bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron Microscopy of a Tumor Virus RNA
Authors: Evenson D. , Scotto A. , Pavlovec A. , Hamilton M. , de Harven E.
Published: June 2020

The structure of Friend leukemia virus (FLV) has been studied by electron microscopy. The virus was harvested from the plasma of infected mice and purified by techniques including differential velocity and isopycnic sucrose gradient centrifugation. Viral nucleic acid was isolated using GuHCl followed by precipitation with ethanol and resuspension in 1 mM dithiothreitol. In initial experiments, the RNA solution was diluted 1:10 into either H2O or 4-8 M urea. Prior to spreading, 1 M ammonium acetate and cytochrome c were added to a final concentration of 0.4 M and 0.01% respectively. Fifty μ1 of this mixture was spread using a glass slide inclined in a ten cm2 trough filled with 15 mM ammonium acetate. Samples were picked up on collodion filmed grids, stained with uranyl acetate and rotary shadowed with Pt:Pd. This method is very similar to the conditions used to study the RNA of avian myeloblastosis virus, murine leukemia virus, and mammary tumor virus (MTV).
Improved Resolution of Stained SV40 DNA Fragments in Dark Field EM
Authors: Ruben G. , Jay E. , Wu R. , Siegel B.
Published: June 2020

The technique for spreading double and single-stranded DNA using a basic protein developed by Kleinschmidt is routine and widely used. After shadowing DNA prepared by this method the cytochrome c on the DNA and in the background gives an apparent increase in length and width of the DNA. The smallest DNA length measurement which has been reported for homogeneous double-stranded molecules is 1300 Å using the Kleinschmidt technique in bright field. In bright field, the uneven background of the cytochrome c film and metal deposit makes size measurements of shorter DNA fragments difficult. In the dark field technique, the resolution limitation is imposed by the stained width of the DNA itself. Thus in principle, much shorter lengths should be measurable.

The resolution limits on double-stranded DNA by the dark field technique have been tested by using suitable restriction enzymes to cleave SV40 DNA to produce a number of discrete DNA fragments of defined lengths.
Application of HVEM to Thick Sections of Diseased Human Kidney
Authors: Barber T.A. , Burkholder P.M.
Published: June 2020

The high voltage transmission electron microscope (HVEM) offers the biologist a means of examining ultrastructure in thick (0.3 to 1.0μ) sections of conventionally enbedded biological material with good Z-axial resolution. The spatial distribution of structures throughout the depth of a specimen may be easily visualized by HVEM and the need for reconstruction from ultrathin serial sections avoided. Effective stereo pair micrographs allowing the 3-D relationships of organellae to be observed are also readily made.

Our preliminary applications of HVEM in the examination of diseased human kidney were made in an effort to gather information on poorly understood renal pathologic changes. These changes include loss or alteration in size of glomerular epithelial and endothelial cells and their processes, changes in thickness or composition of glomerular basement membrane, the deposition of subepithelial or subendothelial electron-dense material, and the occurrence of round or microtubular virus-like particles and crystalline deposits.
The Three Dimensional Structure of NADP + Specific Isocitrate Dehydrogenase of Escherichia Coli
Authors: Germinario Louis T.
Published: June 2020

The NADP+ specific isocitrate dehydrogenase (IDH) three-Ds - isocitrate: NADP+: oxidoreductase (decarboxylating), E.C. 1.1.1.42. of Escherichia coli was recently purified to electrophoretic homogeneity. The enzyme has a molecular weight of 83,000 daltons, exists as a catalytically active dimer with identical subunits of a molecular weight of 42,000 daltons and an isoelectric point of pH 5. The native enzyme crystallizes in the form of a regular octahedron ranging in size from 5 to 30 um. In this investigation the subunit structure (tertiary Structure) and quaternary structure of E. coli IDH is described along with functional implications.

Electrophoretically pure E. coli (F 143/KL259) IDH (.43 mg/ml, specific activity 30.5 enzyme units/mg protein) was maintained in 0.0125 M citrate-phosphate (pH 5.5) containing 20% (v/v) glycerol and 2mM MgCl2 at 4°C. Fenestrated 400 mesh copper grids were pre-coated with gold before overlaying a thin carbon film (∼30Å thick). Enzyme was deposited on the support film by lightly touching a drop of enzyme-buffer solution, followed by positive staining with 1% uranyl acetate (pH 4.7), rinsed gently in the citrate-phosphate buffer and air dried. Denaturation of IDH enzyme complex into its constituent subunits was effected by treating grids containing enzyme with 10M urea and stained and rinsed as indicated above.
Technic for the Study of Small, Soft-Bodied Aurelia with Scanning EM
Authors: Spangenberg Dorothy B. , Kuenning William
Published: June 2020

Rapid advances have been made in the preservation and preparation of cells and soft tissues of vertebrates for scanning electron microscopy (SEM). These technics, however, only rarely have been applied to small soft-bodied invertebrates. When an effort was made to preserve intact metamorphosing Aurelia polyps (strobilae) for SEM studies, it became apparent that special methodology was needed. The following technic was developed:

Aurelia polyps are induced to metamorphose with 1 x 10-5M thyroxine. Strobilae in the desired stage of metamorphosis are fixed in 2 changes of 3% gluteraldehyde for 1 hr. each. They are rinsed 2X in collidine buffer, pH 7.4 (based on). The organisms are dehydrated in grades of acetone from 30% to 100%. To avoid disturbing the strobilae, acetone is added to the dilute acetone every 10 min. to achieve concentrations of 50, 70, and 95%. The strobilae are rinsed 2X in 100% acetone for 5 and 10 minutes each.
Architecture of Radiolitid Rudist (Mollusca) Shell-Wall Structures and its Phylogenetic Implications
Authors: Sturm David H. , Perkins Bob F.
Published: June 2020

Each of the seven families of rudists (Mollusca, Bivalvia, Hippuritacea) is characterized by distinctive shell-wall architectures which reflect phylogenetic relationships within the superfamily. Analysis of the complex, calcareous, cellular wall of the attached valve of the radiolite rudist Eoradiolites davidsoni (Hill) from the Comanche Cretaceous of Central Texas indicates that its wall architecture is an elaboration of the simpler monopleurid rudist wall and supports possible radiolite-monopleurid relationships.

Several well-preserved specimens of E. davidsoni were sectioned, polished, etched, and carbon and gold coated for SEM examination. Maximum shell microstructure detail was displayed by etching with a 0.7% HC1 solution from 80 to 100 seconds.

The shell of E. davidsoni comprises a large, thick-walled, conical, attached valve (AV) and a small, very thin, operculate, free valve (FV) (Fig. 1a). The AV shell is two-layered with a thin inner wall, in which original structures are usually obliterated by recrystallization, and a thick, cellular, outer wall.
A Study of Solute Trapping During Rapid Solidification of Binary Alloys
Authors: Mackey Terrence M. , Kelly Thomas F.
Published: June 2020

BACKGROUND

The very high crystal growth rates which can be produced during pulsed-laser melting provide the opportunity to study non-equilibrium solidification effects under well-defined experimental conditions. In particular, incorporation of solute into the growing crystal in excess of equilibrium solubilities may be achieved. This solute trapping may be pronounced at the highest crystal growth rates and may lead to the absence of microsegregation in non-planar solidification fronts.

Crystal/liquid interface kinetics have been treated by considering the diffusive motion of atoms in the liquid. In this treatment, the crystal growth speed can never exceed the maximum diffusive speed of solute in the liquid, hence solute trapping is not possible. More recently, the collision-limited growth model indicates that for metallic and other simple molecular systems, the speed of sound in the liquid should be the upper limit to crystal growth rates. Consequently, in this latter model of solidification, the crystal growth rate can greatly exceed the maximum solute diffusive speed and solute trapping is possible.
Microstructures and Precipitation in a Rapidly Solidified Copper-Beryllium Alloy
Authors: Guha A.
Published: June 2020

A study of direct strip cast copper-beryllium alloys is of interest to determine if enhanced properties could be obtained from rapidly solidified material compared to those of conventionally processed material. The present investigation was undertaken to characterize the as-cast microstructure of this material and to study the metastable phases which formed in this alloy as a result of precipitation from the rapidly quenched condition.

The melt spinning technique was used to produce ribbons of a copper-beryllium alloy of nominal composition Cu-1.90wt% Be containing 0.25 wt% cobalt. The as-cast ribbon was approximately 0.1 mm thick and 12 mm wide. The Metglas Products Division of Allied Corporation provided the material. As-cast specimens were salt bath aged at 370 C for 5 min or 3 hours. Thin foils for transmission electron microscopy (TEM) were prepared from the melt spun ribbons by electrolytically thinning in a twin-jet electropolisher using a solution of 30% nitric acid in methanol at -30 C and 25 volts. The specimens were examined in a Siemens 102 transmission electron microscope operating at 125 kV.
Use of in Situ Delamination to Evaluate Fracture Micromechanisms in Graphite/Epoxy Laminates
Authors: Jordan William
Published: June 2020

The goal of this research was to better define the deformation and fracture physics of delamination fracture in graphite/epoxy composite materials so that realistic models of the matrix dominated fracture could be developed. A key aspect of this was to develop techniques whereby real time delamination fracture could be observed in a scanning electron microscope.

Macroscopic delamination tests were performed on an M.T.S. tensile machine operated in stroke control. The samples were 2.5 cm by 25 cm with a short starter crack in one end that was placed there when the sample was fabricated. This test procedure is described by Cohen. The test was designed so that the specimens could be tested in opening mode (mode 1) and with increasing amounts of shear up to pure mode 2 (in plane shear). Fracture energy results are shown in Table 1.
Identifying Sources of Sulfate Aerosols Reaching Whiteface Mountain, NY
Authors: Webber James S.
Published: June 2020

INTRODUCTION

“Acid rain” and “acid deposition” are terms no longer confined to the lexicon of atmospheric scientists and 1imnologists. Public awareness of and concern over this phenomenon, particularly as it affects acid-sensitive regions of North America, have increased dramatically in the last five years. Temperate ecosystems are suffering from decreased pH caused by acid deposition. Human health may be directly affected by respirable sulfates and by the increased solubility of toxic trace metals in acidified waters. Even man's monuments are deteriorating as airborne acids etch metal and stone features.

Sulfates account for about two thirds of airborne acids with wet and dry deposition contributing equally to acids reaching surface waters or ground. The industrial Midwest is widely assumed to be the source of most sulfates reaching the acid-sensitive Northeast since S02 emitted as a byproduct of coal combustion in the Midwest dwarfs S02 emitted from all sources in the Northeast.
Electrolytic Extractions of Precipitates From Steel Alloys
Authors: Smith W. H.
Published: June 2020

During aging of an iron based alloy, the degree of preparation has significant effects on the properties of the alloy. Long-term heat treatments can produce rather large precipitates. In order to obtain compositional and/or structural information from these large precipitates, it is often necessary to examine them in the absence of the surrounding matrix. However it has been found that the extraction replica technique is reliable only for particles 1 μn in size or less. Any larger particle tends to stay embedded in the matrix. We have found electrolytic extraction from the this bulk to be the only reliable way to obtain precipitate particles larger than 1 um. By modifying a gravimetric-vacuum filter assembly, a new method of extraction has been developed, eliminating the time consuming and laborious steps of centrifuging the electrolyte, retrieval of precipitates from test tubes, vacuum drying, and acid cleaning of glassware.
Mechanical Microthinning For TEM Specimen Preparation
Authors: Plummer H. K. , Shinozaki S.S.
Published: June 2020

In two previous papers the technique of TEM specimen preparation using only the mechanical abrasion of boxwood tool and a dispersion of diamond powder in glycerin to thin the specimen has been presented with a number of examples shown. It is the intent of this paper to discuss additional details of the technique and to exihibit further examples where mechanical microthinning has been advantageous in obtaining useful information even in the presence of obvious mechanical damage.

A.C.Faberge reported the use of teflon as a fine polishing lap. The grooved surface similar to that shown in Fig.1a, polished exceptionally well but after a short time in use the pocked surface, as seen in Fig.1b, was formed. in Fig.1a, polished exceptionally well but after a short time in use the pocked surface, as seen in Fig.1b, was formed.
Atomic Structure-Sensitive Magnetic Domain Structures of Thin Films
Authors: Tsukahara S.
Published: June 2020

Transmission electron microscopy, TEM, that can serve for observation of both atomic and magnetic structures is useful to investigate structure sensitive magnetic properties. It is most effective when it is applied to thin films for which direct interpretation of the results is possible without considering additional effects through specimen handling for TEM use and modification of dimension dependent magnetic properties.

Transmission Lorentz microscopy, TLM, to observe magnetic domains has been known for a quarter century. Among TLM modes the defocused mode has been most popular due to its simple way of operation. Recent development of TEM made it possible that an average instrument commercially available could be easily operated at any TLM modes to produce high quality images. This paper mainly utilizes the Foucault mode to investigate domain walls and magnetization ripples as the finest details of domain structure.
High-Resolution Observation of Twinning in Fe1-XS Crystals
Authors: Nguyen Thao A. , Hobbs Linn W. , Buseck Peter R.
Published: June 2020

The ordering of iron vacancies in highly nonstoichiometric iron sulfide compounds (Fe1-xS, 0 ⩽ x ⩽ 0.125) at temperature below 425K give rise to at least two different superstructures and a number of possible planar defect configurations. These ordered iron vacancies and associated planar defects are believed to influence greatly the electrical and magnetic properties of Fe1-xS crystals. Extensive efforts, employing high resolution transmission electron microscopy, to characterize the ordering of iron vacancies and associated planar defects have been carried out by Nguyen and Hobbs, Pierce and Buseck, and Nakazawa, et al. In this paper we report the characterization of twin boundaries in iron sulfide crystal of composition nominally Fe9S10.

Many beam lattice images of crushed synthetic Fe9S10 crystals were obtained in a top-entry JEM 200CX transmission electron microscope. Relevant electron optical parameters were Cs = 1.2mm; divergence half-angle α = 0.5mrad; and an objective aperture which allowed electron beams up to 5nm-1 to contribute to the final image.
Direct Structure Imaging In Hydroxyapatite
Authors: Barry J.C.
Published: June 2020

Human tooth enamel is composed 96% by weight of carbonated hydroxyapatite (HAP). It Js believed that the carbonate ions substitute for the phosphate ions in HAP, and it is expected that the carbonate will have an effect on the rate of dissolution of HAP during the carious process in human tooth enamel. In the present study high resolution electron microscope images of synthetic stoichiometric HAP were obtained to explore the possibility of obtaining direct structure images in HAP, and to provide a standard to which human enamel HAP could be compared. Bres et al have pointed out that structure images of HAP may provide a means of studying the substitution by carbonate of phosphate or other ions in biological HAP. The specimens were examined with a top-entry JEOL 4000EX HREM fitted with a Cs = 1.0mm objective pole-piece at 400kV. This 4000EX has demonstrated a structure resolution limit of better than 1.8 Å.
Profile Imaging of Silicon Surface Reconstructions
Authors: Krivanek O.L. , Wood G.J.
Published: June 2020

Electron microscopy at 0.2nm point-to-point resolution, 10-10 torr specimei region vacuum and facilities for in-situ specimen cleaning presents intere; ing possibilities for surface structure determination. Three methods for examining the surfaces are available: reflection (REM), transmission (TEM) and profile imaging. Profile imaging is particularly useful because it giv good resolution perpendicular as well as parallel to the surface, and can therefore be used to determine the relationship between the surface and the bulk structure.
Scanning Reflection Electron Microscopy of 2x1 Domain Structure of Si(111) Surface
Authors: Ou H.-J.
Published: June 2020

Studies of the surface structure of silicon with good spatial resolution made recently by reflection electron microscopy, (REM) have complemented and greatly extended the earlier studies, made by LEED and other methods, of the formation of surface reconstruction superstructures such a the Si(111) 7x7. These studies have not included the 2x1 superstructure on (111) surfaces formed by cleaving Si crystals in ultra-high vacuum. We have now investigated the form of the domains of this 2x1 structure by use of a reconstructed REMEDIE system 2.3 (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies, 1-20keV). This system has shown a spatial resolution of better than 100Å although resolutions of about 300Å may be more common in practise because of the limitations due to probe size, vibration and signal noise.
TEM Study of Precipitation Kinetics of Epsilon Copper in HSLA (A710) Steel
Authors: Pande C.S. , Smith S. , Richards L.E.
Published: June 2020

A710 steel is an agehardening ferritic steel containing 1.2% (wt) copper. After austenitization and quenching at 1100°C, the copper is retained in solid solution. In subsequent aging this copper appears as fine precipitates. It is postulated that these precipitates when initially formed have bcc structure and are coherent with the matrix. They are then very difficult to detect by conventional TEM presumably because of small mismatch between the lattice constants of the copper precipitates and the matrix. Subsequent aging transforms the copper precipitates into incoherent precipitates which can be easily detected by conventional TEM. We have characterized the precipitate kinetics of these incoherent copper precipitates by TEM. These specimens were also characterized by small angle neutron scattering and hardening measurements to detect coherent copper precipitates. A combination of the three techniques has been used to study the precipitation kinetics of copper precipitates. Our results indicate that the transition from coherent to incoherent precipitation is continuous and presumably depends on the size of the precipitate rather than on the actual aging condition.
Oxygen Precipitation in Oxygen-Ion Implanted Silicon
Authors: Carpenter R.W. , Vanderschaeve G. , McClure D.
Published: June 2020

Heat treatment of oxygen-ion implanted CZ-silicon may be expected to induce precipitation of oxygen-rich precipitates when the peak total oxygen concentration is above the oxygen solubility limit, but not far enough above to result in a “buried” SiOx layer. We report here first results of an investigation of oxygen-rich precipitates formed in oxygenimplanted CZ-silicon given a multistep post-irradiation heat treatment with maximum temperatures of 1050°C. The implantation energy and dose were 400kV and 3xl015cm-2 respectively, yielding a peak oxygen concentration of 6.8x1019 cm-3 at a projected range of 1μm, based on LSS statistics. This concentration is about one order of magnitude above the oxygen solubility limit and three orders of magnitude below the stoicheometric oxide concentration.
Structure of the Si-GaAs Interface: Polar on Nonpolar Epitaxy
Authors: Mazur J.H. , Washburn J. , Henderson T. , Klem J. , Masselink W.T. , Fischer R. , Morkoç H.
Published: June 2020

Possibility of growth of epitaxial lll-V (GaAs, InP, GaP, etc.) compound semiconductors on nonpolar substrates (Ge,Si) is of considerable interest from the view point of monolithic integration of lll-V optoelectronic and Si electronic devices. The growth of GaAs and AIGaAs layers on Si substrates is additionally attractive because of good mechanical strength and low cost of Si substrates. However, a principal difficulty in growing polar semiconductors on nonpolar substrates is that there are no preferential bonding sites for cations and anions in the first layer of growth, which can result in antiphase boundaries (APB’s) in addition to defects due to misfit (∼4% for GaAs on Si).

In this work GaAs layers were grown on (100) Si substrates using procedures described elsewhere. The MBE growth started from a first deposition of As as a prelayer on the Si substrate followed by GaAs growth at 580°C. Cross-sectional TEM specimens were prepared using the same procedures as reported earlier for the case of Si-SiO2 cross-sections.
Ultrathin Platinum Crystal Surface Structures
Authors: Hines R. L.
Published: June 2020

The importance of atom layer terraces or steps on platinum surfaces used for catalysis as discussed by Somorjai justifies an extensive investigation of the structure of platinum surfaces through electron microscopy at the atomic resolution level. Experimental and theoretical difficulties complicate the quantitative determination of platinum surface structures but qualitative observation of surface structures on platinum crystals is now possible with good experimental facilities.

Ultrathin platinum crystals with nominal 111 orientation are prepared using the procedure reported by Hines without the application of a carbon backing layer. Platinum films with thicknesses of about ten atom layers are strong enough so that they can be mounted on grids to provide ultrathin platinum crystals for examination of surface structure. Crystals as thin as possible are desired to minimize the theoretical difficulties in analyzing image contrast to determine structure. With the current preparation procedures the crystals frequently cover complete openings on a 400 mesh grid.
Thickness Measurement by EELS
Authors: Egerton R. F. , Cheng S. C.
Published: June 2020

Electron energy-loss spectroscopy offers a rapid method of estimating the local thickness of a TEM specimen. The best-known procedure requires only measurement of the integrated intensity IOunder the zero-loss peak and of the integral Itunder the whole spectrum (up to some suitable energy loss Δ). The thickness t is obtained from the formula:

where λ(β) is the mean free path for inelastic scattering up to some angleβwhich is determined by the collection aperture (e.g. objective aperture in CTEM). In agreement with previous work we find that Eq. (1) is applicable over a wide range of thickness, typically 10-500 nm for EO= 100keV incident energy; see Fig. 1. Some deviation at large thickness might be expected as a result of the angular broadening produced by plural scattering, and because of contributions from electrons elastically scattered through angles greater thanβ.
Quantitative Electron Energy Loss Mapping
Authors: Leapman R.D. , Swyt C.R.
Published: June 2020

The intensity of a characteristic electron energy loss spectroscopy (EELS) image does not, in general, directly reflect the elemental concentration. In fact, the raw core loss image can give a misleading impression of the elemental distribution. This is because the measured core edge signal depends on the amount of plural scattering which can vary significantly from region to region in a sample. Here, we show how the method for quantifying spectra due to Egerton et al. can be extended to maps.
Voltage and Orientation Dependence of Characteristic X-Ray Production in Thin Crystals
Authors: Thomas G. , Krishnan K. M. , Yokota Y. , Hashimoto H.
Published: June 2020

For crystalline materials, an incident plane wave of electrons under conditions of strong dynamical scattering sets up a standing wave within the crystal. The intensity modulations of this standing wave within the crystal unit cell are a function of the incident beam orientation and the acceleration voltage. As the scattering events (such as inner shell excitations) that lead to characteristic x-ray production are highly localized, the x-ray intensities in turn, are strongly determined by the orientation and the acceleration voltage. For a given acceleration voltage or wavelength of the incident wave, it has been shown that this orientation dependence of the characteristic x-ray emission, termed the “Borrmann effect”, can also be used as a probe for determining specific site occupations of elemental additions in single crystals.
X-Ray Microanalysis of Nickel and Cobalt Intensified Peroxidase- Antiperoxidase For Verification of Reaction Sites
Authors: Angel A. , Miller K. , Seybold V. , Kriebel R.
Published: June 2020

Localization of specific substances at the ultrastructural level is dependent on the introduction of chemicals which will complex and impart an electron density at specific reaction sites. Peroxidase-antiperoxidase(PAP) methods have been successfully applied at the electron microscopic level. The PAP complex is localized by addition of its substrate, hydrogen peroxide and an electron donor, usually diaminobenzidine(DAB). On oxidation, DAB forms an insoluble polymer which is able to chelate with osmium tetroxide becoming electron dense. Since verification of reactivity is visual, discrimination of reaction product from osmiophillic structures may be difficult. Recently, x-ray microanalysis has been applied to examine cytochemical reaction precipitates, their distribution in tissues, and to study cytochemical reaction mechanisms. For example, immunoreactive sites labelled with gold have been ascertained by means of x-ray microanalysis.
Electron Beam-Induced Mass Loss in Freeze-Dried Tissue and Protein Samples
Authors: Cantino M.E. , Goddard M.K. , Wilkinson L.E. , Johnson D.E.
Published: June 2020

Quantification in biological x-ray microanalysis depends on accurate evaluation of mass loss. Although several studies have addressed the problem of electron beam induced mass loss from organic samples (eg., 1,2). uncertainty persists as to the dose dependence, the extent of loss, the elemental constituents affected, and the variation in loss for different materials and tissues. in the work described here, we used x-ray counting rate changes to measure mass loss in albumin (used as a quantification standard), salivary gland, and muscle.

In order to measure mass loss at low doses (10-4 coul/cm2 ) large samples were needed. While freeze-dried salivary gland sections of the required dimensions were available, muscle sections of this size were difficult to obtain. To simulate large muscle sections, frog or rat muscle homogenate was injected between formvar films which were then stretched over slot grids and freeze-dried. Albumin samples were prepared by a similar procedure. using a solution of bovine serum albumin in water. Samples were irradiated in the STEM mode of a JEOL 100C.
Mass Loss is Reduced at Liquid Helium Temperature
Authors: Lamvik M.K. , Klatt L.L. , Davilla S.D.
Published: June 2020

Since mass loss is a fundamental limitation in electron microscopy and microanalysis of biological materials it is very valuable to understand the effect of specimen temperature on the mass loss process. An electron energy loss spectrometer has been added to the Duke University Cryomicroscope (fig. 1) to allow a general study of radiation damage effects in specimens held at liquid helium temperature.

The reduction of specimen mass is measured by recording a long series of electron energy loss spectra with a Tracor-Northern TN-5400 analyzer, using the region integration feature of the analyzer to report the number of counts in the zero-loss and inelastic scattering regions of the spectrum.
Ultrastructure of the Cytoskeleton Purified From Macrophages
Authors: Washington L. P. , Browne J. , Igbo T. , Howard G. , Watson C. , Rabon L.
Published: June 2020

The cytoskeleton of mammalian cells consists of families of protein fibers and networks which include microtubules (MT), microfilaments (MF), clathrin baskets (CB), intermediate filaments (IF), and the microtrabeculae lattice (MTL). The networks function in a coordinated, integrated manner to bring about movement/motility of intracellular organelle and membrane traffic. Although much is known about the structure and function of MT and MF, more knowledge is needed to elucidate the ultrastructure, assembly and function of intermediate filaments in non-keratinized mammalian cells.

The objective of this study was to elucidate the ultrastructure of intermediate filaments isolated and purified from cultured mammalian cells.

Macrophages were harvested from the peritoneal cavities of mice. Triton- insoluble fractions of IF were isolated from spread cultures using high salt and low ionic strength buffers. Purified IF were analyzed biochemically. Using poly acrylamide gel electrophoresis IF consists of 4-7 major bands in the molecular weight ranges of 14-90Kd3.
Immunocytochemical Identification of Tubulin Containing Paracrystals in Allogromia Reticulopods
Authors: Rupp Gerald
Published: June 2020

The marine protozoan Allogromia sp, strain NF Lee extends an elaborate reticulopodial network (RN) which contains an elongate microtubule-(MT)-based cytoskeleton. The MTs are located primarily within cytoplasmic fibrils which are visible by light microscopy (LM) in highly flattened or “two dimensionalized” reticulopodia. It was shown previously that allogromiid RNs withdraw in response to hypertonic Mg2+-seawater. An ultrastructural analysis of this phenomenon indicated that large patches of paracrystalline (PC) material, composed of helical filament aggregates, form concomitant with a decrease in MT number. Similar large patches of PC aggregates are also found in juvenile Allogromia before they extend a RN, which disappear during RN formation. Finally, PC aggregates are occasionally seen near microtubules in normal untreated RNs. Thus there is circumstantial evidence to propose that PC aggregates in Allogromia represent an intermediate form of tubulin; however, more definitive biochemical or immunocytochemical data is not available.
Intercisternal Substances of Plant Dictyosomes
Authors: Mollenhauer Hilton H. , James Morré D.
Published: June 2020

Dictyosome cisternae are separated from one another by a minimum spacing of approximately 10 nm. Maintenance of this minimal spacing is due, presumably, to substances in the intercisternal region that bind one cisterna to the next. However, the intercisternal region appears in thin section much like the generalized ground substance of the cell and no distinct binding substances have been identified. Fibers bridging the intercisternal space have been reported but a role for them in the maintenance of dictyosome form has not been confirmed.

The mechanism(s) for binding cisternae together can be broken rapidly by phosphotungstic acid or monovalent salts resulting in the disassembly of dictyosomes and separation of cisternae. Intact, or nearly intact, dictyosomes appear as stacks of highly fenestrated and/or tubular cisternae (Fig. 1). Coated vesicles are associated with the ends of peripheral tubules. Individual cisternae show a broad range of forms from predominantly tubular to predominantly flattened saccular with fenestrae (Fig. 2).
Forensic Uses of Deflection (Y) Modulation and X-Ray Dot Mapping
Authors: Basu S.
Published: June 2020

The imaging capabilities of the scanning electron microscope in conjunction with an energy dispersive x-ray spectrometer (SEM-EDX) allow both topographical and compositional displays that can be readily interpreted. Illustrative evidence of this type would be valuable in forensic determinations, since the associated techniques of image formation, chemical analysis and sample preparation are well understood and documented. Various methods of signal processing are also available, which allow intuitive, stylistic and synthetic interpretation of the image. Forensic applications of two such methods will be stressed in this report using a AMR 1000 SEM. These are deflection modulation (DM) or “Y-modulation” of secondary electron signal^ and x-ray dot mapping.
Ultrastructural Study of Rat Colon Following Psyllium Ingestion
Authors: Lightfoot F.G. , Grau L.E. , Cassidy M.M. , Tadvalkar G.R. , Vahouny G.V.
Published: June 2020

Psyllium hydrophillic mucilloid is a natural gelling fiber consumed by a large population of our society. It is used as a bulk-producing laxative and in the treatment of gastrointestinal disorders such as “Irritable Bowel Syndrome”. The literature pertaining to the ultrastructural effects of this agent is sparse.

This study documents morphological changes induced by psyllium. Animals fed a diet containing 2% psyllium for four weeks were subsequently sacrificed and processed for scanning and transmission electron microscopy. The colon contained fecal material combined with psyllium which conformed to the contour of the luminal surface. This mixture formed surface replicas of the intestinal mucosa. These replicas and their related colonic sites were processed for morphologic analysis.
3D Soft X-Ray Contact Imaging and Image Interpretation
Authors: Cheng (鄰炳今) P. C. , Feder R. , McGowan J. Wm. , Tan (陳金華) K. H. , Shlnozakl D.
Published: June 2020

Recent advances in x-ray contact Imaging provide various viewing methods for magnifying contact Images, these include the use of SEM (Fig. 1, Xenopus Iaevis muscle cell) and TEM (Fig. 2, X. Iaevis muscle cell). It Is rare that one can treat a biological specimen as a two-dimensional object. In order to obtain 3D structural Information of a cell, the general practice is to serially-section the cell. Occasionally, If the cell is sufficiently thin (e.g., cultured fibroblast), stereo Image-pairs can be obtained with a TEM. Since soft x-ray Imaging is capable of looking at a much thicker specimen than electron microscopy, 3D image-pairs will be a useful tool to study cells or tissue sections which are too thick or too dense to be studied by a TEM. With the growing Interest In the application of soft x-ray contact Imaging for biological research, a clear understanding of the physical properties and limitations associated with the technique is essential. A valid conclusion can only be drawn with the knowledge of all the physical properties associated with the Imaging technique.
Defects of Platelet Function Recognized by X-Ray Imaging and Scanning Electron Microscopy
Authors: Baldini M.G. , Morinaga S. , Minasian D. , Feder R. , Sayre D. , Banton V.
Published: June 2020

Contact X-ray imaging is presently developing as an important imaging technique in cell biology. Our recent studies on human platelets have demonstrated that the cytoskeleton of these cells contains photondense structures which can preferentially be imaged by soft X-ray imaging. Our present research has dealt with platelet activation, i.e., the complex phenomena which precede platelet appregation and are associated with profound changes in platelet cytoskeleton. Human platelets suspended in plasma were used. Whole cell mounts were fixed and dehydrated, then exposed to a stationary source of soft X-rays as previously described. Developed replicas and respective grids were studied by scanning electron microscopy (SEM).
Low-Temperature Specimen Preparations For Electron Microscopy and Their Applicability to Plant Materials
Authors: Crang Richard E.
Published: June 2020

Progress in utilizing the technologies of low-temperature sample preparation for botanical materials in the electron microscope has notably lagged behind those of other biological specimens. To a great extent this is due to the structural features of plant materials which are frequently characterized by rigid cell walls, often with a nearly impermeable cuticle, air spaces around parenchymatous tissues, and large central vacuoles of high water content with no structural support. Freezing, or cryofixation, at its best, is capable of preserving otherwise highly labile cellular components for morphological examination by means of transmission electron microscopy. It also instantaneously stops cellular movement which may result in an unnatural distribution of cell contents and/or the formation of artifactual structures within cells. Among microorganisms, it is now believed that mesosomes in bacteria and lomasomes in many fungi may be considered artifacts caused by the slow rate of chemical fixation.
Long-Term Effects of Iron Particle (HZE) Irradiation on Mouse Spermatogonia
Authors: Philpott D. E. , Sapp W. , Williams C. , Stevenson J. , Black S. , Corbett R.
Published: June 2020

High-energy (HZE) cosmic ray particles in space present an environmental hazard, especially to long-duration high altitude space travel. The energy released when these particles slow down and stop in living tissue causes deleterious biological effects, including death of cells. In order to study and quantitate the effects of this radiation, a number of cell systems could be used. The spermatogonial cell population in mouse testes has a rapidly dividing cell population, can be examined three days after irradiation, and is one of the most sensitive tissues to radiation. Therefore, it is ideally suited for quantitative studies of radiation effects. Previous work has shown that the various types of spermatogonial cells differ in their radiation sensitivity and that this can be very easily evaluated with the light/electron microscope. Using the system of staging established by Oak-berg and Huckins, the mixed or single cell population can be evaluated. Our work, using this method, has revealed cell sensitivity at doses as low as one rad. In these experiments, the animals were sacrificed three days post-irradiation because this is the time when maximum cell loss can be viewed. However, we are now reporting long term results of HZE particles using iron irradiation.
Correlation of Vaginal Smears and Surface Structure in the Normal Estrous Cycle of Rats
Authors: Robert C. Kaufmann , Francis K. Khosho , Kofi S. Amankwah
Published: June 2020

Few studies regarding the normal estrous cycle of rats exist in the literature. Only the estrous and diestrous portions of the cycle have been studied in any detail in the spontaneous cycle of the rat. Ultrastructural studies of proestrous have been limited to artificially induced cycles. These artificially induced cycles have been unable to account for all the findings on vaginal smears seen in spontaneous cycles. In this study, vaginal smear findings were correlated to surface ultrastructural findings in the four main phases of spontaneous ovulatory cycles in rats.

Adult female rats of the Sprague-Dawely strain were used and sacrificed during different phases of their cycles. Daily vaginal smears (8-11 a.m.) of at least two consecutive cycles were used to determine the phase of the normal estrous cycle for each rat.
Intramuscular Nerve and Neuromuscular Junction Alteration In Extraocular Muscles of Diabetic Mice
Authors: Pachter Bruce R.
Published: June 2020

Diabetes mellitus is one of the commonest causes of neuropathy. Diabetic neuropathy is a heterogeneous group of neuropathic disorders to which patients with diabetes mellitus are susceptible; more than one kind of neuropathy can frequently occur in the same individual. Abnormalities are also known to occur in nearly every anatomic subdivision of the eye in diabetic patients. Oculomotor palsy appears to be common in diabetes mellitus for their occurrence in isolation to suggest diabetes. Nerves to the external ocular muscles are most commonly affected, particularly the oculomotor or third cranial nerve. The third nerve palsy of diabetes is characteristic, being of sudden onset, accompanied by orbital and retro-orbital pain, often associated with complete involvement of the external ocular muscles innervated by the nerve. While the human and experimental animal literature is replete with studies on the peripheral nerves in diabetes mellitus, there is but a paucity of reported studies dealing with the oculomotor nerves and their associated extraocular muscles (EOMs).
CTEM and HVEM of Rat Liver After Dosing With MDL 18719, A Serum Lipid Lowering Agent
Authors: Barnard Stephen D. , Barnhart James W.
Published: June 2020

MDL-18719 which is (E)-3-[5-(1-oxododecyl)-2-furanyl]-2-propenoic acid has been shown to reduce serum cholesterol and triglycerides when administered orally to test animals. It is structurally related to RMI-14,514 a hypolipidemic drug reported to cause quantitative and qualitative alterations of hepatocellular peroxisomes (microbodies) when administered to rats.

Male Sprague-Dawley rats were treated for 13 days with 0.125% MDL-18719 in the diet then sacrificed. A portion of the liver from each animal was immersed in cold 0.15 M cacodylate-buffered 4% paraformaldehyde, 0.05% dinitrodifluorobenzene, 4% glutaraldehyde fixative solution. Tissue sections 50μ thick were prepared and treated in catalase localization medium. The specimens were osmicated, dehydrated in graded acetones and embedded in epoxy resin. Additional liver specimens from the same rats were prepared in a similar fashion omitting the enzyme localization step. Thin sections were prepared for conventional transmission EM (CTEM), and 0. 5. thick sections were cut for high voltage EM (HVEM).
Staining Serial Thick Sections For High-Voltage Electron Microscopy
Authors: Kinnamon John C. , Sherman Terri A.
Published: June 2020

Ultrastructural studies often require three-dimensional reconstructions from serial electron micrographs. The use of thick sections and high voltage electron microscopy can reduce the numbers of serial sections needed, but we have found that over 300 serial sections (0.5 μm thick) are still needed for our studies of taste bud ultrastructure. Serial reconstructions are almost always done with sections mounted onto formvar-coated slot grids, because they provide an unobscured view of the specimen. Staining and carbon coating several hundred formvar-coated slot grids often results in the loss of serial sections because the formvar films break due to handling during the staining and carbon-coating procedures. In addition, the staining process itself can be tedious and time-consuming when staining thick sections because staining times of hours are often required. Such lengthy staining times may result in staining artifacts due to exposure of the stain to the atmosphere, especially with lead stains.
Techniques For The Preparation of Tissue Samples Containing Injectable Polymer Microcapsules
Authors: Visscher G.E. , Robison R. L. , Argentieri G. J.
Published: June 2020

The use of various bioerodable polymers as drug delivery systems has gained considerable interest in recent years. Among some of the shapes used as delivery systems are films, rods and microcapsules. The work presented here will deal with the techniques we have utilized for the analysis of the tissue reaction to and actual biodegradation of injectable microcapsules. This work has utilized light microscopic (LM), transmission (TEM) and scanning (SEM) electron microscopic techniques. The design of our studies has utilized methodology that would; 1. best characterize the actual degradation process without artifacts introduced by fixation procedures and 2. allow for reproducible results.

In our studies, the gastrocnemius muscle of the rat was chosen as the injection site. Prior to the injection of microcapsules the skin above the sites was shaved and tattooed for later recognition and recovery. 1.0 cc syringes were loaded with the desired quantity of microcapsules and the vehicle (0.5% hydroxypropylmethycellulose) drawn up. The syringes were agitated to suspend the microcapsules in the injection vehicle.
Heavy Atom Cluster Labeling of Biological Specimens
Authors: Lipka J.J. , Hainfeld J.F. , Wall J.S.
Published: June 2020

The Brookhaven STEM is capable of resolving single heavy atoms deposited on thin carbon films with a beam dose > 103 el Å-2 Single heavy atoms, therefore, are unsuitable as fiducial markers on unordered biological specimens because of the high beam dose required for direct visualization. Heavy metal-clusters or heavy metal-containing complexes have been resolved at much lower beam doses, as low as 30 el Å-2, and therefore may be useful as directly visible labels.

The polyamine undecagold (11-Au) cluster ion, [(p-H2NCH2C6H4)3P]7 Au113+, has been used to covalently label the carbohydrate sites of the glycoprotein complex of human haptoglobin hemoglobin (Hp˙Hb) by a route which should be general for any glycoprotein with oxidizable carbohydrate residues. Proteins with reactive lysine residues have been covalently 11-Au labeled by the reactions noted in Scheme 1.
Computational Straightening of Images of Curved Macromolecular Helices by Cubic Spline Interpolation Facilitates Structural Analysis By Fourier Methods
Authors: Steven Alasdair C. , Stall Robert , Steinert Peter M. , Trus Benes L.
Published: June 2020

Powerful methods based on Fourier analysis have been devised for deducing the helical symmetries of macromolecular filaments and reconstructing their 3-dimensional density maps from electron images of negatively stained specimens. However, their applicability is restricted by the requirement that the particles be precisely straight. Only a limited number of specimens are sufficiently rigid to meet this constraint. Filamentous particles that exhibit varying degrees of flexibility constitute a much wider class of specimens, but their curvature impairs the coherence of their diffraction patterns. A solution to this problem is afforded by computational a posteriori straightening, effected by interpolating the digitized images on to a curvilinear coordinate system defined by the curve described by the particle axis. Here, we describe an algorithm for this purpose based on natural cubic spline interpolation, and illustrate its operation with model data and as applied to a flexuous biological specimen.
Alzheimer's Paired Helical Filaments Contain Insoluble Cytoskeletal Elements
Authors: Gambetti P. , Perry G. , Autillo-Gambetti L.
Published: June 2020

Neurofibrillary tangles (NFT) are one of the major pathologic lesions of Alzheimer's disease. These neuronal inclusions are predominantly composed of paired helical filaments (PHF), which consist of two 10 nm filaments winding around each other with an approximately 80 nm periodicity. Besides PHF, NFT comprise also 15 nm filaments, 10 nm filaments which are probably neurofilaments, microtubules and granular material. At variance with the neuronal cytoskeleton, PHF are insoluble in ionic detergent.

Studies at the light microscope level have shown that NFT have unique antigenic determinants as well as determinants in common with elements of the normal neuronal cytoskeleton such as neurofilaments and microtubule-associated proteins. The present study uses immunocytochemistry and cytochemistry at the electron microscope level to assess which NFT component contains these determinants and whether these antigenic determinants are soluble in an ionic detergent.