bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.
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.
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.
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.