bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrathin Support Films for Visualization of Biomolecules
Authors: Williams Robley C. , Glaeser Robert M. , Richards Kenneth E.
Published: June 2020

A simple method has been developed for producing carbon films with a calculated and measured thickness of 4-6Å. The films are self-supporting over areas amounting to as much as 50 percent of the open area of a 200-mesh grid, withstand spray-drop deposition of biomolecules, and are fully as stable under electron impact as are films several times as thick.

The carbon film is deposited upon a freshly cleaved mica surface placed under a rotating disc containing a slot of dimensions such that, except for a small “tab” region at the peripheral end of the mica surface, the film deposited is 5 percent as thick as that deposited on a control mica surface placed immediately above the disc. The slot is so shaped that the “tab” region is about 25 percent as thick as the control. Flotation of the film is accomplished by first inserting the “tab” region into the water. Only the presence of this thicker region allows the whole of the floating film to be localized, since its 5Å-thick portion is usually invisible by reflected light. The film is supported by a reticulation of thick collodion on a 200-mesh grid. This support is made by condensing breath moisture upon an evaporating surface of collodion, which is formed by dipping a microscope slide into a 0.5 percent solution of Parlodion in amyl acetate.
A Rapid Method for Electron Microscopic Examination of Biological Specimens
Authors: Stoner Glenn
Published: June 2020

The purpose of this paper is to demonstrate the use of a method which reduces the sample preparation time for transmission electron microscopy studies to about one minute.

The relatively simple procedure is as follows: When a sample is desired, place 1 mℓ test solution in a 2-5 mℓ container, add 0.1 mℓ of a solution of 0.3 mg/mℓ fibrinogen, immediately insert a 400 mesh E.M. grid held by forceps, withdraw immediately, blot (at the tweezer tip-grid contact point) with filter paper, blow dry with a lab drier, add one drop of stain (2% urinal acetate), blot and blow dry in the above manner. Then immediately insert in the pre-pump chamber of the E.M.

The above process has been used by the author in a variety of biological applications, from studies of fibrin growth from fibrinogen to identification of unknown viruses. The accompaning figures for T4, bacteriophage are given simply to demonstrate the method.
Uranyl Acetate as a Fixative—from pH 2.0 to 8.0
Authors: Mumaw V. R. , Munger B. L.
Published: June 2020

Numerous applications utilizing uranyl acetate as an electron stain for electron microscopy have been described. Uranyl acetate has become a routine stain used in conjunction with lead hydroxide for staining ultrathin sections. En bloc staining with uranyl acetate following osmium tetroxide post-fixation produces undesirable effects on some cytoplasmic components, especially glycogen. Recent studies using uranyl acetate as a fixative and en bloc stain at pH 7.2 before osmification has shown uranyl acetate to have desirable fixation and staining qualities. Tissues treated with uranyl acetate at a pH of 2.0-8.0 were studied. Normal rat tissue was fixed in Karnovsky's paraformaldehyde-glutaraldehyde fixative. The tissue was post-fixed in 0.5% uranyl acetate in water at pH 2.0 and 0.5% uranyl acetate in 0.1M s-collidine with 0.01M oxalic acid at pH 4, pH 6.0, pH 7.2, and pH 8.0 for 1 hour at 4°C. Following several rinses of 0.1M s-collidine buffer, the tissues were treated with 1.33% osmium tetroxide 1 hour at 4°C followed by rapid dehydration in ethanol and embedded in Durcupan ACM. Tissue sections were stained with lead hydroxide.
Acid Phosphatase Activity in Mammalian Parathyroid Glands
Authors: Shannon W. Allen , Roth Sanford I.
Published: June 2020

It has been suggested that the parathyroid secretory granules might represent lysosomes. Since lysosomes are known to contain acid phosphatases (AcPase), this enzymatic activity was investigated with a modified Gomori lead method with β-glycerophosphate as the substrate to determine the relationship of secretory granules to lysosomes in adenomatous and hyperplastic (primary chief cell type) human, and normal bovine, human, and rat parathyroid glands.

Intracellular activity was demonstrated in the lipofuchsin granules and in rare, membrane-limited bodies consistent with lysosomes (Figs. 1 and 2). These lysosomal granules were often irregular in shape and 450 to 850 mμ in diameter. Lead precipitate was also observed in association with some Golgi membranes and cisternae and in a few small Golgi vesicles (Fig.3). There was strong AcPase reactivity in the lumenal cell membranes of the capillary endothelium (Fig. 4) though the cell membranes adjacent to the basement membranes and those of the parathyroid parenchymal cells were devoid of enzymatic activity. No activity was present in the numerous small secretory granules or in the granular endoplasmic reticulum (Figs. 1 and 2).
Chromosome Structure
Authors: Comings David E. , Okada Tadashi A.
Published: June 2020

Various aspects of chromosome structure based on whole mount electron microscopy and biochemical investigations will be discussed. The observations and conclusions include the following. 1. The appearance of half-chromatids is probably the result of an illusion of doubleness produced by the peculiar geometry of coiled structures. We suggest that their existence as an observation is perfectly valid, but the conclusion that they prove there are two independent portions of the chromatid (two DNA helices) is not. 2. The appearance of chromatin in whole mount preparations suggests that purely morphological observations will never convincingly prove whether chromosomes are single or multistranded. 3. Metacentric chromosomes possess a quadripartite centromere region composed of two areas of chromatin fiber association. These have presumably arisen from the fusion of two telocentric chromosomes each with only one area of chromatin fiber association. 4. Whole mount preparations of mitotic chromosomes frequently show the presence of nuclear membrane fragments attached to chromatin fibers at many sites along the full extent of the chromosome.
Effect of Some Metabolic Inhibitors on Vinblastine-Induced Ribosomal-Granular Material Complexes
Authors: Krishan Awtar , Hsu Dora
Published: June 2020

Cells exposed to antitumor plant alkaloids, vinblastine and vincristine sulfate have large proteinacious crystals and complexes of ribosomes, helical polyribosomes and electron-dense granular material (ribosomal complexes) in their cytoplasm, Binding of H3-colchicine by the in vivo crystals shows that they contain microtubular proteins. Association of ribosomal complexes with the crystals suggests that these structures may be interrelated.

In the present study cultured human leukemic lymphoblasts (CCRF-CEM), were incubated with protein and RNA-synthesis inhibitors, p. fluorophenylalanine, puromycin, cycloheximide or actinomycin-D before the addition of crystal-inducing doses of vinblastine to the culture medium. None of these compounds could completely prevent the formation of the ribosomal complexes or the crystals. However, in cells pre-incubated with puromycin, cycloheximide, or actinomycin-D, a reduction in the number and size of the ribosomal complexes was seen. Large helical polyribosomes were absent in the ribosomal complexes of cells treated with puromycin, while in cells exposed to cycloheximide, there was an apparent reduction in the number of ribosomes associated with the ribosomal complexes (Fig. 2).
Fate of Nexus Membranes in Ovarian Granulosa Cells of Intact and Hormone Treated Rats
Authors: Merk Frederick B.
Published: June 2020

Intercellular communication through a junction known as the nexus is thought to coordinate activity in many cell systems. Structures similar to nexuses but identified by different nomenclature have been previously described in granulosa and luteal tissues. Rapid simultaneous changes which normally occur in cells of the preovulatory rat follicle suggest a necessity for cell contacts, particularly in the avascular granulosa. Two forms of nexuses are present in granulosa tissue of developing follicles obtained from mature cycling rats and in similar follicles of immature animals treated with pregnant mare serum gonadotrophin (PMSG). The abutment form joins cells at their surfaces, is continuous with plasma membranes, and is frequently associated with cell processes which protrude into neighboring cells (Fig. 2). The other form is ring-shaped, and appears unattached within the cytoplasm (Fig. 3). These circular profiles probably represent cross sections of nexus-girdled cell processes as well as nexus-bound spheres which may have pinched off the processes.
Demonstration of Retinal Glycogen with Silver Methenamine
Authors: Sedar A. W. , Bresnick G. H.
Published: June 2020

After experimetnal damage to the retina with a variety of procedures Müller cell hypertrophy and migration occurs. According to Kuwabara and others the reactive process in these injuries is evidenced by a marked increase in amount of glycogen in the Müller cells. These cells were considered originally supporting elements with fiber processes extending throughout the retina from inner limiting membrane to external limiting membrane, but are known now to have high lactic acid dehydrogenase activity and the ability to synthesize glycogen. Since the periodic acid-chromic acid-silver methenamine technique was shown to demonstrate glycogen at the electron microscope level, it was selected to react with glycogen in the fine processes of the Müller cell that ramify among the neural elements in various layers of the retina and demarcate these cells cytologically. The Rhesus monkey was chosen as an example of a well vascularized retina and the rabbit as an example of a avascular retina to explore the possibilities of the technique.
Thiouracil-Induced Elastic Tissue Degenerative Changes in Canine Arteries
Authors: Trillo Alberto
Published: June 2020

Unlike other animal species, the dog is relatively resistent to develop hypercholesterolemia and atheromatous lesions even after long periods of cholesterol feeding. This difficulty is, however, eliminated if the thyroid activity is suppressed surgically or pharmacologically. The most common procedure employed is thiouracil administration. During the course of our studies on the response of the vascular wall to various stimuli, it was of interest to assess the possible effects of thiouracil on the mural elements, since information on the subject is almost nonexistent. In this presentation reference will be made only to changes of the internal elastic lamina (IEL) observed in the carotid and femoral arteries of two mongrel young dogs fed purina chow supplemented by thiouracil (100/mg/kg/day) for 3 and 6 months respectively.

The earliest change appeared to consist of an accentuation of the filamentous components of the IEL, formation of fissures or clefts partially filled with a fine fibrillar electron dense material (Fig. 1), and loose bundles of collagen fibrils (Fig. 2). At a later stage, large areas of IEL have a “spongy” appearance with numerous clefts and rarefied areas present.
The Effect of Papain on Rabbit Ear Cartilage
Authors: Sun C. N. , White H. J. , Matsumura Y. , Torii S. , Tanaka K.
Published: June 2020

Intravenous injection of crude papain into young rabbits causes a collapse of the ear. In our work, ear cartilage from young animals was examined by light and electron microscopy prior to, 20 hours after, and one week after injection. Evaporation studies and analyses for mucopolysaccharides (MPS) of the adbominal skin were also performed.
High Voltage Electron Microscopy in Biology
Authors: Ris Hans
Published: June 2020

Conventional electron microscopes operate with accelerating voltages up to 100kV. Because of the scattering of electrons by atoms of the specimen an image with reasonable resolution can only be obtained with very thin specimens. The study of cell structure with the electron microscope became possible only with the introduction of ultramicrotomes which produce sections of plastic-embedded tissues down to about 100A in thickness. It has long been known that useful images could be obtained with much thicker materials at higher accelerating voltages (cf. refs. 1 and 2) and in the early sixties electron microscopes operating at voltages of up to one million Volts were built in Japan and in France. Their capabilities were soon demonstrated in metallurgy but they were ignored until recently by biologists. For one, biologists were busy exploiting the sectioning method and in addition may have been deterred by the knowledge that scattering contrast rapidly decreases at higher accelerating voltage. Only recently has it been realized that excellent contrast is obtained at 500 and 1000kV with the usual heavy metal stains (3,4). High voltage microscopes are now manufactured commercially in England (AEI), France (GESPA) and Japan (Hitachi, Jeol) and should soon be more widely accessible.
Calculations of Contrast from Model Biological Systems
Authors: Cowley J. M. , Grinton G. R.
Published: June 2020

The quantitative interpretation of the contrast of electron micrographs of amorphous or partially crystalline materials depends on the use of an adequate basis of diffraction- and imaging theory. The treatment due to Zeitler and Bahr, which assumes contrast to arise from a pure absorption effect, appears to be a good approximation for calculating the contrast of thin amorphous films with thickness and composition uniform over regions 100Å or more in diameter, but when the scattering properties of the specimen vary over distances of about 10Å or less then phase-contrast predominates.

In order to evaluate the relative importance of these contrast mechanisms for objects now being considered for quantitative study, we have made detailed calculations for model systems designed to represent negatively stained cylindrical rod molecules of protein or similar material. The rods have diameters of 10 to 100Å and the negative staining (one NaW03 molecule in 100Å) is assumed to change the refractive Index and absorption function of the surrounding material.
Transmission Electron Diffraction Analysis by Computer
Authors: Ploc R.A. , Keech G.H.
Published: June 2020

An unambiguous analysis of transmission electron diffraction effects requires two samplings of the reciprocal lattice (RL). However, extracting definitive information from the patterns is difficult even for a general orthorhombic case. The usual procedure has been to deduce the approximate variables controlling the formation of the patterns from qualitative observations. Our present purpose is to illustrate two applications of a computer programme written for the analysis of transmission, selected area diffraction (SAD) patterns; the studies of RL spot shapes and epitaxy.

When a specimen contains fine structure the RL spots become complex shapes with extensions in one or more directions. If the number and directions of these extensions can be estimated from an SAD pattern the exact spot shape can be determined by a series of refinements of the computer input data.
Dynamical Theory of Kikuchi Eletrons
Authors: Tan T. Y.
Published: June 2020

In transmission electron microscopy it is generally believed that for the pairs of Kikuchi lines resulting from inelastic scattering, the line nearer the transmitted spot on the diffraction pattern should always be associated with deficiency of electrons while the other should always contain excess electrons. However, Thomas and Bell demonstrated experimentally that in a case where the incident beam occurs at an exact Bragg angle, the intensities of the lines in a pair reversed, depending only on foil thickness. This color reversal of the Kikuchi line pair is associated with the dynamical behavior of the Kikuchi electrons where crystal absorption plays an essential role.

Based on the two-beam dynamical theory for elastic electrons, a corresponding (two-beam) theory on the fine structures of the Kikuchi electron intensity distributions in relation to the various diffraction and absorption parameters has been formulated. In this theory, the Kikuchi electrons were taken to be those inelastic electrons generated in an infinitesimal thickness of the specimen which subsequently underwent Bragg diffraction. The initial inelastic electron wave amplitudes generated at any position inside the crystal were obtained phenomenologically by considering the decrease in amplitude of the elastic electrons due to absorption by the crystal.
The Anomalous Electron Optical Fresnel Diffraction of an Edge
Authors: Davidoff G.N. , Kendall R.A. , Turner J.N. , Parsons D.F.
Published: June 2020

Although edge diffraction patterns in the electron and light optical systems are often treated as if they are closely related, it has been known for some years that they differ significantly. They were treated as if alike because the relationship between fringe width and defocus in the light optical case agreed fairly well with fringe width calculations for the electron microscope. Theoretical edge diffraction calculations have been done by Hillier and Ramberg and Komrska in the overfocus (real) position for a semitransparent half plane. They have attempted to relate the diffraction pattern to the transmissivity of the half plane and the phase advancement of the wave which passes through the object as opposed to free space. We have found both intensity and displacement anomalies of peaks which show the need for further refinement of the theory.

Through-focus series were taken of polystyrene latex spheres of between 500-2000 Å diameter. Defocus values were between 10μ and 80μ. A triangulation method requiring three spheres (Fig. 1 a,b) was used to locate the same cross-section of each sphere throughout a given series. The location of the geometrical edge in the defocus patterns was obtained by comparison with the infocus micrograph. The displacements of the first and second maxima and the first minimum with defocus are compared with Cornu spiral calculations (Fig. 2).
Magnification Determination for High Resolution Electron Microscopy
Authors: Marsh Peter A. , Mullens Troy J. , Price L. Dale
Published: June 2020

Modern electron microscopes provide film magnifications of X300,000 and higher at resolutions levels below 5 A. However, on these same microscopes it is difficult to obtain a magnification calibration of better than ± 5%, the value given by most microscope manufacturers for the reproducibility of their lenses.

The following internal calibration procedure was developed that provides a magnification calibration of ± 1.6% at the 95% confidence level. The procedure utilized a graphitized ISAF carbon black specimen described in detail by Heidenreich et al.1 (see Figure 1). The particles of this calibration sample contain ordered carbon layer planes having an interplanar spacing (d002) o f 3.44 A, as measured by X-ray diffraction. In addition, these layer planes conform to the carbon particle contours and contain a large number of distortions, including curved and bent layer planes and various types of dislocations.
Dynamics of Pusmalemmal Invagination in the Synchronized Cells of Saccharomyces Cerevisiae
Authors: Ghosh B. K. , Kraeger S. J.
Published: June 2020

Plasmalemma of Saccharomyces cerevisiae invaginates inside the cytoplasm. A double aldehyde fixation technique gave a superior preservation of membrane material compared to that obtained by other procedures.

Stationary phase equal size single cells of Saccharomyces cerevisiae strain 1829 were separated by gravity sedimentation at 4°C on a 0.5, 1.0, 2.0 M discontinuous sorbitol density gradient. The separated cells were washed free of sorbitol and were grown in 1% yeast extract and 1% glucose. Counting under phase microscope showed that the cells were synchronized for 2-3 generations with a generation time of approximately 2 hr. At different time intervals of growth, cells were washed and fixed in a mixture of paraformaldehyde (2%) and gluteraldehyde (2.5%) in 0.1 M phosphate buffer pH 7.0 for 30 min. These cells were fixed in 1% OSO4 in veronal-acetate buffer pH 6.1 for 15 hr and treated with 0.5% uranyl acetate for 2 hr and further embedded in Epon after dehydration. Thin sections were stained in lead citrate for 30 min.
Heat-Etching with a Bullivant Type II Simple Freeze-Cleave Device
Authors: Weinstein Ronald S. , McNutt N. Scott
Published: June 2020

The Type I simple cold block device was described by Bullivant and Ames in 1966 and represented the product of the first successful effort to simplify the equipment required to do sophisticated freeze-cleave techniques. Bullivant, Weinstein and Someda described the Type II device which is a modification of the Type I device and was developed as a collaborative effort at the Massachusetts General Hospital and the University of Auckland, New Zealand. The modifications reduced specimen contamination and provided controlled specimen warming for heat-etching of fracture faces. We have now tested the Mass. General Hospital version of the Type II device (called the “Type II-MGH device”) on a wide variety of biological specimens and have established temperature and pressure curves for routine heat-etching with the device.
Effect of pH on the Fine Structure of Pectic Acid
Authors: Leeper George F.
Published: June 2020

Elementary fibrils, about 35 Å wide, have been demonstrated for cellulose by a variety of techniques. More recently, they have been demonstrated for xylan, chitin, and mannan. However, their existence has not been previously reported for any of the water soluble polysaccharides.

Pectic acid molecules of about 200,000 molecular weight and enzymatically abbreviated derivatives with molecular weights of 60,000 and 9,000 were negatively stained at various pH values with 2% phosphotungstic acid to demonstrate elementary fibrils. The width and degree of fasciation of these elementary fibrils varies with pH. Pectic acid elementary fibrils exhibit a 64 Å dimensional stability above a certain pH value which varies inversely with molecular weight. Below this pH, elementary fibrils exhibit a marked increase in width. At still lower pH values, the elementary fibrils are no longer demonstrable, presumably because of their dissociation to a molecular species.
The Structure and Development of Microbodies in the Fat Body and other Tissues of an Insect (Calpodes Ethlius)
Authors: Locke M. , McMahon J. T.
Published: June 2020

The fat body of insects has always been compared functionally to the liver of vertebrates. Both synthesize and store glycogen and lipid and are concerned with the formation of blood proteins. The comparison becomes even more apt with the discovery of microbodies and the localization of urate oxidase and catalase in insect fat body.

The microbodies are oval to spherical bodies about 1μ across with a depression and dense core on one side. The core is made of coiled tubules together with dense material close to the depressed membrane. The tubules may appear loose or densely packed but always intertwined like liquid crystals, never straight as in solid crystals (Fig. 1). When fat body is reacted with diaminobenzidine free base and H2O2 at pH 9.0 to determine the distribution of catalase, electron microscopy shows the enzyme in the matrix of the microbodies (Fig. 2). The reaction is abolished by 3-amino-1, 2, 4-triazole, a competitive inhibitor of catalase. The fat body is the only tissue which consistantly reacts positively for urate oxidase. The reaction product is sharply localized in granules of about the same size and distribution as the microbodies. The reaction is inhibited by 2, 6, 8-trichloropurine, a competitive inhibitor of urate oxidase.
Comparative Crystallinity and Morphology of Enamel, Dentine, Bone and Amorphous Concretions
Authors: LeGeros Racquel Z. , LeGeros John P. , Trautz Otto R. , Shirra W. Paul
Published: June 2020

The inorganic phase of calcified tissues of vertebrates he an apatite structure [Ca10(PO4)6(OH)2] while the inorganic phase of the invertebrates such as crustaceans is well crystallized calcium carbonate [CaCO3] in the form of either calcite, aragonite, and sometimes, vaterite. In rare cases, “amorphous” deposits are found such as in the concretions of tapeworm (Saginata Marginata), in the tendon of lobster claw, and in the statoconia of the human ear.

Considerable differences in the “crystallinity” of human enamel, bone or dentine, and tapeworm concretions are demonstrated in the size and/or strain broadening of their x-ray diffraction patterns (Fig.1). The pattern of human enamel (1A) demonstrates that it is very well crystallized apatite; whereas the pattern of bone or dentine suggest that it is poorly crystallized (1B); and the pattern of tapeworm concretions (no discernible peaks) indicate an amorphous material (1C).
Ultrastructure of Plant Leaf Tissue Infected with Mite-Borne Viral-Like Pathogens
Authors: Bradfute O. E. , Whitmoyer R. E. , Nault L. R.
Published: June 2020

A pathogen transmitted by the eriophyid mite, Aceria tulipae, infects a number of Gramineae producing symptoms similar to wheat spot mosaic virus (1). An electron microscope study of leaf ultrastructure from systemically infected Zea mays, Hordeum vulgare, and Triticum aestivum showed the presence of ovoid, double membrane bodies (0.1 - 0.2 microns) in the cytoplasm of parenchyma, phloem and epidermis cells (Fig. 1 ).
Mesosome-like Structures in a Blue-green Alga, Phormidium Luridum
Authors: Edwards Mercedes R.
Published: June 2020

The invagination of the plasma membrane (plasmalemma) to form vesicular or lamellar structures, usually called mesosomes (l) or plasmalemmosomes (2), has been extensively documented in bacteria (3) and more recently also in lower eucaryotes (e.g., the fungi, 4). Such structures have “been implicated in septum formation (i.e., cell division of gram-positive bacteria), in respiratory reactions, and in DNA replication.

In photosynthetic bacteria, such as Rhodospirilium rubrum, vesicular structures derived from the plasma membrane were shown by Drews and Giesbrecht (5) to give rise to thylakoids (photosynthetic vesicles or chromatophores). Continuation between the plasma and thylakoidal membranes is readily seen in R. rubrum (6).
Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells
Authors: Awtar Krishan
Published: June 2020

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.
Type VI Glycogenosis
Authors: C. Garancis John , O. Hussa Robert , Lansdale Darrick
Published: June 2020

Type VI glycogenosis is characterized by the phosphorylase deficiency in the liver and as a result of this inborn defect massive glycogen deposits occur in the liver. This report describes the findings of electron microscopic and biochemical analyses of liver and leukocytes from four children affected by Type VI glycogenosis.

The most striking findings in the liver were large pools of cytoplasmic glycogen. These deposits consisted of monoparticulate glycogen with admixture of glycogen rosettes (Fig. 1). In the majority of hepatocytes, the cytoplasm was almost completely occupied by glycogen deposits, deeply embedded in which were few cytoplasmic organelles such as mitochondria, lysosomes and endoplasmic reticulum. Except for the presence of a few giant mitochondria with highly developed cristae and tubules, cytoplasmic organelles were normal in appearance.
Reconstruction of three Dimensional images From Electron Micrographs
Authors: DeRosier D.J.
Published: June 2020

The purpose of image reconstruction is to determine, in an objective way, the three dimensional structure of a particle from a set of two dimensional electron micrographs.1 Data, in the form of optical density measurements, are gathered from the set of micrographs and are used to determine a three dimensional set of densities representing the distribution of matter, or, in most cases, the distribution of the heavy metal stain. This distribution is graphically displayed section by section on transparent sheets which may then be stacked to give the three dimensional image.
The Critical Point Drying Method Applied to Scanning Electron Microscopy of L-929 Cells
Authors: TurnbiLL Charles , E. Philpott Delbert
Published: June 2020

The advent of the scanning electron microscope (SCEM) has renewed interest in preparing specimens by avoiding the forces of surface tension. The present method of freeze drying by Boyde and Barger (1969) and Small and Marszalek (1969) does prevent surface tension but ice crystal formation and time required for pumping out the specimen to dryness has discouraged us. We believe an attractive alternative to freeze drying is the critical point method originated by Anderson (1951; for electron microscopy. He avoided surface tension effects during drying by first exchanging the specimen water with alcohol, amy L acetate and then with carbon dioxide. He then selected a specific temperature (36.5°C) and pressure (72 Atm.) at which carbon dioxide would pass from the liquid to the gaseous phase without the effect of surface tension This combination of temperature and, pressure is known as the "critical point" of the Liquid.
Scanning Electron Microscopy of Adult Aedes Aegypti Mosquitoes
Authors: Colvard Jones Jack , M. Wehrung John
Published: June 2020

Scanning electron microscopy studies were made on young adult male and female Aedes aegypti mosquitoes. Various surface details of the following anatomical parts were examined at various magnifications: compound eyes, antennae, anterior tentorial pits, various mouthparts, halteres, wings, legs, with special reference to the tarsal claws, and the genitalia.

In all instances the mosquitoes were prepared for examination by sacrificing fresh material and spraying the sample with a commercial anti-static solution. This method resulted in droplet-shaped artifacts (particularly around the antennae). However, it was found that the mosquitoes could be examined in the scanning electron microscope for a period of up to 20 minutes without collapsing of the structure.
Ion Beam Etching Op Soft Biological Tissue Maintained At Low Temperatobes
Authors: Echlin P. , Wayte D. , Dronzek B. , Kynaston D.
Published: June 2020

It has already been demonstrated (1) that it is possible to examine labile biological material kept at low temperatures using the temperature controlled stage module which has been developed for the Stereoscan scanning electron microscope. Following the success of these studies, attempts have been made to ion-beam etch soft biological tissue kept at liquid nitrogen temperatures inside the microscope column.

Extremely hydrated plant material and delicate animal tissue were drained or damp dried, placed onto cooled aluminium stubs and rapidly quench frozen in Freon 22 (monochlorodifluoromethane) maintained at its melting point of -146°C by liquid nitrogen.
Image Intensification and Integration System for Electron Microscopy
Authors: Mengers Paul , Horner Jack
Published: June 2020

Introduction - Image intensifier systems developed during recent years are capable of amplifying very dim images produced on a phosphor screen located at the bottom of the column. 1,2 This has permitted reduction of beam current and/or accelerating potential, thereby extending the life of some types of specimens as well as providing other benefits. This paper points out limitations inherent in conventional intensification systems and describes a system designed to improve performance.
Advances in Freeze - Drying Employing Thermoelectric Cooling
Authors: Bendet Irwin , Rizk Nabil
Published: June 2020

Two techniques have been developed in an attempt to eliminate the effect of surface tension forces during the drying of biological materials; namely, the critical point method of Anderson, and the freeze dry procedure of Williams. More recently, a procedure employing thermoelectric cooling was developed in this laboratory. This technique has now received further attention and development.

Out present thermoelectric cooling unit* consists of four ceramic insulated modules connected in cascade, having 62, 31, 3, and 3 thermocouples, respectively (Fig. 1 ). The base stage is welded to a heat sink consisting of a copper block (2 1/2″ × 2″ × 1″), through which serpentines a 1/4″ wide channel, the thickness of the block, and which is connected by two threaded tubes to the base of the evaporating chamber (Fig. 2).
A Simple Dichromatic Stain for Plastic Embedded Tissues
Authors: Mackay G. R. , Mead M. L.
Published: June 2020

Color contrasting of 1 to 2 micron sections of plastic embedded biological material is an important adjunct to electron microscopy. The procedures in general use today are simple and rapid giving monochromatic results, e.g., toluidine blue. Although many di- and polychromatic histologic staining techniques have been modified to obtain a counterstaining effect with plasticembedded tissue, the methods are usually undesirable for routine work because they are time consuming, complicated and often defy good reproducibility.
Migration of Lanthanum Through the Pollen Exine
Authors: R. Rowley John , J. Flynn James
Published: June 2020

Evolutionists have considered the exine as a defense against desiccation during the independent existence of the pollen grain. While a certain level of waterproofing may have been important to plants in their assumption of the terrestrial habit, two characteristics of some contemporary pollen types are inconsistent with the waterproofing idea: 1) some wind pollinated pollen types lack a continuous exine and 2) the pollen protoplasts can survive a high vacuum and subsequently germinate-vacuum storage can even prolong the period of viability.
Electron Microscopy With Minimal Beam Damage
Authors: C. Williams Robley , W. Fisher Harold
Published: June 2020

It has been previously shown that the electron beam as normally used in electron microscopy results in the destruction of molecules of untreated DNA1 and in the obliteration of the finer structures of tobacco mosaic virus embedded 9 in negative stain.

We have developed methods whereby specimen damage by the electron beam is minimized by restricting irradiation of the region to be micrographed to that necessary for photographic exposure. Focusing and stigmatic correction are done on a selected specimen region nearby. In one method, applicable to a Siemens Elmiskop I, a minimal-size beam spot (∼2μ) is first placed near the edge of the viewing screen and visibje in the binocular.
Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas
Authors: Andrew Staehelin L.
Published: June 2020

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.
A SYSTEM FOR PROTECTING AN OIL DIFFUSION PUMP AGAINST FAILURE OF THE MECHANICAL FORE PUMP, COOLING WATER, OR ELECTRICITY
Authors: Bigelow W. C. , Drogosz F. B. , Nitschke S.
Published: June 2020

High vacuum systems with oil diffusion pumps usually have a pressure switch to protect against Insufficient cooling water; however, If left unattended for long periods of time, failure of the mechanical fore pump can occur with equally serious results. The device shown schematically in Fig. 1 has been found to give effective protection against both these failures, yet it is inexpensive and relatively simple to build and operate.

With this system, pressure in the fore pump line is measured by thermocouple vacuum gage TVG (CVC G.TC-004) whose output is monitored by meter relay MRy (Weston 1092 Sensitrol) which is set to close if the pressure rises above about 0.2 torr. This energizes control relay CRy (Potter & Brumfield KA5Y 120VAC SPDT) cutting off power to solenoid-operated fore line valve Vf (Cenco 94280-4 Norm. Closed) which closes to prevent further leakage of air into the diffusion pump
A Simple Device for Multiple Angle Shadow Casting
Authors: Petrali J. P. , Donati E. J. , Mills K. R.
Published: June 2020

A convenient device is described for shadow casting whole-mounted specimens at two angles simultaneously. The unit was used in our laboratory for studying vaccinia virus, conjugated antibody molecules, bacterial fimbriae and flagella, and microcapsules.

The shadowing unit consists of an 8 x 8 x 6 centimeters stainless steel box with two adjustable shelves secured in juxtaposition onto a common piano-type hinge. Each shelf may be independently set to the desired shadowing angle up to 60 degrees. As many as twenty grids may be shadowed at one time.

In addition to the real advantage of double-angled shadowing as a built-in check on emission angles, the unit may be rapidly aligned in any standard evaporator by use of a removable alignment platform which centers the box to the emitting source in the correct physical attitude for shadowing. Further, if desirable, an aperture may be placed in the same manner as the alignment platform for finer resolution.
Scanning Device Combined with Conventional Electron Microscope
Authors: Koike H. , Ueno K. , Watanabe M.
Published: June 2020

Most of substances - organisms as well as crystals — consist of many micro-structures. It is important, in observation, separately to detect information on microareas of the specimen. In this respect, if the capabilities of the scanning electron microscope, such as the ability to detect information with regard to x-rays, secondary electrons, back scatterd electrons, transmitted electrons, and photons, are combined with those of conventional electron microscope, the resultant electron microscope may well be regarded as a new analytical instrument.

With the JEM-100 type electron microscope combined with a scanning device, secondary electron images and transmitted scanning images were obtained. The incident electron probe used in the present scanning device was strongly demagnified by the prefield of the objective lens. In the objective plane the probe size of 30A was obtained.
High Resolution Color Recording for the Scanning Electron Microscope and the Electron Probe
Authors: Lublin P. , Fowler V. J. , Schlafer J.
Published: June 2020

The advantages of color recording in the scanning electron microscope and the electron probe have been previously enumerated. The usual method of recording scanned images from these instruments is by photographing the display from a long-persistence black and white cathode ray tube. Previous attempts at color recording have included a variety of methods utilizing color filters, density traces, and color cathode ray tubes. These methods present difficulties in super-imposition of sequential images and/or poor resolution. Resolution of the cathode ray tube is particularly important in scanning electron microscopy.

A new recorder providing high-resolution color micrographs for both the electron probe and the scanning electron microscope has been constructed. This instrument employs a multi-color laser which is scanned in synchronism with the electron beam in the column to give a point-to-point correlation.
Dynamic Observation of Magnetic Fields in the Scanning Electron Microscope
Authors: Kabaya A. , Russ J. C.
Published: June 2020

The semiconductor industry has made substantial use of the SEM to examine components using voltage contrast.This is a variation in the secondary electron signal caused by the application of voltages to different parts of the sample.It results both from changes in the emission of secondary electrons, and modifications in their trajectories toward the positively charged collector that changes the number of electrons that strike the scintillator and are amplified to become the displayed signal.

There have been a few efforts to observe magnetic contrast in the SEM, but in general the magnetic analog to voltage contrast has been unused.There has been some use of the SEM to study magnetic fields, however.It has been shown that the distortion in the scanning raster caused by an applied field can be used to map the field, but because this uses the action of the field on the high energy primary electrons rather than the secondary electrons, rather strong fields are required.This application is not related to magnetic contrast.
Electron Microscopy of Metal-Matrix Composites
Authors: Lawley A. , Pinnel M. R. , Pattnaik A.
Published: June 2020

As part of a broad program on composite materials, the role of the interface on the micromechanics of deformation of metal-matrix composites is being studied. The approach is to correlate elastic behavior, micro and macroyielding, flow, and fracture behavior with associated structural detail (dislocation substructure, fracture characteristics) and stress-state. This provides an understanding of the mode of deformation from an atomistic viewpoint; a critical evaluation can then be made of existing models of composite behavior based on continuum mechanics. This paper covers the electron microscopy (transmission, fractography, scanning microscopy) of two distinct forms of composite material: conventional fiber-reinforced (aluminum-stainless steel) and directionally solidified eutectic alloys (aluminum-copper). In the former, the interface is in the form of a compound and/or solid solution whereas in directionally solidified alloys, the interface consists of a precise crystallographic boundary between the two constituents of the eutectic.
Residual Defect Microstructures in Thin-Walled Cylinders Subjected to Internal Explosive-Shock Pressure
Authors: Murr L.E. , Foltz J.V. , Altman F.D.
Published: June 2020

In a previous paper, Foltz and Murr made some preliminary observations of residual defect microstructures in cylindrically shock-loaded stainless steel tubing, and compared these observations with those of plane-wave shock-loaded stainless steel sheet samples. In the present study, detailed investigations of the defect microstructures in shock-deformed 304 stainless steel cylinders have indicated that they are nearly identical to those observed in planar shock-loaded stainless steel of essentially identical composition (each with 0.058% C); the density and formation of deformation microtwins is- related to the nominal residual strain.
Applications of Transmission and Scanning Electron Microscopy to Materials Science
Authors: Brown John L.
Published: June 2020

Applying the electron microscope to studies in Materials Science presents a real challenge to the microscopist. The variety in form and composition of sample materials calls for a repertory of techniques spanning many disciplines. For example the art of ultramicrotomy, once the exclusive province of the biologist, can now be applied to hard materials due to the development of the diamond knife by Fernandez-Moran. Figure 1 shows an ultra-microtome section of a barium-saturated muscovite mica flake. The section was cut at right angles to the (001) planes which are represented by the parallel fringes with 10Å periodicity. The alternating fringe intensity indicates substitution of barium for potassium in the layer structure.
Benzylamine Tartrate as an Organic Glass Substrate for Carbon Films by Evaporation
Authors: Faberge A. C.
Published: June 2020

Benzylamine tartrate (m.p. 63°C) seems to be a better and more convenient substrate for making carbon films than any of those previously proposed. Using it in the manner described, it is easy consistently to make batches of specimen grids as open as 200 mesh with no broken squares, and without individual handling of the grids. Benzylamine tartrate (hereafter called B.T.) is a viscous liquid when molten, which sets to a glass. Unlike polymeric substrates it does not swell before dissolving; such swelling of the substrate seems to be a principal cause of breakage of carbon film. Mass spectroscopic examination indicates a vapor pressure less than 10−9 Torr at room temperature.
Defects at Crystalline Interfaces
Authors: Kinsman K. R. , Aaronson H. I.
Published: June 2020

Crystalline interfaces are of two basic types - interfaces in single phase solids separating grains of differing orientation (grain boundaries, sub-grain boundaries, twin boundaries), and interphase interfaces separating crystals which differ in crystal structure and/or composition, as well as relative orientation. Depending upon these variables a particular boundary will have more or less interfacial structure which can be resolved by transmission electron microscopy. The dislocations (line defects) which are imaged at boundaries by electron diffraction contrast effects may be unique to the boundary, i.e., have displacement vectors which are different from those of dislocations found in single phase materials. Analysis may be further complicated by extra diffraction effects such as superimposed Moire patterns (Fig. 1a and 2).
Environmental Wet Cells for Biological Medium Voltage and High Voltage Microscopy
Authors: Parsons D. F.
Published: June 2020

In this laboratory a survey of the major types of ordered biological structures showed that most do not diffract in vacuum. This is the major reason that electron diffraction has not achieved its full potential as a major biological analytical tool. Also, the fine details of ordered structures can not be correctly imaged in the dry state since the image is the Fourier transform of the diffraction pattern. To overcome this limitation we have constructed both thin-window sealed, and aperture-limited hydration chambers both for medium voltage (100 KV) and high voltage (1.0 MV) electron microscopes. Another type of chamber is under construction for the scanning microscope. We find that differentially pumped, aperturelimited chambers show more promise than the film sealed chambers. Since this equipment can be used more continuously, the specimen can be more easily examined and there is less extraneous electron scattering.
An Electron Microscope Study of Interdiffusion and Compound Formation in Ta-Au Thin Films
Authors: Tisone T. C. , Lau S.
Published: June 2020

In a study of the properties of a Ta-Au metallization system for thin film technology application, the interdiffusion between Ta(bcc)-Au, βTa-Au and Ta2M-Au films was studied. Considered here is a discussion of the use of the transmission electron microscope(TEM) in the identification of phases formed and characterization of the film microstructures before and after annealing.

The films were deposited by sputtering onto silicon wafers with 5000 Å of thermally grown oxide. The film thicknesses were 2000 Å of Ta and 2000 Å of Au. Samples for TEM observation were prepared by ultrasonically cutting 3mm disks from the wafers. The disks were first chemically etched from the silicon side using a HNO3 :HF(19:5) solution followed by ion milling to perforation of the Au side.