bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron Microscopy of Mycoplasma Pneumoniae
Authors: Boatman E. S. , Kenny G. E. 
Published: June 2020

Information concerning the morphology and replication of organism of the family Mycoplasmataceae remains, despite over 70 years of study, highly controversial. Due to their small size observations by light microscopy have not been rewarding. Furthermore, not only are these organisms extremely pleomorphic but their morphology also changes according to growth phase. This study deals with the morphological aspects of M. pneumoniae strain 3546 in relation to growth, interaction with HeLa cells and possible mechanisms of replication.The organisms were grown aerobically at 37°C in a soy peptone yeast dialysate medium supplemented with 12% gamma-globulin free horse serum. The medium was buffered at pH 7.3 with TES [N-tris (hyroxymethyl) methyl-2-aminoethane sulfonic acid] at 10mM concentration. The inoculum, an actively growing culture, was filtered through a 0.5 μm polycarbonate “nuclepore” filter to prevent transfer of all but the smallest aggregates. Growth was assessed at specific periods by colony counts and 800 ml samples of organisms were fixed in situ with 2.5% glutaraldehyde for 3 hrs. at 4°C. Washed cells for sectioning were post-fixed in 0.8% OSO4 in veronal-acetate buffer pH 6.1 for 1 hr. at 21°C. HeLa cells were infected with a filtered inoculum of M. pneumoniae and incubated for 9 days in Leighton tubes with coverslips. The cells were then removed and processed for electron microscopy.
An Electronmicroscopic Study of Collateral Nerve Sprouts
Authors: Jew J. , Williams T. H. 
Published: June 2020

One of the major limitations of classical regeneration is that an axon may have to grow a long way before it can re-establish contact with the denervated cells. Fortunately, however, an alternative and more rapid mechanism exists to secure functional recovery. In this process - collateral nerve sprouting - side branches grow out from surviving axons closest to the denervated elements.Collateral nerve sprouting was recognized by Exner before the turn of the century, though at the time his concept went unnoticed. It was shown that collateral sprouts could restore apparently normal function to skeletal muscle. More recent studies have indicated that collateral sprouting is a general property of peripheral nerves both motor and sensory, somatic and autonomic; but its occurrence in the central nervous system is controversial Structural study of collateral nerve sprouts requires the observation of processes having morphological characteristics beyond the resolution capability of the light microscope. In the absence of information about collateral sprouting at the electronmicroscopic level, and because of its clinical relevance, we set ourselves the task of studying the natural history of this process. The present work will serve as a basis for quantitative studies, including those aimed at controlling the rate and extent of collateral nerve sprouting.
The Effect of Sodium Hydroxide Swelling on Fibrillar Size in Cotton Cellulose
Authors: Hebert J. J. , Hensarling T. P. , Jacks T. J. , Berni R. J. 
Published: June 2020

It is known that the cellulose layers in cotton fibers are made up of filament-like units termed fibrils. With the advent of electron microscopical techniques, an extensive effort has been put forth to arrive at a size for these units. The currently accepted value for the diameter of these elementary fibrils is approximately 35 A. U.In this report an indirect staining technique for electron microscopy has been employed to study the effect of mercerizing strength sodium hydroxide on the size of the elementary fibrils in cotton fibers. The method involves the addition of an unsaturated carbon-carbon double bond to the cellulose within the fibril and further reacting the double bond with osmium tetroxide. The compound used in this investigation was acrylic acid which not only has the osmium reactive bond but, because of its short molecular length, allows the osmium to situate itself at a close proximity to the structure under study.
A Stable 44S Intermediate in the Autodigestion of 50S Ribosomal Subunits
Authors: Nisbet John H. , Slayter Henry S. 
Published: June 2020

Wild - type strains of Escherichia coli are known to contain as many as four endogenous nucleases (Ref. 1). These are commonly found associated with the ribosomes after extraction from the cell, but may be removed, with the exception of RNase IV, by washing the ribosomes in NH4Cl (at 0.2 M and higher concentrations). We have examined the effect of these nucleases on the 50S ribosomal subunit of one wild-type strain, K12 (Hfr 3000), by incubating the unwashed particles at 37° in the presence of varying magnesium concentrations.At 10-4 molar magnesium (slower at 10-3 molar), the 50S particle is converted to a species sedimenting at about 44S. About 20% of the total O.D260 is liberated at the same time. Continued incubation leads to the release of more O.D260 material while the RNA remaining in the 44S (Fig. 1) particle is progressively cleaved, eventually to the point where it consists of one principal fragment of molecular weight 0.42 x 106 daltons and several lesser fragments. The ribosomal RNA and proteins have been characterized by acrylamide gel electrophoresis.
Surface Structure in Microtomed Sections Caused by Glass and Diamond Knives
Authors: Black J. Temple , Boldosser William G. 
Published: June 2020

Ultramicrotomy produces plastic deformation in the surfaces of microtomed TEM specimens which can not generally be observed unless special preparations are made. In this study, a typical biological composite of tissue (infundibular thoracic attachment) infiltrated in the normal manner with an embedding epoxy resin (Epon 812 in a 60/40 mixture) was microtomed with glass and diamond knives, both with 45 degree body angle. Sectioning was done in Portor Blum Mt-2 and Mt-1 microtomes. Sections were collected on formvar coated grids so that both the top side and the bottom side of the sections could be examined. Sections were then placed in a vacuum evaporator and self-shadowed with carbon. Some were chromium shadowed at a 30 degree angle. The sections were then examined in a Phillips 300 TEM at 60kv.Carbon coating (C) or carbon coating with chrom shadowing (C-Ch) makes in effect, single stage replicas of the surfaces of the sections and thus allows the damage in the surfaces to be observable in the TEM. Figure 1 (see key to figures) shows the bottom side of a diamond knife section, carbon self-shadowed and chrom shadowed perpendicular to the cutting direction. Very fine knife marks and surface damage can be observed.
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.
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).
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).
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.
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.
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).