bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energy filtering TEM of transfected DNA
Authors: Maleckl Marek 
Published: June 2020

Energy filtering transmission electron microscopy (EFTEM) relies upon spatial separation of imaging electrons based upon their energy within an energy loss spectrum (Ottensmeyer 1986). In particular, EFTEM allows contrast enhancement in the zero loss mode and element mapping with electron spectroscopic imaging.These capabilities find a new application in studies of transgenesis in which constructs, probes, and antibodies are marked with organometallic clusters. Since the basic routes of intracellular trafficking of the transfected DNA have become recognized along with the crucial role played by nuclear pores as the selection gates (Malecki et al., 1995, Malecki and Skowron 1995),the current research is pursued by means of ultramicroscopy.Two strategies were developed for ultrastructural imaging of the transfected plasmid DNA with EFTEM. In both strategies, the transfected cells were cryo-immobilized, embedded in Lowlcryl K4M, and sectioned;plasmid constructs, transfection complexes containing nuclear localization signals, and transfection procedures were described previously (Malecki 1995).In the first strategy, the plasmid DNA was covalently conjugated to Nanogold (Nanoprobes) prior to transfections.
Nature of caveolae in the endothelial cells of toad urinary bladders
Authors: Mia A.J. , Ford J. , Oakford L.X. , Yorio T. 
Published: June 2020

Intact toad urinary hemibladder sacs have been in use for many years as a membrane model for experimental studies of transepithelial aqueous transfer under osmotic gradient. The toad bladder tissue is composed of several cell types. Recently, we reported the presence of a large concentration of caveolae in the granular epithelial cells of toad urinary bladders. Caveolae are microstructures which arise by invagination of the plasma membrane on the cytoplasmic side of the cell. Currently, we report the presence of caveolae in endothelial cells of toad urinary bladder.Urinary hemibladder sacs were excised from doubly-pithed toads, Bufo marinus, fixed using 1% glutaraldehyde in PIPES, postfixed in 1% osmium tetroxide, dehydrated and embedded in epon blocks. Ultrathin sections were exposed to uranyl acetate and lead citrate for transmission electron microscopy. In some cases, the bladder sacs were tied up at the ends of glass tubes and equilibrated in aerated Ringer's solution for 30 min prior to experimental procedures.
Modulation of tubular microstructural self-assembly in galactosylceramides: Influence of N-linked fatty acyl chains
Authors: Kulkarni Vitthal S. , Brown Rhoderick E. 
Published: June 2020

Our recent studies have indicated that aqueous dispersions of galactosylceramides (GalCers) containing nervonoyl [24:1Δ15(CiS)] acyl chains, which constitute the major unsaturated acyl moieties in bovine brain GalCer, form tubular bilayers. In an effort to define the structural parameters that modulate tubule formation, we synthesized a series.of GalCers having successively shortercismonounsaturated acyl chains than the tubule-forming 24:1 GalCer and investigated the resulting microstructural self-assemblies by freeze fracture and deep etch electron microscopy.GalCers having W-linked erucic [22:1Δ13(CiS)], eicosenoic [20:Δ11(CiS)], or oleic [18:Δ9(CiS)] acyl chains were synthesized and purified as previously reported for 24:1 GalCer. Dispersions were prepared by hydrating dry lipid at >90°C with phosphate buffer (pH 6.6) followed by vigorous vortexing and three freeze-thaw cycles. Samples were cryo-fixed from room temperature (22°C) by plunging into liquid propane cooled by liquid nitrogen, were fractured in a Balzers 300 freeze fracture apparatus at -120°C, and were etched for 6 min. at -100°C.
Time-resolved high-resolution electron microscopy of structural transformation in nanocrystalline ZnO films
Authors: Kizuka T. , Tanaka N. 
Published: June 2020

Mechanical properties of polycrystalline materials become anomalous when the grain size and grain boundary length decrease to nanometer scale. For example, ductility and toughness increase significantly in nanometer-grained ceramics (nanocrystalline ceramics). Ductility increases due to appearance of fine-grained-superplastic deformation. Grain boundary migration and interface migration are fundamental processes of the superplastic deformation. Structural transformation of fine grains is a factor which limits the toughness in polycrystalline ceramics because the transformation relaxes internal strain. The behavior of grain boundaries and interfaces, such as diffusion bonding and Czochralski-type crystal growth at ambient temperature, can be analyzed by a time-resolved high-resolution electron microscopy (TRHREM) developed by Kizuka et al.,In the present study, grain boundary migration and successive transformation of crystal structure in nanocrystalline ZnO were investigated by TRHREM.Zinc oxide was vacuum-deposited on air-cleaved (001) surfaces of sodium chloride at 200°C. TRHREM was carried out at room temperature using a 200-kV electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder.
Dynamic Observation of a Surface Reconstruction of Au-Deposited Si Particle
Authors: Kamino T. , Yaguchi T. , Tomita M. , Saka H. 
Published: June 2020

Metal deposition is one of the most effective methods to reconstruct the surface structure of Si, and a number of studies using electron microscopes have been carried out. Endo et al. have studied Au-deposited Si(111) surface by ultra-high vacuum(UHV) scanning electron microscope(SEM), and obtained SEM images of 7 × 7 and 5 × 2-Au structure at 600°C. Ozawa et al. have observed Audeposited Si(111) surface by UHV-transmission electron microscope(TEM) and observed the formation of 5 × 2-Au structure at 700°C. Marks et al. have studied the structure of Au-deposited Si(lll) surface to reconstruct electronic potential on the surface.Recently, we developed a direct heating type- specimen heating holder consists of two heating elements, for use with a conventional analytical TEM, and applied to an in-situ study of the surface reconstruction of Au-deposited Si at high temperature. A schematic drawing of the heating holder is shown in Fig. 1. Tungsten wire with a diameter of 25εm was used as the heating elements. The upper heating element was used for metal deposition, in this case Au, and lower one for the heating of substrate material, in this case Si. The microscope used in the study is a H-9000NAR analytical TEM operated at 300kV. The spherical and chromatic aberration coefficients of the objective lens were 0.69 and 1.4mm, respectively, and the TEM image resolution was 0.175nm
Characterization of reactive phase formation in sputter-deposited Ni/Al multilayer thin films using TEM
Authors: Lucadamo G. , Barmak K. , Michaelsen C. 
Published: June 2020

The subject of reactive phase formation in multilayer thin films of varying periodicity has stimulated much research over the past few years. Recent studies have sought to understand the reactions that occur during the annealing of Ni/Al multilayers. Dark field imaging from transmission electron microscopy (TEM) studies in conjunction with in situ x-ray diffraction measurements, and calorimetry experiments (isothermal and constant heating rate), have yielded new insights into the sequence of phases that occur during annealing and the evolution of their microstructure.In this paper we report on reactive phase formation in sputter-deposited lNi:3Al multilayer thin films with a periodicity A (the combined thickness of an aluminum and nickel layer) from 2.5 to 320 nm. A cross-sectional TEM micrograph of an as-deposited film with a periodicity of 10 nm is shown in figure 1. This image shows diffraction contrast from the Ni grains and occasionally from the Al grains in their respective layers.
New specimen holders for low-angle ion milling of TEM specimens
Authors: Alani R. , Swann P.R. 
Published: June 2020

The important role of milling angle in the preparation of ion milled TEM specimens can not be over emphasized. While higher milling angles produce more rapid milling of specimen surface, ion milling at glancing angles of about 5° or less has become increasingly popular because it produces higher quality specimens and fewer artifacts, especially specimens composed of materials which are difficult to mill. Specimens milled at higher angles are of lower quality and include surface roughness, limited thin areas and differential thinning rates for different constituents in specimen; low angle ion milling overcomes many of these problems.A major requirement for low angle ion milling is a specimen holder with an appropriate line of sight capability. That is, the specimen holder must permit one or more ion beams to be directed against the specimen at angles down to 0°. The “single post specimen holder” is an example of a specimen holder providing low angle ion milling capability.
Industrial applications of TOF-SIMS imaging
Authors: Pachuta Steven J. 
Published: June 2020

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has in recent years become a useful tool for surface analysis in industrial laboratories. All elements and isotopes, as well as many molecular entities, can be detected by SIMS, with most of the signal coming from the outer 10 - 20 Å of the surface. The initial penetration of TOF-SIMS into industry was as an improvement over existing quadrupole instruments, with higher mass range, mass resolution, and sensitivity. The coupling of TOF-SIMS with high brightness liquid metal ion sources greatly expanded the applicability of the technique, making chemical imaging of the outermost monolayers of a surface a routine experiment.Several examples will be presented of TOF-SIMS imaging applied to real-world materials encountered in an industrial analytical laboratory. All results were obtained from a PHI-Evans TFS series instrument equipped with an FEI two-lens 69Ga+ liquid metal ion gun (LMIG). When operated at 25 keV beam energy, a primary ion beam diameter of 2500 Å in continuous mode, and 1-2 μm in pulsed mode, can routinely be obtained.
Three-Dimensional reconstruction of the synaptonemal complex from high-pressure frozen maize meiocytes using IVEM Tomography
Authors: Fung Jennifer C. , Agard David A. , Sedat John W. 
Published: June 2020

The synaptonemal complex (SC) is a key macromolecular assembly formed during meiosis of most eukaryotes. It has a crucial role in maintaining synapsis between homologous chromosomes and in ensuring proper segregation of the homologs through the establishment of functional chiasmata. Recently, biochemical and genetic efforts have begun to identify some of the protein components of the SC. As these efforts progress, a more detailed analysis of SC structure will also be needed to incorporate these new components into the overall organization of the SC.Early efforts into the analysis of SC structure have established that its general architecture is conserved throughout many organisms. The basic features found in every SC are the two lateral elements and the central element, both which run longitudinally between the homologs during the pachytene stage of prophase I. Transverse elements which run perpendicular to the homolog axis through the central region are also often found. Although the general features of the SC are conserved, the internal architecture of these components can differ.
Androgen-induced plasticity at a “vocal” neuromuscular synapse
Authors: Kelley Darcy B. , Tobias Martha L. , Ellisman Mark 
Published: June 2020

Brain and muscle are sexually differentiated tissues in which masculinization is controlled by the secretion of androgens from the testes. Sensitivity to androgen is conferred by the expression of an intracellular protein, the androgen receptor. A central problem of sexual differentiation is thus to understand the cellular and molecular basis of androgen action. We do not understand how hormone occupancy of a receptor translates into an alteration in the developmental program of the target cell. Our studies on sexual differentiation of brain and muscle in Xenopus laevis are designed to explore the molecular basis of androgen induced sexual differentiation by examining how this hormone controls the masculinization of brain and muscle targets.Our approach to this problem has focused on a highly androgen sensitive, sexually dimorphic neuromuscular system: laryngeal muscles and motor neurons of the clawed frog, Xenopus laevis. We have been studying sex differences at a synapse, the laryngeal neuromuscular junction, which mediates sexually dimorphic vocal behavior in Xenopus laevis frogs.
Cisplatin-induced changes in the gastric smooth muscle and its calcium modulation
Authors: Aggarwal S. K. 
Published: June 2020

Cisplatin (cis-Dichlorodiammineplatinum II; CDDP) a potent broad spectrum anti-cancer drug produces severe toxic side effects including kidney damage, nausea and vomiting, loss of hearing, peripheral neuropathy, hypomagnesemia and hypocalcemia. Our studies using rat as the model system show that these toxicities are related to calcium homeostasis and can be controlled through the exogenous administration of calcium before CDDP treatment.Cytochemical and ultrastructural studies in Wistar rats [Crl:(WI)BR] show that CDDP in its hydrolyzed state under low chloride ion concentrations, within the cell, causes uncoupling of oxidative phosphorylation, calcium efflux from the mitochondria, inhibits ATP synthesis, lowers membrane-associated calcium and various membrane transport enzymes. It also induces an increase in the number of lysosomes. CDDP causes a drop in the blood calcium levels with a corresponding increase in the dark cells of the parathyroid gland. In rats CDDP causes hypercontraction of the uterine smooth muscle and an undue distension of the stomach through the noncontractility of its smooth muscle thus inhibiting gastric motility, leading to the development of ulcers.
Mapping DNA and protein in biological samples using the scanning transmission x-ray microscope
Authors: Zhang X. , Balhorn R. , Jacobsen C. , Kirz J. , Williams S. 
Published: June 2020

The Scanning Transmission soft X-ray Microscope (STXM) at the XIA beamline at the National Synchrotron Light Source, Brookhaven National Laboratory, has achieved 50 nm Rayleigh resolution and has been used to image wet biological samples using the natural absorption differences between carbon and water in the water window (between carbon and oxygen K-absorption edges). The step-like jumps in the absorption of soft x-rays by materials as a function of energy have been used for elemental mapping. Examination of these absorption "edges" with high energy resolution resolves fine absorption structures. These fine structures are strongly affected by the atom's local environment, such that they carry detailed information about the atom's chemical state. We have used this chemical sensitivity to distinguish between materials which have similar elemental composition but are chemically different. Images with 50 nm resolution and spectra from a spot size less than (0.2 (μm)2 can be acquired routinely.Figure 1 shows the x-ray absorption fine structure spectra at the carbon absorption edge from DNA and bovine serum albumin (BSA, a typical protein) taken using the STXM.
Scanning luminescence x-ray microscopy: Progress toward selective staining using microspheres
Authors: Jacobsen C. , Fu J. , Mayer S. , Wang Y. , Williams S. 
Published: June 2020

In scanning luminescence x-ray microscopy (SLXM), a high resolution x-ray probe is used to excite visible light emission (see Figs. 1 and 2). The technique has been developed with a goal of localizing dye-tagged biochemically active sites and structures at 50 nm resolution in thick, hydrated biological specimens. Following our initial efforts, Moronne et al. have begun to develop probes based on biotinylated terbium; we report here our progress towards using microspheres for tagging.Our initial experiments with microspheres were based on commercially-available carboxyl latex spheres which emitted ~ 5 visible light photons per x-ray absorbed, and which showed good resistance to bleaching under x-ray irradiation. Other work (such as that by Guo et al.) has shown that such spheres can be used for a variety of specific labelling applications. Our first efforts have been aimed at labelling ƒ actin in Chinese hamster ovarian (CHO) cells. By using a detergent/fixative protocol to load spheres into cells with permeabilized membranes and preserved morphology, we have succeeded in using commercial dye-loaded, spreptavidin-coated 0.03μm polystyrene spheres linked to biotin phalloidon to label f actin (see Fig. 3).
A new family of fluorescent calcium indicators designed to resist leakage or for measuring calcium near membranes
Authors: Poenie Martin , Minta Akwasi , Vorndran Charles 
Published: June 2020

The use of fura-2 as an intracellular calcium indicator is complicated by problems of rapid dye leakage and intracellular compartmentalization which is due to a probenecid sensitive anion transporter. In addition there is increasing evidence for localized microdomains of high calcium signals which may not be faithfully reported by fura-2.We have developed a new family of fura-2 analogs aimed at addressing some of these problems. These new indicators are based on a modified bapta which can be readily derivatized to produce fura-2 analogs with a variety of new properties. The modifications do not affect the chromophore and have little impact on the spectral and metal binding properties of the indicator. One of these new derivatives known as FPE3 is a zwitterionic analog of fura-2 that can be loaded into cells as an acetoxymethyl ester and whose retention in cells is much improved. The improved retention of FPE3 is important for both cuvettebased measurements of cell suspensions and for calcium imaging.
Mitochondrial distribution during oocyte maturation
Authors: Calarco P. 
Published: June 2020

Maturation of an immature oocyte into one capable of being fertilized involves tightly choreographed movements of chromosomes and organelles. Although maturation has been described at the EM level, little information is available on the 3-dimensional distribution of organelles during maturation in living oocytes. Mouse oocyte maturation provides the best model system, and the present study describes the spatial distribution of mitochondria in live oocytes.Immature oocytes were collected from ovaries in embryo culture medium containing IBMX 1/1000 (Sigma) to block maturation. Maturation, initiated by placing oocytes in IBMX-free medium, takes 12 hours at 37°C and 90% matured. Acridine orange (100 μM in medium, 10 min) was used to mark chromatin (data not shown). Mitochondria were labeled with rhodamine 123 (100 μM in medium; Molecular Probes, Oregon) which is cell permeant and accumulates in mitochondria. Live oocytes labeled for 1-2 hours, were rinsed, mounted in medium under oil and examined at various time points by the BioRad MRC-600 confocal laser scanning microscope (CLSM).
Ultrastructural alterations of neuronal cells in gangliogliomas
Authors: Ho K.L. , Garcia J.H. 
Published: June 2020

Gangliogliomas are uncommon glioma of the central nervous system, generally found in the temporal lobe of young individuals with a clinical history of seizures. The tumor is a mixed tumor composed of neoplastic mature ganglion cells and neoplastic glial cells, mostly astrocytes. Although the clinicopathological correlation of this tumor is well documented, few detailed ultrastructural studies have been reported.We studied three cases of ganglioglioma of the temporal lobe and found several unusual ultrastructural features of the neuronal cells: (1) Hirano bodies (eosinophilic rod-like structure), highly organized eosinophilic crystalloid arrays of interlocking filaments that display lattice like configuration. Homogenous electron-dense material may appear as patches permeating the fibrillar structure (Fig. 1). (2) Lafora bodies (polyglucosan bodies), round to oval non-membrane-bound inclusion composed of short branching filaments about 7-10nm in diameter and granular structures (Fig. 2). (3) Pick's bodies, perikaryonal aggregates of straight neurofilaments with or without ribosome association mixed with vesicles, myelin figures and dense bodies.
Detection of spermatophagia in the ejaculate of infertile patients
Authors: de Gallegos L. G. , RamÍrez B. E. , Arce M. A. Y. , González S. D. , Rositas M. R. E. 
Published: June 2020

Among the presently recognized factors related to reproductive anomalies in the human male, are the alterations of semen, mainly represented by defects in spermatic motility or asthenospermia . Autoinmune and infections could be responsible for a number of these cases . In both of these, a distinguishing factor is spermatophagocytosis, which may be unreckognizable in optic microscopy bat which is very apparent in electron microscopy.To study the incidence of this event in cases of asthenoteratozoospermia, and its relation to infections and immune disorders, we studied a series of 60 infertile patients that presented motility defects and a control group of 5 volunteers of proven recent paternity. After 3 to 7 days of sexual abstinence, 1 or 2 semen samples were obtanied from each patient by masturbation. The samples were washed in phosphate buffered saline, double fixed in 2.5% glutaraldehide and 1% osmium tetraoxide and included in epoxi resin by the conventional method. Thick and thin sections were obtained whith a diamon knife and were examined microscopically. Electron micrographs of representative areas were analyzed.
An ultrastructural study of Nosema polyvora blunck infecting the malpighian tubules of Pieris canidia larva
Authors: Cheung W. W. K. , Wang J. B. 
Published: June 2020

Microsporidian protozoans of Nosema spp. are common pathogens of insects in the orders Lepidoptera, Hymenoptera and Orthoptera. They are chronic pathogens that can be transmitted horizontally as well as vertically in susceptible insects. Thus they have the potential of being a microbial insecticide for suppressing insect pests populations. During the course of ultrastructural studies of the malpighian tubules of Pieris canidia we have found that Nosema polyvora Blunck commonly infects the tubules. It is worthwhile to investigate into the ultrastructure of this protozoan in order to better understand the host-parasite relationship.Fourth instar larvae of P. candidia were dissected in phosphate buffered saline and malpighian tubules were isolated for fixation in 2.5% glutaraldehyde in 0.2M phosphate, pH 7.2, for 1 hr. Subsequently, tissues were post-fixed in 1% osmium tetroxide in phosphate buffer and were dehydrated in alcohol/acetone series. Tissues were finally embedded in spurr resin and were cut with a Reichart ultrotome. Sections were stained with uranyl acetate and lead citrate for observation under a Zeiss EM 9S-2 or JEOL JEM CX-II electron microscope.