bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microvesicles derived from activated platelets induce metastasis and angiogenesis in lung cancer
Authors: Janowska‐Wieczorek Anna , Wysoczynski Marcin , Kijowski Jacek , Marquez‐Curtis Leah , Machalinski Bogdan , Ratajczak Janina , Ratajczak Mariusz Z. 
Published: October 2004

AbstractThe role of platelets in tumor progression and metastasis has been recognized but the mechanism of their action remains unclear. Five human lung cancer cell lines (A549, CRL 2066, CRL 2062, HTB 183, HTB 177) and a murine Lewis lung carcinoma (LCC) cell line (for an in vivo model of metastasis) were used to investigate how platelet‐derived microvesicles (PMV), which are circular fragments shed from the surface membranes of activated platelets, and exosomes released from platelet α‐granules, could contribute to metastatic spread. We found that PMV transferred the platelet‐derived integrin CD41 to most of the lung cancer cell lines tested and stimulated the phosphorylation of mitogen‐activated protein kinase p42/44 and serine/threonine kinase as well as the expression of membrane type 1‐matrix metalloproteinase (MT1‐MMP). PMV chemoattracted 4 of the 5 cell lines, with the highly metastatic A549 cells exhibiting the strongest response. In A549 cells, PMV were shown to stimulate proliferation, upregulate cyclin D2 expression and increase trans‐Matrigel chemoinvasion. Furthermore, in these cells, PMV stimulated mRNA expression for angiogenic factors such as MMP‐9, vascular endothelial growth factor, interleukin‐8 and hepatocyte growth factor, as well as adhesion to fibrinogen and human umbilical vein endothelial cells. Intravenous injection of murine PMV‐covered LLC cells into syngeneic mice resulted in significantly more metastatic foci in their lungs and LLC cells in bone marrow than in control animals injected with LCC cells not covered with PMV. Based on these findings, we suggest that PMV play an important role in tumor progression/metastasis and angiogenesis in lung cancer. © 2004 Wiley‐Liss, Inc.
Immunohistological evaluation of single small hepatocellular carcinoma with negative staining of monoclonal antibody Hepatocyte Paraffin 1
Authors: Sugiki Takaaki , Yamamoto Masakazu , Aruga Atsushi , Takasaki Ken , Nakano Masayuki 
Published: October 2004

AbstractBackground and ObjectivesThe sensitivity and specificity of the monoclonal antibody Hepatocyte Paraffin 1 (Hep Par 1) for hepatocellular carcinoma (HCC) are very high, and the usefulness for differential diagnosis of hepatic tumors has been reported. However, there are some cases of HCC with negative staining for Hep Par 1. We examined the histopathological features of HCC with negative staining for Hep Par 1.MethodsWe examined 69 samples of single nodular HCC less than 2 cm in greatest dimension, resected from 1985 to 1994 in our hospital, with immunohistological staining for Hep Par 1, cytokeratin 19 (CK 19), MUC‐1 glycoprotein (MUC‐1), and epithelial membrane antigen (EMA).ResultsHep Par 1 staining was positive in 64 cases (93%) and negative in 5 cases (7%). With regard to the histological structure, 3 of the 5 negative cases were scirrhous HCC. With regard to the grade of histological differentiation, 2 cases were poorly differentiated HCC, 3 cases were moderately differentiated HCC, and no well‐differentiated HCC was found in the negative cases. CK 19, MUC‐1, and EMA staining were negative in all cases.ConclusionsIt is necessary to recognize the existence of Hep Par 1 negative HCC, in particular scirrhous HCC. This may be due to a different mechanism in the earlier stage of hepatocarcinogenesis. J. Surg. Oncol. 2004;88:104–107. © 2004 Wiley‐Liss, Inc.
Einfluss der Rauheit auf die mikrotribologischen Eigenschaften von unterschiedlich strukturierten Siliziumoberflächen bedeckt mit selbstorganisierten Monoschichten
Authors: Hild W. , Hungenbach G. , Schaefer J. A. , Fischer M. , Ahmed S. I.‐U. , Scherge M. 
Published: October 2004

AbstractErscheinungen, wie Reibung, Adhäsion und Benetzbarkeit sich bewegender Teile haben einen großen Einfluss auf die Lebensdauer und mechanischen Eigenschaften von Mikrosystemen. Es ist bekannt, dass Wasser einen negativen Einfluss auf die Lebensdauer hat und zum Verkleben von Bauteilen (Adhäsion) sowie zu hoher Reibung und Verschleiß führt. Hydrophobe selbstorganisierte Monoschichten (SAMs) eliminieren den Einfluss des Wassers und verringern Adhäsion und Reibung. Einen ähnlichen Effekt hat eine Zunahme der Rauheit und die damit verbundene Verringerung der realen Kontaktfläche. Durch Plasma‐Ätzen wurde durch Wahl der Ätzparameter (Leistung, Zeit, Gasfluss, Druck usw.) die Rauheit modifiziert. Es werden die mikrotribologischen Eigenschaften als Funktion der Oberflächentopographie und der Last von natürlichem Oxid auf Si(100) (einer Wasser‐anziehenden Probe) und Si(100) bedeckt mit Octadecyltrichlorsilan (OTS) und Perfluorodecyltrichlorsilan (FDTS) untersucht. Die Reibungs‐Last‐Kurve auf der polierten Oxid‐bedeckten Probe genügt, in Verbindung mit dem Bowden‐Tabor‐Modell, dem Johnson‐Kendall‐Roberts‐Modell und auf den OTS‐bedeckten Proben dem Hertz‐Modell. Für die FDTS‐bedeckten Proben steigt sie linear an. Mit steigender Rauheit sinkt die Reibung für die Oxid‐ und FDTS‐bedeckten Proben. Im Gegensatz dazu erhöht sie sich für OTS und wird linear. Lebensdaueruntersuchungen der Monoschichten in Abhängigkeit von der Last deuten an, dass bei hohen Rauheiten eine geringere Lebensdauer auftritt als bei niedrigen. Außerdem wird der Verschleißmechanismus der Monolagen diskutiert.
Prognose des Abrasivverschleisses bei Bauteilen aus Grobblech mit Methoden der Statistischen Versuchsplanung
Authors: Bauer D. , Pickhan U. , Schröder X. 
Published: October 2004

AbstractDer PIN ABRASION TEST ist ein international anerkannter Versuch zur Messung des Abrasivverschleisses unter Laborbedingungen. Es wird gezeigt, wie mit Hilfe dieses Tests eine Prognose des zu erwartenden Abrasivverschleisses von Bauteilen aus Grobblechen, die aus unterschiedlichen Stahlwerkstoffen bestehen können, möglich ist. Zu diesem Zweck kommt eine spezielle Methode der statistischen Mathematik bei der Planung und Ausführung der Experimente zur Anwendung. Dabei werden sogenannte vollständige 2n‐Pläne nach R. A. Fisher verwendet. Diese berücksichtigen den Einfluss von n=5 Faktoren: Normalkraft, Gleitgeschwindigkeit, Größe, Härte der Abrasivteilchen und Härte der Grobblechwerkstoffe. Die Auswertung der Versuchsergebnisse erfolgt mittels Regressionsanalyse. Es lässt sich eine multilineare mathematische Funktion definieren. Diese Funktion berücksichtigt sämtliche signifikanten Effekte und Wechselwirkungen der Einflussfaktoren und erlaubt eine Prognose des Abrasivverschleisses. Damit lassen sich die Ergebnisse der Laborversuche erfolgreich in die industrielle Praxis übertragen.
Verschleißmechanismen bei moderater und extremer Grenzreibung
Authors: Scherge M. , Pöhlmann K. 
Published: October 2004

AbstractMit einem Stift‐Scheibe‐Tribometer wurden für das System Stahlstift/Stahlscheibe Versuche durchgeführt, die drastisch unterschiedliche Verschleißraten zur Folge hatten. Durch Wahl der Normalkraft wurde die Energiedissipation so eingestellt, dass im ersten Versuch Verschleißraten in der Größenordnung von Nanometern pro Stunde erreicht wurden, während im zweiten Versuch Mikrometer pro Stunde erzielt wurden. Die Proben wurden nach dem Experiment hinsichtlich Struktur und chemischer Zusammensetzung analysiert. Im Bereich der kleinen Verschleißraten dominierten plastisches Fließen und mechanische Vermischung während die hohen Verschleißraten mit starker Topographieänderung und Oxidation einher gingen.
Friction and Wear of Carbon Fibre Filled Polymer Composites at Room and Low Temperatures
Authors: Theiler G. , Hübner W. , Gradt Th. , Klein P. 
Published: October 2004

AbstractIn the cryogenic temperature range common lubricants solidify and therefore, they cannot be applied. Thus, for tribosystems in low temperature environment technical solutions based on good dry lubricating properties of the materials themselves must be found. In this concern polymers are of great interest, because they show comparatively high mechanical strength at low density, and they often possess favourable friction and wear properties at low temperatures. This work presents investigations on the tribological behaviour of carbon fibre (CF) filled PTFE and PEEK composites in a cryogenic environment (liquid nitrogen; T = −196 °C). In general, these materials clearly exhibit lower friction and wear properties at low temperatures than at room temperature, which can be explained mainly by the temperature dependence of the mechanical strength. With increasing amount of carbon fibres in both composites, friction and wear increase. The optimal composition was found to be at 5 wt.% CF for the friction and 15 wt.% CF for the wear values. At low temperatures, the percentage of carbon fibres in PTFE and PEEK composites has not such an important influence as it has at room temperature.
Anisotropic elastic–plastic analysis of shells at large strains. A comparison of multiplicative and additive approaches to enhanced finite element design and constitutive modelling
Authors: Miehe Christian , Apel Nikolas 
Published: October 2004

AbstractThe article presents new aspects of large‐strain anisotropic elastoplastic analyses of shells. On the side of computational shell analysis we focus on recently developed brick‐type mixed finite shell elements based on trilinear displacement interpolations equipped with enhanced strain modes and shell‐typical assumed strain modifications. Here, we compare two classes of this shell element design based on a multiplicative and an additive definition of an enhanced strain measure, respectively. Furthermore, for both types of continuum‐based shell elements we outline unified interfaces to strain‐driven constitutive stress update algorithms of anisotropic finite plasticity. On the side of computational plasticity we investigate two classes of constitutive models suitable for the description of anisotropic elastoplastic response at finite strains. The first framework uses a multiplicative definition of an elastic strain measure based on a plastic map, the second an additively defined elastic strain measure based on a plastic metric. Both constitutive frameworks use Hencky‐type logarithmic strain measures and are specified to a model problem of orthotropic elastic–plastic response of a standard material. The algorithmic treatment of the two constitutive models is based on an incremental variational formulation that defines the stresses and consistent tangent moduli in terms of a function evaluation. We compare the performances of the two finite element formulations and the two constitutive models by means of numerical simulations of sheet drawing processes. For the range of metal plasticity at moderate strains it is shown that results obtained with the different approaches are close to each other, while the additive approaches provide simpler and more efficient settings. Copyright © 2004 John Wiley & Sons, Ltd.
3,6‐linked 9‐alkyl‐9H‐carbazole main‐chain polymers: Preparation and properties
Authors: Iraqi Ahmed , Wataru Isao 
Published: October 2004

AbstractAn investigation into the preparation of poly(9‐alkyl‐9H‐carbazole‐3,6‐diyl)s with palladium catalyzed cross‐coupling reactions of 3‐halo‐6‐halomagnesio‐9‐alkyl‐9H‐carbazoles, generated in situ from their corresponding 3,6‐diiodo‐ and 3,6‐dibromo‐derivatives was undertaken. Monomers with a range of alkyl group substituents with different steric requirements were investigated and their effects on the polymerization were studied. The effects of the nature of halogen substituents on the polymerization reaction were also investigated. Structural analysis of the polymers revealed exclusive 3,6‐linkage between consecutive carbazole repeat units on the polymer chains. The physical properties of these polymers were investigated with spectroscopic, thermal gravimetric analysis, and electrochemical studies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6041–6051, 2004
Analysis of singleton ORFans in fully sequenced microbial genomes
Authors: Siew Naomi , Fischer Daniel 
Published: October 2004

AbstractSingleton sequence ORFans are orphan ORFs (open reading frames) that have no detectable sequence similarity to any other sequence in the databases. ORFans are of particular interest not only as evolutionary puzzles but also because we can learn little about them using bioinformatics tools. Here, we present a first systematic analysis of singleton ORFans in the first 60 fully sequenced microbial genomes. We show that although ORFans have been underemphasized, the number of ORFans is steadily growing, currently accounting for 23,634 sequences. At the same time, the percentage of ORFans as a fraction of all sequences is slowly diminishing, and is currently about 14%. Short ORFans comprise about 61% of all ORFans. The abundance of short ORFans may be due to a yet unexplained artifact. The data also suggest that the number of longer ORFans may soon diminish as more genomes of closely related organisms become available. To better address the questions about the functions and origins of ORFans, we propose to focus further studies on the longer ORFans, with emphasis on three new types of ORFans: ORFan modules, paralogous ORFans, and orthologous ORFans. We conclude that the large number of ORFans reflects an intrinsic property of the genetic material not yet fully understood. Further computational and experimental studies aimed at understanding Nature's protein diversity should also include ORFans. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Molecular dynamics simulations of galectin‐1‐oligosaccharide complexes reveal the molecular basis for ligand diversity
Authors: Ford Michael G. , Weimar Thomas , Köhli Thies , Woods Robert J. 
Published: October 2004

AbstractGalectin‐1 is a member of a protein family historically characterized by its ability to bind carbohydrates containing a terminal galactosyl residue. Galectin‐1 is found in a variety of mammalian tissues as a homodimer of 14.5‐kDa subunits. A number of developmental and regulatory processes have been attributed to the ability of galectin‐1 to bind a variety of oligosaccharides containing the Gal‐β‐(1,4)‐GlcNAc (LacNAcII) sequence. To probe the origin of this permissive binding, solvated molecular dynamics (MD) simulations of several representative galectin‐1‐ligand complexes have been performed. Simulations of structurally defined complexes have validated the computational approach and expanded upon data obtained from X‐ray crystallography and surface plasmon resonance measurements. The MD results indicate that a set of anchoring interactions between the galectin‐1 carbohydrate recognition domain (CRD) and the LacNAc core are maintained for a diverse set of ligands and that substituents at the nonreducing terminus of the oligosaccharide extend into the remainder of a characteristic surface groove. The anionic nature of ligands exhibiting relatively high affinities for galectin‐1 implicates electrostatic interactions in ligand selectivity, which is confirmed by a generalized Born analysis of the complexes. The results suggest that the search for a single endogenous ligand or function for this lectin may be inappropriate and instead support a more general role for galectin‐1, in which the lectin is able to crosslink heterogeneous oligosaccharides displayed on a variety of cell surfaces. Such binding promiscuity provides an explanation for the variety of adhesion phenomena mediated by galectin‐1. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Free energy landscape of protein folding in water: Explicit vs. implicit solvent
Authors: Zhou Ruhong 
Published: October 2004

AbstractThe Generalized Born (GB) continuum solvent model is arguably the most widely used implicit solvent model in protein folding and protein structure prediction simulations; however, it still remains an open question on how well the model behaves in these large‐scale simulations. The current study uses the β‐hairpin from C‐terminus of protein G as an example to explore the folding free energy landscape with various GB models, and the results are compared to the explicit solvent simulations and experiments. All free energy landscapes are obtained from extensive conformation space sampling with a highly parallel replica exchange method. Because solvation model parameters are strongly coupled with force fields, five different force field/solvation model combinations are examined and compared in this study, namely the explicit solvent model: OPLSAA/SPC model, and the implicit solvent models: OPLSAA/SGB (Surface GB), AMBER94/GBSA (GB with Solvent Accessible Surface Area), AMBER96/GBSA, and AMBER99/GBSA. Surprisingly, we find that the free energy landscapes from implicit solvent models are quite different from that of the explicit solvent model. Except for AMBER96/GBSA, all other implicit solvent models find the lowest free energy state not the native state. All implicit solvent models show erroneous salt‐bridge effects between charged residues, particularly in OPLSAA/SGB model, where the overly strong salt‐bridge effect results in an overweighting of a non‐native structure with one hydrophobic residue F52 expelled from the hydrophobic core in order to make better salt bridges. On the other hand, both AMBER94/GBSA and AMBER99/GBSA models turn the β‐hairpin in to an α‐helix, and the α‐helical content is much higher than the previously reported α‐helices in an explicit solvent simulation with AMBER94 (AMBER94/TIP3P). Only AMBER96/GBSA shows a reasonable free energy landscape with the lowest free energy structure the native one despite an erroneous salt‐bridge between D47 and K50. Detailed results on free energy contour maps, lowest free energy structures, distribution of native contacts, α‐helical content during the folding process, NOE comparison with NMR, and temperature dependences are reported and discussed for all five models. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Crystal structures of ferrous horse heart myoglobin complexed with nitric oxide and nitrosoethane
Authors: Copeland Daniel M. , West Ann H. , Richter‐Addo George B. 
Published: October 2004

AbstractThe interactions of nitric oxide (NO) and organic nitroso compounds with heme proteins are biologically important, and adduct formation between NO‐containing compounds and myoglobin (Mb) have served as prototypical systems for studies of these interactions. We have prepared crystals of horse heart (hh) MbNO from nitrosylation of aqua‐metMb crystals, and we have determined the crystal structure of hh MbNO at a resolution of 1.9 Å. The Fe‐N‐O angle of 147° in hh MbNO is larger than the corresponding 112° angle previously determined from the crystal structure of sperm whale MbNO (Brucker et al., Proteins 1998;30:352–356) but is similar to the 150° angle determined from a MS XAFS study of a frozen solution of hh MbNO (Rich et al., J Am Chem Soc 1998;120:10827–10836). The Fe‐N(O) bond length of 2.0 Å (this work) is longer than the 1.75 Å distance determined from the XAFS study and suggests distal pocket influences on FeNO geometry. The nitrosyl N atom is located 3.0 Å from the imidazole Nϵ atom of the distal His64 residue, suggesting electrostatic stabilization of the FeNO moiety by His64. The crystal structure of the nitrosoethane adduct of ferrous hh Mb was determined at a resolution of 1.7 Å. The nitroso O atom of the EtNO ligand is located 2.7 Å from the imidazole Nϵ atom of His64, suggesting a hydrogen bond interaction between these groups. To the best of our knowledge, the crystal structure of hh Mb(EtNO) is the first such determination of a nitrosoalkane adduct of a heme protein. Proteins 2003. © 2003 Wiley‐Liss, Inc.
3D structural model of the G‐protein‐coupled cannabinoid CB2 receptor
Authors: Xie Xiang‐Qun , Chen Jian‐Zhong , Billings Eric M. 
Published: October 2004

AbstractThe potential for therapeutic specificity in regulating diseases and for reduced side effects has made cannabinoid (CB) receptors one of the most important G‐protein‐coupled receptor (GPCR) targets for drug discovery. The cannabinoid (CB) receptor subtype CB2 is of particular interest due to its involvement in signal transduction in the immune system and its increased characterization by mutational and other studies. However, our understanding of their mode of action has been limited by the absence of an experimental receptor structure. In this study, we have developed a 3D model of the CB2 receptor based on the recent crystal structure of a related GPCR, bovine rhodopsin. The model was developed using multiple sequence alignment of homologous receptor sub‐types in humans and mammals, and compared with other GPCRs. Alignments were analyzed with mutation scores, pairwise hydrophobicity profiles and Kyte‐Doolittle plots. The 3D model of the transmembrane segment was generated by mapping the CB2 sequence onto the homologous residues of the rhodopsin structure. The extra‐ and intracellular loop regions of the CB2 were generated by searching for homologous Cα backbone sequences in published structures in the Brookhaven Protein Databank (PDB). Residue side chains were positioned through a combination of rotamer library searches, simulated annealing and minimization. Intermediate models of the 7TM helix bundles were analyzed in terms of helix tilt angles, hydrogen‐bond networks, conserved residues and motifs, possible disulfide bonds. The amphipathic cytoplasmic helix domain was also correlated with biological and site‐directed mutagenesis data. Finally, the model receptor‐binding cavity was characterized using solvent‐accessible surface approach. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Pentalanthanum ethenide(4‐) digermanide(4‐), La5(C2)Ge2
Authors: Carrillo–Cabrera Wilder , Čurda Jan , Peters Karl , Kohout Miroslav , von Schnering Hans Georg 
Published: October 2004

AbstractLa5(C2)Ge2 was obtained as a minor component from the reaction of the elements in corundum crucibles enclosed in stainless steel ampoules at 1360 K. The compound is gray with metallic luster. The crystal structure of La5(C2)Ge2 (space group Pbam, a = 8.873Å, b = 12.946Å, c = 4.273Å; Z = 2; Rgt(F) = 0.069, Rw(F2) = 0.147) is an arrangement of condensed La9 3‐fold capped trigonal prisms and La6 octahedra, centered by Ge atoms and C2 dumbbells, respectively (d(Ge‐La) = 3.173 ‐ 3.887Å; d(C‐La) = 2.42Å (end‐on) and 2.83Å (side‐on); d(C‐C) = 1.34Å). The structure differs from the La2SnS5 structure with covalent S—S bonds only by the replacement of the Sn atoms by C2 dumbbells: La2SnS5 = S5(Sn)La2 ≙ La5(C2)Ge2. The anionic chains of edge‐condensed octahedra [SnS4/2S2]4‐ are replaced by [(C2)La4/2La2] chains, containing remarkable piles of alternating C2 and La2 pairs (d(La‐La) = 3.438Å) with side‐on coordination along the c axis. The formal oxidation states La3+, Ge4‐, C24‐ yield in an excess of three electrons per formula unit. The source of rest electron density of about 2.5 e·Å‐3 is analyzed and discussed. The calculated band structure indicates metallic behavior.