bluuebunny/crossref_metadata_2025 huggingface dataset:
pH dependent gastrin secretion mechanism: an immunocytochemical study
Authors: Galán Torres J.A. , LLorca Gallego A. , González Santander R. , Toledo Lobo M.V. , Martínez Alonso F.J. , Martínez Cuadrado G.
Published: June 2020

Gastrin secretion is induced by vagal stimuli, local distension, peptides or aminoacid solutions, and Ca2+ concentration both in stomach lumen and blood. However, the cellular and molecular mechanisms of gastrin-release are unknown. We have tested the effects of different pH fixative solutions on gastrin distribution by the immunolabeling of antral gastrin cells (G cells).

Samples from different portions of adult dog digestive tract and related glands (salivary glands, liver and pancreas) were embedded in paraffin by conventional methods. Another samples from the antral mucosa of adult dogs and rats were fixed using mixtures of glutaraldehyde and paraformaldehyde at different pH (from 4 to 7,6 pH), and embedded in araldite and Unicryl. For post-embedding immnunocytochemical staining purposes, sections were incubated with pre - diluted policlonal rabbit anti-human gastrin (Zimed Labs.Inc., San Francisco, USA), rinsed in TBS and incubated with a 15 nm gold-conjugated IgG as secondary antibody. These sections were stained with uranil acetate and examined with TEM.
Immunogold localization of β1 integrin in mature avian smooth muscle
Authors: Stromer M.
Published: June 2020

Integrins are α β heterodimeric transmembrane glycoproteins. The extracellular aminoterminal portion of the dimer contains the ligand-binding region and provides a linkage to the extracellular matrix and to other cells. The relatively smaller cytoplasmic carboxyterminal region interacts with the cytoskeleton and specifically interacts with α-actinin and with talin. Integrins are, thus, thought to be involved in signal transduction at the surface of many cell types. Smooth muscle cells contain α1β1integrin which has been immunolocalized in fibroblast focal contacts. Because aα-actinin and talin are components of attachment plaques which are sometimes referred to as plasma membrane-bound dense bodies in smooth muscle, we used immunogold labeling and transmission electron microscopy (TEM) to determine the location of β1integrin at the smooth muscle cell surface.

Strips of smooth muscle from mature chicken gizzards were isometrically clamped and were fixed in 2% paraformaldehyde in modified Krebs Ringer that contained 2mM Ca2+and 2mM Mg2+for 2½ hrs. at 2° C. Fixed strips were cut into 0.5-0.8mm cubes that were immersed in 0.15 M glycine for 1 hr.
Tris-HCL buffer pH 9.5 mixed with 5% urea used for antigen retrieval immunohistochemistry
Authors: Shi S-R. , Cote R.J. , Young L. , Imam S.A. , Taylor C.R.
Published: June 2020

The antigen retrieval (AR) method plays an important role in the high temperature heating AR immunohistochemistry (IHC). It has been demonstrated that the temperature, heating time and pH value of the AR solution are critical factors in determining the effectiveness of AR-IHC(1,2). For example, the intensity of AR-IHC staining of certain antibodies varies greatly according to the pH value of AR solution (2). Although the original discussed metal solution gave good results of AR-IHC (3,4), the potential for toxicity caused concern. A variety of other AR solutions have been tested as possible replacements for the metal solution, in the hope of obtaining better AR-IHC staining results without toxic side effects. Reports include the use of citrate buffer pH 6, urea, and a commercial ‘TUP’ solution. Currently, citrate buffer pH 6 is the most commonly used AR solution. We have posed the question as to whether this is the optimal AR solution for most antibodies used in surgical pathology.
Immunogold labeling of the bacterial surface components of shigella flexneri 2a
Authors: Chen D.H. , Wang G.H. , Zhang H.Q. , Li H.
Published: June 2020

Some bacterial outer membrane components are efficient protective antigens against Shigella spp. Electron microscopic immunogold labeling provides a possibility for investigating the surface exposure of antigens (1). The aim of the present study was to localise surface antigens of Shigella flexneri 2a by using an electron microscopic immunogold labeling technique.

Seven monoclonal antibodies (MAbs: 2A3, 3A6,2E6,1G8,1Al and 4F1) used in this study were produced as described previously (2). Pure cultures of Shigella flaxneri 2a were grown in broth, harvested by centrifugation, prefixed and then immunolabelled by MAbs and anti-mouse IgG conjugated to colloidal gold particles (GAMG15 and GAMG5) respectively. Ultrathin sections of labelled bacteial cells were cut and viewed in a transmission electron microscope (Philips EM 400T).

Electron microscopic examination of the sectioned organisms showed that gold labeling was confined to the outer surface of the bacterial cell wall. Binding of the MAb on whole bacterial cell indicated the antigens recognized by MAbs 3A6, 2E6, 4F1 and 2A3 were exposed on the outer surface of cell membrane (Fig 1, a-c), and those by MAbs 1A1 and 1G8 were not.
Cytochemical localization of calcium in myoblasts of the chick embryo myotome
Authors: González Santander R. , Toledo Lobo M.V. , Martínez Alonso F.J. , Martínez Cuadrado G. , Gánzalez-Santander Martinez M. , Monteagudo M.
Published: June 2020

Muscle fibers are derived from multinucleated myotubes which are themselves formed during embryonic development by the fusion of mononucleated myoblasts. Myoblast fusion results from a sequence of different and highly orchestrated stages demonstrated previously in vitro: recognitionalignment, adhesion and membrane fusion. Like many other fusion systems, myoblast fusion is Ca2+- dependent. The role of Ca2+is multiple since it is needed for muscle cell differentiation, for the alignment stage and it has also been demonstrated that Ca2+influx precedes fusion increasing free intracellular Ca2+. It has been proposed that this increase in free intracellular Ca2+may activate an enzimatic cascade which leads to membrane fusion.

The present study, using the K-pyroantimonate method, describes Ca2+localization and storage in myoblasts before fusion for the first time, since this method had not been applied to skeletal muscle development studies before. Chick embryos from 51 to 108 h. of incubation (Hamburger and Hamilton stages 16 to 25) were used.
A comparison of the Three-Dimensional structures of Z bands in unstimulated and rigor skeletal muscle
Authors: Schroeter J.P. , Edwards R.J. , Goldstein M.A.
Published: June 2020

Previous studies (reviewed in ref. 1) lead to the expectation that Z bands from unstimulated skeletal muscle exhibit the unactivated small square form of the Z band lattice. Rigor Z bands, on the other hand are expected to exhibit the basket-weave form of the Z band lattice associated with activation in skeletal muscle. This Z band structural transition has been investigated by three-dimensional reconstruction of Z bands and nearby I bands in unstimulated and rigor rat soleus muscle. The reconstructions were calculated using the tomographic method of weighted back-projection on a series of electron micrographs of longitudinal thin sections of muscle.

Examination of Z band cross-sections of the reconstructions reveals that the unstimulated muscle does indeed exhibit the expected small square lattice form. Furthermore, Z band cross sections of the rigor reconstructions reveal the expected basket-weave lattice form. The lattice dimensions were 20 +- 1 nra for the small square lattice and 27 +- 4 nm for the basket-weave lattice, consistent with the results from electron micrographs of cross-sections.
Cryoelectron microscopy and image reconstruction of spherical viruses with spot scan and FEG technologies
Authors: Olson N. H. , Lücken U. , Walker S. B. , Otten M. T. , Baker T. S.
Published: June 2020

The field emission gun electron microscope (FEG) is a tool that has the potential to achieve near atomic resolution information of biological macromolecules. The FEG provides a beam with higher spatial and temporal coherence and a better phase contrast transfer function than do microscopes with either tungsten or LaB6 filaments. The FEG is also ideal for spot scan imaging applications because it can produce a small, coherent and very bright spot. In spot scan mode the specimen is exposed to an array of nonoverlapping spots rather man a flood beam. This significantly reduces beam-induced specimen drift.

Frozen-hydrated samples of cowpea chlorotic mottle (CCMV, Fig. 1A) and cowpea severe mosaic virus (CPSMV, Fig. IB) were examined on a Philips CM12 transmission electron microscope equipped with a standard LaB6 gun and on a Philips CM200 equipped with a field emission gun, respectively. The CM12 was operated at 120kV and was externally controlled by means of a spot scan imaging program which produced a series of 250 nm diameter spots on Kodak SO-163 sheet film.
Computer processing of high-resolution images of periodic specimens
Authors: Chiu W. , Schmid M.F. , Jeng T.-W.
Published: June 2020

Cryo-electron microscopy has been developed to the point where one can image thin protein crystals to 3.5 Å resolution. In our study of the crotoxin complex crystal, we can confirm this structural resolution from optical diffractograms of the low dose images. To retrieve high resolution phases from images, we have to include as many unit cells as possible in order to detect the weak signals in the Fourier transforms of the image. Hayward and Stroud proposed to superimpose multiple image areas by combining phase probability distribution functions for each reflection. The reliability of their phase determination was evaluated in terms of a crystallographic “figure of merit”. Grant and co-workers used a different procedure to enhance the signals from multiple image areas by vector summation of the complex structure factors in reciprocal space.
Serial sections and stereoscopy-complementary approaches to three-dimensional reconstruction
Authors: Russ John C. , Hare Thomas M.
Published: June 2020

Modelling of three-dimensional structures, either for purposes of geometrical measurement (eg. volume, surface area) or as an aid to visualization, has traditionally been carried out by a variety of different methods. Biologists, who are usually able to conveniently cut sections through their specimens, often make use of serial sections for this purpose. The most common interpretation of serial section photos has been by printing micrographs on transparent material, aligning them, and stacking them up. Occasionally, physical models of lucite, wood, clay or styrofoam have been constructed using the prints as templates, and with the advent of modern computer equipment, some digitization of the sections and their subsequent viewing or plotting with any viewpoint and orientation has enabled researchers to better see the structures represented. There has even been limited use of stereoscopy, that is, producing plots or on-screen color images of the feature outlines from two different viewpoints which can be visually merged to produce the illusion of relief.
3D reconstruction of the 50s ribosomal subunit of escherichia coli
Authors: Radermacher M. , Wagenknecht T. , Verschoor A. , Frank J.
Published: June 2020

The three-dimensional (3D) structure of the large ribosomal subunit from E. coli was determined from micrographs of a negatively stained 50S particle preparation using our new reconstruction scheme. The 50S subunit occurs in electron microscopical preparations mainly in the crown-view orientation with the interface side of the main body situated parallel to the specimen plane, but in random in plane orientations. An image of such a specimen tilted by a large tilt angle, which inherently contains a conical tilt series of the particle, was used to calculate a 3D reconstruction.
Facts and artifacts in colloidal gold postembedding cytochemistry
Authors: Rendayan Moise
Published: June 2020

The colloidal gold marker was introduced in immunocytochemistry by Faulk and Taylor, in 1971, for the ultrastructural localization of surface antigens. Since then, application of this marker in light and electron microscopy has been growing rapidly. In particular, it has been applied for postembedding labeling of intracellular binding sites and its use has been extended to the various fields of cytochemistry: immunocytochemistry (protein A-gold), IgG-gold), enzyme-cytochemistry and lectincytochemistry. Several reviews have been recently published on colloidal gold labeling techniques and we refer to them for extensive characterization of this marker and its various applications.
Membrane lipid biogenesis and transport
Authors: Dawidowicz E.A.
Published: June 2020

Membrane biogenesis is an essential feature of cellular development and growth. The initial assembly of membrane lipids and proteins occurs primarily in the endoplasmic reticulum (ER). It has been demonstrated that the enzymes involved in the de novo biosynthesis of phospholipids are exclusively located on the cytoplasmic surface of the ER. A rapid transbilayer movement of phospholipids has also been reported in isolated liver microsomes, which is compatible with the movement of newly synthesized lipids to the lumenal surface of the ER. Comparison with the transbilayer movement of phospholipids across protein-free lipid bilayers, has lead to the proposal that a protein which would catalyze the translocation of phospholipids across the ER membrane (“flipase”), might be involved in the assembly of the lipid bilayer of the ER. Since the various membranes in a eukaryotic cell differ markedly in their lipid composition, it is clear that specific sorting and transport of these membrane components must occur.
Tandem scanning reflected light microscopy: How it works and applications
Authors: Boyde Alan , Hadravský Milan , Petran Mojmír , Watson Timothy F. , Jones Sheila J. , Martin Lawrence B. , Reid Stephen A.
Published: June 2020

The principles of tandem scanning reflected light microscopy and the design of recent instruments are fully described elsewhere and here only briefly. The illuminating light is intercepted by a rotating aperture disc which lies in the intermediate focal plane of a standard LM objective. This device provides an array of separate scanning beams which light up corresponding patches in the plane of focus more intensely than out of focus layers. Reflected light from these patches is imaged on to a matching array of apertures on the opposite side of the same aperture disc and which are scanning in the focal plane of the eyepiece. An arrangement of mirrors converts the central symmetry of the disc into congruency, so that the array of apertures which chop the illuminating beam is identical with the array on the observation side. Thus both illumination and “detection” are scanned in tandem, giving rise to the name Tandem Scanning Microscope (TSM). The apertures are arranged on Archimedean spirals: each opposed pair scans a single line in the image.
The use of an energy-filtering electron microscope to reduce chromatic aberration in images of thick biological specimens
Authors: Peachey L. D. , Heath J. P. , Lamprecht G.
Published: June 2020

Biological specimens of cells and tissues generally are considerably thicker than ideal for high resolution transmission electron microscopy. Actual image resolution achieved is limited by chromatic aberration in the image forming electron lenses combined with significant energy loss in the electron beam due to inelastic scattering in the specimen. Increased accelerating voltages (HVEM, IVEM) have been used to reduce the adverse effects of chromatic aberration by decreasing the electron scattering cross-section of the elements in the specimen and by increasing the incident electron energy.
Electron probe x-ray microanalysis and electron microscopy of amino acid absorption and transport by the small intestine: inhibition by chemical poisons and correlation to the elemental composition of the epithelial cells
Authors: Tousimis A. J.
Published: June 2020

The elemental composition of amino acids is similar to that of the major structural components of the epithelial cells of the small intestine and other tissues. Therefore, their subcellular localization and concentration measurements are not possible by x-ray microanalysis. Radioactive isotope labeling: I131-tyrosine, Se75-methionine and S35-methionine have been successfully employed in numerous absorption and transport studies. The latter two have been utilized both in vitro and vivo, with similar results in the hamster and human small intestine. Non-radioactive Selenomethionine, since its absorption/transport behavior is assumed to be the same as that of Se75- methionine and S75-methionine could serve as a compound tracer for this amino acid.
Quick freeze-deep etch analysis of microfilaments in the circumferential bundle of retinal pigmented epithelial cells M vitro
Authors: Kodama Ryuji , Eguchi Goro , Kelley Robert O.
Published: June 2020

Pigmented epithelial cells from embryonic chick retina can transdifferentiate in vitro to express either pigmented (RPE) or lens cell (LC) phenotypes in response to alterations in the external culture environment. These observations suggest that the dedifferentiated phenotype of RPE cells is, at least, bipotential and that expression of either of two differentiated phenotypes is mediated by the cell surface and the associated cytoskeleton.
3-D structure analysis of PhoE porin
Authors: Jap Bing K.
Published: June 2020

The outer membrane of Escherichia coli contains a variety of pore-forming proteins called porins. These proteins have similar molecular weight and amino acid composition, but have substantially different chemical specificities for restricting free diffusion of aqueous solutes. One porin, called PhoE, is preferentially expressed under growth conditions involving phosphate starvation. PhoE porin serves not only as a nonspecific channel for small solutes, but also facilitates the diffusion of phosphate containing solutes as well as other negatively charged compounds.
Edge-projection tomography
Authors: Panitz J. A.
Published: June 2020

A biological structure can be reconstructed in three dimensions from a series of transmission electron microscope (TEM) images taken as a support grid is tilted over a large angle. A back-projection (tomographic) algorithm using a radially weighted Fourier transform of each tilted image can be used for this purpose. The accuracy of reconstructing a nonsymmetric structure is limited by the number of micrographs that can be taken, and by the total tilt angle that can be achieved. Thirty independent views of a nonsymmetric structure (taken over a total tilt angle of ∼180 degrees) are needed to resolve a nonsymmetric structure to ∼3nm.
Mechanoelectrical transduction mediated through cilia in protists
Authors: Machemer H.
Published: June 2020

Unicellular organisms respond to a variety of stimuli, such as light, touch, or chemical action. A Paramecium cell, which meets an obstacle, reverses the swimming direction and eventually resumes forward locomotion in a new direction. It has been a plausible assumption that the cilia are receptors as well as effectors. This view gains support by analogy: ciliary structures exist in various metazoan tissue specialized for stimulus sensation. A previous elegant hypothesis assumed that a ciliary mechanoreceptor employs the ciliary motile machine in reverse in that bending of the axoneme can generate a chemical signal. Recent electrophysiological studies in ciliates have contributed to a re-assessment of the role of cilia in mechanotransduction. This lecture summarizes some experimental evidence as to how the sensory function is organized in a ciliated cell.
Variations of plasti ds in pollen-derivated albino plants of rice
Authors: Chen Y. R. , Huang Y. F. , Lin T. L.
Published: June 2020

Pollen-derivated albino plants often occurred in anther culture and their percentages in few cases reached 100%. Clapham first observed the concentric ring of membrane system, plastoglobuli and starch grains in the plastids of albina barley. In mesophyllous cell of albino rice, the proplastid contained no ribosomes and its development was blocked at the stage of concentric membrane system. In the present study, plastids of different tissues of albino plant were examined.
Deposition and distribution of fungicide smoke particles detected with electron beam analysis
Authors: Krause C. R. , Powell C. C.
Published: June 2020

Low volume pesticide application technology is being used in various agricultural industries to lower application costs and increase efficacy of pesticides. Current methodology to discern the fate and behavior of fungicide particles produced by low volume pesticide application technologies is inadequate. Since low volume applicators generate particles from 1-15μm, direct observation of particle deposition is not feasible with light microscopy using fluorescent dye tracers or other impaction methods. Electron beam analysis (EBA), a combination of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA), offers a direct approach for evaluation of the deposition of fungicide smoke or fumigation particles due to the inherent resolution of the instrumentation. The theory is that knowledge of particle morphology and chemical composition can lead to identification of specific fungicide deposition.
Local shadow angle and heights of intramembrane particles in freeze-fracture replicas of proteoliposomes
Authors: Costello M. J. , Gomez G.
Published: June 2020

The heights of intramembrane particles (IMPs) produced by integral membrane proteins are difficult to obtain because the local shadow angle in the vicinity of the IMPs is not known for typical freeze-fracture experiments. Even though the average shadow inclination angle is set by the operator (usually 20°-45°), fractures normally produce very irregular surfaces. We have devised a procedure for determining the local shadow angle in selected spherical proteoliposomes from which IMP heights can be calculated. The procedure is an extension of a method to determine the true diameter of vesicles in freeze-cleaved aqueous suspensions and relies on the use of a tiltrotation electron microscope stage.
Comparative morphology of Pneumocystis Carinii in Situ and after bronchoalveolar lavage
Authors: Itatani C. A. , Hing A. , Jackson W. , Marshall G.J.
Published: June 2020

Pneumocystis carinii (PC) is an organism capable of causing fatal pneumonia in immune suppressed individuals and has recently gained prominence because of its association with AIDS. A similar organism occurs in rats and infection may be induced with cortisone injections. In order to isolate PC for further study bronchoal veol ar lavage (BAL) was performed. Differences in the ul trastructure of BAL-obtained organisms and PC in situ were observed and are herein reported.
Ultrastructural assessment of cryofractured primate spermatozoon by analytical scanning electron microscopy
Authors: Apkarian R. P. , Gopalkrishnan K.
Published: June 2020

A cryofracture technique for scanning electron microscopy (SEM) was developed to provide an ultrastructural assessment of large numbers of chimpanzee sperm from a single centrifuged pellet. Normal spermatozoon observed in an analytical SEM at high magnification were used to determine the suitability of this technique for preserving the ultrastructural features of many sperm fractured through different regions. Although transmission electron microscopy (TEM) provides fine ultrastructural imaging of primate spermatozoon, this imaging mode does not provide large numbers of sperm in a single sample which can be rapidly scanned for profiles of ultrastructural abnormalities useful in infertility screening.
Surface epithelial ultrastructure of the polycystic ovary in the BB wistar rat
Authors: Kaufmann R. C. , Khosho F. K. , Amankwah K. S.
Published: June 2020

Diabetes decreases the fertility of females, but the mechanisms are not completely understood. In our investigations, we have found that 13% of the female BB Wistar rats that spontaneously developed chemical diabetes had persistent estrous. In this study the ovaries of these rats were examined by scanning electron microscopy(SEM) and compared to normal-cycling controls as well as to rats that had developed polycystic ovaries(PCO) by exposure to constant 1ight.
Intercellular spaces in quick-frozen whole hearts of the frog and mouse
Authors: Sommer  , Wallace N.R. , Nassar R.
Published: June 2020

The geometry of cell apposition has a profound influence on certain electrophysiologic properties of aggregates of cardiac muscle cells, e.g. in bundles of frog versus mouse ventricular muscle. It should be assessed, ideally, in the absence of preparatory procedures that can be expected to change it. Since quick-freezing followed by freeze fracture eliminates all but freezing from the preparatory menue prior to electron microscopy, we have applied this technology to a comparative study of the geometry of intercellular spaces in frog and mouse hearts in an attempt to reproduce its in vivo state with high fidelity.
Ultrastructural and immunocytochemical studies of the extracellular matrix in sea urchin embryos
Authors: Howard Louisa , Spiegel Evelyn , Spiegel Melvin
Published: June 2020

There is currently a broad interest in the extracellular matrix (ECM) of the sea urchin embryo, but little information about its overall morphology. We are beginning to obtain a detailed view of the structure of the ECM by means of thick section stereoimaging techniques and immunolabeling of Lowicrylembedded thin sections.

For thick section images, ruthenium red was used during fixation for better retention of ECM components. 0.38, 0.5 and 1.0μ.m sections were photographed at 100, 200 and 1,000KV respectively. For immunolabeling, embryos were fixed in 1% glutaraldehyde/0.25% paraformaldehyde in 85% seawater containing 0.05M cacodylate buffer, dehydrated and embedded in Lowicryl K4M. Thin sections were incubated with anti-laminin and stained with protein A-colloidal gold (15nm) complex.
Microtubule-organelle associations during generative cell polarization in plumbago zeylanica
Authors: Russell S. D. , Mislan T. W.
Published: June 2020

Sexual reproduction in the flowering plant Plumbago zeylanica is characterized by pollen in which the two sperm cells differ significantly with respect to size, shape and organellar content. The sperm cell with the majority of mitochondria (ave. 256) typically fuses with the central cell to form the nutritive endosperm in which the embryo will develop. The sperm cell containing essentially all of the numerous plastids (ave. 24) and few mitochondria (ave. 40) fuses with the egg to form the embryo. This system of preferential fertilization results in each sperm cell having a predetermined fate upon arrival at the embryo sac. Features determining the distribution of organelles in the sperm cells originate in the polarity of their precursor cell, the generative cell.
3H-galactose and 3H-glucose incorporation into newly synthesized hepatic glycogen in control-fed rats
Authors: Michaels J.E. , Garfield S.A. , Hung J.T. , Smith S.S. , Cardell R.R.
Published: June 2020

3H-galactose (gal) and 3H-glucose (glu) were compared to determine which compound was preferable for pulse labeling newly formed hepatic glycogen. Control fed rats were used to achieve substantial and consistent levels of hepatic glycogen and to stimulate glycogen synthesis.

Rats fed once daily for 4 hr achieved hepatic glycogen levels > 3% wet weight liver prior to injection by tail vein of a tracer dose of 3H-gal or 3H-glu. The rats were sacrificed 15-120 min later and liver was prepared by routine techniques for light (LM) and electron microscopic (EM) radioautography (RAG) and biochemical analysis.
Localization of various phosphatase activities within the golgi apparatus and lysosomes of rat leydig cells
Authors: Lalli M. F. , Lacroix V. , Hermo L. , Clermont Y. , Smith C. E.
Published: June 2020

The testosterone-secreting Leydig cells contain an abundance of smooth endoplasmic reticulum, peroxisomes, mitochondria as well as a large, spheroidal, juxtanuclear Golgi apparatus composed of interconnected stacks of saccules (Figs. 1,2). Each Golgi stack appears to be composed of between 5 to 7 saccules or sacculo-tubular elements (Figs.1,2). These cells also possess pale and dense multivesicular bodies and dense membrane-bound bodies identified assecondary lysosomes, all of which have been shown to be involved in fluid phase and adsorptive endocytosis as well as in receptor mediated endocytosis. The purpose of the present study was to characterize the reactivity of Golgi saccules, multivesicular bodies and lysosomes of Leydig cells for different phosphatases.
Tem as an aid in the rapid diagnosis of canine distemper in wildlife
Authors: Nunamaker C.E. , Williams E.S.
Published: June 2020

Canine distemper, a disease of domestic dogs is also a problem in wild carnivores where it may produce central nervous system disorders. Rapid diagnosis of the disease in wildlife is important for monitoring natural outbreaks and is useful in differentiating causes of central nervous system diseases in these animals where rabies may be a concern. Furthermore, in cases where domestic canines may have come into contact with uncontrolled animals such as wild carnivores, rapid diagnosis is important. Diagnosis of canine distemper can be confirmed by fluorescent antibody techniques or histopathology. Serologic techniques and virus isolation are often too time-consuming to be of value during disease outbreaks. Because the virus is shed in excretions from infected animals during the systemic phase of the infection, feces from live or dead animals can be examined with the transmission electron microscope. Consequently, TEM provides an additional method for the rapid diagnosis of canine distemper virus (CDV).
Mechanism of germ cell degeneration in human and guinea pig testes
Authors: Chakraborty J. , Dewri R. , Jhunjhunwala J.S.
Published: June 2020

The mechanism of germ cell degeneration in the contralateral testes of men with varicocele or torsion of the spermatic cord has not yet been fully elucidated. The major cause of such a gap in our knowledge is due to the lack of a suitable animal model. We used guinea pigs as an experimental animal model, to evaluate the suitability of this animal species to study the testicular pathology.

Unilateral torsion of the spermatic cord was surgically induced in 36 animals. Groups of six animals were sacrificed at intervals of 4,8,12,16,20 and 24 months. Pieces of tissues were obtained from the contralateral testis of each animal. Human testicular biopsies were obtained from patients with either torsion of the spermatic cord or varicocele. Tissue specimens were fixed, dehydrated and embedded in epon following the usual procedure.
Characterization and quantitation of morphological changes induced in bovine endothelial cells by interleukin-2 (IL-2)
Authors: Bucana C. D. , Trial J. , Papp A. C. , Wu K. K.
Published: June 2020

Endothelial cells respond to endotoxins, arachidonic acid, and interferon-alpha by exhibiting a time- and dose-dependent production of prostacyclin which is accompanied by morphological changes in the endothelial cells. Recent studies showed that IL-2 also stimulates production of prostacyclin by endothelial cells. Therefore, the effect of interleukin-2 on the morphology of endothelial cells in vitro and ex vivo was investigated by LM, SEM and TEM. Quantitation of the cell changes in vitro was performed by image analysis and was correlated with time- and dosedependent production of prostacyclin.
Ultrastructure and analytical microprobe analysis of simian lung mite pigments
Authors: Cole R. W. , Kim J. C.
Published: June 2020

In recent years, non-human primates have become indispensable as experimental animals in many fields of biomedical research. Pharmaceutical and related industries alone use about 2000,000 primates a year. Respiratory mite infestations in lungs of old world monkeys are of particular concern because the resulting tissue damage can directly effect experimental results, especially in those studies involving the cardiopulmonary system. There has been increasing documentation of primate parasitology in the past twenty years.
Acetaminophen: fatty enhanced toxicity
Authors: Poolsawat S.S. , Huerta C.A. , Miranda G.A. , Nguyen L.T.
Published: June 2020

Drug toxicity accounts for 10%-30% of all medical in-patients admissions; some of the drug induced illnesses often occur following hospitalization. 5%-6% of medical in-patients deaths are initiated or induced by drug intake (1-4); about one-third of these cases are caused by non-prescription drugs. Acetaminophen, considered among the safest of all over-the-counter analgesics, has been reported to induce fatal hepatic necrosis both in man and animals (5-8). Frequently, adverse drug reactions arise from hypersensitivity to a drug and its side effects, or to drug interactions with food and food additives. This study is undertaken to observe the effect of acetaminophen on the liver when a fatty diet is simultaneously administered.

Swiss Webster mice were individually gavaged with a 286 mg/Kg dosis of acetaminophen for 4 days; control animals received saline alone. Both groups received rat feed plus 20% fat and were euthanized on the 5th day. Liver tissues were either fixed in 2% gluteraldehyde; post-fixed in 1% osmnium tetroxide in 0.1M sodium cacodylate buffer and embedded in Araldite 502 for TEM; or processed for alkaline phosphatase activity (9).

Hepatocyte derived from mice exposed to acetaminophen (Fig. 1) showed increased Golgi Apparatus (GA) and secretory granules (SG) activity. These phenomena appear to be responsible for the elevated alkaline phosphatase activity (Fig. 2) in response to acetaminophen detoxification exerted by the hepatocyte. However, when a fatty diet is incorporated into the study: the hepatocyte exhibited generalized cytoplasmic lysis and increased lipid droplets (Fig. 3), localized coagulative necrosis of the hepatocyte normally found in the caudal and right lobes of the liver (Fig. 4) and increased pynotic hepatocytes (Fig. 5) are noted
Ultrastructure of esophageal epithelium of rats fed Zn-deficient diet
Authors: Yamashiro S. , Bast T. , Bray T.M. , Bettger W.J.
Published: June 2020

It has been shown that animals fed a Zn-deficient diet developed various epithelial lesions. These include parakeratosis of the tongue, larynx and nasal sinuses in the ducks and hypertrophy of esophageal mucosa in the rats and pigs.

Twenty-one weanling, male Wistar rats were equally divided into three groups. Seven rats were fed a diet containing less than 1.1 ppm Zn ad libitum for 3 weeks. Control rats were either pair-fed or fed ad libitum a diet supplemented with 100 ppm Zn. The basal diet was composed of 20% egg white, 10% corn oil, 63.55% glucose hydrate, 1% vitamin premix, 4% mineral premix, 0.25% choline chloride, 0.4% sodium phytate and 0.8% calcium carbonate. Minerals and vitamins additions were according to the AIN-76 recommendations (5).
Liquid crystalline ordering of paired helical filaments in neurofibrillary tangles of Alzheimer's disease
Authors: Clapin D.F. , Montpetit V.J.A.
Published: June 2020

Alzheimer's disease is characterized by the accumulation of abnormal filamentous proteins. The most important of these are amyloid fibrils and paired helical filaments (PHF). PHF are located intraneuronally forming bundles called neurofibrillary tangles. The designation of these structures as "tangles" is appropriate at the light microscopic level. However, localized domains within individual tangles appear to demonstrate a regular spacing which may indicate a liquid crystalline phase. The purpose of this paper is to present a statistical geometric analysis of PHF packing.
Some ultrastructural alterations in brain of a patient with both down'S syndrome and Alzheimer's disease
Authors: Lim B. S. , Kanhouwa S.
Published: June 2020

OG, a 40 year old white male was admitted to the hospital with a diagnosis of Non-psychotic Organic Brain Syndrome with Mogolism. On admission he walked with a shuffling gait and had hypoactive deep tendon reflexes. He had an IQ of 17 on the Stanford Binet scale. The patient was on Dilantin therapy for seizures. Shortly after the third seizure, he suffered from hemorrhagic pneumonia and expired, ending his nearly sixteen years of hospitalization at Saint Elizabeths.
Aortic lesions in copper deficiency: Modification by dietary carbohydrates
Authors: Bielenberg U.
Published: June 2020

Copper deficiency can cause cardiovascular lesions in experimental animals. Previous experiments have shown that the biochemical and itDrphologic lesions induced by deprivation of dietary copper can be suppressed by feeding diets containing starch or can be magnified by a high sucrose diet. In a recent study it was found that the more severe signs of copper deficiency in rats fed sucrose as compared to starch were due to the fructose moiety of sucrose. Although fructose as compared to starch markedly enhanced the symptoms of copper deficiency, the possibility that an effect of dietary carbohydrates due to the nature of the simple carbohydrate (fructose vs glucose) cannot be excluded. The present study was designed to determine if the severity of copper deficiency in rats fed sucrose as compared to starch is due to the glucose as well as the fructose moiety of sucrose. This portion of the study assessed the morphologic changes in aortas of seventy weanling male rats who were fed, for 9 weeks, copper deficient or copper supplemented diets containing either 62% starch, fructose or glucose. The starch-fed copper supplemented group served as the most normal controls. Rats were sacrificed after 9 weeks of dietary treatments. Copper deficiency was verified by reduced serum ceruloplasmin activity and serum and hepatic copper concentration.
Inelastic scattering at surfaces and interfaces
Authors: Ritchie R. H. , Howie A.
Published: June 2020

An important part of condensed matter physics in recent years has involved detailed study of inelastic interactions between swift electrons and condensed matter surfaces. Here we will review some aspects of such interactions.

Surface excitations have long been recognized as dominant in determining the exchange-correlation energy of charged particles outside the surface. Properties of surface and bulk polaritons, plasmons and optical phonons in plane-bounded and spherical systems will be discussed from the viewpoint of semiclassical and quantal dielectric theory. Plasmons at interfaces between dissimilar dielectrics and in superlattice configurations will also be considered.
High-resolution EM study of the gold silicon interface reaction
Authors: Kim M.J. , Carpenter R.W. , Barry J.C.
Published: June 2020

Gold occupies a key role in silicon solid state device technology, for contacts and carrier lifetime control. Gold is added to silicon by evaporation onto HF cleaned Si wafers, followed by annealing at high temperature. The Au-Si binary system is a simple eutectic, with very limited terminal solid solubility and no reported stable intermediate compounds. When Si wafers are HF cleaned and exposed to air, even for very short times, a native oxide film a few nm thickness will form, and be interposed between the Si substrate and the evaporated Au layer. The effect of this film on the interface reaction is of interest. Alternatively, conventional surface research on Au/Si interfaces formed by UHV in-situ cleaning, evaporation and annealing provided evidence for an amorphous Au-Si layer and metastable crystalline Au silicides at the position of the original Au/Si interface.
Observation of dislocations in dynamically loaded Cu-SiO2
Authors: Pritchard D. S.
Published: June 2020

The effect of varying the strain rate loading conditions in compression on a copper single crystal dispersion-hardened with SiO2 particles has been examined. These particles appear as small spherical inclusions in the copper lattice and have a volume fraction of 0.6%. The structure of representative crystals was examined prior to any testing on a transmission electron microscope (TEM) to determine the nature of the dislocations initially present in the tested crystals. Only a few scattered edge and screw dislocations were viewed in those specimens.
Microstructures of straight and wavy interfaces formed in explosively bonded copper single crystals
Authors: Pak Han-ryong , Chen Chung-wen , Inal O. T. , Mukerjee Kali
Published: June 2020

Explosive welding is essentially a solid-phase bonding process, hence any metal can be bonded even if they are totally dissimilar physically and chemically. Our group recently found that a straight interface is superior, with respect to plastic deformation behavior, to a wavy one, in direct contrast to a model that an interlocking structure of a wavy interface produces strong bonds. To obtain some insight into the superiority of such a straight interface, microstructures of copper single crystals (size: 4 x 40 x 130 mm) explosively welded in a parallel standoff configuration are investigated by means of transmission electron microscopy.
Microstructures in explosively consolidated rapidly solidified aluminum powders
Authors: Doyle T. E. , Wright R. N. , Flinn J. E. , Korth G. E.
Published: June 2020

Rapid solidification technology offers the possibility of producing unique, high-strength aluminum alloys to replace titanium in low-temperature aerospace applications. One such new alloy, an extended solid solution in the Al-Co system, was examined in the present work. Although rapid solidification can produce an extended solid solution, the solid solution is prone to decomposition because of cobalt's very limited solubility in aluminum. Dynamic consolidation is a relatively low bulk temperature process and presented the best opportunity for retaining the solid solution in monolithic forms. Analytical electron microscopy was used to study precipitation, grain and subgrain structure, and particle-bonding mechanisms in consolidated Al-Co and pure aluminum powders.
Formation of nickel aluminides under shock-wave loading
Authors: Simonsen I. K. , Horie Y. , Graham R. A.
Published: June 2020

Recently we reported the synthesis of nickel aluminides in a mixture of elemental aluminum and nickel powders under explosive shock-wave loading. The alloy products were found to be readily synthesized and controlled by shockloading conditions. A notable microstructural feature was the presence of unusually small Ni3 Al crystallites having a grain size of about 5 nm. They were found in a region of high shock-induced temperature where there were extensive alloying reactions. In this report we present the observation of similar crystallites in a low temperature region where observed reactions were sparse and localized. The structures of these crystallites were tentatively identified as those of NiAl and Ni2Al3.
Application of Analytical Electron Microscopy to glass-bonded aluminas
Authors: Hockey B.J.
Published: June 2020

Liquid phase sintering represents one of the most common methods of producing aluminas and other ceramic materials. Regardless of the specific processing details, this sintering procedure invariably results in a polycrystalline body containing a certain volume fraction of an intergranular binder phase. This phase is typically a glass, which can control many important properties of the sintered material. Clearly, microstructural characterization - describing not only the physical distribution of the binder phase but also its chemical composition - represents its an important part in the study of these materials.
Crystallization of MgO • Al2 • SiO2 • ZrO2 glasses
Authors: McCoy M. A.
Published: June 2020

Transformation toughening by ZrO2 inclusions in various ceramic matrices has led to improved mechanical properties in these materials. Although the processing of these materials usually involves standard ceramic powder processing techniques, an alternate method of producing ZrO2 particles involves the devtrification of a ZrO2-containing glass. In this study the effects of glass composition (ZrO2 concentration) and heat treatment on the morphology of the crystallization products in a MgO•Al2•SiO2•ZrO2 glass was investigated.
High-resolution TEM studies of mullite formation in metakaolinite
Authors: Sarikaya Mehmet , Aksay IInan A.
Published: June 2020

Studies on the compressive fracture strength (759 MPa at 15000°C) and the flexural strength (700MPaat 1300°C) of polycrystalline mullite (3Al2O3•2SiO2-2Al2O3•SiO2) illustrate its potential for high temperature applications. In the processing of these high strength mullites, molecularly mixed Al2O3-SiO2 precursors are used to enhance mullite formation rates and to achieve microstructural homogeneity in the submicrometer range. Reaction steps leading to the formation of mullite in molecularly mixed systems are not adequately understood. The prevailing problems center around (i) the composition of a spinel phase that forms at around a 980°C exothermic reaction, and (ii) the concurrent or subsequent formation and growth of mullite. Here, we report our high resolution TEM results on the formation of the spinel and mullite phases in a molecularly mixed precursor, metakaolinite (Al2O3•2SiO2).
The evolution of dislocation structure in the creep of hot-isostatically pressed niobium carbide
Authors: Nixon R. D.
Published: June 2020

The kinetics and mechanisms of creep in transition metal carbides are evaluated in order to design engineering structures which incorporate creep behavior. The mechanisms of creep in hot isostatically pressed niobium carbide involves the generation and movement of dislocations which were examined in this material by transmission electron microscopy.

Constant uniaxial compressive stress experiments in the temperature and stress ranges of 1730K to 2100K and 16 MN/m2 to 70 MN/m2 were performed on right circular cylindrical samples of hot isostatically pressed NbC0.74 of average height and diameter 7.6 x 10-3 m and 4.4 x 10-3 m, respectively. These experiments were performed by either applying a single constant stress to the sample at four different temperatures to determine the activation energy of creep or by keeping the sample at one constant temperature and applying four different constant stresses to determine the stress exponent of creep.
Microvoid formation in the grain boundary phase of a sintered Si-Al-O-N ceramic after static fatigue testing
Authors: Hughes M. R. , Nolan T. A. , Chang J.
Published: June 2020

Sintered silicon nitride materials are currently being considered for use in hot flow-path components of gas turbine engines because of their good thermal shock and oxidation resistance as well as strength at high temperatures. These materials, however, have been shown to be susceptible to slow crack growth (SCG) and creep at elevated temperatures. The high-temperature properties are largely determined by the intergranular phase which is composed of the sintering aid residue and may be either amorphous or crystalline depending on sintering and annealing parameters. The silicon nitride examined in this study had reportedly been sintered with Y2O3 (5.86%) and Al2O3 (2.2%) to produce a composite of β'Si3N4 crystals in an amorphous Y-Si-Al-O-N matrix. Static fatique tests performed on test bars of this material resulted in failures originating, via SCG and creep within the intergranular phase, above certain stress loads at 1000°C. These sites and other areas through the cross section of the test bars were examined by SEM and AEM to determine the microstructure and chemistry related to these failure phenomena.
High spatial resolution AEM observations of yttrium segregation in chromia scales grown on Co-45%Cr
Authors: Przybylski K. , Garratt-Reed A. J. , Yurek G. J.
Published: June 2020

The addition of so-called “reactive” elements such as yttrium to alloys is known to enhance the protective nature of Cr2O3 or Al2O3 scales. However, the mechanism by which this enhancement is achieved remains unclear. An A.E.M. study has been performed of scales grown at 1000°C for 25 hr. in pure O2 on Co-45%Cr implanted at 70 keV with 2x1016 atoms/cm2 of yttrium. In the unoxidized alloys it was calculated that the maximum concentration of Y was 13.9 wt% at a depth of about 17 nm. SIMS results showed that in the scale the yttrium remained near the outer surface.