bluuebunny/crossref_metadata_2025 huggingface dataset:
The SNARE protein SNAP‐29 interacts with the GTPase Rab3A: Implications for membrane trafficking in myelinating glia
Authors: Schardt Anke , Brinkmann Bastian G. , Mitkovski Miso , Sereda Michael W. , Werner Hauke B. , Nave Klaus‐Armin
Published: January 2009

During myelin formation, vast amounts of specialized membrane proteins and lipids are trafficked toward the growing sheath in cell surface‐directed transport vesicles. Soluble N‐ethylmaleimide‐sensitive factor (NSF) attachment proteins (SNAPs) are important components of molecular complexes required for membrane fusion. We have analyzed the expression profile and molecular interactions of SNAP‐29 in the nervous system. In addition to its known enrichment in neuronal synapses, SNAP‐29 is abundant in oligodendrocytes during myelination and in noncompact myelin of the peripheral nervous system. By yeast two‐hybrid screen and coimmunoprecipitation, we found that the GTPases Rab3A, Rab24, and septin 4 bind to the N‐terminal domain of SNAP‐29. The interaction with Rab24 or septin 4 was GTP independent. In contrast, interaction between SNAP‐29 and Rab3A was GTP dependent, and colocalization was extensive both in synapses and in myelinating glia. In HEK293 cells, cytoplasmic SNAP‐29 pools were redistributed upon coexpression with Rab3A, and surface‐directed trafficking of myelin proteolipid protein was enhanced by overexpression of SNAP‐29 and Rab3A. Interestingly, the abundance of SNAP‐29 in sciatic nerves was increased during remyelination and in a rat model of Charcot‐Marie‐Tooth disease, two pathological situations with increased myelin membrane biogenesis. We suggest that Rab3A may regulate SNAP‐29‐mediated membrane fusion during myelination. © 2009 Wiley‐Liss, Inc.
Deprivation‐induced dendritic shrinkage might be oppositely affected by the expression of wild‐type and mutated human amyloid precursor protein
Authors: Alpár Alán , Naumann Nicole , Ueberham Uwe , Arendt Thomas , Gärtner Ulrich
Published: January 2009

The physiological role of the amyloid precursor protein (APP) and its proteolytic fragments in the brain is associated with neuronal survival, neurite outgrowth, synaptic formation, and neuronal plasticity. However, malregulation of APP processing leads to disordered balance of fragments, which may results in opposite, degenerative neuronal effects. In the present study, we analyzed in vivo effects of the expression of wild‐type or mutated human APP on afferent deprivation‐induced changes of dendritic morphology. After vibrissectomy, expression of wild‐type human APP prevented diameter shrinkage of dendritic segments as well as dendritic rarefaction of apical arbors. In contrast, mutant human APP expression exacerbated degenerative changes of deprived barrel neurons. Degradation of apical arbors was especially pronounced. Results demonstrate for the first time opposite effects of the expression of wild‐type and mutated human APP on deprivation‐induced dendritic restructuring in vivo. © 2009 Wiley‐Liss, Inc.
Multilevel lateral extra‐cavitary corpectomy and reconstruction for non‐contiguous metastatic lesions to the spine: Case report and literature review
Authors: Keshavarzi Sassan , Aryan Henry E.
Published: January 2009

In patients with metastatic disease to their spine and compromise of neurologic function, the challenge is to accomplish decompression of the neural elements and maintain mechanical stability but limit the risk and morbidity to the patient. In this case report the lateral extracavitary approach is employed to accomplish these tasks through a single approach in a patient with multiple non‐contiguous sites of dorsal as well as ventral cord compression. J. Surg. Oncol. 2009;99:314–317. © 2009 Wiley‐Liss, Inc.
Neurotrophic receptor, tropomyosin‐related kinase B as an independent prognostic marker in gastric cancer patients
Authors: Tanaka Koji , Mohri Yasuhiko , Nishioka Junji , Kobayashi Minako , Ohi Masaki , Miki Chikao , Tonouchi Hitoshi , Nobori Tsutomu , Kusunoki Masato
Published: January 2009

Background and Objectives

Neurotrophic receptor tyrosine kinase TrkB has been associated with clinical outcome and chemotherapy resistance in neuroblastoma and certain human malignancies. Recent studies have focused on the association between metastatic potential and TrkB expression in tumor cells.

Methods

To determine the role of TrkB in gastric cancer, we analyzed TrkB mRNA levels by real‐time reverse transcription polymerase chain reaction in 90 patients with gastric cancer. TrkB levels were correlated with clinicopathological variables. The association between TrkB and overall survival was evaluated by univariate and multivariate analyses.

Results

The mean TrkB level in gastric cancer tissue was 2.96 (range, 0–27.1). Thirty‐eight (42%) of 90 patients showed detectable TrkB levels, whereas the remainder had no detectable TrkB. There was no significant association between clinicopathological variables and TrkB positivity. TrkB level was significantly associated with extent of lymph node metastasis in node positive patients (P = 0.03). TrkB positivity (n = 38) was significantly correlated with worse patient survival (P = 0.03). Multivariate analysis showed TrkB to be an independent prognostic parameter for overall survival (P = 0.04).

Conclusions

TrkB is an independent prognostic marker in patients with gastric cancer and appears to be associated with metastatic potential. J. Surg. Oncol. 2009;99:307–310. © 2009 Wiley‐Liss, Inc.
Identification and expression profiling of microRNAs during bovine oocyte maturation using heterologous approach
Authors: Tesfaye Dawit , Worku Dagnachew , Rings Franca , Phatsara Chirawath , Tholen Ernst , Schellander Karl , Hoelker Michael
Published: January 2009

The accumulation of maternal mRNA and protein during oogenesis for supporting oocyte maturation and the newly fertilised zygote marks the beginning of developmental process in mammals. MicroRNAs (∼18–22 nt long) which are known for post‐transcriptional gene regulation are evidenced for their essential role during animal development. We, therefore, aimed to investigate the expression of miRNAs in immature and in vitro matured bovine oocytes, using heterologous miRNA array platform. To attain this, we used a mercury™ locked nucleic acids (LNA) array (Exiqon, Vedbaek, Denmark) microarray that consist of 454 capture probes for human, mouse and rat miRNAs as registered and annotated in the miRBase release 8.0 at The Wellcome Trust Sanger Institute. Our result revealed the differential expression of 59 miRNAs, of which 31 and 28 miRNAs were found to be preferentially expressed in immature and matured oocytes, respectively. Here, we also report the identification of 32 orthologous miRNAs using a heterologous approach. Expression profiling of selected miRNAs during preimplantation stage embryos showed a distinct temporal expression pattern. After target prediction for selected candidate miRNAs high ranking target mRNA were quantified in immature and matured oocytes and showed a reciprocal expression pattern between the miRNA and the predicted targets suggesting a cause and effect relationship. Mol. Reprod. Dev. 76: 665–677, 2009. © 2009 Wiley‐Liss, Inc.
Magnetic field correlation as a measure of iron‐generated magnetic field inhomogeneities in the brain
Authors: Jensen Jens H. , Szulc Kamila , Hu Caixia , Ramani Anita , Lu Hanzhang , Xuan Liang , Falangola Maria F. , Chandra Ramesh , Knopp Edmond A. , Schenck John , Zimmerman Earl A. , Helpern Joseph A.
Published: January 2009

The magnetic field correlation (MFC) at an applied field level of 3 Tesla was estimated by means of MRI in several brain regions for 21 healthy human adults and 1 subject with aceruloplasminemia. For healthy subjects, highly elevated MFC values compared with surrounding tissues were found within the basal ganglia. These are argued as being primarily the result of microscopic magnetic field inhomogeneities generated by nonheme brain iron. The MFC in the aceruloplasminemia subject was significantly higher than for healthy adults in the globus pallidus, thalamus and frontal white matter, consistent with the known increased brain iron concentration associated with this disease. Magn Reson Med 61:481–485, 2009. © 2009 Wiley‐Liss, Inc.
Gradient moment compensated magnetic resonance spectroscopic imaging
Authors: Kim Dong‐Hyun , Gu Meng , Spielman Daniel M.
Published: January 2009

Spectroscopic imaging applications outside of the brain can suffer from artifacts due to inherent long scan times and susceptibility to motion. A fast spectroscopic imaging sequence has been devised with reduced sensitivity to motion. The sequence uses oscillating readout gradients and acquires k‐space data in a spiral out–in fashion, which allows fast k‐space coverage. We show that a spiral out–in readout acquisition is characterized by small gradient moments, reducing sensitivity to motion‐induced artifacts. Data are acquired comparing the sequence to normal phase encoded spectroscopic imaging and conventional spiral spectroscopic imaging protocols. In addition, in vivo data are acquired from the liver, demonstrating potential usage as a multivoxel fat/water spectroscopic imaging tool. Results indicate that in the presence of motion, ghosting effects are reduced while metabolite signal increases of approximately 10% can be achieved. Magn Reson Med 61:457–461, 2009. © 2009 Wiley‐Liss, Inc.
Broadband slab selection with B mitigation at 7T via parallel spectral‐spatial excitation
Authors: Setsompop Kawin , Alagappan Vijayanand , Gagoski Borjan A. , Potthast Andreas , Hebrank Franz , Fontius Ulrich , Schmitt Franz , Wald L.L. , Adalsteinsson E.
Published: January 2009

Chemical shift imaging benefits from signal‐to‐noise ratio (SNR) and chemical shift dispersion increases at stronger main field such as 7 Tesla, but the associated shorter radiofrequency (RF) wavelengths encountered require B mitigation over both the spatial field of view (FOV) and a specified spectral bandwidth. The bandwidth constraint presents a challenge for previously proposed spatially tailored B mitigation methods, which are based on a type of echovolumnar trajectory referred to as “spokes” or “fast‐kz”. Although such pulses, in conjunction with parallel excitation methodology, can efficiently mitigate large B inhomogeneities and achieve relatively short pulse durations with slice‐selective excitations, they exhibit a narrow‐band off‐resonance response and may not be suitable for applications that require B mitigation over a large spectral bandwidth. This work outlines a design method for a general parallel spectral‐spatial excitation that achieves a target‐error minimization simultaneously over a bandwidth of frequencies and a specified spatial‐domain. The technique is demonstrated for slab‐selective excitation with in‐plane B mitigation over a 600‐Hz bandwidth. The pulse design method is validated in a water phantom at 7T using an eight‐channel transmit array system. The results show significant increases in the pulse's spectral bandwidth, with no additional pulse duration penalty and only a minor tradeoff in spatial B mitigation compared to the standard spoke‐based parallel RF design. Magn Reson Med 61:493–500, 2009. © 2009 Wiley‐Liss, Inc.
Parallel spectroscopic imaging reconstruction with arbitrary trajectories using k‐space sparse matrices
Authors: Gu Meng , Liu Chunlei , Spielman Daniel M.
Published: January 2009

Parallel imaging reconstruction has been successfully applied to magnetic resonance spectroscopic imaging (MRSI) to reduce scan times. For undersampled k‐space data on a Cartesian grid, the reconstruction can be achieved in image domain using a sensitivity encoding (SENSE) algorithm for each spectral data point. Alternative methods for reconstruction with undersampled Cartesian k‐space data are the SMASH and GRAPPA algorithms that do the reconstruction in the k‐space domain. To reconstruct undersampled MRSI data with arbitrary k‐space trajectories, image‐domain‐based iterative SENSE algorithm has been applied at the cost of long computing times. In this paper, a new k‐space domain‐based parallel spectroscopic imaging reconstruction with arbitrary k‐space trajectories using k‐space sparse matrices is applied to MRSI with spiral k‐space trajectories. The algorithm achieves MRSI reconstruction with reduced memory requirements and computing times. The results are demonstrated in both phantom and in vivo studies. Spectroscopic images very similar to that reconstructed with fully sampled spiral k‐space data are obtained at different reduction factors. Magn Reson Med 61:267–272, 2009. © 2009 Wiley‐Liss, Inc.
Nonlinear ΔR effects in perfusion quantification using bolus‐tracking MRI
Authors: Calamante Fernando , Connelly Alan , van Osch Matthias J.P.
Published: January 2009

Dynamic susceptibility contrast MRI involves injection of a contrast agent, whose concentration is estimated from ΔR changes. However, measurement of contrast‐agent concentration is prone to various sources of error; in particular, the commonly assumed linear relationship between contrast agent concentration and ΔR in arterial blood is known to be invalid. In this study, we characterized the associated perfusion errors. Large errors were found when the linear assumption is used; these errors were highly dependent on the choice of tissue relaxivity. The errors were greatly reduced when using the quadratic model, and were further reduced when quantifying perfusion as a relative measure. This study suggests the linear assumption should be abandoned in favor of the quadratic model. Thus, the errors are minimized leading to improved quantification that will enable perfusion MRI to continue to play an important role in quantifying perfusion in brain diseases (e.g., acute stroke). Magn Reson Med 61:486–492, 2009. © 2009 Wiley‐Liss, Inc.
Lung morphology assessment using MRI: A robust ultra‐short TR/TE 2D steady state free precession sequence used in cystic fibrosis patients
Authors: Failo Riccarda , Wielopolski Piotr A. , Tiddens Harm A.W.M. , Hop Wim C.J. , Pozzi Mucelli Roberto , Lequin Maarten H.
Published: January 2009

To evaluate feasibility and diagnostic quality of ultra‐short TR/TE two‐dimensional (2D) steady state free precession (SSFP) MRI for cystic fibrosis (CF) patients. We performed lung MRI at 1.5 Tesla in 20 CF‐patients (6–17 years, 12 males). Axial, coronal, and sagittal sections were acquired in inspiration and expiration with maximum breath‐hold time 10 s. MR and CT images were scored using a modified Brody scoring system to assess bronchiectasis, mucous plugging, atelectasis/consolidations, and air trapping. All images were scored by two experienced observers. A complete MR investigation took maximally 15 min. Maximal breath‐holds were only 10 s and well tolerated. MRI identified major bronchiectasis, mucous plugging and atelectasis. End‐expiratory scans showed patches of parenchyma with reduced signal intensity that may corresponded to areas of trapped air on expiratory CT scans. This MRI protocol based on ultra‐short TR/TE 2D SSFP is quick and well tolerated and provides highly relevant imaging features as seen on CT in CF patients. Most importantly, the SNR of the expiratory scans enables to visualize air trapping. The preliminary results of this study suggest MRI as a noteworthy additional imaging tool for routine monitoring of CF patients. Magn Reson Med 61:299–306, 2009. © 2009 Wiley‐Liss, Inc.
Quantitative magnetization transfer measured pool‐size ratio reflects optic nerve myelin content in ex vivo mice
Authors: Ou Xiawei , Sun Shu‐Wei , Liang Hsiao‐Fang , Song Sheng‐Kwei , Gochberg Daniel F.
Published: January 2009

Optic nerves from mice that have undergone retinal ischemia were examined using a newly implemented quantitative magnetization transfer (qMT) technique. Previously published results indicate that the optic nerve from retinal ischemia mice suffered significant axon degeneration without detectable myelin injury at 3 days after reperfusion. At this time point, we acquired ex vivo qMT parameters from both shiverer mice (which have nearly no myelin) and control mice that have undergone retinal ischemia, and these qMT measures were compared with diffusion tensor imaging (DTI) results. Our findings suggests that the qMT estimated ratio of the pool sizes of the macromolecular and free water protons reflected the different myelin contents in the optic nerves between the shiverer and control mice. This pool size ratio was specific to myelin content only and was not significantly affected by the presence of axon injury in mouse optic nerve 3 days after retinal ischemia. Magn Reson Med 61:364–371, 2009. © 2009 Wiley‐Liss, Inc.
Human whole blood T2 relaxometry at 3 Tesla
Authors: Chen Jean J. , Pike G. Bruce
Published: January 2009

A precise understanding of human blood spin–spin relaxation is of major importance for numerous applications, particularly functional magnetic resonance imaging (fMRI), which is increasingly performed at 3 Tesla. It is well known that T2 measured from partially deoxygenated blood depends on the Carr–Purcell Meiboom–Gill (CPMG) refocusing interval (τ180) and on blood oxygenation (Y), yet debate remains over the quantification of this phenomenon, primarily with respect to the accuracy of its characterization by the diffusion and fast two‐site exchange models. In this study, a detailed characterization of the deoxygenation‐induced T2 reduction in human whole blood, as well as a comprehensive assessment of the role of τ180, were performed at 3 T. The diffusion model was found to better fit the observed T2 behavior as compared with the exchange model. The estimated diffusion‐model parameters suggest the T2 decay enhancement at 3 T is due to a linear increase in the magnitude of deoxygenation‐induced field inhomogeneities with field strength. These findings also confirm the potential of τ180 manipulation in measuring changes in venous blood volume. Magn Reson Med 61:249–254, 2009. © 2009 Wiley‐Liss, Inc.
Phase‐contrast magnetic resonance imaging measurements in intracranial aneurysms in vivo of flow patterns, velocity fields, and wall shear stress: Comparison with computational fluid dynamics
Authors: Boussel Loic , Rayz Vitaliy , Martin Alastair , Acevedo‐Bolton Gabriel , Lawton Michael T. , Higashida Randall , Smith Wade S. , Young William L. , Saloner David
Published: January 2009

Evolution of intracranial aneurysms is known to be related to hemodynamic forces such as wall shear stress (WSS) and maximum shear stress (MSS). Estimation of these parameters can be performed using numerical simulations with computational fluid dynamics (CFD), but can also be directly measured with magnetic resonance imaging (MRI) using a time‐dependent 3D phase‐contrast sequence with encoding of each of the three components of the velocity vectors (7D‐MRV). To study the accuracy of 7D‐MRV in estimating these parameters in vivo, in comparison with CFD, 7D‐MRV and patient‐specific CFD modeling was performed for 3 patients who had intracranial aneurysms. Visual and quantitative analyses of the flow pattern and distribution of velocities, MSS, and WSS were performed using the two techniques. Spearman's coefficients of correlation between the two techniques were 0.56 for the velocity field, 0.48 for MSS, and 0.59 for WSS. Visual analysis and Bland–Altman plots showed good agreement for flow pattern and velocities but large discrepancies for MSS and WSS. These results indicate that 7D‐MRV can be used in vivo to measure velocity flow fields and for estimating MSS and WSS. Currently, however, this method cannot accurately quantify the latter two parameters. Magn Reson Med 61:409–417, 2009. © 2009 Wiley‐Liss, Inc.
PARACEST MRI with improved temporal resolution
Authors: Liu Guanshu , Ali M. Meser , Yoo Byunghee , Griswold Mark A. , Tkach Jean A. , Pagel Mark D.
Published: January 2009

PARAmagnetic Chemical Exchange Saturation Transfer (PARACEST) is a novel contrast mechanism for MRI. A PARACEST MRI methodology with high temporal resolution is highly desired for in vivo MRI applications of molecular imaging. To address this need, a strategy has been developed that includes a long selective saturation period before each repetition of a Rapid Acquisition with Relaxation Enhancement (RARE) pulse sequence. This strategy is suitable for the application of PARACEST contrast agents to environments with long T1 relaxation times. An alternative strategy uses short selective saturation periods before the acquisition of each k‐space trajectory to maintain steady state conditions, which can be implemented with a Fast Low Angle Shot (FLASH) pulse sequence. These short saturation periods lengthen the total scan time as compared to the first approach but compensate for the loss in PARACEST contrast related to T1 relaxation. Both approaches have been demonstrated in vitro and in vivo with significantly improved temporal resolutions as compared to a conventional gradient‐echo PARACEST method without sacrificing CNR efficiency. These demonstrations also adopted a strategy for measuring the PARACEST effect that only requires selective saturation at a single MR frequency, which further improves temporal resolution for PARACEST detection. Magn Reson Med 61:399–408, 2009. © 2009 Wiley‐Liss, Inc.
Axial black blood turbo spin echo imaging of the right ventricle
Authors: Berkowitz Seth J. , Macedo Robson , Malayeri Ashkan A. , Shea Steven M. , Lorenz Christine H. , Calkins Hugh , Vogel‐Claussen Jens , Tandri Harikrishna , Bluemke David A.
Published: January 2009

Black blood turbo spin echo (TSE) imaging of the right ventricle (RV) free wall is highly sensitive to cardiac motion, frequently resulting in nondiagnostic images. Temporal and spatial parameters of a black blood TSE pulse sequence were evaluated for visualization of the RV free wall. Seventy‐four patient studies were retrospectively evaluated for the effects of acquisition timing on image quality. Axial black blood TSE images were acquired on 10 healthy volunteers to assess the role of spatial misregistration on right ventricle visualization; increasing the double inversion recovery (DIR) slice thickness beyond 300% had no effect on image quality (P = 0.2). Thirty‐five patient studies were prospectively evaluated with inversion times (TIs) corresponding to the mid‐diastolic rest period and end‐systole based on visual analysis of a four chamber cine. When TIs were chosen to be within the patients' RV rest period, mean image quality score was significantly improved (2.3 vs 1.86; P < 0.001) and the number of clinically diagnostic images increased from 32% to 46%. Black blood TSE imaging of the RV free wall is highly sensitive to cardiac motion. Image quality can be improved by choosing TIs concordant with the rest period of the patient's RV that may occur at mid‐diastole or end‐systole. Magn Reson Med 61:307–314, 2009. © 2009 Wiley‐Liss, Inc.
Comorbidities of Advanced Lung Disease
Authors: Nations Joel Anthony , Nathan Steven D.
Published: January 2009

Lung disease in advanced stages is often accompanied by multiple comorbidities. Often, these processes lead to significant morbidity and occasionally mortality. Symptoms of pulmonary comorbidities, including pulmonary embolus, pulmonary hypertension, sleep‐disordered breathing, and lung malignancy, may be intertwined with symptoms of advancing lung disease. However, the occurrence of extrapulmonary processes, including depression, diabetes mellitus, osteoporosis, and gastroesophageal reflux disease, may be subtle. Clinicians caring for advanced lung disease should be aware of the many comorbid processes that may accompany advancing lung disease. Mt Sinai J Med 76:53–62, © 2009 Mount Sinai School of Medicine
On the accuracy of finite volume and discontinuous Galerkin discretizations for compressible flow on unstructured grids
Authors: Nogueira X. , Cueto‐Felgueroso L. , Colominas I. , Gómez H. , Navarrina F. , Casteleiro M.
Published: January 2009

This paper presents a comparison between two high‐order methods. The first one is a high‐order finite volume (FV) discretization on unstructured grids that uses a meshfree method (moving least squares (MLS)) in order to construct a piecewise polynomial reconstruction and evaluate the viscous fluxes. The second method is a discontinuous Galerkin (DG) scheme. Numerical examples of inviscid and viscous flows are presented and the solutions are compared. The accuracy of both methods, for the same grid resolution, is similar, although the DG scheme requires a larger number of degrees of freedom than the FV–MLS method. Copyright © 2009 John Wiley & Sons, Ltd.
Polymers containing in‐chain quinone moieties: synthesis and properties
Authors: Hodge Philip , Gautrot Julien E
Published: January 2009

The redox properties of quinones play a key part in photosynthesis and oxidative phosphorylation. This mini‐review focuses on the synthesis and properties of polymers that contain in‐chain quinone units. Many of the syntheses exploit Yamamoto or Suzuki couplings. Most of the polymers that are soluble in organic solvents display interesting electrochemical and optical properties that may be useful for a wide range of applications. Copyright © 2009 Society of Chemical Industry
Heterogeneous ring‐opening polymerization of lactones for biomedical applications
Authors: Khan Javaid H , Schue Francois , George Graeme A
Published: January 2009

Catalysis of the ring‐opening reaction of L‐lactide and ε‐caprolactone to form the corresponding biodegradable polyesters is frequently performed using organometallic compounds such as tin(II) 2‐ethylhexanoate, which operates by a living, coordination insertion mechanism. For biomedical applications, non‐toxic calcium salts have been researched but these rarely approach the same efficiency. The use of heterogeneous immobilized catalysts offers an alternative approach, but competing reactions such as transesterification affect the final molecular weight and polydispersity. The formation of hybrid materials by using silica as the initiation site offers the prospect of biomaterials with novel properties. Copyright © 2009 Society of Chemical Industry
Effects of filler geometry on internal structure and physical properties of polycarbonate composites prepared with various carbon fillers
Authors: Lee Seung Hwan , Kim Jong Hyuk , Choi Sheong Hyun , Kim Seong Yun , Kim Kyeong Wung , Youn Jae Ryoun
Published: January 2009

BACKGROUND: The effects of filler geometry are important for understanding the internal structure and physical properties of polymer composites. To investigate the effects of filler geometry on electrical conductivity as well as morphological and rheological properties, three types of polycarbonate (PC) composites were prepared by melt compounding with a twin‐screw extruder.

RESULTS: The electrical conductivity of PC/carbon black (CB) and PC/graphite (carbon) nanofibre (CNF) composites did not show a percolation threshold through the entire filler loading ranges. However, PC‐blend‐carbon nanotube (CNT) composites showed a percolation electrical threshold for a filler loading of 1.0 to 3.0 wt% and their maximum electrical conductivity approached 10−3 S m−1. PC‐blend‐CB and PC‐blend‐CNF composites showed Newtonian behaviour like pure PC matrix, but PC‐blend‐CNT composites showed yield stress as well as increased storage modulus and strong shear thinning behaviour at low angular frequency and shear rate due to strong interactions generated between CNT–CNT particles as well as PC molecules and CNT particles on the nanometre scale.

CONCLUSIONS: The electrical conductivity of the PC composites with different carbon constituents was well explained by the continuous network structure formed between filler particles. The network structure was confirmed by the good dispersion of fillers as well as by the yield stress and solid‐like behaviour observed in steady and dynamic shear flows. Copyright © 2009 Society of Chemical Industry
Synthesis and properties of hydroxyapatite nanorod‐reinforced polyamide 6 nanocomposites
Authors: Li Lanjie , Yang Guisheng
Published: January 2009

BACKGROUND:Polyamide 6 (PA6)/hydroxyapatite (HA) nanocomposites, which combine the bioactivity and biocompatibility of HA and the excellent mechanical performance of PA6, have emerged as new biomaterials with potential applications in the clinical setting. It has been shown that these nanocomposites show good similarity to natural bone in terms of chemistry and mechanical properties.

RESULTS:In this study, highly crystallized hydroxyapatite nanorods (HANR) were used to fabricate PA6/HA nanocomposites viain situhydrolytic ring‐opening polymerization of ε‐caprolactam. The effect of the HANR on the thermal stability, crystallization behavior and hydrogen bonding of PA6 was investigated using thermogravimetric analysis, differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy, respectively. It was found that HANR can obviously increase the crystallization temperature and decrease the degree of supercooling. In addition, the thermal degeneration temperature of PA6 is also increased by the incorporation of HANR. FTIR analysis of the hydrogen bonded NH stretching vibration revealed that, with increasing HANR loading, the hydrogen bonded NH stretching band shifts to higher frequency and decreases in intensity.

CONCLUSION:The thermal stability and crystallization ability of PA6 are improved considerably by the incorporation of HANR. However, the hydrogen bonding strength is weakened and the degree of ordering of hydrogen bonding is reduced by the incorporation of HANR, which can be explained by the formation of hydrogen bonds at the interface between OH groups of HANR and the NH or CO groups of PA6. Copyright © 2009 Society of Chemical Industry
Biodegradable nanofibrous membrane of zein/silk fibroin by electrospinning
Authors: Yao Chen , Li Xinsong , Song Tangying , Li Yunhui , Pu Yuepu
Published: January 2009

BACKGROUND: Electrospinning of natural polymers offers a promising approach to generate nanofibers with a similar fibrillar structure to that of native extracellular matrix. In the present work, zein/silk fibroin (SF) blends were electrospun with formic acid as solvent to fabricate bicomponent nanofibrous scaffolds for biomedical applications.

RESULTS: The zein/SF electrospun nanofibers had a smaller diameter and narrower diameter distribution than pure zein nanofibers, and the average diameter gradually decreased from 265 to 230 nm with increasing SF content in the blend. The predominant presence of α‐helix zein structure and random coil form of silk I in blend fibrous membranes was confirmed from Fourier transform infrared spectral and wide‐angle X‐ray diffraction data, while conversion to the β‐sheet structure of SF was also detected. The tensile strength of the zein/SF fibrous membranes was improved as the content of SF in the blend fibers increased. A preliminary study of in vitro degradation and cytotoxicity evaluated by MTT assay indicated that biodegradable zein/SF fibrous membranes did not induce cytotoxic effects in an L929 mouse fibroblast system.

CONCLUSION: Biodegradable zein/SF fibrous membranes with good mechanical properties and cytocompatibility combine the beneficial characteristics of the individual components and may be useful for biomedical applications. Copyright © 2009 Society of Chemical Industry
A general strategy for highly efficient nanoparticle dispersing agents based on hybrid dendritic linear block copolymers
Authors: Vestberg Robert , Piekarski Ashley M. , Pressly Eric D. , Van Berkel Kim Y. , Malkoch Michael , Gerbac Jeffrey , Ueno Nobuhiko , Hawker Craig J.
Published: January 2009

A modular approach to the synthesis of a library of hybrid dendritic‐linear copolymers was developed based on RAFT polymerization from monodisperse dendritic macroRAFT agents. By accurately controlling the molecular weight of the linear block, generation number of the dendrimer and the nature of the dendritic chains ends, the performance of these hybrid block copolymers as dispersing agents was optimized for a range of nanoparticles. For titanium dioxide nanoparticles, dispersion in a poly(methyl methacrylate) matrix was maximized with a second generation dendrimer containing four carboxylic acid end groups, and the quality of dispersion was observed to be superior to commercial dispersing agents for TiO2. This approach also allowed novel hybrid dendritic‐linear dispersing agents to be prepared for the dispersion of Au and CdSe nanoparticles based on disulphide and phosphine oxide end groups, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1237–1258, 2009
PCPP derivatives containing carbazole pendant as hole transporting moiety for efficient blue electroluminescence
Authors: Kim Jinwoo , Jin Youngeup , Kim Jaehong , Jung Jaeyeon , Kim Sun Hee , Lee Kwanghee , Suh Hongsuk
Published: January 2009

The syntheses and characterization of poly((2,6‐(4,4‐bis(4‐((2‐ethylhexyl)oxy)phenyl)‐4H‐cyclopenta[def]phenanthrene))‐co‐(2,6‐(4,4‐bis(4‐(((9‐carbazolyl)hexyl)oxy)phenyl))‐4H‐cyclopenta[def]phenanthrene)) (BCzPh‐PCPPs) and poly((2,6‐(4,4‐bis(4‐((2‐ethylhexyl)oxy)phenyl)‐4H‐cyclopenta[def]phenanthrene))‐co‐(2,6‐(4‐(4‐(((9‐carbazolyl)hexyl)oxy)phenyl)‐4‐(4‐((2‐ethylhexyl)oxy)phenyl)‐4H‐cyclopenta[def]phenanthrene))) (CzPh‐PCPPs), with carbazole unit as pendants, are presented. The carbazole moiety, which can improve the hole injection ability, was introduced as a pendant on the PCPP backbone. The devices of the polymers with the configurations of ITO/PEDOT:PSS/polymers/Ca/Al generate EL emission with maximum peaks at 400–450 nm, CIE coordinates of (x = 0.11–0.29, y = 0.11–0.33), low turn‐on voltages of 4–6 V, maximum brightness of 60–810 cd/m2, and luminescence efficiencies of 0.04–0.22 cd/A. The PL spectra of CzPh‐PCPPs films did not show any peak at around 550 nm, which corresponds to keto defect or aggregate/excimer formation, even after annealing for 30 h at 150 °C in air. Out of the series, CzPh‐PCPP1 (PCPP derivative with 10% of carbazole moiety as pendant) shows blue emission with the maximum brightness of 810 cd/m2 at 9 V, and the highest luminescence efficiency of 0.22 cd/A at 395 mA/cm2. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1327–1342, 2009
Mn2(CO)10‐induced controlled/living radical copolymerization of vinyl acetate and methyl acrylate: Spontaneous formation of block copolymers consisting of gradient and homopolymer segments
Authors: Koumura Kazuhiko , Satoh Kotaro , Kamigaito Masami
Published: January 2009

The controlled/living radical polymerization of vinyl acetate (VAc) and its copolymerization with methyl acrylate (MA) were investigated in bulk or fluoroalcohols using manganese complex [Mn2(CO)10] in conjunction with an alkyl iodide (RI) as an initiator under weak visible light. The manganese complex induced the controlled/living radical polymerization of VAc even in the fluoroalcohols without any loss of activity. The RI/Mn2(CO)10 system was also effective for the copolymerization of MA and VAc, in which MA was consumed faster than VAc, and then the remaining VAc was continuously and quantitatively consumed after the complete consumption of MA. The 1H and 13C NMR analyses revealed that the obtained products are block copolymers consisting of gradient MA/VAc segments, in which the VAc content gradually increases, and homopoly(VAc). The use of fluoroalcohols as solvents increased the copolymerization rate, controllability of the molecular weights, and copolymerizability of VAc. The saponification of the VAc units in poly(MA‐grad‐VAc)‐block‐poly(VAc) resulted in the corresponding poly(MA‐co‐γ‐lactone)‐block‐poly(vinyl alcohol) due to the intramolecular cyclization between the hydroxyl and neighboring carboxyl groups in the gradient segments. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1343–1353, 2009
Growth of lightly crosslinked PHEMA brushes and capsule formation using pickering emulsion interface‐initiated ATRP
Authors: Chen Yunhua , Wang Chaoyang , Chen Jianxin , Liu Xinxing , Tong Zhen
Published: January 2009

In this work, growth of lightly crosslinked poly(2‐hydroxyethyl methacrylate) (PHEMA) brushes and subsequent capsule formation using Pickering emulsion interface‐initiated atom transfer radical polymerization (PEII‐ATRP) were investigated. Initiator‐immobilized silica nanoparticles (2.5 initiators/nm2) assembled at the interface of paraffin oil‐in‐water emulsions and ultimately stable Pickering emulsions were formed. PEII‐ATRP was conducted in the water phase of Pickering emulsions from the part of the surfaces of initiator‐immobilized silica nanoparticles exposed to water by using copper(I) chloride/bipyridine as catalyst at 35 °C. As PHEMA has a character of lightly crosslinking when the polymerization occurs in water, novel hybrid capsules (“colloidosomes”) can be obtained and were observed by confocal laser scanning microscope (CLSM) and optical microscopy (OM). The semipermeability of the resultant hollow capsules was demonstrated by the diffusion of 1‐phenylazo‐2‐naphthol. Meanwhile, the conformation of PHEMA chains can be varied in different solvents, which affects the semipermeability of these hybrid hollow capsules. We expect these hollow capsules can be further utilized to develop microdevices for drugs or cells delivery. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1354–1367, 2009
Linking polythiophene chains with vinylene‐bridges: A way to improve charge transport in polymer field‐effect transistors
Authors: Lu Kun , Sun Xiangnan , Liu Yunqi , Di Chongan , Xi Hongxia , Yu Gui , Gao Xike , Du Chunyan
Published: January 2009

A series of novel branched polythiophene derivatives bearing different densities of vinylene‐bridges as linking chains were synthesized by a general synthetic strategy. The organic field‐effect transistors, which were fabricated by spin‐coating the polymer solutions onto octadecyltrichlorosilane‐modified SiO2/Si substrates with top‐contact configuration, afforded a high mobility of 8.0 × 10−3 cm2 V−1 s−1 with an on/off ratio greater than 104 and a threshold voltage of about −3 V in saturation regime. The devices based on these polymers possessed better performance than those of polymers without conjugated bridges and polymers with longer conjugated bridges. These results demonstrated that the combination of conjugated polythiophene backbones and vinylene‐bridges would improve the carrier mobility. As an emerging class of conjugated materials, polymers with vinylene‐bridges as linking chains would open up new opportunities in organic electronics, and their applications in organic electronics are promising. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1381–1392, 2009
Free radical copolymerization of α‐fluoroacrylates for optical materials: Synthesis and characterization
Authors: Cracowski Jean‐Marc , Montembault Véronique , Bosc Dominique , Améduri Bruno , Odobel Fabrice , Fontaine Laurent
Published: January 2009

Copolymers based on 2,2,2‐trifluoroethyl α‐fluoroacrylate (FATRIFE) and 2,2,2‐trichlororoethyl α‐fluoroacrylate (FATRICE) were synthesized in good yields by radical process initiated by tert‐butyl 2,2‐dimethylperoxypropanoate. Molar composition of the obtained poly(FATRIFE‐co‐FATRICE) copolymers were assessed by means of 19F nuclear magnetic resonance spectroscopy. The reactivity ratios, ri, of both comonomers have been measured to be rFATRIFE = 0.56 ± 0.01 and rFATRICE = 0.11 ± 0.01 at 74 °C using the Kelen‐Tüdos method. Thermal and optical properties of the resulting polymers were examined. Thermogravimetric analyses showed good thermal stability, thermal decomposition occurring from 300 °C to 310 °C for all copolymers. Moreover, the glass transition temperature of copolymers varied from 113 °C to 127 °C, increasing with the molar ratio of FATRICE in the copolymers. The refractive indices were measured at 633, 1320, and 1550 nm, ranging from 1.3750 to 1.4812 at 1550 nm and were found to increase linearly with the chlorine content of the copolymer, allowing a precise control of the refractive index. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1403–1411, 2009
Poly(N,N‐dimethylacrylamide) hydrogels obtained by frontal polymerization
Authors: Caria Giuseppe , Alzari Valeria , Monticelli Orietta , Nuvoli Daniele , Kenny Josè M. , Mariani Alberto
Published: January 2009

Frontal polymerization (FP) has been used as an alternative technique for the preparation of poly(N,N‐dimethylacrylamide) hydrogels. Samples were synthesized in bulk, water, or dimethyl sulfoxide (DMSO), and the obtained materials were characterized and compared in terms of their yield, swelling behavior, thermal properties, and morphology. It was found that their features are dependent on the presence and type of the solvent used. Samples prepared in bulk are characterized by the lowest yields and the highest front temperatures (Tmax) and velocities (Vf), whereas those synthesized in water have the highest yields and the lowest values of Tmax and Vf. No significant differences have been found in terms of Tg among the three series of samples. By contrast, the reaction conditions influenced the porous morphology of the samples and, consequently, their swelling capability in water. The swelling ratio ranges from about 670–700% for some samples prepared in water up to 3500% for a sample obtained in DMSO, thus indicating that this parameter can be properly tuned by using the most suitable FP conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1422–1428, 2009
Synthesis and rheology of biodegradable poly(glycolic acid) prepared by melt ring‐opening polymerization of glycolide
Authors: Gautier Estelle , Fuertes Patrick , Cassagnau Philippe , Pascault Jean‐Pierre , Fleury Etienne
Published: January 2009

Ring‐opening polymerization (ROP) of glycolide was studied in melt conditions and in the presence of two different initiators: 1‐dodecanol and 1,4‐butanediol and tin(II) 2‐ethylhexanoate as catalyst. Its subsequent polymerization provided poly(glycolic acid) with controlled molar masses ranging from 2000 to 42,000 g/mol with well‐defined structures characterized by NMR. Their thermal properties were evaluated by DSC analysis, and a glass transition temperature at infinite molar mass (Tg∞) of 44.8 °C was thus calculated. From rheological data, the critical molar mass for entanglement, Mc, was estimated to be near 11,000 g/mol. Furthermore, in situ polymerizations were also performed between the plates of the rheometer within a same temperature range from 210 to 235 °C. The variation of the storage and loss moduli during the polymerization step have been monitored by time sweep oscillatory experiments under an angular frequency ω = 10 rad/s. Finally, the development of an inverse rheological method allowed to calculate the bulk polymerization kinetics in the temperature range 200–230 °C. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1440–1449, 2009
Over‐expression of IκB‐kinase‐ε (IKKε/IKKi) induces secretion of inflammatory cytokines in prostate cancer cell lines
Authors: Péant Benjamin , Diallo Jean‐Simon , Dufour Florent , Le Page Cécile , Delvoye Nathalie , Saad Fred , Mes‐Masson Anne‐Marie
Published: January 2009

BACKGROUND

Elevated inflammatory cytokine levels in serum have been associated with advanced stage metastasis‐related morbidity in prostate cancer. Several studies have shown that IL‐6 and IL‐8 can accelerate the growth of human prostate cancer cell lines. Previous studies, in murine embryonic fibroblasts, have shown that Iκ‐B kinase‐epsilon (IKKε/IKKi)‐deficiency results in the reduction of lipopolysaccharide‐mediated expression of IL‐6.

RESULTS

In this study, we report that over‐expression of IKKε in hormone‐sensitive 22Rv1 and LNCaP prostate cancer cells induces the secretion of several inflammatory cytokines including IL‐6 and IL‐8. Both of these cytokines are secreted by hormone‐refractory PC‐3 prostate cancer cells and IKKε knock‐down in these cells correlates with a strong decrease in IL‐6 secretion. Furthermore, we demonstrate that IKKε over‐expression does not induce the activation of the IKKε classical targets NF‐κB and IRF‐3, two transcription factors involved in the regulation of several cytokines. Finally, we observe that high IKKε expression results in its nuclear translocation, a phenomena that is TBK1‐independent.

CONCLUSIONS

This study identifies IKKε as a potential prostate cancer gene that may favor chronic inflammation and create a tumor‐supporting microenvironment that promotes prostate cancer progression, particularly by the induction of IL‐6 secretion that may act as a positive growth factor in prostate cancer. Prostate 69: 706–718, 2009. © 2009 Wiley‐Liss, Inc.
Protease‐activated receptor‐1 is upregulated in reactive stroma of primary prostate cancer and bone metastasis
Authors: Zhang Xiaotun , Wang Wenbin , True Lawrence D. , Vessella Robert L. , Takayama Thomas K.
Published: January 2009

BACKGROUND

Prostate cancer progression is partly facilitated by tumor–stroma interactions. We recently reported that protease‐activated receptors (PAR‐1 and PAR‐2) are overexpressed in prostate cancer, and PAR‐1 expression in peritumoral stroma is associated with biochemical recurrence. However, the nature of PAR expression in prostate tumor microenvironment is not fully understood. We therefore evaluated PAR‐1 and PAR‐2 expression in primary prostate cancer and bone metastasis.

METHODS

PAR‐1 and PAR‐2 expression in normal, primary prostate cancer and the corresponding bone metastatic tissues were examined by immunohistochemistry, and double‐label immunohistochemistry with the use of additional markers.

RESULTS

PAR‐1 was expressed in peritumoral stroma in the majority of primary cancer tissues (83%). Serial sections and double‐label immunohistochemistry determined that these PAR‐1 expressing stromal cells were predominantly myofibroblasts, the primary cell type in reactive stroma. Analysis of cancer glands revealed that PAR‐1 expression was significantly increased in the reactive stroma around higher Gleason grade cancers. PAR‐2 was predominantly expressed in the primary cancer cells as well as smooth muscle cells but not in reactive stroma. In bone metastasis, PAR‐1 expression in cancer cells was elevated compared to the primary site from the same patient. In the bone reactive stroma, PAR‐1 was present in vascular endothelial cells and fibroblasts, while both PAR‐1 and PAR‐2 were expressed in osteoblasts and osteoclasts.

CONCLUSIONS

In primary prostate cancer and bone metastasis, PAR‐1 is upregulated in reactive stroma and PAR‐2 is uniformly overexpressed in carcinoma cells, suggesting these receptors may play potentially different roles in prostate cancer development and metastasis. Prostate 69: 727–736, 2009. © 2009 Wiley‐Liss, Inc.