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Electrical Component (electrical + component)
Selected AbstractsEndogenous and exogenous dopamine presynaptically inhibits glutamatergic reticulospinal transmission via an action of D2 -receptors on N-type Ca2+ channelsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003Erik Svensson Abstract In this study, the effects of exogenously applied and endogenously released dopamine (DA), a powerful modulator of the lamprey locomotor network, are examined on excitatory glutamatergic synaptic transmission between reticulospinal axons and spinal neurons. Bath application of DA (1,50 µm) reduced the amplitude of monosynaptic reticulospinal-evoked glutamatergic excitatory postsynaptic potentials (EPSPs). The effect of DA was blocked by the D2 -receptor antagonist eticlopride, and mimicked by the selective D2 -receptor agonist 2,10,11 trihydroxy- N -propyl-noraporphine hydrobromide (TNPA). Bath application of the DA reuptake blocker bupropion, which increases the extracellular level of dopamine, also reduced the monosynaptic EPSP amplitude. This effect was also blocked by the D2 -receptor antagonist eticlopride. To investigate if the action of DA was exerted at the presynaptic level, the reticulospinal axon action potentials were prolonged by administering K+ channel antagonists while blocking l -type Ca2+ channels. A remaining Ca2+ component, mainly dependent on N and P/Q channels, was depressed by DA. When DA (25,50 µm) was applied in the presence of ,-conotoxin GVIA, a toxin specific for N-type Ca2+ channels, it failed to affect the monosynaptic EPSP amplitude. DA did not affect the response to extracellularly ejected d -glutamate, the postsynaptic membrane potential, or the electrical component of the EPSPs. DA thus acts at the presynaptic level to modulate reticulospinal transmission. [source] Prostate carcinoma cells selected by long-term exposure to reduced oxygen tension show remarkable biochemical plasticity via modulation of superoxide, HIF-1, levels, and energy metabolismJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2007Jeanne Bourdeau-Heller Cancer cells are able to tolerate levels of O2 that are damaging or lethal to normal cells; we hypothesize that this tolerance is the result of biochemical plasticity which maintains cellular homeostasis of both energy levels and oxidation state. In order to examine this hypothesis, we used different O2 levels as a selective agent during long-term culture of DU145 prostate cancer cells to develop three isogenic cell lines that grow in normoxic (4%), hyperoxic (21%), or hypoxic (1%) O2 conditions. Growth characteristics and O2 consumption differed significantly between these cell lines without changes in ATP levels or altered sensitivity to 2-deoxy- D -glucose, an inhibitor of glycolysis. O2 consumption was significantly higher in the hyperoxic line as was the level of endogenous superoxide. The hypoxic cell line regulated the chemical gradient of the proton motive force (PMF) independent of the electrical component without O2 -dependent changes in Hif-1, levels. In contrast, the normoxic line regulated Hif-1, without tight regulation of the chemical component of the PMF noted in the hypoxic cell line. From these studies, we conclude that selection of prostate cancer cells by long-term exposure to low ambient levels of O2 resulted in cells with unique biochemical properties in which energy metabolism, reactive oxygen species (ROS), and HIF-1, levels are modulated to allow cell survival and growth. Thus, cancer cells exhibit remarkable biochemical plasticity in response to various O2 levels. J. Cell. Physiol. 212:744,752, 2007. © 2007 Wiley-Liss, Inc. [source] 900 MHz modulated electromagnetic fields accelerate the clathrin-mediated endocytosis pathwayBIOELECTROMAGNETICS, Issue 3 2009Mihaela G. Moisescu Abstract We report new data regarding the molecular mechanisms of GSM-induced increase of cell endocytosis rate. Even though endocytosis represents an important physical and biological event for cell physiology, studies on modulated electromagnetic fields (EMF) effects on this process are scarce. In a previous article, we showed that fluid phase endocytosis rate increases when cultured cells are exposed to 900 MHz EMF similar to mobile phones' modulated GSM signals (217 Hz repetition frequency, 576 µs pulse width) and to electric pulses similar to the GSM electrical component. Trying to distinguish the mechanisms sustaining this endocytosis stimulation, we exposed murine melanoma cells to Lucifer Yellow (LY) or to GSM,EMF/electric pulses in the presence of drugs inhibiting the clathrin- or the caveolin-dependent endocytosis. Experiments were performed at a specific absorption rate (SAR) of 3.2 W/kg in a wire patch cell under homogeneously distributed EMF field and controlled temperature (in the range of 28.5,29.5 °C). Thus, the observed increase in LY uptake was not a thermal effect. Chlorpromazine and ethanol, but not Filipin, inhibited this increase. Therefore, the clathrin-dependent endocytosis is stimulated by the GSM,EMF, suggesting that the cellular mechanism affected by the modulated EMF involves vesicles that detach from the cell membrane, mainly clathrin-coated vesicles. Bioelectromagnetics 30:222,230, 2009. © 2008 Wiley-Liss, Inc. [source] Silica-Based, Organically Modified Host Material for Waveguide Structuring by Two-Photon-Induced PhotopolymerizationADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Stefan Krivec Abstract The three-dimensional fabrication of optical waveguides has gained increasing interest in recent years to establish interconnections between electrical components on a very small scale where copper circuits encounter severe limitations. In this work the application of optically clear, organically modified porous silica monoliths and thin films as a host material for polymeric waveguides to be inscribed into the solid host structure by two-photon-induced photopolymerization is investigated. Porosity is generated using a lyotropic liquid crystalline surfactant/solvent system as a template for the solid silica material obtained by a sol,gel transition of a liquid precursor. In order to reduce the brittleness of the purely inorganic material, organic,inorganic co-precursor molecules that contain poly(ethylene glycol) chains are synthesized and added to the mixture, which successfully suppresses macroscopic cracking and leads to flexible thin films. The structure of the thus-obtained porous organic,inorganic hybrid material is investigated by atomic force microscopy. It is shown that the modified material is suitable for infiltration with photocurable monomers and functional polymeric waveguides can be inscribed by selective two-photon-induced photopolymerization. [source] Commercial Exploration of High-Temperature SuperconductivityLASER TECHNIK JOURNAL, Issue 4 2010Excimer Lasers Enable Novel Coated Superconductor Cylinders Superconductivity, which is the condition in which the electrical resistance of a material drops to zero, was discovered nearly 100 years ago. Since that time, large superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR) and big physics experiments have been developed and can now be regarded as being commercial products extending our capabilities in medicine and science. Yet many industrial applications of high temperature superconductivity (HTS) are on the horizon waiting to enter the marketplace. Currently, numerous manufacturers are working on improving and upscaling HTS materials, which operate at liquid nitrogen temperatures, and the most promising configuration for these materials is in the form of long tapes also known as coated conductors. These coated conductors are wound into coils in order to produce electrical components such as motors, magnets, transformers etc. Depending on the component to be made, there is an alternative to fabricating long unit lengths of superconducting tape, and in forming stable robust windings utilizing them. Now, a new technique has been developed which is using pulsed laser deposition (PLD) to deposit a series of layers of superconducting material directly on to the surface of a cylinder and patterning them into coils. This configuration provides a very direct route for the production of components that conventionally involve winding processes. This article explores how coated conductor cylinders can be produced utilizing this technique and explains why industriallyproven excimers represent the optimum choice of laser source for this emergingtechnology. [source] | ||||||||||