannic acid buffered with veronal acetate or phosphate at pH 6.8 to 7.2 for 1.5 hrs to overnight.
Electron Probe Analysis of Vertebrate Smooth Muscle: Distribution of Ca and Ci
Authors: Somlyo Avril V. , Shuman H. , Somlyo A.P. 
Published: June 2020

This is a preliminary report of electron probe analysis of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle cryosectioned without fixation or cryoprotection. The instrumentation and method of electron probe quantitation used (1) and our initial results with cardiac (2) and skeletal (3) muscle have been presented elsewhere.In preparations depolarized with high K (K2SO4) solution, significant calcium peaks were detected over the sarcoplasmic reticulum (Fig 1 and 2) and the continuous perinuclear space. In some of the fibers there were also significant (up to 200 mM/kg dry wt) calcium peaks over the mitochondria. However, in smooth muscle that was not depolarized, high mitochondrial Ca was found in fibers that also contained elevated Na and low K (Fig 3). Therefore, the possibility that these Ca-loaded mitochondria are indicative of cell damage remains to be ruled out.
Quantitation in thin Sections Within the Electron Microscope
Authors: Edie J. 
Published: June 2020

In TEM image formation, the observed contrast variations within thin sections result from differential electron scattering within microregions of varying mass thickness. It is possible to utilize these electron scattering properties to obtain objective information regarding various specimen parameters (1, 2, 3).A pragmatic, empirical approach is described which enables a microscopist to perform physical measurements of thickness of thin sections and estimates of local mass, volume, density and, possibly, molecular configurations within thin sections directly in the microscope. A Faraday cage monitors the transmitted electron beam and permits measurements of electron beam intensities.
Stem Examination of a Protein
Authors: Hainfeld J. , Cooley J. 
Published: June 2020

Glyceraldehyde-3-phosphate dehydrogenase (G3PD) was viewed by darkfield microscopy in the STEM using several specimen preparations including the use of negative stain, positive stains and no stain. Some of the resultant images have been subsequently compared with projections of the molecule computed from atomic coordinates (coordinates provided by M. G. Rossmann, Purdue University). G3PD is a glycolytic enzyme of molecular weight approximately 140,000, exists as a tetramer and is approximately 75 Å in diameter.Fig. 1 shows a negatively stained protein on the left compared to a computed, projected view of the protein on the right. The stain used was methyl amine tungstate. 5-10 Å detail is visible in micrographs taken with this type of preparation. 10 Å detail seems to reproducibly correspond to the known structure. A 5 Å strand, presumably part of the polypeptide from the unfixed protein, is visible in Fig. 2.
Quantitative Energy-Dispersive Analysis
Authors: Reed S.J.B. 
Published: June 2020

INTRODUCTION. Quantitative analysis is possible with an E.D. system, provided its performance is adequate (stability especially). Such a system may be fitted to an electron probe, SEM, TEM, or STEM and used for the analysis of either thick or thin specimens, of which the former are considered primarily here, though in many respects the procedures discussed are equally applicable to thin specimens. Elements in the range Z = 11-30 are primarily of interest (i.e. those with K peaks in the energy range 1-10 keV), though heavy elements with L or M peaks in this energy range can be treated by the methods discussed as well.PEAK IDENTIFICATION. Often the analyst knows the elements present in the specimen. If not,a procedure for identifying peaks in the recorded spectrum is necessary. Various mathematical techniques are available for this purpose (e.g. cross-correlation with a gaussian).
High Resolution Sem Fractography of Te-Embrittled Hastelloy-N
Authors: Braski D. N. 
Published: June 2020

Hastelloy-N (16%Mo-7%Cr-4%Fe-0.55%Mn-0.06%C-bal Ni) has long been a leading candidate material for a molten salt reactor. However, it was recently discovered that small amounts of Te, created by the fission process, caused grain boundary embrittlement in the structural material. Consequently, an alloy development program at this laboratory has directed considerable efforts towards modification of Hastelloy-N to improve its resistance to Te embrittlement and still retain excellent resistance to radiation damage. In this investigation, a JEOL 100C TEM with an energy dispersive x-ray spectrometer (EDX) and high resolution (50 Å) SEM attachments have been used to characterize the grain boundary surfaces of various Hastelloy-N alloys embrittled by Te.Samples of Hastelloy-N were exposed to the tellurium source, Cr3Te4, in a molten salt (LiF + BeF2 + ThF4) or to the vapor above Cr3Te4 in a closed quartz system. All corrosion tests were at 700°C. The samples were subsequently tensile tested to failure at room temperature.
Study of Diffuse Scattering by Means of High Resolution Structure Images
Authors: Iijima Sumio , Anstis G. R. 
Published: June 2020

Disorders in crystals with relatively simple structures which gave diffuse scattering have been extensively studied by X-ray or neutron diffraction methods. All these investigations were based on traditional diffraction methods and observations were made in reciprocal space (note observable diffraction intensities can be considered only in terms of interatomic vectors) and therefore the results obtained there leaves considerable ambiguity, particularly when we try to derive an actual model of the disordered crystals. A solution of this problem will be given only by knowing all atom positions in an assembly of atoms and for this case the observable diffracted intensity is given bywhere (xi,yi) and (xj,yj) represent position vectors of the i th and j th atoms with scattering factors fi and fj from an arbitrary origin. On the other hand, a crystal containing imperfections can be defined by
Determination of the Signal and Noise Power Spectra for Wiener Filtering
Authors: Frank J. 
Published: June 2020

Object restoration from bright field electron micrographs by Wiener filtering has been attempted by several authors (1-4). The linear filtering approach implies that the usual weak phase object assumption is made. In the notation used by Welton and Harris (3), the filter function has the formwhere the power spectra of noise and object, N2(k) and S2(k) and the instrumental transfer function P(k) have to be obtained from measurements. The object power spectrum can be estimated from the atomic scattering factor of the dominating atomic species (3) , from electron diffraction measurements (5), or from the measured image power spectrum
Specimen Charging: Effect on Beam Voltage
Authors: McMillan W. R. , Russ J. C. 
Published: June 2020

Users of electron column instruments have long known of the mischievous results of charging of non-conductive specimens. The consequences can range from slight image degradation to complete chaos, and in the case of reflection electron diffraction sometimes produces images of expanding and collapsing bubbles instead of steady concentric rings.The cure for this trouble has usually been to vacuum coat the specimen with a conductive layer: carbon, gold, and to a limited degree, fine graphite spray-coated on the surface (1,2). Charge neutralizing with alpha-emitting isotopes or electron guns where a general spray of electrons with a few hundred volts of energy is aimed at the entire specimen also have been used to allow incipient charging to leak off to ground.
Observations of Surface Diffusion at the Atomic Level by Means of Microcinematography in the Stem
Authors: Isaacson M. S. , Kopf D. , Parker N. W. , Utlaut M. 
Published: June 2020

We have previously indicated the potential application of the STEM for studying surface phenomena on an atomic scale and noted that direct measurements of atom motion in the STEM could be of use in obtaining an improved understanding of a variety of surface processes. In this paper we would like to present some further observations concerning the motion of heavy atom containing molecules on thin carbon substrates due to thermal diffusion.A typical example of heavy atom containing molecules migrating on a carbon substrate is shown in Fig. 1. The specimen is uranylchloride molecules on an ∼ 20 Å thick carbon film. The dark field micrographs have been taken with 17 second exposures. The beam is not irradiating the field of view between exposures. In this set of micrographs it appears that the uranium atom “spot” is migrating towards the large cluster in the lower portion of the field.
The Microstructure of Fe-Cr-Co-Nb-Al Permanent Magnet
Authors: Okada M. , Homma M. , Kaneko H. , Thomas G. 
Published: June 2020

Fe-Cr-Co permanent magnet alloys are known to be commercially potential magnets, the energy products of which are comparable to those of Alnico V, with good ductility (1). It was recently found that the addition of Nb and A1 to the Fe-Cr-Co alloy system facilitated heat treatments to produce good magnetic properties (2).The present paper describes the microstructure of an Fe-Cr-Co-Nb-Al permanent magnet. An effect of a thermomagnetic treatment on the microstructures is also discussed since a thermomagnetic treatment plays an important role in producing good magnetic properties in this alloy.The magnetic hardening of the alloy is performed by tempering after solution treatment. Upon tempering, a a phase spinodally decomposes into two phases, an iron-rich phase (α1) and a chromium rich phase (α2) (1).The microstructure shown in Fig. 1 results after the Fe-28wt%Cr-15wt%Co-lwt%Nb alloy is tempered at 640°C for 20 min. The decomposition process appears to be isotropic in the alloy. No satellites are observed in the corresponding diffraction pattern.
Electron Microscopy of Lunar Dunite 72417
Authors: Lally J.S. , Nord G.L. , Christie J.M. , Heuer A.H. 
Published: June 2020

Lunar dunite 72417 is a brecciated dunite thought to be an original cumulate from the primary lunar differentiation and crustal formation. The complex olivine deformation structures and fine matrix material have been studied by high voltage transmission electron microscopy to augment geochemical and petrographic studies of other researchers. Our specimen, 72417,9009 is predominantly olivine "clasts" of variable size, set in a "matrix," also of olivine. The clasts and matrix of this breccia are essentially distinguishable only by size. Minor orthopyroxene, plagioclase and metal are also present. The angular "clasts" (largest is 0.3 mm) contain planar boundaries with misorientations of a few degrees (unlike boundaries in olivine tectonites). The finer-grained matrix has a few percent porosity and shows no optical evidence of recrystallization.Substructures in Large Clasts. Several large clasts were examined and show a variable subgrain structure (Fig. la); smaller subgrains tend to be equiaxed and μlpm in size, while the larger subgrains are elongate and up to lOum long.
Analysis of Microgram Tungsten Carbide-Cobalt Cemented Carbides
Authors: Emma T.A. 
Published: June 2020

When small quantities of a grain growth inhibitor are added to starting powders containing submicron WC and Co, the sintered product is a high strength, high hardness alloy. The microstructure of the carbide is quite similar to that of the macrograin variety. For the purposes of this study WC with 10-20% Co alloys containing small amounts of a grain growth inhibitor were examined with the electron microscope to determine grain size and shape, general composition, identification of possible undesirable species, and the disposition of the grain growth inhibitor.During the initial stages of the investigation, fractured surfaces were examined using an RCA-3F microscope converted to operate as a high resolution diffraction instrument with 50 cm camera. Reflection patterns from fractured surfaces showed that the major phase was cobalt with a weaker pattern from WC, indicating that fracture took place inside the cobalt cement. These same surfaces were then treated electrolytically in concentrated sulfuric acid at a temperature in the range between 3 and 8°C to remove the cobalt binder.
TEM Analysis of Long-Period Polytypes in SiC—S
Authors: Shinozaki S. , Sprys J. W. 
Published: June 2020

In reaction sintered SiC (∽ 5um average grain size), about 15% of the grains were found to have long-period structures, which were identifiable by transmission electron microscopy (TEM). In order to investigate the stability of the long-period polytypes at high temperature, crystal structures as well as microstructural changes in the long-period polytypes were analyzed as a function of time in isothermal annealing.Each polytype was analyzed by two methods: (1) Electron diffraction, and (2) Electron micrograph analysis. Fig. 1 shows microdensitometer traces of ED patterns (continuous curves) and calculated intensities (vertical lines) along 10.l row for 6H and 84R (Ramsdell notation). Intensity distributions were calculated based on the Zhdanov notation of (33) for 6H and [ (33)3 (32)2 ]3 for 84R. Because of the dynamical effect in electron diffraction, the observed intensities do not exactly coincide with those intensities obtained by structure factor calculations. Fig. 2 shows the high resolution TEM micrographs, where the striped patterns correspond to direct resolution of the structural lattice periodicities of 6H and 84R structures and the spacings shown in the figures are as expected for those structures.
Physical, Chemical, and Crystallographic Characterization of Anodic Coatings on High Strength Aluminum Base Alloys
Authors: Herfert R. E. , McDevitt N. T. 
Published: June 2020

Durability of adhesive bonded joints in moisture and salt spray environments is essential to USAF aircraft. Structural bonding technology for aerospace applications has depended for many years on the preparation of aluminum surfaces by a sulfuric acid/sodium dichromate (FPL etch) treatment. Recently, specific thin film anodizing techniques, phosphoric acid, and chromic acid anodizing have been developed which not only provide good initial bond strengths but vastly improved environmental durability. These thin anodic films are in contrast to the commonly used thick anodic films such as the sulfuric acid or "hard" sulfuric acid anodic films which are highly corrosion resistant in themselves, but which do not provide good initial bond strengths, particularly in low temperature peel.The objective of this study was to determine the characteristics of anodic films on aluminum alloys that make them corrosion resistant. The chemical composition, physical morphology and structure, and mechanical properties of the thin oxide films were to be defined and correlated with the environmental stability of these surfaces in humidity and salt spray. It is anticipated that anodic film characteristics and corrosion resistance will vary with the anodizing processing conditions.
Exogenous Perioxidase Localization in Irradiated Arteries
Authors: Hampton James C. , Rosario Benjamin , Adee Roy R. 
Published: June 2020

Mice were exposed to 1500 R X-irradiation and sacrificed on days 1,2,3,3.5 and 4 days postexposure. Two to 3 min before sacrifice each mouse received 5 mg horseradish peroxidase (Sigma type II) in 0.5 ml saline by intrasplenic injection. Tissues were fixed in glutaraldehyde-formaldehyde and incubated according to the method of Karnovsky for histochemical localization of horseradish peroxidase (HRP). Unirradiated tissues and irradiated but unincubated tissues were used as controls.Figure 1 shows only moderate staining of the internal elastic lamina (IEL) in a small branch of the mesenteric artery at 3 days postirradiation. No evidence of deposits of HRP reaction product was observed in either the endothelium or smooth muscle of the media.
Ultracytochemistry of Carbonic Anhydrase (CAH) in Erythrocytes and Intestinal Epithelium
Authors: Lightfoot F. G. , Cassidy M. M. , Jackson M. J. 
Published: June 2020

Since the transport of fluid and weak electrolytes by the small intestine is markedly inhibited by acetazolamide we have studied the cytochemical localization of carbonic anhydrase (CAH) in rat jejunum using the erythrocyte as a model system. Pieces of jejunal tissue were glutaraldehyde-fixed, frozen to -20C and 10 micron sections were obtained with a cryostat microtome. Human erythrocytes were similarly fixed, saline-rinsed and embedded in gelatin which was then treated in the same manner as tissue.The histochemical reaction product in light microscopy sections is CoS derived from the precipitation of catalysed CoCO3 formation. The reaction time was 8 minutes and the visible CAH activity in both erythrocytes and jejunum (Fig. 1, 2 and 6) was abolished by 1 X 10-4M acetazolamide.