SEARCH · PubMed Health

Results for “Microscopy, Energy-Filtering Transmission Electron”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed2000

The development of Fresnel contrast analysis, and the interpretation of mean inner potential profiles at interfaces

This paper provides a summary of recent published and unpublished research on the development of Fresnel contrast analysis, a transmission electron microscopy technique for measuring the mean inner potential profile across an interface or a narrow layer. An algorithm for finding a best-fitting potential profile is described, energy-filtered experimental data are analyzed and contributions to Fresnel contrast from surface grooves and space charge are assessed. Many of the conclusions drawn are equally relevant for the interpretation of phases measured using off-axis electron holography.

Journal Article↗

PubMedDate not supplied

Alteration of the calcium content in inner hair cells of the cochlea of the guinea pig after acute noise trauma with and without application of the organic calcium channel blocker diltiazem.

Calcium ions are known to be important to the process of signal transduction across the apical and basal sides of the inner hair cells. Calcium channel antagonists have been demonstrated by light microscopy to provide protection against acoustic trauma. To evaluate the protective effect of calcium channel blocker on the inner ear cells to noise exposure, the amount of the histochemical reaction products formed in the cytoplasm of the inner hair cells of the guinea pig after application of pyroantimonate was measured by an image processing system connected to an energy-filtering transmission electron microscope (EFTEM). Compared to untreated control specimens (experimental animal group I) the amount of precipitable calcium had clearly increased in the inner hair cells of noise-exposed cochleae 60 h after an acute noise trauma (group III). In addition, small electron- lucent areas could be identified in the cytoplasm of the hair cells probably representing damage to the cellular fine structure. When the calcium channel blocker diltiazem was administered without any additional noise exposure the calcium content was drastically reduced in the inner hair cells (group II), but when the antagonist was given before and after acute noise trauma (group IV), the calcium content in the inner hair cells was nearly compared to the amount determined in the untreated group of animals. The role of diltiazem is discussed in respect of tissue protection and to the maintenance of the calcium-dependent physiological processes in the inner hair cells during signal transduction.

Acute Disease↗

PubMed2002

Structure of the (110) antiphase boundary in gallium phosphide.

The morphology of antiphase boundaries in GaP films grown by molecular beam epitaxy on Si (001) has been studied by transmission electron microscopy. The inversion of the crystal polarity between antiphase domains was confirmed by convergent-beam electron diffraction. The APBs were often found to facet parallel to [110] planes. Strong-beam alpha-fringe contrast observed along the (110) facets indicates that adjacent antiphase domains are related by an additional rigid-body lattice translation. Diffraction-contrast analysis shows that this R corresponds to a shear parallel to the [001] direction and a small expansion. The magnitude of the translation was inferred, quantitatively, through a comparison between energy-filtered zero-loss images of the alpha-fringe contrast with numerical calculations. The components of the rigid-body lattice translation were determined to be 0.023 +/- 0.0033 nm in the [001] direction and 0.005 +/- 0.002 nm in the 0 direction. Based upon a geometric model of the [110] antiphase boundary, the lengths of the Ga and P antisite bonds were calculated to be 254 +/- 2 pm and 227 +/- 4 pm, respectively.

Journal Article↗

PubMed1990

Quantitative energy-filtered image analysis in cytochemistry. I. Morphometric analysis of contrast-related images.

A combination of energy-filtered electron microscopy (EFEM) and an image-analyzing system (IBAS/2000) is used for morphometric analyses of cells and (reaction) products. Image contrast is objectively established and segmentation is based upon intrinsic contrasts, in ultrathin sections. Cross-sectioned platinum-stained erythrocytes are used as a model to determine optimal conditions for constant measuring results for contrast, area and perimeter. Results are related to changes in: (1) the objective-lens diaphragm diameter, (2) three most frequently used contrast modes obtainable by electron spectroscopical imaging (ESI) in a Zeiss EM 902 transmission electron microscope (e.g., global, zero loss (or deltaE - 0 eV) and deltaE = 250 eV), and (3) the number of image integrations (1-250X) acquired by real-time video. A thresholding procedure is proposed for objective segmentation of such contrast-related images and applied to measure the area fraction of nuclear chromatin and the diameter of nominal 1 nm colloidal gold particles.

Animals↗

PubMed2000

Trypanosoma cruzi epimastigote endocytic pathway: cargo enters the cytostome and passes through an early endosomal network before storage in reservosomes.

It has been known for many years that trypanosomatids require exogenous essential growth factors in order to divide. Two surface domains are involved in starting nutrient endocytosis: the flagellar pocket and the cytostome. Although the flagellar pocket plays a fundamental role in the endocytic process occurring in several trypanosomatids, we have shown the cytostome as the main structure involved in this process in epimastigote forms of T. cruzi. After one minute of endocytosis, cargo is still found at the cytostome entry as well as along the cytopharynx. After two, five and fifteen minutes of endocytosis, cargo was seen inside vesicles and tubules, prior to fusing with reservosomes. Three-dimensional reconstruction of these tubules and vesicles showed they are interconnected, forming an intricate and branched network, distributed from the perinuclear region to the posterior end of the cell. Whole unfixed parasites that had taken up gold-protein conjugates for fifteen minutes were washed and dried on electron microscope grids. Observation with an energy-filtering transmission electron microscope revealed long gold-filled tubules at the posterior end of the cell. Parasites treated with ammonium chloride had their intracellular traffic slowed down, which allowed us to observe many events of vesicle fusion. The acidic nature of this network was evidenced using acridine orange. Based on pH and protein uptake kinetics we propose that the vesicular-tubular network is the early endosome of Trypanosoma cruzi epimastigotes.

Acridine Orange↗

PubMed2000

Immuno-electron microscopic localization of the alpha(1) and beta(1)-subunits of soluble guanylyl cyclase in the guinea pig organ of corti.

Guanylyl cyclases (GC) catalyze the formation of the intracellular signal molecule cyclic GMP from GTP. For some years it has been known that the heme-containing soluble guanylyl cyclase (sGC) is stimulated by NO and NO-containing compounds. The sGC enzyme consists of two subunits (alpha(1) and beta(1)). In the present study, the alpha(1) and beta(1)-subunits were identified in the guinea pig cochlea at the electron microscopic level using a post-embedding immuno-labeling procedure. Ultrathin sections of LR White embedded specimens were incubated with various concentrations of two rabbit polyclonal antibodies to the alpha(1)- and beta(1)-subunit, respectively. The immunoreactivity was visualized by a gold-labeled secondary antibody in an energy-filtering transmission electron microscope (EFTEM). Marked immunoreactivity for both antibodies was found in the inner and outer hair cells, with numerous gold particles at the border of the cuticular plates, associated with the cell nuclei or attached to electron-dense parts of the cytoplasm. In the pillar cells and apical Deiters cells, soluble guanylyl cyclase immunoreactivity was located at the rim of the cuticular plates and between the microtubuli bundles. Together with the recently identified nitric oxide synthase isoforms [Eur. Arch. Otorhinolaryngol. 254 (1997) 396; Eur. Arch. Otorhinolaryngol. 255 (1998) 483], the soluble guanylyl cyclase may be involved in signalling processes in the organ of Corti.

Animals↗

PubMed1997

Electron spectroscopic imaging analyses of the distribution of phosphorus in Balbiani ring granules and in the surrounding nucleoplasm.

The in situ distribution of phosphorus was studied in unstained ultrathin sections of salivary glands of Chironomus tentans and Ch. thummi larvae using elemental mapping by means of an energy-filtering transmission electron microscope. This distribution was related to the structures observed using contrast enhancement with inelastically scattered electrons at 250 eV. This procedure demonstrated that a phosphorus-containing fibril about 2 nm thick is the common substructure of the following nuclear ribonucleoprotein structural constituents: the Balbiani ring granules, their precursor fibrils seen at the sites of transcription, especially at the Balbiani rings, and the fibres traversing the pore of the nuclear envelope. These phosphorus-containing thin fibrils are sensitive to RNase. Thicker substructural features of the Balbiani ring granules, occurring as a curved ribbon on a dense particle, appear to be formed by the dense packing of the fine fibrils. The Balbiani ring granules located near the nuclear envelope are often linked to it by fine filaments.

Animals↗

PubMed1996

Probing nuclear ultrastructure by electron spectroscopic imaging.

Mammalian nuclei are complex organelles containing many functionally distinct nucleoprotein and protein particles in the size range 20-30 nm. This complexity hinders the study of structure-function relationships within the mammalian nucleus. Element-specific mapping using the energy-filtered transmission electron microscope can provide novel information on protein and nucleic acid density within structures, facilitating the identification of biochemical heterogeneity within morphologically similar structures. We demonstrate that imaging phosphorus, nitrogen and carbon can be useful in the characterization of protein and nucleoprotein structures within the nucleus. Additionally, electron spectroscopic imaging (ESI) may be used to map the distribution of strains relative to unstained material when biochemical-specific staining protocols, such as EDTA-regressive staining of RNA with uranyl acetate, are used. Relative mass may also be determined from ESI images and can be combined with elemental information further to distinguish biological constituents. Using this approach, heterochromatin was found to be variable in nucleic acid content although the morphology appeared relatively homogenous. ESI shows substantial promise for the investigation of structure-function relationships in biological specimens.

Animals↗

PubMed1996

Quantitative electron spectroscopic imaging in bio-medicine: evaluation and application.

Electron spectroscopic imaging (ESI) with the energy-filtering transmission electron microscope enables the investigation of chemical elements in ultrathin biological sections. An analysis technique has been developed to calculate elemental maps and quantitative distributions from ESI sequences. Extensive experience has been obtained with a practical implementation of this technique. A procedure for more robust element detection has been investigated and optimized. With the use of Fe-loaded Chelex beads, the measurement system has been evaluated with respect to the linearity of the element concentration scale, the reproducibility of the measurements and the visual usage of image results. In liver specimens of a patient with an iron storage disease the detectability of iron was tested and we tried to characterize iron-containing components. The concentration measurement scale is approximately linear up to a relative section thickness of approximately equal to 0.5. Monitoring of this parameter is therefore considered to be important. The reproducibility was measured in an experiment with Fe-Chelex. The iron concentration differed by 6.4% between two serial measurements. Element distributions are in many applications interpreted visually. For this purpose the frequently used net-intensity distributions are regarded as unsuitable. For the quantification and visual interpretation of concentration differences mass thickness correction has to be performed. By contrast, for the detection of elements the signal-to-noise ratio is the appropriate criterion. Application of ESI analysis demonstrated the quantitative chemical capabilities of this technique in the investigation of iron storage diseases. Based on an assumed ferritin iron loading in vivo, different iron components can be discerned in liver parenchymal cells of an iron-overloaded patient.

Ferritins↗

PubMed1998

Combined characterization of composite tabular silver halide microcrystals by cryo-EFTEM/EELS and cryo-STEM/EDX techniques.

The combination of cryo-energy filtering transmission electron microscopy (EFTEM)/electron spectroscopic diffraction (ESD)/electron energy-loss spectroscopy (EELS) and cryo-energy-dispersive X-ray (EDX) analysis in the scanning transmission (STEM) and scanning (SEM) modes was applied for the characterization of composite tabular Ag(Br,I) microcrystals. A low-loss fine structure in EEL spectra between 4 and 26 eV was attributed to excitons and plasmons possibly superimposed with interband transitions and many-electron effects. The contrast tuning under the energy-filtering in the low-loss region was used to image the crystal morphology, defect structure (random dislocations and ¿111¿ stacking faults) and bend and edge contours as well as electron excitations in the microcrystals. Sharp extra reflections at commensurate positions in between the main Bragg reflections and diffuse honeycomb contours in ESD patterns of the microcrystals taken near the [111] zone were assigned to the number of defects in the shell region parallel to the grain edges and polyhedral clusters of interstitial silver cations, respectively. The imaginary part of the energy-loss function, Im (-1/epsilon), and the real and imaginary parts, epsilon1 and epsilon2, of the dielectric permittivity were determined by means of a Kramers-Kronig analysis. An assignment of exciton peaks based on calculations of electronic band structure of silver bromide is proposed. Inner-shell excitation bands of silver halide were detected in line with EDX-analyses. The energy-loss near-edge structure (ELNES) of the AgM4,5-edge governed by spin-orbital splitting between the 3d3/2- and 3d5/2-states has been evaluated. Combined silver and halide distributions were obtained by a three-window method (EFTEM) and by EDX/STEM including area mapping and line profiling of iodide.

Bromides↗

PubMed2002

High-resolution analytical TEM of nanostructured materials.

This paper briefly reviews the potential applicability of analytical transmission electron microscopy (TEM) to elucidate both structural and chemical peculiarities of materials at high lateral resolution. Examples of analytical TEM investigations performed by energy-dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), and energy-filtered TEM (EFTEM) are presented for different materials systems including metals, ceramics, and compound semiconductors. In particular, results are given of imaging the element distribution in the interface region between gamma matrix and gamma' precipitate in the nickel-based superalloy SC16 by energy-filtered TEM. For core-shell structured BaTiO(3) particles the chemical composition and even the chemical bonding were revealed by EELS at a resolution of about 1 nm. A sub-nanometer resolution is demonstrated by energy-selective images of the Ga distribution in the surrounding of (In,Ga)As quantum dots. Moreover, the element distribution in (Al,Ga)As/AlAs multilayers with linear concentration gradients in a range of about 10 nm was investigated by EDXS line-profile analyses and EFTEM.

Journal Article↗

PubMed1990

EELS elemental mapping with unconventional methods. II. Applications to biological specimens.

This article presents two applications of image analysis and processing using the unconventional methods described in the companion paper (part I). Both the information analysis via relative entropy measurement and mapping and the factorial analysis of correspondence are demonstrated to be valuable tools for building an elemental map from a set of noisy energy-filtered images recorded in an analytical transmission electron microscope. Although the only technique considered here is electron energy loss spectroscopy, there is no doubt that such methods can be applied to a wide variety of similar problems: only a reduced number of underlying hypotheses are needed.

Algorithms↗

PubMed2000

Valence state mapping of cobalt and manganese using near-edge fine structures

The properties of transition metal oxides are related to the presence of elements with mixed valences. The spectroscopy analysis of the valence states is feasible experimentally, but a spatial mapping of valence states of transition metal elements is a challenge to existing microscopy techniques. In this paper, with the use of valence state information provided by the white lines and near-edge fine structures observed using the electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM), a novel experimental approach is demonstrated to map the valence state distributions of Mn and Co using the ratio of white lines in the energy-filtered TEM. The valence state map is almost independent of specimen thickness in the thickness range adequate for quantitative EELS microanalysis. An optimum spatial resolution of approximately 2 nm has been achieved for a two-phase Co oxides.

Journal Article↗

PubMed1999

Quantification of total calcium in terminal cisternae of skinned muscle fibers by imaging electron energy-loss spectroscopy.

Skinned muscle fibers are ideal model preparations for the investigation of Ca2+ -regulatory mechanisms. Their internal ionic milieu can be easily controlled and distinct physiological states are well defined. We have measured the total Ca content in the terminal cisternae of such preparations using imaging electron energy-loss spectroscopy (Image-EELS) as a new approach for quantification of sub-cellular element distributions. Murine muscle fibers submitted to a standardized calcium-loading procedure were cryo-fixed with a combined solution exchanger/plunge freezing device. Energy-filtered image series were recorded from ultrathin freeze-dried cryosections of samples immobilized in either relaxed or caffeine-contracted state. From these image series, electron energy-loss spectra were extracted by digital image-processing and quantitatively processed by multiple-least-squares-fitting with reference spectra. The calculated fit coefficients were converted to Ca-concentrations by a calibration obtained from Ca-standards. Total Ca-contents in the terminal cisternae of skinned skeletal muscle fibers decreased upon caffeine-induced Ca-release from 123+/-159 (+/-11) to 73+/-102 (+/-8) mmol/kg d.w. (weighted mean +/- SD (+/-SEM)).

Animals↗

PubMed2002

Time-resolved acquisition technique for spatially-resolved electron energy-loss spectroscopy by energy-filtering TEM.

A time-resolved acquisition technique has been investigated for spatially-resolved electron energy-loss spectroscopy by energy-fitering transmission electron microscopy. Plural (10) spectral images were acquired separately at an energy (E) and a position (Y) coordinate. After correction of both specimen and energy drifts by comparing with the original starting spectrum, the 10 spectral images were added to form a new processed spectral image. This time-resolved acquisition technique was found to improve the signal-to-noise ratio to about the square root of ten for 200 s total exposure time without increasing the image blurring problem.

Journal Article↗

PubMed2000

Quantitative intensity measurement of equal thickness fringes in Si and MgO crystal images with an energy-filtering transmission electron microscope using an imaging plate.

Quantitative measurement of intensity profiles of equal thickness fringes has been carried out in Si and MgO crystal images with an energy-filtering transmission electron microscope using an imaging plate. The crystals have a 90 degrees wedge-shape with [110] surfaces for Si and with [100] surfaces for MgO, and are observed under the exact axial incidence of a 200 keV electron beam along the [100] axis for Si and along the [110] axis for MgO. The intensities are measured in bright field and 022 and 040 dark field images for Si, and in bright field and 111, 002, 220, 113, 222, and 004 dark field images for MgO, with and without an energy slit having +/- 5 eV energy width for incident electrons. The intensity profiles obtained from the images are presented as standard experimental data for calculation of electron diffraction intensities. A few simulation programs for high-resolution transmission electron microscopy are checked by comparing the calculated diffraction intensities with the experimental data. The complex potential suitable for matching the data is discussed.

Journal Article↗

PubMed2000

Localization of chromophore absorption signals in TEM with an improved prism-mirror-prism filter.

A corrected prism-mirror-prism electron energy filter with curved entrance and exit faces was designed and incorporated into a Zeiss EM902 transmission electron microscope. The installation of the new filter required little modification to the existing microscope geometry and electronics. The filter had an energy resolution of 1.1 eV over the full image plane (acceptance half angle 10 mradian). The improved energy resolution was applied in studies of the low electron energy loss region that includes molecular orbital excitations or chromophore energy absorptions. Chromophore signal behaviour under electron irradiation was characterized using embedded crystals of hematin and of the dye mercury orange. Images of these crystals confirmed the expected decrease in signal intensity on shifting the selected energy loss from the region of molecular orbital excitations (less than approximately 5 eV) to higher energy losses. Electron irradiation-induced fading of the chromophore signal from hematin and mercury orange yielded similar 1/e dose values of 1.1 x 10(5) e(-) nm(-2) and 1.4 x 10(5) e(-) nm(-2) respectively. In a cellular context, chromophore signals were obtained from energy-filtered images of RIF-1 cell sections containing the photosensitizer chlorin e6 and from sections of BS-C-1 cells with cytoskeletal labelling via FITC-conjugated antibodies. The respective signals were extracted using a dose-dependent method or a shift in selected energy. Chromophore signal distributions were in agreement with fluorescence light microscopic images, but provided detail at higher spatial resolution.

Animals↗

PubMed1991

Contrast in the electron spectroscopic imaging mode of a TEM. IV. Thick specimens imaged by the most-probable energy loss.

When the zero-loss transmission falls below 10(-3) for biological sections of mass-thickness greater than 70 micrograms/cm2, the energy window in the electron spectroscopic imaging (ESI) mode of an energy-filtering electron microscope (EFEM) can be shifted to the most-probable energy loss of the electron energy-loss spectrum. This enables mass-thicknesses up to 150 micrograms/cm2 or thicknesses of 1.5 microns to be examined. Electron energy-loss spectra of thick carbon films calculated by a Fourier method agree with experimental spectra. Measurements of the electron energy-loss spectroscopy and ESI image intensities with an additional platinum film confirm a scattering model for the calculation of the image intensity. This model considers the angular broadening at the most-probable energy loss by introducing an effective illumination aperture of the order of the full-width at half-maximum of the angular distribution.

Fourier Analysis↗