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PubMed1992

Mapping of intracellular halogenous molecules by low and high resolution SIMS microscopy.

The subcellular distribution of halogenous molecules has been studied by SIMS microscopy in cultured cells of a human breast carcinoma (MCF-7 cell line). Two instruments of microanalysis were used. A low lateral resolution ion microscope (SMI 300 CAMECA) and a prototype scanning ion microscope equipped with a cesium gun that gives high lateral resolution images. This apparatus has been developed by G Slodzian, in Onera Laboratories (Office National d'Etudes et de Recherches Aérospatiales). Molecules studied by low lateral resolution ion microscope were halogenous steroids: fluorometholone, triamcinolone, bromocriptine and bromoandrosterone. Analytical images show that the first two compounds are mainly localized in the nuclear structure of MCF-7 cells whereas the last two molecules are localized in cytoplasm of these cells. Images were obtained with a resolution of 1 micron. With the scanning ion microscope, it is now possible to obtain images at the ultrastructural level. Four analytical images can be simultaneously obtained by a single scan of the imaged area, corresponding to a depth of erosion of the section of ten nm. The intranuclear distributions of three pyrimidine analogs, 5-bromo-2'-deoxyuridine, 5-iodo-2'-deoxyuridine and 5-fluorouracil have been studied in phase S and M of MCF-7 cells and these images have been compared to the distribution of sulfur, nitrogen and phosphorus. All these images have been obtained with a lateral resolution better than 100 nm.

Adrenal Cortex Hormones↗

PubMed1994

A real-time and fine resolution analyser used to estimate the instantaneous energy distribution of Doppler signals.

Doppler ultrasound signal analysers in current use require that the signal be stationary within the time interval of processing, and yield average results for that interval. A real-time instantaneous frequency analyser based on the Wigner distribution function (WDF) has been developed, which provides a means of analysing time-varying signals or signals with short stationary time periods, and also produces results with very high instantaneous temporal resolution without causing significant deterioration of frequency resolution. In addition to the real-time processing, the most recent 2.4 s of Doppler signal is stored in the analyser so that the operator can perform further fine analysis and obtain results with very high resolutions in both the time and frequency domains. The pseudo-instantaneous mean frequency (PIMF) and the Pseudo-Instantaneous Power Distribution (PIPD) are calculated and displayed every 4.0 ms in the real-time processing mode, and with a resolution of between 80 microseconds and 2 ms in the fine resolution analysis mode. The analyser utilises an algorithm developed so that the WDF can be calculated efficiently using the conventional Fast Fourier Transform (FFT) method, and the PIPDs are calculated from data that contribute equally.

Signal Processing, Computer-Assisted↗

PubMed1987

A new resolution criterion based on spectral signal-to-noise ratios.

A new criterion for the "useful" resolution of electron micrographs of macromolecular particles is introduced. This criterion is based on estimation of the spatial frequency limit beyond which the spectral signal-to-noise ratio (SSNR) falls below an acceptable baseline. Applicable to both periodic and aperiodic specimens, this approach is particularly apposite for sets of correlation-averaged images. It represents a straightforward and intuitively appealing generalization of the traditional method of estimating the resolution of crystalline specimens from the spectral ranges of periodic reflections in their diffraction patterns. This method allows one to assess how closely the resolution of an averaged image based on N individual images approaches the ultimate resolution obtainable from an indefinitely large number of statistically equivalent images. Inter-relationships between the SSNR and two other measures of resolution, the differential phase residual and the Fourier ring correlation coefficient, are discussed, and their properties compared.

Biopolymers↗

PubMed1989

Three-dimensional reconstructions from incomplete data: interpretability of density maps at "atomic" resolution.

Three dimensional data collection in electron microscopy is normally limited to a range of tilt angles that is less than +/- 90 degrees. Thus, even under the best conditions, experimental values of the structure factors will be missing within a solid cone in reciprocal space. Previous work has already shown that the missing cone of data can produce serious artifacts in three-dimensional density maps at modest resolution, for example approximately 15A. We now report, however, that a missing cone as large as +/- 30 degrees appears to have no serious effect on the three-dimensional density map of a protein at 3.6 A resolution, and we attribute this result to the fact that the electron density features are quite well separated from one another at that resolution. The map calculated with a +/- 30 degree missing cone is, furthermore, no more sensitive to noise (error) than is the full (isotropic) Fourier map. This result does not seem to be unreasonable in view of the fact that less than 14% of the data (i.e., signal) is lost due to the missing cone. Our numerical simulations therefore indicate that there should be no difficulty in interpreting high-resolution Fourier maps that can be produced with data that fall within realistic estimates of achievable resolution, tilt angles, and experimental error.

Electronic Data Processing↗

PubMed1996

High resolution 1H spectra of powdered solids observed by Hahn echo pulse sequence with magic-angle spinning.

The 1H magic-angle spinning (MAS) spectrum for a typical powdered solid is composed of a high resolution component and a broadline component. The high resolution component can be well isolated from the broadline component by the Hahn echo sequence with a long echo time. Compared with CRAMPS experiment, which measures the proton system as a whole, the high resolution echo-MAS method measures only a fraction of the solid, which is usually small at room temperature and quite different from the majority of the solid in both molecular motion and chemical environment. It is shown that for a sample of fumaric acid monoethyl ester, the chemical shifts of the high resolution component are apparently distinguishable from the isotropic chemical shifts of the broadline component in the CRAMPS spectrum as the temperature approaches the melting point. In addition, for a sample of malonic acid, the echo-MAS spectrum is sensitive to moisture and temperature, while its corresponding CRAMPS spectrum is not. It is suggested that the molecules which produce the high resolution component are related to the lattice defects in a solid, including the surface disorder of the polycrystallites, while the molecules that generate the broadline component are located on the rigid lattice of the solid.

Chemical Phenomena↗

PubMed2006

Registration-based approach for reconstruction of high-resolution in utero fetal MR brain images.

RATIONALE AND OBJECTIVES: This paper describes a novel approach to forming high-resolution MR images of the human fetal brain. It addresses the key problem of fetal motion by proposing a registration-refined compounding of multiple sets of orthogonal fast two-dimensional MRI slices, which are currently acquired for clinical studies, into a single high-resolution MRI volume. MATERIALS AND METHODS: A robust multiresolution slice alignment is applied iteratively to the data to correct motion of the fetus that occurs between two-dimensional acquisitions. This is combined with an intensity correction step and a super-resolution reconstruction step, to form a single high isotropic resolution volume of the fetal brain. RESULTS: Experimental validation on synthetic image data with known motion types and underlying anatomy, together with retrospective application to sets of clinical acquisitions, are included. CONCLUSION: Results indicate that this method promises a unique route to acquiring high-resolution MRI of the fetal brain in vivo allowing comparable quality to that of neonatal MRI. Such data provide a highly valuable window into the process of normal and abnormal brain development, which is directly applicable in a clinical setting.

Algorithms↗

PubMed2005

High-resolution ultrasonography in central serous chorioretinopathy.

PURPOSE: To investigate the use of high-resolution ultrasonography for detecting choroidal layer abnormalities in eyes with central serous chorioretinopathy (CSC). DESIGN: Prospective observational case series. METHOD: Optical coherence tomography (OCT) and high-resolution ultrasonography with a 20-MHz immersion probe were performed bilaterally in 10 patients, of whom 5 were affected by unilateral active CSC and 5 by unilateral cystoid macular edema (CME). Ten age-matched control subjects were also investigated. RESULTS: Both OCT and high-resolution ultrasonography showed a macular elevation in eyes with CSC and CME. High-resolution ultrasonography has shown evidence of a nonechogenic linear band under the retinal pigment epithelium in patients affected by CSC. This could be found in neither patients with CME or in control subjects. CONCLUSION: High-resolution ultrasonography can detect a nonechogenic space consistent with hyperpermeability of choroidal capillaries in eyes with active CSC. Shadowing by an altered retinal pigment epithelium cannot be ruled out, however.

Adult↗

PubMed2005

A high-resolution abrasive method for determining diffusion profiles of sorbing radionuclides in dense argillaceous rocks.

The diffusion of (134)Cs(+) and (22)Na(+) in Opalinus Clay (OPA) was studied by in-diffusion laboratory experiments. The diffusive tracer profiles in the rock were determined using a high-resolution abrasive peeling method. The radionuclide activities in the grinding swarf were measured directly via gamma-spectrometry. By choosing the appropriate abrasive paper, a resolution down to 15 microm can be achieved. This is important when analysing strongly sorbing radionuclides such as tri- and tetravalent actinides that show steep, shallow diffusion profiles. In this study, a resolution between 20 and 90 microm was obtained which was sufficient for a good spatial resolution of the diffusion profiles. Both the effective diffusion coefficients and the distribution coefficients of the radionuclides could be determined by applying a single reservoir with decreasing source concentration analysis for a semi-infinite case. In the case of (22)Na(+), effective diffusion coefficients of D(e)=2.0 x 10(-11)m(2)s(-1) and D(e)=1.5 x 10(-11)m(2)s(-1) for Benken (Zurcher Weinland) OPA and Mont Terri OPA, respectively, were derived. The distribution coefficients were K(d)=3.1 x 10(-4) and 0.9 x 10(-4)m(3)kg(-1), respectively. For (134)Cs(+) the effective diffusion coefficients were higher, i.e. D(e)=3.1 x 10(-11)m(2)s(-1) for OPA from Benken and D(e)=3.0 x 10(-11)m(2)s(-1) for OPA from Mont Terri. The distribution coefficients determined were K(d)=0.16 m(3)kg(-1) for Benken and 0.23 m(3)kg(-1) for Mont Terri. Comparison of the data obtained for the weakly sorbing (22)Na(+) with those from earlier through-diffusion experiments showed that there is good agreement between the two methods. In the case of (134)Cs(+) such a comparison was not possible because through-diffusion data are not available. Because through-diffusion methods cannot be applied to strongly sorbing tracers in reasonable time periods, in-diffusion combined with high-resolution abrasive peeling offers an excellent alternative for measuring the diffusion properties of strongly sorbing tracers in dense argillaceous rocks.

Journal Article↗

PubMed2004

Analysis of the influence of image resolution on the discriminating power of trabecular bone architectural parameters.

In the study the influence of image resolution on the discriminating power of different parameters quantifying the architecture of trabecular bone is investigated. High-resolution images of 200-microm-thick sections of young and old trabecular bone are collected. Different architectural parameters are evaluated and shown to be statistically different in both groups of images. Then the resolution of the images is artificially degraded to the level comparable with resolution achievable in vivo. It is shown that although the errors of evaluation are quite large for low-resolution images, the statistical difference present in the original data is still observed for parameters that depend only on the global characteristics of trabecular structure or marrow space, or depend only linearly on the number and area of disconnected parts of marrow space or trabecular structure. The parameters that fulfill such conditions are Euler number, mean area of marrow cavities, star volume and trabecular spacing. The statistical difference disappears for parameters that depend on the number and area of disconnected parts of marrow space or trabecular structure in a nonlinear manner, that is, marrow and trabecular disconnection probabilities, two-point distance and second moment of marrow cavities area distribution. It is shown that the mechanism that leads to the losing of discriminating power does not depend crucially on the estimation error or noise level. This mechanism, which involves an interplay between changes of mean values and standard deviations, is the manifestation of partial volume effect amplified with image segmentation.

Adult↗

PubMed2004

High-resolution optical mapping of intramural virtual electrodes in porcine left ventricular wall.

OBJECTIVE: It is believed that shock-induced intramural virtual electrodes (IVE) play a critical role in defibrillation. IVE were recently demonstrated in the porcine left ventricle (LV), but their origin remains unknown. Macroscopic optical mapping showed that strong shocks induce IVE of only one polarity, which contradicts theoretical predictions. It is hypothesized that IVE have a microscopic origin and that microscopic positive and negative IVE are spatially averaged during macroscopic optical mapping. This hypothesis was examined by mapping V(m) responses at the transmural LV surface with increased optical resolution. METHODS: Rectangular shocks (strength=2-48 V/cm; duration=10 ms) were applied across isolated coronary-perfused porcine LV preparations (n=7) during the action potential plateau and diastole. Shock-induced V(m) responses were measured at low resolution (LR; 1.2 mm/diode) and high resolution (HR; 0.11 mm/diode). RESULTS: During plateau shocks with strength > or =20 V/cm, LR recordings demonstrated only negative DeltaV(m) extending to the cathodal preparation edge. In contrast, HR recordings from this area as well as from intramural locations revealed both positive and negative DeltaV(m) at all shock strengths. During diastolic shocks, only positive polarizations were observed at LR, but both positive and negative polarizations were detected at HR. In areas of negative polarization, large activation delays were found at HR, whereas LR recordings at these locations demonstrated fast activation. CONCLUSIONS: High- and low-resolution optical mapping produced radically different patterns of shock-induced polarization and activation. The occurrence of positive and negative polarizations during plateau and diastolic shocks at high but not low resolution provides evidence for microscopic nature of IVE in LV wall.

Animals↗

PubMed2006

Studying cellular architecture in three dimensions with improved resolution: Ta replicas revisited.

Metal replicas have been used for surface analysis of biological structures with a variety of spatial resolutions. Platinum (Pt) has been the metal of choice because it provides very stable replicas and images of high contrast. Some other metals, such as tantalum (Ta) have been reported to provide better resolution on isolated macromolecular complexes and cellular structures. Our goal is to study the gain in detail with Ta and to evaluate if it provides enough detail and resolution to assist in the study of complex volumes of intact cellular structures obtained by methods that reach molecular resolution. To this purpose Pt and Ta replicas of cellular structures and viruses have been studied by transmission electron microscopy (TEM). Replicas of Ta show new details on the surface of two types of isolated viral particles such as 100 nm bunyaviruses and large, > 300 nm, vaccinia virus (VV). Inside cells, the structural pieces that build VV immature particles are visualized only in Ta replicas. Looking for smaller intracellular complexes, new details are also seen in nuclear pores from Ta replicas. Additional masses, most likely representing the cargo during transport, are distinguished in some of the pores. Visualization of proteins in plasma membranes strongly suggests that detail and resolution of Ta replicas are similar to those estimated for 3D maps currently obtained by electron tomography of viruses and cells.

Animals↗

PubMed2005

Use of vancomycin chiral stationary phase for the enantiomeric resolution of basic and acidic compounds by nano-liquid chromatography.

In this paper we studied the potentiality of nano-liquid chromatography (nano-LC) for the enantiomeric resolution of both basic and acidic compounds of pharmaceutical interest using a vancomycin modified silica stationary phase. Experiments were carried out in a fused silica capillary of 75 microm I.D. packed with chiral modified silica particles of 5 microm diameter, the detection, was done on-line at 195 nm. Enantiomeric resolution of alprenolol, atenolol, metoprolol, oxprenolol, pindolol, propranolol (basic compounds) and some acidic analytes, namely 2-[(5'-benzoyl-2'-hydroxy)phenyl]propionic acid (DF1738Y), 2-[(4'-benzoyloxy-2'-hydroxy)phenyl]propionic acid (DF1770Y), ketoprofen, indoprofen and suprofen was studied by nano-LC utilizing mobile phases containing methanol-acetonitrile-ammonium formate or acetate. The effect of mobile phase composition (buffer type and concentration, organic modifier type and concentration) on chiral resolution (Rs), retention factor (k) and retention time (tR) was also investigated. Good enantiomeric resolution was achieved for basic compounds utilizing the mobile phase containing 90% (MeCN-MeOH)/5% water/5% of 100 mM ammonium acetate pH 4.5. Acidic compounds such as DF1738Y and DF1770Y were better resolved at lower pH 3.5 while ketoprofen, indoprofen and suprofen exhibited the highest resolution at pH 4.5; in this case the mobile phase contained MeOH or MeCN (90%), 5% buffer and 5% of water. The nano-LC method was validated using R-(+)-propranolol as an internal standard finding good repeatability, detection limit, correlation coefficient and recovery and applied to the assay of a pharmaceutical formulation containing a racemic mixture of metoprolol.

Adrenergic beta-Antagonists↗

PubMed2005

Resolution of beta-blockers on a chiral stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid: unusual temperature effect.

A chiral stationary phase (CSP) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid has been successfully employed in the liquid chromatographic resolution of eleven beta-blockers containing a secondary amino functional group. As the result of an effort to find out the optimal mobile phase condition, the mixture of trifluoroacetic acid-triethylamine-ethanol-acetonitrile with the ratio of 0.1/0.5/20/80 (v/v/v/v) was concluded to be the best mobile phase condition, the separation (alpha) and the resolution factors (Rs) for the resolution of 11 beta-blockers being in the range of 1.13-1.85 and 1.36-5.79, respectively. Surprisingly, in contrast to the resolution of other racemic compounds containing a primary amino functional group, the separation factors (alpha) for the resolution of beta-blockers were observed to improve as the column temperature increased and these unusual chromatographic behaviors were rationalized as the entropically controlled enantioselectivity.

Adrenergic beta-Antagonists↗

PubMed2005

From micro to nano: recent advances in high-resolution microscopy.

Improving the spatial resolution of optical microscopes is important for a vast number of applications in the life sciences. Optical microscopy allows intact samples and living cells to be studied in their natural environment, tasks that are not possible with other microscopy methods (e.g. electron microscopy). Major advances in the past two decades have significantly improved microscope resolution. By using interference and structured light methods microscope resolution has been improved to approximately 100 nm, and with non-linear methods a ten times improvement has been demonstrated to a current resolution limit of approximately 30 nm. These methods bring together old theoretical concepts such as interference with novel non-linear methods that improve spatial resolution beyond the limits that were previously assumed to be unreachable.

Image Enhancement↗

PubMed2006

Image quality performance of liquid crystal display systems: influence of display resolution, magnification and window settings on contrast-detail detection.

The aim of this study was to investigate the combined effects of liquid crystal display (LCD) resolution, image magnification and window/level adjustment on the low-contrast performance in soft-copy image interpretation in digital radiography and digital mammography. In addition, the effect of a new LCD noise reduction mechanism on the low-contrast detectability was studied. Digital radiographs and mammograms of two dedicated contrast-detail phantoms (CDRAD 2.0 and CDMAM 3.4) were scored on five LCD devices with varying resolutions (1-3- and 5-megapixel) and one dedicated 5-megapixel cathode ray tube monitor. Two 5-megapixel LCDs were included. The first one was a standard 5-megapixel LCD and the second had a new (Per Pixel Uniformity) noise reduction mechanism. A multi-variate analysis of variance revealed a significant influence of LCD resolution, image magnification and window/level adjustment on the image quality performance assessed with both the CDRAD 2.0 and the CDMAM 3.4 phantoms. The interactive adjustment of brightness and contrast of digital images did not affect the reading time, whereas magnification to full resolution resulted in a significantly slower soft-copy interpretation. For digital radiography applications, a 3-megapixel LCD is comparable with a 5-megapixel CRT monitor in terms of low-contrast performance as well as in reading time. The use of a 2-megapixel LCD is only warranted when radiographs are analysed in full resolution and when using the interactive window/level adjustment. In digital mammography, a 5-megapixel monitor should be the first choice. In addition, the new PPU noise reduction system in the 5-megapixel LCD devices provides significantly better results for mammography reading as compared to a standard 5-magapixel LCD or CRT. If a 3-megapixel LCD is used in mammography setting, a very time-consuming magnification of the digital mammograms would be necessary.

Analysis of Variance↗

PubMed2006

Comparison between high-resolution MRI with a microscopy coil and arthroscopy in triangular fibrocartilage complex injury.

PURPOSE: To determine whether high-resolution magnetic resonance imaging (MRI) could detect injuries to the triangular fibrocartilage complex (TFCC). METHODS: Eleven patients who showed both a positive sign during the ulnocarpal stress test and tenderness at the distal end of the ulna had a high-resolution MRI using a 47-mm diameter microscopy coil. Six regions of the TFCC were investigated for injury: the radial attachment, disc, ulnar attachment of the triangular fibrocartilage (TFC), ulnotriquetral ligament, palmar radioulnar ligament (PRUL), and dorsal radioulnar ligament (DRUL). Arthroscopy was performed subsequently on each patient. RESULTS: For injuries to the radial attachment or the disc of the TFC, a high-resolution MRI showed 100% sensitivity and 100% specificity compared with arthroscopy. In 3 cases in which injury to the ulnar attachment of the TFC was detected with MRI and examination showed a positive piano-key sign and distal radioulnar joint instability, only 1 injury was confirmed with arthrotomy. For MRI diagnosis of an ulnotriquetral ulnolunate attachment injury, the sensitivity was 100% and the specificity was 70%; however, 3 cases had false-positive results. Finally MRI had 100% sensitivity for detecting DRUL and PRUL injuries, although specificities were 75% and 83%, respectively. With MRI there were 2 false-positive DRUL injury diagnoses and 1 false-positive PRUL injury diagnosis. CONCLUSIONS: High-resolution MRI using a microscopy surface coil allowed assessment of each TFCC component and showed a higher accuracy for diagnosing injuries to the radial attachment and the disc of the TFC compared with previous studies. High-resolution MRI, however, was not able to diagnose DRUL, PRUL, or ulnolunate ligament injuries accurately. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.

Adolescent↗

PubMed2004

A Structural-informatics approach for tracing beta-sheets: building pseudo-C(alpha) traces for beta-strands in intermediate-resolution density maps.

We report the development of two computational methods to assist density map interpretation at intermediate resolutions: sheettracer for building pseudo-C(alpha) models of beta-sheets, and a deconvolution method for enhancing features attributed to major secondary structural elements. Sheettracer is tightly coupled with sheetminer, which was developed to locate sheet densities in intermediate-resolution density maps. The results from sheetminer are used as inputs to sheettracer, which employs a multi-step ad hoc morphological analysis of sheet densities to trace individual strands of beta-sheets. The methods were tested on simulated density maps from 12 protein crystal structures that represent a reasonably complete sampling of sheet morphology. The sheet-tracing results were quantitatively assessed in terms of sensitivity, specificity and rms deviations. Furthermore, sheettracer and the deconvolution method were rigorously tested on experimental maps of the lambda2 protein of reovirus at resolutions of 7.6A and 11.8A. Our results clearly demonstrate the capability of sheettracer in building pseudo-C(alpha) models of beta-sheets in intermediate-resolution density maps and the power of the deconvolution method in enhancing the performance of sheettracer. These computational methods, along with other related ones, should facilitate recognition and analysis of folding motifs from experimental data at intermediate resolutions.

Algorithms↗

PubMed2006

Monocyte recruitment in venous thrombus resolution.

OBJECTIVE: To investigate the importance of monocyte recruitment in thrombus resolution and the role of cysteine-cysteine (CC) chemokines and the CC chemokine receptor, CCR2, in this process. METHODS: Peritoneal macrophages, monocyte chemotactic protein 1 (MCP1), or carrier solutions were injected into thrombi induced in the vena cava of rats. Caval thrombi were also formed in CCR2-/- and MCP1-/- mice and in wild-type mice transfected with an adenoviral construct expressing a broad-spectrum CC receptor antagonist. RESULTS: Direct administration of peritoneal macrophages decreased thrombus size by more than fivefold and increased recanalization by more than fourfold compared with controls (P < .001). A 100-ng MCP1dose reduced thrombus size by more than sixfold (P < .01) and increased recanalization by more than sevenfold (P < .01), without affecting macrophage recruitment. Deletion of CCR2 or blockade of all CC chemokines inhibited both monocyte recruitment (P < .05) and thrombus resolution (P < .01), but knocking out MCP-1 had no effect. CONCLUSION: Increasing macrophage numbers in the thrombus enhances its resolution. MCP1 treatment enhances resolution by stimulating recanalization, independent of an effect on monocyte recruitment. CCR2 deficiency has the same effect as blockade of all CC chemokines. CCR2 receptor activation may therefore be an important mechanism in monocyte recruitment into venous thrombi and could be targeted to promote their resolution.

Animals↗