bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulmonary perfusion imaging in the rodent lung using dynamic contrast‐enhanced MRI
Authors: Mistry Nilesh N. , Pollaro James , Song Jiayu , De Lin Ming , Johnson G. Allan 
Published: January 2008

AbstractWith the development of various models of pulmonary disease, there is tremendous interest in quantitative regional assessment of pulmonary function. While ventilation imaging has been addressed to a certain extent, perfusion imaging for small animals has not kept pace. In humans and large animals perfusion can be assessed using dynamic contrast‐enhanced (DCE) MRI with a single bolus injection of a gadolinium (Gd)‐based contrast agent. But the method developed for the clinic cannot be translated directly to image the rodent due to the combined requirements of higher spatial and temporal resolution. This work describes a novel image acquisition technique staggered over multiple, repeatable bolus injections of contrast agent using an automated microinjector, synchronized with image acquisition to achieve dynamic first‐pass contrast enhancement in the rat lung. This allows dynamic first‐pass imaging that can be used to quantify pulmonary perfusion. Further improvements are made in the spatial and temporal resolution by combining the multiple injection acquisition method with Interleaved Radial Imaging and “Sliding window‐keyhole” reconstruction (IRIS). The results demonstrate a simultaneous increase in spatial resolution (<200 μm) and temporal resolution (<200 ms) over previous methods, with a limited loss in signal‐to‐noise‐ratio. Magn Reson Med 59:289–297, 2008. © 2008 Wiley‐Liss, Inc.
In vivo T1ρ mapping in cartilage using 3D magnetization‐prepared angle‐modulated partitioned k‐space spoiled gradient echo snapshots (3D MAPSS)
Authors: Li Xiaojuan , Han Eric T. , Busse Reed F. , Majumdar Sharmila 
Published: January 2008

AbstractFor T1ρ quantification, a three‐dimensional (3D) acquisition is desired to obtain high‐resolution images. Current 3D methods that use steady‐state spoiled gradient‐echo (SPGR) imaging suffer from high SAR, low signal‐to‐noise ratio (SNR), and the need for retrospective correction of contaminating T1 effects. In this study, a novel 3D acquisition scheme—magnetization‐prepared angle‐modulated partitioned‐k‐space SPGR snapshots (3D MAPSS)—was developed and used to obtain in vivo T1ρ maps. Transient signal evolving towards the steady‐state were acquired in an interleaved segmented elliptical centric phase encoding order immediately after a T1ρ magnetization preparation sequence. RF cycling was applied to eliminate the adverse impact of longitudinal relaxation on quantitative accuracy. A variable flip angle train was designed to provide a flat signal response to eliminate the filtering effect in k‐space caused by transient signal evolution. Experiments in phantoms agreed well with results from simulation. The T1ρ values were 42.4 ± 5.2 ms in overall cartilage of healthy volunteers. The average coefficient‐of‐variation (CV) of mean T1ρ values (N = 4) for overall cartilage was 1.6%, with regional CV ranging from 1.7% to 8.7%. The fitting errors using MAPSS were significantly lower (P < 0.05) than those using sequences without RF cycling and variable flip angles. Magn Reson Med 59:298–307, 2008. © 2008 Wiley‐Liss, Inc.
Spectral simplification for resolved glutamate and glutamine measurement using a standard STEAM sequence with optimized timing parameters at 3, 4, 4.7, 7, and 9.4T
Authors: Yang Shaolin , Hu Jiani , Kou Zhifeng , Yang Yihong 
Published: January 2008

AbstractThe C4 multiplet proton resonances of glutamate (Glu) around 2.35 ppm and glutamine (Gln) around 2.45 ppm usually overlap in MR spectra, particularly at low‐ and mid‐field strengths (1.5–4.7T). A spectral simplification approach is introduced that provides unobstructed Glu and Gln measurement using a standard STEAM localization sequence with optimized interpulse timings. The underlying idea is to exploit the dependence of response of a coupled spin system on the echo time (TE) and mixing time (TM) to find an optimum timing set (TE, TM), at which the outer‐wings of C4 “pseudo‐triplet” proton resonances of Glu and Gln are significantly suppressed while the central peaks are maintained. The spectral overlap is thus resolved as the overlap exists exclusively at the outer‐wings and the central peaks are readily separated due to the approximate 0.1‐ppm difference in chemical shift. Density matrix simulation for Glu, Gln, and other overlapping metabolites at 2.3–2.5 ppm was conducted to predict the optimum timing sets. The simulated, phantom, and in vivo results demonstrated that the C4 multiplet proton resonances of Glu and Gln can be resolved for unobstructed detection at 3T, 4T, and 4.7T. For simplicity, only simulated data are illustrated at 7T and 9.4T. Magn Reson Med 59:236–244, 2008. © 2008 Wiley‐Liss, Inc.
ACUT2E TSE‐SSFP: A hybrid method for T2‐weighted imaging of edema in the heart
Authors: Aletras Anthony H. , Kellman Peter , Derbyshire J. Andrew , Arai Andrew E. 
Published: January 2008

AbstractACUT2E TSE‐SSFP is a hybrid between steady state free precession (SSFP) and turbo spin echo (TSE) for bright‐blood T2‐weighted imaging with signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) similar to dark‐blood TSE. TSE‐SSFP uses a segmented SSFP readout during diastole with 180° pulses following a 90° preparation. The 180° refocusing pulses make TSE‐SSFP similar to TSE but TSE‐SSFP uses gradient moment nulling, whereas TSE uses gradient crushing. TSE‐SSFP produced T2‐weighted images with minimal T1 weighting. TSE‐SSFP and TSE had similar SNR (155.9 ± 6.0 vs 160.9 ± 7.0; P = NS) for acute myocardial infarction (MI) and twice the SNR of T2‐prepared SSFP (73.1 ± 3.4, P < 0.001). TSE‐SSFP and TSE had approximately double the CNR of T2‐prepared SSFP for differentiating acute MI from normal myocardium. Imperfect blood suppression, present in all animals on some TSE images, was a problem eliminated by TSE‐SSFP and T2‐prepared SSFP. Magn Reson Med 59:229–235, 2008. © 2008 Wiley‐Liss, Inc.
Numerical simulation of bolt‐supported tunnels by means of a multiphase model conceived as an improved homogenization procedure
Authors: de Buhan Patrick , Bourgeois Emmanuel , Hassen Ghazi 
Published: January 2008

AbstractThis paper examines the possibility of applying a homogenization procedure to analyze the convergence of a tunnel reinforced by bolts, regarded as periodically distributed linear inclusions. Owing to the fact that a classical homogenization method fails to account for the interactions prevailing between the bolts and the surrounding ground and thus tends to significantly overestimate the reinforcement effect in terms of convergence reduction, a so‐called multiphase model is presented and developed, aimed at improving the classical homogenization method. Indeed, according to this model, the bolt‐reinforced ground is represented at the macroscopic scale as the superposition of two mutually interacting continuous phases, describing the ground and the reinforcement network, respectively. It is shown that such a multiphase approach can be interpreted as an extension of the homogenization procedure, thus making it possible to capture the ground–reinforcement interaction in a proper way, provided the constitutive parameters of the model and notably those relating to the interaction law can be identified from the reinforced ground characteristics. The numerical implementation of this model in a finite element method‐based computer code is then carried out, and a first illustrative application is finally presented. Copyright © 2008 John Wiley & Sons, Ltd.
Lack of interleukin‐4 receptor α chain‐dependent signalling promotes azoxymethane‐induced colorectal aberrant crypt focus formation in Balb/c mice
Authors: Ko CWS , Cuthbert RJ , Orsi NM , Brooke DA , Perry SL , Markham AF , Coletta PL , Hull MA 
Published: January 2008

AbstractInterleukin (IL)‐4 receptor (IL‐4R) α chain‐dependent signalling by IL‐4 and IL‐13 promotes tumour growth and metastasis in mouse models of colorectal cancer. However, the role of IL‐4Rα‐dependent signalling during the early, pre‐malignant stages of colorectal carcinogenesis has not been investigated. Therefore, we investigated the effect of deletion of the IL‐4Rα gene on azoxymethane‐induced colorectal aberrant crypt focus (ACF) multiplicity and size in Balb/c mice. IL‐4Rα−/− mice developed significantly more ACFs [median 8, inter‐quartile range (IQR) 4–11.5; n = 9] than wild‐type (WT) animals (median 4, IQR 1–6; n = 9; p = 0.04, Mann–Whitney U‐test). There were significantly higher levels of IL‐4 in serum from azoxymethane‐ and sham‐treated IL‐4Rα−/− mice than WT animals, but no difference in serum IL‐13 levels. In the absence of functional IL‐4Rs, IL‐13 can also signal via the IL‐13Rα2 receptor, leading to induction of transforming growth factor (TGF) β, which has pro‐tumourigenic activity at early stages of intestinal tumourigenesis. We found that mucosal TGFβ mRNA levels and intestinal epithelial cell TGFβ immunoreactivity were significantly higher in IL‐4Rα−/− mice than inWT animals. In summary, IL‐4Rα‐dependent signalling has a protective, anti‐neoplastic role during the post‐initiation phase of azoxymethane‐induced colorectal carcinogenesis in Balb/c mice. Our data should prompt thorough investigation of the role of IL‐4Rα‐dependent signalling during human colorectal carcinogenesis, particularly as antagonism of IL‐4R signalling represents a therapeutic strategy for asthma and other allergic diseases. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Weed species shifts in glyphosate‐resistant crops
Authors: Owen Micheal DK 
Published: January 2008

AbstractThe adoption of glyphosate‐based crop production systems has been one of the most important revolutions in the history of agriculture. Changes in weed communities owing to species that do not respond to current glyphosate‐based management tactics are rapidly increasing. Clearly, glyphosate‐resistant crops (GRCs) do not influence weeds any more than non‐transgenic crops. For most crops, the trait itself is essentially benign in the environment. Rather, the weed control tactics imposed by growers create the ecological selection pressure that ultimately changes the weed communities. This is seen in the adoption of conservation tillage and weed management programs that focus on one herbicide mode of action and have hastened several important weed population shifts. Tillage (disturbance) is one of the primary factors that affect changes in weed communities. The intense selection pressure from herbicide use will result in the evolution of herbicide‐resistant weed biotypes or shifts in the relative prominence of one weed species in the weed community. Changes in weed communities are inevitable and an intrinsic consequence of growing crops over time. The glyphosate‐based weed management tactics used in GRCs impose the selection pressure that supports weed population shifts. Examples of weed population shifts in GRCs include common waterhemp [Amaranthus tuberculatus (Moq ex DC) JD Sauer], horseweed (Conyza canadensis L), giant ragweed (Ambrosia trifida L) and other relatively new weed problems. Growers have handled these weed population shifts with varying success depending on the crop. Copyright © 2008 Society of Chemical Industry
Kinetic studies on aminopeptidase M‐mediated degradation of human hemorphin LVV‐H7 and its N‐terminally truncated products
Authors: John Harald , John Stefanie , Forssmann Wolf‐Georg 
Published: January 2008

AbstractThe human hemorphin LVV‐H7 belongs to the class of µ‐opiod receptor‐binding peptides, which also exhibits significant affinity to insulin‐regulated aminopeptidase (IRAP) thereby affecting IRAP inhibition. The inhibitory potency towards IRAP is of pharmaceutical interest for the treatment of Alzheimer's disease. Consecutive N‐terminal cleavage of the first two amino acid residues of LVV‐H7 affects a drastic increase of the binding affinity (V‐H7) but ultimately leads to its complete abolition after cleavage of the next amino acid residue (H7). Therefore, we investigated LVV‐H7 truncation by aminopeptidase M (AP‐M) identified as a LVV‐H7 degrading enzyme potentially regulating hemorphin activity towards IRAP in vivo. Using a selective quantitative multi‐component capillary zone electrophoretic method (CZE‐UV), we analyzed the AP‐M‐mediated subsequent proteolysis of the hemorphins LVV‐H7 (L32‐F41), VV‐H7 (V33‐F41), and V‐H7 (V34‐F41) in vitro. Incubations were carried out with synthetic hemorphins applied as single substrates or in combination. Maximum velocities (Vmax), catalytic constants (turnover numbers, kcat), and specific enzyme activities (EA) were calculated. L32 cleavage from LVV‐H7 happens more than two‐times faster (kcat: 140 min−1 ± 9%, EA: 1.0 U/mg ± 9%) than V33 cleavage from VV‐H7 (kcat: 61 min−1 ± 10%, EA: 0.43 U/mg ± 10%) or V32 deletion from V‐H7 (kcat: 62 min−1 ± 8%, EA: 0.46 U/mg ± 8%). In contrast, we showed that H7 (Y35‐F41) was neither degraded by porcine AP‐M nor did it act as an inhibitor for this enzyme. Determined turnover numbers were in the same dimension as those reported for dynorphin degradation. This is the first time that AP‐M‐mediated truncation of natural underivatized LVV‐H7 and its physiological metabolites was analyzed to determine kinetic parameters useful for understanding hemorphin processing and designing hemorphin‐derived drug candidates. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Discovery of new analogs of the marine biotoxin azaspiracid in blue mussels (Mytilus edulis) by ultra‐performance liquid chromatography/tandem mass spectrometry
Authors: Rehmann Nils , Hess Philipp , Quilliam Michael A. 
Published: January 2008

AbstractAzaspiracids (AZAs) are a group of lipophilic marine biotoxins that were first discovered in blue mussels harvested in 1995 in Killary Harbour on the west coast of Ireland. At least eight people fell ill after the consumption of contaminated mussels and developed symptoms of nausea, stomach cramps, vomiting and severe diarrhoea. Until now, eleven different analogs of these toxins have been described, with a twelfth one theoretically postulated. This paper describes the detection and identification of twenty new analogs of azaspiracid, including dihydroxy‐AZAs and carboxy‐AZAs, using state‐of‐the‐art techniques including ultra‐performance liquid chromatography (UPLC) and tandem mass spectrometry (MS/MS). Blue mussels (Mytilus edulis) from a toxic event of the northwest coast of Ireland in 2005 were extracted and analysed using LC/MS. The mass spectra obtained from different instruments enabled identification of previously unknown analogs of azaspiracid with additional hydroxyl and carboxyl substituents. Mass fragmentation patterns of the dihydroxy‐AZAs indicated the positions of these substituents to be at the C3 and C23 position. The previously theoretically postulated AZA12 was also observed in this study. Product ion spectra showed the presence of a unique fragment ion at m/z 408 for all C23‐hydroxylated analogs. This fragmentation competes with the fragmentation leading to m/z 362, a fragment ion that has shown to be present in all AZAs. The novel analogs have not been seen in plankton or water samples and are believed to be metabolites of AZAs formed in mussels. All the new AZA analogs were present at low concentrations in the shellfish and it is probably safe to assume that they do not pose a risk for the shellfish consumer. Copyright © 2008 John Wiley & Sons, Ltd. and Crown in the right of Canada
Quantification of human insulin‐like growth factor‐1 and qualitative detection of its analogues in plasma using liquid chromatography/electrospray ionisation tandem mass spectrometry
Authors: Bredehöft Michael , Schänzer Wilhelm , Thevis Mario 
Published: January 2008

AbstractHuman insulin‐like growth factor‐1 (IGF‐1) is a peptide hormone that acts as a mediator of most of the somatotropic effects of growth hormone (GH). Therefore, it is supposed to be a biomarker indicating GH abuse in sports as well as diseases associated with a change in IGF‐1 plasma concentration. It can be applied locally by injection to increase total protein and DNA content in tissues such as skeletal muscle – a highly desirable effect in various sports disciplines. In order to improve its growth‐promoting properties, the primary structure of IGF‐1 has been modified, yielding analogues such as des(1‐3)IGF‐1 and LONG™R3IGF‐1, which show a considerably reduced affinity to the respective binding proteins in plasma and, thus, an increased bioavailability at target tissues. Due to their capability to enhance performance, IGF‐1 and its analogues belong to the prohibited list of the World Anti‐Doping Agency. Hence, it was necessary to develop a reliable assay for the quantification of human IGF‐1 as well as the detection of its derivatives. Immunoaffinity isolation and purification from 60 µL of plasma followed by liquid chromatography/electrospray ionisation tandem mass spectrometry enabled the unequivocal determination of all target analytes. Diagnostic product ions were characterised utilising an Orbitrap mass spectrometer with high resolution/high accuracy properties and employed for triple quadrupole MS/MS analysis. The described assay provided lower limits of detection (LLODs) between 20 and 50 ng/mL, recovery rates between 34–43% and a precision <15% at the LLOD as well as higher concentration levels. In order to prove the applicability of the developed assay, human plasma samples were analysed and the results were compared with the values obtained from a commercially available immunoradiometric assay (IRMA). Four of six samples resulted in concentration ratios with good correlation between both assays, whereas the absolute concentrations were lower for the presented procedure. Copyright © 2008 John Wiley & Sons, Ltd.
Analysis of polycyclic aromatic hydrocarbon sequences in a premixed laminar flame by on‐line time‐of‐flight mass spectrometry
Authors: Panariello Marina , Apicella Barbara , Armenante Mario , Bruno Annalisa , Ciajolo Anna , Spinelli Nicola 
Published: January 2008

AbstractA time‐of‐flight mass spectrometer in reflectron configuration has been used for the real‐time detection of combustion products. The products of a premixed laminar C2H4/O2 flame at atmospheric pressure were sampled along its axis, diluted with inert gas and carried to the ion source as a molecular beam under minimal perturbation. Electron ionization and different optical ionization sources are compared. Photoionization was achieved with laser radiation from a Nd:YAG nanosecond pulsed laser at two different wavelengths in the UV range (266 and 355 nm). The mass spectra obtained using laser wavelength of 355 nm and electron ionization present a series of ions regularly spaced by 18 m/z units up to m/z 2000. This series allowed precise calibration of the instrument for compounds of high molecular weight. Information on the chemical nature of the analyzed species has been obtained by comparing mass spectra produced with different ionization methods. In order to better understand the growth mechanisms, polycyclic aromatic hydrocarbon sequences have been analyzed by fast Fourier transform of the mass spectra. Copyright © 2008 John Wiley & Sons, Ltd.
An investigation of the distribution of minor components in complex polymeric paint formulations using ToF‐SIMS depth profiling
Authors: Hinder Steven J. , Watts John F. , Simmons Garnett C. , Lowe Chris 
Published: January 2008

AbstractA series of complex polymeric paint formulations have been investigated by ToF‐SIMS depth profiling. Employing a Bin+ analysis source and a Buckminster Fullerene (C60) etch source in the dual‐beam mode of operation, depth profiles from poly(vinylidene difluoride) (PVdF), poly(urethane) (PU), polyester (PE) and epoxy‐based commercial coatings were obtained to determine the distribution of minor components included in the coating formulation.The addition of small quantities of additives such as flow agents is known to induce significant changes in the surface composition of the paint. Depth profiles were obtained from a PU primer formulation to which a 35Cl/37Cl labelled flow agent had been added. The depth profiles show that the chlorine tagged component is confined to the surface region of the coating due to segregation of the flow agent to the air/coating surface. Depth profiles obtained from a PVdF topcoat formulation that included a hexamethoxymethyl melamine (HMMM) cross‐linking agent demonstrate that the HMMM intensity is greater at the coating surface than in the bulk. The HMMM depth profile also reveals that the HMMM possesses a depletion zone between the coating bulk and the air/coating surface. Depth profiles obtained from both PE and epoxy primer formulations show that the concentration of inorganic particles included as pigments and anti‐corrosion agents in the coatings is greater in the coating bulk than at the coating surface, demonstrating effective detection of these second phase particles, and that, as expected, they are properly dispersed in the organic phase. The results demonstrate that depth profiling of polymeric coatings, when employing a C60 etch source, can be used to determine the distribution of minor components within cured coatings. Copyright © 2008 John Wiley & Sons, Ltd.
Evaluation of an ultra‐wide bandwidth wireless indoor non‐line‐of‐sight channels
Authors: Wang Yang , Zhang Jie , Zhang Qinyu , Zhang Naitong 
Published: January 2008

AbstractIn this paper, based on the analysis of the experimental data using a new post‐processing method for time‐domain channel measurements, a new double‐cluster statistical model for UWB systems with a bandwidth lower than 1 GHz in non‐line‐of‐sight (NLOS) indoor propagation environment is proposed. By using the proposed model, both the model itself and the parameter estimation of the corresponding model are simplified. By defining the polarity of a particular model parameter, the model has the flexibility to deal with both ‘soft NLOS’ and ‘hard NLOS’ indoor propagation environments. Therefore, the channel impulse responses (CIRs) generated by the proposed model ‘resemble’ the measured CIR better than the SV (Saleh‐‐Valenzuela)/IEEE 802.15.3a model not only in terms of the average values, but also in terms of the cumulative distribution functions (CDFs) of the small‐scale statistics. Copyright © 2008 John Wiley & Sons, Ltd.