SEARCH · PubMed Health

Results for “Resolution”

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 1,603 records · Page 89Linked to original sources

PubMed1999

Evaluation of pannus and vascularization of the metacarpophalangeal and proximal interphalangeal joints in rheumatoid arthritis by high-resolution ultrasound (multidimensional linear array).

OBJECTIVE: To evaluate the extent of intraarticular vascularization and pannus formation in metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of patients with rheumatoid arthritis (RA) by high-resolution ultrasound (US). METHODS: A newly developed, high-resolution multidimensional linear array US was utilized to obtain longitudinal and transverse scans of joints with active RA (n = 21), moderately active RA (n = 39), or inactive RA (n = 93), and of joints from healthy controls (n = 120). RESULTS: Healthy joints had no detectable pannus, whereas pannus could be detected in 52% of the joints with active RA, 82% of the joints with moderately active RA, and 67% of the joints with inactive RA. There was a significant difference in vascularization in the joints of all subgroups of RA patients and those of healthy subjects (P < 0.001). Moreover, vascularization differed significantly among the RA subgroups: inactive versus moderately active RA (P < 0.02) and inactive versus active RA (P < 0.05). Both pannus and vascularization appeared to be localized preferentially on the radial side of the joints. CONCLUSION: Evaluation of pannus and the extent of vascularization within the joints of patients with RA by high-resolution US might be helpful in the assessment of disease activity, and thus influence therapeutic strategies.

Adult↗

PubMedDate not supplied

Distribution and movement of membrane-associated platelet glycoproteins: use of colloidal gold with correlative video-enhanced light microscopy, low-voltage high-resolution scanning electron microscopy, and high-voltage transmission electron microscopy.

Scanning electron microscopy (SEM), especially low-voltage (1 KeV) high-resolution SEM, can be used in conjunction with stereo pair high-voltage (1 MeV) transmission electron microscopy (HVEM) of whole spread cells or thick sections effectively to correlate surface structure with internal structure. Surface features such as microvilli, pits, pseudopodia, ruffles, attached virus, and other surface-related morphologic characteristics can be identified using SEM, while underlying cytoskeletal structure and organelle organization can be viewed by HVEM of the same preparation. However, the need to "prepare" cells for electron microscopy precludes observation in the living state. The use of several types of video-enhanced light microscopy (VLM) permits observation of living cells such that certain surface and internal features can be observed at a relatively high level of resolution or detection. Thus, changes in living cells can be followed, and at appropriate times the cells may be chemically fixed or rapidly frozen and prepared for ultrastructural examination by electron microscopy. We have utilized VLM in conjunction with SEM and HVEM to correlate changes in shape and surface structure with changes in the internal structure of platelets. In addition, we have found it advantageous to use colloidal gold-labeling procedures, because these markers are detectable by all three forms of microscopy. Using this approach we have labeled platelet membrane GPIIb/IIIa, a receptor for RGD-containing adhesive proteins, with gold-fibrinogen or gold-anti-IIb/IIIa. The initial binding and subsequent movement of gold-fibrinogen-IIb/IIIa complexes in living platelets was followed by VLM. The movement of individual labels could be mapped. Subsequent observation by low-voltage (1 KeV) high-resolution SEM and HVEM permits visualization of the same individual receptors tracked by LM. The final position on the membrane or the position-in-transit when fixative was added was determined relative to surface ultrastructure (SEM) and internal, particularly cytoskeletal, ultrastructure (HVEM).

Biological Transport↗

PubMed1993

Banding resolution of human chromosomes: a method of accuracy and simplicity.

Methods of estimating chromosome band resolution have been published but their accuracy has not been established. Banding resolution was determined by 4 methods which included a computerized linear correlation, the sum of bands on chromosomes 1 and 2, interpolation of the number of bands on chromosome 10, and interpolation of the number of bands on chromosomes 1p, 10, 11p, 12q, and X. The sum of bands on chromosomes 1 and 2 multiplied by 6 is the most accurate and simple. The use of a simple and reliable method is important for cytogenetic laboratories to document quality assurance of routine chromosome analyses, to enhance the exchange of information between laboratories, and to establish criteria for appropriate band resolution for specific types of specimens.

Chromosome Banding↗

PubMed1994

Comparison of high resolution chromosome banding and fluorescence in situ hybridization (FISH) for the laboratory evaluation of Prader-Willi syndrome and Angelman syndrome.

The development of probes containing segments of DNA from chromosome region 15q11-q13 provides the opportunity to confirm the diagnosis of Prader-Willi syndrome (PWS) and Angelman syndrome (AS) by fluorescence in situ hybridization (FISH). We have evaluated FISH studies and high resolution chromosome banding studies in 14 patients referred to confirm or rule out PWS and five patients referred to confirm or rule out AS. In four patients (three from the PWS category and 1 from the AS group) chromosome analysis suggested that a deletion was present but FISH failed to confirm the finding. In one AS group patient, FISH identified a deletion not detectable by high resolution banding. Review of the clinical findings in the discrepant cases suggested that the FISH results were correct and high resolution findings were erroneous. Studies with a chromosome 15 alpha satellite probe (D15Z) on both normal and abnormal individuals suggested that incorrect interpretation of chromosome banding may occasionally be attributable to alpha satellite polymorphism but other variation of 15q11-q13 chromosome bands also contributes to misinterpretation. We conclude that patients who have been reported to have a cytogenetic deletion of 15q11-q13 and who have clinical findings inconsistent with PWS and AS should be re-evaluated by molecular genetic techniques.

Angelman Syndrome↗

PubMed2002

Assessing the accuracy of high-resolution X-ray computed tomography of primate trabecular bone by comparisons with histological sections.

Different lines of evidence suggest that trabecular bone architecture contains a functional signal related to an organism's locomotor behavior. An understanding of the interspecific and intraspecific variation in extant nonhuman primate trabecular structure is needed to evaluate its usefulness as a tool to reconstruct the locomotor habits of extinct primates. High-resolution X-ray computed tomography (HRXCT) is a new imaging approach with a resolution in the tens of microns that allows nondestructive access to the internal structure of bony elements. Previous studies indicate that such resolution is necessary to accurately quantify structural parameters of trabecular bone. The primary goal of this study was to test the accuracy of HRXCT by comparing stereological measurements from HRXCT images and histological thin sections of cancellous bone taken from the proximal femur and humerus of baboons. To this end, 11 bone samples were scanned on an HRXCT scanner and then thin-sectioned to reveal the scanned plane. HRXCT images were thresholded using a modified half-maximum height protocol. The stereological measurements included bone volume fraction (BV/TV), trabecular number (Tb.N), bone surface to volume ratio (BS/BV), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp). The measurement errors on the HRXCT images were 10.90% for BV/TV, 6.06% for Tb.N, 14.19% for BS/BV, 14.33% for Tb.Th, and 7.09% for Tb.Sp, but none of these measurements were significantly different from the histological standards (alpha = 0.05). A second goal of this study was to examine the influence of thresholding, a necessary step in any morphometric study using computed tomography, on the accuracy of the quantitative morphometry. Threshold values derived from a modified half-maximum height protocol showed that parameters derived from the region of interest (area in which stereological measurements were later taken) produced better reconstructions of the actual bone structure than threshold values derived from more inclusive areas of bone. We conclude that HRXCT can accurately reconstruct the complex architecture of trabecular bone, and that thresholding is a nontrivial step in trabecular bone studies, with even slight changes in the protocol greatly affecting the morphometric data. HRXCT represents a valuable analytical tool that should be of interest to a great many researchers in physical anthropology because it allows nondestructive access to internal morphology, thereby preserving valuable and limited skeletal collections.

Animals↗

PubMed2002

Diffuse signal abnormalities in the spinal cord in multiple sclerosis: direct postmortem in situ magnetic resonance imaging correlated with in vitro high-resolution magnetic resonance imaging and histopathology.

In this study, we compared direct postmortem in situ (whole-corpse) sagittal spinal cord magnetic resonance imaging (1.5T) of 7 multiple sclerosis cases with targeted high-resolution in vitro axial magnetic resonance imaging (4.7T) and histopathology. On sagittal in situ magnetic resonance imaging, 1 case had a normal spinal cord, 2 had only focal lesions, 3 had a combination of focal and diffuse abnormalities, and 1 had only diffuse abnormalities. All spinal cords showed abnormalities on high-resolution magnetic resonance imaging and histopathology, confirming the existence of diffuse cord changes as genuine multiple sclerosis-related abnormalities while highlighting the limited resolution of in vivo magnetic resonance imaging.

Aged↗

PubMed1992

Utility of high-resolution ultrasound for the diagnosis of dialysis-related amyloidosis.

OBJECTIVE: To evaluate the utility of real-time, high-resolution ultrasound of the shoulder in the diagnosis of dialysis-related amyloidosis. METHODS: We performed a case series study of 2 groups of patients seen at a referral-based clinic in a tertiary care hospital. The shoulders of 13 patients with normal renal function and of 38 patients receiving long-term hemodialysis were studied by real-time, high-resolution ultrasound. All hemodialysis patients were evaluated clinically for the presence of dialysis-related amyloidosis. Surgical specimens of joints were available for all 13 patients with normal renal function and for 17 of the 38 hemodialysis patients. These specimens were evaluated for the presence of beta 2-microglobulin (beta 2m) amyloid by Congo red and immunohistochemical staining. RESULTS: Two ultrasonographic findings were selectively observed in the dialysis patients with clinical and histologic evidence of beta 2m amyloid in comparison with patients with normal renal function and no evidence of amyloid: rotator cuffs greater than 8 mm in thickness and echogenic pads between muscle groups of the rotator cuff. The presence of at least 1 of these 2 findings corresponded to the presence of clinically and histologically evident beta 2m amyloid with a sensitivity of 79% and a specificity of 100%. When additional patients without surgical specimens for histologic confirmation of amyloidosis were included, the sensitivity of these 2 sonographic findings was 72% and the specificity was 97%. CONCLUSION: Real-time, high-resolution ultrasound is a relatively sensitive and highly specific noninvasive adjunct to the clinical diagnosis of beta 2m amyloidosis in patients receiving long-term hemodialysis.

Adult↗

PubMed2005

High-resolution magnetic resonance imaging for the assessment of hand osteoarthritis.

OBJECTIVE: To investigate the use of a novel surface coil for clinically utilized magnetic resonance imaging (MRI) scanners, in order to describe the microanatomic basis for hand osteoarthritis (OA) at all stages of disease. METHODS: MRI of proximal or distal interphalangeal joints was performed in 58 subjects: 16 patients with early OA (symptom duration < or =12 months), 14 patients with chronic OA, 10 patients with clinically normal asymptomatic joints adjacent to arthritic joints, and 18 normal controls. High-resolution images were obtained with displayed pixel dimensions of 80-100 mum using a 1.5T scanner and a 23-mm-diameter surface coil. All joint structures were evaluated. RESULTS: The high-resolution images of every joint structure showed comparable abnormalities in both early and chronic OA, including cartilage loss, bone edema, synovial enhancement, osteophytosis, and erosions. Heberden's and Bouchard's node formation occurred at regions where soft tissue bulged through the capsule between the dorsal tendons and collateral ligaments (CLs). Prominent CL thickening or disruption (100% of OA patients) was evident even in joints where cartilage was partially preserved. Clinically normal joints adjacent to OA hand joints showed thickening and enhancement of CLs which was the most common abnormality seen (80% of OA patients). Older normal subjects showed subtle changes within the CLs. CONCLUSION: Obtaining high-resolution MR images from clinically utilized scanners represents a novel way for exploring the microanatomic basis of hand arthritis and may have considerable potential in the clinical setting. In the present evaluation in nodal OA, previously unappreciated CL abnormalities were especially common.

Aged↗

PubMed2004

Rapid high resolution three dimensional reconstruction of embryos with episcopic fluorescence image capture.

One of the overarching goals in developmental biology is the elucidation of mechanisms that elaborate form and function. To this end, an accurate morphological description of embryonic development is essential. However, visualizing dynamic changes in the three-dimensional (3D) structure of the developing embryo has been a "holy grail" in the field of developmental biology. The fundamental difficulties that have hindered all efforts in 3D reconstruction using two-dimensional (2D) image stacks revolve around the seemingly intractable problems of section registration and distortion. A remarkably simple solution has come about with the development of a new technique referred to as episcopic fluorescence image capture (EFIC). With EFIC imaging, tissue autofluorescence is used to image the block face prior to cutting each section. The 2D resolution obtained is close to that achieved by histology, and such 2D image stacks can be readily reconstructed in 3D. The 3D models generated provide fine structural details with resolution unmatched by 3D reconstructions obtained with any other imaging modalities. Given the perfect registration of EFIC image stacks, another important capability provided by EFIC is digital resectioning in any plane. This provides complete flexibility in the selection of optimal virtual sectioning planes for viewing different features in a specimen, and is invaluable for analyzing dynamic changes in tissue structure in the developing embryo. The capabilities provided by EFIC for rapid high resolution 3D reconstruction together with digital resectioning make this an unparalleled tool for characterizing morphogenetic events in the developing embryo. Although our review is focused on using EFIC for studying embryonic development, it is important to note that there is no intrinsic limitation on the size of the specimen that can be analyzed by EFIC imaging. Overall, EFIC should serve as an important imaging technique that will complement other 3D imaging modalities such as MRI and optical tomography. Given the feasibility of generating EFIC image stacks using cryoembedded or polyethylene glycol (PEG)-embedded specimens, there is the possibility that EFIC may be combined with 3D RNA or protein expression profiling. Together, such studies may help further elucidate the relationship between form and function.

Animals↗

PubMed2001

Kinetic resolution of chiral amines with omega-transaminase using an enzyme-membrane reactor.

A kinetic resolution process for the production of chiral amines was developed using an enzyme-membrane reactor (EMR) and a hollow-fiber membrane contactor with (S)-specific omega-transaminases (omega-TA) from Vibrio fluvialis JS17 and Bacillus thuringiensis JS64. The substrate solution containing racemic amine and pyruvate was recirculated through the EMR and inhibitory ketone product was selectively extracted by the membrane contactor until enantiomeric excess of (R)-amine exceeded 95%. Using the reactor set-up with flat membrane reactor (10-mL working volume), kinetic resolutions of alpha-methylbenzylamine (alpha-MBA) and 1-aminotetralin (200 mM, 50 mL) were carried out. During the operation, concentration of ketone product, i.e., acetophenone or alpha-tetralone, in a substrate reservoir was maintained below 0.1 mM, suggesting efficient removal of the inhibitory ketone by the membrane contactor. After 47 and 32.5 h of operation using 5 U/mL of enzyme, 98.0 and 95.5% ee of (R)-alpha-MBA and (R)-1-aminotetralin were obtained at 49.5 and 48.8% of conversion, respectively. A hollow-fiber membrane reactor (39-mL working volume) was used for a preparative-scale kinetic resolution of 1-aminotetralin (200 mM, 1 L). After 133 h of operation, enantiomeric excess reached 95.6% and 14.3 g of (R)-1-aminotetralin was recovered (97.4% of yield). Mathematical modeling of the EMR process including the membrane contactor was performed to evaluate the effect of residence time. The simulation results suggest that residence time should be short to maintain the concentration of the ketone product in EMR sufficiently low so as to decrease conversion per cycle and, in turn, reduce the inhibition of the omega-TA activity.

Amines↗

PubMed2001

Mass-transfer limitations for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor.

A mathematical model has been developed for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor in which the enzyme-catalyzed reaction (the irreversible uni-uni competitive Michaelis-Menten kinetics is chosen as an example) was coupled with intraparticle diffusion, external mass transfer, and axial dispersion. The effects of mass-transfer limitations, competitive inhibition of substrates, deactivation on the enzyme effective enantioselectivity, and the optical purity and yield of the desired product are examined quantitatively over a wide range of parameters using the orthogonal collocation method. For a first-order reaction, an analytical solution is derived from the mathematical model for slab-, cylindrical-, and spherical-enzyme supports. Based on the analytical solution for the steady-state resolution process, a new concise formulation is presented to predict quantitatively the mass-transfer limitations on enzyme effective enantioselectivity and optical purity and yield of the desired product for a continuous steady-state kinetic resolution process in a fixed-bed reactor.

Bioreactors↗

PubMed2006

A kinetic study of lipase-catalyzed reversible kinetic resolution involving verification at miniplant-scale.

Lipase-catalyzed kinetic resolution of racemates is a popular method for synthesis of chiral synthons. Most of these resolutions are reversible equilibrium limited reactions. For the first time, an extensive kinetic model is proposed for kinetic resolution reactions, which takes into account the full reversibility of the reaction, substrate inhibition by an acyl donor and an acyl acceptor as well as alternative substrate inhibition by each enantiomer. For this purpose, the reversible enantioselective transesterification of (R/S)-1-methoxy-2-propanol with ethyl acetate catalyzed by Candida antarctica lipase B (CAL-B) is investigated. The detailed model presented here is valid for a wide range of substrate and product concentrations. Following model discrimination and the application of Haldane equations to reduce the degree of freedom in parameter estimation, the 11 free parameters are successfully identified. All parameters are fitted to the complete data set simultaneously. Six types of independent initial rate studies provide a solid data basis for the model. The effect of changes in substrate and product concentration on reaction kinetics is discussed. The developed model is used for simulations to study the behavior of reaction kinetics in a fixed bed reactor. The typical plot of enantiomeric excess versus conversion of substrate and product is evaluated at various initial substrate mixtures. The model is validated by comparison with experimental results obtained with a fixed bed reactor, which is part of a fully automated state-of-the-art miniplant.

Enzymes, Immobilized↗

PubMedDate not supplied

Resolution of enantiomers of amino acids by HPLC.

Application of HPLC as a prime tool in the area of enantiomeric resolution has opened doors of success and varied interest. Use of chiral reagents either indirectly (as derivatization reagent) or directly (added to stationary or mobile phase) has led to achieve resolution of a wide range of compounds. Amino acids, being important molecules with simple structure and easy availability, have been extensively studied. A bibliographic survey on HPLC resolution of amino acids and derivatives along with a brief discussion on general methods of enantiomeric separation has been presented.

Amino Acids↗

PubMed2005

The factors that influence the elution order for the resolution of amino acids on vancomycin phase using the polar-organic mobile phases after their pre-column derivatization with electrophilic reagents.

A variety of amino acids were enantioresolved on a vancomycin bonded chiral phase using the polar-organic mobile phases after their pre-column derivatization with electrophilic reagents in alkaline medium. The resolution was highly dependent on the analyte's structure and was enhanced as the aromatic side-chain group on the skeleton of analyte for pi-pi interaction with the chiral selector became available. The steric hindrance resulting from the bulky side-chain group on the analyte also affected the resolution. Elution reversal, not found on the teicoplanin phase under the same chromatographic conditions, was possible through altering the type of reagent used in the derivatizing reaction (e.g. 2,4-difluorophenylisothiocyanate to 2,4-difluorophenylisocyanate). It is believed that the steric hindrance, as a result of the bulky sulfur atom in reagents such as methylisothiocyanate and others examined in this study, was responsible for the reversed elution order. The bulkiness of the substituent on the aromatic ring of derivatizing reagents (i.e. 2,3- and 3,5-dichlorophenylisothiocyanate) was observed to affect the resolution and alter the elution order as well.

Amino Acids↗

PubMed2001

Direct resolution of (+/-)-ephedrine and atropine into their enantiomers by impregnated TLC.

Direct resolution of (+/-)-ephedrine and atropine into their enantiomers was achieved by normal-phase thin layer chromatography on silica gel plates impregnated with optically pure L-tartaric acid and L-histidine, respectively, as chiral selectors. The mobile phases enabling successful resolution were different combinations of acetonitrile-methanol-water. The spots were detected with iodine vapours and the detection limits were 2 and 6 microg, respectively, in terms of the racemate. The effects of concentration of the impregnating reagent, temperature and pH on resolution have been studied.

Acetonitriles↗

PubMed1978

Use of a time averaging computer for high resolution field desorption mass spectrometry.

Field desorption mass spectra often contain few peaks, the largest of which are [M]+. and [M+H]+ ions. Because of this lack of fragmentation accurate mass measurement is of primary concern in field desorption mass spectrometry. Although total ion yield per quantity of sample may rival electron impact or chemical ionization methods, ion yield per unit time is low. For this reason and because of varying [M]+./[M+H]+ ratios, elemental compositions as determined from stable isotope peaks are difficult to obtain. Low ion yield per unit time demands an integrating method for best high resolution results. The use of photoplates to obtain high resolution field desorption data is the only method reported thus far which takes advantage of integrating capability. This paper describes the use of a time averaging computer as an integrator for peak matching high resolution field desorption mass spectrometry using electrical detection. Accuracies better than 20 ppm are consistently obtained. Due to the sensitivity of the technique a wider range of reference compounds can be employed. This method incorporates the advantages of integrating capability with electrical detection, overcoming detection sensitivity problems associated with photoplates.

Adenosine↗

PubMed1991

The characterization of synthetic by-products by B/E linked scanning and high-resolution thermospray mass spectrometry.

Characterization of unknown synthetic by-products from a test synthesis of the experimental inhibitor of HIV-1 reverse transcriptase, BI-RG-587, is presented. Seven impurities were separated and characterized by thermospray liquid chromatography/mass spectrometry using low-resolution, high-resolution, and B/E linked scanning methods. The high-resolution mass measurements which were obtained were accurate to within 10 ppm of structures proposed for synthetic by-products present at the 0.1% level. Linked scans produced daughter ion spectra for each impurity to further aid in the characterization.

Antiviral Agents↗

PubMed2005

High-resolution 8 Tesla imaging of the formalin-fixed normal human hippocampus.

The purpose of this study was to evaluate the capacity of high-resolution magnetic resonance imaging (MRI) to visualize the normal anatomic features of the human hippocampus in vitro, using high field imaging equipment, parameters, and acquisition times appropriate for imaging human subjects in vivo. This research compared high field, high-resolution MRI of formalin-fixed normal human hippocampus specimens to histologic sectioning of the same hippocampus samples. Four specimens were evaluated using an 8 Tesla (T), 80 cm bore whole-body MRI scanner equipped with a 12.7 cm single strut transverse electromagnetic resonator (TEM) coil. Hahn spin echo images were acquired with a repetition time (TR) of 800 msec, echo times (TE) of 20, 50, 90, and 134 msec, and an acquisition time (TA) of 3.25 min. The image quality was superb with demonstration of most of the features of the hippocampus. High field, high-resolution MRI can be used to depict multiple layers of the formalin-fixed human hippocampus in vitro using an 8 T whole-body scanner, a TEM coil, and short acquisition times compatible with human imaging in vivo.

Aged↗