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At least 1,477 records · Page 82Linked to original sources
PubMed1998

Evaluation of a line immunoblot assay for detection of antibodies recognizing extractable nuclear antigens.

Sera (n = 90) giving positive results in a screening test for antibodies to extractable nuclear antigens (ENAs) were tested in a line immunoblot assay that measures antibody reactivity with individual ENAs in a single test field. Results were then compared to those obtained in monospecific ENA antibody enzyme immunoassays (EIAs). Discordant results were resolved by immunodiffusion. Of 540 result pairs (90 sera tested for 6 ENAs [Sm/RNP, Sm, SSA, SSB, Scl-70, Jo-1]), 509 (94%) showed concordance. Immunodiffusion resolved 28 of 31 discordant result pairs in favor of the immunoblot result. After resolution of discordant data, the immunoblot assay exhibited 100% sensitivity for all ENA antibodies except those recognizing Scl-70, for which the sensitivity was 89%; specificity was over 96% for all 6 ENA antibodies. These findings show that a line immunoblot assay for the characterization of ENA antibodies yields results comparable to those obtained using monospecific ENA antibody EIAs. The immunoblot assay is easier and less expensive to perform due to its utilization of a single test field.

Antibodies↗
PubMed2000

Claisen rearrangement of allyl phenyl ether and its sulfur and selenium analogues on electron impact

The electron impact (EI) mass spectrum of allyl phenyl ether (1) includes an ion at m/z 106 that is formed mainly by the loss of CO from the molecular ion, as supported by high resolution and MS/MS data. The formation of the [M - CO](+) ion from 1 can be explained in terms of the Claisen rearrangement of 1 after ionization in the ion source of the mass spectrometer. Similarly, allyl phenyl sulfide (2) and allyl phenyl selenide (3) showed characteristic ions corresponding to [M - CH(3)](+), [M - XH](+) (X = S or Se) and [M - C(2)H(4)](+.), and the formation of these ions are explained via Claisen rearrangement of 2 and 3 in the ion source of the mass spectrometer resulting in a mixture of rearrangement products. The formation of molecular ions of 2-allyl thiophenol and 2-allyl selenophenol as intermediates, that cannot be isolated as the neutrals from the solution phase Claisen rearrangement of 2 and 3, respectively, is clearly indicated in the gas phase. The mass spectra of the rearrangement products obtained from the solution phase reaction were also consistent with the proposal of formation of these products in the ion source of the mass spectrometer. The formation of characteristic fragment ions attributed to the Claisen rearrangement products are also evident in the collision induced dissociation spectra of the corresponding molecular ions. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed2000

Spectroscopic imaging of glutamate C4 turnover in human brain.

One-dimensional spectroscopic imaging of (13)C-4-glutamate turnover is performed in the human brain with a 6 cc nominal voxel resolution at 4T. Data were acquired with an indirect detection approach using a short spin echo single quantum (1)H-(13)C heteronuclear editing method and a 7 cm surface coil with quadrature (13)C decoupling coils. To analyze the data as a function of tissue type, T(1)-based image segmentation through the surface coil was performed to determine the gray and white matter contributions to each voxel. The tricarboxylic acid (TCA) cycle rate in gray and white matter was then determined using a two-compartment model with the tissue fractionation derived from the image segmentation. The mean values for the TCA cycle rate for occipital gray and white matter from three volunteers was 0.88 +/- 0.12 and 0.28 +/- 0.13 respectively, in agreement with literature data.

Brain↗
PubMed2001

Correcting partial volume artifacts of the arterial input function in quantitative cerebral perfusion MRI.

To quantify cerebral perfusion with dynamic susceptibility contrast MRI (DSC-MRI), one needs to measure the arterial input function (AIF). Conventionally, one derives the contrast concentration from the DSC sequence by monitoring changes in either the amplitude or the phase signal on the assumption that the signal arises completely from blood. In practice, partial volume artifacts are inevitable because a compromise has to be reached between the temporal and spatial resolution of the DSC acquisition. As the concentration of the contrast agent increases, the vector of the complex blood signal follows a spiral-like trajectory. In the case of a partial-volume voxel, the spiral is located around the static contribution of the surrounding tissue. If the static contribution of the background tissue is disregarded, estimations of the contrast concentration will be incorrect. By optimizing the correspondence between phase information and amplitude information one can estimate the origin of the spiral, and thereupon correct for partial volume artifacts. This correction is shown to be accurate at low spatial resolutions for phantom data and to improve the AIF determination in a clinical example. Magn Reson Med 45:477-485, 2001.

Artifacts↗
PubMed1993

Pharmacological approaches to the therapy of chronic fatigue syndrome.

Although a variety of pharmacological agents have been used to treat patients with chronic fatigue syndrome none has been shown to effect a complete resolution of symptoms. Data obtained from a retrospective study and from an objective assessment of the aerobic work capacity of patients with this disorder suggest that the underlying pathophysiological abnormality is a disorder of sleep regulation. This results not only in profound fatigue and lethargy but also reduced sensory threshold for pain, disordered temperature regulation, cardiovascular abnormalities, disturbed higher cerebral function and mental depression. Drugs which modulate sleep, such as tricyclic antidepressants, have a limited effect in improving the symptoms that CFS patients experience. We suggest that other agents which affect central nervous system neurotransmitters, particularly serotonin, may have potential in the management of this condition and need to be evaluated in large controlled clinical trials.

Fatigue Syndrome, Chronic↗
PubMed1977

Mass spectrometry of Alternaria mali toxins and related cyclodepsipeptides.

The structures of AM-toxins I, II and III, host specific phytotoxic metabolites of Alternaria mali, can be readily deduced from low and high resolution mass spectral data, since the amino acids and their sequences are demonstrated by this technique. Additionally, the general fragmentation of these compounds by electron impact is discussed by comparing the spectra of analogous synthetic compounds.

Alanine↗
PubMed1977

Source identification of urban airborne polycyclic aromatic hydrocarbons by gas chromatographic mass spectrometry and high resolution mass spectrometry.

Polycyclic aromatic hydrocarbons formed during the combustion of three common fuels (coal, wood and kerosene) were separated and identified by capillary-column gas chromatographic mass spectrometry and were compared to airborne polycyclic aromatic hydrocarbons from Indianapolis, a high coal consuming area, and Boston, a low coal consuming area. High resolution mass spectral data were utilized in the construction of alkyl homolog plots for the comparison of alkyl distribution within each sample.

Air Pollution↗
PubMed1977

Mass spectrometric determination of new prostaglandin derivatives (series A and E).

The reaction of prostaglandins E1, E2, A1 and A2 with a 1:1 mixture of N,O-bis-trimethylsilyltrifluoroacetamide and piperidine favours the quantitative enolization of the 9-keto group of prostaglandins E, thus giving the corresponding tetrakis-TMS derivatives with molecular ions at m/e 642 and m/e 640 for prostaglandins E1 and E2, respectively, and also gives a new type of prostaglandin A-piperidyl-TMS derivative characterized by very strong base peaks at m/e 464 and 462, with molecular ions at m/e 637 and 635 for prostaglandins A1 and A2, respectively. The probable reaction mechanisms prevailing in both cases are discussed in accordance with the low and high resolution mass spectral data presented.

Chemical Phenomena↗
PubMed1990

Bacterial phospholipid analysis by fast atom bombardment mass spectrometry.

The structural analysis of naturally occurring bacterial phospholipids in mixtures by fast atom bombardment (FAB) mass spectrometry are reported. The bacterial strains examined included several genera of actinomycetes, two strains of Escherichia coli, and one strain each of Proteus mirabilis and Pseudomonas aeruginosa. FAB mass spectrometry proved to be a useful tool for the structural identification of phospholipids in mixtures and provided stable pseudo-molecular ions and characteristic fragment ions which permitted the identification of phosphatidylethanolamine and phosphatidyl choline. Information regarding the chain length of the fatty acids, their degree of unsaturation in the chains and the presence of hydroxyl groups was also obtained. The results obtained by FAB mass spectrometry were supported by high-resolution mass spectral data, tandem mass spectrometric studies and FAB mass spectrometry of components which had been separated and partially purified by thin-layer chromatography. Each organism displayed a highly characteristic phospholipid profile suggesting the possible use of FAB mass spectrometry as a method for rapid bacterial detection and identification.

Actinomycetaceae↗
PubMedDate not supplied

Magnetic resonance imaging of the brain with gadopentetate dimeglumine-DTPA: comparison of T1-weighted spin-echo and 3D gradient-echo sequences.

Short TR, short TE, high resolution, 3D gradient-recalled echo (GRE) imaging was evaluated for lesion detection in the brain. High resolution 3D GRE data acquisition was used to reduce partial volume effects and flow artifacts, to better visualize smaller structures, to minimize signal losses caused by field inhomogeneities, and to allow better image reformatting. Spin-echo (SE) and 3D GRE approaches were compared for lesion detection after the administration of an MR contrast agent, gadopentetate dimeglumine. Preliminary clinical studies demonstrated that the signal-to-noise ratio (SNR) in each slice of the GRE scan was worse than that of the SE scan because of the much thicker slices acquired with the SE technique. However, by averaging two adjacent 3D slices, the SNR of the two methods was essentially equivalent. In the averaged GRE slices, large lesions were seen just as well as in the SE images. More importantly, small lesions were better visualized in the thin 3D GRE images than in the thick SE images for the lesions studied in this work and the protocols used. These observations were confirmed by theoretical simulations.

Adolescent↗
PubMed2003

Study of the fragmentation mechanism of novel functionalized macrocycles by Fourier transform ion cyclotron resonance mass spectrometry.

Liquid secondary ion mass spectrometry (L-SIMS) of six new functionalized macrocycles was investigated. All six compounds yielded abundant fragment ions and protonation molecular ions [M + H](+) under L-SIMS conditions. The proposed fragmentation mechanisms were supported by high-resolution accurate mass data from Fourier transform ion cyclotron resonance mass spectrometric and MS(n) experiments on using sustained off-resonance irradiation collision-induced dissociation.

Cyclotrons↗
PubMed1993

Gd(DOTP)5-outer-sphere relaxation enhancement promoted by nitrogen bases.

The relaxation properties of Gd(DOTP)5- (1, 4, 7, 10-tetra-azacyclododecane- N,N',N'',N'''-tetrakis(methylenephosphonic acid)) have been investigated as a function of pH, temperature, concentration, and magnetic field strength. We have found that the complex has one exchangeable water molecule in its inner coordination sphere, at a distance of 3.26 A from the metal ion, and it does not form oligomers in solution in the concentration range 0.2 to 10 mM. The possible presence of two species in solution with an average fractional hydration number is also taken into accounts. The NMRD profiles were recorded at 5 degrees C, 25 degrees C, and 35 degrees C and quantitatively analyzed in terms of the paramagnetic relaxation equations. Interestingly the addition to a solution of the Gd(III)-complex of nitrogen bases results in a marked relaxation enhancement, which shows a strong pH dependence with a maximum around pH = 9. The relaxivity gain has been shown to depend on outer-sphere effects originating from multiple electrostatic interactions between the anionic complex and the organic cations that bring the exchangeable protons of the substrate molecules in to close proximity with the paramagnetic center. High resolution NMR relaxation data for N-methyl-D(-)-glucamine suggest that the hydroxyl group on the beta-carbon plays a role in stabilizing the interaction, presumably through a hydrogen bond with an uncoordinated oxygen atom of the complex.

Chemical Phenomena↗
PubMed1997

Noninvasive comprehensive characterization of renal artery stenosis by combination of STAR angiography and EPISTAR perfusion imaging.

In a small fraction of patients with hypertension, the cause is stenosis of the renal artery. To date, there is no established noninvasive screening technique available to identify this population, for whom treatment with a surgical procedure or percutaneous transluminal angioplasty is often possible. In this study, the sensitivity and specificity of STAR angiography and EPISTAR perfusion imaging in characterizing renal artery stenosis were evaluated in an animal model. Qualitatively, STAR provided projection angiograms that were comparably sensitive to x-ray angiograms but obtained noninvasively. The sensitivity for detecting the stenosis was 100%. The specificity varied according to the definition of the threshold for significance, which varied 78-94%, depending on whether > 70% or > 50% diameter reduction was considered. Improvements in specificity will depend upon use of shorter echo times and higher spatial resolution. Our preliminary data indicate that EPISTAR provides sensitivity and specificity of 100% for characterizing stenosis with diameter reductions of > 70%.

Animals↗
PubMed1998

Imaging lungs using inert fluorinated gases.

Rat lungs were imaged by 19F projection MRI of hexafluoroethane, mixed with 20% oxygen to form the inhaled gas. The 3D image had 700 microm resolution, and the data took 4.3 h to acquire. Free induction decays were collected in the presence of steady magnetic field gradients in 686 different directions. To take advantage of fast relaxation (T1 = 5.9 +/- 0.2 ms), the repetition time was 5 ms. To eliminate signal loss from magnetic field inhomogeneities, data were collected within 2 ms of spin excitation (from 80 micros to 2 ms after the 42-micros pi/2 pulses). The singular value decomposition of the transform from frequency to time domain was used to obtain projections despite the absence of data during and immediately after the RF pulses. Inert fluorinated gas imaging may be less expensive than polarized noble gas imaging and is appropriate for imaging steady-state rather than transient gas concentrations.

Animals↗
PubMed1993

Structure of Paramecium tetraurelia calmodulin at 1.8 A resolution.

The crystal structure of calmodulin (CaM; M(r) 16,700, 148 residues) from the ciliated protozoan Paramecium tetraurelia (PCaM) has been determined and refined using 1.8 A resolution area detector data. The crystals are triclinic, space group P1, a = 29.66, b = 53.79, c = 25.49 A, alpha = 92.84, beta = 97.02, and gamma = 88.54 degrees with one molecule in the unit cell. Crystals of the mammalian CaM (MCaM; Babu et al., 1988) and Drosophila CaM (DCaM; Taylor et al., 1991) also belong to the same space group with very similar cell dimensions. All three CaMs have 148 residues, but there are 17 sequence changes between PCaM and MCaM and 16 changes between PCaM and DCaM. The initial difference in the molecular orientation between the PCaM and MCaM crystals was approximately 7 degrees as determined by the rotation function. The reoriented Paramecium model was extensively refitted using omit maps and refined using XPLOR. The R-value for 11,458 reflections with F > 3 sigma is 0.21, and the model consists of protein atoms for residues 4-147, 4 calcium ions, and 71 solvent molecules. The root mean square (rms) deviations in the bond lengths and bond angles in the model from ideal values are 0.016 A and 3 degrees, respectively. The molecular orientation of the final PCaM model differs from MCaM by only 1.7 degrees. The overall Paramecium CaM structure is very similar to the other calmodulin structures with a seven-turn long central helix connecting the two terminal domains, each containing two Ca-binding EF-hand motifs. The rms deviation in the backbone N, Ca, C, and O atoms between PCaM and MCaM is 0.52 A and between PCaM and DCaM is 0.85 A. The long central helix regions differ, where the B-factors are also high, particularly in PCaM and MCaM. Unlike the MCaM structure, with one kink at D80 in the middle of the linker region, and the DCaM structure, with two kinks at K75 and I85, in our PCaM structure there are no kinks in the helix; the distortion appears to be more gradually distributed over the entire helical region, which is bent with an apparent radius of curvature of 74.5(2) A. The different distortions in the central helical region probably arise from its inherent mobility.

Amino Acid Sequence↗
PubMed2005

Electronic substituent effects in the electron impact mass spectrometry of 2-(arylazo)-4-phenylphenols.

A mass spectrometric study of a set of six novel 2-(arylazo)-4-phenylphenols 1-6 was performed. The electron impact spectra were acquired and analyzed for five of the compounds in order to establish a fragmentation pattern. The suggested pathways were investigated and confirmed by means of tandem mass spectrometry (MS/MS) experiments together with high-resolution accurate mass data. However, the sixth molecule, a sodium sulfonate salt, was studied using fast atom bombardment (FAB) ionization in positive and negative modes. In addition, some electronic substituent effects were investigated by analyzing Hammett-McLafferty linear free energy correlations for some peaks derived from the corresponding molecular ions. Also, the role of the O-H...N hydrogen bond present in the target compounds was analyzed. The roles of these H-bonds were consistent with the corresponding acidity constant values obtained experimentally as well as by theoretical quantum chemistry calculations using HF/6-31 + G(d,p) and B3LYP/6-31G(d,p). Some spectrometric data were correlated with topological properties derived from the atoms-in-molecules (AIM) theory.

Journal Article↗
PubMed2006

Analysis of strychnos alkaloids using electrospray ionization Fourier transform ion cyclotron resonance multi-stage tandem mass spectrometry.

The fragmentations of four strychnos alkaloids have been investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the positive ion mode. Experiments using multi-stage tandem mass spectrometry (ESI-FT-ICR-MSn) allowed us to obtain precise elemental compositions of product ions at high mass resolution. The experimental data demonstrated that the nitrogen bridge and the coordinated oxygen atom on the nitrogen bridge in the alkaloid compounds were the active sites in the MS2 fragmentations. The loss of CH3 or the OCH3 group in those alkaloids, which have an OCH3 substituent, was the dominant fragmentation mode in the MS3 fragmentations. Logical fragmentation schemes for strychnos alkaloids have been proposed and these should be useful for the identification of these compounds.

Alkaloids↗
PubMed1997

Factors determining the size frequency distribution of beta-amyloid (A beta) deposits in Alzheimer's disease.

The size frequency distributions of discrete beta-amyloid (A beta) deposits were studied in single sections of the temporal lobe from patients with Alzheimer's disease. The size distributions were unimodal and positively skewed. In 18/25 (72%) tissues examined, a log normal distribution was a good fit to the data. This suggests that the abundances of deposit sizes are distributed randomly on a log scale about a mean value. Three hypotheses were proposed to account for the data: (1) sectioning in a single plane, (2) growth and disappearance of A beta deposits, and (3) the origin of A beta deposits from clusters of neuronal cell bodies. Size distributions obtained by serial reconstruction through the tissue were similar to those observed in single sections, which would not support the first hypothesis. The log normal distribution of A beta deposit size suggests a model in which the rate of growth of a deposit is proportional to its volume. However, mean deposit size and the ratio of large to small deposits were not positively correlated with patient age or disease duration. The frequency distribution of A beta deposits which were closely associated with 0, 1, 2, 3, or more neuronal cell bodies deviated significantly from a log normal distribution, which would not support the neuronal origin hypothesis. On the basis of the present data, growth and resolution of A beta deposits would appear to be the most likely explanation for the log normal size distributions.

Aged↗