bluuebunny/crossref_metadata_2025_split huggingface dataset:
A bidirectional “αvβ3 integrin‐ERK1/ERK2 MAPK” connection regulates the proliferation of breast cancer cells
Authors: Vellon Luciano , Menendez Javier A. , Lupu Ruth 
Published: May 2006

AbstractIn addition to their role in cell migration and adhesion, integrins elicit a series of transduction events that regulate cell‐cycle progression and apoptosis in a process known as “outside‐in” signaling. A second mode of integrin regulation known as “inside‐out” signaling, in which the activation of major cell transduction cascades can influence the activation status of some integrins, has also been described. Here, we have assessed the role of the extracellular signal‐regulated kinase (ERK1)/ERK2, mitogen‐activated protein kinase (MAPK), and phospoinositide 3‐kinase (PI‐3′K) signaling pathways in the expression and function of αvβ3 integrin in breast cancer models. Pharmacological inhibition of MEK1 and MEK2 with U0126 drastically increased the levels of αvβ3 in Heregulin (HRG)‐overexpressing MDA‐MB‐231 cells (231/WT, 231/VEC) and derivatives transfected with the antisense orientation of the HRG‐β2 full length cDNA (231/ASPOOL, 231/AS31). Interestingly, this was related to a significant decrease of viability and of the S‐ and G2/M subcompartment of the cell cycle in MDA MB 231 cells in response to U0126. Furthermore, specific inhibition of the PI‐3′K pathway with LY294002 also induced an increase of αvβ3 levels but to a lesser extent. Moreover, pretreatment of MDA‐MB‐231 cells with U0126 antagonized the effects of small peptidomimetic αvβ3 antagonists. Remarkably, inhibition of the PI‐3′K/AKT pathway did not exert the same effects, thus suggesting that the “outside‐in” as well as the “inside‐out” αvβ3‐mediated signaling goes primarily through the ERK1/ERK2 MAPK pathway in MDA MB 231 breast cancer cells. Collectively, these results strongly suggest the existence of a bidirectional molecular connection αvβ3‐ERK1/ERK2 MAPK that would regulate breast cancer cells survival and proliferation. © 2006 Wiley‐Liss, Inc.
Role of polyamines in arginine‐dependent colon carcinogenesis in ApcMin/+ mice
Authors: Yerushalmi Hagit F. , Besselsen David G. , Ignatenko Natalia A. , Blohm‐Mangone Karen A. , Padilla‐Torres Jose L. , Stringer David E. , Guillen Jose M. , Holubec Hana , Payne Claire M. , Gerner Eugene W. 
Published: May 2006

AbstractWe evaluated the role of polyamines in arginine‐dependent intestinal tumorigenesis in ApcMin/+ mice. Arginine is a substrate for ornithine synthesis and thus can influence polyamine production. Supplementing the diet with arginine increased intestinal and colonic polyamine levels and colonic carcinogenesis. Inhibiting polyamine synthesis with D,L‐α‐diflouromethylornithine (DFMO) decreased small intestinal and colonic polyamine pools. In mice provided basal diet, but not when supplemented with arginine, DFMO decreased small intestinal tumor number and burden, and increased intestinal apoptosis. In mice provided supplemental arginine in the diet, DFMO induced late apoptosis and decreased tumorigenesis in the colon. DFMO slightly reduced tumor incidence, number, and size while significantly decreasing tumor burden and grade. These changes in colon tumorigenesis did not occur in mice not provided supplemental arginine. Our study indicates that polyamines play unique roles in intestinal and colonic carcinogenesis in ApcMin/+ mice. Inhibition of polyamine synthesis suppresses the arginine‐dependent risk of colon tumorigenesis, resulting in apoptosis induction and decreased tumorigenesis, in this murine model. © 2006 Wiley‐Liss, Inc.
Cell‐cycle regulation and mammalian gametogenesis: A lesson from the unexpected
Authors: Kierszenbaum Abraham L. 
Published: May 2006

AbstractThe progression of mammalian gametogenesis requires a precise balance between cell‐cycle activities and elimination of defective gametogenic cells to ensure the perpetuation of species. Both spermatogonia and oogonia are stem cell populations committed to meiosis with the aim of generating haploid gametes for fertilization. At puberty, mitotically dividing spermatogonial cell cohorts maintain the ability of cell renewal and occupy niches in the seminiferous tubule. In contrast, mitotically dividing oogonial cell cohorts produced in the fetal ovary, are exclusively committed to meiosis and produce primordial follicles housing a primary oocyte surrounded by somatic follicular cells. A consistent physiological event during mammalian gametogenesis is the disposal of spermatogenic cells by apoptosis and ovarian follicles by atresia. Cyclin‐dependent kinases (Cdks) and their cyclin partners coordinate the activities of the cell cycle. An additional cell‐cycle regulatory component is the centrosome. The centrosome harbors regulatory proteins controlling the normal progression of the cell cycle. Changes in individual centrosome proteins can lead to cell‐cycle arrest and a decrease in the genomic protective function of p53 that promotes apoptosis. Disruption of cyclin A1, Cdk2, and Cdk4 expression in transgenic mice results in infertility and gonadal atrophy. Cdk–cyclin complexes interact with regulatory proteins, which may fine‐tune the activities of the complex. One of the many regulatory proteins is p12, a 115 amino acid growth suppressor polypeptide designated p12CDK2AP1, partner of Cdk2 and with binding affinity to DNA polymerase α/primase. Overexpression of p12 is associated with testicular and ovarian atrophy without affecting fertility. Ectopic expression of p12 was driven by the keratin 14 promoter. Keratin 14 is the pairing partner of keratin 5 and both keratins are expressed in testis. The efficiency of keratin promoters in driving ectopic gonadal gene expression, the association of gonadal atrophy with the ectopic expression of a Cdk2 regulatory protein and the centrosome, as a reservoir of cell‐cycle regulatory proteins, open new experimental opportunities to address still lingering questions concerning cell differentiation and division during mammalian gametogenesis. Mol. Reprod. Dev. 939–942, 2006. © 2006 Wiley‐Liss, Inc.
Nerve‐terminal and Schwann‐cell response after nerve injury in the absence of nitric oxide
Authors: Marques Maria Julia , Pereira Elaine Cristina Leite , Minatel Elaine , Neto Humberto Santo 
Published: May 2006

AbstractDystrophic muscles show alterations in the dystrophin–glycoprotein complex and a lack of neuronal nitric oxide (NO) synthase. In mdx mice, presynaptic expression of neuronal NO synthase is decreased, suggesting that presynaptic signaling may be altered in dystrophic muscle. In this study, we examined the nerve‐terminal and Schwann‐cell responses after a crush lesion in control and NO‐deficient mice. Seven days after nerve crush, 24% of control neuromuscular junctions (n = 200) showed ultraterminal sprouts, whereas in NO‐deficient mice this frequency was 28.5% (n = 217; P > 0.05 compared to controls; chi‐square test). Schwann‐cell response did not change in the absence of NO, after a nerve lesion of 7‐day duration. Fourteen days after the lesion, nerve terminals sprouted and Schwann cells showed an extensive network of processes away from the synaptic site in controls. In the absence of NO, there was a dramatic decrease in nerve‐terminal sprouting and Schwann‐cell processes failed to extend away from the endplate. These results show that NO is involved in the nerve‐terminal and Schwann‐cell response to nerve injury. They also suggest that presynaptic molecular signaling may be impaired in dystrophic muscles, and this could influence the innervation and survival of newly formed myofibers generated by cell‐mediated therapies. Muscle Nerve, 2006
The one‐commodity pickup and delivery travelling salesman problem on a path or a tree
Authors: Wang Fan , Lim Andrew , Xu Zhou 
Published: May 2006

AbstractOptimization algorithms for both path and tree topology classes of the one‐commodity pickup and delivery travelling salesman problem (1‐PDTSP) are proposed in this article, which focus on minimizing the route distance to transport products among pickup and delivery customers by a single vehicle with a limited capacity of k. Each pickup customer provides one unit volume of the product while each delivery customer requires one unit volume of the product. For the path case, we propose an O(n2/ min (k,n)) algorithm for any arbitrary k, and two O(n) algorithms for k = 1 and k = ∞. For the tree case, O(n2) and O(n) algorithms are proposed for k = 1 and k = ∞, respectively. Moreover, when k is arbitrary, the problem becomes NP‐hard in the strong sense. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(1), 24–35 2006
A simple algorithm that proves half‐integrality of bidirected network programming
Authors: Bolker Ethan D. , Zaslavsky Thomas 
Published: May 2006

AbstractIn a bidirected graph, each end of each edge is independently oriented. We show how to express any column of the incidence matrix as a half‐integral linear combination of any column basis, through a simplification, based on an idea of Bolker, of a combinatorial algorithm of Appa and Kotnyek. Corollaries are that the inverse of each nonsingular square submatrix has entries 0,
$\pm{1\over 2}$, and ±1, and that a bidirected integral linear program has half‐integral solutions. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(1), 36–38 2006
Minimizing false positives in kinase virtual screens
Authors: Perola Emanuele 
Published: May 2006

AbstractIn spite of recent improvements in docking and scoring methods, high false‐positive rates remain a common issue in structure‐based virtual screening. In this study, the distinctive features of false positives in kinase virtual screens were investigated. A series of retrospective virtual screens on kinase targets was performed on specifically designed test sets, each combining true ligands and experimentally confirmed inactive compounds. A systematic analysis of the docking poses generated for the top‐ranking compounds highlighted key aspects differentiating true hits from false positives. The most recurring feature in the poses of false positives was the absence of certain key interactions known to be required for kinase binding. A systematic analysis of 444 crystal structures of ligand‐bound kinases showed that at least two hydrogen bonds between the ligand and the backbone protein atoms in the kinase hinge region are present in 90% of the complexes, with very little variability across targets. Closer inspection showed that when the two hydrogen bonds are present, one of three preferred hinge‐binding motifs is involved in 96.5% of the cases. Less than 10% of the false positives satisfied these two criteria in the minimized docking poses generated by our standard protocol. Ligand conformational artifacts were also shown to contribute to the occurrence of false positives in a number of cases. Application of this knowledge in the form of docking constraints and post‐processing filters provided consistent improvements in virtual screening performance on all systems. The false‐positive rates were significantly reduced and the enrichment factors increased by an average of twofold. On the basis of these results, a generalized two‐step protocol for virtual screening on kinase targets is suggested. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Molecular dynamics simulation of Leishmania major surface metalloprotease GP63 (leishmanolysin)
Authors: Bianchini Gianluca , Bocedi Alessio , Ascenzi Paolo , Gavuzzo Enrico , Mazza Fernando , Aschi Massimiliano 
Published: May 2006

AbstractOne of the molecular factors contributing to Leishmania sp. virulence and pathogenesis is the major surface metalloprotease GP63, alternatively called leishmanolysin, MSP, and PSP (EC 3.4.24.36). Here, the molecular dynamics simulation of Leishmania major GP63 in water at pH 7 is reported. Upon solvation, GP63 undergoes a sharp structural relaxation with respect to the crystal structure. The fluctuation pattern occurs essentially in solvent‐exposed nonstructured regions. By contrast, the active site turns out to be rigid. Essential dynamics and dynamic‐domain analyses, both carried out on the equilibrated portion of GP63, show that the fingerprint fluctuations of GP63 are practically characterized by the motion of a large part of the N‐terminal domain. These results appear to be in line with substrate recognition and (pro)enzyme activation played by the N‐terminal domain of GP63. A systematic analysis among a series of 10 homologs of GP63 also shows that the residues involved in the interdomain bending result highly conserved. This finding also suggests possible relationship between the maintainance of proteolytic activity and the similarity of the dynamical properties of the related enzymes. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Enhancement‐mode AlGaN/GaN HEMTs on silicon substrate
Authors: Jia Shuo , Cai Yong , Wang Deliang , Zhang Baoshun , Lau Kei May , Chen Kevin J. 
Published: May 2006

AbstractHigh performance enhancement‐mode AlGaN/GaN HEMTs (E‐HEMTs) were demonstrated with samples grown on low‐cost silicon substrate for the first time. The fabrication process is based on fluoride‐based plasma treatment of the gate region and post‐gate annealing at 450 °C. The fabricated E‐HEMTs have nearly the same peak transconductance (Gm) and cut‐off frequencies as the conventional depletion‐mode HEMTs (D‐HEMTs) fabricated on the same wafer, suggesting little mobility degradation caused by the plasma treatment. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of InN on 6H‐SiC by plasma assisted molecular beam epitaxy
Authors: Brown April S. , Kim Tong‐Ho , Choi Soojeong , Wu Pae , Morse Michael , Losurdo Maria , Giangregorio Maria M. , Bruno Giovanni , Moto Akihiro 
Published: May 2006

AbstractWe have investigated the growth of InN films by plasma assisted molecular beam epitaxy on the Si‐face of 6H‐SiC(0001). Growth is performed under In‐rich conditions using a two‐step process consisting of the deposition of a thin, low‐temperature 350 °C InN buffer layer, followed by the subsequent deposition of the InN epitaxial layer at 450 °C. The effect of buffer annealing is investigated. The structural and optical evolution of the growing layer has been monitored in real time using RHEED and spectroscopic ellipsometry. Structural, morphological, electrical and optic properties are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Capacitance characterization of AlN/GaN double‐barrier resonant tunnelling diodes
Authors: Kurakin A. M. , Vitusevich S. A. , Danylyuk S. V. , Naumov A. V. , Foxon C. T. , Novikov S. V. , Klein N. , Lüth H. , Belyaev A. E. 
Published: May 2006

AbstractWe report on the electrical characterization of AlN/GaN/AlN double‐barrier resonant tunnelling diodes (RTDs) using steady‐state current‐voltage and capacitance‐voltage (C‐V) characteristics in a wide frequency range with 2 kHz steps. The C‐V characteristics of a double‐barrier RTD show different behaviour under forward and reverse polarities and a strong dependence on frequency. The monotonous growth of capacitance at forward bias was registered, while a more complicated dependence was observed at reverse voltages. In order to analyse this dependence, a self‐consistent calculation of the potential profile of the structure was performed taking into account polarization effects at the AlN/GaN interfaces. The peculiarities are analysed in the model of possible charge trapping at the interface states. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
NH3/TMI molar ratio dependence of electrical and optical properties for atmospheric‐pressure MOVPE InN
Authors: Yamamoto A. , Miwa H. , Shibata Y. , Hashimoto A. 
Published: May 2006

AbstractThe electrical and optical properties for atmospheric‐pressure MOVPE InN have been studied as a function of NH3/TMI molar ratio during the growth. Residual carrier (electron) concentration is decreased with increasing NH3/TMI molar ratio. PL peak energy is also shifted to a low energy side with increasing NH3/TMI molar ratio. Hall mobility of InN is almost independent on NH3/TMI molar ratio and is rather decreased at a high NH3/TMI molar ratio. The highest mobility is obtained for a sample grown at a relatively low NH3/TMI molar ratio. The grain size of the InN films is decreased with increasing NH3/TMI molar ratio. The lowest carrier concentration of 4.5×1018 cm–3 and highest mobility of 1100 cm2/Vs obtained here are the best data for MOVPE InN ever reported. Based on these results, the most probable candidate for donors and the dominant carrier‐scattering mechanism for atmospheric‐pressure MOVPE InN are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on local Ga and In incorporation of GaInN quantum wells on facets of selectively grown GaN stripes
Authors: Neubert B. , Habel F. , Brückner P. , Scholz F. , Schirra M. , Feneberg M. , Thonke K. , Riemann T. , Christen J. , Beer M. , Zweck J. , Moutchnik G. , Jetter M. 
Published: May 2006

AbstractMultiple GaInN quantum wells (QWs) were grown on side facets with reduced piezoelectric fields (PFs) of selectively grown GaN stripes oriented along the 〈1$ \bar 1 $00〉 and 〈11$ \bar 2 $0〉 directions by metalorganic vapor phase epitaxy (MOVPE). The different luminescence wavelengths observed for the QWs on these facets can be explained by the reduced PFs, additionally the QW thickness depends on the facet type. Although stripes running along 〈1$ \bar 1 $00〉 and 〈11$ \bar 2 $0〉 develop similar triangular or trapezoidal shape, their detailed growth behaviour, electrical and luminescence properties differ significantly pointing to different adsorption/desorption and inter‐facet migration processes of In, Ga and the p‐type dopant Mg. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Suppression of gate leakage current in GaN MOS devices by passivation with photo‐grown Ga2O3
Authors: Wu H.‐M. , Peng L.‐H. 
Published: May 2006

AbstractWe report the use of photo‐enhanced chemical (PEC) technique to form high‐quality metal oxide semiconductor (MOS) devices made of gallium oxide (Ga2O3)/gallium nitride (GaN). Gate leakage current density as low as 2×10–7 A/cm2 at a bias field up to 2 MV/cm is observed in the GaN MOS devices that are formed by novel PEC wet etching and have the top surface and mesa sidewall passivated by the photo‐grown Ga2O3. The depth‐resolved X‐ray photo‐emission spectra (XPS) and atomic‐ratio analysis indicate that a intermediate and thin ∼20 nm GaON layer of graded composition forms the Ga2O3/GaON/GaN system, which releases the interfacial strain and thus minimizes the density of interfacial states. The IV and high‐frequency CV analyses reveal that the Ga2O3 layer can sustain an electrical breakdown field of 3.5 MV/cm and the structures have a low density of interfacial state (Dit) in the order of 1011 eV–1cm–2. We attribute these results to the immunity to surface damage by the novel PEC wet etching and the effective passivation on mesa sidewall and surface formed by the photo‐grown Ga2O3. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhanced emission efficiency of InGaN films with Si doping
Authors: Li Da‐Bing , Liu Yu‐Huai , Katsuno Takuya , Nakao Keisuke , Nakamura Kazuya , Aoki Masakazu , Miyake Hideto , Hiramatsu Kazumasa 
Published: May 2006

AbstractHigh emission efficiency of InGaN films were obtained with Si doping, and the influence of Si doping on structural and optical properties of InGaN epilayers with different Si concentration were investigated in detail by means of high‐resolution X‐ray diffraction (HRXRD), scanning electron microscope (SEM), Cathodoluminescence (CL) and photoluminescence(PL). V‐defects were observed on the surface of InGaN films, and further investigation by CL showed that V‐defects act as nonradiative center, which lower the emission efficiency of InGaN. Meanwhile, it was found that Si doping could improve the crystal quality of InGaN and suppress the formation of V‐defects in InGaN, and hence enhance the emission efficiency of InGaN. One possible mechanism of influence of Si doping on the formation of V‐defects in InGaN was also proposed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of luminous intensity of InGaN light emitting diodes grown on hemispherical patterned sapphire
Authors: Lee Jae‐Hoon , Oh Jeong‐Tak , Park Jin‐Sub , Kim Je‐Won , Kim Yong‐Chun , Lee Jeong‐Wook , Cho Hyung‐Koun 
Published: May 2006

AbstractTo improve the external quantum efficiency, high quality GaN film was grown on hemispherical patterned sapphire by controlling the V/III ratio during the initial growth stage. The luminous intensity of white flash light emitting diode (LED) grown on hemispherical patterned sapphire (HPS) was estinated to be 5.8 cd at a forward current of 150 mA, which is improved by 20% more than that of LED grown on conventional sapphire substrate. The improvement of luminous intensity was explained by considering not only an increase of the extraction efficiency via the suppressed total internal reflection at the corrugated interface but also a decrease of dislocation density. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dislocation behaviour in III‐nitride epitaxial films grown on vicinal sapphire (0001) substrates
Authors: Shen X. Q. , Matsuhata H. , Okumura H. 
Published: May 2006

AbstractDislocation behaviour in AlN and GaN films grown on vicinal sapphire (0001) substrates are investigated using transmission electron microscopy. It is found that the dislocation behaviours strongly depend on the vicinal angle of the substrates. When the vicinal angle is 0.5°, the dislocation lines propagate along the c‐axis and no bending of the dislocation line is found. On the other hand, dislocation bending occurs in the films grown on the 2.0°‐off substrates, which results in the great reduction of the dislocation density in the films. The dislocation loop formation and the combination of two dislocations into one are the main mechanisms for this reduction. The surface morphology (mono‐layer and multilayer step formations) plays an important role in determining the different dislocation behaviours. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of optical‐output‐power degradation in 365‐nm UV‐LEDs
Authors: Mukai Takashi , Morita Daisuke , Yamamoto Masashi , Akaishi Kazuyuki , Matoba Kousuke , Yasutomo Katsuhiro , Kasai Yoshio , Sano Masahiko , Nagahama Shin‐ichi 
Published: May 2006

AbstractThe dependence of UV‐LED lifetime on threading dislocation density(TDD) was examined. UV‐LED structures were grown on standard GaN template(TDD: 1x108/cm2) and ELO‐GaN(TDD: 1x107/cm2), and lifetime testing was performed under a forward current of 500 mA at junction temperature(Tj) of 75 ºC. Lifetime of both LEDs were estimated as 17,600 h (standard GaN template) and 166,000 h (ELO‐GaN), respectively. It was found that GaN underlying layer with TD‐density of 1x107/cm2 is superior to that of 1x108/cm2 in terms of LED lifetime, despite no output power difference. Junction temperature (Tj) dependence of LED lifetime was investigated in use of standard GaN template(1x108/cm2). Tj was varied from 311 K to 422 K. The activation energy was determined to be 0.36 eV. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN blue cathodoluminescence phosphors synthesized with long reaction time in a new reactor
Authors: Kanie Hisashi , Kobayashi Shingo , Sema Yuji 
Published: May 2006

AbstractInGaN microcrystals were grown by two‐stage growth method for 10 hours in a new reactor without clogging an exhaust tube by fine particles. Obtained InGaN showed double peaked cathodoluminescence spectra, violet peak at 385‐389 nm and blue at 438‐444 nm when excited at 5‐15 kV. The uniformity of the blue emission spectra among the crystals were improved for those grown for the 10‐hour reaction time. The yields of emissive GaN and InGaN crystals were not improved. The compatibility of the position of the violet band of the InGaN crystals to that of the GaN crystals and the resemblance of morphology of the GaN and InGaN crystals imply the growth of InGaN on GaN facets in two‐stage growth. The cause of the deterioration of the CL efficiency of the grown InGaN crystals at a low acceleration voltage was discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)