Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “data resolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,009 records · Page 56Linked to original sources
PubMed2001

Direct identification of patency achieved by a bi-directional Glenn shunt procedure: images by volume rendering using electron-beam computed tomography.

The present study aimed to identify the patency achieved by a bi-directional Glenn shunt procedure by shaded volume rendering (VR) images using electron-beam computed tomography (EBCT). A Damus Kay-Stanzel type procedure was performed on a female with hypoplastic left heart syndrome who later received a bi-directional Glenn shunt to increase pulmonary blood flow. In considering the characteristics of the bi-directional Glenn shunt procedure, in which the superior vena cava is connected to the right pulmonary artery, an early phase acquisition protocol with injection of contrast material from the right cubital vein using the step volume scan mode of EBCT was planned to acquire blood flow information. Excellent spatial resolution volume data of the heart and great vessels was obtained from which 3-dimensional images were made. Bi-directional Glenn shunt flow could be observed directly and the complex morphology and relationships between adjacent structures were revealed by 3-dimensional VR imaging. The combination of EBCT and VR can provide useful information to evaluate congenital heart diseases.

Adult↗
PubMed2005

Aspects of computer-aided detection (CAD) and volumetry of pulmonary nodules using multislice CT.

With the superb spatial resolution of modern multislice CT scanners and their ability to complete a thoracic scan within one breath-hold, software algorithms for computer-aided detection (CAD) of pulmonary nodules are now reaching high sensitivity levels at moderate false positive rates. A number of pilot studies have shown that CAD modules can successfully find overlooked pulmonary nodules and serve as a powerful tool for diagnostic quality assurance. Equally important are tools for fast and accurate three-dimensional volume measurement of detected nodules. These allow monitoring of nodule growth between follow-up examinations for differential diagnosis and response to oncological therapy. Owing to decreasing partial volume effect, nodule volumetry is more accurate with high resolution CT data. Several studies have shown the feasibility and robustness of automated matching of corresponding nodule pairs between follow-up examinations. Fast and automated growth rate monitoring with only few reader interactions also adds to diagnostic quality assurance.

Diagnosis, Differential↗
PubMed2004

Fine surface structure of bovine acrosome-intact and reacted spermatozoa observed by atomic force microscopy.

The atomic force microscope (AFM) provides nanometer resolution, topographic data of the natural surface structure of materials. We studied the topology of the surface structure of bovine sperm heads during the acrosome reaction by AFM. In addition, we numerically analyzed the areas of the median sagittal plane of the sperm heads. Bovine frozen-thawed spermatozoa were washed, capacitated by heparin, and incubated with lysophosphatidylcholine (LPC) to induce the acrosome reaction, smeared on a cover glass, air-dried, and observed with AFM using the dynamic force (tapping) mode. AFM analysis of spermatozoa showed the clear surface structure of acrosomes, equatorial segments, postacrosomal regions and necks. Although AFM images of spermatozoa capacitated by heparin had complete acrosomes, most spermatozoa treated with LPC had no acrosomal caps as shown by AFM. These observations coincided with those obtained by light microscopy after staining with naphthol yellow S and erythrosin B. Furthermore, numerical analysis of AFM images indicated that areas of the median sagittal plane of the anterior portions of acrosome-reacted sperm heads (2679 +/- 616 pixels) were approximately 40% less than those of intact heads (4535 +/- 174 pixels, P<0.05). These results indicate that AFM can usefully observe and numerically analyze the fine surface structures of bovine spermatozoa.

Acrosome↗
PubMed2002

Volume image reconstruction for diffuse optical tomography.

Optical tomography is a potential diagnostic method for visualizing optical properties of tissues in vivo. We present an optical tomography method that has been designed for imaging of the human testes, particularly for spectroscopic tumor differentiation. In this application we need to compute three-dimensional distributions of the optical contrast (absorption coefficient) in the tissue in real time. Thus we have given special care to elaborate an efficient inverse algorithm that takes the limitations of spatial resolution and data space point density into account. Our inverse solution is based on a linearization approach and a dedicated object space discretization. Furthermore, we introduce the concept of fuzzy voxels, which enables a reconstruction-inherent image smoothing.

Algorithms↗
PubMed2003

Optical polarization singularities and elliptic stationary points.

Polarization singularities and elliptic stationary points (collectively, elliptic critical points) were measured experimentally via the complex Stokes field S1 + iS2, where S1 and S2 are Stokes parameters. This new, easily implemented method yielded detailed, high-resolution experimental data for all elliptic critical points. These data confirm with high precision the elliptic-field topological sign rule, loop rules, and Stokes singularity relations introduced recently.

Journal Article↗
PubMed2007

Characterizing protein folding transition States using Psi-analysis.

We discuss the implementation of Psi-analysis for the structural characterization of protein folding transition states. In Psi-analysis, engineered bi-histidine metal ion binding sites are introduced at surface positions to stabilize secondary and tertiary structures. The addition of metal ions stabilizes the interaction between the two known histidines in a continuous fashion. Measuring the ratio of transition state stabilization to that of the native state provides information about the presence of the metal binding site in the transition state. Psi-Analysis uses noninvasive surface mutations and does not require specialized equipment, so it can be readily applied to characterize the folding of many proteins. As a result, this method can provide a wealth of high-resolution quantitative data for comparison with theoretical folding simulations. Additionally, investigations of other biological processes also may utilize metal binding sites and Psi-analysis to detect conformational events during catalysis, assembly, and function.

Binding Sites↗
PubMed2004

QM/MM study of energy storage and molecular rearrangements due to the primary event in vision.

The energy storage and the molecular rearrangements due to the primary photochemical event in rhodopsin are investigated by using quantum mechanics/molecular mechanics hybrid methods in conjunction with high-resolution structural data of bovine visual rhodopsin. The analysis of the reactant and product molecular structures reveals the energy storage mechanism as determined by the detailed molecular rearrangements of the retinyl chromophore, including rotation of the (C11-C12) dihedral angle from -11 degrees in the 11-cis isomer to -161 degrees in the all-trans product, where the preferential sense of rotation is determined by the steric interactions between Ala-117 and the polyene chain at the C13 position, torsion of the polyene chain due to steric constraints in the binding pocket, and stretching of the salt bridge between the protonated Schiff base and the Glu-113 counterion by reorientation of the polarized bonds that localize the net positive charge at the Schiff-base linkage. The energy storage, computed at the ONIOM electronic-embedding approach (B3LYP/6-31G*:AMBER) level of theory and the S0-->S1 electronic-excitation energies for the dark and product states, obtained at the ONIOM electronic-embedding approach (TD-B3LYP/6-31G*//B3LYP/6-31G*:AMBER) level of theory, are in very good agreement with experimental data. These results are particularly relevant to the development of a first-principles understanding of the structure-function relations in prototypical G-protein-coupled receptors.

Animals↗
PubMed2005

Membrane thinning due to antimicrobial peptide binding: an atomic force microscopy study of MSI-78 in lipid bilayers.

The interaction of an antimicrobial peptide, MSI-78, with phospholipid bilayers has been investigated using atomic force microscopy, circular dichroism, and nuclear magnetic resonance (NMR). Binding of amphipathic peptide helices with their helical axis parallel to the membrane surface leads to membrane thinning. Atomic force microscopy of supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers in the presence of MSI-78 provides images of the membrane thinning process at a high spatial resolution. This data reveals that the membrane thickness is not reduced uniformly over the entire bilayer area. Instead, peptide binding leads to the formation of distinct domains where the bilayer thickness is reduced by 1.1 +/- 0.2 nm. The data is interpreted using a previously published geometric model for the structure of the peptide-lipid domains. In this model, the peptides reside at the hydrophilic-hydrophobic boundary in the lipid headgroup region, which leads to an increased distance between lipid headgroups. This picture is consistent with concentration-dependent 31P and 2H NMR spectra of MSI-78 in mechanically aligned DMPC bilayers. Furthermore, 2H NMR experiments on DMPC-d54 multilamellar vesicles indicate that the acyl chains of DMPC are highly disordered in the presence of the peptide as is to be expected for the proposed structure of the peptide-lipid assembly.

Antimicrobial Cationic Peptides↗
PubMed2005

A non-Gaussian distribution quantifies distances measured with fluorescence localization techniques.

When single-molecule fluorescence localization techniques are pushed to their lower limits in attempts to measure ever-shorter distances, measurement errors become important to understand. Here we describe the non-Gaussian distribution of measured distances that is the key to proper interpretation of distance measurements. We test it on single-molecule high-resolution colocalization data for a known distance, 10 nm, and find that it gives the correct result, whereas interpretation of the same data with a Gaussian distribution gives a result that is systematically too large.

DNA↗
PubMed2001

High-resolution spectra of bromo methane and methyl bromide obtained by a continuously tunable 10-bar CO2 laser based photoacoustic spectrometer.

High resolution spectral data of 100 ppmV (10(-6) per volume) concentrations of the trace gases bromo methane (BM, CH3Br), and methyl bromide (DME, (CH3)2O), buffered in synthetic air (80% N2, 20% O2) at atmospheric pressure and room temperature are reported. The spectra are recorded with a continuously tunable 10-bar CO2 laser based photoacoustic (PA) spectrometer. The tuning range covers 76 cm(-1) between 9.2 microm (1087 cm(-1)) and 10.7 microm (935 cm(-1)) at a constant narrow line-width of 0.018 cm(-1) (540 MHz). The non-resonant PA measuring cell employs an in-line 10-microphone array. The estimated detection limits for BM and DME are approximately 2 ppmV for a signal-to-noise ratio (SNR) of 3. This corresponds to a calculated detection limit of approximately 76 ppbV for ethylene.

Journal Article↗
PubMed2004

Crystallization and preliminary x-ray analysis of complexes of porcine pancreatic elastase with two natural inhibitors.

Two different natural protease inhibitors, the squash inhibitor MCEI III and the third domain of turkey ovomucoid inhibitor OMTKY3, were crystallized in complexes with porcine pancreatic elastase (PPE). About 700 conditions were screened altogether. Crystals of the complex between MCEI III and PPE were grown in citrate buffer with and without ammonium acetate. X-ray diffraction data were collected to 1.9 angstroms resolution at room temperature using synchrotron radiation. The crystals belong to space group P2(1), with unit-cell parameters a = 49.17, b = 44.59, c = 67.08 angstroms, beta = 110.97 degrees. Crystals of the OMTKY3/PPE complex were obtained in the presence of ammonium sulfate, MES buffer and polyethylene glycol monomethylether (PEG). These crystals of this complex diffracted to 2.1 angstroms resolution and belongs to space group I222, with unit-cell parameters a = 84.58, b = 84.61, c = 89.92 angstroms and diffracted to 2.2 angstroms resolution. The diffraction data were collected using a conventional rotating anode X-ray generator at room temperature. In both cases the presence of inhibitor in the crystals was confirmed by crystallography.

Amino Acid Sequence↗
PubMed2004

New advances in normal mode analysis of supermolecular complexes and applications to structural refinement.

Normal mode analysis is an effective computational method for studying large-amplitude low-frequency molecular deformations that are ubiquitously involved in the functions of biological macromolecules, especially supermolecular complexes. The recent years have witnessed a substantial advance in methodology development in the field. This review is intended to summarize some of the important advances that enable one to simulate deformations of supermolecular complexes at expended resolution- and length-scales, with particular emphasis on the implications in structural refinement against low- to intermediate-resolution structural data such as those from electron cryomicroscopy and fibre diffraction.

Actin Cytoskeleton↗
PubMed2004

Macrolide resistance based on the Erm-mediated rRNA methylation.

Macrolide, lincosamide and streptogramin B (MLSB) antibiotics are extensively used for the treatment of wide variety of clinically important Gram-positive bacteria. MLSB antibiotics inhibit protein biosynthesis by targeting the peptidyl transferase centre within the 50S ribosomal subunit. The most widespread mechanism of bacterial resistance to MLSB antibiotics, reported early after their introduction into clinical practice is the modification of the target site exhibited by a family of rRNA methyltransferases designated Erm. Using S-adenosyl-L-methionine, Erm enzymes catalyze mono- or dimethylation of a specific adenine residue in the 23S rRNA. The methyl group sterically hinders the MLSB binding site and disrupts the hydrogen bonding between the macrolides and the rRNA, thus rendering bacteria resistant. This review summarizes the current understanding of Erm-mediated resistance, in light of high-resolution structural data of bacterial ribosome and with specific focus on the results of recent genetic, biochemical and structural studies of Erm methyltransferases and their cognate rRNA substrate. Although many features of MLSB resistance remain indistinct, the present knowledge can now serve as the guidance for development of both new antimicrobial drugs and potential inhibitors of Erm enzymes, hence providing a new lead to solve the urgent problem of the macrolide resistance based on the ribosome methylation.

Anti-Bacterial Agents↗
PubMedDate not supplied

Audioscan: a high-definition audiometry technique based on constant-level frequency sweeps--a new method with new hearing indicators.

The resolution of data given by traditional fixed-frequency tone audiometry is limited to the number of frequencies tested. Numerical electronics now allow us to bypass the difficulties of controlled-level frequency sweeping. The Audioscan method gives a detailed audiometric curve and is designed to detect even the narrowest notches. The Audioscan method includes the possibility of defining hearing loss indicators containing more information and of increasing the diagnostic power of the audiometry. The applications both in the clinic and in screening are highly promising.

Audiometry↗
PubMedDate not supplied

PACS costs: modelling and simulation.

The advantages to be expected of full-scale PACS implementation are widely described in the literature. In the decision to introduce such systems, costs will also play an important part. The benefits to be achieved should at least outbalance the costs. In this paper the set-up of a software package for cost assessment is described. The configuration requirements have to be determined based on the workload of the radiology department and a PACS model using results of simulation studies. Of course additional user requirements are important input parameters (e.g. number of workstations, screen resolution, etc.). Data on costs of the various configuration components and the expected future trends in these costs will be used to estimate the costs of a specific PACS configuration as a function of time. Savings to be achieved in the various categories of resources will be input (again with their trends) to lead to an overview of the total savings to be expected. The package will result in a graph of the net annual costs as a function of the timing of PACS introduction. In the package a critique module is foreseen that checks whether the data fed into the system are of reasonable agreement with expert opinions.

Computer Simulation↗
PubMed1999

Structural biology of chemokine receptors.

Chemokine receptors are G protein-coupled receptors that mediate migration and activation of leukocytes as an important part of a protective immune response to injury and infection. In addition, chemokine receptors are used by HIV-1 to infect CD4 positive cells. The structural bases of chemokine receptor recognition and signal transduction are currently being investigated. High-resolution X-ray diffraction and NMR spectroscopy of chemokines indicate that all these peptides exhibit a common folding pattern, in spite of its low degree of primary-sequence homology. Chemokines' functional motifs have been identified by mutagenesis studies, and a possible mechanism for receptor recognition and activation is proposed, but high-resolution structure data of chemokine receptors is not yet available. Studies with receptor chimeras have identified the putative extracellular domains as the major selectivity determinants. Single-amino acid substitutions in the extracellular domains produce profound changes in receptor specificity, suggesting that motifs in these domains operate as a restrictive barrier to a common activation motif. Similarly HIV-1 usage of chemokine receptors involve interaction of one or more extracellular domains of the receptor with conserved and variable domains on the viral envelope protein gp 120, indicating a highly complex interaction. Elucidating the structural requirements for receptor interaction with chemokines and with HIV-1 will provide important insights into understanding the mechanisms of chemokine recognition and receptor activation. In addition, this information can greatly facilitate the design of effective immunomodulatory and anti-HIV-1 therapeutic agents.

CD4-Positive T-Lymphocytes↗
PubMed1976

A new 80-lens oscilloscope camera for routine dynamic organ scintigraphy.

A simple, reliable, and cost-effective 80-lens photographic camera records dynamically from the oscilloscope of a scintillation camera without degradation of spatial resolution or data loss. Most physiologic events can be recorded completely and without interruption on a single 9 X 12-cm negative film as 40 sequential time-frames, using one of six available exposures per frame. In addition, 40 simultaneous sequential time-frames of four times the chosen duration may bracket a transient event with increased data density. The 80-lens camera has been used routinely for perfusion scintigraphy of brain, heart, liver, kidneys,and lungs with excellent results.

Aortic Valve Insufficiency↗
PubMed2002

[Simulating photosynthesis and evapotranspiration of winter wheat with a SVAT model].

Two sub-models were added to the developed soil-vegetation-atmosphere transfer model. Of the two sub-models, one was the canopy photosynthesis/stomatal coupled sub-model distinguishing the sun light and shaded leaves, and the second was the simplified growth sub-model considering growth respiration and maintenance respiration. The comparison of measured and simulated daily evapotranspiration showed that the RMSD (root mean standard deviation) of model prediction to observation was 0.65 mm, and MAPD (mean absolute percent difference) was 14%. The daily course of the simulated and measured photosynthesis rates at the top of canopy were in good consistency. With the high-resolution meteorological data, the canopy net photosynthesis and evapotranspiration were simulated over the whole growing season. The sensitivities of maximum leaf area index, environmental CO2 concentration and leaf nitrogen content to evapotranspiration and water use efficiency were also analyzed.

Ecosystem↗