bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of Proliferative Ileitis in Hamsters-Intestinal Amyloidosis
Authors: Jourden Martin G. , Kim James C. S. , Williams Christine S. F. 
Published: June 2020

Proliferative ileitis in hamsters is one of the unique diseases characterized by dehydration, diarrhea, and emaciation. It has been repeatedly found as a major obstacle by those making use of this species in long term research projects. Intensive light microscopic studies have already been conducted; cellular hyperplasia, along with goblet cell hypoplasia and inflammatory changes were observed. Even though non-specific viral agents and other bacterial organisms have been recovered, the overall etiology still remains unknown.Since ultrastructural studies of this problem had not been made, we have examined the ileum of two sick hamsters in hopes of elucidating the etiology and other accompanying ultrastructural changes. The control preparation was found to have numerous, tall microvilli of uniform height and size (Fig. 1). Cytoplasmic organelles, as well as the junctional complexes and desmosomes, were clear and distinct. Numerous mitochondria of various size and shape were found in the underlying region of the brush border (Fig. 2).
Biogenic Amine Identification by Analytical Electron Microscopy
Authors: Wood Joe G. , Harling David 
Published: June 2020

X-Ray microanalysis with the analytical electron microscope (AEM) can be a valuable tool in studying the nervous system. This instrument can identify heavy metal reaction products developed to localize specific biogenic amines (BAs). The reaction involves the formation of an isoquinoline derivative between the unsubstituted BA and glutaraldehyde. This isoquinoline reacts with a chromate salt and the Cr is incorporated into the reaction product.Tissues used in these studies were cat adrenal medulla and monkey median eminence. All tissues were fixed in 4% glutaraldehyde plus 1% sodium molybdate in 0.2 M sodium cacodylate buffer (pH 7.2) for two hours. Tissues were then incubated in a potassium dichromate preparation (pH 4.1) in the same cacodylate buffer. Following incubation, tissues were treated overnight in 4% paraformaldehyde in the cacodylate buffer. Subsequently, alternate blocks were treated with 1% osmium tetroxide. Thin sections were examined in the JEOL-100C Electron Microscope equipped with a goniometer stage, scanning attachment and a Kevex detector/multichannel analyzer system, utilizing a specimen-to-detector distance of less than 20mm.
Morphological Basis for the Photomechanical Response in the Photoreceptors of the Vertebrate Retina
Authors: Adomian Gerald E. , Sjöstrand Fritiof S. 
Published: June 2020

The photoreceptors In certain vertebrate retinas respond mechanically to light. This photomechanical response may Involve extensive changes In cell length. These changes are localized within the myoid region of the inner segment. The responses of rod and cone receptor cells to light are reciprocal. In darkness, the cone myoid Is extended, while that of the rod is shortened. In light, the situation is reversed. The machinery responsible for this intriguing phenomenon has not been elucidated. Therefore, the objective of the present study was to Investigate the morphological basis for myoid elongation and shortening.Retinas from a hybrid of Ictalurus melas and Ictalurus nebulosus were prepared for electron microscopy after varying degrees of light adaptation. Six maximally light adapted animals, four semi-adapted animals, and four maximally dark adapted animals were analyzed quantitatively.Myoids from the shortened receptor cells generally consisted of a supranuclear region which measured approximately four and seven microns In diameter and about nine and five microns in length, In rods and cones, respectively.
SEM of the Cecal Morphology in the Domestic Chicken
Authors: Witlock Dale R. 
Published: June 2020

McNab stated that the cecum may play a nutritional role when normal modes of digestion in the small intestine are impaired. Calhoun on the basis of light microscopic studies indicated that the cecal villi resemble those found in the small intestine. The scanning electron microscope (SEM), with increased resolution, depth of focus, and sampling power; which affords a three dimensional image was the ideal tool for reexamining the morphology of the cecal mucosa.Tissue was removed from four areas of the ceca of 8 White Leghorn cockerels 2 weeks old. Area A, the cecal neck region, Area B, the portion where the neck widens to form the pouch, Area C, the mid-cecal pouch region and Area D, 3-5 mm from the blind end of the ceca. This tissue was fixed (2% glutaraldehyde in 0.2M cacodylate-HCl, pH 7.4), ethanol dehydrated and critical point dried. Freeze fractured material was prepared by the methods of Humphreyset al. The dried specimens were mounted on stubs and coated with gold palladium.
Scanning Electron Microscopy of Endocardial Surface of Right Atrium in Mice
Authors: González-del-Pliego Margarita , Miguel Salazar  , Alfredo Ferra-Velasco  
Published: June 2020

The development of the scanning electron microscope (SEM) has added increasing knowledge to the structure of the various organs, giving us a new dimension to the study of their constituents. Although there are few studies on cardiac tissue using the SEM, these are mainly oriented to describe the myocardial cytoplasmic elements and the myocardial cell surface.Interested in our laboratory in cardiac microcirculation, one of the studies in progress is the openning of the arterioluminal and Thebesian vessels into the cardiac cavities. In the present communication we describe the endocardial surface of the right atrium in mice with particular emphasys on the foraminula of vessels openning into the atrium by using the scanning electron microscope.Right atria from mice were fixed immediately after death in 2.5% cacodylate buffered-glutaraldehyde, pH 7.4 for 3 hrs at 4°C and dehydrated in a graded series of acetone.
Low Temperature Beam Damage to Biological Specimens in the Electron Microscope
Authors: Ramamurti K. , Crewe A. V. , Isaacson M. S. 
Published: June 2020

It is now well recognized that serious limitations to resolution of details obtainable in biological specimens are imposed by the damage inflicted on the specimen by the electron beam. Several techniques, such as minimal exposure and signal averaging, have been proposed to overcome these limitations (see Ref. 1 for brief discussions and further references to literature). However, it would be clearly desirable to minimize the damage itself. A promising approach appears to be to cool the specimen to cryogenic temperatures.It should be emphasized that we do not expect any significant change in the primary damage rate of individual molecules, but we may hope that fragmentation would be reduced which would in turn, reduce the rate of mass loss, and secondary damages.Several studies with cooled specimens have been reported, but most of the results seem to be incluclusive and some of them even mutually contradictory.
Preparation of Frozen-Dried Tissue for Transmission Electron Microscopy: A Simple and Dependable Method
Authors: Terracio Louis , Coulter David 
Published: June 2020

An inexpensive and dependable method for freeze-drying biological tissue for transmission electron microscopy has been developed. Reproducible results can be attained if the following procedure is carefully followed.1) The primary components for the freeze-drier are shown assembled in figure 1. Preheat the 1000 ml pumping chamber containing 5 Å molecular sieve for at least 12 hours at 150° C. Connect the isolation valve to the chamber, close the valve, and stopper the flask with a #8 Neoprene stopper. Supporting the chamber with a ring stand clamp, place it in a Dewar filled with liquid nitrogen and allow it to equilibrate. Connect the drying chamber to the isolation valve and set it up in another Dewar without liquid nitrogen. Remove the #7 Neoprene stopper with its thermometer and specimen block and suspend it apart from the drying chamber with a ring stand clamp. The bulb of the thermometer is not tightly positioned in the specimen block at this time but is about ” above it.
Trimethyllead Acetate as a DNA Backbone Stain for Electron Microscopy
Authors: Kosiara A. , Douglass K. , Beer M. 
Published: June 2020

In the process of developing electron microscopic techniques for sequencing DNA it has become clear that in addition to selective heavy metal labeling of the bases it will be necessary to label the phosphate backbone as well. We have studied the suitability of trimethyllead acetate as a backbone label for high resolution electron microscopy of DNA.The binding of the trimethyllead ion to acetate was studied by acid-base titration and DC conductivity, while the binding to DNA was determined by equilibrium dialysis. Most measurements were done in solutions of low ionic strength, approximating the conditions for staining reactions.Defining the equilibrium constants,and choosing Kaand Kbto fit the titration curve we obtain the experimental values given in Table I.The conductivity of PbMe3Ac was measured in water and in 50%, dioxane. The data were analyzed according to the method of Fuoss and the results are given in Table I.
Depletion and Reconstitution of Active E. Coli Ribosomes
Authors: Boublik M. , Hellmann W. , Jenkins F. 
Published: June 2020

Correlations between structure and function of biological macromolecules have been studied intensively for many years, mostly by indirect methods. High resolution electron microscopy is a unique tool which can provide such information directly by comparing the conformation of biopolymers in their biologically active and inactive state. We have correlated the structure and function of ribosomes, ribonucleoprotein particles which are the site of protein biosynthesis. 70S E. coli ribosomes, used in this experiment, are composed of two subunits - large (50S) and small (30S). The large subunit consists of 34 proteins and two different ribonucleic acid molecules. The small subunit contains 21 proteins and one RNA molecule. All proteins (with the exception of L7 and L12) are present in one copy per ribosome.This study deals with the changes in the fine structure of E. coli ribosomes depleted of proteins L7 and L12. These proteins are unique in many aspects.
Fundamental Studies of Bacterial Leaching Using Bio-Physical Techniques of Transmission Electron Microscopy
Authors: Berry V.K. , Murr L.E. 
Published: June 2020

The role of microorganisms and their reaction with minerals are comparatively newer research areas in the general area of chemical mining, and have considerable scope of further development. The most commonly studied reactions of this type have been associated with microorganisms characterized as Thiobacillus thio-oxidans and Thiobacillus ferroxidans. These microorganisms have the ability to oxidize heavy metal sulfides and elemental sulfur to water soluble sulfates; and ferrous iron to ferric iron.The attachment location of biological microorganisms on minerals has not been reported in the literature as it relates specifically to biogenic metallurgical processes, although an attempt to describe the mode and character of bacterial attachment has been made by some workers. In the current investigation, a thermophillic microbe previously described by Brierley and Brierley and suggested to have a relationship with Sulfolobus was used. This microorganism exhibits an intracellular retractile body un-like Sulfolobus.
Studies on the Pellicular Complex of the Exocrythrocytic Merozoites of the Avian Malarial Parasite (Plasmodium lophurae)
Authors: Meszoely C. A. M. , Beaudoin R. L. , Erbe E. F. , Steere R. L. 
Published: June 2020

Plasmodium lophurae grown in monolayers of cells derived from turkey brains was freeze-fractured after fixation in 1.25% gluteraldehyde. The fixed material was placed in an ascending series of glycerol buffer until a 40% concentration was reached. This preparation was then frozen and fractured at -190°C under vacuum. Both fracture surfaces of the specimen were simultaneously shadowed and carbon coated to obtain complementary replicas. The replicas were studied with the JEM 100-B transmission electron microscope.Previous studies on stained ultrathin sections of the merozoites of mature schizonts show the merozoite to be surrounded by two membranes and an innermost microtubular system. In addition to this pellicular system of the merozoites, the entire schizont is surrounded by a loose limiting membrane. Our studies revealed splitting of the two membranes enclosing the exoerythrocytic merozoite. This resulted in the presence of four fracture faces, each with its own distinct topography.
Mass Loss of Biological Molecules in the Electron Microscope
Authors: Isaacson M. , Langmore J. , Lamvik M. , Lin P. , Golladay S. , Hainfeld J. , Pullman J. , Furlong D. 
Published: June 2020

Although present-day electron microscopes can resolve single atoms, resolution of biological specimens has usually been limited to 20 Å in large part by beam-induced specimen damage. Use of the STEM, which is potentially superior to the CTEM in both contrast and specimen radiation dose necessary to form an image, and development of new specimen preparation techniques may increase resolution somewhat, but the fundamental limitation of radiation damage will still remain. Therefore we have undertaken a study of the modes of radiation damage in electron microscopy with the hope that a better understanding of these processes may aid development of techniques to reduce their effect.We present here direct measurements of the decrease of the elastic and inelastic cross sections due to electron irradiation in the STEM. These measurements cover a wide range in dose rate from less than 10-4 amps/cm2 to 300, encompassing those dose rates found in conventional as well as high resolution scanning microscopy.
Annulate Lamellae in Hindgut Epithelial Cells of Isopoda
Authors: Herold Laura , Goggins J.A. , Witkus E. R. , Vernon G. M. 
Published: June 2020

In an ultra structural study of the digestive tract of the aquatic isopod, Asellus communis, and the terrestrial isopod, Armadillidium vulgare, annulate lamellae were observed in the large epithelial cells of the anterior hindgut. The isopod digestive tract consists of two pairs of hepatopancreatic lobes and a straight tube foregut and hindgut. The foregut extends from the mouth to the area of insertion of the hepatopancreas. The hindgut extends from this area of insertion to the anus.The annulate lamellae consist of a stack of parallelly arranged membranes in the cytoplasm. In A. communis there is defonite continuity between the ends of two adjacent lamellae in the stack (Fig. 1). The number of cisternae comprising the organelle is much greater in A. vulgare than in A. communis. The pores or annulae are also much more numerous in A. vulgare (Fig. 2) than in A. communis.
Microstructural Evolution During Solidification of Al-Fe-Ce Powders
Authors: Chu M. G. , Rioja R. J. , Hildeman G. J. , Denzer D. K. 
Published: June 2020

Al-Fe-Ce alloys produced from gas atomized powders exhibit greater strength at 150°-315°C than conventional aluminum alloys. This higher strength can be attributed to small dispersoids that form during the rapid solidification and precipitates that form after solidification and during consolidation. Understanding the powder microstructure is essential to establishing the relationship between wrought product microstructures and properties. Microstructures present in Al-8 wt% Fe-4 wt% Ce and Al-7 wt% Fe-6 wt% Ce powders (-325 mesh) are presented; in addition, a solidification sequence for atomized droplets is proposed.Analyses include: SEM, TEM, and Chemical Analyses from thin foils via EDXS. Powder samples were compacted into wafers at 200 ksi and subsequently electropolished via the window technique.
The Deflection of Electron Reams Traversing A Crystal Face
Authors: Cowley J.M. , Kang Z.L. 
Published: June 2020

A serious discrepancy exists between the experimental and theoretical results on the deflection of an electron beam passing parallel to, and just outside, the flat face of a crystal. In a previous paper we reported that for a beam of diameter about 15Å traversing the face of a small gold crystal within a distance of 20Å or less, the central spot of the diffraction pattern is seen to be displaced through angles of up to 10-2 radians. Similar observations had been made for MgO crystals. Rough agreement with the observations could be obtained by assuming the beam to be deflected by a potential field extending into the vacuum and having the formwhere ϕo is the inner potential of the crystal and A, B and C are positive constants. This model for the potential field is based on the assumption of an image force modified for small x by a second order term.
A New Method For Calibrating Focusing Steps Of Electron Microscopes
Authors: Hsu Tung 
Published: June 2020

Focusing steps of an electron microscope, i.e., the change of focus, Δf, corresponding to one click on any one of the focus dials must be calibrated. Two methods have been used; measuring the distance between bright field and dark field images of small crystalline particles and measuring the diameters of optical diffractograms obtained from the image of an amorphous specimen.A new method utilizing the large depth of field in reflection electron microscopy (REM) provides a direct means of measuring the focusing steps on the micrograph. The in focus area in an REM image can be recognized as the “least grainy” part or the minimum contrast of images of steps. Using surface steps, particles, or other features as References, the shift of this in focus position due to the variation of objective lens current can be readily measured on the micrograph. This distance is then converted to f by taking account of magnification (calibrated) and the foreshortening factor (calculated from the diffraction pattern).
A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures
Authors: Burke M.G. , Miller M.K. 
Published: June 2020

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.
Evaluation of Concentration Techniques For Small Populations of Gunshot Residue (GSR) Particles Using Calibrated GSR Suspensions
Authors: Zeichner A. , Foner H. A. , Dvorachek M. 
Published: June 2020

It is generally accepted that the best method for the identification of GSR is by scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX), a technique which utilizes not only the chemical composition of the particles but also their size and morphology. Nevertheless, there remain many problems in the effective use of this technique.The main problem is the length of time required to conduct a comprehensive search for GSR in the samples as presented to the SEM. Attempts to solve this problem have been made in two main directions: (1) Concentration of the GSR after sampling onto a small area concomittant with some sort of treatment to remove extraneous interfering matter, and (2) computer-aided mechanization of the searching procedure. The latter approach is still in its very early experimental stages, whilst the methods used in the second approach are in need of further improvement. In particular, there has been no quantitative work on the efficiency of various concentration processes when using very small populations of GSR.
Some Advantages of a 400-Kv High Resolution Analytical Electron Microscopy
Authors: Bando Y. , Matsui Y. , Kitami Y. , Inomata Y. , Oikawa T. , Suzuki S. , Honda T. , Harada Y. 
Published: June 2020

There are some fundamental limitations in the use of the conventional analytical electron microscope (AEM), which restricts notably observation capabilities of high resolution imaging and microanalysis, mainly due to its poor image resolution and low peak to background ratio in EDS and EELS spectra, because operating voltages are lower in the range of 100 to 200 kV. It can be expected that such observation capabilities are very much improved with the increase of the accelerating voltage. From the point of view, a new JEM-4000EX AEM with an intermediate voltage of 400 kV is much prefered. The present paper describes some advantages of the 400 kV high resolution AEM in the use of both high resolution observation and microanalysis in EDS and EELS.Fig.1 shows a phase contrast transfer function (CTF) curve, obtained for the JEM-4000EX with full analytical systems, in which a side entry specimen holder of beryllium stage with tilting angles of 30° in X-Y double axes is used. The EDS detector with a high angle location of 68, an energy analyzer (ASEA40) and a scanning image device (ASID40) are attached to the column.
Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02
Authors: Koo J. Y. , Anderson M. P. 
Published: June 2020

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.
The Microstructure of Steatite (Protoenstatite)
Authors: Lee W. E. , Heuer A. H. 
Published: June 2020

IntroductionTraditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.Experimental3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.