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Electrical Signals (electrical + signal)
Selected AbstractsReagentless Protein Assembly Triggered by Localized Electrical SignalsADVANCED MATERIALS, Issue 9 2009Xiao-Wen Shi Electrode-imposed signals are used to assemble proteins without the need for reactive reagents. The two-step assembly approach uses i) cathodic signals to electrodeposit the amino-polysaccharide chitosan and ii) anodic signals to activate the chitosan film for protein assembly. Proteins are shown to assemble at individual electrode addresses, with spatial selectivity and quantitative control. [source] Regulation of Blood Flow in the MicrocirculationMICROCIRCULATION, Issue 1 2005STEVEN S. SEGAL ABSTRACT The regulation of blood flow has rich history of investigation and is exemplified in exercising skeletal muscle by a concerted interaction between striated muscle fibers and their microvascular supply. This review considers blood flow control in light of the regulation of capillary perfusion by and among terminal arterioles, the distribution of blood flow in arteriolar networks according to metabolic and hemodynamic feedback from active muscle fibers, and the balance between peak muscle blood flow and arterial blood pressure by sympathetic nerve activity. As metabolic demand increases, the locus of regulating oxygen delivery to muscle fibers "ascends" from terminal arterioles, through intermediate distributing arterioles, and into the proximal arterioles and feed arteries, which govern total flow into a muscle. At multiple levels, venules are positioned to provide feedback to nearby arterioles regarding the metabolic state of the tissue through the convection and production of vasodilator stimuli. Electrical signals initiated on smooth muscle and endothelial cells can travel rapidly for millimeters through cell-to-cell conduction via gap junction channels, rapidly coordinating vasodilator responses that govern the distribution and magnitude of blood flow to active muscle fibers. Sympathetic constriction of proximal arterioles and feed arteries can restrict functional hyperemia while dilation prevails in distal arterioles to promote oxygen extraction. With vasomotor tone reflecting myogenic contraction of smooth muscle cells modulated by flow-induced vasodilator production by endothelium, the initiation of functional vasodilation and its modulation by shear stress and sympathetic innervation dictate how and where blood flow is distributed in microvascular networks. A remarkable ensemble of signaling pathways underlie the integration of smooth muscle and endothelial cell function in microvascular networks. These pathways are being defined with new insight as novel approaches are applied to understanding the cellular and molecular mechanisms of blood flow control. [source] Electrical signals and their physiological significance in plantsPLANT CELL & ENVIRONMENT, Issue 3 2007JÖRG FROMM ABSTRACT Electrical excitability and signalling, frequently associated with rapid responses to environmental stimuli, are well known in some algae and higher plants. The presence of electrical signals, such as action potentials (AP), in both animal and plant cells suggested that plant cells, too, make use of ion channels to transmit information over long distances. In the light of rapid progress in plant biology during the past decade, the assumption that electrical signals do not only trigger rapid leaf movements in ,sensitive' plants such as Mimosa pudica or Dionaea muscipula, but also physiological processes in ordinary plants proved to be correct. Summarizing recent progress in the field of electrical signalling in plants, the present review will focus on the generation and propagation of various electrical signals, their ways of transmission within the plant body and various physiological effects. [source] Dynamic changes in the direction of the theta rhythmic drive between supramammillary nucleus and the septohippocampal systemHIPPOCAMPUS, Issue 6 2006Bernat Kocsis Abstract Neurons in the supramammillary nucleus (SUM) of urethane-anesthetized rats fire rhythmically in synchrony with hippocampal theta rhythm. As these neurons project to the septum and hippocampus, it is generally assumed that their role is to mediate ascending activation, leading to the hippocampal theta rhythm. However, the connections between SUM and the septohippocampal system are reciprocal; there is strong evidence that theta remains in the hippocampus after SUM lesions and in the SUM after lesioning the medial septum. The present study examines the dynamics of coupling between rhythmic discharge in the SUM and hippocampal field potential oscillations, using the directionality information carried by the two signals. Using directed transfer function analysis, we demonstrate that during sensory-elicited theta rhythm and also during short episodes of theta acceleration of spontaneous oscillations, the spike train of a subpopulation of SUM neurons contains information predicting future variations in rhythmic field potentials in the hippocampus. In contrast, during slow spontaneous theta rhythm, it is the SUM spike signal that can be predicted from the preceding segment of the electrical signal recorded in the hippocampus. These findings indicate that, in the anesthetized rat, SUM neurons effectively drive theta oscillations in the hippocampus during epochs of sensory-elicited theta rhythm and short episodes of theta acceleration, whereas spontaneous slow theta in the SUM is controlled by descending input from the septohippocampal system. Thus, in certain states, rhythmically firing SUM neurons function to accelerate the septal theta oscillator, and in others, they are entrained by a superordinate oscillatory network. © 2006 Wiley-Liss Inc. [source] Optical mm-wave generation based on phase modulation along with optical filteringMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2007Jianxin Ma Abstract We have investigated the generation and transmission of optical millimeter (mm)-wave signal based on optical phase modulator (PM) and fiber Bragg grating (FBG) filter. With an optimized modulation depth of PM and a higher carrier suppression ratio via a notch filter, the generated optical mm-wave can be transmitted over a long-distance without fading. We have also theoretically analyzed the impact of time shift on the eye closure of optical and electrical signal due to the fiber dispersion, which is well in accord with the experimental results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1787,1793, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22622 [source] Potentiometric Detection of Single Nucleotide Polymorphism by Using a Genetic Field-effect transistorCHEMBIOCHEM, Issue 4 2005Toshiya Sakata Dr. Abstract Potentiometric measurement of allele-specific oligonucleotide hybridization based on the principle of detection of charge-density change at the surface of a gate insulator by using of a genetic field-effect transistor has been demonstrated. Since DNA molecules are negatively charged in aqueous solution, a hybridization event at the gate surface leads to a charge-density change in the channel of the FET and can be directly transduced into an electrical signal without any labeling of target DNA molecules. One of the unique features of our method is to utilize DNA binders such as intercalators as charged species for double-stranded DNA after hybridization, since these are ionized and carry positive charges in aqueous solution. Single-base mismatch of the target DNA could be successfully detected both with the wild-type and with the mutant genetic FETs by controlling the hybridization temperatures and introducing Hoechst 33258 as DNA binder. The genetic FET platform is suitable as a simple, accurate, and inexpensive system for SNP typing in clinical diagnostics. [source] Spontaneous electrical and Ca2+ signals in the mouse renal pelvis that drive pyeloureteric peristalsisCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2010Richard J Lang Summary 1.,Peristalsis in the smooth muscle cell (SMC) wall of the pyeloureteric system is unique in physiology in that the primary pacemaker resides in a population of atypical SMCs situated near the border of the renal papilla. 2.,Atypical SMCs display high-frequency Ca2+ transients upon the spontaneous release of Ca2+ from inositol 1,4,5-trisphosphate (IP3)-dependent stores that trigger cation-selective spontaneous transient depolarizations (STDs). In the presence of nifedipine, these Ca2+ transients and STDs seldom propagate > 100 ,m. Synchronization of STDs in neighbouring atypical SMCs into an electrical signal that can trigger action potential discharge and contraction in the typical SMC layer involves a coupled oscillator mechanism dependent on Ca2+ entry through L-type voltage-operated Ca2+ channels. 3.,A population of spindle- or stellate-shaped cells, immunopositive for the tyrosine receptor kinase kit, is sparsely distributed throughout the pyeloureteric system. In addition, Ca2+ transients and action potentials of long duration occurring at low frequencies have been recorded in a population of fusiform cells, which we have termed interstitial cells of Cajal (ICC)-like cells. 4.,The electrical and Ca2+ signals in ICC-like cells are abolished upon blockade of Ca2+ release from either IP3 - or ryanodine-dependent Ca2+ stores. However, the spontaneous Ca2+ signals in atypical SMCs or ICC-like cells are little affected in W/W,v transgenic mice, which have extensive lesions of their intestinal ICC networks. 5.,In summary, we have developed a model of pyeloureteric pacemaking in which atypical SMCs are indeed the primary pacemakers, but the function of ICC-like cells has yet to be determined. [source] Dynamics of action potential backpropagation in basal dendrites of prefrontal cortical pyramidal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2008Wen-Liang Zhou Abstract Basal dendrites of neocortical pyramidal neurons are relatively short and directly attached to the cell body. This allows electrical signals arising in basal dendrites to strongly influence the neuronal output. Likewise, somatic action potentials (APs) should readily propagate back into the basilar dendritic tree to influence synaptic plasticity. Two recent studies, however, determined that sodium APs are severely attenuated in basal dendrites of cortical pyramidal cells, so that they completely fail in distal dendritic segments. Here we used the latest improvements in the voltage-sensitive dye imaging technique (Zhou et al., 2007) to study AP backpropagation in basal dendrites of layer 5 pyramidal neurons of the rat prefrontal cortex. With a signal-to-noise ratio of >,15 and minimal temporal averaging (only four sweeps) we were able to sample AP waveforms from the very last segments of individual dendritic branches (dendritic tips). We found that in short- (< 150 µm) and medium (150,200 µm in length)-range basal dendrites APs backpropagated with modest changes in AP half-width or AP rise-time. The lack of substantial changes in AP shape and dynamics of rise is inconsistent with the AP-failure model. The lack of substantial amplitude boosting of the third AP in the high-frequency burst also suggests that in short- and medium-range basal dendrites backpropagating APs were not severely attenuated. Our results show that the AP-failure concept does not apply in all basal dendrites of the rat prefrontal cortex. The majority of synaptic contacts in the basilar dendritic tree actually received significant AP-associated electrical and calcium transients. [source] Immunolocalization of BK channels in hippocampal pyramidal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2006Claudia A. Sailer Abstract Neurons are highly specialized cells in which the integration and processing of electrical signals critically depends on the precise localization of ion channels. For large-conductance Ca2+ - activated K+ (BK) channels, targeting to presynaptic membranes in hippocampal pyramidal cells was reported; however, functional evidence also suggests a somatodendritic localization. Therefore we re-examined the subcellular distribution of BK channels in mouse hippocampus using a panel of independent antibodies in a combined approach of conventional immunocytochemistry on cultured neurons, pre- and postembedding electron microscopy and immunoprecipitation. In cultured murine hippocampal neurons, the colocalization of BK channels with both pre- and postsynaptic marker proteins was observed. Electron microscopy confirmed targeting of BK channels to axonal as well as dendritic membranes of glutamatergic synapses in hippocampus. A postsynaptic localization of BK channels was also supported by the finding that the channel coimmunoprecipitated with PSD95, a protein solely expressed in the postsynaptic compartment. These results thus demonstrate that BK channels reside in both post- and presynaptic compartments of hippocampal pyramidal neurons. [source] In-Film Bioprocessing and Immunoanalysis with Electroaddressable Stimuli-Responsive PolysaccharidesADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Xiaohua Yang Abstract Advances in thin-film fabrication are integral to enhancing the power of microelectronics while fabrication methods that allow the integration of biological molecules are enabling advances in bioelectronics. A thin-film-fabrication method that further extends the integration of biology with microelectronics by allowing living biological systems to be assembled, cultured, and analyzed on-chip with the aid of localized electrical signals is described. Specifically, the blending of two stimuli-responsive film-forming polysaccharides for electroaddressing is reported. The first, alginate, can electrodeposit by undergoing a localized sol,gel transition in response to electrode-imposed anodic signals. The second, agarose, can be co-deposited with alginate and forms a gel upon a temperature reduction. Electrodeposition of this dual polysaccharide network is observed to be a simple, rapid, and spatially selective means for assembly. The bioprocessing capabilities are examined by co-depositing a yeast clone engineered to display a variable lymphocyte receptor protein on the cell surface. Results demonstrate the in-film expansion and induction of this cell population. Analysis of the cells' surface proteins is achieved by the electrophoretic delivery of immunoreagents into the film. These results demonstrate a simple and benign means to electroaddress hydrogel films for in-film bioprocessing and immunoanalysis. [source] Diamond Transistor Array for Extracellular Recording From Electrogenic CellsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Markus Dankerl Abstract The transduction of electric signals from cells to electronic devices is mandatory for medical applications such as neuroprostheses and fundamental research on communication in neuronal networks. Here, the use of diamond with its advantages for biological applications as a new material for biohybrid devices for the detection of cell signals is investigated. Using the surface conductivity of hydrogen-terminated single-crystalline diamond substrates, arrays of solution-gate field-effect transistors were fabricated. The characterization of the transistors reveals a good stability in electrolyte solutions for at least 7 days. On these devices, cardiomyocyte-like HL-1 cells as well as human embryonic kidney cells (HEK293), which were stably transfected with potassium channels, are cultured. Both types of cells show healthy growth and good adhesion to the substrate. The diamond transistors are used to detect electrical signals from both types of cells by recording the extracellular potential. For the HL-1 cells, the shape of action potentials can be resolved and the propagation of the signal across the cell layer is visible. Potassium currents of HEK293 cells are activated with the patch-clamp technique in voltage-clamp mode and simultaneously measured with the field-effect transistors. The ion sensitivity of the diamond surface enables the detection of released potassium ions accumulated in the cleft between transistor and cell. [source] Electroaddressing of Cell Populations by Co-Deposition with Calcium Alginate HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Xiao-Wen Shi Abstract Electroaddressing of biological components at specific device addresses is attractive because it enlists the capabilities of electronics to provide spatiotemporally controlled electrical signals. Here, the electrodeposition of calcium alginate hydrogels at specific electrode addresses is reported. The method employs the low pH generated at the anode to locally solubilize calcium ions from insoluble calcium carbonate. The solubilized Ca2+ can then bind alginate to induce this polysaccharide to undergo a localized sol-gel transition. Calcium alginate gel formation is shown to be spatially controlled in the normal and lateral dimensions. The deposition method is sufficiently benign that it can be used to entrap the bacteria E. coli. The entrapped cells are able to grow and respond to chemical inducers in their environment. Also, the entrapped cells can be liberated from the gel network by adding sodium citrate that can compete with alginate for Ca2+ binding. The capabilities of calcium alginate electrodeposition is illustrated by entrapping reporter cells that can recognize the quorum sensing autoinducer 2 (AI-2) signaling molecule. These reporter cells were observed to recognize and respond to AI-2 generated from an external bacterial population. Thus, calcium alginate electrodeposition provides a programmable method for the spatiotemporally controllable assembly of cell populations for cell-based biosensing and for studying cell-cell signaling. [source] Melatonin as a potential therapeutic agent in psychiatric illnessHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 5 2009Maria D. Maldonado Abstract The aim of this review was to summarize the potential use of melatonin in the treatment of mental disorders, specifically bipolar disorders, depression, and schizophrenia. To date, melatonin has been most commonly used in psychiatry because of its hypnotic, rhythm resynchronizing, and antioxidant actions. Here, we examine other properties of the melatonin including its anti-inflammatory, antinociceptive, anxiolytic, and drug detoxification actions as well as its protective effects against neural loss. The brain is an intricate sensory and motor organ which receives information from both the external and internal environments. It transduces information into complex chemical and electrical signals which are transmitted throughout the central nervous system (CNS) and the organism. The pathogenesis of mental disorders remains ambiguous and neuroinflammation has been proposed as a causative agent. We consider the potential contributions of melatonin as therapeutic agent in CNS and during neuroinflammation in mental disorders. Copyright © 2009 John Wiley & Sons, Ltd. [source] Encoding of electrophysiology and other signals in MR imagesJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2007Lars G. Hanson PhD Abstract Purpose To develop a gradient insensitive, generic technique for recording of non-MR signals by use of surplus scanner bandwidth. Materials and Methods Relatively simple battery driven hardware is used to transform one or more signals into radio waves detectable by the MR scanner. Similar to the "magstripe" technique used for encoding of soundtracks in motion pictures, the electrical signals are in this way encoded as artifacts appearing in the MR images or spectra outside the region of interest. The encoded signals are subsequently reconstructed from the signal recorded by the scanner. Results Electrophysiological (EP) eye and heart muscular recording (electrooculography [EOG] and electrocardiography [ECG]) during fast echo planar imaging (EPI) is demonstrated with an expandable, modular 8-channel prototype implementation. The gradient artifacts that would normally be dominating EOG are largely eliminated. Conclusion The method provides relatively inexpensive sampling with inherent microsecond synchronization and it reduces gradient artifacts in physiological recordings significantly. When oversampling is employed, the method is compatible with all MR reconstruction and postprocessing techniques. J. Magn. Reson. Imaging 2007;25:1059,1066. © 2007 Wiley-Liss, Inc. [source] DLGdifferentially localizes Shaker K+ -channels in the central nervous system and retina of DrosophilaJOURNAL OF NEUROCHEMISTRY, Issue 6 2002C. Ruiz-Cańada Abstract Subcellular localization of ion channels is crucial for the transmission of electrical signals in the nervous system. Here we show that Discs-Large (DLG), a member of the MAGUK (membrane-associated guanylate kinases) family in Drosophila, co-localizes with Shaker potassium channels (Sh Kch) in most synaptic areas of the adult brain and in the outer membrane of photoreceptors. However, DLG is absent from axonal tracts in which Sh channels are concentrated. Truncation of the C-terminal of Sh (including the PDZ binding site) disturbs its pattern of distribution in both CNS and retina, while truncation of the guanylate kinase/C-terminal domain of DLG induces ectopic localization of these channels to neuronal somata in the CNS, but does not alter the distribution of channels in photoreceptors. Immunocytochemical, membrane fractionation and detergent solubilization analysis indicate that the C-terminal of Sh Kch is required for proper trafficking to its final destination. Thus, several major conclusions emerge from this study. First, DLG plays a major role in the localization of Shchannels in the CNS and retina. Second, localization of DLG in photoreceptors but not in the CNS seems to depend on its interaction with Sh. Third, the guanylate kinase/C-terminal domain of DLG is involved in the trafficking of Shaker channels but not of DLG in the CNS. Fourth, different mechanisms for the localization of Sh Kch operate in different cell types. [source] Dielectric cell separation of fine needle aspirates from tumor xenograftsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2008Massimo Cristofanilli Abstract As an approach to isolating tumor cells from fine needle biopsy specimens, we investigated a dielectric cell preparation method using an in vivo xenographic tumor model. Cultured human MDA-MB-435 tumor cells were grown as solid tumors in nude mice and fine needle aspiration biopsies were conducted. Biopsied cells were suspended in sucrose medium and collected on slides patterned with microelectrode arrays (electrosmears) energized by electrical signals in the range 10 to 960 kHz. The unlabeled cells adhered to characteristic regions of the slides in accordance with their morphology as a result of dielectric forces. Tumor cells were trapped between 40 and 60 kHz and were separated according to whether they were mitotic, large and complex, or small. Damaged tumor cells were captured at between 60 and 120 kHz; granulocytes between 70 and 90 kHz; lymphocytes between 85 and 105 kHz; healthy erythrocytes between 140 and 180 kHz, and damaged erythrocytes above 180 kHz. Using intrinsic cell characteristics, the electrosmear presented cell subpopulations from fine needle aspiration biopsy specimens in a manner that is compatible with automated slide-based analysis systems. The approach has the potential to facilitate the analysis of the role of cell subpopulations in disease. [source] Electrical signals and their physiological significance in plantsPLANT CELL & ENVIRONMENT, Issue 3 2007JÖRG FROMM ABSTRACT Electrical excitability and signalling, frequently associated with rapid responses to environmental stimuli, are well known in some algae and higher plants. The presence of electrical signals, such as action potentials (AP), in both animal and plant cells suggested that plant cells, too, make use of ion channels to transmit information over long distances. In the light of rapid progress in plant biology during the past decade, the assumption that electrical signals do not only trigger rapid leaf movements in ,sensitive' plants such as Mimosa pudica or Dionaea muscipula, but also physiological processes in ordinary plants proved to be correct. Summarizing recent progress in the field of electrical signalling in plants, the present review will focus on the generation and propagation of various electrical signals, their ways of transmission within the plant body and various physiological effects. [source] Wiring Enzymes in Nanostructures Built with Electrostatically Self-Assembled Thin FilmsCHEMPHYSCHEM, Issue 1 2005Ernesto J. Calvo Prof. Abstract The construction of electrostatically self-assembled intelligent nanostructures on electrodes with redox enzyme layers and redox polymer molecular wires defined in space allowed the analysis of redox charge transport from the redox enzyme to the electrode along nanometric distances. Recent results on the electrical connection of enzymes to electrodes and perspectives of generating electrical signals from molecular recognition in integrated enzyme electrodes are discussed. [source] | |||||||||||||||||||