bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coating thickness of magnetic iron oxide nanoparticles affects R2 relaxivity
Authors: LaConte Leslie E.W. , Nitin Nitin , Zurkiya Omar , Caruntu Daniela , O'Connor Charles J. , Hu Xiaoping , Bao Gang 
Published: October 2007

AbstractPurposeTo evaluate the effect of coating thickness on the relaxivity of iron oxide nanoparticles.Materials and MethodsMonocrystalline superparamagnetic iron oxide nanoparticles (MIONs), coated with a polyethylene glycol (PEG)‐modified, phospholipid micelle coating, with different PEG molecular weights, were prepared. The particle diameters were measured with dynamic light scattering (DLS) and electron microscopy (EM). The R1 and R2 of MIONs were measured using a bench‐top nuclear magnetic resonance (NMR) relaxometer. pH was varied for some measurements. Monte Carlo simulations of proton movement in a field with nanometer‐sized magnetic inhomogeneities were performed.ResultsIncreasing the molecular weight of the PEG portion of the micelle coating increased overall particle diameter. As coating thickness increases, the R2 decreases and the R1 increases. Changing pH has no effect on relaxivity. The Monte Carlo simulations suggest that the effect of coating size on R2 relaxivity is determined by two competing factors: the physical exclusion of protons from the magnetic field and the residence time for protons within the coating zone.ConclusionCoating thickness can significantly impact the R2, and the R2/R1 ratio, of a MION contrast agent. An understanding of the relationship between coating properties and changes in relaxivity is critical for designing magnetic nanoparticle probes for molecular imaging applications using MRI. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Long and short echo time proton magnetic resonance spectroscopic imaging of the healthy aging brain
Authors: McIntyre Dominick J.O. , Charlton Rebecca A. , Markus Hugh S. , Howe Franklyn A. 
Published: October 2007

AbstractPurposeTo investigate the relationship between subject age and white matter brain metabolite concentrations and R2 relaxation rates in a cross‐sectional study of human brain.Materials and MethodsLong‐ and short‐echo proton spectroscopic imaging were used to investigate concentrations and R2 relaxation rates of N‐acetyl aspartate (NAA) + N‐acetyl aspartyl glutamate (NAAG), choline (Cho), creatine (Cr), and myoinositol (mI) in the white matter of the centrum semiovale of 106 healthy volunteers aged 50–90 years; usable data were obtained from 79 subjects. A major aim was to identify which parameters were most sensitive to changes with age. Spectra were analyzed using the LCModel method.ResultsThe apparent R2 of NAA and the LCModel concentration of Cr at short echo time were significantly correlated with age after multiplicity correction. Large lipid resonances were observed in the brain midline of some subjects, the incidence increasing significantly with age. We believe this to result from lipid deposits in the falx cerebri.ConclusionSince only short‐echo spectroscopy showed a robust relationship between Cr and subject age, and detects more metabolites than long echo time, we conclude that short‐echo is superior to long‐echo for future aging studies. Future studies could usefully determine whether the Cr–age relationship is due to changes in concentration, T1, or both. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Interventional cardiovascular procedures guided by real‐time MR imaging: An interactive interface using multiple slices, adaptive projection modes and live 3D renderings
Authors: Guttman Michael A. , Ozturk Cenghizhan , Raval Amish N. , Raman Venkatesh K. , Dick Alexander J. , DeSilva Ranil , Karmarkar Parag , Lederman Robert J. , McVeigh Elliot R. 
Published: October 2007

AbstractPurposeTo develop and test a novel interactive real‐time MRI environment that facilitates image‐guided cardiovascular interventions.Materials and MethodsColor highlighting of device‐mounted receiver coils, accelerated imaging of multiple slices, adaptive projection modes, live three‐dimensional (3D) renderings and other interactive features were utilized to enhance navigation of devices and targeting of tissue.ResultsImages are shown from several catheter‐based interventional procedures performed in swine that benefit from this custom interventional MRI interface. These include endograft repair of aortic aneurysm, balloon septostomy of the cardiac interatrial septum, angioplasty and stenting, and endomyocardial cell injection, all using active catheters containing MRI receiver coils.ConclusionInteractive features not available on standard clinical scanners enhance real‐time MRI for guiding cardiovascular interventional procedures. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Anatomical distribution of 3He apparent diffusion coefficients in severe chronic obstructive pulmonary disease
Authors: Evans Andrea , McCormack David , Ouriadov Alexei , Etemad‐Rezai Roya , Santyr Giles , Parraga Grace 
Published: October 2007

AbstractPurposeTo evaluate the anatomical distribution of apparent diffusion coefficients (ADC) using hyperpolarized helium‐3 (3He) MRI in chronic obstructive pulmonary disease (COPD).Materials and MethodsHyperpolarized 3He MRI was performed in eight healthy and seven COPD subjects under breathhold conditions in the supine position to determine ADC values from diffusion‐weighted images and evaluate anterior–posterior (AP) and superior–inferior (SI) differences.ResultsADC differences between anterior and posterior slices, ΔAP, was 0.06 ±0.01 cm2/second for healthy volunteers and 0.04 ±0.02 cm2/second for COPD subjects and was significant for each subject (P < 0.01). The AP ADC gradient was –3.98 × 10–3 ±0.59 cm2/second/cm for healthy volunteers and –2.04 × 10–3 ±0.89 cm2/second/cm for COPD subjects. The difference in ADC between superior and inferior regions of interest (ROIs), ΔSI, was 0.02 ±0.02 cm2/second for healthy volunteers and 0.10 ±0.09 cm2/second for COPD subjects, which was significant for each subject (P < 0.05). The SI ADC gradient was –0.63 × 10–3 ±2.23 cm2/second/cm for healthy volunteers and –6.61 × 10–3 ±6.68 cm2/second/cm for COPD subjects. ΔAP, AP‐gradient, and SI‐gradient were significantly different between healthy volunteers and COPD subjects (P < 0.05).ConclusionIn all subjects, ADC anatomical differences were significant and mean ADC was dependent on anatomic location and disease status. J. Magn. Reson. Imaging. © 2007 Wiley‐Liss, Inc.
Transcytolemmal water exchange in pharmacokinetic analysis of dynamic contrast‐enhanced MRI data in squamous cell carcinoma of the head and neck
Authors: Kim Sungheon , Quon Harry , Loevner Laurie A. , Rosen Mark A. , Dougherty Lawrence , Kilger Alex M. , Glickson Jerry D. , Poptani Harish 
Published: October 2007

AbstractPurposeTo investigate the effect of transcytolemmal water exchange on the dynamic contrast‐enhanced (DCE) T1‐weighted MRI of human squamous cell carcinomas of the head and neck (HNSCC).Materials and MethodsNine patients with HNSCC nodal metastasis underwent pretreatment DCE‐MRI with a temporal resolution of 2.5 seconds and a spatial resolution of 1 mm × 1 mm × 5 mm at 1.5T. We used two pharmacokinetic models for data analysis: generalized kinetic model (GKM) without considering transcytolemmal water exchange and the shutter‐speed model (SSM), based on a two‐site exchange model for transcytolemmal water exchange. The results were compared in three subgroups of voxels in the tumor depending on the level of contrast enhancement.ResultsSSM was found to be a better fit for more than 75% of pixels of all subjects (P < 0.01) in terms of residual size and Bayesian information criterion (BIC). For all three subgroups based on the contrast enhancement, the median Ktrans values of SSM were 42% to 55% higher than those of GKM and the median ve values of SSM were 116% to 176% larger than those of GKM. The median Ktrans and ve of two models were found significantly different (P < 0.01). The median τi measured by SSM were from 211 to 364 msec.ConclusionThe effect of transcytolemmal water exchange is an important factor that needs to be incorporated for adequate modeling of contrast enhancement dynamics measured by MRI of HNSCC. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
An integrated method for metabolite detection and identification using a linear ion trap/Orbitrap mass spectrometer and multiple data processing techniques: application to indinavir metabolite detection
Authors: Ruan Qian , Peterman Scott , Szewc Mark A. , Ma Li , Cui Dan , Humphreys W. Griffith , Zhu Mingshe 
Published: October 2007

AbstractA new strategy using a hybrid linear ion trap/Orbitrap mass spectrometer and multiple post‐acquisition data mining techniques was evaluated and applied to the detection and characterization of in vitro metabolites of indinavir. Accurate‐mass, full‐scan MS and MS/MS data sets were acquired with a generic data‐dependent method and processed with extracted‐ion chromatography (EIC), mass‐defect filter (MDF), product‐ion filter (PIF), and neutral‐loss filter (NLF) techniques. The high‐resolution EIC process was shown to be highly effective in the detection of common metabolites with predicted molecular weights. The MDF process, which searched for metabolites based on the similarity of mass defects of metabolites to those of indinavir and its core substructures, was able to find uncommon metabolites not detected by the EIC processing. The high‐resolution PIF and NLF processes selectively detected metabolites that underwent fragmentation pathways similar to those of indinavir or its known metabolites. As a result, a total of 15 metabolites including two new indinavir metabolites were detected and characterized in a rat liver S9 incubation sample. Overall, these data mining techniques, which employed distinct metabolite search mechanisms, were complementary and effective in detecting both common and uncommon metabolites. In summary, the results demonstrated that this analytical strategy enables the high‐throughput acquisition of accurate‐mass LC/MS data sets, comprehensive search of a variety of metabolites through the post‐acquisition processes, and effective structural characterization based on elemental compositions of metabolite molecules and their product ions. Copyright © 2007 John Wiley & Sons, Ltd.
Identification of hexose diastereomers by means of tandem mass spectrometry of oxocarbenium ions followed by neural networks analysis
Authors: Madhusudanan K. P. , Srivastava Mukesh 
Published: October 2007

AbstractThe ion abundances in the tandem mass spectra of oxocarbenium ions generated from aldohexoses and ketohexoses under electrospray ionization conditions depend on their stereochemistry. The ratios of the abundances of two of the major ionsm/z85 and 91 are different in the aldohexoses and the ketohexoses. Principal component analysis (PCA) allowed visual differentiation of the hexose isomers. However, identification of an individual hexose was difficult. The data were subjected to neural network analysis (NNA) using a multilayer perceptron (MLP) model. The model was first trained using the data from the 11 hexoses and then used to identify the hexoses using fresh data acquired later. There was 100% identification of the various hexoses. The hexose units in methyl glucoside, mannoside and galactoside could also be identified accurately. The method can therefore be used for the characterization of hexose units from monosaccharides and glycosides. Copyright © 2007 John Wiley & Sons, Ltd.
On‐target sample preparation of 4‐sulfophenyl isothiocyanate‐derivatized peptides using AnchorChip Targets
Authors: Zhang Xumin , Rogowska‐Wrzesinska Adelina , Roepstorff Peter 
Published: October 2007

AbstractDe novo sequencing of tryptic peptides by post source decay (PSD) or collision induced dissociation (CID) analysis using MALDI TOF‐TOF instruments is due to the easy interpretation facilitated by the introduction of N‐terminal sulfonated derivatives. Recently, a stable and cheap reagent, 4‐sulfophenyl isothiocyanate (SPITC), has been successfully used for N‐terminal derivatization. Previously described methods have always used desalting and concentration by reverse‐phase chromatography prior to mass spectrometric analysis. Here we present an on‐target sample preparation method based on AnchorChip target technology. The method was optimized for reduction of by‐products and sensitivity with SPITC‐derivatized tryptic BSA peptides, and successfully applied to protein identification from silver‐stained two‐dimensional electrophoretic gels of fish liver extracts. The method is simple and sensitive and allowed protein identification based on de novo sequencing and BLAST search from species with limited sequence information. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of organosulfates from the photooxidation of isoprene and unsaturated fatty acids in ambient aerosol using liquid chromatography/(−) electrospray ionization mass spectrometry
Authors: Gómez‐González Yadian , Surratt Jason D. , Cuyckens Filip , Szmigielski Rafal , Vermeylen Reinhilde , Jaoui Mohammed , Lewandowski Michael , Offenberg John H. , Kleindienst Tadeusz E. , Edney Edward O. , Blockhuys Frank , Van Alsenoy Christian , Maenhaut Willy , Claeys Magda 
Published: October 2007

AbstractIn the present study, we have characterized in detail the MS2 and MS3 fragmentation behaviors, using electrospray ionization (ESI) in the negative ion mode, of previously identified sulfated isoprene secondary organic aerosol compounds, including 2‐methyltetrols, 2‐methylglyceric acid, 2‐methyltetrol mononitrate derivatives, glyoxal and methylglyoxal. A major fragmentation pathway for the deprotonated molecules of the sulfate esters of 2‐methyltetrols and 2‐methylglyceric acid and of the sulfate derivatives of glyoxal and methylglyoxal is the formation of the bisulfate [HSO4]− anion, while the deprotonated sulfate esters of 2‐methyltetrol mononitrate derivatives preferentially fragment through loss of nitric acid. Rational interpretation of MS2, MS3 and accurate mass data led to the structural characterization of unknown polar compounds in K‐puszta fine aerosol as organosulfate derivatives of photooxidation products of unsaturated fatty acids, i.e. 2‐hydroxy‐1,4‐butanedialdehyde, 4,5‐ and 2,3‐dihydroxypentanoic acids, and 2‐hydroxyglutaric acid, and of α‐pinene, i.e. 3‐hydroxyglutaric acid. The deprotonated molecules of the sulfated hydroxyacids, 2‐methylglyceric acid, 4,5‐ and 2,3‐dihydroxypentanoic acid, and 2‐ and 3‐hydroxyglutaric acids, showed in addition to the [HSO4]− ion (m/z 97) neutral losses of water, CO2 and/or SO3, features that are characteristic of humic‐like substances. The polar organosulfates characterized in the present work are of climatic relevance because they may contribute to the hydrophilic properties of fine ambient aerosol. In addition, these compounds probably serve as ambient tracer compounds for the occurrence of secondary organic aerosol formation under acidic conditions. Copyright © 2007 John Wiley & Sons, Ltd.
Amyloid β‐peptide activates nuclear factor‐κB through an N‐methyl‐D‐aspartate signaling pathway in cultured cerebellar cells
Authors: Kawamoto E. M. , Lepsch L. B. , Boaventura M. F. C. , Munhoz C. D. , Lima L. S. , Yshii L. M. , Avellar M. C. W. , Curi R. , Mattson M. P. , Scavone C. 
Published: October 2007

AbstractAmyloid β‐peptide (Aβ) likely causes functional alterations in neurons well prior to their death. Nuclear factor‐κB (NF‐κB), a transcription factor that is known to play important roles in cell survival and apoptosis, has been shown to be modulated by Aβ in neurons and glia, but the mechanism is unknown. Because Aβ has also been shown to enhance activation of N‐methyl‐D‐aspartate (NMDA) receptors, we investigated the role of NMDA receptor‐mediated intracellular signaling pathways in Aβ‐induced NF‐κB activation in primary cultured rat cerebellar cells. Cells were treated with different concentrations of Aβ1–40 (1 or 2 μM) for different periods (6, 12, or 24 hr). MK‐801 (NMDA antagonist), manumycin A and FTase inhibitor 1 (farnesyltransferase inhibitors), PP1 (Src‐family tyrosine kinase inhibitor), PD98059 [mitogen‐activated protein kinase (MAPK) inhibitor], and LY294002 [phosphatidylinositol 3‐kinase (PI3‐k) inhibitor] were added 20 min before Aβ treatment of the cells. Aβ induced a time‐ and concentration‐dependent activation of NF‐κB (1 μM, 12 hr); both p50/p65 and p50/p50 NF‐κB dimers were involved. This activation was abolished by MK‐801 and attenuated by manumycin A, FTase inhibitor 1, PP1, PD98059, and LY294002. Aβ at 1 μM increased the expression of inhibitory protein IκB, brain‐derived neurotrophic factor, inducible nitric oxide synthase, tumor necrosis factor‐α, and interleukin‐1β as shown by RT‐PCR assays. Collectively, these findings suggest that Aβ activates NF‐κB by an NMDA‐Src‐Ras‐like protein through MAPK and PI3‐k pathways in cultured cerebellar cells. This pathway may mediate an adaptive, neuroprotective response to Aβ. © 2007 Wiley‐Liss, Inc.
NR1 and GluR2 expression mediates excitotoxicity in chronic hypobaric hypoxia
Authors: Hota Sunil K. , Barhwal Kalpana , Singh Shashi. B. , Sairam M. , Ilavazhagan Govindasamy 
Published: October 2007

AbstractHypobaric hypoxia has been reported to cause memory dysfunction. The possible molecular mechanism involved, however, remains to be explored. The role that glutamate and its receptors play in causing excitotoxicity in ischemia and neurodegenerative diseases indicates the possible occurrence of a similar phenomenon in hypobaric hypoxia. The present study aimed to elucidate the molecular events occurring at glutamatergic synapses in hypobaric hypoxia using Sprague‐Dawley rats as a model system. The animals were exposed to an altitude of 7,600 m for different durations. Hypobaric hypoxia was found to cause oxidative stress, chromatin condensation, and neurodegeneration. A temporal change in the expression of the ionotropic receptors of glutamate was also observed. Expression of theN‐methyl‐D‐aspartate (NMDA) receptor increased, and expression of glutamate receptor subunit 2 of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazoleproprionate receptor decreased. We also observed increased activity of glutamate dehydrogenase, indicating greater synthesis and release of glutamate after 3 and 7 days of exposure. Administration of a selective NMDA antagonist during exposure was found to ameliorate neuronal degeneration, providing evidence for the occurrence of excitotoxicity in hypobaric hypoxia. Our study indicates that excitotoxicity occurs in hypobaric hypoxia. This study also indicates the appropriate period for drug administration during exposure to hypobaric hypoxia and establishes ionotropic receptors of glutamate as potential therapeutic targets for ameliorating high‐altitude‐induced cognitive dysfunction. © 2007 Wiley‐Liss, Inc.
Coherent structures in urban roughness sublayer turbulence
Authors: Christen Andreas , van Gorsel Eva , Vogt Roland 
Published: October 2007

AbstractData measured within and above an urban street canyon is used to analyse the importance of coherent structures in turbulent transfer. The atmosphere was probed simultaneously at six different heights from the base of the street canyon up to 2.2 times the mean building height. Integral length scales, joint probability densities, quadrant measures and wavelet‐based conditional sampling techniques are used to picture momentum and sensible heat exchange in the urban roughness sublayer. Layers directly at roof height show smallest length scales. With increasing distance from roofs, length scales increase, both up to higher levels above the roofs and also down to the base of the street canyon. Quadrant analysis indicates that turbulent momentum and sensible heat fluxes are strongly sweep‐dominated in large parts of the street canyon and close to the roofs. Only at the highest measurement levels do ejections slightly dominate exchange. Exchange is intermittent where length scales are largest, namely in the lower street canyon and at higher levels in the urban roughness sublayer. At rooftop, exchange is more efficient and least intermittent. A wavelet‐based detection is used to reconstruct time‐height cross‐sections of paired events measured at multiple levels simultaneously. Two types of sharp scalar fronts were identified—sweeps followed by ejections and ejections followed by sweeps. Both are important in transporting momentum and sensible heat. Copyright © 2007 Royal Meteorological Society
Amount of characteristic compounds in 15 cultivars of onion (Allium cepa L.) in controlled field trials
Authors: Vågen Ingunn M , Slimestad Rune 
Published: October 2007

AbstractBACKGROUND: In order to develop the production of sweet onions (Allium cepa L.) and onions with a high content of flavonols and fibre in Norway, it was necessary to evaluate available cultivars with respect to their content of selected chemical compounds. A field trial with 15 different cultivars was conducted at Landvik in southern Norway. Compounds that reflect onion pungency and sweetness (pyruvate, sugars) and parameters known to have a beneficial impact on health (fructo‐oligosaccharides (FOS), flavonols, antioxidant capacity) were analysed.RESULTS: The sweetest onions with respect to low content of pyruvate and high amount of fructose and glucose ranged in pyruvate content from 2.7 to 3.6 µmol mL−1. These cultivars were juicy and contained low amounts of FOS and total flavonols. The most pungent onions contained the highest amounts of FOS among the cultivars: 4.53, 3.80 and 5.81 g per 100 g fresh weight (FW) respectively. They also had a high content of flavonols (86.6, 159.2 and 97.6 mg per 100 g FW) and high dry weight content (14.6, 13.5 and 15.6 g per 100 g).CONCLUSION: The sweetest onion cultivars were found to be ‘NUN 9746’, ‘Musica’, ‘Domenica Supersweet’, ‘Colossus’ and ‘Cronus’. The most pungent cultivars were ‘Powell Brown’ and ‘Tilbury’, which also contained the highest amounts of flavonols and gave the highest Trolox equivalent antioxidant capacity (TEAC) values among the 15 cultivars. Copyright © 2007 Society of Chemical Industry
Unsaturated Polyamides from Bio‐Based Z‐octadec‐9‐enedioic Acid
Authors: Pardal Francis , Salhi Slim , Rousseau Brigitte , Tessier Martine , Claude Sylvain , Fradet Alain 
Published: October 2007

AbstractA series of polyamides based on Z‐octadec‐9‐enedioic acid, a bio‐based unsaturated monomer, and aliphatic‐, cycloaliphatic‐, or benzylic diamines were synthesized and characterized by 1H and 13C NMR analysis, size exclusion chromatography (SEC), DSC, and dynamic‐mechanical analysis (DMA). The high reaction temperature (250 °C) did not lead to the degradation of diacid unit double bonds and unsaturated polyamides were obtained. The aliphatic unsaturated polyamides are semi‐crystalline polymers of high molar mass, relatively flexible at room temperature. The cycloaliphatic unsaturated polyamides are semi‐crystalline or amorphous, present higher melting and glass transition temperatures and are much more rigid. The aliphatic and aliphatic–aromatic unsaturated polyamides present lower Tg and Tm as compared to their parent saturated polymers.magnified image
Parallel Algorithm for Cell Dynamics Simulation of Block Copolymers
Authors: Guo Xiaohu , Pinna Marco , Zvelindovsky Andrei V. 
Published: October 2007

AbstractCell dynamics simulation (CDS) is a very promising approach to model dynamic processes in block copolymer systems at the mesoscale level. It is difficult to implement a real time and experimental‐scale simulation with traditional serial algorithms because of the expensive computation. A parallel, spatial decomposition‐based algorithm for large‐scale CDS is proposed. With the efficient strategy of domain decomposition and the fast method of neighbouring points location, we greatly reduce the calculating and communicating cost. The numerical results indicate that the proposed parallel algorithm can provide an efficient procedure for computer simulation of block copolymer systems of experimental size.magnified image