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Cell Interface (cell + interface)
Selected AbstractsToll-like receptor engagement stimulates anti-snRNP autoreactive B cells for activationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2006Chuanlin Ding Abstract Autoreactive B cells are the source of pathogenic autoantibodies (autoAb) in systemic lupus erythematosus (SLE). Previous studies have demonstrated that anti-small nuclear ribonucleoprotein particles (snRNP) B cells from normal background mice tolerize T cells in the periphery and do not secrete autoAb. In this study, we examined whether these anti-snRNP B cells can be activated for autoAb production by the engagement of Toll-like receptors (TLR). Anti-snRNP B cells proliferated vigorously and secreted abundant anti-snRNP autoAb upon exposure to CpG or polyriboinosinic polyribocytidylic acid [poly,(I:C)] in vitro. In addition, the costimulatory molecules CD80 and CD86 were up-regulated. While both anti-snRNP B cells and wild-type B cells produced similar levels of IL-6 and IL-10, anti-snRNP B cells secreted predominately IFN-, in response to CpG or poly,(I:C) stimulation. Furthermore, we showed that in vivo engagement of TLR stimulated immature anti-snRNP B cells to further differentiate and produce autoAb and form germinal centers. The activated anti-snRNP B cells became expanded and migrated into the T-B cell interface. Moreover, TLR engagement directly or indirectly activated autoreactive B cells via a CD4 T cell-independent manner. These results provide in vitro and in vivo evidence that BCR/TLR co-engagement promotes the activation of anti-snRNP B cells for autoAb production. [source] Early cytoskeletal rearrangement during dendritic cell maturation enhances synapse formation and Ca2+ signaling in CD8+ T cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2004Marco Averbeck Abstract The interplay between dendritic cells (DC) and T cells is a dynamic process critically depending on DC maturation. Ca2+ influx is one of the initial events occurring during DC/T cell contacts. To determine how DC maturation influences DC/T cell contacts, time-lapse video microscopy was established using TCR-transgenic CD8+ T cells from P14 mice. DC maturation shifted DC/T cell contacts from short-lived interactions with transient Ca2+ influx in T cells to long-lasting interactions and sustained Ca2+ influx of 30,min and more. Follow-up of DC/T cell interactions after 2,h using confocal microscopy revealed that long-lasting Ca2+ responses in T cells were preferentially associated with the formation of an immunological synapse involving CD54 and H2-Kb at the DC/T cell interface. Such synapse formation preceded MHC or B7 up-regulation, since DC developed into potent Ca2+ stimulators 7,h after initiation of maturation. Instead, the enhanced capacity of 7,h-matured DC to induce sustained Ca2+ responses in CD8+ T cells is critically dependent on the polarization and rearrangement of the cytoskeleton, as shown by Clostridium difficile toxin B inhibitor experiments. These data indicate that already very early after receiving a maturation stimulus, DC display enhanced cytoskeletal activity resulting in the rapid formation of immunological synapses and effective CD8+ T cell stimulation. [source] Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (KCa) and connexins: possible relationship to vasodilator function?JOURNAL OF ANATOMY, Issue 5 2006Shaun L. Sandow Abstract Activation of endothelial cell small- (S) and intermediate- (I) conductance calcium-activated potassium channels (KCa) and current or molecular transfer via myoendothelial gap junctions underlies endothelium-derived hyperpolarization leading to vasodilation. The mechanism underlying the KCa component of vasodilator activity and the characteristics of gap junctions are targets for the selective control of vascular function. In the rat mesenteric artery, where myoendothelial gap junctions and connexin (Cx) 40 are critical for the transmission of the endothelial cell hyperpolarization to the smooth muscle, SKCa and IKCa provide different facets of the endothelium-derived hyperpolarization response, being critical for the hyperpolarization and repolarization phases, respectively. The present study addressed the question of whether this functional separation of responses may be related to the spatial localization of the associated channels? The distribution of endothelial SKCa and IKCa and Cx subtype(s) were examined in the rat mesenteric artery using conventional confocal and high-resolution ultrastructural immunohistochemistry. At the internal elastic lamina,smooth muscle cell interface at internal elastic lamina holes (as potential myoendothelial gap junction sites), strong punctate IKCa, Cx37 and Cx40 expression was present. SKCa, Cx37, Cx40 and Cx43 were localized to adjacent endothelial cell gap junctions. High-resolution immunohistochemistry demonstrated IKCa and Cx37-conjugated gold to myoendothelial gap junction-associated endothelial cell projections. Clear co-localization of KCa and Cxs suggests a causal relationship between their activity and the previously described differential functional activation of SKCa and IKCa. Such precise localizations may represent a selective target for control of vasodilator function and vascular tone. [source] Porous silicon as a cell interface for bone tissue engineeringPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007Wei Sun Abstract A novel cell interface has been constructed on porous silicon. We have demonstrated that nano- to macro-scale porous architectures have promising osteoconductive potentials. Macroporous silicon (pore opening 1,2 µm) is especially favorable for osteoblast adhesion, growth, protein synthesis and mineralization. An electronic/optoelectronic controllable medical implant with both scaffolding and drug delivery functions may be created for orthopaedic tissue engineering with this material. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The effect of oxygen on interface microstructure evolution in CdS/CdTe solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2002D.S. Albin Microstructural changes at the CdS/CdTe solar cell interface where close-spaced sublimation (CSS) is used as the growth technique to deposit the p -type CdTe absorber layer are studied by systematic layer characterization at various stages during heterojunction growth. CdS layers grown by both chemical bath deposition (CBD) and CSS provide a basis for determining the effects of CdS crystallinity, grain size, and oxygen content on the subsequent CdTe layer. As-grown CBD CdS films exhibit small grains and variations in optical properties attributed to film impurities. In contrast, CSS yields CdS films with good crystallinity, larger grains, and nearly ideal optical properties. The hexagonal nature of CSS-grown CdS is seen to nucleate hexagonal CdTe during the initial stages of CdTe film growth. Cubic CdS deposited by CBD in contrast promotes cubic CdTe nucleation. Oxygen anneals in the latter case can aid hexagonal CdTe nucleation. Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) of the CdS/CdTe interface show CdS-dependent differences in interdiffusion at the interface. This interdiffusion appears to be determined by the oxygen level in the CdS. When low-oxygen-containing CSS CdS films are used, sulfur diffusion is substantial, leading to significant consumption of the CdS layer. When these same films are annealed in oxygen, the consumption is reduced. Te diffusion into the CdS layer is also observed to decrease with oxygen anneals. Optical modeling shows that Te alloying with the CdS layer can greatly reduce the short-circuit current of CdS/CdTe devices. Copyright © 2002 John Wiley & Sons, Ltd. [source] Cloning and functional characterization of a novel connexin expressed in somites of Xenopus laevisDEVELOPMENTAL DYNAMICS, Issue 3 2005Teun P. De Boer Abstract Connexin-containing gap junctions play an essential role in vertebrate development. More than 20 connexin isoforms have been identified in mammals. However, the number identified in Xenopus trails with only six isoforms described. Here, identification of a new connexin isoform from Xenopus laevis is described. Connexin40.4 was found by screening expressed sequence tag databases and carrying out polymerase chain reaction on genomic DNA. This new connexin has limited amino acid identity with mammalian (<50%) connexins, but conservation is higher (,62%) with fish. During Xenopus laevis development, connexin40.4 was first expressed after the mid-blastula transition. There was prominent expression in the presomitic paraxial mesoderm and later in the developing somites. In adult frogs, expression was detected in kidney and stomach as well as in brain, heart, and skeletal muscle. Ectopic expression of connexin40.4 in HEK293 cells, resulted in formation of gap junction like structures at the cell interfaces. Similar ectopic expression in neural N2A cells resulted in functional electrical coupling, displaying mild, asymmetric voltage dependence. We thus cloned a novel connexin from Xenopus laevis, strongly expressed in developing somites, with no apparent orthologue in mammals. Developmental Dynamics 233:864,871, 2005. © 2005 Wiley-Liss, Inc. [source] Docosahexaenoic acid (22:6n-3) enrichment of membrane phospholipids increases gap junction coupling capacity in cultured astrocytesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006Gaelle Champeil-Potokar Abstract Although it is agreed that n-3 polyunsaturated fatty acids (PUFAs) are important for brain function, it has yet to be demonstrated how they are involved in precise cellular mechanisms. We investigated the role of enhanced n-3 PUFA in astrocyte membranes on the gap junction capacity of these cells. Astrocytes isolated from newborn rat cortices were grown in medium supplemented with docosahexaenoic acid (DHA), the main n-3 PUFA in cell membranes, or arachidonic acid (AA), the main n-6 PUFA, plus an antioxidant (,-tocopherol or N -acetyl-cystein) to prevent peroxidation. The resulting three populations of astrocytes differed markedly in their n-3 : n-6 PUFA ratios in phosphatidylethanolamine and phosphatidylcholine, the main phospholipids in membranes. DHA-supplemented cells had a physiological high n-3 : n-6 ratio (1.58), unsupplemented cells had a low n-3 : n-6 ratio (0.66) and AA-supplemented cells had a very low n-3 : n-6 ratio (0.36), with excess n-6 PUFA. DHA-supplemented astrocytes had a greater gap junction capacity than unsupplemented cells or AA-supplemented cells. The enhanced gap junction coupling of DHA-enriched cells was associated with a more functional distribution of connexin 43 at cell interfaces (shown by immunocytochemistry) and more of the main phosphorylated isoform of connexin 43. These findings suggest that the high n-3 : n-6 PUFA ratio that occurs naturally in astrocyte membranes is needed for optimal gap junction coupling in these cells. [source] Developing implicit pressure-weighted upwinding scheme to calculate steady and unsteady flows on unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2008M. Darbandi Abstract The finite-volume methods normally utilize either simple or complicated mathematical expressions to interpolate the fluxes at the cell faces of their unstructured volumes. Alternatively, we benefit from the advantages of both finite-volume and finite-element methods and estimate the advection terms on the cell faces using an inclusive pressure-weighted upwinding scheme extended on unstructured grids. The present pressure-based method treats the steady and unsteady flows on a collocated grid arrangement. However, to avoid a non-physical spurious pressure field pattern, two mass flux per volume expressions are derived at the cell interfaces. The dual advantages of using an unstructured-based discretization and a pressure-weighted upwinding scheme result in obtaining high accurate solutions with noticeable progress in the performance of the primitive method extended on the structured grids. The accuracy and performance of the extended formulations are demonstrated by solving different standard and benchmark problems. The results show that there are excellent agreements with both benchmark and analytical solutions as well as experimental data. Copyright © 2007 John Wiley & Sons, Ltd. [source] Simulation of shallow flows over variable topographies using unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 5 2006A. Mohammadian Abstract Simulation of shallow flows over variable topographies is a challenging case for most available shock-capturing schemes. This problem arises because the source terms and flux gradients are not balanced in the numerical computations. Treatments for this problem generally work well on structured grids, but they are usually too expensive, and most of them are not directly applicable to unstructured grids. In this paper we propose two efficient methods to treat the source terms without upwinding and to satisfy the compatibility condition on unstructured grids. In the first method, the calculation of the bed slope source term is performed by employing a compatible approximation of water depth at the cell interfaces. In the second one, different components of the bed slope term are considered separately and a compatible discretization of the components is proposed. The present treatments are applicable for most schemes including the Roe's method without changing the performance of the original scheme for smooth topographies. Copyright © 2006 John Wiley & Sons, Ltd. [source] Immune synapses formed with measles virus-infected dendritic cells are unstable and fail to sustain T cell activationCELLULAR MICROBIOLOGY, Issue 8 2007Yoanna Shishkova Summary Interaction with dendritic cells (DCs) is considered as central to immunosuppression induced by viruses, including measles virus (MV). Commonly, viral infection of DCs abrogates their ability to promote T cell expansion, yet underlying mechanisms at a cellular level are undefined. We found that MV-infected DCs only subtly differed from LPS-matured with regard to integrin activation, acquisition of a migratory phenotype and motility. Similarly, the organization of MV-DC/T cell interfaces was consistent with that of functional immune synapses with regard to CD3 clustering and MHC class II surface recruitment. The majority of MV-DC/T cell conjugates was, however, unstable and only promoted abortive T cell activation. Thus, MV-infected DCs retain activities required for initiating, but not sustaining T cell conjugation and activation. This is partially rescued if surface expression of the MV glycoproteins on DCs is abolished by infection with a recombinant MV encoding VSV G protein instead, indicating that these contribute directly to synapse destabilization and thereby act as effectors of T cell inhibition. [source] An approximate-state Riemann solver for the two-dimensional shallow water equations with porosityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2010P. Finaud-Guyot Abstract PorAS, a new approximate-state Riemann solver, is proposed for hyperbolic systems of conservation laws with source terms and porosity. The use of porosity enables a simple representation of urban floodplains by taking into account the global reduction in the exchange sections and storage. The introduction of the porosity coefficient induces modified expressions for the fluxes and source terms in the continuity and momentum equations. The solution is considered to be made of rarefaction waves and is determined using the Riemann invariants. To allow a direct computation of the flux through the computational cells interfaces, the Riemann invariants are expressed as functions of the flux vector. The application of the PorAS solver to the shallow water equations is presented and several computational examples are given for a comparison with the HLLC solver. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||