bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Basis for Pulsations in the Eye of a Snail, Helix aspersa
Authors: Eakin Richard M. , Brandenburger Jean L.
Published: June 2020

We have discovered a remarkable motion in the eye of the snail Helix aspersa, namely, regular contractions, about one per second, which are dependent upon light within the visible spectrum from approximately 440 nm to 640 nm. To observe the pulsations, an eye must be extirpated and its lens removed by an incision in the cornea. If a pulsating eye is placed in the dark, contractions cease, but they commence again within 10 to 30 seconds upon re-illumination. What is the mechanism for this motion?

First, the pigmented supportive cells possess longitudinally arranged bundles of microfilaments which might be contractile, like filaments of actin. Single microfilaments measure about 40 Å in diameter.
Ultrastructural Investigation of the “Light Flash” Phenomenon Seen by our Astronauts
Authors: Philpott Delbert E. , Corbett R. , Black Sam , Turnbill Charles
Published: June 2020

The light flashes seen by astronauts on their flights to the moon are believed to be caused by “heavy primaries” passing through the eyes. In order to learn more about this phenomenon and its effect on the retina, pocket mouse retinas were exposed to nitrogen beams (the heaviest nuclei available at Lawrence Radiation Laboratory) and also the evoked response from X-rays on rabbit eyes was observed.

Pocket mouse retinas were exposed to nitrogen beams for the first time in the Berkeley Bevatron Accelerator. The pocket mice were positioned so as to expose one eye while the other eye was left unexposed. Both eyes were compared with controls (Fig. 1).
The Rootlets in the Mammalian Oviductal Epithelial Cilia
Authors: Nayak R. K. , Wu A. S. H.
Published: June 2020

Fawcett commented that the striated rootlets compared to those of lower animals are rarely observed in mammals. Recently, Brenner suggested that rootlets are not found in all mammalian cilia but are present in rhesus monkey and human oviduct. In this study, the presence of such rootlets in the guinea pig, rabbit, porcine, and bovine oviductal epithelial cilia have been demonstrated. Furthermore, the effects of steroids on the oviductal cilia and rootlets have been studied. The tissues used for this study were obtained from 2% rabbits, 8 guinea pigs, 8 cows, and 12 gilts. Small pieces of tissue were fixed in cold 3% cacodylate buffered glutaraldehyde, postfixed in 1% osmic acid; embedded in epon and processed for electron microscopy in the usual way.
Physical Preservation Methods for Biological Material
Authors: Bullivant Stanley
Published: June 2020

This review will be limited to physical preservation methods involving freezing, and will include discussion of freeze-drying, freeze-substitution, ultracryomicrotomy and freezeetching. Pre-treatment and freezing steps can be considered as common to all techniques.

The most common pre-treatment is soaking in a cold 20% glycerol solution to provide protection against ice crystal formation. Glutaraldehyde fixation is often used before freezing. With special freezing techniques no pretreatment may be necessary.

Freezing should be so rapid that it does not produce ice crystals larger than 2nm. in diameter. Following glycerol treatment, immersion in Freon 12 at its melting point of -155 C is adequate. Freezing in boiling liquid nitrogen is not usually satisfactory.
Polyethylene Glycol Diacrylates as Embedding Media for Electronmicroscopy
Authors: Peterson Richard G.
Published: June 2020

Histochemistry on sections of electron microscopic tissue has been limited by the techniques available. Most embedment procedures cause changes in the chemistry and structure of the tissue. These effects are mainly due to the fixation with aldehydes, osmium or the dehydration necessary to embed the tissue in currently used plastics. A search for something which might be more effective has led us to the polyethylene glycol diacrylates (Polysciences, Inc.). These monomers are soluble, or partly soluble in water, are not lipid solvents, and are readily polymerized into sectionable plastics at room temperature or lower with U. V. light.

Tissue from rats was fixed by either perfusion or immersion in aldehydes of various compositions. Tissue was infiltrated with polyethylene glycol 400 diacrylate containing 1% benzoin.
Nucleic Acid Molecules Prepared by Monolayer Techniques
Authors: Lang Dimitrij
Published: June 2020

The success of the protein monolayer technique for electron microscopy of individual DNA molecules is based on the prevention of aggregation and orientation of the molecules during drying on specimen grids. DNA adsorbs first to a surface-denatured, insoluble cytochrome c monolayer which is then transferred to grids, without major distortion, by touching. Fig. 1 shows three basic procedures which, modified or not, permit the study of various important properties of nucleic acids, either in concert with other methods or exclusively:

1) Molecular weights relative to DNA standards as well as number distributions of molecular weights can be obtained from contour length measurements with a sample standard deviation between 1 and 4%.
Hydration Stages—Achievements and Obstacles
Authors: Matricardi V.R. , Subjeck J. , Parsons D.F.
Published: June 2020

As we have previously reported our laboratory has developed and perfected a dynamically pumped hydration stage. The stage consists of four collinear apertures: two 100μ and two 200μ. The two 100μ apertures straddle the specimen and define the specimen chamber. The two 200μ apertures define the intermediate chamber which is independently pumped by a normal cryotrapped forepump. The whole stage is translated in order to move the apertures collinear with the beam by the normal specimen translation mechanism, through the bore of the upper polepiece. The specimen may be moved within its 1.2mm gap by an independent translation mechanism thereby allowing the full area of the grid to be examined. Water vapor evaporates from the source and continuously flows out of the apertures thereby providing a very effective anticontamination device.
Structural Variations of Polyphosphate Bodies in Blue-Green Algae
Authors: Sicko Linda M.
Published: June 2020

Polyphosphate appears to be a ubiquitous component of all microorganisms. Electron microscopic examination of blue-green algae reveals bodies which are usually spherical, and have a wide range of electron densities. From work conducted in our laboratory, it appears that the image of the polyphosphate bodies varies with the culture conditions as well as the stage of development under constant culture conditions. The following report describes the various images one can observe.

For most experiments, the blue-green algae were fixed by the method of Pankratz and Bowen. The algae were pelleted, the culture media poured off, and the pellet was resuspended in 1% OsO4 buffered at pH 6.2 for 3 hours at room temperature.
Quantitative Ultrastructural Study of Mitochondrial Form After Partial Hepatectomy
Authors: Jann Brown W. , Verity M. Anthony
Published: June 2020

Induced swelling of isolated residual rat and mouse liver mitochondria following partial removal has been shown to be diminished. This observation can be explained by two possible mechanisms; (a) the conformation of organelles in residual liver is altered and already swollen prior to isolation or, (b) the isolated mitochondria are rendered unreactive to certain swelling inducing systems because of specific changes that have occurred in the membrane.

In order to evaluate the former of these proposed mechanisms, quantitative morphometric analysis of the heterogeneity of mitochondria has been attempted in situ by ultrastructural techniques after the manner of Bahr.
Specimen Collection Effect in Scanning Electron Microscopy Images
Authors: Temple Black J. , Guerrero Jose
Published: June 2020

In the SEM, contrast in the image is the result of variations in the volume secondary electron emission and backscatter emission which reaches the detector and serves to intensity modulate the signal for the CRT's. This emission is a function of the accelerating potential, material density, chemistry, crystallography, local charge effects, surface morphology and especially the angle of the incident electron beam with the particular surface site. Aside from the influence of object inclination, the surface morphology is the most important feature In producing contrast. “Specimen collection“ is the name given the shielding of the collector by adjacent parts of the specimen, producing much image contrast. This type of contrast can occur for both secondary and backscatter electrons even though the secondary electrons take curved paths to the detector-collector.

Figure 1 demonstrates, in a unique and striking fashion, the specimen collection effect. The subject material here is Armco Iron, 99.85% purity, which was spark machined.
Modification of the High Voltage Supply of an Electron Microscope for Improved Stability
Authors: Gauldin R. E. , Wittry D. B.
Published: June 2020

The high voltage power supplies of older transmission electron microscopes lack the feedback regulation that provides the exceptional voltage stability found in modern instruments, A method has been devised to apply feedback control to an existing high voltage supply. The modification requires few changes in the original power supply circuitry and uses relatively inexpensive, commercially available components.

A stable accelerating voltage is required to achieve high resolution in transmission electron microscopy; an analysis of the chromatic aberration for a resolution of 2 Å leads to a required voltage stability of about one part in 105 over the period of exposure A stable accelerating voltage is also required when the microscope is used with a magnetic prism electron spectrometer for “selected area“ electron spectrometry. The stability of the accelerating voltage should be significantly better than the thermal energy spread of the electrons if the full resolution of the spectrometer is to be realized.
Single Atom Visibility
Authors: Crewe A. V. , Wall J. , Langmore J. , Isaacson M.
Published: June 2020

Single heavy atoms of potential usefulness as heavy atom labels for biological molecules are presently being studied by two techniques. A small computer interfaced directly to a high resolution 30 kv scanning transmission electron microscope (STEM) is used to measure the elastic scattering cross-sections of each heavy atom (e.g. Thorium) or aggregates of heavy atoms in a selected field of the microscope. Histograms of the scattering cross-sections can be made to determine the average crosssection. Statistical analysis of the parameters listed below for the carbon film background and heavy atom signals give the most useful evaluation of heavy atom visibility. Model compounds with covalently bound iodine and mercury atoms spaced greater than 5 Å apart are also being studied to determine the elastic scattering cross-sections and to evaluate radiation damage from molecules with a well defined geometry.
Cellulose Acetate Reverse Osmosis Membrane Structure
Authors: Plummer H. K. , Eichen E. , Melvin C. D.
Published: June 2020

Much of the work reported in the literature on cellulose acetate reverse osmosis membranes has raised new and important questions with regard to the dense or “active” layer of these membranes. Several thickness values and structures have been attributed to the dense layer. To ensure the correct interpretation of the cellulose acetate structure thirteen different preparative techniques have been used in this investigation. These thirteen methods included various combinations of water substitution, freeze drying, freeze sectioning, fracturing, embedding, and microtomy techniques with both transmission and scanning electron microscope observations.

It was observed that several factors can cause a distortion of the structure during sample preparation. The most obvious problem of water removal can cause swelling, shrinking, and folds. Improper removal of embedding materials, when used, can cause a loss of electron image contrast and, or structure which could hinder interpretation.
Contrast in High Resolution Images of Crystals
Authors: Fejes P. L.
Published: June 2020

An attempt is made to understand experimentally observed high resolution electron microscope images. Iijima has obtained images that are good representations of the crystal potentials for a resolution of about 3Å using a defocus corresponding to the “optimum defocus condition”. This is to be expected for a thin phase object. However, Iijima's images are obtained from crystals having thicknesses of 100Å and greater for which the maximum phase change is more than 10 radians, and so the thin phase object approximation is not expected to be valid. These images must therefore be explained by other means.

Many beam calculations have been made on thick crystals using a trial crystals structure as shown in Fig. 1. A metal atom sits at the centre of each octahedral site with oxygen atoms at the corners. This structure contains blocks of 3 x 3 octahedra of the type found in disordered samples of Ti2Nb10O29 as shown in Fig. 2.
Reconstruction of Two-Dimensional Projections of GP 32*I
Authors: Cohen H.A. , Chiu W. , Hosoda J.
Published: June 2020

GP 32 (molecular weight 35000) is a T4 bacteriophage protein that destabilizes the DNA helix. The fragment GP32*I (77% of the total weight), which destabilizes helices better than does the parent molecule, crystallizes as platelets thin enough for electron diffraction and electron imaging. In this paper we discuss the structure of this protein as revealed in images reconstructed from stained and unstained crystals.

Crystals were prepared as previously described. Crystals for electron microscopy were pelleted from the buffer suspension, washed in distilled water, and resuspended in 1% glucose. Two lambda droplets were placed on grids over freshly evaporated carbon, allowed to sit for five minutes, and then were drained. Stained crystals were prepared the same way, except that prior to draining the droplet, two lambda of aqueous 1% uranyl acetate solution were applied for 20 seconds. Micrographs were produced using less than 2 e/Å2for unstained crystals or less than 8 e/Å2for stained crystals.
Precipitation in Al-Li-Cu Alloys
Authors: O'Neal J. E. , Sankaran K. K.
Published: June 2020

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.

Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).

The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.
The Microstructure of Mechanically Alloyed Al-4Mg Alloy
Authors: Kang Sung K.
Published: June 2020

The mechanical alloying of powders by high-energy ball milling is one of the recent technologies for the production of heat-resistant oxide-dispersion-strengthened (ODS) alloys. This technique has been successfully applied to Fe-, Ni-, and Al-base alloys. The microstructure and properties of mechanically alloyed (MA) materials are quite different from those produced by conventional ingot metallurgy. Many questions remain unanswered about the structure-property relations of MA materials. The study of these relationships is difficult because of very small grain size and the presence of dispersoids, precipitates, dislocation substructure, and texture.

A detailed investigation of the microstructure is necessary to understand the unique properties of these materials. In the present paper, some of the microstructural information about a MA Al-4%Mg alloy is reported. A study of the structure of the MA powders and the structure of the consolidated MA alloys is required in order to relate the processing parameters to the alloy properties. Various electron-optical and X-ray diffraction techniques have been employed for this purpose.
The Study of Ordered Alloys by Means of Electron Diffraction and High Resolution Electron Microscopy : Application to Au4-xMn
Authors: Van Tendeloo G. , Amelinckx S.
Published: June 2020

The study of ordered alloys by means of conventional X-ray diffraction methods is hampered by the fact that even single crystals of such alloys are invariably fragmented in symmetry related domains; unscrambling of such combined patterns into mono domain patterns is usually not straightforward. In electron diffraction it is on the other hand often possible to select a single domain on the image and obtain a mono-domain diffraction pattern.

The use of suitable high resolution imaging techniques allows often to derive a trial structure, for which the image and the diffraction pattern can be calculated and compared with the observations. It is our intention to demonstrate how the combined use of both techniques allows the determination of crystal structures of rather complicated alloys in the gold-manganese and gold-magnesium systems.
High Resolution Observations of Ion-Milling Induced Transformation in Synthetic Hollandses
Authors: Headley T. J.
Published: June 2020

Oxide phases having the hollandite structure have been identified in multiphase ceramic waste forms being developed for radioactive waste disposal. High resolution studies of phases in the waste forms described in Ref. [2] were initiated to examine them for fine scale structural differences compared to natural mineral analogs. Two hollandites were studied: a (Ba,Cs,K)-titan-ate with minor elements in solution that is produced in the waste forms, and a synthesized BaAl2Ti6O16 phase containing ∼ 4.7 wt% Cs2O. Both materials were consolidated by hot pressing at temperatures above 1100°C. Samples for high resolution microscopy were prepared both by ion-milling (7kV argon ions) and by crushing and dispersing the fragments on holey carbon substrates. The high resolution studies were performed in a JEM 200CX/SEG operating at 200kV.
Analytical Microscopic Investigation of Commercial Oxide Dispersion Strengthened Alloys
Authors: Raghavan M. , Klein C. , Petkovic-Luton R.
Published: June 2020

Oxide particles in three commercial Yttria Dispersion Strengthened alloys were analyzed using an analytical electron microscope. The following are the alloy compositions:

Both thin samples and extracted residue of oxides were used for electron microscopic analysis. These samples were prepared by conventional electropolishing followed by ion thinning. Extraction of oxides was conducted in a conventional electrolyte. The extract was centrifuged, cleaned and supported on carbon film for examination. Analysis of particles in the range of 200-700 Å was conducted on the extracted residue while particles in the range of about 750-1500 Å were analyzed in the thin sample. The X-ray microanalysis data were corrected for absorption, including oxygen where necessary, using techniques described before (1).

X-ray microanalysis and microdiffraction analysis indicated that besides aluminum oxide, these alloys could contain up to four distinct aluminum-yttrium oxides.
Spacings and Intensities of Weak-Beam Dark Field Thickness Fringes
Authors: Avalos-Borja M. , Heinemann K.
Published: June 2020

Weak-beam dark field (WBDF) TEM produces narrowly spaced equal-thickness fringes in wedge-shaped crystals. Using non-systematic diffraction conditions, we have shown elsewhere that simple 2-beam kinematical theory (KT) calculations yield average fringe spacings that are for most practical purposes as satisfactorily accurate as the average spacings obtained from optimized multibeam dynamical theory (DT) calculations, As Fig. 1 shows, this result holds for deviations from the Bragg condition as low as 2x10-1 nm-1, and the differences between the results from the two calculational methods become increasingly insignificant for larger excitation errors. (Unless otherwise noted, all results reported here are for gold crystals, using the 200 beam at 100 KV; the DT calculations were made for 74 beams, using the selection criterion D as discussed in ref. [3]).
A Method for Computing Electron Microscope Images with Partial Coherence, Hollow Cone Illumination and Virtual Apertures
Authors: Krakow William
Published: June 2020

Image formation in the electron microscope when the illumination is partially coherent has been studied in some detail and partial coherence envelope functions have also been developed for axial illumination and weak phase objects. These envelope functions have been applied to crystalline strong phase objects where the effect of the Ewald sphere was discounted. The effect of axial beam divergence has been considered explicitly for crystalline materials where separate dynamical diffraction and image computations were performed for each beam inclination and the resultant image was a summation of these separate images.

Computer programs have been designed which calculate image intensities not only for axial illumination partial coherence but for titled beam illumination, cone illumination or any arrangement of incident beam inclinations where there is partial coherence (virtual apertures). Here the effect of the beam tilt on dynamical diffraction is neglected so that repeated multislice computations are avoided.
Advances in the EM of Polymers
Authors: Sawyer L. C.
Published: June 2020

Recent advances in Analytical Electxon Microscopy (AEM) have changed the methods by which microicopists study polymer and fiber morphology. As polymeric materialis play a major role in our way of living - clothing, shelter, fuel, chemicals - the interest has spread from a small group of theoretical physicists to the larger group of applications scientists. Until forty years ago, optical microscopy (OM) provided the only microicopical means of observing the morphology of materials. Then transmission electron microscopes (TEM) brought a new depth and resolution of fine structures not previously known. The methodology of preparing materials for TEM, ultramicrotomy and replication, are revealing but tedious and replete with artifacts. Bridging the gap between OM and TEM the scanning electron microscopes (SEM), in use over the past fifteen years, have provided easily available and interpretable surface images of fibers, fabrics, membranes, films and composites. Finally, the limited resolution of the SEM has been improved by the use of modern composite instruments known as analytical electron microscopes (AEM).
Scanning Transmission Electron Microscopy (STEM) of Annelid Extracellular Hemoglobins
Authors: Kapp O. H. , Ohtsuki M. , Vinogradov S. N. , Crewe A. V.
Published: June 2020

Scanning transmission electron microscopy (STEM) was used to study the structure of the extracellular hemoglobin of the annelid Lumbricus terrestris. These are giant molecules possessing a molecular weight of approximately 3.9 x 106and appear in electron micrographs as a hexagonal bilayer, The samples for this study were diluted to 100 μg/ml with distilled water and applied to a thin ( ∽15 Å) carbon substrate supported on a microgrid. One percent (w/v) uranyl acetate solution was used for negative staining for 2 minutes and dried in air. STEM images were recorded using both a high resolution CRT with 1024 x 1024 picture elements and an on-line computer recording with 512 x 512 pixels. The images were rotated in on-line fashion with the computer to enhance contrast.

The hemoglobin of Lumbricus assumes three common positions on the substrate (Fig. 1). The top view (Fig. la) demonstrates that the 1/12th subunits possess an approximately pentagonal shape with a central region of low protein density.
Horseradish Peroxidase Uptake by Rod Photoreceptor Inner Segments Accompanies Outer Segment Disc Assembly
Authors: Besharse Joseph C. , Forestner Donna M.
Published: June 2020

We have suggested that large, membrane vesicles found in the periciliary region of rod photoreceptor inner segments (RIS) contain precursors destined for incorporation into discs of the outer segment (ROS). It has also been shown, however, that endocytosis of extracellular horseradish peroxidase (HRP) occurs in inner segments, suggesting an endocytic origin for some vesicles. As part of an evaluation of the vesicle hypothesis, we examined the extent to which endocytic mechanisms contribute to vesicle populations found in the ellipsoid region of the RIS. HRP uptake was examined in isolated retinas from Xenopus laevis which had been maintained in a Ringer solution in light or darkness for 5 to 120 minutes. To verify that ROS disc assembly actually occurred during HRP incubations, we preincubated retinas for 40 minutes in a mixture of tritiated amino acids (leucine, valine and phenylalanine) to label protein precursors of ROS discs. Labeled retinas were then incubated in cold medium with or without HRP for 2 hours.
LM and SEM of Epoxy Embedded Lung Sections Containing Hard Particles
Authors: Schidlovsky G. , Ruffing R. , Drew R. T.
Published: June 2020

Presence of hard particles in tissues destined for morphological analysis precludes TEM because of sectioning difficulties. Frequent occurrence of focal lesions requires observation of tissue areas larger than those imposed by TEM limitations. SEM has no specimen size limitation. Secondary electron (SE) and backscatter electron (BSE) imaging modes allow observation of specimens with thicknesses comparable to those used in LM. Following Humphrey's observations (1979) on SE/SEM imaging of RF/O2-plasma etched epoxy embedded sections, we have developed protocols that allow (1) imaging of 1 cm2 sections containing glass, coal, or other particles; (2) alternate LM and SEM of the same section; (3) cutting thin sections of the same embedment for TEM; (4) LM and SEM imaging and X-ray analysis in any desired sequence on the same section cut with a 2.5 cm wide glass knife on an LKB Ultrotome IV; and (5) an AC oxygen plasma etching mode.
Electron Microscopic Characterization of Insect Hemocytes
Authors: Wittig Gertraude
Published: June 2020

The fine structure of insect hemocytes has been the subject of very few investigations. In particular, the hemocytes of Lepidoptera have received almost no attention. The study presented here was carried out on the armyworm, Pseudaletia unipuncta. Hemocytes of the larva were fixed 2 to 4 days after molt to the sixth instar and studied in ultrathin sections.

Microplasmatocytes (Fig. 1) were the most important phagocytes of army-worm hemolymph. They were relatively small, spherical cells with a small, round or lobed nucleus. Distensions of the perinuclear cisterna (p) were frequent and sometimes continuous with the rough endoplasmic reticulum (e). The latter formed greatly distended cisternae which almost filled the whole cytoplasm. The cisternae contained an amorphous material which appeared to be condensed in certain sacs (at e). Mitochondria (m) were rare, and they had tubular cristae. Up to four Golgi complexes (g) were identified in a microplasmatocyte section. Structured granules (sg) were specific for this cell type. Microfibrils (f) traversed the whole cytoplasm but were most frequent around the nucleus (N) and under the cell membrane.
Hepatic Congestion Induced by Partial Occlusion of the Hepatic Veins in Healthy Dogs
Authors: Dawoud F. R. , Ghidoni J. J.
Published: June 2020

The inferior vena cava and hepatic veins of twenty randomly selected normal dogs (22-27 kg) were exposed through a right transthoracic, transdiaphragmatic incision. The small hepatic vein from the middle lobe of the liver was routinely ligated. After the hepatic vein draining the left 3 lobes of the liver was catheterized from the right external jugular vein, a tape was passed around that hepatic vein. The pressure in the intrahepatic part of the hepatic vein was measured and recorded before and after reducing the main left hepatic vein to the size of the catheter by tying the tape. The catheter was cut short and inserted into the jugular vein to establish limited hepatic drainage through a lumen of known and constant cross section; the catheters were accessible for additional pressure measurements. The animals were killed according to a predetermined schedule at 1, 3, 7, and 15 days. Specimens for light and electron microscopy were taken from the congested and uncongested lobes of the liver. Tissues were fixed in cold cacodylate buffered 5% glutaraldehyde and postfixed with osmium. Tissue blocks were rapidly dehydrated and embedded in a mixture of Maraglas, D.E.R. 732, and DDSA.
Fine Structure of Cytochalasin Induced Polyploid Cells
Authors: Krishan Awtar , Bohonos Nestor
Published: June 2020

Cytochalasin B, a mould metabolite from Helminthosporium dermatioideum has been shown to interfere with specific cell activities such as cytoplasmic cleavage and cell movement. Cells undergoing nuclear division in the presence of cytochalasin B are unable to complete the separation of the resulting daughter cells. In time-lapse studies, the daughter cells coalesce after an initial unsuccessful attempt at separation and form large multinucleate polyploid cells. The present report describes the fine structure of the large polyploid cells induced in Earle's L-cell monolayer cultures by exposure to cytochalasin B (lγ/ml) for 92 hours.

In the present material we have seen as many as 7 nuclei in these polyploid cells. Treatment with cytochalasin B for longer periods of time (6 to 7 days, with one medium change on the 3rd day) did not increase the number of nuclei beyond the 7 nuclei stage. Figure 1 shows a large polyploid cell with four nuclei. These nuclei are indistinguishable in their fine structure from those of the cells from control cultures but often show unusually large numbers of cytoplasmic invaginations and extensions of the nuclear surface (Figure 2).
Daunomycin Nephrosis with Special Reference to Cross-Striated Fibrils in Glomeruli
Authors: Sternberg Stephen S.
Published: June 2020

Daunomycin, a glycosidic antibiotic isolated from cultures of Streptomyces peucetius, consists of a chromophor (daunomycinone) linked to an amino sugar (daunosamine). It is inhibitory to the growth of He La and KB cells in culture, and has antitumor activity in rodents and man. Daunomycin complexes with DNA and has been shown to inhibit both DNA and RNA synthesis.

Rats given a single intravenous injection of 20 mg/kg (ca LD50)rapidly develop severe bone marrow depression, and damage to lymphoid tissues and intestinal crypts. Recovery from the initial toxicity to proliferative tissues takes place within several days but shortly, thereafter, a nephrotic syndrome develops. The renal phase of intoxication is manifested by proteinuria, hypoalbuminemia, elevation of α1 globulin, anarsarca, hyperlipemia, and hypercholesterolemia.
Lattice Defects in Stainless Steel Shock-Loaded to Pressures Above 1 Megabar
Authors: Murr L. E. , Rose M. F.
Published: June 2020

Previous investigations of defect structures in 304 stainless steel shock loaded in the pressure range 120-425 kilobars by the authors have indicated a consistent increase in the specimen residual microhardness with pressure; and direct observations of specimen microstructures by transmission electron microscopy revealed a consistent increase in deformation twin-fault density with increasing shock pressure. Recent extensions of this research in the very high pressure range have indicated that the residual microhardness continues to rise to a maximum of 384(VHN-200 gm load) at about 750 kilobars in comparison with a starting (annealed sample) microhardness of 161. At pressures above 800 kilobars, the hardness decreases; and at 1200 kilobars the microhardness is observed to be 312.

Shock loading at 1.2 megabars was accomplished by employing 0.007 in. thick specimens of 304 stainless steel (measuring 1 in. on a side) in a sandwich assembly recently described by Rose and Grace. A flying plate, explosively initiated by a plane-wave generator and an HMX-95-5 main charge imparted a plane shock pulse of approximately 2 microseconds duration to the sandwich. Thin samples for examination by electron transmission were prepared by electropolishing the recovered samples² as previously described by Murr
Fission Gas Bubbles in Fractured UO2
Authors: Katz O. M.
Published: June 2020

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.
Crystallographic Characterization of Dislocation Loops in Irradiated Tungsten
Authors: Rau Robert C.
Published: June 2020

Previous work has shown that post-irradiation annealing, at temperatures near 1100°C, produces resolvable dislocation loops in tungsten irradiated to fast (E > 1 MeV) neutron fluences of about 4 x 1019 n/cm2 or greater. To crystallographically characterize these loops, tilting experiments were carried out in the electron microscope on a polycrystalline specimen which had been irradiated to 1.5 × 1021 n/cm2 at reactor ambient temperature (∼ 70°C), and subseouently annealed for 315 hours at 1100°C. This treatment produced large loops averaging 1000 Å in diameter, as shown in the micrographs of Fig. 1. The orientation of this grain was near (001), and tilting was carried out about axes near [100], [10] and [110].
Improvements & Performance of the Hitachi 200KV Electron Microscope
Authors: Katagiri S. , Akahori H. , Ueno S. , Iwama A.
Published: June 2020

1.

Electron gun - A new high voltage cable and porcelain insulator has been developed. A successful study of superior surface treatment of the insulator and improved means of sealing the cable resulted in eliminating surface discharge of the insulator. Since an electrode discharge and surface discharge of an insulator cannot be completely eliminated in a vacuum of the order of 10-5 to 10-6 torr, an high capacity vacuum system is employed to assure high vacuum and a discharge free system. Further, small quantities of inert gases such as N2, Ar, He etc. is introduced into the gun chamber to maintain a vacuum of 1 to 2 x 10-4 torr.

2.

Evacuating system.

At 200KV it is necessary in a single stage electron gun to provide greater insulating distance to inhibit discharges. Consequently, the electron gun chamber is inevitably larger. The gun chamber volume of this electron microscope is 32 liter. A 4″ diameter single manifold and 1200 liter/sec. oil diffusion pump comprise the evacuating system.
Hitachi Scanning Electron Microscope
Authors: Fujiyasu T. , Hara K. , Tamura H.
Published: June 2020

The demand for scanning electron microscopes is growing rapidly and exciting new fields of application have developed for this type of instrument. Hitachi, Ltd. has developed this type of instrument the details of which are described in this paper.

A three stage demagnification lens system is used in the instrument. External magnetic and electrical disturbances and mechanical vibrations have been reduced.

Aperture plates with different bore diameters are located above the condenser lens and deflection coil and the objective lens to reduce contamination by the fixed apertures in these lenses. An electromagnetic stigmator is provided in the objective lens field.

The specimen stage permits X-, Y- and Z- axes movements as well as rotational tilting. The rotational tilting is such that its central axis is always coincident with the optical axis independent of the X-, Y- and Z- axes movements. Terminals are also provided which permit voltage measurements and to observe the electrical potential distribution of semi conductors.
Cytoskeletal control of neuronal geometry: A serial EM analysis
Authors: Stevens John K. , Trogadis Judy
Published: June 2020

The cytoskeleton plays a direct role in controlling neurite shape. To quantitatively study both the three dimensional shape and the sub-micron structure of the cytoskeleton requires complete serial reconstruction at the Electron Microscopic level. We have devised a computer reconstruction system specifically for this purpose.

The system uses a 35mm film copy of 3.25 x 4.00 inch EM negative as the data source. The film is placed into a high speed film transport (15 frames/second), which is mounted on a X,Y and rotation stage controlled by stepping motors. The 35mm film is viewed through a stepping motor controlled zoom lens mounted on a high resolution (1119 x 1024) video camera. A high resolution frame grabber controlled by the computer can store one complete frame. Thus, the live image and a stored image may be displayed alternately on a high resolution monitor. Finally, a graphics overlay and mouse connected to the computer can be used to align successive sections via the stepping motors, as well as to trace the outlines of a profile, or of a microtubule.
The application of video-enhanced constrast/differential interference constrast microscopy in conjunction with whole mount electron microscopy to the study of organelle transport
Authors: Hayden J. H.
Published: June 2020

In a previous study, Allen video-enhanced constrast/differential interference constrast (AVEC-DIC) microscopy was used in conjunction with immunofluorescence microscopy to demonstrate that organelles and vesicle move in either direction along linear elements composed of microtubules. However, this study was limited in that the number of microtubules making up a linear element could not be determined. To overcome this limitation, we have used AVEC-DIC microscopy in conjunction with whole mount electron microscopy.

Keratocytes from Rana pipiens were grown on glass coverslips as described elsewhere. Gold London Finder grids were Formvar- and carbon coated, and sterilized by exposure to ultraviolet light. It is important to select a Formvar film that gives a grey reflection when it is floated on water. A silver film is too thick and will detract from the image in the light microscope.
Quantitative recovery of virus from blood plasma using a polycarbonate filter purification procedure
Authors: Miller M. F. , Gagne G. D. , Lesniewski R. , Peterson D. A.
Published: June 2020

Polycarbonate filters (Nuclepore Corporation, Pleasanton, CA) have beep used for sizing particulates such as virus particles and liposomes. Unlike nitrocellulose, polyester and other types of filters which are comprised of a relatively thick meshwork of interwoven fibers, polycarbonate filters are thin and contain precisely sized, straight-bore holes (Fig. 1). These features suggest that loss of particles due to nonspecific adsorption or entrapment in the filter matrix might be less for polycarbonate filters. In the present study, we have devised a purification technique based on the sequential filtration of blood plasma through a series of polycarbonate filters. The technique was evaluated by seeding chimpanzee blood plasma with human rotavirus (65-70 nm dia.) and determining recovery of purified virus using a sensitive electron microscope virus particle counting technique.

Whole normal blood plasma (10 ml) was seeded with highly purified rotavirus to a final concentration of about 1010 particles per ml.
Modeling of Longitudinal Sections of Sickle Hemoglobin Fascicles
Authors: Bradlow Ann R. , Carragher Bridget , McDade William A. , Josephs Robert
Published: June 2020

In vivo, deoxyhemoglobin S fibers associate into bundles, or fascicles. It is the formation of these bundles within red blood cells which leads to the clinical manifestations of sickle cell disease. A similar phenomenon is observed in vitro. Fascicles are initially small and poorly ordered but, with time, become progressively larger, more tightly packed and more highly ordered. The most tightly packed fascicles display crystalline order and form “crystals of fibers”. We have constructed computer generated models of longitudinal projections of crystalline fascicles of sickle hemoglobin (HbS) fibers. A comparison of the models with electron micrographs provides a means of accurately determining the three dimensional packing arrangement of fibers and the nature of the fiber-fiber interactions within fascicles.

Electron micrographs of longitudinal sections of well ordered fascicles reveal a number of characteristic views, one of which is shown in figure 2a. The different views observed in the micrographs arise because of differing orientations of fascicle sections relative to the angle of projection. This was demonstrated by experiments in which the specimen was tilted about its long axis. Different views could be interconverted by varying the angle of tilt.
Further Observations on the Fine Structure of “Tubular Aggregates”
Authors: Montpetit V.J.A. , Dancea S. , Skinner C.R. , Kawahara H.
Published: June 2020

Accumulations of densely packed long straight tubules, usually at the periphery of skeletal muscle fibers, have been referred to as “tubular aggregates”. They have been described mainly in type II muscle fibers and do not appear to be associated with a specific disease entity. The nature and origin of the abnormal tubular structures remain enigmatic. Some authors have postulated that they arise from lateral sacs of sarcoplasmic reticulum while others maintain that a mitochondrial or sarcolemmal origin is more plausible. This unsettled dispute over their origin prompted us to pursue a more detailed ultrastructural study of their components.

A fifty-three year old male presented with a short history of pains in the quadriceps muscles and bitemporal areas. A chronic periarteritis of uncertain etiology was present in the temporal artery and quadriceps muscle. Cryostat sections of the latter revealed numerous subsarcolemmal masses of material which stained basophilic with hematoxylin and eosin, bright red with modified trichrome and intensively with the NADH tetrazolium reductase reaction.
Quality films from carbon fiber evaporation for thorough coverage of TEM grids
Authors: Tempel N. , Ledbetter M. C.
Published: June 2020

Carbon films have been a support of choice for high resolution electron microscopy since the introduction of vacuum evaporation of carbon. The desirable qualities of carbon films and methods of producing them has been extensively reviewed. It is difficult to get a high yield of grids by many of these methods, especially if virtually all of the windows must be covered with a tightly bonded, quality film of predictable thickness. We report here a method for producing carbon foils designed to maximize these attributes: 1) coverage of virtually all grid windows, 2) freedom from holes, wrinkles or folds, 3) good adhesion between film and grid, 4) uniformity of film and low noise structure, 5) predictability of film thickness, and 6) reproducibility.

Our method utilizes vacuum evaporation of carbon from a fiber onto celloidin film and grid bars, adhesion of the film complex to the grid by carbon-carbon contact, and removal of the celloidin by acetone dissolution. Materials must be of high purity, and cleanliness must be rigorously maintained.
Formation process of silicide at Pt-Si (111) interface
Authors: yokota Y. , Hashimoto H.
Published: June 2020

The initial stage of the reaction process forming the platinum silicide at Pt/Si (111) interfaces have been investigated by a high resolution electron microscope in both “flat-on” [1] and “cross-sectional” mode.

First, platinum of 11 nm thickness was deposited on a Si (111) wafer. For observing the specimen in “flat-on” mode, the top surface and edge of the specimen were covered by paraffin and etched chemically using CP-4 reagent from backside. The specimen for observing in “cross-sectional” mode was prepared as follows. The Si wafer was cut into slips of 3mm width. After stacking 4 to 6 slips together with epoxy resin, the stacks were sliced to a thickness of 0.3-0.4mm by a diamond saw. The slices were mechanically polished to a thickness lower than 0.05mm and then thinned by Ar ion beam.

The formation process of platinum silicide (PtSi) was observed in a cross-sectional specimen.
The formation of a gold/silicon alloy by electron-beam heating of codeposited thin films
Authors: Sharma R. , Robison W. , Eyring L.
Published: June 2020

Studies of metal-semiconductor interactions have been of great interest in recent years because of the need to understand the behavior of semiconductor device junctions. The gold-silicon system has been studied by Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). An amorphous gold si 1icide is assumed to form at the metal-semiconductor interface. Different Au silicides are reported to be formed after heat treatment of Au films on a silicon substrate in ultra-high vacuum. Similar results have been observed for bulk samples by x-ray diffraction. The exact process of the diffusion of reactants and structure of the silicides formed is still being debated. Studies of the system by electron diffraction and high resolution microscopy is reported here.

Thin films of Au/Si (200-300 Å) were deposited on a (100) NaCl crystal face by evaporating Au and Si simultaneously at the same rate in a vacuum of 10-9 Torr at room temperature.
The interaction between basal-twin boundaries and a glassy phase in α-Alumina compacts
Authors: Simpson Yonn Kouh , Carter C. Barry
Published: June 2020

Understanding the nature of glass/crystalline interfaces is not only of fundamental scientific interest but is directly relevant to the liquid-phase sintering of polycrystalline ceramics such as α-alumina. Faceting behavior of alumina in the presence of SiO2 glass has been of much interest in the field of sintering with respect to the grain growth and the grain boundary mobility during sintering. The study of grain boundaries containing a glassy phase in alumina compacts is difficult however, since many of the TEM techniques presently available for the identification of a glassy phase at grain boundaries can give ambiguous results due to grain boundary grooving. A method for systematically studying glassy / crystalline interfaces without such ambiguity is therefore needed. Part of this study of the interaction of grain boundaries in alumina with an anorthite-based glassy phase is presented here.

Previous systematic studies4 of different low-index surfaces of single crystal alumina showed that there is strong anisotropy in the faceting behavior of alumina and in the mobility of these facets in the presence of an anorthite-based glassy phase.