Sample records for voltage sensitive calcium

  1. Voltage sensitive calcium channels (VSCC) in cultured neuronal hybrid cells

    Energy Technology Data Exchange (ETDEWEB)

    Richard, C.L.; U' Prichard, D.C.; Noronha-Blob, L.


    Calcium entry via VSCC has been identified in selected, neuronal clonal cell lines using /sup 45/Ca uptake and the fluorescent calcium indicator, quin 2. VSCC in NG108-15 hybrid cells, differentiated with dibutyryl cyclic AMP (1 mM, 4 days) have been further characterized. Depolarization (50 mM K/sup +/, dp) resulted in a rapid (15 sec) influx of Ca/sup 2 +/. Intracellular calcium concentrations were elevated approx. 3 fold from 223 +- 68 nM to 666 +- 74 nM. Dp-sensitive calcium entry was voltage dependent, independent of Na/sup +/, stimulated (40%) by the agonist Bay K 8644 ( and blocked by divalent cations ( range) and organic calcium channel antagonists (nM range) Bay K 8644, in the absence of KCl, failed to stimulate Ca/sup 2 +/ influx. Tetrodotoxin (TTX) and tetraethylammonium had no effect on VSCC activity. Blockage of VSCC by nimodipine was reversed by increasing Ca/sup 2 +/ ions. IC/sub 50/ values were right shifted from 6.5 nM (1mM/sup 0/Ca/sup 2 +/) to 840 nM (10 mM Ca/sup 2 +/). Ca/sup 2 +/ entry was also stimulated by veratridine (VE), in a Na/sup +//sub 0/-sensitive manner. VE-induced Ca/sup 2 +/ entry was voltage-independent, TTX-sensitive, and was only 25% of dp-sensitive Ca/sup 2 +/ entry. These results together indicate that VSCC in neuronal cells offer a useful system for studying ion channel regulation.

  2. New Conotoxin SO-3 Targeting N-type Voltage-Sensitive Calcium Channels

    Directory of Open Access Journals (Sweden)

    Lei Wen


    Full Text Available Selective blockers of the N-type voltage-sensitive calcium (CaV channels are useful in the management of severe chronic pain. Here, the structure and function characteristics of a novel N-type CaV channel blocker, SO-3, are reviewed. SO-3 is a 25-amino acid conopeptide originally derived from the venom of Conus striatus, and contains the same 4-loop, 6-cysteine framework (C-C-CC-C-C as O-superfamily conotoxins. The synthetic SO-3 has high analgesic activity similar to ω-conotoxin MVIIA (MVIIA, a selective N-type CaV channel blocker approved in the USA and Europe for the alleviation of persistent pain states. In electrophysiological studies, SO-3 shows more selectivity towards the N-type CaV channels than MVIIA. The dissimilarity between SO-3 and MVIIA in the primary and tertiary structures is further discussed in an attempt to illustrate the difference in selectivity of SO-3 and MVIIA towards N-type CaV channels.

  3. Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations (United States)

    Taft, William C.; Delorenzo, Robert J.


    Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

  4. AHR-16303B, a novel antagonist of 5-HT2 receptors and voltage-sensitive calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Barrett, R.J.; Appell, K.C.; Kilpatrick, B.F.; Proakis, A.G.; Nolan, J.C.; Walsh, D.A. (A. H. Robins Research Labs., Richmond, VA (USA))


    In vivo and in vitro methods were used to characterize AHR-16303B, a novel compound with antagonistic action at 5-HT2 receptors and voltage-sensitive calcium channels. The 5-HT2 receptor-antagonistic properties of AHR-16303B were demonstrated by inhibition of (a) (3H)ketanserin binding to rat cerebral cortical membranes (IC50 = 165 nM); (b) 5-hydroxytryptamine (5-HT)-induced foot edema in rats (minimum effective dose, (MED) = 0.32 mg/kg orally, p.o.); (c) 5-HT-induced vasopressor responses in spontaneously hypertensive rats (SHR) (ID50 = 0.18 mg/kg intravenously (i.v.), 1.8 mg/kg p.o.), (d) 5-HT-induced antidiuresis in rats (MED = 1 mg/kg p.o.), and (e) platelet aggregation induced by 5-HT + ADP (IC50 = 1.5 mM). The calcium antagonist properties of AHR-16303B were demonstrated by inhibition of (a) (3H)nimodipine binding to voltage-sensitive calcium channels on rabbit skeletal muscle membranes (IC50 = 15 nM), (b) KCl-stimulated calcium flux into cultured PC12 cells (IC50 = 81 nM), and (c) CaCl2-induced contractions of rabbit thoracic aortic strips (pA2 = 8.84). AHR-16303B had little or no effect on binding of radioligands to dopamine2 (DA2) alpha 1, alpha 2, H1, 5-HT1 alpha, beta 2, muscarinic M1, or sigma opioid receptors; had no effect on 5-HT3 receptor-mediated vagal bradycardia; and had only minor negative inotropic, chronotropic, and dromotropic effects on isolated guinea pig atria. In conscious SHR, 30 mg/kg p.o. AHR-16303B completely prevented the vasopressor responses to i.v. 5-HT, and decreased blood pressure (BP) by 24% 3 h after dosing.

  5. Voltage-gated calcium flux mediatesEscherichia colimechanosensation. (United States)

    Bruni, Giancarlo N; Weekley, R Andrew; Dodd, Benjamin J T; Kralj, Joel M


    Electrically excitable cells harness voltage-coupled calcium influx to transmit intracellular signals, typically studied in neurons and cardiomyocytes. Despite intense study in higher organisms, investigations of voltage and calcium signaling in bacteria have lagged due to their small size and a lack of sensitive tools. Only recently were bacteria shown to modulate their membrane potential on the timescale of seconds, and little is known about the downstream effects from this modulation. In this paper, we report on the effects of electrophysiology in individual bacteria. A genetically encoded calcium sensor expressed in Escherichia coli revealed calcium transients in single cells. A fusion sensor that simultaneously reports voltage and calcium indicated that calcium influx is induced by voltage depolarizations, similar to metazoan action potentials. Cytoplasmic calcium levels and transients increased upon mechanical stimulation with a hydrogel, and single cells altered protein concentrations dependent on the mechanical environment. Blocking voltage and calcium flux altered mechanically induced changes in protein concentration, while inducing calcium flux reproduced these changes. Thus, voltage and calcium relay a bacterial sense of touch and alter cellular lifestyle. Although the calcium effectors remain unknown, these data open a host of new questions about E. coli , including the identity of the underlying molecular players, as well as other signals conveyed by voltage and calcium. These data also provide evidence that dynamic voltage and calcium exists as a signaling modality in the oldest domain of life, and therefore studying electrophysiology beyond canonical electrically excitable cells could yield exciting new findings.

  6. ATP-sensitive voltage- and calcium-dependent chloride channels in sarcoplasmic reticulum vesicles from rabbit skeletal muscle. (United States)

    Kourie, J I


    Chloride channels in the sarcoplasmic reticulum (SR) are thought to play an essential role in excitation-contraction (E-C) coupling by balancing charge movement during calcium release and uptake. In this study the nucleotide-sensitivity of Cl- channels in the SR from rabbit skeletal muscle was investigated using the lipid bilayer technique. Two distinct ATP-sensitive Cl- channels that differ in their conductance and kinetic properties and in the mechanism of ATP-induced channel inhibition were observed. The first, a nonfrequent 150 pS channel was inhibited by trans (luminal) ATP, and the second, a common 75 pS small chloride (SCl) channel was inhibited by cis (cytoplasmic) ATP. In the case of the SCl channel the ATP-induced reversible decline in the values of current (maximal current amplitude, Imax and integral current, I') and kinetic parameters (frequency of opening FO, probability of the channel being open PO, mean open TO and closed Tc times) show a nonspecific block of the voltage- and Ca2+-dependent SCl channel. ATP was a more potent blocker from the cytoplasmic side than from the luminal side of the channel. The SCl channel block was not due to Ca2+ chelation by ATP, nor to phosphorylation of the channel protein. The inhibitory action of ATP was mimicked by the nonhydrolyzable analogue adenylylimidodiphosphate (AMP-PNP) in the absence of Mg2+. The inhibitory potency of the adenine nucleotides was charge dependent in the following order ATP4- > ADP3- > > > AMP2-. The data suggest that ATP-induced effects are mediated via an open channel block mechanism. Modulation of the SCl channel by [ATP]cis and [Ca2+]cis indicates that (i) this channel senses the bioenergetic state of the muscle fiber and (ii) it is linked to the ATP-dependent cycling of the Ca2+ between the SR and the sarcoplasm.

  7. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, G H; Belhage, B; Schousboe, A


    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect imm...... of THIP-treated cultures. This suggests that primarily low affinity GABAA-receptors are closely associated with Ca2+ channels and this may be important for the ability of these receptors to mediate an inhibitory action on transmitter release even under extreme depolarizing conditions....

  8. Molecular and functional identification of cyclic AMP-sensitive BKCa potassium channels (ZERO variant) and L-type voltage-dependent calcium channels in single rat juxtaglomerular cells

    DEFF Research Database (Denmark)

    Friis, Ulla G; Jørgensen, Finn; Andreasen, Ditte


    , respectively. Double immunofluorescence confirmed the presence of BKCa and renin in the same cell. cAMP increased the outward current by 1.6-fold, and this was inhibited by 74% with iberiotoxin. Expression of the cAMP-sensitive splice variant (ZERO) of BKCa was confirmed in single-sampled JG cells by RT......-PCR. The resting membrane potential of JG cells was -32 mV and activation of BKCa with cAMP hyperpolarized cells on average 16 mV, and inhibition with TEA depolarized cells by 17 mV. The cells displayed typical high-voltage activated calcium currents sensitive to the L-type Ca(v) blocker calciseptine. RT......-PCR analysis and double-immunofluorescence labeling showed coexpression of renin and L-type Ca(v) 1.2. The cAMP-mediated increase in exocytosis (measured as membrane capacitance) was inhibited by depolarization to +10 mV, and this inhibitory effect was blocked with calciseptine, whereas K+-blockers had...

  9. Dual pathways of calcium entry in spike and plateau phases of luteinizing hormone release from chicken pituitary cells: sequential activation of receptor-operated and voltage-sensitive calcium channels by gonadotropin-releasing hormone

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, J.S.; Wakefield, I.K.; King, J.A.; Mulligan, G.P.; Millar, R.P.


    It has previously been shown that, in pituitary gonadotrope cells, the initial rise in cytosolic Ca2+ induced by GnRH is due to a Ca2+ mobilization from intracellular stores. This raises the possibility that the initial transient spike phase of LH release might be fully or partially independent of extracellular Ca2+. We have therefore characterized the extracellular Ca2+ requirements, and the sensitivity to Ca2+ channel blockers, of the spike and plateau phases of secretion separately. In the absence of extracellular Ca2+ the spike and plateau phases were inhibited by 65 +/- 4% and 106 +/- 3%, respectively. Both phases exhibited a similar dependence on concentration of extracellular Ca2+. However, voltage-sensitive Ca2+ channel blockers D600 and nifedipine had a negligible effect on the spike phase, while inhibiting the plateau phase by approximately 50%. In contrast, ruthenium red, Gd3+ ions, and Co2+ ions inhibited both spike and plateau phases to a similar extent as removal of extracellular Ca2+. A fraction (35 +/- 4%) of spike phase release was resistant to removal of extracellular Ca2+. This fraction was abolished after calcium depletion of the cells by preincubation with EGTA in the presence of calcium ionophore A23187, indicating that it depends on intracellular Ca2+ stores. Neither absence of extracellular Ca2+, nor the presence of ruthenium red or Gd3+ prevented mobilization of 45Ca2+ from intracellular stores by GnRH. We conclude that mobilization of intracellular stored Ca2+ is insufficient by itself to account for full spike phase LH release.

  10. Voltage-Gated Calcium Channels in Nociception (United States)

    Yasuda, Takahiro; Adams, David J.

    Voltage-gated calcium channels (VGCCs) are a large and functionally diverse group of membrane ion channels ubiquitously expressed throughout the central and peripheral nervous systems. VGCCs contribute to various physiological processes and transduce electrical activity into other cellular functions. This chapter provides an overview of biophysical properties of VGCCs, including regulation by auxiliary subunits, and their physiological role in neuronal functions. Subsequently, then we focus on N-type calcium (Cav2.2) channels, in particular their diversity and specific antagonists. We also discuss the role of N-type calcium channels in nociception and pain transmission through primary sensory dorsal root ganglion neurons (nociceptors). It has been shown that these channels are expressed predominantly in nerve terminals of the nociceptors and that they control neurotransmitter release. To date, important roles of N-type calcium channels in pain sensation have been elucidated genetically and pharmacologically, indicating that specific N-type calcium channel antagonists or modulators are particularly useful as therapeutic drugs targeting chronic and neuropathic pain.

  11. Calcium binding and voltage gating in Cx46 hemichannels. (United States)

    Pinto, Bernardo I; Pupo, Amaury; García, Isaac E; Mena-Ulecia, Karel; Martínez, Agustín D; Latorre, Ramón; Gonzalez, Carlos


    The opening of connexin (Cx) hemichannels in the membrane is tightly regulated by calcium (Ca 2+ ) and membrane voltage. Electrophysiological and atomic force microscopy experiments indicate that Ca 2+ stabilizes the hemichannel closed state. However, structural data show that Ca 2+ binding induces an electrostatic seal preventing ion transport without significant structural rearrangements. In agreement with the closed-state stabilization hypothesis, we found that the apparent Ca 2+ sensitivity is increased as the voltage is made more negative. Moreover, the voltage and Ca 2+ dependence of the channel kinetics indicate that the voltage sensor movement and Ca 2+ binding are allosterically coupled. An allosteric kinetic model in which the Ca 2+ decreases the energy necessary to deactivate the voltage sensor reproduces the effects of Ca 2+ and voltage in Cx46 hemichannels. In agreement with the model and suggesting a conformational change that narrows the pore, Ca 2+ inhibits the water flux through Cx hemichannels. We conclude that Ca 2+ and voltage act allosterically to stabilize the closed conformation of Cx46 hemichannels.

  12. Coupled dynamics of voltage and calcium in paced cardiac cells (United States)

    Shiferaw, Yohannes; Sato, Daisuke; Karma, Alain


    We investigate numerically and analytically the coupled dynamics of transmembrane voltage and intracellular calcium cycling in paced cardiac cells using a detailed physiological model, and its reduction to a three-dimensional discrete map. The results provide a theoretical framework to interpret various experimentally observed modes of instability ranging from electromechanically concordant and discordant alternans to quasiperiodic oscillations of voltage and calcium.

  13. Voltage-dependent mobilization of intracellular calcium in skeletal muscle. (United States)

    Schneider, M F


    In skeletal muscle calcium is released from the sarcoplasmic reticulum (SR), an internal organelle, in response to changes in the voltage across the transverse tubule (T-tubule) membrane, an external membrane system that is distinct from the SR but in close proximity to it. For T-tubule voltage changes within the physiological range, calcium release can be turned on or off on a time scale of milliseconds. The control of calcium release from the SR appears to involve at least three functional components: a voltage sensor in the T-tubule membrane, a calcium channel in the SR, and a mechanism for coupling the voltage sensor to the channel. Movement of charged or dipolar molecules within the T-tubule membrane is thought to serve as the voltage sensor. Such intramembrane charge movement (Q) can be monitored electrically and can be compared with the rate of calcium release from the SR. Calcium release is calculated from cytosolic calcium transients measured with a metallochromic indicator. Comparison of Q and the rate of release in the same isolated muscle fibre indicates that this rate is directly proportional to the amount of charge displaced in excess of a 'threshold' amount. The nature of the coupling mechanism between T-tubules and SR remains to be established but present observations impose some restrictions on possible mechanisms.

  14. Calcium-sensitive immunoaffinity chromatography

    DEFF Research Database (Denmark)

    Henriksen, Maiken L; Lindhardt Madsen, Kirstine; Skjoedt, Karsten


    Immunoaffinity chromatography is a powerful fractionation technique that has become indispensable for protein purification and characterization. However, it is difficult to retrieve bound proteins without using harsh or denaturing elution conditions, and the purification of scarce antigens...... to homogeneity may be impossible due to contamination with abundant antigens. In this study, we purified the scarce, complement-associated plasma protein complex, collectin LK (CL-LK, complex of collectin liver 1 and kidney 1), by immunoaffinity chromatography using a calcium-sensitive anti-collectin-kidney-1 m...... chromatography was superior to the traditional immunoaffinity chromatographies and resulted in a nine-fold improvement of the purification factor. The technique is applicable for the purification of proteins in complex mixtures by single-step fractionation without the denaturation of eluted antigens...

  15. Calcium-induced voltage gating in single conical nanopores. (United States)

    Siwy, Zuzanna S; Powell, Matthew R; Petrov, Alexander; Kalman, Eric; Trautmann, Christina; Eisenberg, Robert S


    We examine time signals of ion current through single conically shaped nanopores in the presence of sub-millimolar concentrations of calcium ions. We show that calcium induces voltage-dependent ion current fluctuations in time in addition to the previously reported negative incremental resistance (Nano Lett. 2006, 6, 473-477). These current fluctuations occur on the millisecond time scale at voltages at which the effect of negative incremental resistance was observed. We explain the fluctuations as results of transient binding of calcium ions to carboxyl groups on the pore walls that cause transient changes in electric potential inside a conical nanopore. We support this explanation by recordings of ion current in the presence of manganese ions that bind to carboxyl groups 3 orders of magnitude more tightly than calcium ions. The system of a single conical nanopore with calcium ions is compared to a semiconductor device of a unijunction transistor in electronic circuits. A unijunction transistor also exhibits negative incremental resistance and current instabilities.

  16. Potassium Sensitive Optical Nanosensors Containing Voltage Sensitive Dyes. (United States)

    Xie, Xiaojiang; Gutiérrez, Agustín; Trofimov, Valentin; Szilagyi, Istvan; Soldati, Thierry; Bakker, Eric


    lonophore-based ion-selective optical nanosensors have been explored for a number of years. Voltage sensitive dyes (VSDs) have been introduced into this type of sensors only very recently, forming a new class of analytical tools. Here, K(+)-sensitive nanospheres incorporating a lipophilic VSD were successfully fabricated and characterized. The nanosensors were readily delivered into the social amoeba Dictyostelium discoideum in a non-invasive manner, forming a promising new platform for intracellular ion quantification and imaging.

  17. Palette of fluorinated voltage-sensitive hemicyanine dyes (United States)

    Yan, Ping; Acker, Corey D.; Zhou, Wen-Liang; Lee, Peter; Bollensdorff, Christian; Negrean, Adrian; Lotti, Jacopo; Sacconi, Leonardo; Antic, Srdjan D.; Kohl, Peter; Mansvelder, Huibert D.; Pavone, Francesco S.; Loew, Leslie M.


    Optical recording of membrane potential permits spatially resolved measurement of electrical activity in subcellular regions of single cells, which would be inaccessible to electrodes, and imaging of spatiotemporal patterns of action potential propagation in excitable tissues, such as the brain or heart. However, the available voltage-sensitive dyes (VSDs) are not always spectrally compatible with newly available optical technologies for sensing or manipulating the physiological state of a system. Here, we describe a series of 19 fluorinated VSDs based on the hemicyanine class of chromophores. Strategic placement of the fluorine atoms on the chromophores can result in either blue or red shifts in the absorbance and emission spectra. The range of one-photon excitation wavelengths afforded by these new VSDs spans 440–670 nm; the two-photon excitation range is 900–1,340 nm. The emission of each VSD is shifted by at least 100 nm to the red of its one-photon excitation spectrum. The set of VSDs, thus, affords an extended toolkit for optical recording to match a broad range of experimental requirements. We show the sensitivity to voltage and the photostability of the new VSDs in a series of experimental preparations ranging in scale from single dendritic spines to whole heart. Among the advances shown in these applications are simultaneous recording of voltage and calcium in single dendritic spines and optical electrophysiology recordings using two-photon excitation above 1,100 nm. PMID:23169660

  18. Voltage-Gated Calcium Channel Antagonists and Traumatic Brain Injury

    Directory of Open Access Journals (Sweden)

    Bruce Lyeth


    Full Text Available Traumatic brain injury (TBI is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca2+]i. These fluxes in [Ca2+]i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

  19. Voltage-Sensitive Load Controllers for Voltage Regulation and Increased Load Factor in Distribution Systems

    DEFF Research Database (Denmark)

    Douglass, Philip James; Garcia-Valle, Rodrigo; Østergaard, Jacob


    This paper presents a novel controller design for controlling appliances based on local measurements of voltage. The controller finds the normalized voltage deviation accounting for the sensitivity of voltage measurements to appliance state. The controller produces a signal indicating desired pow...

  20. Regulation of voltage-gated calcium channels by proteolysis (United States)

    Kathryn, ABELE; Jian, YANG


    Voltage gated calcium channels (VGCCs) are multi-subunit membrane proteins present in a variety of tissues and control many essential physiological processes. Due to their vital importance, VGCCs are regulated by a myriad of proteins and signaling pathways. Here we review the literature on the regulation of VGCCs by proteolysis of the pore-forming α1 subunit, Cavα1. This form of regulation modulates channel function and degradation and affects cellular gene expression and excitability. L-type Ca2+ channels are proteolyzed in two ways, depending on tissue localization. In the heart and skeletal muscle, the distal C-terminus of Cavα1 is cleaved and acts as an autoinhibitor when it reassociates with the proximal C-terminus. Relief of this autoinhibition underlies the β-adrenergic stimulation-induced enhancement of cardiac and skeletal muscle calcium currents, part of the “fight or flight” response. Proteolysis of the distal C-terminus of L-type channels also occurs in the brain and is probably catalyzed by a calpain-like protease. In some brain regions, the entire C-terminus of L-type Ca2+ channels can be cleaved by an unknown protease and translocates to the nucleus acting as a transcription factor. The distal C-terminus of P/Q-channel Cavα1 is also proteolyzed and translocates to the nucleus. Truncated forms of the PQ-channel Cavα1 are produced by many disease-causing mutations and interfere with the function of full-length channels. Truncated forms of N-type channel Cavα1, generated by mutagenesis, affect the expression of full-length channels. New forms of proteolysis of VGCC subunits remain to be discovered and may represent a fruitful area of VGCC research. PMID:23090491

  1. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, Trine Meldgaard; Belhage, B


    The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...

  2. Calcium current-dependent and voltage-dependent inactivation of calcium channels in Helix aspersa (United States)

    Brown, A. M.; Morimoto, K.; Tsuda, Y.; Wilson, D. L.


    -exponential inactivation process that persists in the presence of EGTAi is similar to that occurring when extracellular Ba ion carries current through the Ca channel. Steady-state inactivation also persists and is similar in the two cases. Therefore it is concluded that inactivation is voltage-dependent as well as Ca current-dependent. 8. Diffusion models that included reasonable values for the effect of binding on diffusion, even when combined with declining influxes, did not account for this `mixed' form of calcium- and voltage-dependent inactivation. A compartmental model in which the particular kinetic model of voltage-dependent inactivation was not critical described the Ca current-dependent inactivation. PMID:6275075

  3. Lack of direct evidence for a functional role of voltage-operated calcium channels in juxtaglomerular cells

    DEFF Research Database (Denmark)

    Kurtz, A; Skott, O; Chegini, S


    In this study we have examined the role of voltage-gated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intrace...

  4. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, T M; Belhage, B


    using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...... channels were differentially distributed in somata, neurites and nerve terminals. omega-conotoxin MVIIC (omega-CgTx MVIIC) inhibited approximately 40% of the Ca(2+)-rise in both somata and neurites and 60% of the potassium induced [3H]GABA release, indicating that the Q-type channel is the quantitatively...... in cytosolic calcium concentration. The results of this investigation demonstrate that pharmacologically distinct types of voltage dependent calcium channels are differentially localized in cell bodies, neurites and nerve terminals of mouse cortical neurons but that the Q-type calcium channel appears...

  5. Voltage-sensitive rhodol with enhanced two-photon brightness. (United States)

    Kulkarni, Rishikesh U; Kramer, Daniel J; Pourmandi, Narges; Karbasi, Kaveh; Bateup, Helen S; Miller, Evan W


    We have designed, synthesized, and applied a rhodol-based chromophore to a molecular wire-based platform for voltage sensing to achieve fast, sensitive, and bright voltage sensing using two-photon (2P) illumination. Rhodol VoltageFluor-5 (RVF5) is a voltage-sensitive dye with improved 2P cross-section for use in thick tissue or brain samples. RVF5 features a dichlororhodol core with pyrrolidyl substitution at the nitrogen center. In mammalian cells under one-photon (1P) illumination, RVF5 demonstrates high voltage sensitivity (28% ΔF/F per 100 mV) and improved photostability relative to first-generation voltage sensors. This photostability enables multisite optical recordings from neurons lacking tuberous sclerosis complex 1, Tsc1, in a mouse model of genetic epilepsy. Using RVF5, we show that Tsc1 KO neurons exhibit increased activity relative to wild-type neurons and additionally show that the proportion of active neurons in the network increases with the loss of Tsc1. The high photostability and voltage sensitivity of RVF5 is recapitulated under 2P illumination. Finally, the ability to chemically tune the 2P absorption profile through the use of rhodol scaffolds affords the unique opportunity to image neuronal voltage changes in acutely prepared mouse brain slices using 2P illumination. Stimulation of the mouse hippocampus evoked spiking activity that was readily discerned with bath-applied RVF5, demonstrating the utility of RVF5 and molecular wire-based voltage sensors with 2P-optimized fluorophores for imaging voltage in intact brain tissue.


    NARCIS (Netherlands)



    We have investigated the effects of the C-terminal amyloid precursor protein fragment His 657-Lys 676 upon calcium currents in NG108-15 neuroblastoma x glioma hybrid cells. The amyloid precursor protein fragment His 657-Lys 676 (1-10 mu M) did not affect calcium currents pel se, but clearly blocked

  7. Recording membrane potential changes through photoacoustic voltage sensitive dye

    DEFF Research Database (Denmark)

    Zhang, Haichong K.; Kang, Jeeun; Yan, Ping


    systems for external detection. In contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near infrared light excitation and ultrasound detection. In this work, we develop the theoretical concept whereby the voltage-dependent quenching......Monitoring of the membrane potential is possible using voltage sensitive dyes (VSD), where fluorescence intensity changes in response to neuronal electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo...... the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate the voltage sensing capability of the dye, but also indicate the necessity of considering both fluorescence and absorbance spectral sensitivities in order to optimize...

  8. A minimalist model of calcium-voltage coupling in GnRH cells

    Energy Technology Data Exchange (ETDEWEB)

    Rennie, Martin; Chan, Rossanna; Duan Wen; Sneyd, James [Department of Mathematics, University of Auckland, Auckland 1142 (New Zealand); Schneider, David, E-mail: [Departamento de Fisica, Comision Nacional de Energia Atomica. Av. del Libertador 8250, 1429 Buenos Aires (Argentina)


    We present a minimalist model to describe the interplay between burst firing and calcium dynamics in Gonadotropin-releasing hormone (GnRH) cells. This model attempts to give a qualitative representation of Duan's model [3], and it comprises two FithzHugh-Nagumo (FHN) coupled systems describing the dynamics of the membrane potential and calcium concentration in the GnRH cells. Within the framework of our minimalist model, we find that the calcium subsystem drives burst firing by making the voltage subsystem to undergo a Hopf bifurcation. Specifically, fast relaxation oscillations occur in a specific region of the c-z plane (c being the calcium concentration, and z a calcium-dependent gating variable). Slow calcium oscillations, instead, are carried by the voltage subsystem by successive shifts of the calcium steady state, and have the net effect of an external perturbation. The full comprehension of the phase-plane of the voltage subsystem and the 3-dimensional phase-space of the calcium subsystem ultimately allows us to study the behaviours of the entire model under the change of certain parameters. Those special parameters do not necessarily follow realistic assumptions, but merely intend to mimic some pharmacological tests which have been performed experimentally and also simulated by Duan's model under the corresponding physiological considerations.

  9. Glycosylation of voltage-gated calcium channels in health and disease

    Czech Academy of Sciences Publication Activity Database

    Lazniewska, Joanna; Weiss, Norbert


    Roč. 1859, č. 5 (2017), s. 662-668 ISSN 0005-2736 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channels * voltage-gated calcium channels * N-glycosylation * ancillary subunit * trafficking * stability Subject RIV: CE - Biochemistry Impact factor: 3.498, year: 2016

  10. The allosteric site regulates the voltage sensitivity of muscarinic receptors. (United States)

    Hoppe, Anika; Marti-Solano, Maria; Drabek, Matthäus; Bünemann, Moritz; Kolb, Peter; Rinne, Andreas


    Muscarinic receptors (M-Rs) for acetylcholine (ACh) belong to the class A of G protein-coupled receptors. M-Rs are activated by orthosteric agonists that bind to a specific site buried in the M-R transmembrane helix bundle. In the active conformation, receptor function can be modulated either by allosteric modulators, which bind to the extracellular receptor surface or by the membrane potential via an unknown mechanism. Here, we compared the modulation of M 1 -Rs and M 3 -Rs induced by changes in voltage to their allosteric modulation by chemical compounds. We quantified changes in receptor signaling in single HEK 293 cells with a FRET biosensor for the G q protein cycle. In the presence of ACh, M 1 -R signaling was potentiated by voltage, similarly to positive allosteric modulation by benzyl quinolone carboxylic acid. Conversely, signaling of M 3 -R was attenuated by voltage or the negative allosteric modulator gallamine. Because the orthosteric site is highly conserved among M-Rs, but allosteric sites vary, we constructed "allosteric site" M 3 /M 1 -R chimeras and analyzed their voltage dependencies. Exchanging the entire allosteric sites eliminated the voltage sensitivity of ACh responses for both receptors, but did not affect their modulation by allosteric compounds. Furthermore, a point mutation in M 3 -Rs caused functional uncoupling of the allosteric and orthosteric sites and abolished voltage dependence. Molecular dynamics simulations of the receptor variants indicated a subtype-specific crosstalk between both sites, involving the conserved tyrosine lid structure of the orthosteric site. This molecular crosstalk leads to receptor subtype-specific voltage effects. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

    Directory of Open Access Journals (Sweden)

    Aldo A Rodríguez Menchaca


    Full Text Available Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidilinositol 4,5-bisphosphate (PIP2. Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav channels were shown to be regulated bidirectionally by PIP2. On one hand, PIP2 stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv channels PIP2 was first shown to prevent N-type inactivation. Careful examination of the effects of PIP2 on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP2 and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP2 is the hyperpolarization-activated cyclic nucleotide-gated (HCN channel. PIP2 has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP2-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP2 dual effects on SpIH channels. The dual regulation of these very different ion channels, all of which are voltage dependent, points to conserved mechanisms of regulation of these channels by PIP2.

  12. T-type voltage-gated calcium channels regulate the tone of mouse efferent arterioles

    DEFF Research Database (Denmark)

    Poulsen, Christian B; Al-Mashhadi, Rozh H; Cribbs, Leanne L


    Voltage-gated calcium channels are important for the regulation of renal blood flow and the glomerular filtration rate. Excitation-contraction coupling in afferent arterioles is known to require activation of these channels and we studied their role in the regulation of cortical efferent arteriol...... publication, 10 November 2010; doi:10.1038/ki.2010.429....

  13. New Role of P/Q-type Voltage-gated Calcium Channels

    DEFF Research Database (Denmark)

    Hansen, Pernille B L


    Voltage-gated calcium channels are important for the depolarization-evoked contraction of vascular smooth muscle cells (SMCs), with L-type channels being the classical channel involved in this mechanism. However, it has been demonstrated that the CaV2.1 subunit, which encodes a neuronal isoform o...

  14. calcium-sensitivity of smooth muscle contraction in the isolated ...

    African Journals Online (AJOL)

    Dr Olaleye

    The higher the calcium concentration to which the tissue was exposed during activation, the greater was desensitization. The progressive loss in sensitivity could be attenuated by restricting the range of free calcium used for CRCs to between 1μM and 300μM Ca2+. Results were similar whether activation was by NA or high ...

  15. LRRK2 regulates voltage-gated calcium channel function.

    Directory of Open Access Journals (Sweden)

    Cade eBedford


    Full Text Available Voltage-gated Ca2+ (CaV channels enable Ca2+ influx in response to membrane depolarization. CaV2.1 channels are localized to the presynaptic membrane of many types of neurons where they are involved in triggering neurotransmitter release. Several signaling proteins have been identified as important CaV2.1 regulators including protein kinases, G-proteins and Ca2+ binding proteins. Recently, we discovered that leucine rich repeat kinase 2 (LRRK2, a protein associated with inherited Parkinson’s disease, interacts with specific synaptic proteins and influences synaptic transmission. Since synaptic proteins functionally interact with CaV2.1 channels and synaptic transmission is triggered by Ca2+ entry via CaV2.1, we investigated whether LRRK2 could impact CaV2.1 channel function. CaV2.1 channel properties were measured using whole cell patch clamp electrophysiology in HEK293 cells transfected with CaV2.1 subunits and various LRRK2 constructs. Our results demonstrate that both wild type LRRK2 and the G2019S LRRK2 mutant caused a significant increase in whole cell Ca2+ current density compared to cells expressing only the CaV2.1 channel complex. In addition, LRRK2 expression caused a significant hyperpolarizing shift in voltage-dependent activation while having no significant effect on inactivation properties. These functional changes in CaV2.1 activity are likely due to a direct action of LRRK2 as we detected a physical interaction between LRRK2 and the β3 CaV channel subunit via coimmunoprecipitation. Furthermore, effects on CaV2.1 channel function are dependent on LRRK2 kinase activity as these could be reversed via treatment with a LRRK2 inhibitor. Interestingly, LRRK2 also augmented endogenous voltage-gated Ca2+ channel function in PC12 cells suggesting other CaV channels could also be regulated by LRRK2. Overall, our findings support a novel physiological role for LRRK2 in regulating CaV2.1 function that could have implications for how

  16. Construction and use of a zebrafish heart voltage and calcium optical mapping system, with integrated electrocardiogram and programmable electrical stimulation (United States)

    Lin, Eric; Craig, Calvin; Lamothe, Marcel; Sarunic, Marinko V.; Beg, Mirza Faisal


    Zebrafish are increasingly being used as a model of vertebrate cardiology due to mammalian-like cardiac properties in many respects. The size and fecundity of zebrafish make them suitable for large-scale genetic and pharmacological screening. In larger mammalian hearts, optical mapping is often used to investigate the interplay between voltage and calcium dynamics and to investigate their respective roles in arrhythmogenesis. This report outlines the construction of an optical mapping system for use with zebrafish hearts, using the voltage-sensitive dye RH 237 and the calcium indicator dye Rhod-2 using two industrial-level CCD cameras. With the use of economical cameras and a common 532-nm diode laser for excitation, the rate dependence of voltage and calcium dynamics within the atrial and ventricular compartments can be simultaneously determined. At 140 beats/min, the atrial action potential duration was 36 ms and the transient duration was 53 ms. With the use of a programmable electrical stimulator, a shallow rate dependence of 3 and 4 ms per 100 beats/min was observed, respectively. In the ventricle the action potential duration was 109 ms and the transient duration was 124 ms, with a steeper rate dependence of 12 and 16 ms per 100 beats/min. Synchronous electrocardiograms and optical mapping recordings were recorded, in which the P-wave aligns with the atrial voltage peak and R-wave aligns with the ventricular peak. A simple optical pathway and imaging chamber are detailed along with schematics for the in-house construction of the electrocardiogram amplifier and electrical stimulator. Laboratory procedures necessary for zebrafish heart isolation, cannulation, and loading are also presented. PMID:25740339

  17. Voltage gated calcium channels negatively regulate protective immunity to Mycobacterium tuberculosis.

    Directory of Open Access Journals (Sweden)

    Shashank Gupta

    Full Text Available Mycobacterium tuberculosis modulates levels and activity of key intracellular second messengers to evade protective immune responses. Calcium release from voltage gated calcium channels (VGCC regulates immune responses to pathogens. In this study, we investigated the roles of VGCC in regulating protective immunity to mycobacteria in vitro and in vivo. Inhibiting L-type or R-type VGCC in dendritic cells (DCs either using antibodies or by siRNA increased calcium influx in an inositol 1,4,5-phosphate and calcium release calcium activated channel dependent mechanism that resulted in increased expression of genes favoring pro-inflammatory responses. Further, VGCC-blocked DCs activated T cells that in turn mediated killing of M. tuberculosis inside macrophages. Likewise, inhibiting VGCC in infected macrophages and PBMCs induced calcium influx, upregulated the expression of pro-inflammatory genes and resulted in enhanced killing of intracellular M. tuberculosis. Importantly, compared to healthy controls, PBMCs of tuberculosis patients expressed higher levels of both VGCC, which were significantly reduced following chemotherapy. Finally, blocking VGCC in vivo in M. tuberculosis infected mice using specific antibodies increased intracellular calcium and significantly reduced bacterial loads. These results indicate that L-type and R-type VGCC play a negative role in M. tuberculosis infection by regulating calcium mobilization in cells that determine protective immunity.

  18. Dehydroepiandrosterone (DHEA) inhibits voltage-gated T-type calcium channels. (United States)

    Chevalier, M; Gilbert, G; Lory, P; Marthan, R; Quignard, J F; Savineau, J P


    Dehydroepiandrosterone (DHEA) and its sulfated form, DHEAS, are the most abundant steroid hormones in the mammalian blood flow. DHEA may have beneficial effects in various pathophysiological conditions such as cardiovascular diseases or deterioration of the sense of well-being. However to date, the cellular mechanism underlying DHEA action remains elusive and may involve ion channel modulation. In this study, we have characterized the effect of DHEA on T-type voltage-activated calcium channels (T-channels), which are involved in several cardiovascular and neuronal diseases. Using the whole-cell patch-clamp technique, we demonstrate that DHEA inhibits the three recombinant T-channels (Ca(V)3.1, Ca(V)3.2 and Ca(V)3.3) expressed in NG108-15 cell line, as well as native T-channels in pulmonary artery smooth muscle cells. This effect of DHEA is both concentration (IC(50) between 2 and 7μM) and voltage-dependent and results in a significant shift of the steady-state inactivation curves toward hyperpolarized potentials. Consequently, DHEA reduces window T-current and inhibits membrane potential oscillations induced by Ca(V)3 channels. DHEA inhibition is not dependent on the activation of nuclear androgen or estrogen receptors and implicates a PTX-sensitive Gi protein pathway. Functionally, DHEA and the T-type inhibitor NNC 55-0396 inhibited KCl-induced contraction of pulmonary artery rings and their effect was not cumulative. Altogether, the present data demonstrate that DHEA inhibits T-channels by a Gi protein dependent pathway. DHEA-induced alteration in T-channel activity could thus account for its therapeutic action and/or physiological effects. Copyright © 2012 Elsevier Inc. All rights reserved.

  19. Fetal calcium regulates branching morphogenesis in the developing human and mouse lung: involvement of voltage-gated calcium channels.

    Directory of Open Access Journals (Sweden)

    Sarah C Brennan

    Full Text Available Airway branching morphogenesis in utero is essential for optimal postnatal lung function. In the fetus, branching morphogenesis occurs during the pseudoglandular stage (weeks 9-17 of human gestation, embryonic days (E11.5-16.5 in mouse in a hypercalcaemic environment (~1.7 in the fetus vs. ~1.1-1.3 mM for an adult. Previously we have shown that fetal hypercalcemia exerts an inhibitory brake on branching morphogenesis via the calcium-sensing receptor. In addition, earlier studies have shown that nifedipine, a selective blocker of L-type voltage-gated Ca(2+ channels (VGCC, inhibits fetal lung growth, suggesting a role for VGCC in lung development. The aim of this work was to investigate the expression of VGCC in the pseudoglandular human and mouse lung, and their role in branching morphogenesis. Expression of L-type (CaV1.2 and CaV1.3, P/Q type (CaV2.1, N-type (CaV2.2, R-type (CaV2.3, and T-type (CaV3.2 and CaV3.3 VGCC was investigated in paraffin sections from week 9 human fetal lungs and E12.5 mouse embryos. Here we show, for the first time, that Cav1.2 and Cav1.3 are expressed in both the smooth muscle and epithelium of the developing human and mouse lung. Additionally, Cav2.3 was expressed in the lung epithelium of both species. Incubating E12.5 mouse lung rudiments in the presence of nifedipine doubled the amount of branching, an effect which was partly mimicked by the Cav2.3 inhibitor, SNX-482. Direct measurements of changes in epithelial cell membrane potential, using the voltage-sensitive fluorescent dye DiSBAC2(3, demonstrated that cyclic depolarisations occur within the developing epithelium and coincide with rhythmic occlusions of the lumen, driven by the naturally occurring airway peristalsis. We conclude that VGCC are expressed and functional in the fetal human and mouse lung, where they play a role in branching morphogenesis. Furthermore, rhythmic epithelial depolarisations evoked by airway peristalsis would allow for branching to

  20. In Situ Optical Mapping of Voltage and Calcium in the Heart (United States)

    Ewart, Paul; Ashley, Euan A.; Loew, Leslie M.; Kohl, Peter; Bollensdorff, Christian; Woods, Christopher E.


    Electroanatomic mapping the interrelation of intracardiac electrical activation with anatomic locations has become an important tool for clinical assessment of complex arrhythmias. Optical mapping of cardiac electrophysiology combines high spatiotemporal resolution of anatomy and physiological function with fast and simultaneous data acquisition. If applied to the clinical setting, this could improve both diagnostic potential and therapeutic efficacy of clinical arrhythmia interventions. The aim of this study was to explore this utility in vivo using a rat model. To this aim, we present a single-camera imaging and multiple light-emitting-diode illumination system that reduces economic and technical implementation hurdles to cardiac optical mapping. Combined with a red-shifted calcium dye and a new near-infrared voltage-sensitive dye, both suitable for use in blood-perfused tissue, we demonstrate the feasibility of in vivo multi-parametric imaging of the mammalian heart. Our approach combines recording of electrophysiologically-relevant parameters with observation of structural substrates and is adaptable, in principle, to trans-catheter percutaneous approaches. PMID:22876327

  1. Simultaneous mapping of membrane voltage and calcium in zebrafish heart in vivo reveals chamber-specific developmental transitions in ionic currents

    Directory of Open Access Journals (Sweden)

    Jennifer H Hou


    Full Text Available The cardiac action potential (AP and the consequent cytosolic Ca2+ transient are key indicators of cardiac function. Natural developmental processes, as well as many drugs and pathologies change the waveform, propagation, or variability (between cells or over time of these parameters. Here we apply a genetically encoded dual-function calcium and voltage reporter (CaViar to study the development of the zebrafish heart in vivo between 1.5 and 4 days post fertilization (dpf. We developed a high-sensitivity spinning disk confocal microscope and associated software for simultaneous three-dimensional optical mapping of voltage and calcium. We produced a transgenic zebrafish line expressing CaViar under control of the heart-specific cmlc2 promoter, and applied ion channel blockers at a series of developmental stages to map the maturation of the action potential in vivo. Early in development, the AP initiated via a calcium current through L-type calcium channels. Between 90 – 102 hours post fertilization (hpf, the ventricular AP switched to a sodium-driven upswing, while the atrial AP remained calcium driven. In the adult zebrafish heart, a sodium current drives the AP in both the atrium and ventricle. Simultaneous voltage and calcium imaging with genetically encoded reporters provides a new approach for monitoring cardiac development, and the effects of drugs on cardiac function.

  2. Voltage-gated calcium channels of Paramecium cilia. (United States)

    Lodh, Sukanya; Yano, Junji; Valentine, Megan S; Van Houten, Judith L


    Paramecium cells swim by beating their cilia, and make turns by transiently reversing their power stroke. Reversal is caused by Ca2+ entering the cilium through voltage-gated Ca2+ (CaV) channels that are found exclusively in the cilia. As ciliary Ca2+ levels return to normal, the cell pivots and swims forward in a new direction. Thus, the activation of the CaV channels causes cells to make a turn in their swimming paths. For 45 years, the physiological characteristics of the Paramecium ciliary CaV channels have been known, but the proteins were not identified until recently, when the P. tetraurelia ciliary membrane proteome was determined. Three CaVα1 subunits that were identified among the proteins were cloned and confirmed to be expressed in the cilia. We demonstrate using RNA interference that these channels function as the ciliary CaV channels that are responsible for the reversal of ciliary beating. Furthermore, we show that Pawn (pw) mutants of Paramecium that cannot swim backward for lack of CaV channel activity do not express any of the three CaV1 channels in their ciliary membrane, until they are rescued from the mutant phenotype by expression of the wild-type PW gene. These results reinforce the correlation of the three CaV channels with backward swimming through ciliary reversal. The PwB protein, found in endoplasmic reticulum fractions, co-immunoprecipitates with the CaV1c channel and perhaps functions in trafficking. The PwA protein does not appear to have an interaction with the channel proteins but affects their appearance in the cilia. © 2016. Published by The Company of Biologists Ltd.

  3. The effects of intracellular pH changes on resting cytosolic calcium in voltage-clamped snail neurones (United States)

    Willoughby, Debbie; Thomas, Roger C; Schwiening, Christof J


    We have investigated the effects of changing intracellular pH on intracellular free calcium concentration ([Ca2+]i) in voltage-clamped neurones of the snail Helix aspersa. Intracellular pH (pHi) was measured using the fluorescent dye 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS) and changed using weak acids and weak bases. Changes in [Ca2+]i were recorded using either fura-2 or calcium-sensitive microelectrodes. Acidification of the neurones with 5 mM or 20 mM propionate (∼0.2 or 0.3 pH units acidification, respectively) caused a small reduction in resting [Ca2+]i of 5 ± 2 nM (n = 4) and 7 ± 16 nM (n = 4), respectively. The removal of the 20 mM propionate after ∼40 min superfusion resulted in an alkalinization of ∼0.35 pH units and an accompanying rise in resting [Ca2+]i of 31 ± 9 nM (n = 4, P Helix neurones induced by superfusion with 3 mM concentrations of the weak bases trimethylamine (TMA), ammonium chloride (NH4Cl) and procaine were accompanied by significant (P < 0.05) increases in resting [Ca2+]i of 42 ± 4 nM (n = 26), 30 ± 7 nM (n = 5) and 36 ± 4 nM (n = 3), respectively. The effect of TMA (0.5-6 mM) on [Ca2+]i was dose dependent with an increase in [Ca2+]i during pHi increases of less than 0.1 pH units (0.5 mM TMA). Superfusion of neurones with zero calcium (1 mM EGTA) Ringer solution inhibited depolarization-induced calcium increases but not the calcium increase produced by the first exposure to TMA (3 mM). In the prolonged absence of extracellular calcium (∼50 min) TMA-induced calcium rises were decreased by 64 ± 10% compared to those seen in the presence of external calcium (P < 0.05). The calcium rise induced by TMA (3 mM) was reduced by 60 ± 5% following a 10 min period of superfusion with caffeine (10 mM) to deplete the endoplasmic reticulum (ER) stores of calcium (P < 0.05). Cyclopiazonic acid (10-30 μM CPA), an inhibitor of the ER calcium pump, inhibited the calcium rise produced by TMA (3 mM) and NH4Cl (3 mM) by 61 ± 4% compared

  4. Microdamage induced calcium efflux from bone matrix activates intracellular calcium signaling in osteoblasts via L-type and T-type voltage-gated calcium channels. (United States)

    Jung, Hyungjin; Best, Makenzie; Akkus, Ozan


    Mechanisms by which bone microdamage triggers repair response are not completely understood. It has been shown that calcium efflux ([Ca(2+)]E) occurs from regions of bone undergoing microdamage. Such efflux has also been shown to trigger intracellular calcium signaling ([Ca(2+)]I) in MC3T3-E1 cells local to damaged regions. Voltage-gated calcium channels (VGCCs) are implicated in the entry of [Ca(2+)]E to the cytoplasm. We investigated the involvement of VGCC in the extracellular calcium induced intracellular calcium response (ECIICR). MC3T3-E1 cells were subjected to one dimensional calcium efflux from their basal aspect which results in an increase in [Ca(2+)]I. This increase was concomitant with membrane depolarization and it was significantly reduced in the presence of Bepridil, a non-selective VGCC inhibitor. To identify specific type(s) of VGCC in ECIICR, the cells were treated with selective inhibitors for different types of VGCC. Significant changes in the peak intensity and the number of [Ca(2+)]I oscillations were observed when L-type and T-type specific VGCC inhibitors (Verapamil and NNC55-0396, respectively) were used. So as to confirm the involvement of L- and T-type VGCC in the context of microdamage, cells were seeded on devitalized notched bone specimen, which were loaded to induce microdamage in the presence and absence of Verapamil and NNC55-0396. The results showed significant decrease in [Ca(2+)]I activity of cells in the microdamaged regions of bone when L- and T-type blockers were applied. This study demonstrated that extracellular calcium increase in association with damage depolarizes the cell membrane and the calcium ions enter the cell cytoplasm by L- and T-type VGCCs. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. How voltage-gated calcium channels gate forms of homeostatic synaptic plasticity

    Directory of Open Access Journals (Sweden)

    C. Andrew eFrank


    Full Text Available Throughout life, animals face a variety of challenges such as developmental growth, the presence of toxins, or changes in temperature. Neuronal circuits and synapses respond to challenges by executing an array of neuroplasticity paradigms. Some paradigms allow neurons to up- or downregulate activity outputs, while countervailing ones ensure that outputs remain within appropriate physiological ranges. A growing body of evidence suggests that homeostatic synaptic plasticity (HSP is critical in the latter case. Voltage-gated calcium channels gate forms of HSP. Presynaptically, the aggregate data show that when synapse activity is weakened, homeostatic signaling systems can act to correct impairments, in part by increasing calcium influx through presynaptic CaV2-type channels. Increased calcium influx is often accompanied by parallel increases in the size of active zones and the size of the readily releasable pool of presynaptic vesicles. These changes coincide with homeostatic enhancements of neurotransmitter release. Postsynaptically, there is a great deal of evidence that reduced network activity and loss of calcium influx through CaV1-type calcium channels also results in adaptive homeostatic signaling. Some adaptations drive presynaptic enhancements of vesicle pool size and turnover rate via retrograde signaling, as well as de novo insertion of postsynaptic neurotransmitter receptors. Enhanced calcium influx through CaV1 after network activation or single cell stimulation can elicit the opposite response – homeostatic depression via removal of excitatory receptors.There exist intriguing links between HSP and calcium channelopathies – such as forms of epilepsy, migraine, ataxia, and myasthenia. The episodic nature of some of these disorders suggests alternating periods of stable and unstable function. Uncovering information about how calcium channels are regulated in the context of HSP could be relevant toward understanding these and other

  6. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential (United States)

    Zamponi, Gerald W.; Striessnig, Joerg; Koschak, Alexandra


    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type CaV1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (CaV3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (CaV2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., CaV1.2 and CaV1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective CaV1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson’s disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and

  7. H2O2augments cytosolic calcium in nucleus tractus solitarii neurons via multiple voltage-gated calcium channels. (United States)

    Ostrowski, Tim D; Dantzler, Heather A; Polo-Parada, Luis; Kline, David D


    Reactive oxygen species (ROS) play a profound role in cardiorespiratory function under normal physiological conditions and disease states. ROS can influence neuronal activity by altering various ion channels and transporters. Within the nucleus tractus solitarii (nTS), a vital brainstem area for cardiorespiratory control, hydrogen peroxide (H 2 O 2 ) induces sustained hyperexcitability following an initial depression of neuronal activity. The mechanism(s) associated with the delayed hyperexcitability are unknown. Here we evaluate the effect(s) of H 2 O 2 on cytosolic Ca 2+ (via fura-2 imaging) and voltage-dependent calcium currents in dissociated rat nTS neurons. H 2 O 2 perfusion (200 µM; 1 min) induced a delayed, slow, and moderate increase (~27%) in intracellular Ca 2+ concentration ([Ca 2+ ] i ). The H 2 O 2 -mediated increase in [Ca 2+ ] i prevailed during thapsigargin, excluding the endoplasmic reticulum as a Ca 2+ source. The effect, however, was abolished by removal of extracellular Ca 2+ or the addition of cadmium to the bath solution, suggesting voltage-gated Ca 2+ channels (VGCCs) as targets for H 2 O 2 modulation. Recording of the total voltage-dependent Ca 2+ current confirmed H 2 O 2 enhanced Ca 2+ entry. Blocking VGCC L, N, and P/Q subtypes decreased the number of cells and their calcium currents that respond to H 2 O 2 The number of responder cells to H 2 O 2 also decreased in the presence of dithiothreitol, suggesting the actions of H 2 O 2 were dependent on sulfhydryl oxidation. In summary, here, we have shown that H 2 O 2 increases [Ca 2+ ] i and its Ca 2+ currents, which is dependent on multiple VGCCs likely by oxidation of sulfhydryl groups. These processes presumably contribute to the previously observed delayed hyperexcitability of nTS neurons in in vitro brainstem slices. Copyright © 2017 the American Physiological Society.

  8. Turing instability mediated by voltage and calcium diffusion in paced cardiac cells. (United States)

    Shiferaw, Yohannes; Karma, Alain


    In cardiac cells, the coupling between the voltage across the cell membrane (V(m)) and the release of calcium (Ca) from intracellular stores is a crucial ingredient of heart function. Under abnormal conditions and/or rapid pacing, both the action potential duration and the peak Ca concentration in the cell can exhibit well known period-doubling oscillations referred to as "alternans," which have been linked to sudden cardiac death. Fast diffusion of V(m) keeps action potential duration alternans spatially synchronized over the approximately 150-mum-length scale of a cell, but slow diffusion of Ca ions allows Ca alternans within a cell to become spatially asynchronous, as observed in some experiments. This finding raises the question: When are Ca alternans spatially in-phase or out-of-phase on subcellular length scales? This question is investigated by using a spatially distributed model of Ca cycling coupled to V(m). Our main finding is the existence of a Turing-type symmetry breaking instability mediated by V(m) and Ca diffusion that causes Ca alternans to become spontaneously out-of-phase at opposite ends of a cardiac cell. Pattern formation is governed by the interplay of short-range activation of Ca alternans, because of a dynamical instability of Ca cycling, and long-range inhibition of Ca alternans by V(m) alternans through Ca-sensitive membrane ionic currents. These results provide a striking example of a Turing instability in a biological context where the morphogens can be clearly identified, as well as a potential link between dynamical instability on subcellular scales and life-threatening cardiac disorders.

  9. Voltage-Sensitive Ion Channels Biophysics of Molecular Excitability

    CERN Document Server

    Leuchtag, H. Richard


    Voltage-sensitive ion channels are macromolecules embedded in the membranes of nerve and muscle fibers of animals. Because of their physiological functions, biochemical structures and electrical switching properties, they are at an intersection of biology, chemistry and physics. Despite decades of intensive research under the traditional approach of gated structural pores, the relation between the structure of these molecules and their function remains enigmatic. This book critically examines physically oriented approaches not covered in other ion-channel books. It looks at optical and thermal as well as electrical data, and at studies in the frequency domain as well as in the time domain. Rather than presenting the reader with only an option of mechanistic models at an inappropriate pseudo-macroscopic scale, it emphasizes concepts established in organic chemistry and condensed state physics. The book’s approach to the understanding of these unique structures breaks with the unproven view of ion channels as...

  10. desensitisation and calcium-sensitivity in the isolated perfused rat ...

    African Journals Online (AJOL)

    Dr Olaleye


  11. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels. (United States)

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H


    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  12. Role of calcium influx through voltage-operated calcium channels and of calcium mobilization in the physiology of Schistosoma mansoni muscle contractions. (United States)

    Mendonça-Silva, D L; Novozhilova, E; Cobbett, P J R; Silva, C L M; Noël, F; Totten, M I J; Maule, A G; Day, T A


    We tested the hypothesis that voltage-operated Ca2+ channels mediate an extracellular Ca2+ influx in muscle fibres from the human parasite Schistosoma mansoni and, along with Ca2+ mobilization from the sarcoplasmic reticulum, contribute to muscle contraction. Indeed, whole-cell voltage clamp revealed voltage-gated inward currents carried by divalent ions with a peak current elicited by steps to +20 mV (from a holding potential of -70 mV). Depolarization of the fibres by elevated extracellular K+ elicited contractions that were completely dependent on extracellular Ca2+ and inhibited by nicardipine (half inhibition at 4.1 microM). However these contractions were not very sensitive to other classical blockers of voltage-gated Ca2+ channels, indicating that the schistosome muscle channels have an atypical pharmacology when compared to their mammalian counterparts. Futhermore, the contraction induced by 5 mM caffeine was inhibited after depletion of the sarcoplasmic reticulum either with thapsigargin (10 microM) or ryanodine (10 microM). These data suggest that voltage-operated Ca2+ channels do contribute to S. mansoni contraction as does the mobilization of stored Ca2+, despite the small volume of sarcoplasmic reticulum in schistosome smooth muscles.

  13. GABA(A) Increases Calcium in Subventricular Zone Astrocyte-Like Cells Through L- and T-Type Voltage-Gated Calcium Channels

    DEFF Research Database (Denmark)

    Young, Stephanie Z; Platel, Jean-Claude; Nielsen, Jakob V


    induced Ca(2+) increases in 40-50% of SVZ astrocytes. GABA(A)-induced Ca(2+) increases were prevented with nifedipine and mibefradil, blockers of L- and T-type voltage-gated calcium channels (VGCC). The L-type Ca(2+) channel activator BayK 8644 increased the percentage of GABA(A)-responding astrocyte...

  14. Electromagnetic fields act via activation of voltage-gated calcium channels to produce beneficial or adverse effects


    Pall, Martin L


    The direct targets of extremely low and microwave frequency range electromagnetic fields (EMFs) in producing non-thermal effects have not been clearly established. However, studies in the literature, reviewed here, provide substantial support for such direct targets. Twenty-three studies have shown that voltage-gated calcium channels (VGCCs) produce these and other EMF effects, such that the L-type or other VGCC blockers block or greatly lower diverse EMF effects. Furthermore, the voltage-gat...

  15. Spatiotemporal patterns of voltage and calcium signaling in heart cells and tissue (United States)

    Karma, Alain


    This talk will describe recent progress made in understanding oscillatory patterns of voltage and calcium signals that precede the onset of electromechanical wave turbulence in the main chambers of the heart. Results will illustrate how both physiologically detailed and abstract models have proven useful to cope with the bewildering molecular complexity of cardiac biology and to bridge phenomena on cellular and tissue scales. A main conclusion is that those oscillatory patterns can be self-organized, resulting from symmetry-breaking linear instabilities, or/and a manifestation of underling tissue heterogeneities. Thus studying the evolution of those patterns provides a valuable indirect probe of complex physiological processes that render the heart susceptible to the sudden onset of lethal heart rhythm disorders.

  16. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels

    DEFF Research Database (Denmark)

    Hansen, P B L


    Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L......-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular...... vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore...

  17. Modulating the Voltage-sensitivity of a Genetically Encoded Voltage Indicator. (United States)

    Jung, Arong; Rajakumar, Dhanarajan; Yoon, Bong-June; Baker, Bradley J


    Saturation mutagenesis was performed on a single position in the voltage-sensing domain (VSD) of a genetically encoded voltage indicator (GEVI). The VSD consists of four transmembrane helixes designated S1-S4. The V220 position located near the plasma membrane/extracellular interface had previously been shown to affect the voltage range of the optical signal. Introduction of polar amino acids at this position reduced the voltage-dependent optical signal of the GEVI. Negatively charged amino acids slightly reduced the optical signal by 33 percent while positively charge amino acids at this position reduced the optical signal by 80%. Surprisingly, the range of V220D was similar to that of V220K with shifted optical responses towards negative potentials. In contrast, the V220E mutant mirrored the responses of the V220R mutation suggesting that the length of the side chain plays in role in determining the voltage range of the GEVI. Charged mutations at the 219 position all behaved similarly slightly shifting the optical response to more negative potentials. Charged mutations to the 221 position behaved erratically suggesting interactions with the plasma membrane and/or other amino acids in the VSD. Introduction of bulky amino acids at the V220 position increased the range of the optical response to include hyperpolarizing signals. Combining The V220W mutant with the R217Q mutation resulted in a probe that reduced the depolarizing signal and enhanced the hyperpolarizing signal which may lead to GEVIs that only report neuronal inhibition.

  18. A sensitive differential capacitance to voltage converter for sensor applications

    NARCIS (Netherlands)

    Lotters, Joost Conrad; Lötters, Joost Conrad; Olthuis, Wouter; Veltink, Petrus H.; Bergveld, Piet


    There is a need for capacitance to voltage converters (CVC's) for differential capacitive sensors like pressure sensors and accelerometers which can measure both statically and dynamically. A suitable CVC is described in this paper. The CVC proposed is based on a symmetrical structure containing two

  19. Phylogeny unites animal sodium leak channels with fungal calcium channels in an ancient, voltage-insensitive clade. (United States)

    Liebeskind, Benjamin J; Hillis, David M; Zakon, Harold H


    Proteins in the superfamily of voltage-gated ion channels mediate behavior across the tree of life. These proteins regulate the movement of ions across cell membranes by opening and closing a central pore that controls ion flow. The best-known members of this superfamily are the voltage-gated potassium, calcium (Ca(v)), and sodium (Na(v)) channels, which underlie impulse conduction in nerve and muscle. Not all members of this family are opened by changes in voltage, however. NALCN (NA(+) leak channel nonselective) channels, which encode a voltage-insensitive "sodium leak" channel, have garnered a growing interest. This study examines the phylogenetic relationship among Na(v)/Ca(v) voltage-gated and voltage-insensitive channels in the eukaryotic group Opisthokonta, which includes animals, fungi, and their unicellular relatives. We show that NALCN channels diverged from voltage-gated channels before the divergence of fungi and animals and that the closest relatives of NALCN channels are fungal calcium channels, which they functionally resemble.

  20. Lavender oil-potent anxiolytic properties via modulating voltage dependent calcium channels.

    Directory of Open Access Journals (Sweden)

    Anita M Schuwald

    Full Text Available Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.

  1. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels (United States)

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah


    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  2. Dynamic and static calcium gradients inside large snail (Helix aspersa) neurones detected with calcium-sensitive microelectrodes. (United States)

    Thomas, Roger C; Postma, Marten


    We have used quartz Ca2+-sensitive microelectrodes (CASMs) in large voltage-clamped snail neurones to investigate the inward spread of Ca2+ after a brief depolarisation. Both steady state and [Ca2+]i transients changed with depth of penetration. When the CASM tip was within 20 microm of the far side of the cell the [Ca2+]i transient time to peak was 4.4+/-0.5s, rising to 14.7+/-0.7s at a distance of 80 microm. We estimate that the Ca2+ transients travelled centripetally at an average speed of 6 microm2 s(-1) and decreased in size by half over a distance of about 45 microm. Cyclopiazonic acid had little effect on the size and time to peak of Ca2+ transients but slowed their recovery significantly. This suggests that the endoplasmic reticulum curtails rather than reinforces the transients. Injecting the calcium buffer BAPTA made the Ca2+ transients more uniform in size and increased their times to peak and rates of recovery near the membrane. We have developed a computational model for the transients, which includes diffusion, uptake and Ca2+ extrusion. Good fits were obtained with a rather large apparent diffusion coefficient of about 90+/-20 microm2 s(-1). This may assist fast recovery by extrusion.

  3. Voltage-dependent sodium channels and calcium-activated potassium channels in human odontoblasts in vitro. (United States)

    Ichikawa, Hideki; Kim, Hyong-Jung; Shuprisha, Apichai; Shikano, Tetsuo; Tsumura, Maki; Shibukawa, Yoshiyuki; Tazaki, Masakazu


    Transmembrane ionic signaling regulates many cellular processes in both physiological and pathologic settings. In this study, the biophysical properties of voltage-dependent Na(+) channels in odontoblasts derived from human dental pulp (HOB cells) were investigated together with the effect of bradykinin on intracellular Ca(2+) signaling and expression of Ca(2+)-activated K(+) channels. Ionic channel activity was characterized by using whole-cell patch-clamp recording and fura-2 fluorescence. Mean resting membrane potential in the HOB cells was -38 mV. Depolarizing steps from a holding potential of -80 mV activated transient voltage-dependent inward currents with rapid activation/inactivation properties. At a holding potential of -50 mV, no inward current was recorded. Fast-activation kinetics exhibited dependence on membrane potential, whereas fast-inactivation kinetics did not. Steady-state inactivation was described by a Boltzmann function with a half-maximal inactivation potential of -70 mV, indicating that whereas the channels were completely inactivated at physiological resting membrane potential, they could be activated when the cells were hyperpolarized. Inward currents disappeared in Na(+)-free extracellular solution. Bradykinin activated intracellular Ca(2+)-releasing and influx pathways. When the HOB cells were clamped at a holding potential of -50 mV, outward currents were recorded at positive potentials, indicating sensitivity to inhibitors of intermediate-conductance Ca(2+)-activated K(+) channels. Human odontoblasts expressed voltage-dependent Na(+) channels, bradykinin receptors, and Ca(2+)-activated K(+) channels, which play an important role in driving cellular functions by channel-receptor signal interaction and membrane potential regulation. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  4. Conotoxins as Tools to Understand the Physiological Function of Voltage-Gated Calcium (CaV Channels

    Directory of Open Access Journals (Sweden)

    David Ramírez


    Full Text Available Voltage-gated calcium (CaV channels are widely expressed and are essential for the completion of multiple physiological processes. Close regulation of their activity by specific inhibitors and agonists become fundamental to understand their role in cellular homeostasis as well as in human tissues and organs. CaV channels are divided into two groups depending on the membrane potential required to activate them: High-voltage activated (HVA, CaV1.1–1.4; CaV2.1–2.3 and Low-voltage activated (LVA, CaV3.1–3.3. HVA channels are highly expressed in brain (neurons, heart, and adrenal medulla (chromaffin cells, among others, and are also classified into subtypes which can be distinguished using pharmacological approaches. Cone snails are marine gastropods that capture their prey by injecting venom, “conopeptides”, which cause paralysis in a few seconds. A subset of conopeptides called conotoxins are relatively small polypeptides, rich in disulfide bonds, that target ion channels, transporters and receptors localized at the neuromuscular system of the animal target. In this review, we describe the structure and properties of conotoxins that selectively block HVA calcium channels. We compare their potency on several HVA channel subtypes, emphasizing neuronal calcium channels. Lastly, we analyze recent advances in the therapeutic use of conotoxins for medical treatments.

  5. Clinical features of neuromuscular disorders in patients with N-type voltage-gated calcium channel antibodies

    Directory of Open Access Journals (Sweden)

    Andreas Totzeck


    Full Text Available Neuromuscular junction disorders affect the pre- or postsynaptic nerve to muscle transmission due to autoimmune antibodies. Members of the group like myasthenia gravis and Lambert-Eaton syndrome have pathophysiologically distinct characteristics. However, in practice, distinction may be difficult. We present a series of three patients with a myasthenic syndrome, dropped-head syndrome, bulbar and respiratory muscle weakness and positive testing for anti-N-type voltage-gated calcium channel antibodies. In two cases anti-acetylcholin receptor antibodies were elevated, anti-P/Q-type voltage-gated calcium channel antibodies were negative. All patients initially responded to pyridostigmine with a non-response in the course of the disease. While one patient recovered well after treatment with intravenous immunoglobulins, 3,4-diaminopyridine, steroids and later on immunosuppression with mycophenolate mofetil, a second died after restriction of treatment due to unfavorable cancer diagnosis, the third patient declined treatment. Although new antibodies causing neuromuscular disorders were discovered, clinical distinction has not yet been made. Our patients showed features of pre- and postsynaptic myasthenic syndrome as well as severe dropped-head syndrome and bulbar and axial muscle weakness, but only anti-N-type voltage-gated calcium channel antibodies were positive. When administered, one patient benefited from 3,4-diaminopyridine. We suggest that this overlap-syndrome should be considered especially in patients with assumed seronegative myasthenia gravis and lack of improvement under standard therapy.

  6. Small-cell lung cancer with voltage-gated calcium channel antibody-positive paraneoplastic limbic encephalitis: a case report. (United States)

    Kaira, Kyoichi; Okamura, Takashi; Takahashi, Hiroki; Horiguchi, Norio; Sunaga, Noriaki; Hisada, Takeshi; Yamada, Masanobu


    Paraneoplastic limbic encephalitis is a rare neurological syndrome and clinically characterized by cognitive dysfunction, memory impairment, seizures and psychiatric symptoms. Paraneoplastic limbic encephalitis is most frequently found in small-cell lung cancer, among various malignancies, and antineuronal antibodies are related to the autoimmune mechanism. We experienced a rare case of a patient with small-cell lung cancer with anti-voltage-gated calcium channel antibody-positive paraneoplastic limbic encephalitis. A 61-year-old Japanese man with a history of smoking cigarettes presented with seizure, confusion and personality change in acute onset. Brain magnetic resonance imaging showed high signal intensity on T2-weighted image in his right temporal lobe, suggestive of limbic encephalitis. A mediastinoscopy of the lymph node revealed small-cell lung carcinoma, and he was staged as having limited stage disease. Antibodies against P/Q-type and N-type voltage-gated calcium channel were positive and Hu antibody was negative. He was started on chemotherapy of carboplatin plus etoposide with concurrent thoracic radiotherapy. Neurological symptoms were gradually improved after systemic chemotherapy. We should be alert to the potential of malignant neoplasms associated with paraneoplastic limbic encephalitis when we examine a patient with cancer with neurological disorders such as personality change, disorientation, unconsciousness and memory loss. A clinical marker such as voltage-gated calcium channel antibody may help our diagnosis in clinical practice.

  7. Improvement of Transformer Relay Protection Sensitivity with Wide Range of Voltage Control

    Directory of Open Access Journals (Sweden)

    V. V. Kourganov


    Full Text Available The paper shows that it is possible to increase a design sensitivity coefficient of the transformer relay protection with voltage switch  ∆UРПН= ±16%  due to application of more precise method for calculation of minimum and maximum short circuit currents beyond  a transformer with intermediate branches of  a load control switch that correspond to an actual voltage variation range in 110 kV networks.

  8. Alcohol Dependence Disrupts Amygdalar L-Type Voltage-Gated Calcium Channel Mechanisms. (United States)

    Varodayan, Florence P; de Guglielmo, Giordano; Logrip, Marian L; George, Olivier; Roberto, Marisa


    L-type voltage-gated calcium channels (LTCCs) are implicated in several psychiatric disorders that are comorbid with alcoholism and involve amygdala dysfunction. Within the amygdala, the central nucleus (CeA) is critical in acute alcohol's reinforcing actions, and its dysregulation in human alcoholics drives their negative emotional state and motivation to drink. Here we investigated the specific role of CeA LTCCs in the effects of acute alcohol at the molecular, cellular physiology, and behavioral levels, and their potential neuroadaptation in alcohol-dependent rats. Alcohol increases CeA activity (neuronal firing rates and GABA release) in naive rats by engaging LTCCs, and intra-CeA LTCC blockade reduces alcohol intake in nondependent rats. Alcohol dependence reduces CeA LTCC membrane abundance and disrupts this LTCC-based mechanism; instead, corticotropin-releasing factor type 1 receptors (CRF1s) mediate alcohol's effects on CeA activity and drive the escalated alcohol intake of alcohol-dependent rats. Collectively, our data indicate that alcohol dependence functionally alters the molecular mechanisms underlying the CeA's response to alcohol (from LTCC- to CRF1-driven). This mechanistic switch contributes to and reflects the prominent role of the CeA in the negative emotional state that drives excessive drinking.SIGNIFICANCE STATEMENT The central amygdala (CeA) plays a critical role in the development of alcohol dependence. As a result, much preclinical alcohol research aims to identify relevant CeA neuroadaptions that promote the transition to dependence. Here we report that acute alcohol increases CeA neuronal activity in naive rats by engaging L-type calcium channels (LTCCs) and that intra-CeA LTCC blockade reduces alcohol intake in nondependent rats. Alcohol dependence disrupts this LTCC-based mechanism; instead, corticotropin-releasing factor type 1 receptors (CRF1s) mediate alcohol's effects on CeA activity and drive the escalated alcohol intake of alcohol

  9. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels. (United States)

    Hansen, P B L


    Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore, by different mechanisms, T-type channels may contribute to both constriction and dilation of the arterioles. Finally, P-/Q-type channels are involved in the regulation of human intrarenal arterial contractility. The calcium blockers used in the clinic affect not only L-type but also P-/Q- and T-type channels. Therefore, the distinct effect obtained by inhibiting a given subtype or set of channels under experimental settings should be considered when choosing a calcium blocker for treatment. T-type channels seem to be crucial for regulating the GFR and the filtration fraction. Use of blockers is expected to lead to preferential efferent vasodilation, reduction of glomerular pressure and proteinuria. Therefore, renovascular T-type channels might provide novel therapeutic targets, and may have superior renoprotective effects compared to conventional calcium blockers. Acta Physiologica © 2013 Scandinavian Physiological Society.

  10. Asymmetrical Fault Correction for the Sensitive Loads Using a Current Regulated Voltage Source Inverter

    Directory of Open Access Journals (Sweden)

    Syed Sabir Hussain Bukhari


    Full Text Available Numerous industrial applications involve loads that are very sensitive to electrical supply instabilities. These instances involve various types of voltage imbalances as well as more serious disturbances such as symmetrical and asymmetrical faults. This paper proposes a cost-effective voltage imbalance and asymmetrical fault correction solution for the three phase sensitive loads utilizing an industry-standard current regulated voltage source inverter by connecting it in parallel to the grid mains powering to the sensitive load. The inverter regulates the current for the load and never permits it to go beyond a prescribed value under any type of asymmetrical fault condition, which ensures high power regulating and conditioning capacities. Experimental results are obtained from a small laboratory size prototype to validate the operation of the proposed technique.

  11. Sensitivity based Assessment of Transient Voltage Sags caused by Rotor Swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob


    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator...... on the voltage magnitude at a load bus and the effect of load variation on the generator’s power injection. It is shown that these sensitivities give valuable information to identify critical generator-load pairs and locations for applying preventive control measures....

  12. Derivation and application of sensitivities to assess transient voltage sags caused by rotor swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob


    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator...... on the voltage magnitude at a load bus and the effect of load variation on the generator’s power injection. It is shown that these sensitivities give valuable information to identify critical generator–load pairs and locations for applying preventive control measures....

  13. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora (United States)

    Senatore, Adriano; Raiss, Hamad; Le, Phuong


    Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it. PMID:27867359

  14. Physiology and evolution of voltage-gated calcium channels in early diverging animal phyla: Cnidaria, Placozoa, Porifera and Ctenophora

    Directory of Open Access Journals (Sweden)

    Adriano Senatore


    Full Text Available Voltage-gated calcium (Cav channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca2+ signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling, gene expression (excitation-transcription coupling, pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling, regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca2+-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when many of these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.

  15. Physiology and Evolution of Voltage-Gated Calcium Channels in Early Diverging Animal Phyla: Cnidaria, Placozoa, Porifera and Ctenophora. (United States)

    Senatore, Adriano; Raiss, Hamad; Le, Phuong


    Voltage-gated calcium (Cav) channels serve dual roles in the cell, where they can both depolarize the membrane potential for electrical excitability, and activate transient cytoplasmic Ca(2+) signals. In animals, Cav channels play crucial roles including driving muscle contraction (excitation-contraction coupling), gene expression (excitation-transcription coupling), pre-synaptic and neuroendocrine exocytosis (excitation-secretion coupling), regulation of flagellar/ciliary beating, and regulation of cellular excitability, either directly or through modulation of other Ca(2+)-sensitive ion channels. In recent years, genome sequencing has provided significant insights into the molecular evolution of Cav channels. Furthermore, expanded gene datasets have permitted improved inference of the species phylogeny at the base of Metazoa, providing clearer insights into the evolution of complex animal traits which involve Cav channels, including the nervous system. For the various types of metazoan Cav channels, key properties that determine their cellular contribution include: Ion selectivity, pore gating, and, importantly, cytoplasmic protein-protein interactions that direct sub-cellular localization and functional complexing. It is unclear when these defining features, many of which are essential for nervous system function, evolved. In this review, we highlight some experimental observations that implicate Cav channels in the physiology and behavior of the most early-diverging animals from the phyla Cnidaria, Placozoa, Porifera, and Ctenophora. Given our limited understanding of the molecular biology of Cav channels in these basal animal lineages, we infer insights from better-studied vertebrate and invertebrate animals. We also highlight some apparently conserved cellular functions of Cav channels, which might have emerged very early on during metazoan evolution, or perhaps predated it.

  16. Involvement of a pertussis toxin-sensitive G-protein in excitation-contraction coupling of intact and cut-end voltage-clamped skeletal muscle fibres. (United States)

    Mouzou, A; Poindessault, J P; Raymond, G


    In voltage-clamped frog muscle fibres 10 ng/ml PTX induced a decrease (approximately 35%) of tension when applied externally. Internal application in cut-end fibres significantly depressed tension after 20 min. This effect increased with time to reach 65% after 60 min. PTX shifted the voltage-dependent inactivation curve of tension by 30 mV towards hyperpolarizations and this was counteracted by raising external calcium concentration. The toxin induced a parallel decrease in tension and voltage-sensitive charge movement (49 +/- 9% and 52 +/- 6% respectively; n = 6). This was not counteracted by prior impregnation with forskolin. Internally applied GTP gamma S (500 microM) induced a simultaneous increase in tension (57 +/- 5%) and charge amount displaced (40 +/- 7%). By contrast, GDP beta S decreased tension and charge movement by 35 +/- 5% and 36 +/- 6% respectively.

  17. Sensitive detection of voltage transients using differential intensity surface plasmon resonance system. (United States)

    Abayzeed, Sidahmed A; Smith, Richard J; Webb, Kevin F; Somekh, Michael G; See, Chung W


    This paper describes theoretical and experimental study of the fundamentals of using surface plasmon resonance (SPR) for label-free detection of voltage. Plasmonic voltage sensing relies on the capacitive properties of metal-electrolyte interface that are governed by electrostatic interactions between charge carriers in both phases. Externally-applied voltage leads to changes in the free electron density in the surface of the metal, shifting the SPR position. The study shows the effects of the applied voltage on the shape of the SPR curve. It also provides a comparison between the theoretical and experimental response to the applied voltage. The response is presented in a universal term that can be used to assess the voltage sensitivity of different SPR instruments. Finally, it demonstrates the capacity of the SPR system in resolving dynamic voltage signals; a detection limit of 10mV with a temporal resolution of 5ms is achievable. These findings pave the way for the use of SPR systems in the detection of electrical activity of biological cells.

  18. α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor activation protects against phencyclidine-induced caspase-3 activity by activating voltage-gated calcium channels. (United States)

    Timpe, Jennifer M; Wang, Cheng Z; Kim, Jisoo; Johnson, Kenneth M


    Phencyclidine (PCP) is a noncompetitive, open channel blocker of the N-methyl-D-aspartate (NMDA) receptor-ion channel complex. When administered to immature animals, it is known to cause apoptotic neurodegeneration in several regions, and this is followed by olanzapine-sensitive, schizophrenia-like behaviors in late adolescence and adulthood. Clarification of its mechanism of action could yield data that would help to inform the treatment of schizophrenia. In our initial experiments, we found that α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) inhibited PCP-induced apoptosis in organotypic neonatal rat brain slices in a concentration-dependent and 6-cyano-7-nitroquinoxaline-2,3-dione-sensitive manner. Calcium signaling pathways are widely implicated in apoptosis, and PCP prevents calcium influx through NMDA receptor channels. We therefore hypothesized that AMPA could protect against this effect by activation of voltage-dependent calcium channels (VDCCs). In support of this hypothesis, pretreatment with the calcium channel blocker cadmium chloride eliminated AMPA-mediated protection against PCP. Furthermore, the L-type VDCC inhibitor nifedipine (10 µM) fully abrogated the effects of AMPA, suggesting that L-type VDCCs are required for AMPA-mediated protection against PCP-induced neurotoxicity. Whereas the P/Q-type inhibitor ω-agatoxin TK (200 nM) reduced AMPA protection by 51.7%, the N-type VDCC inhibitor ω-conotoxin (2 µM) had no effect. Decreased AMPA-mediated protection following cotreatment with K252a, a TrkB inhibitor, suggests that brain-derived neurotrophic factor signaling plays an important role. By analogy, these results suggest that activation of L-type, and to a lesser extent P/Q-type, VDCCs might be advantageous in treating conditions associated with diminished NMDAergic activity during early development. © 2014 Wiley Periodicals, Inc.

  19. Cloning, chromosomal localization, and functional expression of the alpha 1 subunit of the L-type voltage-dependent calcium channel from normal human heart

    NARCIS (Netherlands)

    Schultz, D; Mikala, G; Yatani, A; Engle, D B; Iles, D E; Segers, B; Sinke, R J; Weghuis, D O; Klöckner, U; Wakamori, M


    A unique structural variant of the cardiac L-type voltage-dependent calcium channel alpha 1 subunit cDNA was isolated from libraries derived from normal human heart mRNA. The deduced amino acid sequence shows significant homology to other calcium channel alpha 1 subunits. However, differences from

  20. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J


    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are i......Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons...... and are involved in the release of these peptides to different stimuli. We have examined the presence and importance of VGCCs in controlling the CGRP release from rat dura mater, freshly isolated trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Each of the four VGCCs, P/Q-, N-, and L- and T...... the potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ¿-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  1. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J


    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are i......Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons...... and are involved in the release of these peptides to different stimuli. We have examined the presence and importance of VGCCs in controlling the CGRP release from rat dura mater, freshly isolated trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Each of the four VGCCs, P/Q-, N-, and L- and T...... the potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ω-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  2. Diabetes-Induced Inhibition of Voltage-Dependent Calcium Channels in the Retinal Microvasculature: Role of Spermine (United States)

    Matsushita, Kenji; Fukumoto, Masanori; Kobayashi, Takatoshi; Kobayashi, Masato; Ishizaki, Eisuke; Minami, Masahiro; Katsumura, Kozo; Liao, Sophie D.; Wu, David M.; Zhang, Ting


    Purpose. Although decentralized control of blood flow is particularly important in the retina, knowledge of the functional organization of the retinal microvasculature is limited. Here, the authors characterized the distribution and regulation of L-type voltage-dependent calcium channels (VDCCs) within the most decentralized operational complex of the retinal vasculature—the feeder vessel/capillary unit—which consists of a capillary network plus the vessel linking it with a myocyte-encircled arteriole. Methods. Perforated-patch recordings, calcium-imaging, and time-lapse photography were used to assess VDCC-dependent changes in ionic currents, intracellular calcium, abluminal cell contractility, and lumen diameter, in microvascular complexes freshly isolated from the rat retina. Results. Topographical heterogeneity was found in the distribution of functional VDCCs; VDCC activity was markedly greater in feeder vessels than in capillaries. Experiments showed that this topographical distribution occurs, in large part, because of the inhibition of capillary VDCCs by a mechanism dependent on the endogenous polyamine spermine. An operational consequence of functional VDCCs predominantly located in the feeder vessels is that voltage-driven vasomotor responses are generated chiefly in this portion of the feeder vessel/capillary unit. However, early in the course of diabetes, this ability to generate voltage-driven vasomotor responses becomes profoundly impaired because of the inhibition of feeder vessel VDCCs by a spermine-dependent mechanism. Conclusions. The regulation of VDCCs by endogenous spermine not only plays a critical role in establishing the physiological organization of the feeder vessel/capillary unit, but also may contribute to dysfunction of this decentralized operational unit in the diabetic retina. PMID:20484578

  3. Lung adenocarcinoma with Lambert–Eaton myasthenic syndrome indicated by voltage-gated calcium channel: a case report

    Directory of Open Access Journals (Sweden)

    Arai Hiromasa


    Full Text Available Abstract Introduction Lambert–Eaton myasthenic syndrome is a rare disorder and it is known as a paraneoplastic neurological syndrome. Small cell lung cancer often accompanies this syndrome. Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma is extremely rare; there are only a few reported cases worldwide. Case presentation A 75-year-old Japanese man with a past history of chronic rheumatoid arthritis and Sjögren syndrome was diagnosed with Lambert–Eaton myasthenic syndrome by electromyography and serum anti-P/Q-type voltage-gated calcium channel antibody level preceding the diagnosis of lung cancer. A chest computed tomography to screen for malignant lesions revealed an abnormal shadow in the lung. Although a histopathological examination by bronchoscopic study could not reveal the malignancy, lung cancer was mostly suspected after the results of a chest computed tomography and [18F]-fluorodeoxyglucose positron emission tomography. An intraoperative diagnosis based on the frozen section obtained by tumor biopsy was adenocarcinoma so the patient underwent a lobectomy of the right lower lobe and lymph node dissection with video-assisted thoracoscopic surgery. The permanent pathological examination was the same as the frozen diagnosis (pT2aN1M0: Stage IIa: TNM staging 7th edition. Immunohistochemistry revealed that most of the cancer cells were positive for P/Q-type voltage-gated calcium channel. Conclusions Our case is a rare combination of Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma, rheumatoid arthritis and Sjögren syndrome, and to the best of our knowledge it is the first report that indicates the presence of voltage-gated calcium channel in lung adenocarcinoma by immunostaining.

  4. Simple sensitive radioreceptor assay for calcium antagonist drugs

    Energy Technology Data Exchange (ETDEWEB)

    Gould, R.J.; Murphy, K.M.M.; Snyder, S.H.


    A radioreceptor assay for calcium channel antagonist drugs described here is based on the ability of these drugs to affect /sup 3/H-nitrendipine binding to calcium channels. All the known calcium channel antagonists may be assayed in this manner. The assay can detect 10-100 nM nimodipine, 10-100 nM nifedipine, 3-30 prenylamine, 0.1 - 1.0 verapamil and 3-30 diltiazem. These values cover the range of concentrations of calcium channel antagonists that are clinically important. As the radioreceptor assay detects active metabolites as well as the parent drugs, it should prove a useful adjunct in cardiovascular therapy. The method is more reproducible, simpler and less expensive than other methods such as high pressure liquid chromatography.

  5. High sensitivity double relaxation oscillation superconducting quantum interference devices with large transfer from flux to voltage

    Energy Technology Data Exchange (ETDEWEB)

    Adelerhof, D.J.; Kawai, J.; Uehara, G.; Kado, H. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 303 (Japan)


    Double relaxation oscillation superconducting quantum interference devices (SQUIDs) (DROSs) based on Nb/AlO{sub {ital x}} tunnel junctions have been fabricated and characterized. The estimated relaxation frequencies range from 400 MHz up to 14 GHz. Transfer coefficients from flux to voltage of 2 up to 7 mV/{phi}{sub 0} have been obtained. Both the intrinsic flux noise and the performance in a flux-locked loop with direct-voltage readout have been determined. Special attention is paid to the effect of damping resistors on the sensitivity of DROSs. The intrinsic sensitivity improves with increasing relaxation frequency, leveling off to a value of 13{ital h} at relaxation frequencies above 2--3 GHz for SQUID inductances of about 30 pH. This sensitivity is very close to the theoretical maximum sensitivity of 6{ital h} of a comparable standard type dc SQUID. In a flux-locked loop based on direct-voltage readout, a noise level of 0.55 {mu}{phi}{sub 0}/{radical}Hz corresponding to an energy sensitivity of 34{ital h} has been obtained for a DROS with a SQUID inductance of 29 pH. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Voltage dependence of membrane charge movement and calcium release in frog skeletal muscle fibres. (United States)

    Rakowski, R F; Best, P M; James-Kracke, M R


    Voltage dependent membrane charge movement (gating current) and the release of Ca2+ from intracellular stores have been measured simultaneously in intact frog skeletal muscle fibres. Charge movement was measured using the three microelectrode voltage clamp technique. Ca2+ release was measured using the metallochromic indicator dye arsenazo III. Fibres were bathed in 2.3 X hypertonic solutions to prevent contraction. Rb+, tetraethylammonium and tetrodotoxin (TTX) were used to eliminate voltage-dependent ionic currents. The maximum rate of Ca2+ release from the sarcoplasmic reticulum in response to voltage-clamp step depolarizations to 0 mV was calculated using the dye-related parameters of model 2 of Baylor et al. (1983) and a method described in the Appendix for calculating a scaling factor (1 + p) that accounts for the additional Ca2+ buffering power of the indicator dye. The estimates of the maximum rate of Ca2+ release at 5-6 degrees C ranged from 3 to 19 microM ms-1 in the 17 fibres examined. The mean value was 8.9 +/- 1.1 microM ms-1 (S.E.M.) The maximum rate of Ca2+ release was linearly related to the magnitude of the nonlinear membrane change moved during suprathreshold depolarizing steps. The voltage dependence of charge movement and the maximum rate of Ca2+ releases were nearly identical at 6 degrees C. The voltage-dependence of the delay between the test step and the onset of Ca2+ release could be adequately described by an equation having the same functional form as the voltage dependence of nonlinear charge movement. The relationship between the test pulse voltage and the delay was shifted to more negative voltages and to shorter delays as the temperature was raised from 6 degrees C to 15 degrees C. The inactivation of Ca2+ release was found to occur at more negative holding voltages and to be more steeply voltage dependent than the immobilization of nonlinear membrane charge movement. The above data are discussed using the 'hypothetical coupler' model

  7. Bio-Inspired Carbon Monoxide Sensors with Voltage-Activated Sensitivity

    KAUST Repository

    Savagatrup, Suchol


    Carbon monoxide (CO) outcompetes oxygen when binding to the iron center of hemeproteins, leading to a reduction in blood oxygen level and acute poisoning. Harvesting the strong specific interaction between CO and the iron porphyrin provides a highly selective and customizable sensor. We report the development of chemiresistive sensors with voltage-activated sensitivity for the detection of CO comprising iron porphyrin and functionalized single-walled carbon nanotubes (F-SWCNTs). Modulation of the gate voltage offers a predicted extra dimension for sensing. Specifically, the sensors show a significant increase in sensitivity toward CO when negative gate voltage is applied. The dosimetric sensors are selective to ppm levels of CO and functional in air. UV/Vis spectroscopy, differential pulse voltammetry, and density functional theory reveal that the in situ reduction of FeIII to FeII enhances the interaction between the F-SWCNTs and CO. Our results illustrate a new mode of sensors wherein redox active recognition units are voltage-activated to give enhanced and highly specific responses.

  8. Bio-Inspired Carbon Monoxide Sensors with Voltage-Activated Sensitivity. (United States)

    Savagatrup, Suchol; Schroeder, Vera; He, Xin; Lin, Sibo; He, Maggie; Yassine, Omar; Salama, Khaled N; Zhang, Xi-Xiang; Swager, Timothy M


    Carbon monoxide (CO) outcompetes oxygen when binding to the iron center of hemeproteins, leading to a reduction in blood oxygen level and acute poisoning. Harvesting the strong specific interaction between CO and the iron porphyrin provides a highly selective and customizable sensor. We report the development of chemiresistive sensors with voltage-activated sensitivity for the detection of CO comprising iron porphyrin and functionalized single-walled carbon nanotubes (F-SWCNTs). Modulation of the gate voltage offers a predicted extra dimension for sensing. Specifically, the sensors show a significant increase in sensitivity toward CO when negative gate voltage is applied. The dosimetric sensors are selective to ppm levels of CO and functional in air. UV/Vis spectroscopy, differential pulse voltammetry, and density functional theory reveal that the in situ reduction of FeIII to FeII enhances the interaction between the F-SWCNTs and CO. Our results illustrate a new mode of sensors wherein redox active recognition units are voltage-activated to give enhanced and highly specific responses. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Neurotransmitter Release Can Be Stabilized by a Mechanism That Prevents Voltage Changes Near the End of Action Potentials from Affecting Calcium Currents. (United States)

    Clarke, Stephen G; Scarnati, Matthew S; Paradiso, Kenneth G


    At chemical synapses, presynaptic action potentials (APs) activate voltage-gated calcium channels, allowing calcium to enter and trigger neurotransmitter release. The duration, peak amplitude, and shape of the AP falling phase alter calcium entry, which can affect neurotransmitter release significantly. In many neurons, APs do not immediately return to the resting potential, but instead exhibit a period of depolarization or hyperpolarization referred to as an afterpotential. We hypothesized that presynaptic afterpotentials should alter neurotransmitter release by affecting the electrical driving force for calcium entry and calcium channel gating. In support of this, presynaptic calcium entry is affected by afterpotentials after standard instant voltage jumps. Here, we used the mouse calyx of Held synapse, which allows simultaneous presynaptic and postsynaptic patch-clamp recording, to show that the postsynaptic response is affected significantly by presynaptic afterpotentials after voltage jumps. We therefore tested the effects of presynaptic afterpotentials using simultaneous presynaptic and postsynaptic recordings and AP waveforms or real APs. Surprisingly, presynaptic afterpotentials after AP stimuli did not alter calcium channel responses or neurotransmitter release appreciably. We show that the AP repolarization time course causes afterpotential-induced changes in calcium driving force and changes in calcium channel gating to effectively cancel each other out. This mechanism, in which electrical driving force is balanced by channel gating, prevents changes in calcium influx from occurring at the end of the AP and therefore acts to stabilize synaptic transmission. In addition, this mechanism can act to stabilize neurotransmitter release when the presynaptic resting potential changes. The shape of presynaptic action potentials (APs), particularly the falling phase, affects calcium entry and small changes in calcium influx can produce large changes in

  10. Spectral Properties and Orientation of Voltage-Sensitive Dyes in Lipid Membranes

    KAUST Repository

    Matson, Maria


    Voltage-sensitive dyes are frequently used for probing variations in the electric potential across cell membranes. The dyes respond by changing their spectral properties: measured as shifts of wavelength of absorption or emission maxima or as changes of absorption or fluorescence intensity. Although such probes have been studied and used for decades, the mechanism behind their voltage sensitivity is still obscure. We ask whether the voltage response is due to electrochromism as a result of direct field interaction on the chromophore or to solvatochromism, which is the focus of this study, as result of changed environment or molecular alignment in the membrane. The spectral properties of three styryl dyes, di-4-ANEPPS, di-8-ANEPPS, and RH421, were investigated in solvents of varying polarity and in model membranes using spectroscopy. Using quantum mechanical calculations, the spectral dependence of monomer and dimer ANEPPS on solvent properties was modeled. Also, the kinetics of binding to lipid membranes and the binding geometry of the probe molecules were found relevant to address. The spectral properties of all three probes were found to be highly sensitive to the local environment, and the probes are oriented nearly parallel with the membrane normal. Slow binding kinetics and scattering in absorption spectra indicate, especially for di-8-ANEPPS, involvement of aggregation. On the basis of the experimental spectra and time-dependent density functional theory calculations, we find that aggregate formation may contribute to the blue-shifts seen for the dyes in decanol and when bound to membrane models. In conclusion, solvatochromic and other intermolecular interactions effects also need to be included when considering electrochromic response voltage-sensitive dyes. © 2012 American Chemical Society.

  11. Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina (United States)

    Müller, Luis Pérez de Sevilla; Sargoy, Allison; Fernández-Sánchez, Laura; Rodriguez, Allen; Liu, Janelle; Cuenca, Nicolás; Brecha, Nicholas


    High voltage activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes including the influx of extracellular Ca2+, neurotransmitter release, gene transcription and synaptic plasticity. These channels consist of a primary α1 pore-forming subunit, which is associated with an extracellular α2δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α2δ3 subunit in the mouse and rat retina is unknown. In this study, using RT-PCR a single band at ~305 bp corresponding to the predicted size of the α2δ3 subunit fragment was in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123 kDa band. Immunohistochemistry using an affinity purified antibody to the α2δ3 subunit revealed immunoreactive cell bodies in the ganglion cell layer (GCL) and inner nuclear layer (INL), and immunoreactive processes in the inner plexiform layer (IPL) and the outer plexiform layer (OPL). α2δ3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine and bipolar cells, and photoreceptors, but not by horizontal cells. The expression of the α2δ3 calcium channel subunit to multiple cell types suggests this subunit participates widely in Ca channel-mediated signaling in the retina. PMID:25631988

  12. Voltage-activated currents through calcium channels in normal bovine lactotrophs. (United States)

    Cobbett, P; Ingram, C D; Mason, W T


    The properties of whole cell Ba2+ currents were studied in immunocytochemically identified, normal bovine lactotrophs using the patch clamp technique. In the current clamp mode, current-induced and spontaneous Ba2+ action potentials were recorded. These were of longer duration and showed less inactivation with stimulation frequency when compared with Na+ action potentials. Under voltage clamp, isolated Ba2+ currents had an activation threshold of about -35 mV and peak value at -15 mV to +20 mV. Inactivation of the current to a potential-dependent, non-zero steady-state level indicated the presence of one rapidly and one slowly inactivating component to the current. These two components were also distinguished by: (1) the voltage dependence of the inactivation time constant of the current, (2) the differential frequency-dependent inactivation of the peak and steady-state currents, and (3) the presence of two half-inactivation potentials for the current. Analysis of the ensemble current variance of the non-inactivating component gave a single-channel amplitude of 0.19 pA at 0 mV and a slope conductance of 3 pS. Fluctuation analysis of the voltage-activated Ba2+ current noise revealed two time constants, one which was voltage dependent and the other was independent of potential. The contribution of these two currents to Ca2+-dependent hormone secretion remains to be clarified.

  13. Calcium Electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha


    BACKGROUND: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill...... efficacy-and normal cell sensitivity. METHODS: Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780......), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). RESULTS: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p

  14. Second and third generation voltage-sensitive fluorescent proteins for monitoring membrane potential

    Directory of Open Access Journals (Sweden)

    Amelie Perron


    Full Text Available Over the last decade, optical neuroimaging methods have been enriched by engineered biosensors derived from fluorescent protein (FP reporters fused to protein detectors that convert physiological signals into changes of intrinsic FP fluorescence. These FP-based indicators are genetically encoded, and hence targetable to specific cell populations within networks of heterologous cell types. Among this class of biosensors, the development of optical probes for membrane potential is both highly desirable and challenging. A suitable FP voltage sensor would indeed be a valuable tool for monitoring the activity of thousands of individual neurons simultaneously in a non-invasive manner. Previous prototypic genetically-encoded FP voltage indicators achieved a proof of principle but also highlighted several difficulties such as poor cell surface targeting and slow kinetics. Recently, we developed a new series of FRET-based Voltage-Sensitive Fluorescent Proteins (VSFPs, referred to as VSFP2s, with efficient targeting to the plasma membrane and high responsiveness to membrane potential signaling in excitable cells. In addition to these FRET-based voltage sensors, we also generated a third series of probes consisting of single FPs with response kinetics suitable for the optical imaging of fast neuronal signals. These newly available genetically-encoded reporters for membrane potential will be instrumental for future experimental approaches directed toward the understanding of neuronal network dynamics and information processing in the brain. Here, we review the development and current status of these novel fluorescent probes.

  15. Imaging Neuronal Seal Resistance on Silicon Chip using Fluorescent Voltage-Sensitive Dye (United States)

    Braun, Dieter; Fromherz, Peter


    The electrical sheet resistance between living cells grown on planar electronic contacts of semiconductors or metals is a crucial parameter for bioelectronic devices. It determines the strength of electrical signal transduction from cells to chips and from chips to cells. We measured the sheet resistance by applying AC voltage to oxidized silicon chips and by imaging the voltage change across the attached cell membrane with a fluorescent voltage-sensitive dye. The phase map of voltage change was fitted with a planar core-coat conductor model using the sheet resistance as a free parameter. For nerve cells from rat brain on polylysine as well as for HEK293 cells and MDCK cells on fibronectin we find a similar sheet resistance of 10 MΩ. Taking into account the independently measured distance of 50 nm between chip and membrane for these cells, we obtain a specific resistance of 50 Ωcm that is indistinguishable from bulk electrolyte. On the other hand, the sheet resistance for erythrocytes on polylysine is far higher, at ∼1.5 GΩ. Considering the distance of 10 nm, the specific resistance in the narrow cleft is enhanced to 1500 Ωcm. We find this novel optical method to be a convenient tool to optimize the interface between cells and chips for bioelectronic devices. PMID:15298937

  16. desensitisation and calcium-sensitivity in the isolated perfused rat ...

    African Journals Online (AJOL)

    Dr Olaleye

    1) to 2.35 (for calcium buffer 6); glucose11.1; cocaine, 4μM; propranolol, 1μM; and EDTA. (ethylenediaminetetra-acetic acid disodium salt), 23μM. The composition of the series of buffered salines is shown in table 1. Another saline solution used in some experiments (examining the Ca2+ dependence of the contraction ...

  17. Calcium (United States)

    ... Turn to calcium-fortified (or "calcium-set") tofu, soy milk, tempeh, soy yogurt, and cooked soybeans (edamame). Calcium-fortified foods. Look for calcium-fortified orange juice, soy or rice milk, breads, and cereal. Beans. You can get decent ...

  18. Structure-function of proteins interacting with the alpha1 pore-forming subunit of high voltage-activated calcium channel

    Directory of Open Access Journals (Sweden)

    Alan eNeely


    Full Text Available Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, high-voltage-activated calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1 associated with four additional polypeptide chains β, α2, δ and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of high-voltage-activated calcium channels.

  19. 'Blue' voltage-sensitive dyes for studying spatiotemporal dynamics in the brain: visualizing cortical waves. (United States)

    Geng, Xinling; Wu, Jian-Young


    Among many distinct contributions made by Amiram Grinvald's group, the "Blue dyes" is a special gift for visualizing cortical population neuronal activity. The excitation wavelength of blue dyes has minimal overlap with the absorption of hemoglobin, and hence has minimal pulsation artifacts. This advantage leads to high signal-to-noise ratio optical recordings of cortical activity, with sensitivity as good as that of local field potential recordings. High sensitivity imaging allows for recording of spontaneous and evoked activity in single trials without spatial or temporal averaging, and has benefitted many scientists in their research projects. Single trial recording is particularly important for studying the cortex, because spontaneous and ongoing activities interact with sensory evoked events, creating rich dynamics in the wave patterns. Signal averaging in space and time would diminish the dynamic components in the patterns. Here, we discuss how the blue dyes help to achieve high-sensitivity voltage-sensitive dye imaging of spontaneous and evoked cortical activities. Spontaneous cortical activity has a constantly changing spatial pattern and temporal frequency, making it impossible to average in space and time. Amiran Grinvald's invention of blue dyes made it possible to examine the spatiotemporal patterns of cortical dynamics, about 15 years before the first useful genetically coded voltage proteins became available.

  20. Transmembrane potential measurements on plant cells using the voltage-sensitive dye ANNINE-6. (United States)

    Flickinger, Bianca; Berghöfer, Thomas; Hohenberger, Petra; Eing, Christian; Frey, Wolfgang


    The charging of the plasma membrane is a necessary condition for the generation of an electric-field-induced permeability increase of the plasmalemma, which is usually explained by the creation and the growth of aqueous pores. For cells suspended in physiological buffers, the time domain of membrane charging is in the submicrosecond range. Systematic measurements using Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) protoplasts stained with the fast voltage-sensitive fluorescence dye ANNINE-6 have been performed using a pulsed laser fluorescence microscopy setup with a time resolution of 5 ns. A clear saturation of the membrane voltage could be measured, caused by a strong membrane permeability increase, commonly explained by enhanced pore formation, which prevents further membrane charging by external electric field exposure. The field strength dependence of the protoplast's transmembrane potential V (M) shows strong asymmetric saturation characteristics due to the high resting potential of the plants plasmalemma. At the pole of the hyperpolarized hemisphere of the cell, saturation starts at an external field strength of 0.3 kV/cm, resulting in a measured transmembrane voltage shift of ∆V(M) = -150 mV, while on the cathodic (depolarized) cell pole, the threshold for enhanced pore formation is reached at a field strength of approximately 1.0 kV/cm and ∆V(M) = 450 mV, respectively. From this asymmetry of the measured maximum membrane voltage shifts, the resting potential of BY-2 protoplasts at the given experimental conditions can be determined to V(R) = -150 mV. Consequently, a strong membrane permeability increase occurs when the membrane voltage diverges |V(M)| = 300 mV from the resting potential of the protoplast. The largest membrane voltage change at a given external electric field occurs at the cell poles. The azimuthal dependence of the transmembrane potential, measured in angular intervals of 10° along the circumference of the cell, shows a flattening

  1. Three native somatostatin isoforms differentially affect membrane voltage-sensitive ion currents in goldfish somatotrophs. (United States)

    Yu, Y; Ali, D W; Chang, J P


    Message encoding for three isoforms of somatostatin (SS) peptides, SS-14, goldfish brain (gb)SS-28 and [Pro²]SS-14, are expressed in goldfish hypothalamus and pituitary tissues. All three native goldfish SSs are active in reducing basal and stimulated growth hormone (GH) responses in cultured goldfish pituitary cells, although with different potencies and efficacies. In the present study, we examined the effects of these three endogenous SSs on electrophysiological properties of goldfish somatotrophs and their physiological relevance. Voltage-sensitive K+ , Ca²+ and Na+ channels in identified goldfish somatotrophs in primary culture were isolated using whole-cell, amphotericin B-perforated patch-clamp techniques. None of the three SSs affected Na+ currents but all three SSs increased maximal K+ current magnitude, with SS-14 being the most effective. [Pro²]SS14 did not affect Ba²+ currents through voltage-sensitive Ca²+ channels but SS14 decreased the magnitude of early and late Ba²+ currents, whereas gbSS-28 reduced that of the late Ba²+ current. Under current-clamp conditions, SS14 and gbSS28 attenuated evoked action potential magnitudes by 34% and 18%, respectively, although [Pro²]SS14 had no effects. However, all three SSs decreased basal intracellular Ca²+ levels ([Ca²+ ](i)) and suppressed basal GH release. These data suggest that, although the ability of SS-14 and gbSS-28 to decrease basal [Ca²+](i) and GH release can be explained, at least in part, by their attenuating effects on cell excitability and current flow through voltage-sensitive Ca²+ channels, [Pro²]SS14-induced reduction in GH responses and [Ca²+](i) cannot be explained by changes in Ca²+ channel properties. © 2010 The Authors. Journal of Neuroendocrinology © 2010 Blackwell Publishing Ltd.

  2. Seeing the forest through the trees: towards a unified view on physiological calcium regulation of voltage-gated sodium channels. (United States)

    Van Petegem, Filip; Lobo, Paolo A; Ahern, Christopher A


    Voltage-gated sodium channels (Na(V)s) underlie the upstroke of the action potential in the excitable tissues of nerve and muscle. After opening, Na(V)s rapidly undergo inactivation, a crucial process through which sodium conductance is negatively regulated. Disruption of inactivation by inherited mutations is an established cause of lethal cardiac arrhythmia, epilepsy, or painful syndromes. Intracellular calcium ions (Ca(2+)) modulate sodium channel inactivation, and multiple players have been suggested in this process, including the cytoplasmic Na(V) C-terminal region including two EF-hands and an IQ motif, the Na(V) domain III-IV linker, and calmodulin. Calmodulin can bind to the IQ domain in both Ca(2+)-bound and Ca(2+)-free conditions, but only to the DIII-IV linker in a Ca(2+)-loaded state. The mechanism of Ca(2+) regulation, and its composite effect(s) on channel gating, has been shrouded in much controversy owing to numerous apparent experimental inconsistencies. Herein, we attempt to summarize these disparate data and propose a novel, to our knowledge, physiological mechanism whereby calcium ions promote sodium current facilitation due to Ca(2+) memory at high-action-potential frequencies where Ca(2+) levels may accumulate. The available data suggest that this phenomenon may be disrupted in diseases where cytoplasmic calcium ion levels are chronically high and where targeted phosphorylation may decouple the Ca(2+) regulatory machinery. Many Na(V) disease mutations associated with electrical dysfunction are located in the Ca(2+)-sensing machinery and misregulation of Ca(2+)-dependent channel modulation is likely to contribute to disease phenotypes. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. The L-Type Voltage-Gated Calcium Channel Ca [subscript V] 1.2 Mediates Fear Extinction and Modulates Synaptic Tone in the Lateral Amygdala (United States)

    Temme, Stephanie J.; Murphy, Geoffrey G.


    L-type voltage-gated calcium channels (LVGCCs) have been implicated in both the formation and the reduction of fear through Pavlovian fear conditioning and extinction. Despite the implication of LVGCCs in fear learning and extinction, studies of the individual LVGCC subtypes, Ca[subscript V]1.2 and Ca[subscript V] 1.3, using transgenic mice have…

  4. Calcium-sensitivity of smooth muscle contraction in the isolated ...

    African Journals Online (AJOL)

    sensitivity of smooth muscle contraction were studied in the isolated perfused rat tail artery, employing the activators noradrenaline (NA) (3ìM) sand potassium chloride (KC1) (100mM). Experiments were conduced in Ca2+ - buffered saline.

  5. Persistent slow inward calcium current in voltage-clamped hippocampal neurones of the guinea-pig. (United States)

    Brown, D A; Griffith, W H


    CA1 and CA3 neurones in transverse slices of guinea-pig hippocampus were voltage clamped through a single micro-electrode, and perfused with Krebs solution containing 0.5 microM-tetrodotoxin and 10 mM-tetraethylammonium at (normally) 24-26 degrees C. Slow inward currents of less than or equal to 0.5 nA were recorded during depolarizing voltage commands to membrane potentials positive to between -40 and -30 mV. These currents peaked at 100-300 msec after the onset of the depolarizing command, then subsequently declined during continuing depolarization. This decline could be ascribed to a developing outward current since repolarizing inward current tails showed no diminution up to 700 msec. No clear evidence for time-dependent inactivation of the inward current could be obtained. A persistent component of inward current could be detected when the membrane potential was maintained above the inward current threshold, such that small hyperpolarizing commands induced an outward relaxation and large hyperpolarizations produced an inward tail current. The inward current was depressed by removing external Ca, or by adding 0.2-0.5 mM-Cd, or 0.1 mM-verapamil, and was increased by adding 1 mM-Ba. A possible role for this persistent inward current in generating the slow membrane depolarization underlying burst discharges in these neurones is discussed. In some neurones (primarily CA1), an additional fast spike-like current was recorded, which was blocked by Cd or Mn and depressed by a depolarizing pre-pulse. It is suggested that this was a manifestation of the previously-reported dendritic Ca spike.

  6. calcium-sensitivity of smooth muscle contraction in the isolated ...

    African Journals Online (AJOL)

    Dr Olaleye

    The peaked first curve makes correction of responses to ringer-tissue variability difficult. Furthermore, comparison of Ca2+ sensitivity in different conditions, even in a single tissue, is not straightforward when the “slope” and maximum are changing. We have expressed all pressor responses as a percentage of the 1st ...

  7. Computational optogenetics: empirically-derived voltage- and light-sensitive channelrhodopsin-2 model.

    Directory of Open Access Journals (Sweden)

    John C Williams

    Full Text Available Channelrhodospin-2 (ChR2, a light-sensitive ion channel, and its variants have emerged as new excitatory optogenetic tools not only in neuroscience, but also in other areas, including cardiac electrophysiology. An accurate quantitative model of ChR2 is necessary for in silico prediction of the response to optical stimulation in realistic tissue/organ settings. Such a model can guide the rational design of new ion channel functionality tailored to different cell types/tissues. Focusing on one of the most widely used ChR2 mutants (H134R with enhanced current, we collected a comprehensive experimental data set of the response of this ion channel to different irradiances and voltages, and used these data to develop a model of ChR2 with empirically-derived voltage- and irradiance- dependence, where parameters were fine-tuned via simulated annealing optimization. This ChR2 model offers: 1 accurate inward rectification in the current-voltage response across irradiances; 2 empirically-derived voltage- and light-dependent kinetics (activation, deactivation and recovery from inactivation; and 3 accurate amplitude and morphology of the response across voltage and irradiance settings. Temperature-scaling factors (Q10 were derived and model kinetics was adjusted to physiological temperatures. Using optical action potential clamp, we experimentally validated model-predicted ChR2 behavior in guinea pig ventricular myocytes. The model was then incorporated in a variety of cardiac myocytes, including human ventricular, atrial and Purkinje cell models. We demonstrate the ability of ChR2 to trigger action potentials in human cardiomyocytes at relatively low light levels, as well as the differential response of these cells to light, with the Purkinje cells being most easily excitable and ventricular cells requiring the highest irradiance at all pulse durations. This new experimentally-validated ChR2 model will facilitate virtual experimentation in neural and

  8. Distribution of high-voltage-activated calcium channels in cultured gamma-aminobutyric acidergic neurons from mouse cerebral cortex. (United States)

    Timmermann, Daniel B; Westenbroek, Ruth E; Schousboe, Arne; Catterall, William A


    The localization of voltage-gated calcium channel (VGCC) alpha(1) subunits in cultured GABAergic mouse cortical neurons was examined by immunocytochemical methods. Ca(v)1.2 and Ca(v)1.3 subunits of L-type VGCCs were found in cell bodies and dendrites of GABA-immunopositive neurons. Likewise, the Ca(v)2.3 subunit of R-type VGCCs was expressed in a somatodendritic pattern. Ca(v)2.2 subunits of N-type channels were found exclusively in small varicosities that were identified as presynaptic nerve terminals based on their expression of synaptic marker proteins. Two splice variants of the Ca(v)2.1 subunit of P/Q-type VGCCs showed widely differing expression patterns. The rbA isoform displayed a purely somatodendritic staining pattern, whereas the BI isoform was confined to axon-like fibers and nerve terminals. The nerve terminals of these cultured GABAergic neurons express Ca(v)2.2 either alone or in combination with Ca(v)2.1 (BI isoform) but never express Ca(v)2.1 alone. The functional association between VGCCs and the neurotransmitter release machinery was probed using the FM1-43 dye-labeling technique. N-type VGCCs were found to be tightly coupled to exocytosis in these cultured cortical neurons, and P-type VGCCs were also important in a fraction of the cells. The predominant role of N-type VGCCs in neurotransmitter release and the specific localization of the BI isoform of Ca(v)2.1 in the nerve terminals of these neurons distinguish them from previously studied central neurons. The complementary localization patterns observed for two different isoforms of the Ca(v)2.1 subunits provide direct evidence for alternative splicing as a means of generating functional diversity among neuronal calcium channels. Copyright 2002 Wiley-Liss, Inc.

  9. Antispasmodic and vasodilator activities of Morinda citrifolia root extract are mediated through blockade of voltage dependent calcium channels. (United States)

    Gilani, Anwarul Hassan; Mandukhail, Saf-ur-Rehman; Iqbal, Javeid; Yasinzai, Masoom; Aziz, Nauman; Khan, Aslam; Najeeb-ur-Rehman


    Morinda citrifolia (Noni) is an edible plant with wide range of medicinal uses. It occurs exclusively in tropical climate zone from India through Southeast Asia and Australia to Eastern Polynesia and Hawaii. The objective of this study was to explore the possible mode(s) of action for its antispasmodic, vasodilator and cardio-suppressant effects to rationalize its medicinal use in gut and cardiovascular disorders. Isolated tissue preparations such as, rabbit jejunum, rat and rabbit aorta and guinea pig atria were used to test the antispasmodic and cardiovascular relaxant effects and the possible mode of action(s) of the 70% aqueous-ethanolic extract of Morinda citrifolia roots (Mc.Cr). The Mc.Cr produced a concentration-dependent relaxation of spontaneous and high K(+) induced contractions in isolated rabbit jejunum preparations. It also caused right ward shift in the concentration response curves of Ca(++), similar to that of verapamil. In guinea-pig right atria, Mc.Cr caused inhibition of both atrial force and rate of spontaneous contractions. In rabbit thoracic aortic preparations, Mc.Cr also suppressed contractions induced by phenylephrine (1.0 μM) in normal- Ca(++) and Ca(++)-free kreb solutions and by high K(+), similar to that of verapamil. In rat thoracic aortic preparations, Mc.Cr also relaxed the phenylephrine (1.0 μM)-induced contractions. The vasodilatory responses were not altered in the presence of L-NAME (0.1 mM) or atropine (1.0 μM) and removal of endothelium. These results suggest that the spasmolytic and vasodilator effects of Mc.Cr root extract are mediated possibly through blockade of voltage-dependent calcium channels and release of intracellular calcium, which may explain the medicinal use of Morinda citrifolia in diarrhea and hypertension. However, more detailed studies are required to assess the safety and efficacy of this plant.

  10. Electromagnetic fields act via activation of voltage-gated calcium channels to produce beneficial or adverse effects. (United States)

    Pall, Martin L


    The direct targets of extremely low and microwave frequency range electromagnetic fields (EMFs) in producing non-thermal effects have not been clearly established. However, studies in the literature, reviewed here, provide substantial support for such direct targets. Twenty-three studies have shown that voltage-gated calcium channels (VGCCs) produce these and other EMF effects, such that the L-type or other VGCC blockers block or greatly lower diverse EMF effects. Furthermore, the voltage-gated properties of these channels may provide biophysically plausible mechanisms for EMF biological effects. Downstream responses of such EMF exposures may be mediated through Ca(2+) /calmodulin stimulation of nitric oxide synthesis. Potentially, physiological/therapeutic responses may be largely as a result of nitric oxide-cGMP-protein kinase G pathway stimulation. A well-studied example of such an apparent therapeutic response, EMF stimulation of bone growth, appears to work along this pathway. However, pathophysiological responses to EMFs may be as a result of nitric oxide-peroxynitrite-oxidative stress pathway of action. A single such well-documented example, EMF induction of DNA single-strand breaks in cells, as measured by alkaline comet assays, is reviewed here. Such single-strand breaks are known to be produced through the action of this pathway. Data on the mechanism of EMF induction of such breaks are limited; what data are available support this proposed mechanism. Other Ca(2+) -mediated regulatory changes, independent of nitric oxide, may also have roles. This article reviews, then, a substantially supported set of targets, VGCCs, whose stimulation produces non-thermal EMF responses by humans/higher animals with downstream effects involving Ca(2+) /calmodulin-dependent nitric oxide increases, which may explain therapeutic and pathophysiological effects. © 2013 The Author. Journal of Cellular and Molecular Medicine Published by Foundation for Cellular and Molecular

  11. Sigma-1 receptor agonist increases axon outgrowth of hippocampal neurons via voltage-gated calcium ions channels. (United States)

    Li, Dong; Zhang, Shu-Zhuo; Yao, Yu-Hong; Xiang, Yun; Ma, Xiao-Yun; Wei, Xiao-Li; Yan, Hai-Tao; Liu, Xiao-Yan


    Sigma-1 receptors (Sig-1Rs) are unique endoplasmic reticulum proteins that have been implicated in both neurodegenerative and ischemic diseases, such as Alzheimer's disease and stroke. Accumulating evidence has suggested that Sig-1R plays a role in neuroprotection and axon outgrowth. The underlying mechanisms of Sig-1R-mediated neuroprotection have been well elucidated. However, the mechanisms underlying the effects of Sig-1R on axon outgrowth are not fully understood. To clarify this issue, we utilized immunofluorescence to compare the axon lengths of cultured naïve hippocampal neurons before and after the application of the Sig-1R agonist, SA4503. Then, electrophysiology and immunofluorescence were used to examine voltage-gated calcium ion channel (VGCCs) currents in the cell membranes and growth cones. We found that Sig-1R activation dramatically enhanced the axonal length of the naïve hippocampal neurons. Application of the Sig-1R antagonist NE100 and gene knockdown techniques both demonstrated the effects of Sig-1R. The growth-promoting effect of SA4503 was accompanied by the inhibition of voltage-gated Ca2+ influx and was recapitulated by incubating the neurons with the L-type, N-type, and P/Q-type VGCC blockers, nimodipine, MVIIA and ω-agatoxin IVA, respectively. This effect was unrelated to glial cells. The application of SA4503 transformed the growth cone morphologies from complicated to simple, which favored axon outgrowth. Sig-1R activation can enhance axon outgrowth and may have a substantial influence on neurogenesis and neurodegenerative diseases. © 2017 John Wiley & Sons Ltd.

  12. Modulation of Low-Voltage-Activated Inward Current Permeable to Sodium and Calcium by DARPP-32 Drives Spontaneous Firing of Insect Octopaminergic Neurosecretory Cells. (United States)

    Lapied, Bruno; Defaix, Antoine; Stankiewicz, Maria; Moreau, Eléonore; Raymond, Valérie


    Identification of the different intracellular pathways that control phosphorylation/dephosphorylation process of ionic channels represents an exciting alternative approach for studying the ionic mechanisms underlying neuronal pacemaker activity. In the central nervous system of the cockroach Periplaneta americana, octopaminergic neurons, called dorsal unpaired median (DUM; DUM neurons), generate spontaneous repetitive action potentials. Short-term cultured adult DUM neurons isolated from the terminal abdominal ganglion (TAG) of the nerve cord were used to study the regulation of a tetrodotoxin-sensitive low-voltage-activated (LVA) channel permeable to sodium and calcium (Na/Ca), under whole cell voltage- and current-clamp conditions. A bell-shaped curve illustrating the regulation of the amplitude of the maintained current vs. [ATP]i was observed. This suggested the existence of phosphorylation mechanisms. The protein kinase A (PKA) inhibitor, H89 and elevating [cyclic adenosine 3', 5' monophosphate, cAMP]i, increased and decreased the current amplitude, respectively. This indicated a regulation of the current via a cAMP/PKA cascade. Furthermore, intracellular application of PP2B inhibitors, cyclosporine A, FK506 and PP1/2A inhibitor, okadaic acid decreased the current amplitude. From these results and because octopamine (OA) regulates DUM neuron electrical activity via an elevation of [cAMP]i, we wanted to know if, like in vertebrate dopaminergic neurons, OA receptor (OAR) stimulation could indirectly affect the current via PKA-mediated phosphorylation of Dopamine- and cAMP-regulated Phosphoprotein-32 (DARPP-32) known to inhibit PP1/2A. Experiments were performed using intracellular application of phospho-DARPP-32 and non-phospho-DARPP-32. Phospho-DARPP-32 strongly reduced the current amplitude whereas non-phospho-DARPP-32 did not affect the current. All together, these results confirm that DARPP-32-mediated inhibition of PP1/2A regulates the maintained sodium/calcium

  13. Levosimendan improves calcium sensitivity of diaphragm muscle fibres from a rat model of heart failure

    NARCIS (Netherlands)

    Hees, H.W.H. van; Andrade Acuna, G.L.; Linkels, M.; Dekhuijzen, P.N.R.; Heunks, L.M.A.


    BACKGROUND AND PURPOSE: Diaphragm muscle weakness occurs in patients with heart failure (HF) and is associated with exercise intolerance and increased mortality. Reduced sensitivity of diaphragm fibres to calcium contributes to diaphragm weakness in HF. Here we have investigated the ability of the

  14. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels (United States)

    Neely, Alan; Hidalgo, Patricia


    Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels. PMID:24917826

  15. Altered voltage-gated calcium channels in rat inferior colliculus neurons contribute to alcohol withdrawal seizures (United States)

    N’Gouemo, Prosper


    We have previously reported that enhanced susceptibility to alcohol withdrawal seizures (AWS) parallels the enhancement of the current density of high-threshold voltage-gated Ca2+ (CaV) channels in rat inferior colliculus (IC) neurons. However, whether this increased current density is a cause or consequence of AWS is unclear. Here, I report changes in the current density of CaV channels in IC neurons during the course of alcohol withdrawal and the potential anticonvulsant effect of intra-IC infusions of L- and P-type CaV channel antagonists. Whole-cell currents were activated by depolarizing pulses using barium as the charge carrier. Currents and seizure susceptibility were evaluated in control animals 3 h after alcohol intoxication, as well as 3 h (before AWS), 24 h (when AWS susceptibility is maximal), and 48 h (when AWS susceptibility is no longer present) after alcohol withdrawal. Nifedipine, nimodipine (L-type antagonists) or ω-agatoxin TK (P-type antagonist) were infused intra-IC to probe the role of CaV channels in the pathogenesis of AWS. CaV current density and conductance in IC neurons were significantly increased 3 and 24 h after alcohol withdrawal compared with the control group or the group tested 3 h following ethanol intoxication. Blockade of L-type CaV channels within the IC completely suppressed AWS, and inhibition of P-type channels reduced AWS severity. These findings suggest that the enhancement of CaV currents in IC neurons occurs prior to AWS onset and that alterations in L- and P-type CaV channels in these neurons may underlie the pathogenesis of AWS. PMID:25914156

  16. Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol. (United States)

    Dopico, Alejandro M; Bukiya, Anna N; Singh, Aditya K


    Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Alternative splicing modulates diltiazem sensitivity of cardiac and vascular smooth muscle Cav1.2 calcium channels (United States)

    Zhang, Heng Yu; Liao, Ping; Wang, Jue Jin; Yu, De Jie; Soong, Tuck Wah


    Background and purpose: As a calcium channel blocker, diltiazem acts mainly on the voltage-gated calcium channels, Cav1.2, for its beneficial effects in cardiovascular diseases such as hypertension, angina and/or supraventricular arrhythmias. However, the effects of diltiazem on different isoforms of Cav1.2 channels expressed in heart and vascular smooth muscles remain to be investigated. Here, we characterized the effects of diltiazem on the splice variants of Cav1.2 channels, predominant in cardiac and vascular smooth muscles. Experimental approach: Cardiac and smooth muscle isoforms of Cav1.2 channels were expressed in human embryonic kidney cells and their electrophysiological properties were characterized using whole-cell patch-clamp techniques. Key results: Under closed-channel and use-dependent block (0.03 Hz), cardiac splice variant Cav1.2CM was less sensitive to diltiazem than two major smooth muscle splice variants, Cav1.2SM and Cav1.2b. Cav1.2CM has a more positive half-inactivation potential than the smooth muscle channels, and diltiazem shifted it less to negative potential. Additionally, the current decay was slower in Cav1.2CM channels. When we modified alternatively spliced exons of cardiac Cav1.2CM channels into smooth muscle exons, we found that all three loci contribute to the different diltiazem sensitivity between cardiac and smooth muscle splice isoforms. Conclusions and implications: Alternative splicing of Cav1.2 channels modifies diltiazem sensitivity in the heart and blood vessels. Gating properties altered by diltiazem are different in the three channels. PMID:20649567

  18. Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25

    Directory of Open Access Journals (Sweden)

    Medler Kathryn F


    Full Text Available Abstract Background Taste receptor cells are responsible for transducing chemical stimuli from the environment and relaying information to the nervous system. Bitter, sweet and umami stimuli utilize G-protein coupled receptors which activate the phospholipase C (PLC signaling pathway in Type II taste cells. However, it is not known how these cells communicate with the nervous system. Previous studies have shown that the subset of taste cells that expresses the T2R bitter receptors lack voltage-gated Ca2+ channels, which are normally required for synaptic transmission at conventional synapses. Here we use two lines of transgenic mice expressing green fluorescent protein (GFP from two taste-specific promoters to examine Ca2+ signaling in subsets of Type II cells: T1R3-GFP mice were used to identify sweet- and umami-sensitive taste cells, while TRPM5-GFP mice were used to identify all cells that utilize the PLC signaling pathway for transduction. Voltage-gated Ca2+ currents were assessed with Ca2+ imaging and whole cell recording, while immunocytochemistry was used to detect expression of SNAP-25, a presynaptic SNARE protein that is associated with conventional synapses in taste cells. Results Depolarization with high K+ resulted in an increase in intracellular Ca2+ in a small subset of non-GFP labeled cells of both transgenic mouse lines. In contrast, no depolarization-evoked Ca2+ responses were observed in GFP-expressing taste cells of either genotype, but GFP-labeled cells responded to the PLC activator m-3M3FBS, suggesting that these cells were viable. Whole cell recording indicated that the GFP-labeled cells of both genotypes had small voltage-dependent Na+ and K+ currents, but no evidence of Ca2+ currents. A subset of non-GFP labeled taste cells exhibited large voltage-dependent Na+ and K+ currents and a high threshold voltage-gated Ca2+ current. Immunocytochemistry indicated that SNAP-25 was expressed in a separate population of taste cells

  19. Calcium (United States)

    ... and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system. It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with ...

  20. S-petasin and butterbur lactones dilate vessels through blockage of voltage gated calcium channels and block DNA synthesis. (United States)

    Sheykhzade, Majid; Smajilovic, Sanela; Issa, Ali; Haunso, Stig; Christensen, Søren Brøgger; Tfelt-Hansen, Jacob


    Eremophilanlactones isolated from roots of Petasites hybridus (L.) G.M. et Sch. (Asteraceae) and S-petasin have vasodilatory effects with pD(2) -log (EC(50)) values of 6.01+/-0.08, 5.24+/-0.10, 4.74+/-0.13, and 5.43+/-0.06 for S-petasin, the (Z)-3-methylthioacrylic ester of 2beta-hydroxy-8betaH-7(11)-eremophilene-12,8-olide, the angelic ester of 2beta-hydroxy-8alphaH-7(11)-eremophilene-12,8-olide, and the angelic ester of 2beta-hydroxy-8betaH-7(11)-eremophilene-12,8-olide, respectively, in the mesenteric arteries. The pD(2) values were somewhat lower for all compounds in aortic segments. The vasodilation was caused by a blockage of the voltage gated calcium channels. S-petasin, (Z)-3-methylthioacrylic ester of 2beta-hydroxy-8betaH-7(11)-eremophilene-12,8-olide, and the angelic ester of 2beta-hydroxy-8alphaH-7(11)-eremophilene-12,8-olide displayed similar potencies in inhibiting DNA synthesis in cardiomyocytes and vascular smooth muscle cells.

  1. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain (United States)

    Vink, S; Alewood, PF


    Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Cav2.2 in particular, other VGCC subtypes such as Cav3.2 have recently come to the forefront of analgesic research. Venom peptides from marine cone snails have been proven to be a valuable tool in neuroscience, playing a major role in the identification and characterization of VGCC subtypes and producing the first conotoxin-based drug on the market, the ω-conotoxin, ziconotide. This peptide potently and selectively inhibits Cav2.2, resulting in analgesia in chronic pain states. However, this drug is only available via intrathecal administration, and adverse effects and a narrow therapeutic window have limited its use in the clinic. Other Cav2.2 inhibitors are currently in development and offer the promise of an improved route of administration and safety profile. This review assesses the potential of targeting VGCCs for analgesic development, with a main focus on conotoxins that block Cav2.2 and the developments made to transform them into therapeutics. PMID:22725651

  2. A Rare Case of Cerebellar Ataxia Due to Voltage-Gated Calcium Channel and Glutamic Acid Decarboxylase Autoantibodies. (United States)

    Annunziata, Giuseppe; Lobo, Pamela; Carbuccia, Cristian


    BACKGROUND Autoimmune cerebellar ataxia can be paraneoplastic in nature or can occasionally present without evidence of an ongoing malignancy. The detection of specific autoantibodies has been statistically linked to different etiologies. CASE REPORT A 55-year-old African-American woman with hypertension and a past history of morbid obesity and uncontrolled diabetes status post gastric bypass four years prior to the visit (with significantly improved body mass index and hemoglobin A1c controlled at the time of the clinical encounter) presented to the office complaining of gradual onset of unsteadiness and recurrent falls for the past three years, as well as difficulties coordinating routine daily activities. The neurologic exam showed moderate dysarthria and ataxic gait with bilateral dysmetria and positive Romberg test. Routine laboratory test results were only remarkable for a mild elevation of erythrocyte sedimentation rate, and most laboratory and imaging tests for common causes of ataxia failed to demonstrate an etiology. Upon further workup, evidence of anti-voltage-gated calcium channel and anti-glutamic acid decarboxylase antibody was demonstrated. She was then treated with intravenous immunoglobulins with remarkable clinical improvement. CONCLUSIONS We present a case of antibody-mediated ataxia not associated with malignancy. While ataxia is rarely related to autoantibodies, in such cases it is critical to understand the etiology of this disabling condition in order to treat it correctly. Clinicians should be aware of the possible association with specific autoantibodies and the necessity to rule out an occult malignancy in such cases.

  3. Developmental regulation of expression of the alpha 1 and alpha 2 subunits mRNAs of the voltage-dependent calcium channel in a differentiating myogenic cell line. (United States)

    Varadi, G; Orlowski, J; Schwartz, A


    The voltage-dependent calcium channel (VDCC) in skeletal muscle probably plays a key role in transducing membrane charge movement to the calcium release channel. We report here that the expression of VDCC alpha 1 and alpha 2 mRNAs is developmentally regulated in differentiating C2C12 myogenic cells. The alpha 1 mRNA is not detectable in the myoblast form of C2C12 cells while its expression is induced 20-fold in differentiated myotubes. In contrast, the alpha 2 mRNA is weakly expressed in myoblasts but is also induced upon myogenic differentiation.

  4. Calcium dysregulation via L-type voltage-dependent calcium channels and ryanodine receptors underlies memory deficits and synaptic dysfunction during chronic neuroinflammation. (United States)

    Hopp, Sarah C; D'Angelo, Heather M; Royer, Sarah E; Kaercher, Roxanne M; Crockett, Alexis M; Adzovic, Linda; Wenk, Gary L


    Chronic neuroinflammation and calcium (Ca(+2)) dysregulation are both components of Alzheimer's disease. Prolonged neuroinflammation produces elevation of pro-inflammatory cytokines and reactive oxygen species which can alter neuronal Ca(+2) homeostasis via L-type voltage-dependent Ca(+2) channels (L-VDCCs) and ryanodine receptors (RyRs). Chronic neuroinflammation also leads to deficits in spatial memory, which may be related to Ca(+2) dysregulation. The studies herein use an in vivo model of chronic neuroinflammation: rats were infused intraventricularly with a continuous small dose of lipopolysaccharide (LPS) or artificial cerebrospinal fluid (aCSF) for 28 days. The rats were treated with the L-VDCC antagonist nimodipine or the RyR antagonist dantrolene. LPS-infused rats had significant memory deficits in the Morris water maze, and this deficit was ameliorated by treatment with nimodipine. Synaptosomes from LPS-infused rats had increased Ca(+2) uptake, which was reduced by a blockade of L-VDCCs either in vivo or ex vivo. Taken together, these data indicate that Ca(+2) dysregulation during chronic neuroinflammation is partially dependent on increases in L-VDCC function. However, blockade of the RyRs also slightly improved spatial memory of the LPS-infused rats, demonstrating that other Ca(+2) channels are dysregulated during chronic neuroinflammation. Ca(+2)-dependent immediate early gene expression was reduced in LPS-infused rats treated with dantrolene or nimodipine, indicating normalized synaptic function that may underlie improvements in spatial memory. Pro-inflammatory markers are also reduced in LPS-infused rats treated with either drug. Overall, these data suggest that Ca(+2) dysregulation via L-VDCCs and RyRs play a crucial role in memory deficits resulting from chronic neuroinflammation.

  5. Differential effects of voltage-gated calcium channel blockers on calcium channel alpha-2-delta-1 subunit protein-mediated nociception. (United States)

    Chang, E; Chen, X; Kim, M; Gong, N; Bhatia, S; Luo, Z D


    Overexpression of the voltage-gated calcium channel (VGCC) alpha-2-delta1 subunit protein (Cav α2 δ1 ) has been shown to cause pain states. However, whether VGCC are involved in pain states driven by abnormal Cav α2 δ1 expression is not known. Intrathecal injection of N-, P/Q- and L-type VGCC blockers were tested in two models: a transgenic neuronal Cav α2 δ1 overexpression (TG) model with behavioural hypersensitivity and a spinal nerve ligation (SNL) model with Cav α2 δ1 overexpression in sensory pathways and neuropathy pain states. The nociceptive response to mechanical stimuli was significantly attenuated in both models with ω-conotoxin GVIA (an N-type VGCC blocker) and nifedipine (an L-type VGCC blocker), in which ω-conotoxin GVIA appeared more potent than nifedipine. Treatments with ω-agatoxin IVA (P-VGCC blocker), but not ω-conotoxin MVIIC (Q-VGCC blocker) had similar potency in the TG model as the N-type VGCC blocker, while both ω-agatoxin IVA and ω-conotoxin MVIIC had minimal effects in the SNL model compared with controls. These findings suggest that, at the spinal level, N- and L-type VGCC are likely involved in behavioural hypersensitivity states driven by Cav α2 δ1 overexpression. Q-type VGCC has minimal effects in both models. The anti-nociceptive effects of P-type VGCC blocker in the Cav α2 δ1 TG mice, but minimally at the SNL model with presynaptic Cav α2 δ1 up-regulation, suggest that its potential action site(s) is at the post-synaptic and/or supraspinal level. These findings support that N-, L- and P/Q-type VGCC have differential contributions to behavioural hypersensitivity modulated by Cav α2 δ1 dysregulation at the spinal cord level. © 2014 European Pain Federation - EFIC®

  6. Sandia National Laboratories Small-Scale Sensitivity Testing (SSST) Report: Calcium Nitrate Mixtures with Various Fuels.

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Jason Joe [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)


    Based upon the presented sensitivity data for the examined calcium nitrate mixtures using sugar and sawdust, contact handling/mixing of these materials does not present hazards greater than those occurring during handling of dry PETN powder. The aluminized calcium nitrate mixtures present a known ESD fire hazard due to the fine aluminum powder fuel. These mixtures may yet present an ESD explosion hazard, though this has not been investigated at this time. The detonability of these mixtures will be investigated during Phase III testing.

  7. Voltage-sensitive styryl dyes as singlet oxygen targets on the surface of bilayer lipid membrane. (United States)

    Sokolov, V S; Gavrilchik, A N; Kulagina, A O; Meshkov, I N; Pohl, P; Gorbunova, Yu G


    Photosensitizers are widely used as photodynamic therapeutic agents killing cancer cells by photooxidation of their components. Development of new effective photosensitive molecules requires profound knowledge of possible targets for reactive oxygen species, especially for its singlet form. Here we studied photooxidation of voltage-sensitive styryl dyes (di-4-ANEPPS, di-8-ANEPPS, RH-421 and RH-237) by singlet oxygen on the surface of bilayer lipid membranes commonly used as cell membrane models. Oxidation was induced by irradiation of a photosensitizer (aluminum phthalocyanine tetrasulfonate) and monitored by the change of dipole potential on the surface of the membrane. We studied the drop of the dipole potential both in the case when the dye molecules were adsorbed on the same side of the lipid bilayer as the photosensitizer (cis-configuration) and in the case when they were adsorbed on the opposite side (trans-configuration). Based on a simple model, we determined the rate of oxidation of the dyes from the kinetics of change of the potential during and after irradiation. This rate is proportional to steady-state concentration of singlet oxygen in the membrane under irradiation. Comparison of the oxidation rates of various dyes reveals that compounds of ANEPPS series are more sensitive to singlet oxygen than RH type dyes, indicating that naphthalene group is primarily responsible for their oxidation. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Calcium (United States)

    ... from dietary supplements are linked to a greater risk of kidney stones, especially among older adults. But calcium from foods does not appear to cause kidney stones. For most people, other factors (such as not drinking enough fluids) probably have ...

  9. Enigma homolog 1 scaffolds protein kinase D1 to regulate the activity of the cardiac L-type voltage-gated calcium channel. (United States)

    Maturana, Andrés D; Wälchli, Sébastien; Iwata, Miki; Ryser, Stephan; Van Lint, Johannes; Hoshijima, Masahiko; Schlegel, Werner; Ikeda, Yasuhiro; Tanizawa, Katsuyuki; Kuroda, Shun'ichi


    In cardiomyocytes, protein kinase D1 (PKD1) plays a central role in the response to stress signals. From a yeast two-hybrid assay, we have identified Enigma Homolog 1 (ENH1) as a new binding partner of PKD1. Since in neurons, ENH1, associated with protein kinase Cepsilon, was shown to modulate the activity of N-type calcium channels, and the pore-forming subunit of the cardiac L-type voltage-gated calcium channel, alpha1C, possesses a potential phosphorylation site for PKD1, we studied here a possible role of ENH1 and PKD1 in the regulation of the cardiac L-type voltage-gated calcium channel. PKD1-interacting proteins were searched by yeast two-hybrid screening. In vivo protein interactions in cardiomyocytes isolated from heart ventricles of newborn rats were tested by co-immunoprecipitation. Small interfering RNA and a dominant negative mutant of PKD1 were delivered into cardiomyocytes by use of an adenovirus. Calcium currents were measured by the patch-clamp technique. Both ENH1 and PKD1 interact with alpha1C in cardiomyocytes. This interaction is increased upon stimulation. Silencing of ENH1 prevented the binding of PKD1 to alpha1C. Moreover, a dominant negative mutant of PKD1 or the silencing of ENH1 inhibited the alpha-adrenergic-induced increase of L-type calcium currents. We found a new binding partner, ENH1, and a new target, alpha1C, for PKD1 in neonatal rat cardiomyocytes. We propose a model where ENH1 scaffolds PKD1 to alpha1C in order to form a signalling complex that regulates the activity of cardiac L-type voltage-gated Ca(2+) channels.

  10. AKAP150-mediated TRPV1 sensitization is disrupted by calcium/calmodulin

    Directory of Open Access Journals (Sweden)

    Shapiro Mark S


    Full Text Available Abstract Background The transient receptor potential vanilloid type1 (TRPV1 is expressed in nociceptive sensory neurons and is sensitive to phosphorylation. A-Kinase Anchoring Protein 79/150 (AKAP150 mediates phosphorylation of TRPV1 by Protein Kinases A and C, modulating channel activity. However, few studies have focused on the regulatory mechanisms that control AKAP150 association with TRPV1. In the present study, we identify a role for calcium/calmodulin in controlling AKAP150 association with, and sensitization of, TRPV1. Results In trigeminal neurons, intracellular accumulation of calcium reduced AKAP150 association with TRPV1 in a manner sensitive to calmodulin antagonism. This was also observed in transfected Chinese hamster ovary (CHO cells, providing a model for conducting molecular analysis of the association. In CHO cells, the deletion of the C-terminal calmodulin-binding site of TRPV1 resulted in greater association with AKAP150, and increased channel activity. Furthermore, the co-expression of wild-type calmodulin in CHOs significantly reduced TRPV1 association with AKAP150, as evidenced by total internal reflective fluorescence-fluorescence resonance energy transfer (TIRF-FRET analysis and electrophysiology. Finally, dominant-negative calmodulin co-expression increased TRPV1 association with AKAP150 and increased basal and PKA-sensitized channel activity. Conclusions the results from these studies indicate that calcium/calmodulin interferes with the association of AKAP150 with TRPV1, potentially extending resensitization of the channel.


    Volatile organic solvents such as toluene (TOL) and trichloroethylene perturb nervous system function and share characteristic effects with other central nervous system depressants such as anesthetic gasses, ethanol, benzodiazepines and barbiturates. Recently, mechanistic studies...

  12. Differential expression of T- and L-type voltage-dependent calcium channels in renal resistance vessels

    DEFF Research Database (Denmark)

    Hansen, Pernille B. Lærkegaard; Jensen, Boye L.; Andreasen, D


    a significant increase of calcium in response to K(+) (100 mmol/L) in isolated afferent arterioles (140+/-25%) and in juxtamedullary efferent arterioles (118+/-21%). These calcium responses were attenuated by the L-type antagonist calciseptine and by the T-type antagonist mibefradil. Intracellular calcium...

  13. Meta-Analysis of Public Microarray Datasets Reveals Voltage-Gated Calcium Gene Signatures in Clinical Cancer Patients.

    Directory of Open Access Journals (Sweden)

    Chih-Yang Wang

    Full Text Available Voltage-gated calcium channels (VGCCs are well documented to play roles in cell proliferation, migration, and apoptosis; however, whether VGCCs regulate the onset and progression of cancer is still under investigation. The VGCC family consists of five members, which are L-type, N-type, T-type, R-type and P/Q type. To date, no holistic approach has been used to screen VGCC family genes in different types of cancer. We analyzed the transcript expression of VGCCs in clinical cancer tissue samples by accessing ONCOMINE (, a web-based microarray database, to perform a systematic analysis. Every member of the VGCCs was examined across 21 different types of cancer by comparing mRNA expression in cancer to that in normal tissue. A previous study showed that altered expression of mRNA in cancer tissue may play an oncogenic role and promote tumor development; therefore, in the present findings, we focus only on the overexpression of VGCCs in different types of cancer. This bioinformatics analysis revealed that different subtypes of VGCCs (CACNA1C, CACNA1D, CACNA1B, CACNA1G, and CACNA1I are implicated in the development and progression of diverse types of cancer and show dramatic up-regulation in breast cancer. CACNA1F only showed high expression in testis cancer, whereas CACNA1A, CACNA1C, and CACNA1D were highly expressed in most types of cancer. The current analysis revealed that specific VGCCs likely play essential roles in specific types of cancer. Collectively, we identified several VGCC targets and classified them according to different cancer subtypes for prospective studies on the underlying carcinogenic mechanisms. The present findings suggest that VGCCs are possible targets for prospective investigation in cancer treatment.

  14. Comprehensive behavioral analysis of voltage-gated calcium channel beta-anchoring and -regulatory protein knockout mice (United States)

    Nakao, Akito; Miki, Takafumi; Shoji, Hirotaka; Nishi, Miyuki; Takeshima, Hiroshi; Miyakawa, Tsuyoshi; Mori, Yasuo


    Calcium (Ca2+) influx through voltage-gated Ca2+ channels (VGCCs) induces numerous intracellular events such as neuronal excitability, neurotransmitter release, synaptic plasticity, and gene regulation. It has been shown that genes related to Ca2+ signaling, such as the CACNA1C, CACNB2, and CACNA1I genes that encode VGCC subunits, are associated with schizophrenia and other psychiatric disorders. Recently, VGCC beta-anchoring and -regulatory protein (BARP) was identified as a novel regulator of VGCC activity via the interaction of VGCC β subunits. To examine the role of the BARP in higher brain functions, we generated BARP knockout (KO) mice and conducted a comprehensive battery of behavioral tests. BARP KO mice exhibited greatly reduced locomotor activity, as evidenced by decreased vertical activity, stereotypic counts in the open field test, and activity level in the home cage, and longer latency to complete a session in spontaneous T-maze alteration test, which reached “study-wide significance.” Acoustic startle response was also reduced in the mutants. Interestingly, they showed multiple behavioral phenotypes that are seemingly opposite to those seen in the mouse models of schizophrenia and its related disorders, including increased working memory, flexibility, prepulse inhibition, and social interaction, and decreased locomotor activity, though many of these phenotypes are statistically weak and require further replications. These results demonstrate that BARP is involved in the regulation of locomotor activity and, possibly, emotionality. The possibility was also suggested that BARP KO mice may serve as a unique tool for investigating the pathogenesis/pathophysiology of schizophrenia and related disorders. Further evaluation of the molecular and physiological phenotypes of the mutant mice would provide new insights into the role of BARP in higher brain functions. PMID:26136667

  15. The Requirement of L-Type Voltage-Dependent Calcium Channel (L-VDCC) in the Rapid-Acting Antidepressant-Like Effects of Scopolamine in Mice. (United States)

    Yu, Hanjie; Li, Mengmeng; Shen, Xinbei; Lv, Dan; Sun, Xin; Wang, Jinting; Gu, Xinmei; Hu, Jingning; Wang, Chuang


    Previous studies have shown that a low dose of scopolamine produces rapid-acting antidepressant-like actions in rodents. Understanding the mechanisms underlying this effect and the dose-dependent variations of drug responses remains an important task. L-type voltage-dependent calcium channels were found to mediate rapid-acting antidepressant effects of certain medications (e.g., ketamine). Therefore, it is of great interest to determine the involvement of L-type voltage-dependent calcium channels in the action of scopolamine. Herein, we investigated the mechanisms underlying behavioral responses to various doses of scopolamine in mice to clarify the involvement of L-type voltage-dependent calcium channels in its modes of action. Open field test, novel object recognition test, and forced swimming test were performed on mice administered varied doses of scopolamine (0.025, 0.05, 0.1, 1, and 3 mg/kg, i.p.) alone or combined with L-type voltage-dependent calcium channel blocker verapamil (5 mg/kg, i.p.). Then, the changes in brain-derived neurotrophic factor and neuropeptide VGF (nonacronymic) levels in the hippocampus and prefrontal cortex of these mice were analyzed. Low doses of scopolamine (0.025 and 0.05 mg/kg) produced significant antidepressant-like effects in the forced swimming test, while higher doses (1 and 3 mg/kg) resulted in significant memory deficits and depressive-like behaviors. Moreover, the behavioral changes in responses to various doses may be related to the upregulation (0.025 and 0.05 mg/kg) and downregulation (1 and 3 mg/kg) of brain-derived neurotrophic factor and VGF in the hippocampus and prefrontal cortex in mice. We further found that the rapid-acting antidepressant-like effects and the upregulation on brain-derived neurotrophic factor and VGF produced by a low dose of scopolamine (0.025 mg/kg) were completely blocked by verapamil. These results indicate that L-type voltage-dependent calcium channels are likely involved in the behavioral

  16. Biasing Voltage Dependence of Sensitivity of Electron Beam Evaporated SnO2 Thin Film CO Sensor

    Directory of Open Access Journals (Sweden)

    Sardar M. Ayub Durrani


    Full Text Available Thin films of tin oxide were deposited by electron beam evaporation. The effectsof the sensor biasing voltage and film thickness on the CO-sensing of tin oxide thin filmswere investigated. The films were characterized using X-ray diffraction and X-rayphotoelectron spectroscopy All the films were found to be amorphous. The current-voltagecharacteristic of the sensor in air has shown that semiconductor-metal interface formsSchottky barrier. It was found that the CO-sensing properties depend on the sensor biasingvoltage and film thickness. For lower biasing voltages the sensitivity was much higher thanfor the higher voltages. It was found that the sensitivity of the films to CO increased withthe film thickness.

  17. Low Gate Voltage Operated Multi-emitter-dot H+ Ion-Sensitive Gated Lateral Bipolar Junction Transistor (United States)

    Yuan, Heng; Zhang, Ji-Xing; Zhang, Chen; Zhang, Ning; Xu, Li-Xia; Ding, Ming; Patrick, J. Clarke


    A low gate voltage operated multi-emitter-dot gated lateral bipolar junction transistor (BJT) ion sensor is proposed. The proposed device is composed of an arrayed gated lateral BJT, which is driven in the metal-oxide-semiconductor field-effect transistor (MOSFET)-BJT hybrid operation mode. Further, it has multiple emitter dots linked to each other in parallel to improve ionic sensitivity. Using hydrogen ionic solutions as reference solutions, we conduct experiments in which we compare the sensitivity and threshold voltage of the multi-emitter-dot gated lateral BJT with that of the single-emitter-dot gated lateral BJT. The multi-emitter-dot gated lateral BJT not only shows increased sensitivity but, more importantly, the proposed device can be operated under very low gate voltage, whereas the conventional ion-sensitive field-effect transistors cannot. This special characteristic is significant for low power devices and for function devices in which the provision of a gate voltage is difficult.

  18. Interface Modification of Dye-sensitized Solar Cells with Pivalic Acid to Enhance the Open-circuit Voltage

    KAUST Repository

    Li, Xin


    Pivalic acid (PVA) was used as a new coadsorbent to dye-sensitized solar cells (DSCs) to modify the interface between the TiO2 films and electrolyte. The addition of PVA improved the light-to-electricity conversion efficiency of devices by 8% by enhancing the open-circuit voltage. Copyright © 2009 The Chemical Society of Japan.

  19. Short-Term Facilitation at a Detonator Synapse Requires the Distinct Contribution of Multiple Types of Voltage-Gated Calcium Channels. (United States)

    Chamberland, Simon; Evstratova, Alesya; Tóth, Katalin


    Neuronal calcium elevations are shaped by several key parameters, including the properties, density, and the spatial location of voltage-gated calcium channels (VGCCs). These features allow presynaptic terminals to translate complex firing frequencies and tune the amount of neurotransmitter released. Although synchronous neurotransmitter release relies on both P/Q- and N-type VGCCs at hippocampal mossy fiber-CA3 synapses, the specific contribution of VGCCs to calcium dynamics, neurotransmitter release, and short-term facilitation remains unknown. Here, we used random-access two-photon calcium imaging together with electrophysiology in acute mouse hippocampal slices to dissect the roles of P/Q- and N-type VGCCs. Our results show that N-type VGCCs control glutamate release at a limited number of release sites through highly localized Ca 2+ elevations and support short-term facilitation by enhancing multivesicular release. In contrast, Ca 2+ entry via P/Q-type VGCCs promotes the recruitment of additional release sites through spatially homogeneous Ca 2+ elevations. Altogether, our results highlight the specialized contribution of P/Q- and N-types VGCCs to neurotransmitter release. SIGNIFICANCE STATEMENT In presynaptic terminals, neurotransmitter release is dynamically regulated by the transient opening of different types of voltage-gated calcium channels. Hippocampal giant mossy fiber terminals display extensive short-term facilitation during repetitive activity, with a large several fold postsynaptic response increase. Though, how giant mossy fiber terminals leverage distinct types of voltage-gated calcium channels to mediate short-term facilitation remains unexplored. Here, we find that P/Q- and N-type VGCCs generate different spatial patterns of calcium elevations in giant mossy fiber terminals and support short-term facilitation through specific participation in two mechanisms. Whereas N-type VGCCs contribute only to the synchronization of multivesicular release

  20. Sensitivity of the threshold voltage of organic thin-film transistors to light and water

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Cong; Marinov, Ognian; Deen, M. Jamal; Selvaganapathy, Ponnambalam Ravi [McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1 (Canada); Wu, Yiliang [Xerox Research Centre, 2660 Speakman Dr., Mississauga, Ontario L5K 2L1 (Canada)


    Analyses of extensive experiments with organic thin-film transistors (OTFTs) indicate that the threshold voltage V{sub T} of an OTFT has a temporal differential sensitivity. In particular, V{sub T} changes initially by changing the light illumination intensity or making/removing a contact of water with the organic semiconductor. Keeping the conditions stationary, then the initial shift of V{sub T} diminishes, since the time dependence of V{sub T} gradually recovers the OTFT to the state before applying the change in the environmental conditions. While still causing a differential and time-variant shift of V{sub T}, the deionized water does not have a dramatic impact on OTFTs that use the polymer DKPP-βT (diketopyrrolopyrrole β-unsubstituted quaterthiophene) as the active semiconductor material. Observations for the impact of water are made from experiments with an OTFT that has a microfluidic channel on the top the electrical channel, with the water in the microfluidic channel in direct contact with the electrical channel of the OTFT. This arrangement of electrical and microfluidic channels is a novel structure of the microfluidic OTFT, suitable for sensing applications of liquid analytes by means of organic electronics.

  1. Deltamethrin affects the expression of voltage-gated calcium channel α1 subunits and the locomotion, egg-laying, foraging behavior of Caenorhabditis elegans. (United States)

    Zeng, Rune; Yu, Xing; Tan, Xing; Ye, Shan; Ding, Zhong


    Deltamethrin belongs to the class of synthetic pyrethroids, which are being widely used as insecticides in agricultural practices. Voltage-gated sodium channels (VGSCs) are the primary targets of these chemicals for toxicity to insects. Caenorhabditis elegans (C. elegans) does not have VGSCs but is susceptible to deltamethrin. Recent findings have suggested that pyrethroids can affect voltage-gated calcium channels (VGCCs). However, it remains elusive whether deltamethrin induces toxicity to C. elegans via modulating the activity of VGCCs. To identify the potential target of deltamethrin, we exposed C. elegans to different concentrations of deltamethrin and Ca(2+) channel blockers for different times, characterized the behavioral toxicity of deltamethrin on C. elegans, and determined the expression of egl-19, unc-2, and cca-1, which encode the α1-subunit of the L-, R/N/P/Q-, and T-type VGCC, respectively. We found that deltamethrin inhibited the locomotion, egg-laying and foraging ability of C. elegans in a concentration dependent manner. We also showed that body length of worms on agar plates containing 200mgL(-1) deltamethrin for 12h was not significantly different from controls, whereas the cholinesterase inhibitor carbofuran caused hypercontraction which is a characteristic of organophosphates and carbamates, suggesting that deltamethrin's mode of action is distinct from those nematicides. In addition, unc-2 was significantly up-regulated following 0.05mgL(-1) deltamethrin exposure for 24h; while egl-19 and cca-1 were significantly up-regulated following 5 and 50mgL(-1) deltamethrin exposure for 24h. Further tests of worms' sensitivity and expression of three α1-subunits of VGCC to Ca(2+) channel blockers indicate that deltamethrin may induce toxic behavior C. elegans via modulation of the expression of the α1-subunits of VGCC. This study provides insights into the linkage between deltamethrin-induced toxic behavior and the regulation of α1-subunits of VGCC

  2. Effect of applied voltage on surface properties of anodised titanium in mixture of β-glycerophosphate (β-GP) and calcium acetate (CA)

    Energy Technology Data Exchange (ETDEWEB)

    Chuan, Lee Te, E-mail:; Rathi, Muhammad Fareez Mohamad, E-mail:; Abidin, Muhamad Yusuf Zainal, E-mail:; Abdullah, Hasan Zuhudi, E-mail:; Idris, Maizlinda Izwana, E-mail: [Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor (Malaysia)


    Anodic oxidation is a surface modification method which combines electric field driven metal and oxygen ion diffusion for formation of oxide layer on the anode surface. This method has been widely used to modify the surface morphology of biomaterial especially titanium. This study aimed to investigate the effect of applied voltage on titanium. Specifically, the titanium foil was anodised in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA) with different applied voltage (50-350 V), electrolyte concentration (0.04 M β-GP + 0.4 M CA), anodising time (10minutes) and current density (50 and 70{sup −2}) at room temperature. Surface oxide properties of anodised titanium were characterised by digital single-lens reflex camera (DSLR camera), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM). At lower applied voltage (≤150 V), surface of titanium foils were relatively smooth. With increasing applied voltage (≥250 V), the oxide layer became more porous and donut-shaped pores were formed on the surface of titanium foils. The AFM results indicated that the surface roughness of anodised titanium increases with increasing of applied voltage. The porous and rough surface is able to promote the osseointegration and reduce the suffering time of patient.

  3. Activation of Ih and TTX-sensitive sodium current at subthreshold voltages during CA1 pyramidal neuron firing. (United States)

    Yamada-Hanff, Jason; Bean, Bruce P


    We used dynamic clamp and action potential clamp techniques to explore how currents carried by tetrodotoxin-sensitive sodium channels and HCN channels (Ih) regulate the behavior of CA1 pyramidal neurons at resting and subthreshold voltages. Recording from rat CA1 pyramidal neurons in hippocampal slices, we found that the apparent input resistance and membrane time constant were strongly affected by both conductances, with Ih acting to decrease apparent input resistance and time constant and sodium current acting to increase both. We found that both Ih and sodium current were active during subthreshold summation of artificial excitatory postsynaptic potentials (EPSPs) generated by dynamic clamp, with Ih dominating at less depolarized voltages and sodium current at more depolarized voltages. Subthreshold sodium current-which amplifies EPSPs-was most effectively recruited by rapid voltage changes, while Ih-which blunts EPSPs-was maximal for slow voltage changes. The combined effect is to selectively amplify rapid EPSPs. We did similar experiments in mouse CA1 pyramidal neurons, doing voltage-clamp experiments using experimental records of action potential firing of CA1 neurons previously recorded in awake, behaving animals as command voltages to quantify flow of Ih and sodium current at subthreshold voltages. Subthreshold sodium current was larger and subthreshold Ih was smaller in mouse neurons than in rat neurons. Overall, the results show opposing effects of subthreshold sodium current and Ih in regulating subthreshold behavior of CA1 neurons, with subthreshold sodium current prominent in both rat and mouse CA1 pyramidal neurons and additional regulation by Ih in rat neurons. Copyright © 2015 the American Physiological Society.

  4. Bias voltage dependence of a flux-sensitive Al/GaAs/Al (SNS) interferometer

    DEFF Research Database (Denmark)

    Kutchinsky, Jonatan; Taboryski, Rafael Jozef; Hansen, Jørn Bindslev


    voltage of the order of a few microvolts the device is driven out of resonance and the conductance oscillations are extinguished. However, at higher bias voltage corresponding to the superconducting energy gap of Al (178 mu V) the conductance oscillations reappear but with reduced amplitude...

  5. Actions of a hydrogen sulfide donor (NaHS) on transient sodium, persistent sodium, and voltage-gated calcium currents in neurons of the subfornical organ. (United States)

    Kuksis, Markus; Ferguson, Alastair V


    Hydrogen sulfide (H2S) is an endogenously found gasotransmitter that has been implicated in a variety of beneficial physiological functions. This study was performed to investigate the cellular mechanisms underlying actions of H2S previously observed in subfornical organ (SFO), where H2S acts to regulate blood pressure through a depolarization of the membrane and an overall increase in the excitability of SFO neurons. We used whole cell patch-clamp electrophysiology in the voltage-clamp configuration to analyze the effect of 1 mM NaHS, an H2S donor, on voltage-gated potassium, sodium, and calcium currents. We observed no effect of NaHS on potassium currents; however, both voltage-gated sodium currents (persistent and transient) and the N-type calcium current had a depolarized activation curve and an enhanced peak-induced current in response to a series of voltage-step and ramp protocols run in the control and NaHS conditions. These effects were not responsible for the previously observed depolarization of the membrane potential, as depolarizing effects of H2S were still observed following block of these conductances with tetrodotoxin (5 μM) and ω-conotoxin-GVIA (100 nM). Our studies are the first to investigate the effect of H2S on a variety of voltage-gated conductances in a single brain area, and although they do not explain mechanisms underlying the depolarizing actions of H2S on SFO neurons, they provide evidence of potential mechanisms through which this gasotransmitter influences the excitability of neurons in this important brain area as a consequence of the modulation of multiple ion channels. Copyright © 2015 the American Physiological Society.

  6. Enhanced Dynamic Voltage Stability Support by VSC-HVDC for Offshore Wind Applications using Trajectory Sensitivity Analysis

    DEFF Research Database (Denmark)

    Liu, Hongzhi; Chen, Zhe; Liu, Leo


    The integration of large-scale wind power plants changes the structure, configuration and operation of conventional power systems and brings challenges to the security and stability of power systems. Dynamic voltage stability of power systems with high wind penetration is one of the critical issues....... In this paper, VSC-HVDC transmission system is used to integrate a large-scale wind power plant into the onshore power grid. For different voltage support strategies of VSC-HVDC, a trajectory sensitivity analysisbased approach is proposed to find the minimum onshore VSC capacity with which the VSC-HVDC can...

  7. Voltage-sensitive dye imaging of transcranial magnetic stimulation-induced intracortical dynamics. (United States)

    Kozyrev, Vladislav; Eysel, Ulf T; Jancke, Dirk


    Transcranial magnetic stimulation (TMS) is widely used in clinical interventions and basic neuroscience. Additionally, it has become a powerful tool to drive plastic changes in neuronal networks. However, highly resolved recordings of the immediate TMS effects have remained scarce, because existing recording techniques are limited in spatial or temporal resolution or are interfered with by the strong TMS-induced electric field. To circumvent these constraints, we performed optical imaging with voltage-sensitive dye (VSD) in an animal experimental setting using anaesthetized cats. The dye signals reflect gradual changes in the cells' membrane potential across several square millimeters of cortical tissue, thus enabling direct visualization of TMS-induced neuronal population dynamics. After application of a single TMS pulse across visual cortex, brief focal activation was immediately followed by synchronous suppression of a large pool of neurons. With consecutive magnetic pulses (10 Hz), widespread activity within this "basin of suppression" increased stepwise to suprathreshold levels and spontaneous activity was enhanced. Visual stimulation after repetitive TMS revealed long-term potentiation of evoked activity. Furthermore, loss of the "deceleration-acceleration" notch during the rising phase of the response, as a signature of fast intracortical inhibition detectable with VSD imaging, indicated weakened inhibition as an important driving force of increasing cortical excitability. In summary, our data show that high-frequency TMS changes the balance between excitation and inhibition in favor of an excitatory cortical state. VSD imaging may thus be a promising technique to trace TMS-induced changes in excitability and resulting plastic processes across cortical maps with high spatial and temporal resolutions.

  8. Positive inotropic effects of the calcium sensitizer CGP 48506 in guinea pig myocardium. (United States)

    Zimmermann, N; Bokník, P; Gams, E; Herzig, J W; Neumann, J; Schmitz, W; Scholz, H; Wenzlaff, H


    In isolated papillary muscles from reserpinized guinea pigs, CGP 48506 increased force of contraction in a concentration-dependent and reversible manner, starting at 10 mumol/l and reaching 364.14 +/- 46.10% of predrug values at 100 mumol/l. The positive inotropic effect of CGP 48506 was not sensitive to 10 mumol/l carbachol. The positive inotropic effect of CGP 48506 was accompanied by increases in time to peak tension and in time of relaxation amounting to 223.37 +/- 6.87% and 247.10 +/- 9.34% of control, respectively, at 100 mumol/l (n = 10). CGP 48506 sensitized trabeculae from guinea pig hearts to calcium with an EC50 value of 22 mumol/l. However, CGP 48506 (up to 300 mumol/l) did not affect the activity of cardiac PDE isoenzymes I to IV. Likewise, CGP 48506 (up to 100 mumol/l) did not increase phosphorylation of select cardiac regulatory proteins or cyclic AMP content in guinea pig ventricular cardiomyocytes and did not affect cardiac phosphorylase phosphatase activity. CGP 48506 is the first pharmacological agent with noteworthy calcium-sensitizing properties that has been found to be devoid of inhibitory activity on cardiac PDE.

  9. Simultaneous Quantification of Spatially Discordant Alternans in Voltage and Intracellular Calcium in Langendorff-Perfused Rabbit Hearts and Inconsistencies with Models of Cardiac Action Potentials and Ca Transients

    Directory of Open Access Journals (Sweden)

    Ilija Uzelac


    Full Text Available Rationale: Discordant alternans, a phenomenon in which the action potential duration (APDs and/or intracellular calcium transient durations (CaDs in different spatial regions of cardiac tissue are out of phase, present a dynamical instability for complex spatial dispersion that can be associated with long-QT syndrome (LQTS and the initiation of reentrant arrhythmias. Because the use of numerical simulations to investigate arrhythmic effects, such as acquired LQTS by drugs is beginning to be studied by the FDA, it is crucial to validate mathematical models that may be used during this process.Objective: In this study, we characterized with high spatio-temporal resolution the development of discordant alternans patterns in transmembrane voltage (Vm and intracellular calcium concentration ([Cai]+2 as a function of pacing period in rabbit hearts. Then we compared the dynamics to that of the latest state-of-the-art model for ventricular action potentials and calcium transients to better understand the underlying mechanisms of discordant alternans and compared the experimental data to the mathematical models representing Vm and [Cai]+2 dynamics.Methods and Results: We performed simultaneous dual optical mapping imaging of Vm and [Cai]+2 in Langendorff-perfused rabbit hearts with higher spatial resolutions compared with previous studies. The rabbit hearts developed discordant alternans through decreased pacing period protocols and we quantified the presence of multiple nodal points along the direction of wave propagation, both in APD and CaD, and compared these findings with results from theoretical models. In experiments, the nodal lines of CaD alternans have a steeper slope than those of APD alternans, but not as steep as predicted by numerical simulations in rabbit models. We further quantified several additional discrepancies between models and experiments.Conclusions: Alternans in CaD have nodal lines that are about an order of magnitude steeper

  10. CaV2.2 Gates Calcium-Independent but Voltage-Dependent Secretion in Mammalian Sensory Neurons. (United States)

    Chai, Zuying; Wang, Changhe; Huang, Rong; Wang, Yuan; Zhang, Xiaoyu; Wu, Qihui; Wang, Yeshi; Wu, Xi; Zheng, Lianghong; Zhang, Chen; Guo, Wei; Xiong, Wei; Ding, Jiuping; Zhu, Feipeng; Zhou, Zhuan


    Action potential induces membrane depolarization and triggers intracellular free Ca 2+ concentration (Ca 2+ )-dependent secretion (CDS) via Ca 2+ influx through voltage-gated Ca 2+ channels. We report a new type of somatic exocytosis triggered by the action potential per se-Ca 2+ -independent but voltage-dependent secretion (CiVDS)-in dorsal root ganglion neurons. Here we uncovered the molecular mechanism of CiVDS, comprising a voltage sensor, fusion machinery, and their linker. Specifically, the voltage-gated N-type Ca 2+ channel (Ca V 2.2) is the voltage sensor triggering CiVDS, the SNARE complex functions as the vesicle fusion machinery, the "synprint" of Ca V 2.2 serves as a linker between the voltage sensor and the fusion machinery, and ATP is a cargo of CiVDS vesicles. Thus, CiVDS releases ATP from the soma while CDS releases glutamate from presynaptic terminals, establishing the Ca V 2.2-SNARE "voltage-gating fusion pore" as a novel pathway co-existing with the canonical "Ca 2+ -gating fusion pore" pathway for neurotransmitter release following action potentials in primary sensory neurons. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Voltage sensitivity based reactive power control on VSC-HVDC in a wind farm connected hybrid multi-infeed HVDC system

    DEFF Research Database (Denmark)

    Liu, Yan; Chen, Zhe


    With increasing application of both Line Commutated Converter based High Voltage Direct Current (LCC-HVDC) systems and Voltage Source Converter based HVDC (VSC-HVDC) links, a new type of system structure named Hybrid Multi-Infeed HVDC (HMIDC) system is formed in the modern power systems. This paper...... presents the operation and control method of the wind farm connected HMIDC system. The wind power fluctuation takes large influence to the system voltages. In order to reduce the voltage fluctuation of LCC-HVDC infeed bus caused by the wind power variation, a voltage sensitivity-based reactive power...

  12. Plants sensitivity on nickel under different conditions of iron or calcium concentration in the nutrient medium

    Directory of Open Access Journals (Sweden)

    Renata Matraszek


    Full Text Available The sensitivity of six vegetable plants on nickel at early stages of their growth was investigated by index of tolerance. Besides the possibility of nickel fitostabilization by additional application of iron or calcium was tested. The experiment was conducted on Petri dishes. Different concentrations of nickel (0; 0,03; 0,06mM Ni as nickel sulphate, iron (0,05; O,OlmM Fe as Fe2+ citrate and calcium (0,50; 0,75; lmM Ca as calcium carbonate were added. Taking into consideration the sensitivity, investigated vegetables can be ordered in the following way: Cucurbita pepo conv. giromontiina L.>Lactuca sativa L.>Sinapis alba L.>Spinacia oleracea L.=Zea mays var. saccharata Kcke.>Phaseolus vulgaris L. Positive, statistically significant effect ofnickel fitostabilization (0,03 or 0,06mM Ni on elongative growth by the iron application (0,10mM Fe was shown for Zea mays var. saccharata Kcke independently of Ni concentration in the nutrient medium as well as for Sinapis alba L. and Phaseolus vulgaris L. in 0,06mM Ni. Addition as much as 0,75mM Ca in the presence 0,03mM Ni had positive result on Sinapis alba L and Phaseolus vulgaris L. seedlings as well as on Zea mays var. saccharata Kcke and Lactuca sativa L. roots and Cucurbita pepo convar. giromontiina L. shoots. Addition of 0,75mM Ca in the presence 0,06mM Ni promoted elongative growth of Zea mays var. saccharata Kcke seedlings. Application lmM Ca resulted in the promotion of elongative growth of Zea mays var. saccharata Kcke. roots (0,03mM Ni as well as Spinacia oleracea L. roots (0,06mM Ni.

  13. Intracellular Ca2+ Regulation in Calcium Sensitive Phenotype of Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)



    Full Text Available Intracellular cytosolic Ca2+ concentration accumulation plays an essential information in Saccharomyces cerevisiae i.e. to explain cellular mechanism of Ca2+ sensitive phenotype. Disruption both S. cerevisiae PPase PTP2 and MSG5 genes showed an inhibited growth in the presence of Ca2+. On the other hand, by using Luminocounter with apoaequorin system, a method based upon luminescent photoprotein aequorin, intracellular Ca2+ concentration was accumulated as a consequence of calcium sensitive phenotype of S. cerevisiae. This fact indicated that PPase ptp2Δ and msg5Δ were involved in intracellular Ca2+ transport in addition their already known pathways i.e Mitogen Activated Protein Kinase cell wall integrity pathway, high osmolarity glycerol (HOG pathway, and pheromone response FUS3 pathway.

  14. SGK3 Sensitivity of Voltage Gated K+ Channel Kv1.5 (KCNA5

    Directory of Open Access Journals (Sweden)

    Musaab Ahmed


    Full Text Available Background: The serum & glucocorticoid inducible kinase isoform SGK3 is a powerful regulator of several transporters, ion channels and the Na+/K+ ATPase. Targets of SGK3 include the ubiquitin ligase Nedd4-2, which is in turn a known regulator of the voltage gated K+ channel Kv1.5 (KCNA5. The present study thus explored whether SGK3 modifies the activity of the voltage gated K+ channel KCNA5, which participates in the regulation of diverse functions including atrial cardiac action potential, activity of vascular smooth muscle cells, insulin release and tumour cell proliferation. Methods: cRNA encoding KCNA5 was injected into Xenopus oocytes with and without additional injection of cRNA encoding wild-type SGK3, constitutively active S419DSGK3, inactive K191NSGK3 and/or wild type Nedd4-2. Voltage gated K+ channel activity was quantified utilizing dual electrode voltage clamp. Results: Voltage gated current in KCNA5 expressing Xenopus oocytes was significantly enhanced by wild-type SGK3 and S419DSGK3, but not by K191NSGK3. SGK3 was effective in the presence of ouabain (1 mM and thus did not require Na+/K+ ATPase activity. Coexpression of Nedd4-2 decreased the voltage gated current in KCNA5 expressing Xenopus oocytes, an effect largely reversed by additional coexpression of SGK3. Conclusion: SGK3 is a positive regulator of KCNA5, which is at least partially effective by abrogating the effect of Nedd4-2.

  15. Phase-sensitive detection of both inductive and non-inductive ac voltages in ferromagnetic resonance (United States)

    Weiler, Mathias; Shaw, Justin M.; Nembach, Hans T.; Schoen, Martin A.; Boone, Carl T.; Silva, Thomas J.


    Spin pumping causes significant damping in ultrathin ferromagnetic/normal metal (NM) multilayers via spin-current generation of both dc and ac character in the NM system. While the nonlinear dc component has been investigated in detail by utilization of the inverse spin Hall effect (iSHE) in NMs, much less is known about the linear ac component that is presumably much larger in the small-excitation limit. We measured generated ac voltages in a wide variety of Permalloy/NM multilayers via vector-network-analyzer ferromagnetic resonance. We employ a custom, impedance-matched, broadband microwave coupler that features a ferromagnetic thin film reference resonator to accurately compare ac voltage amplitudes and phases between varieties of multilayers. By use of the fact that inductive and ac iSHE signals are phase-shifted by π/2, we find that inductive signals are major contributors in all investigated samples. It is only by comparison of the phase and amplitude of the recorded ac voltages between multiple samples that we can extract the non-inductive contributions due to spin-currents. Voltages due to the ac iSHE in Permalloy(10nm)/platinum(5nm) bilayers are weaker than inductive signals, in agreement with calculations based upon recent theoretical predictions. M.W. acknowledges financial support by the German Academic Exchange service (DAAD).

  16. Basal and Activated Calcium Sensitization Mediated by RhoA/Rho Kinase Pathway in Rats with Genetic and Salt Hypertension

    Czech Academy of Sciences Publication Activity Database

    Behuliak, Michal; Bencze, Michal; Vaněčková, Ivana; Kuneš, Jaroslav; Zicha, Josef


    Roč. 2017, January (2017), č. článku 8029728. ISSN 2314-6133 R&D Projects: GA ČR(CZ) GP14-16225P; GA MZd(CZ) NV15-25396A Institutional support: RVO:67985823 Keywords : calcium sensitization * RhoA/Rho kinase * fasudil * calcium influx * nifedipine * BAY K8644 Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 2.476, year: 2016

  17. "Slow" Voltage-Dependent Inactivation of CaV2.2 Calcium Channels Is Modulated by the PKC Activator Phorbol 12-Myristate 13-Acetate (PMA.

    Directory of Open Access Journals (Sweden)

    Lei Zhu

    Full Text Available CaV2.2 (N-type voltage-gated calcium channels (Ca2+ channels play key roles in neurons and neuroendocrine cells including the control of cellular excitability, neurotransmitter / hormone secretion, and gene expression. Calcium entry is precisely controlled by channel gating properties including multiple forms of inactivation. "Fast" voltage-dependent inactivation is relatively well-characterized and occurs over the tens-to- hundreds of milliseconds timeframe. Superimposed on this is the molecularly distinct, but poorly understood process of "slow" voltage-dependent inactivation, which develops / recovers over seconds-to-minutes. Protein kinases can modulate "slow" inactivation of sodium channels, but little is known about if/how second messengers control "slow" inactivation of Ca2+ channels. We investigated this using recombinant CaV2.2 channels expressed in HEK293 cells and native CaV2 channels endogenously expressed in adrenal chromaffin cells. The PKC activator phorbol 12-myristate 13-acetate (PMA dramatically prolonged recovery from "slow" inactivation, but an inactive control (4α-PMA had no effect. This effect of PMA was prevented by calphostin C, which targets the C1-domain on PKC, but only partially reduced by inhibitors that target the catalytic domain of PKC. The subtype of the channel β-subunit altered the kinetics of inactivation but not the magnitude of slowing produced by PMA. Intracellular GDP-β-S reduced the effect of PMA suggesting a role for G proteins in modulating "slow" inactivation. We postulate that the kinetics of recovery from "slow" inactivation could provide a molecular memory of recent cellular activity and help control CaV2 channel availability, electrical excitability, and neurotransmission in the seconds-to-minutes timeframe.

  18. Evaluation of the strengthening of the conditions of voltage security using sensitivity analysis; Avaliacao do reforco das condicoes da seguranca de tensao utilizando a analise de sensibilidade

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, A.L.S.; Costa, V.M. da; Peres, W. [Universidade Federal de Juiz de Fora (UFJF), MG (Brazil). Faculdade de Engenharia], Emails:,,; Prada, R.B. [Pontificia Universidade Catolica (PUC-Rio), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Eletrica], Email:


    Voltage stability or voltage security analysis has motivated an expressive attention of power systems researchers. In this work, a simple and fast method evaluates voltage security and proposes conditions to improve the loading margin. System analysis is carried out in terms of active power transmission path. Sensitivity analysis provides the most adequate buses to active and reactive power redispatch. A sequential iterative methodology to reinforce system conditions is presented. (author)

  19. Pulsed voltage deposited lead selenide thin film as efficient counter electrode for quantum-dot-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Bin Bin [Key Laboratory of Macromolecular Science of Shaanxi Province & School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Department of Chemical Engineering, Institute of Chemical Industry, Shaanxi Institute of Technology, Xi’an 710300 (China); Wang, Ye Feng [Key Laboratory of Macromolecular Science of Shaanxi Province & School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Wang, Xue Qing [Faculty of Chemical, Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024 (China); Zeng, Jing Hui, E-mail: [Key Laboratory of Macromolecular Science of Shaanxi Province & School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China)


    Highlights: • PbSe thin film is deposited on FTO glass by a pulse voltage electrodeposition method. • The thin film is used as counter electrode (CE) in quantum dot-sensitized solar cell. • Superior electrocatalytic activity and stability in the polysulfide electrolyte is received. • The narrow band gap characteristics and p-type conductivity enhances the cell efficiency. • An efficiency of 4.67% is received for the CdS/CdSe co-sensitized solar cells. - Abstract: Lead selenide (PbSe) thin films were deposited on fluorine doped tin oxide (FTO) glass by a facile one-step pulse voltage electrodeposition method, and used as counter electrode (CE) in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). A power conversion efficiency of 4.67% is received for the CdS/CdSe co-sensitized solar cells, which is much better than that of 2.39% received using Pt CEs. The enhanced performance is attributed to the extended absorption in the near infrared region, superior electrocatalytic activity and p-type conductivity with a reflection of the incident light at the back electrode in addition. The physical and chemical properties were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), reflectance spectra, electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The present work provides a facile pathway to an efficient CE in the QDSSCs.

  20. The ?2? Subunit and Absence Epilepsy: Beyond Calcium Channels?

    National Research Council Canada - National Science Library

    Roberta Celli; Ines Santolini; Michela Guiducci; Gilles van Luijtelaar; Pasquale Parisi; Pasquale Striano; Roberto Gradini; Giuseppe Battaglia; Richard T. Ngomba; Ferdinando Nicoletti


    .... Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The ?2...

  1. Estradiol inhibits depolarization-evoked exocytosis in PC12 cells via N-type voltage-gated calcium channels.

    NARCIS (Netherlands)

    Adams, K.L.; Maxson, M.M.; Mellander, L.; Westerink, R.H.S.|info:eu-repo/dai/nl/239425952; Ewing, A.G.


    Fast neuromodulatory effects of 17-β-estradiol (E2) on cytosolic calcium concentration ([Ca(2+)](i)) have been reported in many cell types, but little is known about its direct effects on vesicular neurotransmitter secretion (exocytosis). We examined the effects of E2 on depolarization-evoked

  2. Protein kinase D regulates the human cardiac L-type voltage-gated calcium channel through serine 1884. (United States)

    Aita, Yusuke; Kurebayashi, Nagomi; Hirose, Shigehisa; Maturana, Andrés D


    Protein kinase D (PKD) regulates the activity of the L-type calcium channel in rat ventricular cardiomyocytes. However, the functional target residues of PKD on the L-type calcium channel remain to be identified. Our aim was to identify the functional phosphorylation sites of PKD on the human L-type calcium channel. The pore subunit of the human CaV1.2 (hCaV1.2) was stably expressed in HEK293 cells. Both the expression of a dominant-negative mutant of PKD and the mutation of serine 1884 but not serine 1930, putative targets of PKD, strongly reduced L-type calcium currents and single channel activity without affecting the channel's expression at the plasma membrane. Our results suggest that serine 1884 is essential for the regulation of hCaV1.2 by PKD. Copyright © 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  3. Accuracy and Radiation Dose Reduction Using Low-Voltage Computed Tomography Coronary Artery Calcium Scoring With Tin Filtration

    NARCIS (Netherlands)

    Tesche, Christian; De Cecco, Carlo N.; Vliegenthart, Rozemarijn; Albrecht, Moritz Moritz H.; Varga-Szemes, Akos; Duguay, Taylor M.; Ebersberger, Ullrich; Bayer, Richard R.; Canstein, Christian; Schmidt, Bernhard; Allmendinger, Thomas; Litwin, Sheldon E.; Morris, Pamela B.; Flohr, Thomas G.; Hoffmann, Ellen; Schoepf, U. Joseph


    This study prospectively investigated the accuracy and radiation dose reduction of CT coronary artery calcium scoring (CACS) using a 100 kVp acquisition protocol with tin filtration (Sn100 kVp) compared with the standard 120 kVp acquisition protocol; 70 patients (59% men, 62.1 10.7 years) who

  4. Electromagnetic fields (UHF) increase voltage sensitivity of membrane ion channels; possible indication of cell phone effect on living cells. (United States)

    Ketabi, N; Mobasheri, H; Faraji-Dana, R


    The effects of ultra high frequency (UHF) nonionizing electromagnetic fields (EMF) on the channel activities of nanopore forming protein, OmpF porin, were investigated. The voltage clamp technique was used to study the single channel activity of the pore in an artificial bilayer in the presence and absence of the electromagnetic fields at 910 to 990 MHz in real time. Channel activity patterns were used to address the effect of EMF on the dynamic, arrangement and dielectric properties of water molecules, as well as on the hydration state and arrangements of side chains lining the channel barrel. Based on the varied voltage sensitivity of the channel at different temperatures in the presence and absence of EMF, the amount of energy transferred to nano-environments of accessible groups was estimated to address the possible thermal effects of EMF. Our results show that the effects of EMF on channel activities are frequency dependent, with a maximum effect at 930 MHz. The frequency of channel gating and the voltage sensitivity is increased when the channel is exposed to EMF, while its conductance remains unchanged at all frequencies applied. We have not identified any changes in the capacitance and permeability of membrane in the presence of EMF. The effect of the EMF irradiated by cell phones is measured by Specific Absorption Rate (SAR) in artificial model of human head, Phantom. Thus, current approach applied to biological molecules and electrolytes might be considered as complement to evaluate safety of irradiating sources on biological matter at molecular level.

  5. Differential rescue of spatial memory deficits in aged rats by L-type voltage-dependent calcium channel and ryanodine receptor antagonism. (United States)

    Hopp, S C; D'Angelo, H M; Royer, S E; Kaercher, R M; Adzovic, L; Wenk, G L


    Age-associated memory impairments may result as a consequence of neuroinflammatory induction of intracellular calcium (Ca(+2)) dysregulation. Altered L-type voltage-dependent calcium channel (L-VDCC) and ryanodine receptor (RyR) activity may underlie age-associated learning and memory impairments. Various neuroinflammatory markers are associated with increased activity of both L-VDCCs and RyRs, and increased neuroinflammation is associated with normal aging. In vitro, pharmacological blockade of L-VDCCs and RyRs has been shown to be anti-inflammatory. Here, we examined whether pharmacological blockade of L-VDCCs or RyRs with the drugs nimodipine and dantrolene, respectively, could improve spatial memory and reduce age-associated increases in microglia activation. Dantrolene and nimodipine differentially attenuated age-associated spatial memory deficits but were not anti-inflammatory in vivo. Furthermore, RyR gene expression was inversely correlated with spatial memory, highlighting the central role of Ca(+2) dysregulation in age-associated memory deficits. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

  6. The Nitric Oxide Donor SNAP-Induced Amino Acid Neurotransmitter Release in Cortical Neurons. Effects of Blockers of Voltage-Dependent Sodium and Calcium Channels (United States)

    Merino, José Joaquín; Arce, Carmen; Naddaf, Ahmad; Bellver-Landete, Victor; Oset-Gasque, Maria Jesús; González, María Pilar


    Background The discovery that nitric oxide (NO) functions as a signalling molecule in the nervous system has radically changed the concept of neuronal communication. NO induces the release of amino acid neurotransmitters but the underlying mechanisms remain to be elucidated. Findings The aim of this work was to study the effect of NO on amino acid neurotransmitter release (Asp, Glu, Gly and GABA) in cortical neurons as well as the mechanism underlying the release of these neurotransmitters. Cortical neurons were stimulated with SNAP, a NO donor, and the release of different amino acid neurotransmitters was measured by HPLC. The involvement of voltage dependent Na+ and Ca2+ channels as well as cGMP in its mechanism of action was evaluated. Conclusions Our results indicate that NO induces release of aspartate, glutamate, glycine and GABA in cortical neurons and that this release is inhibited by ODQ, an inhibitor of soluble guanylate cyclase. Thus, the NO effect on amino acid neurotransmission could be mediated by cGMP formation in cortical neurons. Our data also demonstrate that the Na+ and Ca2+ voltage- dependent calcium channels are involved in the NO effects on cortical neurons. PMID:24598811

  7. Stapled Voltage-Gated Calcium Channel (CaV) α-Interaction Domain (AID) Peptides Act As Selective Protein-Protein Interaction Inhibitors of CaV Function. (United States)

    Findeisen, Felix; Campiglio, Marta; Jo, Hyunil; Abderemane-Ali, Fayal; Rumpf, Christine H; Pope, Lianne; Rossen, Nathan D; Flucher, Bernhard E; DeGrado, William F; Minor, Daniel L


    For many voltage-gated ion channels (VGICs), creation of a properly functioning ion channel requires the formation of specific protein-protein interactions between the transmembrane pore-forming subunits and cystoplasmic accessory subunits. Despite the importance of such protein-protein interactions in VGIC function and assembly, their potential as sites for VGIC modulator development has been largely overlooked. Here, we develop meta-xylyl (m-xylyl) stapled peptides that target a prototypic VGIC high affinity protein-protein interaction, the interaction between the voltage-gated calcium channel (CaV) pore-forming subunit α-interaction domain (AID) and cytoplasmic β-subunit (CaVβ). We show using circular dichroism spectroscopy, X-ray crystallography, and isothermal titration calorimetry that the m-xylyl staples enhance AID helix formation are structurally compatible with native-like AID:CaVβ interactions and reduce the entropic penalty associated with AID binding to CaVβ. Importantly, electrophysiological studies reveal that stapled AID peptides act as effective inhibitors of the CaVα1:CaVβ interaction that modulate CaV function in an CaVβ isoform-selective manner. Together, our studies provide a proof-of-concept demonstration of the use of protein-protein interaction inhibitors to control VGIC function and point to strategies for improved AID-based CaV modulator design.

  8. Interaction Of GCAP1 With Retinal Guanylyl Cyclase And Calcium: Sensitivity to Fatty Acylation

    Directory of Open Access Journals (Sweden)

    Igor V. Peshenko


    Full Text Available Guanylyl cyclase activating proteins (GCAP1 are calcium/magnesium binding proteins within neuronal calcium sensor proteins group (NCS of the EF-hand proteins superfamily. GCAPs activate retinal guanylyl cyclase (RetGC in vertebrate photoreceptors in response to light-dependent fall of the intracellular free Ca2+ concentrations. GCAPs consist of four EF-hand domains and contain N-terminal fatty acylated glycine, which in GCAP1 is required for the normal activation of RetGC. We analyzed the effects of a substitution prohibiting N-myristoylation (Gly2 → Ala on the ability of the recombinant GCAP1 to co-localize with its target enzyme when heterologously expressed in HEK293 cells. We also compared Ca2+ binding and RetGC-activating properties of the purified non-acylated G2A mutant and C14:0 acylated GCAP1 in vitro. The G2A GCAP1 expressed with a C-terminal GFP tag was able to co-localize with the cyclase, albeit less efficiently than the wild type, but much less effectively stimulated cyclase activity in vitro. Ca2+ binding isotherm of the G2A GCAP1 was slightly shifted toward higher free Ca2+ concentrations and so was Ca2+ sensitivity of RetGC reconstituted with the non-acylated mutant. At the same time, myristoylation had little effect on the high-affinity Ca2+-binding in the EF-hand that is proximal to the myristoyl residue in the three-dimensional GCAP1 structure. These data indicate that the N-terminal fatty acyl group may alter the activity of EF-hands in the distal portion of the GCAP1 molecule via presently unknown intramolecular mechanism.

  9. Effectiveness of nano-calcium phosphate paste on sensitivity during and after bleaching: a randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Alessandro Dourado LOGUERCIO


    Full Text Available The study aimed to evaluate the effectiveness of in-office bleaching and associated tooth sensitivity on application of nano-calcium phosphate paste as desensitizing agent. Bleaching was performed with 35% hydrogen peroxide gel in 40 patients who were randomly divided into placebo and nano-calcium phosphate paste groups. Bleaching efficacy (BE was evaluated using a value-oriented Vita shade guide. Tooth sensitivity was recorded using a numeric rating scale (0–4 during bleaching and up to 48 h after each session. The primary outcome of absolute risk of tooth sensitivity was compared using the Fisher’s exact test (α = 0.05. The intensity of tooth sensitivity and the efficacy of in-office bleaching were also statistically evaluated. No significant differences in absolute risk and intensity of tooth sensitivity were detected between the groups (p = 1.0 and p = 0.53, respectively. BE was also found to be similar between the groups (p = 0.67. Although the use of a nano-calcium phosphate paste associated with fluoride and potassium nitrate did not influence the whitening outcome, but it also did not reduce bleaching-induced tooth sensitivity.

  10. Effectiveness of nano-calcium phosphate paste on sensitivity during and after bleaching: a randomized clinical trial. (United States)

    Loguercio, Alessandro Dourado; Tay, Lidia Yileng; Herrera, Daniel Rodrigo; Bauer, Jose; Reis, Alessandra


    The study aimed to evaluate the effectiveness of in-office bleaching and associated tooth sensitivity on application of nano-calcium phosphate paste as desensitizing agent. Bleaching was performed with 35% hydrogen peroxide gel in 40 patients who were randomly divided into placebo and nano-calcium phosphate paste groups. Bleaching efficacy (BE) was evaluated using a value-oriented Vita shade guide. Tooth sensitivity was recorded using a numeric rating scale (0-4) during bleaching and up to 48 h after each session. The primary outcome of absolute risk of tooth sensitivity was compared using the Fisher's exact test (α = 0.05). The intensity of tooth sensitivity and the efficacy of in-office bleaching were also statistically evaluated. No significant differences in absolute risk and intensity of tooth sensitivity were detected between the groups (p = 1.0 and p = 0.53, respectively). BE was also found to be similar between the groups (p = 0.67). Although the use of a nano-calcium phosphate paste associated with fluoride and potassium nitrate did not influence the whitening outcome, but it also did not reduce bleaching-induced tooth sensitivity.

  11. T-type calcium channel Cav3.2 deficient mice show elevated anxiety, impaired memory and reduced sensitivity to psychostimulants.

    Directory of Open Access Journals (Sweden)

    Giuseppe eGangarossa


    Full Text Available The fine-tuning of neuronal excitability relies on a tight control of Ca2+ homeostasis. The low voltage-activated T-type calcium channels (Cav3.1, Cav3.2 and Cav3.3 isoforms play a critical role in regulating these processes. Despite their wide expression throughout the central nervous system, the implication of T-type Cav3.2 isoform in brain functions is still poorly characterized. Here we investigate the effect of genetic ablation of this isoform in affective disorders, including anxiety, cognitive functions as well as sensitivity to drugs of abuse. Using a wide range of behavioral assays we show that genetic ablation of the cacna1h gene results in an anxiety-like phenotype, whereas novelty-induced locomotor activity is unaffected. Deletion of the T-type channel Cav3.2 also triggers impairment of hippocampus-dependent recognition memories. Acute and sensitized hyperlocomotion induced by d-amphetamine and cocaine are dramatically reduced in T-type Cav3.2 deficient mice. In addition, the administration of the T-type blocker TTA-A2 prevented the expression of locomotor sensitization observed in wildtype mice. In conclusion, our data reveal that physiological activity of this specific Ca2+ channel is required for affective and cognitive behaviors. Moreover, our work highlights the interest of T-type channel blockers as therapeutic strategies to reverse drug-associated alterations.

  12. Differential Effect of Renal Cortical and Medullary Interstitial Fluid Calcium on Blood Pressure Regulation in Salt-Sensitive Hypertension. (United States)

    Pointer, Mildred A; Eley, Shaleka; Anderson, Lauren; Waters, Brittany; Royall, Brittany; Nichols, Sheena; Wells, Candace


    Hypercalciuria is a frequent characteristic of hypertension. In this report we extend our earlier studies investigating the role of renal interstitial fluid calcium (ISF(Ca))(2+) as a link between urinary calcium excretion and blood pressure in the Dahl salt-sensitive (DS) hypertensive model. Dahl salt-sensitive and salt-resistant (DR) rats were placed on control (0.45%) and high (8%) salt diets to determine if changes in renal cortical and medullary ISF(Ca)(2+)correlated with changes in urinary calcium excretion and blood pressure. We observed that renal ISFCa(2+) was predicted by urinary calcium excretion (P blood pressure (P blood pressure in DS rats (P blood pressure in the DR rats under the conditions of this study. We interpret these findings to suggest that decreased renal cortical ISF(Ca)(2+) plays a role in the increase in blood pressure following a high salt diet in salt hypertension perhaps by mediating renal vasoconstriction; the role of medullary calcium remains to be fully understood. Further studies are needed to determine the mechanism of the altered renal ISF(Ca)(2+) and its role in blood pressure regulation. © American Journal of Hypertension, Ltd 2014. All rights reserved. For Permissions, please email:

  13. Gαi2- and Gαi3-specific regulation of voltage-dependent L-type calcium channels in cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Sara Dizayee

    Full Text Available BACKGROUND: Two pertussis toxin sensitive G(i proteins, G(i2 and G(i3, are expressed in cardiomyocytes and upregulated in heart failure. It has been proposed that the highly homologous G(i isoforms are functionally distinct. To test for isoform-specific functions of G(i proteins, we examined their role in the regulation of cardiac L-type voltage-dependent calcium channels (L-VDCC. METHODS: Ventricular tissues and isolated myocytes were obtained from mice with targeted deletion of either Gα(i2 (Gα(i2 (-/- or Gα(i3 (Gα(i3 (-/-. mRNA levels of Gα(i/o isoforms and L-VDCC subunits were quantified by real-time PCR. Gα(i and Ca(vα(1 protein levels as well as protein kinase B/Akt and extracellular signal-regulated kinases 1/2 (ERK1/2 phosphorylation levels were assessed by immunoblot analysis. L-VDCC function was assessed by whole-cell and single-channel current recordings. RESULTS: In cardiac tissue from Gα(i2 (-/- mice, Gα(i3 mRNA and protein expression was upregulated to 187 ± 21% and 567 ± 59%, respectively. In Gα(i3 (-/- mouse hearts, Gα(i2 mRNA (127 ± 5% and protein (131 ± 10% levels were slightly enhanced. Interestingly, L-VDCC current density in cardiomyocytes from Gα(i2 (-/- mice was lowered (-7.9 ± 0.6 pA/pF, n = 11, p<0.05 compared to wild-type cells (-10.7 ± 0.5 pA/pF, n = 22, whereas it was increased in myocytes from Gα(i3 (-/- mice (-14.3 ± 0.8 pA/pF, n = 14, p<0.05. Steady-state inactivation was shifted to negative potentials, and recovery kinetics slowed in the absence of Gα(i2 (but not of Gα(i3 and following treatment with pertussis toxin in Gα(i3 (-/-. The pore forming Ca(vα(1 protein level was unchanged in all mouse models analyzed, similar to mRNA levels of Ca(vα(1 and Ca(vβ(2 subunits. Interestingly, at the cellular signalling level, phosphorylation assays revealed abolished carbachol-triggered activation of ERK1/2 in mice lacking Gα(i2. CONCLUSION: Our data provide novel evidence for an isoform

  14. PYK2: A Calcium-sensitive Protein Tyrosine Kinase Activated in Response to Fertilization of the Zebrafish Oocyte (United States)

    Sharma, Dipika; Kinsey, William H.


    Fertilization begins with binding and fusion of a sperm with the oocyte, a process that triggers a high amplitude calcium transient which propagates through the oocyte and stimulates a series of preprogrammed signal transduction events critical for zygote development. Identification of the pathways downstream of this calcium transient remains an important step in understanding the basis of zygote quality. The present study demonstrates that the calcium-calmodulin sensitive protein tyrosine kinase PYK2 is a target of the fertilization-induced calcium transient in the zebrafish oocyte and that it plays an important role in actin-mediated events critical for sperm incorporation. At fertilization, PYK2 was activated initially at the site of sperm-oocyte interaction and was closely associated with actin filaments forming the fertilization cone. Later PYK2 activation was evident throughout the entire oocyte cortex, however activation was most intense over the animal hemisphere. Fertilization-induced PYK2 activation could be blocked by suppressing calcium transients in the ooplasm via injection of BAPTA as a calcium chelator. PYK2 activation could be artificially induced in unfertilized oocytes by injection of IP3 at concentrations sufficient to induce calcium release. Functionally, suppression of PYK2 activity by chemical inhibition or by injection of a dominant-negative construct encoding the N-terminal ERM domain of PKY2 inhibited formation of an organized fertilization cone and reduced the frequency of successful sperm incorporation. Together, the above findings support a model in which PYK2 responds to the fertilization-induced calcium transient by promoting reorganization of the cortical actin cytoskeleton to form the fertilization cone. PMID:23084926

  15. N- and L-type voltage-gated calcium channels mediate fast calcium transients in axonal shafts of mouse peripheral nerve.

    Directory of Open Access Journals (Sweden)

    Ruxandra eBarzan


    Full Text Available In the peripheral nervous system a vast number of axons are accommodated within fiber bundles that constitute peripheral nerves. A major function of peripheral axons is to propagate action potentials along their length, and hence they are equipped with Na+ and K+ channels, which ensure successful generation, conduction and termination of each action potential. However little is known about Ca2+ ion channels expressed along peripheral axons and their possible functional significance. The goal of the present study was to test whether voltage-gated Ca2+ channels (VGCCs are present along peripheral nerve axons in situ and mediate rapid activity-dependent Ca2+ elevations under physiological circumstances. To address this question we used mouse sciatic nerve slices, Ca2+ indicator Oregon Green BAPTA-1, and 2-photon Ca2+ imaging in fast line scan mode (500 Hz. We report that transient increases in intra-axonal Ca2+ concentration take place along peripheral nerve axons in situ when axons are stimulated electrically with single pulses. Furthermore, we show for the first time that Ca2+ transients in peripheral nerves are fast, i.e. occur in a millisecond time-domain. Combining Ca2+ imaging and pharmacology with specific blockers of different VGCCs subtypes we demonstrate that Ca2+ transients in peripheral nerves are mediated mainly by N-type and L-type VGCCs. Discovery of fast Ca2+ entry into the axonal shafts through VGCCs in peripheral nerves suggests that Ca2+ may be involved in regulation of action potential propagation and/or properties in this system, or mediate neurotransmitter release along peripheral axons as it occurs in the optic nerve and white matter of the central nervous system.

  16. Thin film organic photodetectors for indirect X-ray detection demonstrating low dose rate sensitivity at low voltage operation

    Energy Technology Data Exchange (ETDEWEB)

    Starkenburg, Daken J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA; Johns, Paul M. [Nuclear Engineering Program, University of Florida, Gainesville, Florida 32611, USA; Detection Systems Group, Pacific Northwest National Laboratory, Richland, Washington 99354, USA; Baciak, James E. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA; Nuclear Engineering Program, University of Florida, Gainesville, Florida 32611, USA; Nino, Juan C. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA; Xue, Jiangeng [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA


    Developments in the field of organic semiconductors have generated organic photodetectors with high quantum efficiency, wide spectral sensitivity, low power consumption, and unique form factors that are flexible and conformable to their substrate shape. In this work, organic photodetectors coupled with inorganic CsI(Tl) scintillators are used to showcase the low dose rate sensitivity that is enabled when high performance organic photodetectors and scintillator crystals are integrated. The detection capability of these organic-inorganic coupled systems to high energy radiation highlights their potential as an alternative to traditional photomultiplier tubes for nuclear spectroscopy applications. When exposed to Bremsstrahlung radiation produced from an X-ray generator, SubPc:C60, AlPcCl:C70, and P3HT:PC61BM thin film photodetectors with active layer thicknesses less than 100 nm show detection of incident radiation at low and no applied bias. Remarkably low dose rates, down to at least 0.28 µGy/s, were detectable with a characteristic linear relationship between exposure rate and photodetector current output. These devices also demonstrate sensitivities as high as 5.37 mC Gy-1 cm-2 when coupled to CsI(Tl). Additionally, as the tube voltage across the X-ray generator was varied, these organic-inorganic systems showed their ability to detect a range of continuous radiation spectra spanning several hundred keV.

  17. Thin film organic photodetectors for indirect X-ray detection demonstrating low dose rate sensitivity at low voltage operation (United States)

    Starkenburg, Daken J.; Johns, Paul M.; Baciak, James E.; Nino, Juan C.; Xue, Jiangeng


    Developments in the field of organic semiconductors have generated organic photodetectors with high quantum efficiency, wide spectral sensitivity, low power consumption, and unique form factors that are flexible and conformable to their substrate shape. In this work, organic photodetectors coupled with inorganic CsI(Tl) scintillators are used to showcase the low dose rate sensitivity that is enabled when high performance organic photodetectors and scintillator crystals are integrated. The detection capability of these organic-inorganic coupled systems to high energy radiation highlights their potential as an alternative to traditional photomultiplier tubes for nuclear spectroscopy applications. When exposed to Bremsstrahlung radiation produced from an X-ray generator, SubPc:C60, AlPcCl:C70, and P3HT:PC61BM thin film photodetectors with active layer thicknesses less than 100 nm show detection of incident radiation at low and no applied bias. Remarkably low dose rates, down to at least 0.18 μGy/s, were detectable with a characteristic linear relationship between exposure rate and photodetector current output. These devices also demonstrate sensitivities as high as 5.37 mC Gy-1 cm-2 when coupled to CsI(Tl). Additionally, as the tube voltage across the X-ray generator was varied, these organic-inorganic systems showed their ability to detect a range of continuous radiation spectra spanning several hundred keV.

  18. Influence of discharge voltage on the sensitivity of the resultant sputtered NiO thin films toward hydrogen gas

    Energy Technology Data Exchange (ETDEWEB)

    Khalaf, Mohammed K. [Center of Applied Physics, Directorate of Materials Research, Ministry of Science and Technology, Baghdad (Iraq); Mutlak, Rajaa H. [Dept. of Physics, College of Science, University of Baghdad, Ministry of Higher Education and Scientific Research, Baghdad (Iraq); Khudiar, Ausama I., E-mail: [Center of Applied Physics, Directorate of Materials Research, Ministry of Science and Technology, Baghdad (Iraq); Hial, Qahtan G. [Dept. of Physics, College of Science, University of Baghdad, Ministry of Higher Education and Scientific Research, Baghdad (Iraq)


    Nickel oxide thin films were deposited on glass substrates as the main gas sensor for H{sub 2} by the DC sputtering technique at various discharge voltages within the range of 1.8–2.5 kV. Their structural, optical and gas sensing properties were investigated by XRD, AFM, SEM, ultraviolet visible spectroscopy and home-made gas sensing measurement units. A diffraction peak in the direction of NiO (200) was observed for the sputtered films, thereby indicating that these films were polycrystalline in nature. The optical band gap of the films decreased from 3.8 to 3.5 eV when the thickness of the films was increased from 83.5 to 164.4 nm in relation to an increase in the sputtering discharge voltage from 1.8 to 2.5 kV, respectively. The gas sensitivity performance of the NiO films that were formed was studied and the electrical responses of the NiO-based sensors toward different H{sub 2} concentrations were also considered. The sensitivity of the gas sensor increased with the working temperature and H{sub 2} gas concentration. The thickness of the NiO thin films was also an important parameter in determining the properties of the NiO films as H{sub 2} sensors. It was shown in this study that NiO films have the capability to detect H{sub 2} concentrations below 3% in wet air, a feature that allows this material to be used directly for the monitoring of the environment.

  19. Influence of discharge voltage on the sensitivity of the resultant sputtered NiO thin films toward hydrogen gas (United States)

    Khalaf, Mohammed K.; Mutlak, Rajaa H.; Khudiar, Ausama I.; Hial, Qahtan G.


    Nickel oxide thin films were deposited on glass substrates as the main gas sensor for H2 by the DC sputtering technique at various discharge voltages within the range of 1.8-2.5 kV. Their structural, optical and gas sensing properties were investigated by XRD, AFM, SEM, ultraviolet visible spectroscopy and home-made gas sensing measurement units. A diffraction peak in the direction of NiO (200) was observed for the sputtered films, thereby indicating that these films were polycrystalline in nature. The optical band gap of the films decreased from 3.8 to 3.5 eV when the thickness of the films was increased from 83.5 to 164.4 nm in relation to an increase in the sputtering discharge voltage from 1.8 to 2.5 kV, respectively. The gas sensitivity performance of the NiO films that were formed was studied and the electrical responses of the NiO-based sensors toward different H2 concentrations were also considered. The sensitivity of the gas sensor increased with the working temperature and H2 gas concentration. The thickness of the NiO thin films was also an important parameter in determining the properties of the NiO films as H2 sensors. It was shown in this study that NiO films have the capability to detect H2 concentrations below 3% in wet air, a feature that allows this material to be used directly for the monitoring of the environment.

  20. Point mutation of a conserved aspartate, D69, in the muscarinic M2 receptor does not modify voltage-sensitive agonist potency. (United States)

    Ågren, Richard; Sahlholm, Kristoffer; Nilsson, Johanna; Århem, Peter


    The muscarinic M 2 receptor (M 2 R) has been shown to display voltage-sensitive agonist binding, based on G protein-activated inward rectifier potassium channel (GIRK) opening and radioligand binding at different membrane voltages. A conserved aspartate in transmembrane segment (TM) II of M 2 R, D69, has been proposed as the voltage sensor. While a recent paper instead presented evidence of tyrosines in TMs III, VI, and VII acting as voltage sensors, these authors were not able to record GIRK channel activation by a D69N mutant M 2 R. In the present study, we succeeded in recording ACh-induced GIRK channel activation by this mutant at -80 and 0 mV. The acetylcholine EC 50 was about 2.5-fold higher at 0 mV, a potency shift very similar to that observed at wild-type M 2 R, indicating that voltage sensitivity persists at the D69N mutant. Thus, our present observations corroborate the notion that D69 is not responsible for voltage sensitivity of the M 2 R. Copyright © 2018 Elsevier Inc. All rights reserved.

  1. Role of voltage-gated sodium, potassium and calcium channels in the development of cocaine-associated cardiac arrhythmias (United States)

    O'Leary, Michael E; Hancox, Jules C


    Cocaine is a highly active stimulant that alters dopamine metabolism in the central nervous system resulting in a feeling of euphoria that with time can lead to addictive behaviours. Cocaine has numerous deleterious effects in humans including seizures, vasoconstriction, ischaemia, increased heart rate and blood pressure, cardiac arrhythmias and sudden death. The cardiotoxic effects of cocaine are indirectly mediated by an increase in sympathomimetic stimulation to the heart and coronary vasculature and by a direct effect on the ion channels responsible for maintaining the electrical excitability of the heart. The direct and indirect effects of cocaine work in tandem to disrupt the co-ordinated electrical activity of the heart and have been associated with life-threatening cardiac arrhythmias. This review focuses on the direct effects of cocaine on cardiac ion channels, with particular focus on sodium, potassium and calcium channels, and on the contributions of these channels to cocaine-induced arrhythmias. Companion articles in this edition of the journal examine the epidemiology of cocaine use (Wood & Dargan [1]) and the treatment of cocaine-associated arrhythmias (Hoffmann [2]). PMID:20573078

  2. Differential neuroprotective and anti-inflammatory effects of L-type voltage dependent calcium channel and ryanodine receptor antagonists in the substantia nigra and locus coeruleus. (United States)

    Hopp, Sarah C; Royer, Sarah E; D'Angelo, Heather M; Kaercher, Roxanne M; Fisher, David A; Wenk, Gary L


    Neuroinflammation and degeneration of catecholaminergic brainstem nuclei occur early in neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Neuroinflammation increases levels of pro-inflammatory cytokines and reactive oxygen species which can alter neuronal calcium (Ca(+2)) homoeostasis via L-type voltage dependent calcium channels (L-VDCCs) and ryanodine receptors (RyRs). Alterations in Ca(+2) channel activity in the SN and LC can lead to disruption of normal pacemaking activity in these areas, contributing to behavioral deficits. Here, we utilized an in vivo model of chronic neuroinflammation: rats were infused intraventricularly with a continuous small dose (0.25 μg/h) of lipopolysaccharide (LPS) or artificial cerebrospinal fluid (aCSF) for 28 days. Rats were treated with either the L-VDCC antagonist nimodipine or the RyR antagonist dantrolene. LPS-infused rats had significant motor deficits in the accelerating rotarod task as well as abnormal behavioral agitation in the forced swim task and open field. Corresponding with these behavioral deficits, LPS-infused rats also had significant increases in microglia activation and loss of tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra pars compacta (SNpc) and locus coeruleus (LC). Treatment with nimodipine or dantrolene normalized LPS-induced abnormalities in the rotarod and forced swim, restored the number of TH-immunoreactive cells in the LC, and significantly reduced microglia activation in the SNpc. Only nimodipine significantly reduced microglia activation in the LC, and neither drug increased TH immunoreactivity in the SNpc. These findings demonstrate that the Ca(+2) dysregulation in the LC and SN brainstem nuclei is differentially altered by chronic neuroinflammation. Overall, targeting Ca + 2 dysregulation may be an important target for ameliorating neurodegeneration in the SNpc and LC.

  3. Cisplatin alters the function and expression of N-type voltage-gated calcium channels in the absence of morphological damage of sensory neurons. (United States)

    Leo, Markus; Schmitt, Linda-Isabell; Jastrow, Holger; Thomale, Jürgen; Kleinschnitz, Christoph; Hagenacker, Tim


    Platinum-based chemotherapeutic agents, such as cisplatin, are still frequently used for treating various types of cancer. Besides its high effectiveness, cisplatin has several serious side effects. One of the most common side effects is dorsal root ganglion (DRG) neurotoxicity. However, the mechanisms underlying this neurotoxicity are still unclear and controversially discussed. Cisplatin-mediated modulation of voltage-gated calcium channels (VGCCs) in the DRG neurons has been shown to alter intracellular calcium homeostasis, a process critical for the induction of neurotoxicity. Using the whole-cell patch-clamp technique, immunostaining, behavioural experiments and electron microscopy (EM) of rat DRGs, we here demonstrate that cisplatin-induced neurotoxicity is due to functional alteration of VGCC, but not due to morphological damage. In vitro application of cisplatin (0.5 µM) increased N-type VGCC currents ( ICa(V)) in small DRG neurons. Repetitive in vivo administration of cisplatin (1.5 mg/kg, cumulative 12 mg/kg) increased the protein level of N-type VGCC over 26 days, with the protein level being increased for at least 14 days after the final cisplatin administration. Behavioural studies revealed that N-type VGCCs are crucial for inducing symptoms of cisplatin-related neuropathic pain, such as thermal and mechanical hyperalgesia. EM and histology showed no evidence of any structural damage, apoptosis or necrosis in DRG cells after cisplatin exposure for 26 days. Furthermore, no nuclear DNA damage in sensory neurons was observed. Here, we provide evidence for a mainly functionally driven induction of neuropathic pain by cisplatin.

  4. Cisplatin-induced neuropathic pain is mediated by upregulation of N-type voltage-gated calcium channels in dorsal root ganglion neurons. (United States)

    Leo, Markus; Schmitt, Linda-Isabell; Erkel, Martin; Melnikova, Margarita; Thomale, Jürgen; Hagenacker, Tim


    Cisplatin is important in the treatment of various types of cancer. Although it is highly effective, it also has severe side effects, with neurotoxicity in dorsal root ganglion (DRG) neurons being one of the most common. The key mechanisms of neurotoxicity are still controversially discussed; however, disturbances of the calcium homeostasis in DRG neurons have been suggested to mediate cisplatin neurotoxicity. By using the whole-cell patch-clamp technique, immunostaining and behavioral experiments with Sprague-Dawley rats, we examined the influence of short- and long-term exposure to cisplatin on voltage-gated calcium channel (VGCC) currents (ICa(V)) in small DRG neurons. In vitro exposure to cisplatin reduced ICa(V) in a concentration-dependent manner (0.01-50μM; 13.8-77.3%; IC50 5.07μM). Subtype-specific measurements of VGCCs showed differential effects on ICa(V). While the ICa(V) of P/Q-, L- and T-type VGCCs were reduced, ICa(V) of N-type VGCCs were increased by 30.3% during depolarization to 0mV. Exposure of DRG neurons to cisplatin (0.5 or 5μM) for 24-48h in vitro significantly increased a CaMK II-mediated ICa(V) current density. Immunostaining and western blot analysis revealed an increase of N-type VGCC protein level in DRG neurons 24h after cisplatin exposure. Cisplatin-mediated activation of caspase-3 was prevented by inhibition of N-type VGCCs using Ɯ-conotoxin MVIIA. Behavioral experiments showed that Ɯ-conotoxin MVIIA treatment prevented neuropathic syndromes in vivo by inhibiting upregulation of the N-type protein level. Here we show evidence for the first time for a crucial role of N-type VGCC in the genesis of cisplatin-induced polyneuropathy. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Spinal morphine but not ziconotide or gabapentin analgesia is affected by alternative splicing of voltage-gated calcium channel CaV2.2 pre-mRNA. (United States)

    Jiang, Yu-Qiu; Andrade, Arturo; Lipscombe, Diane


    Presynaptic voltage-gated calcium Ca(V)2.2 channels play a privileged role in spinal level sensitization following peripheral nerve injury. Direct and indirect inhibitors of Ca(V)2.2 channel activity in spinal dorsal horn are analgesic in chronic pain states. Ca(V)2.2 channels represent a family of splice isoforms that are expressed in different combinations according to cell-type. A pair of mutually exclusive exons in the Ca(V)2.2 encoding Cacna1b gene, e37a and e37b, differentially influence morphine analgesia. In mice that lack exon e37a, which is enriched in nociceptors, the analgesic efficacy of intrathecal morphine against noxious thermal stimuli is reduced. Here we ask if sequences unique to e37a influence: the development of abnormal thermal and mechanical sensitivity associated with peripheral nerve injury; and the actions of two other classes of analgesics that owe part or all of their efficacy to Ca(V)2.2 channel inhibition. We find that: i) the analgesic efficacy of morphine, but not ziconotide or gabapentin, is reduced in mice lacking e37a, ii) the induction and maintenance of behaviors associated with sensitization that accompany peripheral nerve injury, do not require e37a-specific sequence, iii) intrathecal morphine, but not ziconotide or gabapentin analgesia to thermal stimuli is significantly lower in wild-type mice after peripheral nerve injury, iv) the analgesic efficacy of ziconotide and gabapentin to mechanical stimuli is reduced following nerve injury, and iv) intrathecal morphine analgesia to thermal stimuli in mice lacking e37a is not further reduced by peripheral nerve injury. Our findings show that the analgesic action of morphine, but not ziconotide or gabapentin, to thermal stimuli is linked to which Cacna1b exon, e37a or e37b, is selected during alternative pre-mRNA splicing.

  6. S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK channels

    Directory of Open Access Journals (Sweden)

    Michael J Shipston


    Full Text Available Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK channels are important determinants of their (pathophysiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs and acyl thioesterases. (APTs. S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signalling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease.

  7. Sulfhydryl modification induces calcium entry through IP₃-sensitive store-operated pathway in activation-dependent human neutrophils.

    Directory of Open Access Journals (Sweden)

    Leiting Pan

    Full Text Available As the first line of host defense, neutrophils are stimulated by pro-inflammatory cytokines from resting state, facilitating the execution of immunomodulatory functions in activation state. Sulfhydryl modification has a regulatory role in a wide variety of physiological functions through mediation of signaling transductions in various cell types. Recent research suggested that two kinds of sulfhydryl modification, S-nitrosylation by exogenous nitric oxide (NO and alkylation by N-ethylmaleimide (NEM, could induce calcium entry through a non-store-operated pathway in resting rat neutrophils and DDT₁MF-2 cells, while in active human neutrophils a different process has been observed by us. In the present work, data showed that NEM induced a sharp rising of cytosolic calcium concentration ([Ca²⁺](c without external calcium, followed by a second [Ca²⁺](c increase with readdition of external calcium in phorbol 12-myristate 13-acetate (PMA-activated human neutrophils. Meanwhile, addition of external calcium did not cause [Ca²⁺](c change of Ca²⁺-free PMA-activated neutrophils before application of NEM. These data indicated that NEM could induce believable store-operated calcium entry (SOCE in PMA-activated neutrophils. Besides, we found that sodium nitroprusside (SNP, a donor of exogenous NO, resulted in believable SOCE in PMA-activated human neutrophils via S-nitrosylation modification. In contrast, NEM and SNP have no effect on [Ca²⁺](c of resting neutrophils which were performed in suspension. Furthermore, 2-Aminoethoxydiphenyl borate, a reliable blocker of SOCE and an inhibitor of inositol 1,4,5-trisphosphate (IP₃ receptor, evidently abolished SNP and NEM-induced calcium entry at 75 µM, while preventing calcium release in a concentration-dependent manner. Considered together, these results demonstrated that NEM and SNP induced calcium entry through an IP₃-sensitive store-operated pathway of human neutrophils via sulfhydryl

  8. Efficiency enhancement using voltage biasing for ferroelectric polarization in dye-sensitized solar cells (United States)

    Kim, Sangmo; Song, Myoung Geun; Bark, Chung Wung


    Dye-sensitized solar cells (DSSCs) are one of the most promising third generation solar cells that have been extensively researched over the past decade as alternative to silicon-based solar cells, due to their low production cost and high energy-conversion efficiency. In general, a DSSC consists of a transparent electrode, a counter electrode, and an electrolyte such as dye. To achieve high power-conversion efficiency in cells, many research groups have focused their efforts on developing efficient dyes for liquid electrolytes. In this work, we report on the photovoltaic properties of DSSCs fabricated using a mixture of TiO2 with nanosized Fe-doped bismuth lanthanum titanate (nFe-BLT) powder). Firstly, nFe-BLT powders were prepared using a high-energy ball milling process and then, TiO2 and nFe-BLT powders were stoichiometrically blended. Direct current (DC) bias of 20 MV/m was applied to lab-made DSSCs. With the optimal concentration of nFe-BLT doped in the electrode, their light-to-electricity conversion efficiency could be improved by ∼64% compared with DSSCs where no DC bias was applied.

  9. Immunolocalization of a voltage-gated calcium channel β subunit in the tentacles and cnidocytes of the Portuguese man-of-war, Physalia physalis. (United States)

    Bouchard, Christelle; Anderson, Peter A V


    This study investigated the localization of a voltage-gated calcium channel (VGCC) β subunit in the tentacles and cnidocytes of the Portuguese man-of-war using confocal immunocytochemistry. An antibody specific to the Ca(2+) channel β subunit of the Portuguese-man-of-war (PpCaVβ) was generated, and characterized by Western immunoblotting. The antibody labeling was widespread in the ectoderm of cnidosacs of the tentacles. The binding of the antibody on isolated cnidocytes was distributed at the base of the cell and appeared as multiple strong fluorescent plaques located around the basal hemisphere of the cell. The distribution of PpCaVβ in the cnidocyte is consistent with previous studies on other hydrozoans that demonstrated that cnidocytes convey sensory information to other cnidocytes through chemical synapses in which the cnidocyte is pre-synaptic to elements of the animal's nervous system. Importantly and surprisingly, PpCaVβ did not localize to the apical surface of the cnidocyte where the exocytotic events involved in cnidocyst discharge are thought to take place. © 2014 Marine Biological Laboratory.

  10. Zona pellucida from fertilised human oocytes induces a voltage-dependent calcium influx and the acrosome reaction in spermatozoa, but cannot be penetrated by sperm

    Directory of Open Access Journals (Sweden)

    Jouannet Pierre


    Full Text Available Abstract Background The functions of three zona glycoproteins, ZP1, ZP2 and ZP3 during the sperm-zona pellucida (ZP interaction are now well established in mice. The expression of an additional zona glycoprotein, ZPB/4, in humans, led us to reconsider the classical mouse model of gamete interaction. We investigated the various functions of human ZP (hZP during the interaction of spermatozoa with fertilised and unfertilised oocytes. Results The hZP of fertilised oocytes retained their ability to bind sperm (albeit less strongly than that from unfertilised oocytes, to induce an intraspermatic calcium influx through voltage-dependent channels similar to that observed with hZP from unfertilised oocytes and to promote the acrosome reaction at a rate similar to that induced by the ZP of unfertilised oocytes (61.6 ± 6.2% vs60.7 ± 9.1% respectively. Conversely, the rate of hZP penetrated by sperm was much lower for fertilised than for unfertilised oocytes (19% vs 57% respectively, p Conclusion The change in ZP function induced by fertilisation could be different in human and mouse species. Our results suggest a zona blocking to polyspermy based at the sperm penetration level in humans.

  11. Calcium-Sensitive MRI Contrast Agents Based on Superparamagnetic Iron Oxide Nanoparticles and Calmodulin

    National Research Council Canada - National Science Library

    Tatjana Atanasijevic; Maxim Shusteff; Peter Fam; Alan Jasanoff


    We describe a family of calcium indicators for magnetic resonance imaging (MRI), formed by combining a powerful iron oxide nanoparticle-based contrast mechanism with the versatile calciumsensing protein calmodulin and its targets...

  12. Reduced expression and activation of voltage-gated sodium channels contributes to blunted baroreflex sensitivity in heart failure rats. (United States)

    Tu, Huiyin; Zhang, Libin; Tran, Thai P; Muelleman, Robert L; Li, Yu-Long


    Voltage-gated sodium (Na(v)) channels are responsible for initiation and propagation of action potential in the neurons. To explore the mechanisms of chronic heart failure (CHF)-induced baroreflex dysfunction, we measured the expression and current density of Na(v) channel subunits (Na(v)1.7, Na(v)1.8, and Na(v)1.9) in the aortic baroreceptor neurons and investigated the role of Na(v) channels in aortic baroreceptor neuron excitability and baroreflex sensitivity in sham and CHF rats. CHF was induced by left coronary artery ligation. The development of CHF (6-8 weeks after the coronary ligation) was confirmed by hemodynamic and morphological characteristics. Immunofluorescent data indicated that Na(v)1.7 was expressed in A-type (myelinated) and C-type (unmyelinated) nodose neurons, but Na(v)1.8 and Na(v)1.9 were expressed only in C-type nodose neurons. Real-time RT-PCR and Western blot data showed that CHF reduced mRNA and protein expression levels of Na(v) channels in nodose neurons. In addition, using the whole-cell patch-clamp technique, we found that Na(v) current density and cell excitability of the aortic baroreceptor neurons were lower in CHF rats than that in sham rats. Aortic baroreflex sensitivity was blunted in anesthetized CHF rats, compared with that in sham rats. Furthermore, Na(v) channel activator (rATX II, 100 nM) significantly enhanced Na(v) current density and cell excitability of aortic baroreceptor neurons and improved aortic baroreflex sensitivity in CHF rats. These results suggest that reduced expression and activation of the Na(v) channels are involved in the attenuation of baroreceptor neuron excitability, which subsequently contributes to the impairment of baroreflex in CHF state.

  13. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    National Research Council Canada - National Science Library

    Celli, R; Santolini, I; Guiducci, M; Luijtelaar, E.L.J.M. van; Parisi, P; Striano, P; Gradini, R; Battaglia, G; Ngomba, R.T; Nicoletti, F


    .... Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The α2δ...

  14. Store-operated calcium entry and increased endothelial cell permeability. (United States)

    Norwood, N; Moore, T M; Dean, D A; Bhattacharjee, R; Li, M; Stevens, T


    We hypothesized that myosin light chain kinase (MLCK) links calcium release to activation of store-operated calcium entry, which is important for control of the endothelial cell barrier. Acute inhibition of MLCK caused calcium release from inositol trisphosphate-sensitive calcium stores and prevented subsequent activation of store-operated calcium entry by thapsigargin, suggesting that MLCK serves as an important mechanism linking store depletion to activation of membrane calcium channels. Moreover, in voltage-clamped single rat pulmonary artery endothelial cells, thapsigargin activated an inward calcium current that was abolished by MLCK inhibition. F-actin disruption activated a calcium current, and F-actin stabilization eliminated the thapsigargin-induced current. Thapsigargin increased endothelial cell permeability in the presence, but not in the absence, of extracellular calcium, indicating the importance of calcium entry in decreasing barrier function. Although MLCK inhibition prevented thapsigargin from stimulating calcium entry, it did not prevent thapsigargin from increasing permeability. Rather, inhibition of MLCK activity increased permeability that was especially prominent in low extracellular calcium. In conclusion, MLCK links store depletion to activation of a store-operated calcium entry channel. However, inhibition of calcium entry by MLCK is not sufficient to prevent thapsigargin from increasing endothelial cell permeability.

  15. Inhibition of veratridine-induced delayed inactivation of the voltage-sensitive sodium channel by synthetic analogs of crambescin B. (United States)

    Tsukamoto, Tadaaki; Chiba, Yukie; Nakazaki, Atsuo; Ishikawa, Yuki; Nakane, Yoshiki; Cho, Yuko; Yotsu-Yamashita, Mari; Nishikawa, Toshio; Wakamori, Minoru; Konoki, Keiichi


    Crambescin B carboxylic acid, a synthetic analog of crambescin B, was recently found to inhibit the voltage-sensitive sodium channels (VSSC) in a cell-based assay using neuroblastoma Neuro 2A cells. In the present study, whole-cell patch-clamp recordings were conducted with three heterologously expressed VSSC subtypes, Na v 1.2, Na v 1.6 and Na v 1.7, in a human embryonic kidney cell line HEK293T to further characterize the inhibition of VSSC by crambescin B carboxylic acid. Contrary to the previous observation, crambescin B carboxylic acid did not inhibit peak current evoked by depolarization from the holding potential of -100mV to the test potential of -10mV in the absence or presence of veratridine (VTD). In the presence of VTD, however, crambescin B carboxylic acid diminished VTD-induced sustained and tail currents through the three VSSC subtypes in a dose-dependent manner, whereas TTX inhibited both the peak current and the VTD-induced sustained and tail currents through all subtypes of VSSC tested. We thus concluded that crambescin B carboxylic acid does not block VSSC in a similar manner to TTX but modulate the action of VTD, thereby causing an apparent block of VSSC in the cell-based assay. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Spatio-temporal Distribution of Epileptiform Potentials in the Hippocampal Slice: Recordings with Voltage-sensitive Dyes. (United States)

    Albowitz, Birgit; Kuhnt, Ulrich


    Voltage-sensitive dyes and fast optical recording techniques were used to monitor the spatio-temporal activity pattern of epileptiform potentials in hippocampal slices from guinea pigs. Epileptiform potentials were induced by adding 4-aminopyridine to the bath solution and applying single pulse stimulation either to the stratum pyramidale of area CA3 or to the stratum radiatum of area CA1. Optical activity as well as intra- or extracellular electrical activity were recorded from area CA1. There was a good correlation between optical and intracellular records from the same site. The spatio-temporal activity pattern of control and epileptiform potentials elicited by stimulation of CA1 was similar for the initial part of the potential. Then, epileptiform changes became apparent throughout the vertical extent of pyramidal neurons. Qualitative changes occurred in the stratum moleculare, reflecting activity of apical dendrites, such changes occurred even more strongly in the stratum oriens, reflecting activity of basal dendrites. The activity in the stratum oriens occurred relatively late, so that it cannot account for the initiation of epileptic discharges. It might, however, play an important role in the synchronization and spread of epileptiform potentials. The investigation of the horizontal distribution of potentials throughout the entire area CA1 indicates that different mechanisms are involved in the spread of epileptiform activity elicited by stimulation of CA1 and stimulation of CA3.

  17. Mechanisms of NMDA Receptor- and Voltage-Gated L-Type Calcium Channel-Dependent Hippocampal LTP Critically Rely on Proteolysis That Is Mediated by Distinct Metalloproteinases. (United States)

    Wiera, Grzegorz; Nowak, Daria; van Hove, Inge; Dziegiel, Piotr; Moons, Lieve; Mozrzymas, Jerzy W


    Long-term potentiation (LTP) is widely perceived as a memory substrate and in the hippocampal CA3-CA1 pathway, distinct forms of LTP depend on NMDA receptors (nmdaLTP) or L-type voltage-gated calcium channels (vdccLTP). LTP is also known to be effectively regulated by extracellular proteolysis that is mediated by various enzymes. Herein, we investigated whether in mice hippocampal slices these distinct forms of LTP are specifically regulated by different metalloproteinases (MMPs). We found that MMP-3 inhibition or knock-out impaired late-phase LTP in the CA3-CA1 pathway. Interestingly, late-phase LTP was also decreased by MMP-9 blockade. When both MMP-3 and MMP-9 were inhibited, both early- and late-phase LTP was impaired. Using immunoblotting, in situ zymography, and immunofluorescence, we found that LTP induction was associated with an increase in MMP-3 expression and activity in CA1 stratum radiatum. MMP-3 inhibition and knock-out prevented the induction of vdccLTP, with no effect on nmdaLTP. L-type channel-dependent LTP is known to be impaired by hyaluronic acid digestion. We found that slice treatment with hyaluronidase occluded the effect of MMP-3 blockade on LTP, further confirming a critical role for MMP-3 in this form of LTP. In contrast to the CA3-CA1 pathway, LTP in the mossy fiber-CA3 projection did not depend on MMP-3, indicating the pathway specificity of the actions of MMPs. Overall, our study indicates that the activation of perisynaptic MMP-3 supports L-type channel-dependent LTP in the CA1 region, whereas nmdaLTP depends solely on MMP-9. Various types of long-term potentiation (LTP) are correlated with distinct phases of memory formation and retrieval, but the underlying molecular signaling pathways remain poorly understood. Extracellular proteases have emerged as key players in neuroplasticity phenomena. The present study found that L-type calcium channel-dependent LTP in the CA3-CA1 hippocampal projection is critically regulated by the activity

  18. Stimulation of NOX2 in isolated hearts reversibly sensitizes RyR2 channels to activation by cytoplasmic calcium. (United States)

    Donoso, Paulina; Finkelstein, José Pablo; Montecinos, Luis; Said, Matilde; Sánchez, Gina; Vittone, Leticia; Bull, Ricardo


    The response of ryanodine receptor (RyR) channels to cytoplasmic free calcium concentration ([Ca(2+)]) is redox sensitive. Here, we report the effects of a mild oxidative stress on cardiac RyR (RyR2) channels in Langendorff perfused rat hearts. Single RyR2 channels from control ventricles displayed the same three responses to Ca(2+) reported in other mammalian tissues, characterized by low, moderate, or high maximal activation. A single episode of 5 min of global ischemia, followed by 1 min of reperfusion, enhanced 2.3-fold the activity of NOX2 compared to controls and changed the frequency distribution of the different responses of RyR2 channels to calcium, favoring the more active ones: high activity response increased and low activity response decreased with respect to controls. This change was fully prevented by perfusion with apocynin or VAS 2870 before ischemia and totally reversed by the extension of the reperfusion period to 15 min. In vitro activation of NOX2 in control SR vesicles mimicked the effect of the ischemia/reperfusion episode on the frequencies of emergence of single RyR2 channel responses to [Ca(2+)] and increased 2.2-fold the rate of calcium release in Ca(2+)-loaded SR vesicles. In vitro changes were reversed at the single channel level by DTT and in isolated SR vesicles by glutaredoxin. Our results indicate that in whole hearts a mild oxidative stress enhances the response of cardiac RyR2 channels to calcium via NOX2 activation, probably by S-glutathionylation of RyR2 protein. This change is transitory and fully reversible, suggesting a possible role of redox modification in the physiological response of cardiac RyR2 to cellular calcium influx. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Activation of endogenous c-Src or a related tyrosine kinase by intracellular (pY)EEI peptide increases voltage-operated calcium channel currents in rabbit ear artery cells. (United States)

    Wijetunge, S; Hughes, A D


    The effect of activation of endogenous c-Src tyrosine kinase by (pY)EEI peptide was examined on voltage-operated calcium channel (VOC) currents in arterial smooth muscle cells. In single rabbit ear artery cells intracellular application of (pY)EEI peptide increased calcium channel currents. Inactive, non-phosphorylated YEEI peptide had no effect on currents. Peptide-A, a 21 amino acid inhibitor of c-Src inhibited currents and prevented the effect of (pY)EEI peptide on calcium channel currents. These results indicate that activation of intrinsic c-Src increases VOC and support a role for c-Src in the regulation of VOC in vascular smooth muscle cells.

  20. Distribution of TTX-sensitive voltage-gated sodium channels in primary sensory endings of mammalian muscle spindles. (United States)

    Carrasco, Dario I; Vincent, Jacob A; Cope, Timothy C


    Knowledge of the molecular mechanisms underlying signaling of mechanical stimuli by muscle spindles remains incomplete. In particular, the ionic conductances that sustain tonic firing during static muscle stretch are unknown. We hypothesized that tonic firing by spindle afferents depends on sodium persistent inward current (INaP) and tested for the necessary presence of the appropriate voltage-gated sodium (NaV) channels in primary sensory endings. The NaV 1.6 isoform was selected for both its capacity to produce INaP and for its presence in other mechanosensors that fire tonically. The present study shows that NaV 1.6 immunoreactivity (IR) is concentrated in heminodes, presumably where tonic firing is generated, and we were surprised to find NaV 1.6 IR strongly expressed also in the sensory terminals, where mechanotransduction occurs. This spatial pattern of NaV 1.6 IR distribution was consistent for three mammalian species (rat, cat, and mouse), as was tonic firing by primary spindle afferents. These findings meet some of the conditions needed to establish participation of INaP in tonic firing by primary sensory endings. The study was extended to two additional NaV isoforms, selected for their sensitivity to TTX, excluding TTX-resistant NaV channels, which alone are insufficient to support firing by primary spindle endings. Positive immunoreactivity was found for NaV 1.1 , predominantly in sensory terminals together with NaV 1.6 and for NaV 1.7 , mainly in preterminal axons. Differential distribution in primary sensory endings suggests specialized roles for these three NaV isoforms in the process of mechanosensory signaling by muscle spindles. NEW & NOTEWORTHY The molecular mechanisms underlying mechanosensory signaling responsible for proprioceptive functions are not completely elucidated. This study provides the first evidence that voltage-gated sodium channels (NaVs) are expressed in the spindle primary sensory ending, where NaVs are found at every site

  1. Inhibitory effect of L-type voltage-dependent calcium channel blocker on response of urinary bladder with acute ethanol intoxication. (United States)

    Oh, Mi Mi; Bae, Jae Hyun; Kim, Je Jong; Kim, Hyung Jee; Moon, Du Geon; Lee, Jeong Gu


    This study was performed to assess the effect of L-type voltage-dependent calcium channel (VDCC) blocker (dilitiazem) on the response of the urinary bladder with ethanol intoxication in in vivo and in vitro studies. Sprague-Dawley rats were used for in vivo and in vitro studies. The strips were divided into 5 groups according to pretreatment. Group I-A was treated with ethanol (0.1%), group I-B with ethanol (0.5%), group II with diltiazem treatment (10(-6) M), group III-A with pretreatment of diltiazem (10(-6) M) with ethanol intoxication (0.1%) and group III-B with pretreatment of diltiazem with ethanol intoxication (0.5%). The carbachol-induced tension was compared before and after each pretreatment. In separate in vivo experiments, the changes of maximal vesical pressure and intercontraction interval after intra-arterial administration of each agent (identical grouping with in vitro study) were monitored. The carbachol-induced contractions in group I-A, group I-B, group II, group III-A and group III-B were significantly decreased after each pretreatment (95 ± 2.73%, 92.6 ± 2.5%, 65.4 ± 2.0%, 52.61 ± 5.16%, 14.9 ± 1.4% of the control). The degree of increment of intercontraction interval and decrement of maximal vesical pressure showed a significant difference in the presence of diltiazem and ethanol intoxication (0.5%) compared with the diltiazem-treated and ethanol-intoxicated groups (0.5%). There is a possibility that ethanol and L-type VDCC blockers have synergistic depressive effect on bladder contractility and that ethanol and L-type VDCC blockers act through a common ionic pathway. Copyright © 2010 S. Karger AG, Basel.

  2. Cytoplasmic location of α1A voltage-gated calcium channel C-terminal fragment (Cav2.1-CTF aggregate is sufficient to cause cell death.

    Directory of Open Access Journals (Sweden)

    Makoto Takahashi

    Full Text Available The human α1A voltage-dependent calcium channel (Cav2.1 is a pore-forming essential subunit embedded in the plasma membrane. Its cytoplasmic carboxyl(C-tail contains a small poly-glutamine (Q tract, whose length is normally 4∼19 Q, but when expanded up to 20∼33Q, the tract causes an autosomal-dominant neurodegenerative disorder, spinocerebellar ataxia type 6 (SCA6. A recent study has shown that a 75-kDa C-terminal fragment (CTF containing the polyQ tract remains soluble in normal brains, but becomes insoluble mainly in the cytoplasm with additional localization to the nuclei of human SCA6 Purkinje cells. However, the mechanism by which the CTF aggregation leads to neurodegeneration is completely elusive, particularly whether the CTF exerts more toxicity in the nucleus or in the cytoplasm. We tagged recombinant (rCTF with either nuclear-localization or nuclear-export signal, created doxycyclin-inducible rat pheochromocytoma (PC12 cell lines, and found that the CTF is more toxic in the cytoplasm than in the nucleus, the observations being more obvious with Q28 (disease range than with Q13 (normal-length. Surprisingly, the CTF aggregates co-localized both with cAMP response element-binding protein (CREB and phosphorylated-CREB (p-CREB in the cytoplasm, and Western blot analysis showed that the quantity of CREB and p-CREB were both decreased in the nucleus when the rCTF formed aggregates in the cytoplasm. In human brains, polyQ aggregates also co-localized with CREB in the cytoplasm of SCA6 Purkinje cells, but not in other conditions. Collectively, the cytoplasmic Cav2.1-CTF aggregates are sufficient to cause cell death, and one of the pathogenic mechanisms may be abnormal CREB trafficking in the cytoplasm and reduced CREB and p-CREB levels in the nuclei.

  3. Mechanistic exploration of cancer stem cell marker voltage-dependent calcium channel α2δ1 subunit-mediated chemotherapy resistance in small cell lung cancer. (United States)

    Yu, Jiangyong; Wang, Shuhang; Zhao, Wei; Duan, Jianchun; Wang, Zhijie; Chen, Hanxiao; Tian, Yanhua; Wang, Di; Zhao, Jun; An, Tongtong; Bai, Hua; Wu, Meina; Wang, Jie


    Chemo-resistance in small cell lung cancer (SCLC) is reportedly attributed to the existence of resistant cancer stem cells (CSCs). Studies involving CSC-specific markers and related mechanisms in SCLC remain limited. The current study explored the role of the voltage-dependent calcium channel α2δ1 subunit as a CSC marker in chemo-resistant SCLC, and explored the potential mechanisms of α2δ1-mediated chemo-resistance and strategies of overcoming the resistance. α2δ1 positive cells were identified and isolated from SCLC cell lines and patient derived xenografts (PDXs) models, and CSC-like properties were subsequently verified. Transcriptome sequencing and Western Blotting were carried out to identify pathways involved in α2δ1-mediated chemo-resistance in SCLC. Additionally, possible interventions to overcome ɑ2δ1 mediated chemo-resistance were examined. Different proportions of α2δ1+ cells were identified in SCLC cell lines and PDX models. ɑ2δ1 positive cells exhibited CSC-like properties (self-renewal, tumorigenic, differentiation potential and high-expression of genes related to CSCs and drug-resistance). Chemotherapy induced the enrichment of α2δ1+ cells instead of CD133+ cells in PDXs, and an increased proportion of α2δ1+ cells corresponded to increased chemo-resistance. Activation and over-expression of Erk in the ɑ2δ1 positive H1048 cell line was identified at the protein level. 1B50-1 mAb was observed to improve the efficacy of chemotherapy and delay relapse as maintenance therapy in PDX models. SCLC cells expressing α2δ1 demonstrated CSC-like properties, and may contribute to chemo-resistance. Erk may play a key role in α2δ1 mediated chemo-resistance. 1B50-1 inhibitors may serve as potential anti-SCLC drugs. Copyright ©2018, American Association for Cancer Research.

  4. Oxaliplatin administration increases expression of the voltage-dependent calcium channel α2δ-1 subunit in the rat spinal cord

    Directory of Open Access Journals (Sweden)

    Ken Yamamoto


    Full Text Available Oxaliplatin is a chemotherapeutic agent that is effective against various types of cancer including colorectal cancer. Acute cold hyperalgesia is a serious side effect of oxaliplatin treatment. Although the therapeutic drug pregabalin is beneficial for preventing peripheral neuropathic pain by targeting the voltage-dependent calcium channel α2δ-1 (Cavα2δ-1 subunit, the effect of oxaliplatin-induced acute cold hypersensitivity is uncertain. To analyze the contribution of the Cavα2δ-1 subunit to the development of oxaliplatin-induced acute cold hypersensitivity, Cavα2δ-1 subunit expression in the rat spinal cord was analyzed after oxaliplatin treatment. Behavioral assessment using the acetone spray test showed that 6 mg/kg oxaliplatin-induced cold hypersensitivity 2 and 4 days later. Oxaliplatin-induced acute cold hypersensitivity 4 days after treatment was significantly inhibited by pregabalin (50 mg/kg, p.o.. Oxaliplatin (6 mg/kg, i.p. treatment increased the expression level of Cavα2δ-1 subunit mRNA and protein in the spinal cord 2 and 4 days after treatment. Immunohistochemistry showed that oxaliplatin increased Cavα2δ-1 subunit protein expression in superficial layers of the spinal dorsal horn 2 and 4 days after treatment. These results suggest that oxaliplatin treatment increases Cavα2δ-1 subunit expression in the superficial layers of the spinal cord and may contribute to functional peripheral acute cold hypersensitivity.

  5. The ethanol withdrawal syndrome: A role for dihydropyridine-sensitive calcium channels in neuronal hyperexcitability states

    Energy Technology Data Exchange (ETDEWEB)

    Whittington, M.A.


    This project investigated the effects of dihydropyridine calcium channel blockers on behavioral and electrophysiological aspects of ethanol withdrawal. The effects of the dihydropyridine (+)-PN 200-110, on changes in neuronal function during ethanol withdrawal, were compared with effects on changes caused by the GABAergic convulsant drug bicuculline. Behavioral correlates of ethanol withdrawal were measured in two strains of mice using a rating of handling-induced convulsions. Concurrent chronic treatment with ethanol and the dihydropyridine calcium channel blockers ([plus minus])-nitrendipine, ([plus minus])-nimodipine or ([plus minus])-PN 200-110 prevented withdrawal-induced increased in convulsive behavior. This effect was dose dependent. The duration of chronic treatment with calcium channel blocker affected the degree of protection against increases in convulsive behavior seen during ethanol withdrawal. Concurrent chronic treatment with ethanol, and the mixed calcium channel activator/blocker ([plus minus])-BAY K 8644, prevented ethanol withdrawal-induced increases in convulsive behavior. Single acute injections of nitrendipine immediately on cessation of chronic treatment with ethanol, or 2h later, reduced withdrawal-induced increases in convulsive behavior in a dose-dependent manner throughout the 12h test period. Slices isolated from mice after chronic ethanol treatment showed a complex, time-dependent pattern of changes in the above measurements, culminating in epileptiform discharges seen from 4h to 7h into withdrawal.

  6. Normal and malignant cells exhibit differential responses to calcium electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Krüger, Mie Barthold; Mangalanathan, Uma M.


    Calcium electroporation may offer a simple general tool for anticancer therapy. Transient permeabilization of cancer cell membranes created by applying short, high-voltage pulses in tumors enables high calcium influxes that trigger cell death. In this study, we compared the relative sensitivity...... of different human tumor models and normal tissues to calcium electroporation. Plasma membrane Ca(2+)-ATPase (PMCA) protein expression was confirmed in vitro in all cancer cell lines and normal primary dermal fibroblasts studied. In all tumor types tested in vivo, calcium electroporation effectively induced...... tissue after calcium electroporation but decreased in skin tissue 4 hours after treatment to levels comparable with untreated controls, whereas calcium content endured at high levels in tumor tissue. Mechanistic experiments in vitro indicated that calcium influx was similar in fibroblasts and cancer...

  7. Mapping of dihydropyridine binding residues in a less sensitive invertebrate L-type calcium channel (LCa v 1). (United States)

    Senatore, Adriano; Boone, Adrienne; Lam, Stanley; Dawson, Taylor F; Zhorov, Boris; Spafford, J David


    Invertebrate L-type calcium channel, LCa(v) 1, isolated from the pond snail Lymnaea stagnalis is nearly indistinguishable from mammalian Ca(v) 1.2 (α1C) calcium channel in biophysical characteristics observed in vitro. These L-type channels are likely constrained within a narrow range of biophysical parameters to perform similar functions in the snail and mammalian cardiovascular systems. What distinguishes snail and mammalian L-type channels is a difference in dihydropyridine sensitivity: 100 nM isradipine exhibits a significant block of mammalian Ca(v) 1.2 currents without effect on snail LCa(v)1 currents. The native snail channel serves as a valuable surrogate for validating key residue differences identified from previous experimental and molecular modeling work. As predicted, three residue changes in LCa(v)1 (N_3o18, F_3i10, and I_4i12) replaced with DHP-sensing residues in respective positions of Ca(v) 1.2, (Q_3o18, Y_3i10, and M_4i12) raises the potency of isradipine block of LCa(v)1 channels to that of mammalian Ca(v) 1.2. Interestingly, the single N_3o18_Q mutation in LCa(v) 1 channels lowers DHP sensitivity even further and the triple mutation bearing enhanced isradipine sensitivity, still retains a reduced potency of agonist, (S)-Bay K8644.

  8. Iterative beam-hardening correction with advanced modeled iterative reconstruction in low voltage CT coronary calcium scoring with tin filtration: Impact on coronary artery calcium quantification and image quality. (United States)

    Tesche, Christian; De Cecco, Carlo N; Schoepf, U Joseph; Duguay, Taylor M; Albrecht, Moritz H; Caruso, Damiano; Varga-Szemes, Akos; Lesslie, Virginia W; Ebersberger, Ullrich; Canstein, Christian; Thilo, Christian; Hoffmann, Ellen; Allmendinger, Thomas; Nance, John W

    We investigated the impact of iterative beam-hardening correction (IBHC) with advanced modeled iterative reconstruction (ADMIRE) of ultra-low radiation-dose tin filtered (Sn100 kVp) CACS acquisitions on image quality, calcium quantification, and risk classification. CT data of 60 patients (55% male, age 62.3 ± 9.8years) who underwent a 3rd generation dual-source CACS scan using a prospectively ECG-triggered 100 kVp sequential acquisition protocol with tin filtration (Sn100 kVp) were reconstructed using IBHC with filtered back projection (FBP) and ADMIRE with strength levels of three and five. Image noise was calculated and Agatston scores were derived from all reconstructions. Image noise, Agatston score categories, and percentile-based cardiac risk categorization of the respective reconstruction techniques were compared. The mean estimated radiation dose equivalent of CACS acquisitions in the study population was 0.20 ± 0.07 mSv. Mean image noise significantly decreased with ADMIRE compared to FBP (both p reconstructions were significantly different in a paired comparison (median [25th and 75th percentile]): FBP 34.7 [1.9, 153.6], ADMIRE 3 28.6 [1.1, 134.5], ADMIRE 5 22.7 [0.3, 116.8]; both p Iterative reconstruction using IBHC ADMIRE in low voltage, ultra-low dose CACS with tin filtration significantly decreased image noise. However, it also reduced Agatston scores compared to FBP, which may have an impact on subsequent cardiac risk classification, although risk reclassification occurred only in a modest number of subjects. Copyright © 2017 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

  9. Voltage imaging to understand connections and functions of neuronal circuits (United States)

    Antic, Srdjan D.; Empson, Ruth M.


    Understanding of the cellular mechanisms underlying brain functions such as cognition and emotions requires monitoring of membrane voltage at the cellular, circuit, and system levels. Seminal voltage-sensitive dye and calcium-sensitive dye imaging studies have demonstrated parallel detection of electrical activity across populations of interconnected neurons in a variety of preparations. A game-changing advance made in recent years has been the conceptualization and development of optogenetic tools, including genetically encoded indicators of voltage (GEVIs) or calcium (GECIs) and genetically encoded light-gated ion channels (actuators, e.g., channelrhodopsin2). Compared with low-molecular-weight calcium and voltage indicators (dyes), the optogenetic imaging approaches are 1) cell type specific, 2) less invasive, 3) able to relate activity and anatomy, and 4) facilitate long-term recordings of individual cells' activities over weeks, thereby allowing direct monitoring of the emergence of learned behaviors and underlying circuit mechanisms. We highlight the potential of novel approaches based on GEVIs and compare those to calcium imaging approaches. We also discuss how novel approaches based on GEVIs (and GECIs) coupled with genetically encoded actuators will promote progress in our knowledge of brain circuits and systems. PMID:27075539

  10. Comparison of two voltage-sensitive dyes and their suitability for long-term imaging of neuronal activity.

    Directory of Open Access Journals (Sweden)

    Stephanie Preuss

    Full Text Available One of the key approaches for studying neural network function is the simultaneous measurement of the activity of many neurons. Voltage-sensitive dyes (VSDs simultaneously report the membrane potential of multiple neurons, but often have pharmacological and phototoxic effects on neuronal cells. Yet, to study the homeostatic processes that regulate neural network function long-term recordings of neuronal activities are required. This study aims to test the suitability of the VSDs RH795 and Di-4-ANEPPS for optically recording pattern generating neurons in the stomatogastric nervous system of crustaceans with an emphasis on long-term recordings of the pyloric central pattern generator. We demonstrate that both dyes stain pyloric neurons and determined an optimal concentration and light intensity for optical imaging. Although both dyes provided sufficient signal-to-noise ratio for measuring membrane potentials, Di-4-ANEPPS displayed a higher signal quality indicating an advantage of this dye over RH795 when small neuronal signals need to be recorded. For Di-4-ANEPPS, higher dye concentrations resulted in faster and brighter staining. Signal quality, however, only depended on excitation light strength, but not on dye concentration. RH795 showed weak and slowly developing phototoxic effects on the pyloric motor pattern as well as slow bleaching of the staining and is thus the better choice for long-term experiments. Low concentrations and low excitation intensities can be used as, in contrast to Di-4-ANEPPS, the signal-to-noise ratio was independent of excitation light strength. In summary, RH795 and Di-4-ANEPPS are suitable for optical imaging in the stomatogastric nervous system of crustaceans. They allow simultaneous recording of the membrane potential of multiple neurons with high signal quality. While Di-4-ANEPPS is better suited for short-term experiments that require high signal quality, RH795 is a better candidate for long-term experiments

  11. Fast voltage-sensitive dye imaging of excitatory and inhibitory synaptic transmission in the rat granular retrosplenial cortex. (United States)

    Nixima, Ken'ichi; Okanoya, Kazuo; Ichinohe, Noritaka; Kurotani, Tohru


    Rodent granular retrosplenial cortex (GRS) has dense connections between the anterior thalamic nuclei (ATN) and hippocampal formation. GRS superficial pyramidal neurons exhibit distinctive late spiking (LS) firing property and form patchy clusters with prominent apical dendritic bundles. The aim of this study was to investigate spatiotemporal dynamics of signal transduction in the GRS induced by ATN afferent stimulation by using fast voltage-sensitive dye imaging in rat brain slices. In coronal slices, layer 1a stimulation, which presumably activated thalamic fibers, evoked propagation of excitatory synaptic signals from layers 2-4 to layers 5-6 in a direction perpendicular to the layer axis, followed by transverse signal propagation within each layer. In the presence of ionotropic glutamate receptor antagonists, inhibitory responses were observed in superficial layers, induced by direct activation of inhibitory interneurons in layer 1. In horizontal slices, excitatory signals in deep layers propagated transversely mainly from posterior to anterior via superficial layers. Cortical inhibitory responses upon layer 1a stimulation in horizontal slices were weaker than those in the coronal slices. Observed differences between coronal and horizontal planes suggest anisotropy of the intracortical circuitry. In conclusion, ATN inputs are processed differently in coronal and horizontal planes of the GRS and then conveyed to other cortical areas. In both planes, GRS superficial layers play an important role in signal propagation, which suggests that superficial neuronal cascade is crucial in the integration of multiple information sources.NEW & NOTEWORTHY Superficial neurons in the rat granular retrosplenial cortex (GRS) show distinctive late-spiking (LS) firing property. However, little is known about spatiotemporal dynamics of signal transduction in the GRS. We demonstrated LS neuron network relaying thalamic inputs to deep layers and anisotropic distribution of inhibition

  12. Reduced voltage sensitivity of activation of P/Q-type Ca2+ channels is associated with the ataxic mouse mutation rolling Nagoya (tg(rol)). (United States)

    Mori, Y; Wakamori, M; Oda, S; Fletcher, C F; Sekiguchi, N; Mori, E; Copeland, N G; Jenkins, N A; Matsushita, K; Matsuyama, Z; Imoto, K


    Recent genetic analyses have revealed an important association of the gene encoding the P/Q-type voltage-dependent Ca(2+) channel alpha(1A) subunit with hereditary neurological disorders. We have identified the ataxic mouse mutation, rolling Nagoya (tg(rol)), in the alpha(1A) gene that leads to a charge-neutralizing arginine-to-glycine substitution at position 1262 in the voltage sensor-forming segment S4 in repeat III. Ca(2+) channel currents in acutely dissociated Purkinje cells, where P-type is the dominant type, showed a marked decrease in slope and a depolarizing shift by 8 mV of the conductance-voltage curve and reduction in current density in tg(rol) mouse cerebella, compared with those in wild-type. Compatible functional change was induced by the tg(rol) mutation in the recombinant alpha(1A) channel, indicating that a defect in voltage sensor of P/Q-type Ca(2+) channels is the direct consequence of the tg(rol) mutation. Furthermore, somatic whole-cell recording of mutant Purkinje cells displayed only abortive Na(+) burst activity and hardly exhibited Ca(2+) spike activity in cerebellar slices. Thus, in tg(rol) mice, reduced voltage sensitivity, which may derive from a gating charge defect, and diminished activity of the P-type alpha(1A) Ca(2+) channel significantly impair integrative properties of Purkinje neurons, presumably resulting in locomotor deficits.

  13. A near-infrared fluorescent voltage-sensitive dye allows for moderate-throughput electrophysiological analyses of human induced pluripotent stem cell-derived cardiomyocytes (United States)

    Lopez-Izquierdo, Angelica; Warren, Mark; Riedel, Michael; Cho, Scott; Lai, Shuping; Lux, Robert L.; Spitzer, Kenneth W.; Benjamin, Ivor J.; Jou, Chuanchau J.


    Human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM)-based assays are emerging as a promising tool for the in vitro preclinical screening of QT interval-prolonging side effects of drugs in development. A major impediment to the widespread use of human iPSC-CM assays is the low throughput of the currently available electrophysiological tools. To test the precision and applicability of the near-infrared fluorescent voltage-sensitive dye 1-(4-sulfanatobutyl)-4-{β[2-(di-n-butylamino)-6-naphthyl]butadienyl}quinolinium betaine (di-4-ANBDQBS) for moderate-throughput electrophysiological analyses, we compared simultaneous transmembrane voltage and optical action potential (AP) recordings in human iPSC-CM loaded with di-4-ANBDQBS. Optical AP recordings tracked transmembrane voltage with high precision, generating nearly identical values for AP duration (AP durations at 10%, 50%, and 90% repolarization). Human iPSC-CMs tolerated repeated laser exposure, with stable optical AP parameters recorded over a 30-min study period. Optical AP recordings appropriately tracked changes in repolarization induced by pharmacological manipulation. Finally, di-4-ANBDQBS allowed for moderate-throughput analyses, increasing throughput >10-fold over the traditional patch-clamp technique. We conclude that the voltage-sensitive dye di-4-ANBDQBS allows for high-precision optical AP measurements that markedly increase the throughput for electrophysiological characterization of human iPSC-CMs. PMID:25172899

  14. The β4subunit of the voltage-gated calcium channel (Cacnb4) regulates the rate of cell proliferation in Chinese Hamster Ovary cells. (United States)

    Rima, Mohamad; Daghsni, Marwa; De Waard, Stephan; Gaborit, Nathalie; Fajloun, Ziad; Ronjat, Michel; Mori, Yasuo; Brusés, Juan L; De Waard, Michel


    The β subunits of Voltage-Gated Calcium Channel (VGCC) are cytosolic proteins that interact with the VGCC pore -forming subunit and participate in the trafficking of the channel to the cell membrane and in ion influx regulation. β subunits also exert functions independently of their binding to VGCC by translocation to the cell nucleus including the control of gene expression. Mutations of the neuronal Cacnb4 (β 4 ) subunit are linked to human neuropsychiatric disorders including epilepsy and intellectual disabilities. It is believed that the pathogenic phenotype induced by these mutations is associated with channel-independent functions of the β 4 subunit. In this report, we investigated the role of β 4 subunit in cell proliferation and cell cycle progression and examined whether these functions could be altered by a pathogenic mutation. To this end, stably transfected Chinese Hamster Ovary (CHO-K1) cells expressing either rat full-length β 4 or the rat C-terminally truncated epileptic mutant variant β 1-481 were generated. The subcellular localization of both proteins differed significantly. Full-length β 4 localizes almost exclusively in the cell nucleus and concentrates into the nucleolar compartment, while the C-terminal-truncated β 1-481 subunit was less concentrated within the nucleus and absent from the nucleoli. Cell proliferation was found to be reduced by the expression of β 4 , while it was unaffected by the epileptic mutant. Also, full-length β 4 interfered with cell cycle progression by presumably preventing cells from entering the S-phase via a mechanism that partially involves endogenous B56δ, a regulatory subunit of the phosphatase 2A (PP2A) that binds β 4 but not β 1-481 . Analysis of β 4 subcellular distribution during the cell cycle revealed that the protein is highly expressed in the nucleus at the G1/S transition phase and that it is translocated out of the nucleus during chromatin condensation and cell division. These results

  15. Normal and Malignant Cells Exhibit Differential Responses to Calcium Electroporation. (United States)

    Frandsen, Stine K; Krüger, Mie B; Mangalanathan, Uma M; Tramm, Trine; Mahmood, Faisal; Novak, Ivana; Gehl, Julie


    Calcium electroporation may offer a simple general tool for anticancer therapy. Transient permeabilization of cancer cell membranes created by applying short, high-voltage pulses in tumors enables high calcium influxes that trigger cell death. In this study, we compared the relative sensitivity of different human tumor models and normal tissues to calcium electroporation. Plasma membrane Ca(2+)-ATPase (PMCA) protein expression was confirmed in vitro in all cancer cell lines and normal primary dermal fibroblasts studied. In all tumor types tested in vivo, calcium electroporation effectively induced necrosis, with a range of sensitivities observed (36%-88%) 2 days after treatment. Necrosis was induced using calcium concentrations of 100-500 mmol/L and injection volumes 20%-80% of tumor volume. Notably, only limited effects were seen in normal tissue. Calcium content increased >7-fold in tumor and skin tissue after calcium electroporation but decreased in skin tissue 4 hours after treatment to levels comparable with untreated controls, whereas calcium content endured at high levels in tumor tissue. Mechanistic experiments in vitro indicated that calcium influx was similar in fibroblasts and cancer cells. However, we observed decreased PMCA expression in cancer cells compared with fibroblasts, offering a potential explanation for the different calcium content in tumor cells versus normal tissues. Overall, our results suggest that calcium electroporation can elicit a rapid and selective necrosis of solid tumors, with limited deleterious effects on surrounding normal tissues. Cancer Res; 77(16); 4389-401. ©2017 AACR. ©2017 American Association for Cancer Research.


    Directory of Open Access Journals (Sweden)

    L. V. Egshatyan


    Full Text Available Aim. To evaluate the effect of parathyroidectomy and cinacalcet on anemia, lipid profile and blood pressure (BP in uremic hyperparathyroidism.Material and methods. Uremic patients (n=39 treated with hemodialysis and having secondary hyperparathyroidism were included into the study. Radical parathyroidectomy was performed in 21 patients, 18 patients were treated with cinacalcet. BP measurement, determination of blood levels of albumin, total calcium, phosphorus, total cholesterol (TC, low (LDL and high density lipoproteins, triglycerides, intact parathyroid hormone, and hemoglobin were performed in all patients initially and during treatment. Doses of antihypertensive and erythropoiesis-stimulating agents were also assessed.Results. Calcium-phosphorus metabolism indices improved after 6 months of cinacalcet therapy and parathyroidectomy (p<0.05. BP reduction not requiring antihypertensive drugs dose adjustment was found in patients treated with cinacalcet. Significant BP reduction (p<0.05 was observed after parathyroidectomy and it required antihypertensive drugs cancellation or dose lowering. Cinacalcet therapy and parathyroidectomy led to increase in hemoglobin level by 2.02% (p=0.143 and 7.6% (p=0.029, respectively, as well as reduction in weekly dose of erythropoiesis-stimulating drugs by 2.7% (p=0.875 and 8.9% (p=0.751, respectively. Significant (p<0.05 decrease in LDL (5.6%, and triglycerides (23.7% levels was found in patients treated with cinacalcet. Reduction (p<0.05 in total cholesterol (1.4% and LDL (4.3% levels was observed after parathyroidectomy.Conclusion. The pleiotropic effects (reduction in BP and atherogenic lipids levels, as well as decrease in anemia resistant to the action of erythropoiesis-stimulating agents were found after parathyroidectomy and cinacalcet therapy additionally to calcium-phosphorus metabolism improvement.

  17. Discovery of a novel calcium-sensitive fluorescent probe for α-ketoglutarate. (United States)

    Gan, Lin-Lin; Chen, Lin-Hai; Nan, Fa-Jun


    α-Ketoglutarate (α-KG), a pivotal metabolite in energy metabolism, has been implicated in nonalcoholic fatty liver disease (NAFLD) and several cancers. It is recently proposed that plasma α-KG is a surrogate biomarker of NAFLD. Here, we report the development of a novel "turn-on" chemosensor for α-KG that contains a coumarin moiety as a fluorophore. Using benzothiazole-coumarin (BTC) as inspiration, we designed a probe for calcium ion recognition that possesses a unique fluorophore compared with previously reported probes for α-KG measurement. This chemosensor is based on the specific Schiff base reaction and the calcium ion recognition property of the widely used calcium indicator BTC. The probe was synthesized, and a series of parallel experiments were conducted to optimize the chemical recognition process. Compared to the initial weak fluorescence, a remarkable 7.6-fold enhancement in fluorescence intensity (I/I0 at 495 nm) was observed for the conditions in which the probe (1 μmol/L), α-KG (50 μmol/L), and Ca2+ (100 μmol/L) were incubated at 30 °C in EtOH. The probe displayed good selectivity for α-KG even in an environment with an abundance of amino acids and other interfering species such as glutaric acid. We determined that the quantitative detection range of α-KG in EtOH was between 5 and 50 μmol/L. Finally, probe in serum loaded with α-KG (10 mmol/L) showed a 7.4-fold fluorescence enhancement. In summary, a novel probe for detecting the biomarker α-KG through a typical Schiff base reaction has been discovered. With further optimization, this probe may be a good alternative for detecting the physiological metabolite α-KG.

  18. Sex difference in the sensitivity of cardiac mitochondrial permeability transition pore to calcium load

    Czech Academy of Sciences Publication Activity Database

    Milerová, Marie; Drahota, Zdeněk; Chytilová, Anna; Tauchmannová, Kateřina; Houštěk, Josef; Ošťádal, Bohuslav


    Roč. 412, 1-2 (2016), s. 147-154 ISSN 0300-8177 R&D Projects: GA ČR(CZ) GB14-36804G; GA MZd(CZ) NT14050; GA ČR(CZ) GA13-10267S; GA ČR(CZ) GAP303/12/1162 Institutional support: RVO:67985823 Keywords : heart * mitochondrial permeability transition pore * sex difference * calcium-induced swelling Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 2.669, year: 2016

  19. Fluorescence Based Characterization of Calcium Sensitizer Action on the Troponin Complex

    Energy Technology Data Exchange (ETDEWEB)

    Schlecht, William; Li, King-Lun; Hu, Dehong; Dong, Wen-Ji


    By examining the behavior of each Ca2+ -sensitizer on cTnC at different levels of reconstitution (cTnI-cTnC, full troponin, or full troponin in thin filament) the importance of these proteins on sensitizer efficacy was evaluated, lending insight into the mechanism of action behind each drug. A fluorescence based approach was used to monitor the opening and closing of cardiac troponin C's hydrophobic pocket in the presence and absence of four common Ca2+ -sensitizers: EMD 57033, levosimendan, bepridil and pimobendan. Ca2+ -titration experiments were employed to determine the effect on Ca2+- sensitivity and cooperativity of cTnC opening, while stopped flow experiments were used to investigate the impact on cTnC relaxation kinetics. This study shows EMD 57033 is unable to sensitize cTnC to Ca2+, and likely requires the presence of myosin to illicit a response. Levosimendan, bepridil, and pimobendan were all able to increase the sensitivity of cTnC for Ca2+ to varying degrees; levosimendan and pimobendan reduced the rate of cTnC closing, while bepridil increased this rate. Additionally the same experiments were run on thin filament samples containing cTnT (T204E), a known Ca2+- blunting phosphorylation mimic. Levosimendan, bepridil, and pimobendan were found to elevate the Ca2+-sensitivity of cTnT(T204E) containing thin filaments to within range of the wild type thin filaments.

  20. Activation of a cGMP-sensitive calcium-dependent chloride channel may cause transition from calcium waves to whole-cell oscillations in smooth muscle cells

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian; Aalkjær, Christian; Nilsson, Holger


    In vitro, alpha-adreno receptor stimulation of rat mesenteric small arteries often leads to a rhythmic change in wall tension, vasomotion. Within the individual smooth muscle cells of the vascular wall, vasomotion is often preceded by a period of asynchronous calcium waves. Abruptly, these low......-frequency waves may transform into high-frequency whole-cell calcium oscillations. Simultaneously, multiple cells synchronize leading to rhythmic generation of tension. We present a mathematical model of vascular smooth muscle cells that aims at characterizing this sudden transition. Simulations show calcium...... waves sweeping through the cytoplasm when the SR is stimulated to release calcium. A rise in cyclic guanosine monophosphate (cGMP) leads to the experimentally observed transition from waves to whole-cell calcium oscillations. At the same time membrane potential starts to oscillate and the frequency...

  1. Activation of a cGMP-sensitive calcium-dependent chloride channel may cause transition from calcium waves to whole cell oscillations in smooth muscle cells

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian Brings; Aalkjær, Christian; Nilsson, Holger


    In vitro, alpha-adrenoreceptor stimulation of rat mesenteric small arteries often leads to a rhythmic change in wall tension, i.e., vasomotion. Within the individual smooth muscle cells of the vascular wall, vasomotion is often preceded by a period of asynchronous calcium waves. Abruptly, these low......-frequency waves may transform into high-frequency whole cell calcium oscillations. Simultaneously, multiple cells synchronize, leading to rhythmic generation of tension. We present a mathematical model of vascular smooth muscle cells that aims at characterizing this sudden transition. Simulations show calcium...... waves sweeping through the cytoplasm when the sarcoplasmic reticulum (SR) is stimulated to release calcium. A rise in cGMP leads to the experimentally observed transition from waves to whole cell calcium oscillations. At the same time, membrane potential starts to oscillate and the frequency...

  2. Reductions in calcium uptake induced in rat brain synaptosomes by ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kandasamy, S.B.; Howerton, T.C.; Hunt, W.A. (Armed Forces Radiobiology Research Institute, Bethesda, MD (USA))


    Gamma irradiation (60Co) reduced KCl-stimulated voltage-dependent 45Ca2+ uptake in whole-brain, cortical, and striatal synaptosomes. The time course (3, 10, 30, and 60 s) of calcium uptake by irradiated (3 Gy) and nonirradiated synaptosomes, as well as the effect of KCl (15-65 mM), was measured in whole-brain synaptosomes. The fastest and highest rate of depolarization-dependent calcium uptake occurred at 3 s with 65 mM KCl. Irradiation reduced calcium uptake at all incubation times and KCl concentrations. Bay K 8644 enhancement of KCl-stimulated calcium influx was also reduced by radiation exposure. Nimodipine binding to dihydropyridine (DHP) L-type calcium channel receptors was not altered following radiation exposure. These results demonstrate an inhibitory effect of ionizing radiation on the voltage-sensitive calcium channels in rat brain synaptosomes that are not mediated by DHP receptors.

  3. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Kozuka, M.; Ito, T.; Hirose, S.; Takahashi, K.; Hagiwara, H.


    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using /sup 125/I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.

  4. A blocker of N- and T-type voltage-gated calcium channels attenuates ethanol-induced intoxication, place preference, self-administration, and reinstatement. (United States)

    Newton, Philip M; Zeng, Lily; Wang, Victoria; Connolly, Jacklyn; Wallace, Melisa J; Kim, Chanki; Shin, Hee-Sup; Belardetti, Francesco; Snutch, Terrance P; Messing, Robert O


    There is a clear need for new therapeutics to treat alcoholism. Here, we test our hypothesis that selective inhibitors of neuronal calcium channels will reduce ethanol consumption and intoxication, based on our previous studies using knock-out mice and cell culture systems. We demonstrate that pretreatment with the novel mixed N-type and T-type calcium channel antagonist 1-(6,6-bis(4-fluorophenyl)hexyl)-4-(3,4,5-trimethoxybenzyl)piperazine (NP078585) reduced ethanol intoxication. NP078585 also attenuated the reinforcing and rewarding properties of ethanol, measured by operant self-administration and the expression of an ethanol conditioned place preference, and abolished stress-induced reinstatement of ethanol seeking. NP078585 did not affect alcohol responses in mice lacking N-type calcium channels. These results suggest that selective calcium channel inhibitors may be useful in reducing acute ethanol intoxication and alcohol consumption by human alcoholics.

  5. Presence of a thapsigargin-sensitive calcium pump in Trypanosoma evansi: Immunological, physiological, molecular and structural evidences. (United States)

    Pérez-Gordones, M C; Serrano, M L; Rojas, H; Martínez, J C; Uzcanga, G; Mendoza, M


    In higher eukaryotes, the sarco-endoplasmic reticulum (ER) Ca(2+)-ATPase (SERCA) is characterized for its high sensitivity to low concentrations of thapsigargin (TG), a very specific inhibitor. In contrast, SERCA-like enzymes with different sensitivities to TG have been reported in trypanosomatids. Here, we characterized a SERCA-like enzyme from Trypanosoma evansi and evaluated its interaction with TG. Confocal fluorescence microscopy using BODIPY FL TG and specific anti-SERCA antibodies localized the T. evansi SERCA-like enzyme in the ER and confirmed its direct interaction with TG. Moreover, the use of either 1 μM TG or 25 μM 2',5'-di (tert-butyl)-1,4-benzohydroquinone prevented the reuptake of Ca(2+) and consequently produced a small increase in the parasite cytosolic calcium concentration in a calcium-free medium, which was released from the ER pool. A 3035 bp-sequence coding for a protein with an estimated molecular mass of 110.2 kDa was cloned from T. evansi. The corresponding gene product contained all the invariant residues and conserved motifs found in other P-type ATPases but lacked the calmodulin binding site. Modeling of the three-dimensional structure of the parasite enzyme revealed that the amino acid changes found in the TG-SERCA binding pocket do not compromise the interaction between the enzyme and the inhibitor. Therefore, we concluded that T. evansi possesses a SERCA-like protein that is inhibited by TG. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Effects of dragon's blood resin and its component loureirin B on tetrodotoxin-sensitive voltage-gated sodium currents in rat dorsal root ganglion neurons. (United States)

    Xiangming, Liu; Su, Chen; Shijin, Yin; Zhinan, Mei


    Using whole-cell patch clamp technique on the membrane of freshly isolated dorsal root ganglion (DRG) neurons, the effects of dragon's blood resin and its important component loureirin B on tetrodotoxin-sensitive (TTX-S) voltage-gated sodium currents were observed. The results show that both blood resin and loureirin B could suppress TTX-S voltage-gated sodium currents in a dose-dependent way. The peak current amplitudes and the steady-state activation and inactivation curves are also made to shift by 0.05% blood resin and 0.2 mmol/L loureirin B. These results demonstrate that the effects of blood resin on TTX-S sodium current may contribute to loureirin B in blood resin. Perhaps the analgesic effect of blood resin is caused partly by loureirin B directly interfering with the nociceptive transmission of primary sensory neurons.

  7. Cd(2+) sensitivity and permeability of a low voltage-activated Ca(2+) channel with CatSper-like selectivity filter. (United States)

    Garza-López, Edgar; Chávez, Julio César; Santana-Calvo, Carmen; López-González, Ignacio; Nishigaki, Takuya


    CatSper is a sperm-specific Ca(2+) channel that plays an essential role in the male fertility. However, its biophysical properties have been poorly characterized mainly due to its deficient heterologous expression. As other voltage-gated Ca(2+) channels (CaVs), CatSper possesses a conserved Ca(2+)-selective filter motif ([T/S]x[D/E]xW) in the pore region. Interestingly, CatSper conserves four aspartic acids (DDDD) as the negatively charged residues in this motif while high voltage-activated CaVs have four glutamic acids (EEEE) and low voltage-activated CaVs possess two glutamic acids and two aspartic acids (EEDD). Previous studies based on site-directed mutagenesis of L- and T-type channels showed that the number of D seems to have a negative correlation with their cadmium (Cd(2+)) sensitivity. These results suggest that CatSper (DDDD) would have low sensitivity to Cd(2+). To explore Cd(2+)-sensitivity and -permeability of CatSper, we performed two types of experiments: 1) Electrophysiological analysis of heterologously expressed human CaV3.1 channel and three pore mutants (DEDD, EDDD and DDDD), 2) Cd(2+) imaging of human spermatozoa with FluoZin-1. Electrophysiological studies showed a significant increase in Cd(2+) and manganese (Mn(2+)) currents through the CaV3.1 mutants as well as a reduction in the inhibitory effect of Cd(2+) on the Ca(2+) current. In fluorescence imaging with human sperm, we observed an increase in Cd(2+) influx potentiated by progesterone, a potent activator of CatSper. These results support our hypothesis, namely that Cd(2+)-sensitivity and -permeability are related to the absolute number of D in the Ca(2+)-selective filter independently to the type of the Cav channels. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Linking crystal structure with temperature-sensitive vibrational modes in calcium carbonate minerals. (United States)

    Xu, Ben; Poduska, Kristin M


    We demonstrate a correlation between how an IR-active vibrational mode responds to temperature changes and how it responds to crystallinity differences. Infrared (IR) spectroscopy was used to track changes in carbonate-related vibrational modes in three different CaCO3 polymorphs (calcite, aragonite, and vaterite) and CaMg(CO3)2 (dolomite) during heating. Of the three characteristic IR-active carbonate modes, the in-plane bending mode (ν4) shows the most pronounced changes with heating in polymorphs that have planar carbonate arrangements (calcite, aragonite, and dolomite). In contrast, this mode is virtually unchanged in vaterite, which has a canted arrangement of carbonate units. We correlate these trends with recent studies that identified the ν4 mode as most susceptible to changes related to crystallinity differences in calcite and amorphous calcium carbonate. Thus, our results suggest that studies of packing arrangements could provide a generalizable approach to identify the most diagnostic vibrational modes for tracking either temperature-dependent or crystallinity-related effects in IR-active solids.

  9. Ce3+-sensitized red Mn2+ luminescence in calcium aluminoborate phosphor material (United States)

    Puchalska, M.; Zych, E.


    Ce3+ doped and Ce3+,Mn2+ co-doped calcium aluminoborate (CAB) phosphors were synthesised by solid-state reaction method and their optical properties were studied. X-ray powder diffraction, SEM and TEM studies indicated the crystallization of the main trigonal CaAl2B2O7 phase and the presence of an additional non-crystalline phase. It was also observed that increasing dopant concentration promotes phase separation. Hence, both series of phosphors demonstrated the changes in luminescence properties via activator concentration variation. Upon UV excitation (λex = 310 nm) Ce3+ doped and Ce3+,Mn2+ co-doped materials yielded intensive blue and pinkish luminescence, respectively. The spectra of CAB:Ce3+ samples showed a broad emission band due to 5d→4f transition of Ce3+, which broadened and shifted to longer wavelengths with increasing dopant content. Mn2+ co-doping caused appearance of another broad-band emission with a maximum of 680 nm, resulting from the 4T1(4G) →6A1(6S) transition of Mn2+. Detailed analysis of the emission and excitation spectra as well as decay time traces as a function of dopant concentration showed that efficient resonant energy transfer mainly occurs between Ce3+ and Mn2+ incorporated in the non-crystalline phase in CAB material. The estimated values of energy transfer efficiency of CAB:Ce3+(3%),Mn2+(4%) is close to 52%.

  10. Parameter Sensitivity Analysis of Stochastic Models Provides Insights into Cardiac Calcium Sparks


    Lee, Young-Seon; Liu, Ona Z.; Hwang, Hyun Seok; Knollmann, Bjorn C.; Sobie, Eric A.


    We present a parameter sensitivity analysis method that is appropriate for stochastic models, and we demonstrate how this analysis generates experimentally testable predictions about the factors that influence local Ca2+ release in heart cells. The method involves randomly varying all parameters, running a single simulation with each set of parameters, running simulations with hundreds of model variants, then statistically relating the parameters to the simulation results using regression met...

  11. Calcium Homeostasis Modulator 1-Like Currents in Rat Fungiform Taste Cells Expressing Amiloride-Sensitive Sodium Currents. (United States)

    Bigiani, Albertino


    Salt reception by taste cells is still the less understood transduction process occurring in taste buds, the peripheral sensory organs for the detection of food chemicals. Although there is evidence suggesting that the epithelial sodium channel (ENaC) works as sodium receptor, yet it is not clear how salt-detecting cells signal the relevant information to nerve endings. Taste cells responding to sweet, bitter, and umami substances release ATP as neurotransmitter through a nonvesicular mechanism. Three different channel proteins have been proposed as conduit for ATP secretion: pannexin channels, connexin hemichannels, and calcium homeostasis modulator 1 (CALHM1) channels. In heterologous expression systems, these channels mediate outwardly rectifying membrane currents with distinct biophysical and pharmacological properties. I therefore tested whether also salt-detecting taste cells were endowed with these currents. To this aim, I applied the patch-clamp techniques to single cells in isolated taste buds from rat fungiform papillae. Salt-detecting cells were functionally identified by exploiting the effect of amiloride, which induces a current response by shutting down ENaCs. I looked for the presence of outwardly rectifying currents by using appropriate voltage-clamp protocols and specific pharmacological tools. I found that indeed salt-detecting cells possessed these currents with properties consistent with the presence, at least in part, of CALHM1 channels. Unexpectedly, CALHM1-like currents in taste cells were potentiated by known blockers of pannexin, suggesting a possible inhibitory action of this protein on CALMH1. These findings indicate that communication between salt-detecting cells and nerve endings might involve ATP release by CALMH1 channels. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail:

  12. Surface acidity and solid-state compatibility of excipients with an acid-sensitive API: case study of atorvastatin calcium. (United States)

    Govindarajan, Ramprakash; Landis, Margaret; Hancock, Bruno; Gatlin, Larry A; Suryanarayanan, Raj; Shalaev, Evgenyi Y


    The objectives of this study were to measure the apparent surface acidity of common excipients and to correlate the acidity with the chemical stability of an acid-sensitive active pharmaceutical ingredient (API) in binary API-excipient powder mixtures. The acidity of 26 solid excipients was determined by two methods, (i) by measuring the pH of their suspensions or solutions and (ii) the pH equivalent (pHeq) measured via ionization of probe molecules deposited on the surface of the excipients. The chemical stability of an API, atorvastatin calcium (AC), in mixtures with the excipients was evaluated by monitoring the appearance of an acid-induced degradant, atorvastatin lactone, under accelerated storage conditions. The extent of lactone formation in AC-excipient mixtures was presented as a function of either solution/suspension pH or pHeq. No lactone formation was observed in mixtures with excipients having pHeq > 6, while the lactone levels were pronounced (> 0.6% after 6 weeks at 50°C/20% RH) with excipients exhibiting pHeq 6, 3-6, and API, were identified based on pHeq measurements. The incompatibility prediction was confirmed in the chemical stability tests using AC as an example of an acid-sensitive API.

  13. Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells.

    Directory of Open Access Journals (Sweden)

    Jolene Atia


    Full Text Available Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the 'conductance repertoire' being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations.

  14. Visualization of Peripheral Neuron Sensitization in a Surgical Mouse Model of Osteoarthritis by In Vivo Calcium Imaging. (United States)

    Miller, Rachel E; Kim, Yu Shin; Tran, Phuong B; Ishihara, Shingo; Dong, Xinzhong; Miller, Richard J; Malfait, Anne-Marie


    To develop a method for analyzing sensory neuron responses to mechanical stimuli in vivo, and to evaluate whether these neuronal responses change after destabilization of the medial meniscus (DMM). DMM or sham surgery was performed in 10-week-old male C57BL/6 wild-type or Pirt-GCaMP3+/- mice. All experiments were performed 8 weeks after surgery. Knee and hind paw hyperalgesia were assessed in wild-type mice. The retrograde label DiI was injected into the ipsilateral knee to quantify the number of knee-innervating neurons in the L4 dorsal root ganglion (DRG) in wild-type mice. In vivo calcium imaging was performed on the ipsilateral L4 DRG of Pirt-GCaMP3+/- mice as mechanical stimuli (paw pinch, knee pinch, or knee twist) were applied to the ipsilateral hind limb. Eight weeks after surgery, mice subjected to DMM had more hyperalgesia in the knee and hind paw compared to mice subjected to sham surgery. Intraarticular injection of DiI labeled similar numbers of neurons in the L4 DRG of mice subjected to sham surgery and mice subjected to DMM. Increased numbers of sensory neurons responded to all 3 mechanical stimuli in mice subjected to DMM, as assessed by in vivo calcium imaging. The majority of responses in mice subjected to sham surgery and mice subjected to DMM were in small to medium-sized neurons, consistent with the size of nociceptors. The magnitude of responses was similar between mice subjected to sham surgery and mice subjected to DMM. Our findings indicate that increased numbers of small to medium-sized DRG neurons respond to mechanical stimuli 8 weeks after DMM surgery, suggesting that nociceptors have become sensitized by lowering the response threshold. © 2017, American College of Rheumatology.

  15. Acute exposure to low-level CW and GSM-modulated 900 MHz radiofrequency does not affect Ba 2+ currents through voltage-gated calcium channels in rat cortical neurons. (United States)

    Platano, Daniela; Mesirca, Pietro; Paffi, Alessandra; Pellegrino, Monica; Liberti, Micaela; Apollonio, Francesca; Bersani, Ferdinando; Aicardi, Giorgio


    We have studied the non-thermal effects of radiofrequency (RF) electromagnetic fields (EMFs) on Ba(2+) currents (I Ba 2+) through voltage-gated calcium channels (VGCC), recorded in primary cultures of rat cortical neurons using the patch-clamp technique. To assess whether low-level acute RF field exposure could modify the amplitude and/or the voltage-dependence of I Ba 2+, Petri dishes containing cultured neurons were exposed for 1-3 periods of 90 s to 900 MHz RF-EMF continuous wave (CW) or amplitude-modulated according to global system mobile communication standard (GSM) during whole-cell recording. The specific absorption rates (SARs) were 2 W/kg for CW and 2 W/kg (time average value) for GSM-modulated signals, respectively. The results obtained indicate that single or multiple acute exposures to either CW or GSM-modulated 900 MHz RF-EMFs do not significantly alter the current amplitude or the current-voltage relationship of I Ba 2+, through VGCC. (c) 2007 Wiley-Liss, Inc.

  16. A Blocker of N- and T-type Voltage-Gated Calcium Channels Attenuates Ethanol-Induced Intoxication, Place Preference, Self-Administration, and Reinstatement


    Newton, Philip M.; Zeng, Lily; Wang, Victoria; Connolly, Jacklyn; Wallace, Melisa Joellan; Kim, Chanki; Shin, Hee-sup; Belardetti, Francesco; Snutch, Terrance P; Messing, Robert O.


    There is a clear need for new therapeutics to treat alcoholism. Here, we test our hypothesis that selective inhibitors of neuronal calcium channels will reduce ethanol consumption and intoxication, based on our previous studies using knock-out mice and cell culture systems. We demonstrate that pretreatment with the novel mixed N-type and T-type calcium channel antagonist 1-(6,6-bis(4-fluorophenyl)hexyl)-4-(3,4,5-trimethoxybenzyl)piperazine (NP078585) reduced ethanol intoxication. NP078585 als...

  17. Elimination of bus voltage impact on temperature sensitive electrical parameter during turn-on transition for junction temperature estimation of high-power IGBT modules

    DEFF Research Database (Denmark)

    Luo, Haoze; Iannuzzo, Francesco; Blaabjerg, Frede


    Junction temperature is of great importance to safe operating area of IGBT modules. Various information of the IGBT operating state is reflected on electrical characteristics during turn-on transient. A unified extraction method for internal junction temperature via dynamic thermo-sensitive elect......Junction temperature is of great importance to safe operating area of IGBT modules. Various information of the IGBT operating state is reflected on electrical characteristics during turn-on transient. A unified extraction method for internal junction temperature via dynamic thermo......-sensitive electrical parameters (DTSEP) during turn-on transient is proposed. Two DTSEP, turn-on delay time (tdon) and the maximum increasing rate of collector current dic/dt(max), are combined to eliminate the bus voltage impact. Using the inherent emitter-auxiliary inductor LeE in high-power modules, the temperature...

  18. Coexpression of voltage-dependent calcium channels Cav1.2, 2.1a, and 2.1b in vascular myocytes

    DEFF Research Database (Denmark)

    Andreasen, Ditte; Friis, Ulla G; Uhrenholt, Torben R


    Voltage-dependent Ca2+ channels Cav1.2 (L type) and Cav2.1 (P/Q type) are expressed in vascular smooth muscle cells (VSMCs) and are important for the contraction of renal resistance vessels. In the present study we examined whether native renal VSMCs coexpress L-, P-, and Q-type Ca2+ currents. Th...

  19. Parameter sensitivity analysis of stochastic models provides insights into cardiac calcium sparks. (United States)

    Lee, Young-Seon; Liu, Ona Z; Hwang, Hyun Seok; Knollmann, Bjorn C; Sobie, Eric A


    We present a parameter sensitivity analysis method that is appropriate for stochastic models, and we demonstrate how this analysis generates experimentally testable predictions about the factors that influence local Ca(2+) release in heart cells. The method involves randomly varying all parameters, running a single simulation with each set of parameters, running simulations with hundreds of model variants, then statistically relating the parameters to the simulation results using regression methods. We tested this method on a stochastic model, containing 18 parameters, of the cardiac Ca(2+) spark. Results show that multivariable linear regression can successfully relate parameters to continuous model outputs such as Ca(2+) spark amplitude and duration, and multivariable logistic regression can provide insight into how parameters affect Ca(2+) spark triggering (a probabilistic process that is all-or-none in a single simulation). Benchmark studies demonstrate that this method is less computationally intensive than standard methods by a factor of 16. Importantly, predictions were tested experimentally by measuring Ca(2+) sparks in mice with knockout of the sarcoplasmic reticulum protein triadin. These mice exhibit multiple changes in Ca(2+) release unit structures, and the regression model both accurately predicts changes in Ca(2+) spark amplitude (30% decrease in model, 29% decrease in experiments) and provides an intuitive and quantitative understanding of how much each alteration contributes to the result. This approach is therefore an effective, efficient, and predictive method for analyzing stochastic mathematical models to gain biological insight. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  20. Roles of subthreshold calcium current and sodium current in spontaneous firing of mouse midbrain dopamine neurons. (United States)

    Puopolo, Michelino; Raviola, Elio; Bean, Bruce P


    We used a preparation of acutely dissociated neurons to quantify the ionic currents driving the spontaneous firing of substantia nigra pars compacta neurons, isolated from transgenic mice in which the tyrosine hydroxylase promoter drives expression of human placental alkaline phosphatase (PLAP) on the outer surface of the cell membrane. Dissociated neurons identified by fluorescent antibodies to PLAP showed firing properties similar to those of dopaminergic neurons in brain slice, including rhythmic spontaneous firing of broad action potentials and, in some cells, rhythmic oscillatory activity in the presence of tetrodotoxin (TTX). Spontaneous activity in TTX had broader, smaller spikes than normal pacemaking and was stopped by removal of external calcium. Normal pacemaking was also consistently silenced by replacement of external calcium by cobalt and was slowed by more specific calcium channel blockers. Nimodipine produced a slowing of pacemaking frequency. Pacemaking was also slowed by the P/Q-channel blocker omega-Aga-IVA, but the N-type channel blocker omega-conotoxin GVIA had no effect. In voltage-clamp experiments, using records of pacemaking as command voltage, cobalt-sensitive current and TTX-sensitive current were both sizeable at subthreshold voltages between spikes. Cobalt-sensitive current was consistently larger than TTX-sensitive current at interspike voltages from -70 to -50 mV, with TTX-sensitive current larger at voltages positive to -45 mV. These results support previous evidence for a major role of voltage-dependent calcium channels in driving pacemaking of midbrain dopamine neurons and suggest that multiple calcium channel types contribute to this function. The results also show a significant contribution of subthreshold TTX-sensitive sodium current.

  1. Effects of conformational peptide probe DP4 on bidirectional signaling between DHPR and RyR1 calcium channels in voltage-clamped skeletal muscle fibers. (United States)

    Olojo, Rotimi O; Hernández-Ochoa, Erick O; Ikemoto, Noriaki; Schneider, Martin F


    In skeletal muscle, excitation-contraction coupling involves the activation of dihydropyridine receptors (DHPR) and type-1 ryanodine receptors (RyR1) to produce depolarization-dependent sarcoplasmic reticulum Ca²⁺ release via orthograde signaling. Another form of DHPR-RyR1 communication is retrograde signaling, in which RyRs modulate the gating of DHPR. DP4 (domain peptide 4), is a peptide corresponding to residues Leu²⁴⁴²-Pro²⁴⁷⁷ of the central domain of the RyR1 that produces RyR1 channel destabilization. Here we explore the effects of DP4 on orthograde excitation-contraction coupling and retrograde RyR1-DHPR signaling in isolated murine muscle fibers. Intracellular dialysis of DP4 increased the peak amplitude of Ca²⁺ release during step depolarizations by 64% without affecting its voltage-dependence or kinetics, and also caused a similar increase in Ca²⁺ release during an action potential waveform. DP4 did not modify either the amplitude or the voltage-dependence of the intramembrane charge movement. However, DP4 augmented DHPR Ca²⁺ current density without affecting its voltage-dependence. Our results demonstrate that the conformational changes induced by DP4 regulate both orthograde E-C coupling and retrograde RyR1-DHPR signaling. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  2. Assessing soil calcium depletion following growth and harvesting of Sitka spruce plantation forestry in the acid sensitive Welsh uplands

    Directory of Open Access Journals (Sweden)

    B. Reynolds


    Full Text Available A simple mass balance has been used to estimate soil calcium depletion during the growth of a 50 year old Sitka spruce crop on acid, base-poor peaty podzol soils in upland Wales. Growth of the crop will deplete the soil calcium reserve by an amount (205 kg Ca ha-1 approximately equivalent to the exchangeable calcium pool to the bottom of the profile and equal to 14% of the total soil calcium reserve to the bottom of the B horizon. Despite these predictions, measurements of exchangeable calcium show no differences beneath mature forest and acid grassland, implying that i weathering rates in forest soils are greater than long-term estimates and predictions by the PROFILE soil chemistry model ii the trees can access other sources of calcium or iii there are significant errors in the mass balance. Following stem-only harvesting, growth of a 50 year old second rotation crop will lead to further depletion of soil calcium, but this amount (79 kg Ca ha-1, is less than for a second rotation crop following whole-tree harvesting (197 kg Ca ha-1. After the first crop, stem-only harvesting would allow a further 18 rotations before depletion of the total calcium reserve to the bottom of the B horizon. Whole-tree harvesting would allow for seven rotations after the first crop. These calculations assume that all sources of calcium are equally available to the crop. This can only be resolved by dynamic modelling of the calcium cycle at the ecosystem scale based on appropriate field measurements. The potential for significant soil acidification is therefore greater following whole-tree harvesting and, in line with current recommendations (Nisbet et al., 1997, this technique should probably be avoided on acidic, nutrient-poor soils unless remedial measures are included to enhance the soil base cation status.

  3. Trolox-sensitive reactive oxygen species regulate mitochondrial morphology, oxidative phosphorylation and cytosolic calcium handling in healthy cells. (United States)

    Distelmaier, Felix; Valsecchi, Federica; Forkink, Marleen; van Emst-de Vries, Sjenet; Swarts, Herman G; Rodenburg, Richard J T; Verwiel, Eugène T P; Smeitink, Jan A M; Willems, Peter H G M; Koopman, Werner J H


    Cell regulation by signaling reactive oxygen species (sROS) is often incorrectly studied through extracellular oxidant addition. Here, we used the membrane-permeable antioxidant Trolox to examine the role of sROS in mitochondrial morphology, oxidative phosphorylation (OXPHOS), and cytosolic calcium (Ca(2+)) handling in healthy human skin fibroblasts. Trolox treatment reduced the levels of 5-(and-6)-chloromethyl-2',7'-dichlorodihydro-fluorescein (CM-H(2)DCF) oxidizing ROS, lowered cellular lipid peroxidation, and induced a less oxidized mitochondrial thiol redox state. This was paralleled by increased glutathione- and mitofusin-dependent mitochondrial filamentation, increased expression of fully assembled mitochondrial complex I, elevated activity of citrate synthase and OXPHOS enzymes, and a higher cellular O(2) consumption. In contrast, Trolox did not alter hydroethidium oxidation, cytosolic thiol redox state, mitochondrial NAD(P)H levels, or mitochondrial membrane potential. Whole genome expression profiling revealed that Trolox did not trigger significant changes in gene expression, suggesting that Trolox acts downstream of this process. Cytosolic Ca(2+) transients, induced by the hormone bradykinin, were of a higher amplitude and decayed faster in Trolox-treated cells. These effects were dose-dependently antagonized by hydrogen peroxide. Our findings suggest that Trolox-sensitive sROS are upstream regulators of mitochondrial mitofusin levels, morphology, and function in healthy human skin fibroblasts. This information not only facilitates the interpretation of antioxidant effects in cell models (of oxidative-stress), but also contributes to a better understanding of ROS-related human pathologies, including mitochondrial disorders.

  4. Calcium dobesilate reduces endothelin-1 and high-sensitivity C-reactive protein serum levels in patients with diabetic retinopathy. (United States)

    Javadzadeh, Alireza; Ghorbanihaghjo, Amir; Adl, Farzad Hami; Andalib, Dima; Khojasteh-Jafari, Hassan; Ghabili, Kamyar


    To determine the benefits of calcium dobesilate (CaD) administration on endothelial function and inflammatory status in patients with diabetic retinopathy through measurement of serum levels of endothelin-1 and high-sensitivity C-reactive protein (hsCRP). In a double-blind, randomized clinical trial, 90 patients with either severe nonproliferative or proliferative diabetic retinopathy and with blood glucose level of 120-200 mg/dl were randomly allocated to treatment with either CaD tablets (500 mg daily) or placebo for 3 months. Visual acuity, intraocular pressure, and macular status were performed before the study. The serum levels of endothelin-1 and hsCRP were evaluated in both groups before and at the third month of the trial. The median serum level of hsCRP significantly differed between the groups 3 months following the CaD or placebo administration (2.2 mg/l in the CaD group versus 3.7 mg/l in the placebo group, p=0.01). The mean endothelin-1 serum level was 0.69±0.32 pg/ml in the CaD group and 0.86±0.30 pg/ml in the placebo group (p=0.01). Furthermore, in the CaD group, the serum levels of both endothelin-1 and hsCRP were significantly decreased 3 months after administration of CaD (p<0.001). Administration of the CaD in the patients with diabetic retinopathy may reduce the serum levels of endothelin-1 and hsCRP. This might imply amelioration of the endothelial function and inflammatory status following CaD therapy in these patients.

  5. Compensatory Internalization of Pma1 in V-ATPase Mutants in Saccharomyces cerevisiae Requires Calcium- and Glucose-Sensitive Phosphatases. (United States)

    Velivela, Swetha Devi; Kane, Patricia M


    Loss of V-ATPase activity in organelles, whether through V-ATPase inhibition or V-ATPase ( vma) mutations, triggers a compensatory downregulation of the essential plasma membrane proton pump, Pma1 in S. cerevisiae We have previously determined that the a-arrestin Rim8 and ubiquitin ligase Rsp5 are essential for Pma1 ubiquination and endocytosis in response to loss of V-ATPase activity. Here, we show that Pma1 endocytosis in V-ATPase mutants does not require Rim101 pathway components upstream and downstream of Rim8, indicating that Rim8 is acting independently in Pma1 internalization. We find that two phosphatases, the calcium-responsive phosphatase, calcineurin and glucose-sensitive phosphatase, Glc7 (PP1) and one of the Glc7 regulatory subunits, Reg1, exhibit negative synthetic genetic interactions with vma mutants, and demonstrate that both phosphatases are essential for ubiquitination and endocytic downregulation of Pma1 in these mutants.  Although both acute and chronic loss of V-ATPase activity trigger internalization of approximately 50% of surface Pma1, a comparable reduction in Pma1 expression in a pma1-007 mutant neither compensates for loss of V-ATPase activity nor stops further Pma1 endocytosis. The results indicate that cell surface level of Pma1 is not directly sensed and that internalized Pma1 may play a role in compensating for loss of V-ATPase-dependent acidification.  Taken together, these results provide new insights into crosstalk between two major proton pumps central to cellular pH control. Copyright © 2017, Genetics.

  6. The α2δ subunit and absence epilepsy: Beyond calcium channels?

    NARCIS (Netherlands)

    Celli, R.; Santolini, I.; Guiducci, M.; Luijtelaar, E.L.J.M. van; Parisi, P.; Striano, P.; Gradini, R.; Battaglia, G.; Ngomba, R.T.; Nicoletti, F.


    Spike-wave discharges, underlying absence seizures, are generated within a cortico-thalamo-cortical network that involves the somatosensory cortex, the reticular thalamic nucleus, and the ventrobasal thalamic nuclei. Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the

  7. Neonatal maternal deprivation sensitizes voltage-gated sodium channel currents in colon-specific dorsal root ganglion neurons in rats. (United States)

    Hu, Shufen; Xiao, Ying; Zhu, Liyan; Li, Lin; Hu, Chuang-Ying; Jiang, Xinghong; Xu, Guang-Yin


    Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by abdominal pain in association with altered bowel movements. The underlying mechanisms of visceral hypersensitivity remain elusive. This study was designed to examine the role for sodium channels in a rat model of chronic visceral hyperalgesia induced by neonatal maternal deprivation (NMD). Abdominal withdrawal reflex (AWR) scores were performed on adult male rats. Colon-specific dorsal root ganglion (DRG) neurons were labeled with DiI and acutely dissociated for measuring excitability and sodium channel current under whole-cell patch-clamp configurations. The expression of Na(V)1.8 was analyzed by Western blot and quantitative real-time PCR. NMD significantly increased AWR scores, which lasted for ~6 wk in an association with hyperexcitability of colon DRG neurons. TTX-resistant but not TTX-sensitive sodium current density was greatly enhanced in colon DRG neurons in NMD rats. Compared with controls, activation curves showed a leftward shift in NMD rats whereas inactivation curves did not differ significantly. NMD markedly accelerated the activation time of peak current amplitude without any changes in inactivation time. Furthermore, NMD remarkably enhanced expression of Na(V)1.8 at protein levels but not at mRNA levels in colon-related DRGs. The expression of Na(V)1.9 was not altered after NMD. These data suggest that NMD enhances TTX-resistant sodium activity of colon DRG neurons, which is most likely mediated by a leftward shift of activation curve and by enhanced expression of Na(V)1.8 at protein levels, thus identifying a specific molecular mechanism underlying chronic visceral pain and sensitization in patients with IBS.

  8. PID, 2-DOF PID and Mixed Sensitivity Loop-Shaping Based Robust Voltage Control of Quadratic Buck DC-DC Converter

    Directory of Open Access Journals (Sweden)

    Fateh Ounis


    Full Text Available DC-DC Quadratic Buck Converter (QBC is largely used in applications where the high step-down conversion ratio is required. In the practical implementation, QBC is subject to uncertainties, disturbance, and sensor noise. To address the QBC control problems, a two-degree of freedom PID (2-DOF PID is designed in the robust control framework. Further, for comparison purpose, a one-degree of freedom PID (1-DOF PID and mixed sensitivity loop-shaping (MS-LS controller are also proposed. Considering QBC parasitic components, the QBC small-signal transfer function is derived based on a practical approach. Sensitivity functions are used to specify the desired design requirements, and non-smooth optimization is used to tune both PID's parameters. The three control structures are implemented and tested in the Matlab/Simulink environment. As attested by simulation results, the 2-DOF PID exhibits a better regulation accuracy with enhanced robust stability and robust performance for a wide range of supply voltage/load variation and sensor noise effect.

  9. Interactions of phosphatase and tensin homologue (PTEN) proteins with phosphatidylinositol phosphates: insights from molecular dynamics simulations of PTEN and voltage sensitive phosphatase. (United States)

    Kalli, Antreas C; Devaney, Isabel; Sansom, Mark S P


    The phosphatase and tensin homologue (PTEN) and the Ciona intestinalis voltage sensitive phosphatase (Ci-VSP) are both phosphatidylinositol phosphate (PIP) phosphatases that contain a C2 domain. PTEN is a tumor suppressor protein that acts as a phosphatase on PIP3 in mammalian cell membranes. It contains two principal domains: a phosphatase domain (PD) and a C2 domain. Despite detailed structural and functional characterization, less is known about its mechanism of interaction with PIP-containing lipid bilayers. Ci-VSP consists of an N-terminal transmembrane voltage sensor domain and a C-terminal PTEN domain, which in turn contains a PD and a C2 domain. The nature of the interaction of the PTEN domain of Ci-VSP with membranes has not been well established. We have used multiscale molecular dynamics simulations to define the interaction mechanisms of PTEN and of the Ci-VSP PTEN domains with PIP-containing lipid bilayers. Our results suggest a novel mechanism of association of the PTEN with such bilayers, in which an initial electrostatics-driven encounter of the protein and bilayer is followed by reorientation of the protein to optimize its interactions with PIP molecules in the membrane. Although a PIP3 molecule binds close to the active site of PTEN, our simulations suggest a further conformational change of the protein may be required for catalytically productive binding to occur. Ci-VSP interacted with membranes in an orientation comparable to that of PTEN but bound directly to PIP-containing membranes without a subsequent reorientation step. Again, PIP3 bound close to the active site of the Ci-VSP PD, but not in a catalytically productive manner. Interactions of Ci-VSP with the bilayer induced clustering of PIP molecules around the protein.

  10. Giant magnetoimpedance intrinsic impedance and voltage sensitivity of rapidly solidified Co{sub 66}Fe{sub 2}Cr{sub 4}Si{sub 13}B{sub 15} amorphous wire for highly sensitive sensors applications

    Energy Technology Data Exchange (ETDEWEB)

    Das, Tarun K.; Mandal, Sushil K. [CSIR - National Metallurgical Laboratory, NDE and Magnetic Materials Group, MST Division, Jamshedpur (India); Banerji, Pallab [Indian Institute of Technology, Kharagpur, Materials Science Centre, Kharagpur (India)


    We report a systematic study of the influence of wire length, L, dependence of giant magneto-impedance (GMI) sensitivity of Co{sub 66}Fe{sub 2}Cr{sub 4}Si{sub 13}B{sub 15} soft magnetic amorphous wire of diameter ∝ 100 μm developed by in-water quenching technique. The magnetization behaviour (hysteresis loops) of the wire with different length (L = 1, 2, 3, 5, 8 and 10 cm) has been evaluated by fuxmetric induction method. It was observed that the behaviour of the hysteresis loops change drastically with the wire length, being attributed to the existence of a critical length, L{sub C}, found to be around 3 cm. GMI measurements have been taken using automated GMI measurement system and the GMI sensitivities in terms of intrinsic impedance sensitivity (S{sub Ω/Am}{sup -1}) and voltage sensitivity (S{sub V/Am}{sup -1}) of the wire have been evaluated under optimal bias field and excitation current. It was found that the maximum (S{sub Ω/Am}{sup -1}){sub max} ∼ 0.63 Ω/kAm{sup -1}/cm and (S{sub V/Am}{sup -1}){sub max} ∼ 3.10 V/kAm{sup -1}/cm were achieved at a critical length L{sub C} ∝ 3 cm of the wire for an AC current of 5 mA and a frequency of 5 MHz. These findings provide crucial insights for optimization of the geometrical dimensions of magnetic sensing elements and important practical guidance for designing high sensitive GMI sensors. The relevant combinations of magnetic material parameters and operating conditions that optimize the sensitivity are highlighted. (orig.)

  11. A toxin from the spider Phoneutria nigriventer that blocks calcium channels coupled to exocytosis (United States)

    Guatimosim, C; Romano-Silva, M A; Cruz, J S; Beirão, P S L; Kalapothakis, E; Moraes-Santos, T; Cordeiro, M N; Diniz, C R; Gomez, M V; Prado, M A M


    The aim of the present experiments was to investigate the pharmacological action of a toxin from the spider Phoneutria nigriventer, Tx3-3, on the function of calcium channels that control exocytosis of synaptic vesicles. Tx3-3, in confirmation of previous work, diminished the intracellular calcium increase induced by membrane depolarization with KCl (25 mM) in rat cerebrocortical synaptosomes. The toxin was very potent (IC50 0.9 nM) at inhibiting calcium channels that regulate calcium entry in synaptosomes. In addition, Tx3-3 blocked the exocytosis of synaptic vesicles, as measured with the fluorescent dye FM1-43. Using ω-toxins that interact selectively with distinct neuronal calcium channels, we investigated whether the target of Tx3-3 overlaps with known channels that mediate exocytosis. The results indicate that the main population of voltage-sensitive calcium channels altered by Tx3-3 can also be inhibited by ω-agatoxin IVA, an antagonist of P/Q calcium channels. ω-conotoxin GVIA, which inhibits N type calcium channels did not decrease significantly the entry of calcium or exocytosis of synaptic vesicles in depolarized synaptosomes. It is concluded that Tx3-3 potently inhibits ω-agatoxin IVA-sensitive calcium channels, which are involved in controlling exocytosis in rat brain cortical synaptosomes. PMID:9351520

  12. Long-term habituation of the gill-withdrawal reflex in Aplysia requires gene transcription, calcineurin and L-type voltage-gated calcium channels

    Directory of Open Access Journals (Sweden)

    Joseph eEsdin


    Full Text Available Although habituation is possibly the simplest form of learning, we still do not fully understand the neurobiological basis of habituation in any organism. To advance the goal of a comprehensive understanding of habituation, we have studied long-term habituation (LTH of the gill-withdrawal reflex (GWR in the marine snail Aplysia californica. Previously, we showed that habituation of the GWR in a reduced preparation lasts for up to 12 hr, and depends on protein synthesis, as well as activation of protein phosphatases 1 and 2A and postsynaptic glutamate receptors. Here, we have used the reduced preparation to further analyze the mechanisms of LTH in Aplysia. We found that LTH of the GWR depends on RNA synthesis because it was blocked by both the irreversible transcriptional inhibitor actinomycin-D and the reversible transcriptional inhibitor, 5,6-dichlorobenzimidazole riboside (DRB. In addition, LTH requires activation of protein phosphatase 2B (calcineurin, because it was disrupted by ascomycin. Finally, LTH was blocked by nitrendipine, which indicates that activation of L-type voltage-gated Ca2+ channels is required for this form of learning. Together with our previous results, the present results indicate that exclusively presynaptic mechanisms, although possibly sufficient for short-term habituation, are insufficient for LTH. Rather, LTH must involve postsynaptic, as well as presynaptic, mechanisms.

  13. CRMP-2 peptide mediated decrease of high and low voltage-activated calcium channels, attenuation of nociceptor excitability, and anti-nociception in a model of AIDS therapy-induced painful peripheral neuropathy

    Directory of Open Access Journals (Sweden)

    Piekarz Andrew D


    Full Text Available Abstract Background The ubiquity of protein-protein interactions in biological signaling offers ample opportunities for therapeutic intervention. We previously identified a peptide, designated CBD3, that suppressed inflammatory and neuropathic behavioral hypersensitivity in rodents by inhibiting the ability of collapsin response mediator protein 2 (CRMP-2 to bind to N-type voltage-activated calcium channels (CaV2.2 [Brittain et al. Nature Medicine 17:822–829 (2011]. Results and discussion Here, we utilized SPOTScan analysis to identify an optimized variation of the CBD3 peptide (CBD3A6K that bound with greater affinity to Ca2+ channels. Molecular dynamics simulations demonstrated that the CBD3A6K peptide was more stable and less prone to the unfolding observed with the parent CBD3 peptide. This mutant peptide, conjugated to the cell penetrating motif of the HIV transduction domain protein TAT, exhibited greater anti-nociception in a rodent model of AIDS therapy-induced peripheral neuropathy when compared to the parent TAT-CBD3 peptide. Remarkably, intraperitoneal administration of TAT-CBD3A6K produced none of the minor side effects (i.e. tail kinking, body contortion observed with the parent peptide. Interestingly, excitability of dissociated small diameter sensory neurons isolated from rats was also reduced by TAT-CBD3A6K peptide suggesting that suppression of excitability may be due to inhibition of T- and R-type Ca2+ channels. TAT-CBD3A6K had no effect on depolarization-evoked calcitonin gene related peptide (CGRP release compared to vehicle control. Conclusions Collectively, these results establish TAT-CBD3A6K as a peptide therapeutic with greater efficacy in an AIDS therapy-induced model of peripheral neuropathy than its parent peptide, TAT-CBD3. Structural modifications of the CBD3 scaffold peptide may result in peptides with selectivity against a particular subset of voltage-gated calcium channels resulting in a multipharmacology of

  14. A study of the formation of amorphous calcium phosphate and hydroxyapatite on melt quenched Bioglass using surface sensitive shallow angle X-ray diffraction. (United States)

    Martin, R A; Twyman, H; Qiu, D; Knowles, J C; Newport, R J


    Melt quenched silicate glasses containing calcium, phosphorous and alkali metals have the ability to promote bone regeneration and to fuse to living bone. These glasses, including 45S5 Bioglass((R)) [(CaO)(26.9)(Na(2)O)(24.4)(SiO(2))(46.1)(P(2)O(5))(2.6)], are routinely used as clinical implants. Consequently there have been numerous studies on the structure of these glasses using conventional diffraction techniques. These studies have provided important information on the atomic structure of Bioglass((R)) but are of course intrinsically limited in the sense that they probe the bulk material and cannot be as sensitive to thin layers of near-surface dissolution/growth. The present study therefore uses surface sensitive shallow angle X-ray diffraction to study the formation of amorphous calcium phosphate and hydroxyapatite on Bioglass((R)) samples, pre-reacted in simulated body fluid (SBF). Unreacted Bioglass((R)) is dominated by a broad amorphous feature around 2.2 A(-1) which is characteristic of sodium calcium silicate glass. After reacting Bioglass((R)) in SBF a second broad amorphous feature evolves ~1.6 A(-1) which is attributed to amorphous calcium phosphate. This feature is evident for samples after only 4 h reacting in SBF and by 8 h the amorphous feature becomes comparable in magnitude to the background signal of the bulk Bioglass((R)). Bragg peaks characteristic of hydroxyapatite form after 1-3 days of reacting in SBF.

  15. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna


    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... optimization. The proposed method is used to calculate the voltage bands and droop settings of PV inverters at each node by the supervisory controller. The local controller of each PV inverter implements the volt/var control and if necessary, the active power curtailment as per the received settings and based...... on measured local voltages. The advantage of the proposed method is that the calculated reactive power and active power droop settings enable fair contribution of the PV inverters at each node to the voltage regulation. Simulation studies are conducted using DigSilent Power factory software on a simplified...

  16. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna


    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... analysis, which is simple for computation and requires moderate automation and communication infrastructure. The proposed method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system...

  17. Imaging voltage in neurons (United States)

    Peterka, Darcy S.; Takahashi, Hiroto; Yuste, Rafael


    In the last decades, imaging membrane potential has become a fruitful approach to study neural circuits, especially in invertebrate preparations with large, resilient neurons. At the same time, particularly in mammalian preparations, voltage imaging methods suffer from poor signal to noise and secondary side effects, and they fall short of providing single-cell resolution when imaging of the activity of neuronal populations. As an introduction to these techniques, we briefly review different voltage imaging methods (including organic fluorophores, SHG chromophores, genetic indicators, hybrid, nanoparticles and intrinsic approaches), and illustrate some of their applications to neuronal biophysics and mammalian circuit analysis. We discuss their mechanisms of voltage sensitivity, from reorientation, electrochromic or electro-optical phenomena, to interaction among chromophores or membrane scattering, and highlight their advantages and shortcomings, commenting on the outlook for development of novel voltage imaging methods. PMID:21220095

  18. Automated system with LabVIEW for the obtention of voltage plateau, graphic of sensitivity and operation voltage in an ionization chamber; Sistema automatizado con LabVIEW para la obtencion de meseta de voltaje, grafica de sensitividad y voltaje de operacion en una camara de ionizacion

    Energy Technology Data Exchange (ETDEWEB)

    Cruz E, P. [Instituto Nacional de Investigaciones Nucleares, Departamento de Ingenieria Electronica, A.P. 18-1027, 11801 Mexico D.F. (Mexico)


    The work developed for the Laguna Verde Nuclear Power Central allows to obtain the voltage plateau, graphic of sensitivity and operation voltage of three types of ionization chambers which are used in their monitoring systems of process radiation. The automated system is based in a personal computer (Pc) for controlling and acquiring data from the different instruments used, its programming was realized with virtual instruments (LabVIEW, National Instruments software). The system also realizes a diagnosis of the ionization chamber and determine whether the parameters obtained are inside of the manufacturer specifications, that is to say, it determines when the ionization chamber must be replaced. (Author)

  19. Scientific evidence contradicts findings and assumptions of Canadian Safety Panel 6: microwaves act through voltage-gated calcium channel activation to induce biological impacts at non-thermal levels, supporting a paradigm shift for microwave/lower frequency electromagnetic field action. (United States)

    Pall, Martin L


    This review considers a paradigm shift on microwave electromagnetic field (EMF) action from only thermal effects to action via voltage-gated calcium channel (VGCC) activation. Microwave/lower frequency EMFs were shown in two dozen studies to act via VGCC activation because all effects studied were blocked by calcium channel blockers. This mode of action was further supported by hundreds of studies showing microwave changes in calcium fluxes and intracellular calcium [Ca2+]i signaling. The biophysical properties of VGCCs/similar channels make them particularly sensitive to low intensity, non-thermal EMF exposures. Non-thermal studies have shown that in most cases pulsed fields are more active than are non-pulsed fields and that exposures within certain intensity windows have much large biological effects than do either lower or higher intensity exposures; these are both consistent with a VGCC role but inconsistent with only a heating/thermal role. Downstream effects of VGCC activation include calcium signaling, elevated nitric oxide (NO), NO signaling, peroxynitrite, free radical formation, and oxidative stress. Downstream effects explain repeatedly reported biological responses to non-thermal exposures: oxidative stress; single and double strand breaks in cellular DNA; cancer; male and female infertility; lowered melatonin/sleep disruption; cardiac changes including tachycardia, arrhythmia, and sudden cardiac death; diverse neuropsychiatric effects including depression; and therapeutic effects. Non-VGCC non-thermal mechanisms may occur, but none have been shown to have effects in mammals. Biologically relevant safety standards can be developed through studies of cell lines/cell cultures with high levels of different VGCCs, measuring their responses to different EMF exposures. The 2014 Canadian Report by a panel of experts only recognizes thermal effects regarding safety standards for non-ionizing radiation exposures. Its position is therefore contradicted by each

  20. Calcium - urine (United States)

    Urinary Ca+2; Kidney stones - calcium in urine; Renal calculi - calcium in your urine; Parathyroid - calcium in urine ... Urine calcium level can help your provider: Decide on the best treatment for the most common type of kidney ...

  1. Resilient architecture design for voltage variation

    CERN Document Server

    Reddi, Vijay Janapa


    Shrinking feature size and diminishing supply voltage are making circuits sensitive to supply voltage fluctuations within the microprocessor, caused by normal workload activity changes. If left unattended, voltage fluctuations can lead to timing violations or even transistor lifetime issues that degrade processor robustness. Mechanisms that learn to tolerate, avoid, and eliminate voltage fluctuations based on program and microarchitectural events can help steer the processor clear of danger, thus enabling tighter voltage margins that improve performance or lower power consumption. We describe

  2. In Vivo Voltage-Sensitive Dye Study of Lateral Spreading of Cortical Activity in Mouse Primary Visual Cortex Induced by a Current Impulse. (United States)

    Fehérvári, Tamás Dávid; Okazaki, Yuka; Sawai, Hajime; Yagi, Tetsuya


    In the mammalian primary visual cortex (V1), lateral spreading of excitatory potentials is believed to be involved in spatial integrative functions, but the underlying cortical mechanism is not well understood. Visually-evoked population-level responses have been shown to propagate beyond the V1 initial activation site in mouse, similar to higher mammals. Visually-evoked responses are, however, affected by neuronal circuits prior to V1 (retina, LGN), making the separate analysis of V1 difficult. Intracortical stimulation eliminates these initial processing steps. We used in vivo RH1691 voltage-sensitive dye (VSD) imaging and intracortical microstimulation in adult C57BL/6 mice to elucidate the spatiotemporal properties of population-level signal spreading in V1 cortical circuits. The evoked response was qualitatively similar to that measured in single-cell electrophysiological experiments in rodents: a fast transient fluorescence peak followed by a fast and a slow decrease or hyperpolarization, similar to EPSP and fast and slow IPSPs in single cells. The early cortical response expanded at speeds commensurate with long horizontal projections (at 5% of the peak maximum, 0.08-0.15 m/s) however, the bulk of the VSD signal propagated slowly (at half-peak maximum, 0.05-0.08 m/s) suggesting an important role of regenerative multisynaptic transmission through short horizontal connections in V1 spatial integrative functions. We also found a tendency for a widespread and fast cortical response suppression in V1, which was eliminated by GABAA-antagonists gabazine and bicuculline methiodide. Our results help understand the neuronal circuitry involved in lateral spreading in V1.

  3. In Vivo Voltage-Sensitive Dye Study of Lateral Spreading of Cortical Activity in Mouse Primary Visual Cortex Induced by a Current Impulse.

    Directory of Open Access Journals (Sweden)

    Tamás Dávid Fehérvári

    Full Text Available In the mammalian primary visual cortex (V1, lateral spreading of excitatory potentials is believed to be involved in spatial integrative functions, but the underlying cortical mechanism is not well understood. Visually-evoked population-level responses have been shown to propagate beyond the V1 initial activation site in mouse, similar to higher mammals. Visually-evoked responses are, however, affected by neuronal circuits prior to V1 (retina, LGN, making the separate analysis of V1 difficult. Intracortical stimulation eliminates these initial processing steps. We used in vivo RH1691 voltage-sensitive dye (VSD imaging and intracortical microstimulation in adult C57BL/6 mice to elucidate the spatiotemporal properties of population-level signal spreading in V1 cortical circuits. The evoked response was qualitatively similar to that measured in single-cell electrophysiological experiments in rodents: a fast transient fluorescence peak followed by a fast and a slow decrease or hyperpolarization, similar to EPSP and fast and slow IPSPs in single cells. The early cortical response expanded at speeds commensurate with long horizontal projections (at 5% of the peak maximum, 0.08-0.15 m/s however, the bulk of the VSD signal propagated slowly (at half-peak maximum, 0.05-0.08 m/s suggesting an important role of regenerative multisynaptic transmission through short horizontal connections in V1 spatial integrative functions. We also found a tendency for a widespread and fast cortical response suppression in V1, which was eliminated by GABAA-antagonists gabazine and bicuculline methiodide. Our results help understand the neuronal circuitry involved in lateral spreading in V1.

  4. Multifunctional Iodide-Free Polymeric Ionic Liquid for Quasi-Solid-State Dye-Sensitized Solar Cells with a High Open-Circuit Voltage. (United States)

    Lin, Yi-Feng; Li, Chun-Ting; Lee, Chuan-Pei; Leu, Yow-An; Ezhumalai, Yamuna; Vittal, R; Chen, Ming-Chou; Lin, Jiang-Jen; Ho, Kuo-Chuan


    A polymeric ionic liquid, poly(oxyethylene)-imide-imidazolium selenocyanate (POEI-IS), was newly synthesized and used for a multifunctional gel electrolyte in a quasi-solid-state dye-sensitized solar cell (QSS-DSSC). POEI-IS has several functions: (a) acts as a gelling agent for the electrolyte of the DSSC, (b) possesses a redox mediator of SeCN(-), which is aimed to form a SeCN(-)/(SeCN)3(-) redox couple with a more positive redox potential than that of traditional I(-)/I3(-), (c) chelates the potassium cations through the lone pair electrons of the oxygen atoms of its poly(oxyethylene)-imide-imidazolium (POEI-I) segments, and (d) obstructs the recombination of photoinjected electrons with (SeCN)3(-) ions in the electrolyte through its POEI-I segments. Thus, the POEI-IS renders a high open-circuit voltage (VOC) to the QSS-DSSC due to its functions of b-d and prolongs the stability of the cell due to its function of a. The QSS-DSSC with the gel electrolyte containing 30 wt % of the POEI-IS in liquid selenocyanate electrolyte exhibited a high VOC of 825.50 ± 3.51 mV and a high power conversion efficiency (η) of 8.18 ± 0.02%. The QSS-DSSC with 30 wt % POEI-IS retained up to 95% of its initial η after an at-rest stability test with the period of more than 1,000 h.

  5. The obesity-related peptide leptin sensitizes cardiac mitochondria to calcium-induced permeability transition pore opening and apoptosis.

    Directory of Open Access Journals (Sweden)

    Eduardo Martinez-Abundis

    Full Text Available The obesity-related 16 kDa peptide leptin is synthesized primarily in white adipocytes although its production has been reported in other tissues including the heart. There is emerging evidence that leptin may contribute to cardiac pathology especially that related to myocardial remodelling and heart failure. In view of the importance of mitochondria to these processes, the goal of the present study is to determine the effect of leptin on mitochondria permeability transition pore opening and the potential consequence in terms of development of apoptosis. Experiments were performed using neonatal rat ventricular myocytes exposed to 3.1 nM (50 ng/ml leptin for 24 hours. Mitochondrial transition pore opening was analyzed as the capacity of mitochondria to retain the dye calcein-AM in presence of 200 µM CaCl2. Leptin significantly increased pore opening although the effect was markedly more pronounced in digitonin-permeabilized myocytes in the presence of calcium with both effects prevented by the transition pore inhibitor sanglifehrin A. These effects were associated with increased apoptosis as evidenced by increased TUNEL staining and caspase 3 activity, both of which were prevented by the transition pore inhibitor sanglifehrin A. Leptin enhanced Stat3 activation whereas a Stat 3 inhibitor peptide prevented leptin-induced mitochondrial transition pore opening as well as the hypertrophic and pro-apoptotic effects of the peptide. Inhibition of the RhoA/ROCK pathway prevented the hypertrophic response to leptin but had no effect on increased pore opening following leptin administration. We conclude that leptin can enhance calcium-mediated, Stat3-dependent pro-apoptotic effects as a result of increased mitochondrial transition pore opening and independently of its hypertrophic actions. Leptin may therefore contribute to mitochondrial dysfunction and the development of apoptosis in the diseased myocardium particularly under conditions of excessive

  6. Expression and characterization of the calcium-activated photoprotein from the ctenophore Bathocyroe fosteri: insights into light-sensitive photoproteins. (United States)

    Powers, Meghan L; McDermott, Amy G; Shaner, Nathan C; Haddock, Steven H D


    Calcium-binding photoproteins have been discovered in a variety of luminous marine organisms [1]. Recent interest in photoproteins from the phylum Ctenophora has stemmed from cloning and expression of several photoproteins from this group [2-5]. Additional characterization has revealed unique biochemical properties found only in ctenophore photoproteins, such as inactivation by light. Here we report the cloning, expression, and characterization of the photoprotein responsible for luminescence in the deep-sea ctenophore Bathocyroe fosteri. This animal was of particular interest due to the unique broad color spectrum observed in live specimens [6]. Full-length sequences were identified by BLAST searches of known photoprotein sequences against Bathocyroe transcripts obtained from 454 sequencing. Recombinantly expressed Bathocyroe photoprotein (BfosPP) displayed an optimal coelenterazine-loading pH of 8.5, and produced calcium-triggered luminescence with peak wavelengths closely matching the 493 nm peak observed in the spectrum of live B. fosteri specimens. Luminescence from recombinant BfosPP was inactivated most efficiently by UV and blue light. Primary structure alignment of BfosPP with other characterized photoproteins showed very strong sequence similarity to other ctenophore photoproteins and conservation of EF-hand motifs. Both alignment and structural prediction data provide more insight into the formation of the coelenterazine-binding domain and the probable mechanism of photoinactivation. Copyright © 2012 Elsevier Inc. All rights reserved.

  7. Suggestive evidence for association between L-type voltage-gated calcium channel (CACNA1C) gene haplotypes and bipolar disorder in Latinos: a family-based association study (United States)

    Gonzalez, Suzanne; Xu, Chun; Ramirez, Mercedes; Zavala, Juan; Armas, Regina; Contreras, Salvador A; Contreras, Javier; Dassori, Albana; Leach, Robin J; Flores, Deborah; Jerez, Alvaro; Raventós, Henriette; Ontiveros, Alfonso; Nicolini, Humberto; Escamilla, Michael


    Objectives Through recent genome-wide association studies (GWAS), several groups have reported significant association between variants in the alpha 1C subunit of the L-type voltage-gated calcium channel (CACNA1C) and bipolar disorder (BP) in European and European-American cohorts. We performed a family-based association study to determine whether CACNA1C is associated with BP in the Latino population. Methods This study consisted of 913 individuals from 215 Latino pedigrees recruited from the United States, Mexico, Guatemala, and Costa Rica. The Illumina GoldenGate Genotyping Assay was used to genotype 58 single-nucleotide polymorphisms (SNPs) that spanned a 602.9 kb region encompassing the CACNA1C gene including two SNPs (rs7297582 and rs1006737) previously shown to associate with BP. Individual SNP and haplotype association analyses were performed using Family-Based Association Test (version 2.0.3) and Haploview (version 4.2) software. Results An eight-locus haplotype block that included these two markers showed significant association with BP (global marker permuted p = 0.0018) in the Latino population. For individual SNPs, this sample had insufficient power (10%) to detect associations with SNPs with minor effect (odds ratio = 1.15). Conclusions Although we were not able to replicate findings of association between individual CACNA1C SNPs rs7297582 and rs1006737 and BP, we were able to replicate the GWAS signal reported for CACNA1C through a haplotype analysis that encompassed these previously reported significant SNPs. These results provide additional evidence that CACNA1C is associated with BP and provides the first evidence that variations in this gene might play a role in the pathogenesis of this disorder in the Latino population. PMID:23437964

  8. Plasma membrane calcium channels in cancer: Alterations and consequences for cell proliferation and migration. (United States)

    Déliot, Nadine; Constantin, Bruno


    The study of calcium channels in molecular mechanisms of cancer transformation is still a novel area of research. Several studies, mostly conducted on cancer cell lines, however support the idea that a diversity of plasma membrane channels participates in the remodeling of Ca2+ homeostasis, which regulates various cancer hallmarks such as uncontrolled multiplication and increase in migration and invasion abilities. However few is still understood concerning the intracellular signaling cascades mobilized by calcium influx participating to cancer cell behavior. This review intends to gather some of these pathways dependent on plasma membrane calcium channels and described in prostate, breast and lung cancer cell lines. In these cancer cell types, the calcium channels involved in calcium signaling pathways promoting cancer behaviors are mostly non-voltage activated calcium channels and belong to the TRP superfamily (TRPC, TPRPV and TRPM families) and the Orai family. TRP and Orai channels are part of many signaling cascades involving the activation of transmembrane receptors by extracellular ligand from the tumor environment. TRPV can sense changes in the physical and chemical environment of cancer cells and TRPM7 are stretch activated and sensitive to cholesterol. Changes in activation and or expression of plasma-membrane calcium channels affect calcium-dependent signaling processes relevant to tumorigenesis. The studies cited in this review suggest that an increase in plasma membrane calcium channel expression and/or activity sustain an elevated calcium entry (constitutive or under the control of extracellular signals) promoting higher cell proliferation and migration in most cases. A variety of non-voltage-operated calcium channels display change expression and/or activity in a same cancer type and cooperate to the same process relevant to cancer cell behavior, or can be involved in a different sequence of events during the tumorigenesis. This article is part of a

  9. Probenecid Improves Cardiac Function in Patients With Heart Failure With Reduced Ejection Fraction In Vivo and Cardiomyocyte Calcium Sensitivity In Vitro. (United States)

    Robbins, Nathan; Gilbert, Mark; Kumar, Mohit; McNamara, James W; Daly, Patrick; Koch, Sheryl E; Conway, Ginger; Effat, Mohamed; Woo, Jessica G; Sadayappan, Sakthivel; Rubinstein, Jack


    Transient receptor potential vanilloid 2 is a calcium channel activated by probenecid. Probenecid is a Food and Drug Administration-approved uricosuric drug that has recently been shown to induce positive lusitropic and inotropic effects in animal models through cardiomyocyte transient receptor potential vanilloid 2 activation. The aim of this study was to test the hypothesis that oral probenecid can improve cardiac function and symptomatology in patients with heart failure with reduced ejection fraction and to further elucidate its calcium-dependent effects on myocyte contractility. The clinical trial recruited stable outpatients with heart failure with reduced ejection fraction randomized in a single-center, double-blind, crossover design. Clinical data were collected including a dyspnea assessment, physical examination, ECG, echocardiogram to assess systolic and diastolic function, a 6-minute walk test, and laboratory studies. In vitro force generation studies were performed on cardiomyocytes isolated from murine tissue exposed to probenecid or control treatments. The clinical trial recruited 20 subjects (mean age 57 years, mean baseline fractional shortening of 13.6±1.0%). Probenecid therapy increased fractional shortening by 2.1±1.0% compared with placebo -1.7±1.0% ( P =0.007). Additionally, probenecid improved diastolic function compared with placebo by decreasing the E/E' by -2.95±1.21 versus 1.32±1.21 in comparison to placebo ( P =0.03). In vitro probenecid increased myofilament force generation (92.36 versus 80.82 mN/mm 2 , P Probenecid improves cardiac function with minimal effects on symptomatology and no significant adverse effects after 1 week in patients with heart failure with reduced ejection fraction and increases force development and calcium sensitivity at the cardiomyocyte level. URL: Unique identifier: NCT01814319. © 2018 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

  10. Calcium-activated-calcineurin reduces the In vitro and In vivo sensitivity of fluconazole to Candida albicans via Rta2p.

    Directory of Open Access Journals (Sweden)

    Yu Jia

    Full Text Available Due to the emergence of drug-resistance, first-line therapy with fluconazole (FLC increasingly resulted in clinical failure for the treatment of candidemia. Our previous studies found that in vitro RTA2 was involved in the calcineurin-mediated resistance to FLC in C. albicans. In this study, we found that calcium-activated-calcineurin significantly reduced the in vitro sensitivity of C. albicans to FLC by blocking the impairment of FLC to the plasma membrane via Rta2p. Furthermore, we found that RTA2 itself was not involved in C. albicans virulence, but the disruption of RTA2 dramatically increased the therapeutic efficacy of FLC in a murine model of systemic candidiasis. Conversely, both re-introduction of one RTA2 allele and ectopic expression of RTA2 significantly reduced FLC efficacy in a mammalian host. Finally, we found that calcium-activated-calcineurin, through its target Rta2p, dramatically reduced the efficacy of FLC against candidemia. Given the critical roles of Rta2p in controlling the efficacy of FLC, Rta2p can be a potential drug target for antifungal therapies.

  11. Voltage Sensors Monitor Harmful Static (United States)


    A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.

  12. Pharmacological analysis of calcium antagonist receptors

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, I.J.


    This work focuses on two aspects of the action of calcium antagonist drugs, namely, the interaction of drugs with receptors for verapamil-like calcium antagonists, and the interactions of drugs with voltage-sensitive calcium fluxes in rat brain synaptosomes. From binding studies I have found that the ligand of choice for labeling the verapamil receptor is (-)(/sup 3/H)desmethoxy-verapamil. This drug labels potently, reversibly and stereoselectively two receptors in membranes prepared from rat brain and rabbit skeletal muscle tissues. In equilibrium studies dihydropyridine calcium antagonists interact in a non-competitive fashion, while many non-DHPs are apparently competitive. In-depth kinetic studies in skeletal muscle membranes indicate that the two receptors are linked in a negative heterotropic fashion, and that low-affinity binding of (-) (/sup 3/H)desmethoxy-verapamil may be to the diltiazem receptor. However, these studies were not able to distinguish between the hypothesis that diltiazem binds to spatially separate, allosterically coupled receptors, and the hypothesis that diltiazem binds to a subsite of the verapamil receptor.

  13. Relaxant effect of tetrazepam on rat uterine smooth muscle: role of calcium movement. (United States)

    Perez-Guerrero, C; Herrera, M D; Marhuenda, E


    Tetrazepam is a benzodiazepine derivative clinically used as a muscle relaxant. The aim of the present work was to examine its effect on uterine smooth muscle of the rat in estrus. Tetrazepam required micromolar concentrations to relax contractile responses induced by KCl and acetylcholine in Ca2+ solution, but not oxytocin-induced contraction. In Ca(2+)-free solution, tetrazepam inhibited Ca(2+)-induced contractions in depolarized uterus and vanadate-induced contractions. We suggest that tetrazepam relaxes contractile responses induced by activation of voltage-sensitive calcium channels and receptor-operated calcium channels with little selectivity or that it antagonizes the effect of calcium at subsequent steps, possibly intracellular stores sensitive to vanadate but not sensitive to oxytocin. The inhibition of contraction of rat uterus is not related to high-affinity peripheral benzodiazepine binding sites.

  14. Calcium Carbonate (United States)

    Calcium carbonate is a dietary supplement used when the amount of calcium taken in the diet is not ... for healthy bones, muscles, nervous system, and heart. Calcium carbonate also is used as an antacid to relieve ...

  15. Calcium supplements (United States)

    ... this page: // Calcium supplements To use the sharing features on this page, please enable JavaScript. WHO SHOULD TAKE CALCIUM SUPPLEMENTS? Calcium is an important mineral for the ...

  16. Discovery and Development of Calcium Channel Blockers

    Directory of Open Access Journals (Sweden)

    Théophile Godfraind


    Full Text Available In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan and Heibrunn (USA experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are

  17. Photocontrol of Voltage-Gated Ion Channel Activity by Azobenzene Trimethylammonium Bromide in Neonatal Rat Cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Sheyda R Frolova

    Full Text Available The ability of azobenzene trimethylammonium bromide (azoTAB to sensitize cardiac tissue excitability to light was recently reported. The dark, thermally relaxed trans- isomer of azoTAB suppressed spontaneous activity and excitation propagation speed, whereas the cis- isomer had no detectable effect on the electrical properties of cardiomyocyte monolayers. As the membrane potential of cardiac cells is mainly controlled by activity of voltage-gated ion channels, this study examined whether the sensitization effect of azoTAB was exerted primarily via the modulation of voltage-gated ion channel activity. The effects of trans- and cis- isomers of azoTAB on voltage-dependent sodium (INav, calcium (ICav, and potassium (IKv currents in isolated neonatal rat cardiomyocytes were investigated using the whole-cell patch-clamp technique. The experiments showed that azoTAB modulated ion currents, causing suppression of sodium (Na+ and calcium (Ca2+ currents and potentiation of net potassium (K+ currents. This finding confirms that azoTAB-effect on cardiac tissue excitability do indeed result from modulation of voltage-gated ion channels responsible for action potential.

  18. A dynamic voltage restorer (DVR) with selective harmonic compensation at medium voltage level

    DEFF Research Database (Denmark)

    Newman, M.J.; Holmes, D.G.; Nielsen, J.G.


    Dynamic voltage restorers (DVRs) are now becoming more established in industry to reduce the impact of voltage sags to sensitive loads. However, DVRs spend most of their time in standby mode, since voltage sags occur very infrequently, and hence their utilization is low. In principle, it would...... voltage harmonic compensation capabilities with minimal effect on the sag compensation performance of the basic DVR. The proposed controller has been experimentally verified on a medium-voltage (10 kV) three-phase DVR prototype under a range of conditions, including distorted supply voltages, nonlinear...... loads, and operation during distorted voltage sags....

  19. Chronic fluoxetine treatment increases NO bioavailability and calcium-sensitive potassium channels activation in rat mesenteric resistance arteries. (United States)

    Pereira, Camila A; Ferreira, Nathanne S; Mestriner, Fabiola L; Antunes-Rodrigues, José; Evora, Paulo R B; Resstel, Leonardo B M; Carneiro, Fernando S; Tostes, Rita C


    Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), has effects beyond its antidepressant properties, altering, e.g., mechanisms involved in blood pressure and vasomotor tone control. Although many studies have addressed the acute impact of fluoxetine on the cardiovascular system, there is a paucity of information on the chronic vascular effects of this SSRI. We tested the hypothesis that chronic fluoxetine treatment enhances the vascular reactivity to vasodilator stimuli by increasing nitric oxide (NO) signaling and activation of potassium (K+) channels. Wistar rats were divided into two groups: (I) vehicle (water for 21 days) or (II) chronic fluoxetine (10 mg/kg/day in the drinking water for 21 days). Fluoxetine treatment increased endothelium-dependent and independent vasorelaxation (analyzed by mesenteric resistance arteries reactivity) as well as constitutive NO synthase (NOS) activity, phosphorylation of eNOS at Serine1177 and NO production, determined by western blot and fluorescence. On the other hand, fluoxetine treatment did not alter vascular expression of neuronal and inducible NOS or guanylyl cyclase (GC). Arteries from fluoxetine-treated rats exhibited increased relaxation to pinacidil. Increased acetylcholine vasorelaxation was abolished by a calcium-activated K+ channel (KCa) blocker, but not by an inhibitor of KATP channels. On the other hand, vascular responses to Bay 41-2272 and 8-bromo-cGMP were similar between the groups. In conclusion, chronic fluoxetine treatment increases endothelium-dependent and independent relaxation of mesenteric resistance arteries by mechanisms that involve increased eNOS activity, NO generation, and KCa channels activation. These effects may contribute to the cardiovascular effects associated with chronic fluoxetine treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Absence epilepsy in tottering mutant mice is associated with calcium channel defects. (United States)

    Fletcher, C F; Lutz, C M; O'Sullivan, T N; Shaughnessy, J D; Hawkes, R; Frankel, W N; Copeland, N G; Jenkins, N A


    Mutations at the mouse tottering (tg) locus cause a delayed-onset, recessive neurological disorder resulting in ataxia, motor seizures, and behavioral absence seizures resembling petit mal epilepsy in humans. A more severe allele, leaner (tg(la)), also shows a slow, selective degeneration of cerebellar neurons. By positional cloning, we have identified an alpha1A voltage-sensitive calcium channel gene that is mutated in tg and tg(la) mice. The alpha1A gene is widely expressed in the central nervous system with prominent, uniform expression in the cerebellum. alpha1A expression does not mirror the localized pattern of cerebellar degeneration observed in tg(la) mice, providing evidence for regional differences in biological function of alpha1A channels. These studies define the first mutations in a mammalian central nervous system-specific voltage-sensitive calcium channel and identify the first gene involved in absence epilepsy.

  1. Calcium signaling in taste cells. (United States)

    Medler, Kathryn F


    The sense of taste is a common ability shared by all organisms and is used to detect nutrients as well as potentially harmful compounds. Thus taste is critical to survival. Despite its importance, surprisingly little is known about the mechanisms generating and regulating responses to taste stimuli. All taste responses depend on calcium signals to generate appropriate responses which are relayed to the brain. Some taste cells have conventional synapses and rely on calcium influx through voltage-gated calcium channels. Other taste cells lack these synapses and depend on calcium release to formulate an output signal through a hemichannel. Beyond establishing these characteristics, few studies have focused on understanding how these calcium signals are formed. We identified multiple calcium clearance mechanisms that regulate calcium levels in taste cells as well as a calcium influx that contributes to maintaining appropriate calcium homeostasis in these cells. Multiple factors regulate the evoked taste signals with varying roles in different cell populations. Clearly, calcium signaling is a dynamic process in taste cells and is more complex than has previously been appreciated. This article is part of a Special Issue entitled: 13th European Symposium on Calcium. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. AMP-activated Protein Kinase Phosphorylates Cardiac Troponin I at Ser-150 to Increase Myofilament Calcium Sensitivity and Blunt PKA-dependent Function* (United States)

    Nixon, Benjamin R.; Thawornkaiwong, Ariyoporn; Jin, Janel; Brundage, Elizabeth A.; Little, Sean C.; Davis, Jonathan P.; Solaro, R. John; Biesiadecki, Brandon J.


    AMP-activated protein kinase (AMPK) is an energy-sensing enzyme central to the regulation of metabolic homeostasis. In the heart AMPK is activated during cardiac stress-induced ATP depletion and functions to stimulate metabolic pathways that restore the AMP/ATP balance. Recently it was demonstrated that AMPK phosphorylates cardiac troponin I (cTnI) at Ser-150 in vitro. We sought to determine if the metabolic regulatory kinase AMPK phosphorylates cTnI at Ser-150 in vivo to alter cardiac contractile function directly at the level of the myofilament. Rabbit cardiac myofibrils separated by two-dimensional isoelectric focusing subjected to a Western blot with a cTnI phosphorylation-specific antibody demonstrates that cTnI is endogenously phosphorylated at Ser-150 in the heart. Treatment of myofibrils with the AMPK holoenzyme increased cTnI Ser-150 phosphorylation within the constraints of the muscle lattice. Compared with controls, cardiac fiber bundles exchanged with troponin containing cTnI pseudo-phosphorylated at Ser-150 demonstrate increased sensitivity of calcium-dependent force development, blunting of both PKA-dependent calcium desensitization, and PKA-dependent increases in length dependent activation. Thus, in addition to the defined role of AMPK as a cardiac metabolic energy gauge, these data demonstrate AMPK Ser-150 phosphorylation of cTnI directly links the regulation of cardiac metabolic demand to myofilament contractile energetics. Furthermore, the blunting effect of cTnI Ser-150 phosphorylation cross-talk can uncouple the effects of myofilament PKA-dependent phosphorylation from β-adrenergic signaling as a novel thin filament contractile regulatory signaling mechanism. PMID:22493448

  3. AMP-activated protein kinase phosphorylates cardiac troponin I at Ser-150 to increase myofilament calcium sensitivity and blunt PKA-dependent function. (United States)

    Nixon, Benjamin R; Thawornkaiwong, Ariyoporn; Jin, Janel; Brundage, Elizabeth A; Little, Sean C; Davis, Jonathan P; Solaro, R John; Biesiadecki, Brandon J


    AMP-activated protein kinase (AMPK) is an energy-sensing enzyme central to the regulation of metabolic homeostasis. In the heart AMPK is activated during cardiac stress-induced ATP depletion and functions to stimulate metabolic pathways that restore the AMP/ATP balance. Recently it was demonstrated that AMPK phosphorylates cardiac troponin I (cTnI) at Ser-150 in vitro. We sought to determine if the metabolic regulatory kinase AMPK phosphorylates cTnI at Ser-150 in vivo to alter cardiac contractile function directly at the level of the myofilament. Rabbit cardiac myofibrils separated by two-dimensional isoelectric focusing subjected to a Western blot with a cTnI phosphorylation-specific antibody demonstrates that cTnI is endogenously phosphorylated at Ser-150 in the heart. Treatment of myofibrils with the AMPK holoenzyme increased cTnI Ser-150 phosphorylation within the constraints of the muscle lattice. Compared with controls, cardiac fiber bundles exchanged with troponin containing cTnI pseudo-phosphorylated at Ser-150 demonstrate increased sensitivity of calcium-dependent force development, blunting of both PKA-dependent calcium desensitization, and PKA-dependent increases in length dependent activation. Thus, in addition to the defined role of AMPK as a cardiac metabolic energy gauge, these data demonstrate AMPK Ser-150 phosphorylation of cTnI directly links the regulation of cardiac metabolic demand to myofilament contractile energetics. Furthermore, the blunting effect of cTnI Ser-150 phosphorylation cross-talk can uncouple the effects of myofilament PKA-dependent phosphorylation from β-adrenergic signaling as a novel thin filament contractile regulatory signaling mechanism.

  4. Compartmentalized beta subunit distribution determines characteristics and ethanol sensitivity of somatic, dendritic, and terminal large-conductance calcium-activated potassium channels in the rat central nervous system. (United States)

    Wynne, P M; Puig, S I; Martin, G E; Treistman, S N


    Neurons are highly differentiated and polarized cells, whose various functions depend upon the compartmentalization of ion channels. The rat hypothalamic-neurohypophysial system (HNS), in which cell bodies and dendrites reside in the hypothalamus, physically separated from their nerve terminals in the neurohypophysis, provides a particularly powerful preparation in which to study the distribution and regional properties of ion channel proteins. Using electrophysiological and immunohistochemical techniques, we characterized the large-conductance calcium-activated potassium (BK) channel in each of the three primary compartments (soma, dendrite, and terminal) of HNS neurons. We found that dendritic BK channels, in common with somatic channels but in contrast to nerve terminal channels, are insensitive to iberiotoxin. Furthermore, analysis of dendritic BK channel gating kinetics indicates that they, like somatic channels, have fast activation kinetics, in contrast to the slow gating of terminal channels. Dendritic and somatic channels are also more sensitive to calcium and have a greater conductance than terminal channels. Finally, although terminal BK channels are highly potentiated by ethanol, somatic and dendritic channels are insensitive to the drug. The biophysical and pharmacological properties of somatic and dendritic versus nerve terminal channels are consistent with the characteristics of exogenously expressed alphabeta1 versus alphabeta4 channels, respectively. Therefore, one possible explanation for our findings is a selective distribution of auxiliary beta1 subunits to the somatic and dendritic compartments and beta4 to the terminal compartment. This hypothesis is supported immunohistochemically by the appearance of distinct punctate beta1 or beta4 channel clusters in the membrane of somatic and dendritic or nerve terminal compartments, respectively.

  5. Inhibitory effect of calcium channel blockers on proliferation of human glioma cells in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Kunert-Radek, J.; Stepien, H.; Lyson, K.; Pawlikowski, M.; Radek, A.


    The effects of 2 specific calcium channel blockers, verapamil and nimodipine, on the proliferation of human glioma tumour cells were investigated in vitro. Tumour tissues for primary cell cultures were obtained bioptically from 3 patients with the histopathological diagnosis of glioblastoma. The (/sup 3/H)-thymidine incorporation into glioma tumour cells DNA was used as a sensitive index of the cell proliferation. It was found that varapamil (10/sup 4/-10/sup 5/M) and nimodipine (10/sup 4/-10/sup 6/M) significantly inhibited the (/sup 3/H)-thymidine uptake in a dose-related manner. The inhibitory effect of both calcium channel antagonists was reversed by stimultancous addition of calcium chloride (5x10/sup 3/M). These results indicate that verapamil and nimodipine may exert an antiproliferative effect on glioma cells growth acting through a blokade of specific voltage-dependent calcium channels.

  6. Regulation of Spinal Substance P Release by Intrathecal Calcium Channel Blockade (United States)

    Takasusuki, Toshifumi; Yaksh, Tony L.


    Background We investigated the role of different voltage sensitive calcium channels expressed at presynaptic afferent terminals in substance P release and on nociceptive behavior evoked by intraplantar formalin by examining the effects of intrathecally delivered N- (ziconotide), T- (mibefradil) and L-type voltage sensitive calcium channels blockers (diltiazem and verapamil). Methods Rats received intrathecal pretreatment with saline or doses of morphine, ziconotide, mibefradil, diltiazem or verapamil. The effect of these injections upon flinching evoked by intraplantar formalin (5%, 50μl) was quantified. To assess substance P release, the incidence of neurokinin 1 receptor internalization in the ipsilateral and contralateral lamina I was determined in immunofluorescent stained tissues. Results Intrathecal morphine (20μg), ziconotide (0.3, 0.6 and 1μg), mibefradil (100μg, but not 50μg), diltiazem (500μg, but not 300μg) and verapamil (200μg, but not 50 and 100μg) reduced paw flinching in phase 2 as compared to vehicle control (P Ziconotide (0.3, 0.6 and 1μg) and morphine (20μg) significantly inhibited neurokinin 1 receptor internalization (P < 0.05), but mibefradil, diltiazem and verapamil at the highest doses had no effect. Conclusion These results emphasize the role in vivo of N-, but not T- and L-type voltage sensitive calcium channels in mediating the stimulus evoked substance P release from small primary afferents and suggest that T- and L-type voltage sensitive calcium channels blockers exert antihyperalgesic effects by an action on other populations of afferents or mechanisms involving post synaptic excitability. PMID:21577088

  7. /sup 3/H)Nitrendipine binding to calcium channels in bovine and rat pituitary

    Energy Technology Data Exchange (ETDEWEB)

    Titeler, M.; De Souza, E.B.; Kuhar, M.J.


    (/sup 3/H)Nitrendipine was used to label sites in homogenates of bovine anterior and neurointermediate lobes of the pituitary gland. The amount of specific binding in the anterior lobe was 1.82 +/- 0.30 pmol/g wet weight of tissue and the KD was 1.44 +/- 0.02 X 10(-10) M. Preliminary experiments indicated a similar amount of binding in bovine neurointermediate lobe. In competition studies nimodipine and nisoldipine (two potent voltage-sensitive calcium channel blockers) displayed IC50 values of 1.6 and 6.8 X 10(-10) M, respectively. Verapamil and the verapamil-like calcium channel blockers D-600 and tiapamil competed in a complex manner for the (/sup 3/H)nitrendipine specific binding to bovine anterior pituitary homogenates. Autoradiographical studies demonstrated specific (/sup 3/H)nitrendipine binding sites distributed approximately equally in the anterior and posterior lobes, but not in the intermediate lobe of the rat pituitary. In general the properties of (/sup 3/H)nitrendipine binding in the pituitary tissue resemble strongly the properties of (/sup 3/H)nitrendipine binding in the brain which is believed to be to voltage-sensitive calcium channels. These results provide support for the hypothesis that calcium channels are involved in pituitary hormone secretion and that drugs that interact with calcium channels may modulate the secretory process directly at the level of the pituitary.

  8. Effect of caffeine on intramembrane charge movement and calcium transients in cut skeletal muscle fibres of the frog. (United States)

    Kovács, L; Szücs, G


    had equal but smaller peak amplitudes, shorter latency times and the same magnitude of voltage-independent rate coefficients for the declining phase as in the control solution.9. The twitch potentiating effect of caffeine can be explained by its facilitating calcium release from the sarcoplasmic reticulum, while the re-uptake rate is not modified. The apparent inhibition of re-uptake can be related to the enhanced release of calcium due to caffeine effect. Due to the sensitizing effect of caffeine on the sarcoplasmic reticulum membrane, smaller amounts of charge are needed to reach the contraction threshold than without caffeine.

  9. Myosin light chain kinase is necessary for post-shock mesenteric lymph drainage enhancement of vascular reactivity and calcium sensitivity in hemorrhagic-shocked rats

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.P.; Niu, C.Y.; Zhao, Z.G.; Zhang, L.M.; Si, Y.H. [Institute of Microcirculation, Hebei North University, Hebei (China)


    Vascular hyporeactivity is an important factor in irreversible shock, and post-shock mesenteric lymph (PSML) blockade improves vascular reactivity after hemorrhagic shock. This study explored the possible involvement of myosin light chain kinase (MLCK) in PSML-mediated vascular hyporeactivity and calcium desensitization. Rats were divided into sham (n=12), shock (n=18), and shock+drainage (n=18) groups. A hemorrhagic shock model (40±2 mmHg, 3 h) was established in the shock and shock+drainage groups. PSML drainage was performed from 1 to 3 h from start of hypotension in shock+drainage rats. Levels of phospho-MLCK (p-MLCK) were determined in superior mesenteric artery (SMA) tissue, and the vascular reactivity to norepinephrine (NE) and sensitivity to Ca{sup 2+} were observed in SMA rings in an isolated organ perfusion system. p-MLCK was significantly decreased in the shock group compared with the sham group, but increased in the shock+drainage group compared with the shock group. Substance P (1 nM), an agonist of MLCK, significantly elevated the decreased contractile response of SMA rings to both NE and Ca{sup 2+} at various concentrations. Maximum contractility (E{sub max}) in the shock group increased with NE (from 0.179±0.038 to 0.440±0.177 g/mg, P<0.05) and Ca{sup 2+} (from 0.515±0.043 to 0.646±0.096 g/mg, P<0.05). ML-7 (0.1 nM), an inhibitor of MLCK, reduced the increased vascular response to NE and Ca{sup 2+} at various concentrations in the shock+drainage group (from 0.744±0.187 to 0.570±0.143 g/mg in E{sub max} for NE and from 0.729±0.037 to 0.645±0.056 g/mg in E{sub max} for Ca{sup 2+}, P<0.05). We conclude that MLCK is an important contributor to PSML drainage, enhancing vascular reactivity and calcium sensitivity in rats with hemorrhagic shock.

  10. Myofilament Calcium Sensitivity: Mechanistic Insight into TnI Ser-23/24 and Ser-150 Phosphorylation Integration. (United States)

    Salhi, Hussam E; Hassel, Nathan C; Siddiqui, Jalal K; Brundage, Elizabeth A; Ziolo, Mark T; Janssen, Paul M L; Davis, Jonathan P; Biesiadecki, Brandon J


    Troponin I (TnI) is a major regulator of cardiac muscle contraction and relaxation. During physiological and pathological stress, TnI is differentially phosphorylated at multiple residues through different signaling pathways to match cardiac function to demand. The combination of these TnI phosphorylations can exhibit an expected or unexpected functional integration, whereby the function of two phosphorylations are different than that predicted from the combined function of each individual phosphorylation alone. We have shown that TnI Ser-23/24 and Ser-150 phosphorylation exhibit functional integration and are simultaneously increased in response to cardiac stress. In the current study, we investigated the functional integration of TnI Ser-23/24 and Ser-150 to alter cardiac contraction. We hypothesized that Ser-23/24 and Ser-150 phosphorylation each utilize distinct molecular mechanisms to alter the TnI binding affinity within the thin filament. Mathematical modeling predicts that Ser-23/24 and Ser-150 phosphorylation affect different TnI affinities within the thin filament to distinctly alter the Ca2+-binding properties of troponin. Protein binding experiments validate this assertion by demonstrating pseudo-phosphorylated Ser-150 decreases the affinity of isolated TnI for actin, whereas Ser-23/24 pseudo-phosphorylation is not different from unphosphorylated. Thus, our data supports that TnI Ser-23/24 affects TnI-TnC binding, while Ser-150 phosphorylation alters TnI-actin binding. By measuring force development in troponin-exchanged skinned myocytes, we demonstrate that the Ca2+ sensitivity of force is directly related to the amount of phosphate present on TnI. Furthermore, we demonstrate that Ser-150 pseudo-phosphorylation blunts Ser-23/24-mediated decreased Ca2+-sensitive force development whether on the same or different TnI molecule. Therefore, TnI phosphorylations can integrate across troponins along the myofilament. These data demonstrate that TnI Ser-23

  11. Myofilament Calcium Sensitivity: Mechanistic Insight into TnI Ser-23/24 and Ser-150 Phosphorylation Integration

    Directory of Open Access Journals (Sweden)

    Hussam E Salhi


    Full Text Available Troponin I (TnI is a major regulator of cardiac muscle contraction and relaxation. During physiological and pathological stress, TnI is differentially phosphorylated at multiple residues through different signaling pathways to match cardiac function to demand. The combination of these TnI phosphorylations can exhibit an expected or unexpected functional integration, whereby the function of two phosphorylations are different than that predicted from the combined function of each individual phosphorylation alone. We have shown that TnI Ser-23/24 and Ser-150 phosphorylation exhibit functional integration and are simultaneously increased in response to cardiac stress. In the current study, we investigated the functional integration of TnI Ser-23/24 and Ser-150 to alter cardiac contraction. We hypothesized that Ser-23/24 and Ser-150 phosphorylation each utilize distinct molecular mechanisms to alter the TnI binding affinity within the thin filament. Mathematical modeling predicts that Ser-23/24 and Ser-150 phosphorylation affect different TnI affinities within the thin filament to distinctly alter the Ca2+-binding properties of troponin. Protein binding experiments validate this assertion by demonstrating pseudo-phosphorylated Ser-150 decreases the affinity of isolated TnI for actin, whereas Ser-23/24 pseudo-phosphorylation is not different from unphosphorylated. Thus, our data supports that TnI Ser-23/24 affects TnI-TnC binding, while Ser-150 phosphorylation alters TnI-actin binding. By measuring force development in troponin-exchanged skinned myocytes, we demonstrate that the Ca2+ sensitivity of force is directly related to the amount of phosphate present on TnI. Furthermore, we demonstrate that Ser-150 pseudo-phosphorylation blunts Ser-23/24-mediated decreased Ca2+-sensitive force development whether on the same or different TnI molecule. Therefore, TnI phosphorylations can integrate across troponins along the myofilament. These data demonstrate

  12. Voltage Dependence of a Neuromodulator-Activated Ionic Current123 (United States)


    Abstract The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca2+, but that, in conditions of low Ca2+, calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca2+/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR. PMID:27257619

  13. Temperature-Sensitive Cav1.2 Calcium Channels Support Intrinsic Firing of Pyramidal Neurons and Provide a Target for the Treatment of Febrile Seizures (United States)

    Radzicki, Daniel; Yau, Hau-Jie; Pollema-Mays, Sarah L.; Mlsna, Lauren; Cho, Kangho; Koh, Sookyong


    Febrile seizures are associated with increased brain temperature and are often resistant to treatments with antiepileptic drugs, such as carbamazepine and phenytoin, which are sodium channel blockers. Although they are clearly correlated with the hyperthermic condition, the precise cellular mechanisms of febrile seizures remain unclear. We performed patch-clamp recordings from pyramidal cells in acute rat brain slices at temperatures up to 40°C and found that, at ≥37°C, L-type calcium channels are active at unexpectedly hyperpolarized potentials and drive intrinsic firing, which is also supported by a temperature-dependent, gadolinium-sensitive sodium conductance. Pharmacological data, RT-PCR, and the current persistence in Cav1.3 knock-out mice suggested a critical contribution of Cav1.2 subunits to the temperature-dependent intrinsic firing, which was blocked by nimodipine. Because intrinsic firing may play a critical role in febrile seizures, we tested the effect of nimodipine in an in vivo model of febrile seizures and found that this drug dramatically reduces both the incidence and duration of febrile seizures in rat pups, suggesting new possibilities of intervention for this important pathological condition. PMID:23761887

  14. Increased mitochondrial calcium sensitivity and abnormal expression of innate immunity genes precede dopaminergic defects in Pink1-deficient mice.

    Directory of Open Access Journals (Sweden)

    Ravi S Akundi


    Full Text Available PTEN-induced kinase 1 (PINK1 is linked to recessive Parkinsonism (EOPD. Pink1 deletion results in impaired dopamine (DA release and decreased mitochondrial respiration in the striatum of mice. To reveal additional mechanisms of Pink1-related dopaminergic dysfunction, we studied Ca²+ vulnerability of purified brain mitochondria, DA levels and metabolism and whether signaling pathways implicated in Parkinson's disease (PD display altered activity in the nigrostriatal system of Pink1⁻/⁻ mice.Purified brain mitochondria of Pink1⁻/⁻ mice showed impaired Ca²+ storage capacity, resulting in increased Ca²+ induced mitochondrial permeability transition (mPT that was rescued by cyclosporine A. A subpopulation of neurons in the substantia nigra of Pink1⁻/⁻ mice accumulated phospho-c-Jun, showing that Jun N-terminal kinase (JNK activity is increased. Pink1⁻/⁻ mice 6 months and older displayed reduced DA levels associated with increased DA turnover. Moreover, Pink1⁻/⁻ mice had increased levels of IL-1β, IL-12 and IL-10 in the striatum after peripheral challenge with lipopolysaccharide (LPS, and Pink1⁻/⁻ embryonic fibroblasts showed decreased basal and inflammatory cytokine-induced nuclear factor kappa-β (NF-κB activity. Quantitative transcriptional profiling in the striatum revealed that Pink1⁻/⁻ mice differentially express genes that (i are upregulated in animals with experimentally induced dopaminergic lesions, (ii regulate innate immune responses and/or apoptosis and (iii promote axonal regeneration and sprouting.Increased mitochondrial Ca²+ sensitivity and JNK activity are early defects in Pink1⁻/⁻ mice that precede reduced DA levels and abnormal DA homeostasis and may contribute to neuronal dysfunction in familial PD. Differential gene expression in the nigrostriatal system of Pink1⁻/⁻ mice supports early dopaminergic dysfunction and shows that Pink1 deletion causes aberrant expression of genes that regulate

  15. Cardiovascular profile of the calcium sensitizer EMD 57033 in open-chest anaesthetized pigs with regionally stunned myocardium (United States)

    de Zeeuw, Sandra; Trines, Serge A I P; Krams, Rob; Verdouw, Pieter D; Duncker, Dirk J


    Ca2+ sensitizers enhance systolic function, but may impair relaxation in vitro; these effects may differ in stunned and normal myocardium. We therefore studied the effect of EMD 57033 on systolic and diastolic function of normal and stunned porcine myocardium in vivo.Myocardial stunning by 15 min coronary occlusion and 30 min reperfusion abolished systolic shortening (SS) (baseline 13±1%) and decreased end-systolic elastance (Ees) from 67±7 to 47±5 mmHg mm−1 (both P<0.05). Maximum rate of fall of myocardial elastance (dE/dtmin) decreased from −850±100 to −320±30 mmHg mm−1 s−1, while the time constant τe of the decay of elastance increased from 58±3 to 68±6 ms (both P<0.05). End-diastolic elastance (Eed) was unchanged although the zero pressure intercept (L0,ed) had increased.In the stunned region, EMD 57033 (0.2 mg kg−1 min−1 for 60 min, i.v., n=7) increased SS to 19±2%, Ees to 287±40 mmHg mm−1, dE/dtmin to −3630±640 mmHg mm−1 s−1 and decreased τe to 50±3 ms, while Eed remained unchanged. In the normal region, EMD 57033 increased SS from 14±2 to 18±3%, Ees from 59±4 to 263±23 mmHg mm−1, dE/dtmin from −480±70 to −2280±700 mmHg mm−1 s−1 and decreased τe from 91±12 to 61±3 ms (all P<0.05), while Eed remained unchanged. These responses were minimally affected by adrenoceptor blockade (n=7). Vehicle (n=7) had no effect on either region.EMD 57033 increased cardiac output (up to 27±8%) and LVdP/dtmax (86±19%). Mean aortic pressure decreased (19±7%) due to systemic vasodilation that was not amenable to blockade of adrenoceptors or NO synthesis.In conclusion, EMD 57033 restored systolic and diastolic function of stunned myocardium, and produced similar improvements in systolic and diastolic function in normal myocardium. PMID:10742297

  16. Power conditioning using dynamic voltage restorers under different voltage sag types

    Directory of Open Access Journals (Sweden)

    Ahmed M. Saeed


    Full Text Available Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs. By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

  17. Power conditioning using dynamic voltage restorers under different voltage sag types. (United States)

    Saeed, Ahmed M; Abdel Aleem, Shady H E; Ibrahim, Ahmed M; Balci, Murat E; El-Zahab, Essam E A


    Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

  18. Enhanced pre-synaptic glutamate release in deep-dorsal horn contributes to calcium channel alpha-2-delta-1 protein-mediated spinal sensitization and behavioral hypersensitivity

    Directory of Open Access Journals (Sweden)

    Dickenson Anthony H


    Full Text Available Abstract Nerve injury-induced expression of the spinal calcium channel alpha-2-delta-1 subunit (Cavα2δ1 has been shown to mediate behavioral hypersensitivity through a yet identified mechanism. We examined if this neuroplasticity modulates behavioral hypersensitivity by regulating spinal glutamatergic neurotransmission in injury-free transgenic mice overexpressing the Cavα2δ1 proteins in neuronal tissues. The transgenic mice exhibited hypersensitivity to mechanical stimulation (allodynia similar to the spinal nerve ligation injury model. Intrathecally delivered antagonists for N-methyl-D-aspartate (NMDA and α-amino-3-hydroxyl-5-methylisoxazole-4-propionic acid (AMPA/kainate receptors, but not for the metabotropic glutamate receptors, caused a dose-dependent allodynia reversal in the transgenic mice without changing the behavioral sensitivity in wild-type mice. This suggests that elevated spinal Cavα2δ1 mediates allodynia through a pathway involving activation of selective glutamate receptors. To determine if this is mediated by enhanced spinal neuronal excitability or pre-synaptic glutamate release in deep-dorsal horn, we examined wide-dynamic-range (WDR neuron excitability with extracellular recording and glutamate-mediated excitatory postsynaptic currents with whole-cell patch recording in deep-dorsal horn of the Cavα2δ1 transgenic mice. Our data indicated that overexpression of Cavα2δ1 in neuronal tissues led to increased frequency, but not amplitude, of miniature excitatory post synaptic currents mediated mainly by AMPA/kainate receptors at physiological membrane potentials, and also by NMDA receptors upon depolarization, without changing the excitability of WDR neurons to high intensity stimulation. Together, these findings support a mechanism of Cavα2δ1-mediated spinal sensitization in which elevated Cavα2δ1 causes increased pre-synaptic glutamate release that leads to reduced excitation thresholds of post-synaptic dorsal

  19. Regression of glomerular and tubulointerstitial injuries by dietary salt reduction with combination therapy of angiotensin II receptor blocker and calcium channel blocker in Dahl salt-sensitive rats.

    Directory of Open Access Journals (Sweden)

    Kazi Rafiq

    Full Text Available A growing body of evidence indicates that renal tissue injuries are reversible. We investigated whether dietary salt reduction with the combination therapy of angiotensin II type 1 receptor blocker (ARB plus calcium channel blocker (CCB reverses renal tissue injury in Dahl salt-sensitive (DSS hypertensive rats. DSS rats were fed a high-salt diet (HS; 4% NaCl for 4 weeks. Then, DSS rats were given one of the following for 10 weeks: HS diet; normal-salt diet (NS; 0.5% NaCl, NS + an ARB (olmesartan, 10 mg/kg/day, NS + a CCB (azelnidipine, 3 mg/kg/day, NS + olmesartan + azelnidipine or NS + hydralazine (50 mg/kg/day. Four weeks of treatment with HS diet induced hypertension, proteinuria, glomerular sclerosis and hypertrophy, glomerular podocyte injury, and tubulointerstitial fibrosis in DSS rats. A continued HS diet progressed hypertension, proteinuria and renal tissue injury, which was associated with inflammatory cell infiltration and increased proinflammatory cytokine mRNA levels, NADPH oxidase activity and NADPH oxidase-dependent superoxide production in the kidney. In contrast, switching to NS halted the progression of hypertension, renal glomerular and tubular injuries. Dietary salt reduction with ARB or with CCB treatment further reduced blood pressure and partially reversed renal tissues injury. Furthermore, dietary salt reduction with the combination of ARB plus CCB elicited a strong recovery from HS-induced renal tissue injury including the attenuation of inflammation and oxidative stress. These data support the hypothesis that dietary salt reduction with combination therapy of an ARB plus CCB restores glomerular and tubulointerstitial injury in DSS rats.

  20. Molecular basis of calcium-sensitizing and desensitizing mutations of the human cardiac troponin C regulatory domain: a multi-scale simulation study.

    Directory of Open Access Journals (Sweden)

    Peter Michael Kekenes-Huskey

    Full Text Available Troponin C (TnC is implicated in the initiation of myocyte contraction via binding of cytosolic Ca²⁺ and subsequent recognition of the Troponin I switch peptide. Mutations of the cardiac TnC N-terminal regulatory domain have been shown to alter both calcium binding and myofilament force generation. We have performed molecular dynamics simulations of engineered TnC variants that increase or decrease Ca²⁺ sensitivity, in order to understand the structural basis of their impact on TnC function. We will use the distinction for mutants that are associated with increased Ca²⁺ affinity and for those mutants with reduced affinity. Our studies demonstrate that for GOF mutants V44Q and L48Q, the structure of the physiologically-active site II Ca²⁺ binding site in the Ca²⁺-free (apo state closely resembled the Ca²⁺-bound (holo state. In contrast, site II is very labile for LOF mutants E40A and V79Q in the apo form and bears little resemblance with the holo conformation. We hypothesize that these phenomena contribute to the increased association rate, k(on, for the GOF mutants relative to LOF. Furthermore, we observe significant positive and negative positional correlations between helices in the GOF holo mutants that are not found in the LOF mutants. We anticipate these correlations may contribute either directly to Ca²⁺ affinity or indirectly through TnI association. Our observations based on the structure and dynamics of mutant TnC provide rationale for binding trends observed in GOF and LOF mutants and will guide the development of inotropic drugs that target TnC.

  1. Random insertion of split-cans of the fluorescent protein venus into Shaker channels yields voltage sensitive probes with improved membrane localization in mammalian cells. (United States)

    Jin, Lei; Baker, Bradley; Mealer, Robbie; Cohen, Lawrence; Pieribone, Vincent; Pralle, Arnd; Hughes, Thomas


    FlaSh-YFP, a fluorescent protein (FP) voltage sensor that is a fusion of the Shaker potassium channel with yellow fluorescent protein (YFP), is primarily expressed in the endoplasmic reticulum (ER) of mammalian cells, possibly due to misfolded monomers. In an effort to improve plasma membrane expression, the FP was split into two non-fluorescent halves. Each half was randomly inserted into Shaker monomers via a transposon reaction. Shaker subunits containing the 5' half were co-expressed with Shaker subunits containing the 3' half. Tetramerization of Shaker subunits is required for re-conjugation of the FP. The misfolded monomers trapped in ER are unlikely to tetramerize and reconstitute the beta-can structure, and thus intracellular fluorescence might be reduced. This split-can transposon approach yielded 56 fluorescent probes, 30 (54%) of which were expressed at the plasma membrane and were capable of optically reporting changes in membrane potential. The largest signal from these novel FP-sensors was a -1.4% in ΔF/F for a 100 mV depolarization, with on time constants of about 15 ms and off time constants of about 200 ms. This split-can transposon approach has the potential to improve other multimeric probes. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Altered expression of the voltage-gated calcium channel subunit alpha(2)delta-1: A comparison between two experimental models of epilepsy and a sensory nerve ligation model of neuropathic pain

    Czech Academy of Sciences Publication Activity Database

    Nieto-Rostro, M.; Sandhu, G.; Bauer, C. S.; Jiruška, Přemysl; Jefferys, J. G. R.; Dolphin, A. C.


    Roč. 283, Dec (2014), s. 124-137 ISSN 0306-4522 R&D Projects: GA MZd(CZ) NT14489 Institutional support: RVO:67985823 Keywords : calcium channel * dorsal root ganglion (DRG) * alpha2delta subunit * epilepsy * neuropathic pain * reactive gliosis Subject RIV: FH - Neurology Impact factor: 3.357, year: 2014

  3. A breakthrough therapy for dentin hypersensitivity: how dental products containing 8% arginine and calcium carbonate work to deliver effective relief of sensitive teeth. (United States)

    Petrou, Irene; Heu, Rod; Stranick, Mike; Lavender, Stacey; Zaidel, Lynette; Cummins, Diane; Sullivan, Richard J; Hsueh, Carlin; Gimzewski, James K


    These studies have utilized a range of state-of-the-art surface techniques to gain insight into the mechanism of action of a new technology for dentin hypersensitivity relief based upon arginine and calcium carbonate and, in particular, to address important questions regarding the nature and extent of dentin tubule occlusion. Confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) have been used to assess tubule occlusion. Energy dispersive x-ray (EDX) and electron spectroscopy for chemical analysis (ESCA) have been used to identify the composition of the dentin plug. CLSM has also been used to compare the mechanism of action of the toothpaste and the desensitizing prophylaxis paste, to address whether both the arginine and the calcium carbonate components are essential to occlusion, to identify the location of the arginine within the occluded dentin, and to demonstrate resistance of the occlusion to acid challenge. Hydraulic conductance has been used to assess the effectiveness of the arginine-calcium carbonate technology in arresting dentin fluid movement, to evaluate the effects of pulpal pressure on the robustness of the occlusion, and to confirm the resistance of the occlusion to an acid challenge. The CLSM, SEM, and AFM studies demonstrate that the arginine-calcium carbonate technology is highly effective in rapidly and completely occluding dentin tubules. The EDX and ESCA studies show that the dentin surface deposit and occluded tubule plug contain high levels of calcium and phosphate, as well as carbonate. CLSM has confirmed that the toothpaste and the desensitizing prophylaxis paste have the same mechanism of action, that the arginine and calcium carbonate components are both essential to the effectiveness of these products, and that the arginine becomes incorporated into the dentin plug. The hydraulic conductance studies demonstrate that the occlusion provided by the arginine-calcium carbonate

  4. Macroeconomic Assessment of Voltage Sags

    Directory of Open Access Journals (Sweden)

    Sinan Küfeoğlu


    Full Text Available The electric power sector has changed dramatically since the 1980s. Electricity customers are now demanding uninterrupted and high quality service from both utilities and authorities. By becoming more and more dependent on the voltage sensitive electronic equipment, the industry sector is the one which is affected the most by voltage disturbances. Voltage sags are one of the most crucial problems for these customers. The utilities, on the other hand, conduct cost-benefit analyses before going through new investment projects. At this point, understanding the costs of voltage sags become imperative for planning purposes. The characteristics of electric power consumption and hence the susceptibility against voltage sags differ considerably among different industry subsectors. Therefore, a model that will address the estimation of worth of electric power reliability for a large number of customer groups is necessary. This paper introduces a macroeconomic model to calculate Customer Voltage Sag Costs (CVSCs for the industry sector customers. The proposed model makes use of analytical data such as value added, annual energy consumption, working hours, and average outage durations and provides a straightforward, credible, and easy to follow methodology for the estimation of CVSCs.

  5. Induction of divalent cation permeability by heterologous expression of a voltage sensor domain. (United States)

    Arima, Hiroki; Tsutsui, Hidekazu; Sakamoto, Ayako; Yoshida, Manabu; Okamura, Yasushi


    The voltage sensor domain (VSD) is a protein domain that confers sensitivity to membrane potential in voltage-gated ion channels as well as the voltage-sensing phosphatase. Although VSDs have long been considered to function as regulatory units acting on adjacent effectors, recent studies have revealed the existence of direct ion permeation paths in some mutated VSDs and in the voltage-gated proton channel. In this study, we show that calcium currents are evoked upon membrane hyperpolarization in cells expressing a VSD derived from an ascidian voltage-gated ion channel superfamily. Unlike the previously reported omega-pore in the Shaker K + channel and rNav1.4, mutations are not required. From electrophysiological experiments in heterologous expression systems, we found that the conductance is directly mediated by the VSD itself and is carried by both monovalent and divalent cations. This is the first report of divalent cation permeation through a VSD-like structure. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Tetrodotoxin-sensitive α-subunits of voltage-gated sodium channels are relevant for inhibition of cardiac sodium currents by local anesthetics. (United States)

    Stoetzer, C; Doll, T; Stueber, T; Herzog, C; Echtermeyer, F; Greulich, F; Rudat, C; Kispert, A; Wegner, F; Leffler, A


    The sodium channel α-subunit (Nav) Nav1.5 is regarded as the most prevalent cardiac sodium channel required for generation of action potentials in cardiomyocytes. Accordingly, Nav1.5 seems to be the main target molecule for local anesthetic (LA)-induced cardiotoxicity. However, recent reports demonstrated functional expression of several "neuronal" Nav's in cardiomyocytes being involved in cardiac contractility and rhythmogenesis. In this study, we examined the relevance of neuronal tetrodotoxin (TTX)-sensitive Nav's for inhibition of cardiac sodium channels by the cardiotoxic LAs ropivacaine and bupivacaine. Effects of LAs on recombinant Nav1.2, 1.3, 1.4, and 1.5 expressed in human embryonic kidney cell line 293 (HEK-293) cells, and on sodium currents in murine, cardiomyocytes were investigated by whole-cell patch clamp recordings. Expression analyses were performed by reverse transcription PCR (RT-PCR). Cultured cardiomyocytes from neonatal mice express messenger RNA (mRNA) for Nav1.2, 1.3, 1.5, 1.8, and 1.9 and generate TTX-sensitive sodium currents. Tonic and use-dependent block of sodium currents in cardiomyocytes by ropivacaine and bupivacaine were enhanced by 200 nM TTX. Inhibition of recombinant Nav1.5 channels was similar to that of TTX-resistant currents in cardiomyocytes but stronger as compared to inhibition of total sodium current in cardiomyocytes. Recombinant Nav1.2, 1.3, 1.4, and 1.5 channels displayed significant differences in regard to use-dependent block by ropivacaine. Finally, bupivacaine blocked sodium currents in cardiomyocytes as well as recombinant Nav1.5 currents significantly stronger in comparison to ropivacaine. Our data demonstrate for the first time that cardiac TTX-sensitive sodium channels are relevant for inhibition of cardiac sodium currents by LAs.

  7. Gender specific hippocampal whole genome transcriptome data from mice lacking the Cav2.3 R-type or Cav3.2 T-type voltage-gated calcium channel

    Directory of Open Access Journals (Sweden)

    Anna Papazoglou


    Full Text Available Voltage-gated Ca2+ channels are of central relevance in mediating numerous intracellular and transcellular processes including excitation-contraction coupling, excitation secretion-coupling, hormone and neurotransmitter release and gene expression. The Cav2.3 R-type Ca2+ channel is a high-voltage activated channel which plays a crucial role in neurotransmitter release, long-term potentiation and hormone release. Furthermore, Cav2.3 R-type channels were reported to be involved in ictogenesis, epileptogenesis, fear behavior, sleep, pre-and postsynaptic integration and rhythmicity within the hippocampus. Cav3 T-type Ca2+ channels are low-voltage activated and also widely expressed throughout the brain enabling neurons to switch between different firing patterns and to modulate burst activity. Disruption of T-type Ca2+ current has been related to sleep disorders, epilepsy, Parkinson׳s disease, depression, schizophrenia and pain. Cav3.2 ablation was further attributed to elevated anxiety and hippocampal alterations resulting in impaired long-term potentiation and memory. Given the importance of Cav2.3 and Cav3.2 voltage-gated Ca2+ channels within the CNS, particularly the hippocampus, we collected gender specific microarray transcriptome data of murine hippocampal RNA probes using the Affymetrix Exon Expression Chip Mouse Gene 1.0 ST v1. Information presented here includes transcriptome data from Cav2.3+/+, Cav2.3+/−, Cav2.3−/−, Cav3.2+/+, Cav3.2+/− and Cav3.2−/− mice from both genders, the protocol and list of primers used for genotyping animals, the hippocampal RNA isolation procedure and quality controls.

  8. High-sensitivity C-reactive protein is associated with the presence of coronary artery calcium in subjects with normal blood pressure but not in subjects with hypertension. (United States)

    Sung, Joo-Wook; Lee, Sung Ho; Byrne, Christopher D; Chung, Pil-Wook; Won, Yu Sam; Sung, Ki-Chul


    An association has been described between high sensitivity C-reactive protein (hs-CRP) and cardiovascular disease (CVD) in some studies but not in others. This finding may be explained by a differential impact of inflammation according to the absence or presence of certain co-existing risk factors. Because hypertension may be an effect modifier of inflammation on CVD, our aim was to investigate the relationship between hs-CRP and pre-clinical atherosclerosis in subjects with normal blood pressure and hypertension. Data were analyzed from 14,584 Korean subjects. Subjects were stratified according to: a) 6030 (41.3%) patients with normal blood pressure (hypertension (120-139 mmHg and 80-89 mmHg) and c) 2924 (20.0%) patients with hypertension (≥140/90 mmHg). Prevalence and odds ratio for the association between increased hs-CRP (>2 mg/L) and presence of CAC (coronary artery calcium) were calculated. In both normal and pre-hypertensive groups, the prevalence of CAC >0 was higher in subjects with increased hs-CRP concentrations (>2 mg/L). Adjusting for age, sex, cerebrovascular accident, coronary heart disease and diabetes mellitus, lifestyle, obesity, fasting glucose, triglyceride, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol concentrations, there was a significant association between higher hs-CRP levels (>2 mg/L) and CAC score in the normal group (OR 1.55, 95% CI 1.11-2.16; p = 0.010); a borderline significant association in the pre-hypertensive group (OR 1.33, 95% CI 0.99-1.76; p = 0.054); and no association in the hypertensive group (OR 1.01, 95% CI 0.76-1.33; p = 0.94). Higher hs-CRP levels (>2 mg/L) are associated with pre-clinical atherosclerosis in subjects with normal blood pressure but not hypertension. Copyright © 2014 IMSS. Published by Elsevier Inc. All rights reserved.

  9. Effects of Anandamide and Noxious Heat on Intracellular Calcium Concentration in Nociceptive DRG Neurons of Rats

    National Research Council Canada - National Science Library

    Tilo Fischbach; Wolfgang Greffrath; Hermann Nawrath; Rolf-Detlef Treede


    ...+-free extracellular solution. Neither exclusion of voltage-gated sodium channels nor additional blockade of voltage-gated calcium channels of the L-, N-, and/or T-type, significantly reduced the anandamide...

  10. Calcium signalling through L-type calcium channels: role in pathophysiology of spinal nociceptive transmission. (United States)

    Roca-Lapirot, Olivier; Radwani, Houda; Aby, Franck; Nagy, Frédéric; Landry, Marc; Fossat, Pascal


    L-type voltage-gated calcium channels are ubiquitous channels in the CNS. L-type calcium channels (LTCs) are mostly post-synaptic channels regulating neuronal firing and gene expression. They play a role in important physio-pathological processes such as learning and memory, Parkinson's disease, autism and, as recognized more recently, in the pathophysiology of pain processes. Classically, the fundamental role of these channels in cardiovascular functions has limited the use of classical molecules to treat LTC-dependent disorders. However, when applied locally in the dorsal horn of the spinal cord, the three families of LTC pharmacological blockers - dihydropyridines (nifedipine), phenylalkylamines (verapamil) and benzothiazepines (diltiazem) - proved effective in altering short-term sensitization to pain, inflammation-induced hyperexcitability and neuropathy-induced allodynia. Two subtypes of LTCs, Cav 1.2 and Cav 1.3, are expressed in the dorsal horn of the spinal cord, where Cav 1.2 channels are localized mostly in the soma and proximal dendritic shafts, and Cav 1.3 channels are more distally located in the somato-dendritic compartment. Together with their different kinetics and pharmacological properties, this spatial distribution contributes to their separate roles in shaping short- and long-term sensitization to pain. Cav 1.3 channels sustain the expression of plateau potentials, an input/output amplification phenomenon that contributes to short-term sensitization to pain such as prolonged after-discharges, dynamic receptive fields and windup. The Cav 1.2 channels support calcium influx that is crucial for the excitation-transcription coupling underlying nerve injury-induced dorsal horn hyperexcitability. These subtype-specific cellular mechanisms may have different consequences in the development and/or the maintenance of pathological pain. Recent progress in developing more specific compounds for each subunit will offer new opportunities to modulate LTCs

  11. DVR(Dynamic Voltage Restorer)

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. DVR(Dynamic Voltage Restorer). Supply voltage Sag compensation. Supply voltage Swell Compensation. Balancing the Load voltage. Compensation of Supply Voltage Harmonics.

  12. Experimental validation of a high voltage pulse measurement method.

    Energy Technology Data Exchange (ETDEWEB)

    Cular, Stefan; Patel, Nishant Bhupendra; Branch, Darren W.


    This report describes X-cut lithium niobates (LiNbO3) utilization for voltage sensing by monitoring the acoustic wave propagation changes through LiNbO3 resulting from applied voltage. Direct current (DC), alternating current (AC) and pulsed voltage signals were applied to the crystal. Voltage induced shift in acoustic wave propagation time scaled quadratically for DC and AC voltages and linearly for pulsed voltages. The measured values ranged from 10 - 273 ps and 189 ps 2 ns for DC and non-DC voltages, respectively. Data suggests LiNbO3 has a frequency sensitive response to voltage. If voltage source error is eliminated through physical modeling from the uncertainty budget, the sensors U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

  13. Different calcium sources control somatic versus dendritic SK channel activation during action potentials. (United States)

    Jones, Scott L; Stuart, Greg J


    Small-conductance calcium-activated potassium (SK) channels play an important role in regulating neuronal excitability. While SK channels at the soma have long been known to contribute to the medium afterhyperpolarization (mAHP), recent evidence indicates they also regulate NMDA receptor activation in dendritic spines. Here we investigate the activation of SK channels in spines and dendrites of rat cortical pyramidal neurons during action potentials (APs), and compare this to SK channel activation at the soma. Using confocal calcium imaging, we demonstrate that the inhibition of SK channels with apamin results in a location-dependent increase in calcium influx into dendrites and spines during backpropagating APs (average increase, ~40%). This effect was occluded by block of R-type voltage-dependent calcium channels (VDCCs), but not by inhibition of N- or P/Q-type VDCCs, or block of calcium release from intracellular stores. During these experiments, we noticed that the calcium indicator (Oregon Green BAPTA-1) blocked the mAHP. Subsequent experiments using low concentrations of EGTA (1 mm) produced the same result, suggesting that somatic SK channels are not tightly colocalized with their calcium source. Consistent with this idea, all known subtypes of VDCCs except R-type were calcium sources for the apamin-sensitive mAHP at the soma. We conclude that SK channels in spines and dendrites of cortical pyramidal neurons regulate calcium influx during backpropagating APs in a distance-dependent manner, and are tightly coupled to R-type VDCCs. In contrast, SK channels activated by APs at the soma of these neurons are weakly coupled to a variety of VDCCs.

  14. Presynaptic calcium signalling in cerebellar mossy fibres

    DEFF Research Database (Denmark)

    Thomsen, Louiza Bohn; Jörntell, Henrik; Midtgaard, Jens


    Whole-cell recordings were obtained from mossy fibre terminals in adult turtles in order to characterize the basic membrane properties. Calcium imaging of presynaptic calcium signals was carried out in order to analyse calcium dynamics and presynaptic GABA B inhibition. A tetrodotoxin (TTX....... Calcium imaging using Calcium-Green dextran revealed a stimulus-evoked all-or-none TTX-sensitive calcium signal in simple and complex rosettes. All compartments of a complex rosette were activated during electrical activation of the mossy fibre, while individual simple and complex rosettes along an axon...... appeared to be isolated from one another in terms of calcium signalling. CGP55845 application showed that GABA B receptors mediated presynaptic inhibition of the calcium signal over the entire firing frequency range of mossy fibres. A paired-pulse depression of the calcium signal lasting more than 1 s...

  15. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation (United States)

    Davis, S. J.; Scott, L. L.; Ordemann, G.; Philpo, A.; Cohn, J.; Pierce-Shimomura, J. T.


    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca2+ bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca2+ bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action. PMID:26113050

  16. Distinct Calcium Sources Support Multiple Modes of Synaptic Release from Cranial Sensory Afferents. (United States)

    Fawley, Jessica A; Hofmann, Mackenzie E; Andresen, Michael C


    Most craniosensory afferents have unmyelinated axons expressing TRP Vanilloid 1 (TRPV1) receptors in synaptic terminals at the solitary tract nucleus (NTS). Neurotransmission from these synapses is characterized by substantial asynchronous EPSCs following action potential-synched EPSCs and high spontaneous rates that are thermally sensitive. The present studies blocked voltage-activated calcium channels (CaV) using the nonselective CaV blocker Cd(2+) or the specific N-type blocker ω-conotoxin GVIA to examine the calcium dependence of the synchronous, asynchronous, spontaneous, and thermally gated modes of release. In rat brainstem slices containing caudal NTS, shocks to the solitary tract (ST) triggered synchronous ST-EPSCs and trailing asynchronous EPSCs. Cd(2+) or GVIA efficiently reduced both synchronous and asynchronous EPSCs without altering spontaneous or thermal-evoked transmission. Activation of TRPV1 with either the selective agonist resiniferatoxin (150 pm) or temperature augmented basal sEPSC rates but failed to alter the synchronous or asynchronous modes of release. These data indicate that calcium sourced through TRPV1 has no access to the synchronous or asynchronous release mechanism(s) and conversely that CaV-sourced calcium does not interact with the thermally evoked mode of release. Buffering intracellular calcium with EGTA-AM or BAPTA-AM reduced asynchronous EPSC rates earlier and to a greater extent than synchronous ST-EPSC amplitudes without altering sEPSCs or thermal sensitivity. Buffering therefore distinguishes asynchronous vesicles as possessing a highly sensitive calcium sensor located perhaps more distant from CaV than synchronous vesicles or thermally evoked vesicles from TRPV1. Together, our findings suggest separate mechanisms of release for spontaneous, asynchronous and synchronous vesicles that likely reside in unique, spatially separated vesicle domains. Most craniosensory fibers release glutamate using calcium entry from two

  17. Calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum in skeletal muscle fibers. (United States)

    Simon, B J; Klein, M G; Schneider, M F


    The steady-state calcium dependence of inactivation of calcium release from the sarcoplasmic reticulum was studied in voltage-clamped, cut segments of frog skeletal muscle fibers containing two calcium indicators, fura-2 and anti-pyrylazo III (AP III). Fura-2 fluorescence was used to monitor resting calcium and relatively small calcium transients during small depolarizations. AP III absorbance signals were used to monitor larger calcium transients during larger depolarizations. The rate of release (Rrel) of calcium from the sarcoplasmic reticulum was calculated from the calcium transients. The equilibrium calcium dependence of inactivation of calcium release was determined using 200-ms prepulses of various amplitudes to elevate [Ca2+] to various steady levels. Each prepulse was followed by a constant test pulse. The suppression of peak Rrel during the test pulse provided a measure of the extent of inactivation of release at the end of the prepulse. The [Ca2+] dependence of inactivation indicated that binding of more than one calcium ion was required to inactivate each release channel. Half-maximal inactivation was produced at a [Ca2+] of approximately 0.3 microM. Variation of the prepulse duration and amplitude showed that the suppression of peak release was consistent with calcium-dependent inactivation of calcium release but not with calcium depletion. The same calcium dependence of inactivation was obtained using different amplitude test pulses to determine the degree of inactivation. Prepulses that produced near maximal inactivation of release during the following test pulse produced no suppression of intramembrane charge movement during the test pulse, indicating that inactivation occurred at a step beyond the voltage sensor for calcium release. Three alternative set of properties that were assumed for the rapidly equilibrating calcium-binding sites intrinsic to the fibers gave somewhat different Rrel records, but gave very similar calcium dependence of

  18. Selective compensation of voltage harmonics in grid-connected microgrids

    DEFF Research Database (Denmark)

    Savaghebi, Mehdi; Vasquez, Juan Carlos; Jalilian, Alireza


    In this paper, a novel approach is proposed for selective compensation of main voltage harmonics in a grid-connected microgrid. The aim of compensation is to provide a high voltage quality at the point of common coupling (PCC). PCC voltage quality is of great importance due to sensitive loads tha...... to an acceptable level....

  19. Voltage sag source location based on instantaneous energy detection

    DEFF Research Database (Denmark)

    Chen, Zhe; Xinzhou, Dong; Wei, Kong


    Voltage sag is the major power quality problem, which could disrupt the operation of sensitive equipment. This paper presents the applications of instantaneous energy direction for voltage sag source detection. Simulations have been performed to provide the analysis for system with distributed...... generation units. The studies show that the presented method can effectively detect the location of the voltage sag source....

  20. Design and control of single-phase dynamic voltage restorer

    Indian Academy of Sciences (India)

    Dynamic voltage restorer (DVR) is a custom power device used in electrical distribution system for power quality improvement. It ensures regulated voltage supply to the sensitive loads, even in case of voltage sag and swell disturbances in the distribution network. It is a series connected device and compensates voltagesag ...

  1. Loop-voltage tomography in tokamaks using transient synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, N.J.; Kritz, A.H. (Princeton Univ., NJ (USA). Plasma Physics Lab.; Hunter Coll., New York, NY (USA). Dept. of Physics)


    The loop voltage in tokamaks is particularly difficult to measure anywhere but at the plasma periphery. A brief, deliberate, perturbation of hot plasma electrons, however, produces a transient radiation response that is sensitive to this voltage. We investigate how such a radiation response can be used to diagnose the loop voltage. 24 refs., 6 figs.

  2. Control and Testing of a Dynamic Voltage Restorer (DVR) at Medium Voltage Level

    DEFF Research Database (Denmark)

    Nielsen, John Godsk; Newman, Michael; Nielsen, Hans Ove


    The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high...... power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a Distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies...... duration voltage sags were created using a controllable LV breaker fed by a 630 kVA Distribution transformer placed upstream of the sensitive load. The fault currents in excess of 12 kA were designed and created to obtain the required voltage sags. It is concluded the DVR works well in all operating...

  3. Voltage-gated proton (H(v)1) channels, a singular voltage sensing domain. (United States)

    Castillo, Karen; Pupo, Amaury; Baez-Nieto, David; Contreras, Gustavo F; Morera, Francisco J; Neely, Alan; Latorre, Ramon; Gonzalez, Carlos


    The main role of voltage-gated proton channels (Hv1) is to extrude protons from the intracellular milieu when, mediated by different cellular processes, the H(+) concentration increases. Hv1 are exquisitely selective for protons and their structure is homologous to the voltage sensing domain (VSD) of other voltage-gated ion channels like sodium, potassium, and calcium channels. In clear contrast to the classical voltage-dependent channels, Hv1 lacks a pore domain and thus permeation necessarily occurs through the voltage sensing domain. Hv1 channels are activated by depolarizing voltages, and increases in internal proton concentration. It has been proposed that local conformational changes of the transmembrane segment S4, driven by depolarization, trigger the molecular rearrangements that open Hv1. However, it is still unclear how the electromechanical coupling is achieved between the VSD and the potential pore, allowing the proton flux from the intracellular to the extracellular side. Here we provide a revised view of voltage activation in Hv1 channels, offering a comparative scenario with other voltage sensing channels domains. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  4. The metabolic impact of β-hydroxybutyrate on neurotransmission: Reduced glycolysis mediates changes in calcium responses and KATP channel receptor sensitivity

    DEFF Research Database (Denmark)

    Lund, Trine Meldgaard; Ploug, K.B.; Iversen, Anne


    -hydroxybutyrate might change neuronal function as there is a known coupling between metabolism and neurotransmission. The purpose of this study was to shed light on the effects of the ketone body β-hydroxybutyrate on glycolysis and neurotransmission in cultured murine glutamatergic neurons. Previous studies have shown...... an effect of β-hydroxybutyrate on glucose metabolism, and the present study further specified this by showing attenuation of glycolysis when β-hydroxybutyrate was present in these neurons. In addition, the NMDA receptor-induced calcium responses in the neurons were diminished in the presence of β...... to a combination of glucose and R-β-hydroxybutyrate in cultured neurons. Using the latter combination, glycolysis was diminished, NMDA receptor-induced calcium responses were lower, and the KATP channel blocker glibenclamide caused a higher transmitter release....

  5. Model of intracellular calcium cycling in ventricular myocytes. (United States)

    Shiferaw, Y; Watanabe, M A; Garfinkel, A; Weiss, J N; Karma, A


    We present a mathematical model of calcium cycling that takes into account the spatially localized nature of release events that correspond to experimentally observed calcium sparks. This model naturally incorporates graded release by making the rate at which calcium sparks are recruited proportional to the whole cell L-type calcium current, with the total release of calcium from the sarcoplasmic reticulum (SR) being just the sum of local releases. The dynamics of calcium cycling is studied by pacing the model with a clamped action potential waveform. Experimentally observed calcium alternans are obtained at high pacing rates. The results show that the underlying mechanism for this phenomenon is a steep nonlinear dependence of the calcium released from the SR on the diastolic SR calcium concentration (SR load) and/or the diastolic calcium level in the cytosol, where the dependence on diastolic calcium is due to calcium-induced inactivation of the L-type calcium current. In addition, the results reveal that the calcium dynamics can become chaotic even though the voltage pacing is periodic. We reduce the equations of the model to a two-dimensional discrete map that relates the SR and cytosolic concentrations at one beat and the previous beat. From this map, we obtain a condition for the onset of calcium alternans in terms of the slopes of the release-versus-SR load and release-versus-diastolic-calcium curves. From an analysis of this map, we also obtain an understanding of the origin of chaotic dynamics.

  6. Calcium Electroporation: Evidence for Differential Effects in Normal and Malignant Cell Lines, Evaluated in a 3D Spheroid Model. (United States)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha; Gehl, Julie; Rols, Marie-Pierre


    Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill efficacy-and normal cell sensitivity. Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (pspheroids was neither affected after calcium electroporation nor electrochemotherapy using bleomycin, indicating that calcium electroporation, like electrochemotherapy, will have limited adverse effects on the surrounding normal tissue when treating with calcium electroporation. The intracellular ATP level, which has previously been shown to be depleted after calcium electroporation, was measured in the spheroids after treatment. The results showed a dramatic decrease in the intracellular ATP level (pspheroid types-malignant as well as normal. In conclusion, calcium electroporation seems to be more effective in inducing cell death in cancer cell spheroids than in a normal fibroblast spheroid, even though intracellular ATP level is depleted in all spheroid types after treatment. These results may indicate an important therapeutic window for this therapy; although further studies are needed in vivo and in patients to investigate the effect of calcium electroporation on surrounding normal tissue when treating tumors.

  7. Voltage Sag Source Location Based on Instantaneous Energy Detection

    DEFF Research Database (Denmark)

    Chen, Zhe; Kong, Wei; Dong, Xinzhou


    Voltage sag is a major power quality problem, which could disrupt the operation of voltage-sensitive equipment. This paper presents the method based on variation components-based instantaneous energy for voltage sag source detection. Simulations have been performed to provide the thorough analysis...... for system with distributed generation units. The studies show that the presented method can effectively detect the location of voltage sag source....

  8. Voltage harmonic elimination with RLC based interface smoothing filter (United States)

    Chandrasekaran, K.; Ramachandaramurthy, V. K.


    A method is proposed for designing a Dynamic Voltage Restorer (DVR) with RLC interface smoothing filter. The RLC filter connected between the IGBT based Voltage Source Inverter (VSI) is attempted to eliminate voltage harmonics in the busbar voltage and switching harmonics from VSI by producing a PWM controlled harmonic voltage. In this method, the DVR or series active filter produces PWM voltage that cancels the existing harmonic voltage due to any harmonic voltage source. The proposed method is valid for any distorted busbar voltage. The operating VSI handles no active power but only harmonic power. The DVR is able to suppress the lower order switching harmonics generated by the IGBT based VSI. Good dynamic and transient results obtained. The Total Harmonic Distortion (THD) is minimized to zero at the sensitive load end. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of RLC filter. Simulated results are presented.

  9. The Use of Ratiometric Fluorescence Measurements of the Voltage Sensitive Dye Di-4-ANEPPS to Examine Action Potential Characteristics and Drug Effects on Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes. (United States)

    Hortigon-Vinagre, M P; Zamora, V; Burton, F L; Green, J; Gintant, G A; Smith, G L


    Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and higher throughput platforms have emerged as potential tools to advance cardiac drug safety screening. This study evaluated the use of high bandwidth photometry applied to voltage-sensitive fluorescent dyes (VSDs) to assess drug-induced changes in action potential characteristics of spontaneously active hiPSC-CM. Human iPSC-CM from 2 commercial sources (Cor.4U and iCell Cardiomyocytes) were stained with the VSD di-4-ANEPPS and placed in a specialized photometry system that simultaneously monitors 2 wavebands of emitted fluorescence, allowing ratiometric measurement of membrane voltage. Signals were acquired at 10 kHz and analyzed using custom software. Action potential duration (APD) values were normally distributed in cardiomyocytes (CMC) from both sources though the mean and variance differed significantly (APD 90 : 229 ± 15 ms vs 427 ± 49 ms [mean ± SD, P < 0.01]; average spontaneous cycle length: 0.99 ± 0.02 s vs 1.47 ± 0.35 s [mean ± SD, P < 0.01], Cor.4U vs iCell CMC, respectively). The 10-90% rise time of the AP (T rise ) was ∼6 ms and was normally distributed when expressed as 1/[Formula: see text] in both cell preparations. Both cell types showed a rate dependence analogous to that of adult human cardiac cells. Furthermore, nifedipine, ranolazine, and E4031 had similar effects on cardiomyocyte electrophysiology in both cell types. However, ranolazine and E4031 induced early after depolarization-like events and high intrinsic firing rates at lower concentrations in iCell CMC. These data show that VSDs provide a minimally invasive, quantitative, and accurate method to assess hiPSC-CM electrophysiology and detect subtle drug-induced effects for drug safety screening while highlighting a need to standardize experimental protocols across preparations. © The Author 2016. Published by Oxford University Press on behalf of the Society of

  10. Voltage control of ferromagnetic resonance

    Directory of Open Access Journals (Sweden)

    Ziyao Zhou


    Full Text Available Voltage control of magnetism in multiferroics, where the ferromagnetism and ferroelectricity are simultaneously exhibiting, is of great importance to achieve compact, fast and energy efficient voltage controllable magnetic/microwave devices. Particularly, these devices are widely used in radar, aircraft, cell phones and satellites, where volume, response time and energy consumption is critical. Researchers realized electric field tuning of magnetic properties like magnetization, magnetic anisotropy and permeability in varied multiferroic heterostructures such as bulk, thin films and nanostructure by different magnetoelectric (ME coupling mechanism: strain/stress, interfacial charge, spin–electromagnetic (EM coupling and exchange coupling, etc. In this review, we focus on voltage control of ferromagnetic resonance (FMR in multiferroics. ME coupling-induced FMR change is critical in microwave devices, where the electric field tuning of magnetic effective anisotropic field determines the tunability of the performance of microwave devices. Experimentally, FMR measurement technique is also an important method to determine the small effective magnetic field change in small amount of magnetic material precisely due to its high sensitivity and to reveal the deep science of multiferroics, especially, voltage control of magnetism in novel mechanisms like interfacial charge, spin–EM coupling and exchange coupling.

  11. Calcium in plant cells

    Directory of Open Access Journals (Sweden)

    V. V. Schwartau


    Full Text Available The paper gives the review on the role of calcium in many physiological processes of plant organisms, including growth and development, protection from pathogenic influences, response to changing environmental factors, and many other aspects of plant physiology. Initial intake of calcium ions is carried out by Ca2+-channels of plasma membrane and they are further transported by the xylem owing to auxins’ attractive ability. The level of intake and selectivity of calcium transport to ove-ground parts of the plant is controlled by a symplast. Ca2+enters to the cytoplasm of endoderm cells through calcium channels on the cortical side of Kaspary bands, and is redistributed inside the stele by the symplast, with the use of Ca2+-АТPases and Ca2+/Н+-antiports. Owing to regulated expression and activity of these calcium transporters, calclum can be selectively delivered to the xylem. Important role in supporting calcium homeostasis is given to the vacuole which is the largest depo of calcium. Regulated quantity of calcium movement through the tonoplast is provided by a number of potential-, ligand-gated active transporters and channels, like Ca2+-ATPase and Ca2+/H+ exchanger. They are actively involved in the inactivation of the calcium signal by pumping Ca2+ to the depo of cells. Calcium ATPases are high affinity pumps that efficiently transfer calcium ions against the concentration gradient in their presence in the solution in nanomolar concentrations. Calcium exchangers are low affinity, high capacity Ca2+ transporters that are effectively transporting calcium after raising its concentration in the cell cytosol through the use of protons gradients. Maintaining constant concentration and participation in the response to stimuli of different types also involves EPR, plastids, mitochondria, and cell wall. Calcium binding proteins contain several conserved sequences that provide sensitivity to changes in the concentration of Ca2+ and when you

  12. The mechanoelectric feedback: a novel "calcium clamp" method, using tetanic contraction, for testing the role of the intracellular free calcium. (United States)

    Yaniv, Yael; Levy, Carmit; Landesberg, Amir


    Mechanical perturbations affect the membrane action potential, a phenomenon denoted as the mechanoelectric feedback (MEF), and may elicit cardiac arrhythmias. Two plausible mechanisms were suggested to explain this phenomenon: (i) stretch-activated channels (SACs) within the cell membrane and (ii) modulation of the action potential by the intracellular Ca(2+) (the Calcium hypothesis). The intracellular Ca(2+) varies mainly due to the effects of the mechanical perturbations on the affinity of troponin for calcium. The present study concentrates on the unique experimental methods that allow differentiating between the effects of SAC and Ca(2+) on the action potential. This is achieved by controlling the sarcomere lengths (SLs) independently of the intracellular Ca(2+) concentration, in the intact fiber. A dedicated experimental setup allowed simultaneous measurements of the membrane potential and the mechanical performance (Force and SL). The action potential was measured by voltage-sensitive dye (Di-4-ANEPPS). The SL was measured by laser diffraction technique and was controlled by a fast servomotor. The intracellular Ca(2+) was controlled (calcium clamp) by imposing stable tetanic contractions at various extracellular calcium concentrations ([Ca(2+)](0)s). Tetanus was obtained by 8 Hz stimulation in the presence of cyclopiazonic acid (CPA) (30 muM). Isolated trabeculae from a rat's right ventricle were studied at different SLs and [Ca(2+)](0)s. The experimental data strongly support the calcium hypothesis. Although the action potential duration (APD) decreases at longer SL, the [Ca(2+)](0) has a significantly larger effect on the APD. The APD decreases as the [Ca(2+)](0) increases. Understanding the underlying mechanism opens new research avenues for the development of therapeutic modalities for cardiac arrhythmias.

  13. Technological Aspects: High Voltage

    CERN Document Server

    Faircloth, D.C.


    This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

  14. High voltage test techniques

    CERN Document Server

    Kind, Dieter


    The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

  15. High voltage engineering

    CERN Document Server

    Rizk, Farouk AM


    Inspired by a new revival of worldwide interest in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission, High Voltage Engineering merges the latest research with the extensive experience of the best in the field to deliver a comprehensive treatment of electrical insulation systems for the next generation of utility engineers and electric power professionals. The book offers extensive coverage of the physical basis of high-voltage engineering, from insulation stress and strength to lightning attachment and protection and beyond. Presenting information critical to the design, selec

  16. Stray voltage mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies


    This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

  17. Endoplasmic reticulum calcium stores in dendritic spines. (United States)

    Segal, Menahem; Korkotian, Eduard


    Despite decades of research, the role of calcium stores in dendritic spines structure, function and plasticity is still debated. The reasons for this may have to do with the multitude of overlapping calcium handling machineries in the neuron, including stores, voltage and ligand gated channels, pumps and transporters. Also, different cells in the brain are endowed with calcium stores that are activated by different receptor types, and their differential compartmentalization in dendrites, spines and presynaptic terminals complicates their analysis. In the present review we address several key issues, including the role of calcium stores in synaptic plasticity, their role during development, in stress and in neurodegenerative diseases. Apparently, there is increasing evidence for a crucial role of calcium stores, especially of the ryanodine species, in synaptic plasticity and neuronal survival.

  18. Highly efficient iodide/triiodide dye-sensitized solar cells with gel-coated reduce graphene oxide/single-walled carbon nanotube composites as the counter electrode exhibiting an open-circuit voltage of 0.90 V. (United States)

    Zheng, Huiqin; Neo, Chin Yong; Ouyang, Jianyong


    To increase the open-circuit voltage (Voc) of dye-sensitized solar cells (DSCs), it is crucial to enhance the photovoltaic efficiency of DSCs. Here, we report an effective method to significantly improve the Voc and photovoltaic efficiency of DSCs by using gel-coated composites of reduced graphene oxide (rGO) and single-walled carbon nanotubes (SWCNTs) as the counter electrode. Gel-coated rGO-SWCNT composites outperform Pt, rGO and SWCNTs in catalyzing the reduction of I3(-) and functioning as the counter electrode of DSCs. The Voc and power conversion efficiency (PCE) are 0.86 V and 8.37% for fresh DSCs with the composite of 80 wt % rGO and 20 wt % SWCNTs, significantly higher than those (Voc = 0.77 V, PCE = 7.79%) of control DSCs with Pt fabricated by pyrolysis as the counter electrode. The Voc value of DSCs with rGO-SWCNT composites as the counter electrode further increases to 0.90 V after one week. The high Voc and PCE are ascribed to the synergetic effects of rGO and SWCNTs in reducing the overpotential of the I3(-) reduction. RGO with high specific surface area can have high electrocatalytic activity, whereas SWCNTs give rise to high conductivity for the composites and facilitate the penetration of the redox species into rGO sheets by preventing the agglomeration of the rGO sheets. To the best of our knowledge, this is the first time to report iodide/triiodide DSCs with both high Voc and PCE.

  19. Get Enough Calcium (United States)

    ... Calcium Print This Topic En español Get Enough Calcium Browse Sections The Basics Overview Foods and Vitamins ... women, don't get enough calcium. How much calcium do I need every day? Women: If you ...

  20. Calcium carbonate overdose (United States)

    Tums overdose; Calcium overdose ... Calcium carbonate can be dangerous in large amounts. ... Some products that contain calcium carbonate are certain: ... and mineral supplements Other products may also contain calcium ...

  1. Separation of intramembrane charging components in low-calcium solutions in frog skeletal muscle. (United States)

    Huang, C L


    The inactivation of charge movement components by small (-100 to -70 mV) shifts in holding potential was examined in voltage-clamped intact amphibian muscle fibers in low [Ca2+], Mg(2+)-containing solutions. The pulse protocols used both large voltage excursions and smaller potential steps that elicited prolonged (q gamma) transients. Charge species were distinguished through the pharmacological effects of tetracaine. These procedures confirmed earlier observations in cut fibers and identified the following new properties of the q gamma charge. First, q gamma, previously defined as the tetracaine-sensitive charge, is also the component primarily responsible for the voltage-dependent inactivation induced by conditions of low extracellular [Ca2+]. Second, this inactivation separates a transient that includes a "hump" component and which has kinetics and a voltage dependence distinct from the monotonic decay that remains. Third, q gamma, previously associated with delayed charge movements, can also contribute significant charge transfer at early times. These findings suggest that the parallel inhibition of calcium signals and charge movements reported in low [Ca2+] solutions arises from influences on q gamma charge (Brum et al., 1988a, b). They also reconcile reports that implicate tetracaine-sensitive (q gamma) charge in excitation-contraction coupling with evidence that early intramembrane events are also involved in this process (Pizarro et al., 1989). Finally, they are relevant to hypotheses of possible feedback or feed-forward roles of q gamma in excitation-contraction coupling.

  2. Voltage Unbalance and Harmonic Compensation in Microgrids by Cooperation of Distributed Generators and Active Power Filters

    DEFF Research Database (Denmark)

    Hashempour, Mohammad M.; Savaghebi, Mehdi; Quintero, Juan Carlos Vasquez


    , selective virtual impedance and voltage/current regulators. Based on the secondary control, at first voltage harmonic compensation and voltage unbalance compensation of point of common coupling (PCC), that might includes sensitive loads, is carried out by DGs. Voltage compensation of PCC by DGs may cause...

  3. Hysteresis in voltage-gated channels. (United States)

    Villalba-Galea, Carlos A


    Ion channels constitute a superfamily of membrane proteins found in all living creatures. Their activity allows fast translocation of ions across the plasma membrane down the ion's transmembrane electrochemical gradient, resulting in a difference in electrical potential across the plasma membrane, known as the membrane potential. A group within this superfamily, namely voltage-gated channels, displays activity that is sensitive to the membrane potential. The activity of voltage-gated channels is controlled by the membrane potential, while the membrane potential is changed by these channels' activity. This interplay produces variations in the membrane potential that have evolved into electrical signals in many organisms. These signals are essential for numerous biological processes, including neuronal activity, insulin release, muscle contraction, fertilization and many others. In recent years, the activity of the voltage-gated channels has been observed not to follow a simple relationship with the membrane potential. Instead, it has been shown that the activity of voltage-gated channel displays hysteresis. In fact, a growing number of evidence have demonstrated that the voltage dependence of channel activity is dynamically modulated by activity itself. In spite of the great impact that this property can have on electrical signaling, hysteresis in voltage-gated channels is often overlooked. Addressing this issue, this review provides examples of voltage-gated ion channels displaying hysteretic behavior. Further, this review will discuss how Dynamic Voltage Dependence in voltage-gated channels can have a physiological role in electrical signaling. Furthermore, this review will elaborate on the current thoughts on the mechanism underlying hysteresis in voltage-gated channels.

  4. Calcium Impact on Milk Gels Formation

    DEFF Research Database (Denmark)

    Koutina, Glykeria

    Calcium is one of the several elements that can be found in milk distributed between the micellar and the serum milk phase. Calcium is important from a nutritional point of view, but its contribution to the functional and structural properties of dairy products has only recently been...... acknowledgement. The presence of calcium in a dynamic equilibrium between the serum and the micellar milk phase make the distribution susceptible to certain physicochemical conditions and to technological treatments of milk resulting in fluctuations in pH and temperature and also sensitive to addition of calcium...... salts. The perturbation of calcium equilibria by these factors will affect the final properties of acid, calcium and rennet milk gels. By decreasing the pH from 6.0 to 5.2 (acid gels), the calcium equilibrium was significantly affected by temperature (4, 20, 30, 40 oC), and different combinations...

  5. Voltage verification unit (United States)

    Martin, Edward J [Virginia Beach, VA


    A voltage verification unit and method for determining the absence of potentially dangerous potentials within a power supply enclosure without Mode 2 work is disclosed. With this device and method, a qualified worker, following a relatively simple protocol that involves a function test (hot, cold, hot) of the voltage verification unit before Lock Out/Tag Out and, and once the Lock Out/Tag Out is completed, testing or "trying" by simply reading a display on the voltage verification unit can be accomplished without exposure of the operator to the interior of the voltage supply enclosure. According to a preferred embodiment, the voltage verification unit includes test leads to allow diagnostics with other meters, without the necessity of accessing potentially dangerous bus bars or the like.

  6. Alpha 1B-receptors and intracellular calcium mediate sympathetic nerve induced constriction of rat irideal blood vessels. (United States)

    Gould, D J; Hill, C E


    The present study has investigated the receptors involved in the non-cholinergic nerve mediated constriction of the larger blood vessels (30-50 microns) within the rat iris. This response was blocked by the alpha-adrenoceptor antagonist, benextramine (10(5) M). Furthermore, the response was more sensitive to blockade by the alpha 1 antagonist, prazosin (IC50 9 x 10(-10) M), than to blockade by the alpha 2 antagonist, yohimbine (IC50 2 x 10(-7) M), or the adrenergic antagonist, WB4101 (IC50 2 x 10(-8) M), and was abolished by chloroethylclonidine (10(-5) M). These results suggest the involvement of alpha 1B-adrenoceptors. The nerve mediated constriction was not blocked by the voltage-dependent calcium channel blocking drugs, nifedipine (10(-6) M), verapamil (10(-6) M) or diltiazem (10(-6) M), but was completely abolished by the intracellular calcium mobilizer, caffeine (10(-3) M), supporting the hypothesis that alpha 1B-adrenoceptors are activated following nerve stimulation. Dantrolene (10(-4) M), which interferes with calcium release from the sarcoplasmic reticulum, reduced the nerve mediated constriction by 40% as did thapsigargin (2 x 10(-6) M), which inhibits the calcium ATPase responsible for uptake of calcium into intracellular stores. When influx of calcium was blocked by verapamil (10(-6) M), thapsigargin, but not dantrolene, completely abolished the response. Noradrenaline (10(-5) M) produced a vasoconstriction in the presence or absence of external calcium although the latter response was significantly smaller than the former. Vasoconstriction produced by a submaximal concentration of noradrenaline (10(-6) M), was completely prevented by pretreatment with chloroethylclonidine. The data indicate that noradrenaline released from sympathetic nerves causes a constriction of arterioles in the iris by activating alpha 1B-adrenoceptors and releasing calcium from dantrolene sensitive and insensitive intracellular stores, followed by inflow of calcium through

  7. Calcium-sensitive regulation of monoamine oxidase-A contributes to the production of peroxyradicals in hippocampal cultures: implications for Alzheimer disease-related pathology

    Directory of Open Access Journals (Sweden)

    Li XinMin


    Full Text Available Abstract Background Calcium (Ca2+ has recently been shown to selectively increase the activity of monoamine oxidase-A (MAO-A, a mitochondria-bound enzyme that generates peroxyradicals as a natural by-product of the deamination of neurotransmitters such as serotonin. It has also been suggested that increased intracellular free Ca2+ levels as well as MAO-A may be contributing to the oxidative stress associated with Alzheimer disease (AD. Results Incubation with Ca2+ selectively increases MAO-A enzymatic activity in protein extracts from mouse hippocampal HT-22 cell cultures. Treatment of HT-22 cultures with the Ca2+ ionophore A23187 also increases MAO-A activity, whereas overexpression of calbindin-D28K (CB-28K, a Ca2+-binding protein in brain that is greatly reduced in AD, decreases MAO-A activity. The effects of A23187 and CB-28K are both independent of any change in MAO-A protein or gene expression. The toxicity (via production of peroxyradicals and/or chromatin condensation associated with either A23187 or the AD-related β-amyloid peptide, which also increases free intracellular Ca2+, is attenuated by MAO-A inhibition in HT-22 cells as well as in primary hippocampal cultures. Conclusion These data suggest that increases in intracellular Ca2+ availability could contribute to a MAO-A-mediated mechanism with a role in AD-related oxidative stress.

  8. The plasminogen binding site of the C-type lectin tetranectin is located in the carbohydrate recognition domain, and binding is sensitive to both calcium and lysine

    DEFF Research Database (Denmark)

    Graversen, Jonas Heilskov; Lorentsen, R H; Jacobsen, C


    Tetranectin, a homotrimeric protein belonging to the family of C-type lectins and structurally highly related to corresponding regions of the mannose-binding proteins, is known specifically to bind the plasminogen kringle 4 protein domain, an interaction sensitive to lysine. Surface plasmon...

  9. Calcium paradox and calcium entry blockers

    NARCIS (Netherlands)

    Ruigrok, T.J.C.; Slade, A.M.; Nayler, W.G.; Meijler, F.L.


    Reperfusion of isolated hearts with calcium-containing solution after a short period of calcium-free perfusion results in irreversible cell damage (calcium paradox). This phenomenon is characterized by an excessive influx of calcium into the cells, the rapid onset of myocardial contracture,

  10. Computational analysis of calcium signaling and membrane electrophysiology in cerebellar Purkinje neurons associated with ataxia

    Directory of Open Access Journals (Sweden)

    Brown Sherry-Ann


    Full Text Available Abstract Background Mutations in the smooth endoplasmic reticulum (sER calcium channel Inositol Trisphosphate Receptor type 1 (IP3R1 in humans with the motor function coordination disorders Spinocerebellar Ataxia Types 15 and 16 (SCA15/16 and in a corresponding mouse model, the IP3R1delta18/delta18 mice, lead to reduced IP3R1 levels. We posit that increasing IP3R1 sensitivity to IP3 in ataxias with reduced IP3R1 could restore normal calcium response. On the other hand, in mouse models of the human polyglutamine (polyQ ataxias, SCA2, and SCA3, the primary finding appears to be hyperactive IP3R1-mediated calcium release. It has been suggested that the polyQ SCA1 mice may also show hyperactive IP3R1. Yet, SCA1 mice show downregulated gene expression of IP3R1, Homer, metabotropic glutamate receptor (mGluR, smooth endoplasmic reticulum Ca-ATP-ase (SERCA, calbindin, parvalbumin, and other calcium signaling proteins. Results We create a computational model of pathological alterations in calcium signaling in cerebellar Purkinje neurons to investigate several forms of spinocerebellar ataxia associated with changes in the abundance, sensitivity, or activity of the calcium channel IP3R1. We find that increasing IP3R1 sensitivity to IP3 in computational models of SCA15/16 can restore normal calcium response if IP3R1 abundance is not too low. The studied range in IP3R1 levels reflects variability found in human and mouse ataxic models. Further, the required fold increases in sensitivity are within experimental ranges from experiments that use IP3R1 phosphorylation status to adjust its sensitivity to IP3. Results from our simulations of polyglutamine SCAs suggest that downregulation of some calcium signaling proteins may be partially compensatory. However, the downregulation of calcium buffer proteins observed in the SCA1 mice may contribute to pathology. Finally, our model suggests that the calcium-activated voltage-gated potassium channels may provide an

  11. Anion-sensitive regions of L-type CaV1.2 calcium channels expressed in HEK293 cells.

    Directory of Open Access Journals (Sweden)

    Norbert Babai


    Full Text Available L-type calcium currents (I(Ca are influenced by changes in extracellular chloride, but sites of anion effects have not been identified. Our experiments showed that CaV1.2 currents expressed in HEK293 cells are strongly inhibited by replacing extracellular chloride with gluconate or perchlorate. Variance-mean analysis of I(Ca and cell-attached patch single channel recordings indicate that gluconate-induced inhibition is due to intracellular anion effects on Ca(2+ channel open probability, not conductance. Inhibition of CaV1.2 currents produced by replacing chloride with gluconate was reduced from approximately 75%-80% to approximately 50% by omitting beta subunits but unaffected by omitting alpha(2delta subunits. Similarly, gluconate inhibition was reduced to approximately 50% by deleting an alpha1 subunit N-terminal region of 15 residues critical for beta subunit interactions regulating open probability. Omitting beta subunits with this mutant alpha1 subunit did not further diminish inhibition. Gluconate inhibition was unchanged with expression of different beta subunits. Truncating the C terminus at AA1665 reduced gluconate inhibition from approximately 75%-80% to approximately 50% whereas truncating it at AA1700 had no effect. Neutralizing arginines at AA1696 and 1697 by replacement with glutamines reduced gluconate inhibition to approximately 60% indicating these residues are particularly important for anion effects. Expressing CaV1.2 channels that lacked both N and C termini reduced gluconate inhibition to approximately 25% consistent with additive interactions between the two tail regions. Our results suggest that modest changes in intracellular anion concentration can produce significant effects on CaV1.2 currents mediated by changes in channel open probability involving beta subunit interactions with the N terminus and a short C terminal region.

  12. Voltage-gated sodium channels in taste bud cells

    Directory of Open Access Journals (Sweden)

    Williams Mark E


    Full Text Available Abstract Background Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. Results We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. Conclusion SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.

  13. Design and Control of a Dynamic Voltage Restorer

    DEFF Research Database (Denmark)

    Nielsen, John Godsk

    of the described events can be a potential problem for sensitiv loads. During the thesis knowledge is gathered about power quality and power electronics for voltage quality improvements. In addition knowledge about the design and control of a DVR either connected at the low voltage or the medium voltage level......This thesis is the main results from a Ph.D. project under the research programme "Local Compensation" at Aalborg University. The main topics in the thesis are the design and control of a Dynamic Voltage Restorer (DVR). The DVR is a series connected device, which primarily can protect sensitive...... electric consumers against voltage dips and surges in the medium and low voltage distribution grid. The thesis first gives an introduction to relevant power quality issues for a DVR and power electronic controllers for voltage dip mitigation. Thereafter the operation and the elements in a DVR are described...

  14. Calibration of Voltage Transformers and High- Voltage Capacitors at NIST (United States)

    Anderson, William E.


    The National Institute of Standards and Technology (NIST) calibration service for voltage transformers and high-voltage capacitors is described. The service for voltage transformers provides measurements of ratio correction factors and phase angles at primary voltages up to 170 kV and secondary voltages as low as 10 V at 60 Hz. Calibrations at frequencies from 50–400 Hz are available over a more limited voltage range. The service for high-voltage capacitors provides measurements of capacitance and dissipation factor at applied voltages ranging from 100 V to 170 kV at 60 Hz depending on the nominal capacitance. Calibrations over a reduced voltage range at other frequencies are also available. As in the case with voltage transformers, these voltage constraints are determined by the facilities at NIST. PMID:28053409

  15. High voltage engineering fundamentals

    CERN Document Server

    Kuffel, E; Hammond, P


    Provides a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation system; basic ionisation and decay processes in gases and breakdown mechanisms of gaseous, liquid and solid dielectrics; partial discharges and modern discharge detectors; and over

  16. Glutamine Substitution at Alanine1649 in the S4–S5 Cytoplasmic Loop of Domain 4 Removes the Voltage Sensitivity of Fast Inactivation in the Human Heart Sodium Channel (United States)

    Tang, Lihui; Chehab, Nabil; Wieland, Steven J.; Kallen, Roland G.


    Normal activation–inactivation coupling in sodium channels insures that inactivation is slow at small but rapid at large depolarizations. M1651Q/M1652Q substitutions in the cytoplasmic loop connecting the fourth and fifth transmembrane segments of Domain 4 (S4–S5/D4) of the human heart sodium channel subtype 1 (hH1) affect the kinetics and voltage dependence of inactivation (Tang, L., R.G. Kallen, and R. Horn. 1996. J. Gen. Physiol. 108:89–104.). We now show that glutamine substitutions NH2-terminal to the methionines (L1646, L1647, F1648, A1649, L1650) also influence the kinetics and voltage dependence of inactivation compared with the wild-type channel. In contrast, mutations at the COOH-terminal end of the S4–S5/D4 segment (L1654, P1655, A1656) are without significant effect. Strikingly, the A1649Q mutation renders the current decay time constants virtually voltage independent and decreases the voltage dependences of steady state inactivation and the time constants for the recovery from inactivation. Single-channel measurements show that at negative voltages latency times to first opening are shorter and less voltage dependent in A1649Q than in wild-type channels; peak open probabilities are significantly smaller and the mean open times are shorter. This indicates that the rate constants for inactivation and, probably, activation are increased at negative voltages by the A1649Q mutation reminiscent of Y1494Q/ Y1495Q mutations in the cytoplasmic loop between the third and fourth domains (O'Leary, M.E., L.Q. Chen, R.G. Kallen, and R. Horn. 1995. J. Gen. Physiol. 106:641–658.). Other substitutions, A1649S and A1649V, decrease but fail to eliminate the voltage dependence of time constants for inactivation, suggesting that the decreased hydrophobicity of glutamine at either residues A1649 or Y1494Y1495 may disrupt a linkage between S4–S5/D4 and the interdomain 3–4 loop interfering with normal activation–inactivation coupling. PMID:9565402

  17. Spatiotemporal intracellular calcium dynamics during cardiac alternans (United States)

    Restrepo, Juan G.; Karma, Alain


    Cellular calcium transient alternans are beat-to-beat alternations in the peak cytosolic calcium concentration exhibited by cardiac cells during rapid electrical stimulation or under pathological conditions. Calcium transient alternans promote action potential duration alternans, which have been linked to the onset of life-threatening ventricular arrhythmias. Here we use a recently developed physiologically detailed mathematical model of ventricular myocytes to investigate both stochastic and deterministic aspects of intracellular calcium dynamics during alternans. The model combines a spatially distributed description of intracellular calcium cycling, where a large number of calcium release units are spatially distributed throughout the cell, with a full set of ionic membrane currents. The results demonstrate that ion channel stochasticity at the level of single calcium release units can influence the whole-cell alternans dynamics by causing phase reversals over many beats during fixed frequency pacing close to the alternans bifurcation. They also demonstrate the existence of a wide range of dynamical states. Depending on the sign and magnitude of calcium-voltage coupling, calcium alternans can be spatially synchronized or desynchronized, in or out of phase with action potential duration alternans, and the node separating out-of-phase regions of calcium alternans can be expelled from or trapped inside the cell. This range of states is found to be larger than previously anticipated by including a robust global attractor where calcium alternans can be spatially synchronized but out of phase with action potential duration alternans. The results are explained by a combined theoretical analysis of alternans stability and node motion using general iterative maps of the beat-to-beat dynamics and amplitude equations.

  18. Diuretics and disorders of calcium homeostasis. (United States)

    Grieff, Marvin; Bushinsky, David A


    Diuretics commonly are administered in disorders of sodium balance. Loop diuretics inhibit the Na-K-2Cl transporter and also increase calcium excretion. They are often used in the treatment of hypercalcemia. Thiazide diuretics block the thiazide-sensitive NaCl transporter in the distal convoluted tubule, and can decrease calcium excretion. They are often used in the treatment of nephrolithiasis. Carbonic anhydrase inhibitors decrease bicarbonate absorption and the resultant metabolic acidosis can increase calcium excretion. Their use can promote nephrocalcinosis and nephrolithiasis. This review will address the use of diuretics on disorders of calcium homeostasis. Copyright © 2011 Elsevier Inc. All rights reserved.

  19. Coronary Calcium Scan (United States)

    ... Back To Health Topics / Coronary Calcium Scan Coronary Calcium Scan Also known as Calcium Scan Test A coronary calcium scan is a CT scan of your heart that detects and measures the amount of calcium in the walls of your coronary arteries. Overview ...

  20. A calcium-sensitive feed-forward loop regulating the expression of the ATP-gated purinergic P2X7 receptor via specificity protein 1 and microRNA-22. (United States)

    Engel, Tobias; Brennan, Gary P; Sanz-Rodriguez, Amaya; Alves, Mariana; Beamer, Edward; Watters, Orla; Henshall, David C; Jimenez-Mateos, Eva M


    Cells have developed complex transcriptional regulatory mechanisms to maintain intracellular homeostasis and withstand pathophysiological stressors. Feed-forward loops comprising transcription factors that drive expression of both target gene and a microRNA as negative regulator, are gaining increasing recognition as key regulatory elements of cellular homeostasis. The ATP-gated purinergic P2X7 receptor (P2X7R) is an important driver of inflammation and has been implicated in the pathogenesis of numerous brain diseases including epilepsy. Changes in P2X7R expression have been reported in both experimental models and in epilepsy patients but the mechanism(s) controlling P2X7R levels remain incompletely understood. The specificity protein 1 (Sp1) has been shown to induce P2X7R transcription in vitro and recent data has identified microRNA-22 as a post-transcriptional repressor of P2X7R expression after seizures. In the present study we show that Sp1 can induce the transcription of both microRNA-22 and P2X7R in vitro during increased neuronal activity and in vivo in a mouse model of status epilepticus. We further show that Sp1-driven microRNA-22 transcription is calcium-sensitive and Sp1 occupancy of the microRNA-22 promoter region is blocked under conditions of seizure activity sufficient to elicit neuronal death. Taken together, our results suggest a neuronal activity-dependent P2X7R expression which is induced by the transcription factor Sp1 and repressed in a calcium-dependent manner by microRNA-22. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Device for monitoring cell voltage (United States)

    Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE


    A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

  2. A cyclic GMP-dependent calcium-activated chloride current in smooth-muscle cells from rat mesenteric resistance arteries

    DEFF Research Database (Denmark)

    Matchkov, Vladimir; Aalkjær, Christian; Nilsson, Holger


    M) in the pipette solution. The current was found to be a calcium-activated chloride current with an absolute requirement for cyclic GMP (EC50 6.4 microM). The current could be activated by the constitutively active subunit of PKG. Current activation was blocked by the protein kinase G antagonist Rp-8-Br-PET...... no voltage or time dependence. It was inhibited by nickel and zinc ions in the micromolar range, but was unaffected by cobalt and had a low sensitivity to inhibition by the chloride channel blockers niflumic acid, DIDS, and IAA-94. The properties of this current in mesenteric artery smooth-muscle cells...

  3. RF transconductor linearization robust to process, voltage and temperature variations

    NARCIS (Netherlands)

    Kundur Subramaniyan, H.; Klumperink, Eric A.M.; Srinivasan, Venkatesh; Kiaei, Ali; Nauta, Bram


    Software-defined radio receivers increasingly exploit linear RF V-I conversion, instead of RF voltage gain, to improve interference robustness. Unfortunately, the linearity of CMOS inverters, which are often used to implement V-I conversion, is highly sensitive to Process, Voltage and Temperature

  4. Calcium source (image) (United States)

    Getting enough calcium to keep bones from thinning throughout a person's life may be made more difficult if that person has ... as a tendency toward kidney stones, for avoiding calcium-rich food sources. Calcium deficiency also effects the ...

  5. Calcium and bones (image) (United States)

    Calcium is one of the most important minerals for the growth, maintenance, and reproduction of the human ... body, are continually being re-formed and incorporate calcium into their structure. Calcium is essential for the ...

  6. Calcium hydroxide poisoning (United States)

    Hydrate - calcium; Lime milk; Slaked lime ... Calcium hydroxide ... These products contain calcium hydroxide: Cement Limewater Many industrial solvents and cleaners (hundreds to thousands of construction products, flooring strippers, brick cleaners, cement ...

  7. Calcium Pyrophosphate Deposition (CPPD) (United States)

    ... Patient / Caregiver Diseases & Conditions Calcium Pyrophosphate Deposition (CPPD) Calcium Pyrophosphate Deposition (CPPD) Fast Facts The risk of ... young people, too. Proper diagnosis depends on detecting calcium pyrophosphate crystals in the fluid of an affected ...

  8. Calcium blood test (United States)

    ... page: // Calcium blood test To use the sharing features on this page, please enable JavaScript. The calcium blood test measures the level of calcium in the blood. ...

  9. Nanosecond pulsed electric fields depolarize transmembrane potential via voltage-gated K+, Ca2+and TRPM8 channels in U87 glioblastoma cells. (United States)

    Burke, Ryan C; Bardet, Sylvia M; Carr, Lynn; Romanenko, Sergii; Arnaud-Cormos, Delia; Leveque, Philippe; O'Connor, Rodney P


    Nanosecond pulsed electric fields (nsPEFs) have a variety of applications in the biomedical and biotechnology industries. Cancer treatment has been at the forefront of investigations thus far as nsPEFs permeabilize cellular and intracellular membranes leading to apoptosis and necrosis. nsPEFs may also influence ion channel gating and have the potential to modulate cell physiology without poration of the membrane. This phenomenon was explored using live cell imaging and a sensitive fluorescent probe of transmembrane voltage in the human glioblastoma cell line, U87 MG, known to express a number of voltage-gated ion channels. The specific ion channels involved in the nsPEF response were screened using a membrane potential imaging approach and a combination of pharmacological antagonists and ion substitutions. It was found that a single 10ns pulsed electric field of 34kV/cm depolarizes the transmembrane potential of cells by acting on specific voltage-sensitive ion channels; namely the voltage and Ca2 + gated BK potassium channel, L- and T-type calcium channels, and the TRPM8 transient receptor potential channel. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Mechanism of electromechanical coupling in voltage-gated potassium channels

    Directory of Open Access Journals (Sweden)

    Rikard eBlunck


    Full Text Available Voltage-gated ion channels play a central role in the generation of action potentials in the nervous system. They are selective for one type of ion – sodium, calcium or potassium. Voltage-gated ion channels are composed of a central pore that allows ions to pass through the membrane and four peripheral voltage sensing domains that respond to changes in the membrane potential. Upon depolarization, voltage sensors in voltage-gated potassium channels (Kv undergo conformational changes driven by positive charges in the S4 segment and aided by pairwise electrostatic interactions with the surrounding voltage sensor. Structure-function relations of Kv channels have been investigated in detail, and the resulting models on the movement of the voltage sensors now converge to a consensus; the S4 segment undergoes a combined movement of rotation, tilt and vertical displacement in order to bring 3-4 e+ each through the electric field focused in this region. Nevertheless, the mechanism by which the voltage sensor movement leads to pore opening, the electromechanical coupling, is still not fully understood. Thus, recently, electromechanical coupling in different Kv channels has been investigated with a multitude of techniques including electrophysiology, 3D crystal structures, fluorescence spectroscopy and molecular dynamics simulations. Evidently, the S4-S5 linker, the covalent link between the voltage sensor and pore, plays a crucial role. The linker transfers the energy from the voltage sensor movement to the pore domain via an interaction with the S6 C-termini, which are pulled open during gating. In addition, other contact regions have been proposed. This review aims to provide (i an in-depth comparison of the molecular mechanisms of electromechanical coupling in different Kv channels; (ii insight as to how the voltage sensor and pore domain influence one another; and (iii theoretical predictions on the movement of the cytosolic face of the KV channels

  11. Affect of Voltage Sags on Electro-magnetic Contactor (United States)

    Iyoda, Isao; Ando, Yoshitaro; Pounyakhet, Sompathana; Hirata, Masaya; Ise, Toshifumi

    Sensitivity of electro-magnetic contactors for voltage sags is studied by experiments and simulations. An experimental circuit with a semiconductor fault switch that controls the phase angle of system voltage at the initial point of voltage sags is developed. The phase angle is a new parameter for voltage sags. The operating characteristics of the contactor are evaluated in various conditions. It is found that shallow sags may cause faster trips of contactors compared to deep sags in some cases. The reason of this phenomenon is analyzed with simulations.

  12. Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar


    problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate voltage sags in the CIGRE Low Voltage (LV) test network and networks like this. The voltage sags, for the tested cases in the CIGRE LV test network are mainly due to three phase faults....... The compensation of voltage sags in the different parts of CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0.......Any problem in voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM), Dynamic Voltage Restorer (DVR) etc. are commonly used for the mitigation of voltage...

  13. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation. (United States)

    Davis, S J; Scott, L L; Ordemann, G; Philpo, A; Cohn, J; Pierce-Shimomura, J T


    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca(2+) bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca(2+) bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action. © 2015 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

  14. Control of IsAHP in mouse hippocampus CA1 pyramidal neurons by RyR3-mediated calcium-induced calcium release.

    NARCIS (Netherlands)

    Y. Vrede, van de; Fossier, P.; Baux, G.; Joëls, M.; Chameau, P.J.P.


    In several neuronal preparations, the ryanodine-sensitive calcium store was reported to participate in the generation of slow afterhyperpolarization currents (IsAHP) involved in spike frequency adaptation. We show that calcium release from the ryanodine-sensitive calcium store is a major determinant

  15. Mitigation of Unbalanced Voltage Sags and Voltage Unbalance in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar


    . The voltage problems dealt with in this paper are to show how to mitigate unbalanced voltage sags and voltage unbalance in the CIGRE Low Voltage (LV) test network and net-works like this. The voltage unbalances, for the tested cases in the CIGRE LV test network are mainly due to single phase loads and due...... to unbalanced faults. The compensation of unbalanced voltage sags and voltage unbalance in the CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0.......Any problem with voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM) etc. can be used to mitigate the voltage problems in the distribution system...

  16. Geomagnetism and Induced Voltage (United States)

    Abdul-Razzaq, W.; Biller, R. D.


    Introductory physics laboratories have seen an influx of "conceptual integrated science" over time in their classrooms with elements of other sciences such as chemistry, biology, Earth science, and astronomy. We describe a laboratory to introduce this development, as it attracts attention to the voltage induced in the human brain as it…

  17. Restoration of the response of the middle cerebral artery of the rat to acidosis in hyposmotic hyponatremia by the opener of large-conductance calcium sensitive potassium channels (BKCa). (United States)

    Aleksandrowicz, Marta; Dworakowska, Beata; Dolowy, Krzysztof; Kozniewska, Ewa


    Hyposmotic hyponatremia (the decrease of extracellular concentration of sodium ions from 145 to 121 mM and the decrease of hyposmolality from 300 to 250 mOsm/kg H2O) impairs response of the middle cerebral artery (MCA) to acetylcholine and NO donor (S-nitroso-N-acetyl-DL-penicillamine). Since acidosis activates a similar intracellular signaling pathway, the present study was designed to verify the hypothesis that the response of the MCA to acidosis is impaired during acute hyposmotic hyponatremia due to abnormal NO-related signal transduction in vascular smooth muscle cells. Studies performed on isolated, cannulated, and pressurized rat MCA revealed that hyposmotic hyponatremia impaired the response of the MCA to acidosis and this was associated with hyposmolality rather than with decreased sodium ion concentration. Response to acidosis was restored by the BKCa but not by the KATP channel activator. Patch-clamp electrophysiology performed on myocytes freshly isolated from MCAs, demonstrated that hyposmotic hyponatremia does not affect BKCa currents but decreases the voltage-dependency of the activation of the BKCa channels in the presence of a specific opener of these channels. Our study suggests that reduced sensitivity of BKCa channels in the MCA to agonists results in the lack of response of this artery to acidosis during acute hyposmotic hyponatremia.

  18. Compensation Performance for Induction Motor Load of Voltage Dip Compensator (United States)

    Nagamoto, Takamichi; Takayama, Katsumi; Kai, Takaaki

    The variable speed drives of the power electronics application are the most sensitive to the voltage dip that is caused by power system fault. Variable speed drives are composed by the converter, the voltage source inverter and induction motor. They could fall into operation failure by wrong control in the converter when degree of the voltage dip exceeds 15% and 10ms. Therefore, important loads are equipped with the voltage dip compensation. Since the load characteristic of the converter equals nearly the impedance load, the induction motors connected directly to power supply are more sensitive to the output voltage waveform of the compensator than the converter. Thus, the induction motors are used as the important load (compensated load) on the simulation. The simulations of the compensation performance to the induction motors are carried out by using simulation tool PSCAD/EMTDC. It is confirmed that the goal of the compensation performance is able to be achieved.

  19. Dynamic Voltage Restorer Based on Combination of Feed Back and Feed Forward PI

    Directory of Open Access Journals (Sweden)

    Dimas Anton A


    Full Text Available Dynamic voltage restorer (DVR is one of equipments to protect sensitive load from voltage drop. DVR is installed series with line feeder by serial transformer which injecting voltage when under voltage occurs. This research is investigate the capability of DVR, which controlled by combination of feed back and feed forward PI, to handle voltage sag and interruption. DVR controls have been designed and implemented in DVR prototype. As a result, in simulation, DVR can maintain voltage in range 90% - 105% nominal voltage. Voltage at load side can be restored to 1 pu and 0.79 pu when voltage sag and interruption respectively. Furthermore, DVR prototype can restore 0.95 pu when voltage sag and 0.54 pu when interruption.

  20. A comparison of total calcium, corrected calcium, and ionized calcium concentrations as indicators of calcium homeostasis among hypoalbuminemic dogs requiring intensive care. (United States)

    Sharp, Claire R; Kerl, Marie E; Mann, F A


    (1) To evaluate whether total calcium (tCa) correlates with ionized calcium (iCa) in hypoalbuminemic dogs; (2) to evaluate whether calcium adjusted for albumin (Alb), or total protein (TP), or both accurately predict iCa concentrations and hence can be used to monitor calcium homeostasis in critically ill hypoalbuminemic dogs; and (3) to evaluate factors associated with any potential discrepancy in calcium classification between corrected total and ionized values. Prospective observational clinical study. Small animal intensive care unit in a veterinary medical teaching hospital. Twenty-eight client-owned dogs with hypoalbuminemia. None. iCa was determined using ion-specific electrode methodology, on heparinized plasma. The tCa concentration was adjusted for Alb and TP using published equations. In total 29% (8/28) of the hypoalbuminemic, critically ill dogs in this study were hypocalcemic at intensive care unit admission, as determined by iCa measurement. Corrected calcium values failed to accurately classify calcium status in 67.9% and 64.3% of cases, according to whether the Alb-adjusted or TP-adjusted values, respectively, were used. The sensitivity and specificity of the tCa to evaluate hypocalcemia was 100% and 47%, respectively. The sensitivity and specificity of the correction formulae were 37.5% and 79% for the Alb-adjusted values and 37.5% and 74% for TP-adjusted values. tCa overestimated the presence of hypocalcemia and underestimated the presence of normocalcemia, while corrected calcium values overestimated the presence of normocalcemia and underestimated the presence of hypocalcemia. Calcium homeostasis in hypoalbuminemic critically ill dogs should be evaluated by iCa concentrations rather than tCa or calcium adjusted for Alb or TP. Given that tCa has 100% sensitivity for detecting hypocalcemia in this population it is recommended that all hypoalbuminemic and critically ill patients with low tCa should be evaluated with an iCa measurement.

  1. Synaptic calcium regulation in hair cells of the chicken basilar papilla. (United States)

    Im, Gi Jung; Moskowitz, Howard S; Lehar, Mohammed; Hiel, Hakim; Fuchs, Paul Albert


    Cholinergic inhibition of hair cells occurs by activation of calcium-dependent potassium channels. A near-membrane postsynaptic cistern has been proposed to serve as a store from which calcium is released to supplement influx through the ionotropic ACh receptor. However, the time and voltage dependence of acetylcholine (ACh)-evoked potassium currents reveal a more complex relationship between calcium entry and release from stores. The present work uses voltage steps to regulate calcium influx during the application of ACh to hair cells in the chicken basilar papilla. When calcium influx was terminated at positive membrane potential, the ACh-evoked potassium current decayed exponentially over ∼100 ms. However, at negative membrane potentials, this current exhibited a secondary rise in amplitude that could be eliminated by dihydropyridine block of the voltage-gated calcium channels of the hair cell. Calcium entering through voltage-gated channels may transit through the postsynaptic cistern, since ryanodine and sarcoendoplasmic reticulum calcium-ATPase blockers altered the time course and magnitude of this secondary, voltage-dependent contribution to ACh-evoked potassium current. Serial section electron microscopy showed that efferent and afferent synaptic structures are juxtaposed, supporting the possibility that voltage-gated influx at afferent ribbon synapses influences calcium homeostasis during long-lasting cholinergic inhibition. In contrast, spontaneous postsynaptic currents ("minis") resulting from stochastic efferent release of ACh were made briefer by ryanodine, supporting the hypothesis that the synaptic cistern serves primarily as a calcium barrier and sink during low-level synaptic activity. Hypolemmal cisterns such as that at the efferent synapse of the hair cell can play a dynamic role in segregating near-membrane calcium for short-term and long-term signaling. Copyright © 2014 the authors 0270-6474/14/3416688-10$15.00/0.

  2. Blood Levels of S-100 Calcium-Binding Protein B, High-Sensitivity C-Reactive Protein, and Interleukin-6 for Changes in Depressive Symptom Severity after Coronary Artery Bypass Grafting: Prospective Cohort Nested within a Randomized, Controlled Trial (United States)

    Pearlman, Daniel M.; Brown, Jeremiah R.; MacKenzie, Todd A.; Hernandez, Felix; Najjar, Souhel


    Background Cross-sectional and retrospective studies have associated major depressive disorder with glial activation and injury as well as blood–brain barrier disruption, but these associations have not been assessed prospectively. Here, we aimed to determine the relationship between changes in depressive symptom severity and in blood levels of S-100 calcium-binding protein B (S-100B), high-sensitivity C-reactive protein, and interleukin-6 following an inflammatory challenge. Methods Fifty unselected participants were recruited from a randomized, controlled trial comparing coronary artery bypass grafting procedures performed with versus without cardiopulmonary bypass for the risk of neurocognitive decline. Depressive symptom severity was measured at baseline, discharge, and six-month follow-up using the Beck Depression Inventory II (BDI-II). The primary outcome of the present biomarker study was acute change in depressive symptom severity, defined as the intra-subject difference between baseline and discharge BDI-II scores. Blood biomarker levels were determined at baseline and 2 days postoperative. Results Changes in S-100B levels correlated positively with acute changes in depressive symptom severity (Spearman ρ, 0.62; P = 0.0004) and accounted for about one-fourth of their observed variance (R2, 0.23; P = 0.0105). This association remained statistically significant after adjusting for baseline S-100B levels, age, weight, body-mass index, or β-blocker use, but not baseline BDI-II scores (P = 0.064). There was no statistically significant association between the primary outcome and baseline S-100B levels, baseline high-sensitivity C-reactive protein or interleukin-6 levels, or changes in high-sensitivity C-reactive protein or interleukin-6 levels. Among most participants, levels of all three biomarkers were normal at baseline and markedly elevated at 2 days postoperative. Conclusions Acute changes in depressive symptom severity were specifically

  3. Deployment of low-voltage regulator considering existing voltage control in medium-voltage distribution systems

    Directory of Open Access Journals (Sweden)

    Hiroshi Kikusato


    Full Text Available Many photovoltaic (PV systems have been installed in distribution systems. This installation complicates the maintenance of all voltages within the appropriate range in all low-voltage distribution systems (LVDSs because the trends in voltage fluctuation differ in each LVDS. The installation of a low-voltage regulator (LVR that can accordingly control the voltage in each LVDS has been studied as a solution to this problem. Voltage control in a medium-voltage distribution system must be considered to study the deployment of LVRs. In this study, we installed LVRs in the LVDSs in which the existing voltage-control scheme cannot prevent voltage deviation and performed a numerical simulation by using a distribution system model with PV to evaluate the deployment of the LVRs.

  4. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.


    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  5. High Voltage Seismic Generator (United States)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin


    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  6. Increased voltage photovoltaic cell (United States)

    Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)


    A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

  7. Voltage Controlled Dynamic Demand Response

    DEFF Research Database (Denmark)

    Bhattarai, Bishnu Prasad; Bak-Jensen, Birgitte; Mahat, Pukar


    central or dispersed generations might not be sufficient for future scenario. One of the effective methods to cope with this scenario is to enable demand response. This paper proposes a dynamic voltage regulation based demand response technique to be applied in low voltage (LV) distribution feeders....... An adaptive dynamic model has been developed to determine composite voltage dependency of an aggregated load on feeder level. Following the demand dispatch or control signal, optimum voltage setting at the LV substation is determined based on the voltage dependency of the load. Furthermore, a new technique...... has been proposed to estimate the voltage at consumer point of connection (POC) to ensure operation within voltage limits. Finally, the effectiveness of the proposed method is analyzed comprehensively with reference to three different scenarios on a low voltage (LV) feeder (Borup feeder) owned...

  8. Bradykinin-evoked changes in cytosolic calcium and membrane currents in cultured bovine pulmonary artery endothelial cells. (United States)

    Cannell, M B; Sage, S O


    1. Cultured bovine pulmonary artery endothelial cells were voltage clamped using a single microelectrode while cytosolic free calcium concentration ([Ca2+]i) was simultaneously measured using the fluorescent calcium indicator, Indo-1. 2. The resting current-voltage relationship was non-linear and exhibited marked inward rectification near the resting potential. In about 60% of cells examined, superfusion of saline resulted in a hyperpolarization and decrease in inward current. This result did not depend on the presence of agonist and is consistent with the presence of extracellular potassium accumulation in restricted spaces around the cell and the known dependence of the inward rectifier. In other cells there was no effect. 3. Resting [Ca2+]i was sensitive to membrane potential, decreasing continuously with membrane depolarization over the range -70 to +60 mV. This result is consistent with a simple pump-leak model and suggests that voltage-dependent calcium channels are not present in these cells. 4. Bradykinin (10 microM) increased [Ca2+]i after a delay of approximately 3 s. [Ca2+]i reached a peak after a further 3 s and declined over several minutes. 5. During the rise in [Ca2+]i evoked by application of bradykinin, there were no changes in the current-voltage relationship of the cell. These results question the role of a receptor-operated non-selective cation channel in mediating the increase in [Ca2+]i. This observation, coupled with the observed delay in the agonist-evoked response suggests that a second messenger system is involved in mediating the increase in [Ca2+]i. 6. Changes in the current-voltage relation started to occur about 30 s after the application of agonist. These changes could be explained by the activation of large-conductance potassium and non-selective cation channels with a reversal potential near 0 mV. The latter channels may mediate the plateau phase of the agonist-evoked response. 7. The results are discussed with respect to the

  9. Low-voltage polyphasic circuits (United States)

    Baird, William H.; Jaynes, Michael L.


    Experimentation with polyphasic voltages is greatly simplified when microcontrollers are used to generate multiple square waves with fixed phase offsets. Each square wave is sent through a simple second-order Sallen-Key filter to produce an approximately sinusoidal voltage signal. The microcontroller allows the reproduction of split-phase and three-phase voltage relationships, mirroring those commonly distributed on the North American power grid, at safe voltage levels.

  10. High voltage variable diameter insulator (United States)

    Vanecek, David L.; Pike, Chester D.


    A high voltage feedthrough assembly (10) having a tubular insulator (15) extending between the ground plane ring (16) and the high voltage ring (30). The insulator (15) is made of Pyrex and decreases in diameter from the ground plane ring (16) to the high voltage ring (30), producing equipotential lines almost perpendicular to the wall (27) of the insulator (15) to optimize the voltage-holding capability of the feedthrough assembly (10).

  11. Voltage-gated Potassium Channels as Therapeutic Drug Targets


    Wulff, Heike; Castle, Neil A.; Pardo, Luis A.


    The human genome contains 40 voltage-gated potassium channels (KV) which are involved in diverse physiological processes ranging from repolarization of neuronal or cardiac action potentials, over regulating calcium signaling and cell volume, to driving cellular proliferation and migration. KV channels offer tremendous opportunities for the development of new drugs for cancer, autoimmune diseases and metabolic, neurological and cardiovascular disorders. This review first discusses pharmacologi...

  12. Evidence for functional diversity between the voltage-gated proton channel Hv1 and its closest related protein HVRP1.

    Directory of Open Access Journals (Sweden)

    Iris H Kim

    Full Text Available The Hv1 channel and voltage-sensitive phosphatases share with voltage-gated sodium, potassium, and calcium channels the ability to detect changes in membrane potential through voltage-sensing domains (VSDs. However, they lack the pore domain typical of these other channels. NaV, KV, and CaV proteins can be found in neurons and muscles, where they play important roles in electrical excitability. In contrast, VSD-containing proteins lacking a pore domain are found in non-excitable cells and are not involved in neuronal signaling. Here, we report the identification of HVRP1, a protein related to the Hv1 channel (from which the name Hv1 Related Protein 1 is derived, which we find to be expressed primarily in the central nervous system, and particularly in the cerebellum. Within the cerebellar tissue, HVRP1 is specifically expressed in granule neurons, as determined by in situ hybridization and immunohistochemistry. Analysis of subcellular distribution via electron microscopy and immunogold labeling reveals that the protein localizes on the post-synaptic side of contacts between glutamatergic mossy fibers and the granule cells. We also find that, despite the similarities in amino acid sequence and structural organization between Hv1 and HVRP1, the two proteins have distinct functional properties. The high conservation of HVRP1 in vertebrates and its cellular and subcellular localizations suggest an important function in the nervous system.

  13. The involvement of the Mid1/Cch1/Yvc1 calcium channels in Aspergillus fumigatus virulence.

    Directory of Open Access Journals (Sweden)

    Patrícia Alves de Castro

    Full Text Available Aspergillus fumigatus is a major opportunistic pathogen and allergen of mammals. Calcium homeostasis and signaling is essential for numerous biological processes and also influences A. fumigatus pathogenicity. The presented study characterized the function of the A. fumigatus homologues of three Saccharomyces cerevisiae calcium channels, voltage-gated Cch1, stretch-activated Mid1 and vacuolar Yvc1. The A. fumigatus calcium channels cchA, midA and yvcA were regulated at transcriptional level by increased calcium levels. The YvcA::GFP fusion protein localized to the vacuoles. Both ΔcchA and ΔmidA mutant strains showed reduced radial growth rate in nutrient-poor minimal media. Interestingly, this growth defect in the ΔcchA strain was rescued by the exogenous addition of CaCl2. The ΔcchA, ΔmidA, and ΔcchA ΔmidA strains were also sensitive to the oxidative stress inducer, paraquat. Restriction of external Ca(2+ through the addition of the Ca(2+-chelator EGTA impacted upon the growth of the ΔcchA and ΔmidA strains. All the A. fumigatus ΔcchA, ΔmidA, and ΔyvcA strains demonstrated attenuated virulence in a neutropenic murine model of invasive pulmonary aspergillosis. Infection with the parental strain resulted in a 100% mortality rate at 15 days post-infection, while the mortality rate of the ΔcchA, ΔmidA, and ΔyvcA strains after 15 days post-infection was only 25%. Collectively, this investigation strongly indicates that CchA, MidA, and YvcA play a role in A. fumigatus calcium homeostasis and virulence.

  14. Charge-pump voltage converter (United States)

    Brainard, John P [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM


    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  15. Porous polymer film calcium ion chemical sensor and method of using the same (United States)

    Porter, M.D.; Chau, L.K.


    A method of measuring calcium ions is disclosed wherein a calcium sensitive reagent, calcichrome, is immobilized on a porous polymer film. The reaction of the calcium sensitive reagent to the Ca(II) is then measured and concentration determined as a function of the reaction. 1 figure.

  16. Exposure to extremely low frequency electromagnetic fields alters the calcium dynamics of cultured entorhinal cortex neurons. (United States)

    Luo, Fen-Lan; Yang, Nian; He, Chao; Li, Hong-Li; Li, Chao; Chen, Fang; Xiong, Jia-Xiang; Hu, Zhi-An; Zhang, Jun


    Previous studies have revealed that extremely low frequency electromagnetic field (ELF-EMF) exposure affects neuronal dendritic spine density and NMDAR and AMPAR subunit expressions in the entorhinal cortex (EC). Although calcium signaling has a critical role in control of EC neuronal functions, however, it is still unclear whether the ELF-EMF exposure affects the EC neuronal calcium homeostasis. In the present study, using whole-cell recording and calcium imaging, we record the whole-cell inward currents that contain the voltage-gated calcium currents and show that ELF-EMF (50Hz, 1mT or 3mT, lasting 24h) exposure does not influence these currents. Next, we specifically isolate the high-voltage activated (HVA) and low-voltage activated (LVA) calcium channels-induced currents. Similarly, the activation and inactivation characteristics of these membrane calcium channels are also not influenced by ELF-EMF. Importantly, ELF-EMF exposure reduces the maximum amplitude of the high-K(+)-evoked calcium elevation in EC neurons, which is abolished by thapsigargin, a Ca(2+) ATPase inhibitor, to empty the intracellular calcium stores of EC neurons. Together, these findings indicate that ELF-EMF exposure specifically influences the intracellular calcium dynamics of cultural EC neurons via a calcium channel-independent mechanism. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Substitutions in Calcium Aluminates and Calcium Aluminoferrites. (United States)


  18. Transient voltage sharing in series-coupled high voltage switches

    Directory of Open Access Journals (Sweden)

    Editorial Office


    Full Text Available For switching voltages in excess of the maximum blocking voltage of a switching element (for example, thyristor, MOSFET or bipolar transistor such elements are often coupled in series - and additional circuitry has to be provided to ensure equal voltage sharing. Between each such series element and system ground there is a certain parasitic capacitance that may draw a significant current during high-speed voltage transients. The "open" switch is modelled as a ladder network. Analy­sis reveals an exponential progression in the distribution of the applied voltage across the elements. Overstressing thus oc­curs in some of the elements at levels of the total voltage that are significantly below the design value. This difficulty is overcome by grading the voltage sharing circuitry, coupled in parallel with each element, in a prescribed manner, as set out here.

  19. The effect of verapamil and diltiazem on cardiac stimulant effect of adrenaline and calcium chloride on isolated frog heart


    Lakhavat Sudhakar, Naveen Kumar T, Tadvi NA, Venkata Rao Y


    Background: Calcium channel blockers block voltage dependent L-type of calcium channel and thus reduce the frequency of opening of these channels in response to depolarization. The result is a marked decrease in transmembrane calcium current associated with long lasting relaxation of vascular smooth muscle, reduction in contractility in cardiac muscle, decrease in pacemaker activity in the SA node and decrease in conduction velocity in the AV node. Among Calcium channel blockers verapamil, ...

  20. Ziconotide, an intrathecally administered N-type calcium channel antagonist for the treatment of chronic pain. (United States)

    Wermeling, Daniel P


    Ziconotide is a novel peptide that blocks the entry of calcium into neuronal N-type voltage-sensitive calcium channels, preventing the conduction of nerve signals. N-type calcium channels are present in the superficial laminae of the dorsal horn of the spinal cord. In various animal models of pain, intrathecal administration of ziconotide blocked nerve transmission and nociception. The United States Food and Drug Administration recently approved ziconotide intrathecal infusion for the management of severe chronic pain in patients who require intrathecal therapy and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies, or intrathecal morphine. The drug has a narrow therapeutic window and a lag time for the onset and offset of analgesia and adverse events. In early clinical trials, frequent and severe psychiatric and central nervous system adverse effects were associated with rapid intrathecal infusion (0.4 microg/hr) and frequent up-titration (every 12 hrs). Therefore, patients with psychiatric symptoms are not candidates for this drug. Drug trials of external intrathecal catheters and microinfusion devices demonstrated a 3% risk of meningitis. A low initial infusion rate of 0.1 microg/hour and limiting infusion rate increases to 2-3 times/week are now recommended. Patients responsive to intrathecal ziconotide require an implanted infusion system to receive long-term therapy.

  1. Can total cardiac calcium predict the coronary calcium score? (United States)

    Pressman, Gregg S; Crudu, Vitalie; Parameswaran-Chandrika, Anoop; Romero-Corral, Abel; Purushottam, Bhaskar; Figueredo, Vincent M


    Mitral annular calcification (MAC) shares the same risk factors as atherosclerosis and is associated with coronary artery disease as well as cardiovascular events. However, sensitivity and positive predictive value are low. We hypothesized that a global echocardiographic calcium score would better predict coronary atherosclerotic burden, as assessed by coronary artery calcium score (CAC), than MAC alone. An echocardiographic score was devised to measure global cardiac calcification in a semi-quantitative manner; this included calcification in the aortic valve and root, the mitral valve and annulus, and the sub-mitral apparatus. This score, and a simplified version, were compared with a similar calcification score by CT scan, as well as the CAC. There was a good correlation between the two global calcification scores; the echocardiographic score also correlated with CAC. Using CAC >400 as a measure of severe coronary atherosclerosis, an echocardiographic score ≥5 had a positive predictive value of 60%. Importantly, the simplified score performed equally well (≥3 had a positive predictive value of 62%). Global cardiac calcification, assessed by CT scan or echocardiography, correlates with the extent of coronary calcium. A semi-quantitative calcium score can be easily applied during routine echocardiographic interpretation and can alert the reader to the possibility of severe coronary atherosclerosis. Copyright © 2009 Elsevier Ireland Ltd. All rights reserved.

  2. Benchmarking of Voltage Sag Generators

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang


    to guide these grid-connected distributed power generation systems. In order to verify the response of such systems for voltage disturbance, mainly for evaluation of voltage sags/dips, a Voltage Sag Generator (VSG) is needed. This paper evaluates such sag test devices according to IEC 61000 in order...... to provide cheaper solutions to test against voltage sags. Simulation and experimental results demonstrate that the shunt impedance based VSG solution is the easiest and cheapest one for laboratory test applications. The back-to-back fully controlled converter based VSG is the most flexible solution......The increased penetration of renewable energy systems, like photovoltaic and wind power systems, rises the concern about the power quality and stability of the utility grid. Some regulations for Low Voltage Ride-Through (LVRT) for medium voltage or high voltage applications, are coming into force...

  3. Local perinuclear calcium signals associated with mitosis-entry in early sea urchin embryos



    Using calcium-sensitive dyes together with their dextran conjugates and confocal microscopy, we have looked for evidence of localized calcium signaling in the region of the nucleus before entry into mitosis, using the sea urchin egg first mitotic cell cycle as a model. Global calcium transients that appear to originate from the nuclear area are often observed just before nuclear envelope breakdown (NEB). In the absence of global increases in calcium, confocal microscopy using Calcium Green- 1...

  4. RETRACTED ARTICLE: Dynamic voltage restorer controller using grade algorithm

    Directory of Open Access Journals (Sweden)

    S. Deepa


    Full Text Available This paper deals with the terminology and various issues about power quality problems. This problem occurs owing to voltage sag, swell, harmonics, and surges. The sustained overvoltage and undervoltage originated from power system may often damage/or disrupt computerized process. Voltage sags and harmonics disturb the power quality and this can be overcome by custom power device called dynamic voltage restorer (DVR. The DVR is normally installed between the source voltage and critical or sensitive load. The vital role of DVR depends on the efficiency of the control technique involved in switching circuit of the inverter. In this paper, Combination of improved grade algorithm with fuzzy membership function is used to decide the Proportional-Integral coefficients. The DVR works well both in balanced and unbalanced conditions of voltages. The simulation results show the efficiency of the proposed method.

  5. Calcium channel blocker overdose (United States)

    ... page: // Calcium-channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium-channel blockers are a type of medicine used to ...

  6. Fenoprofen calcium overdose (United States)

    ... page: // Fenoprofen calcium overdose To use the sharing features on this page, please enable JavaScript. Fenoprofen calcium is a type of medicine called a nonsteroidal ...

  7. Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

    Directory of Open Access Journals (Sweden)

    William J.B. Heffernan


    Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

  8. Time course of activation of calcium release from sarcoplasmic reticulum in skeletal muscle.


    Simon, B J; Schneider, M F


    Myoplasmic free calcium transients were measured with antipyrylazo III in voltage clamped segments of frog skeletal muscle fibers and were used to calculate the rate of release (Rrel) of calcium from the sarcoplasmic reticulum. Intramembrane charge movement was measured for the same pulses in the same fibers. During a depolarizing pulse Rrel rose to an early peak and then decayed relatively rapidly but incompletely due to calcium-dependent inactivation (Schneider M.F., and B.J. Simon. 1988. J...

  9. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus. (United States)

    Chameau, Pascal; Qin, Yongjun; Spijker, Sabine; Smit, August Benjamin; Smit, Guus; Joëls, Marian


    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover, we addressed the putative gene targets that eventually lead to the enhanced calcium currents. Electrophysiological recordings were performed in nucleated patches that allow excellent voltage control. Calcium currents in these patches almost exclusively involve N- and L-type channels. We found that L- but not N-type calcium currents were largely enhanced after treatment with a high dose of corticosterone sufficient to activate glucocorticoid receptors. Voltage dependency and kinetic properties of the currents were unaffected by the hormone. Nonstationary noise analysis suggests that the increased current is not caused by a larger unitary conductance, but rather to a doubling of the number of functional channels. Quantitative real-time PCR revealed that transcripts of the Ca(v)1 subunits encoding for the N- or L-type calcium channels are not upregulated in the mouse CA1 area; instead, a strong, direct, and consistent upregulation of the beta4 subunit was observed. This indicates that the corticosteroid-induced increase in number of L-type calcium channels is not caused by a simple transcriptional regulation of the pore-forming subunit of the channels.

  10. Calcium and Mitosis (United States)

    Hepler, P.


    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  11. Extracellular protons enable activation of the calcium-dependent chloride channel TMEM16A. (United States)

    Cruz-Rangel, Silvia; De Jesús-Pérez, José J; Aréchiga-Figueroa, Iván A; Rodríguez-Menchaca, Aldo A; Pérez-Cornejo, Patricia; Hartzell, H Criss; Arreola, Jorge


    The calcium-activated chloride channel TMEM16A provides a pathway for chloride ion movements that are key in preventing polyspermy, allowing fluid secretion, controlling blood pressure, and enabling gastrointestinal activity. TMEM16A is opened by voltage-dependent calcium binding and regulated by permeant anions and intracellular protons. Here we show that a low proton concentration reduces TMEM16A activity while maximum activation is obtained when the external proton concentration is high. In addition, protonation conditions determine the open probability of TMEM16A without changing its calcium sensitivity. External glutamic acid 623 (E623) is key for TMEM16A's ability to respond to external protons. At physiological pH, E623 is un-protonated and TMEM16A is activated when intracellular calcium increases; however, under acidic conditions E623 is partially protonated and works synergistically with intracellular calcium to activate the channel. These findings are critical for understanding physiological and pathological processes that involve changes in pH and chloride flux via TMEM16A. Transmembrane protein 16A (TMEM16A), also known as ANO1, the pore-forming subunit of a Ca(2+) -dependent Cl(-) channel (CaCC), is activated by direct, voltage-dependent, binding of intracellular Ca(2+) . Endogenous CaCCs are regulated by extracellular protons; however, the molecular basis of such regulation remains unidentified. Here, we evaluated the effects of different extracellular proton concentrations ([H(+) ]o ) on mouse TMEM16A expressed in HEK-293 cells using whole-cell and inside-out patch-clamp recordings. We found that increasing the [H(+) ]o from 10(-10) to 10(-5.5)  m caused a progressive increase in the chloride current (ICl ) that is described by titration of a protonatable site with pK = 7.3. Protons regulate TMEM16A in a voltage-independent manner, regardless of channel state (open or closed), and without altering its apparent Ca(2+) sensitivity. Noise analysis

  12. Calcium en cardioplegie

    NARCIS (Netherlands)

    Ruigrok, T.J.C.; Meijler, F.L.


    Coronary perfusion with a calcium-free solution, followed by reperfusion with a calcium containing solution, may result in acute myocardial cell death and in irreversible loss of the e1ectrical and mechanical activity of the heart. This phenomenon is known as the calcium paradox. A number of

  13. L- and T-type voltage-gated Ca2+ channels in human granulosa cells: functional characterization and cholinergic regulation. (United States)

    Platano, Daniela; Magli, M Cristina; Ferraretti, Anna Pia; Gianaroli, Luca; Aicardi, Giorgio


    Using the whole-cell configuration of the patch-clamp technique, we have characterized two types of ionic currents through voltage-dependent Ca2+ channels in human granulosa cells. One is long-lasting, activates at approximately -20 mV, reaches the peak at approximately +20 mV, has an inactivation time constant of 132.5 +/- 5.6 msec at 20 mV, and is sensitive to dihydropyridines. The other is transient, activates at approximately -40 mV, peaks at approximately -10 mV, has an inactivation time constant of 38.8 +/- 1.8 msec at -10 mV, displays a voltage-dependent inactivation, and is sensitive to 100 microm Ni2+, but not to dihydropyridines. Biophysical and pharmacological properties of these currents indicate that they are gated through L- and T-type calcium channels, respectively. The cholinergic receptor agonist carbachol (50 microm) reduces the amplitude of the currents through both L-type (-34.7 +/- 6.4%; n = 10) and T-type (-52.6 +/- 7.4%; n = 8) channels, suggesting a possible role of these channels in the cholinergic regulation of human ovarian functions.

  14. Inhibition of large conductance calcium-dependent potassium ...

    African Journals Online (AJOL)

    We tested the hypothesis that Rho-kinase inhibits the large-conductance, calcium and voltage dependent potassium (BKCa) channels thereby promoting vasoconstriction. Our results show that the Rho-kinase inhibitor, Y-27632, induced concentration-dependent relaxation in rat mesenteric artery. The selective BKCa ...

  15. Short-range intercellular calcium signaling in bone

    DEFF Research Database (Denmark)

    Jørgensen, Niklas Rye


    mechanism involves the passage of a small messenger through gap junctions to the cytoplasm of the neighboring cells, inducing depolarization of the plasma membrane with subsequent opening of membrane bound voltage-operated calcium channels. Next, we found that osteoblasts can propagate these signals...

  16. Enhanced current and voltage regulators for stand-alone applications

    DEFF Research Database (Denmark)

    Federico, de Bosio; Pastorelli, Michele; Antonio DeSouza Ribeiro, Luiz


    State feedback decoupling permits to achieve a better dynamic response for Voltage Source in stand-alone applications. The design of current and voltage regulators is performed in the discrete-time domain since it provides better accuracy and allows direct pole placement. As the attainable...... bandwidth of the current loop is mainly limited by computational and PWM delays, a lead compensator structure is proposed to overcome this limitation. The design of the voltage regulator is based on the Nyquist criterion, verifying to guarantee a high sensitivity peak. Discrete-time domain implementation...

  17. Chondroitin sulfates act as extracellular gating modifiers on voltage-dependent ion channels. (United States)

    Vigetti, Davide; Andrini, Olga; Clerici, Moira; Negrini, Daniela; Passi, Alberto; Moriondo, Andrea


    Chondroitin sulfates are glycosaminoglycans bound to core proteins of proteoglycans in the extracellular matrix and perineuronal nets surrounding many types of neurones. Chondroitin 4- and chondroitin 6- sulfate can bind calcium ions with different affinities, depending on their sulfation position. Extracellular calcium plays a key role in determining the transmembrane potential sensed by voltage-operated ion channels (VOCs) by means of the "surface screening effect" theory (Gouy-Chapman-Stern theory). We wanted to test whether chondroitin sulfates at physiological concentration can effectively modulate the gating properties of VOCs. We recorded in patch-clamp experiments the shift of h and voltage-dependent calcium currents activation curves of Xenopus laevis photoreceptors perfused with chondroitin sulfate solutions in physiological extracellular calcium concentration. We found that chondroitin 4- and 6- sulfate, with different capabilities, can shift the activation curve of h and voltage-dependent calcium channels, compatibly with the surface screening effect theory. We conclude that chondroitin sulfates can alter VOCs gating by modulating the calcium concentration in the extracellular microenvironment. This phenomenon may explain why alterations in the chondroitin sulfation and abundance in the extracellular matrix are found along with altered neuronal function in pathological conditions. Copyright 2008 S. Karger AG, Basel.

  18. Calcium channels in the brain as targets for the calcium-channel modulators used in the treatment of neurological disorders

    NARCIS (Netherlands)



    Recent investigations of calcium channels in brain cells by voltage-clamp techniques have revealed that, in spite of electrophysiological similarities, the pharmacological properties of these channels differ considerably from channels in peripheral tissues, e.g., heart and smooth muscle. Therefore,

  19. Characterization of voltage-gated Ca(2+ conductances in layer 5 neocortical pyramidal neurons from rats.

    Directory of Open Access Journals (Sweden)

    Mara Almog

    Full Text Available Neuronal voltage-gated Ca(2+ channels are involved in electrical signalling and in converting these signals into cytoplasmic calcium changes. One important function of voltage-gated Ca(2+ channels is generating regenerative dendritic Ca(2+ spikes. However, the Ca(2+ dependent mechanisms used to create these spikes are only partially understood. To start investigating this mechanism, we set out to kinetically and pharmacologically identify the sub-types of somatic voltage-gated Ca(2+ channels in pyramidal neurons from layer 5 of rat somatosensory cortex, using the nucleated configuration of the patch-clamp technique. The activation kinetics of the total Ba(2+ current revealed conductance activation only at medium and high voltages suggesting that T-type calcium channels were not present in the patches. Steady-state inactivation protocols in combination with pharmacology revealed the expression of R-type channels. Furthermore, pharmacological experiments identified 5 voltage-gated Ca(2+ channel sub-types - L-, N-, R- and P/Q-type. Finally, the activation of the Ca(2+ conductances was examined using physiologically derived voltage-clamp protocols including a calcium spike protocol and a mock back-propagating action potential (mBPAP protocol. These experiments enable us to suggest the possible contribution of the five Ca(2+ channel sub-types to Ca(2+ current flow during activation under physiological conditions.

  20. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz


    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  1. Dissociation of charge movement from calcium release and calcium current in skeletal myotubes by gabapentin. (United States)

    Alden, Kris J; García, Jesús


    The skeletal muscle L-type calcium channel or dihydropyridine receptor (DHPR) plays an integral role in excitation-contraction (E-C) coupling. Its activation initiates three sequential events: charge movement (Q(r)), calcium release, and calcium current (I(Ca,L)). This relationship suggests that changes in Q(r) might affect release and I(Ca,L). Here we studied the effect of gabapentin (GBP) on the three events generated by DHPRs in skeletal myotubes in culture. GBP specifically binds to the alpha(2)/delta(1) subunit of the brain and skeletal muscle DHPR. Myotubes were stimulated with a protocol that included a depolarizing prepulse to inactivate voltage-dependent proteins other than DHPRs. Gabapentin (50 microM) significantly increased Q(r) while decreasing the rate of rise of calcium transients. Gabapentin also reduced the maximum amplitude of the I(Ca,L) (as we previously reported) without modifying the kinetics of activation. Exposure of GBP-treated myotubes to 10 microM nifedipine prevented the increase of Q(r) promoted by this drug, indicating that the extra charge recorded originated from DHPRs. Our data suggest that GBP dissociates the functions of the DHPR from the initial voltage-sensing step and implicates a role for the alpha(2)/delta(1) subunit in E-C coupling.

  2. Exploration of fluorescent protein voltage probes based on circularly permuted fluorescent proteins

    Directory of Open Access Journals (Sweden)

    Sunita G Gautam


    Full Text Available Genetically-encoded fluorescent protein voltage sensors are promising tools for optical monitoring of the electrical activity of cells. Over the last decade, several designs of fusion proteins have been explored and some of them have proven to be sensitive enough to record membrane voltage transients from single mammalian cells. Most prominent are the families of VSFPs (Voltage Sensitive Fluorescent Proteins that utilize the voltage sensor domain of Ci-VSP (Ciona Intestinalis voltage sensor-containing phosphatase. The voltage sensitivity of the fluorescence readout of these previously reported membrane potential indicators is achieved either via a change in the efficiency of fluorescence resonance energy transfer (FRET between two fluorescent protein (FP spectral variants or via modulation in the fluorescence intensity of a single FP. Here, we report our exploration on a third VSFP design principle based on circularly-permuted fluorescent protein (cpFP variants. Using circularly-permuted EGFP derived from GCaMP2 and two newly generated circularly-permuted variants of the far-red emitting protein named mKate, we generated and characterized a series of voltage-sensitive probes wherein the cpFPs were fused to the voltage sensor domain of Ci-VSP. The most promising variants were based on circularly permuted mKate with new N- and C-termini given by residues 180 and 182. Even so their voltage sensitivity was relatively modest, they constitute a proof of principle for this novel protein design.

  3. L-type calcium channels refine the neural population code of sound level. (United States)

    Grimsley, Calum Alex; Green, David Brian; Sivaramakrishnan, Shobhana


    The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (CaL: CaV1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of CaL to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. CaL is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, CaL activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, CaL boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, CaL either suppresses or enhances firing at sound levels that evoke maximum firing. CaL multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level. Copyright © 2016 the American Physiological Society.

  4. Methods and Strategies for Overvoltage Prevention in Low Voltage Distribution Systems with PV

    DEFF Research Database (Denmark)

    Hashemi Toghroljerdi, Seyedmostafa; Østergaard, Jacob


    absorption by PV inverters, application of active medium voltage to low voltage (MV/LV) transformers, active power curtailment, and demand response (DR). Coordination between voltage control units by localized, distributed, and centralized voltage control methods is compared using the voltage sensitivity...... to handle a high share of PV power. This paper provides an in-depth review of methods and strategies proposed to prevent overvoltage in LV grids with PV, and discusses the effectiveness, advantages, and disadvantages of them in detail. Based on the mathematical framework presented in the paper...

  5. Ziconotide: neuronal calcium channel blocker for treating severe chronic pain. (United States)

    Miljanich, G P


    Ziconotide (PRIALT) is a neuroactive peptide in the final stages of clinical development as a novel non-opioid treatment for severe chronic pain. It is the synthetic equivalent of omega-MVIIA, a component of the venom of the marine snail, Conus magus. The mechanism of action underlying ziconotide's therapeutic profile derives from its potent and selective blockade of neuronal N-type voltage-sensitive calcium channels (N-VSCCs). Direct blockade of N-VSCCs inhibits the activity of a subset of neurons, including pain-sensing primary nociceptors. This mechanism of action distinguishes ziconotide from all other analgesics, including opioid analgesics. In fact, ziconotide is potently anti-nociceptive in animal models of pain in which morphine exhibits poor anti-nociceptive activity. Moreover, in contrast to opiates, tolerance to ziconotide is not observed. Clinical studies of ziconotide in more than 2,000 patients reveal important correlations to ziconotide's non-clinical pharmacology. For example, ziconotide provides significant pain relief to severe chronic pain sufferers who have failed to obtain relief from opiate therapy and no evidence of tolerance to ziconotide is seen in these patients. Contingent on regulatory approval, ziconotide will be the first in a new class of neurological drugs: the N-type calcium channel blockers, or NCCBs. Its novel mechanism of action as a non-opioid analgesic suggests ziconotide has the potential to play a valuable role in treatment regimens for severe chronic pain. If approved for clinical use, ziconotide will further validate the neuroactive venom peptides as a source of new and useful medicines.

  6. Calcium channel blocker poisoning

    Directory of Open Access Journals (Sweden)

    Miran Brvar


    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  7. Methodology for Determination of the Number of Equipment Malfunctions Due to Voltage Sags

    Directory of Open Access Journals (Sweden)

    Alena Otcenasova


    Full Text Available This article deals with the assessment of the reliability of sensitive equipment due to voltage sags. The most frequent problems of power quality are voltage sags. Equipment that cannot withstand short-term voltage sag is defined as sensitive device. Sensitivity of such equipment can be described by the voltage–tolerance curves. A device (generator to generate voltage sags (also interruptions with duration at least 1 ms has been designed and developed for this purpose. Equipment sensitive to voltage sags was tested using this generator. Overall, five types of sensitive equipment were tested: personal computers, fluorescent lamps, drives with speed control, programmable logic controllers, and contactors. The measured sensitivity curves of these devices have been used to determine the number of trips (failures due to voltage sags. Two probabilistic methods (general probability method and cumulative probability method to determine probability of equipment failure occurrence are used. These methods were applied to real node in the distribution system with its actual performance of voltage sags/swells. The calculations also contain different levels of sensitivity of the sensitive equipment.

  8. Voltage Mode Universal Biquad Using CCCII

    Directory of Open Access Journals (Sweden)

    Ashish Ranjan


    Full Text Available This paper proposes a multi-input single-output (MISO second-order active-C voltage mode (VM universal filter using two second-generation current-controlled current conveyors (CCCIIs and two equal-valued capacitors. The proposed circuit realizes low pass, band pass, high pass, all pass, and notch responses from the same topology. The filter uses-minimum number of passive components and no resistor which is suitable for IC Design. The filter enjoys low-sensitivity performance and exhibits electronic and orthogonal tunability of pole frequency (0 and quality factor (0 via bias current of CCCIIs. PSPICE simulation results confirm the theory.

  9. Maturation of calcium-dependent GABA, glycine, and glutamate release in the glycinergic MNTB-LSO pathway.

    Directory of Open Access Journals (Sweden)

    Javier Alamilla

    Full Text Available The medial nucleus of the trapezoid body (MNTB is a key nucleus in high-fidelity temporal processing that underlies sound localization in the auditory brainstem. While the glycinergic principal cells of the MNTB project to all primary nuclei of the superior olive, during development the projection from MNTB to the lateral superior olive (LSO is of interest because this immature inhibitory projection is known to undergo tonotopic refinement during an early postnatal period, and because during this period individual MNTB terminals in the LSO transiently release glycine GABA and glutamate. Developmental changes in calcium-dependent release are understood to be required to allow various auditory nuclei to follow high frequency activity; however, little is known about maturation of calcium-dependent release in the MNTB-LSO pathway, which has been presumed to have less stringent requirements for high-fidelity temporal following. In acute brainstem slices of rats age postnatal day 1 to 15 we recorded whole-cell responses in LSO principal neurons to electrical stimulation in the MNTB in order to measure sensitivity to external calcium, the contribution of different voltage-gated calcium channel subtypes to vesicular release, and the maturation of these measures for both GABA/glycine and glutamate transmission. Our results establish that release of glutamate at MNTB-LSO synapses is calcium-dependent. Whereas no significant developmental changes were evident for glutamate release, GABA/glycine release underwent substantial changes over the first two postnatal weeks: soon after birth L-type, N-type, and P/Q-type voltage-gated calcium channels (VGCCs together mediated release, but after hearing onset P/Q-type VGCCs predominated. Blockade of P/Q-type VGCCs reduced the estimated quantal number for GABA/gly and glutamate transmission at P5-8 and the frequency of evoked miniature glycinergic events at P12-15, without apparent effects on spontaneous release of

  10. Gamma-hydroxybutyrate receptor function determined by stimulation of rubidium and calcium movements from NCB-20 neurons. (United States)

    Kemmel, V; Taleb, O; Andriamampandry, C; Aunis, D; Maitre, M


    Gamma-Hydroxybutyrate is derived from GABA in brain and plays specific functional roles in the CNS. It is thought to exert a tonic inhibitory control on dopamine and GABA release in certain brain areas, through specific gamma-hydroxybutyrate receptors. Apart from modifying certain calcium currents, the specific transduction mechanism induced by stimulation of gamma-hydroxybutyrate receptors remains largely unknown. We investigated the possible contribution of K(+) channels to the hyperpolarization phenomena generally induced by gamma-hydroxybutyrate in brain, by monitoring (86)Rb(+) movements in a neuronal cell line (NCB-20 cells), which expresses gamma-hydroxybutyrate receptors. Physiological concentrations of gamma-hydroxybutyrate (5-25 microM) induce a slow efflux of (86)Rb(+), which peaks at 5-15 min and returns to baseline levels 20 min later after constant stimulation. This effect can be reproduced by the gamma-hydroxybutyrate receptor agonist NCS-356 and blocked by the gamma-hydroxybutyrate receptor antagonist 6,7,8,9-tetrahydro-5-[H]-benzocycloheptene-5-ol-4-ylidene. The GABA(B) receptor antagonist CGP 55845 has no effect on gamma-hydroxybutyrate-induced (86)Rb(+) efflux. The pharmacology of this gamma-hydroxybutyrate-dependent efflux of (86)Rb(+) is in favor of the involvement of tetraethylammonium and charybdotoxin insensitive, apamin sensitive Ca(2+) activated K(+) channels, identifying them as small conductance calcium activated channels. We demonstrated a gamma-hydroxybutyrate dose-dependent entry of calcium ions into NCB-20 neuroblastoma cells at resting potential. Electrophysiological data showed that this Ca(2+) entry corresponded mainly to a left-hand shift of the current/voltage relation of the T-type calcium channel. This process must at least partially trigger small conductance calcium activated channel activation leading to gamma-hydroxybutyrate-induced hyperpolarization.

  11. Stray voltage and milk quality: a review. (United States)

    Reinemann, Douglas J


    If animal contact voltage reaches sufficient levels, animals coming into contact with grounded devices may receive a mild electric shock that can cause a behavioral response. At voltage levels that are just perceptible to the animal, behaviors indicative of perception (eg, flinches) may result with little change in normal routines. At higher exposure levels, avoidance behaviors may result. The direct effect of animal contact with electrical current can range from: • Mild behavioral reactions indicative of sensation, to • Involuntary muscle contraction, or twitching, to • Intense behavioral responses indicative of pain. The indirect effects of these behaviors can vary considerably depending on the specifics of the contact location, level of current flow, body pathway, frequency of occurrence, and many other factors related to the daily activities of animals. There are several common situations of concern in animal environments: • Animals avoiding certain exposure locations, which may result in: X Reduced water intake if exposure is required for animals to access watering devices, X Reduced feed intake if exposure is required for animals to accesses feeding devices or locations. • Difficulty of moving or handling animals in areas of voltage/current exposure• The physiologic implications of the release of stress hormones produced by contact with painful stimuli. The severity of response will depend on the amount of electrical current (measured in milliamps) flowing through the animal’s body, the pathway it takes through the body, and the sensitivity of the individual animal. The results of the combined current dose-response experiments, voltage exposure response experiments, and measurements of body and contact resistances is consistent with the lowest (worst case) cow + contact resistance as low as 500 as estimated by Lefcourt that may occur in some unusual situations on farms (firm application of the muzzle to a wet metallic watering device and hoof

  12. The NH2terminus regulates voltage-dependent gating of CALHM ion channels. (United States)

    Tanis, Jessica E; Ma, Zhongming; Foskett, J Kevin


    Calcium homeostasis modulator protein-1 (CALHM1) and its Caenorhabditis elegans (ce) homolog, CLHM-1, belong to a new family of physiologically important ion channels that are regulated by voltage and extracellular Ca 2+ (Ca 2+ o ) but lack a canonical voltage-sensing domain. Consequently, the intrinsic voltage-dependent gating mechanisms for CALHM channels are unknown. Here, we performed voltage-clamp experiments on ceCLHM-1 chimeric, deletion, insertion, and point mutants to assess the role of the NH 2 terminus (NT) in CALHM channel gating. Analyses of chimeric channels in which the ceCLHM-1 and human (h)CALHM1 NH 2 termini were interchanged showed that the hCALHM1 NT destabilized channel-closed states, whereas the ceCLHM-1 NT had a stabilizing effect. In the absence of Ca 2+ o , deletion of up to eight amino acids from the ceCLHM-1 NT caused a hyperpolarizing shift in the conductance-voltage relationship with little effect on voltage-dependent slope. However, deletion of nine or more amino acids decreased voltage dependence and induced a residual conductance at hyperpolarized voltages. Insertion of amino acids into the NH 2 -terminal helix also decreased voltage dependence but did not prevent channel closure. Mutation of ceCLHM-1 valine 9 and glutamine 13 altered half-maximal activation and voltage dependence, respectively, in 0 Ca 2+ In 2 mM Ca 2+ o , ceCLHM-1 NH 2 -terminal deletion and point mutant channels closed completely at hyperpolarized voltages with apparent affinity for Ca 2+ o indistinguishable from wild-type ceCLHM-1, although the ceCLHM-1 valine 9 mutant exhibited an altered conductance-voltage relationship and kinetics. We conclude that the NT plays critical roles modulating voltage dependence and stabilizing the closed states of CALHM channels. Copyright © 2017 the American Physiological Society.

  13. Effect of selected factors on the current flow and voltage loss at ...

    African Journals Online (AJOL)

    In this paper, laboratory scale study was conducted to investigate the current flow and voltage loss at the electrodes in the electrochemical treatment of a tropical laterite. Three different tests using calcium chloride (CC) as anolyte and sodium chloride (SC) as catholyte (NC); SC as anolyte and Phosphoric acid (PA) as ...

  14. Artificial intelligence techniques for voltage control

    Energy Technology Data Exchange (ETDEWEB)

    Ekwue, A.; Cheng, D.T.Y.; Macqueen, J.F.


    In electric power systems, the advantages of reactive power dispatching or optimisation include improved utilisation of reactive power sources and hence reduction in reactive power flows and real losses of the system; unloading of the system and equipment as a result of reactive flow reduction; the power factors of generation are improved and system security is enhanced; reduced voltage gradients and somewhat higher voltages which result across the system from improved operation; deferred capital investment is new reactive power sources as a result of improved utilisation of existing equipment; and for the National Grid Company plc (NGC), the main advantage is reduced out-of-merit operation. The problem of reactive power control has been studied and widely reported in the literature. Non-linear programming methods as well as linear programming techniques for constraint dispatch have been described. Static optimisation of reactive power sources by the use of sensitivity analysis was described by Kishore and Hill. Long range optimum var planning has been considered and the optimum amount and location of network reactive compensation so as to maintain the system voltage within the desired limits, while operating under normal and various insecurity states, have also been studied using several methods. The objective of this chapter is therefore to review conventional methods as well as AI techniques for reactive power control. (Author)

  15. Calcium electrotransfer for termination of transgene expression in muscle

    DEFF Research Database (Denmark)

    Hojman, Pernille; Spanggaard, Iben; Olsen, Caroline Holkman


    Gene electrotransfer is expanding in clinical use, thus we have searched for an emergency procedure to stop transgene expression in case of serious adverse events. Calcium is cytotoxic at high intracellular levels, so we tested effects of calcium electrotransfer on transgene expression in muscle....... A clinical grade calcium solution (20 µl, 168 mM) was injected into transfected mouse or rat tibialis cranialis muscle. Ca(2+) uptake was quantified using calcium 45 ((45)Ca), and voltage and time between injection and pulsation were varied. Extinction of transgene expression was investigated by using both...... showed muscle damage and subsequent regeneration. Electrotransfer of isotonic CaCl(2) terminates transgenic protein expression in muscles and may be used for contingency elimination of transgene expression....

  16. Diffusion voltage in polymer light emitting diodes measured with electric field induced second harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, P.K.; Rafaelsen, J.; Pedersen, T.G.; Pedersen, K. [Department of Physics and Nanotechnology, Aalborg University, Pontoppidanstraede 103, 9220 Aalborg East (Denmark)


    We apply electric field induced second harmonic (EFISH) to polymer light emitting diodes (PLEDs) and demonstrate the ability to determine the diffusion voltage in PLED devices. The EFISH signal is proportional to the square of the effective field, which is the sum of the diffusion voltage and the applied voltage. By minimizing the EFISH-signal as a function of the applied voltage, the diffusion voltage is determined by measuring the applied voltage that cancels out the diffusion voltage. The PLEDs are fabricated with indium tin oxide (ITO) as the hole injecting contact and two different electron injecting contacts, namely aluminum and calcium. The diffusion voltage originates from the rearranged charges caused by the difference in Fermi levels in the materials in the PLEDs. Different contacts will thus cause different diffusion voltages. We demonstrate here that the EFISH signal is proportional to the square of the effective field in both reverse and forward bias, and discuss the dependence on contact materials. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Arrays of ZnO/AZO (Al-doped ZnO) nanocables: a higher open circuit voltage and remarkable improvement of efficiency for CdS-sensitized solar cells. (United States)

    Deng, Jianping; Wang, Minqiang; Liu, Jing; Song, Xiaohui; Yang, Zhi


    Photoelectrode of nanocables (NCs) structure of ZnO nanowires (NWs) coated with Al-doped ZnO (AZO) shells was investigated for CdS quantum dots sensitized solar cells (QDSSCs). ZnO NWs serve as the frame for the preparation of AZO shells, in which electron transport more rapidly due to the more higher electron mobility of AZO (n-ZnO) than that of i-ZnO. AZO shells were assembled onto the surface of ZnO NWs via a spin-coating method. Optical band-gap of the ZnO/AZO films varies from 3.19 eV for pure ZnO to 3.25 eV for AZO (15%) depending on the Al-doping concentration. The PL intensity of AZO/ZnO, V(oc), J(sc) and η of the cells first increased and then decreased with the increase in the Al-doping (from 0% to 20%) and post-annealed temperature. Remarkably, the value of V(oc) can achieve above 0.8 V after Al-doping. The dark current and absorption spectrum provided direct evidence of the increase in J(sc) and V(oc), respectively. Moreover, we discussed the effect of Al-doping on optical band-gap of the samples and the transfer of electron. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

  18. Calcium dependent current recordings in Xenopus laevis oocytes in microgravity (United States)

    Wuest, Simon L.; Roesch, Christian; Ille, Fabian; Egli, Marcel


    Mechanical unloading by microgravity (or weightlessness) conditions triggers profound adaptation processes at the cellular and organ levels. Among other mechanisms, mechanosensitive ion channels are thought to play a key role in allowing cells to transduce mechanical forces. Previous experiments performed under microgravity have shown that gravity affects the gating properties of ion channels. Here, a method is described to record a calcium-dependent current in native Xenopus laevis oocytes under microgravity conditions during a parabolic flight. A 3-voltage-step protocol was applied to provoke a calcium-dependent current. This current increased with extracellular calcium concentration and could be reduced by applying extracellular gadolinium. The custom-made ;OoClamp; hardware was validated by comparing the results of the 3-voltage-step protocol to results obtained with a well-established two-electrode voltage clamp (TEVC). In the context of the 2nd Swiss Parabolic Flight Campaign, we tested the OoClamp and the method. The setup and experiment protocol worked well in parabolic flight. A tendency that the calcium-dependent current was smaller under microgravity than under 1 g condition could be observed. However, a conclusive statement was not possible due to the small size of the data base that could be gathered.

  19. Power-MOSFET Voltage Regulator (United States)

    Miller, W. N.; Gray, O. E.


    Ninety-six parallel MOSFET devices with two-stage feedback circuit form a high-current dc voltage regulator that also acts as fully-on solid-state switch when fuel-cell out-put falls below regulated voltage. Ripple voltage is less than 20 mV, transient recovery time is less than 50 ms. Parallel MOSFET's act as high-current dc regulator and switch. Regulator can be used wherever large direct currents must be controlled. Can be applied to inverters, industrial furnaces photovoltaic solar generators, dc motors, and electric autos.

  20. Understanding alternative splicing of Cav1.2 calcium channels for a new approach towards individualized medicine (United States)

    Liao, Ping; Soong, Tuck Wah


    Calcium channel blockers (CCBs) are widely used to treat cardiovascular diseases such as hypertension, angina pectoris, hypertrophic cardiomyopathy, and supraventricular tachycardia. CCBs selectively inhibit the inward flow of calcium ions through voltage-gated calcium channels, particularly Cav1.2, that are expressed in the cardiovascular system. Changes to the molecular structure of Cav1.2 channels could affect sensitivity of the channels to blockade by CCBs. Recently, extensive alternative splicing was found in Cav1.2 channels that generated wide phenotypic variations. Cardiac and smooth muscles express slightly different, but functionally important Cav1.2 splice variants. Alternative splicing could also modulate the gating properties of the channels and giving rise to different responses to inhibition by CCBs. Importantly, alternative splicing of Cav1.2 channels may play an important role to influence the outcome of many cardiovascular disorders. Therefore, the understanding of how alternative splicing impacts Cav1.2 channels pharmacology in various diseases and different organs may provide the possibility for individualized therapy with minimal side effects. PMID:23554629

  1. Choice of operating voltage for a transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Egerton, R.F., E-mail:


    An accelerating voltage of 100–300 kV remains a good choice for the majority of TEM or STEM specimens, avoiding the expense of high-voltage microscopy but providing the possibility of atomic resolution even in the absence of lens-aberration correction. For specimens thicker than a few tens of nm, the image intensity and scattering contrast are likely to be higher than at lower voltage, as is the visibility of ionization edges below 1000 eV (as required for EELS elemental analysis). In thick (>100 nm) specimens, higher voltage ensures less beam broadening and better spatial resolution for STEM imaging and EDX spectroscopy. Low-voltage (e.g. 30 kV) TEM or STEM is attractive for a very thin (e.g. 10 nm) specimen, as it provides higher scattering contrast and fewer problems for valence-excitation EELS. Specimens that are immune to radiolysis suffer knock-on damage at high current densities, and this form of radiation damage can be reduced or avoided by choosing a low accelerating voltage. Low-voltage STEM with an aberration-corrected objective lens (together with a high-angle dark-field detector and/or EELS) offers atomic resolution and elemental identification from very thin specimens. Conventional TEM can provide atomic resolution in low-voltage phase-contrast images but requires correction of chromatic aberration and preferably an electron-beam monochromator. Many non-conducting (e.g. organic) specimens damage easily by radiolysis and radiation damage then determines the TEM image resolution. For bright-field scattering contrast, low kV can provide slightly better dose-limited resolution if the specimen is very thin (a few nm) but considerably better resolution is possible from a thicker specimen, for which higher kV is required. Use of a phase plate in a conventional TEM offers the most dose-efficient way of achieving atomic resolution from beam-sensitive specimens. - Highlights: • 100–300 kV accelerating voltage is suitable for TEM specimens of typical

  2. Equilibrium fluctuation relations for voltage coupling in membrane proteins. (United States)

    Kim, Ilsoo; Warshel, Arieh


    energy barrier that follow the trend of the equilibrium fluctuation relation and the Marcus theory of electron transfer. These energetics also allow for a direct estimation of the voltage dependence of channel activation (Q-V curve), offering a quantitative rationale for a correlation between the voltage dependence parabolas and the Q-V curve, upon site-directed mutagenesis or drug binding. Taken together, by introducing the voltage coupling as the energy gap reaction coordinate, our framework brings new perspectives to the thermodynamic models of voltage activation in voltage-sensitive membrane proteins, offering an a framework for a better understating of the structure-function correlations of voltage gating in ion channels as well as electrogenic phenomena in ion pumps and transporters. Significantly, this formulation also provides a powerful bridge between the CG model of voltage coupling and the conventional macroscopic treatments. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Calcium-41 concentration in terrestrial materials: prospects for dating of pleistocene samples

    Energy Technology Data Exchange (ETDEWEB)

    Henning, W.; Bell, W.A.; Billquist, P.J.; Glagola, B.G.; Kutschera, W.; Liu, Z.; Lucas, H.F.; Paul, M.; Rehm, K.E.; Yntema, J.L.


    Calcium-41 bas been suggested as a new tool for radiometric dating in the range of 10/sup 5/ to 10/sup 6/ years. The concentration of cosmogenic calcium-41 in natural samples of terrestrial origin has now been determined by high-sensitivity accelerator mass spectrometry after pre-enrichment in calcium-41 with an isotope separator. Ratios of calcium-41 to total calcium between 2 x 10/sup -14/ and 3 x 10/sup -15/ were measured for samples of contemporary bovine bone and from limestone deposits. Some prospects for the use of calcium-41 for dating Middle and Late Pleistocene bone and for other geophysical applications are discussed.

  4. Inactivation kinetics and pharmacology distinguish two calcium currents in mouse pancreatic B-cells

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, W.F.; Satin, L.S.; Cook, D.L. (Univ. of Washington School of Medicine, Seattle (USA))


    Voltage-dependent calcium currents were studied in cultured adult mouse pancreatic B-cells using the whole-cell voltage-clamp technique. When calcium currents were elicited with 10-sec depolarizing command pulses, the time course of inactivation was well fit by the sum of two exponentials. The more rapidly-inactivating component had a time constant of 75 +/- 5 msec at 0 mV and displayed both calcium influx- and voltage-dependent inactivation, while the more slowly-inactivating component had a time constant of 2750 +/- 280 msec at 0 mV and inactivated primarily via voltage. The fast component was subject to greater steady-state inactivation at holding potentials between -100 and -40 mV and activated at a lower voltage threshold. This component was also significantly reduced by nimodipine (0.5 microM) when a holding potential of -100 mV was used, whereas the slow component was unaffected. In contrast, the slow component was greatly increased by replacing external calcium with barium, while the fast component was unchanged. Cadmium (1-10 microM) displayed a voltage-dependent block of calcium currents consistent with a greater effect on the high-threshold, more-slowly inactivating component. Taken together, the data suggest that cultured mouse B-cells, as with other insulin-secreting cells we have studied, possess at least two distinct calcium currents. The physiological significance of two calcium currents having distinct kinetic and steady-state inactivation characteristics for B-cell burst firing and insulin secretion is discussed.

  5. Acidosis and Urinary Calcium Excretion

    DEFF Research Database (Denmark)

    Alexander, R Todd; Cordat, Emmanuelle; Chambrey, Régine


    Metabolic acidosis is associated with increased urinary calcium excretion and related sequelae, including nephrocalcinosis and nephrolithiasis. The increased urinary calcium excretion induced by metabolic acidosis predominantly results from increased mobilization of calcium out of bone and inhibi...

  6. voltage compensation using artificial neural network

    African Journals Online (AJOL)

    Offor Theophilos

    VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF. RUMUOLA ... using artificial neural network (ANN) controller based dynamic voltage restorer (DVR). ... substation by simulating with sample of average voltage for Omerelu, Waterlines, Rumuola, Shell Industrial and Barracks.

  7. Calcium and bones (United States)

    ... eat in their diet. Vitamin D is the hormone that helps the gut absorb more calcium. Many older adults have common risks that make bone health worse. Calcium intake in the diet (milk, cheese, yogurt) is low. Vitamin D levels are ...

  8. Calcium D-saccharate

    DEFF Research Database (Denmark)

    Garcia, André Castilho; Hedegaard, Martina Vavrusova; Skibsted, Leif Horsfelt


    Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, Kassoc = 1032 ± 80, ΔHassoc......° = -34 ± 6 kJ mol-1, and ΔSassoc° = -55 ± 9 J mol-1 K-1, were determined electrochemically. Calcium d-saccharate is sparingly soluble, with a solubility product, Ksp, of (6.17 ± 0.32) × 10-7 at 25 °C, only moderately increasing with the temperature: ΔHsol° = 48 ± 2 kJ mol-1, and ΔSassoc° = 42 ± 7 J mol-1...... K-1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d...

  9. Extracellular Calcium and Magnesium

    African Journals Online (AJOL)

    ABSTRACT. The cause of preeclampsia remains unknown and calcium and magnesium supplement are being suggested as means of prevention. The objective of this study was to assess magnesium and calcium in the plasma and cerebrospinal fluid of Nigerian women with preedamp sia and eclampsia. Setting was ...

  10. Voltage Controlled Perpendicular Magnetic Anisotropy. (United States)

    Noviasky, Nicholas; Sabirianov, Ildar; Cao, Shi; Zhang, Xiaozhe; Sokolov, Andrei; Kirianov, Eugene; Dowben, Peter; Ilie, Carolina C.; University of Nebraska at Lincoln Team; State University of New York at Oswego Collaboration

    Here we report the voltage controlled perpendicular magnetic anisotropy of a multilayer stack composed of P-type silicon substrate/ Gd2O3/ Co/ Pt grown by pulsed laser deposition (PLD) under ultra-high vacuum conditions. For examination of the voltage effect on magnetic properties of the samples, we performed magneto optical Kerr effect (MOKE) measurements. The results show a clear inverse relationship between voltage and coercivity. The exchange of oxygen ions which occurs at the interface between gadolinium oxide and cobalt may increase the cobalt oxide concentration within the optical interface layer. One potential application for this research could be the creation of a voltage controlled magnetic tunneling junction memory storage device. Proper implementation may be able to combine non-volatility with higher areal densities and low power consumption. NSF Research Experience for Faculty and Students at Undergraduate Institutions Program, UNL- MRSEC.

  11. Modular High Voltage Power Supply

    Energy Technology Data Exchange (ETDEWEB)

    Newell, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    The goal of this project is to develop a modular high voltage power supply that will meet the needs of safeguards applications and provide a modular plug and play supply for use with standard electronic racks.

  12. A Voltage Quality Detection Method

    DEFF Research Database (Denmark)

    Chen, Zhe; Wei, Mu


    This paper presents a voltage quality detection method based on a phase-locked loop (PLL) technique. The technique can detect the voltage magnitude and phase angle of each individual phase under both normal and fault power system conditions. The proposed method has the potential to evaluate various...... power quality disturbances, such as interruptions, sags and imbalances. Simulation studies have been performed. The effectiveness of the proposed method has been demonstrated under the simulated typical power disturbances....

  13. Medium voltage substation insulation coordination

    Energy Technology Data Exchange (ETDEWEB)

    Caccia, M.; Gambirasio, D. (SAE Sadelmi, Milan (Italy))


    With reference to the provisions contained in applicable CEI (Italian Electrotechnical Committee) and IEC (International Electrotechnical Commission) normatives, a review is made of design criteria for the coordination of medium voltage substation switchgear and control gear. The design problematics are discussed with reference to optimization of neutral grounding, three phase ac short circuit calculation methods, and methods for the evaluation of voltages in fault conditions.

  14. Reliability criteria for voltage stability

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Carson W.; Silverstein, Brian L. [Bonneville Power Administration, Portland, OR (United States)


    In face of costs pressures, there is need to allocate scare resources more effectively in order to achieve voltage stability. This naturally leads to development of probabilistic criteria and notions of rick management. In this paper it is presented a discussion about criteria for long term voltage stability limited to the case in which the time frames are topically several minutes. (author) 14 refs., 1 fig.

  15. Electro-optical voltage transformer (United States)

    Xu, Yan; Ye, Miaoyuan; Cui, Ying


    The work introduces an optical fiber voltage transformer based on the Pockels effect. The transformer is different from a conventional electric-magnetic voltage transformer. A crystal BGO is used as sensor that is sealed in SF6 gas container; the measured signal is transferred by optical fiber in the Electro-Optical Voltage Transformer (EOVT). The principles and composition of EOVT is described here. The system consists of three parts: capacitive divider, optical sensor and electronics module. According to the analysis of factors that influence on the accuracy of measurement, the main ones, temperature and pressure of SF6, are corrected by means of signal digital process. The performances of 110kV EOVT were tested. The results show that the accuracy of EOVT could achieve 0.5 percent. Compared to a conventional electric-magnetic voltage transformer, the advantages of 110kV EOVT are higher accuracy, low cost, small volume, excellent dynamic characteristics and immunity from electromagnetic interference. In particular the low voltage is effectively isolated from the high voltage by means of the optical fiber.


    NARCIS (Netherlands)



    It is shown that heat-induced increase of intracellular calcium does not correlate with hyperthermic cell killing. Six different cell lines were investigated; in four (EAT, HeLa S3, L5178Y-R and L5178Y-S) heat treatments killing 90% of the cells did not affect the levels of intracellular free

  17. Spontaneous and CRH-Induced Excitability and Calcium Signaling in Mice Corticotrophs Involves Sodium, Calcium, and Cation-Conducting Channels. (United States)

    Zemkova, Hana; Tomić, Melanija; Kucka, Marek; Aguilera, Greti; Stojilkovic, Stanko S


    Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.

  18. Spatial distribution of calcium-gated chloride channels in olfactory cilia. (United States)

    French, Donald A; Badamdorj, Dorjsuren; Kleene, Steven J


    In vertebrate olfactory receptor neurons, sensory cilia transduce odor stimuli into changes in neuronal membrane potential. The voltage changes are primarily caused by the sequential openings of two types of channel: a cyclic-nucleotide-gated (CNG) cationic channel and a calcium-gated chloride channel. In frog, the cilia are 25 to 200 µm in length, so the spatial distributions of the channels may be an important determinant of odor sensitivity. To determine the spatial distribution of the chloride channels, we recorded from single cilia as calcium was allowed to diffuse down the length of the cilium and activate the channels. A computational model of this experiment allowed an estimate of the spatial distribution of the chloride channels. On average, the channels were concentrated in a narrow band centered at a distance of 29% of the ciliary length, measured from the base of the cilium. This matches the location of the CNG channels determined previously. This non-uniform distribution of transduction proteins is consistent with similar findings in other cilia. On average, the two types of olfactory transduction channel are concentrated in the same region of the cilium. This may contribute to the efficient detection of weak stimuli.

  19. Excitation-calcium release uncoupling in aged single human skeletal muscle fibers. (United States)

    Delbono, O; O'Rourke, K S; Ettinger, W H


    The biological mechanisms underlying decline in muscle power and fatigue with age are not completely understood. The contribution of alterations in the excitation-calcium release coupling in single muscle fibers was explored in this work. Single muscle fibers were voltage-clamped using the double Vaseline gap technique. The samples were obtained by needle biopsy of the vastus lateralis (quadriceps) from 9 young (25-35 years; 25.9 +/- 9.1; 5 female and 4 male) and 11 old subjects (65-75 years; 70.5 +/- 2.3; 6 f, 5 m). Data were obtained from 36 and 39 fibers from young and old subjects, respectively. Subjects included in this study had similar physical activity. Denervated and slow-twitch muscle fibers were excluded from this study. A significant reduction of maximum charge movement (Qmax) and DHP-sensitive Ca current were recorded in muscle fibers from the 65-75 group. Qmax values were 7.6 +/- 0.9 and 3.2 +/- 0.3 nC/muF for young and old muscle fibers, respectively (P charge inactivation or interconversion (charge 1 to charge 2) were found. The peak Ca current was (-)4.7 +/- 0.08 and (-)2.15 +/- 0.11 muA/muF for young and old fibers, respectively (P muscle fibers, respectively. Caffeine (0.5 mM) induced potentiation of the peak calcium transient in both groups. The decrease in the voltage-/Ca-dependent Ca release ratio in old fibers (0.18 +/- 0.02) compared to young fibers (0.47 +/- 0.03) (P skeletal muscle and, the reduction of Ca release is due to DHPR-ryanodine receptor uncoupling in fast-twitch fibers. These alterations can account, at least partially for the skeletal muscle function impairment associated with aging.

  20. Calmodulin activation by calcium transients in the postsynaptic density of dendritic spines.

    Directory of Open Access Journals (Sweden)

    Daniel X Keller


    Full Text Available The entry of calcium into dendritic spines can trigger a sequence of biochemical reactions that begins with the activation of calmodulin (CaM and ends with long-term changes to synaptic strengths. The degree of activation of CaM can depend on highly local elevations in the concentration of calcium and the duration of transient increases in calcium concentration. Accurate measurement of these local changes in calcium is difficult because the spaces are so small and the numbers of molecules are so low. We have therefore developed a Monte Carlo model of intracellular calcium dynamics within the spine that included calcium binding proteins, calcium transporters and ion channels activated by voltage and glutamate binding. The model reproduced optical recordings using calcium indicator dyes and showed that without the dye the free intracellular calcium concentration transient was much higher than predicted from the fluorescent signal. Excitatory postsynaptic potentials induced large, long-lasting calcium gradients across the postsynaptic density, which activated CaM. When glutamate was released at the synapse 10 ms before an action potential occurred, simulating activity patterns that strengthen hippocampal synapses, the calcium gradient and activation of CaM in the postsynaptic density were much greater than when the order was reversed, a condition that decreases synaptic strengths, suggesting a possible mechanism underlying the induction of long-term changes in synaptic strength. The spatial and temporal mechanisms for selectivity in CaM activation demonstrated here could be used in other signaling pathways.

  1. Unbalanced Voltage Compensation in Low Voltage Residential AC Grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Munk-Nielsen, Stig


    This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling. The vol......This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling....... The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases....

  2. Calcium sensing in exocytosis

    DEFF Research Database (Denmark)

    Gustavsson, Natalia; Wu, Bingbing; Han, Weiping


    Neurotransmitters, neuropeptides and hormones are released through regulated exocytosis of synaptic vesicles and large dense core vesicles. This complex and highly regulated process is orchestrated by SNAREs and their associated proteins. The triggering signal for regulated exocytosis is usually...... an increase in intracellular calcium levels. Besides the triggering role, calcium signaling modulates the precise amount and kinetics of vesicle release. Thus, it is a central question to understand the molecular machineries responsible for calcium sensing in exocytosis. Here we provide an overview of our...

  3. Improved Thévenin equivalent methods for real-time voltage stability assessment

    DEFF Research Database (Denmark)

    Perez, Angel; Jóhannsson, Hjörtur; Østergaard, Jacob


    An improved Thévenin equivalent method for real-time voltage stability assessment that uses wide-area information from synchrophasors is proposed. The improvements are a better modeling of the limited synchronous generators, and a processing that anticipates the effect of field current limiters, ...... with the sensitivity-based voltage stability assessment method is explored....

  4. Electrode voltage fall and total voltage of a transient arc (United States)

    Valensi, F.; Ratovoson, L.; Razafinimanana, M.; Masquère, M.; Freton, P.; Gleizes, A.


    This paper deals with an experimental study of the components of a transient arc total voltage with duration of a few tens of ms and a current peak close to 1000 A. The cathode tip is made of graphite whereas the flat anode is made either of copper or of graphite; the electrodes gap is a few mm. The analysis of the electrical parameters is supported and validated by fast imaging and by two models: the first one is a 2D physical model of the arc allowing to calculate both the plasma temperature field and the arc voltage; the second model is able to estimate the transient heating of the graphite electrode. The main aim of the study was to detect the possible change of the cathode voltage fall (CVF) during the first instants of the arc. Indeed it is expected that during the first ms the graphite cathode is rather cool and the main mechanism of the electron emission should be the field effect emission, whereas after several tens of ms the cathode is strongly heated and thermionic emission should be predominant. We have observed some change in the apparent CVF but we have shown that this apparent change can be attributed to the variation of the solid cathode resistance. On the other hand, the possible change of CVF corresponding to the transition between a ‘cold’ and a ‘hot’ cathode should be weak and could not be characterized considering our measurement uncertainty of about 2 V. The arc column voltage (ACV) was estimated by subtracting the electrode voltage fall from the total arc voltage. The experimental transient evolution of the ACV is in very good agreement with the theoretical variation predicted by the model, showing the good ability of the model to study this kind of transient arc.

  5. Automated Voltage Control in LHCb

    CERN Document Server

    Granado Cardoso, L; Jacobsson, R


    LHCb is one of the 4 LHC experiments. In order to ensure the safety of the detector and to maximize efficiency, LHCb needs to coordinate its own operations, in particular the voltage configuration of the different subdetectors, according to the accelerator status. A control software has been developed for this purpose, based on the Finite State Machine toolkit and the SCADA system used for control throughout LHCb (and the other LHC experiments). This software permits to efficiently drive both the Low Voltage (LV) and High Voltage (HV) systems of the 10 different sub-detectors that constitute LHCb, setting each sub-system to the required voltage (easily configurable at run-time) based on the accelerator state. The control software is also responsible for monitoring the state of the Sub-detector voltages and adding it to the event data in the form of status-bits. Safe and yet flexible operation of the LHCb detector has been obtained and automatic actions, triggered by the state changes of the ...

  6. Bone repair in calcium-deficient rats: comparison of xylitol+calcium carbonate with calcium carbonate, calcium lactate and calcium citrate on the repletion of calcium. (United States)

    Hämäläinen, M M


    The potential value of xylitol in calcium therapy was evaluated by comparing the effect of dietary xylitol (50 g/kg diet) + calcium carbonate with the effects of calcium carbonate, calcium lactate and calcium citrate on bone repair of young male rats after the rats consumed for 3 wk a calcium-deficient diet (0.2 g Ca/kg diet). After this calcium-depletion period, the rats were fed for 2 wk one of four diets, each containing 5 g Ca/kg diet as one of the four dietary calcium sources. The diet of the control animals was supplemented with CaCO3 (5 g Ca/kg diet) throughout the study. The Ca-deficient rats showed low bone mass, low serum calcium and high serum 1,25-dihydroxycholecalciferol, parathyroid hormone (1-34 fraction) and osteocalcin concentrations. They also excreted magnesium, phosphate and hydroxyproline in the urine in high concentrations, and had high bone alkaline phosphatase and tartrate-resistant acid phosphatase activities. Most of these changes were reversed by the administered of the calcium salts. The highest recoveries of femoral dry weight, calcium, magnesium and phosphate were observed in the groups receiving xylitol+CaCO3 and calcium lactate. Calcium lactate and calcium citrate caused low serum phosphate concentration compared with rats receiving CaCO3 and with the age-matched Ca-replete controls. Xylitol-treated rats excreted more calcium and magnesium in urine than did the other rats, probably due to increased absorption of these minerals from the gut. These results suggest that dietary xylitol improves the bioavailability of calcium salts.

  7. Development of a New Cascade Voltage-Doubler for Voltage Multiplication

    Directory of Open Access Journals (Sweden)

    Arash Toudeshki


    Full Text Available For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  8. Development of a New Cascade Voltage-Doubler for Voltage Multiplication


    Toudeshki, Arash; Mariun, Norman; Hizam, Hashim; Abdul Wahab, Noor Izzri


    For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  9. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors


    Okuma, Takanori; Yasuura, Hiroto


    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  10. Ryanodine receptor gating controls generation of diastolic calcium waves in cardiac myocytes (United States)

    Petrovič, Pavol; Valent, Ivan; Cocherová, Elena; Pavelková, Jana


    The role of cardiac ryanodine receptor (RyR) gating in the initiation and propagation of calcium waves was investigated using a mathematical model comprising a stochastic description of RyR gating and a deterministic description of calcium diffusion and sequestration. We used a one-dimensional array of equidistantly spaced RyR clusters, representing the confocal scanning line, to simulate the formation of calcium sparks. Our model provided an excellent description of the calcium dependence of the frequency of diastolic calcium sparks and of the increased tendency for the production of calcium waves after a decrease in cytosolic calcium buffering. We developed a hypothesis relating changes in the propensity to form calcium waves to changes of RyR gating and tested it by simulation. With a realistic RyR gating model, increased ability of RyR to be activated by Ca2+ strongly increased the propensity for generation of calcium waves at low (0.05–0.1-µM) calcium concentrations but only slightly at high (0.2–0.4-µM) calcium concentrations. Changes in RyR gating altered calcium wave formation by changing the calcium sensitivity of spontaneous calcium spark activation and/or the average number of open RyRs in spontaneous calcium sparks. Gating changes that did not affect RyR activation by Ca2+ had only a weak effect on the propensity to form calcium waves, even if they strongly increased calcium spark frequency. Calcium waves induced by modulating the properties of the RyR activation site could be suppressed by inhibiting the spontaneous opening of the RyR. These data can explain the increased tendency for production of calcium waves under conditions when RyR gating is altered in cardiac diseases. PMID:26009544

  11. Voltage Quality of Grid Connected Wind Turbines

    DEFF Research Database (Denmark)

    Chen, Zhe; Blaabjerg, Frede; Sun, Tao


    Grid connected wind turbines may cause quality problems, such as voltage variation and flicker. This paper discusses the voltage variation and flicker emission of grid connected wind turbines with doubly-fed induction generators. A method to compensate flicker by using a voltage source converter...... (VSC) based STATCOM is presented, which shows it is an efficient mean to improve voltage quality....

  12. Calcium – how and why?

    Indian Academy of Sciences (India)


    Calcium is among the most commonly used ions, in a multitude of biological functions, so much so that it is impossible to imagine life without calcium. In this article I have attempted to address the question as to how calcium has achieved this status with a brief mention of the history of calcium research in biology. It appears ...

  13. Effects of caffeine on calcium release from the sarcoplasmic reticulum in frog skeletal muscle fibres. (United States)

    Klein, M G; Simon, B J; Schneider, M F


    1. Resting myoplasmic [Ca2+] and [Ca2+] transients (delta [Ca2+]) were monitored using Fura-2 fluorescence and Antipyrylazo III absorbance signals from voltage-clamped segments of cut frog skeletal muscle fibres in the presence and absence of 0.5 mM-caffeine. The rate of release (Rrel) of calcium from the sarcoplasmic reticulum was calculated from delta [Ca2+]. 2. delta [Ca2+] and Rrel were increased in caffeine for all pulses. The decline of delta [Ca2+] was slower after a given pulse in caffeine than without caffeine. Resting [Ca2+] was slightly elevated in caffeine. 3. The voltage dependence of the peak value of Rrel and of the steady level of Rrel at the end of a 60-120 ms pulse were both shifted towards more negative voltages in caffeine. For relatively small pulses the voltage at which a given release waveform was observed was also shifted to more negative voltages. 4. Intramembrane charge movements measured in the same fibres in which the above changes in Rrel were observed showed no significant changes in caffeine. 5. In caffeine calcium release continued for many milliseconds after the end of a short (10 ms) pulse. Continued release after a pulse was not observed without caffeine and was probably due to positive feedback of elevated [Ca2+] on calcium release resulting from calcium-induced calcium release in caffeine. 6. Intramembrane charge movements after short pulses showed no change in caffeine that could account for the continued calcium release after the pulse. 7. Continued release after short pulses in caffeine decreased as the pulse duration was increased and was absent for pulses of 60 ms or longer. Rrel also inactivated during such pulses. 8. Relatively large and long conditioning pulses in caffeine suppressed both the peak Rrel and the continued release after short pulses. Peak release and continued release after short pulses recovered in parallel with increasing recovery time following suppression by a conditioning pulse in caffeine. 9. These

  14. Calcium and Your Child (United States)

    ... Milk Allergy Figuring Out Food Labels What's a Vegetarian? Osteoporosis Minerals Your Bones Mineral Chart Vitamin D ... Need to Drink Milk? Lactose Intolerance Becoming a Vegetarian Soy Foods and Health Calcium Bones, Muscles, and ...

  15. Stoichiometry of Calcium Medicines (United States)

    Pinto, Gabriel


    The topic of calcium supplement and its effects on human lives is presented in the way of questions to the students. It enables the students to realize the relevance of chemistry outside the classroom surrounding.

  16. Magnesium, calcium and cancer

    National Research Council Canada - National Science Library

    Anghileri, Leopoldo J


    Magnesium ion (Mg(2+)) and calcium ion (Ca(2+)) control a diverse and important range of cellular processes, such as gene transcription, cell proliferation, neoplastic transformation, immune response and therapeutic treatment...

  17. Portable High Voltage Impulse Generator

    Directory of Open Access Journals (Sweden)

    S. Gómez


    Full Text Available This paper presents a portable high voltage impulse generator which was designed and built with insulation up to 20 kV. This design was based on previous work in which simulation software for standard waves was developed. Commercial components and low-cost components were used in this work; however, these particular elements are not generally used for high voltage applications. The impulse generators used in industry and laboratories are usually expensive; they are built to withstand extra high voltage and they are big, making them impossible to transport. The proposed generator is portable, thereby allowing tests to be made on devices that cannot be moved from their location. The results obtained with the proposed impulse generator were satisfactory in terms of time and waveforms compared to other commercial impulse generators and the standard impulse wave simulator.

  18. Voltage Control of Magnetic Anisotropy (United States)

    Hao, Guanhua; Cao, Shi; Noviasky, Nick; Ilie, Carolina; Sokolov, Andre; Yin, Yuewei; Xu, Xiaoshan; Dowben, Peter

    Pd/Co/Gd2O3/Si heterostructures were fabricated via pulsed laser deposition and e-beam evaporation. Hysteresis loops, obtained by longitudinal magneto-optical Kerr-effect (MOKE) measurements, indicates an initial in-plane magnetic anisotropy. Applying a perpendicular voltage on the sample, the differences between the polar and longitudinal MOKE and anomalous Hall effect data indicates there is a reversible change in magnetic anisotropy, from in-plane to out-of-plane, with applied voltage. Prior work by others suggests that the change in magnetic anisotropy is due to redox reactions at the Co/Gd2O3 interference. Voltage controlled magnetism can result from changing interfacial chemistry and does not always require a magneto-electric coupling tensor.

  19. Ultra High Voltage Surge Waveforms Measurement Using an Optical Transducer

    Directory of Open Access Journals (Sweden)

    Francisco G. PEÑA-LECONA


    Full Text Available Ultra high voltage surge waveforms measurement by means of a portable optical transducer is presented. The sensor system uses a transducer element based on the longitudinal electro-optic effect with a double pass configuration to obtain a better sensitivity. The transducer head is allocated to one meter of distance from the generating element of electric field and it is able to measure waveform surges from 515 kV up to 1090 kV with fast response. It is demonstrated that the telemetry of ultra high voltage surge waveforms can be successfully done by means of this proposed optical transducer.

  20. MOS switched-capacitor filters using voltage inverter switches (United States)

    Fettweis, A.; Pandel, J.; Herbst, D.; Hoefflinger, B.; Schweer, R.


    The paper examines MOS switched-capacitor filters which use voltage inverter switches. Low-sensitivity switched-capacitor filters imitating LC and LC/unit-element structures can be built by means of capacitances, ordinary switches, and voltage inverter switches; the latter are simply realizable by electronic means. It was found that there are no restrictions on the operating rate (other than those resulting from the Nyquist theorem), or on the location of the attenuation poles; it was also found that the effects of parasitic capacitances can be overcome by proper design techniques. The experimental results of an integrated third-order low-pass filter are in agreement with theory.

  1. T-type calcium channel: a privileged gate for calcium entry and control of adrenal steroidogenesis

    Directory of Open Access Journals (Sweden)

    Michel Florian Rossier


    Full Text Available Intracellular calcium plays a crucial role in modulating a variety of functions such as muscle contraction, hormone secretion, gene expression or cell growth. Calcium signaling has been however shown to be more complex than initially thought. Indeed, it is confined within cell microdomains and different calcium channels are associated with different functions, as shown by various channelopathies.Sporadic mutations on voltage-operated L-type calcium channels in adrenal glomerulosa cells have been shown recently to be the second most prevalent genetic abnormalities present in human aldosterone-producing adenoma. The observed modification of the threshold of activation of the mutated channels not only provides an explanation for this gain of function but reminds us on the importance of maintaining adequate electrophysiological characteristics to make channels able to exert specific cellular functions. Indeed, the contribution to steroid production of the various calcium channels expressed in adrenocortical cells is not equal and the reason has been investigated for a long time. Given the very negative resting potential of these cells, and the small membrane depolarization induced by their physiological agonists, low threshold T-type calcium channels are particularly well suited for responding under these conditions and conveying calcium into the cell, at the right place for controlling steroidogenesis. In contrast, high threshold L-type channels are normally activated by much stronger cell depolarizations. The fact that dihydropyridine calcium antagonists, specific for L-type channels, are poorly efficient for reducing aldosterone secretion either in vivo or in vitro, strongly supports the view that these two types of channels differently affect steroid biosynthesis.Whether a similar analysis is transposable to fasciculata cells and cortisol secretion is one of the questions addressed in the present review. No similar mutations on L-type or T

  2. A genetic screen for dihydropyridine (DHP)-resistant worms reveals new residues required for DHP-blockage of mammalian calcium channels. (United States)

    Kwok, Trevor C Y; Hui, Kwokyin; Kostelecki, Wojciech; Ricker, Nicole; Selman, Guillermo; Feng, Zhong-Ping; Roy, Peter John


    Dihydropyridines (DHPs) are L-type calcium channel (Ca(v)1) blockers prescribed to treat several diseases including hypertension. Ca(v)1 channels normally exist in three states: a resting closed state, an open state that is triggered by membrane depolarization, followed by a non-conducting inactivated state that is triggered by the influx of calcium ions, and a rapid change in voltage. DHP binding is thought to alter the conformation of the channel, possibly by engaging a mechanism similar to voltage dependent inactivation, and locking a calcium ion in the pore, thereby blocking channel conductance. As a Ca(v)1 channel crystal structure is lacking, the current model of DHP action has largely been achieved by investigating the role of candidate Ca(v)1 residues in mediating DHP-sensitivity. To better understand DHP-block and identify additional Ca(v)1 residues important for DHP-sensitivity, we screened 440,000 randomly mutated Caenorhabditis elegans genomes for worms resistant to DHP-induced growth defects. We identified 30 missense mutations in the worm Ca(v)1 pore-forming (alpha(1)) subunit, including eleven in conserved residues known to be necessary for DHP-binding. The remaining polymorphisms are in eight conserved residues not previously associated with DHP-sensitivity. Intriguingly, all of the worm mutants that we analyzed phenotypically exhibited increased channel activity. We also created orthologous mutations in the rat alpha(1C) subunit and examined the DHP-block of current through the mutant channels in culture. Six of the seven mutant channels examined either decreased the DHP-sensitivity of the channel and/or exhibited significant residual current at DHP concentrations sufficient to block wild-type channels. Our results further support the idea that DHP-block is intimately associated with voltage dependent inactivation and underscores the utility of C. elegans as a screening tool to identify residues important for DHP interaction with mammalian Ca(v)1

  3. Calcium-binding properties of a calcium-dependent protein kinase from Plasmodium falciparum and the significance of individual calcium-binding sites for kinase activation. (United States)

    Zhao, Y; Pokutta, S; Maurer, P; Lindt, M; Franklin, R M; Kappes, B


    Calcium-dependent protein kinase from Plasmodium falciparum (PfCPK) is a multidomain protein composed of an N-terminal kinase domain connected via a linker region to a C-terminal CaM-like calcium-binding domain. The kinase can be activated by Ca2+ alone and associates with 45Ca2+. Here we describe the calcium-binding properties of the kinase and the significance of the individual calcium-binding sites with respect to enzymatic activation, as well as the Ca(2+)-induced conformational change as detected by circular dichroism. As predicted from the cDNA sequence, the kinase has four EF-hand calcium-binding sites in the C-terminal domain. To understand the roles of the individual calcium-binding sites, two series of mutations were generated at the individual EF-hand motifs. The highly conserved glutamic acid residue at position 12 in each calcium-binding loop was mutated to either lysine or glutamine, and therefore a total of eight mutants were generated. Either of these mutations (to lysine or glutamine) is sufficient to eliminate calcium binding at the mutated site. Sites I and II appear to be crucial for both Ca(2+)-induced conformational change and enzymatic activation. Whereas mutations at site II almost completely abolish kinase activity, mutations at site I are also deleterious and dramatically reduce the sensitivity of the Ca(2+)-induced conformational change and the Ca(2+)-dependent activation. Mutations at sites III and IV have minor effects.

  4. Minimal model for calcium alternans due to SR release refractoriness (United States)

    Cantalapiedra, Inma R.; Alvarez-Lacalle, Enrique; Peñaranda, Angelina; Echebarria, Blas


    In the heart, rapid pacing rates may induce alternations in the strength of cardiac contraction, termed pulsus alternans. Often, this is due to an instability in the dynamics of the intracellular calcium concentration, whose transients become larger and smaller at consecutive beats. This alternation has been linked experimentally and theoretically to two different mechanisms: an instability due to (1) a strong dependence of calcium release on sarcoplasmic reticulum (SR) load, together with a slow calcium reuptake into the SR or (2) to SR release refractoriness, due to a slow recovery of the ryanodine receptors (RyR2) from inactivation. The relationship between calcium alternans and refractoriness of the RyR2 has been more elusive than the corresponding SR Ca load mechanism. To study the former, we reduce a general calcium model, which mimics the deterministic evolution of a calcium release unit, to its most basic elements. We show that calcium alternans can be understood using a simple nonlinear equation for calcium concentration at the dyadic space, coupled to a relaxation equation for the number of recovered RyR2s. Depending on the number of RyR2s that are recovered at the beginning of a stimulation, the increase in calcium concentration may pass, or not, over an excitability threshold that limits the occurrence of a large calcium transient. When the recovery of the RyR2 is slow, this produces naturally a period doubling bifurcation, resulting in calcium alternans. We then study the effects of inactivation, calcium diffusion, and release conductance for the onset of alternans. We find that the development of alternans requires a well-defined value of diffusion while it is less sensitive to the values of inactivation or release conductance.

  5. Role of calcium in gonadotropin releasing hormone-induced luteinizing hormone secretion from the bovine pituitary

    Energy Technology Data Exchange (ETDEWEB)

    Kile, J.P.


    The hypothesis was tested that GnRH acts to release LH by increasing calcium uptake by gonadotroph which in turn stimulates calcium-calmodulin activity and results in LH release from bovine pituitary cells as it does in the rat. Pituitary glands of calves (4-10 months of age) were enzymatically dispersed (0.2% collagenase) and grown for 5 days to confluency in multiwell plates (3 x 10/sup 5//well). Cells treated with GnRH Ca/sup + +/ ionophore A23187, and ouabain all produced significant releases of LH release in a pronounced all or none fashion, while thorough washing of the cells with 0.5 mM EGTA in Ca/sup + +/-free media prevented the action of GnRH. GnRH caused a rapid efflux of /sup 45/Ca/sup + +/. Both GnRH-stimulated /sup 45/Ca efflux and LH release could be partially blocked by verapamil GnRH-induced LH release could also be blocked by nifedipine and tetrodotoxin, although these agents did not affect /sup 45/Ca efflux. The calmodulin antagonists calmidazolium and W7 were found to block GnRH induced LH release, as well as LH release induced by theophylline, KC PGE/sub 2/ and estradiol. These data indicated that: (1) calcium is required for GnRH action, but extracellular Ca/sup + +/ does not regulate LH release; (2) GnRH elevates intracellular Ca/sup + +/ by opening both voltage sensitive and receptor mediated Ca/sup + +/ channels; (3) activation of calmodulin is one mechanism involved in GnRH-induced LH release.

  6. Reporting sodium channel activity using calcium flux: pharmacological promiscuity of cardiac Nav1.5. (United States)

    Zhang, Hongkang; Zou, Beiyan; Du, Fang; Xu, Kaiping; Li, Min


    Voltage-gated sodium (Nav) channels are essential for membrane excitability and represent therapeutic targets for treating human diseases. Recent reports suggest that these channels, e.g., Nav1.3 and Nav1.5, are inhibited by multiple structurally distinctive small molecule drugs. These studies give reason to wonder whether these drugs collectively target a single site or multiple sites in manifesting such pharmacological promiscuity. We thus investigate the pharmacological profile of Nav1.5 through systemic analysis of its sensitivity to diverse compound collections. Here, we report a dual-color fluorescent method that exploits a customized Nav1.5 [calcium permeable Nav channel, subtype 5 (SoCal5)] with engineered-enhanced calcium permeability. SoCal5 retains wild-type (WT) Nav1.5 pharmacological profiles. WT SoCal5 and SoCal5 with the local anesthetics binding site mutated (F1760A) could be expressed in separate cells, each with a different-colored genetically encoded calcium sensor, which allows a simultaneous report of compound activity and site dependence. The pharmacological profile of SoCal5 reveals a hit rate (>50% inhibition) of around 13% at 10 μM, comparable to that of hERG. The channel activity is susceptible to blockage by known drugs and structurally diverse compounds. The broad inhibition profile is highly dependent on the F1760 residue in the inner cavity, which is a residue conserved among all nine subtypes of Nav channels. Both promiscuity and dependence on F1760 seen in Nav1.5 were replicated in Nav1.4. Our evidence of a broad inhibition profile of Nav channels suggests a need to consider off-target effects on Nav channels. The site-dependent promiscuity forms a foundation to better understand Nav channels and compound interactions. Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics.

  7. Study on the ability of Shanghai UHV AC grid access point voltage regulation (United States)

    Chen, Wentao; Xia, Hui; Han, Wenxuan; Yang, Xiu


    Shanghai as China’s highest load density and largest urban power grid, located in the end position of East China Power Grid, is an important access point of East China UHV AC power grid. Making sure the voltage of UHV power grid placement has enough regulation ability is an important condition for safe operation of the system. The basic measures of system voltage regulation are given and the possible problems of voltage of UHV power grid are analyzed in the actual operation. Using sensitivity analysis method to calculate the ability of Shanghai UHV power grid placement voltage regulation after East China UHV AC target grid operation.

  8. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.


    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate

  9. In vivo calcium imaging of evoked calcium