bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxide scales on yttrium-implanted Ni-Cr alloys
Authors: Yang C.H.
Published: June 2020

There has been much interest recently in the use of ion implantation for surface alloying as a method of improving corrosion resistance. Surface implanted yttrium improves the oxidation resistance of Ni-20%Cr alloys with regard to the more rapid development of a complete Cr2O3 scale and, especially, its adherence during thermal cycling. For the present investigation, both unimplanted and Y-implanted Ni-20%Cr (280 keV ions to a dose of 2 x 1016 ions/cm2) were obtained from Stott et al. (1) and were oxidized in air at 1000°C for 15 mins., with ∼ 10 μm thick oxide scale being formed on the alloy surface. Both parallel and transverse sections were examined on a Phillips EM 400T analytical electron microscope.
Preliminary results of fumarase structure determination by application of HVEM
Authors: Kramp Douglas C. , Valdivia Enrique
Published: June 2020

Glaeser and others have suggested that low-dose microscopy of thick, crystalline macromolecules might be more advantageously carried out at higher voltages. To investigate this, the HVEM has been constantly improved by redesign and modification of existing components in order to improve its reliability, stability, versatility, and ease of operation. This has been achieved by improvements in the camera, vacuum system, vibration reduction and installation of an image intensified TV camera with digital image memory; online PDP 11/23 computer for real time 2D FFT computations ; minimal exposure system ; digital fine control of focus, push button selection of five magnifications with independent control of C2; and design of a new cold stage for imaging of protein crystals. Further, a set of programs which provide for image analysis and processing, and synthesis of protein structures from electron micrographs of protein crystal arrays developed at Donner Laboratory, UC Berkeley, has now been implemented on a VAX 11/780 computer associated with the Astronony department at Madison.
Study of structural defects in zeolites by high-resolution electron microscopy and Fourier analysis methods
Authors: Domínguez J. M. , Acosta N. D. R.
Published: June 2020

For thin crystals and weak-phase objects, the phase grating approximation indicates that intensities are directly proportional to the projected lattice potencial VZ (x, y). Additionnally at the optimum focus condition, i. e. γ = π/2 (see ref. (2) for details) both electron diffraction and optical transform patterns are identical. Therefore, for very thin crystals, i.e. t < 102A, and several types of zeolites, including ZSM-5, Faujasites X, Y, erionites and A-type zeolites, the main assumptions of the phase grating approximation hold, making possible a complete study of structural features taking place at a nearly atomic scale. The method used to characterize the ultraestrncture of those zeolites are high resolution electron microscopy, Fourier analysis in the computer of the digitized micrographs and Laser optical diffractometry.
Microstructure of trona sorbents from fossil fuel plant full-scale dry injection tests
Authors: Greer R. T. , Zhang D. T.
Published: June 2020

The use of dry sorbents for the removal of SO2 from the flue gas of coal-fired power plants is of interest in reducing the complexity of SO2 removal and appears to offer economic incentives. In 1982, the Electric Power Research Institute, Public Service company of Colorado (PSCCO), and Multi-Mineral Corporation co-sponsored a full-scale demonstration of the dry injection process at the Cameo Station, Unit 1, of PSCCO near Grand Junction, Colorado.

Laboratory comparative studies of nahcolite (NaHCO3), trona and soda ash Na2CO3) with that exposed to gas streams of air or of SO2 at elevated temperatures have been reported to provide microstructural data (from SEM) for correlation with microchemical information and phase identification for possible reactions of these materials which may occur under conditions for injection of a dry sorbent at the utility plant, and which may bear on the effectiveness of SO2 reaction with sorbents.
Endocytosis and the lysosomal apparatus of rat Leydig cells
Authors: Lalli M.F. , Hermo L. , Clermont Y.
Published: June 2020

The Leydig cells of the rat testis which are involved in testosterone production contain an abundance of smooth endoplasmic reticulum and mitochondria (Figs. 2,6). These cells also possess many peroxisomes, lysosomes and multivesicular bodies (MVB's). On the cell surface, the plasma membrane contains numerous short microvilli, small invaginations and large plasmalemmal folds which appear to engulf extracellular fluid. There are also many large dilated vacuoles adjacent to the cell surface. The purpose of the present study is to determine if these cells show endocytic activity and to differentiate by various cytochemical means lysosomal elements from peroxisomes.

To identify lysosomes, tissue chopper sections of 2% glutaraldehyde-fixed testes (containing 2.5% dextran) were incubated in media containing thiamine monophosphate as a substrate (Lalli, 1983) to demonstrate the presence of acid phosphatase or in media containing P-nitrocatechol sulfate for the demonstration of arylsulfatase (Hopsu-Havu et al., 1967).
Variations in shape of corneal facets in wasp eyes: Correlative microscopy by SEM and replicas examined by LM (Hymenoptera: vespidae)
Authors: Lesseps Roland , Khalaf Kamel
Published: June 2020

The compound eye of wasps and of insects generally has an outer surface divided into corneal facets, each facet being the outer end of a visual unit, the ommatidium. Each facet is formed by the secretions of two epidermal cells. The shape of each facet is usually regarded by entomologists as being hexagonal. Recent studies, however, have found that although hexagonal shapes were indeed predominant in lepidopteran facets, pentagonal and heptagonal shapes were often present as well. The purposes of the present study were to determine the facet shape in representatives of another order of insects, Hymenoptera, and to correlate the LM visualizations of replicas with SEM observation.
Development of iron granules in honey bee oenocytes
Authors: Kuterbach Deborah A.
Published: June 2020

Foraging honey bees are believed to use the earth's magnetic field, among other cues, in order to home. It has been reported that the abdomen of the honey bee contains magnetite and iron particles have been localized within abdominal oenocytes. Light microscopic investigations reveal that morphologically detectable iron granules are present only in adult animals older than six days after eclosion (emergence from the comb). This is a report of an ultrastructural examination of the oenocytes during the development of the worker honey bee (Apis mellifera) with particular emphasis on the time of appearance, number, and size of iron granules within the cells.

Specimens of the different developmental stages were removed from brood comb, fixed in 2.5% glutaraldehyde in 5mM sodium cacodylate buffer pH 7.3, washed, and post-fixed with 1% osmium tetroxide. In order to preserve the lipid-rich material, rapid dehydration was accomplished by three changes of 50% acetone and two changes of 100% acetone before embedding in Polybed 812 epoxy resin.
High Voltage Scanning Electron Microscopy for Observing Magnetic Domains
Authors: Yamamoto T. , Tsuno K. , Nishizawa H.
Published: June 2020

Magnetic domain contrast in a SEM image of cubic ferromagnetic materials enhances with increasing accelerating voltage. It was shown that a high voltage SEM was effective for observing the domain structure in a very small saturation magnetization material. It is however known that the high voltage SEM observation is not so desirable because of increased electron diffusion. Thus further investigations are still needed. By utilizing a 200 kV SEM, JSEM-200, with the backscattered mode, we have found that the increased accelerating voltage results not only in the enhancement of magnetic contrast but also in a great reduction of topographical contrast caused by the surface projections as well as that of electron channeling contrast (see Figs. 1 and 2). Moreover we successfully observed the domain structures of a Goss-oriented 3% Si-Fe sheet whose surface was covered by an insulator (like glass) film of 4.5 μm in thickness (see Fig. 3). The domains were clearly observed at 200 kV but unobservable at 100 kV. These features are particularly useful for studying the domain structures in the practical materials.
Deformation Mechanisms of Aluminum at High Temperatures: in situ Straining Experiments in H.V.E.M.
Authors: Caillard D. , Muchin P. , Martin J. L.
Published: June 2020

Aluminium single crystals have been deformed on a straining holder between room temperature and 550° C in a H.V.E.M. Observations are recorded on still photographs or movies.

Evidence is shown of crosslip and dislocation climb.

1) The formation of dislocation subboundaries has been observed at high temperature and low stresses. The increase with time of dislocation density of each boundary is explained and the coalescence of low angle subboundaries into high angle ones, is described on the basis of our observations by a model involving dislocation climb, different from the one proposed formerly by Dunn and Hibbard.
Medium Energy Electron Study of Surface Structures Formed upon Oxidation of Copper
Authors: Landry J. D. , Højlund Nielsen P. E. , Hembree G. , Cowley J. M.
Published: June 2020

The oxidation of single crystal surfaces of copper with low oxygen pressure and high temperature have previously been examined by optical microscopy, microgravimetry, transmission electron microscopy and RHEED. These studies have revealed the formation of a hexagonal two-dimensional structure, followed by three dimensional nuclei of various regular shapes. In this study we have performed in situ oxidation in our REMEDIE system. The instrument was described at previous EMSA meetings. The instrument utilizes medium energy (1 to 15kV) electron diffraction, secondary electron imaging, and diffracted electron imaging (dark field imaging) in scanning mode. There is provision for specimen heating to 1000°C and ion beam cleaning in ultra high vacuum environment (2x10-9 Torr). The aim of this study was to examine the relationship between the 2-D and 3-D structures with the possibility of revealing transport of material on the surface.
Morphology of Charred, Flame-Retardant Cotton/Polyester Fabrics
Authors: Boylston E. K. , Muller L. L.
Published: June 2020

Microscopical examinations of charred substances are means of studying and interpreting the events of pyrolysis. How pyrolysis is retarded by certain finishes for textiles is of current interest. This paper describes the charring of cotton/polyester blended fabrics and interprets the sequential physical events that occur during pyrolysis. A cotton/polyester blend fabric treated with aqueous emulsions of tetrakis(hydroxymethyl)phosphonium chloride urea, trimethylolmethylglycoluril and poly(vinyl bromide) was the model for investigation. Charred surfaces from fabrics treated with other flameretardant agents have been described elsewhere.
Electron Energy Analysis of Germanium and Silica Layers on Silicon Substrates
Authors: Ditchfield R. W. , Cullis A. G.
Published: June 2020

An energy analyzing transmission electron microscope of the Möllenstedt type was used to measure the electron energy loss spectra given by various layer structures to a spatial resolution of 100Å. The technique is an important, method of microanalysis and has been used to identify secondary phases in alloys and impurity particles incorporated into epitaxial Si films.

Layers Formed by the Epitaxial Growth of Ge on Si Substrates Following studies of the epitaxial growth of Ge on (111) Si substrates by vacuum evaporation, it was important to investigate the possible mixing of these two elements in the grown layers. These layers consisted of separate growth centres which were often triangular and oriented in the same sense, as shown in Fig. 1.
Thickness Dependence in Secondary Electron Emission from Carbon
Authors: Voreades D.
Published: June 2020

Secondary electrons are used in making topographical pictures of specimens in the scanning electron microscope. A better understanding of the secondary emission process will contribute in improving the resolution in this mode of operation.

Recent experiments have indicated first that the escape depth of secondary electrons is a few atomic layers at the surface of the solid and second that the backscattered electrons are much more efficient in producing secondaries than the incoming ones. The results vary considerably. However, any model that one makes, for example similar to that of Jonker, consistent with these recent experimental results, will have the thickness as an important parameter.
An Application of Strongly Excited Objective Lens to Low Loss Image
Authors: Kokubo Y. , Ueno K. , Iwatsuki M. , Koike H.
Published: June 2020

In recent years, analytical methods for surface layers such as IMMA, Auger analysis, and ESCA have been developed and put to practical use with considerable results. The analyzable microarea on the specimen surface, however, is limited to 1 mmø with ESCA, 3 with IMMA and 0.5 μø with Auger analysis---all these values are considerably large as compared with 100 to 200Å areas which are presently analyzable on thin film specimens, by use of the energy dispersive X-ray spectrometer or the electron energy analyzer on the conventional electron microscope. These three methods involve more---problems the inability to provide information on diffraction patterns and the difficulty in obtaining any established quantitation method.
The Performance of a Thermal Field Emission Gun
Authors: Maher Dennis M. , Joy David C.
Published: June 2020

Although the "cold" field emission gun has been used successfully for both transmission and scanning electron microscopy it requires ultra-high vacuum which is not obtained easily when such a gun is interfaced to a conventional microscope system. Recently, the "thermal" field emission gun (TFEG) in which the emitting tip is held at around 1700°K has been proposed as an alternative electron source for such applications. Under this condition the tip is cleaned continuously, and surface asperities are smoothed, therefore stable operation is possible in a high vacuum. In this paper we report on the build-up characteristics, current stability and brightness of a TFEG which has been interfaced to a JEOL JEM 100B microscope equipped with a scanning attachment. The gun consists of a (111) tungsten emitter set on a rhenium filament, three anodes and a two stage magnetic alignment system. The gun chamber is ion pumped to a pressure in the range 6xl0-8 to 2xl0-9 torr.
Dynamical Scattering in Crystalline Biological Specimens. I. Criteria of Validity for Scattering Approximations
Authors: Glaeser Robert M. , Jap Bing K.
Published: June 2020

The dynamical scattering effect, which can be described as the failure of the first Born approximation, is perhaps the most important factor that has prevented the widespread use of electron diffraction intensities for crystallographic structure determination. It would seem to be quite certain that dynamical effects will also interfere with structure analysis based upon electron microscope image data, whenever the dynamical effect seriously perturbs the diffracted wave. While it is normally taken for granted that the dynamical effect must be taken into consideration in materials science applications of electron microscopy, very little attention has been given to this problem in the biological sciences.
Practical Resolution Enhancement in Bright Field Electron Microscopy by Computer Processing
Authors: Welton T. A.
Published: June 2020

The arguments and methods previously given have been converted into a full set of programs for the 360/91 or 360/195 computers. The input data is a tape (Photo-Scan or Boiler and Chivens) bearing optical density values (the image function , obtained by a scanning micro-densitometer. Program XFøRM obtains the Fourier transform of a selected data square (2M × 2M points, where M ≤ 11) and deposits the resulting on disk and/or tape. Program SPEC obtains the power spectrum of the data and deposits it on disk and/or tape. Program FILT analyzes by the methods of Refs. 1 and 2 to obtain the required approximation to the Wiener filter function , which is then deposited on disk and/or tape.
Methods for Implementing Computer Image Processing to Obtain Heavy—Light Atom Discrimination
Authors: Welles Kenneth
Published: June 2020

A linear theory and method of image reconstruction from a focal series of electron micrographs has been developed Successful processing by this method could give an enhancement of heavy atoms (e.g., U) over a Carbon background by a factor of 20-50X. Figures 1a-1c illustrate the processing of a series of five computer modeled micrographs. Figure lc shows the contrast enhancement of a Hg atom, over the carbon substrate. The practicality of this method, using computers to correct for the aberrant transfer functions, depends on several considerations. Correct relative orientation of the original images, accurately known optical parameters, and determining the limits set by non-linear effects such as substrate thickness (curvature of the Ewald sphere) are all essential for effective reconstruction of the complex image. The tolerance of. the process to these parameters have been examined using an analytical model and the allowable displacements and inaccuracies were obtained that still would provide for enhanced heavy-light atom discrimination.
The Importance of the Detector Angle in STEM Imaging of Crystals
Authors: Joy David C. , Maher Dennis M.
Published: June 2020

The image obtained in a scanning transmission electron microscope (STEM) is related to that obtained, under otherwise identical conditions, in the conventional transmission electron microscope (CTEM) by the principle of reciprocity. This principle is only applicable under rigorously defined mathematical conditions which are difficult to achieve in practice, nevertheless its general validity has been demonstrated experimentally for both amorphous and crystalline materials. The principle of reciprocity states, in part, that if equivalent beam cone angles are utilized then the STEM and CTEM images should be similar. Conversely, for a given set of electron-optical conditions in the STEM mode, the expected form of the images can be deduced from a knowledge of the CTEM image under reciprocally related conditions.
Simultaneous Study of Both the Surface and Interior Structure of Biological Specimens in a Scanning Electron Microscope
Authors: Lin P. S. D. , Crewe A. V.
Published: June 2020

In contrast to optical and transmission electron microscopes, which probe the interior, the scanning electron microscope usually only reveals the exterior structure of the specimen to the biologist. This is due both to the collection of secondary electrons as signal and to the practice of coating the specimen with various heavy, noble metals.

Taking advantage of their penetrating power, one can use backscattered electrons to study the interior structure of the biological specimen in a scanning electron microscope. Here a block of specimen is first stained by means similar to those practiced in transmission electron microscopy. Then a coating of carbon is applied to supress the undesirable specimen charge-up. Although the resolution in this mode will be degraded by electron-atom scattering events, this approach promises to yield more histochemical information than studying merely the topography of the specimen.
STEM Electron Diffraction from Areas less than 30Å; Application to Amorphous Films
Authors: Geiss R. H.
Published: June 2020

A technique of selective micro-area transmission electron diffraction has been developed using the Philips 301 TEM with a scanning (STEM) attachment. With this technique we are able to obtain electron diffraction patterns from selected areas less than 30 Å in diameter or about 103 atoms! This is to be compared with the best published results which show selected area diffraction (SAD) from areas at least 100 Å in diameter, approximately 105 atoms, or the conventional SAD techniques applicable to areas down to 2000 Å diameter, approximately 5 x 106 atoms. (The number of atoms was calculated assuming a 50 Å thick film of a f.c.c. structure with ao = 5 Å.) The selected micro-area capability was proven by experimentally obtaining discrete single crystal diffraction patterns from an array of evaporated gold particles some less than 30 Å diameter and separated by 30 Å or less, Fig. 1.
The Preparation of Tungsten Coil Filaments for Transmission Electron Microscopy
Authors: Koch Edward F.
Published: June 2020

The process of forming a lamp filament from 218 tungsten wire involves coiling the wire around a mandrel. The coil on the mandrel is then annealed at 1550 C to "set" the coil, that is, to keep it from uncoiling. As result of this process, the structure and properties of the wire in the coil are changed from what they were in the as-drawn condition. If lamp filament behavior is to be related to properties and structure of the wire, these must be determined for coiled wire and for coils which have been subjected to various flashing treatments. Preparation of thin foils from very small diameter coil wire becomes even more difficult since in addition to the restrictions on specimen diameter, the wires are very brittle as a result of annealing at temperatures high enough to cause polygonization. Thus, a technique of increasing the wire diameter by depositing tungsten on the coil was devised.
Replication of Water Droplets
Authors: Basu Samarendra , Parsons Donald F.
Published: June 2020

This report provides a test of the physical ability to replicate wet surfaces using a hydration chamber. By using water droplets as the test object, we have removed the uncertainties of testing the chamber technique using biological cells and tissues. The principle of operation of the hydration chamber and the physical aspects of the technique have been described in another report at this meeting. The SiO replicas are shadowed with Pt-C at 35°, stripped and then observed in a transmission electron microscope (TEM).

Two approaches have been made to prove that SiO replicas are formed on liquid water droplets. In the first one, the droplets have been condensed on a hydrophobic substrate by supersaturating the chamber with water vapor (Fig. 1(a)).
Characterization of Si Single Crystals by Conductivity Mode Scanning Electron Microscopy
Authors: Leamy H. J. , de Kock A. J. R. , Kimerling L. C. , Ferris S. D.
Published: June 2020

We have recently examined the microscopic electrical inhomogeneities present in dislocation free, floating zone, Si crystals grown under various conditions by conductivity mode scanning electron microscopy. Schottky barriers produced by evaporation of thin Au-Pd (on N type) or Ti (on P type) electrodes were employed in order to eliminate possible changes in defect structure or electrical activity during production of a diffused junction.

Doped and undoped crystals, as well as crystals subjected to special treatments, such as melt quenching were examined in this study. Prior to SEM analysis, each crystal was characterized by preferential etching, Cu or Li decoration, and x-ray topography. All of the defects detected by these methods, save C impurity striations detected via their dilatation of the Si lattice in x-ray topographs, were observed in the SEM experiments. For example, “swirl” defects of both type “A” (large) and type “B” (small) were readily revealed via the enhanced recombination rate of electron beam injected carriers in their vicinity (see Figs. 1 and 2).
Scanning Electron Microscope Facility for in situ Observations of Ion Implanted Surfaces
Authors: Thomas G. J. , Bauer W.
Published: June 2020

In previous studies of high dose He implantation of metals, observations of the resulting surface deformation were made after specific dose levels were attained. The present work describes a recently constructed system which allows scanning electron microscopy observation during implantation. A number of advantages can be gained by this approach. First, considerably more data can be obtained on a given sample so that, for example, the precise dose dependence of surface deformation can be determined. The technique also allows direct observation of deformation either above or below room temperature andin addition, quantitative information on the rates of blister formation and growth can be obtained. The rapidity with which surface features develop during implantation requires continuous and rapid storage of the sample image. Commercially available video recording equipment, with appropriate modification, has been used for this purpose.

In preliminary studies, a comparison has been made of surface deformation due to He implantation of a hydride (TiH2), annealed Ti metal, and cold worked Ti.
Gamma-Irradiation Induced Coarsening of the γ’ Precipitate in a Nickel-Aluminum Alloy
Authors: Allen C. W. , Fiore N. F.
Published: June 2020

Gamma-irradiation is known to produce significant damage in non-metallic materials, ranging from color centers in alkali halide crystals and the dissociation of sulfur in CdS to enhanced diffusion of solute in semiconductors. There is a growing body of evidence that changes also occur in metals where an effect is not expected on the usual theoretical bases. The evidence includes gamma-irradiation enhanced catalytic activity of silver accompanied by morphological changes of the catalyst particles and pronounced microstructural changes in several commercial aluminum alloys as well as high purity Al-Mg alloys. In the latter case, TEM studies showed that precipitates may be dissolved and reprecipitated during irradiation at room temperature. The mechanism for such changes is not understood. It is important to investigate the possibility of such damage in the types of alloy systems which may be called into service as components of future fusion reactors, the first wall of which will be exposed to intense gamma flux.
Dynamic Scanning Electron Microscopy of Small Particles
Authors: W. Krakow  , Nixon W. C.
Published: June 2020

The scanning electron microscope (SEM) can be run at television scanning rates and used with a video tape recorder to observe dynamic specimen changes. With a conventional tungsten source, a low noise TV image is obtained with a field of view sufficient to cover the area of the specimen to be recorded. Contrast and resolution considerations have been elucidated and many changing specimens have been studied at TV rates.

To extend the work on measuring the magnitude of charge and field distributions of small particles in the SEM, we have investigated their motion and electrostatic interaction at TV rates. Fig. 1 shows a time sequence of polystyrene spheres on a conducting grating surface inclined to the microscope axis. In (la) there are four particles present in the field of view, while in (lb) a fifth particle has moved into view.
What Improvement in Electron Microscopy and Electron Diffraction Results from Using Wet Biological Materials?
Authors: Parsons Donald F.
Published: June 2020

It is now possible to work with wet materials by using environmental chambers. Biologists would like to evaluate the advantages of this development. The unknowns are: (a) the difficulty of constructing the equipment and it's commercial availability, (b) the problems in preparing wet specimens and viewing them, (c) the resolution and contrast available (d) the difficulties peculiar to wet specimens and (e) the advantages of wet over frozen specimens. Finally, there remains the question - can living cells be examined? This talk will attempt to answer these questions. Routine wet electron microscopy has followed the introduction of differentially pumped chambers in place of film sealed chambers. Electron diffraction patterns of wet protein crystals (Fig. 1) provide a sensitive test of the performance of hydration chambers. If the vapor pressure drops more than 10% below saturation the pattern disappears due to the disorganization of drying.
Ultrastructure of Persisting Mitotic Nucleoli of Mung Beans
Authors: Braselton J. P.
Published: June 2020

Although nucleoli are generally believed to disperse during mitotic prophase, various groups of algae, fungi, and protozoans regularly possess persisting, in some cases “autonomous,” nucleoli during mitosis. Persisting nucleoli also occur in some higher plants and animals, but there have been only a few ultrastructural observations of such nucleoli. This study was initiated to better characterize cell divisions of a plant in which nucleoli regularly persist during mitosis.

Aceto-carmine squash preparations for staining nucleoli for light microscopy reveal that mung bean primary roots possess mitotic divisions in which over 90% of the metaphases exhibit nucleoli. One micrometer sections of plastic embedded tissue stained with aqueous methylene blue for light microscopy also show nucleoli at metaphase (Fig. 1). Light microscopic observations show that some metaphase nucleoli are roughly spherical and occur on or near the equatorial plate; some are elongated perpendicularly to the plane of the equatorial plate and extend toward one or the other, or both, pole(s); while others appear spherical and occur at either pole.
Electron Microprobe Analysis of Particles in the Insect Vector of Maize Streak
Authors: Kimura Michio , Seveus Lahja , Maramorosch Karl
Published: June 2020

Virus like particles in cells of maize streak diseased Zea mais L. plants have been described by Plavsic-Banjac and Maramorosch and by Sylvester et al. The observations suggested that maize streak disease is caused by a virus. During a follow up study in our laboratory, crystalline accumulations of electron dense particles were observed in the gut lumen and epithelial cells of Cicadulina mbila leafhoppers, confined to maize streak diseased plants, as is shown in Fig. 1. The crystalline accumulations consisted of numerous electron dense, spherical particles, approximately 9.5-10.5 nm in diameter. The particleswithin crystalline structures were oriented in a zigzag pattern with an angle of 120°. Although the particles resembled morphologically the presumptive maize streak virus, an electron microprobe analysis determined that they contained iron, as shown in Figs. 2 and 3.
Vasogenic Edema in the Injured Spinal Cord: Possible Role of Microtubules in Endothelial Vesicular Transport of HRP
Authors: Beggs John L. , Waggener John D. , Miller Wanda
Published: June 2020

The genesis of edema in the central nervous system (CNS) parallels changes in the blood-brain barrier (BBB). The anatomical seat of the BBB is located in the endothelium of the CNS. The presence of interendothelial tight junctions and the low rate of pinocytotic (vesicular) activity constitute the main features of the BBB. Based on the fate of intravascular horseradish peroxidase (HRP), mechanisms of edema genesis have been elucidated. A vesicular mechanism appears to play a role in the formation of edema in the injured (compression) spinal cord.

Following spinal cord compression injury (200 gm/cm2-5 min), circulating HRP traversed the endothelium and entered extracellular spaces of the cord parenchyma (Fig. 1). Most microvessels in the injured and adjacent areas exhibited an intensified endothelial vesicular uptake of HRP (Figs. 1, 3). In areas of intense endothelial vesicular activity, the frequency of microtubules (MT) appeared to be increased (Figs. 2, 3).
Acute Response of Cerebral Tissue Following Periods of Ischemic Insult
Authors: Dodson Ronald F. , Tagashira Yukio , Chu Lena W.F. , Scates Ronald W.
Published: June 2020

The complex pathophysiological and pathomorphological events which occur following a cerebrovascular accident (stroke) in man can be studied in animal models by the induction of temporary cerebral ischemia. One of the most consistently reproducible models involved the surgical occlusion of the middle cerebral artery (MCA) through a transorbital surgical technique.

Through this approach, the acute response of cerebral tissue was studied in squirrel monkeys following respective occlusive periods of either 15 min, 30 min, 1,2,3,4 or 24 hours.

At the conclusion of the occlusive interval, the surgical clip was removed from the right MCA and the animals were subjected to whole body perfusion with 500mls of 3% glutaraldehyde/0.1 M phosphate system. Tissue samples were dissected from the right (involved) and left (uninvolved) cortical areas (temporal, insular and parietal) and basal ganglia (putamen, caudate and globus pallidus).
Light and Electron Microscopic Findings after Acute Lung Injury
Authors: Trant M. , Jamison R. , Palmer D. , Light R. , George R.
Published: June 2020

The death of a previously healthy 14-year-old boy on the tenth day following accidental fresh-water drowning allowed us to study light and electron microscopic findings of adult respiratory distress syndrome (ARDS) in a previously healthy lung. The patient was treated initially for aspiration pneumonia with corticosteroids and antibiotics, and later received high concentrations of inspired oxygen during mechanical ventilation.

Autopsy permission was obtained at the time of death. Six percent gludaraldehyde in Clark's buffer containing methylene blue was injected into the right upper lobe within 20 minutes of cardiac arrest and an autopsy was performed approximately 3 hours later. Fixed tissues (marked with the blue dye) were removed, sectioned, washed briefly in Clark's buffer and post-fixed in 2 percent OsO4; in Clark's buffer for 2 hours. These were dehydrated in a graded ethanol series and embedded in Epon 812. Ultra thin sections were double-stained with lead citrate and uranyl acetate and examined using the Phillips Model 300 electron microscope.
Quantitation of Fluorophosphate - Reactive Esterase Sites in Rat Liver Using Electron Microscope Autoradiography
Authors: Budd G. C.
Published: June 2020

Following the application of 10-4 molar tritium labeled diisopropyl fluorophosphate (3H-DFP) to fresh or glutaraldehyde fixed rat liver, fluorophosphate-reactive (FPR) sites within the hepatocytes were measured using quantitative electron microscope autoradiography (EMARG). Based on the distribution of autoradiographic silver grains, most of the FPR sites were concentrated in the rough and smooth endoplasmic reticulum and associated ground cytoplasm. Cytoplasmic granules, comprising autophagic and residual granules also contained FPR sites. The average concentration of sites within each of these cytoplasmic structures was obtained from combined morphometric and grain density analyses of the EMARGs and light microscope sections of the same epoxy embedded liver specimens.
The Use of Transmission Electron Microscopy to Characterize Differentiated Rat Lung Cells Cultured in Vitro
Authors: Teel Robert W. , Douglas William H. J.
Published: June 2020

Pulmonary surfactant stabilizes alveolar volumes by lowering surface tension at the alveolar fluid-air interface. Its formation has been correlated with the presence of osmiophilic lamellar bodies in the cytoplasm of type II alveolar pneumonocytes. Inadequate surfactant production is considered responsible for respiratory distress syndrome or hyaline membrane disease in premature infants. Biochemical studies of the synthesis, storage, and secretion of surfactant are made difficult by the heterogeneity of cells in intact lung. This paper describes the use of transmission electron microscopy as a tool for the morphological characterization of type II pneumonocytes in an in vitro model system for studying synthesis, storage, and secretion of pulmonary surfactant.

Lungs from fetal rats at 19 days gestation are removed, minced, washed and then dissociated at 37°C in an enzymatic solution containing 0.1% trypsin, 0.1% collagenase and 1% chicken serum in calcium-magnesium-free saline.
Potassium-Osmium-Cyanide Complex (POCC) to Replace Osmium Tetroxide in Cytochemistry and Staining of Biological Membranes
Authors: Allen Shannon W. , Hoshino Yoshinobu , Seligman Arnold M.
Published: June 2020

Ferrocyanide-reduced osmium tetroxide has been introduced by de Bruyn and Kamovsky primarily as an ultrastructural stain and by Karnovsky secondarily as a possible method to increase contrast in existing cytochemical methods requiring conventional osmication. de Bruyn's staining medium consists of 1.65% potassium ferricyanide [K3Fe(CN)6] in 1% osmium tetroxide (OSO4) while Kamovsky's consists of 1.5% K3Fe(CN)6 in 1% osmium tetroxide. The staining complex has been proposed by de Bruyn (3) to be:

We report here our experience in comparing this staining medium with OSO4. Various rat tissues, e.g., adrenal, epididymus, heart, kidney, liver, prostate and testis were fixed in 3% glutaraldehyde-O.1 M phosphate (pH 7.4) and postfixed in potassium-osmium-cyanide complex (POCC) staining medium (1.5% K3Fe(CN)6 in 1% osmium tetroxide). In addition, liver and kidney were fixed in freshly de- polymerized 2% paraformaldehyde-0.1 M phosphate (pH 7.4) and postfixed in POCC.
Structure of Freeze Etched Reconstituted Liposomes Revealed in the Absence of Cryoprotectants
Authors: Ruben G.C. , Telford J.N.
Published: June 2020

Liposomes prepared from soybean asolectin and suspended in 250 mM sucrose are found in the sucrose eutectic after freeze etching. The membrane surfaces of these vesicles adjacent to the fracture faces cannot be revealed by etching the non-sublimable sucrose eutectic. Consequently, the freeze etched substructure of liposomes in sucrose are subject to ambiguous interpretation. In the absence of sucrose or other eutectic forming cryoprotectants, it should be possible to resolve the freeze fractured liposomal structure following a period of etching. A buffer, forming no eutectic upon freezing could accomplish this objective. Distilled water is not recommended as this would osmotically disrupt the liposomal membrane structure prior to freezing. The formation of buffer freezing eutectic structures are dependent upon the buffer used and its concentration. Tris-HCl at a concentration of 10 mM, pH 7.4, does not form a freezing eutectic.
Human Stapes Crura: Normal Ultrastructure. Scanning Electron Microscopic Findings
Authors: Graham M.D.
Published: June 2020

The recent development of the scanning electron microscope has added great impetus to the study of ultrastructural details of normal human ossicles. A thorough description of the ultrastructure of the human ossicles is required in order to determine changes associated with disease processes following medical or surgical treatment.

Human stapes crura were obtained at the time of surgery for clinical otosclerosis and from human cadaver material. The specimens to be examined by the scanning electron microscope were fixed immediately in the operating room in a cold phosphate buffered 2% gluteraldehyde solution, washed with Ringers, post fixed in cold 1% osmic acid and dehydrated in graded alcohol. Specimens were transferred from alcohol to a series of increasing concentrations of ethyl alcohol and amyl acetate. The tissue was then critical point dried, secured to aluminum stubs and coated with gold, approximately 150A thick on a rotating stage in a vacuum evaporator. The specimens were then studied with the Kent-Cambridge S4-10 Scanning Electron Microscope at an accelerating voltage of 20KV.
Electron Probe Analysis and Cryoultramicrotomy of Cardiac Muscle: Mitochondrial Granules
Authors: Somlyo Avril V. , Silcox J. , Somlyo A.P.
Published: June 2020

The contribution of mitochondria to the regulation of cytoplasmic calcium levels in the heart is an unsettled question. In certain pathological conditions, mitochondrial granules thought to contain calcium have been found in fixed myocardium.

Mouse ventricular myocardium, papillary muscle and trabeculae, unfixed and without cryoprotectants, were quick-frozen in Freon 22 cooled in liquid N2 or in liquid N2 slush. Sections were cut with glass knives at -100-120° C, placed on Cu or carbon coated nylon grids, and dried on a cold block at l0-2-10-5 Torr. Some sections were vapor stained with crystalline Os under vacuum, but the analyses reported are of unstained sections. Even 5 minute “pre-fixation” with glutaraldehyde, before cryoultramicrotomy, or staining of unfixed frozen thin sections with NH4 molybdate removed elements of interest (e.g.: K).

The morphological detail detectable by inherent contrast or Os vapor staining varied in different preparations and even in different regions of the same sections. In fortuitous examples (Fig. 1) the filament lattice could be clearly demonstrated.
Serial Reconstruction of Multiply Innervated Fibers in Mouse Extraocular Muscle
Authors: Pachter Bruce R. , Davidowitz Jacob , Breinin Goodwin M.
Published: June 2020

Extraocular muscle of many mammalian species has been shown to contain two categories of striated muscle fibers, differing from each other in terms of their neuromuscular junctions. One type of fiber is singly-innervated by elaborate end plates comparable to those of the skeletal musculature. The other fiber type is multiply-innervated by numerous small and relatively simple myoneural junctions. The organization of extraocular muscle remains to be clarified, both as to the number of distinguishable subpopulations of singly- and multiply-innervated fibers (MIF), as well as the topographical distribution of such respective fiber sub-populations within the muscle. In the present study, mouse superior rectus was initially examined by light microscopy in serial 15 micron Epon sections; in such sections neuromuscular junctions are detectable by phase contrast. Thick sections of interest were subsequently recut at 1 micron and ultrathin thicknesses for further detailed study. The ultrastructure of given fibers was thus sampled repeatedly along their length thereby providing an index of the variability of several morphologic criteria.
High Voltage Electron Microscopy of the T-System in Slow Fibers of the Frog Cruralis Muscle
Authors: Bailey Craig H. , Peachey Lee D.
Published: June 2020

Knowledge of the form, distribution, and quantity of transverse tubules (T-system) in frog skeletal muscle has been useful in understanding the inward spread of the electrical signal that triggers contraction.

Utilizing selective staining and high voltage electron stereoscopy, we have re-examined the T-system in frog slow fibers with the hope of extending the findings of earlier structural studies and of providing a more complete morphological foundation for correlation with physiological models.

The T-system of slow fibers was selectively stained by soaking distal fiber bundles of frog (Rana pipiens) cruralis muscles in horseradish peroxidase and incubating according to the method of Graham and Karnovsky. Transverse and longitudinal 1.0 μm thick slices were examined at an accelerating voltage of 1000 kV using the JEM-1000 microscope at Boulder, Colorado. Preliminary HVEM observations of cruralis muscle slow fibers have revealed an aplanar network of cylindrical tubules that follow a tortous pathway and exhibit a considerable longitudinally oriented component (Figure 1).
The Effect of Androgen Depletion and Replacement on the Epithelium of the Seminal Vesicle of the Aging Rat
Authors: Allison Venita F.
Published: June 2020

In 1930, Moore, Hughes and Gallager reported that after castration seminal vesicle epithelial cell atrophy occurred and that cell regeneration could be achieved with daily injections of testis extract. Electron microscopic studies have confirmed those observations and have shown that testosterone injections restore the epithelium of the seminal vesicle in adult castrated male rats. Studies concerned with the metabolism of androgens point out that dihydrotestosterone stimulates cell proliferation and that other metabolites of testosterone probably influence secretory function in certain target cells.

Although the influence of androgens on adult seminal vesicle epithelial cytology is well documented, little is known of the effect of androgen depletion and replacement on those cells in aging animals. The present study is concerned with the effect of castration and testosterone injection on the epithelium of the seminal vesicle of aging rats.
Fine Structure of Micromitochondria in Spermatozoa of the Mexican Axolotl, Ambystoma Mexicanum.
Authors: Keyhani E. , Lemanski L.F.
Published: June 2020

The differentiation of the male germ cells into mature spermatozoa is of particular interest to understanding the development and differentiation of organelles in eukaryotic cells. The extensive nucleo-cytoplasmic modifications leading to the formation of spermatozoa depend on the sequential activation of the genes, the production of adequate energy for transport and biosynthetic processes, and the maintenance of homeostasis within the cells. The assumption is that mitochondria play a key role in these processes and that the change in their structure preceeds cellular differentiation.

The characteristics of the mitochondria in the spermatozoa of the Ambystoma Mexicanum are that they are extremely small, exhibiting an unusual arrangement of their cristae, and their peculiar organization in mature spermatozoa which has been previously reported. The histogram of Fig. 1 shows the size distribution of the small mitochondria compared to the mitochondria from rat liver and mouse kidney.
A High Resolution Cytochemical Study of Nuclear ATPase in Human Spermatozoa
Authors: Sosa A. , Calzada L.
Published: June 2020

The dependence of nuclear metabolism on the function of the nuclear membrane is not well understood. Whether or not the function of the nuclear membrane is partial or totally responsible of the repressed template activity of human sperm nucleus has not at present been elucidated. One of the membrane-bound enzymatic activities which is concerned with the mechanisms whereby substances are thought to cross cell membranes is adenosintriphosphatase (ATPase). This prompted its characterization and distribution by high resolution photogrammetry on isolated human sperm nuclei. Isolated human spermatozoa nuclei were obtained as previously described. ATPase activity was demonstrated by the method of Wachstein and Meisel modified by Marchesi and Palade. ATPase activity was identified as dense and irregularly distributed granules confined to the internal leaflet of the nuclear membrane. Within the nucleus the appearance of the reaction product occurs as homogenous and dense precipitates in the interchromatin space.
Negative Staining of F-Actin in situ with Tannic Acid
Authors: LaFountain James R. , Thomas Herbert R.
Published: June 2020

Since the introduction of tannic acid as an additive in glutaraldehyde fixatives for electron microscopy, there have been numerous reports of ultrastructural findings that were not detectable after fixation without tannic acid. We have used tannic acid in studies on the spindle apparatus in insect spermatocytes to show that microtubules of the spindle are composed of 13 protofilaments. Tannic acid accumulates at the periphery of subunits of microtubules and with osmium stains those regions, leaving the subunits unstained. Hence, the subunits appear negatively stained.

We have found that in addition to microtubules, other filamentous structures in cells appear negatively stained after fixation with glutaraldehyde-tannic acid. The most noteable are actin filaments in muscle cells. We report here results obtained from mouse striated muscle.

Segments of gastrocnemius and vastus lateralis muscles are dissected in 3% glutaraldehyde in 0.1 M cacodylate buffer and subsequently fixed for 1 hr in the above fixative containing tannic acid (Mallinckrodt) in concentrations of 4 and 8%. Both concentrations gave similar results.