bluuebunny/crossref_metadata_2025 huggingface dataset:
p53 Levels Positively Correlate with Carotid Intima‐media Thickness in Patients with Subclinical Atherosclerosis
Authors: Chen Wenqiang , Wang Fen , Li Zongxin , Huang Xiaobo , Wang Ningqun , Dong Zhizhi , Sun Ping
Published: December 2009

Background

The level of circulating p53 is related to inflammation in asymptomatic subjects with cardiovascular risk factors. Whether p53 is associated with the severity of atherosclerosis remains to be determined.

Hypothesis

This study examines the relationship of systemic p53 levels with atherosclerotic risk factors and subclinical atherosclerosis.

Methods

Circulating levels of p53 and markers of inflammation were measured in 356 subjects with cardiovascular risk factors but who were free from clinical cardiovascular disease. Subclinical atherosclerosis was evaluated by both the mean carotid intima‐media thickness (IMT) and the presence of atherosclerotic plaques with the use of B‐mode ultrasound in all subjects.

Results

p53 levels were positively correlated with age (r = 0.382, P < 0.001), intercellular adhesion molecular‐1 (ICAM‐1; r = 0.510, P < 0.01), vascular cell adhesion molecular‐1 (VCAM‐1; r = 0.497, P < 0.01), E‐selectin (r = 0.337, P < 0.01), and carotid IMT (r = 0.594, P < 0.01). The association between p53 and IMT remained significant in multiple regression analysis (P < 0.01) when controlling for traditional atherosclerotic risk factors and inflammatory markers.

Conclusion

Higher plasma p53 levels were associated with an increase in inflammatory markers, as well as increased carotid IMT. Circulating p53 may be useful in identifying subclinical atherosclerosis in subjects symptomatically free from cardiovascular disease. Copyright © 2009 Wiley Periodicals, Inc.
Statin Therapy Decreases Myocardial Function as Evaluated Via Strain Imaging
Authors: Rubinstein Jack , Aloka Feras , Abela George S.
Published: December 2009

Objectives

The purpose of this study was to evaluate the effects of statin therapy on myocardial function as measured with echocardiography with tissue Doppler imaging (TDI) and strain imaging (SI) independent of its lipid‐lowering effect.

Background

Statin use is known to improve outcomes in the primary and secondary prevention of ischemic heart disease, but their use is also associated with myopathy, muscle weakness and in rare cases, rhabdomyolysis. We sought to evaluate whether TDI and SI is able to identify changes in myocardial function associated with statin use.

Methods

Myocardial function was evaluated in 28 patients via echocardiography with TDI and SI. We identified 12 patients (5 females) without overt cardiovascular disease (including hypertension, smoking, and diabetes) that were on statin therapy and compared their echocardiographic findings with 16 (12 females) age, sex, and cholesterol–profile‐matched controls. Tissue Doppler imaging parameters of diastolic (E′/A′ and E/E′) and systolic (S′) function were measured. Regional systolic function was obtained by SI in 4‐chamber, 2‐chamber, long axis, and average global views.

Results

There was no significant difference in myocardial function as measured by Doppler and minor differences as measured via TDI among the 2 groups. There was significantly better function noted with SI in the control group vs the statin group in the 4‐chamber (−19.05% ± 2.45% vs −16.47% ± 2.37% P = 0.009), 2‐chamber (−20.30% ± 2.66% vs −17.45% ± 4.29% P = 0.03), long axis (−17.63% ± 3.79% vs −13.83% ± 3.74% P = 0.01), and average global (−19.0% ± 2.07% vs −15.91% ± 2.81% P = 0.004) views.

Conclusion

Statin therapy is associated with decreased myocardial function as evaluated with SI. Copyright © 2009 Wiley Periodicals, Inc.
Variability of Peripheral Arterial Tonometry in the Measurement of Endothelial Function in Healthy Men
Authors: Liu Jianmin , Wang Jingzhu , Jin Yan , Roethig Hans J. , Unverdorben Martin
Published: December 2009

Measurement of endothelial function using peripheral arterial tonometry (PAT) has been reported to be significantly correlated with coronary blood flow. Repetitive PAT measurements were performed in 22 healthy male subjects at test intervals of 1 hour (5 times within a day) and 0.5 hours (7 times within a day) to evaluate the variability of the reactive hyperemia index (RHI). A total of 10 subjects underwent additional repetitive PAT at 2 hour intervals (7 times within a day) for 3 consecutive days to evaluate the diurnal effects and day‐to‐day reproducibility. The RHI from each test was computed automatically based on a 15 minute recording of pulse wave amplitude changes of the fingers in response to reactive hyperemia induced by a 5 minute occlusion of the brachial artery. Intrasubject variability of RHI at different test intervals, defined as the coefficient of variation (CV) was 15.3% ± 5.3%, 16.1%± 7.8%, and 22.6% ± 3.9% for the tests at 0.5 hour, 1 hour, and 2 hour intervals, respectively. Reactive hyperemia indices measured at the same time points on each of the 3 days were not statistically significant. The interday reproducibility, presented as intraclass correlation coefficients (ICC) ranged from − 0.07 to 0.47. We conclude that repetitive PAT measurements have no carryover effect on RHI at 1 hour, and 2 hour intervals, and the RHI measured at 0.5 hour intervals is associated with a trend of increase. The interday reproducibility is relatively low and the intrasubject variability of RHI is similar to those observed in studies of flow‐mediated dilation using brachial artery ultrasound scanning. Copyright © 2009 Wiley Periodicals, Inc.
Is Right Ventricular Outflow Tract Pacing Superior to Right Ventricular Apex Pacing in Patients with Normal Cardiac Function?
Authors: Gong Xue , Su Yangang , Pan Wenzhi , Cui Jie , Liu Shaowen , Shu Xianhong
Published: December 2009

Background

Whether right ventricular outflow tract (RVOT) pacing is superior to right ventricular apex (RVA) pacing in terms of ventricular synchrony, cardiac function, and remodeling in patients with normal cardiac function is still unknown.

Hypothesis

Right ventricular outflow tract pacing is superior to RVA pacing in patients with normal cardiac function.

Methods

A total of 96 consecutive patients with high or third‐degree atrial ventricular block were enrolled and randomized into 2 groups: RVOT pacing group (n = 48) and RVA pacing group (n = 48). Tissue Doppler imaging (TDI) and 2D echocardiography were performed to study left ventricular (LV) systolic and diastolic synchrony, LV volumes, and function.

Results

There were no significant differences in baseline characteristics between the 2 groups. Left ventricular systolic asynchrony is more severe in the RVA pacing group than in the RVOT pacing group (P < 0.05), while diastolic synchrony is not significantly (NS) different between the 2 groups after pacing. There were no significant differences with respect to the mean myocardial systolic (Sm) and early diastolic velocities (Em), LV ejection fraction, LV end‐diastolic and systolic volume in the 2 groups at 12 months of follow‐up (all NS).

Conclusions

Although RVOT pacing caused more synchronous LV contraction compared with RVA pacing, it had no benefit over RVA pacing in aspect of preventing cardiac remodeling and preserving LV systolic function after 12 months of pacing in patients with normal cardiac function. Copyright © 2009 Wiley Periodicals, Inc.
Work‐hardening characteristics of Zn‐Ti alloy single crystals
Authors: Boczkal G. , Mikulowski B. , Oertel C.‐G. , Skrotzki W.
Published: December 2009

Shear stress – shear strain curves of 0.14 at.%Ti alloyed Zn single crystals were measured in compression at different temperatures and shear strain rates. The work‐hardening coefficient for basal slip increases with decreasing temperature and increasing shear strain rate. The work‐hardening characteristics are compared with those reported for Zn single crystals with different constituents and purities. It is discussed with respect to the interaction of dislocations with dislocations, vacancies, vacancy agglomerates and solute atoms. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis, structure and optical properties of zinc oxide hexagonal microprisms
Authors: Kumari L. , Li W. Z.
Published: December 2009

Zinc oxide (ZnO) pencil‐head‐like (PHL) microprisms were synthesized by a hydrothermal route using a zinc (Zn) plate as a source and substrate. The structural analysis confirmed the formation of ZnO with hexagonal wurtzite phase on the hexagonal Zn substrate and the growth of the ZnO microparticles along the [101] direction. The room temperature photoluminescence (PL) of the ZnO microprisms showed a sharp UV emission band located at around 380 nm, which is expected to originate from the radiative recombination of free excitons. The sharp UV emission band, with a full width at half‐maximum of about 15 nm and an extremely weak visible emission, confirms the high crystal quality of the synthesized ZnO microprisms. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient mechanism for establishing IP connectivity in next‐generation networks
Authors: Campos Rui , Ricardo Manuel
Published: December 2009

The changes in the communication paradigm envisioned for next‐generation networks (NGNs), with peer‐to‐peer/symmetric attachments gaining momentum and two Internet Protocol (IP) versions coexisting, will pose new challenges to mobile communication networks. Traditional IP auto‐configuration mechanisms will not work properly, since they were designed mostly having in mind a client–server/asymmetric attachment model, they assume a single IP version paradigm, and they target the auto‐configuration of devices only. The IST Ambient Networks (ANs) project has introduced a new concept—the AN—that enables handling every communication entity, either a single device or an entire network, as an AN. This paper describes a new efficient mechanism, named Basic Connectivity (BC) mechanism, for auto‐configuring IP connectivity between attaching ANs. A proof‐of‐concept prototype, experimental results, and theoretical analysis show that BC suites the future networking paradigm and represents a solution more efficient than the current trial‐and‐error mechanism for auto‐configuring IP connectivity. Copyright © 2009 John Wiley & Sons, Ltd.
Synchronous ipsilateral Warthin tumor encased by a separate mucoepidermoid carcinoma of the parotid gland: A case report and review of the literature
Authors: Srivastava Sucheta , Nadelman Celina
Published: December 2009

Fine‐needle aspiration (FNA) is a cost effective and low morbidity procedure in the initial assessment of salivary gland tumors. However, cytological assessment of ipsilateral synchronous tumors (which make up less than 0.3% of all salivary gland neoplasms) may pose diagnostic challenges. Therefore, a wholesome approach, including FNA with clinical and radiological correlation, is of utmost importance. Here, we report a unique case of Warthin tumor encased by a separate high‐grade mucoepidermoid carcinoma that was first diagnosed on FNA. Another striking feature seen was the presence of chronic sialadenitis in the surrounding nonneoplastic salivary gland. The presence of two different neoplasms in the background of chronic sialadenitis raises the question of a possible causal relationship. Traditionally, there has been diagnostic difficulty when dealing with synchronous tumors of the salivary gland and the background of chronic sialadenitis may further complicate the diagnosis. FNA is very helpful and can give important cues to the diagnosis. Diagn. Cytopathol. 2010. © 2009 Wiley‐Liss, Inc.
A posteriori error of a discontinuous Galerkin scheme for compressible miscible displacement problems with molecular diffusion and dispersion
Authors: Yang Jiming
Published: December 2009

A kind of compressible miscible displacement problems including molecular diffusion and dispersion in porous media is studied. A symmetric interior penalty discontinuous Galerkin method is applied to the coupled system of flow and transport. Explicit a posteriori error estimates are obtained based on the duality argument, approximation properties and residual notations. The resulting error bound is shown to be reliable and worthwhile for guiding dynamic mesh adaptivity. Copyright © 2009 John Wiley & Sons, Ltd.
Lattice Boltzmann study of bubble entrapment during droplet impact
Authors: Huang Jun Jie , Shu Chang , Chew Yong Tian
Published: December 2009

The entrapment ofbubbleduring droplet impact on solid surfaces was studied by using a phase‐field lattice Boltzmann model (LBM). Numerous three‐dimensional simulations were performed and several types of entrapment were found under specific impact conditions. Some cases are similar to previous studies, whereas others are reported for the first time. Dissections of the entrapment processes were carried out, and detailed analyses of the flow fields and interface motions were provided at selected moments for certain cases. The effects of the Reynolds number, the Weber number and the surface wettability were analyzed based on the observation. Besides, some computational issues of phase‐field simulations were discussed for the present problem. Finally, the impact condition to prevent entrapment was preliminarily estimated in terms of the Ohnesorge number upon examination of numerous simulations. Copyright © 2009 John Wiley & Sons, Ltd.
Carbon‐Supported CoSe2 Nanoparticles for Oxygen Reduction Reaction in Acid Medium
Authors: Feng Y. J. , He T. , Alonso‐Vante N.
Published: December 2009

Carbon‐supported CoSe2 nanoparticles, as non‐precious metal cathodic catalyst, were prepared via the in situ surfactant‐free method with the conventional heating. Structural and electrochemical properties of the obtained 20 wt.‐% CoSe2/C nanoparticles were investigated by means of powder X‐ray diffraction (PXRD), differential thermal gravimetric analysis (DTA‐DTG) and rotating disc electrode (RDE) techniques. CoSe2 nanoparticles have two kinds of crystal structure after heat treatment under nitrogen at different temperature: orthorhombic at 250 and 300 °C; cubic at 400 and 430 °C. The latter structure has higher oxygen reduction activity than the former in 0.5 M H2SO4. CoSe2/C nanoparticles after heat treatment from 250 to 430 °C, have an onset potential from 0.78 to 0.81 V versus the reference hydrogen electrode (RHE) in O2‐saturated 0.5 M H2SO4 at 25 °C. 20 wt.‐% CoSe2/C nanoparticles, after heat treatment at 300 °C, promote ca. 3.5 electrons, per oxygen molecule, transferred during the oxygen reduction process. They have an oxidation wave centred at 0.96 V versus RHE and display higher methanol tolerance as compared to 20 wt.‐% Pt/C (E‐TEK).
MMP‐2 alters VEGF expression via αVβ3 integrin‐mediated PI3K/AKT signaling in A549 lung cancer cells
Authors: Chetty Chandramu , Lakka Sajani S. , Bhoopathi Praveen , Rao Jasti S.
Published: December 2009

Vascular endothelial growth factor (VEGF) is one of the most important angiogenic growth factors for tumor angiogenesis. Here, we sought to explore whether RNA interference (RNAi) targeting matrix metalloproteinase‐2 (MMP‐2) could disrupt VEGF‐mediated angiogenesis in lung cancer. MMP‐2 siRNA inhibited lung cancer cell‐induced tube formation of endothelial cells in vitro; addition of recombinant human‐MMP‐2 restored angiogenesis. MMP‐2 transcriptional suppression decreased VEGF, phosphatidylinositol 3‐kinase (PI3K) protein levels and AKT phosphorylation in lung cancer cells. In addition, MMP‐2 suppression decreased hypoxia inducible factor‐1α (HIF‐1α), a transcription factor for VEGF, as determined by electrophoretic mobility shift assay (EMSA). We also show that MMP‐2 suppression disrupted PI3K dependent VEGF expression; ectopic expression of myr‐AKT restored VEGF inhibition. Further, MMP‐2 suppression decreased the interaction of integrin‐αVβ3 and MMP‐2 as confirmed by immunoprecipitation analyses. Studies with either function blocking integrin‐αVβ3 antibody or MMP‐2 specific inhibitor (ARP‐100) indicate that suppression of MMP‐2 decreased integrin‐αVβ3‐mediated induction of PI3K/AKT leading to decreased VEGF expression. Moreover, A549 xenograft tissue sections from mice that treated with MMP‐2 siRNA showed reduced expression of VEGF and the angiogenic marker, factor‐VIII. The inhibition of tumor angiogenesis in MMP‐2 suppressed tumor sections was associated with decreased co‐localization of integrin‐αVβ3 and MMP‐2. In summary, these data provide new insights into the mechanisms underlying MMP‐2‐mediated VEGF expression in lung tumor angiogenesis.
The impact of macroeconomic uncertainty on firms' changes in financial leverage
Authors: Baum Christopher F. , Chakraborty Atreya , Liu Boyan
Published: December 2009

We investigate the relationship between a firm's measures of corporate governance, macroeconomic uncertainty and changes in leverage. Recent research highlights the role of governance in financing decisions. Previous research also indicates that macroeconomic uncertainty affects a firm's ability to borrow. In this paper we investigate how both these channels of influence affects firms' financing decisions. Our findings show that macroeconomic uncertainty has an important role to play, both by itself and in interaction with a measure of corporate governance. Copyright © 2009 John Wiley & Sons, Ltd.
The behavior of emerging market sovereigns' credit default swap premiums and bond yield spreads
Authors: Adler Michael , Song Jeong
Published: December 2009

We test whether credit risk for Emerging Market Sovereigns is priced equally in the credit default swap (CDS) and bond markets. The parity relationship between CDS premiums and bond yield spreads (BYS), that was tested and largely confirmed in the literature, is mostly rejected. Prices below par can result in positive basis, i.e. CDS premiums that are greater than BYS and vice versa. To adjust for the non‐par price, we construct the BYS implied by the term structure of CDS premiums for various maturities. We are able to restore the parity relation and confirm the equivalence of credit risk pricing in the CDS and bond markets for many countries that have bonds with non‐par prices and time varying credit quality. We detect non‐parity even after the adjustment mainly in countries in Latin America, where the bases are larger than the bid–ask spreads in the market. We also find that the repo rates of bonds decrease around episodes of credit quality deterioration, which helps the basis remain positive. Copyright © 2009 John Wiley & Sons, Ltd.
Mean–variance econometric analysis of household portfolios
Authors: Miniaci Raffaele , Pastorello Sergio
Published: December 2009

We investigate households' portfolio choice using a microeconometric approach derived from mean–variance optimization. We assume that households have heterogeneous expectations on the distribution of excess returns and that they cannot take short positions in risky assets. Assuming two such assets, we derive an explicit solution of the model characterized by four possible portfolio regimes, which are analyzed using two structural probit and tobit specifications with three latent state variables. Both specifications are estimated by weighted maximum likelihood on a cross‐section of US households drawn from the 2004 SCF. The tobit specification is simulated in order to evaluate the regressors' effects on regime probabilities and asset demands. We also assess to what extent the predicted state variables are consistent with the self‐reported expected returns and risk aversion elicited from the SCF questionnaire. Copyright © 2009 John Wiley & Sons, Ltd.
The QM‐MM interface for CHARMM‐deMon
Authors: Lev Bogdan , Zhang Rui , de la Lande Aurélien , Salahub Dennis , Noskov Sergei Yu
Published: December 2009

We present a new QM/MM interface for fast and efficient simulations of organic and biological molecules. The CHARMM/deMon interface has been developed and tested to perform minimization and atomistic simulations for multi‐particle systems. The current features of this QM/MM interface include readability for molecular dynamics, tested compatibility with Free Energy Perturbation simulations (FEP) using the dual topology/single coordinate method. The current coupling scheme uses link atoms, but further extensions of the code to incorporate other available schemes are planned. We report the performance of different levels of theory for the treatment of the QM region, while the MM region was represented by a classical force‐field (CHARMM27) or a polarizable force‐field based on a simple Drude model. The current QM/MM implementation can be coupled to the dual‐thermostat method and the VV2 integrator to run molecular dynamics simulations. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010
Sequential steps underlying neuronal plasticity induced by a transient exposure to gabazine
Authors: Pegoraro Silvia , Broccard Frédéric D. , Ruaro Maria Elisabetta , Bianchini Daniele , Avossa Daniela , Pastore Giada , Bisson Giacomo , Altafini Claudio , Torre Vincent
Published: December 2009

Periods of intense electrical activity can initiate neuronal plasticity leading to long lasting changes of network properties. By combining multielectrode extracellular recordings with DNA microarrays, we have investigated in rat hippocampal cultures the temporal sequence of events of neuronal plasticity triggered by a transient exposure to the GABAAreceptor antagonist gabazine (GabT). GabT induced a synchronous bursting pattern of activity. The analysis of electrical activity identified three main phases during neuronal plasticity induced by GabT: (i) immediately after termination of GabT, an early synchronization (E‐Sync) of the spontaneous electrical activity appears that progressively decay after 3–6 h. E‐Sync is abolished by inhibitors of the ERK1/2 pathway but not by inhibitors of gene transcription; (ii) the evoked response (induced by a single pulse of extracellular electrical stimulation) was maximally potentiated 3–10 h after GabT (M‐LTP); and (iii) at 24 h the spontaneous electrical activity became more synchronous (L‐Sync). The genome‐wide analysis identified three clusters of genes: (i) an early rise of transcription factors (Cluster 1), primarily composed by members of the EGR and Nr4a families, maximally up‐regulated 1.5 h after GabT; (ii) a successive up‐regulation of some hundred genes, many of which known to be involved in LTP (Cluster 2), 3 h after GabT likely underlying M‐LTP. Moreover, in Cluster 2 several genes coding for K+channels are down‐regulated at 24 h. (iii) Genes in Cluster 3 are up‐regulated at 24 h and are involved in cellular homeostasis. This approach allows relating different steps of neuronal plasticity to specific transcriptional profiles. J. Cell. Physiol. 222: 713–728, 2010. © 2009 Wiley‐Liss, Inc.
Sexually dimorphic tegumental gland openings in Laniatores (Arachnida, Opiliones), with new data on 23 species
Authors: Willemart Rodrigo H. , Pérez‐González Abel , Farine Jean‐Pierre , Gnaspini Pedro
Published: December 2009

Sexually dimorphic glands often release sexual pheromones both in vertebrates and invertebrates. Species of Laniatores (Arachnida, Opiliones) seem to depend on chemical communication but few studies have addressed this topic. In this study, we review the literature for the Phalangida and present new data for 23 species of Laniatores. In 16 taxa, we found previously undescribed sexually dimorphic glandular openings on the femur, patella, metatarsus, and tarsus of legs I and metatarsus of legs III and IV. For the other species, we provide scanning electron micrographs of previously undescribed sexually dimorphic setae and pegs located on swollen regions of the legs. We also list additional species in which males have swollen regions on the legs, including the tibia, metatarsus, and tarsus of legs I, trochanter and tibia of legs II, femur, metatarsus, and tarsus of legs III, and metatarsus and tarsus of legs IV. The function and biological role of the secretions released by these glands are discussed. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.
Fat and water magnetic resonance imaging
Authors: Bley Thorsten A. , Wieben Oliver , François Christopher J. , Brittain Jean H. , Reeder Scott B.
Published: December 2009

A wide variety of fat suppression and water–fat separation methods are used to suppress fat signal and improve visualization of abnormalities. This article reviews the most commonly used techniques for fat suppression and fat–water imaging including 1) chemically selective fat suppression pulses “FAT‐SAT”; 2) spatial‐spectral pulses (water excitation); 3) short inversion time (TI) inversion recovery (STIR) imaging; 4) chemical shift based water–fat separation methods; and finally 5) fat suppression and balanced steady‐state free precession (SSFP) sequences. The basic physical background of these techniques including their specific advantages and disadvantages is given and related to clinical applications. This enables the reader to understand the reasons why some fat suppression methods work better than others in specific clinical settings. J. Magn. Reson. Imaging 2010;31:4–18. © 2009 Wiley‐Liss, Inc.
Short echo time MR spectroscopy of brain tumors: Grading of cerebral gliomas by correlation analysis of normalized spectral amplitudes
Authors: Weis Jan , Ring Patrik , Olofsson Tommie , Ortiz‐Nieto Francisco , Wikström Johan
Published: December 2009

Purpose:

To process single voxel spectra of low‐ and high‐grade gliomas. To propose correlation analysis of the scatter plots of normalized spectral amplitudes as a pattern recognition tool for the classification (grading) of brain tumors. To propose a spectrum processing approach that improves the differentiation of proton spectra with dominating macromolecule and lipid peaks.

Materials and Methods:

LCModel was used to process spectra. Mean metabolite concentrations and mean normalized spectra were obtained for normal white matter and for gliomas. The mean spectra of macromolecules and lipids (ML) in the range 1.4–0.9 ppm, and mean difference spectra (DS) without ML and lactate were computed. Correlation analysis of the scatter plot of the patient and mean normalized spectral amplitudes and dispersion of the scatter plot points were used for classification and grading of tumors.

Results:

It was found advantageous to perform the classifications using DS spectra. The shape of ML spectrum and concentration of tCr seem to be a good markers for glioma grade.

Conclusion:

Combining a qualitative comparison of the patient and mean DS spectra of the tumors using correlation analysis of normalized spectra amplitudes with a quantitative comparison of metabolite concentrations is a powerful tool in studying brain lesions. J. Magn. Reson. Imaging 2010;31:39–45. © 2009 Wiley‐Liss, Inc.
Objective and subjective evaluation of adaptive speech enhancement methods for functional MRI
Authors: Ramachandran Venkat R. , Panahi Issa M.S. , Milani Ali A.
Published: December 2009

Purpose:

To recover speech corrupted by functional magnetic resonance imaging (fMRI) acoustic noise using two‐channel adaptive speech enhancement techniques.

Materials and Methods:

Speech corrupted by noise generated from a 3 T MRI scanner was recorded using diffuse‐field microphones and a data acquisition board. Multiband and subband adaptive speech enhancement methods are used to recover the speech signal from the recordings. Normalized least mean squares (NLMS) algorithm was used for updating the filter coefficients in each band.

Results:

The methods are successful in enhancing the speech quality. They are successful in improving the convergence rate of the adaptive filter. Multiband and subband methods have a similar performance in terms of noise reduction and in the subjective tests. The subband method introduces less speech distortion compared to the multiband method. The subband method requires a lower number of computations per sample.

Conclusion:

Adaptive speech enhancement techniques are effective in reducing fMRI background noise in the recordings. Based on the analysis, we conclude that subband‐based methods are more suited for enhancing speech corrupted by fMRI noise. J. Magn. Reson. Imaging 2010;31:46–55. © 2009 Wiley‐Liss, Inc.
Diurnal stability of γ‐aminobutyric acid concentration in visual and sensorimotor cortex
Authors: Evans Christopher John , McGonigle David John , Edden Richard Anthony Edward
Published: December 2009

Purpose:

To establish the diurnal stability of edited magnetic resonance spectroscopy measurements of gamma‐aminobutyric acid (GABA) in visual and sensorimotor regions of the brain.

Materials and Methods:

GABA measurements were made in two regions of the brain (an occipital, “visual” region and a “sensorimotor” region centered on the precentral gyrus) using the MEGA‐PRESS editing method, scanning eight healthy adults at five timepoints during a single day. GABA concentration was quantified from the ratio of the GABA integral to the unsuppressed water signal.

Results:

No significant effect of time on GABA concentration was seen (P = 0.35). GABA was shown to be significantly more concentrated in visual regions than in sensorimotor regions (1.10 i.u. and 1.03 i.u., respectively; P = 0.050). Coefficients of variability (CVs) across all subjects of 9.1% and 12% (visual and sensorimotor) were significantly higher than mean within‐subjects CVs of 6.5% and 8.8.

Conclusion:

This study demonstrates the excellent reproducibility of MEGA‐PRESS detection of GABA, demonstrating that the method is sufficiently sensitive to detect inter‐subject variability, and suggests that (within the sensitivity limits of current measurements) time of day can be ignored in the design of MRS studies of visual and sensorimotor regions. J. Magn. Reson. Imaging 2010;31:204–209. © 2009 Wiley‐Liss, Inc.
Improved correction of spatial inhomogeneities of surface coils in quantitative analysis of first‐pass myocardial perfusion imaging
Authors: Kremers Frans P.P.J. , Hofman Mark B.M. , Groothuis Jan G.J. , Jerosch‐Herold Michael , Beek Aernout M. , Zuehlsdorff Sven , Nielles‐Vallespin Sonia , van Rossum Albert C. , Heethaar Robert M.
Published: December 2009

Purpose:

To test whether image normalization using either a separate 3D proton‐density (PD)‐weighted prescan, or 2D PD‐weighted images prior to the perfusion series, improves correction of differences in spatial sensitivity induced by radiofrequency (RF) surface receiver coils. Originally, this correction was applied using the baseline signal in the myocardium before arrival of the contrast agent. This is of importance, as quantitative analysis of magnetic resonance (MR) myocardial perfusion using deconvolution with the arterial input assumes equal signal sensitivity over the heart.

Materials and Methods:

First‐pass myocardial perfusion measurements were obtained in 13 patients without known coronary artery disease. Absolute perfusion values were assessed for 18 myocardial segments without any normalization and using the three different normalization methods.

Results:

Using 2D or 3D PD‐weighted normalization, similar mean perfusion values were found, but with reduced spatial variance over the 18 segments. The relative dispersion of perfusion at rest was 23% and 35% for the 3D prescan normalization and the baseline normalization, respectively. With 2D and 3D PD‐weighted prescan normalization the relative dispersion was closer to the expected physiological heterogeneity.

Conclusion:

PD‐weighted prescan normalization proved to be a valuable addition to quantitative analysis of myocardial perfusion, and better than baseline‐based normalization. J. Magn. Reson. Imaging 2010;31:227–233. © 2009 Wiley‐Liss, Inc.
Diffusion‐weighted images differentiate benign from malignant thyroid nodules
Authors: Erdem Gulnur , Erdem Tamer , Muammer Hakki , Mutlu Deniz Yakar , Fırat Ahmet Kemal , Sahin Ibrahim , Alkan Alpay
Published: December 2009

Purpose:

To reveal the possible role of diffusion‐weighted images (DWI) in the differential diagnosis of benign and malignant thyroid nodules by comparing the results of fine‐needle aspiration cytology (FNAC).

Materials and Methods:

In an 18‐month period (December 2005 to May 2007), 27 cases with benign thyroid nodules with a total of 52 benign nodules, nine cases with thyroid gland malignancy, and 24 healthy control cases were included in the study. Cases that were indicated to undergo to FNAC examination and sent by a clinician for biopsy to the radiology unit were included in the study to assess the cytopathologic confirmation of the clinic, ultrasonographic, and magnetic resonance imaging (MRI) findings.

Results:

The mean apparent diffusion coefficient (ADC) values of thyroid nodules were 2745.3 ± 601.1 × 10−6 mm2/s (1605–3899 × 10−6mm2/s) in the benign group and 695.2 ± 312.5 × 10−6mm2/s (165–1330 × 10−6mm2/s) in the malignant group. Normal thyroid tissues had mean ADC values of 1344.1 ± 276.4 × 10−6 mm2/s (1015–1764 × 10−6mm2/s). The ADC values of three subgroups were significantly different (P = 0.0001). A reduced ADC was observed in most types of malignant tumors due to the consequent decrease of the extracellular extravascular space.

Conclusion:

Our preliminary results showed that ADC values of nodules may provide useful data about the nature of a thyroid nodule. J. Magn. Reson. Imaging 2010;31:94–100. © 2009 Wiley‐Liss, Inc.
Neural specificity of acupuncture stimulation at pericardium 6: Evidence from an FMRI study
Authors: Bai Lijun , Yan Hao , Li Linling , Qin Wei , Chen Peng , Liu Peng , Gong Qiyong , Liu Yijun , Tian Jie
Published: December 2009

Purpose:

To investigate the neural specificity of pericardium PC6, with the same meridian acupoint PC7 and a treatment‐irrelevant acupoint GB37 as separate controls.

Materials and Methods:

Functional magnetic resonance imaging (MRI) of the whole brain was performed in 36 healthy subjects receiving acupuncture at three acupoints, respectively: the study acupoint (PC6), and control acupoints (PC7 and GB37). A novel nonrepeated event‐related (NRER) design paradigm was applied to separately detect neural activities related to different stages of acupuncture (needling manipulation and post‐acupuncture rest epoch). Psychophysical responses (Deqi sensations) were also assessed.

Results:

Neuroimaging studies of PC6 presented extensive signal attenuations in the cerebrocerebellar and subcortical areas, whereas acupuncture at GB37 induced widespread signal potentiations. In addition, acupuncture at PC6, in comparison with stimulations at PC7 and GB37, selectively evoked neural responses of the insula, hypothalamus, and flocculonodular lobe of cerebellum (nodulus and uvula).

Conclusion:

These findings may provide preliminary evidence for specific involvements of the cerebellar‐hypothalamus and insula following acupuncture at PC6, which underlies the autonomic regulation of vestibular functions. The predominantly time‐prolonged deactivations in these areas may also serve the clinical efficacy of PC6 in producing a sedative or tranquilizing effect in antiemetic treatment. J. Magn. Reson. Imaging 2010;31:71–77. © 2009 Wiley‐Liss, Inc.
Early identification of aortic valve sclerosis using iron oxide enhanced MRI
Authors: Hamilton Amanda M. , Rogers Kem A. , Belisle Andre J.L. , Ronald John A. , Rutt Brian K. , Weissleder Ralph , Boughner Derek R.
Published: December 2009

Purpose:

To test the ability of MION‐47 enhanced MRI to identify tissue macrophage infiltration in a rabbit model of aortic valve sclerosis (AVS).

Materials and Methods:

The aortic valves of control and cholesterol‐fed New Zealand White rabbits were imaged in vivo pre‐ and 48 h post‐intravenous administration of MION‐47 using a 1.5 Tesla (T) MR clinical scanner and a CINE fSPGR sequence. MION‐47 aortic valve cusps were imaged ex vivo on a 3.0T whole‐body MR system with a custom gradient insert coil and a three‐dimensional (3D) FIESTA sequence and compared with aortic valve cusps from control and cholesterol‐fed contrast‐free rabbits. Histopathological analysis was performed to determine the site of iron oxide uptake.

Results:

MION‐47 enhanced the visibility of both control and cholesterol‐fed rabbit valves in in vivo images. Ex vivo image analysis confirmed the presence of significant signal voids in contrast‐administered aortic valves. Signal voids were not observed in contrast‐free valve cusps. In MION‐47 administered rabbits, histopathological analysis revealed iron staining not only in fibrosal macrophages of cholesterol‐fed valves but also in myofibroblasts from control and cholesterol‐fed valves.

Conclusion:

Although iron oxide labeling of macrophage infiltration in AVS has the potential to detect the disease process early, a macrophage‐specific iron compound rather than passive targeting may be required. J. Magn. Reson. Imaging 2010;31:110–116. © 2009 Wiley‐Liss, Inc.
Scan‐rescan reproducibility of carotid atherosclerotic plaque morphology and tissue composition measurements using multicontrast MRI at 3T
Authors: Li Feiyu , Yarnykh Vasily L. , Hatsukami Thomas S. , Chu Baocheng , Balu Niranjan , Wang Jinnan , Underhill Hunter R. , Zhao Xihai , Smith Robin , Yuan Chun
Published: December 2009

Purpose:

To evaluate interscan reproducibility of both vessel morphology and tissue composition measurements of carotid atherosclerosis using a fast, optimized, 3T multicontrast protocol.

Materials and Methods:

A total of 20 patients with carotid stenosis >15% identified by duplex ultrasound were recruited for two independent 3T MRI (Philips) scans within one month. A multicontrast protocol including five MR sequences was applied: TOF, T1‐/T2‐/PD‐weighted and magnetization‐prepared rapid acquisition gradient‐echo (MP‐RAGE). Carotid artery morphology (wall volume, lumen volume, total vessel volume, normalized wall index, and mean/maximum wall thickness) and plaque component size (lipid rich/necrotic core, calcification, and hemorrhage) were measured over two time points.

Results:

After exclusion of images with poor image quality, 257 matched locations from 18 subjects were available for analysis. For the quantitative carotid morphology measurements, coefficient of variation (CV) ranged from 2% to 15% and intraclass correlation coefficient (ICC) ranged from 0.87 to 0.99. Except for maximum wall thickness (ICC = 0.87), all ICC were larger than 0.90. For the quantitative plaque composition measurements, the ICC of the volume and relative content of lipid rich/necrotic core and calcification were larger than 0.90 with CV ranging from 22% to 32%.

Conclusion:

The results from the multicontrast high‐resolution 3T MR study show high reliability for carotid morphology and plaque component measurements. 3T MRI is a reliable tool for longitudinal clinical trials, with shorter scan time compared to 1.5T. J. Magn. Reson. Imaging 2010;31:168–176. © 2009 Wiley‐Liss, Inc.
Measuring aortic diameter with different MR techniques: Comparison of three‐dimensional (3D) navigated steady‐state free‐precession (SSFP), 3D contrast‐enhanced magnetic resonance angiography (CE‐MRA), 2D T2 black blood, and 2D cine SSFP
Authors: Potthast Silke , Mitsumori Lee , Stanescu Luana A. , Richardson Michael L. , Branch Kelley , Dubinsky Theodore J. , Maki Jeffrey H.
Published: December 2009

Purpose:

To compare nongated three‐dimensional (3D) contrast‐enhanced magnetic resonance angiography (CE‐MRA) with 3D‐navigated cardiac‐gated steady‐state free‐precession bright blood (3D‐nav SSFP) and noncontrast 2D techniques for ascending aorta dimension measurements.

Materials and Methods:

Twenty‐five clinical exams were reviewed to evaluate the ascending aorta at 1.5T using: breathhold cine bright blood (SSFP), cardiac‐triggered T2 black blood (T2 BB), axial 3D‐nav SSFP, and nongated 3D CE‐MRA. Three radiologists independently measured aortic size at three specified locations for each sequence. Means, SDs, interobserver correlation, and vessel edge sharpness were statistically evaluated.

Results:

Measurements were greatest for 3D‐nav SSFP and 3D CE‐MRA and smallest for T2 BB. There was no significant difference between 3D‐nav SSFP and 3D CE‐MRA (P = 0.43–0.86), but significance was observed comparing T2 BB to all sequences. Interobserver agreement was uniformly >0.9, with T2 BB best, followed closely by 3D‐nav SSFP and 2D cine SSFP, and 3D CE‐MRA being the worst. Edge sharpness was significantly poorer for 3D CE‐MRA compared to the other sequences (P < 0.001).

Conclusion:

If diameter measurements are the main clinical concern, 3D‐nav SSFP appears to be the best choice, as it has a sharp edge profile, is easy to acquire and postprocess, and shows very good interobserver correlation. J. Magn. Reson. Imaging 2010;31:177–184. © 2009 Wiley‐Liss, Inc.
Cerebral asymmetry in patients with schizophrenia: A voxel‐based morphometry (VBM) and diffusion tensor imaging (DTI) study
Authors: Takao Hidemasa , Abe Osamu , Yamasue Hidenori , Aoki Shigeki , Kasai Kiyoto , Ohtomo Kuni
Published: December 2009

Purpose:

To evaluate the differences in gray‐ and white‐matter asymmetry between schizophrenia patients and normal subjects.

Materials and Methods:

Forty‐eight right‐handed patients with chronic schizophrenia (24 males and 24 females) and 48 right‐handed age‐ and sex‐matched healthy controls (24 males and 24 females) were included in this study. The effects of diagnosis on gray‐matter volume asymmetry and white‐matter fractional anisotropy (FA) asymmetry were evaluated with use of voxel‐based morphometry (VBM) and voxel‐based analysis of FA maps derived from diffusion tensor imaging (DTI), respectively.

Results:

The mean gray‐ and white‐matter volumes were significantly smaller in the schizophrenia group than in the control group. The voxel‐based morphometry (VBM) showed no significant effect of diagnosis on gray‐matter volume asymmetry. The voxel‐based analysis of DTI also showed no significant effect of diagnosis on white‐matter FA asymmetry.

Conclusion:

Our results of voxel‐based analyses showed no significant differences in either gray‐matter volume asymmetry or white‐matter FA asymmetry between schizophrenia patients and normal subjects. J. Magn. Reson. Imaging 2010;31:221–226. © 2009 Wiley‐Liss, Inc.
B1 transmission‐field inhomogeneity and enhancement ratio errors in dynamic contrast‐enhanced MRI (DCE‐MRI) of the breast at 3T
Authors: Azlan Che A. , Di Giovanni Pierluigi , Ahearn Trevor S. , Semple Scott I.K. , Gilbert Fiona J. , Redpath Thomas W.
Published: December 2009

Purpose:

To quantify B1 transmission‐field inhomogeneity in breast imaging of normal volunteers at 3T using 3D T1‐weighted spoiled gradient echo and to assess the resulting errors in enhancement ratio (ER) measured in dynamic contrast‐enhanced MRI (DCE‐MRI) studies of the breast.

Materials and Methods:

A total of 25 volunteers underwent breast imaging at 3T and the B1 transmission‐fields were mapped. Gel phantoms that simulate pre‐ and postcontrast breast tissue T1 were developed. The effects of B1‐field inhomogeneity on ER, as measured using a 3D spoiled gradient echo sequence, were investigated by computer simulation and experiments on gel phantoms.

Results:

It was observed that by using the patient orientation and MR scanner employed in this study, the B1 transmission‐field field is always reduced toward the volunteer's right side. The median B1‐field in the right breast is reduced around 40% of the expected B1‐field. For some volunteers the amplitude was reduced by more than 50%. Computer simulation and experiment showed that a reduction in B1‐field decreases ER. This reduction increases with both B1‐field error and contrast agent uptake.

Conclusion:

B1 transmission‐field inhomogeneity is a critical issue in breast imaging at 3T and causes errors in quantifying ER. These errors would be sufficient to reduce the conspicuity of a malignant lesion and could result in reduced sensitivity for cancer detection. J. Magn. Reson. Imaging 2010;31:234–239. © 2009 Wiley‐Liss, Inc.
Modern lipid‐, carbohydrate‐, and peptide‐based delivery systems for peptide, vaccine, and gene products
Authors: Simerska Pavla , Moyle Peter M. , Toth Istvan
Published: December 2009

Research related to peptide, vaccine, and gene delivery has grown exponentially over the last decade. In this review, we discuss the development of delivery systems for peptides, gene and vaccine products. Special focus is given to different lipidation and glycosylation strategies to improve the metabolic stability and membrane permeability of therapeutics, and their targeting to specific sites. The synthetic methods for preparation of the systems are also described. © 2009 Wiley Periodicals, Inc. Med Res Rev, 31, No. 4, 520–547, 2011
The design of orally bioavailable 2, 5‐diketopiperazine oxytocin antagonists: from concept to clinical candidate for premature labor
Authors: Borthwick Alan D. , Liddle John
Published: December 2009

A short, efficient and highly stereoselective synthesis has been developed for a series of 6‐indanyl‐3‐alkyl‐7‐aryl/heterocyclic‐(3R, 6R, 7R)‐2, 5‐diketopiperazine amides that are potent and selective oxytocin (OT) antagonists. Property‐based design using an estimate of human oral absorption enabled focus to be directed to those templates with the greatest chance of delivering high bioavailability in humans. This led to the 2′, 4′‐difluorophenyl dimethylamide 40, a highly potent (pKi=9.2) and selective OT antagonist (>1,000‐fold selectivity vs. the human vasopressin receptors V1a, V2, and V1b) with good oral bioavailability (>50%) in the rat and dog. Increased solubility and an improved Cyp450 profile was achieved with a range of 2′‐substituted 7‐(1′,3′‐oxazol‐4′‐yl)‐(3R,6R,7R)‐2,5‐diketopiperazine amides and branching at the α‐carbon of the 3‐butyl group led to a superior rat pharmacokinetic profile that resulted in the discovery of the 2′‐methyl‐1′,3′‐oxazol‐4′‐yl morpholine amide derivative 74 GSK221149A (Retosiban), which had the best oral exposure and bioavailability in the rat. Retosiban has sub‐nanomolar affinity (Ki=0.65 nM) for the oxytocin receptor with >1400‐fold selectivity over the closely related vasopressin receptors. It has good solubility, low protein binding and has a good Cyp450 profile with no significant inhibition IC50>100 µM. Retosiban is >15‐fold more potent at the human oxytocin receptor than atosiban (a marketed i.v, peptide OT antagonist) and it has been shown to be an effective tocolytic by i.v. and by oral administration in rats, and was selected for progression as a potential clinical candidate for preterm labor.  © 2009 Wiley Periodicals, Inc. Med Res Rev 31:576‐604, 2011
When does two‐grid optimality carry over to the V‐cycle?
Authors: Napov Artem , Notay Yvan
Published: December 2009

We investigate additional condition(s) that confirm that a V‐cycle multigrid method is satisfactory (say, optimal) when it is based on a two‐grid cycle with satisfactory (say, level‐independent) convergence properties. The main tool is McCormick's bound on the convergence factor (SIAM J. Numer. Anal. 1985; 22:634–643), which we showed in previous work to be the best bound for V‐cycle multigrid among those that are characterized by a constant that is the maximum (or minimum) over all levels of an expression involving only two consecutive levels; that is, that can be assessed considering only two levels at a time. We show that, given a satisfactorily converging two‐grid method, McCormick's bound allows us to prove satisfactory convergence for the V‐cycle if and only if the norm of a given projector is bounded at each level. Moreover, this projector norm is simple to estimate within the framework of Fourier analysis, making it easy to supplement a standard two‐grid analysis with an assessment of the V‐cycle potentialities. The theory is illustrated with a few examples that also show that the provided bounds may give a satisfactory sharp prediction of the actual multigrid convergence. Copyright © 2009 John Wiley & Sons, Ltd.
Peristaltic flow of a Carreau fluid in a channel with different wave forms
Authors: Hayat T. , Saleem Najma , Ali N.
Published: December 2009

This investigation deals with the peristaltic motion of a Carreau fluid in a planar channel by employing long wavelength approximation. Five wave forms are chosen. Explicit solutions of longitudinal velocity and pressure gradient are derived. The pumping and trapping phenomena are properly examined. Comparison is made for the flow characteristics of the various selected wave forms. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010