WorldWideScience

Sample records for voltage-dependent inwardly rectifying

  1. Flow- and voltage-dependent blocking effect of ethosuximide on the inward rectifier K⁺ (Kir2.1) channel.

    Science.gov (United States)

    Huang, Chiung-Wei; Kuo, Chung-Chin

    2015-08-01

    Absence seizures are manifestations of abnormal thalamocortical oscillations characterized by spike-and-wave complexes in EEG. Ethosuximide (ETX) is one of the principal medications against absence seizures. We investigate the effect of ETX on the Kir2.1 channel, a prototypical inward rectifier K(+) channel possibly playing an important role in the setting of neuronal membrane potential. We demonstrate that the outward currents of Kir2.1 channels are significantly inhibited by intracellular ETX. We further show that the movement of neutral molecule ETX in the Kir2.1 channel is accompanied by ∼1.2 K(+), giving rise to the vivid voltage dependence of ETX unbinding rate. Moreover, the apparent affinity (K d ) of ETX in the channels are decreased by single-point mutations involving M183, E224, and S165, and especially by double mutations involving T141/S165, which always also disrupt the flux-coupling feature of ETX block. Molecular dynamics simulation demonstrates narrowing of the pore at ∼D172 by binding of ETX to S165 or T141. ETX block of the Kir2.1 channels may cause a modest but critical depolarization of the relevant neurons, decreasing available T-type Ca(2+) channels and consequently lessening pathological thalamocortical burst discharges.

  2. INWARD RECTIFIERS AND THEIR REGULATION BY ENDOGENOUS POLYAMINES

    Directory of Open Access Journals (Sweden)

    Victoria A Baronas

    2014-08-01

    Full Text Available Inwardly-rectifying potassium (Kir channels contribute to maintenance of the resting membrane potential and regulation of electrical excitation in many cell types. Strongly rectifying Kir channels exhibit a very steep voltage dependence resulting in silencing of their activity at depolarized membrane voltages. The mechanism underlying this steep voltage dependence is blockade by endogenous polyamines. These small multifunctional, polyvalent metabolites enter the long Kir channel pore from the intracellular side, displacing multiple occupant ions as they migrate to a stable binding site in the transmembrane region of the channel. Numerous structure-function studies have revealed structural elements of Kir channels that determine their susceptibility to polyamine block, and enable the steep voltage dependence of this process. In addition, various channelopathies have been described that result from alteration of the polyamine sensitivity or activity of strongly rectifying channels. The primary focus of this article is to summarize current knowledge of the molecular mechanisms of polyamine block, and provide some perspective on lingering uncertainties related to this physiologically important mechanism of ion channel blockade. We also briefly review some of the important and well understood physiological roles of polyamine sensitive, strongly rectifying Kir channels, primarily of the Kir2 family.

  3. Addictive drugs, arrhythmias, and cardiac inward rectifiers.

    Science.gov (United States)

    Bébarová, Markéta; Hořáková, Zuzana; Kula, Roman

    2016-06-14

    In many addictive drugs including alcohol and nicotine, proarrhythmic effects were reported. This review provides an overview of the current knowledge in this field (with a focus on the inward rectifier potassium currents) to promote the lacking data and appeal for their completion, thus, to improve understanding of the proarrhythmic potential of addictive drugs.

  4. Locale and chemistry of spermine binding in the archetypal inward rectifier Kir2.1.

    Science.gov (United States)

    Kurata, Harley T; Zhu, Emily A; Nichols, Colin G

    2010-05-01

    Polyamine block of inwardly rectifying potassium (Kir) channels underlies their steep voltage dependence observed in vivo. We have examined the potency, voltage dependence, and kinetics of spermine block in dimeric Kir2.1 constructs containing one nonreactive subunit and one cysteine-substituted subunit before and after modification by methanethiosulfonate (MTS) reagents. At position 169C (between the D172 "rectification controller" and the selectivity filter), modification by either 2-aminoethyl MTS (MTSEA) or 2-(trimethylammonium)ethyl MTS (MTSET) reduced the potency and voltage dependence of spermine block, consistent with this position overlapping the spermine binding site. At position 176C (between D172 and the M2 helix bundle crossing), modification by MTSEA also weakened spermine block. In contrast, MTSET modification of 176C dramatically slowed the kinetics of spermine unblock, with almost no effect on potency or voltage dependence. The data are consistent with MTSET modification of 176C introducing a localized barrier in the inner cavity, resulting in slower spermine entry into and exit from a "deep" binding site (likely between the D172 rectification controller and the selectivity filter), but leaving the spermine binding site mostly unaffected. These findings constrain the location of deep spermine binding that underlies steeply voltage-dependent block, and further suggest important chemical details of high affinity binding of spermine in Kir2.1 channels-the archetypal model of strong inward rectification.

  5. Characterization of inward-rectifier K+ channel inhibition by antiarrhythmic piperazine.

    Science.gov (United States)

    Xu, Yanping; Lu, Zhe

    2004-12-14

    Strong inward-rectifier K(+) (Kir) channels play a significant role in shaping the cardiac action potential: they help produce its long plateau and accelerate its rate of repolarization. Consequently, genetic deletion of the gene encoding the strongly rectifying K(+) channel IRK1 (Kir2.1) prolongs the cardiac action potential in mice. In principle, broadening the action potential lengthens the refractory period, which may in turn be antiarrhythmogenic. Interestingly, previous studies showed that piperazine, an inexpensive and safe anthelmintic, both inhibits IRK1 channels and is antiarrhythmic in some animal preparations. This potential pharmacological benefit motivated us to further characterize the energetic, kinetic, and molecular properties of IRK1 inhibition by piperazine. We show how its blocking characteristics, in particular, its shallow voltage dependence, allow piperazine to be effective even in the presence of high-affinity polyamine blockers. We also examine the channel selectivity of piperazine and its molecular determinants.

  6. Muscarinic activation of inwardly rectifying K+ conductance reduces EPSPs in rat hippocampal CA1 pyramidal cells

    Science.gov (United States)

    Seeger, Thomas; Alzheimer, Christian

    2001-01-01

    To determine how acetylcholine (ACh) modulates the somatodendritic processing of EPSPs, we performed whole-cell recordings from CA1 pyramidal cells of hippocampal slices and examined the effect of the cholinergic agonist, carbachol (CCh), on α-amino-3-hydroxy-5-methyl isoxazole-4-propionate (AMPA) EPSPs, miniature EPSPs, and EPSP-like waveforms evoked by brief dendritic glutamate pulses (glutamate-evoked postsynaptic potentials, GPSPs). Although CCh is known to enhance the intrinsic excitability of the neuron in several ways, activation of atropine-sensitive (muscarinic) receptors on the apical dendrite or the soma of CA1 pyramidal cells consistently reduced the amplitude of EPSPs and GPSPs. Cholinergic inhibition of evoked and simulated EPSP waveforms displayed considerable voltage dependence, with the amplitude of the postsynaptic potentials progressively declining with membrane hyperpolarization indicating the involvement of an inwardly rectifying current. Extracellular Ba2+ (200 μm) and tertiapin (30 nm), a novel and selective blocker of G protein-activated, inwardly rectifying K+ (GIRK) channels, completely blocked the effect of CCh on GPSP amplitude. Muscarinic reduction of GPSPs was not sensitive to the M1 receptor-preferring antagonist, pirenzepine, but was suppressed by the M2 receptor-preferring antagonist, methoctramine, and by the allosteric M2 receptor antagonist, gallamine. In voltage-clamp recordings, CCh induced an ion current displaying inward rectification in the hyperpolarizing direction, which was identified as a GIRK current based on its sensitivity to low Ba2+ and tertiapin. Its pharmacological profile paralleled that of the cholinergic GPSP reduction. We link the observed reduction of postsynaptic potentials to the cholinergic activation of a GIRK conductance, which serves to partially shunt excitatory synaptic input. PMID:11533131

  7. G-protein-coupled inward rectifier potassium current contributes to ventricular repolarization

    DEFF Research Database (Denmark)

    Liang, Bo; Nissen, Jakob D; Laursen, Morten;

    2014-01-01

    The purpose of this study was to investigate the functional role of G-protein-coupled inward rectifier potassium (GIRK) channels in the cardiac ventricle.......The purpose of this study was to investigate the functional role of G-protein-coupled inward rectifier potassium (GIRK) channels in the cardiac ventricle....

  8. Inhibition of G protein-activated inwardly rectifying K+ channels by different classes of antidepressants.

    Directory of Open Access Journals (Sweden)

    Toru Kobayashi

    Full Text Available Various antidepressants are commonly used for the treatment of depression and several other neuropsychiatric disorders. In addition to their primary effects on serotonergic or noradrenergic neurotransmitter systems, antidepressants have been shown to interact with several receptors and ion channels. However, the molecular mechanisms that underlie the effects of antidepressants have not yet been sufficiently clarified. G protein-activated inwardly rectifying K(+ (GIRK, Kir3 channels play an important role in regulating neuronal excitability and heart rate, and GIRK channel modulation has been suggested to have therapeutic potential for several neuropsychiatric disorders and cardiac arrhythmias. In the present study, we investigated the effects of various classes of antidepressants on GIRK channels using the Xenopus oocyte expression assay. In oocytes injected with mRNA for GIRK1/GIRK2 or GIRK1/GIRK4 subunits, extracellular application of sertraline, duloxetine, and amoxapine effectively reduced GIRK currents, whereas nefazodone, venlafaxine, mianserin, and mirtazapine weakly inhibited GIRK currents even at toxic levels. The inhibitory effects were concentration-dependent, with various degrees of potency and effectiveness. Furthermore, the effects of sertraline were voltage-independent and time-independent during each voltage pulse, whereas the effects of duloxetine were voltage-dependent with weaker inhibition with negative membrane potentials and time-dependent with a gradual decrease in each voltage pulse. However, Kir2.1 channels were insensitive to all of the drugs. Moreover, the GIRK currents induced by ethanol were inhibited by sertraline but not by intracellularly applied sertraline. The present results suggest that GIRK channel inhibition may reveal a novel characteristic of the commonly used antidepressants, particularly sertraline, and contributes to some of the therapeutic effects and adverse effects.

  9. G protein-coupled inwardly rectifying potassium channels in dorsal root ganglion neurons

    Institute of Scientific and Technical Information of China (English)

    Xiao-fei GAO; Hai-lin ZHANG; Zhen-dong YOU; Chang-lin LU; Cheng HE

    2007-01-01

    Aim: G protein-coupled inwardly rectifying potassium channels (GIRK) are important for neuronal signaling and membrane excitability. In the present study, we intend to find whether GIRK channels express functionally in adult rat dorsal root ganglion (DRG) neurons. Methods: We used RT-PCR to detect mRNA for4 subunits of GIRK in the adult DRG. The whole-cell patch clamp recording was used to confirm GIRK channels functionally expressed. Results: The mRNA for the 4 subunits of GIRK were detected in the adult DRG. GTPγS enhanced inwardly rectifying potassium (K+) currents of the DRG neurons, while Ba2+inhibited such currents. Furthermore, the GIRK channels were shown to be coupled to the GABAB receptor, a member of the G protein-coupled receptor family, as baclofen increased the inwardly rectifying K+ currents. Conclusion: GIRK channels are expressed and functionally coupled with GABAB receptors in adult rat DRG neurons.

  10. Functional expression of a Kir2.1-like inwardly rectifying potassium channel in mouse mammary secretory cells.

    Science.gov (United States)

    Kamikawa, Akihiro; Ishikawa, Toru

    2014-02-01

    K(+) channels in mammary secretory (MS) cells are believed to play a role in transcellular electrolyte transport and thus determining ionic composition of the aqueous phase of milk. However, direct evidence for specific K(+) channel activity in native MS cells is lacking at the single-cell level. Here, we show for the first time that an inwardly rectifying K(+) (Kir) channel is functionally expressed in fully differentiated MS cells that were freshly isolated from the mammary gland of lactating mice. Using the standard whole cell patch-clamp technique, we found that mouse MS cells consistently displayed a K(+) current, whose electrophysiological properties are similar to those previously reported for Kir2.x channels, particularly Kir2.1: 1) current-voltage relationship with strong inward rectification, 2) slope conductance approximately proportional to the square root of external K(+) concentration, 3) voltage- and time-dependent and high-affinity block by external Ba(2+), and 4) voltage-dependent inhibition by external Cs(+). Accordingly, RT-PCR analysis revealed the gene expression of Kir2.1, but not Kir2.2, Kir2.3, and Kir2.4, in lactating mouse mammary gland, and immunohistochemical staining showed Kir2.1 protein expression in the secretory cells. Cell-attached patch recordings from MS cells revealed that a 31-pS K(+) channel with strong inward rectification was likely active at the resting membrane potential. Collectively, the present work demonstrates that a functional Kir2.1-like channel is expressed in lactating mouse MS cells. We propose that the channel might be involved, at least in part, in secretion and/or preservation of ionic components of milk stored into the lumen of these cells.

  11. Hydrogen Sulfide Regulates Inward-Rectifying K+ Channels in Conjunction with Stomatal Closure1[OPEN

    Science.gov (United States)

    Papanatsiou, Maria; Scuffi, Denisse; Blatt, Michael R.; García-Mata, Carlos

    2015-01-01

    Hydrogen sulfide (H2S) is the third biological gasotransmitter, and in animals, it affects many physiological processes by modulating ion channels. H2S has been reported to protect plants from oxidative stress in diverse physiological responses. H2S closes stomata, but the underlying mechanism remains elusive. Here, we report the selective inactivation of current carried by inward-rectifying K+ channels of tobacco (Nicotiana tabacum) guard cells and show its close parallel with stomatal closure evoked by submicromolar concentrations of H2S. Experiments to scavenge H2S suggested an effect that is separable from that of abscisic acid, which is associated with water stress. Thus, H2S seems to define a unique and unresolved signaling pathway that selectively targets inward-rectifying K+ channels. PMID:25770153

  12. Conductance properties of the inwardly rectifying channel, Kir3.2: molecular and Brownian dynamics study.

    Science.gov (United States)

    Hilder, Tamsyn A; Chung, Shin-Ho

    2013-02-01

    Using the recently unveiled crystal structure, and molecular and Brownian dynamics simulations, we elucidate several conductance properties of the inwardly rectifying potassium channel, Kir3.2, which is implicated in cardiac and neurological disorders. We show that the pore is closed by a hydrophobic gating mechanism similar to that observed in Kv1.2. Once open, potassium ions move into, but not out of, the cell. The asymmetrical current-voltage relationship arises from the lack of negatively charged residues at the narrow intracellular mouth of the channel. When four phenylalanine residues guarding the intracellular gate are mutated to glutamate residues, the channel no longer shows inward rectification. Inward rectification is restored in the mutant Kir3.2 when it becomes blocked by intracellular Mg(2+). Tertiapin, a polypeptide toxin isolated from the honey bee, is known to block several subtypes of the inwardly rectifying channels with differing affinities. We identify critical residues in the toxin and Kir3.2 for the formation of the stable complex. A lysine residue of tertiapin protrudes into the selectivity filter of Kir3.2, while two other basic residues of the toxin form hydrogen bonds with acidic residues located just outside the channel entrance. The depth of the potential of mean force encountered by tertiapin is -16.1kT, thus indicating that the channel will be half-blocked by 0.4μM of the toxin.

  13. Analysis of G-protein-activated inward rectifying K(+) (GIRK) channel currents upon GABAB receptor activation in rat supraoptic neurons.

    Science.gov (United States)

    Harayama, Nobuya; Kayano, Tomohiko; Moriya, Taiki; Kitamura, Naoki; Shibuya, Izumi; Tanaka-Yamamoto, Keiko; Uezono, Yasuhito; Ueta, Yoichi; Sata, Takeyoshi

    2014-12-03

    While magnocellular neurons in the supraoptic nucleus (SON) possess rich Gi/o-mediated mechanisms, molecular and cellular properties of G-protein-activated inwardly rectifying K(+) (GIRK) channels have been controversial. Here, properties of GIRK channels are examined by RT-PCR and whole-cell patch-clamp techniques in rat SON neurons. Patch clamp experiments showed that the selective GABAB agonist, baclofen, enhanced currents in a high K(+) condition. The baclofen-enhanced currents exhibited evident inward rectification and were blocked by the selective GABAB antagonist, CGP55845A, the IRK channel blocker, Ba(2+), and the selective GIRK channel blocker, tertiapin, indicating that baclofen activates GIRK channels via GABAB receptors. The GIRK currents were abolished by N-ethylmaleimide pretreatment, and prolonged by GTPγS inclusion in the patch pipette, suggesting that Gi/o proteins are involved. RT-PCR analysis revealed mRNAs for all four GIRK 1-4 channels and for both GABABR1 and GABABR2 receptors in rat SON. However, the concentration-dependency of the baclofen-induced activation of GIRK currents had an EC50 of 110 µM, which is about 100 times higher than that of baclofen-induced inhibition of voltage-dependent Ca(2+) channels. Moreover, baclofen caused no significant changes in the membrane potential and the firing rate. These results suggest that although GIRK channels can be activated by GABAB receptors via the Gi/o pathway, this occurs at high agonist concentrations, and thus may not be a physiological mechanism regulating the function of SON neurons. This property that the membrane potential receives little influence from GIRK currents seems to be uncommon for CNS neurons possessing rich Gi/o-coupled receptors, and could be a special feature of rat SON neurons. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Inward-rectifying potassium channelopathies: new insights into disorders of sodium and potassium homeostasis.

    Science.gov (United States)

    Cheng, Chih-Jen; Sung, Chih-Chien; Huang, Chou-Long; Lin, Shih-Hua

    2015-03-01

    Inward-rectifying potassium (Kir) channels allow more inward than outward potassium flux when channels are open in mammalian cells. At physiological resting membrane potentials, however, they predominantly mediate outward potassium flux and play important roles in regulating the resting membrane potential in diverse cell types and potassium secretion in the kidneys. Mutations of Kir channels cause human hereditary diseases collectively called Kir channelopathies, many of which are characterized by disorders of sodium and potassium homeostasis. Studies on these genetic Kir channelopathies have shed light on novel pathophysiological mechanisms, including renal sodium and potassium handling, potassium shifting in skeletal muscles, and aldosterone production in the adrenal glands. Here, we review several recent advances in Kir channels and their clinical implications in sodium and potassium homeostasis.

  15. G-protein-coupled inward rectifier potassium channels involved in corticostriatal presynaptic modulation.

    Science.gov (United States)

    Meneses, David; Mateos, Verónica; Islas, Gustavo; Barral, Jaime

    2015-09-01

    Presynaptic modulation has been associated mainly with calcium channels but recent data suggests that inward rectifier potassium channels (K(IR)) also play a role. In this work we set to characterize the role of presynaptic K(IR) channels in corticostriatal synaptic transmission. We elicited synaptic potentials in striatum by stimulating cortical areas and then determined the synaptic responses of corticostriatal synapsis by using paired pulse ratio (PPR) in the presence and absence of several potassium channel blockers. Unspecific potassium channels blockers Ba(2+) and Cs(+) reduced the PPR, suggesting that these channels are presynaptically located. Further pharmacological characterization showed that application of tertiapin-Q, a specific K(IR)3 channel family blocker, also induced a reduction of PPR, suggesting that K(IR)3 channels are present at corticostriatal terminals. In contrast, exposure to Lq2, a specific K(IR)1.1 inward rectifier potassium channel, did not induce any change in PPR suggesting the absence of these channels in the presynaptic corticostriatal terminals. Our results indicate that K(IR)3 channels are functionally expressed at the corticostriatal synapses, since blockage of these channels result in PPR decrease. Our results also help to explain how synaptic activity may become sensitive to extracellular signals mediated by G-protein coupled receptors. A vast repertoire of receptors may influence neurotransmitter release in an indirect manner through regulation of K(IR)3 channels.

  16. Decreased inward rectifier potassium current IK1 in dystrophin-deficient ventricular cardiomyocytes.

    Science.gov (United States)

    Rubi, Lena; Koenig, Xaver; Kubista, Helmut; Todt, Hannes; Hilber, Karlheinz

    2017-03-04

    Kir2.x channels in ventricular cardiomyocytes (most prominently Kir2.1) account for the inward rectifier potassium current IK1, which controls the resting membrane potential and the final phase of action potential repolarization. Recently it was hypothesized that the dystrophin-associated protein complex (DAPC) is important in the regulation of Kir2.x channels. To test this hypothesis, we investigated potential IK1 abnormalities in dystrophin-deficient ventricular cardiomyocytes derived from the hearts of Duchenne muscular dystrophy mouse models. We found that IK1 was substantially diminished in dystrophin-deficient cardiomyocytes when compared to wild type myocytes. This finding represents the first functional evidence for a significant role of the DAPC in the regulation of Kir2.x channels.

  17. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K+ Current: A Simulation Study

    Science.gov (United States)

    Zhang, Yue; Li, Qince; Zhang, Henggui

    2016-01-01

    Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K+ current (IK1). In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker. PMID:26998484

  18. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K+ Current: A Simulation Study

    Directory of Open Access Journals (Sweden)

    Yue Zhang

    2016-01-01

    Full Text Available Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs could show pacemaker activity, which was induced by depressing inward-rectifier K+ current (IK1. In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker.

  19. Characterization of the chicken inward rectifier K+ channel IRK1/Kir2.1 gene

    Directory of Open Access Journals (Sweden)

    Locke Emily

    2004-11-01

    Full Text Available Abstract Background Inward rectifier potassium channels (IRK contribute to the normal function of skeletal and cardiac muscle cells. The chick inward rectifier K+ channel cIRK1/Kir2.1 is expressed in skeletal muscle, heart, brain, but not in liver; a distribution similar but not identical to that of mouse Kir2.1. We set out to explore regulatory domains of the cIRK1 promoter that enhance or inhibit expression of the gene in different cell types. Results We cloned and characterized the 5'-flanking region of cIRK1. cIRK1 contains two exons with splice sites in the 5'-untranslated region, a structure similar to mouse and human orthologs. cIRK1 has multiple transcription initiation sites, a feature also seen in mouse. However, while the chicken and mouse promoter regions share many regulatory motifs, cIRK1 possesses a GC-richer promoter and a putative TATA box, which appears to positively regulate gene expression. We report here the identification of several candidate cell/tissue specific cIRK1 regulatory domains by comparing promoter activities in expressing (Qm7 and non-expressing (DF1 cells using in vitro transcription assays. Conclusion While multiple transcription initiation sites and the combinatorial function of several domains in activating cIRK1 expression are similar to those seen in mKir2.1, the cIRK1 promoter differs by the presence of a putative TATA box. In addition, several domains that regulate the gene's expression differentially in muscle (Qm7 and fibroblast cells (DF1 were identified. These results provide fundamental data to analyze cIRK1 transcriptional mechanisms. The control elements identified here may provide clues to the tissue-specific expression of this K+ channel.

  20. Role of inward rectifier potassium channels in salivary gland function and sugar feeding of the fruit fly, Drosophila melanogaster

    Science.gov (United States)

    The arthropod salivary gland is of critical importance for horizontal transmission of pathogens, yet a detailed understanding of the ion conductance pathways responsible for saliva production and excretion is lacking. A superfamily of potassium ion channels, known as inward rectifying potassium (Ki...

  1. ATP-sensitive inwardly rectifying potassium channel modulators alter cardiac function in honey bees.

    Science.gov (United States)

    O'Neal, Scott T; Swale, Daniel R; Bloomquist, Jeffrey R; Anderson, Troy D

    2017-05-01

    ATP-sensitive inwardly rectifying potassium (KATP) channels couple cellular metabolism to the membrane potential of the cell and play an important role in a variety of tissue types, including the insect dorsal vessel, making them a subject of interest not only for understanding invertebrate physiology, but also as a potential target for novel insecticides. Most of what is known about these ion channels is the result of work performed in mammalian systems, with insect studies being limited to only a few species and physiological systems. The goal of this study was to investigate the role that KATP channels play in regulating cardiac function in a model social insect, the honey bee (Apis mellifera), by examining the effects that modulators of these ion channels have on heart rate. Heart rate decreased in a concentration-dependent manner, relative to controls, with the application of the KATP channel antagonist tolbutamide and KATP channel blockers barium and magnesium, whereas heart rate increased with the application of a low concentration of the KATP channel agonist pinacidil, but decreased at higher concentrations. Furthermore, pretreatment with barium magnified the effects of tolbutamide treatment and eliminated the effects of pinacidil treatment at select concentrations. The data presented here confirm a role for KATP channels in the regulation of honey bee dorsal vessel contractions and provide insight into the underlying physiology that governs the regulation of bee cardiac function. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Keppen-Lubinsky Syndrome Is Caused by Mutations in the Inwardly Rectifying K+ Channel Encoded by KCNJ6

    OpenAIRE

    Masotti, Andrea; Uva, Paolo; Davis-Keppen, Laura; Basel-Vanagaite, Lina; Cohen, Lior; Pisaneschi, Elisa; Celluzzi, Antonella; Bencivenga, Paola; Fang, Mingyan; Tian, Mingyu; Xu, Xun; Cappa, Marco; Dallapiccola, Bruno

    2015-01-01

    Keppen-Lubinsky syndrome (KPLBS) is a rare disease mainly characterized by severe developmental delay and intellectual disability, microcephaly, large prominent eyes, a narrow nasal bridge, a tented upper lip, a high palate, an open mouth, tightly adherent skin, an aged appearance, and severe generalized lipodystrophy. We sequenced the exomes of three unrelated individuals affected by KPLBS and found de novo heterozygous mutations in KCNJ6 (GIRK2), which encodes an inwardly rectifying potassi...

  3. Regulating role of acetylcholine and its antagonists in inward rectified K~+ channels from guard cell protoplasts of Vicia faba

    Institute of Scientific and Technical Information of China (English)

    冷强; 花宝光; 郭玉海; 娄成后

    2000-01-01

    The inward rectified potassium current of Vicia faba guard cell protoplasts treated with acetylcholine (ACh) or the antagonists of its receptors were recorded by employing the patch clamp technique. The results show that ACh at lower concentrations increases the inward K+ current, in contrast, ACh at higher concentrations inhibits it. Treated with d-Tubocurarine (d-Tub), an antagonist of the nicotine ACh receptor (nAChR) inhibits the inward K+ current by 30%. Treated with atropine (Atr), an antagonist of the muscarine (Mus) ACh receptor (mAChR) also inhibits it by 36%. However, if guard cell protoplasts are treated with d-Tub and Atr together, the inward K+ current is inhibited by 60%-75%. Tetraethylammonium chloride (TEA), a strong inhibitor of K+ channels has no effect on the inward K+ current regulated by ACh, suggesting that there are inward K+ channels modulated by AChRs on the membrane of the guard cell protoplasts. These data demonstrate an ACh-regulated mechanism for stomatal movement.

  4. Regulating role of acetylcholine and its antagonists in inward rectified K+ channels from guard cell protoplasts of Vicia faba

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The inward rectified potassium current of Vicia faba guard cell protoplasts treated with acetylcholine (ACh) or the antagonists of its receptors were recorded by employing the patch clamp technique. The results show that ACh at lower concentrations increases the inward K+ current, in contrast, ACh at higher concentrations inhibits it. Treated with d-Tubocurarine (d-Tub), an antagonist of the nicotine ACh receptor (nAChR) inhibits the inward K+ current by 30%. Treated with atropine (Atr), an antagonist of the muscarine (Mus) ACh receptor (mAChR) also inhibits it by 36%.However,if guard cell protoplasts are treated with d-Tub and Atr together, the inward K+ current is inhibited by 60%-75%. Tetraethylammonium chloride (TEA), a strong inhibitor of K+ channels has no effect on the inward K+ current regulated by ACh, suggesting that there are inward K+ channels modulated by AChRs on the membrane of the guard cell protoplasts. These data demonstrate an ACh-regulated mechanism for stomatal movement.

  5. Molecular characterization of genes encoding inward rectifier potassium (Kir) channels in the bed bug (Cimex lectularius).

    Science.gov (United States)

    Mamidala, Praveen; Mittapelly, Priyanka; Jones, Susan C; Piermarini, Peter M; Mittapalli, Omprakash

    2013-04-01

    The molecular genetics of inward-rectifier potassium (Kir) channels in insects is poorly understood. To date, Kir channel genes have been characterized only from a few representative dipterans (i.e., fruit flies and mosquitoes). The goal of the present study was to characterize Kir channel cDNAs in a hemipteran, the bed bug (Cimex lectularius). Using our previously reported bed bug transcriptome (RNA-seq), we identified two cDNAs that encode putative Kir channels. One was a full-length cDNA that encodes a protein belonging to the insect 'Kir3' clade, which we designate as 'ClKir3'. The other was a partial cDNA that encodes a protein with similarity to both the insect 'Kir1' and 'Kir2' clades, which we designate as 'ClKir1/2'. Quantitative real-time PCR analysis revealed that ClKir1/2 and ClKir3 exhibited peak expression levels in late-instar nymphs and early-instar nymphs, respectively. Furthermore, ClKir3, but not ClKir1/2, showed tissue-specific expression in Malpighian tubules of adult bed bugs. Lastly, using an improved procedure for delivering double-stranded RNA (dsRNA) to male and female bed bugs (via the cervical membrane) we demonstrate rapid and systemic knockdown of ClKir3 transcripts. In conclusion, we demonstrate that the bed bug possesses at least two genes encoding Kir channels, and that RNAi is possible for at least Kir3, thereby offering a potential approach for elucidating the roles of Kir channel genes in bed bug physiology.

  6. Nicotine at clinically relevant concentrations affects atrial inward rectifier potassium current sensitive to acetylcholine.

    Science.gov (United States)

    Bébarová, Markéta; Matejovič, Peter; Švecová, Olga; Kula, Roman; Šimurdová, Milena; Šimurda, Jiří

    2017-02-03

    Nicotine abuse is associated with variety of diseases including arrhythmias, most often atrial fibrillation (AF). Altered inward rectifier potassium currents including acetylcholine-sensitive current I K(Ach) are known to be related to AF pathogenesis. Since relevant data are missing, we aimed to investigate I K(Ach) changes at clinically relevant concentrations of nicotine. Experiments were performed by the whole cell patch clamp technique at 23 ± 1 °C on isolated rat atrial myocytes. Nicotine was applied at following concentrations: 4, 40 and 400 nM; ethanol at 20 mM (∼0.09%). Nicotine at 40 and 400 nM significantly activated constitutively active component of I K(Ach) with the maximum effect at 40 nM (an increase by ∼100%); similar effect was observed at -110 and -50 mV. Changes at 4 nM nicotine were negligible on average. Coapplication of 40 nM nicotine and 20 mM ethanol (which is also known to activate this current) did not show cumulative effect. In the case of acetylcholine-induced component of I K(Ach), a dual effect of nicotine and its correlation with the current magnitude in control were apparent: the current was increased by nicotine in the cells showing small current in control and vice versa. The effect of 40 and 400 nM nicotine on acetylcholine-induced component of I K(Ach) was significantly different at -110 and -50 mV. We conclude that nicotine at clinically relevant concentrations significantly increased constitutively active component of I K(Ach) and showed a dual effect on its acetylcholine-induced component, similarly as ethanol. Synchronous application of nicotine and ethanol did not cause additive effect.

  7. Expression of G-protein inwardly rectifying potassium channels (GIRKs in lung cancer cell lines

    Directory of Open Access Journals (Sweden)

    Schuller Hildegard M

    2005-08-01

    Full Text Available Abstract Background Previous data from our laboratory has indicated that there is a functional link between the β-adrenergic receptor signaling pathway and the G-protein inwardly rectifying potassium channel (GIRK1 in human breast cancer cell lines. We wanted to determine if GIRK channels were expressed in lung cancers and if a similar link exists in lung cancer. Methods GIRK1-4 expression and levels were determined by reverse transcription polymerase chain reaction (RT-PCR and real-time PCR. GIRK protein levels were determined by western blots and cell proliferation was determined by a 5-bromo-2'-deoxyuridine (BrdU assay. Results GIRK1 mRNA was expressed in three of six small cell lung cancer (SCLC cell lines, and either GIRK2, 3 or 4 mRNA expression was detected in all six SCLC cell lines. Treatment of NCI-H69 with β2-adrenergic antagonist ICI 118,551 (100 μM daily for seven days led to slight decreases of GIRK1 mRNA expression levels. Treatment of NCI-H69 with the β-adrenergic agonist isoproterenol (10 μM decreased growth rates in these cells. The GIRK inhibitor U50488H (2 μM also inhibited proliferation, and this decrease was potentiated by isoproterenol. In the SCLC cell lines that demonstrated GIRK1 mRNA expression, we also saw GIRK1 protein expression. We feel these may be important regulatory pathways since no expression of mRNA of the GIRK channels (1 & 2 was found in hamster pulmonary neuroendocrine cells, a suggested cell of origin for SCLC, nor was GIRK1 or 2 expression found in human small airway epithelial cells. GIRK (1,2,3,4 mRNA expression was also seen in A549 adenocarcinoma and NCI-H727 carcinoid cell lines. GIRK1 mRNA expression was not found in tissue samples from adenocarcinoma or squamous cancer patients, nor was it found in NCI-H322 or NCI-H441 adenocarcinoma cell lines. GIRK (1,3,4 mRNA expression was seen in three squamous cell lines, GIRK2 was only expressed in one squamous cell line. However, GIRK1 protein

  8. Inward Rectifier K+ Currents Are Regulated by CaMKII in Endothelial Cells of Primarily Cultured Bovine Pulmonary Arteries.

    Directory of Open Access Journals (Sweden)

    Lihui Qu

    Full Text Available Endothelium lines the interior surface of vascular walls and regulates vascular tones. The endothelial cells sense and respond to chemical and mechanical stimuli in the circulation, and couple the stimulus signals to vascular smooth muscles, in which inward rectifier K+ currents (Kir play an important role. Here we applied several complementary strategies to determine the Kir subunit in primarily cultured pulmonary arterial endothelial cells (PAECs that was regulated by the Ca2+/calmodulin (CaM-dependent protein kinase II (CaMKII. In whole-cell voltage clamp, the Kir currents were sensitive to micromolar concentrations of extracellular Ba2+. In excised inside-out patches, an inward rectifier K+ current was observed with single-channel conductance 32.43 ± 0.45 pS and Popen 0.27 ± 0.04, which were consistent with known unitary conductance of Kir 2.1. RT-PCR and western blot results showed that expression of Kir 2.1 was significantly stronger than that of other subtypes in PAECs. Pharmacological analysis of the Kir currents demonstrated that insensitivity to intracellular ATP, pinacidil, glibenclamide, pH, GDP-β-S and choleratoxin suggested that currents weren't determined by KATP, Kir2.3, Kir2.4 and Kir3.x. The currents were strongly suppressed by exposure to CaMKII inhibitor W-7 and KN-62. The expression of Kir2.1 was inhibited by knocking down CaMKII. Consistently, vasodilation was suppressed by Ba2+, W-7 and KN-62 in isolated and perfused pulmonary arterial rings. These results suggest that the PAECs express an inward rectifier K+ current that is carried dominantly by Kir2.1, and this K+ channel appears to be targeted by CaMKII-dependent intracellular signaling systems.

  9. Inhibition by acrolein of light-induced stomatal opening through inhibition of inward-rectifying potassium channels in Arabidopsis thaliana.

    Science.gov (United States)

    Islam, Md Moshiul; Ye, Wenxiu; Matsushima, Daiki; Khokon, Md Atiqur Rahman; Munemasa, Shintaro; Nakamura, Yoshimasa; Murata, Yoshiyuki

    2015-01-01

    Acrolein is a reactive α,β-unsaturated aldehyde derived from lipid peroxides, which are produced in plants under a variety of stress. We investigated effects of acrolein on light-induced stomatal opening using Arabidopsis thaliana. Acrolein inhibited light-induced stomatal opening in a dose-dependent manner. Acrolein at 100 μM inhibited plasma membrane inward-rectifying potassium (Kin) channels in guard cells. Acrolein at 100 μM inhibited Kin channel KAT1 expressed in a heterologous system using Xenopus leaves oocytes. These results suggest that acrolein inhibits light-induced stomatal opening through inhibition of Kin channels in guard cells.

  10. Keppen-Lubinsky syndrome is caused by mutations in the inwardly rectifying K+ channel encoded by KCNJ6.

    Science.gov (United States)

    Masotti, Andrea; Uva, Paolo; Davis-Keppen, Laura; Basel-Vanagaite, Lina; Cohen, Lior; Pisaneschi, Elisa; Celluzzi, Antonella; Bencivenga, Paola; Fang, Mingyan; Tian, Mingyu; Xu, Xun; Cappa, Marco; Dallapiccola, Bruno

    2015-02-05

    Keppen-Lubinsky syndrome (KPLBS) is a rare disease mainly characterized by severe developmental delay and intellectual disability, microcephaly, large prominent eyes, a narrow nasal bridge, a tented upper lip, a high palate, an open mouth, tightly adherent skin, an aged appearance, and severe generalized lipodystrophy. We sequenced the exomes of three unrelated individuals affected by KPLBS and found de novo heterozygous mutations in KCNJ6 (GIRK2), which encodes an inwardly rectifying potassium channel and maps to the Down syndrome critical region between DIRK1A and DSCR4. In particular, two individuals shared an in-frame heterozygous deletion of three nucleotides (c.455_457del) leading to the loss of one amino acid (p.Thr152del). The third individual was heterozygous for a missense mutation (c.460G>A) which introduces an amino acid change from glycine to serine (p.Gly154Ser). In agreement with animal models, the present data suggest that these mutations severely impair the correct functioning of this potassium channel. Overall, these results establish KPLBS as a channelopathy and suggest that KCNJ6 (GIRK2) could also be a candidate gene for other lipodystrophies. We hope that these results will prompt investigations in this unexplored class of inwardly rectifying K(+) channels.

  11. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K⁺ Current: A Simulation Study.

    Science.gov (United States)

    Zhang, Yue; Wang, Kuanquan; Li, Qince; Zhang, Henggui

    2016-01-01

    Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K(+) current (I K1). In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker.

  12. Stress-induced glucocorticoid signaling remodels neurovascular coupling through impairment of cerebrovascular inwardly rectifying K+ channel function.

    Science.gov (United States)

    Longden, Thomas A; Dabertrand, Fabrice; Hill-Eubanks, David C; Hammack, Sayamwong E; Nelson, Mark T

    2014-05-20

    Studies of stress effects on the brain have traditionally focused on neurons, without considering the cerebral microcirculation. Here we report that stress impairs neurovascular coupling (NVC), the process that matches neuronal activity with increased local blood flow. A stressed phenotype was induced in male rats by administering a 7-d heterotypical stress paradigm. NVC was modeled by measuring parenchymal arteriole (PA) vasodilation in response to neuronal stimulation in amygdala brain slices. After stress, vasodilation of PAs to neuronal stimulation was greatly reduced, and dilation of isolated PAs to external K(+) was diminished, suggesting a defect in smooth muscle inwardly rectifying K(+) (KIR) channel function. Consistent with these observations, stress caused a reduction in PA KIR2.1 mRNA and smooth muscle KIR current density, and blocking KIR channels significantly inhibited NVC in control, but not in stressed, slices. Delivery of corticosterone for 7 d (without stressors) or RU486 (before stressors) mimicked and abrogated NVC impairment by stress, respectively. We conclude that stress causes a glucocorticoid-mediated decrease in functional KIR channels in amygdala PA myocytes. This renders arterioles less responsive to K(+) released from astrocytic endfeet during NVC, leading to impairment of this process. Because the fidelity of NVC is essential for neuronal health, the impairment characterized here may contribute to the pathophysiology of brain disorders with a stress component.

  13. An insecticide resistance-breaking mosquitocide targeting inward rectifier potassium channels in vectors of Zika virus and malaria.

    Science.gov (United States)

    Swale, Daniel R; Engers, Darren W; Bollinger, Sean R; Gross, Aaron; Inocente, Edna Alfaro; Days, Emily; Kanga, Fariba; Johnson, Reed M; Yang, Liu; Bloomquist, Jeffrey R; Hopkins, Corey R; Piermarini, Peter M; Denton, Jerod S

    2016-11-16

    Insecticide resistance is a growing threat to mosquito control programs around the world, thus creating the need to discover novel target sites and target-specific compounds for insecticide development. Emerging evidence suggests that mosquito inward rectifier potassium (Kir) channels represent viable molecular targets for developing insecticides with new mechanisms of action. Here we describe the discovery and characterization of VU041, a submicromolar-affinity inhibitor of Anopheles (An.) gambiae and Aedes (Ae.) aegypti Kir1 channels that incapacitates adult female mosquitoes from representative insecticide-susceptible and -resistant strains of An. gambiae (G3 and Akron, respectively) and Ae. aegypti (Liverpool and Puerto Rico, respectively) following topical application. VU041 is selective for mosquito Kir channels over several mammalian orthologs, with the exception of Kir2.1, and is not lethal to honey bees. Medicinal chemistry was used to develop an analog, termed VU730, which retains activity toward mosquito Kir1 but is not active against Kir2.1 or other mammalian Kir channels. Thus, VU041 and VU730 are promising chemical scaffolds for developing new classes of insecticides to combat insecticide-resistant mosquitoes and the transmission of mosquito-borne diseases, such as Zika virus, without harmful effects on humans and beneficial insects.

  14. Eliciting renal failure in mosquitoes with a small-molecule inhibitor of inward-rectifying potassium channels.

    Directory of Open Access Journals (Sweden)

    Rene Raphemot

    Full Text Available Mosquito-borne diseases such as malaria and dengue fever take a large toll on global health. The primary chemical agents used for controlling mosquitoes are insecticides that target the nervous system. However, the emergence of resistance in mosquito populations is reducing the efficacy of available insecticides. The development of new insecticides is therefore urgent. Here we show that VU573, a small-molecule inhibitor of mammalian inward-rectifying potassium (Kir channels, inhibits a Kir channel cloned from the renal (Malpighian tubules of Aedes aegypti (AeKir1. Injection of VU573 into the hemolymph of adult female mosquitoes (Ae. aegypti disrupts the production and excretion of urine in a manner consistent with channel block of AeKir1 and renders the mosquitoes incapacitated (flightless or dead within 24 hours. Moreover, the toxicity of VU573 in mosquitoes (Ae. aegypti is exacerbated when hemolymph potassium levels are elevated, suggesting that Kir channels are essential for maintenance of whole-animal potassium homeostasis. Our study demonstrates that renal failure is a promising mechanism of action for killing mosquitoes, and motivates the discovery of selective small-molecule inhibitors of mosquito Kir channels for use as insecticides.

  15. Characteristics of the inward-rectifying potassium current in mouse ventricular myocytes and its relation to early after-depolarization

    Institute of Scientific and Technical Information of China (English)

    周盈颖; 郝雪梅; 范劲松; 刘泰(木逢)

    1996-01-01

    The properties of the inward-rectifying potassium current (IK1) were studied in the single myocytes isolated from adult mouse ventricles by the whole-cell patch-damp technique for the first time. Most of the properties of IK1 including channel conductances, activation, inactivation, rectification and external K+ sensitivity in mouse ventricular myocyte were similar to those in other species, but the current-voltage (1-V) curve of mouse ventricular myocyte showed no negative slope, i.e the slope in the range of membrane potential 50 mV positive to the reversal potential (VRev) was virtually flat and remained at a low current level ((59±39) pA). Under the superfusion of Tyrode’s solution with 3mmol/L K+ and 3mmol/L Cs+, IK1 in the above region nearly decreased to zero, and then the early after-depolarization (EAD) occurred. The results suggest that this distinctive characteristic of IK1 in mouse ventricular myocyte may relate to the high susceptibility to EA0 in mouse myocardium. The inhibition of IK1 se

  16. Synergistic activation of G protein-gated inwardly rectifying potassium channels by cholesterol and PI(4,5)P2.

    Science.gov (United States)

    Bukiya, Anna N; Rosenhouse-Dantsker, Avia

    2017-07-01

    G-protein gated inwardly rectifying potassium (GIRK or Kir3) channels play a major role in the control of the heart rate, and require the membrane phospholipid phosphatidylinositol-bis-phosphate (PI(4,5)P2) for activation. Recently, we have shown that the activity of the heterotetrameric Kir3.1/Kir3.4 channel that underlies atrial KACh currents was enhanced by cholesterol. Similarly, the activities of both the Kir3.4 homomer and its active pore mutant Kir3.4* (Kir3.4_S143T) were also enhanced by cholesterol. Here we employ planar lipid bilayers to investigate the crosstalk between PI(4,5)P2 and cholesterol, and demonstrate that these two lipids act synergistically to activate Kir3.4* currents. Further studies using the Xenopus oocytes heterologous expression system suggest that PI(4,5)P2 and cholesterol act via distinct binding sites. Whereas PI(4,5)P2 binds to the cytosolic domain of the channel, the putative binding region of cholesterol is located at the center of the transmembrane domain overlapping the central glycine hinge region of the channel. Together, our data suggest that changes in the levels of two key membrane lipids - cholesterol and PI(4,5)P2 - could act in concert to provide fine-tuning of Kir3 channel function. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Dual modulation of inward rectifier potassium currents in olfactory neuronal cells by promiscuous G protein coupling of the oxytocin receptor.

    Science.gov (United States)

    Gravati, Marta; Busnelli, Marta; Bulgheroni, Elisabetta; Reversi, Alessandra; Spaiardi, Paolo; Parenti, Marco; Toselli, Mauro; Chini, Bice

    2010-09-01

    Oxytocin receptor is a seven transmembrane receptor widely expressed in the CNS that triggers G(i) or G(q) protein-mediated signaling cascades leading to the regulation of a variety of neuroendocrine and cognitive functions. We decided to investigate whether and how the promiscuous receptor/G protein coupling affects neuronal excitability. As an experimental model, we used the immortalized gonadotropin-releasing hormone-positive GN11 cell line displaying the features of immature, migrating olfactory neurons. Using RT-PCR analysis, we detected the presence of oxytocin receptors whose stimulation by oxytocin led to the accumulation of inositol phosphates and to the inhibition of cell proliferation, and the expression of several inward rectifier (IR) K+ channel subtypes. Moreover, electrophysiological and pharmacological inspections using whole-cell patch-clamp recordings evidenced that in GN11 cells, IR channel subtypes are responsive to oxytocin. In particular, we found that: (i) peptide activation of receptor either inhibited or stimulated IR conductances, and (ii) IR current inhibition was mediated by a pertussis toxin-resistant G protein presumably of the G(q/11) subtype, and by phospholipase C, whereas IR current activation was achieved via receptor coupling to a pertussis toxin-sensitive G(i/o) protein. The findings suggest that neuronal excitability might be tuned by a single peptide receptor that mediates opposing effects on distinct K+ channels through the promiscuous coupling to different G proteins.

  18. Short-term desensitization of G-protein-activated, inwardly rectifying K+ (GIRK) currents in pyramidal neurons of rat neocortex.

    Science.gov (United States)

    Sickmann, Thomas; Alzheimer, Christian

    2003-10-01

    Whole cell recordings from acutely isolated rat neocortical pyramidal cells were performed to study the kinetics and the mechanisms of short-term desensitization of G-protein-activated, inwardly rectifying K+ (GIRK) currents during prolonged application (5 min) of baclofen, adenosine, or serotonin. Most commonly, desensitization of GIRK currents was characterized by a biphasic time course with average time constants for fast and slow desensitization in the range of 8 and 120 s, respectively. The time constants were independent of the agonist used to evoke the current. The biphasic time course was preserved in perforated-patch recordings, indicating that neither component of desensitization is attributable to cell dialysis. Desensitization of GIRK currents displayed a strong heterologous component in that application of a second agonist substantially reduced the responsiveness to a test agonist. Fast desensitization, but not slow desensitization, was lost in cells loaded with GDP, suggesting that the hydrolysis cycle of G proteins might underlie the initial, rapid current decline. Hydrolysis of phosphatidylinositol biphosphate is an unlikely candidate underlying short-term desensitization, because both components of desensitization were preserved in the presence of the phospholipase C inhibitor U73122. We conclude that short-term desensitization does neither result from receptor downregulation nor from altered channel gating but might involve modifications of the G-protein-dependent pathway that serves to translate receptor activation into channel opening.

  19. Biophysical characterization of inwardly rectifying potassium currents (I(K1) I(K,ACh), I(K,Ca)) using sinus rhythm or atrial fibrillation action potential waveforms

    DEFF Research Database (Denmark)

    Tang, Chuyi; Skibsbye, Lasse; Yuan, Lei

    2015-01-01

    to voltage protocols adapted from atrial action potentials recorded in human tissue at 1 and 3 Hz. The current recordings were performed in the HEK-293 heterologous cell system expressing either I(K1), I(K,ACh) or I(K,Ca) to establish the individual contribution of each of these currents during the voltage...... changes of atrial action potential waveforms. I(K1) primarily contributes to the atrial electrophysiology at the latter part of repolarization and during the diastolic phase, while both I(K,Ca) under high [Ca2+]i and I(K,ACh) contribute relatively most during repolarization.......Although several physiological, pathophysiological and regulatory properties of classical inward rectifier K+ current I(K1), G-protein coupled inwardly-rectifying K+ current I(K,ACh) and the small-conductance Ca2+ activated K+ current I(K,Ca) have been identified, quantitative biophysical details...

  20. Crystal Structure of the Eukaryotic Strong Inward-Rectifier K[superscript +] Channel Kir2.2 at 3.1 Å Resolution

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Xiao; Avalos, Jose L.; Chen, Jiayun; MacKinnon, Roderick; (Rockefeller)

    2010-03-29

    Inward-rectifier potassium (K{sup +}) channels conduct K{sup +} ions most efficiently in one direction, into the cell. Kir2 channels control the resting membrane voltage in many electrically excitable cells, and heritable mutations cause periodic paralysis and cardiac arrhythmia. We present the crystal structure of Kir2.2 from chicken, which, excluding the unstructured amino and carboxyl termini, is 90% identical to human Kir2.2. Crystals containing rubidium (Rb{sup +}), strontium (Sr{sup 2+}), and europium (Eu{sup 3+}) reveal binding sites along the ion conduction pathway that are both conductive and inhibitory. The sites correlate with extensive electrophysiological data and provide a structural basis for understanding rectification. The channel's extracellular surface, with large structured turrets and an unusual selectivity filter entryway, might explain the relative insensitivity of eukaryotic inward rectifiers to toxins. These same surface features also suggest a possible approach to the development of inhibitory agents specific to each member of the inward-rectifier K{sup +} channel family.

  1. Expression and localization of inwardly rectifying potassium channel Kit2.1 in glia cells of native bovine retina

    Institute of Scientific and Technical Information of China (English)

    PAN Ai-hua; LUO Xue-gang

    2005-01-01

    Objective The purpose of this study is to identify the molecular basis of the contacting -neuron membrane K+ conductance in glia cells of native bovine retina. Methods RT-PCR, Northern blot and Western blot analyses were used to detect the expression of the inwardly rectifying K+ (Kir) channel subunits Kir2.1 in native bovine RPE and neural retina. The distribution of Kir2.1 protein was determined in frozen sections of bovine retina-RPEchoroid by indirect immunofluorescence analysis. Results RT-PCR analysis reveals Kir2.1 transcript in both RPE and neural retina. In Northern blots, Kir2.1 probe hybridizes to an appropriately sized-transcript in neural retina but not in RPE. In Western blots, Kir2.1 antibody recognizes a major monomer of about 60 kDa in neural retina but not in RPE. Immunofluorescence reveals that Kir2.1 immunostaining is expressed at many parts of Muller cells, especially in the membrane domains of Muller cells that contact retinal neurons, i. e. , along the two stem processes,over the soma, and in the side branches extending into the synaptic layers. No immunostaining is seen in RPE. Doubling staining shows that Kir2.1 proteins and glutamine synthetase proteins which are a marker of Muller cell co-localized well. Conclusions These results reveal that Kir2.1 is localized in the Muller cells, no Kir2.1 in RPE. These data suggests that Kir2.1 may be involved in the transport of K+ in the bovine neural retina.

  2. Dynamic expression of genes encoding subunits of inward rectifier potassium (Kir) channels in the yellow fever mosquito Aedes aegypti.

    Science.gov (United States)

    Yang, Zhongxia; Statler, Bethanie-Michelle; Calkins, Travis L; Alfaro, Edna; Esquivel, Carlos J; Rouhier, Matthew F; Denton, Jerod S; Piermarini, Peter M

    2017-02-01

    Inward rectifier potassium (Kir) channels play fundamental roles in neuromuscular, epithelial, and endocrine function in mammals. Recent research in insects suggests that Kir channels play critical roles in the development, immune function, and excretory physiology of fruit flies and/or mosquitoes. Moreover, our group has demonstrated that mosquito Kir channels may serve as valuable targets for the development of novel insecticides. Here we characterize the molecular expression of 5 mRNAs encoding Kir channel subunits in the yellow fever mosquito, Aedes aegypti: Kir1, Kir2A-c, Kir2B, Kir2B', and Kir3. We demonstrate that 1) Kir mRNA expression is dynamic in whole mosquitoes, Malpighian tubules, and the midgut during development from 4th instar larvae to adult females, 2) Kir2B and Kir3 mRNA levels are reduced in 4th instar larvae when reared in water containing an elevated concentration (50mM) of KCl, but not NaCl, and 3) Kir mRNAs are differentially expressed in the Malpighian tubules, midgut, and ovaries within 24h after blood feeding. Furthermore, we provide the first characterization of Kir mRNA expression in the anal papillae of 4th instar larval mosquitoes, which indicates that Kir2A-c is the most abundant. Altogether, the data provide the first comprehensive characterization of Kir mRNA expression in Ae. aegypti and offer insights into the putative physiological roles of Kir subunits in this important disease vector. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Cholesterol up-regulates neuronal G protein-gated inwardly rectifying potassium (GIRK) channel activity in the hippocampus.

    Science.gov (United States)

    Bukiya, Anna N; Durdagi, Serdar; Noskov, Sergei; Rosenhouse-Dantsker, Avia

    2017-04-14

    Hypercholesterolemia is a well known risk factor for the development of neurodegenerative disease. However, the underlying mechanisms are mostly unknown. In recent years, it has become increasingly evident that cholesterol-driven effects on physiology and pathophysiology derive from its ability to alter the function of a variety of membrane proteins including ion channels. Yet, the effect of cholesterol on G protein-gated inwardly rectifying potassium (GIRK) channels expressed in the brain is unknown. GIRK channels mediate the actions of inhibitory brain neurotransmitters. As a result, loss of GIRK function can enhance neuron excitability, whereas gain of GIRK function can reduce neuronal activity. Here we show that in rats on a high-cholesterol diet, cholesterol levels in hippocampal neurons are increased. We also demonstrate that cholesterol plays a critical role in modulating neuronal GIRK currents. Specifically, cholesterol enrichment of rat hippocampal neurons resulted in enhanced channel activity. In accordance, elevated currents upon cholesterol enrichment were also observed in Xenopus oocytes expressing GIRK2 channels, the primary GIRK subunit expressed in the brain. Furthermore, using planar lipid bilayers, we show that although cholesterol did not affect the unitary conductance of GIRK2, it significantly enhanced the frequency of channel openings. Last, combining computational and functional approaches, we identified two putative cholesterol-binding sites in the transmembrane domain of GIRK2. These findings establish that cholesterol plays a critical role in modulating GIRK activity in the brain. Because up-regulation of GIRK function can reduce neuronal activity, our findings may lead to novel approaches for prevention and therapy of cholesterol-driven neurodegenerative disease. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  4. Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein-coupled inwardly rectifying (GIRK) channels.

    Science.gov (United States)

    Hablitz, L M; Molzof, H E; Paul, J R; Johnson, R L; Gamble, K L

    2014-11-15

    G protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time-of-day information. We sought to determine whether G protein-coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day-time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light-dark (LD) cycle than wild-type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non-photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY-induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non-photic-like phase advance of PER2::LUC rhythms on a Per2(Luc+/-) background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day-time resting membrane potential, providing a mechanism for the fine tuning responses to non-photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated.

  5. Investigations on contribution of glial inwardly-rectifying K+ current to membrane potential and ion flux: An experimental and theoretical study

    Directory of Open Access Journals (Sweden)

    Sheng-Nan Wu

    2015-01-01

    Full Text Available The inwardly rectifying K+ current [IK(IR] allows large inward K+ currents at potentials negative to K+ equilibrium potential (EK and it becomes small outward K+ currents at those positive to EK. How changes of such currents enriched in glial cells can influence the functions of glial cell, neurons, or both is not clearly defined, although mutations of Kir4.1 channels have been demonstrated to cause serious neurological disorders. In this study, we identified the presence of IK(IR in human glioma cells (U373 and U87 cells. The amplitude of IK(IR in U373 cells was subject to inhibition by amitriptyline, arecoline, or BaCl2. The activity of inwardly rectifying K+ channels was also clearly detected, and single-channel conductance of these channels was calculated to be around 23 pS. Moreover, based on a simulation model derived from neuron–glial interaction mediated by ion flux, we further found out that incorporation of glial IK(IR conductance into the model can significantly contribute to regulation of extracellular K+ concentrations and glial resting potential, particularly during high-frequency stimulation. Glial cells and neurons can mutually modulate their expression of ion channels through K+ ions released into the extracellular space. It is thus anticipated that glial IK(IR may be a potential target utilized to influence the activity of neuronal and glial cells as well as their interaction.

  6. Voltage-dependent K+ currents contribute to heterogeneity of olfactory ensheathing cells

    Science.gov (United States)

    Rela, Lorena; Piantanida, Ana Paula; Bordey, Angelique; Greer, Charles A.

    2015-01-01

    The olfactory nerve is permissive for axon growth throughout life. This has been attributed in part to the olfactory ensheathing glial cells that encompass the olfactory sensory neuron fascicles. Olfactory ensheathing cells also promote axon growth in vitro and when transplanted in vivo to sites of injury. The mechanisms involved remain largely unidentified owing in part to the limited knowledge of the physiological properties of ensheathing cells. Glial cells rely for many functions on the properties of the potassium channels expressed; however, those expressed in ensheathing cells are unknown. Here we show that olfactory ensheathing cells express voltage-dependent potassium currents compatible with inward rectifier (Kir) and delayed rectifier (KDR) channels. Together with gap junction coupling, these contribute to the heterogeneity of membrane properties observed in olfactory ensheathing cells. The relevance of K+ currents expressed by ensheathing cells is discussed in relation to plasticity of the olfactory nerve. PMID:25856239

  7. Selective inhibition of the Kir2 family of inward rectifier potassium channels by a small molecule probe: the discovery, SAR and pharmacological characterization of ML133

    Science.gov (United States)

    Wang, Hao-Ran; Wu, Meng; Yu, Haibo; Long, Shunyou; Stevens, Amy; Engers, Darren W.; Sackin, Henry; Daniels, J. Scott; Dawson, Eric S.; Hopkins, Corey R.; Lindsley, Craig W.; Li, Min; McManus, Owen B

    2011-01-01

    The Kir inward rectifying potassium channels have a broad tissue distribution and are implicated in a variety of functional roles. At least seven classes (Kir1 – Kir7) of structurally related inward rectifier potassium channels are known, and there are no selective small molecule tools to study their function. In an effort to develop selective Kir2.1 inhibitors, we performed a high-throughput screen (HTS) of more than 300,000 small molecules within the MLPCN for modulators of Kir2.1 function. Here we report one potent Kir2.1 inhibitor, ML133, which inhibits Kir2.1 with IC50 of 1.8 μM at pH 7.4 and 290 nM at pH 8.5, but exhibits little selectivity against other members of Kir2.x family channels. However, ML133 has no effect on Kir1.1 (IC50 > 300 μM), and displays weak activity for Kir4.1 (76 μM) and Kir7.1 (33 μM), making ML133 the most selective small molecule inhibitor of the Kir family reported to date. Due to the high homology within the Kir family, the channels share a common design of a pore region flanked by two transmembrane domains, identification of site(s) critical for isoform specificity would be an important basis for future development of more specific and potent Kir inhibitors. Using chimeric channels between Kir2.1 and Kir1.1 and site-directed mutagenesis, we have identified D172 and I176 within M2 segment of Kir2.1 as molecular determinants critical for the potency of ML133 mediated inhibition. Double mutation of the corresponding residues of Kir1.1 to those of Kir2.1 (N171D and C175I) transplants ML133 inhibition to Kir1.1. Together, the combination of a potent, Kir2 family selective inhibitor and identification of molecular determinants for the specificity provides both a tool and a model system to enable further mechanistic studies of modulation of Kir2 inward rectifier potassium channels. PMID:21615117

  8. Mitochondrial ATP-sensitive potassium channel activity and hypoxic preconditioning are independent of an inwardly rectifying potassium channel subunit in Caenorhabditis elegans.

    Science.gov (United States)

    Wojtovich, Andrew P; DiStefano, Peter; Sherman, Teresa; Brookes, Paul S; Nehrke, Keith

    2012-02-17

    Hypoxic preconditioning (HP) is an evolutionarily-conserved mechanism that protects an organism against stress. The mitochondrial ATP-sensitive K(+) channel (mK(ATP)) plays an essential role in the protective signaling, but remains molecularly undefined. Several lines of evidence suggest that mK(ATP) may arise from an inward rectifying K(+) channel (Kir). The genetic model organism Caenorhabditis elegans exhibits HP and displays mK(ATP) activity. Here, we investigate the tissue expression profile of the three C. elegans Kir genes and demonstrate that mutant strains where the irk genes have been deleted either individually or in combination can be protected by HP and exhibit robust mK(ATP) channel activity in purified mitochondria. These data suggest that the mK(ATP) in C. elegans does not arise from a Kir derived channel.

  9. Mitochondrial ATP-sensitive potassium channel activity and hypoxic preconditioning are independent of an inwardly rectifying potassium channel subunit in C. elegans

    Science.gov (United States)

    Wojtovich, Andrew P.; DiStefano, Peter; Sherman, Teresa; Brookes, Paul S.; Nehrke, Keith

    2012-01-01

    Hypoxic preconditioning (HP) is an evolutionarily-conserved mechanism that protects an organism against stress. The mitochondrial ATP-sensitive K+ channel (mKATP) plays an essential role in the protective signaling, but remains molecularly undefined. Several lines of evidence suggest that mKATP may arise from an inward rectifying K+ channel (Kir). The genetic model organism C. elegans exhibits HP and displays mKATP activity. Here, we investigate the tissue expression profile of the three C. elegans Kir genes and demonstrate that mutant strains where the irk genes have been deleted either individually or in combination can be protected by HP and exhibit robust mKATP channel activity in purified mitochondria. These data suggest that the mKATP in C. elegans does not arise from a Kir derived channel. PMID:22281198

  10. Diverse levels of an inwardly rectifying potassium conductance generate heterogeneous neuronal behavior in a population of dorsal cochlear nucleus pyramidal neurons.

    Science.gov (United States)

    Leao, Ricardo M; Li, Shuang; Doiron, Brent; Tzounopoulos, Thanos

    2012-06-01

    Homeostatic mechanisms maintain homogeneous neuronal behavior among neurons that exhibit substantial variability in the expression levels of their ionic conductances. In contrast, the mechanisms, which generate heterogeneous neuronal behavior across a neuronal population, remain poorly understood. We addressed this problem in the dorsal cochlear nucleus, where principal neurons exist in two qualitatively distinct states: spontaneously active or not spontaneously active. Our studies reveal that distinct activity states are generated by the differential levels of a Ba(2+)-sensitive, inwardly rectifying potassium conductance (K(ir)). Variability in K(ir) maximal conductance causes variations in the resting membrane potential (RMP). Low K(ir) conductance depolarizes RMP to voltages above the threshold for activating subthreshold-persistent sodium channels (Na(p)). Once Na(p) channels are activated, the RMP becomes unstable, and spontaneous firing is triggered. Our results provide a biophysical mechanism for generating neural heterogeneity, which may play a role in the encoding of sensory information.

  11. Hypotonicity activates a voltage-dependent membrane conductance in N2a neuroblastoma cells.

    Science.gov (United States)

    Taruno, Akiyuki; Marunaka, Yoshinori

    2017-03-04

    To maintain cellular and bodily homeostasis, cells respond to extracellular stimuli including osmotic stress by activating various ion channels, which have been implicated in many physiological and pathophysiological conditions. However, cellular osmosensory mechanisms remain elusive. Here, we report a novel voltage-dependent current in N2a cells activated by exposure to hypotonic stress. After a hypotonic challenge, N2a cells sequentially develop two distinct currents. The volume-regulated anion channel (VRAC) current emerges first and, after a delay, activation of a previously uncharacterized strongly outwardly rectifying current follows. The latter, delayed current (Id) is insensitive to NPPB, a nonspecific blocker of Cl(-) channels, and intracellular Mg(2+), which inhibits VRAC and swelling-activated TRPM3 and TRPM7 channels. Replacement of extracellular Na(+) with NMDG(+) reduces inward tail currents, suggesting that Id is mediated by cations. Finally, Id shows voltage-dependent activation with slow activation kinetics and half-maximal activation at +76 mV. These pharmacological and biophysical characteristics of Id are distinct from those of known osmotic cell swelling-activated ion channels. In conclusion, our data identify and characterize a novel osmotically-activated, voltage-dependent ion channel in N2a cells.

  12. Cellular elements for seeing in the dark: voltage-dependent conductances in cockroach photoreceptors

    Directory of Open Access Journals (Sweden)

    Salmela Iikka

    2012-08-01

    Full Text Available Abstract Background The importance of voltage-dependent conductances in sensory information processing is well-established in insect photoreceptors. Here we present the characterization of electrical properties in photoreceptors of the cockroach (Periplaneta americana, a nocturnal insect with a visual system adapted for dim light. Results Whole-cell patch-clamped photoreceptors had high capacitances and input resistances, indicating large photosensitive rhabdomeres suitable for efficient photon capture and amplification of small photocurrents at low light levels. Two voltage-dependent potassium conductances were found in the photoreceptors: a delayed rectifier type (KDR and a fast transient inactivating type (KA. Activation of KDR occurred during physiological voltage responses induced by light stimulation, whereas KA was nearly fully inactivated already at the dark resting potential. In addition, hyperpolarization of photoreceptors activated a small-amplitude inward-rectifying (IR current mediated at least partially by chloride. Computer simulations showed that KDR shapes light responses by opposing the light-induced depolarization and speeding up the membrane time constant, whereas KA and IR have a negligible role in the majority of cells. However, larger KA conductances were found in smaller and rapidly adapting photoreceptors, where KA could have a functional role. Conclusions The relative expression of KA and KDR in cockroach photoreceptors was opposite to the previously hypothesized framework for dark-active insects, necessitating further comparative work on the conductances. In general, the varying deployment of stereotypical K+ conductances in insect photoreceptors highlights their functional flexibility in neural coding.

  13. Decreases of voltage-dependent K+ currents densities in ventricular myocytes of guinea pigs by chronic oxidant stress

    Institute of Scientific and Technical Information of China (English)

    De-li DONG; Yan LIU; Yu-hong ZHOU; Wei-hua SONG; He WANG; Bao-feng YANG

    2004-01-01

    AIM: To determine the changes of delayed rectifier K+ currents (Ik) and inward rectifier K+ currents (Ik1) in the ventricular myocytes of guinea pigs during the gradual apoptotic process by the chronic oxidant stress treatment.METHODS: H2O250 μmol/L (24 h) was used for inducing apoptosis in the cardiomyocytes culture of neonatal rats and to treat the isolated ventricular myocytes of adult guinea pigs in vitro for 24 h. Apoptosis was evaluated by TUNEL methods and voltage-dependent K+ currents were recorded by patch-clamp techniques. RESULTS: H2O250 μmol/L (24 h) induced cell apoptosis in the cardiomyocytes culture of neonatal rats. This concentration was used to treat the isolated ventricular myocytes of adult guinea pigs in vitro for 24 h and the voltage-dependent K+currents densities (Ik, Ik1) were down-regulated. The densities of the delayed rectifier K+ currents (Ik) in 50 μmol/L H2O2 group were 2.52±0.57 pA/pF vs 5.73±1.84 pA/pF in the control group at +50 mV (n=8, P<0.01). The densities of the inward rectifier K+ currents (Ik1) in 50 μmol/L H2O2 group were -13.9±2.70 pA/pF, 2.52±0.57 pA/pF vs -59.7± 11.9 pA/pF, 5.73± 1.84 pA/pF in the control group at -120 mV (n=8, P<0.01) and -40 mV (n=8, P<0.05), respectively. The extent of inward rectifier property of Ik1 was weakened by 50μmol/L H2O2 treatment. CONCLUSION: The densities of Ik, Ik1 in the cardiomyocytes of guinea pigs were downregulated and the inward rectifier property of Ik1 was weakened during the gradual apoptotic process after 50 μmol/L H2O2 treatment for 24 h.

  14. Regulation of the instantaneous inward rectifier and the delayed outward rectifier potassium channels by Captopril and Angiotensin II via the Phosphoinositide-3 kinase pathway in volume-overload-induced hypertrophied cardiac myocytes

    Science.gov (United States)

    Alvin, Zikiar; Laurence, Graham G.; Coleman, Bernell R.; Zhao, Aiqiu; Hajj-Moussa, Majd; Haddad, Georges E.

    2011-01-01

    Summary Background Early development of cardiac hypertrophy may be beneficial but sustained hypertrophic activation leads to myocardial dysfunction. Regulation of the repolarizing currents can be modulated by the activation of humoral factors, such as angiotensin II (ANG II) through protein kinases. The aim of this work is to assess the regulation of IK and IK1 by ANG II through the PI3-K pathway in hypertrophied ventricular myocytes. Material/Methods Cardiac eccentric hypertrophy was induced through volume-overload in adult male rats by aorto-caval shunt (3 weeks). After one week half of the rats were given captopril (2 weeks; 0.5 g/l/day) and the other half served as control. The voltage-clamp and western blot techniques were used to measure the delayed outward rectifier potassium current (IK) and the instantaneous inward rectifier potassium current (IK1) and Akt activity, respectively. Results Hypertrophied cardiomyocytes showed reduction in IK and IK1. Treatment with captopril alleviated this difference seen between sham and shunt cardiomyocytes. Acute administration of ANG II (10−6M) to cardiocytes treated with captopril reduced IK and IK1 in shunts, but not in sham. Captopril treatment reversed ANG II effects on IK and IK1 in a PI3-K-independent manner. However in the absence of angiotensin converting enzyme inhibition, ANG II increased both IK and IK1 in a PI3-K-dependent manner in hypertrophied cardiomyocytes. Conclusions Thus, captopril treatment reveals a negative effect of ANG II on IK and IK1, which is PI3-K independent, whereas in the absence of angiotensin converting enzyme inhibition IK and IK1 regulation is dependent upon PI3-K. PMID:21709626

  15. Over-Expression of Dopamine D2 Receptor and Inwardly Rectifying Potassium Channel Genes in Drug-Naive Schizophrenic Peripheral Blood Lymphocytes as Potential Diagnostic Markers

    Directory of Open Access Journals (Sweden)

    Ágnes Zvara

    2005-01-01

    Full Text Available Schizophrenia is one of the most common neuropsychiatric disorders affecting nearly 1% of the human population. Current diagnosis of schizophrenia is based on complex clinical symptoms. The use of easily detectable peripheral molecular markers could substantially help the diagnosis of psychiatric disorders. Recent studies showed that peripheral blood lymphocytes (PBL express subtypes of D1 and D2 subclasses of dopamine receptors. Recently, dopamine receptor D3 (DRD3 was found to be over-expressed in schizophrenic PBL and proposed to be a diagnostic and follow-up marker for schizophrenia. In this study we screened PBL of 13 drug-naive/drug-free schizophrenic patients to identify additional markers of schizophrenia. One of the benefits of our study is the use of blood samples of non-medicated, drug-naive patients. This excludes the possibility that changes detected in gene expression levels might be attributed to the medication rather than to the disorder itself. Among others, genes for dopamine receptor D2 (DRD2 and the inwardly rectifying potassium channel (Kir2.3 were found to be over-expressed in microarray analysis. Increased mRNA levels were confirmed by quantitative real-time PCR (QRT-PCR using the SybrGreen method and dual labeled TaqMan probes. The use of both molecular markers allows a more rapid and precise prediction of schizophrenia and might help find the optimal medication for schizophrenic patients.

  16. Over-expression of dopamine D2 receptor and inwardly rectifying potassium channel genes in drug-naive schizophrenic peripheral blood lymphocytes as potential diagnostic markers.

    Science.gov (United States)

    Zvara, Agnes; Szekeres, György; Janka, Zoltán; Kelemen, János Z; Cimmer, Csongor; Sántha, Miklós; Puskás, László G

    2005-01-01

    Schizophrenia is one of the most common neuropsychiatric disorders affecting nearly 1% of the human population. Current diagnosis of schizophrenia is based on complex clinical symptoms. The use of easily detectable peripheral molecular markers could substantially help the diagnosis of psychiatric disorders. Recent studies showed that peripheral blood lymphocytes (PBL) express subtypes of D1 and D2 subclasses of dopamine receptors. Recently, dopamine receptor D3 (DRD3) was found to be over-expressed in schizophrenic PBL and proposed to be a diagnostic and follow-up marker for schizophrenia. In this study we screened PBL of 13 drug-naive/drug-free schizophrenic patients to identify additional markers of schizophrenia. One of the benefits of our study is the use of blood samples of non-medicated, drug-naive patients. This excludes the possibility that changes detected in gene expression levels might be attributed to the medication rather than to the disorder itself. Among others, genes for dopamine receptor D2 (DRD2) and the inwardly rectifying potassium channel (Kir2.3) were found to be over-expressed in microarray analysis. Increased mRNA levels were confirmed by quantitative real-time PCR (QRT-PCR) using the SybrGreen method and dual labeled TaqMan probes. The use of both molecular markers allows a more rapid and precise prediction of schizophrenia and might help find the optimal medication for schizophrenic patients.

  17. Mutation analysis of the inwardly rectifying K(+) channels KCNJ6 (GIRK2) and KCNJ3 (GIRK1) in juvenile myoclonic epilepsy.

    Science.gov (United States)

    Hallmann, K; Durner, M; Sander, T; Steinlein, O K

    2000-02-07

    Genetic factors play a major role in the etiology of idiopathic generalized epilepsy. However, in most syndromes, especially the common ones, multiple genetic factors seem to be involved. Mutations in K(+) channel genes have previously found to be associated with epilepsy both in humans and in mice. The weaver mice phenotype, characterized by ataxia, tremor, male infertility, and tonic-clonic seizures, is caused by a point mutation in the inwardly rectifier K(+) channel gene KCNJ6 (GIRK2). A knockout mouse model deprived of functional KCNJ6 protein is susceptible to spontaneous and provoked seizures without showing the histological signs of neuronal cell death found in the weaver mouse. Thus, the KCNJ6 gene seems to play an important role in seizure control. We therefore performed a mutation analysis of KCNJ6 and the related KCNJ3 gene in 38 patients with juvenile myoclonic epilepsy (JME). Two novel same-sense nucleotide exchanges were identified, but none of these changed the coding sequence. These results do not support a major role for the KCNJ6/KCNJ3 heteromeric receptor in the etiology of JME. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:8-11, 2000

  18. Amyloid-β induces synaptic dysfunction through G protein-gated inwardly rectifying potassium channels in the fimbria-CA3 hippocampal synapse

    Directory of Open Access Journals (Sweden)

    Mauricio O. Nava-Mesa

    2013-07-01

    Full Text Available Last evidences suggest that, in Alzheimer's disease (AD early stage, Amyloid-β (Aβ peptide induces an imbalance between excitatory and inhibitory neurotransmission systems resulting in the functional impairment of neural networks. Such alterations are particularly important in the septohippocampal system where learning and memory processes take place depending on accurate oscillatory activity tuned at fimbria-CA3 synapse. Here, the acute effects of Aβ on CA3 pyramidal neurons and their synaptic activation from septal part of the fimbria were studied in rats. A triphasic postsynaptic response defined by an excitatory potential (EPSP followed by both early and late inhibitory potentials (IPSP was evoked. The EPSP was glutamatergic acting on ionotropic receptors. The early IPSP was blocked by GABAA antagonists whereas the late IPSP was removed by GABAB antagonists. Aβ perfusion induced recorded cells to depolarize, increase their input resistance and decrease the late IPSP. Aβ action mechanism was localized at postsynaptic level and most likely linked to GABAB-related ion channels conductance decrease. In addition, it was found that the specific pharmacological modulation of the GABAB receptor effector, G-protein-coupled inward rectifier potassium (GirK channels, mimicked all Aβ effects previously described. Thus, our findings suggest that Aβ altering GirK channels conductance in CA3 pyramidal neurons might have a key role in the septohippocampal activity dysfunction observed in AD.

  19. Pharmacological validation of an inward-rectifier potassium (Kir channel as an insecticide target in the yellow fever mosquito Aedes aegypti.

    Directory of Open Access Journals (Sweden)

    Matthew F Rouhier

    Full Text Available Mosquitoes are important disease vectors that transmit a wide variety of pathogens to humans, including those that cause malaria and dengue fever. Insecticides have traditionally been deployed to control populations of disease-causing mosquitoes, but the emergence of insecticide resistance has severely limited the number of active compounds that are used against mosquitoes. Thus, to improve the control of resistant mosquitoes there is a need to identify new insecticide targets and active compounds for insecticide development. Recently we demonstrated that inward rectifier potassium (Kir channels and small molecule inhibitors of Kir channels offer promising new molecular targets and active compounds, respectively, for insecticide development. Here we provide pharmacological validation of a specific mosquito Kir channel (AeKir1 in the yellow fever mosquito Aedes aegypti. We show that VU590, a small-molecule inhibitor of mammalian Kir1.1 and Kir7.1 channels, potently inhibits AeKir1 but not another mosquito Kir channel (AeKir2B in vitro. Moreover, we show that a previously identified inhibitor of AeKir1 (VU573 elicits an unexpected agonistic effect on AeKir2B in vitro. Injection of VU590 into the hemolymph of adult female mosquitoes significantly inhibits their capacity to excrete urine and kills them within 24 h, suggesting a mechanism of action on the excretory system. Importantly, a structurally-related VU590 analog (VU608, which weakly blocks AeKir1 in vitro, has no significant effects on their excretory capacity and does not kill mosquitoes. These observations suggest that the toxic effects of VU590 are associated with its inhibition of AeKir1.

  20. Upregulation of the inwardly rectifying potassium channel Kir2.1 (KCNJ2) modulates multidrug resistance of small-cell lung cancer under the regulation of miR-7 and the Ras/MAPK pathway

    OpenAIRE

    Liu, Huanxin; Huang, Jie; Peng, Juan; WU, Xiaoxia; Zhang, Yan; Zhu, Weiliang; Guo, Linlang

    2015-01-01

    Background KCNJ2/Kir2.1, a member of the classical inwardly rectifying potassium channel family, is commonly expressed in a wide range of tissues and cell types. Previous studies indicated that Kir2.1 may be associated with SCLC multidrug resistance (MDR). However, whether Kir2.1 can regulate MDR and its underlying mechanisms remain poorly understood in SCLC. Methods KCNJ2/Kir2.1 expression was examined in tissues from fifty-two SCLC cases by immunohistochemistry. Overexpression or knockdown ...

  1. The voltage dependence of Ih in human myelinated axons

    Science.gov (United States)

    Howells, James; Trevillion, Louise; Bostock, Hugh; Burke, David

    2012-01-01

    HCN channels are responsible for Ih, a voltage-gated inwardly rectifying current activated by hyperpolarization. This current appears to be more active in human sensory axons than motor and may play a role in the determination of threshold. Differences in Ih are likely to be responsible for the high variability in accommodation to hyperpolarization seen in different subjects. The aim of this study was to characterise this current in human axons, both motor and sensory. Recordings of multiple axonal excitability properties were performed in 10 subjects, with a focus on the changes in threshold evoked by longer and stronger hyperpolarizing currents than normally studied. The findings confirm that accommodation to hyperpolarization is greater in sensory than motor axons in all subjects, but the variability between subjects was greater than the modality difference. An existing model of motor axons was modified to take into account the behaviour seen with longer and stronger hyperpolarization, and a mathematical model of human sensory axons was developed based on the data collected. The differences in behaviour of sensory and motor axons and the differences between different subjects are best explained by modulation of the voltage dependence, along with a modest increase of expression of the underlying conductance of Ih. Accommodation to hyperpolarization for the mean sensory data is fitted well with a value of −94.2 mV for the mid-point of activation (V0.5) of Ih as compared to −107.3 mV for the mean motor data. The variation in response to hyperpolarization between subjects is accounted for by varying this parameter for each modality (sensory: −89.2 to −104.2 mV; motor −87.3 to −127.3 mV). These voltage differences are within the range that has been described for physiological modulation of Ih function. The presence of slowly activated Ih isoforms on both motor and sensory axons was suggested by modelling a large internodal leak current and a masking of

  2. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    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.

  3. The Eag domain regulates the voltage-dependent inactivation of rat Eag1 K+ channels.

    Directory of Open Access Journals (Sweden)

    Ting-Feng Lin

    Full Text Available Eag (Kv10 and Erg (Kv11 belong to two distinct subfamilies of the ether-à-go-go K+ channel family (KCNH. While Erg channels are characterized by an inward-rectifying current-voltage relationship that results from a C-type inactivation, mammalian Eag channels display little or no voltage-dependent inactivation. Although the amino (N-terminal region such as the eag domain is not required for the C-type inactivation of Erg channels, an N-terminal deletion in mouse Eag1 has been shown to produce a voltage-dependent inactivation. To further discern the role of the eag domain in the inactivation of Eag1 channels, we generated N-terminal chimeras between rat Eag (rEag1 and human Erg (hERG1 channels that involved swapping the eag domain alone or the complete cytoplasmic N-terminal region. Functional analyses indicated that introduction of the homologous hERG1 eag domain led to both a fast phase and a slow phase of channel inactivation in the rEag1 chimeras. By contrast, the inactivation features were retained in the reverse hERG1 chimeras. Furthermore, an eag domain-lacking rEag1 deletion mutant also showed the fast phase of inactivation that was notably attenuated upon co-expression with the rEag1 eag domain fragment, but not with the hERG1 eag domain fragment. Additionally, we have identified a point mutation in the S4-S5 linker region of rEag1 that resulted in a similar inactivation phenotype. Biophysical analyses of these mutant constructs suggested that the inactivation gating of rEag1 was distinctly different from that of hERG1. Overall, our findings are consistent with the notion that the eag domain plays a critical role in regulating the inactivation gating of rEag1. We propose that the eag domain may destabilize or mask an inherent voltage-dependent inactivation of rEag1 K+ channels.

  4. Discovery, characterization and structure-activity relationships of an inhibitor of inward rectifier potassium (Kir channels with preference for Kir2.3, Kir3.X and Kir7.1

    Directory of Open Access Journals (Sweden)

    Jerod S Denton

    2011-11-01

    Full Text Available The inward rectifier family of potassium (Kir channels is comprised of at least 16 family members exhibiting broad and often overlapping cellular, tissue or organ distributions. The discovery of disease-causing mutations in humans and experiments on knockout mice has underscored the importance of Kir channels in physiology and in some cases raised questions about their potential as drug targets. However, the paucity of potent and selective small-molecule modulators targeting specific family members has with few exceptions mired efforts to understand their physiology and assess their therapeutic potential. A growing body of evidence suggests that GIRK (G protein-regulated inward rectifier K channels of the Kir3.X subfamily may represent novel targets for the treatment of atrial fibrillation. In an effort to expand the molecular pharmacology of GIRK, we performed a thallium (Tl+ flux-based high-throughput screen (HTS of a Kir1.1 inhibitor library for modulators of GIRK. One compound, termed VU573, exhibited 10-fold selectivity for GIRK over Kir1.1 (IC50 = 1.9 M and 19 M, respectively and was therefore selected for further study. In electrophysiological experiments performed on Xenopus laevis oocytes and mammalian cells, VU573 inhibited Kir3.1/3.2 (neuronal GIRK and Kir3.1/3.4 (cardiac GIRK channels with equal potency and preferentially inhibited GIRK, Kir2.3 and Kir7.1 over Kir1.1 and Kir2.1. Tl+ flux assays were established for Kir2.3 and the M125R pore mutant of Kir7.1 to support medicinal chemistry efforts to develop more potent and selective analogs for these channels. The structure-activity relationships of VU573 revealed few analogs with improved potency, however two compounds retained most of their activity toward GIRK and Kir2.3 and lost activity toward Kir7.1. We anticipate that the VU573 series will be useful for exploring the physiology and structure-function relationships of these Kir channels.

  5. VOLTAGE-DEPENDENT SODIUM AND POTASSIUM, BUT NO CALCIUM CONDUCTANCES IN DDT1 MF-2 SMOOTH-MUSCLE CELLS

    NARCIS (Netherlands)

    MOLLEMAN, A; NELEMANS, A; VANDENAKKER, J; DUIN, M; DENHERTOG, A

    1991-01-01

    Voltage-dependent inward and outward membrane currents were investigated in the DDT1 MF-2 smooth muscle cell line using the whole-cell patch-clamp technique. Application of a pulse protocol with subsequent depolarizing voltage steps elicited an inactivating inward current and a non-inactivating outw

  6. G-Protein Inwardly Rectifying Potassium Channel 1 (GIRK1 Knockdown Decreases Beta-Adrenergic, MAP Kinase and Akt Signaling in the MDA-MB-453 Breast Cancer Cell Line

    Directory of Open Access Journals (Sweden)

    Michael W. Hance

    2008-01-01

    Full Text Available Previous data from our laboratory have indicated that there is a functional link between the beta-adrenergic receptor signaling pathway and the G-protein inwardly rectifying potassium channel (GIRK1 in breast cancer cell lines and that these pathways are involved in growth regulation of these cells. To determine functionality, MDA-MB-453 breast cancer cells were stimulated with ethanol, known to open GIRK channels. Decreased GIRK1 protein levels were seen after treatment with 0.12% ethanol. In addition, serum-free media completely inhibited GIRK1 protein expression. This data indicates that there are functional GIRK channels in breast cancer cells and that these channels are involved in cellular signaling. In the present research, to further define the signaling pathways involved, we performed RNA interference (siRNA studies. Three stealth siRNA constructs were made starting at bases 1104, 1315, and 1490 of the GIRK1 sequence. These constructs were transfected into MDA-MB-453 cells, and both RNA and protein were isolated. GIRK1, β2-adrenergic and 18S control levels were determined using real-time PCR 24 hours after transfection. All three constructs decreased GIRK1 mRNA levels. However, β2 mRNA levels were unchanged by the GIRK1 knockdown. GIRK1 protein levels were also reduced by the knockdown, and this knockdown led to decreases in beta-adrenergic, MAP kinase and Akt signaling.

  7. Voltage-dependent ionic channels in differentiating neural precursor cells collected from adult mouse brains six hours post-mortem.

    Science.gov (United States)

    Bellardita, Carmelo; Bolzoni, Francesco; Sorosina, Melissa; Marfia, Giovanni; Carelli, Stephana; Gorio, Alfredo; Formenti, Alessandro

    2012-04-01

    A novel type of adult neural precursor cells (NPCs) has been isolated from the subventricular zone of the mouse 6 hr after animal death (T6-NPCs). This condition is supposed to select hypoxia-resistant cells of scientific and clinical interest. Ionic channels are ultimately the expression of the functional maturation of neurons, so the aim of this research was to characterize the pattern of the main voltage-dependent ionic channels in T6-NPCs differentiating to a neuronal phenotype, comparing it with NPCs isolated soon after death (T0-NPCs). T6- and T0-NPCs grow in medium containing epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). Differentiation was performed in small wells without the addition of growth factors, in the presence of adhesion molecules, fetal bovine serum, and leukemia inhibitory factor. Ionic currents, recorded by means of whole-cell patch-clamp, namely, I(Ca2+) HVA, both L- and non-L-type, I(K+) delayed rectifying, I(K+) inward rectifier, transient I(K+A) , and TTX-sensitive I(Na+) have been found, although Na(+) currents were found in only a small percentage of cells and after the fifth week of differentiation. No significant differences in current types, density, orcell capacitance were observed between T6-NPCs and T0-NPCs. The sequence in which the markers appear in new neural cells is not necessarily a fixed program, but the discrepancies in morphological, biochemical, and electrophysiological maturation of mouse NPCs to neurons, possibly different in vivo, suggest that the various steps of the differentiation are independently regulated. Therefore, in addition to morphological and biochemical data, functional tests should be considered for characterizing the maturation of neurons.

  8. 白藜芦醇甙增强大鼠心室肌细胞内向整流钾通道电流%Enhancement of polydatin on inward rectifier potassium channel current in rat ventricular myocytes

    Institute of Scientific and Technical Information of China (English)

    魏燕; 周京京; 杨晶; 张娇; 张利萍; 张翼

    2013-01-01

    本研究旨在应用全细胞膜片钳技术观察白藜芦醇甙(polydatin)对大鼠心室肌细胞瞬时外向钾通道电流(Ito)、稳态外向钾通道电流(Iss)和内向整流钾通道电流(IK1)的影响.结果显示:(1)白藜芦醇甙(10 μmol/L以上浓度)可通过非浓度依赖性方式增加心室肌细胞IK1.(2)白藜芦醇甙对心室肌细胞Ito无影响,对Ito的激活、失活和失活后的恢复动力学亦无影响.(3)白藜芦醇甙对心室肌细胞Iss无明显影响.以上结果提示,白藜芦醇甙对大鼠心室肌细胞IK1具有激活作用,可增加IK1,但对Ito和Iss无明显影响;白藜芦醇甙对IK1的作用可能是其抗心律失常作用的离子机制之一.%The aim of this study was to investigate the effect of polydatin on transient outward potassium channel current (Ito),steadystate outward potassium channel current (Iss) and inward rectifier potassium channel current (IK1) in ventricular myocytes of rat using the whole-cell patch clamp technique.The results showed:(1) Polydatin (above 10 μmol/L) increasedIK1 of ventricular myocytes in a non-concentration dependent manner.(2) Polydatin neither had any effect on Ito peak current of ventricular myocytes,nor changed activation,inactivation and recovery kinetics of Ito.(3) Polydatin had no effect on Iss of ventricular myocytes.These results suggest that polydatin enhances IK1 channel activity,but has no effect on Ito and Iss channels in rat ventricular myocytes,which might be one of the ionic mechanisms for antiarrhythmic effect of polydatin.

  9. Zn2+ regulates Kv2.1 voltage-dependent gating and localization following ischemia

    OpenAIRE

    Aras, Mandar A.; Saadi, Robert A.; Aizenman, Elias

    2009-01-01

    The delayed-rectifier K+ channel Kv2.1 exists in highly phosphorylated somatodendritic clusters. Ischemia induces rapid Kv2.1 dephosphorylation and a dispersal of these clusters, accompanied by a hyperpolarizing shift in their voltage-dependent activation kinetics. Transient modulation of Kv2.1 activity and localization following ischemia is dependent on a rise in intracellular Ca2+and the protein phosphatase calcineurin. Here, we show that neuronal free Zn2+also plays a critical role in the ...

  10. Voltage-dependent currents in microvillar receptor cells of the frog vomeronasal organ.

    Science.gov (United States)

    Trotier, D; Døving, K B; Rosin, J F

    1993-08-01

    Vomeronasal receptor cells are differentiated bipolar neurons with a long dendrite bearing numerous microvilli. Isolated cells (with a mean dendritic length of 65 microns) and cells in mucosal slices were studied using whole-cell and Nystatin-perforated patch-clamp recordings. At rest, the membrane potential was -61 +/- 13 mV (mean +/- SD; n = 61). Sixty-four per cent of the cells had a resting potential in the range of -60 to -86 mV, with almost no spontaneous action potential. The input resistance was in the G omega range and overshooting repetitive action potentials were elicited by injecting depolarizing current pulses in the range of 2-10 pA. Voltage-dependent currents were characterized under voltage-clamp conditions. A transient fast inward current activating near -45 mV was blocked by tetrodotoxin. In isolated cells, it was half-deactivated at a membrane potential near -75 mV. An outward K+ current was blocked by internal Cs+ ions or by external tetraethylammonium or Ba2+ ions. A calcium-activated voltage-dependent potassium current was blocked by external Cd2+ ions. A voltage-dependent Ca2+ current was observed in an iso-osmotic BaCl2 solution. Finally, a hyperpolarization-activated inward current was recorded. Voltage-dependent currents in these microvillar olfactory receptor neurons appear qualitatively similar to those already described in ciliated olfactory receptor cells located in the principal olfactory epithelium.

  11. Ropivacaine-Induced Contraction Is Attenuated by Both Endothelial Nitric Oxide and Voltage-Dependent Potassium Channels in Isolated Rat Aortae

    Directory of Open Access Journals (Sweden)

    Seong-Ho Ok

    2013-01-01

    Full Text Available This study investigated endothelium-derived vasodilators and potassium channels involved in the modulation of ropivacaine-induced contraction. In endothelium-intact rat aortae, ropivacaine concentration-response curves were generated in the presence or absence of the following inhibitors: the nonspecific nitric oxide synthase (NOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, the neuronal NOS inhibitor Nω-propyl-L-arginine hydrochloride, the inducible NOS inhibitor 1400W dihydrochloride, the nitric oxide-sensitive guanylyl cyclase (GC inhibitor ODQ, the NOS and GC inhibitor methylene blue, the phosphoinositide-3 kinase inhibitor wortmannin, the cytochrome p450 epoxygenase inhibitor fluconazole, the voltage-dependent potassium channel inhibitor 4-aminopyridine (4-AP, the calcium-activated potassium channel inhibitor tetraethylammonium (TEA, the inward-rectifying potassium channel inhibitor barium chloride, and the ATP-sensitive potassium channel inhibitor glibenclamide. The effect of ropivacaine on endothelial nitric oxide synthase (eNOS phosphorylation in human umbilical vein endothelial cells was examined by western blotting. Ropivacaine-induced contraction was weaker in endothelium-intact aortae than in endothelium-denuded aortae. L-NAME, ODQ, and methylene blue enhanced ropivacaine-induced contraction, whereas wortmannin, Nω-propyl-L-arginine hydrochloride, 1400W dihydrochloride, and fluconazole had no effect. 4-AP and TEA enhanced ropivacaine-induced contraction; however, barium chloride and glibenclamide had no effect. eNOS phosphorylation was induced by ropivacaine. These results suggest that ropivacaine-induced contraction is attenuated primarily by both endothelial nitric oxide and voltage-dependent potassium channels.

  12. Voltage dependence of Na translocation by the Na/K pump.

    Science.gov (United States)

    Nakao, M; Gadsby, D C

    During each complete reaction cycle, the Na/K pump transports three Na ions out across the cell membrane and two K ions in. The resulting net extrusion of positive charge generates outward membrane current but, until now, it was unclear how that net charge movement occurs. Reasonable possibilities included a single positive charge moving outwards during Na translocation; or a single negative charge moving inwards during K translocation; or either positive or negative charges moving during both translocation steps, but in unequal quantities. Any step that involves net charge movement through the membrane must have voltage-dependent transition rates. Here we report measurements of transient, voltage-dependent, displacement currents generated by the pump when its normal Na/K transport cycle has been interrupted by removal of external K and it is thus constrained to carry out Na/Na exchange. The quantity and voltage sensitivity of the charge moved during these transient currents suggests that Na translocation includes a voltage-dependent transition involving movement of one positive charge across the membrane. This single step can thus fully account for the electrogenic nature of Na/K exchange. The result provides important new insight into the molecular mechanism of active cation transport.

  13. The mechanism of inward rectification in Kir channels: A novel kinetic model with non-equilibrium thermodynamics approach.

    Science.gov (United States)

    Hsieh, Chi-Pan; Chiang, Cheng-Chin; Huang, Chiung-Wei

    2016-05-01

    The mechanisms of the strong inward rectification in inward rectifier K(+) (Kir) channels are controversial because the drop in electrical potential due to the movement of the blocker and coupling ions is insufficient to explain the steep voltage-dependent block near the equilibrium potential. Here, we study the "driving force"-dependent block in Kir channels with a novel approach incorporating concepts from the non-equilibrium thermodynamics of small systems, and computer kinetic simulations based on the experimental data of internal Ba(2+) block on Kir2.1 channels. The steep exponential increase in the apparent binding rate near the equilibrium potential is explained, when the encounter frequency is construed as the likelihood of transfer events down or against the electrochemical potential gradient. The exponent of flux ratio, nf=2.62, implies that the blockage of the internal blocker may be coupled with the outward transport of 2 to 3K(+) ions. The flux-coupled block in the single-file multi-ion pore can be demonstrated by the concentration gradient alone, as well as when the driving force is the electrochemical potential difference across the membrane.

  14. Voltage dependence of the Na-K pump.

    Science.gov (United States)

    De Weer, P; Gadsby, D C; Rakowski, R F

    1988-01-01

    Present evidence demonstrates that the Na-K pump rate is voltage dependent, whereas early work was largely inconclusive. The I-V relationship has a positive slope over a wide voltage range, and the existence of a negative slope region is now doubtful. Monotonic voltage dependence is consistent with the reaction cycle containing a single voltage-dependent step. Recent measurements suggest that this voltage-dependent step occurs during Na translocation and may be deocclusion of Na+. In addition, two results suggest that K translocation is voltage insensitive: (a) large positive potentials appear to have no influence on Rb-Rb exchange or associated conformational transitions; and (b) transient currents associated with Na translocation appear to involve movement of a single charge, which is sufficient for a 3Na-2K cycle. The simplest interpretation is that the pump's cation binding sites supply two negative charges. Pre-steady-state measurements demonstrate that Na translocation precedes the pump cycle's rate-limiting step, presumably K translocation. But, because K translocation seems voltage insensitive, the voltage dependence of the steady-state pump rate probably reflects that of the concentration of the intermediate entering this slow step. Further pump current and flux data (both transient and steady-state), carefully determined over a range of conditions, should increase our understanding of the voltage-dependent step(s) in the Na-K pump cycle.

  15. 慢性间歇性低压低氧对大鼠心肌细胞内向整流钾通道的影响%EFFECT OF CHRONIC INTERMITTENT HYPOBARIC HYPOXIA ON INWARD RECTIFIER POTASSIUM CHANNEL IN VENTRICULAR MYOCYTES OF RATS

    Institute of Scientific and Technical Information of China (English)

    斯琴高娃; 魏燕; 宋胜利; 周京京; 杨晶; 张翼

    2012-01-01

    Objective To investigate the effect of chronic intermittent hypobaric hypoxia ( CIHH ) on inward rectifier potassium channel current ( Ikl ) in ventricular myocytes of rats. Methods Rats were experienced CIHH exposure in a hypobaric chamber, and whole cell patch - clamp was used to record Ikl in ventricular myocytes of rats. Results There was no significant difference of Ikl in ventricular myocytes between CIHH and control rats under the normal condition ( P > 0. 05 ). During simulated ischemia,Ikl was decreased ( P 0.05);模拟缺血导致大鼠心肌细胞Ik1明显降低(P<0.05),CIHH处理28d大鼠心室肌细胞Ik1降低达(20±25)%(n=10),CIHH处理42d大鼠心室肌细胞Ik1降低达(17±22)%(n=10),明显小于control大鼠心室肌细胞Ik1降低的(46±11)%(n=10,P<0.05).结论 CIHH可有效对抗模拟缺血对大鼠心肌细胞Ik1的抑制,可能是CIHH抗心律失常作用的离子机制之一.

  16. A new pH-sensitive rectifying potassium channel in mitochondria from the embryonic rat hippocampus.

    Science.gov (United States)

    Kajma, Anna; Szewczyk, Adam

    2012-10-01

    Patch-clamp single-channel studies on mitochondria isolated from embryonic rat hippocampus revealed the presence of two different potassium ion channels: a large-conductance (288±4pS) calcium-activated potassium channel and second potassium channel with outwardly rectifying activity under symmetric conditions (150/150mM KCl). At positive voltages, this channel displayed a conductance of 67.84pS and a strong voltage dependence at holding potentials from -80mV to +80mV. The open probability was higher at positive than at negative voltages. Patch-clamp studies at the mitoplast-attached mode showed that the channel was not sensitive to activators and inhibitors of mitochondrial potassium channels but was regulated by pH. Moreover, we demonstrated that the channel activity was not affected by the application of lidocaine, an inhibitor of two-pore domain potassium channels, or by tertiapin, an inhibitor of inwardly rectifying potassium channels. In summary, based on the single-channel recordings, we characterised for the first time mitochondrial pH-sensitive ion channel that is selective for cations, permeable to potassium ions, displays voltage sensitivity and does not correspond to any previously described potassium ion channels in the inner mitochondrial membrane. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

  17. Noise Properties of Rectifying Nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Powell, M R; Sa, N; Davenport, M; Healy, K; Vlassiouk, I; Letant, S E; Baker, L A; Siwy, Z S

    2011-02-18

    Ion currents through three types of rectifying nanoporous structures are studied and compared for the first time: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit non-equilibrium 1/f noise, thus the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics, and formation of vortices and non-linear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields inducing secondary effects in the pore such as enhanced water dissociation.

  18. Effects of piperine on abnormalities of inward rectifier potassium current and ultra rapid delayed rectifier potassium current induced by hydrogen peroxide in rabbit atrial myocytes%胡椒碱减轻H2O2引起的兔心房肌细胞内向整流钾电流及超速激活延迟整流钾电流的异常改变

    Institute of Scientific and Technical Information of China (English)

    刘岩; 李泱; 林琨; 田苗; 王玉堂; 单兆亮

    2012-01-01

    目的:研究胡椒碱对H2O2引起的兔单个心房肌细胞内向整流钾电流(IK1)及超速激活的延迟整流钾电流(IKUr)异常的影响.方法:采用全细胞膜片钳技术分析50 μmol/L H2O2对兔单个心房肌细胞IK1和IKUr的影响,并研究预先应用7 μmol/L胡椒碱对其的保护作用.结果:7 μmol/L胡椒碱对正常兔心房肌细胞IK1和IKUr及其通道动力学无显著影响.在50 μmol/L H2O2作用下,兔心房肌细胞IK1峰值由(-148.2±16.7)pA/pF降低至(-64.2±9.8)pA/pF (P<0.05),电流-电压曲线上移;而IKUr峰值由(16.0±2.1)pA/pF降低至(6.1±1.4)pA/pF (P<0.05),电流-电压曲线下移,通道稳态激活曲线右移,通道稳态失活曲线左移及恢复时间减慢,而且存在频率依赖性特征.预先给予7 μmol/L胡椒碱,明显减轻H2O2对IK1和IKUr的抑制作用(P<0.01),并可减少H2O2对超速激活延迟整流钾通道动力学的异常影响.结论:胡椒碱可减轻氧化应激对心房肌细胞IK1和IKUr的影响.%AIM: To study the proleclive effect of piperine on abnormalilyies of inward rectifier potassium cur-rent ( IK1 ) and ultra rapid delayed rectifier polassium currenl ( IKUT) induced by hydrogen peroxide ( H2 O2 ) in single rabbil alrial myocytes. METHODS: The technique of whole - cell patch - clamp was used Lo study the effecl of H2 O2 at concen-tralion of 50 μmol/L on IK1 and /Kut in single rabbil alrial myocyles. The proleclive effecl of prelrealmenl with piperine (7 μmol/L) was also observed. RESULTS:The piperine al concenlralion of 7 μmol/L had no significant effecl on IK1 and IKUt and their channel dynamics. In the presence of H2O2 at concenlralion of 50 μmol/L, the peak currents of /K1 and /KUT reduced significanlly ( P < 0. 05 ) . The sleady - state aclivalion curve of /Kut was shifted right, the sleady - state inaclivalion curve of IKUt was shifted left, and the recovery from inaclivalion of IKUt was shifted downward. The IKUt showed frequency -dependenl characteristics

  19. Upregulation of inward rectifying currents and Fabry disease neuropathy.

    Science.gov (United States)

    Geevasinga, Nimeshan; Tchan, Michel; Sillence, David; Vucic, Steve

    2012-12-01

    Peripheral neuropathy and neuropathic pain are common clinical manifestations of Fabry disease (FD). Although the mechanisms underlying the development of sensory neuropathy remain to be fully elucidated, a chronic ischemic process was proposed. Consequently, this study utilized axonal excitability techniques to gain further insights into the pathophysiological mechanisms underlying the development of FD neuropathy. Median motor and sensory axonal excitability studies were undertaken in 13 FD patients and results were compared to 19 healthy subjects. A "fanning-in" of threshold electrotonus, suggestive of membrane depolarization, was evident only in motor axons in FD patients. In contrast, the sensory axons exhibited a lower threshold in FD (p < 0.05) and a significantly increased hyperpolarizing current/threshold (I/V) gradient (FD 0.48 ± 0.03; controls, 0.31 ± 0.02, p < 0.001), which correlated with clinical scores of disease severity (Rho = 0.65, p < 0.05), neuropathy (Rho = 0.54, p < 0.05) and neuropathic pain (Rho = 0.56, p < 0.05). These findings indicate that upregulation of I(h) , rather than ischemia, may underlie the sensory symptoms and possibly development of neuropathy in FD. Modulation of sensory I(h) may prove therapeutically useful in Fabry disease.

  20. Voltage-dependent gating of hERG potassium channels

    Directory of Open Access Journals (Sweden)

    Yen May eCheng

    2012-05-01

    Full Text Available The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4-S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-a-go-go related gene, hERG, which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure-function relationships underlying voltage-dependent gating in Shaker and hERG channels, with a focus on the roles of the voltage sensing domain and the S4-S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter charge interactions. More recent data suggest that key amino acid differences in the hERG voltage sensing unit and S4-S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor.

  1. Pharmacology of the human cell voltage-dependent cation channel. Part II: inactivation and blocking

    DEFF Research Database (Denmark)

    Bennekou, Poul; Barksmann, Trine L.; Kristensen, Berit I.

    2004-01-01

    Human red cells; Nonselective voltage-dependent cation channel; NSVDC channel; Thiol group reagents......Human red cells; Nonselective voltage-dependent cation channel; NSVDC channel; Thiol group reagents...

  2. Voltage-dependent Ca2+ channel and Na+ channel in frog taste cells.

    Science.gov (United States)

    Kashiwayanagi, M; Miyake, M; Kurihara, K

    1983-01-01

    Frog taste cells were hyperpolarized by injecting an inward current pulse, and regenerative anode-break potentials were observed at the termination of the current pulse. The results obtained are as follows. 1) The magnitude of the anode-break potentials increased with the extent of hyperpolarization of taste cells and reached a saturation level around -200 mV. 2) The magnitudes of the anode-break potentials observed in 80 different taste cells hyperpolarized to about -200 mV were distributed widely from cell to cell. The average magnitude was 39 mV. 3) The anode-break potentials were recorded after the lingual artery was perfused with artificial solutions containing various channel blockers. The results indicated that the anode-break potentials are composed of Na+ and Ca2+ components. 4) The slope of the current-voltage relation obtained with cells hyperpolarized to 100 mV was appreciably decreased above -50 mV by application of tetrodotoxin to the perfusing solution. Discussion was made on possible roles of the voltage-dependent Na+ and Ca2+ channels in the electrotonic spreading of the depolarization at the receptor membranes to the synaptic area and in releasing a chemical transmitter.

  3. Electrical Pacing of Cardiac Tissue Including Potassium Inward Rectification.

    Science.gov (United States)

    Galappaththige, Suran; Roth, Bradley J

    2015-01-01

    In this study cardiac tissue is stimulated electrically through a small unipolar electrode. Numerical simulations predict that around an electrode are adjacent regions of depolarization and hyperpolarization. Experiments have shown that during pacing of resting cardiac tissue the hyperpolarization is often inhibited. Our goal is to determine if the inward rectifying potassium current (IK1) causes the inhibition of hyperpolarization. Numerical simulations were carried out using the bidomain model with potassium dynamics specified to be inward rectifying. In the simulations, adjacent regions of depolarization and hyperpolarization were observed surrounding the electrode. For cathodal currents the virtual anode produces a hyperpolarization that decreases over time. For long duration pulses the current-voltage curve is non-linear, with very small hyperpolarization compared to depolarization. For short pulses, the hyperpolarization is more prominent. Without the inward potassium rectification, the current voltage curve is linear and the hyperpolarization is evident for both long and short pulses. In conclusion, the inward rectification of the potassium current explains the inhibition of hyperpolarization for long duration stimulus pulses, but not for short duration pulses.

  4. Electrical Pacing of Cardiac Tissue Including Potassium Inward Rectification.

    Directory of Open Access Journals (Sweden)

    Suran Galappaththige

    Full Text Available In this study cardiac tissue is stimulated electrically through a small unipolar electrode. Numerical simulations predict that around an electrode are adjacent regions of depolarization and hyperpolarization. Experiments have shown that during pacing of resting cardiac tissue the hyperpolarization is often inhibited. Our goal is to determine if the inward rectifying potassium current (IK1 causes the inhibition of hyperpolarization. Numerical simulations were carried out using the bidomain model with potassium dynamics specified to be inward rectifying. In the simulations, adjacent regions of depolarization and hyperpolarization were observed surrounding the electrode. For cathodal currents the virtual anode produces a hyperpolarization that decreases over time. For long duration pulses the current-voltage curve is non-linear, with very small hyperpolarization compared to depolarization. For short pulses, the hyperpolarization is more prominent. Without the inward potassium rectification, the current voltage curve is linear and the hyperpolarization is evident for both long and short pulses. In conclusion, the inward rectification of the potassium current explains the inhibition of hyperpolarization for long duration stimulus pulses, but not for short duration pulses.

  5. Manipulating the voltage dependence of tunneling spin torques

    KAUST Repository

    Manchon, Aurelien

    2012-10-01

    Voltage-driven spin transfer torques in magnetic tunnel junctions provide an outstanding tool to design advanced spin-based devices for memory and reprogrammable logic applications. The non-linear voltage dependence of the torque has a direct impact on current-driven magnetization dynamics and on devices performances. After a brief overview of the progress made to date in the theoretical description of the spin torque in tunnel junctions, I present different ways to alter and control the bias dependence of both components of the spin torque. Engineering the junction (barrier and electrodes) structural asymmetries or controlling the spin accumulation profile in the free layer offer promising tools to design effcient spin devices.

  6. Lack of negatively charged residues at the external mouth of Kir2.2 channels enable the voltage-dependent block by external Mg2+.

    Directory of Open Access Journals (Sweden)

    Junwei Li

    Full Text Available Kir channels display voltage-dependent block by cytosolic cations such as Mg2+ and polyamines that causes inward rectification. In fact, cations can regulate K channel activity from both the extracellular and intracellular sides. Previous studies have provided insight into the up-regulation of Kir channel activity by extracellular K+ concentration. In contrast, extracellular Mg2+ has been found to reduce the amplitude of the single-channel current at milimolar concentrations. However, little is known about the molecular mechanism of Kir channel blockade by external Mg2+ and the relationship between the Mg2+ blockade and activity potentiation by permeant K+ ions. In this study, we applied an interactive approach between theory and experiment. Electrophysiological recordings on Kir2.2 and its mutants were performed by heterologous expression in Xenopus laevis oocytes. Our results confirmed that extracellular Mg2+ could reduce heterologously expressed WT Kir2.2 currents in a voltage dependent manner. The kinetics of inhibition and recovery of Mg2+ exhibit a 3∼4s time constant. Molecular dynamics simulation results revealed a Mg2+ binding site located at the extracellular mouth of Kir2.2 that showed voltage-dependent Mg2+ binding. The mutants, G119D, Q126E and H128D, increased the number of permeant K+ ions and reduced the voltage-dependent blockade of Kir2.2 by extracellular Mg2+.

  7. [Role of voltage-dependent ion channels in epileptogenesis].

    Science.gov (United States)

    Ricard-Mousnier, B; Couraud, F

    1993-10-01

    The aim of this review is to gather information in favour of the involvement of voltage-dependent ion channels in epileptogenesis. Although, up to now, no study has shown that epilepsy is accompanied by a modification in the activity to these channels, the recently acquired knowledge of their physiology allows to presume would favor their involvement in epileptogenesis. The results from electrophysiological studies are as follows: a persistent sodium current increases neuronal excitability whereas potassium currents have an inhibitory role. In particular, calcium-dependent potassium current are involved in the post-hyperpolarization phases which follows PDS. Calcium currents are also involved in the genesis of the "bursting pacemaker" activity displayed by the neurons presumed to be inducers of the epileptic activity. Biochemical data has shown that as a consequence of epileptic activity, sodium and calcium channels are down regulated. This down-regulation could be a way to reduces neuronal hyperexcitability. Pharmacological data demonstrate the drugs which activate calcium channels or which inhibit potassium channels have a convusilvant effect. On the contrary, agents which block calcium or sodium channels or which properties. Among the latter ones, some antiepileptic drugs can be found. In summary situations which lead to increase in calcium and sodium currents and/or to an inhibition in potassium currents are potentially epileptogenic.

  8. Conductance hysteresis in the voltage-dependent anion channel.

    Science.gov (United States)

    Rappaport, Shay M; Teijido, Oscar; Hoogerheide, David P; Rostovtseva, Tatiana K; Berezhkovskii, Alexander M; Bezrukov, Sergey M

    2015-09-01

    Hysteresis in the conductance of voltage-sensitive ion channels is observed when the transmembrane voltage is periodically varied with time. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, because the focus was solely on the channel opening branches of the hysteresis loops. We studied the hysteretic response of a multichannel VDAC system to a triangular voltage ramp the frequency of which was varied over three orders of magnitude, from 0.5 mHz to 0.2 Hz. We found that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, suggesting broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, quasi-equilibrium two-state behavior is observed for hysteresis branches corresponding to VDAC opening. This enables calculation of the usual equilibrium gating parameters, gating charge and voltage of equipartitioning, which were found to be almost insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, and, in the opening branch, follows quasi-equilibrium paths.

  9. Phosphorylation of purified mitochondrial Voltage-Dependent Anion Channel by c-Jun N-terminal Kinase-3 modifies channel voltage-dependence

    Directory of Open Access Journals (Sweden)

    Rajeev Gupta

    2017-06-01

    Full Text Available Voltage-Dependent Anion Channel (VDAC phosphorylated by c-Jun N-terminal Kinase-3 (JNK3 was incorporated into the bilayer lipid membrane. Single-channel electrophysiological properties of the native and the phosphorylated VDAC were compared. The open probability versus voltage curve of the native VDAC displayed symmetry around the voltage axis, whereas that of the phosphorylated VDAC showed asymmetry. This result indicates that phosphorylation by JNK3 modifies voltage-dependence of VDAC.

  10. SPS rectifier stations

    CERN Multimedia

    CERN PhotoLab

    1974-01-01

    The first of the twelves SPS rectifier stations for the bending magnets arrived at CERN at the end of the year. The photograph shows a station with the rectifiers on the left and in the other three cubicles the chokes, capacitors and resistor of the passive filter.

  11. trans-Caryophyllene, a Natural Sesquiterpene, Causes Tracheal Smooth Muscle Relaxation through Blockade of Voltage-Dependent Ca2+ Channels

    Directory of Open Access Journals (Sweden)

    Jader Santos Cruz

    2012-10-01

    Full Text Available trans-Caryophyllene is a major component in the essential oils of various species of medicinal plants used in popular medicine in Brazil. It belongs to the chemical class of the sesquiterpenes and has been the subject of a number of studies. Here, we evaluated the effects of this compound in airway smooth muscle. The biological activities of trans-caryophyllene were examined in isolated bath organs to investigate the effect in basal tonus. Electromechanical and pharmacomechanical couplings were evaluated through the responses to K+ depolarization and exposure to acetylcholine (ACh, respectively. Isolated cells of rat tracheal smooth muscle were used to investigate trans-caryophyllene effects on voltage-dependent Ca2+ channels by using the whole-cell voltage-clamp configuration of the patch-clamp technique. trans-Caryophyllene showed more efficiency in the blockade of electromechanical excitation-contraction coupling while it has only minor inhibitory effect on pharmacomechanical coupling. Epithelium removal does not modify tracheal smooth muscle response elicited by trans-caryophyllene in the pharmacomechanical coupling. Under Ca2+-free conditions, pre-exposure to trans-caryophyllene did not reduce the contraction induced by ACh in isolated rat tracheal smooth muscle, regardless of the presence of intact epithelium. In the whole-cell configuration, trans-caryophyllene (3 mM, inhibited the inward Ba2+ current (IBa to approximately 50% of control levels. Altogether, our results demonstrate that trans-caryophyllene has anti-spasmodic activity on rat tracheal smooth muscle which could be explained, at least in part, by the voltage-dependent Ca2+ channels blockade.

  12. G Protein-induced Trafficking of Voltage-dependent Calcium Channels

    National Research Council Canada - National Science Library

    Eugene Tombler; Nory Jun Cabanilla; Paul Carman; Natasha Permaul; John J. Hall; Ryan W. Richman; Jessica Lee; Jennifer Rodriguez; Dan P. Felsenfeld; Robert F. Hennigan; María A. Diversé-Pierluissi

    2006-01-01

    .... Here we report a novel mechanism for G protein-mediated modulation of neuronal voltage-dependent calcium channels that involves the destabilization and subsequent removal of calcium channels from the plasma membrane...

  13. Analytical Model for Voltage-Dependent Photo and Dark Currents in Bulk Heterojunction Organic Solar Cells

    OpenAIRE

    2016-01-01

    A physics-based explicit mathematical model for the external voltage-dependent forward dark current in bulk heterojunction (BHJ) organic solar cells is developed by considering Shockley-Read-Hall (SRH) recombination and solving the continuity equations for both electrons and holes. An analytical model for the external voltage-dependent photocurrent in BHJ organic solar cells is also proposed by incorporating exponential photon absorption, dissociation efficiency of bound electron-hole pairs (...

  14. Pharmacology of the human red cell voltage-dependent cation channel Part I. Activation by clotrimazole and analogues

    DEFF Research Database (Denmark)

    Barksmann, Trine Lyberth; Kristensen, Berit I.; Christophersen, Palle.

    2004-01-01

    Human red cells, Nonselective voltage dependent cation channel, NSVDC channel, Gárdos channel blockers, NSVDC channel activators......Human red cells, Nonselective voltage dependent cation channel, NSVDC channel, Gárdos channel blockers, NSVDC channel activators...

  15. Actin Dynamics Regulates Voltage-Dependent Calcium-Permeable Channels of the Vicia faba Guard Cell Plasma Membrane

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

    Free cytosolic Ca~(2+) ([Ca~(2+)]_(cyt)) is an ubiquitous second messenger in plant cell signaling, and [Ca~(2+)]_(cyt) elevation is associated with Ca~(2+)-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca~(2+) channels and their regulation remains limited in planta. A type of voltage-dependent Ca~(2+)-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba~(2+) and Ca~(2+), and their activities can be inhibited by micromolar Gd~(3+). The unitary conductance and the reversal potential of the channels depend on the Ca~(2+) or Ba~(2+) gradients across the plasma membrane. The inward whole-cell Ca~(2+) (Ba~(2+)) current, as well as the unitary current amplitude and NP. of the single Ca~(2+) channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NP_o of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.

  16. Inward-Outward Connections In Internationalization

    OpenAIRE

    Welch, L S; Luostarinen, R K

    1991-01-01

    In this article the impact of the inward and outward sides of internationalization on each other is examined. The effect of the inward process on later outward moves has been the subject of limited research, although some evidence from Australian studies of licensing and franchising indicates that the inward steps can sometimes play an important preparatory role in the outward process. Governments have for some time been using inward international flows to force a reverse process - for exampl...

  17. Rectifier cabinet static breaker

    Science.gov (United States)

    Costantino, Jr, Roger A.; Gliebe, Ronald J.

    1992-09-01

    A rectifier cabinet static breaker replaces a blocking diode pair with an SCR and the installation of a power transistor in parallel with the latch contactor to commutate the SCR to the off state. The SCR serves as a static breaker with fast turnoff capability providing an alternative way of achieving reactor scram in addition to performing the function of the replaced blocking diodes. The control circuitry for the rectifier cabinet static breaker includes on-line test capability and an LED indicator light to denote successful test completion. Current limit circuitry provides high-speed protection in the event of overload.

  18. Effects of in vitro and in vivo lead exposure on voltage-dependent calcium channels in central neurons of Lymnaea stagnalis.

    Science.gov (United States)

    Audesirk, G

    1987-01-01

    Currents through calcium channels of members of an identified cluster of neurons (B cells) in the pond snail Lymnaea stagnalis were studied under voltage clamp. The normal physiological saline was modified to maximize the visibility of voltage-dependent calcium currents and minimize contamination by other currents. Barium was used as the charge carrier for the calcium channels. Depolarizing voltage steps induce an inward current, the magnitude of which varies with the barium concentration. In brains taken from animals not exposed in vivo to lead, in vitro addition of lead acetate to the recording medium (0.25 to 14 microM) inhibits the barium current by 59 +/- 14% (mean +/- s.d.), in a manner that is independent of the lead concentration. The magnitude of the residual current still varies with the barium concentration. The voltage dependence of the current appears to be unaffected by lead. In contrast to some other calcium-channel blockers, such as cobalt, the inhibition of barium currents by in vitro lead exposure is irreversible, at least in short-term experiments. Contrary to expectations based on these in vitro results, barium currents in B cells of animals exposed to 5 microM lead for 6 to 12 weeks in vivo were approximately twice as large as barium currents in B cells from unexposed controls, when both were recorded in lead-free saline. It is possible that chronic in vivo lead exposure causes an increase in the number of calcium channels in these neurons.

  19. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    Energy Technology Data Exchange (ETDEWEB)

    Manipatruni, Sasikanth, E-mail: sasikanth.manipatruni@intel.com; Nikonov, Dmitri E.; Young, Ian A. [Exploratory Integrated Circuits, Components Research, Intel Corp., Hillsboro, Oregon 97124 (United States)

    2014-05-07

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  20. Novel expression and regulation of voltage-dependent potassium channels in placentas from women with preeclampsia.

    Science.gov (United States)

    Mistry, Hiten D; McCallum, Laura A; Kurlak, Lesia O; Greenwood, Iain A; Broughton Pipkin, Fiona; Tribe, Rachel M

    2011-09-01

    Preeclampsia is associated with structural/functional alterations in placental and maternal vasculature. Voltage-dependant potassium channels encoded by KCNQ1-5 genes have been detected in several types of blood vessels where they promote vascular relaxation. Voltage-dependant potassium channel function can be modulated by KCNE1-5-encoded accessory proteins. The aim of this study was to determine whether KCNQ and KCNE genes are differentially expressed in placentas from women with preeclampsia compared with normotensive controls and to examine any differences in those who delivered preterm (voltage-dependant potassium channels are expressed and markedly modulated in placentas from preeclamptic women. Differential expression of isoforms may lead to altered cell proliferation. The correlation between KCNQ3 and KCNE5 expression is indicative of a novel channel complex and warrants further investigation.

  1. Topology optimization of viscoelastic rectifiers

    DEFF Research Database (Denmark)

    Jensen, Kristian Ejlebjærg; Szabo, Peter; Okkels, Fridolin

    2012-01-01

    An approach for the design of microfluidic viscoelastic rectifiers is presented based on a combination of a viscoelastic model and the method of topology optimization. This presumption free approach yields a material layout topologically different from experimentally realized rectifiers...

  2. Screening of potassium inwardly-rectifying channel KCNJ11 gene mutation in patients with type 2 diabetes mellitus and poor β cell function in Shanghai%上海地区胰岛功能不足的2型糖尿病患者钾离子内向整流通道蛋白KCNJ11基因突变筛查

    Institute of Scientific and Technical Information of China (English)

    唐珊珊; 张蓉; 王从容; 胡承; 江枫; 虞伟慧; 包玉倩; 贾伟平

    2012-01-01

    Objective To investigate the prevalence of mutation of potassium inwardly-rectifying channel KCNJ11 gene in type 2 diabetes mellitus with pancreatic dysfunction in Shanghai.Methods Fortyone patients (30 male,11 female) with type 2 diabetes mellitus were enrolled,whose average age was (57 ±12) years old and fasting C-peptide were all less than 0.20 μg/L in OGTT test and with negative antibody test.General data such as age,gender,family history,anthropometric parameters were collected.The PCRdirect sequencing was employed to detect the KCNJ11 gene mutation and analyze the frequencies of the discovered mutations and variants.We compared genotype frequency differences between our experiment and The International HapMap Project Chinese database by the chi-square test.Results Only one synonymous mutation (S274S) was found in one participant.Moreover,we also identified four variants in this study,rs5215,rs5218,rs5219 and rs1800854.The allele frequencies of the four variants had no significant differences between our study and HapMap Chinese database ( the x2 value was 0.010,0.391,0.025,0.407,respectively,and all P > 0.05 ).Conclusion The KCNJ11 gene mutation may not the major cause of diabetes patients with pancreatic dysfunction.%目的 了解上海地区胰岛功能不足的糖尿病患者钾离子内向整流通道蛋白J亚单位11号成员(KCNJ11)基因突变的发生情况.方法 选取上海市第六人民医院内分泌代谢科住院2型糖尿病患者41例,其中男30例,女11例,平均年龄(57±12)岁,胰岛β细胞自身抗体谷氨酸脱羧酶(GAD)、酪氨酸磷酸酶(IA2)检查阴性且糖耐量试验空腹C肽均≤0.20μg/L.应用聚合酶链反应直接测序法进行基因突变筛查.用卡方检验来比较本实验得出的基因型频率与国际人类基因组单体型图计划(HapMap)中国人数据库是否存在差异.结果 在1例患者中见到1个同义突变(即S274S).此外,还发现4个变异位点,分别为rs5215、rs5218、rs5219

  3. KCNQ1 Channels Voltage Dependence through a Voltage-dependent Binding of the S4-S5 Linker to the Pore Domain*

    OpenAIRE

    2010-01-01

    Voltage-dependent potassium (Kv) channels are tetramers of six transmembrane domain (S1–S6) proteins. Crystallographic data demonstrate that the tetrameric pore (S5–S6) is surrounded by four voltage sensor domains (S1–S4). One key question remains: how do voltage sensors (S4) regulate pore gating? Previous mutagenesis data obtained on the Kv channel KCNQ1 highlighted the critical role of specific residues in both the S4-S5 linker (S4S5L) and S6 C terminus (S6T). From these data, we hypothesiz...

  4. hERG S4-S5 linker acts as a voltage-dependent ligand that binds to the activation gate and locks it in a closed state.

    Science.gov (United States)

    Malak, Olfat A; Es-Salah-Lamoureux, Zeineb; Loussouarn, Gildas

    2017-12-01

    Delayed-rectifier potassium channels (hERG and KCNQ1) play a major role in cardiac repolarization. These channels are formed by a tetrameric pore (S5-S6) surrounded by four voltage sensor domains (S1-S4). Coupling between voltage sensor domains and the pore activation gate is critical for channel voltage-dependence. However, molecular mechanisms remain elusive. Herein, we demonstrate that covalently binding, through a disulfide bridge, a peptide mimicking the S4-S5 linker (S4-S5L) to the channel S6 C-terminus (S6T) completely inhibits hERG. This shows that channel S4-S5L is sufficient to stabilize the pore activation gate in its closed state. Conversely, covalently binding a peptide mimicking S6T to the channel S4-S5L prevents its inhibiting effect and renders the channel almost completely voltage-independent. This shows that the channel S4-S5L is necessary to stabilize the activation gate in its closed state. Altogether, our results provide chemical evidence that S4-S5L acts as a voltage-controlled ligand that binds S6T to lock the channel in a closed state, elucidating the coupling between voltage sensors and the gate in delayed rectifier potassium channels and potentially other voltage-gated channels.

  5. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    Science.gov (United States)

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

    2014-11-01

    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.

  6. Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel

    Energy Technology Data Exchange (ETDEWEB)

    Gaudioso, Christelle; Carlier, Edmond; Youssouf, Fahamoe [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Clare, Jeffrey J. [Eaton Pharma Consulting, Eaton Socon, Cambridgeshire PE19 8EF (United Kingdom); Debanne, Dominique [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Alcaraz, Gisele, E-mail: gisele.alcaraz@univmed.fr [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France)

    2011-07-29

    Highlights: {yields} Both Ca{sup ++}-Calmodulin (CaM) and Ca{sup ++}-free CaM bind to the C-terminal region of Nav1.1. {yields} Ca{sup ++} and CaM have both opposite and convergent effects on I{sub Nav1.1}. {yields} Ca{sup ++}-CaM modulates I{sub Nav1.1} amplitude. {yields} CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. {yields} Ca{sup ++} alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channel expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca{sup ++} depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca{sup ++} could bind the Nav1.1 C-terminal region with micromolar affinity.

  7. EMC Increasing of PWM Rectifier in Comparison with Classical Rectifier

    Directory of Open Access Journals (Sweden)

    R. Dolecek

    2008-12-01

    Full Text Available Pulse width modulated rectifier is a very popular topic nowadays. The modern industrial production demands continuous and lossless conversion of electrical energy parameters. This need leads to wide spread of power semiconductor converters. The rapid development in power electronics and microprocessor technology enables to apply sophisticated control methods that eliminate negative side effects of the power converters on the supply network. The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption. That is why the PWM rectifier is being examined. In comparison with the phase controlled rectifier it can be controlled to consume nearly sinusoidal current with power factor equal to unity. Another advantage is its capability of energy recuperation. The PWM rectifier can assert itself for its good behavior in many applications, for example as an input rectifier in indirect frequency converter, or in traction. Traction vehicles equipped with PWM rectifier do not consume reactive power, do not load the supply network with higher harmonics, and the recuperation is possible. The paper deals with the PWM rectifier functional model realization and examination. Electromagnetic compatibility of PWM rectifier and classical phase controlled rectifier is compared on the basis of the input current harmonic analysis.

  8. Solid state thermal rectifier

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-07-05

    Thermal rectifiers using linear nanostructures as core thermal conductors have been fabricated. A high mass density material is added preferentially to one end of the nanostructures to produce an axially non-uniform mass distribution. The resulting nanoscale system conducts heat asymmetrically with greatest heat flow in the direction of decreasing mass density. Thermal rectification has been demonstrated for linear nanostructures that are electrical insulators, such as boron nitride nanotubes, and for nanostructures that are conductive, such as carbon nanotubes.

  9. Charges in the cytoplasmic pore control intrinsic inward rectification and single-channel properties in Kir1.1 and Kir2.1 channels.

    Science.gov (United States)

    Chang, Hsueh-Kai; Yeh, Shih-Hao; Shieh, Ru-Chi

    2007-02-01

    An E224G mutation of the Kir2.1 channel generates intrinsic inward rectification and single-channel fluctuations in the absence of intracellular blockers. In this study, we showed that positively charged residues H226, R228 and R260, near site 224, regulated the intrinsic inward rectification and single-channel properties of the E224G mutant. By carrying out systematic mutations, we found that the charge effect on the intrinsic inward rectification and single-channel conductance is consistent with a long-range electrostatic mechanism. A Kir1.1 channel where the site equivalent to E224 in the Kir2.1 channel is a glycine residue does not show inward rectification or single-channel fluctuations. The G223K and N259R mutations of the Kir1.1 channel induced intrinsic inward rectification and reduced the single-channel conductance but did not generate large open-channel fluctuations. Substituting the cytoplasmic pore of the E224G mutant into the Kir1.1 channel induced open-channel fluctuations and intrinsic inward rectification. The single-channel conductance of the E224G mutant showed inward rectification. Also, a voltage-dependent gating mechanism decreased open probability during depolarization and contributed to the intrinsic inward rectification in the E224G mutant. In addition to an electrostatic effect, a close interaction of K(+) with channel pore may be required for generating open-channel fluctuations in the E224G mutant.

  10. 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

    2001-01-01

    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...

  11. Lavender Oil-Potent Anxiolytic Properties via Modulating Voltage Dependent Calcium Channels

    OpenAIRE

    2013-01-01

    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, bioc...

  12. A comparative study of the action of tolperisone on seven different voltage dependent sodium channel isoforms.

    Science.gov (United States)

    Hofer, Doris; Lohberger, Birgit; Steinecker, Bibiane; Schmidt, Kurt; Quasthoff, Stefan; Schreibmayer, Wolfgang

    2006-05-24

    The specific, acute interaction of tolperisone, an agent used as a muscle relaxant and for the treatment of chronic pain conditions, with the Na(v1.2), Na(v1.3), Na(v1.4), Na(v1.5), Na(v1.6), Na(v1.7), and Na(v1.8) isoforms of voltage dependent sodium channels was investigated and compared to that of lidocaine. Voltage dependent sodium channels were expressed in the Xenopus laevis oocyte expression system and sodium currents were recorded with the two electrode voltage clamp technique. Cumulative dose response relations revealed marked differences in IC(50) values between the two drugs on identical isoforms, as well as between isoforms. A detailed kinetic analysis uncovered that tolperisone as well as lidocaine exhibited their blocking action not only via state dependent association/dissociation with voltage dependent sodium channels, but a considerable fraction of inhibition is tonic, i.e. permanent and basic in nature. Voltage dependent activation was affected to a minor extent only. A shift in steady-state inactivation to more negative potentials could be observed for most drug/isoform combinations. The contribution of this shift to overall block was, however, small at drug concentrations resulting in considerable overall block. Recovery from inactivation was affected notably by both drugs. Lidocaine application led to a pronounced prolongation of the time constant of the fast recovery process for the Na(v1.3), Na(v1.5), and Na(v1.7) isoforms, indicating common structural properties in the local anesthetic receptor site of these three proteins. Interestingly, this characteristic drug action was not observed for tolperisone.

  13. Proper Voltage-Dependent Ion Channel Function in Dysferlin-Deficient Cardiomyocytes.

    Science.gov (United States)

    Rubi, Lena; Gawali, Vaibhavkumar S; Kubista, Helmut; Todt, Hannes; Hilber, Karlheinz; Koenig, Xaver

    2015-01-01

    Dysferlin plays a decisive role in calcium-dependent membrane repair in myocytes. Mutations in the encoding DYSF gene cause a number of myopathies, e.g. limb-girdle muscular dystrophy type 2B (LGMD2B). Besides skeletal muscle degenerative processes, dysferlin deficiency is also associated with cardiac complications. Thus, both LGMD2B patients and dysferlin-deficient mice develop a dilated cardiomyopathy. We and others have recently reported that dystrophin-deficient ventricular cardiomyocytes from mouse models of Duchenne muscular dystrophy show significant abnormalities in voltage-dependent ion channels, which may contribute to the pathophysiology in dystrophic cardiomyopathy. The aim of the present study was to investigate if dysferlin, like dystrophin, is a regulator of cardiac ion channels. By using the whole cell patch-clamp technique, we compared the properties of voltage-dependent calcium and sodium channels, as well as action potentials in ventricular cardiomyocytes isolated from the hearts of normal and dysferlin-deficient (dysf) mice. In contrast to dystrophin deficiency, the lack of dysferlin did not impair the ion channel properties and left action potential parameters unaltered. In connection with normal ECGs in dysf mice these results suggest that dysferlin deficiency does not perturb cardiac electrophysiology. Our study demonstrates that dysferlin does not regulate cardiac voltage-dependent ion channels, and implies that abnormalities in cardiac ion channels are not a universal characteristic of all muscular dystrophy types. © 2015 S. Karger AG, Basel.

  14. Development of voltage-dependent calcium, sodium, and potassium currents in Xenopus spinal neurons.

    Science.gov (United States)

    O'Dowd, D K; Ribera, A B; Spitzer, N C

    1988-03-01

    Action potentials of embryonic nerve and muscle cells often have a different ionic dependence and longer duration than those of mature cells. The action potential of spinal cord neurons from Xenopus laevis exhibits a prominent calcium component at early stages of development that diminishes with age as the impulse becomes principally sodium dependent. Whole-cell voltage-clamp analysis has been undertaken to characterize the changes in membrane currents during development of these neurons in culture. Four voltage-dependent currents of cells were identified and examined during the first day in vitro, when most of the change in the action potential occurs. There are no changes in the peak density of the calcium current (ICa), its voltage dependence, or time to half-maximal activation; a small increase in inactivation is apparent. The major change in sodium current (INa) is a 2-fold increase in its density. In addition, more subtle changes in the kinetics of the macroscopic sodium current were noted. The peak density of voltage-dependent potassium current (IKv) increases 3-fold, and this current becomes activated almost twice as fast. No changes were noted in the extent of its inactivation. The calcium-dependent potassium current (IKc) consists of an inactivating and a sustained component. The former increases 2-fold in peak current density, and the latter increases similarly at less depolarized voltages. The changes in these currents contribute to the decrease in duration and the change in ionic dependence of the impulse.

  15. Voltage Dependence of Conformational Dynamics and Subconducting States of VDAC-1.

    Science.gov (United States)

    Briones, Rodolfo; Weichbrodt, Conrad; Paltrinieri, Licia; Mey, Ingo; Villinger, Saskia; Giller, Karin; Lange, Adam; Zweckstetter, Markus; Griesinger, Christian; Becker, Stefan; Steinem, Claudia; de Groot, Bert L

    2016-09-20

    The voltage-dependent anion channel 1 (VDAC-1) is an important protein of the outer mitochondrial membrane that transports energy metabolites and is involved in apoptosis. The available structures of VDAC proteins show a wide β-stranded barrel pore, with its N-terminal α-helix (N-α) bound to its interior. Electrophysiology experiments revealed that voltage, its polarity, and membrane composition modulate VDAC currents. Experiments with VDAC-1 mutants identified amino acids that regulate the gating process. However, the mechanisms for how these factors regulate VDAC-1, and which changes they trigger in the channel, are still unknown. In this study, molecular dynamics simulations and single-channel experiments of VDAC-1 show agreement for the current-voltage relationships of an "open" channel and they also show several subconducting transient states that are more cation selective in the simulations. We observed voltage-dependent asymmetric distortions of the VDAC-1 barrel and the displacement of particular charged amino acids. We constructed conformational models of the protein voltage response and the pore changes that consistently explain the protein conformations observed at opposite voltage polarities, either in phosphatidylethanolamine or phosphatidylcholine membranes. The submicrosecond VDAC-1 voltage response shows intrinsic structural changes that explain the role of key gating amino acids and support some of the current gating hypotheses. These voltage-dependent protein changes include asymmetric barrel distortion, its interaction with the membrane, and significant displacement of N-α amino acids.

  16. Proper Voltage-Dependent Ion Channel Function in Dysferlin-Deficient Cardiomyocytes

    Directory of Open Access Journals (Sweden)

    Lena Rubi

    2015-06-01

    Full Text Available Background/Aims: Dysferlin plays a decisive role in calcium-dependent membrane repair in myocytes. Mutations in the encoding DYSF gene cause a number of myopathies, e.g. limb-girdle muscular dystrophy type 2B (LGMD2B. Besides skeletal muscle degenerative processes, dysferlin deficiency is also associated with cardiac complications. Thus, both LGMD2B patients and dysferlin-deficient mice develop a dilated cardiomyopathy. We and others have recently reported that dystrophin-deficient ventricular cardiomyocytes from mouse models of Duchenne muscular dystrophy show significant abnormalities in voltage-dependent ion channels, which may contribute to the pathophysiology in dystrophic cardiomyopathy. The aim of the present study was to investigate if dysferlin, like dystrophin, is a regulator of cardiac ion channels. Methods and Results: By using the whole cell patch-clamp technique, we compared the properties of voltage-dependent calcium and sodium channels, as well as action potentials in ventricular cardiomyocytes isolated from the hearts of normal and dysferlin-deficient (dysf mice. In contrast to dystrophin deficiency, the lack of dysferlin did not impair the ion channel properties and left action potential parameters unaltered. In connection with normal ECGs in dysf mice these results suggest that dysferlin deficiency does not perturb cardiac electrophysiology. Conclusion: Our study demonstrates that dysferlin does not regulate cardiac voltage-dependent ion channels, and implies that abnormalities in cardiac ion channels are not a universal characteristic of all muscular dystrophy types.

  17. Voltage-dependent calcium channels from brain incorporated into planar lipid bilayers

    Science.gov (United States)

    Nelson, Mark T.; French, Robert J.; Krueger, Bruce K.

    1984-03-01

    Many important physiological processes, including neurotransmitter release and muscle contraction1-3, are regulated by the concentration of Ca2+ ions in the cell. Levels of cytoplasmic Ca2+ can be elevated by the entry of Ca2+ ions through voltage-dependent channels which are selective for Ca2+, Ba2+ and Sr2+ ions4-14. We have measured currents through single, voltage-dependent calcium channels from rat brain that have been incorporated into planar lipid bilayers. Channel gating was voltage-dependent: membrane depolarization increased the channel open times and decreased the closed times. The channels were selective for divalent cations over monovalent ions. The well-known calcium channel blockers, lanthanum and cadmium, produced a concentration-dependent reduction of the apparent single-channel conductance. Contrary to expectations14, the nature of the divalent cation carrying current through the channel affected not only the single-channel conductance, but also the channel open times, with mean open times being shortest for barium.

  18. Endocytic regulation of voltage-dependent potassium channels in the heart.

    Science.gov (United States)

    Ishii, Kuniaki; Norota, Ikuo; Obara, Yutaro

    2012-01-01

    Understanding the regulation of cardiac ion channels is critical for the prevention of arrhythmia caused by abnormal excitability. Ion channels can be regulated by a change in function (qualitative) and a change in number (quantitative). Functional changes have been extensively investigated for many ion channels including cardiac voltage-dependent potassium channels. By contrast, the regulation of ion channel numbers has not been widely examined, particularly with respect to acute modulation of ion channels. This article briefly summarizes stimulus-induced endocytic regulation of major voltage-dependent potassium channels in the heart. The stimuli known to cause their endocytosis include receptor activation, drugs, and low extracellular [K(+)], following which the potassium channels undergo either clathrin-mediated or caveolin-mediated endocytosis. Receptor-mediated endocytic regulation has been demonstrated for Kv1.2, Kv1.5, KCNQ1 (Kv7.1), and Kv4.3, while drug-induced endocytosis has been demonstrated for Kv1.5 and hERG. Low [K(+)](o)-induced endocytosis might be unique for hERG channels, whose electrophysiological characteristics are known to be under strong influence of [K(+)](o). Although the precise mechanisms have not been elucidated, it is obvious that major cardiac voltage-dependent potassium channels are modulated by endocytosis, which leads to changes in cardiac excitability.

  19. KCNQ1 channels voltage dependence through a voltage-dependent binding of the S4-S5 linker to the pore domain.

    Science.gov (United States)

    Choveau, Frank S; Rodriguez, Nicolas; Abderemane Ali, Fayal; Labro, Alain J; Rose, Thierry; Dahimène, Shehrazade; Boudin, Hélène; Le Hénaff, Carole; Escande, Denis; Snyders, Dirk J; Charpentier, Flavien; Mérot, Jean; Baró, Isabelle; Loussouarn, Gildas

    2011-01-07

    Voltage-dependent potassium (Kv) channels are tetramers of six transmembrane domain (S1-S6) proteins. Crystallographic data demonstrate that the tetrameric pore (S5-S6) is surrounded by four voltage sensor domains (S1-S4). One key question remains: how do voltage sensors (S4) regulate pore gating? Previous mutagenesis data obtained on the Kv channel KCNQ1 highlighted the critical role of specific residues in both the S4-S5 linker (S4S5(L)) and S6 C terminus (S6(T)). From these data, we hypothesized that S4S5(L) behaves like a ligand specifically interacting with S6(T) and stabilizing the closed state. To test this hypothesis, we designed plasmid-encoded peptides corresponding to portions of S4S5(L) and S6(T) of the voltage-gated potassium channel KCNQ1 and evaluated their effects on the channel activity in the presence and absence of the ancillary subunit KCNE1. We showed that S4S5(L) peptides inhibit KCNQ1, in a reversible and state-dependent manner. S4S5(L) peptides also inhibited a voltage-independent KCNQ1 mutant. This inhibition was competitively prevented by a peptide mimicking S6(T), consistent with S4S5(L) binding to S6(T). Val(254) in S4S5(L) is known to contact Leu(353) in S6(T) when the channel is closed, and mutations of these residues alter the coupling between the two regions. The same mutations introduced in peptides altered their effects, further confirming S4S5(L) binding to S6(T). Our results suggest a mechanistic model in which S4S5(L) acts as a voltage-dependent ligand bound to its receptor on S6 at rest. This interaction locks the channel in a closed state. Upon plasma membrane depolarization, S4 pulls S4S5(L) away from S6(T), allowing channel opening.

  20. Distribution of voltage-dependent and intracellular Ca2+ channels in submucosal neurons from rat distal colon.

    Science.gov (United States)

    Rehn, Matthias; Bader, Sandra; Bell, Anna; Diener, Martin

    2013-09-01

    We recently observed a bradykinin-induced increase in the cytosolic Ca2+ concentration in submucosal neurons of rat colon, an increase inhibited by blockers of voltage-dependent Ca2+ (Ca(v)) channels. As the types of Ca(v) channels used by this part of the enteric nervous system are unknown, the expression of various Ca(v) subunits has been investigated in whole-mount submucosal preparations by immunohistochemistry. Submucosal neurons, identified by a neuronal marker (microtubule-associated protein 2), are immunoreactive for Ca(v)1.2, Ca(v)1.3 and Ca(v)2.2, expression being confirmed by reverse transcription plus the polymerase chain reaction. These data agree with previous observations that the inhibition of L- and N-type Ca2+ currents strongly inhibits the response to bradykinin. However, whole-cell patch-clamp experiments have revealed that bradykinin does not enhance Ca2+ inward currents under voltage-clamp conditions. Consequently, bradykinin does not directly interact with Ca(v) channels. Instead, the kinin-induced Ca2+ influx is caused indirectly by the membrane depolarization evoked by this peptide. As intracellular Ca2+ channels on Ca(2+)-storing organelles can also contribute to Ca2+ signaling, their expression has been investigated by imaging experiments and immunohistochemistry. Inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) have been functionally demonstrated in submucosal neurons loaded with the Ca(2+)-sensitive fluorescent dye, fura-2. Histamine, a typical agonist coupled to the phospholipase C pathway, induces an increase in the fura-2 signal ratio, which is suppressed by 2-aminophenylborate, a blocker of IP3 receptors. The expression of IP3R1 has been confirmed by immunohistochemistry. In contrast, ryanodine, tested over a wide concentration range, evokes no increase in the cytosolic Ca2+ concentration nor is there immunohistochemical evidence for the expression of ryanodine receptors in these neurons. Thus, rat submucosal neurons are equipped

  1. Rectified Forces in Rubidium

    Science.gov (United States)

    Grove, Timothy Todd

    The forces exerted on a three-level atom by a bichromatic standing-wave field are investigated. A theoretical analysis shows that the standing-wave dipole force can be rectified, i.e., maintain its sign over many optical wavelengths. Three systems in particular are studied: the lambda, the vee, and the cascade. Experimental results for the rubidium 5S --> 5P --> 5D cascade system are used to confirm the theory. The nearly coincident transition wavelengths for this system (780.0 nm and 776.0 nm) provide potential wells repeating at the beat wavelength (71 μm) which can accumulate laser cooled atoms. This force may have future applications in forming deep neutral atom traps as well as in the creation of new elements for atom optics. Two-color, two-photon spectroscopy of the 5D_{5/2}cascade system (5S --> 5P --> 5D) was also performed.

  2. Voltage-dependent metabolic regulation of Kv2.1 channels in pancreatic beta-cells.

    Science.gov (United States)

    Yoshida, Masashi; Nakata, Masanori; Yamato, Shiho; Dezaki, Katsuya; Sugawara, Hitoshi; Ishikawa, San-e; Kawakami, Masanobu; Yada, Toshihiko; Kakei, Masafumi

    2010-05-28

    Voltage-gated potassium channels (Kv channels) play a crucial role in formation of action potentials in response to glucose stimulation in pancreatic beta-ells. We previously reported that the Kv channel is regulated by glucose metabolism, particularly by MgATP. We examined whether the regulation of Kv channels is voltage-dependent and mechanistically related with phosphorylation of the channels. In rat pancreatic beta-cells, suppression of glucose metabolism with low glucose concentrations of 2.8mM or less or by metabolic inhibitors decreased the Kv2.1-channel activity at positive membrane potentials, while increased it at potentials negative to -10 mV, suggesting that modulation of Kv channels by glucose metabolism is voltage-dependent. Similarly, in HEK293 cells expressing the recombinant Kv2.1 channels, 0mM but not 10mM MgATP modulated the channel activity in a manner similar to that in beta-cells. Both steady-state activation and inactivation kinetics of the channel were shifted toward the negative potential in association with the voltage-dependent modulation of the channels by cytosolic dialysis of alkaline phosphatase in beta-cells. The modulation of Kv-channel current-voltage relations were also observed during and after glucose-stimulated electrical excitation. These results suggest that the cellular metabolism including MgATP production and/or channel phosphorylation/dephosphorylation underlie the physiological modulation of Kv2.1 channels during glucose-induced insulin secretion.

  3. Purification and Characterization of Two Voltage-Dependent Anion Channel Isoforms from Plant Seeds1

    Science.gov (United States)

    Abrecht, Helge; Wattiez, Ruddy; Ruysschaert, Jean-Marie; Homblé, Fabrice

    2000-01-01

    Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 m urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates. PMID:11080295

  4. Admittance Spectroscopy in CZTSSe: Metastability Behavior and Voltage Dependent Defect Study

    Energy Technology Data Exchange (ETDEWEB)

    Koeper, Mark J.; Hages, Charles J.; Li, Jian V.; Levi, Dean; Agrawal, Rakesh

    2016-11-21

    Admittance spectroscopy has been performed on a CZTSSe device with a carrier injection pretreatment and under electronically relaxed conditions to demonstrate metastability behavior. We show that the measurements with the carrier injection pretreatment demonstrate two admittance signatures while the relaxed measurement demonstrates only one admittance signature with a different activation energy. Additionally, voltage dependent admittance spectroscopy was performed using the carrier injection pretreatment method at each of the applied voltage bias. The activation energies of the two admittance signatures were calculated and are shown to be independent of the voltage bias.

  5. Vascular inward rectifier K+ channels as external K+ sensors in the control of cerebral blood flow.

    Science.gov (United States)

    Longden, Thomas A; Nelson, Mark T

    2015-04-01

    For decades it has been known that external K(+) ions are rapid and potent vasodilators that increase CBF. Recent studies have implicated the local release of K(+) from astrocytic endfeet-which encase the entirety of the parenchymal vasculature-in the dynamic regulation of local CBF during NVC. It has been proposed that the activation of KIR channels in the vascular wall by external K(+) is a central component of these hyperemic responses; however, a number of significant gaps in our knowledge remain. Here, we explore the concept that vascular KIR channels are the major extracellular K(+) sensors in the control of CBF. We propose that K(+) is an ideal mediator of NVC, and discuss KIR channels as effectors that produce rapid hyperpolarization and robust vasodilation of cerebral arterioles. We provide evidence that KIR channels, of the KIR 2 subtype in particular, are present in both the endothelial and SM cells of parenchymal arterioles and propose that this dual positioning of KIR 2 channels increases the robustness of the vasodilation to external K(+), enables the endothelium to be actively engaged in NVC, and permits electrical signaling through the endothelial syncytium to promote upstream vasodilation to modulate CBF.

  6. Nitric oxide suppresses stomatal opening by inhibiting inward-rectifying Kin channels in Arabidopsis guard cells

    Institute of Scientific and Technical Information of China (English)

    XUE ShaoWu; YANG Pin; HE YiKun

    2008-01-01

    We explore nitric oxide (NO) effect on K+in channels in Arabidopsis guard cells. We observed NO inhib-ited K+in currents when Ca2+ chelator EGTA (Ethylene glycol-bis(2-aminoethylether)-N,N,N',N'tetraacetic acid) was not added in the pipette solution; K+in currents were not sensitive to NO when cytosolic Ca2+ was chelated by EGTA. NO inhibited the Arabidopsis stomatal opening, but when EGTA was added in the bath solution, inhibition effect of NO on stomatal opening vanished. Thus, it implies that NO ele-vates cytosolic Ca2+ by activating plasma membrane Ca2+ channels firstly, then inactivates K+in chan-nels, resulting in stomatal opening suppressed subsequently.

  7. INHIBITION OF INWARD RECTIFYING TONOPLAST CHANNELS BY A VACUOLAR FACTOR - PHYSIOLOGICAL AND KINETIC IMPLICATIONS

    NARCIS (Netherlands)

    MAATHUIS, FJM; PRINS, HBA

    1991-01-01

    Regulation of ion-channel activity must take place in order to regulate ion transport. In case of tonoplast ion channels, this is possible on both the cytoplasmic and the vacuolar side. Isolated vacuoles of young Vigna unguiculata seedlings show no or hardly any channel activity at tonoplast potenti

  8. Amphipathic antenna of an inward rectifier K+ channel responds to changes in the inner membrane leaflet.

    Science.gov (United States)

    Iwamoto, Masayuki; Oiki, Shigetoshi

    2013-01-01

    Membrane lipids modulate the function of membrane proteins. In the case of ion channels, they bias the gating equilibrium, although the underlying mechanism has remained elusive. Here we demonstrate that the N-terminal segment (M0) of the KcsA potassium channel mediates the effect of changes in the lipid milieu on channel gating. The M0 segment is a membrane-anchored amphipathic helix, bearing positively charged residues. In asymmetric membranes, the M0 helix senses the presence of negatively charged phospholipids on the inner leaflet. Upon gating, the M0 helix revolves around the axis of the helix on the membrane surface, inducing the positively charged residues to interact with the negative head groups of the lipids so as to stabilize the open conformation (i.e., the "roll-and-stabilize model"). The M0 helix is thus a charge-sensitive "antenna," capturing temporary changes in lipid composition in the fluidic membrane. This unique type of sensory device may be shared by various types of membrane proteins.

  9. Inwardly rectifying potassium channel 4.1 expression in post-traumatic syringomyelia.

    Science.gov (United States)

    Najafi, E; Stoodley, M A; Bilston, L E; Hemley, S J

    2016-03-11

    Post-traumatic syringomyelia (PTS) is a serious neurological disorder characterized by fluid filled cavities that develop in the spinal cord. PTS is thought to be caused by an imbalance between fluid inflow and outflow in the spinal cord, but the underlying mechanisms are unknown. The ion channel Kir4.1 plays an important role in the uptake of K(+) ions from the extracellular space and release of K(+) ions into the microvasculature, generating an osmotic gradient that drives water movement. Changes in Kir4.1 expression may contribute to disturbances in K(+) homeostasis and subsequently fluid imbalance. Here we investigated whether changes in Kir4.1 protein expression occur in PTS. Western blotting and immunohistochemistry were used to evaluate Kir4.1 and glial fibrillary acidic protein (GFAP) expression in a rodent model of PTS at 3 days, 1, 6 or 12 weeks post-surgery. In Western blotting experiments, Kir4.1 expression increased 1 week post-surgery at the level of the cavity. Immunohistochemical analysis examined changes in the spinal parenchyma directly in contact with the syrinx cavity. In these experiments, there was a significant decrease in Kir4.1 expression in PTS animals compared to controls at 3 days and 6 weeks post-surgery, while an up-regulation of GFAP in PTS animals was observed at 1 and 12 weeks. This suggests that while overall Kir4.1 expression is unchanged at these time-points, there are many astrocytes surrounding the syrinx cavity that are not expressing Kir4.1. The results demonstrate a disturbance in the removal of K(+) ions in tissue surrounding a post-traumatic syrinx cavity. It is possible this contributes to water accumulation in the injured spinal cord leading to syrinx formation or exacerbation of the underlying pathology.

  10. Analytical Model for Voltage-Dependent Photo and Dark Currents in Bulk Heterojunction Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Mesbahus Saleheen

    2016-05-01

    Full Text Available A physics-based explicit mathematical model for the external voltage-dependent forward dark current in bulk heterojunction (BHJ organic solar cells is developed by considering Shockley-Read-Hall (SRH recombination and solving the continuity equations for both electrons and holes. An analytical model for the external voltage-dependent photocurrent in BHJ organic solar cells is also proposed by incorporating exponential photon absorption, dissociation efficiency of bound electron-hole pairs (EHPs, carrier trapping, and carrier drift and diffusion in the photon absorption layer. Modified Braun’s model is used to compute the electric field-dependent dissociation efficiency of the bound EHPs. The overall net current is calculated considering the actual solar spectrum. The mathematical models are verified by comparing the model calculations with various published experimental results. We analyze the effects of the contact properties, blend compositions, charge carrier transport properties (carrier mobility and lifetime, and cell design on the current-voltage characteristics. The power conversion efficiency of BHJ organic solar cells mostly depends on electron transport properties of the acceptor layer. The results of this paper indicate that improvement of charge carrier transport (both mobility and lifetime and dissociation of bound EHPs in organic blend are critically important to increase the power conversion efficiency of the BHJ solar cells.

  11. Voltage dependence of rate functions for Na+ channel inactivation within a membrane

    CERN Document Server

    Vaccaro, Samuel R

    2015-01-01

    The inactivation of a Na+ channel occurs when the activation of the charged S4 segment of domain IV, with rate functions $\\alpha_{i}$ and $\\beta_{i}$, is followed by the binding of an intracellular hydrophobic motif which blocks conduction through the ion pore, with rate functions $\\gamma_{i}$ and $\\delta_{i}$. During a voltage clamp of the Na+ channel, the solution of the master equation for inactivation reduces to the relaxation of a rate equation when the binding of the inactivation motif is rate limiting ($\\alpha_{i} \\gg \\gamma_{i}$ and $\\beta_{i} \\gg \\delta_{i}$). The voltage dependence of the derived forward rate function for Na+ channel inactivation has an exponential dependence on the membrane potential for small depolarizations and approaches a constant value for larger depolarizations, whereas the voltage dependence of the backward rate function is exponential, and each rate has a similar form to the Hodgkin-Huxley empirical rate functions for Na+ channel inactivation in the squid axon.

  12. The effects of S4 segments on the voltage-dependence of inactivation for Cav3.1 calcium channels

    Institute of Scientific and Technical Information of China (English)

    LI JunYing

    2007-01-01

    T-type calcium channels exhibit fast voltage-dependent inactivation,for which the underlying structure-function relationship still remains unclear.To investigate the roles of S4 segments in voltage-dependent inactivation of T-type calcium channels,we created S4 replacement chimeras between Cav3.1 calcium channels(fast voltage-dependent inactivation)and Cav1.2 calcium channels(little oltage-dependent inactivation)by replacing S4s in Cav3.1 with the corresponding regions in Cav1.2.Wild type and chimeric channels were expressed in Xenopus oocytes and channel currents were recorded with two-electrode voltage-clamp.We showed that replacing S4 region in domain I shifted voltage-dependence for inactivation of Cav3.1 to the left,and the V0.5 inact and kinact value were significantly changed.However replacing S4s in domains Ⅱ-Ⅳ had no effects on the voltage-dependent inactivation properties.These results suggest that the roles of S4 segments in domains Ⅰ-Ⅳ are different,and S4 in domain I is likely to be involved in voltage-dependent Inactivation process.Its movement during membrane depolarization may trigger a conformational change in the inactivation gate.

  13. Increased HCN channel driven inward rectification in benign cramp fasciculation syndrome.

    Science.gov (United States)

    Czesnik, Dirk; Howells, James; Negro, Francesco; Wagenknecht, Melanie; Hanner, Susanne; Farina, Dario; Burke, David; Paulus, Walter

    2015-11-01

    Muscle cramps are a common complaint associated with sudden painful involuntary contractions of a muscle. The mechanisms responsible for muscle cramps are still not clear. Axonal excitability and multi-unit electromyography studies were performed in 20 patients suffering from benign cramp fasciculation syndrome, not currently on medication. The measures of axonal excitability suggested greater inward rectification, indicative of an increase in Ih. Mathematical modelling suggested that the data were best explained by depolarization of the voltage dependence of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. Parameters associated with polarization of resting membrane potential were not changed. These findings suggest that a role for HCN channels may become apparent during the rhythmic discharge associated with a voluntary contraction. Consistent with this view, patients had higher motor unit discharge rates than healthy controls during maximal voluntary effort.

  14. Inward propagating chemical waves in Taylor vortices.

    Science.gov (United States)

    Thompson, Barnaby W; Novak, Jan; Wilson, Mark C T; Britton, Melanie M; Taylor, Annette F

    2010-04-01

    Advection-reaction-diffusion (ARD) waves in the Belousov-Zhabotinsky reaction in steady Taylor-Couette vortices have been visualized using magnetic-resonance imaging and simulated using an adapted Oregonator model. We show how propagating wave behavior depends on the ratio of advective, chemical and diffusive time scales. In simulations, inward propagating spiral flamelets are observed at high Damköhler number (Da). At low Da, the reaction distributes itself over several vortices and then propagates inwards as contracting ring pulses--also observed experimentally.

  15. Inwardly rotating spirals in nonuniform excitable media.

    Science.gov (United States)

    Gao, Xiang; Feng, Xia; Cai, Mei-chun; Li, Bing-wei; Ying, He-ping; Zhang, Hong

    2012-01-01

    Inwardly rotating spirals (IRSs) have attracted great attention since their observation in an oscillatory reaction-diffusion system. However, IRSs have not yet been reported in planar excitable media. In the present work we investigate rotating waves in a nonuniform excitable medium, consisting of an inner disk part surrounded by an outer ring part with different excitabilities, by numerical simulations of a simple FitzHugh-Nagumo model. Depending on the excitability of the medium as well as the inhomogeneity, we find the occurrence of IRSs, of which the excitation propagates inwardly to the geometrical spiral tip.

  16. A vesicle-trafficking protein commandeers Kv channel voltage sensors for voltage-dependent secretion.

    Science.gov (United States)

    Grefen, Christopher; Karnik, Rucha; Larson, Emily; Lefoulon, Cécile; Wang, Yizhou; Waghmare, Sakharam; Zhang, Ben; Hills, Adrian; Blatt, Michael R

    2015-01-01

    Growth in plants depends on ion transport for osmotic solute uptake and secretory membrane trafficking to deliver material for wall remodelling and cell expansion. The coordination of these processes lies at the heart of the question, unresolved for more than a century, of how plants regulate cell volume and turgor. Here we report that the SNARE protein SYP121 (SYR1/PEN1), which mediates vesicle fusion at the Arabidopsis plasma membrane, binds the voltage sensor domains (VSDs) of K(+) channels to confer a voltage dependence on secretory traffic in parallel with K(+) uptake. VSD binding enhances secretion in vivo subject to voltage, and mutations affecting VSD conformation alter binding and secretion in parallel with channel gating, net K(+) concentration, osmotic content and growth. These results demonstrate a new and unexpected mechanism for secretory control, in which a subset of plant SNAREs commandeer K(+) channel VSDs to coordinate membrane trafficking with K(+) uptake for growth.

  17. Selective modulation of cellular voltage dependent calcium channels by hyperbaric pressure - a suggested HPNS partial mechanism

    Directory of Open Access Journals (Sweden)

    Ben eAviner

    2014-05-01

    Full Text Available Professional deep sea divers experience motor and cognitive impairment, known as High Pressure Neurological Syndrome (HPNS, when exposed to pressures of 100 msw (1.1MPa and above, considered to be the result of synaptic transmission alteration. Previous studies have indicated modulation of presynaptic Ca2+ currents at high pressure. We directly measured for the first time pressure effects on the currents of voltage dependent Ca2+ channels (VDCCs expressed in Xenopus oocytes. Pressure selectivity augmented the current in CaV1.2 and depressed it in CaV3.2 channels. Pressure application also affected the channels' kinetics, such as ƮRise, ƮDecay. Pressure modulation of VDCCs seems to play an important role in generation of HPNS signs and symptoms.

  18. G protein-induced trafficking of voltage-dependent calcium channels.

    Science.gov (United States)

    Tombler, Eugene; Cabanilla, Nory Jun; Carman, Paul; Permaul, Natasha; Hall, John J; Richman, Ryan W; Lee, Jessica; Rodriguez, Jennifer; Felsenfeld, Dan P; Hennigan, Robert F; Diversé-Pierluissi, María A

    2006-01-20

    Calcium channels are well known targets for inhibition by G protein-coupled receptors, and multiple forms of inhibition have been described. Here we report a novel mechanism for G protein-mediated modulation of neuronal voltage-dependent calcium channels that involves the destabilization and subsequent removal of calcium channels from the plasma membrane. Imaging experiments in living sensory neurons show that, within seconds of receptor activation, calcium channels are cleared from the membrane and sequestered in clathrin-coated vesicles. Disruption of the L1-CAM-ankyrin B complex with the calcium channel mimics transmitter-induced trafficking of the channels, reduces calcium influx, and decreases exocytosis. Our results suggest that G protein-induced removal of plasma membrane calcium channels is a consequence of disrupting channel-cytoskeleton interactions and might represent a novel mechanism of presynaptic inhibition.

  19. The Mechanism of Voltage Dependent Gating of the NaChBac Prokaryotic Sodium Channel

    Science.gov (United States)

    Decaen, Paul G.

    Electrical signaling in cells depends on selective conductance of ions through membrane proteins called 'voltage gated ion channels'. These channels are characterized by their ability turn on and off the flow of ionic current by opening and closing their conductive pore in response to changes in membrane potential. The opening and closing of the pore is a mechanically linked to conformational movement of the positively charged fourth transmembrane segment (S4) in 'the voltage sensor' region. How the S4 moves in response to membrane potential is a controversial subject. In this thesis, we used the prokaryotic sodium channel NaChBac as our model sodium channel to study voltage dependent movement of the S4 in the voltage sensor. We use a disulfide-locking method where we introduced pairs of cysteines in the voltage sensor that crosslink and trap the S4 in its path after depolarization. We screened over one hundred mutations of the NaChBac channel in the whole cell patch clamp assay and demonstrated discrete and sequential voltage dependent ion pair interactions that occur in at least three states between the positively charged residues of the S4 segment and the acidic residues in the S1, S2 and S3 segments. In conjunction with structural modeling of the voltage sensor and our disulfide locking data, we propose that the S4 moves in and out of the plane of the membrane 8-13 A, forming distinct gating charge interactions with counter charges of the voltage sensor and adopts a 310 helix over a portion of its structure during activation. These findings are compatible with the sliding helix model and refine our understanding of the structural determinates of voltage sensor function in voltage gated ion channels.

  20. PIP2 regulation of KCNQ channels: biophysical and molecular mechanisms for lipid modulation of voltage-dependent gating

    Directory of Open Access Journals (Sweden)

    Mark Alan Zaydman

    2014-05-01

    Full Text Available Voltage-gated potassium (Kv channels contain voltage-sensing (VSD and pore-gate (PGD structural domains. During voltage-dependent gating, conformational changes in the two domains are coupled giving rise to voltage-dependent opening of the channel. In addition to membrane voltage, KCNQ (Kv7 channel opening requires the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2. Recent studies suggest that PIP2 serves as a cofactor to mediate VSD-PGD coupling in KCNQ1 channels. In this review, we put these findings in the context of the current understanding of voltage-dependent gating, lipid modulation of Kv channel activation, and PIP2-regulation of KCNQ channels. We suggest that lipid-mediated coupling of functional domains is a common mechanism among KCNQ channels that may be applicable to other Kv channels and membrane proteins.

  1. PIP2 regulation of KCNQ channels: biophysical and molecular mechanisms for lipid modulation of voltage-dependent gating.

    Science.gov (United States)

    Zaydman, Mark A; Cui, Jianmin

    2014-01-01

    Voltage-gated potassium (Kv) channels contain voltage-sensing (VSD) and pore-gate (PGD) structural domains. During voltage-dependent gating, conformational changes in the two domains are coupled giving rise to voltage-dependent opening of the channel. In addition to membrane voltage, KCNQ (Kv7) channel opening requires the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2). Recent studies suggest that PIP2 serves as a cofactor to mediate VSD-PGD coupling in KCNQ1 channels. In this review, we put these findings in the context of the current understanding of voltage-dependent gating, lipid modulation of Kv channel activation, and PIP2-regulation of KCNQ channels. We suggest that lipid-mediated coupling of functional domains is a common mechanism among KCNQ channels that may be applicable to other Kv channels and membrane proteins.

  2. Over Expression of Voltage Dependent Anion Channel 2 (VDAC2 in Muscles of Electrically Stunned Chickens

    Directory of Open Access Journals (Sweden)

    Norshahida Abu Samah, Azura Amid, and Faridah Yusof

    2011-12-01

    Full Text Available Water bath stunning is a common practice in commercial slaughterhouses. Such treatment is economic and in line with animal welfare practice. However, the conditions applied for the stunning process may vary from a slaughterhouse to another slaughterhouse. Such a loose regulation on the stunning procedure has opened up doors for food adulteration such as over dose stunning. In this study, a simple and reliable approach using proteomics have been developed to study the effect of different currents and voltages in stunning on the protein expression of the chickens. Protein profiles of the chickens were constructed in order to detect any differences in protein expression and modifications. The different voltage studied were 10 V, 40 V and 70 V while the values for current studied were 0.25 A, 0.5 A, and 0.75 A. After the proteomics analyses using 2D Platinum ImageMaster 6.0 and Matrix-assisted laser desorption ionization- time of flight (MALDI TOF spectrometry identification, Voltage dependent anion channel 2 (VDAC2 was identified to be over expressed in the muscle sample of over stunned chicken. The over expression of VDAC2 was confirmed at the transcriptional level of RNA expression. Real Time PCR showed that all over stunned samples contained higher mRNA expression level for VDAC2 genes. The mRNA level of VDAC2 was up-regulated by 59.87 fold change when normalized with housekeeping gene. In conclusion, VDAC2 could serve as potential biomarkers for identification of electrically stimulated chickens. The existence of these biomarkers will help to monitor the slaughtering and stunning process in the future. It will revolutionize the food authentication field and give a new breathe to the meat industry.ABSTRAK: Kaedah "waterbath stunning" merupakan amalan biasa di pusat-pusat penyembelihan. Kaedah ini adalah ekonomik dan selari dengan amalan kebajikan haiwan. Walaubagaimanapun, syarat-syarat yang digunakan untuk proses kejutan tersebut mungkin

  3. Charged Residues at the First Transmembrane Region Contribute to the Voltage Dependence of the Slow Gate of Connexins.

    Science.gov (United States)

    Pinto, Bernardo I; García, Isaac E; Pupo, Amaury; Retamal, Mauricio A; Martínez, Agustín D; Latorre, Ramón; González, Carlos

    2016-07-22

    Connexins (Cxs) are a family of membrane-spanning proteins that form gap junction channels and hemichannels. Connexin-based channels exhibit two distinct voltage-dependent gating mechanisms termed slow and fast gating. Residues located at the C terminus of the first transmembrane segment (TM-1) are important structural components of the slow gate. Here, we determined the role of the charged residues at the end of TM-1 in voltage sensing in Cx26, Cx46, and Cx50. Conductance/voltage curves obtained from tail currents together with kinetics analysis reveal that the fast and slow gates of Cx26 involves the movement of two and four charges across the electric field, respectively. Primary sequence alignment of different Cxs shows the presence of well conserved glutamate residues in the C terminus of TM-1; only Cx26 contains a lysine in that position (lysine 41). Neutralization of lysine 41 in Cx26 increases the voltage dependence of the slow gate. Swapping of lysine 41 with glutamate 42 maintains the voltage dependence. In Cx46, neutralization of negative charges or addition of a positive charge in the Cx26 equivalent region reduced the slow gate voltage dependence. In Cx50, the addition of a glutamate in the same region decreased the voltage dependence, and the neutralization of a negative charge increased it. These results indicate that the charges at the end of TM-1 are part of the slow gate voltage sensor in Cxs. The fact that Cx42, which has no charge in this region, still presents voltage-dependent slow gating suggests that charges still unidentified also contribute to the slow gate voltage sensitivity.

  4. Voltage dependence of proton pumping by bacteriorhodopsin mutants with altered lifetime of the M intermediate.

    Directory of Open Access Journals (Sweden)

    Sven Geibel

    Full Text Available The light-driven proton pump bacteriorhodopsin (BR from Halobacterium salinarum is tightly regulated by the [H(+] gradient and transmembrane potential. BR exhibits optoelectric properties, since spectral changes during the photocycle are kinetically controlled by voltage, which predestines BR for optical storage or processing devices. BR mutants with prolonged lifetime of the blue-shifted M intermediate would be advantageous, but the optoelectric properties of such mutants are still elusive. Using expression in Xenopus oocytes and two-electrode voltage-clamping, we analyzed photocurrents of BR mutants with kinetically destabilized (F171C, F219L or stabilized (D96N, D96G M intermediate in response to green light (to probe H(+ pumping and blue laser flashes (to probe accumulation/decay of M. These mutants have divergent M lifetimes. As for BR-WT, this strictly correlates with the voltage dependence of H(+ pumping. BR-F171C and BR-F219L showed photocurrents similar to BR-WT. Yet, BR-F171C showed a weaker voltage dependence of proton pumping. For both mutants, blue laser flashes applied during and after green-light illumination showed reduced M accumulation and shorter M lifetime. In contrast, BR-D96G and BR-D96N exhibited small photocurrents, with nonlinear current-voltage curves, which increased strongly in the presence of azide. Blue laser flashes showed heavy M accumulation and prolonged M lifetime, which accounts for the strongly reduced H(+ pumping rate. Hyperpolarizing potentials augmented these effects. The combination of M-stabilizing and -destabilizing mutations in BR-D96G/F171C/F219L (BR-tri shows that disruption of the primary proton donor Asp-96 is fatal for BR as a proton pump. Mechanistically, M destabilizing mutations cannot compensate for the disruption of Asp-96. Accordingly, BR-tri and BR-D96G photocurrents were similar. However, BR-tri showed negative blue laser flash-induced currents even without actinic green light, indicating

  5. Cortisone dissociates voltage-dependent K+ channel from its beta subunit

    Science.gov (United States)

    Pan, Yaping; Weng, Jun; Kabaleeswaran, Venkataraman; Li, Huiguang; Cao, Yu; Bhosle, Rahul C.; Zhou, Ming

    2009-01-01

    The Shaker family voltage-dependent potassium channels (Kv1) are expressed in a wide variety of cells and essential for cellular excitability. In humans, loss-of-function mutations of Kv1 channels lead to hyperexcitability and are directly linked to episodic ataxia and atrial fibrillation. All Kv1 channels assemble with beta subunits (Kvβ) and certain Kvβs, for example Kvβ1, have an N-terminal segment that closes a channel by the N-type inactivation mechanism. In principle dissociation of Kvβ1, although never reported, should eliminate inactivation and thus potentiate Kv1 current. We found that cortisone increases mammalian (rat) Kv1 channel activity by binding to Kvβ1. A crystal structure of the Kvβ-cortisone complex was solved to 1.82 Å resolution and revealed novel cortisone binding sites. Further studies demonstrated that cortisone promotes dissociation of Kvβ. The new mode of channel modulation may be explored by native or synthetic ligands to fine tune cellular excitability. PMID:18806782

  6. RAS-RAF-MEK-dependent oxidative cell death involving voltage-dependent anion channels.

    Science.gov (United States)

    Yagoda, Nicholas; von Rechenberg, Moritz; Zaganjor, Elma; Bauer, Andras J; Yang, Wan Seok; Fridman, Daniel J; Wolpaw, Adam J; Smukste, Inese; Peltier, John M; Boniface, J Jay; Smith, Richard; Lessnick, Stephen L; Sahasrabudhe, Sudhir; Stockwell, Brent R

    2007-06-14

    Therapeutics that discriminate between the genetic makeup of normal cells and tumour cells are valuable for treating and understanding cancer. Small molecules with oncogene-selective lethality may reveal novel functions of oncoproteins and enable the creation of more selective drugs. Here we describe the mechanism of action of the selective anti-tumour agent erastin, involving the RAS-RAF-MEK signalling pathway functioning in cell proliferation, differentiation and survival. Erastin exhibits greater lethality in human tumour cells harbouring mutations in the oncogenes HRAS, KRAS or BRAF. Using affinity purification and mass spectrometry, we discovered that erastin acts through mitochondrial voltage-dependent anion channels (VDACs)--a novel target for anti-cancer drugs. We show that erastin treatment of cells harbouring oncogenic RAS causes the appearance of oxidative species and subsequent death through an oxidative, non-apoptotic mechanism. RNA-interference-mediated knockdown of VDAC2 or VDAC3 caused resistance to erastin, implicating these two VDAC isoforms in the mechanism of action of erastin. Moreover, using purified mitochondria expressing a single VDAC isoform, we found that erastin alters the permeability of the outer mitochondrial membrane. Finally, using a radiolabelled analogue and a filter-binding assay, we show that erastin binds directly to VDAC2. These results demonstrate that ligands to VDAC proteins can induce non-apoptotic cell death selectively in some tumour cells harbouring activating mutations in the RAS-RAF-MEK pathway.

  7. Functional unit size of the neurotoxin receptors on the voltage-dependent sodium channel.

    Science.gov (United States)

    Angelides, K J; Nutter, T J; Elmer, L W; Kempner, E S

    1985-03-25

    Radiation inactivation was used in situ to determine the functional unit sizes of the neurotoxin receptors of the voltage-dependent sodium channel from rat brain. Frozen or lyophilized synaptosomes were irradiated with high energy electrons generated by a linear accelerator and assayed for [3H]saxitoxin, 125I-Leiurus quinquestriatus quinquestriatus (alpha-scorpion toxin), 125I-Centruroides suffusus suffusus (beta-scorpion toxin), and batrachotoxinin-A 20 alpha-[3H]benzoate binding activity. The functional unit size of the neurotoxin receptors determined in situ by target analysis are 220,000 for saxitoxin, 263,000 for alpha-scorpion toxin, and 45,000 for beta-scorpion toxin. Analysis of the inactivation curve for batrachotoxinin-A 20 alpha-benzoate binding to the channel yields two target sizes of Mr approximately 287,000 (50%) and approximately 51,000 (50%). The results are independent of the purity of the membrane preparation. Comparison of the radiation inactivation data with the protein composition of the rat brain sodium channel indicates that there are at least two functional components.

  8. Pharmacological Investigation of Voltage-dependent Ca2+ Channels in Human Ejaculatory Sperm in vitro

    Institute of Scientific and Technical Information of China (English)

    LI Lu; LIU Jihong; LI Jiagui; YE Zhangqun

    2006-01-01

    The types of the voltage-dependent calcium channels (VDCCs) in human ejaculatory sperm and the effects of calcium channel blocker (CCB) on human sperm motility parameters in vitro were investigated. The human sperm motility parameters in vitro in response to the pharmacological agents nifedipine (NIF, inhibitor of L-type VDCC) and ω-conotoxin (GVIA, inhibitor of N-type VDCC) were compared and analyzed statistically. The results showed that NIF (1, 5, 10 μmol/L)could not only significantly affect human sperm's shape but also spermatozoa motility after incubated at least 10 min in vitro (P<0.001). GVIA (0.1, 0.5 and 1 μmol/L) could just only significantly affect human sperm's progressive motility (a %+b %) after incubated for 20 min in vitro (P<0.01), but they both could not significantly affect spermic abnormality rate. It is suggested that L-type VDCC, non L-type VDCCs and isoform of L-type VDCC exist in the cell membrane of human sperm solely or together, and they participate in the spermic physiological processes especially the spermic motility.

  9. Tetrahydroacridine inhibits voltage-dependent Na+ current in guinea-pig ventricular myocytes

    Institute of Scientific and Technical Information of China (English)

    Wei WANG; Yi-ping WANG; Guo-yuan HU

    2004-01-01

    AIM: To study the effects of tetrahydroacridine (tacrine) on voltage-gated Na+ channels in cardiac tissues.METHODS: Single ventricular myocytes were enzymatically dissociated from adult guinea-pig heart. Voltagedependent Na+ current was recorded using whole cell voltage-clamp technique. RESULTS: (1) Tacrine reversibly inhibited Na+ current with an IC50 value of 120 μmol/L (95 % confidence range: 108-133 μmol/L). (2) The inhibitory effects of tacrine on Na+ current exhibited both a tonic nature and use-dependence. (3) Tacrine at 100 μmol/L caused a negative shift (about 10 mV) in the voltage-dependence of steady-state inactivation of Na+ current, and retarded its recovery from inactivation, but did not affect its activation curve. (4) Intracellular application of tacrine significantly inhibited Na+ current. CONCLUSION: In addition to blocking other voltage-gated ion channels,tacrine blocked Na+ channels in guinea-pig ventricular myocytes. Tactine acted as inactivation stabilizer of Na+channels in cardiac tissues.

  10. Regulation of mitochondrial function by voltage dependent anion channels in ethanol metabolism and the Warburg effect.

    Science.gov (United States)

    Lemasters, John J; Holmuhamedov, Ekhson L; Czerny, Christoph; Zhong, Zhi; Maldonado, Eduardo N

    2012-06-01

    Voltage dependent anion channels (VDAC) are highly conserved proteins that are responsible for permeability of the mitochondrial outer membrane to hydrophilic metabolites like ATP, ADP and respiratory substrates. Although previously assumed to remain open, VDAC closure is emerging as an important mechanism for regulation of global mitochondrial metabolism in apoptotic cells and also in cells that are not dying. During hepatic ethanol oxidation to acetaldehyde, VDAC closure suppresses exchange of mitochondrial metabolites, resulting in inhibition of ureagenesis. In vivo, VDAC closure after ethanol occurs coordinately with mitochondrial uncoupling. Since acetaldehyde passes through membranes independently of channels and transporters, VDAC closure and uncoupling together foster selective and more rapid oxidative metabolism of toxic acetaldehyde to nontoxic acetate by mitochondrial aldehyde dehydrogenase. In single reconstituted VDAC, tubulin decreases VDAC conductance, and in HepG2 hepatoma cells, free tubulin negatively modulates mitochondrial membrane potential, an effect enhanced by protein kinase A. Tubulin-dependent closure of VDAC in cancer cells contributes to suppression of mitochondrial metabolism and may underlie the Warburg phenomenon of aerobic glycolysis. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.

  11. Regulation of KV channel voltage-dependent activation by transmembrane β subunits

    Directory of Open Access Journals (Sweden)

    Xiaohui eSun

    2012-04-01

    Full Text Available Voltage-activated K+ (KV channels are important for shaping action potentials and maintaining resting membrane potential in excitable cells. KV channels contain a central pore-gate domain (PGD surrounded by four voltage-sensing domains (VSD. The VSDs will change conformation in response to alterations of the membrane potential thereby inducing the opening of the PGD. Many KV channels are heteromeric protein complexes containing auxiliary β subunits. These β subunits modulate channel expression and activity to increase functional diversity and render tissue specific phenotypes. This review focuses on the KV β subunits that contain transmembrane (TM segments including the KCNE family and the β subunits of large conductance, Ca2+- and voltage-activated K+ (BK channels. These TM β subunits affect the voltage-dependent activation of KV α subunits. Experimental and computational studies have described the structural location of these β subunits in the channel complexes and the biophysical effects on VSD activation, PGD opening and VSD-PGD coupling. These results reveal some common characteristics and mechanistic insights into KV channel modulation by TM β subunits.

  12. Regional Characteristics and Effects of Inward FDI

    DEFF Research Database (Denmark)

    Kokko, Ari; Kravtsova, Victoria

    2012-01-01

    This paper contributes to the analysis of the impact of FDI on host countries by taking into account the regional dimension of spillover effects. Focusing on the case of Ukraine, we explore the effects of inward FDI on changes in productivity, technology, and effciency in local firms...... mainly driven by the development in western Ukraine, whereas inward FDI in eastern Ukraine did not seem to have any impact on local productivity growth and technical change. !ese results arguably reflect deep economic and institutional differences between the two parts of Ukraine, which have led...... to differences in the character of incoming FDI and differences in the ability of local firms to benefit from FDI. The conclusion is that the impact of FDI on the host economy may vary even at the sub-national level, depending on the specific local environment....

  13. State based factors affecting inward FDI employment

    Directory of Open Access Journals (Sweden)

    Lucyna Kornecki

    2012-12-01

    Full Text Available This empirical research investigates state based factors affecting the inward FDI employment among fifty states of the United States, uses annual data for the period of time from 1997 to 2007 and identifies several state-specific determinants of FDI employment. The results indicate that the major factors exerting positive impact on inward US FDI employment are: real wages, infrastructure, unionization level, educational attainment, FDI stock and manufacturing density.  In addition, the results show that gross state product growth rate, real per capita taxes and share of scientists and engineers have negative impact on FDI employment. Our findings indicate the importance of selected variables in evaluating the effects of FDI flow.Keywords: FDI, Growth, Employment, State, Economy

  14. The voltage dependence of GABAA receptor gating depends on extracellular pH.

    Science.gov (United States)

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W

    2005-11-28

    Recent studies have indicated that changes in extracellular pH and in membrane voltage affect the gamma-amino-n-butyric acid type A receptor gating mainly by altering desensitization and binding. To test whether the effects of membrane potential and pH are additive, their combined actions were investigated. By analyzing the current responses to rapid gamma-amino-n-butyric acid applications, we found that the current to voltage relationship was close to linear at acid pH but the increasing pH induced an inward rectification. Desensitization was enhanced at depolarizing potentials, but this strongly depended on pH, being weak at acidic and strong at basic pH values. A similar trend was observed for the onset rate of responses to saturating gamma-amino-n-butyric acid concentration. These data provide evidence that the voltage sensitivity of GABAA receptors depends on extracellular pH.

  15. The voltage dependence of GABAA receptor gating depends on extracellular pH

    Science.gov (United States)

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W.

    2007-01-01

    Recent studies have indicated that changes in extracellular pH and in membrane voltage affect the γ-amino-n-butyric acid type A receptor gating mainly by altering desensitization and binding. To test whether the effects of membrane potential and pH are additive, their combined actions were investigated. By analyzing the current responses to rapid γ-amino-n-butyric acid applications, we found that the current to voltage relationship was close to linear at acid pH but the increasing pH induced an inward rectification. Desensitization was enhanced at depolarizing potentials, but this strongly depended on pH, being weak at acidic and strong at basic pH values. A similar trend was observed for the onset rate of responses to saturating γ-amino-n-butyric acid concentration. These data provide evidence that the voltage sensitivity of GABAA receptors depends on extracellular pH. PMID:16272885

  16. RTD application in low power UHF rectifiers

    Science.gov (United States)

    Sinyakin, V. Yu; Makeev, M. O.; Meshkov, S. A.

    2016-08-01

    In the current work, the problem of UHF RFID passive tag sensitivity increase is considered. Tag sensitivity depends on HF signal rectifier efficiency and antenna-rectifier impedance matching. Possibility of RFID passive tag sensitivity increase up to 10 times by means of RTD use in HF signal rectifier in comparison with tags based on Schottky barrier diode is shown.

  17. The human red cell voltage-dependent cation channel. Part III: Distribution homogeneity and pH dependence

    DEFF Research Database (Denmark)

    Bennekou, P.; Barksmann, T. L.; Christophersen, P.

    2006-01-01

    The homogeneity of the distribution of the non-selective voltage-dependent cation channel (the NSVDC channel) in the human erythrocyte, and the pH dependence was investigated. Activation of this channel caused a uniform cellular dehydration, which was characterized by the changes in the erythrocyte...

  18. Origin of the voltage dependence of G-protein regulation of P/Q-type Ca2+ channels.

    Science.gov (United States)

    Zhang, Yun; Chen, Yu-Hang; Bangaru, Saroja D; He, Linling; Abele, Kathryn; Tanabe, Shihori; Kozasa, Tohru; Yang, Jian

    2008-12-24

    G-protein (Gbetagamma)-mediated voltage-dependent inhibition of N- and P/Q-type Ca(2+) channels contributes to presynaptic inhibition and short-term synaptic plasticity. The voltage dependence derives from the dissociation of Gbetagamma from the inhibited channels, but the underlying molecular and biophysical mechanisms remain largely unclear. In this study we investigated the role in this process of Ca(2+) channel beta subunit (Ca(v)beta) and a rigid alpha-helical structure between the alpha-interacting domain (AID), the primary Ca(v)beta docking site on the channel alpha(1) subunit, and the pore-lining IS6 segment. Gbetagamma inhibition of P/Q-type channels was reconstituted in giant inside-out membrane patches from Xenopus oocytes. Large populations of channels devoid of Ca(v)beta were produced by washing out a mutant Ca(v)beta with a reduced affinity for the AID. These beta-less channels were still inhibited by Gbetagamma, but without any voltage dependence, indicating that Ca(v)beta is indispensable for voltage-dependent Gbetagamma inhibition. A truncated Ca(v)beta containing only the AID-binding guanylate kinase (GK) domain could fully confer voltage dependence to Gbetagamma inhibition. Gbetagamma did not alter inactivation properties, and channels recovered from Gbetagamma inhibition exhibited the same activation property as un-inhibited channels, indicating that Gbetagamma does not dislodge Ca(v)beta from the inhibited channel. Furthermore, voltage-dependent Gbetagamma inhibition was abolished when the rigid alpha-helix between the AID and IS6 was disrupted by insertion of multiple glycines, which also eliminated Ca(v)beta regulation of channel gating, revealing a pivotal role of this rigid alpha-helix in both processes. These results suggest that depolarization-triggered movement of IS6, coupled to the subsequent conformational change of the Gbetagamma-binding pocket through a rigid alpha-helix induced partly by the Ca(v)beta GK domain, causes the

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

    Science.gov (United States)

    Schuwald, Anita M; Nöldner, Michael; Wilmes, Thomas; Klugbauer, Norbert; Leuner, Kristina; Müller, Walter E

    2013-01-01

    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.

  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. Voltage-dependent modulation of cardiac ryanodine receptors (RyR2 by protamine.

    Directory of Open Access Journals (Sweden)

    Paula L Diaz-Sylvester

    Full Text Available It has been reported that protamine (>10 microg/ml blocks single skeletal RyR1 channels and inhibits RyR1-mediated Ca2+ release from sarcoplasmic reticulum microsomes. We extended these studies to cardiac RyR2 reconstituted into planar lipid bilayers. We found that protamine (0.02-20 microg/ml added to the cytosolic surface of fully activated RyR2 affected channel activity in a voltage-dependent manner. At membrane voltage (V(m; SR lumen-cytosol = 0 mV, protamine induced conductance transitions to several intermediate states (substates as well as full block of RyR2. At V(m>10 mV, the substate with the highest level of conductance was predominant. Increasing V(m from 0 to +80 mV, decreased the number of transitions and residence of the channel in this substate. The drop in current amplitude (full opening to substate had the same magnitude at 0 and +80 mV despite the approximately 3-fold increase in amplitude of the full opening. This is more similar to rectification of channel conductance induced by other polycations than to the action of selective conductance modifiers (ryanoids, imperatoxin. A distinctive effect of protamine (which might be shared with polylysines and histones but not with non-peptidic polycations is the activation of RyR2 in the presence of nanomolar cytosolic Ca2+ and millimolar Mg2+ levels. Our results suggest that RyRs would be subject to dual modulation (activation and block by polycationic domains of neighboring proteins via electrostatic interactions. Understanding these interactions could be important as such anomalies may be associated with the increased RyR2-mediated Ca2+ leak observed in cardiac diseases.

  2. Vestibular integrator neurons have quadratic functions due to voltage dependent conductances.

    Science.gov (United States)

    Magnani, Christophe; Eugène, Daniel; Idoux, Erwin; Moore, Lee E

    2013-12-01

    The nonlinear properties of the dendrites of the prepositus hypoglossi nucleus (PHN) neurons are essential for the operation of the vestibular neural integrator that converts a head velocity signal to one that controls eye position. A novel system of frequency probing, namely quadratic sinusoidal analysis (QSA), was used to decode the intrinsic nonlinear behavior of these neurons under voltage clamp conditions. Voltage clamp currents were measured at harmonic and interactive frequencies using specific nonoverlapping stimulation frequencies. Eigenanalysis of the QSA matrix reduces it to a remarkably compact processing unit, composed of just one or two dominant components (eigenvalues). The QSA matrix of rat PHN neurons provides signatures of the voltage dependent conductances for their particular dendritic and somatic distributions. An important part of the nonlinear response is due to the persistent sodium conductance (gNaP), which is likely to be essential for sustained effects needed for a neural integrator. It was found that responses in the range of 10 mV peak to peak could be well described by quadratic nonlinearities suggesting that effects of higher degree nonlinearities would add only marginal improvement. Therefore, the quadratic response is likely to sufficiently capture most of the nonlinear behavior of neuronal systems except for extremely large synaptic inputs. Thus, neurons have two distinct linear and quadratic functions, which shows that piecewise linear + quadratic analysis is much more complete than just piecewise linear analysis; in addition quadratic analysis can be done at a single holding potential. Furthermore, the nonlinear neuronal responses contain more frequencies over a wider frequency band than the input signal. As a consequence, they convert limited amplitude and bandwidth input signals to wider bandwidth and more complex output responses. Finally, simulations at subthreshold membrane potentials with realistic PHN neuron models

  3. Voltage dependent potassium channel remodeling in murine intestinal smooth muscle hypertrophy induced by partial obstruction.

    Directory of Open Access Journals (Sweden)

    Dong-Hai Liu

    Full Text Available Partial obstruction of the small intestine causes obvious hypertrophy of smooth muscle cells and motility disorder in the bowel proximate to the obstruction. To identify electric remodeling of hypertrophic smooth muscles in partially obstructed murine small intestine, the patch-clamp and intracellular microelectrode recording methods were used to identify the possible electric remodeling and Western blot, immunofluorescence and immunoprecipitation were utilized to examine the channel protein expression and phosphorylation level changes in this research. After 14 days of obstruction, partial obstruction caused obvious smooth muscle hypertrophy in the proximally located intestine. The slow waves of intestinal smooth muscles in the dilated region were significantly suppressed, their amplitude and frequency were reduced, whilst the resting membrane potentials were depolarized compared with normal and sham animals. The current density of voltage dependent potassium channel (KV was significantly decreased in the hypertrophic smooth muscle cells and the voltage sensitivity of KV activation was altered. The sensitivity of KV currents (IKV to TEA, a nonselective potassium channel blocker, increased significantly, but the sensitivity of IKv to 4-AP, a KV blocker, stays the same. The protein levels of KV4.3 and KV2.2 were up-regulated in the hypertrophic smooth muscle cell membrane. The serine and threonine phosphorylation levels of KV4.3 and KV2.2 were significantly increased in the hypertrophic smooth muscle cells. Thus this study represents the first identification of KV channel remodeling in murine small intestinal smooth muscle hypertrophy induced by partial obstruction. The enhanced phosphorylations of KV4.3 and KV2.2 may be involved in this process.

  4. Voltage dependent potassium channel remodeling in murine intestinal smooth muscle hypertrophy induced by partial obstruction.

    Science.gov (United States)

    Liu, Dong-Hai; Huang, Xu; Guo, Xin; Meng, Xiang-Min; Wu, Yi-Song; Lu, Hong-Li; Zhang, Chun-Mei; Kim, Young-chul; Xu, Wen-Xie

    2014-01-01

    Partial obstruction of the small intestine causes obvious hypertrophy of smooth muscle cells and motility disorder in the bowel proximate to the obstruction. To identify electric remodeling of hypertrophic smooth muscles in partially obstructed murine small intestine, the patch-clamp and intracellular microelectrode recording methods were used to identify the possible electric remodeling and Western blot, immunofluorescence and immunoprecipitation were utilized to examine the channel protein expression and phosphorylation level changes in this research. After 14 days of obstruction, partial obstruction caused obvious smooth muscle hypertrophy in the proximally located intestine. The slow waves of intestinal smooth muscles in the dilated region were significantly suppressed, their amplitude and frequency were reduced, whilst the resting membrane potentials were depolarized compared with normal and sham animals. The current density of voltage dependent potassium channel (KV) was significantly decreased in the hypertrophic smooth muscle cells and the voltage sensitivity of KV activation was altered. The sensitivity of KV currents (IKV) to TEA, a nonselective potassium channel blocker, increased significantly, but the sensitivity of IKv to 4-AP, a KV blocker, stays the same. The protein levels of KV4.3 and KV2.2 were up-regulated in the hypertrophic smooth muscle cell membrane. The serine and threonine phosphorylation levels of KV4.3 and KV2.2 were significantly increased in the hypertrophic smooth muscle cells. Thus this study represents the first identification of KV channel remodeling in murine small intestinal smooth muscle hypertrophy induced by partial obstruction. The enhanced phosphorylations of KV4.3 and KV2.2 may be involved in this process.

  5. Conopressin affects excitability, firing, and action potential shape through stimulation of transient and persistent inward currents in mulluscan neurons.

    Science.gov (United States)

    van Soest, P F; Kits, K S

    1998-04-01

    The molluscan vasopressin/oxytocin-related neuropeptide conopressin activates two persistent inward currents in neurons from the anterior lobe of the right cerebral ganglion of Lymnaea stagnalis that are involved in the control of male copulatory behavior. The low-voltage-activated (LVA) current is activated at a wide range of membrane potentials, its amplitude being only weakly voltage dependent. The high-voltage-activated (HVA) current is activated at potentials positive to -40 mV only and shows a steep voltage dependence. Occurrence of both currents varies from cell to cell, some expressing both and others only the HVA current. In most neurons that have the LVA current, a conopressin-independent persistent inward current (INSR) is found that resembles the HVA current in its voltage dependence. The functional importance of the LVA and HVA currents was studied under current-clamp conditions in isolated anterior lobe neurons. In cells exhibiting both current types, the effect of activation of the LVA current alone was investigated as follows: previously recorded LVA current profiles were injected into the neurons, and the effects were compared with responses induced by conopressin. Both treatments resulted in a strong depolarization and firing activity. No differences in firing frequency and burst duration were observed, indicating that activation of the LVA current is sufficient to evoke bursts. In cells exhibiting only the HVA current, the effect of conopressin on the response to a depolarizing stimulus was tested. Conopressin reversibly increased the number of action potentials generated by the stimulus, suggesting that the HVA current enhances excitability and counteracts accommodation. Conopressin enhanced action potential broadening during depolarizing stimuli in many neurons. Voltage-clamp experiments performed under ion-selective conditions revealed the presence of transient sodium and calcium currents. Using the action potential clamp technique, it was

  6. Inward Leakage in Tight-Fitting PAPRs

    Directory of Open Access Journals (Sweden)

    Frank C. Koh

    2011-01-01

    Full Text Available A combination of local flow measurement techniques and fog flow visualization was used to determine the inward leakage for two tight-fitting powered air-purifying respirators (PAPRs, the 3M Breathe-Easy PAPR and the SE 400 breathing demand PAPR. The PAPRs were mounted on a breathing machine head form, and flows were measured from the blower and into the breathing machine. Both respirators leaked a little at the beginning of inhalation, probably through their exhalation valves. In both cases, the leakage was not enough for fog to appear at the mouth of the head form.

  7. Effects of arsenic trioxide on voltage-dependent potassium channels and on cell proliferation of human multiple myeloma cells

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jin; WANG Wei; WEI Qing-fang; FENG Tie-ming; TAN Li-jun; YANG Bao-feng

    2007-01-01

    @@ Arsenic trioxide (ATO) can induce cellular apoptosis and inhibit the activities of multiple myeloma (MM)cells in vitro,1 but how it works is not very clear. Recent studies showed that ATO worked on the voltagedependent potassium channel and L-type calcium channel in myocardial cells,2-5 but the effect of ATO on ion channels of tumor cells was rarely reported. As the potassium channel plays an important role in controlling cell proliferation,6 we studied the effects of ATO on the voltage-dependent potassium current (Ikv) of the voltage-dependent potassium channel in an MM cell line,and probed into the relationship between changes of the Ikv caused by ATO and cell proliferation.

  8. State-dependent FRET reports calcium- and voltage-dependent gating-ring motions in BK channels

    OpenAIRE

    Miranda, Pablo; Contreras, Jorge E.; Plested, Andrew J. R.; Sigworth, Fred J.; Holmgren, Miguel; Giraldez, Teresa

    2013-01-01

    Large-conductance voltage- and calcium-dependent potassium channels (BK, “Big K+”) are important controllers of cell excitability. In the BK channel, a large C-terminal intracellular region containing a “gating-ring” structure has been proposed to transduce Ca2+ binding into channel opening. Using patch-clamp fluorometry, we have investigated the calcium and voltage dependence of conformational changes of the gating-ring region of BK channels, while simultaneously monitoring channel conductan...

  9. VOLTAGE STABILITY ASSESSMENT FOR WIND FARMS INTEGRATION INTO ELECTRICITY GRIDS WITH AND WITHOUT CONSIDERATION OF VOLTAGE DEPENDENT LOADS

    Directory of Open Access Journals (Sweden)

    TOMA R.

    2016-09-01

    Full Text Available The paper presents a comparative study between the effects on voltage stability of the integration of a wind farm into the electricity grid with or without voltage dependent loads in the context of different locations of a synchronous compensator from the grid. The P-V curves are built by using the PowerFactory DigSilent 15.2.2 and a DPL script that implements a simplified form of the Continuation Power Flow method.

  10. The action of a phorbol ester on voltage-dependent parameters of the sodium current in isolated hippocampal neurons.

    Science.gov (United States)

    Chizhmakov, I V; Klee, M R

    1994-03-01

    The action of a phorbol ester (phorbol-12,13-diacetate) on the voltage-activated sodium current has been investigated by the voltage-clamp method in acutely isolated pyramidal neurons from rat hippocampus. The intracellular perfusion of isolated pyramidal neurons for 30-40 min induced a gradual 10-15 mV shift in both the current-voltage relationship and voltage-dependent steady-state inactivation to more negative potentials. The application of phorbol ester (1-10 microM) to isolated neurons for the same time increased the amplitude of sodium current by 15-20%, shifted the above-mentioned voltage-dependent parameters for an additional 10-15 mV in the same direction and changed the slope of the steady-state inactivation curve. In contrast, after prolonged incubation of slices in the phorbol ester-containing solution (1-10 microM) for 0.5-3 h, subsequent application of phorbol ester at the same concentration caused neither the addition shift of the voltage-dependent characteristics of sodium channels nor the change of the slope of the steady-state inactivation curve. However, in this case an increase in the amplitude of sodium current by 15-20% during 30-40 min intracellular perfusion was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. Phosphoinositide 5- and 3-phosphatase activities of a voltage-sensing phosphatase in living cells show identical voltage dependence.

    Science.gov (United States)

    Keum, Dongil; Kruse, Martin; Kim, Dong-Il; Hille, Bertil; Suh, Byung-Chang

    2016-06-28

    Voltage-sensing phosphatases (VSPs) are homologs of phosphatase and tensin homolog (PTEN), a phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] 3-phosphatase. However, VSPs have a wider range of substrates, cleaving 3-phosphate from PI(3,4)P2 and probably PI(3,4,5)P3 as well as 5-phosphate from phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and PI(3,4,5)P3 in response to membrane depolarization. Recent proposals say these reactions have differing voltage dependence. Using Förster resonance energy transfer probes specific for different PIs in living cells with zebrafish VSP, we quantitate both voltage-dependent 5- and 3-phosphatase subreactions against endogenous substrates. These activities become apparent with different voltage thresholds, voltage sensitivities, and catalytic rates. As an analytical tool, we refine a kinetic model that includes the endogenous pools of phosphoinositides, endogenous phosphatase and kinase reactions connecting them, and four exogenous voltage-dependent 5- and 3-phosphatase subreactions of VSP. We show that apparent voltage threshold differences for seeing effects of the 5- and 3-phosphatase activities in cells are not due to different intrinsic voltage dependence of these reactions. Rather, the reactions have a common voltage dependence, and apparent differences arise only because each VSP subreaction has a different absolute catalytic rate that begins to surpass the respective endogenous enzyme activities at different voltages. For zebrafish VSP, our modeling revealed that 3-phosphatase activity against PI(3,4,5)P3 is 55-fold slower than 5-phosphatase activity against PI(4,5)P2; thus, PI(4,5)P2 generated more slowly from dephosphorylating PI(3,4,5)P3 might never accumulate. When 5-phosphatase activity was counteracted by coexpression of a phosphatidylinositol 4-phosphate 5-kinase, there was accumulation of PI(4,5)P2 in parallel to PI(3,4,5)P3 dephosphorylation

  12. Men navigating inward and outward through depression.

    Science.gov (United States)

    Ramirez, Jeffery L; Badger, Terry A

    2014-02-01

    Understanding of depression among men remains poor. When compared to women, men remain under diagnosed for depression and continue to commit suicide four times the rate of women. This grounded theory study explored the social psychological process that occurred in men who suffered from depression. Nine men participated in the study that ranged in age, educational level, and marital status. The theory that emerged from this study was Navigating Inward and Outward Through Depression. This study uncovered six stages men navigated through: being different, concealing feelings disconnecting, hitting bottom, acknowledging and confronting and healing with others. This study advances our understanding of men and depression by providing meanings to the behaviors men express when depressed. Based on these findings, further research can lead to better screening tools and early diagnosis of depression in men. © 2014.

  13. Some Topologies of High Quality Rectifiers

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Several basic classes of three-phase high-quality rectifiers are described.Both single-switch and six-switch three-phase rectifier topologiescan be derived from parent dc-dc converters.Single-switch rectifiers are compared with the basic six-switch PWM rectifiers performingsimilar power conversion functions,using the measures of total semiconductor stress and active semiconductor utilization.The singleswitchapproach is shown to utilize the semiconductor devices more effectively.Zero current switching and multiresonant approaches are foundto exhibit low switch stress over a wide range of operating points,with lowTHD.

  14. Effect of etomidate on voltage-dependent potassium currents in rat isolated hippocampal pyramidal neurons

    Institute of Scientific and Technical Information of China (English)

    TAN Hong-yu; SUN Li-na; WANG Xiao-liang; YE Tie-hu

    2010-01-01

    Background Previous studies demonstrated general anesthetics affect potassium ion channels, which may be one of the mechanisms of general anesthesia. Because the effect of etomidate on potassium channels in rat hippocampus which is involved in memory function has not been studied, we investigated the effects of etomidate on both delayed rectifier potassium current (I_((K(DR))) and transient outward potassium current (I_((K(A))) in acutely dissociated rat hippocampal pyramidal neurons.Methods Single rat hippocampal pyramidal neurons from male Wistar rats of 7-10 days were acutely dissociated by enzymatic digestion and mechanical dispersion according to the methods of Kay and Wong with slight modification. Voltage-clamp recordings were performed in the whole-cell patch clamp configuration. Currents were recorded with a List EPC-10 amplifier and data were stored in a computer using Pulse 8.5. Student's paired two-tail t test was used for data analysis. Results At the concentration of 100 μmol/L, etomidate significantly inhibited I_(K(DR)) by 49.2% at +40 mV when depolarized from -110 mV (P 0.05). The IC_(50) value of etomidate for blocking I_(K(DR)) was calculated as 5.4 μmol/L, with a Hill slope of 2.45. At the presence of 10 μmol/L etomidate, the V_(1/2) of activation curve was shifted from (17.3±1.5) mV to (10.7±9.9) mV (n=8, P <0.05), the V_(1/2) of inactivation curve was shifted from (-18.3±2.2) mV to (-45.3±9.4) mV (n=8, P <0.05). Etomidate 10 μmol/L shifted both the activation curve and inactivation curve of I_(K(DR)) to negative potential, but mainly affected the inactivation kinetics.Conclusions Etomidate potently inhibited I_(K(DR)) but not I_(K(A)) in rat hippocampal pyramidal neurons. I_(K(DR)) was inhibited by etomidate in a concentration-dependent manner, while I_(K(A)) remained unaffected.

  15. Effect of angiotensin II-induced arterial hypertension on the voltage-dependent contractions of mouse arteries.

    Science.gov (United States)

    Fransen, Paul; Van Hove, Cor E; Leloup, Arthur J A; Schrijvers, Dorien M; De Meyer, Guido R Y; De Keulenaer, Gilles W

    2016-02-01

    Arterial hypertension (AHT) affects the voltage dependency of L-type Ca(2+) channels in cardiomyocytes. We analyzed the effect of angiotensin II (AngII)-induced AHT on L-type Ca(2+) channel-mediated isometric contractions in conduit arteries. AHT was induced in C57Bl6 mice with AngII-filled osmotic mini-pumps (4 weeks). Normotensive mice treated with saline-filled osmotic mini-pumps were used for comparison. Voltage-dependent contractions mediated by L-type Ca(2+) channels were studied in vaso-reactive studies in vitro in isolated aortic and femoral arteries by using extracellular K(+) concentration-response (KDR) experiments. In aortic segments, AngII-induced AHT significantly sensitized isometric contractions induced by elevated extracellular K(+) and depolarization. This sensitization was partly prevented by normalizing blood pressure with hydralazine, suggesting that it was caused by AHT rather than by direct AngII effects on aortic smooth muscle cells. The EC50 for extracellular K(+) obtained in vitro correlated significantly with the rise in arterial blood pressure induced by AngII in vivo. The AHT-induced sensitization persisted when aortic segments were exposed to levcromakalim or to inhibitors of basal nitric oxide release. Consistent with these observations, AngII-treatment also sensitized the vaso-relaxing effects of the L-type Ca(2+) channel blocker diltiazem during K(+)-induced contractions. Unlike aorta, AngII-treatment desensitized the isometric contractions to depolarization in femoral arteries pointing to vascular bed specific responses of arteries to hypertension. AHT affects the voltage-dependent L-type Ca(2+) channel-mediated contraction of conduit arteries. This effect may contribute to the decreased vascular compliance in AHT and explain the efficacy of Ca(2+) channel blockers to reduce vascular stiffness and central blood pressure in AHT.

  16. Analysis and Comparison of Voltage Dependent Charging Strategies for Single-Phase Electric Vehicles in an Unbalanced Danish Distribution Grid

    DEFF Research Database (Denmark)

    Álvarez, Jorge Nájera; Knezovic, Katarina; Marinelli, Mattia

    2016-01-01

    This paper studies four voltage dependent solutions for modulating the charging of multiple Electric Vehicles (EVs) in a real Danish network. Uncontrolled EV charging, especially in grid with high EV penetration, can result in overloaded lines and transformers, low-voltages and other performance......-in on phases with lower voltages are constrained during the charging period. In order to solve instability issues which may occur due to lack of communication between the controllers, several improvements are applied to the aforementioned droop control. Simulation results demonstrate the performance...

  17. 75 FR 20546 - Total Inward Leakage Requirements for Respirators

    Science.gov (United States)

    2010-04-20

    ... HUMAN SERVICES 42 CFR Part 84 RIN 0920-AA33 Total Inward Leakage Requirements for Respirators AGENCY... Respirators,'' published in the Federal Register on October 30, 2009 (74 FR 56141). The comment period on this... total inward leakage (TIL) requirements for half-mask air-purifying particulate respirators approved...

  18. 19 CFR 4.62 - Accounting for inward cargo.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Accounting for inward cargo. 4.62 Section 4.62 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY VESSELS IN FOREIGN AND DOMESTIC TRADES Foreign Clearances § 4.62 Accounting for inward...

  19. Does Inward FDI Promote or Hinder Outward FDI?

    DEFF Research Database (Denmark)

    Liu, Ying; Li, Ming Hua; Lu, Jiangyong

    In this paper we evaluate the mechanisms underlying dynamic linkages between inward FDI and outward internationalization in the Chinese automobile industry. While several studies have examined the relationship between outward and inward investment using empirical data, this is among the first...

  20. Development of a voltage-dependent current noise algorithm for conductance-based stochastic modelling of auditory nerve fibres.

    Science.gov (United States)

    Badenhorst, Werner; Hanekom, Tania; Hanekom, Johan J

    2016-12-01

    This study presents the development of an alternative noise current term and novel voltage-dependent current noise algorithm for conductance-based stochastic auditory nerve fibre (ANF) models. ANFs are known to have significant variance in threshold stimulus which affects temporal characteristics such as latency. This variance is primarily caused by the stochastic behaviour or microscopic fluctuations of the node of Ranvier's voltage-dependent sodium channels of which the intensity is a function of membrane voltage. Though easy to implement and low in computational cost, existing current noise models have two deficiencies: it is independent of membrane voltage, and it is unable to inherently determine the noise intensity required to produce in vivo measured discharge probability functions. The proposed algorithm overcomes these deficiencies while maintaining its low computational cost and ease of implementation compared to other conductance and Markovian-based stochastic models. The algorithm is applied to a Hodgkin-Huxley-based compartmental cat ANF model and validated via comparison of the threshold probability and latency distributions to measured cat ANF data. Simulation results show the algorithm's adherence to in vivo stochastic fibre characteristics such as an exponential relationship between the membrane noise and transmembrane voltage, a negative linear relationship between the log of the relative spread of the discharge probability and the log of the fibre diameter and a decrease in latency with an increase in stimulus intensity.

  1. Blockade of the voltage-dependent sodium current in isolated rat hippocampal neurons by tetrodotoxin and lidocaine.

    Science.gov (United States)

    Kaneda, M; Oyama, Y; Ikemoto, Y; Akaike, N

    1989-04-10

    The effects of tetrodotoxin and lidocaine on the voltage-dependent sodium current (INa) were studied in the CA1 pyramidal neurons isolated acutely from rat hippocampus using a 'concentration-clamp' technique which combines the intracellular perfusion with a rapid external solution change within a few ms. Tetrodotoxin (TTX) exerted its inhibitory action in time- and dose-dependent manner on the peak amplitude of INa without any apparent effects on both the current activation and inactivation processes of the current. The time course for reaching a steady-state of the inhibitory action shortened with increasing TTX concentration, but the time course of recovery from the inhibition after washing out the toxin was quite the same at any concentrations used. Lidocaine also inhibited dose-dependently the INa, though with slightly accelerating both the activation and inactivation processes. The time courses for reaching the steady-state inhibition and the recovery from the inhibition were much shorter than those in the case of TTX. The results indicate that the voltage-dependent sodium channel of mammalian brain neuron is TTX-sensitive as well as that of peripheral neuron and that the mode of TTX inhibition on the INa is quite different from that of lidocaine.

  2. Reversal of HCN channel voltage dependence via bridging of the S4-S5 linker and Post-S6.

    Science.gov (United States)

    Prole, David L; Yellen, Gary

    2006-09-01

    Voltage-gated ion channels possess charged domains that move in response to changes in transmembrane voltage. How this movement is transduced into gating of the channel pore is largely unknown. Here we show directly that two functionally important regions of the spHCN1 pacemaker channel, the S4-S5 linker and the C-linker, come into close proximity during gating. Cross-linking these regions with high-affinity metal bridges or disulfide bridges dramatically alters channel gating in the absence of cAMP; after modification the polarity of voltage dependence is reversed. Instead of being closed at positive voltage and activating with hyperpolarization, modified channels are closed at negative voltage and activate with depolarization. Mechanistically, this reversal of voltage dependence occurs as a result of selectively eliminating channel deactivation, while retaining an existing inactivation process. Bridging also alters channel activation by cAMP, showing that interaction of these two regions can also affect the efficacy of physiological ligands.

  3. The antimalarial drug mefloquine inhibits cardiac inward rectifier K+ channels: evidence for interference in PIP2-channel interaction.

    Science.gov (United States)

    López-Izquierdo, Angélica; Ponce-Balbuena, Daniela; Moreno-Galindo, Eloy G; Aréchiga-Figueroa, Iván A; Rodríguez-Martínez, Martín; Ferrer, Tania; Rodríguez-Menchaca, Aldo A; Sánchez-Chapula, José A

    2011-04-01

    The antimalarial drug mefloquine was found to inhibit the KATP channel by an unknown mechanism. Because mefloquine is a Cationic amphiphilic drug and is known to insert into lipid bilayers, we postulate that mefloquine interferes with the interaction between PIP2 and Kir channels resulting in channel inhibition. We studied the inhibitory effects of mefloquine on Kir2.1, Kir2.3, Kir2.3(I213L), and Kir6.2/SUR2A channels expressed in HEK-293 cells, and on IK1 and IKATP from feline cardiac myocytes. The order of mefloquine inhibition was Kir6.2/SUR2A ≈ Kir2.3 (IC50 ≈ 2 μM) > Kir2.1 (IC50 > 30 μM). Similar results were obtained in cardiac myocytes. The Kir2.3(I213L) mutant, which enhances the strength of interaction with PIP2 (compared to WT), was significantly less sensitive (IC50 = 9 μM). In inside-out patches, continuous application of PIP2 strikingly prevented the mefloquine inhibition. Our results support the idea that mefloquine interferes with PIP2-Kir channels interactions.

  4. Assembly of ROMK1 (Kir 1.1a) inward rectifier K+ channel subunits involves multiple interaction sites.

    Science.gov (United States)

    Koster, J C; Bentle, K A; Nichols, C G; Ho, K

    1998-04-01

    The ROMK1 (Kir 1.1a) channel is formed by a tetrameric complex of subunits, each characterized by cytoplasmic N- and C-termini and a core region of two transmembrane helices flanking a pore-forming segment. To delineate the general regions mediating the assembly of ROMK1 subunits we constructed epitope-tagged N-terminal, C-terminal, and transmembrane segment deletion mutants. Nonfunctional subunits with N-terminal, core region, and C-terminal deletions had dominant negative effects when coexpressed with wild-type ROMK1 subunits in Xenopus oocytes. In contrast, coexpression of these nonfunctional subunits with Kv 2.1 (DRK1) did not suppress Kv 2.1 currents in control oocytes. Interactions between epitope-tagged mutant and wild-type ROMK1 subunits were studied in parallel by immunoprecipitating [35S]-labeled oocyte membrane proteins. Complexes containing both wild-type and mutant subunits that retained H5, M2, and C-terminal regions were coimmunoprecipitated to a greater extent than complexes consisting of wild-type and mutant subunits with core region and/or C-terminal deletions. The present findings are consistent with the hypothesis that multiple interaction sites located in the core region and cytoplasmic termini of ROMK1 subunits mediate homomultimeric assembly.

  5. Extracellular Linkers Completely Transplant the Voltage Dependence from Kv1.2 Ion Channels to Kv2.1.

    Science.gov (United States)

    Elinder, Fredrik; Madeja, Michael; Zeberg, Hugo; Århem, Peter

    2016-10-18

    The transmembrane voltage needed to open different voltage-gated K (Kv) channels differs by up to 50 mV from each other. In this study we test the hypothesis that the channels' voltage dependences to a large extent are set by charged amino-acid residues of the extracellular linkers of the Kv channels, which electrostatically affect the charged amino-acid residues of the voltage sensor S4. Extracellular cations shift the conductance-versus-voltage curve, G(V), by interfering with these extracellular charges. We have explored these issues by analyzing the effects of the divalent strontium ion (Sr(2+)) on the voltage dependence of the G(V) curves of wild-type and chimeric Kv channels expressed in Xenopus oocytes, using the voltage-clamp technique. Out of seven Kv channels, Kv1.2 was found to be most sensitive to Sr(2+) (50 mM shifted G(V) by +21.7 mV), and Kv2.1 to be the least sensitive (+7.8 mV). Experiments on 25 chimeras, constructed from Kv1.2 and Kv2.1, showed that the large Sr(2+)-induced G(V) shift of Kv1.2 can be transferred to Kv2.1 by exchanging the extracellular linker between S3 and S4 (L3/4) in combination with either the extracellular linker between S5 and the pore (L5/P) or that between the pore and S6 (LP/6). The effects of the linker substitutions were nonadditive, suggesting specific structural interactions. The free energy of these interactions was ∼20 kJ/mol, suggesting involvement of hydrophobic interactions and/or hydrogen bonds. Using principles from double-layer theory we derived an approximate linear equation (relating the voltage shifts to altered ionic strength), which proved to well match experimental data, suggesting that Sr(2+) acts on these channels mainly by screening surface charges. Taken together, these results highlight the extracellular surface potential at the voltage sensor as an important determinant of the channels' voltage dependence, making the extracellular linkers essential targets for evolutionary selection.

  6. [Role of calcineurin in down-regulation of left ventricular transmural voltage- dependent K(+) currents in mice with heart failure].

    Science.gov (United States)

    Shi, Chen-Xia; Dong, Fang; Chang, Yan-Chao; Wang, Xiao-Feng; Xu, Yan-Fang

    2015-08-25

    The aim of the present study was to investigate the role of calcineurin in the down-regulation of left ventricular transmural voltage-dependent K(+) currents in heart failure. Transverse aorta was banded by using microsurgical techniques to create mouse heart failure model. Sham-operated (Sham) or aorta banded (Band) mice were randomized to receive calcineurin inhibitor cyclosporine A (CsA) or vehicle. The densities and kinetic properties of voltage-dependent K(+) currents, as well as action potential (AP), of left ventricular subendocardial (Endo) and subepicardial (Epi) myocytes were determined by using whole-cell patch-clamp technique. The results showed that calcineurin activity was significant higher in Endo myocytes than that in Epi ones in all the groups. Compared with Sham group, Band mice showed significantly increased calcineurin activity both in Endo and Epi myocytes. CsA significantly reduced calcineurin activity in Band mice. CsA treatment in Band mice partially reversed the down-regulation of Ito density, completely reversed the down-regulation of IK,slow density both in Endo and Epi myocytes, and Iss density in Endo myocytes. In addition, CsA treatment in Band mice partially antagonized the prolongation of action potential duration (APD), and APD at 50% (APD50) and 90% repolarization (APD90) were significantly reduced. Because of non-parallel shortening of APD in Endo and Epi myocytes, the ratio of Endo/Epi APD90 was reduced from 4.8:1 in Band mice to 2.6:1 in CsA-treated mice, which was close to that in Sham mice. The results suggest that non-parallel activation of calcineurin in Endo and Epi myocytes contributes to the down-regulation of transmural voltage-dependent K(+) currents and the amplification of transmural dispersion of repolarization (TDR) in left ventricular failure hearts. Inhibition of calcineurin may be a potential new therapeutic strategy to prevent and cure arrhythmias and sudden death in heart failure.

  7. 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;

    2001-01-01

    .2 protein was demonstrated by immunochemical labeling of rat preglomerular vasculature and juxtamedullary efferent arterioles and vasa recta. Cortical efferent arterioles were not immunopositive. Recordings of intracellular calcium concentration with digital fluorescence imaging microscopy showed......The distribution of voltage-dependent calcium channels in kidney pre- and postglomerular resistance vessels was determined at the molecular and functional levels. Reverse transcription-polymerase chain reaction analysis of microdissected rat preglomerular vessels and cultured smooth muscle cells...... showed coexpression of mRNAs for T-type subunits (Ca(V)3.1, Ca(V)3.2) and for an L-type subunit (Ca(V)1.2). The same expression pattern was observed in juxtamedullary efferent arterioles and outer medullary vasa recta. No calcium channel messages were detected in cortical efferent arterioles. Ca(V)1...

  8. Characterization and functional analysis of voltage-dependent anion channel 1 (VDAC1) from orange-spotted grouper (Epinephelus coioides).

    Science.gov (United States)

    Shi, Yan; Zhao, Zhe; Hong, Xiaoyou; Chen, Kunci; Zhu, Xinping

    2014-07-01

    The voltage-dependent anion channel (VDAC) is a highly conserved integral protein of mitochondria in different eukaryotic species. It forms a selective channel in the mitochondrial outer membrane that serves as the controlled pathway for small metabolites and ions. In this study, a VDAC gene, EcVDAC1, was isolated from orange-spotted grouper (Epinephelus coioides). The EcVDAC1 exhibits ubiquitous expression in various tissues of orange-spotted grouper and is upregulated in liver, gill, and spleen after stimulation with lipopolysaccharides (LPS). Subcellular localization analysis shows that the EcVDAC1 protein colocalized with the mitochondria. A caspase-3 assay demonstrates that overexpression of the EcVDAC1 induced apoptotic cell death in fathead minnow cells. The data presented in this study provide new information regarding the relationship between LPS and the EcVDAC1 gene, suggesting that the fish VDAC1 gene may play an important role in antibacterial immune response.

  9. Selective serotonin reuptake inhibitor sertraline inhibits voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells

    Indian Academy of Sciences (India)

    HAN SOL KIM; HONGLIANG LI; HYE WON KIM; SUNG EUN SHIN; IL-WHAN CHOI; AMY L FIRTH; HYOWEON BANG; YOUNG MIN BAE; WON SUN PARK

    2016-12-01

    We examined the effects of the selective serotonin reuptake inhibitor (SSRI) sertraline on voltage-dependent K+ (Kv)channels in freshly isolated rabbit coronary arterial smooth muscle cells using the voltage-clamp technique. Sertralinedecreased the Kv channel current in a dose-dependent manner, with an IC50 value of 0.18 μM and a slope value (Hillcoefficient) of 0.61. Although the application of 1 μM sertraline did not affect the steady-state activation curves,sertraline caused a significant, negative shift in the inactivation curves. Pretreatment with another SSRI, paroxetine,had no significant effect on Kv currents and did not alter the inhibitory effects of sertraline on Kv currents. From theseresults, we concluded that sertraline dose-dependently inhibited Kv currents independently of serotonin reuptakeinhibition by shifting inactivation curves to a more negative potential.

  10. Selective serotonin reuptake inhibitor sertraline inhibits voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells.

    Science.gov (United States)

    Kim, Han Sol; Li, Hongliang; Kim, Hye Won; Shin, Sung Eun; Choi, Il-Whan; Firth, Amy L; Bang, Hyoweon; Bae, Young Min; Park, Won Sun

    2016-12-01

    We examined the effects of the selective serotonin reuptake inhibitor (SSRI) sertraline on voltage-dependent K+ (Kv) channels in freshly isolated rabbit coronary arterial smooth muscle cells using the voltage-clamp technique. Sertraline decreased the Kv channel current in a dose-dependent manner, with an IC50 value of 0.18 mu M and a slope value (Hill coefficient) of 0.61. Although the application of 1 mu M sertraline did not affect the steady-state activation curves, sertraline caused a significant, negative shift in the inactivation curves. Pretreatment with another SSRI, paroxetine, had no significant effect on Kv currents and did not alter the inhibitory effects of sertraline on Kv currents. From these results, we concluded that sertraline dose-dependently inhibited Kv currents independently of serotonin reuptake inhibition by shifting inactivation curves to a more negative potential.

  11. Temperature and bias voltage dependence of Co/Pd multilayer-based magnetic tunnel junctions with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, Zoe, E-mail: zkugler@physik.uni-bielefeld.d [Bielefeld University, Department of Physics, Universitaetsstr. 25, 33615 Bielefeld (Germany); Drewello, Volker; Schaefers, Markus; Schmalhorst, Jan; Reiss, Guenter; Thomas, Andy [Bielefeld University, Department of Physics, Universitaetsstr. 25, 33615 Bielefeld (Germany)

    2011-01-15

    Temperature- and bias voltage-dependent transport measurements of magnetic tunnel junctions (MTJs) with perpendicularly magnetized Co/Pd electrodes are presented. Magnetization measurements of the Co/Pd multilayers are performed to characterize the electrodes. The effects of the Co layer thickness in the Co/Pd bilayers, the annealing temperature, the Co thickness at the MgO barrier interface, and the number of bilayers on the tunneling magneto resistance (TMR) effect are investigated. TMR-ratios of about 11% at room temperature and 18.5% at 13 K are measured and two well-defined switching fields are observed. The results are compared to measurements of MTJs with Co-Fe-B electrodes and in-plane anisotropy.

  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

    2001-01-01

    The distribution of voltage-dependent calcium channels in kidney pre- and postglomerular resistance vessels was determined at the molecular and functional levels. Reverse transcription-polymerase chain reaction analysis of microdissected rat preglomerular vessels and cultured smooth muscle cells...... showed coexpression of mRNAs for T-type subunits (Ca(V)3.1, Ca(V)3.2) and for an L-type subunit (Ca(V)1.2). The same expression pattern was observed in juxtamedullary efferent arterioles and outer medullary vasa recta. No calcium channel messages were detected in cortical efferent arterioles. Ca(V)1.......2 protein was demonstrated by immunochemical labeling of rat preglomerular vasculature and juxtamedullary efferent arterioles and vasa recta. Cortical efferent arterioles were not immunopositive. Recordings of intracellular calcium concentration with digital fluorescence imaging microscopy showed...

  13. Voltage dependence of Hodgkin-Huxley rate functions for a multistage K+ channel voltage sensor within a membrane

    Science.gov (United States)

    Vaccaro, S. R.

    2014-11-01

    The activation of a K+channel sensor in two sequential stages during a voltage clamp may be described as the translocation of a Brownian particle in an energy landscape with two large barriers between states. A solution of the Smoluchowski equation for a square-well approximation to the potential function of the S4 voltage sensor satisfies a master equation and has two frequencies that may be determined from the forward and backward rate functions. When the higher-frequency terms have small amplitude, the solution reduces to the relaxation of a rate equation, where the derived two-state rate functions are dependent on the relative magnitude of the forward rates (α and γ ) and the backward rates (β and δ ) for each stage. In particular, the voltage dependence of the Hodgkin-Huxley rate functions for a K+channel may be derived by assuming that the rate functions of the first stage are large relative to those of the second stage—α ≫γ and β ≫δ . For a Shaker IR K+ channel, the first forward and backward transitions are rate limiting (α <γ and δ ≪β ), and for an activation process with either two or three stages, the derived two-state rate functions also have a voltage dependence that is of a similar form to that determined for the squid axon. The potential variation generated by the interaction between a two-stage K+ ion channel and a noninactivating Na+ ion channel is determined by the master equation for K+channel activation and the ionic current equation when the Na+channel activation time is small, and if β ≪δ and α ≪γ , the system may exhibit a small amplitude oscillation between spikes, or mixed-mode oscillation, in which the slow closed state modulates the K+ ion channel conductance in the membrane.

  14. Functional coupling between sodium-activated potassium channels and voltage-dependent persistent sodium currents in cricket Kenyon cells.

    Science.gov (United States)

    Takahashi, Izumi; Yoshino, Masami

    2015-10-01

    In this study, we examined the functional coupling between Na(+)-activated potassium (KNa) channels and Na(+) influx through voltage-dependent Na(+) channels in Kenyon cells isolated from the mushroom body of the cricket Gryllus bimaculatus. Single-channel activity of KNa channels was recorded with the cell-attached patch configuration. The open probability (Po) of KNa channels increased with increasing Na(+) concentration in a bath solution, whereas it decreased by the substitution of Na(+) with an equimolar concentration of Li(+). The Po of KNa channels was also found to be reduced by bath application of a high concentration of TTX (1 μM) and riluzole (100 μM), which inhibits both fast (INaf) and persistent (INaP) Na(+) currents, whereas it was unaffected by a low concentration of TTX (10 nM), which selectively blocks INaf. Bath application of Cd(2+) at a low concentration (50 μM), as an inhibitor of INaP, also decreased the Po of KNa channels. Conversely, bath application of the inorganic Ca(2+)-channel blockers Co(2+) and Ni(2+) at high concentrations (500 μM) had little effect on the Po of KNa channels, although Cd(2+) (500 μM) reduced the Po of KNa channels. Perforated whole cell clamp analysis further indicated the presence of sustained outward currents for which amplitude was dependent on the amount of Na(+) influx. Taken together, these results indicate that KNa channels could be activated by Na(+) influx passing through voltage-dependent persistent Na(+) channels. The functional significance of this coupling mechanism was discussed in relation to the membrane excitability of Kenyon cells and its possible role in the formation of long-term memory.

  15. Topologically subordered rectifiable spaces and compactifications

    CERN Document Server

    Lin, Fucai

    2011-01-01

    A topological space $G$ is said to be a {\\it rectifiable space} provided that there are a surjective homeomorphism $\\phi :G\\times G\\rightarrow G\\times G$ and an element $e\\in G$ such that $\\pi_{1}\\circ \\phi =\\pi_{1}$ and for every $x\\in G$ we have $\\phi (x, x)=(x, e)$, where $\\pi_{1}: G\\times G\\rightarrow G$ is the projection to the first coordinate. In this paper, we mainly discuss the rectifiable spaces which are suborderable, and show that if a rectifiable space is suborderable then it is metrizable or a totally disconnected P-space, which improves a theorem of A.V. Arhangel'ski\\v\\i\\ in \\cite{A20092}. As an applications, we discuss the remainders of the Hausdorff compactifications of GO-spaces which are rectifiable, and we mainly concerned with the following statement, and under what condition $\\Phi$ it is true. Statement: Suppose that $G$ is a non-locally compact GO-space which is rectifiable, and that $Y=bG\\setminus G$ has (locally) a property-$\\Phi$. Then $G$ and $bG$ are separable and metrizable. Moreo...

  16. Conducting and voltage-dependent behaviors of potassium ion channels reconstituted from diaphragm sarcoplasmic reticulum: comparison with the cardiac isoform.

    Science.gov (United States)

    Picher, M; Decrouy, A; Rousseau, E

    1996-02-21

    Sarcoplasmic reticulum (SR) K+ channels from canine diaphragm were studied upon fusion of longitudinal and junctional membrane vesicles into planar lipid bilayers (PLB). The large-conductance cation selective channel (gamma(max) = 250 pS; Km = 33 mM) displays long-lasting open events which are much more frequent at positive than at negative voltages. A major subconducting state about 45% of the fully-open state current amplitude was occasionally observed at all voltages. The voltage-dependence of the open probability displays a sigmoid relationship that was fitted by the Boltzmann equation and expressed in terms of thermodynamic parameters, namely the free energy (delta Gi) and the effective gating charge (Zs): delta Gi = 0.27 kcal/mol and Zs = -1.19 in 250 mM potassium gluconate (K-gluconate). Kinetic analyses also confirmed the voltage-dependent gating behavior of this channel, and indicate the implication of at least two open and three closed states. The diaphragm SR K+ channel shares several biophysical properties with the cardiac isoform: g = 180 pS, delta Gi = 0.75 kcal/mol, Zs = -1.45 in 150 mM K-gluconate, and a similar sigmoid P(o)/voltage relationship. Little is known about the regulation of the diaphragm and cardiac SR K+ channels. The conductance and gating of these channels were not influenced by physiological concentrations of Ca2+ (0.1 microM-1 mM) or Mg2+ (0.25-1 mM), as well as by cGMP (25-100 microM), lemakalim (1-100 microM), glyburide (up to 10 microM) or charybdotoxin (45-200 nM), added either to the cis or to the trans chamber. The apparent lack of biochemical or pharmacological modulation of these channels implies that they are not related to any of the well characterized surface membrane K+ channels. On the other hand, their voltage sensitivity strongly suggests that their activity could be modulated by putative changes in SR membrane potential that might occur during calcium fluxes.

  17. Block of the delayed rectifier current (IK) by the 5-HT3 antagonists ondansetron and granisetron in feline ventricular myocytes.

    OpenAIRE

    de Lorenzi, F G; Bridal, T R; Spinelli, W

    1994-01-01

    1. We investigated the effects of two 5-HT3 antagonists, ondansetron and granisetron, on the action potential duration (APD) and the delayed rectifier current (IK) of feline isolated ventricular myocytes. Whole-cell current and action potential recordings were performed at 37 degrees C with the patch clamp technique. 2. Ondansetron and granisetron blocked IK with a KD of 1.7 +/- 1.0 and 4.3 +/- 1.7 microM, respectively. At a higher concentration (30 microM), both drugs blocked the inward rect...

  18. Full-wave current conveyor precision rectifier

    Directory of Open Access Journals (Sweden)

    Đukić Slobodan R.

    2008-01-01

    Full Text Available A circuit that provides precision rectification of small signal with low temperature sensitivity for frequencies up to 100 kHz without waveform distortion is presented. It utilizes an improved second type current conveyor based on current-steering output stage and biased silicon diodes. The use of a DC current source to bias the rectifying diodes provides higher temperature stability and lower DC offset level at the output. Proposed design of the precision rectifier ensures good current transfer linearity in the range that satisfy class A of the amplifier and good voltage transfer characteristic for low level signals. Distortion during the zero crossing of the input signal is practically eliminated. Design of the proposed rectifier is realized with standard components.

  19. Voltage-dependent potassium currents during fast spikes of rat cerebellar Purkinje neurons: inhibition by BDS-I toxin.

    Science.gov (United States)

    Martina, Marco; Metz, Alexia E; Bean, Bruce P

    2007-01-01

    We characterized the kinetics and pharmacological properties of voltage-activated potassium currents in rat cerebellar Purkinje neurons using recordings from nucleated patches, which allowed high resolution of activation and deactivation kinetics. Activation was exceptionally rapid, with 10-90% activation in about 400 mus at +30 mV, near the peak of the spike. Deactivation was also extremely rapid, with a decay time constant of about 300 mus near -80 mV. These rapid activation and deactivation kinetics are consistent with mediation by Kv3-family channels but are even faster than reported for Kv3-family channels in other neurons. The peptide toxin BDS-I had very little blocking effect on potassium currents elicited by 100-ms depolarizing steps, but the potassium current evoked by action potential waveforms was inhibited nearly completely. The mechanism of inhibition by BDS-I involves slowing of activation rather than total channel block, consistent with the effects described in cloned Kv3-family channels and this explains the dramatically different effects on currents evoked by short spikes versus voltage steps. As predicted from this mechanism, the effects of toxin on spike width were relatively modest (broadening by roughly 25%). These results show that BDS-I-sensitive channels with ultrafast activation and deactivation kinetics carry virtually all of the voltage-dependent potassium current underlying repolarization during normal Purkinje cell spikes.

  20. Voltage-Dependent Anion Channel 1(VDAC1) Participates the Apoptosis of the Mitochondrial Dysfunction in Desminopathy

    Science.gov (United States)

    Mo, Yanqing; Gong, Qi; Jiang, Aihua; Zhao, Jing

    2016-01-01

    Desminopathies caused by the mutation in the gene coding for desmin are genetically protein aggregation myopathies. Mitochondrial dysfunction is one of pathological changes in the desminopathies at the earliest stage. The molecular mechanisms of mitochondria dysfunction in desminopathies remain exclusive. VDAC1 regulates mitochondrial uptake across the outer membrane and mitochondrial outer membrane permeabilization (MOMP). Relationships between desminopathies and Voltage-dependent anion channel 1 (VDAC1) remain unclear. Here we successfully constructed the desminopathy rat model, evaluated with conventional stains, containing hematoxylin and eosin (HE), Gomori Trichrome (MGT), (PAS), red oil (ORO), NADH-TR, SDH staining and immunohistochemistry. Immunofluorescence results showed that VDAC1 was accumulated in the desmin highly stained area of muscle fibers of desminopathy patients or desminopathy rat model compared to the normal ones. Meanwhile apoptosis related proteins bax and ATF2 were involved in desminopathy patients and desminopathy rat model, but not bcl-2, bcl-xl or HK2.VDAC1 and desmin are closely relevant in the tissue splices of deminopathies patients and rats with desminopathy at protein lever. Moreover, apoptotic proteins are also involved in the desminopathies, like bax, ATF2, but not bcl-2, bcl-xl or HK2. This pathological analysis presents the correlation between VDAC1 and desmin, and apoptosis related proteins are correlated in the desminopathy. Furthermore, we provide a rat model of desminopathy for the investigation of desmin related myopathy. PMID:27941998

  1. Inhibitory effect of resveratrol on the proliferation of GH3 pituitary-adenoma cells and voltage-dependent potassium current

    Institute of Scientific and Technical Information of China (English)

    Ming Chu; Lanlan Wei; Chao Wang; Yu Cheng; Kongbin Yang; Baofeng Yang

    2006-01-01

    BACKGROUND:Recent researches indicate that activation of potassium channel is likely to cause many kinds of cells to proliferate and differentiate;using chemical to block the potassium channel can restrain the proliferation of small lung-cancer cells.breast cancer.prostate cancer and human lymphocyte,etc.Previous researches proved that resveratrol(RE),a selective estrogen receptor modulator(SERM).could inhibit growth of GH3 calls,induce apoptosis,and resist tumor through interfering K+ channel.OBJECTIVE:To investigate the effects of RE on Voltage-dependent K+ current [Ik(v)] and cell proliferation in GH3 pituitary-tumor cells.DESIGN:Observational contrast study.SETTING:Department of Neurosurgery.the First Clinical Hospital of Harbin Medical University;Department of Microbiology,Harbin Medical University;Department of Pharmacology,Harbin Medical University.MATERIALS: GH3 pituitary-tumor cell line of rats was purchased from the American Type Culture Collection (ATCC).RE and[3-(4,5-dimethylthiazo1-2-y1)-2.5-diphenyl-tetrazolium bromide](MTT)were obtained from Sigma Chemical CO,St Louis,USA;Ham's F-10 medium from Gibco BRL;Equine serum and fetal bovine serum from Hyclone Laboratories,Logan,UT;FACSCalibur flow cytometer from BD Company,USA.RE was dissolved in ethanol and stored at-20 ℃.It was diluted to different concentrations (10.50,100 μmol/L)with medium and extra cellular solution when needed.rhe final concentration of ethanol was Jess than 0.01%.METHODS:The experiment was carried out in the Department of Microbiology and Pharmacology of Harbin Medical University from March 2005 to January 2006.①Cell preparation:Proliferating indexes affected by 10.50 and 100 μmol/L RE were measured with MTT,respectively.0.0001 volume fraction of ethan ol was added into control group.Inhibitory rate of cellular growth was calculated as the following formula:Inhibitory rate (%)=(1-A value in experimental group/A value in control group)x100%.The experiments mentioned above were

  2. Multiphasic profiles for voltage-dependent K+ channels: Reanalysis of data of MacKinnon and coworkers

    CERN Document Server

    Nissen, Per

    2016-01-01

    In a study of the role that voltage-dependent K+ channels may have in the mechanosensation of living cells (Schmidt et al. Proc Soc Natl Acad Sci USA 109: 10352-10357. 2012), the data were as conventionally done fitted by a Boltzmann function. However, as also found for other data for ion channels, this interpretation must be rejected in favor of a multiphasic profile, a series of straight lines separated by discontinuous transitions, quite often in the form of noncontiguities (jumps). The data points in the present study are often very unevenly distributed around the curvilinear profiles. Thus, for 43 of the 75 profiles, the probability is less than 5% that the uneven distribution is due to chance, for 26 the probability is less than 1%, and for 12 the probability is less than 0.1%, giving a vanishingly low overall probability for all profiles. Especially at low voltages, the differences between the fits to curvilinear and multiphasic profiles may be huge. In the multiphasic profiles, adjacent lines are quit...

  3. Correlation character of ionic current fluctuations: analysis of ion current through a voltage-dependent potassium single channel.

    Science.gov (United States)

    Tong-Han, Lan; Huang, Xi; Jia-Rui, Lin

    2005-10-03

    The gating of ion channels has widely been modeled by assuming the transition between open and closed states is a memoryless process. Nevertheless, the statistical analysis of an ionic current signal recorded from voltage dependence K(+) single channel is presented. Calculating the sample auto-correlation function of the ionic current based on the digitized signals, rather than the sequence of open and closed states duration time. The results provide evidence for the existence of memory. For different voltages, the ion channel current fluctuation has different correlation attributions. The correlations in data generated by simulation of two Markov models, on one hand, auto-correlation function of the ionic current shows a weaker memory, after a delayed period of time, the attribute of memory does not exist; on the other hand, the correlation depends on the number of states in the Markov model. For V(p)=-60 mV pipette potential, spectral analysis of ion channel current was conducted, the result indicates that the spectrum is not a flat spectrum, the data set from ionic current fluctuations shows considerable variability with a broad 1/f -like spectrum, alpha=1.261+/-0.24. Thus the ion current fluctuations give information about the kinetics of the channel protein, the results suggest the correlation character of ion channel protein nonlinear kinetics regardless of whether the channel is in open or closed state.

  4. Scorpion toxin prolongs an inactivation phase of the voltage-dependent sodium current in rat isolated single hippocampal neurons.

    Science.gov (United States)

    Kaneda, M; Oyama, Y; Ikemoto, Y; Akaike, N

    1989-05-15

    The effects of scorpion toxin on the voltage-dependent sodium current (INa) of CA1 pyramidal neurons isolated from rat hippocampus were studied under the single-electrode voltage-clamp condition using a 'concentration-clamp' technique. The toxin increased the peak amplitude of INa and prolonged its inactivation phase in a time- and dose-dependent manner. Inactivation phase of INa proceeded with two exponential components in the absence (control) and presence of the toxin. In the toxin-treated neurons, both the time constant of slow component and its fractional contribution to the total current increased dose-dependently while the fractional contribution of the fast one decreased in a dose-dependent fashion without changing its time constant. Actions of scorpion toxin on the sodium channels of hippocampal pyramidal neurons were essentially similar to those of peripheral preparations. Therefore, it can be concluded that the sodium channels of mammalian brain neurons have structures and functions similar to peripheral channels.

  5. Inhibition of rat hippocampal excitability by the plant alkaloid 3-acetylaconitine mediated by interaction with voltage-dependent sodium channels.

    Science.gov (United States)

    Ameri, A

    1997-02-01

    The effects of the Aconitum alkaloid 3-acetylaconitine on neuronal activity were investigated in the slice preparation and on cultivated neurons of rat hippocampus by extracellular and patch-clamp recordings, respectively. 3-Acetylaconitine (0.01-1 microM) diminished the orthodromic and antidromic population spike in a concentration-dependent manner. The inhibitory action of the drug was preceded by a transiently enhanced excitability. The latency of onset of the inhibition was accelerated by increased stimulation frequency, whereas recovery during washout of the alkaloid was accelerated by decreased stimulation frequency. Moreover, the inhibitory effect of 3-acetylaconitine was evaluated in two different models of epileptiform activity induced either by blockade of GABA receptors by bicuculline (10 microM) or by a nominal Mg(2+)-free bathing medium. In accordance with the activity-dependent mode of action, this compound abolished the synaptically evoked population spikes in the presence of bicuculline or nominal Mg(2+)-free bathing medium, respectively. Whole-cell patch-clamp recordings revealed an interaction of 3-acetylaconitine with the voltage-dependent sodium channel. At a concentration of 1 microM, 3-acetylaconitine did not affect the peak amplitude of the sodium current, but shifted the current-voltage relationship in the hyperpolarized direction such that sodium currents were already activated at the resting potential.

  6. Voltage-dependent motion of the catalytic region of voltage-sensing phosphatase monitored by a fluorescent amino acid.

    Science.gov (United States)

    Sakata, Souhei; Jinno, Yuka; Kawanabe, Akira; Okamura, Yasushi

    2016-07-05

    The cytoplasmic region of voltage-sensing phosphatase (VSP) derives the voltage dependence of its catalytic activity from coupling to a voltage sensor homologous to that of voltage-gated ion channels. To assess the conformational changes in the cytoplasmic region upon activation of the voltage sensor, we genetically incorporated a fluorescent unnatural amino acid, 3-(6-acetylnaphthalen-2-ylamino)-2-aminopropanoic acid (Anap), into the catalytic region of Ciona intestinalis VSP (Ci-VSP). Measurements of Anap fluorescence under voltage clamp in Xenopus oocytes revealed that the catalytic region assumes distinct conformations dependent on the degree of voltage-sensor activation. FRET analysis showed that the catalytic region remains situated beneath the plasma membrane, irrespective of the voltage level. Moreover, Anap fluorescence from a membrane-facing loop in the C2 domain showed a pattern reflecting substrate turnover. These results indicate that the voltage sensor regulates Ci-VSP catalytic activity by causing conformational changes in the entire catalytic region, without changing their distance from the plasma membrane.

  7. Voltage-dependent anion channels (VDACs, porin) expressed in the plasma membrane regulate the differentiation and function of human osteoclasts.

    Science.gov (United States)

    Kotake, Shigeru; Yago, Toru; Kawamoto, Manabu; Nanke, Yuki

    2013-01-01

    Fewer molecules have been identified on human than murine osteoclasts, the former differing from murine osteoclasts in many ways. We show that voltage-dependent anion channels (VDACs, porin) are expressed in the plasma membrane of human osteoclasts. A search for novel proteins expressed in the plasma membrane of human osteoclasts identified VDAC. Anti-VDAC antibodies inhibited human osteoclastogenesis in vitro. VDAC expression was detected in membranes by immunoelectron microscopy and immunocytochemical double staining. The VDAC protein functions as a Cl(-) channel. VDACs regulate bone resorption, which show using Osteologic™ plates. The epitope of the antibody lay within a 10-amino acid sequence in the VDAC. The findings suggest that the VDAC is, at least partly, a novel Cl(-) channel regulating the differentiation and function of human osteoclasts. VDACs may play a crucial role in acidifying the resorption lacunae between osteoclasts and bone. Inhibitors of VDACs could be used to treat diseases involving increased resorption, such as osteoporosis, rheumatoid arthritis, and Paget's disease. © 2012 International Federation for Cell Biology.

  8. The voltage-dependent K+ channels Kv1.3 and Kv1.5 in human cancer

    Science.gov (United States)

    Comes, Núria; Bielanska, Joanna; Vallejo-Gracia, Albert; Serrano-Albarrás, Antonio; Marruecos, Laura; Gómez, Diana; Soler, Concepció; Condom, Enric; Ramón y Cajal, Santiago; Hernández-Losa, Javier; Ferreres, Joan C.; Felipe, Antonio

    2013-01-01

    Voltage-dependent K+ channels (Kv) are involved in a number of physiological processes, including immunomodulation, cell volume regulation, apoptosis as well as differentiation. Some Kv channels participate in the proliferation and migration of normal and tumor cells, contributing to metastasis. Altered expression of Kv1.3 and Kv1.5 channels has been found in several types of tumors and cancer cells. In general, while the expression of Kv1.3 apparently exhibits no clear pattern, Kv1.5 is induced in many of the analyzed metastatic tissues. Interestingly, evidence indicates that Kv1.5 channel shows inversed correlation with malignancy in some gliomas and non-Hodgkin's lymphomas. However, Kv1.3 and Kv1.5 are similarly remodeled in some cancers. For instance, expression of Kv1.3 and Kv1.5 correlates with a certain grade of tumorigenicity in muscle sarcomas. Differential remodeling of Kv1.3 and Kv1.5 expression in human cancers may indicate their role in tumor growth and their importance as potential tumor markers. However, despite of this increasing body of information, which considers Kv1.3 and Kv1.5 as emerging tumoral markers, further research must be performed to reach any conclusion. In this review, we summarize what it has been lately documented about Kv1.3 and Kv1.5 channels in human cancer. PMID:24133455

  9. The voltage-dependent K(+) channels Kv1.3 and Kv1.5 in human cancer.

    Science.gov (United States)

    Comes, Núria; Bielanska, Joanna; Vallejo-Gracia, Albert; Serrano-Albarrás, Antonio; Marruecos, Laura; Gómez, Diana; Soler, Concepció; Condom, Enric; Ramón Y Cajal, Santiago; Hernández-Losa, Javier; Ferreres, Joan C; Felipe, Antonio

    2013-10-10

    Voltage-dependent K(+) channels (Kv) are involved in a number of physiological processes, including immunomodulation, cell volume regulation, apoptosis as well as differentiation. Some Kv channels participate in the proliferation and migration of normal and tumor cells, contributing to metastasis. Altered expression of Kv1.3 and Kv1.5 channels has been found in several types of tumors and cancer cells. In general, while the expression of Kv1.3 apparently exhibits no clear pattern, Kv1.5 is induced in many of the analyzed metastatic tissues. Interestingly, evidence indicates that Kv1.5 channel shows inversed correlation with malignancy in some gliomas and non-Hodgkin's lymphomas. However, Kv1.3 and Kv1.5 are similarly remodeled in some cancers. For instance, expression of Kv1.3 and Kv1.5 correlates with a certain grade of tumorigenicity in muscle sarcomas. Differential remodeling of Kv1.3 and Kv1.5 expression in human cancers may indicate their role in tumor growth and their importance as potential tumor markers. However, despite of this increasing body of information, which considers Kv1.3 and Kv1.5 as emerging tumoral markers, further research must be performed to reach any conclusion. In this review, we summarize what it has been lately documented about Kv1.3 and Kv1.5 channels in human cancer.

  10. Probing the gate--voltage-dependent surface potential of individual InAs nanowires using random telegraph signals.

    Science.gov (United States)

    Salfi, Joe; Paradiso, Nicola; Roddaro, Stefano; Heun, Stefan; Nair, Selvakumar V; Savelyev, Igor G; Blumin, Marina; Beltram, Fabio; Ruda, Harry E

    2011-03-22

    We report a novel method for probing the gate-voltage dependence of the surface potential of individual semiconductor nanowires. The statistics of electronic occupation of a single defect on the surface of the nanowire, determined from a random telegraph signal, is used as a measure for the local potential. The method is demonstrated for the case of one or two switching defects in indium arsenide (InAs) nanowire field effect transistors at temperatures T=25-77 K. Comparison with a self-consistent model shows that surface potential variation is retarded in the conducting regime due to screening by surface states with density Dss≈10(12) cm(-2) eV(-1). Temperature-dependent dynamics of electron capture and emission producing the random telegraph signals are also analyzed, and multiphonon emission is identified as the process responsible for capture and emission of electrons from the surface traps. Two defects studied in detail had capture activation energies of EB≈50 meV and EB≈110 meV and cross sections of σ∞≈3×10(-19) cm2 and σ∞≈2×10(-17) cm2, respectively. A lattice relaxation energy of Sℏω=187±15 meV was found for the first defect.

  11. Voltage-dependent anion channels modulate mitochondrial metabolism in cancer cells: regulation by free tubulin and erastin.

    Science.gov (United States)

    Maldonado, Eduardo N; Sheldon, Kely L; DeHart, David N; Patnaik, Jyoti; Manevich, Yefim; Townsend, Danyelle M; Bezrukov, Sergey M; Rostovtseva, Tatiana K; Lemasters, John J

    2013-04-26

    Respiratory substrates and adenine nucleotides cross the mitochondrial outer membrane through the voltage-dependent anion channel (VDAC), comprising three isoforms--VDAC1, 2, and 3. We characterized the role of individual isoforms in mitochondrial metabolism by HepG2 human hepatoma cells using siRNA. With VDAC3 to the greatest extent, all VDAC isoforms contributed to the maintenance of mitochondrial membrane potential, but only VDAC3 knockdown decreased ATP, ADP, NAD(P)H, and mitochondrial redox state. Cells expressing predominantly VDAC3 were least sensitive to depolarization induced by increased free tubulin. In planar lipid bilayers, free tubulin inhibited VDAC1 and VDAC2 but not VDAC3. Erastin, a compound that interacts with VDAC, blocked and reversed mitochondrial depolarization after microtubule destabilizers in intact cells and antagonized tubulin-induced VDAC blockage in planar bilayers. In conclusion, free tubulin inhibits VDAC1/2 and limits mitochondrial metabolism in HepG2 cells, contributing to the Warburg phenomenon. Reversal of tubulin-VDAC interaction by erastin antagonizes Warburg metabolism and restores oxidative mitochondrial metabolism.

  12. Asymmetric gear rectifies random robot motion

    Science.gov (United States)

    Li, He; Zhang, H. P.

    2013-06-01

    We experimentally study the dynamics of centimetric robots and their interactions with rotary gears through inelastic collisions. Under the impacts of self-propelled robots, a gear with symmetric teeth diffuses with no preferred direction of motion. An asymmetric gear, however, rectifies random motion of nearby robots which, in return, exert a torque on the gear and drive it into unidirectional motion. Rectification efficiency increases with the degree of gear asymmetry. Our work demonstrates that asymmetric environments can be used to rectify and extract energy from random motion of macroscopic self-propelled particles.

  13. DC Motor Drive with PFC Rectifier

    Directory of Open Access Journals (Sweden)

    Lascu Mihaela

    2008-05-01

    Full Text Available The goal of this work is to study theperformances of a hybrid controller used to controlDC Motor drive with a single-phase power factorcorrection rectifier. This study is made usingcomputer simulation (Simulink. The first part isdevoted to the control system of the DC Motors. Inthe second part, the design of the hybrid controllerwill be presented. The third part is the design ofthe fast response single-phase boost power factorcorrection rectifier. The last parts are devoted tosimulation and experimental results.

  14. Effects of different kinds of stretch on voltage-dependent calcium current in antrial circular smooth muscle cells of the guinea-pig%不同牵张刺激对豚鼠胃窦环行肌细胞电压依赖性钙电流的影响

    Institute of Scientific and Technical Information of China (English)

    许文燮; 李英; 吴龙仁; 李在琉

    2000-01-01

    利用全细胞膜片钳技术,在胃窦环行肌细胞上观察了不同方式的牵张刺激对电压依赖性钙电流的影响,探讨牵张刺激对胃窦平滑肌细胞电压依赖性钙电流的作用.用低渗性溶液灌流细胞引起的牵张刺激首先增加电压依赖性钙电流,接着激活一种内向性钳制电流.钙电流的增加发生在灌流后1 min内,而内向性钳制电流在细胞明显膨胀之后缓慢激活.低渗和正压引起的细胞膨胀明显增加电压依赖性钙离子电流,而利用两个电极直接牵拉细胞则不出现钙电流增加效应.结果提示: 细胞膜牵张增强电压依赖性钙通道的活性,而这一作用可能与牵拉引起的细胞所受的膜张力或/和牵拉的方向有关.%In order to elucidate the effect of membrane stretch on ionic currents, we employed the whole-cell patch-clamp technique to investigate the effects of different kinds of stretch on voltage-dependent calcium currents in antrial circular smooth muscle cells of the guinea-pig. The membrane stretch induced by superfusing the smooth muscle cells with hyposmotic bath solution enhanced voltage-operated calcium current and activated inward holding current. The increase in calcium current occurred within 1 minute of superfusion and the sustained inward holding current was slowly activated after prominent cell swelling. Voltage-dependent calcium currents (Ica) were significantly increased by membrane stretch which was induced by cell swelling and cell inflation, but was not affected by direct longitudinal stretch (110~130%) using two electrodes.The results suggest that the cell membrane stretch can increase voltage-dependent calcium channel activity and the effect of stretch on calcium channels was related to the membrane tension and/or the direction of membrane stretch.

  15. Planet heating prevents inward migration of planetary cores

    CERN Document Server

    Benítez-Llambay, Pablo; Koenigsberger, Gloria; Szulágyi, Judit

    2015-01-01

    Planetary systems are born in the disks of gas, dust and rocky fragments that surround newly formed stars. Solid content assembles into ever-larger rocky fragments that eventually become planetary embryos. These then continue their growth by accreting leftover material in the disc. Concurrently, tidal effects in the disc cause a radial drift in the embryo orbits, a process known as migration. Fast inward migration is predicted by theory for embryos smaller than three to five Earth masses. With only inward migration, these embryos can only rarely become giant planets located at Earth's distance from the Sun and beyond, in contrast with observations. Here we report that asymmetries in the temperature rise associated with accreting infalling material produce a force (which gives rise to an effect that we call "heating torque") that counteracts inward migration. This provides a channel for the formation of giant planets and also explains the strong planet-metallicity correlation found between the incidence of gia...

  16. Entropy production and inward heat pinch of plasma

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka [National Inst. for Fusion Science, Nagoya (Japan); Itoh, Sanae

    1996-02-01

    Heat pinch phenomena in the plasma with peripheral heating is discussed from the view point of thermodynamics. The entropy production rate associated with inward energy flow in the presence of energy exchange between electrons and ions is calculated. The inward energy flow can increase the total entropy production rate. It is conjectured that the outward energy flow of colder species (say ions) could sustain the energy flux of hotter species (say electrons) in the core, which flows into the direction of higher temperature. (author)

  17. 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

    1993-01-01

    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 t

  18. Laserlike Vibrational Instability in Rectifying Molecular Conductors

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Hedegård, Per; Brandbyge, Mads

    2011-01-01

    We study the damping of molecular vibrations due to electron-hole pair excitations in donor-acceptor (D-A) type molecular rectifiers. At finite voltage additional nonequilibrium electron-hole pair excitations involving both electrodes become possible, and contribute to the stimulated emission and...

  19. Poly(ethylene glycol-cholesterol inhibits L-type Ca2+ channel currents and augments voltage-dependent inactivation in A7r5 cells.

    Directory of Open Access Journals (Sweden)

    Rikuo Ochi

    Full Text Available Cholesterol distributes at a high density in the membrane lipid raft and modulates ion channel currents. Poly(ethylene glycol cholesteryl ether (PEG-cholesterol is a nonionic amphipathic lipid consisting of lipophilic cholesterol and covalently bound hydrophilic PEG. PEG-cholesterol is used to formulate lipoplexes to transfect cultured cells, and liposomes for encapsulated drug delivery. PEG-cholesterol is dissolved in the external leaflet of the lipid bilayer, and expands it to flatten the caveolae and widen the gap between the two leaflets. We studied the effect of PEG-cholesterol on whole cell L-type Ca(2+ channel currents (I(Ca,L recorded from cultured A7r5 arterial smooth muscle cells. The pretreatment of cells with PEG-cholesterol decreased the density of ICa,L and augmented the voltage-dependent inactivation with acceleration of time course of inactivation and negative shift of steady-state inactivation curve. Methyl-β-cyclodextrin (MβCD is a cholesterol-binding oligosaccharide. The enrichment of cholesterol by the MβCD:cholesterol complex (cholesterol (MβCD caused inhibition of I(Ca,L but did not augment voltage-dependent inactivation. Incubation with MβCD increased I(Ca,L, slowed the time course of inactivation and shifted the inactivation curve to a positive direction. Additional pretreatment by a high concentration of MβCD of the cells initially pretreated with PEG-cholesterol, increased I(Ca,L to a greater level than the control, and removed the augmented voltage-dependent inactivation. Due to the enhancement of the voltage-dependent inactivation, PEG-cholesterol inhibited window I(Ca,L more strongly as compared with cholesterol (MβCD. Poly(ethylene glycol conferred to cholesterol the efficacy to induce sustained augmentation of voltage-dependent inactivation of I(Ca,L.

  20. Altered ischemic cerebral injury in mice lacking αIE subunit of the voltage-dependent Ca2+ channel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Objective ①To set up a stable and reproducible focal cerebral infarct modelin mice; (②To examine theinvolvement of αIE subunit of voltage-dependent Ca2 + channel in cerebral ischemic injury. Methods Male C57BL/6J Jclmice 8 ~ 12w and F4 ~ F6αIE subunit of Ca2+ channel mutant mice were both used in this study. All animals were allowedto freely access to food and water before and after operation. Animals were anesthetized with pentobarbital sodium 60mg/kg,ip. Rectal temperature was continuously monitored before, during and after operation, and maintained at (36.6 +0.1 )°C by a autoregulating pad. To produce pilot models, the middle cerebral artery (MCA) was occluded either by sur-gical ligation or electrical coagulation and in some models the common carotid artery (CCA) was surgically ligated in tan-dem. In our latter work the MCA was cut off soon after it was ligated or coagulated in order to make sure that the bloodflow was occluded completely. The MCA was coagulated or ligated with a bipolar coagulator or microsurgery suture at thesite just superior to the rhinal fissure. Twenty~four hours after the operation, the mice were anesthetized and decapitated,then their brains were dissected from the skull and put into cold artificial brain spinal fluid as soon as possible. Lmm thickcoronal sections were cut by vibratome and stained with 2% 2,3,5-triphenyltetrazolium chloride (TTC) at 37°C for30min. Every section was photographed positively and the whole infarction volume was calculated by summing up the in-farction volumes of all sections by NIH Image System. Infarction ratio ( % ) was also calculated by the following fommula:(contralateral volume-ipsilateral undamaged volume)/contralateral volume × 100% to eliminate the influence of edema.In brief, the mutant mice were produced with gene targeting technique. F4 ~ F6 mice were used in this experiment. Alloffsprings were genotyped by the polymerase chain reaction (PCR) and the genotypes remained umknown

  1. Voltage dependence of Hodgkin-Huxley rate functions for a multistage K^{+} channel voltage sensor within a membrane.

    Science.gov (United States)

    Vaccaro, S R

    2014-11-01

    The activation of a K^{+} channel sensor in two sequential stages during a voltage clamp may be described as the translocation of a Brownian particle in an energy landscape with two large barriers between states. A solution of the Smoluchowski equation for a square-well approximation to the potential function of the S4 voltage sensor satisfies a master equation and has two frequencies that may be determined from the forward and backward rate functions. When the higher-frequency terms have small amplitude, the solution reduces to the relaxation of a rate equation, where the derived two-state rate functions are dependent on the relative magnitude of the forward rates (α and γ) and the backward rates (β and δ) for each stage. In particular, the voltage dependence of the Hodgkin-Huxley rate functions for a K^{+} channel may be derived by assuming that the rate functions of the first stage are large relative to those of the second stage-α≫γ and β≫δ. For a Shaker IR K^{+} channel, the first forward and backward transitions are rate limiting (αchannel and a noninactivating Na^{+} ion channel is determined by the master equation for K^{+} channel activation and the ionic current equation when the Na^{+} channel activation time is small, and if β≪δ and α≪γ, the system may exhibit a small amplitude oscillation between spikes, or mixed-mode oscillation, in which the slow closed state modulates the K^{+} ion channel conductance in the membrane.

  2. The Voltage-dependent Anion Channel 1 Mediates Amyloid β Toxicity and Represents a Potential Target for Alzheimer Disease Therapy.

    Science.gov (United States)

    Smilansky, Angela; Dangoor, Liron; Nakdimon, Itay; Ben-Hail, Danya; Mizrachi, Dario; Shoshan-Barmatz, Varda

    2015-12-25

    The voltage-dependent anion channel 1 (VDAC1), found in the mitochondrial outer membrane, forms the main interface between mitochondrial and cellular metabolisms, mediates the passage of a variety of molecules across the mitochondrial outer membrane, and is central to mitochondria-mediated apoptosis. VDAC1 is overexpressed in post-mortem brains of Alzheimer disease (AD) patients. The development and progress of AD are associated with mitochondrial dysfunction resulting from the cytotoxic effects of accumulated amyloid β (Aβ). In this study we demonstrate the involvement of VDAC1 and a VDAC1 N-terminal peptide (VDAC1-N-Ter) in Aβ cell penetration and cell death induction. Aβ directly interacted with VDAC1 and VDAC1-N-Ter, as monitored by VDAC1 channel conductance, surface plasmon resonance, and microscale thermophoresis. Preincubated Aβ interacted with bilayer-reconstituted VDAC1 and increased its conductance ∼ 2-fold. Incubation of cells with Aβ resulted in mitochondria-mediated apoptotic cell death. However, the presence of non-cell-penetrating VDAC1-N-Ter peptide prevented Aβ cellular entry and Aβ-induced mitochondria-mediated apoptosis. Likewise, silencing VDAC1 expression by specific siRNA prevented Aβ entry into the cytosol as well as Aβ-induced toxicity. Finally, the mode of Aβ-mediated action involves detachment of mitochondria-bound hexokinase, induction of VDAC1 oligomerization, and cytochrome c release, a sequence of events leading to apoptosis. As such, we suggest that Aβ-mediated toxicity involves mitochondrial and plasma membrane VDAC1, leading to mitochondrial dysfunction and apoptosis induction. The VDAC1-N-Ter peptide targeting Aβ cytotoxicity is thus a potential new therapeutic strategy for AD treatment.

  3. Thiazolidinedione insulin sensitizers alter lipid bilayer properties and voltage-dependent sodium channel function: implications for drug discovery.

    Science.gov (United States)

    Rusinova, Radda; Herold, Karl F; Sanford, R Lea; Greathouse, Denise V; Hemmings, Hugh C; Andersen, Olaf S

    2011-08-01

    The thiazolidinediones (TZDs) are used in the treatment of diabetes mellitus type 2. Their canonical effects are mediated by activation of the peroxisome proliferator-activated receptor γ (PPARγ) transcription factor. In addition to effects mediated by gene activation, the TZDs cause acute, transcription-independent changes in various membrane transport processes, including glucose transport, and they alter the function of a diverse group of membrane proteins, including ion channels. The basis for these off-target effects is unknown, but the TZDs are hydrophobic/amphiphilic and adsorb to the bilayer-water interface, which will alter bilayer properties, meaning that the TZDs may alter membrane protein function by bilayer-mediated mechanisms. We therefore explored whether the TZDs alter lipid bilayer properties sufficiently to be sensed by bilayer-spanning proteins, using gramicidin A (gA) channels as probes. The TZDs altered bilayer elastic properties with potencies that did not correlate with their affinity for PPARγ. At concentrations where they altered gA channel function, they also altered the function of voltage-dependent sodium channels, producing a prepulse-dependent current inhibition and hyperpolarizing shift in the steady-state inactivation curve. The shifts in the inactivation curve produced by the TZDs and other amphiphiles can be superimposed by plotting them as a function of the changes in gA channel lifetimes. The TZDs' partition coefficients into lipid bilayers were measured using isothermal titration calorimetry. The most potent bilayer modifier, troglitazone, alters bilayer properties at clinically relevant free concentrations; the least potent bilayer modifiers, pioglitazone and rosiglitazone, do not. Unlike other TZDs tested, ciglitazone behaves like a hydrophobic anion and alters the gA monomer-dimer equilibrium by more than one mechanism. Our results provide a possible mechanism for some off-target effects of an important group of drugs, and

  4. Photoaffinity labeling with cholesterol analogues precisely maps a cholesterol-binding site in voltage-dependent anion channel-1.

    Science.gov (United States)

    Budelier, Melissa M; Cheng, Wayland W L; Bergdoll, Lucie; Chen, Zi-Wei; Janetka, James W; Abramson, Jeff; Krishnan, Kathiresan; Mydock-McGrane, Laurel; Covey, Douglas F; Whitelegge, Julian P; Evers, Alex S

    2017-06-02

    Voltage-dependent anion channel-1 (VDAC1) is a highly regulated β-barrel membrane protein that mediates transport of ions and metabolites between the mitochondria and cytosol of the cell. VDAC1 co-purifies with cholesterol and is functionally regulated by cholesterol, among other endogenous lipids. Molecular modeling studies based on NMR observations have suggested five cholesterol-binding sites in VDAC1, but direct experimental evidence for these sites is lacking. Here, to determine the sites of cholesterol binding, we photolabeled purified mouse VDAC1 (mVDAC1) with photoactivatable cholesterol analogues and analyzed the photolabeled sites with both top-down mass spectrometry (MS), and bottom-up MS paired with a clickable, stable isotope-labeled tag, FLI-tag. Using cholesterol analogues with a diazirine in either the 7 position of the steroid ring (LKM38) or the aliphatic tail (KK174), we mapped a binding pocket in mVDAC1 localized to Thr(83) and Glu(73), respectively. When Glu(73) was mutated to a glutamine, KK174 no longer photolabeled this residue, but instead labeled the nearby Tyr(62) within this same binding pocket. The combination of analytical strategies employed in this work permits detailed molecular mapping of a cholesterol-binding site in a protein, including an orientation of the sterol within the site. Our work raises the interesting possibility that cholesterol-mediated regulation of VDAC1 may be facilitated through a specific binding site at the functionally important Glu(73) residue. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  5. Voltage-dependent changes in specific membrane capacitance caused by prestin, the outer hair cell lateral membrane motor.

    Science.gov (United States)

    Santos-Sacchi, Joseph; Navarrete, Enrique

    2002-05-01

    In the outer hair cell (OHC), membrane capacitance principally derives from two components - that associated with lateral membrane sensor/motor charge movement, and that proportional to the membrane surface area (C(sa)). We used measures of membrane capacitance to test a model hypothesis that OHC lateral membrane molecular motors, recently identified as the protein prestin, fluctuate between two area states. By measuring membrane capacitance in native OHCs or prestin-transfected HEK cells at extreme voltages (+/-200 mV) where motor-derived charge movement is small or absent, we observed that C(sa) depends on the state of the motors, or correspondingly on membrane voltage. Deiters cells or control HEK cells, which lack motors, do not show this dependence. We modeled the voltage-dependent change in C(sa) as a Boltzmann process with the same parameters that describe the charge movement of the motors' voltage sensors. C(sa) is 3.28+/-0.75 pF (mean +/-SD; n=23) larger during extreme hyperpolarization, and the number of motors in OHCs and prestin-transfected HEK cells correlates with the magnitude of Delta C(sa)( r=0.78). Although these data are consistent with the area motor model, the corresponding area change, assuming 0.5 microF/cm(2) under constant membrane thickness, is unphysiologically large, and indicates that the capacitance change must result from changes not only in lateral membrane area but also specific capacitance. Thus, we conclude that a conformational change in the lateral membrane motor, prestin, additionally alters the dielectric constant and/or thickness of the lateral plasma membrane.

  6. Charged residues distribution modulates selectivity of the open state of human isoforms of the voltage dependent anion-selective channel.

    Science.gov (United States)

    Amodeo, Giuseppe Federico; Scorciapino, Mariano Andrea; Messina, Angela; De Pinto, Vito; Ceccarelli, Matteo

    2014-01-01

    Voltage Dependent Anion-selective Channels (VDACs) are pore-forming proteins located in the outer mitochondrial membrane. They are responsible for the access of ions and energetic metabolites into the inner membrane transport systems. Three VDAC isoforms exist in mammalian, but their specific role is unknown. In this work we have performed extensive (overall ∼5 µs) Molecular Dynamics (MD) simulations of the human VDAC isoforms to detect structural and conformational variations among them, possibly related to specific functional roles of these proteins. Secondary structure analysis of the N-terminal domain shows a high similarity among the three human isoforms of VDAC but with a different plasticity. In particular, the N-terminal domain of the hVDAC1 is characterized by a higher plasticity, with a ∼20% occurrence for the 'unstructured' conformation throughout the folded segment, while hVDAC2, containing a peculiar extension of 11 amino acids at the N-terminal end, presents an additional 310-helical folded portion comprising residues 10' to 3, adhering to the barrel wall. The N-terminal sequences of hVDAC isoforms are predicted to have a low flexibility, with possible consequences in the dynamics of the human VDACs. Clear differences were found between hVDAC1 and hVDAC3 against hVDAC2: a significantly modified dynamics with possible important consequence on the voltage-gating mechanism. Charge distribution inside and at the mouth of the pore is responsible for a different preferential localization of ions with opposite charge and provide a valuable rationale for hVDAC1 and hVDAC3 having a Cl-/K+ selectivity ratio of 1.8, whereas hVDAC2 of 1.4. Our conclusion is that hVDAC isoforms, despite sharing a similar scaffold, have modified working features and a biological work is now requested to give evidence to the described dissimilarities.

  7. Transient voltage-dependent potassium currents are reduced in NTS neurons isolated from renal wrap hypertensive rats.

    Science.gov (United States)

    Belugin, Sergei; Mifflin, Steve

    2005-12-01

    Whole cell patch-clamp measurements were made in neurons enzymatically dispersed from the nucleus of the solitary tract (NTS) to determine if alterations occur in voltage-dependent potassium channels from rats made hypertensive (HT) by unilateral nephrectomy/renal wrap for 4 wk. Some rats had the fluorescent tracer DiA applied to the aortic nerve before the experiment to identify NTS neurons receiving monosynaptic baroreceptor afferent inputs. Mean arterial pressure (MAP) was greater in 4-wk HT (165 +/- 5 mmHg, n = 26, P NTS neurons from NT and HT rats. At activation voltages from -10 to +10 mV, TOCs were significantly less in HT neurons compared with those observed in NT neurons (P NTS neurons from NT and HT rats and was not different comparing neurons from NT and HT rats. However, examination of the subset of NTS neurons exhibiting somatic DiA fluorescence revealed that DiA-labeled neurons from HT rats had a significantly shorter duration delayed excitation (n = 8 cells, P = 0.022) than DiA-labeled neurons from NT rats (n = 7 cells). Neurons with delayed excitation from HT rats had a significantly broader first action potential (AP) and a slower maximal downstroke velocity of repolarization compared with NT neurons with delayed excitation (P = 0.016 and P = 0.014, respectively). The number of APs in the first 200 ms of a sustained depolarization was greater in HT than NT neurons (P = 0.012). These results suggest that HT of 4-wk duration reduces TOCs in NTS neurons, and this contributes to reduced delayed excitation and increased AP responses to depolarizing inputs. Such changes could alter baroreflex function in hypertension.

  8. 46 CFR 120.360 - Semiconductor rectifier systems.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Semiconductor rectifier systems. 120.360 Section 120.360... INSTALLATION Power Sources and Distribution Systems § 120.360 Semiconductor rectifier systems. (a) Each semiconductor rectifier system must have an adequate heat removal system that prevents overheating. (b) Where...

  9. 46 CFR 129.360 - Semiconductor-rectifier systems.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Semiconductor-rectifier systems. 129.360 Section 129.360... INSTALLATIONS Power Sources and Distribution Systems § 129.360 Semiconductor-rectifier systems. (a) Each semiconductor-rectifier system must have an adequate heat-removal system to prevent overheating. (b) If...

  10. 46 CFR 183.360 - Semiconductor rectifier systems.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360... TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor rectifier systems. (a) Each semiconductor rectifier system must have an adequate heat removal system that...

  11. The rectified second law of thermodynamics.

    Science.gov (United States)

    Ben-Amotz, Dor; Honig, J M

    2006-10-12

    Equilibrium thermodynamics is combined with Jarzynski's irreversible work theorem to quantify the excess entropy produced by irreversible processes. The resulting rectified form of the second law parallels the first law, in the sense that it facilitates the experimental measurement of excess entropy changes resulting from irreversible work and heat exchanges, just as the first law quantifies energy changes produced by either reversible or irreversible work and heat exchanges. The general form of the rectified second law is further applied to a broad class of quasi-static irreverisble (QSI) processes, for which all of the thermodynamic functions of both the system and surroundings remain continuously well-defined, thus facilitating excess entropy measurements by integrating exact differential functions along QSI paths. The results are illustrated by calculating the mechanical and thermal excess entropy produced by the irreversible unfolding of an RNA molecule.

  12. Reduction of Harmonics by 18-Pulse Rectifier

    Directory of Open Access Journals (Sweden)

    Stanislav Kocman

    2008-01-01

    Full Text Available Operation of such electrical devices as data processing and electronics devices, adjustable speed drives or uninterruptible power supply can cause problems by generating harmonic currents into the network, from which they are supplied. Effects of these harmonic currents are various, they can get worse the quality of supply voltage in the network or to have negative influences on devices connected to this network. There are various technical solutions for reduction of harmonics. One of them is using of multi-pulse rectifiers, whereas the 18-pulse rectifier in the structure of adjustable speed drive is briefly presented in this paper including some results of its behaviour. The examined experimental measurements confirmed its very good efficiency in the harmonic mitigation.

  13. Menger curvature and rectifiability in metric spaces

    OpenAIRE

    2012-01-01

    We show that for any metric space $X$ the condition \\[ \\int_X\\int_X\\int_X c(z_1,z_2,z_3)^2\\, d\\Hm z_1\\, d\\Hm z_2\\, d\\Hm z_3 < \\infty, \\] where $c(z_1,z_2,z_3)$ is the Menger curvature of the triple $(z_1,z_2,z_3)$, guarantees that $X$ is rectifiable.

  14. Rotating field transformers eliminate rectifier harmonics

    Energy Technology Data Exchange (ETDEWEB)

    Pastor, C.E. [Westinghouse Motor Co., Round Rock, TX (United States); Buckle, K.A. [Univ. of South Florida, Tampa, FL (United States); Luce, J.W. [Luce (John W.), Tampa, FL (United States)

    1995-10-01

    The rotating field transformer is a static device that has the same magnetic field as a three phase motor. When used to feed diode rectifiers, it converts ac to dc with low ripple on the output voltage and remarkably low current distortion on the input. Filters are not needed. This is a timely development because it is an economical and very effective solution to the growing problem of power system harmonics.

  15. Time-resolved photoluminescence measurements for determining voltage-dependent charge-separation efficiencies of subcells in triple-junction solar cells

    Science.gov (United States)

    Tex, David M.; Ihara, Toshiyuki; Akiyama, Hidefumi; Imaizumi, Mitsuru; Kanemitsu, Yoshihiko

    2015-01-01

    Conventional external quantum-efficiency measurement of solar cells provides charge-collection efficiency for approximate short-circuit conditions. Because this differs from actual operating voltages, the optimization of high-quality tandem solar cells is especially complicated. Here, we propose a contactless method, which allows for the determination of the voltage dependence of charge-collection efficiency for each subcell independently. By investigating the power dependence of photoluminescence decays, charge-separation and recombination-loss time constants are obtained. The upper limit of the charge-collection efficiencies at the operating points is then obtained by applying the uniform field model. This technique may complement electrical characterization of the voltage dependence of charge collection, since subcells are directly accessible.

  16. A Stochastic Model of Inward Diffusion in Magnetospheric Plasmas

    CERN Document Server

    Sato, Naoki

    2014-01-01

    The inward diffusion of particles, often observed in magnetospheric plasmas (either naturally created stellar ones or laboratory devices) creates a spontaneous density gradient, which seemingly contradicts the entropy principle. We construct a theoretical model of diffusion that can explain the inward diffusion in a dipole magnetic field. The key is the identification of the proper coordinates on which an appropriate diffusion operator can be formulated. The effective phase space is foliated by the adiabatic invariants; on the symplectic leaf, the invariant measure (by which the entropy must be calculated) is distorted, by the inhomogeneous magnetic field, with respect to the conventional Lebesgue measure of the natural phase space. The collision operator is formulated to be consistent to the ergodic hypothesis on the symplectic leaf, i.e., the resultant diffusion must diminish gradients on the proper coordinates. The non-orthogonality of the cotangent vectors of the configuration space causes a coupling betw...

  17. On the inward drift of runaway electrons in plateau regime

    CERN Document Server

    Hu, Di

    2016-01-01

    The well observed inward drift of current carrying runaway electrons during runaway plateau regime after disruption is studied by considering the phase space dynamic of runaways in a large aspect ratio toroidal system. We consider the case where the toroidal field is unperturbed and the toroidal symmetry of the system is preserved. The invariance of canonical angular momentum in such system requires runaways to drift horizontally in configuration space for any given change in momentum space. The dynamic of this drift can be obtained by taking the variation of canonical angular momentum. It is then found that runaway electrons will always drift inward as long as they are decelerating. This drift motion is essentially non-linear, since the current is carried by runaways themselves, and any runaway drift relative to the magnetic axis will cause further displacement of the axis itself. A simplified analytical model is constructed to describe such inward drift both in ideal wall case and no wall case, and the runa...

  18. Planet heating prevents inward migration of planetary cores.

    Science.gov (United States)

    Benítez-Llambay, Pablo; Masset, Frédéric; Koenigsberger, Gloria; Szulágyi, Judit

    2015-04-02

    Planetary systems are born in the disks of gas, dust and rocky fragments that surround newly formed stars. Solid content assembles into ever-larger rocky fragments that eventually become planetary embryos. These then continue their growth by accreting leftover material in the disk. Concurrently, tidal effects in the disk cause a radial drift in the embryo orbits, a process known as migration. Fast inward migration is predicted by theory for embryos smaller than three to five Earth masses. With only inward migration, these embryos can only rarely become giant planets located at Earth's distance from the Sun and beyond, in contrast with observations. Here we report that asymmetries in the temperature rise associated with accreting infalling material produce a force (which gives rise to an effect that we call 'heating torque') that counteracts inward migration. This provides a channel for the formation of giant planets and also explains the strong planet-metallicity correlation found between the incidence of giant planets and the heavy-element abundance of the host stars.

  19. Adenine nucleotides and intracellular Ca2+ regulate a voltage-dependent and glucose-sensitive potassium channel in neurosecretory cells.

    Science.gov (United States)

    Onetti, C G; Lara, J; García, E

    1996-05-01

    Effects of membrane potential, intracellular Ca2+ and adenine nucleotides on glucose-sensitive channels from X organ (XO) neurons of the crayfish were studied in excised inside-out patches. Glucose- sensitive channels were selective to K+ ions; the unitary conductance was 112 pS in symmetrical K+, and the K+ permeability (PK) was 1.3 x 10(-13) cm x s(-1). An inward rectification was observed when intracellular K+ was reduced. Using a quasi-physiological K+ gradient, a non-linear K+ current/voltage relationship was found showing an outward rectification and a slope conductance of 51 pS. The open-state probability (Po) increased with membrane depolarization as a result of an enhancement of the mean open time and a shortening of the longer period of closures. In quasi-physio- logical K+ concentrations, the channel was activated from a threshold of about -60 mV, and the activation midpoint was -2 mV. Po decreased noticeably at 50 microM internal adenosine 5'-triphosphate (ATP), and single-channel activity was totally abolished at 1 mM ATP. Hill analysis shows that this inhibition was the result of simultaneous binding of two ATP molecules to the channel, and the half-blocking concentration of ATP was 174 microM. Internal application of 5'-adenylylimidodiphosphate (AMP-PNP) as well as glibenclamide also decreased Po. By contrast, the application of internal ADP (0.1 to 2 mM) activated this channel. An optimal range of internal free Ca2+ ions (0.1 to 10 microM) was required for the activation of this channel. The glucose--sensitive K+ channel of XO neurons could be considered as a subtype of ATP-sensitive K+ channel, contributing substantially to macroscopic outward current.

  20. Three -Phase PFC Rectifier with Phase - Modular Y-Rectifier for LED Lamp

    Directory of Open Access Journals (Sweden)

    Narin Watanakul

    2015-10-01

    Full Text Available The paper was to study ac/dc three phase PFC rectifier for LED lamp. The performance normally of the rectifier having is current low quality and low power factor and high total harmonics distortion current. Therefore, the objectives in this a paper going to improving power factor and reduce harmonics current. In this paper to propose power factor correction (PFC with phase- modular Y-rectifier, boost type converter circuit using by one cycle control (OCC. For high performance method and tested of the result for realize that can solve power factor and reduce harmonic current. The research papers, conclusions for study and evaluate the circuit can be operation and suitable for use with LED 50 W (LED lamp. The data collected by MATLAB Simulation are used in comparison with the experimental tester of results.

  1. Cloning and characterization of a human delayed rectifier potassium channel gene.

    Science.gov (United States)

    Albrecht, B; Lorra, C; Stocker, M; Pongs, O

    1993-01-01

    A human genomic DNA library was screened for sequences homologues to the rat delayed rectifier Kv 2.1 (DRK1) K+ channel cDNA. Three phages were isolated which hybridized to Kv 2.1 cDNA probes. Alignment of the human genomic DNA sequence with the rat cDNA sequence indicated that the open reading frame (ORF) is interrupted by a large intervening sequence, that separates exons encoding the membrane spanning core region of the K+ channel polypeptide. The Kv 2.1 gene occurs once in the human genome and has been mapped to chromosome 20. The human, mouse and rat Kv 2.1 proteins have been highly conserved, showing only a few substitutions outside of the membrane spanning domains in the amino- and carboxy-terminal cytoplasmic domains. Nevertheless, expression of human DRK1 channels in Xenopus oocytes showed that mouse, rat and human Kv 2.1 channels have distinct pharmacological and electrophysiological properties. The observed differences in activation, voltage-dependence, 4-aminopyridine sensitivity and single-channel conductance have to be attributed to amino acid substitutions in the amino-and/or carboxy-terminal cytoplasmic domains. Obviously, these domains of Kv 2.1 channels influence biophysical K+ channel properties, which are thought to be determined solely by the membrane spanning core domain of potassium channels.

  2. Voltage-dependent regulation of CaV2.2 channels by Gq-coupled receptor is facilitated by membrane-localized β subunit.

    Science.gov (United States)

    Keum, Dongil; Baek, Christina; Kim, Dong-Il; Kweon, Hae-Jin; Suh, Byung-Chang

    2014-10-01

    G protein-coupled receptors (GPCRs) signal through molecular messengers, such as Gβγ, Ca(2+), and phosphatidylinositol 4,5-bisphosphate (PIP2), to modulate N-type voltage-gated Ca(2+) (CaV2.2) channels, playing a crucial role in regulating synaptic transmission. However, the cellular pathways through which GqPCRs inhibit CaV2.2 channel current are not completely understood. Here, we report that the location of CaV β subunits is key to determining the voltage dependence of CaV2.2 channel modulation by GqPCRs. Application of the muscarinic agonist oxotremorine-M to tsA-201 cells expressing M1 receptors, together with CaV N-type α1B, α2δ1, and membrane-localized β2a subunits, shifted the current-voltage relationship for CaV2.2 activation 5 mV to the right and slowed current activation. Muscarinic suppression of CaV2.2 activity was relieved by strong depolarizing prepulses. Moreover, when the C terminus of β-adrenergic receptor kinase (which binds Gβγ) was coexpressed with N-type channels, inhibition of CaV2.2 current after M1 receptor activation was markedly reduced and delayed, whereas the delay between PIP2 hydrolysis and inhibition of CaV2.2 current was decreased. When the Gβγ-insensitive CaV2.2 α1C-1B chimera was expressed, voltage-dependent inhibition of calcium current was virtually abolished, suggesting that M1 receptors act through Gβγ to inhibit CaV2.2 channels bearing membrane-localized CaV β2a subunits. Expression of cytosolic β subunits such as β2b and β3, as well as the palmitoylation-negative mutant β2a(C3,4S), reduced the voltage dependence of M1 muscarinic inhibition of CaV2.2 channels, whereas it increased inhibition mediated by PIP2 depletion. Together, our results indicate that, with membrane-localized CaV β subunits, CaV2.2 channels are subject to Gβγ-mediated voltage-dependent inhibition, whereas cytosol-localized β subunits confer more effective PIP2-mediated voltage-independent regulation. Thus, the voltage dependence of

  3. An Inductorless Self-Controlled Rectifier for Piezoelectric Energy Harvesting

    Science.gov (United States)

    Lu, Shaohua; Boussaid, Farid

    2015-01-01

    This paper presents a high-efficiency inductorless self-controlled rectifier for piezoelectric energy harvesting. High efficiency is achieved by discharging the piezoelectric device (PD) capacitance each time the current produced by the PD changes polarity. This is achieved automatically without the use of delay lines, thereby making the proposed circuit compatible with any type of PD. In addition, the proposed rectifier alleviates the need for an inductor, making it suitable for on-chip integration. Reported experimental results show that the proposed rectifier can harvest up to 3.9 times more energy than a full wave bridge rectifier. PMID:26610492

  4. Three-Phase Back PWM-PFC Rectifier

    Institute of Scientific and Technical Information of China (English)

    Yasuyuki Nishida

    2005-01-01

    A new 3-phase back (or current-source-type) PWM-PFC rectifier is proposed in this paper. The necessity,the advantages and disadvantages of this type PWM rectifier are discussed first.Then,the new power circuit topology and the modulation scheme to eliminate or mitigate the disadvantages and obtain further new advantages of the buck PWM rectifier are introduced.The features of the new rectifier, i.e., high efficiency, simple modulation process, robustness of the line-current modulation for distortion of the utility voltages and DC current ripples have been confirmed through experimental results obtained from a 12kW prototype.

  5. An Inductorless Self-Controlled Rectifier for Piezoelectric Energy Harvesting

    Directory of Open Access Journals (Sweden)

    Shaohua Lu

    2015-11-01

    Full Text Available This paper presents a high-efficiency inductorless self-controlled rectifier for piezoelectric energy harvesting. High efficiency is achieved by discharging the piezoelectric device (PD capacitance each time the current produced by the PD changes polarity. This is achieved automatically without the use of delay lines, thereby making the proposed circuit compatible with any type of PD. In addition, the proposed rectifier alleviates the need for an inductor, making it suitable for on-chip integration. Reported experimental results show that the proposed rectifier can harvest up to 3.9 times more energy than a full wave bridge rectifier.

  6. High Voltage GaN Schottky Rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  7. Rab3 interacting molecule 3 mutations associated with autism alter regulation of voltage-dependent Ca²⁺ channels.

    Science.gov (United States)

    Takada, Yoshinori; Hirano, Mitsuru; Kiyonaka, Shigeki; Ueda, Yoshifumi; Yamaguchi, Kazuma; Nakahara, Keiko; Mori, Masayuki X; Mori, Yasuo

    2015-09-01

    Autism is a neurodevelopmental psychiatric disorder characterized by impaired reciprocal social interaction, disrupted communication, and restricted and stereotyped patterns of interests. Autism is known to have a strong genetic component. Although mutations in several genes account for only a small proportion of individuals with autism, they provide insight into potential biological mechanisms that underlie autism, such as dysfunction in Ca(2+) signaling, synaptic dysfunction, and abnormal brain connectivity. In autism patients, two mutations have been reported in the Rab3 interacting molecule 3 (RIM3) gene. We have previously demonstrated that RIM3 physically and functionally interacts with voltage-dependent Ca(2+) channels (VDCCs) expressed in neurons via the β subunits, and increases neurotransmitter release. Here, by introducing corresponding autism-associated mutations that replace glutamic acid residue 176 with alanine (E176A) and methionine residue 259 with valine (M259V) into the C2B domain of mouse RIM3, we demonstrate that both mutations partly cancel the suppressive RIM3 effect on voltage-dependent inactivation of Ba(2+) currents through P/Q-type CaV2.1 recombinantly expressed in HEK293 cells. In recombinant N-type CaV2.2 VDCCs, the attenuation of the suppressive RIM3 effect on voltage-dependent inactivation is conserved for M259V but not E176A. Slowing of activation speed of P/Q-type CaV2.1 currents by RIM3 is abolished in E176A, while the physical interaction between RIM3 and β subunits is significantly attenuated in M259V. Moreover, increases by RIM3 in depolarization-induced Ca(2+) influx and acetylcholine release are significantly attenuated by E176A in rat pheochromocytoma PC12 cells. Thus, our data raise the interesting possibility that autism phenotypes are elicited by synaptic dysfunction via altered regulation of presynaptic VDCC function and neurotransmitter release.

  8. High-Efficiency Harmonically Terminated Diode and Transistor Rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    Roberg, M; Reveyrand, T; Ramos, I; Falkenstein, EA; Popovic, Z

    2012-12-01

    This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class-F-1 GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source-pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class-F-1 PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98-Omega resistor.

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

    DEFF Research Database (Denmark)

    Andreasen, Ditte; Friis, Ulla Glenert; Uhrenholt, Torben Rene

    2006-01-01

    , and blocking P-type currents (omega-agatoxin IVA 10 nmol/L) led to 20.2+/-3.0% inhibition, whereas 300 nmol/L of omega agatoxin IVA (blocking P/Q-type) inhibited 45.0+/-7.3%. In rat aortic smooth muscle cells (A7r5), blockade of L-type channels resulted in 28.5+/-6.1% inhibition, simultaneous blockade of L...... microscopy revealed expression of both channels in all of the smooth muscle cells. Whole-cell patch clamp on single preglomerular VSMCs from mice showed L-, P-, and Q-type currents. Blockade of the L-type currents by calciseptine (20 nmol/L) inhibited 35.6+/-3.9% of the voltage-dependent Ca2+ current......-type and P-type channels inhibited 58.0+/-11.8%, and simultaneous inhibition of L-, P-, and Q-type channels led to blockade (88.7+/-5.6%) of the Ca2+ current. We conclude that aortic and renal preglomerular smooth muscle cells express L-, P-, and Q-type voltage-dependent Ca2+ channels in the rat and mouse....

  10. Structural mapping of the voltage-dependent sodium channel. Distance between the tetrodotoxin and Centruroides suffusus suffusus II beta-scorpion toxin receptors.

    Science.gov (United States)

    Darbon, H; Angelides, K J

    1984-05-25

    A 7- dimethylaminocoumarin -4-acetate fluorescent derivative of toxin II from the venom of the scorpion Centruroides suffusus suffusus (Css II) has been prepared to study the structural, conformational, and cellular properties of the beta-neurotoxin receptor site on the voltage-dependent sodium channel. The derivative retains high affinity for its receptor site on the synaptosomal sodium channel with a KD of 7 nM and site capacity of 1.5 pmol/mg of synaptosomal protein. The fluorescent toxin is very environmentally sensitive and the fluorescence emission upon binding indicates that the Css II receptor is largely hydrophobic. Binding of tetrodotoxin or batrachotoxin does not alter the spectroscopic properties of bound Css II, whereas toxin V from Leiurus quinquestriatus effects a 10-nm blue shift to a more hydrophobic environment. This is the first direct indication of conformational coupling between these separate neurotoxin receptor sites. The distance between the tetrodotoxin and Css II scorpion toxin receptors on the sodium channel was measured by fluorescence resonance energy transfer. Efficiencies were measured by both donor quenching and acceptor-sensitized emission. The distance between these two neurotoxin sites is about 34 A. The implications of these receptor locations together with other known molecular distances are discussed in terms of a molecular structure of the voltage-dependent sodium channel.

  11. Functional coupling between large-conductance potassium channels and Cav3.2 voltage-dependent calcium channels participates in prostate cancer cell growth

    Directory of Open Access Journals (Sweden)

    Florian Gackière

    2013-07-01

    It is strongly suspected that potassium (K+ channels are involved in various aspects of prostate cancer development, such as cell growth. However, the molecular nature of those K+ channels implicated in prostate cancer cell proliferation and the mechanisms through which they control proliferation are still unknown. This study uses pharmacological, biophysical and molecular approaches to show that the main voltage-dependent K+ current in prostate cancer LNCaP cells is carried by large-conductance BK channels. Indeed, most of the voltage-dependent current was inhibited by inhibitors of BK channels (paxillin and iberiotoxin and by siRNA targeting BK channels. In addition, we reveal that BK channels constitute the main K+ channel family involved in setting the resting membrane potential in LNCaP cells at around −40 mV. This consequently promotes a constitutive calcium entry through T-type Cav3.2 calcium channels. We demonstrate, using single-channel recording, confocal imaging and co-immunoprecipitation approaches, that both channels form macromolecular complexes. Finally, using flow cytometry cell cycle measurements, cell survival assays and Ki67 immunofluorescent staining, we show that both BK and Cav3.2 channels participate in the proliferation of prostate cancer cells.

  12. Altered calcium homeostasis in motor neurons following AMPA receptor but not voltage-dependent calcium channels' activation in a genetic model of amyotrophic lateral sclerosis.

    Science.gov (United States)

    Guatteo, Ezia; Carunchio, Irene; Pieri, Massimo; Albo, Federica; Canu, Nadia; Mercuri, Nicola B; Zona, Cristina

    2007-10-01

    Amyotrophic lateral sclerosis (ALS) is a late-onset progressive neurodegenerative disease characterized by a substantial loss of motor neurons in the spinal cord, brain stem and motor cortex. By combining electrophysiological recordings with imaging techniques, clearance/buffering capacity of cultured spinal cord motor neurons after a calcium accumulation has been analyzed in response to AMPA receptors' (AMPARs') activation and to depolarizing stimuli in a genetic mouse model of ALS (G93A). Our studies demonstrate that the amplitude of the calcium signal in response to AMPARs' or voltage-dependent calcium channels' activation is not significantly different in controls and G93A motor neurons. On the contrary, in G93A motor neurons, the [Ca(2+)](i) recovery to basal level is significantly slower compared to control neurons following AMPARs but not voltage-dependent calcium channels' activation. This difference was not observed in G93A cultured cortical neurons. This observation is the first to indicate a specific alteration of the calcium clearance linked to AMPA receptors' activation in G93A motor neurons and the involvement of AMPA receptor regulatory proteins controlling both AMPA receptor functionality and the sequence of events connected to them.

  13. Structural Optimization of Non-Newtonian Rectifiers

    DEFF Research Database (Denmark)

    Jensen, Kristian Ejlebjærg; Okkels, Fridolin

    . In this context it is natural to look for other sources of non-linearity and one possibility is to introduce a non-Newtonian working fluid. Non-Newtonian properties are due to stretching of large particles/molecules in the fluid and this is commonly seen for biological samples in “lab-on-a-chip” systems....... The strength of non-Newtonian effects does not depend on the device size. Furthermore a non-Newtonian working fluid removes symmetry properties such that geometry influence is reintroduced, and indeed non-Newtonian effects have been used in experimentally realized microfluidic rectitifiers[1]. The rectifiers...... optimization, which is a kind of design optimization where nothing is assumed about the topology of the design. We will apply a high-level implementation of topology optimization using the density method in a commercial finite element package[2]. However, the modeling of non-Newtonian fluids remains a major...

  14. Bivariate phase-rectified signal averaging

    CERN Document Server

    Schumann, Aicko Y; Bauer, Axel; Schmidt, Georg

    2008-01-01

    Phase-Rectified Signal Averaging (PRSA) was shown to be a powerful tool for the study of quasi-periodic oscillations and nonlinear effects in non-stationary signals. Here we present a bivariate PRSA technique for the study of the inter-relationship between two simultaneous data recordings. Its performance is compared with traditional cross-correlation analysis, which, however, does not work well for non-stationary data and cannot distinguish the coupling directions in complex nonlinear situations. We show that bivariate PRSA allows the analysis of events in one signal at times where the other signal is in a certain phase or state; it is stable in the presence of noise and impassible to non-stationarities.

  15. Membrane potential bistability in nonexcitable cells as described by inward and outward voltage-gated ion channels.

    Science.gov (United States)

    Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

    2014-10-30

    The membrane potential of nonexcitable cells, defined as the electrical potential difference between the cell cytoplasm and the extracellular environment when the current is zero, is controlled by the individual electrical conductance of different ion channels. In particular, inward- and outward-rectifying voltage-gated channels are crucial for cell hyperpolarization/depolarization processes, being amenable to direct physical study. High (in absolute value) negative membrane potentials are characteristic of terminally differentiated cells, while low membrane potentials are found in relatively depolarized, more plastic cells (e.g., stem, embryonic, and cancer cells). We study theoretically the hyperpolarized and depolarized values of the membrane potential, as well as the possibility to obtain a bistability behavior, using simplified models for the ion channels that regulate this potential. The bistability regions, which are defined in the multidimensional state space determining the cell state, can be relevant for the understanding of the different model cell states and the transitions between them, which are triggered by changes in the external environment.

  16. Localization Factors and Inward Foreign Direct Investment in Greece

    Directory of Open Access Journals (Sweden)

    Nuno Carlos LEITÃO

    2010-06-01

    Full Text Available This study examines the foreign direct investment (FDI attractiveness for Greece as a host country in the period 1998-2007. The purpose of this paper is to analyze the impact of variables, such as market size, labour costs, trade openness, taxes, inflation and economic stability. The manuscript applies a panel data approach (Fixed Effects estimator and GMM system estimator. In contrast to previous studies, this paper used a dynamic panel data to solve the problems of serial correlation and endogeneity. The empirical results indicate that the market size, trade openness, and labour costs are significant factors to explain inward FDI to Greece. These results indicate that the FDI attracting will be influenced by market size. Our results also show that Greece has some problems of macroeconomic stability, which discourages the investors.

  17. Entoptic perceptions of spiral waves and rare inward spirals.

    Science.gov (United States)

    Pearce, Ida

    2015-06-01

    This report concerns Entoptic Rotating Spiral Waves as observed and documented by the author over a period of 46 years (1962-2008). The manifestations of these state-dependent, elusive rotating spiral entities were brief, emerging only during sleep-to-waking arousal epochs (in limbo). The images were seen only with closed lids in favorable ambient lighting-here, termed the umbral view. The clusters of rotating spiral entities emerge briefly to conscious view; their angular subtenses are estimated to be between 1° and 4°, and the rotations at ten-turns per second. Epochs of these activities commonly continued for about 20 s, with longevity of each visible entity up to 4 s. 90% of all observed entities were circular and outwardly levorotary; 5% were elliptical, appearing only as horizontal (prolate) entities. Overlapping units were rare, and were chiefly elliptical. Observations of twin spirals were also rare, seen in counter rotations, each twin inwardly rotating.

  18. Empirical Analysis: Business Cycles and Inward FDI in China

    Directory of Open Access Journals (Sweden)

    Qiyun Fang

    2007-01-01

    Full Text Available It is well-known that the current speeding-up of globalization has been, on one hand, spreading macro economic effects around the world, while, on the other, fueling firms’ activities of crossing national borders. Then, are there any links between these two influences? In this paper, we chose China as our subject, to try to clarify it. A set of models for Granger Causality test and VAR Impulse Responses were constructed and some econometric estimations and empirical analysis were made by employing the latest 20-year authorized annual statistic data. And the findings clearly indicated that firms’ (foreign activities (inward FDI do respond pro-cyclically to business cycle developments in a long term.

  19. Empirical Analysis II: Business Cycles and Inward FDI in China

    Directory of Open Access Journals (Sweden)

    Yahya Sharahili

    2008-01-01

    Full Text Available It is well-known that the current speeding-up of globalization has been, on one hand, spreading macro economic effects around the world, while, on the other, fueling firms’ activities of crossing national borders. Then, are there any links between these two influences? As we have concluded in previous research that inward FDI and business cycle development do pro-cyclically relate on Granger base, this paper will further discuss “how do they react to each other?” Again, we chose China as subject and employed the 1983~2004 authorized annual statistic data. By constructing an Endogenous Growth model, we, after processing Correlation Analysis and testing the coefficient significance of each variable, found out the original momentum of Chinese economic growth and explored whether there exist some long-term relationship through Johansen Co-integration Test.

  20. Octopamine increases the excitability of neurons in the snail feeding system by modulation of inward sodium current but not outward potassium currents

    Directory of Open Access Journals (Sweden)

    Szabó Henriette

    2005-12-01

    Full Text Available Abstract Background Although octopamine has long been known to have major roles as both transmitter and modulator in arthropods, it has only recently been shown to be functionally important in molluscs, playing a role as a neurotransmitter in the feeding network of the snail Lymnaea stagnalis. The synaptic potentials cannot explain all the effects of octopamine-containing neurons on the feeding network, and here we test the hypothesis that octopamine is also a neuromodulator. Results The excitability of the B1 and B4 motoneurons in the buccal ganglia to depolarising current clamp pulses is significantly (P IA current and a sustained IK delayed-rectifier current, but neither was modulated by octopamine in any of these three buccal neurons. The fast inward current was eliminated in sodium – free saline and so is likely to be carried by sodium ions. 10 μM octopamine enhanced this current by 33 and 45% in the B1 and B4 motoneurons respectively (P Conclusion We conclude that octopamine is also a neuromodulator in snails, changing the excitability of the buccal neurons. This is supported by the close relationship from the voltage clamp data, through the quantitative simulation, to the action potential threshold, changing the properties of neurons in a rhythmic network. The increase in inward sodium current provides an explanation for the polycyclic modulation of the feeding system by the octopamine-containing interneurons, making feeding easier to initiate and making the feeding bursts more intense.

  1. Analytic capacity, rectifiability, menger curvature and the Cauchy integral

    CERN Document Server

    Pajot, Hervé

    2002-01-01

    Based on a graduate course given by the author at Yale University this book deals with complex analysis (analytic capacity), geometric measure theory (rectifiable and uniformly rectifiable sets) and harmonic analysis (boundedness of singular integral operators on Ahlfors-regular sets). In particular, these notes contain a description of Peter Jones' geometric traveling salesman theorem, the proof of the equivalence between uniform rectifiability and boundedness of the Cauchy operator on Ahlfors-regular sets, the complete proofs of the Denjoy conjecture and the Vitushkin conjecture (for the latter, only the Ahlfors-regular case) and a discussion of X. Tolsa's solution of the Painlevé problem.

  2. Rectified optical force on dark-state atoms

    Science.gov (United States)

    Korsunsky, E. A.; Kosachiov, D. V.

    1997-12-01

    We show that an imperfection of velocity-selective coherent population trapping (VSCPT) in three-level atoms excited by standing light waves causes a rectified force on cooled atoms. The rectified force as well as the cooling force are calculated both analytically and numerically for 0953-4075/30/24/010/img5 and cascade three-level systems. Combination of these forces with the VSCPT mechanism can lead to localization of very cold atoms in potential wells created by the rectified force. This effect should be taken into account in experiments with VSCPT in standing waves, and can be used for realizing superlattices of cold atoms, in particular, cold Rydberg atoms.

  3. Formal Verification of Full-Wave Rectifier: A Case Study

    CERN Document Server

    Lata, Kusum

    2009-01-01

    We present a case study of formal verification of full-wave rectifier for analog and mixed signal designs. We have used the Checkmate tool from CMU [1], which is a public domain formal verification tool for hybrid systems. Due to the restriction imposed by Checkmate it necessitates to make the changes in the Checkmate implementation to implement the complex and non-linear system. Full-wave rectifier has been implemented by using the Checkmate custom blocks and the Simulink blocks from MATLAB from Math works. After establishing the required changes in the Checkmate implementation we are able to efficiently verify the safety properties of the full-wave rectifier.

  4. Physics-Based Compact Model for CIGS and CdTe Solar Cells: From Voltage-Dependent Carrier Collection to Light-Enhanced Reverse Breakdown: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xingshu; Alam, Muhammad Ashraful; Raguse, John; Garris, Rebekah; Deline, Chris; Silverman, Timothy

    2015-10-15

    In this paper, we develop a physics-based compact model for copper indium gallium diselenide (CIGS) and cadmium telluride (CdTe) heterojunction solar cells that attributes the failure of superposition to voltage-dependent carrier collection in the absorber layer, and interprets light-enhanced reverse breakdown as a consequence of tunneling-assisted Poole-Frenkel conduction. The temperature dependence of the model is validated against both simulation and experimental data for the entire range of bias conditions. The model can be used to characterize device parameters, optimize new designs, and most importantly, predict performance and reliability of solar panels including the effects of self-heating and reverse breakdown due to partial-shading degradation.

  5. Voltage-Dependent Anion Channel 2 of Arabidopsis thaliana (AtVDAC2 Is Involved in ABA-Mediated Early Seedling Development

    Directory of Open Access Journals (Sweden)

    Xufeng Li

    2009-05-01

    Full Text Available The voltage-dependent anion channel (VDAC is the major transport protein in the outer membrane of mitochondria and plays crucial roles in energy metabolism, apoptosis, and metabolites transport. In plants, the expression of VDACs can be affected by different stresses, including drought, salinity and pathogen defense. In this study, we investigated the expression pattern of AtVDAC2 in A. thaliana and found ABA suppressed the accumulation of AtVDAC2 transcripts. Further, phenotype analysis of this VDAC deregulated-expression transgenic Arabidopsis plants indicated that AtVDAC2 anti-sense line showed an ABA-insensitivity phenotype during the early seedling development under ABA treatment. The results suggested that AtVDAC2 might be involved in ABA signaling in A. thaliana.

  6. Reduced KCNQ4-encoded voltage-dependent potassium channel activity underlies impaired ß-adrenoceptor-mediated relaxation of renal arteries in hypertension

    DEFF Research Database (Denmark)

    Chadha, Preet S; Zunke, Friederike; Zhu, Hai-Lei;

    2012-01-01

    KCNQ4-encoded voltage-dependent potassium (Kv7.4) channels are important regulators of vascular tone that are severely compromised in models of hypertension. However, there is no information as to the role of these channels in responses to endogenous vasodilators. We used a molecular knockdown...... strategy, as well as pharmacological tools, to examine the hypothesis that Kv7.4 channels contribute to ß-adrenoceptor-mediated vasodilation in the renal vasculature and underlie the vascular deficit in spontaneously hypertensive rats. Quantitative PCR and immunohistochemistry confirmed gene and protein...... spontaneously hypertensive rats, which was associated with ˜60% decrease in Kv7.4 abundance. This study provides the first evidence that Kv7 channels contribute to ß-adrenoceptor-mediated vasodilation in the renal vasculature and that abrogation of Kv7.4 channels is strongly implicated in the impaired ß...

  7. Involvement of presynaptic voltage-dependent Kv3 channel in endothelin-1-induced inhibition of noradrenaline release from rat gastric sympathetic nerves.

    Science.gov (United States)

    Nakamura, Kumiko; Shimizu, Takahiro; Tanaka, Kenjiro; Taniuchi, Keisuke; Yokotani, Kunihiko

    2012-11-05

    We previously reported that two types of K(+) channels, the BK type Ca(2+)-activated K(+) channel coupled with phospholipase C (PLC) and the voltage-dependent K(+) channel (Kv channel), are, respectively, involved in the prostanoid TP receptor- and muscarinic M(2) receptor-mediated inhibition of noradrenaline (NA) release from rat gastric sympathetic nerves. In the present study, therefore, we examined whether these K(+) channels are involved in endothelin-1-induced inhibition of NA release, using an isolated, vascularly perfused rat stomach. The gastric sympathetic postganglionic nerves around the left gastric artery were electrically stimulated twice at 2.5 Hz for 1 min, and endothelin-1 was added during the second stimulation. Endothelin-1 (1, 2 and 10 nM) dose-dependently inhibited gastric NA release. Endothelin-1 (2 nM)-induced inhibition of NA release was neither attenuated by PLC inhibitors [U-73122 (3 μM) and ET-18-OCH(3) (3 μM)] nor by Ca(2+)-activated K(+) channel blockers [charybdotoxin (0.1 μM) (a blocker of BK type K(+) channel) and apamin (0.3 μM) (a blocker of SK type K(+) channel)]. The endothelin-1-induced inhibitory response was also not attenuated by α-dendrotoxin (0.1 μM) (a selective inhibitor of Kv1 channel), but abolished by 4-aminopyridine (20 μM) (a selectively inhibitory dose for Kv3 channel). These results suggest the involvement of a voltage-dependent Kv3 channel in the endothelin-1-induced inhibition of NA release from the gastric sympathetic nerves in rats.

  8. Heparin/heparan sulfates bind to and modulate neuronal L-type (Cav1.2) voltage-dependent Ca(2+) channels.

    Science.gov (United States)

    Garau, Gianpiero; Magotti, Paola; Heine, Martin; Korotchenko, Svetlana; Lievens, Patricia Marie-Jeanne; Berezin, Vladimir; Dityatev, Alexander

    2015-12-01

    Our previous studies revealed that L-type voltage-dependent Ca(2+) channels (Cav1.2 L-VDCCs) are modulated by the neural extracellular matrix backbone, polyanionic glycan hyaluronic acid. Here we used isothermal titration calorimetry and screened a set of peptides derived from the extracellular domains of Cav1.2α1 to identify putative binding sites between the channel and hyaluronic acid or another class of polyanionic glycans, such as heparin/heparan sulfates. None of the tested peptides showed detectable interaction with hyaluronic acid, but two peptides derived from the first pore-forming domain of Cav1.2α1 subunit bound to heparin. At 25 °C the binding of the peptide P7 (MGKMHKTCYN) was at ~50 μM, and that of the peptide P8 (GHGRQCQNGTVCKPGWDGPKHG) was at ~21 μM. The Cav1.2α1 first pore forming segment that contained both peptides maintained a high affinity for heparin (~23 μM), integrating their enthalpic and entropic binding contributions. Interaction between heparin and recombinant as well as native full-length neuronal Cav1.2α1 channels was confirmed using the heparin-agarose pull down assay. Whole cell patch clamp recordings in HEK293 cells transfected with neuronal Cav1.2 channels revealed that enzymatic digestion of highly sulfated heparan sulfates with heparinase 1 affects neither voltage-dependence of channel activation nor the level of steady state inactivation, but did speed up channel inactivation. Treatment of hippocampal cultures with heparinase 1 reduced the firing rate and led to appearance of long-lasting bursts in the same manner as treatment with the inhibitor of L-VDCC diltiazem. Thus, heparan sulfate proteoglycans may bind to and regulate L-VDCC inactivation and network activity.

  9. Cyanocobalamin, vitamin B12, depresses glutamate release through inhibition of voltage-dependent Ca2+ influx in rat cerebrocortical nerve terminals (synaptosomes).

    Science.gov (United States)

    Hung, Kun-Long; Wang, Chia-Chuan; Huang, Chia-Yu; Wang, Su-Jane

    2009-01-14

    The effect of cyanocobalamin, vitamin B12, on glutamate release in isolated nerve terminals (synaptosomes) prepared from rat prefrontal cortex was examined. Cyanocobalamin inhibited the release of glutamate evoked by 4-aminopyridine in a concentration-dependent manner. The inhibitory action of cyanocobalamin was blocked by the vesicular transporter inhibitor bafilomycin A1, not by the glutamate transporter inhibitor L-transpyrrolidine-2,4-dicarboxylic acid or the nontransportable glutamate inhibitor DL-threo-beta-benzyloxyaspartate, indicating that this release inhibition results from a reduction of vesicular exocytosis and not from an inhibition of Ca(2+)-independent efflux via glutamate transporter. Examination of the effect of cyanocobalamin on cytosolic free Ca(2+) concentration revealed that the inhibition of glutamate release could be attributed to a reduction in voltage-dependent Ca(2+) influx. Consistent with this, the N- and P/Q-type Ca(2+) channel blocker omega-conotoxin MVIIC, largely attenuated the inhibitory effect of cyanocobalamin on 4-aminopyridine-evoked glutamate release, but the Ca(2+) release inhibitor dantrolene had no effect. Cyanocobalamin did not alter the resting synaptosomal membrane potential or 4-aminopyridine-mediated depolarization; thus, the inhibition of 4-aminopyridine-evoked Ca(2+) influx and glutamate release produced by cyanocobalamin was not due to its decreasing synaptosomal excitability. In addition, cyanocobalamin-mediated inhibition of 4-aminopyridine-evoked Ca(2+) influx and glutamate release was significantly attenuated by protein kinase C inhibitors GF109203X and Ro318220. Furthermore, 4-aminopyridine-induced phosphorylation of protein kinase C was significantly reduced by cyanocobalamin. These results suggest that cyanocobalamin effects a decrease in protein kinase C activation, which subsequently reduces the Ca(2+) entry through voltage-dependent N- and P/Q-type Ca(2+) channels to cause a decrease in evoked glutamate

  10. "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.

  11. The agonist-specific voltage dependence of M2 muscarinic receptors modulates the deactivation of the acetylcholine-gated K(+) current (I KACh).

    Science.gov (United States)

    Moreno-Galindo, Eloy G; Alamilla, Javier; Sanchez-Chapula, José A; Tristani-Firouzi, Martin; Navarro-Polanco, Ricardo A

    2016-07-01

    Recently, it has been shown that G protein-coupled receptors (GPCRs) display intrinsic voltage sensitivity. We reported that the voltage sensitivity of M2 muscarinic receptor (M2R) is also ligand specific. Here, we provide additional evidence to understand the mechanism underlying the ligand-specific voltage sensitivity of the M2R. Using ACh, pilocarpine (Pilo), and bethanechol (Beth), we evaluated the agonist-specific effects of voltage by measuring the ACh-activated K(+) current (I KACh) in feline and rabbit atrial myocytes and in HEK-293 cells expressing M2R-Kir3.1/Kir3.4. The activation of I KACh by the muscarinic agonist Beth was voltage insensitive, suggesting that the voltage-induced conformational changes in M2R do not modify its affinity for this agonist. Moreover, deactivation of the Beth-evoked I KACh was voltage insensitive. By contrast, deactivation of the ACh-induced I KACh was significantly slower at -100 mV than at +50 mV, while an opposite effect was observed when I KACh was activated by Pilo. These findings are consistent with the voltage affinity pattern observed for these three agonists. Our findings suggest that independent of how voltage disturbs the receptor binding site, the voltage dependence of the signaling pathway is ultimately determined by the agonist. These observations emphasize the pharmacological potential to regulate the M2R-parasympathetic associated cardiac function and also other cellular signaling pathways by exploiting the voltage-dependent properties of GPCRs.

  12. Measuring the inward FDI potential of South African regions

    Directory of Open Access Journals (Sweden)

    W. Krugell

    2008-12-01

    Full Text Available Purpose: The purpose of this paper is to construct an index that captures the factors expected to affect a local economy's attractiveness to foreign investors. Problem statement: Following South Africa's reintegration into the world economy in 1994, foreign direct investment has been seen as a potential driver of growth and development. Concerns about the low investment rate in South Africa raise the possibility of augmenting domestic with foreign investment expenditure. The potential of technology spillovers and skills transfer from foreign direct investment have also been emphasised. As a result, Trade and Investment South Africa is involved in identifying, packaging and promoting investment opportunities. However, investments tend to be place-specific and this has lead to the decentralisation of foreign direct investment promotion. Currently the nine provincial development agencies are competing to attract investors and the larger local governments are also getting involved in the fray. This paper argues that some places have better potential to attract foreign investment than others. A first step to use scarce investment promotion resources more efficiently would be to measure the inward FDI potential of South African regions. Approach: This paper uses principal components analysis to construct an index that captures the factors expected to affect a local economy's attractiveness to foreign investors. This approach draws on UNCTAD's Inward FDI Potential Index and applies it to 354 magisterial districts in South Africa for the periods 1996, 2001 and 2006. The index creates a summary measure of FDI potential.Findings: The results show that different places present differential potential in urbanization and localization economies and market size. The high-potential locations are typically found in or around the major agglomerations, but there are a few smaller places on the periphery that offer FDI potential. Contribution: The index should aid

  13. Graphene Triangular Ballistic Rectifier: Fabrication and Characterisation

    Science.gov (United States)

    Auton, Gregory; Kumar, Roshan Krishna; Hill, Ernie; Song, Aimin

    2016-09-01

    It has been shown that graphene can demonstrate ballistic transport at room temperature. This opens up a range of practical applications that do not require graphene to have a band gap, which is one of the most significant challenges for its use in the electronics industry. Here, the very latest high mobility graphene (>100,000 cm2 V-1 s-1) fabrication techniques will be demonstrated so that one such device, called the triangular ballistic rectifier (TBR), can be characterised. The TBR is a four-terminal device with a triangular anti-dot at their intersection; two sides of the triangle are positioned and angled such that ballistic carriers from the two input electrodes are redirected like billiard balls to one of the two output contacts irrespective of the instantaneous polarity of the input. A responsivity of 2400 mV mW-1 is demonstrated at room temperature from a low-frequency input signal. The ballistic nature of the device is justified and explained in more detail with low-temperature measurements.

  14. Maximal rectification ratios for bi-segment thermal rectifiers

    CERN Document Server

    Shih, Tien-Mo; Guo, Ziquan; Liu, Guangcao; Merlitz, Holger; Pagni, Patrick J; Chen, Zhong

    2014-01-01

    We study bi-segment thermal rectifiers whose forward heat fluxes are greater than reverse counterparts. Presently, a shortcoming of thermal rectifiers is that the rectification ratio, namely the forward flux divided by the reverse flux, remains too small for practical applications. In this study, we have managed to discover and theoretically derive the ultimate limit of such ratios, which are validated by numerical simulations, experiments, and micro-scale Hamiltonian-oscillator analyses. For rectifiers whose thermal conductivities are linear with the temperature, this limit is simply a numerical value of 3. For those whose conductivities are nonlinear with temperatures, the maxima equal $\\kappa_{max}/\\kappa_{min}$, where the two extremes denote values of the solid segment materials that can be possibly found or fabricated within a reasonable temperature range on earth. Recommendations for manufacturing high-ratio rectifiers are also given with examples.

  15. Maximal rectification ratios for idealized bi-segment thermal rectifiers.

    Science.gov (United States)

    Shih, Tien-Mo; Gao, Zhaojing; Guo, Ziquan; Merlitz, Holger; Pagni, Patrick J; Chen, Zhong

    2015-08-04

    Thermal rectifiers whose forward heat fluxes are greater than reverse counterparts have been extensively studied. Here we have discovered, idealized, and derived the ultimate limit of such rectification ratios, which are partially validated by numerical simulations, experiments, and micro-scale Hamiltonian-oscillator analyses. For rectifiers whose thermal conductivities (κ) are linear with the temperature, this limit is simply a numerical value of 3. For those whose conductivities are nonlinear with temperatures, the maxima equal κmax/κmin, where two extremes denote values of the solid segment materials that can be possibly found or fabricated within a reasonable temperature range. Recommendations for manufacturing high-ratio rectifiers are also given with examples. Under idealized assumptions, these proposed rectification limits cannot be defied by any bi-segment thermal rectifiers.

  16. 2009 NOAA Ortho-rectified Mosaic of Brunswick Georgia

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2011 NOAA Ortho-rectified Mosaic of Casco Bay, Maine

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2011 NOAA Ortho-rectified Mosaic of Yabucoa, Puerto Rico

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2011 NOAA Ortho-rectified Mosaic of Searsport Maine

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2009 NOAA Ortho-rectified Mosaic of Brunswick Georgia

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2011 NOAA Ortho-rectified Mosaic of Galveston, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2011 NOAA Ortho-rectified Mosaic of Baltimore, Maryland

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. Thin-film semiconductor rectifier has improved properties

    Science.gov (United States)

    1966-01-01

    Cadmium selenide-zinc selenide film is used as a thin film semiconductor rectifier. The film is vapor-deposited in a controlled concentration gradient into a glass substrate to form the required junctions between vapor-deposited gold electrodes.

  4. 2011 NOAA Ortho-rectified Mosaic of Mayaquez, Puerto Rico

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2012 NOAA Ortho-rectified Color Mosaic of Richmond, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2012 NOAA Ortho-rectified Color Mosaic of Bangor, Washington

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. Driving force-dependent block by internal Ba(2+) on the Kir2.1 channel: Mechanistic insight into inward rectification.

    Science.gov (United States)

    Hsieh, Chi-Pan; Kuo, Chung-Chin; Huang, Chiung-Wei

    2015-07-01

    The Kir2.1 channel is characterized by strong inward rectification; however, the mechanism of the steep voltage dependence near the equilibrium potential remains to be investigated. Here, we studied the internal Ba(2+) block of the Kir2.1 channel expressed in Xenopus oocytes. We showed that the driving force and thus the K(+) ion flux significantly influenced the apparent affinity of the block by internal Ba(2+). Kinetic analysis revealed that the binding rate shifted with the driving force and changed steeply near the equilibrium point, either in the presence or absence of the transmembrane electrical field. The unbinding rate was determined by the intrinsic affinity of the site. Mutagenesis studies revealed that the high-affinity binding site for Ba(2+) was located near T141 at the internal entrance of the selectivity filter. The steep change of the blocking affinity near the equilibrium potential may result from the flux-coupling effect in the single-file, multi-ion cytoplasmic pore.

  8. 19 CFR 4.7a - Inward manifest; information required; alternative forms.

    Science.gov (United States)

    2010-04-01

    ... (Customs Form 1302 or a Customs-approved electronic equivalent) must list all the inward foreign cargo on... Declaration, either on Customs Form 1302, or on a separate sheet or Customs-approved electronic equivalent... 19 Customs Duties 1 2010-04-01 2010-04-01 false Inward manifest; information required;...

  9. Kardar-Parisi-Zhang Interfaces with Inward Growth

    Science.gov (United States)

    Fukai, Yohsuke T.; Takeuchi, Kazumasa A.

    2017-07-01

    We study the (1 +1 )-dimensional Kardar-Parisi-Zhang (KPZ) interfaces growing inward from ring-shaped initial conditions, experimentally and numerically, using growth of a turbulent state in liquid-crystal electroconvection and an off-lattice Eden model, respectively. To realize the ring initial condition experimentally, we introduce a holography-based technique that allows us to design the initial condition arbitrarily. Then, we find that fluctuation properties of ingrowing circular interfaces are distinct from those for the curved or circular KPZ subclass and, instead, are characterized by the flat subclass. More precisely, we find an asymptotic approach to the Tracy-Widom distribution for the Gaussian orthogonal ensemble and the Airy1 spatial correlation, as long as time is much shorter than the characteristic time determined by the initial curvature. Near this characteristic time, deviation from the flat KPZ subclass is found, which can be explained in terms of the correlation length and the circumference. Our results indicate that the sign of the initial curvature has a crucial role in determining the universal distribution and correlation functions of the KPZ class.

  10. Wireless power transmission for biomedical implants: The role of near-zero threshold CMOS rectifiers.

    Science.gov (United States)

    Mohammadi, Ali; Redoute, Jean-Michel; Yuce, Mehmet R

    2015-01-01

    Biomedical implants require an electronic power conditioning circuitry to provide a stable electrical power supply. The efficiency of wireless power transmission is strongly dependent on the power conditioning circuitry specifically the rectifier. A cross-connected CMOS bridge rectifier is implemented to demonstrate the impact of thresholds of rectifiers on wireless power transfer. The performance of the proposed rectifier is experimentally compared with a conventional Schottky diode full wave rectifier over 9 cm distance of air and tissue medium between the transmitter and receiver. The output voltage generated by the CMOS rectifier across a 1 KΩ resistive load is around twice as much as the Schottky rectifier.

  11. Analysis of Single Phase PWM Rectifier for Different Applications

    Science.gov (United States)

    Mitra, Arkendu; Chowdhuri, Sumana

    2017-04-01

    This research work investigates the various applications of a PWM rectifier based on its input power factor. Most of the cases, the papers describe the operation of the rectifier used for unity power factor (UPF) operation. Beside this mode of operation, this paper compiles the application of the rectifier as STATCOM also, where the rectifier deals only with reactive power exchange. In this work, the controller is implemented by inserting a loop for reference input of phase angle which will be compared with the actual one, so that user can operate the rectifier at any power factor. Some basic formulae are derived for the input current, active power and reactive power based on which the control circuit is to be designed. Here two Proportional-Integral (PI) controllers are used. A brief description of tuning these two PI controllers is incorporated in this paper. Also some calculations are given to determine the harmonic factors of the input line current from which it is found that the rectifier when operated in each mode operation, the order of the harmonics are very low.

  12. Scalar Controlled Boost PWM Rectifier for Micro Wind Energy Systems

    Directory of Open Access Journals (Sweden)

    J. Chelladurai

    2015-05-01

    Full Text Available Uses of Permanent Magnet Synchronous Generators (PMSG are increasing in variable speed micro-Wind Energy Conversion Systems (WECS. In stand-alone or grid-connected Micro-WECS, extraction of maximum power is vital. To extract maximum power output and to obtain a constant DC bus voltage from variable magnitude and variable frequency voltage output of PMSG and generally a two stage scheme namely i conventional diode bridge rectifier and ii DC-DC Boost/Buck/Buck-Boost converters are used. In this study, a single stage Scalar Controlled PWM (SCPWM Boost Rectifier is proposed in order to minimize the current harmonics and to improve the power factor on source side. The modeling and simulation of PMSG based wind generator and SCPWM Boost rectifier was developed in MATLAB. The harmonic content in the input current waveform of the proposed SCPWM rectifier is compared with the conventional three-phase bridge rectifier. The Simulation results show the effectiveness of the PWM Boost rectifier in terms of effective utilization of source, improved efficiency and harmonic mitigation for PMSG based Wind Generator. Simulation results demonstrate the effectiveness of the proposed system in reducing the current and voltage THD on source side.

  13. Analysis of Single Phase PWM Rectifier for Different Applications

    Science.gov (United States)

    Mitra, Arkendu; Chowdhuri, Sumana

    2016-06-01

    This research work investigates the various applications of a PWM rectifier based on its input power factor. Most of the cases, the papers describe the operation of the rectifier used for unity power factor (UPF) operation. Beside this mode of operation, this paper compiles the application of the rectifier as STATCOM also, where the rectifier deals only with reactive power exchange. In this work, the controller is implemented by inserting a loop for reference input of phase angle which will be compared with the actual one, so that user can operate the rectifier at any power factor. Some basic formulae are derived for the input current, active power and reactive power based on which the control circuit is to be designed. Here two Proportional-Integral (PI) controllers are used. A brief description of tuning these two PI controllers is incorporated in this paper. Also some calculations are given to determine the harmonic factors of the input line current from which it is found that the rectifier when operated in each mode operation, the order of the harmonics are very low.

  14. Over-Expression of Dopamine D2 Receptor and Inwardly Rectifying Potassium Channel Genes in Drug-Naive Schizophrenic Peripheral Blood Lymphocytes as Potential Diagnostic Markers

    OpenAIRE

    Ágnes Zvara; György Szekeres; Zoltán Janka; Kelemen, János Z.; Csongor Cimmer; Miklós Sántha; Puskás, László G.

    2005-01-01

    Schizophrenia is one of the most common neuropsychiatric disorders affecting nearly 1% of the human population. Current diagnosis of schizophrenia is based on complex clinical symptoms. The use of easily detectable peripheral molecular markers could substantially help the diagnosis of psychiatric disorders. Recent studies showed that peripheral blood lymphocytes (PBL) express subtypes of D1 and D2 subclasses of dopamine receptors. Recently, dopamine receptor D3 (DRD3) was found to be over-exp...

  15. Characterization and variation of a human inwardly-rectifying-K-channel gene (KCNJ6): a putative ATP-sensitive K-channel subunit.

    Science.gov (United States)

    Sakura, H; Bond, C; Warren-Perry, M; Horsley, S; Kearney, L; Tucker, S; Adelman, J; Turner, R; Ashcroft, F M

    1995-06-26

    The ATP-sensitive K-channel plays a central role in insulin release from pancreatic beta-cells. We report here the cloning of the gene (KCNJ6) encoding a putative subunit of a human ATP-sensitive K-channel expressed in brain and beta-cells, and characterisation of its exon-intron structure. Screening of a somatic cell mapping panel and fluorescent in situ hybridization place the gene on chromosome 21 (21q22.1-22.2). Analysis of single-stranded conformational polymorphisms revealed the presence of two silent polymorphisms (Pro-149: CCG-CCA and Asp-328: GAC-GAT) with similar frequencies in normal and non-insulin-dependent diabetic patients.

  16. Genetic variation in the inwardly rectifying K channel subunits KCNJ3 (GIRK1) and KCNJ5 (GIRK4) in patients with sinus node dysfunction

    DEFF Research Database (Denmark)

    Holmegard, Haya N; Theilade, Juliane; Benn, Marianne

    2010-01-01

    BACKGROUND: Sinus node dysfunction (SND) is a heterogeneous disorder of unknown etiology characterized by a variety of supraventricular arrhythmias with symptoms of syncope, palpitations, and dizziness. The mechanism underlying the abnormal rhythm is incompletely understood. OBJECTIVE: Because...

  17. Assignment of human G-protein-coupled inward rectifier K{sup +} channel homolog GIRK3 gene to chromosome 1q21-q23

    Energy Technology Data Exchange (ETDEWEB)

    Lesage, F.; Fink, M.; Barhanin, J. [CNRS, Valbonne (France)] [and others

    1995-10-10

    More than 20 genes that encode voltage-gated and Ca{sup 2+}-dependent K{sup +} channels have been identified. These channels are involved in a wide variety of biological functions such as neuronal and muscle excitability, hormone secretion, and osmotic regulation. Two voltage-gated K{sup +} channel genes, KCNA1 and HERG, have been related to neurological and cardiac inherited disorders in humans. Missense mutations in the KCNA1 gene lead to episodic ataxia/myokimia syndrome. Missense, splice donor, and deletion mutations in the HERG gene have been shown to cause long QT syndrome. These two channels belong to the superfamily of cationic channels, which share the characteristic structural features of six transmembrane domains and one segment (called 115) involved in pore formation. 17 refs., 1 fig.

  18. Inhibitory Effects of Glycyrrhetinic Acid on the Delayed Rectifier Potassium Current in Guinea Pig Ventricular Myocytes and HERG Channel

    Directory of Open Access Journals (Sweden)

    Delin Wu

    2013-01-01

    Full Text Available Background. Licorice has long been used to treat many ailments including cardiovascular disorders in China. Recent studies have shown that the cardiac actions of licorice can be attributed to its active component, glycyrrhetinic acid (GA. However, the mechanism of action remains poorly understood. Aim. The effects of GA on the delayed rectifier potassium current (IK, the rapidly activating (IKr and slowly activating (IKs components of IK, and the HERG K+ channel expressed in HEK-293 cells were investigated. Materials and Methods. Single ventricular myocytes were isolated from guinea pig myocardium using enzymolysis. The wild type HERG gene was stably expressed in HEK293 cells. Whole-cell patch clamping was used to record IK (IKr, IKs and the HERG K+ current. Results. GA (1, 5, and 10 μM inhibited IK (IKr, IKs and the HERG K+ current in a concentration-dependent manner. Conclusion. GA significantly inhibited the potassium currents in a dose- and voltage-dependent manner, suggesting that it exerts its antiarrhythmic action through the prolongation of APD and ERP owing to the inhibition of IK (IKr, IKs and HERG K+ channel.

  19. Diverse expression of delayed rectifier K+ channel subtype transcripts in several types of smooth muscles of the rat.

    Science.gov (United States)

    Ohya, S; Tanaka, M; Watanabe, M; Maizumi, Y

    2000-06-01

    Diverse expression of voltage dependent K+ (Kv) channels was examined in smooth muscles (SMs); carotid artery (CA), mesenteric artery (MA), urinary bladder (UB), and vas deferens (VD) of the rat, using RT-PCR based analyses. Among eight Kv channel subtypes examined (Kv 1.1, Kv 1.2, Kv 1.5, Kv 1.6, Kv 2.1, Kv 2.2, Kv 3.1, and Kv 3.2), expression of three delayed rectifier Kv (KD) channel (Kv 1.2, Kv 1.5, and Kv 2.1) transcripts was observed in these SMs. To determine precisely the expression levels of the transcripts encoding K(D) subtypes, those of three K(D) subtypes (Kv 1.2, Kv 1.5, and Kv 2.1) were determined by competitive PCR. In vascular SM tissues, CA and MA, Kv 1.2 and Kv 1.5 transcripts were expressed at relatively high levels, whereas in visceral SM tissues, UB and VD, Kv 2.1 transcripts were expressed at the relatively high levels. These results suggest that the diverse expression of K(D) subtypes is, at least in part, responsible for differences in electrical excitability and also for the variation of the electrophysiological and pharmacological phenotypes as tonic and phasic SMs.

  20. A CACNA1C variant associated with reduced voltage-dependent inactivation, increased CaV1.2 channel window current, and arrhythmogenesis.

    Directory of Open Access Journals (Sweden)

    Jessica A Hennessey

    Full Text Available Mutations in CACNA1C that increase current through the CaV1.2 L-type Ca2+ channel underlie rare forms of long QT syndrome (LQTS, and Timothy syndrome (TS. We identified a variant in CACNA1C in a male child of Filipino descent with arrhythmias and extracardiac features by candidate gene sequencing and performed functional expression studies to electrophysiologically characterize the effects of the variant on CaV1.2 channels. As a baby, the subject developed seizures and displayed developmental delays at 30 months of age. At age 5 years, he displayed a QTc of 520 ms and experienced recurrent VT. Physical exam at 17 years of age was notable for microcephaly, short stature, lower extremity weakness and atrophy with hyperreflexia, spastic diplegia, multiple dental caries and episodes of rhabdomyolysis. Candidate gene sequencing identified a G>C transversion at position 5731 of CACNA1C (rs374528680 predicting a glycine>arginine substitution at residue 1911 (p.G1911R of CaV1.2. The allele frequency of this variant is 0.01 in Malays, but absent in 984 Caucasian alleles and in the 1000 genomes project. In electrophysiological analyses, the variant decreased voltage-dependent inactivation, thus causing a gain of function of CaV1.2. We also observed a negative shift of V1/2 of activation and positive shift of V1/2 of channel inactivation, resulting in an increase of the window current. Together, these suggest a gain-of-function effect on CaV1.2 and suggest increased susceptibility for arrhythmias in certain clinical settings. The p.G1911R variant was also identified in a case of sudden unexplained infant death (SUID, for which an increasing number of clinical observations have demonstrated can be associated with arrhythmogenic mutations in cardiac ion channels. In summary, the combined effects of the CACNA1C variant to diminish voltage-dependent inactivation of CaV1.2 and increase window current expand our appreciation of mechanisms by which a gain of

  1. Involvement of inositol 1,4,5-trisphosphate formation in the voltage-dependent regulation of the Ca(2+) concentration in porcine coronary arterial smooth muscle cells.

    Science.gov (United States)

    Yamamura, Hisao; Ohya, Susumu; Muraki, Katsuhiko; Imaizumi, Yuji

    2012-08-01

    The involvement of inositol 1,4,5-trisphosphate (IP(3)) formation in the voltage-dependent regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) was examined in smooth muscle cells of the porcine coronary artery. Slow ramp depolarization from -90 to 0 mV induced progressive [Ca(2+)](i) increase. The slope was reduced or increased in the presence of Cd(2+) or (±)-1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-[trifluoromethyl]-phenyl)pyridine-3-carboxlic acid methyl ester (Bay K 8644), respectively. The decrease in [Ca(2+)](i) via the membrane hyperpolarization induced by K(+) channel openers (levcromakalim and Evans blue) under current clamp was identical to that under voltage clamp. The step hyperpolarization from -40 to -80 mV reduced [Ca(2+)](i) uniformly over the whole-cell area with a time constant of ∼10 s. The [Ca(2+)](i) at either potential was unaffected by heparin, an inhibitor of IP(3) receptors. Alternatively, [Ca(2+)](i) rapidly increased in the peripheral regions by depolarization from -80 to 0 mV and stayed at that level (∼400 nM) during a 60-s pulse. When the pipette solution contained IP(3) pathway blockers [heparin, 2-aminoethoxydiphenylborate, xestospongin C, or 1-[6-[((17β)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione (U73122)], the peak [Ca(2+)](i) was unchanged, but the sustained [Ca(2+)](i) was gradually reduced by ∼250 nM within 30 s. In the presence of Cd(2+), a long depolarization period slightly increased the [Ca(2+)](i), which was lower than that in the presence of heparin alone. In coronary arterial myocytes, the sustained increase in the [Ca(2+)](i) during depolarization was partly caused by the Ca(2+) release mediated by the enhanced formation of IP(3). The initial [Ca(2+)](i) elevation triggered by the Ca(2+) influx though voltage-dependent Ca(2+) channels may be predominantly responsible for the activation of phospholipase C for IP(3) formation.

  2. A metamaterial electromagnetic energy rectifying surface with high harvesting efficiency

    Science.gov (United States)

    Duan, Xin; Chen, Xing; Zhou, Lin

    2016-12-01

    A novel metamaterial rectifying surface (MRS) for electromagnetic energy capture and rectification with high harvesting efficiency is presented. It is fabricated on a three-layer printed circuit board, which comprises an array of periodic metamaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes. Perfect impedance matching is engineered at two interfaces, i.e. one between free space and the surface, and the other between the metamaterial particles and the rectifiers, which are connected through optimally positioned vias. Therefore, the incident electromagnetic power is captured with almost no reflection by the metamaterial particles, then channeled maximally to the rectifiers, and finally converted to direct current efficiently. Moreover, the rectifiers are behind the metal ground, avoiding the disturbance of high power incident electromagnetic waves. Such a MRS working at 2.45 GHz is designed, manufactured and measured, achieving a harvesting efficiency up to 66.9% under an incident power density of 5 mW/cm2, compared with a simulated efficiency of 72.9%. This high harvesting efficiency makes the proposed MRS an effective receiving device in practical microwave power transmission applications.

  3. Forgetting of long-term memory requires activation of NMDA receptors, L-type voltage-dependent Ca2+ channels, and calcineurin

    Science.gov (United States)

    Sachser, Ricardo Marcelo; Santana, Fabiana; Crestani, Ana Paula; Lunardi, Paula; Pedraza, Lizeth Katherine; Quillfeldt, Jorge Alberto; Hardt, Oliver; de Oliveira Alvares, Lucas

    2016-01-01

    In the past decades, the cellular and molecular mechanisms underlying memory consolidation, reconsolidation, and extinction have been well characterized. However, the neurobiological underpinnings of forgetting processes remain to be elucidated. Here we used behavioral, pharmacological and electrophysiological approaches to explore mechanisms controlling forgetting. We found that post-acquisition chronic inhibition of the N-methyl-D-aspartate receptor (NMDAR), L-type voltage-dependent Ca2+ channel (LVDCC), and protein phosphatase calcineurin (CaN), maintains long-term object location memory that otherwise would have been forgotten. We further show that NMDAR activation is necessary to induce forgetting of object recognition memory. Studying the role of NMDAR activation in the decay of the early phase of long-term potentiation (E-LTP) in the hippocampus, we found that ifenprodil infused 30 min after LTP induction in vivo blocks the decay of CA1-evoked postsynaptic plasticity, suggesting that GluN2B-containing NMDARs activation are critical to promote LTP decay. Taken together, these findings indicate that a well-regulated forgetting process, initiated by Ca2+ influx through LVDCCs and GluN2B-NMDARs followed by CaN activation, controls the maintenance of hippocampal LTP and long-term memories over time. PMID:26947131

  4. Evidence for functional interaction of plasma membrane electron transport, voltage-dependent anion channel and volume-regulated anion channel in frog aorta

    Indian Academy of Sciences (India)

    Rashmi P Rao; J Prakasa Rao

    2010-12-01

    Frog aortic tissue exhibits plasma membrane electron transport (PMET) owing to its ability to reduce ferricyanide even in the presence of mitochondrial poisons, such as cyanide and azide. Exposure to hypotonic solution (108 mOsmol/kg H2O) enhanced the reduction of ferricyanide in excised aortic tissue of frog. Increment in ferricyanide reductase activity was also brought about by the presence of homocysteine (100 M dissolved in isotonic frog Ringer solution), a redox active compound and a potent modulator of PMET. Two plasma-membrane-bound channels, the volume regulated anion channel (VRAC) and the voltage-dependent anion channel (VDAC), are involved in the response to hypotonic stress. The presence of VRAC and VDAC antagonists–tamoxifen, glibenclamide, fluoxetine and verapamil, and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS), respectively–inhibited this enhanced activity brought about by either hypotonic stress or homocysteine. The blockers do not affect the ferricyanide reductase activity under isotonic conditions. Taken together, these findings indicate a functional interaction of the three plasma membrane proteins, namely, ferricyanide reductase (PMET), VDAC and VRAC.

  5. Correlation between Barrier Width, Barrier Height, and DC Bias Voltage Dependences on the Magnetoresistance Ratio in Ir-Mn Exchange Biased Single and Double Tunnel Junctions

    Science.gov (United States)

    Saito, Yoshiaki; Amano, Minoru; Nakajima, Kentaro; Takahashi, Shigeki; Sagoi, Masayuki; Inomata, Koichiro

    2000-10-01

    Dual spin-valve-type double tunnel junctions (DTJs) of Ir-Mn/CoFe/AlOx/Co90Fe10/AlOx/CoFe/Ir-Mn and spin-valve-type single tunnel junctions (STJs) of Ir-Mn/CoFe/AlOx/CoFe/Ni-Fe were fabricated using an ultrahigh vacuum sputtering system, conventional photolithography and ion-beam milling. The STJs could be fabricated with various barrier heights by changing the oxidization conditions during deposition and changing the annealing temperature after deposition, while the AlOx layer thickness remained unchanged. There was a correlation between barrier width, height estimated using Simmons’ expressions, and dc bias voltage dependence on the MR ratio. The VB dependence on the tunneling magnetoresistance (TMR) ratio was mainly related to the barrier width, and the decrease in the TMR ratio with increasing bias voltage is well explained, taking into account the spin-independent two-step tunneling via defect states in the barrier, as a main mechanism, at room temperature. Under optimized oxidization and annealing conditions, the maximum TMR ratio at a low bias voltage, and the dc bias voltage value at which the TMR ratio decreases in value by half (V1/2) were 42.4% and 952 mV in DTJs, and 49.0% and 425 mV in STJs, respectively.

  6. Ca2+ channel inhibitor NNC 55-0396 inhibits voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells.

    Science.gov (United States)

    Son, Youn Kyoung; Hong, Da Hye; Li, Hongliang; Kim, Dae-Joong; Na, Sung Hun; Park, Hongzoo; Jung, Won-Kyo; Choi, Il-Whan; Park, Won Sun

    2014-01-01

    We demonstrated the inhibitory effect of NNC 55-0396, a T-type Ca(2+) channel inhibitor, on voltage-dependent K(+) (K(V)) channels in freshly isolated rabbit coronary arterial smooth muscle cells. NNC 55-0396 decreased the amplitude of K(V) currents in a concentration-dependent manner, with an IC(50) of 0.080 μM and a Hill coefficient of 0.76.NNC 55-0396 did not affect steady-state activation and inactivation curves, indicating that the compound does not affect the voltage sensitivity of K(V) channel gating. Both the K(V) currents and the inhibitory effect of NNC 55-0396 on K(V) channels were not altered by depletion of extracellular Ca(2+) or intracellular ATP, suggesting that the inhibitory effect of NNC 55-0396 is independent of Ca(2+)-channel activity and phosphorylation-dependent signaling cascades. From these results, we concluded that NNC 55-0396 dosedependently inhibits K(V) currents, independently of Ca(2+)-channel activity and intracellular signaling cascades.

  7. Forgetting of long-term memory requires activation of NMDA receptors, L-type voltage-dependent Ca2+ channels, and calcineurin.

    Science.gov (United States)

    Sachser, Ricardo Marcelo; Santana, Fabiana; Crestani, Ana Paula; Lunardi, Paula; Pedraza, Lizeth Katherine; Quillfeldt, Jorge Alberto; Hardt, Oliver; Alvares, Lucas de Oliveira

    2016-03-07

    In the past decades, the cellular and molecular mechanisms underlying memory consolidation, reconsolidation, and extinction have been well characterized. However, the neurobiological underpinnings of forgetting processes remain to be elucidated. Here we used behavioral, pharmacological and electrophysiological approaches to explore mechanisms controlling forgetting. We found that post-acquisition chronic inhibition of the N-methyl-D-aspartate receptor (NMDAR), L-type voltage-dependent Ca(2+) channel (LVDCC), and protein phosphatase calcineurin (CaN), maintains long-term object location memory that otherwise would have been forgotten. We further show that NMDAR activation is necessary to induce forgetting of object recognition memory. Studying the role of NMDAR activation in the decay of the early phase of long-term potentiation (E-LTP) in the hippocampus, we found that ifenprodil infused 30 min after LTP induction in vivo blocks the decay of CA1-evoked postsynaptic plasticity, suggesting that GluN2B-containing NMDARs activation are critical to promote LTP decay. Taken together, these findings indicate that a well-regulated forgetting process, initiated by Ca(2+) influx through LVDCCs and GluN2B-NMDARs followed by CaN activation, controls the maintenance of hippocampal LTP and long-term memories over time.

  8. Differential rescue of spatial memory deficits in aged rats by L-type voltage-dependent calcium channel and ryanodine receptor antagonism.

    Science.gov (United States)

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

    2014-11-01

    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.

  9. α-Synuclein Shows High Affinity Interaction with Voltage-dependent Anion Channel, Suggesting Mechanisms of Mitochondrial Regulation and Toxicity in Parkinson Disease.

    Science.gov (United States)

    Rostovtseva, Tatiana K; Gurnev, Philip A; Protchenko, Olga; Hoogerheide, David P; Yap, Thai Leong; Philpott, Caroline C; Lee, Jennifer C; Bezrukov, Sergey M

    2015-07-24

    Participation of the small, intrinsically disordered protein α-synuclein (α-syn) in Parkinson disease (PD) pathogenesis has been well documented. Although recent research demonstrates the involvement of α-syn in mitochondrial dysfunction in neurodegeneration and suggests direct interaction of α-syn with mitochondria, the molecular mechanism(s) of α-syn toxicity and its effect on neuronal mitochondria remain vague. Here we report that at nanomolar concentrations, α-syn reversibly blocks the voltage-dependent anion channel (VDAC), the major channel of the mitochondrial outer membrane that controls most of the metabolite fluxes in and out of the mitochondria. Detailed analysis of the blockage kinetics of VDAC reconstituted into planar lipid membranes suggests that α-syn is able to translocate through the channel and thus target complexes of the mitochondrial respiratory chain in the inner mitochondrial membrane. Supporting our in vitro experiments, a yeast model of PD shows that α-syn toxicity in yeast depends on VDAC. The functional interactions between VDAC and α-syn, revealed by the present study, point toward the long sought after physiological and pathophysiological roles for monomeric α-syn in PD and in other α-synucleinopathies.

  10. A perturbation-based model for rectifier circuits

    Directory of Open Access Journals (Sweden)

    Vipin B. Vats

    2006-01-01

    Full Text Available A perturbation-theoretic analysis of rectifier circuits is presented. The governing differential equation of the half-wave rectifier with capacitor filter is analyzed by expanding the output voltage as a Taylor series with respect to an artificially introduced parameter in the nonlinearity of the diode characteristic as is done in quantum theory. The perturbation parameter introduced in the analysis is independent of the circuit components as compared to the method presented by multiple scales. The various terms appearing in the perturbation series are then modeled in the form of an equivalent circuit. This model is subsequently used in the analysis of full-wave rectifier. Matlab simulation results are included which confirm the validity of the theoretical formulations. Perturbation analysis acts a helpful tool in analyzing time-varying systems and chaotic systems.

  11. When does inward technology licensing facilitate firms’ NPD performance? Evidence from China

    DEFF Research Database (Denmark)

    Li-Ying, Jason; Wang, Yuandi; Salomo, Søren

    2013-01-01

    has reached a stage that is way beyond simple linear relationships, the appropriate question to ask is perhaps not whether inward technology licensing has a positive effect on firms’ NPD performance; instead, it is more sense-making to ask under what conditions inward technology licensing better...... firms, and factors regarding licensees’ external environment. Using a unique longitudinal dataset containing information about 141 Chinese firms’ licensing activities, we find support for our hypotheses that there is a positive relationship between inward technology and NPD performance. This positive...... licensing, the relationship between inward technology licensing and licensee firms’ subsequent NPD performance has not yet found convincing evidence. Since our understanding, shared with many other likeminded scholars and practitioners, about the dynamics between resource, institutions and firm performance...

  12. Fixed Point Curve for Weakly Inward Contractions and Approximate Fixed Point Property

    Institute of Scientific and Technical Information of China (English)

    P. Riyas; K. T. Ravindran

    2013-01-01

    In this paper, we discuss the concept of fixed point curve for linear interpo-lations of weakly inward contractions and establish necessary condition for a nonex-pansive mapping to have approximate fixed point property.

  13. The effects of outward forced convective flow on inward diffusion in human dentine in vitro.

    Science.gov (United States)

    Pashley, D H; Matthews, W G

    1993-07-01

    In vitro experiments were conducted to evaluate the influence of outward forced convective flow on the inward diffusion of radioactive iodide. When the smear layer was present, application of 15 cmH2O (1.47 kPa) outward-directed filtration pressure reduced the inward flux of iodide by about 10-20% depending upon the hydraulic conductance of each specimen. When the smear layer was removed by acid etching, the same 1.47 kPa pressure lowered the inward iodide flux by as much as 60%, depending on the hydraulic conductance. The results demonstrate the importance of the balance between inward diffusion and outward bulk-fluid movement on the rate of permeation of exogenous solutes.

  14. Inward technology transfer as an interactive process: A case study of ICI.

    OpenAIRE

    Trott, Paul

    1993-01-01

    This thesis sets out to explore the area of inward technology transfer and in particular the notion of "receptivity". A conceptual framework is developed which identifies four major components of the inward technology transfer process. These are: "Awareness"- "Association"-"Assimilation"-"Application". Using this conceptual device a series of investigations are undertaken into three of these components. These studies are conducted within a number of businesses within ICI Che...

  15. The Determinants of Inward Foreign Direct Investment: the Case of Malaysia

    OpenAIRE

    Yong Ting Aw; Tuck Cheong Tang

    2009-01-01

    This study empirically explores the role of corruption, and the impact of China joining the WTO in 2001 on inward foreign direct investment (FDI) in Malaysia. From the empirical tests, this study suggests:- (1) FDI and its determinants are cointegrated; (2) Openness, interest rate, inflation rate, the joining of China into the WTO, and the level of corruption are the major determinants explaining inward FDI in Malaysia, both in the long-run as well as short- run. In general, these findings do...

  16. Enhanced rectifying response from metal-insulator-insulator-metal junctions

    Science.gov (United States)

    Maraghechi, P.; Foroughi-Abari, A.; Cadien, K.; Elezzabi, A. Y.

    2011-12-01

    We present on a metal-insulator-insulator-metal quantum electronic tunneling devices suitable for high speed rectifiers. Through the introduction of double oxide layer between similar metallic electrodes, a cascaded potential barrier is formed which alters the electron tunneling mechanism at forward versus the reverse bias. The cascaded potential barrier engineering manifests itself in both a highly nonlinear and asymmetric I-V junction characteristic. It is envisioned that high speed rectifiers and mixers having extraordinary nonlinearity can be realized through the incorporation of the cascaded potential barrier architecture and dissimilar metallic electrodes.

  17. Three-phase bridge rectifiers with freewheeling diodes

    CERN Document Server

    Hausler, M

    1973-01-01

    Freewheeling diodes are used in controlled rectifiers working in one quadrant only in order to reduce the reactive power and the d.c.- voltage ripple. In addition the freewheeling diodes allow a higher d.c.-current at low d.c.-voltages. The mean value of the freewheeling current depends on the d.c.-current, the load, and the stray-reactance of the rectifier transformer. This paper describes how the freewheeling current can be determined with these parameters. Results for some typical cases are shown in diagrams. (2 refs).

  18. Fabrication and characterization of the organic rectifying junctions by electrolysis

    Science.gov (United States)

    Karimov, Khasan; Ahmad, Zubair; Ali, Rashid; Noor, Adnan; Akmal, M.; Najeeb, M. A.; Shakoor, R. A.

    2017-08-01

    Unlike the conventional solution processable deposition techniques, in this study, we propose a novel and economical method for the fabrication of organic rectifying junctions. The solutions of the orange dye, copper phthalocyanine and NaCl were deposited on the surface-type interdigitated silver electrodes using electrolysis technique. Using the current-voltage (I-V) characteristics, the presence of rectifying behavior in the samples has been confirmed. This phenomenon, in principle, can be used for fabrication of the diodes, transistors and memory devices.

  19. Locus of spatial attention determines inward-outward anisotropy in crowding.

    Science.gov (United States)

    Petrov, Yury; Meleshkevich, Olga

    2011-04-01

    It has long been known that an outward mask is much more disruptive than an inward mask in crowding (H. Bouma, 1973). We show that the locus of attention strongly affects this inward-outward anisotropy, removing it in some conditions and reversing it in others. In a 2AFC paradigm, subjects identified whether a high-contrast Gabor target of a given orientation was presented left or right of fixation. When a fixed eccentricity (8°) was used, the outward plaid mask produced much stronger crowding than the inward mask. When 7°, 8°, and 9° eccentricities were interleaved within the same run, diffusing attention, the inward and outward masks produced the same amount of crowding for all three eccentricities. When target identification was contingent on a foveal cue, biasing attention inward, the inward mask produced stronger crowding. Finally, a new contrast-detection paradigm was used to demonstrate that attention is generally mislocalized outward of the target, which may explain the commonly observed anisotropy in crowding. Our results suggest that spatial attention is intimately involved in the mechanism of crowding.

  20. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co{sub 3}O{sub 4}-PVA/p-Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Bilkan, Çiğdem, E-mail: cigdembilkan@gmail.com [Department of Physics, Faculty of Sciences, The University of Çankırı Karatekin, 18100 Çankırı (Turkey); Azizian-Kalandaragh, Yashar [Department of Physics, Faculty of Science, The University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Altındal, Şemsettin [Department of Physics, Faculty of Sciences, The University of Gazi, 06500 Ankara (Turkey); Shokrani-Havigh, Roya [Department of Physics, Faculty of Science, The University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of)

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV–vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε′, ε″) and electric modulus (M′ and M″), loss tangent (tanδ), and ac electrical conductivity (σ{sub ac}) values of Al/Co{sub 3}O{sub 4}-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε′, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σ{sub dc} and σ{sub ac}, respectively. The M′ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M′ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and N{sub ss} effects with increasing frequency.

  1. Alterations of voltage-dependent calcium channel currents in basilar artery smooth muscle cells at early stage of subarachnoid hemorrhage in a rabbit model.

    Directory of Open Access Journals (Sweden)

    Xianqing Shi

    Full Text Available OBJECTIVE: To investigate the changes in the currents of voltage-dependent calcium channels (VDCCs in smooth muscle cells of basilar artery in a rabbit model of subarachnoid hemorrhage (SAH. METHODS: New Zealand white rabbits were randomly divided into five groups: sham (C, normal (N, 24 hours (S1, 48 hours (S2 and 72 hours (S3 after SAH. Non-heparinized autologous arterial blood (1 ml/kg was injected into the cisterna magna to create SAH after intravenous anesthesia, and 1 ml/kg of saline was injected into cisterna magna in the sham group. Rabbits in group N received no injections. Basilar artery in S1, S2, S3 group were isolated at 24, 48, 72 hours after SAH. Basilar artery in group C was isolated at 72 hours after physiological saline injection. Basilar artery smooth muscle cells were isolated for all groups. Whole-cell patch-clamp technique was utilized to record cell membrane capacitance and VDCCs currents. The VDCCs antagonist nifedipine was added to the bath solution to block the Ca(++ channels currents. RESULTS: There were no significant differences in the number of cells isolated, the cell size and membrane capacitance among all the five groups. VDCC currents in the S1-S3 groups had higher amplitudes than those in control and sham groups. The significant change of current amplitude was observed at 72 hours after SAH, which was higher than those of 24 and 48 hours. The VDCCs were shown to expression in human artery smooth muscle cells. CONCLUSIONS: The changes of activation characteristics and voltage-current relationship at 72 hours after SAH might be an important event which leads to a series of molecular events in the microenvironment of the basilar artery smooth muscle cells. This may be the key time point for potential therapeutic intervention against subarachnoid hemorrhage.

  2. Delta receptors are required for full inhibitory coupling of mu-receptors to voltage-dependent Ca(2+) channels in dorsal root ganglion neurons.

    Science.gov (United States)

    Walwyn, Wendy; John, Scott; Maga, Matthew; Evans, Christopher J; Hales, Tim G

    2009-07-01

    Recombinant micro and delta opioid receptors expressed in cell lines can form heterodimers with distinctive properties and trafficking. However, a role for opioid receptor heterodimerization in neurons has yet to be identified. The inhibitory coupling of opioid receptors to voltage-dependent Ca(2+) channels (VDCCs) is a relatively inefficient process and therefore provides a sensitive assay of altered opioid receptor function and expression. We examined micro-receptor coupling to VDCCs in dorsal root ganglion neurons of delta(+/+), delta(+/-), and delta(-/-) mice. Neurons deficient in delta receptors exhibited reduced inhibition of VDCCs by morphine and [D-Ala(2),Phe(4),Gly(5)-ol]-enkephalin (DAMGO). An absence of delta receptors caused reduced efficacy of DAMGO without affecting potency. An absence of delta receptors reduced neither the density of VDCCs nor their inhibition by either the GABA(B) receptor agonist baclofen or intracellular guanosine 5'-O-(3-thio)triphosphate. Flow cytometry revealed a reduction in micro-receptor surface expression in delta(-/-) neurons without altered DAMGO-induced internalization. There was no change in micro-receptor mRNA levels. D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2)-sensitive mu-receptor-coupling efficacy was fully restored to delta(+/+) levels in delta(-/-) neurons by expression of recombinant delta receptors. However, the dimerization-deficient delta-15 construct expressed in delta(-/-) neurons failed to fully restore the inhibitory coupling of micro-receptors compared with that seen in delta(+/+) neurons, suggesting that, although not essential for micro-receptor function, micro-delta receptor dimerization contributes to full micro-agonist efficacy. Because DAMGO exhibited a similar potency in delta(+/+) and delta(-/-) neurons and caused similar levels of internalization, the role for heterodimerization is probably at the level of receptor biosynthesis.

  3. A conserved threonine in the S1-S2 loop of KV7.2 and K V7.3 channels regulates voltage-dependent activation.

    Science.gov (United States)

    Füll, Yvonne; Seebohm, Guiscard; Lerche, Holger; Maljevic, Snezana

    2013-06-01

    The voltage-gated potassium channels KV7.2 and KV7.3 (KCNQ2/3 genes) play an important role in regulating neuronal excitability. More than 50 KCNQ2/3 mutations have been identified to cause an inherited form of epilepsy in newborns. For two of those (E119G and S122L) found in the S1-S2 region of KV7.2, we previously showed a decreased channel availability mainly at action potential subthreshold voltages caused by a slight depolarizing shift of the activation curve. Interestingly, recent studies revealed that a threonine residue within the S1-S2 loop, highly conserved among different classes of KV channels, is crucial for both their function and surface expression. To investigate the functional role of the homologous threonine residues in KV7.2 (T114) and KV7.3 (T144) channels, we replaced them with alanine and examined the electrophysiological properties using heterologous expression in CHO cells and whole cell patch clamping. Channels comprising mutant subunits yielded decreased potassium currents with slowed activation and accelerated deactivation kinetics. However, the most striking effect was a depolarizing shift in the voltage dependence of activation reaching +30 mV upon co-expression of both mutant subunits. Potential interactions of T114 within the channel were analyzed by creating a 3D homology model of KV7.2 in an open state suggesting that this residue plays a central role in the formation of a stable interface between the S1-S2 and the S5 segment helices. This could be the explanation why substitution of the conserved threonine in KV7.2 and KV7.3 channels destabilizes the open and favors the closed state of these channels.

  4. 线粒体电压依赖性阴离子通道与心血管疾病%Voltage-dependent Anion Channel and Cardiovascular Diseases

    Institute of Scientific and Technical Information of China (English)

    夏晶

    2013-01-01

    电压依赖性阴离子通道(VDAC)是位于线粒体外膜的通道蛋白,是线粒体与细胞质之间转运ATP以及其他代谢产物的主要通道,在线粒体代谢和细胞生长中发挥重要调控作用.近期研究发现,在心肌缺血再灌、糖尿病、心衰、高血压和动脉粥样硬化时,VDAC表达明显增加,引起细胞内钙离子循环紊乱、氧化应激,进而导致细胞凋亡,已成为心血管疾病研究的新热点.本文就VDAC的分子功能,调控及其在心血管疾病中的作用和相关机制进行综述.%The voltage-dependent anion channel (VDAC),a mitochondrial membrane channel protein located in the outer of mitochondrial membrane,is the main pathway between mitochondria and cytoplasm exchanging ADP,ATP,and other metabolites,and plays an important role in mitochondrial metabolism and cell growth.A growing evidence showed that VDAC was increased in cardiovascular diseases including myocardial ischemia and reperfusion,diabetes,heart failure,hypertension and atherosclerosis.The abnormal state of VDAC will result in cell death by inducing calcium cycling dysfunction and oxidative stress.And VDAC has become a hot topic in the field of cardiovascular diseases research.In this article,we will introduce the molecular function and regulation of VDAC and its role in cardiovascular diseases.

  5. IgG anti-GalNAc-GD1a antibody inhibits the voltage-dependent calcium channel currents in PC12 pheochromocytoma cells.

    Science.gov (United States)

    Nakatani, Yoshihiko; Nagaoka, Takumi; Hotta, Sayako; Utsunomiya, Iku; Yoshino, Hiide; Miyatake, Tadashi; Hoshi, Keiko; Taguchi, Kyoji

    2007-03-01

    We investigated the effects of IgG anti-GalNAc-GD1a antibodies, produced by immunizing rabbits with GalNAc-GD1a, on the voltage-dependent calcium channel (VDCCs) currents in nerve growth factor (NGF)-differentiated PC12 pheochromocytoma cells. VDCCs currents in NGF-differentiated PC12 cells were recorded using the whole-cell patch-clamp technique. Immunized rabbit serum that had a high titer of anti-GalNAc-GD1a antibodies inhibited the VDCCs currents in the NGF-differentiated PC12 cells (36.0+/-9.6% reduction). The inhibitory effect of this serum was reversed to some degree within 3-4 min by washing with bath solution. Similarly, application of purified IgG from rabbit serum immunized with GalNAc-GD1a significantly inhibited the VDCCs currents in PC12 cells (30.6+/-2.5% reduction), and this inhibition was recovered by washing with bath solution. Furthermore, the inhibitory effect was also observed in the GalNAc-GD1a affinity column binding fraction (reduction of 31.1+/-9.85%), while the GalNAc-GD1a affinity column pass-through fraction attenuated the inhibitory effect on VDCCs currents. Normal rabbit serum and normal rabbit IgG did not affect the VDCCs currents in the PC12 cells. In an immunocytochemical study using fluorescence staining, the PC12 cells were stained using GalNAc-GD1a binding fraction. These results indicate that anti-GalNAc-GD1a antibodies inhibit the VDCCs currents in NGF-differentiated PC12 cells.

  6. Reduced KCNQ4-encoded voltage-dependent potassium channel activity underlies impaired β-adrenoceptor-mediated relaxation of renal arteries in hypertension.

    Science.gov (United States)

    Chadha, Preet S; Zunke, Friederike; Zhu, Hai-Lei; Davis, Alison J; Jepps, Thomas A; Olesen, Søren P; Cole, William C; Moffatt, James D; Greenwood, Iain A

    2012-04-01

    KCNQ4-encoded voltage-dependent potassium (Kv7.4) channels are important regulators of vascular tone that are severely compromised in models of hypertension. However, there is no information as to the role of these channels in responses to endogenous vasodilators. We used a molecular knockdown strategy, as well as pharmacological tools, to examine the hypothesis that Kv7.4 channels contribute to β-adrenoceptor-mediated vasodilation in the renal vasculature and underlie the vascular deficit in spontaneously hypertensive rats. Quantitative PCR and immunohistochemistry confirmed gene and protein expression of KCNQ1, KCNQ3, KCNQ4, KCNQ5, and Kv7.1, Kv7.4, and Kv7.5 in rat renal artery. Isoproterenol produced concentration-dependent relaxation of precontracted renal arteries and increased Kv7 channel currents in isolated smooth muscle cells. Application of the Kv7 blocker linopirdine attenuated isoproterenol-induced relaxation and current. Isoproterenol-induced relaxations were also reduced in arteries incubated with small interference RNAs targeted to KCNQ4 that produced a ≈60% decrease in Kv7.4 protein level. Relaxation to isoproterenol and the Kv7 activator S-1 were abolished in arteries from spontaneously hypertensive rats, which was associated with ≈60% decrease in Kv7.4 abundance. This study provides the first evidence that Kv7 channels contribute to β-adrenoceptor-mediated vasodilation in the renal vasculature and that abrogation of Kv7.4 channels is strongly implicated in the impaired β-adrenoceptor pathway in spontaneously hypertensive rats. These findings may provide a novel pathogenic link between arterial dysfunction and hypertension.

  7. Voltage-dependent anion channels (VDACs) promote mitophagy to protect neuron from death in an early brain injury following a subarachnoid hemorrhage in rats.

    Science.gov (United States)

    Li, Jian; Lu, Jianfei; Mi, Yongjie; Shi, Zhao; Chen, Chunhua; Riley, John; Zhou, Changman

    2014-07-21

    The term mitophagy is coined to describe the selective removal of mitochondria by autophagy but the process itself is still contentious, especially in the early period following subarachnoid hemorrhage (SAH). In the present study, we investigated the role of mitophagy following 48h after SAH injury in rats. Specifically evaluating whether mitophagy, through voltage dependant anion channels (VDACs) interacting with microtubule-associated protein 1 light chain 3, could orchestrate the induction of apoptotic and necrotic cell death in neurons, a VDAC1siRNA and an activitor Rapamycian (RAPA), were engaged. One hundred and twelve male Sprague-Dawley rats were randomly divided into 4 groups: Sham, SAH, SAH+VDAC1siRNA, and SAH+RAPA. Outcomes measured included mortality rate, brain edema, BBB disruption, and neurobehavioral testing. We also used western blotting techniques to analyze the expressions of key mitophagic/autophagic proteins and pro-apoptotic protein such as ROS, VDAC1, LC-3II and Caspase-3. Rapamycin treatment significantly improved the mortality rate, cerebral edema, and neurobehavioral deficits; apoptotic and necrotic cell death in neurons were reduced by Rapamycin following SAH injury. However, VDAC1siRNA worsened the brain injury following SAH. Immunohistochemical staining and western blot analysis demonstrated a decreased expression of VDAC1, LC3II, and an increase of ROS and Caspase-3 followed by VDAC1siRNA administration. In conclusion, mitophagy induced by VDAC1 following SAH injury may in fact play a significant role in neuroprotection, the mechanism which may be through the attenuation of the apoptosic and necrosic molecular pathways. This translates a preservation of functional integrity and an improvement in mortality.

  8. Voltage-dependent gating of hyperpolarization-activated, cyclic nucleotide-gated pacemaker channels: molecular coupling between the S4-S5 and C-linkers.

    Science.gov (United States)

    Decher, Niels; Chen, Jun; Sanguinetti, Michael C

    2004-04-02

    Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels have a transmembrane topology that is highly similar to voltage-gated K(+) channels, yet HCN channels open in response to membrane hyperpolarization instead of depolarization. The structural basis for the "inverted" voltage dependence of HCN gating and how voltage sensing by the S1-S4 domains is coupled to the opening of the intracellular gate formed by the S6 domain are unknown. Coupling could arise from interaction between specific residues or entire transmembrane domains. We previously reported that the mutation of specific residues in the S4-S5 linker of HCN2 (i.e. Tyr-331 and Arg-339) prevented normal channel closure presumably by disruption of a crucial interaction with the activation gate. Here we hypothesized that the C-linker, a carboxyl terminus segment that connects S6 to the cyclic nucleotide binding domain, interacts with specific residues of the S4-S5 linker to mediate coupling. The recently solved structure of the C-linker of HCN2 indicates that an alpha-helix (the A'-helix) is located near the end of each S6 domain, the presumed location of the activation gate. Ala-scanning mutagenesis of the end of S6 and the A'-helix identified five residues that were important for normal gating as mutations disrupted channel closure. However, partial deletion of the C-linker indicated that the presence of only two of these residues was required for normal coupling. Further mutation analyses suggested that a specific electrostatic interaction between Arg-339 of the S4-S5 linker and Asp-443 of the C-linker stabilizes the closed state and thus participates in the coupling of voltage sensing and activation gating in HCN channels.

  9. The N-Terminal Peptides of the Three Human Isoforms of the Mitochondrial Voltage-Dependent Anion Channel Have Different Helical Propensities.

    Science.gov (United States)

    Guardiani, Carlo; Scorciapino, Mariano Andrea; Amodeo, Giuseppe Federico; Grdadolnik, Joze; Pappalardo, Giuseppe; De Pinto, Vito; Ceccarelli, Matteo; Casu, Mariano

    2015-09-15

    The voltage-dependent anion channel (VDAC) is the main mitochondrial porin allowing the exchange of ions and metabolites between the cytosol and the mitochondrion. In addition, VDAC was found to actively interact with proteins playing a fundamental role in the regulation of apoptosis and being of central interest in cancer research. VDAC is a large transmembrane β-barrel channel, whose N-terminal helical fragment adheres to the channel interior, partially closing the pore. This fragment is considered to play a key role in protein stability and function as well as in the interaction with apoptosis-related proteins. Three VDAC isoforms are differently expressed in higher eukaryotes, for which distinct and complementary roles are proposed. In this work, the folding propensity of their N-terminal fragments has been compared. By using multiple spectroscopic techniques, and complementing the experimental results with theoretical computer-assisted approaches, we have characterized their conformational equilibrium. Significant differences were found in the intrinsic helical propensity of the three peptides, decreasing in the following order: hVDAC2 > hVDAC3 > hVDAC1. In light of the models proposed in the literature to explain voltage gating, selectivity, and permeability, as well as interactions with functionally related proteins, our results suggest that the different chemicophysical properties of the N-terminal domain are possibly correlated to different functions for the three isoforms. The overall emerging picture is that a similar transmembrane water accessible conduit has been equipped with not identical domains, whose differences can modulate the functional roles of the three VDAC isoforms.

  10. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co3O4-PVA/p-Si structures

    Science.gov (United States)

    Bilkan, Çiğdem; Azizian-Kalandaragh, Yashar; Altındal, Şemsettin; Shokrani-Havigh, Roya

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε‧, ε″) and electric modulus (M‧ and M″), loss tangent (tanδ), and ac electrical conductivity (σac) values of Al/Co3O4-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε‧, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σdc and σac, respectively. The M‧ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M‧ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and Nss effects with increasing frequency.

  11. The calmodulin inhibitor CGS 9343B inhibits voltage-dependent K{sup +} channels in rabbit coronary arterial smooth muscle cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongliang; Hong, Da Hye; Kim, Han Sol; Kim, Hye Won [Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 200-701 (Korea, Republic of); Jung, Won-Kyo [Department of Biomedical Engineering, Center for Marine-Integrated Biomedical Technology (BK21 Plus), Pukyong National University, Busan 608-737 (Korea, Republic of); Na, Sung Hun [Institute of Medical Sciences, Department of Obstetrics and Gynecology, Kangwon National University Hospital, School of Medicine, Kangwon National University, Chuncheon, 200-701 (Korea, Republic of); Jung, In Duk; Park, Yeong-Min [Department of Immunology, Lab of Dendritic Cell Differentiation and Regulation, College of Medicine, Konkuk University, Chungju 380-701 (Korea, Republic of); Choi, Il-Whan, E-mail: cihima@inje.ac.kr [Department of Microbiology, Inje University College of Medicine, Busan, 614-735 (Korea, Republic of); Park, Won Sun, E-mail: parkws@kangwon.ac.kr [Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 200-701 (Korea, Republic of)

    2015-06-15

    We investigated the effects of the calmodulin inhibitor CGS 9343B on voltage-dependent K{sup +} (Kv) channels using whole-cell patch clamp technique in freshly isolated rabbit coronary arterial smooth muscle cells. CGS 9343B inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC{sub 50}) value of 0.81 μM. The decay rate of Kv channel inactivation was accelerated by CGS 9343B. The rate constants of association and dissociation for CGS 9343B were 2.77 ± 0.04 μM{sup −1} s{sup −1} and 2.55 ± 1.50 s{sup −1}, respectively. CGS 9343B did not affect the steady-state activation curve, but shifted the inactivation curve toward to a more negative potential. Train pulses (1 or 2 Hz) application progressively increased the CGS 9343B-induced Kv channel inhibition. In addition, the inactivation recovery time constant was increased in the presence of CGS 9343B, suggesting that CGS 9343B-induced inhibition of Kv channel was use-dependent. Another calmodulin inhibitor, W-13, did not affect Kv currents, and did not change the inhibitory effect of CGS 9343B on Kv current. Our results demonstrated that CGS 9343B inhibited Kv currents in a state-, time-, and use-dependent manner, independent of calmodulin inhibition. - Highlights: • We investigated the effects of CGS 9394B on Kv channels. • CGS 9394B inhibited Kv current in a state-, time-, and use-dependent manner. • Caution is required when using CGS 9394B in vascular function studies.

  12. The episodic ataxia type 1 mutation I262T alters voltage-dependent gating and disrupts protein biosynthesis of human Kv1.1 potassium channels.

    Science.gov (United States)

    Chen, Szu-Han; Fu, Ssu-Ju; Huang, Jing-Jia; Tang, Chih-Yung

    2016-01-18

    Voltage-gated potassium (Kv) channels are essential for setting neuronal membrane excitability. Mutations in human Kv1.1 channels are linked to episodic ataxia type 1 (EA1). The EA1-associated mutation I262T was identified from a patient with atypical phenotypes. Although a previous report has characterized its suppression effect, several key questions regarding the impact of the I262T mutation on Kv1.1 as well as other members of the Kv1 subfamily remain unanswered. Herein we show that the dominant-negative effect of I262T on Kv1.1 current expression is not reversed by co-expression with Kvβ1.1 or Kvβ2 subunits. Biochemical examinations indicate that I262T displays enhanced protein degradation and impedes membrane trafficking of Kv1.1 wild-type subunits. I262T appears to be the first EA1 mutation directly associated with impaired protein stability. Further functional analyses demonstrate that I262T changes the voltage-dependent activation and Kvβ1.1-mediated inactivation, uncouples inactivation from activation gating, and decelerates the kinetics of cumulative inactivation of Kv1.1 channels. I262T also exerts similar dominant effects on the gating of Kv1.2 and Kv1.4 channels. Together our data suggest that I262T confers altered channel gating and reduced functional expression of Kv1 channels, which may account for some of the phenotypes of the EA1 patient.

  13. high power facto high power factor high power factor hybrid rectifier ...

    African Journals Online (AJOL)

    eobe

    increase in the number of electrical loads that some kind of ... application, the rectifiers, particularly in Gr setting, are .... Copyright© Faculty of Engineering, sity of Nigeria ... PRINCIPLE OF THE PROPOSED HYBRID RECTIFIER. PRINCIPLE OF ...

  14. Fully controlled 5-phase, 10-pulse, line commutated rectifier

    Directory of Open Access Journals (Sweden)

    Mahmoud I. Masoud

    2015-12-01

    Full Text Available The development and production of multiphase machines either generators or motors, specially five-phase, offers improved performance compared to three-phase counterpart. Five phase generators could generate power in applications such as, but not limited to, wind power generation, electric vehicles, aerospace, and oil and gas. The five-phase generator output requires converter system such as ac–dc converters. In this paper, a fully controlled 10-pulse line commutated rectifier, suitable to be engaged with wind energy applications, fed from five-phase source is introduced. A shunt active power filter (APF is used to improve power factor and supply current total harmonic distortion (THD. Compared to three-phase converters, 6-pulse or 12-pulse rectifiers, the 10-pulse rectifier engaged with 5-phase source alleviate their drawbacks such as high dc ripples and no need for electric gear or phase shifting transformer. MATLAB/SIMULINK platform is used as a simulation tool to investigate the performance of the proposed rectifier.

  15. Gate-controlled rectifying behavior in C70@SWNT networks.

    Science.gov (United States)

    Guo, Ao; Fu, Yunyi; Liu, Jia; Guan, Lunhui; Shi, Zujin; Gu, Zhennan; Huang, Ru; Zhang, Xing

    2006-05-25

    We report the gate-controlled rectification behavior in C(70)@SWNT networks at room temperature in air. The electrical transport characteristics can be fitted well with the conventional Schottky diode model. The origin of the rectifying behavior in fullerene peapod networks device is qualitatively discussed. This paper demonstrates a strategy for diode fabrication based on peapod networks.

  16. 35 GHz integrated circuit rectifying antenna with 33 percent efficiency

    Science.gov (United States)

    Yoo, T.-W.; Chang, K.

    1991-01-01

    A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33 percent conversion efficiency has been achieved. The circuit should have applications in microwave/millimeter-wave power transmission and detection.

  17. Pulse-Width Control in Ladder Structure Four-Phase Rectifier for AC-Electromotive

    Science.gov (United States)

    Ivanov, V. V.; Myatez, S. V.; Langeman, E. G.; Schurov, N. I.

    2016-04-01

    Based on these studies the ways of power factor of the single-phase rectifiers operating in a single-phase AC network improving are suggested. The ladder four-phase rectifier is offered as a technical mean using a pulse-width method of controlling the rectified voltage. The pulse-width control efficiency as a way of the power factor rectifier with a ladder structure for AC electromotive improving is evaluated.

  18. MPC-SVM method for Vienna rectifier with PMSG used in Wind Turbine Systems

    DEFF Research Database (Denmark)

    Lee, June-Seok; Bak, Yeongsu; Lee, Kyo-Beum

    2016-01-01

    Using a Vienna rectifier as the machine-side rectifier of back-to-back converter is advantageous in terms of size and cost compared to three-level topologies and for this reason, the Vienna rectifier has been used in Wind Turbine Systems (WTS). This paper proposes a Model Predictive Control (MPC)...

  19. Inflammatory cytokine signaling in insulin producing beta-cells enhances the colocalization correlation coefficient between L-type voltage-dependent calcium channel and calcium-sensing receptor.

    Science.gov (United States)

    Parkash, Jai

    2008-08-01

    The immunological processes in type 1 diabetes and metabolic/inflammatory disorder in type 2 diabetes converge on common signaling pathway(s) leading to beta-cell death in these two diseases. The cytokine-mediated beta-cell death seems to be dependent on voltage-dependent calcium channel (VDCC)-mediated Ca2+ entry. The Ca2+ handling molecular networks control the homeostasis of [Ca2+]i in the beta-cell. The activity and membrane density of VDCC are regulated by several mechanisms including G protein-coupled receptors (GPCRs). CaR is a 123-kDa seven transmembrane extracellular Ca2+ sensing protein that belongs to GPCR family C. Tumor necrosis factor-alpha (TNF-alpha), is a cytokine widely known to activate nuclear factor-kappaB (NF-kappaB) transcription in beta-cells. To obtain a better understanding of TNF-alpha-induced molecular interactions between CaR and VDCC, confocal fluorescence measurements were performed on insulin-producing beta-cells exposed to varying concentrations of TNF-alpha and the results are discussed in the light of increased colocalization correlation coefficient. The insulin producing beta-cells were exposed to 5, 10, 20, 30, and 50 ng/ml TNF-alpha for 24 h at 37 degrees . The cells were then immunolabelled with antibodies directed against CaR, VDCC, and NF-kappaB. The confocal fluorescence imaging data showed enhancement in the colocalization correlation coefficient between CaR and VDCC in beta-cells exposed to TNF-alpha thereby indicating increased membrane delimited spatial interactions between these two membrane proteins. TNF-alpha-induced colocalization of VDCC with CaR was inhibited by nimodipine, an inhibitor of L-type VDCC thereby suggesting that VDCC activity is required for spatial interactions with CaR. The 3-D confocal fluorescence imaging data also demonstrated that addition of TNF-alpha to RIN cells led to the translocation of NF-kappaB from the cytoplasm to the nucleus. Such molecular interactions between CaR and VDCC in tissues

  20. Transcriptional upregulation of α2δ-1 elevates arterial smooth muscle cell voltage-dependent Ca2+ channel surface expression and cerebrovascular constriction in genetic hypertension.

    Science.gov (United States)

    Bannister, John P; Bulley, Simon; Narayanan, Damodaran; Thomas-Gatewood, Candice; Luzny, Patrik; Pachuau, Judith; Jaggar, Jonathan H

    2012-10-01

    A hallmark of hypertension is an increase in arterial myocyte voltage-dependent Ca2+ (CaV1.2) currents that induces pathological vasoconstriction. CaV1.2 channels are heteromeric complexes composed of a pore-forming CaV1.2α1 with auxiliary α2δ and β subunits. Molecular mechanisms that elevate CaV1.2 currents during hypertension and the potential contribution of CaV1.2 auxiliary subunits are unclear. Here, we investigated the pathological significance of α2δ subunits in vasoconstriction associated with hypertension. Age-dependent development of hypertension in spontaneously hypertensive rats was associated with an unequal elevation in α2δ-1 and CaV1.2α1 mRNA and protein in cerebral artery myocytes, with α2δ-1 increasing more than CaV1.2α1. Other α2δ isoforms did not emerge in hypertension. Myocytes and arteries of hypertensive spontaneously hypertensive rats displayed higher surface-localized α2δ-1 and CaV1.2α1 proteins, surface α2δ-1:CaV1.2α1 ratio, CaV1.2 current density and noninactivating current, and pressure- and depolarization-induced vasoconstriction than those of Wistar-Kyoto controls. Pregabalin, an α2δ-1 ligand, did not alter α2δ-1 or CaV1.2α1 total protein but normalized α2δ-1 and CaV1.2α1 surface expression, surface α2δ-1:CaV1.2α1, CaV1.2 current density and inactivation, and vasoconstriction in myocytes and arteries of hypertensive rats to control levels. Genetic hypertension is associated with an elevation in α2δ-1 expression that promotes surface trafficking of CaV1.2 channels in cerebral artery myocytes. This leads to an increase in CaV1.2 current-density and a reduction in current inactivation that induces vasoconstriction. Data also suggest that α2δ-1 targeting is a novel strategy that may be used to reverse pathological CaV1.2 channel trafficking to induce cerebrovascular dilation in hypertension.

  1. Temperature and voltage dependence of barrier height and ideality factor in Au/0.07 graphene-doped PVA/n-Si structures

    Science.gov (United States)

    Altındal Yerişkin, S.; Balbaşı, M.; Demirezen, S.

    2017-01-01

    In this study, Au/0.07 graphene-doped PVA/n-Si structures were fabricated and current conduction mechanism in these structures were investigated in the temperature range of 80-380 K through forward bias current-voltage (I-V) measurements. Main electrical parameters were extracted from I-V data. Zero-bias barrier height (overline{Φ}_{B0} ) and ideality factor (n) were found strong functions of temperature and their values ranged from 0.234 eV and 4.98 (at 80 K) to 0.882 eV and 1.15 (at 380 K), respectively. Φ ap versus q/2kT plot was drawn to obtain an evidence of a Gaussian distribution of the barrier heights (BHs) and it revealed two distinct linear regions with different slopes and intercepts. The mean values of BH (Φ Bo) and zero-bias standard deviation (σ s ) were obtained from the intercept and slope of the linear regions of this plot as 1.30 eV and 0.16 V for the first region (280-380 K) and 0.74 eV and 0.085 V for the second region (80-240 K), respectively. Thus, the values of overline{Φ}_{B0} and effective Richardson constant (A*) were also found from the intercept and slope of the modified Richardson plot [ln(I s /T 2) - q 2 σ {/o 2} /2k 2 T 2 vs q/kT] as 1.31 eV and 130 A/cm2 K2 for the first region and 0.76 eV and 922 A/cm2 K2 for the second region, respectively. The value of A* for the first region was very close to the theoretical value for n-Si (112 A/cm2 K2). The energy density distribution profile of surface states (Nss) was also extracted from the forward bias I-V data by taking into account voltage dependent effective BH (Φe) and n.

  2. Inward currents induced by ischemia in rat spinal cord dorsal horn neurons

    Directory of Open Access Journals (Sweden)

    Gu Jianguo G

    2007-04-01

    Full Text Available Abstract Hypoxia and ischemia occur in the spinal cord when blood vessels of the spinal cord are compressed under pathological conditions such as spinal stenosis, tumors, and traumatic spinal injury. Here by using spinal cord slice preparations and patch-clamp recordings we investigated the influence of an ischemia-simulating medium on dorsal horn neurons in deep lamina, a region that plays a significant role in sensory hypersensitivity and pathological pain. We found that the ischemia-simulating medium induced large inward currents in dorsal horn neurons recorded. The onset of the ischemia-induced inward currents was age-dependent, being onset earlier in older animals. Increases of sensory input by the stimulation of afferent fibers with electrical impulses or by capsaicin significantly speeded up the onset of the ischemia-induced inward currents. The ischemia-induced inward currents were abolished by the glutamate receptor antagonists CNQX (20 μM and APV (50 μM. The ischemia-induced inward currents were also substantially inhibited by the glutamate transporter inhibitor TBOA (100 μM. Our results suggest that ischemia caused reversal operation of glutamate transporters, leading to the release of glutamate via glutamate transporters and the subsequent activation of glutamate receptors in the spinal dorsal horn neurons.

  3. Identification and characterization of inward K ~+-channels in plasma membranes of Arabidopsis root cortex cells

    Institute of Scientific and Technical Information of China (English)

    于川江; 武维华

    1999-01-01

    Patch clamping whole-cell reeording techniques were apphed to study the inward K+ channels in Arabidopsis root cortex cells. The inward K+-channels in the plasma membranes of the root cortex cell protoplasts were activated by hyperpolarized membrane potentials. The channels were highly selective tor K+ ions over Na+ ions. The channel activity was significantly inbibited by the external TEA(?) or Ba(?) The changes in cytoplasmic Ca2+ concentrations did not affect the whole-cell inward K+-currents. The possible asso(?)ation betw(?)en the channel selectivity to K+ and Na(?) ions and plant salt-tolerance was also discussed.

  4. Numerical modeling of inward and outward melting of high temperature PCM in a vertical cylinder

    Science.gov (United States)

    Riahi, S.; Saman, W. Y.; Bruno, F.; Tay, N. H. S.

    2016-05-01

    Numerical study of inward and outward melting of a high temperature PCM in cylindrical enclosures were performed, using FLUENT 15. For validation purposes, numerical modeling of inward melting of a low temperature PCM was initially conducted and the predicted results were compared with the experimental data from the literature. The validated model for the low temperature PCM was used for two high temperature cases; inward melting of a high temperature PCM in a cylindrical enclosure and outward melting in a cylindrical case with higher aspect ratio. The results of this study show that the numerical model developed is capable of capturing the details of melting process with buoyancy driven convection for RaPCM and can be used for the design and optimization of a latent heat thermal storage unit.

  5. Effects of the PKC inhibitors chelerythrine and bisindolylmaleimide I (GF 109203X) on delayed rectifier K+ currents.

    Science.gov (United States)

    Harmati, Gábor; Papp, Ferenc; Szentandrássy, Norbert; Bárándi, László; Ruzsnavszky, Ferenc; Horváth, Balázs; Bányász, Tamás; Magyar, János; Panyi, György; Krasznai, Zoltán; Nánási, Péter P

    2011-02-01

    Protein kinase C (PKC) inhibitors are useful tools for studying PKC-dependent regulation of ion channels. For this purpose, high PKC specificity is a basic requirement excluding any direct interaction between the PKC inhibitor and the ion channel. In the present study, the effects of two frequently applied PKC inhibitors, chelerythine and bisindolylmaleimide I, were studied on the rapid and slow components of the delayed rectifier K(+) current (I(Kr) and I(Ks)) in canine ventricular cardiomyocytes and on the human ether-à-go-go-related gene (hERG) channels expressed in human embryonic kidney (HEK) cells. The whole cell version of the patch clamp technique was used in all experiments. Chelerythrine and bisindolylmaleimide I (both 1 μM) suppressed I(Kr) in canine ventricular cells. This inhibition developed rapidly, suggesting a direct drug-channel interaction. In HEK cells heterologously expressing hERG channels, chelerythrine and bisindolylmaleimide I blocked hERG current in a concentration-dependent manner, having EC(50) values of 0.11 ± 0.01 and 0.76 ± 0.04 μM, respectively. Both chelerythrine and bisindolylmaleimide I strongly modified gating kinetics of hERG--voltage dependence of activation was shifted towards more negative voltages and activation was accelerated. Deactivation was slowed by bisindolylmaleimide I but not by chelerythrine. I(Ks) was not significantly altered by bisindolylmaleimide I and chelerythrine. No significant effect of 0.1 μM bisindolylmaleimide I or 0.1 μM PMA (PKC activator) was observed on I(Kr) arguing against significant contribution of PKC to regulation of I(Kr). It is concluded that neither chelerythrine nor bisindolylmaleimide I is suitable for selective PKC blockade due to their direct blocking actions on the hERG channel.

  6. Inward Diffusion and Acceleration of Particles Driven by Turbulent Fluctuations in Magnetosphere

    CERN Document Server

    Ushida, Y; Sato, N; Yoshida, Z

    2016-01-01

    Charged particles in a magnetosphere are spontaneously attracted to a planet while increasing their kinetic energy via inward diffusion process. A constraint on particles' micro-scale adiabatic invariants restricts the class of motions available to the system, giving rise to a proper frame on which particle diffusion occurs. We investigate the inward diffusion process by numerical simulation of particles on constrained phase space. The results reveal the emergence of inhomogeneous density gradient and anisotropic heating, which is consistent with spacecraft observations, experimental observations, and the recently formulated diffusion model on the constrained phase space.

  7. Inward Cationic Diffusion and Formation of Silica-Rich Surface Nanolayer of Glass

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Deubener, Joachim; Yue, Yuanzheng

    2009-01-01

    This paper reports a chemical approach for obtaining a silica-rich nanolayer on the surface of a vanadium-bearing silicate glass. The approach involves depletion of earth alkaline ions (Mg2+ and Ca2+) from the glass surface by means of inward diffusion of those ions, i.e., diffusion from the surf......This paper reports a chemical approach for obtaining a silica-rich nanolayer on the surface of a vanadium-bearing silicate glass. The approach involves depletion of earth alkaline ions (Mg2+ and Ca2+) from the glass surface by means of inward diffusion of those ions, i.e., diffusion from...

  8. Phase Cascade Bridge Rectifier Array in a 2-D lattice

    CERN Document Server

    Nazari, M; Hong, M K; Mohanty, P; Erramilli, S; Narayan, O

    2016-01-01

    We report on a novel rectification phenomenon in a 2-D lattice network consisting of $N\\times N$ sites with diode and AC source elements with controllable phases. A phase cascade configuration is described in which the current ripple in a load resistor goes to zero in the large $N$ limit, enhancing the rectification efficiency without requiring any external capacitor or inductor based filters. The integrated modular configuration is qualitatively different from conventional rectenna arrays in which the source, rectifier and filter systems are physically disjoint. Exact analytical results derived using idealized diodes are compared to a realistic simulation of commercially available diodes. Our results on nonlinear networks of source-rectifier arrays are potentially of interest to a fast evolving field of distributed power networks.

  9. ISGV Self-rectifying Turbine Design For Thermoacoustic Application

    Science.gov (United States)

    Sammak, Shervin; Asghary, Maryam; Ghorbanian, Kaveh

    2014-11-01

    Thermoacoustic engines produce the acoustic power from wasted heat and then electricity can be generated from acoustic power. Utilizing self-rectifying turbine after a thermoacoustic engine allows for deploying standard generators with high enough rotational speed that remarkably reduce abrasion, size and cost and significantly increase efficiency and controllability in comparison with linear alternators. In this paper, by evaluating all different type of self-rectifying turbine, impulse turbine with self-piched controlled (ISGV) is chosen as the most appropriate type for this application. This kind of turbine is designed in detail for a popular engine, thermoacoustic stirling heat engine (TASHE). In order to validate the design, a full scale size of designed turbine is modeled in ANSYS CFX. As a result, optimum power and efficiency gained based on numerical data.

  10. Harmonic-free line-commutated ac/dc rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    Villablanca, Miguel E. [Electrical Engineering Department, University of Santiago, P.O. Box 10233, Santiago (Chile)

    2009-11-15

    In this paper both a method and apparatus are applied to different configurations of line-commutated ac/dc rectifiers to reduce the distortion of currents flowing from the ac supply. The load may be either inductive or capacitive. The technology involves an accurate shaping of the dc current by using two self-commutated switches. This dc-current shaping is reflected back into the shaping of the ac input currents, which become pure sine waves. Thyristor-based rectifying operation is possible with a simple control circuit, which is able to deal with both rapid load variations and failures in the self-commutated switches. Furthermore, the overlap conduction of bridge thyristors is eliminated completely. Experimental verification is provided from a 400-V 30-kVA 50-Hz laboratory prototype. (author)

  11. 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

  12. Fast switching wideband rectifying circuit for future RF energy harvesting

    Science.gov (United States)

    Asmeida, Akrem; Mustam, Saizalmursidi Md; Abidin, Z. Z.; Ashyap, A. Y. I.

    2017-09-01

    This paper presents the design and simulation of fast switching microwave rectifying circuit for ultra wideband patch antenna over a dual-frequency band (1.8 GHz for GSM and 2.4 GHz for ISM band). This band was chosen due to its high signal availability in the surrounding environment. New rectifying circuit topology with pair-matching trunks is designed using Advanced Design System (ADS) software. These trunks are interfaced with power divider to achieve good bandwidth, fast switching and high efficiency. The power divider acts as a good isolator between the trunks and its straightforward design structure makes it a good choice for a single feed UWB antenna. The simulated results demonstrate that the maximum output voltage is 2.13 V with an input power of -5 dBm. Moreover, the rectifier offers maximum efficiency of 86% for the input power of -5 dBm at given band, which could easily power up wireless sensor networks (WSN) and other small devices sufficiently.

  13. Inward FDI and demand for skills in manufacturing firms in Sweden

    DEFF Research Database (Denmark)

    Bandick, Roger; Hansson, Pär

    2009-01-01

    We observe a substantial increase in foreign ownership in Sweden in the 1990s. Did that have any effect on relative demand for skilled labor? Has technology transfers-often associated with inward FDI-led to an increased demand for skills due to skilled-biased technical change? Are there any groun...

  14. Musculoskeletal work preceding the outward and inward Tkachev on uneven bars in artistic gymnastics.

    Science.gov (United States)

    Kerwin, David G; Irwin, Gareth

    2010-03-01

    Outward facing Tkachevs on uneven bars have been the traditional technique employed by artistic gymnasts. Changes in bar spacing and judging have increased the popularity of the inward version of the skill, in which the gymnast faces towards the low bar as she straddles over the high bar. The purpose of this study was to compare these two variants of the women's Tkachev to examine the influence of the positioning of the low bar on the musculoskeletal demands placed on the gymnast. 3-D DLT reconstructed data sets from digitised video images of straddle Tkachevs performed at the 2000 Sydney Olympics were analysed. Five performances of each variant were compared using kinematics and inverse dynamics. Mean hip and shoulder kinematics were similar for both variants of the Tkachev, but for the inward, gymnasts released later, travelled higher and re-grasped earlier than for the outward. Hip joint moments were similar for both variants while shoulder moments were different. Total musculoskeletal demands were similar for both variants, although the distribution was markedly different with the shoulders contributing positively for the outward and negatively for the inward. Implications for training specificity, along with potential future developments for the inward variant, have been highlighted.

  15. Inward FDI and demand for skills in manufacturing firms in Sweden

    DEFF Research Database (Denmark)

    Bandick, Roger; Hansson, Pär

    2009-01-01

    We observe a substantial increase in foreign ownership in Sweden in the 1990s. Did that have any effect on relative demand for skilled labor? Has technology transfers-often associated with inward FDI-led to an increased demand for skills due to skilled-biased technical change? Are there any grounds...

  16. RF rectifiers for EM power harvesting in a Deep Brain Stimulating device.

    Science.gov (United States)

    Hosain, Md Kamal; Kouzani, Abbas Z; Tye, Susannah; Kaynak, Akif; Berk, Michael

    2015-03-01

    A passive deep brain stimulation (DBS) device can be equipped with a rectenna, consisting of an antenna and a rectifier, to harvest energy from electromagnetic fields for its operation. This paper presents optimization of radio frequency rectifier circuits for wireless energy harvesting in a passive head-mountable DBS device. The aim is to achieve a compact size, high conversion efficiency, and high output voltage rectifier. Four different rectifiers based on the Delon doubler, Greinacher voltage tripler, Delon voltage quadrupler, and 2-stage charge pumped architectures are designed, simulated, fabricated, and evaluated. The design and simulation are conducted using Agilent Genesys at operating frequency of 915 MHz. A dielectric substrate of FR-4 with thickness of 1.6 mm, and surface mount devices (SMD) components are used to fabricate the designed rectifiers. The performance of the fabricated rectifiers is evaluated using a 915 MHz radio frequency (RF) energy source. The maximum measured conversion efficiency of the Delon doubler, Greinacher tripler, Delon quadrupler, and 2-stage charge pumped rectifiers are 78, 75, 73, and 76 % at -5 dBm input power and for load resistances of 5-15 kΩ. The conversion efficiency of the rectifiers decreases significantly with the increase in the input power level. The Delon doubler rectifier provides the highest efficiency at both -5 and 5 dBm input power levels, whereas the Delon quadrupler rectifier gives the lowest efficiency for the same inputs. By considering both efficiency and DC output voltage, the charge pump rectifier outperforms the other three rectifiers. Accordingly, the optimised 2-stage charge pumped rectifier is used together with an antenna to harvest energy in our DBS device.

  17. Rectifying calibration error of Goldmann applanation tonometer is easy!

    Directory of Open Access Journals (Sweden)

    Nikhil S Choudhari

    2014-01-01

    Full Text Available Purpose: Goldmann applanation tonometer (GAT is the current Gold standard tonometer. However, its calibration error is common and can go unnoticed in clinics. Its company repair has limitations. The purpose of this report is to describe a self-taught technique of rectifying calibration error of GAT. Materials and Methods: Twenty-nine slit-lamp-mounted Haag-Streit Goldmann tonometers (Model AT 900 C/M; Haag-Streit, Switzerland were included in this cross-sectional interventional pilot study. The technique of rectification of calibration error of the tonometer involved cleaning and lubrication of the instrument followed by alignment of weights when lubrication alone didn′t suffice. We followed the South East Asia Glaucoma Interest Group′s definition of calibration error tolerance (acceptable GAT calibration error within ±2, ±3 and ±4 mm Hg at the 0, 20 and 60-mm Hg testing levels, respectively. Results: Twelve out of 29 (41.3% GATs were out of calibration. The range of positive and negative calibration error at the clinically most important 20-mm Hg testing level was 0.5 to 20 mm Hg and -0.5 to -18 mm Hg, respectively. Cleaning and lubrication alone sufficed to rectify calibration error of 11 (91.6% faulty instruments. Only one (8.3% faulty GAT required alignment of the counter-weight. Conclusions: Rectification of calibration error of GAT is possible in-house. Cleaning and lubrication of GAT can be carried out even by eye care professionals and may suffice to rectify calibration error in the majority of faulty instruments. Such an exercise may drastically reduce the downtime of the Gold standard tonometer.

  18. Study of 18-Pulse Rectifier Utilizing Hexagon Connected 3-Phase to 9-Phase Transformer

    Directory of Open Access Journals (Sweden)

    Ahmad Saudi Samosir

    2008-04-01

    Full Text Available The 18-pulse converter, using Y or -connected differential autotransformer, is very interesting since it allows natural high power factor correction. The lowest input current harmonic components are the 17th and 19th. The Transformer is designed to feed three six-pulse bridge rectifiers displaced in phase by 200. This paper present a high power factor three-phase rectifier bases on 3-phase to 9-phase transformer and 18-pulse rectifier. The 9-phase polygon-connected transformer followed by 18-pulse diode rectifiers ensures the fundamental concept of natural power factor correction. Simulation results to verify the proposed concept are shown in this paper.

  19. Beta-scorpion toxin effects suggest electrostatic interactions in domain II of voltage-dependent sodium channels. : Electrostatic interactions between segments IIS2, IIS3 and IIS4 of Na+ channel.

    OpenAIRE

    Mantegazza, Massimo; Cestèle, Sandrine

    2005-01-01

    International audience; Beta-scorpion toxins specifically modulate the voltage dependence of sodium channel activation by acting through a voltage-sensor trapping model. We used mutagenesis, functional analysis and the action of beta-toxin as tools to investigate the existence and role in channel activation of molecular interactions between the charged residues of the S2, S3 and S4 segments in domain II of sodium channels. Mutating to arginine the acidic residues of the S2 and S3 transmembran...

  20. Looking inward

    Directory of Open Access Journals (Sweden)

    Arne Melberg

    2011-01-01

    Full Text Available This article presents an analysis of the transformations in the poetics of Rainer M. Rilke. According to the author, the essential impulse for the inception of this evolution had been provided by the encounter of the poet with a series of paintings by French artist Paul Cézanne. The author outlines particular traits in Rilkean poetic variants of modernism: the poet, drawing inspiration from the very same sources as many of his contemporaries (such as, for example, cubists, proposed his own conception of a poetic language. The most important element that constitutes a poem and a poetic image is the rhythm, the fundamental component in the organization of the text. Painterly “overlapping” of planes in a poem becomes thus a kind of a “breath” to take, that opens up a poem to the infinity underlined in the subject. From the experience gained in the visual arts concerning the “attitude and insight”, in turn, a poem attempts to organize a new arrangement for the presented space — ambiguous and in a constant movement.

  1. Self-Organization and Heating by Inward Diffusion in Magnetospheric Plasmas

    CERN Document Server

    Sato, N; Kawazura, Y

    2015-01-01

    Through the process of inward diffusion, a strongly localized clump of plasma is created in a magnetosphere. The creation of the density gradient, instead of the usual flattening by a diffusion process, can be explained by the topological constraints given by the adiabatic invariants of magnetized particles. After developing a canonical formalism for the standard guiding center dynamics in a dipole magnetic field, we complete our attempt to build a statistical mechanics on a constrained phase space by discussing the construction principles of the associated diffusion operator. We then investigate the heating mechanism associated with inward diffusion: as particles move toward regions of higher magnetic field, they experience preferential heating of the perpendicular (with respect to the magnetic field) temperature in order to preserve the magnetic moment. A relationship between conservation of bounce action and temperature isotropy emerged. We further show that this behavior is scaled by the diffusion paramet...

  2. Displacement Pumping of Liquids Radially Inward on Centrifugal Microfluidic Platforms in Motion

    Directory of Open Access Journals (Sweden)

    Eric D. Salin

    2011-12-01

    Full Text Available We describe two novel centrifugal microfluidic platform designs that enable passive pumping of liquids radially inward while the platform is in motion. The first design uses an immiscible liquid to displace an aqueous solution back towards the center of the platform, while the second design uses an arbitrary pumping liquid with a volume of air between it and the solution being pumped. Both designs demonstrated the ability to effectively pump 55% to 60% of the solution radially inward at rotational frequencies as low as 400 rpm (6.7 Hz to 700 rpm (11.7 Hz. The pumping operations reached completion within 120 s and 400 s respectively. These platform designs for passive pumping of liquids do not require moving parts or complex fabrication techniques. They offer great potential for increasing the number of sequential operations that can be performed on centrifugal microfluidic platforms, thereby reducing a fundamental limitation often associated with these platforms.

  3. State Based Factors Affecting inward FDI Employment in the U.S. Economy

    Directory of Open Access Journals (Sweden)

    Lucyna Kornecki

    2016-01-01

    Full Text Available This empirical research investigates state based factors affecting the inward FDI employment among fifty states of the United States, uses annual data for the period of time from 1997 to 2007 and identifies several state-specific determinants of FDI employment. The results indicate that the major factors exerting positive impact on inward US FDI employment are: real wages, infrastructure, unionization level, educational attainment, FDI stock and manufacturing density. In addition, the results show that gross state product growth rate, real per capita taxes and share of scientists and engineers have negative impact on FDI employment. Our findings indicate the importance of selected variables in evaluating the effects of FDI flow.

  4. Can turned inward patella predict an excess of femoral anteversion during gait in spastic diplegic children?

    Science.gov (United States)

    Simon, Anne-Laure; Presedo, Ana; Ilharreborde, Brice; Mallet, Cindy; Mazda, Keyvan; Penneçot, Georges-François

    2014-06-01

    Determining patellar orientation in the transverse plane during observational gait analysis is a fundamental aspect of physical examinations. Many physicians consider that an abnormal position of the patella in the transverse planes is only explained by a rotational abnormality of the proximal femur. A total of 188 spastic diplegic children with cerebral palsy were reviewed (376 lower limbs). The physical examination included observation of patellar orientation at midstride and measuring femoral anteversion (FA). All patients also underwent 3-dimensional (3D) computerized gait analysis of pelvic and hip rotation kinematics. Observational gait analysis and videotapes found 103 children (206 lower limbs) with inturned patella at midstance. Kinematic data from 3D gait analysis showed that the visual impression of turned inward patella was erroneous in 48 limbs. Of the remaining 158 lower limbs, 117 (74%) exhibited excessive FA and 41 (26%) did not. Of the 117 with excessive FA, kinematics showed only 66 (56%) with excessive internal hip rotation (with or without excessive internal pelvic rotation). Of the 41 lower limbs without excessive FA, 25 were explained by excessive internal pelvic rotation and 16 were explained by excessive internal hip rotation (isolated spasticity and/or contracture of internal rotator muscles). Turned inward patella was caused by isolated excessive internal pelvic rotation in 48%, excessive internal hip rotation in 35% (including 44 cases with excessive FA and 12 cases with isolated spasticity and/or contracture of internal hip rotators), and excessive internal hip rotation combined with excessive internal pelvic rotation in 17%. Excessive FA was not the only cause of turned inward patella gait and could not explain this gait anomaly by itself. Excessive internal pelvic rotation was the most frequent cause of turned inward patella gait. Level IV.

  5. Two phase, inward-then-outward migration of Jupiter and Saturn in the gaseous Solar Nebula

    CERN Document Server

    Pierens, Arnaud

    2011-01-01

    It has recently been shown that the terrestrial planets and asteroid belt can be reproduced if the giant planets underwent an inward-then-outward migration (the "Grand Tack"; Walsh et al 2011). Inward migration occurs when Jupiter opens a gap and type II migrates inward. The planets "tack" and migrate outward when Saturn reaches the gap-opening mass and is caught in the 3:2 resonance with Jupiter. The aim is to test the viability of the Grand Tack model and to study the dynamical evolution of Jupiter and Saturn during their growth from 10 Earth masses cores. We have performed numerical simulations using a grid-based hydrodynamical code. Most of our simulations assume an isothermal equation of state for the disk but a subset use a fully-radiative version of the code. For an isothermal disk the two phase migration of Jupiter and Saturn is very robust and independent of the mass-growth history of these planets provided the disk is cool enough. For a radiative disk the we find some outcomes with two phase migrati...

  6. The sea anemone Bunodosoma caissarum toxin BcIII modulates the sodium current kinetics of rat dorsal root ganglia neurons and is displaced in a voltage-dependent manner.

    Science.gov (United States)

    Salceda, Emilio; López, Omar; Zaharenko, André J; Garateix, Anoland; Soto, Enrique

    2010-03-01

    Sea anemone toxins bind to site 3 of the sodium channels, which is partially formed by the extracellular linker connecting S3 and S4 segments of domain IV, slowing down the inactivation process. In this work we have characterized the actions of BcIII, a sea anemone polypeptide toxin isolated from Bunodosoma caissarum, on neuronal sodium currents using the patch clamp technique. Neurons of the dorsal root ganglia of Wistar rats (P5-9) in primary culture were used for this study (n=65). The main effects of BcIII were a concentration-dependent increase in the sodium current inactivation time course (IC(50)=2.8 microM) as well as an increase in the current peak amplitude. BcIII did not modify the voltage at which 50% of the channels are activated or inactivated, nor the reversal potential of sodium current. BcIII shows a voltage-dependent action. A progressive acceleration of sodium current fast inactivation with longer conditioning pulses was observed, which was steeper as more depolarizing were the prepulses. The same was observed for other two anemone toxins (CgNa, from Condylactis gigantea and ATX-II, from Anemonia viridis). These results suggest that the binding affinity of sea anemone toxins may be reduced in a voltage-dependent manner, as has been described for alpha-scorpion toxins.

  7. Chronic electroconvulsive stimulation but not chronic restraint stress modulates mRNA expression of voltage-dependent potassium channels Kv7.2 and Kv11.1 in the rat piriform cortex

    DEFF Research Database (Denmark)

    Hjæresen, Marie-Louise; Hageman, Ida; Plenge, Per

    2008-01-01

    The mechanisms by which stress and electroconvulsive therapy exert opposite effects on the course of major depression are not known. Potential candidates might include the voltage-dependent potassium channels. Potassium channels play an important role in maintaining the resting membrane potential...... and controlling neuronal excitability. To explore this hypothesis, we examined the effects of one or several electroconvulsive stimulations and chronic restraint stress (6 h/day for 21 days) on the expression of voltage-dependent potassium channel Kv7.2, Kv11.1, and Kv11.3 mRNA in the rat brain using in situ...... hybridization. Repeated, but not acute, electroconvulsive stimulation increased Kv7.2 and Kv11.1 mRNA levels in the piriform cortex. In contrast, restraint stress had no significant effect on mRNA expression of Kv7.2, Kv11.1, or Kv11.3 in any of the brain regions examined. Thus, it appears that the investigated...

  8. 2015 NOAA Ortho-rectified Mosaic of Ortho-rectified Below Mean High Water Color Mosaic of Jacksonville, Florida: Integrated Ocean and Coastal Mapping Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. The effects of outward forced convective flow on inward diffusion of potassium across human dentin.

    Science.gov (United States)

    Pashley, David H; Agee, Kelli; Zhang, Yi; Smith, Anita; Tavss, Edward A; Gambogi, Robert J

    2002-08-01

    To measure the inward flux of potassium across human dentin disks, in vitro, in the absence and then in the presence of a simulated pulpal pressure (PP), before and after brushing with two desensitizing dentifrices. Dentin discs were made from extracted unerupted third molars and etched with 6% citric acid to remove the smear layers. The hydraulic conductance (Lp or outward fluid movement) of the discs was measured before and after brushing for 2 minutes with two desensitizing dentifrices, Colgate Sensitive Maximum Strength or Sensodyne Fresh Mint, both dentifrices containing 5% potassium nitrate. The potassium flux was measured at a pressure of 0 cm H2O, and a simulated pulpal pressure of 20 cm H2O. The results showed the Colgate-brushed specimens had lower Lp (P Sensodyne or with saline. The Colgate-brushed specimens had a corresponding lower K+ flux, at a PP = 0 cm H2O, than specimens brushed with saline, but were not significantly different than specimens brushed with Sensodyne dentifrice. However, when the pressure was increased from 0 to 20 cm H2O, to simulate outward dentin fluid pressure, there were significant decreases in K+ flux across all three treatment groups, but the K+ flux of the Colgate-brushed specimens were affected the least, resulting in the Colgate-brushed specimens having significantly (P Sensodyne dentifrice-brushed groups. The magnitude of reduction in K+ flux in going from 0 cm H2O to 20 cm H2O was demonstrated to be linearly related to the magnitude of the Lp of the brushed specimens. Hence, a small Lp corresponded to a small reduction in K+ flux, and a correspondingly large K+ flux at 20 cm H2O. An explanation of this phenomenon is that a decrease in the Lp of dentin, produced by brushing, corresponds to a decreased outward dentin fluid flow. This lowers the outward K+ convective flow and also lowers the inward K+ diffusion. However, since the decrease of the outward K+ convective flow is greater than the decrease of the inward K

  10. Powers of Traction Rectifier Substation of DC ELectric Railways 3kV

    Directory of Open Access Journals (Sweden)

    Josef Palecek

    2004-01-01

    Full Text Available The article states main principles of dimensioning of traction supply stations DC traction current system. it also provides detailed results of the traction rectifier substation Ostrava-Svinov load measurement. The measured valued are subsequently used for calculation of characteristic coefficients, whitch make it possible to dimension rectifier groups.

  11. Three-phase diode rectifiers with low harmonics current injection methods

    CERN Document Server

    Pejovic, Predrag

    2007-01-01

    Presents results of numerous research papers in the area of current injection based rectifiers. This book discusses the principles of current injection, followed by an analysis of various magnetic current injection devices. It concludes with a chapter where the results are generalized to three-phase full-bridge thyristor rectifiers.

  12. A Novel Current-Mode Full-Wave Rectifier Based on One CDTA and Two Diodes

    Directory of Open Access Journals (Sweden)

    F. Khateb

    2010-09-01

    Full Text Available Precision rectifiers are important building blocks for analog signal processing. The traditional approach based on diodes and operational amplifiers (OpAmps exhibits undesirable effects caused by limited OpAmp slew rate and diode commutations. In the paper, a full-wave rectifier based on one CDTA and two Schottky diodes is presented. The PSpice simulation results are included.

  13. Three Phase Six-Switch PWM Buck Rectifier with Power Factor Improvement

    DEFF Research Database (Denmark)

    Zafar Ullah Khan, M; Mohsin Naveed, M.; Hussain, Dil Muhammad Akbar

    2013-01-01

    Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, Three Phase Six-Switch PWM Buck Rectifier[1] is presented which operates at nearly unity power factor and provides...

  14. Three Phase Six-Switch PWM Buck Rectifier with Power Factor Improvement

    DEFF Research Database (Denmark)

    Zafar Ullah Khan, M; Mohsin Naveed, M.; Hussain, Dil Muhammad Akbar

    2013-01-01

    Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, Three Phase Six-Switch PWM Buck Rectifier[1] is presented which operates at nearly unity power factor and provid...

  15. Self-Biased Differential Rectifier with Enhanced Dynamic Range for Wireless Powering

    KAUST Repository

    Ouda, Mahmoud H.

    2016-08-29

    A self-biased, cross-coupled, differential rectifier is proposed with enhanced power-conversion efficiency over an extended range of input power. A prototype is designed for UHF 433MHz RF power-harvesting applications and is implemented using 0.18μm CMOS technology. The proposed rectifier architecture is compared to the conventional cross-coupled rectifier. It demonstrates an improvement of more than 40% in the rectifier power conversion efficiency (PCE) and an input power range extension of more than 50% relative to the conventional crosscoupled rectifier. A sensitivity of -15.2dBm (30μW) input power for 1V output voltage and a peak power-conversion efficiency of 65% are achieved for a 50kω load. © 2004-2012 IEEE.

  16. Effect of temperature on rectified diffusion during ultrasound-induced heating.

    Science.gov (United States)

    Webb, Ian R; Payne, Stephen J; Coussios, Constantin-C

    2011-11-01

    Experimental observations of delayed-onset cavitation during ultrasound insonation have been suggested as being caused by a change in the size distribution of the bubble population due to rectified diffusion. To investigate this hypothesis, a single bubble model is used here to explore the effect of heating and the subsequent elevated temperatures on the rectified diffusion process. Numerical solution of the model, which includes the temperature dependences of seven relevant physical parameters, allows quantification of the change in the pressure threshold for rectified diffusion, as well as the importance of the bulk liquid saturation concentration in determining bubble evolution. Although elevated temperatures and liquid supersaturation reduce the rectified diffusion threshold, it remains coincident with the inertial cavitation thresholds at submicron bubble sizes at all temperatures. This observation suggests that changes in the nucleation environment, rather than bubble growth due to rectified diffusion, is a more likely cause of delayed-onset cavitation events.

  17. Voltage mode electronically tunable full-wave rectifier

    Science.gov (United States)

    Petrović, Predrag B.; Vesković, Milan; Đukić, Slobodan

    2017-01-01

    The paper presents a new realization of bipolar full-wave rectifier of input sinusoidal signals, employing one MO-CCCII (multiple output current controlled current conveyor), a zero-crossing detector (ZCD), and one resistor connected to fixed potential. The circuit provides the operating frequency up to 10 MHz with increased linearity and precision in processing of input voltage signal, with a very low harmonic distortion. The errors related to the signal processing and errors bound were investigated and provided in the paper. The PSpice simulations are depicted and agree well with the theoretical anticipation. The maximum power consumption of the converter is approximately 2.83 mW, at ±1.2 V supply voltages.

  18. Ordered Mesostructured CdS Nanowire Arrays with Rectifying Properties

    Directory of Open Access Journals (Sweden)

    Yuan Na

    2009-01-01

    Full Text Available Abstract Highly ordered mesoporous CdS nanowire arrays were synthesized by using mesoporous silica as hard template and cadmium xanthate (CdR2 as a single precursor. Upon etching silica, mesoporous CdS nanowire arrays were produced with a yield as high as 93 wt%. The nanowire arrays were characterized by XRD, N2adsorption, TEM, and SEM. The results show that the CdS products replicated from the mesoporous silica SBA-15 hard template possess highly ordered hexagonal mesostructure and fiber-like morphology, analogous to the mother template. The current–voltage characteristics of CdS nanoarrays are strongly nonlinear and asymmetrical, showing rectifying diode-like behavior.

  19. Stability analysis of direct current control in current source rectifier

    DEFF Research Database (Denmark)

    Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    Current source rectifier with high switching frequency has a great potential for improving the power efficiency and power density in ac-dc power conversion. This paper analyzes the stability of direct current control based on the time delay effect. Small signal model including dynamic behaviors...... of dc link is developed to identify the control plants of grid ac current control and dc current control. Analysis on the poles and zeros under dq frame is carried out. Base on this model, it turns out that the phase lag caused by the time delay can stabilized the grid ac current control while reduces...... the stable region for dc current control. Simulation and experimental results are presented to validate the theoretical analysis....

  20. Measurement of Phase Dependent Impedance for 3-phase Diode Rectifier

    DEFF Research Database (Denmark)

    Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

    2016-01-01

    This paper presents a new method to measure the phase dependent impedance from an experimental set up. Though most of power electronics based system is gradually migrating to IGBT based voltage source converter due to their controllability, the rectifier composed of diode or thyristor components...... are still widely used in AC-DC applications because of their cost effectiveness and reliability. However, these topologies generate harmonic problems in their network due to their switching instant variation caused by the frequency and phase of grid voltage. Hence, a lot of solutions have been proposed...... application. It is found that the phase dependent impedance shows different properties with the impedance profiles, which have been proposed in the research. This paper explains a method to measure the phase dependent impedance profile from an experimental set up. Furthermore, the results are compared...

  1. Hot electron pump: a plasmonic rectifying antenna (Presentation Recording)

    Science.gov (United States)

    Yanik, Ahmet A.; Hossain, Golam I.

    2015-09-01

    Plasmonic nanostructures have been widely explored to improve absorption efficiency of conventional solar cells, either by employing them as a light scatterer, or as a source of local field enhancement. Unavoidable ohmic loss associated with the plasmonic metal nanostructures in visible spectrum, limits the efficiency improvement of photovoltaic devices by employing this local photon density of states (LDOS) engineering approach. Instead of using plasmonic structures as efficiency improving layer, recently, there has been a growing interest in exploring plasmoinc nanoparticle as the active medium for photovoltaic device. By extracting hot electrons that are created in metallic nanoparticles in a non-radiative Landau decay of surface plasmons, many novel plasmonic photovoltaic devices have been proposed. Moreover, these hot electrons in metal nanoparticles promises high efficiency with a spectral response that is not limited by the band gap of the semiconductors (active material of conventional solar cell). In this work, we will show a novel photovoltaic configuration of plasmonic nanoparticle that acts as an antenna by capturing free space ultrahigh frequency electromagnetic wave and rectify them through an ultrafast hot electron pump and eventually inject DC current in the contact of the device. We will introduce a bottom-up quantum mechanical approach model to explain fundamental physical processes involved in this hot electron pump rectifying antenna and it's ultrafast dynamics. Our model is based on non-equilibrium Green's function formalism, a robust theoretical framework to investigate transport and design nanoscale electronic devices. We will demonstrate some fundamental limitations that go the very foundations of quantum mechanics.

  2. Success and failures of inward-looking development in Cuba (1990-2008): opportunities and problems for small farmers

    OpenAIRE

    Botella Rodríguez, Elisa

    2014-01-01

    While the rest of Latin America followed outward-looking policies of agrarian development during the 1990s and early 2000s, Cuba implemented an inward-looking model during this period. In the midst of the most severe crisis in its history, the Special Period, Cuba dramatically shifted from export dependency to inward-looking development. Cuba is a unique case in terms of agricultural development. Cuba’s agricultural development model provoked important transformations in the country’s agricul...

  3. BACE1 modulates gating of KCNQ1 (Kv7.1) and cardiac delayed rectifier KCNQ1/KCNE1 (IKs).

    Science.gov (United States)

    Agsten, Marianne; Hessler, Sabine; Lehnert, Sandra; Volk, Tilmann; Rittger, Andrea; Hartmann, Stephanie; Raab, Christian; Kim, Doo Yeon; Groemer, Teja W; Schwake, Michael; Alzheimer, Christian; Huth, Tobias

    2015-12-01

    KCNQ1 (Kv7.1) proteins form a homotetrameric channel, which produces a voltage-dependent K(+) current. Co-assembly of KCNQ1 with the auxiliary β-subunit KCNE1 strongly up-regulates this current. In cardiac myocytes, KCNQ1/E1 complexes are thought to give rise to the delayed rectifier current IKs, which contributes to cardiac action potential repolarization. We report here that the type I membrane protein BACE1 (β-site APP-cleaving enzyme 1), which is best known for its detrimental role in Alzheimer's disease, but is also, as reported here, present in cardiac myocytes, serves as a novel interaction partner of KCNQ1. Using HEK293T cells as heterologous expression system to study the electrophysiological effects of BACE1 and KCNE1 on KCNQ1 in different combinations, our main findings were the following: (1) BACE1 slowed the inactivation of KCNQ1 current producing an increased initial response to depolarizing voltage steps. (2) Activation kinetics of KCNQ1/E1 currents were significantly slowed in the presence of co-expressed BACE1. (3) BACE1 impaired reconstituted cardiac IKs when cardiac action potentials were used as voltage commands, but interestingly augmented the IKs of ATP-deprived cells, suggesting that the effect of BACE1 depends on the metabolic state of the cell. (4) The electrophysiological effects of BACE1 on KCNQ1 reported here were independent of its enzymatic activity, as they were preserved when the proteolytically inactive variant BACE1 D289N was co-transfected in lieu of BACE1 or when BACE1-expressing cells were treated with the BACE1-inhibiting compound C3. (5) Co-immunoprecipitation and fluorescence recovery after photobleaching (FRAP) supported our hypothesis that BACE1 modifies the biophysical properties of IKs by physically interacting with KCNQ1 in a β-subunit-like fashion. Strongly underscoring the functional significance of this interaction, we detected BACE1 in human iPSC-derived cardiomyocytes and murine cardiac tissue and observed

  4. Different inward and outward conduction mechanisms in NaVMs suggested by molecular dynamics simulations.

    Directory of Open Access Journals (Sweden)

    Song Ke

    2014-07-01

    Full Text Available Rapid and selective ion transport is essential for the generation and regulation of electrical signaling pathways in living organisms. Here, we use molecular dynamics (MD simulations with an applied membrane potential to investigate the ion flux of bacterial sodium channel NaVMs. 5.9 µs simulations with 500 mM NaCl suggest different mechanisms for inward and outward flux. The predicted inward conductance rate of ∼27±3 pS, agrees with experiment. The estimated outward conductance rate is 15±3 pS, which is considerably lower. Comparing inward and outward flux, the mean ion dwell time in the selectivity filter (SF is prolonged from 13.5±0.6 ns to 20.1±1.1 ns. Analysis of the Na+ distribution revealed distinct patterns for influx and efflux events. In 32.0±5.9% of the simulation time, the E53 side chains adopted a flipped conformation during outward conduction, whereas this conformational change was rarely observed (2.7±0.5% during influx. Further, simulations with dihedral restraints revealed that influx is less affected by the E53 conformational flexibility. In contrast, during outward conduction, our simulations indicate that the flipped E53 conformation provides direct coordination for Na+. The free energy profile (potential of mean force calculations indicates that this conformational change lowers the putative barriers between sites SCEN and SHFS during outward conduction. We hypothesize that during an action potential, the increased Na+ outward transition propensities at depolarizing potentials might increase the probability of E53 conformational changes in the SF. Subsequently, this might be a first step towards initiating slow inactivation.

  5. French Military Adaptation in the Afghan War: Looking Inward or Outward?

    DEFF Research Database (Denmark)

    Schmitt, Olivier

    2016-01-01

    For some, a specific feature of the French armed forces' adaptation process would be the capacity to look inward instead of outward in order to identify relevant solutions to tactical/doctrinal problems. This article questions such a narrative, and argues that the French armed forces are as quick...... as any to borrow from other countries’ experiences. In order to do so, this article introduces the concept of ‘selective emulation’, and compares the French and German military adaptation processes in Afghanistan. The article argues that there is indeed something distinctive about French military...... adaptation, but it is not what the fiercest defenders of the French ‘exceptionalism’ usually account for....

  6. Foreign vs. domestic: What determines the origin of Chinese firms’ inward technology licensing?

    DEFF Research Database (Denmark)

    Li-Ying, Jason; Wang, Yuandi

    2012-01-01

    The increasing prominence of cross-border technology sourcing urges us to ask a question: what factors and conditions may influence firms' decisions of sourcing technology domestically or internationally? Research on this topic is scattered in the literature but a comprehensive understanding...... categories of factors that are relevant in this respect: (1) technology supplier’s characteristics; (2) technology seeker’s characteristics; (3) features of technology itself; and (4) external contextual factors. We test our hypotheses based on Chinese firms’ inward technology licensing. We found well...

  7. Paleomagnetic evidence for dynamo activity driven by inward crystallisation of a metallic asteroid

    Science.gov (United States)

    Bryson, James F. J.; Weiss, Benjamin P.; Harrison, Richard J.; Herrero-Albillos, Julia; Kronast, Florian

    2017-08-01

    The direction in which a planetary core solidifies has fundamental implications for the feasibility and nature of dynamo generation. Although Earth's core is outwardly solidifying, the cores of certain smaller planetary bodies have been proposed to inwardly solidify due to their lower central pressures. However, there have been no unambiguous observations of inwardly solidified cores or the relationship between this solidification regime and planetary magnetic activity. To address this gap, we present the results of complimentary paleomagnetic techniques applied to the matrix metal and silicate inclusions within the IVA iron meteorites. This family of meteorites has been suggested to originate from a planetary core that had its overlaying silicate mantle removed by collisions during the early solar system. This process is thought to have produced a molten ball of metal that cooled rapidly and has been proposed to have inwardly solidified. Recent thermal evolution models of such a body predict that it should have generated an intense, multipolar and time-varying dynamo field. This field could have been recorded as a remanent magnetisation in the outer, cool layers of a solid crust on the IVA parent core. We find that the different components in the IVA iron meteorites display a range of paleomagnetic fidelities, depending crucially on the cooling rate of the meteorite. In particular, silicate inclusions in the quickly cooled São João Nepomuceno meteorite are poor paleomagnetic recorders. On the other hand, the matrix metal and some silicate subsamples from the relatively slowly cooled Steinbach meteorite are far better paleomagnetic recorders and provide evidence of an intense (≳100 μT) and directionally varying (exhibiting significant changes on a timescale ≲200 kyr) magnetic field. This is the first demonstration that some iron meteorites record ancient planetary magnetic fields. Furthermore, the observed field intensity, temporal variability and dynamo

  8. Voltage-dependent capacitance behavior and underlying mechanisms in metal-insulator-metal capacitors with Al2O3-ZrO2-SiO2 nano-laminates

    Science.gov (United States)

    Zhu, Bao; Liu, Wen-Jun; Wei, Lei; Ding, Shi-Jin

    2016-04-01

    Nano-laminates consisting of high-permittivity dielectrics and SiO2 have been extensively studied for radio frequency metal-insulator-metal (MIM) capacitors because of their superior voltage linearity and low leakage current. However, there are no reports on the capacitance-voltage (C-V) characteristics at a high sweep voltage range. In this work, an interesting variation in the voltage-dependent capacitance that forms a ‘ω’-like shape is demonstrated for the MIM capacitors with Al2O3/ZrO2/SiO2 nano-laminates. As the thickness ratio of the SiO2 film to the total insulator increases to around 0.15, the C-V curve changes from an upward parabolic shape to a ‘ω’ shape. This can be explained based on the competition between the orientation polarization from SiO2 and the electrode polarization from Al2O3 and ZrO2. When the SiO2 film is very thin, the electrode polarization dominates in the MIM capacitor, generating a positive curvature C-V curve. When the thickness of SiO2 is increased, the orientation polarization is enhanced and thus both polarizations are operating in the MIM capacitors. This leads to the appearance of a multiple domain C-V curve containing positive and negative curvatures. Therefore, good consistency between the experimental results and the theoretical simulations is demonstrated. Such voltage-dependent capacitance behavior is not determined by the stack structure of the insulator, measurement frequency and oscillator voltage, but by the thickness ratio of the SiO2 film to the whole insulator. These findings are helpful to engineer MIM capacitors with good voltage linearity.

  9. Enhanced Rectification Efficiency In Cascaded Ballistic GaAs/AlGaAs Rectifiers

    Science.gov (United States)

    Wieser, U.; Knop, M.; Koop, P.; Kunze, U.; Reuter, D.; Wieck, A. D.

    2007-04-01

    We report on an enhanced efficiency of inertial-ballistic rectification in a cascade of rectifier stages. Each rectifier stage is composed of a pair of current injecting branches which oppositely merge into a central voltage stem. The voltages obtained at both ends of the stem enable to separate inertial-ballistic and mode-controlled rectification. In a cascade composed of two rectifier stages the total inertial-ballistic signal is enhanced compared to the single contributions while the mode-controlled signal is almost unaffected.

  10. Current and Voltage Conveyors in Current- and Voltage-Mode Precision Full-Wave Rectifiers

    Directory of Open Access Journals (Sweden)

    J. Koton

    2011-04-01

    Full Text Available In this paper new versatile precision full-wave rectifiers using current and/or voltage conveyors as active elements and two diodes are presented. The performance of these circuit solutions is analysed and compared to the opamp based precision rectifier. To analyze the behavior of the functional blocks, the frequency dependent RMS error and DC transient value are evaluated for different values of input voltage amplitudes. Furthermore, experimental results are given that show the feasibilities of the conveyor based rectifiers superior to the corresponding operational amplifier based topology.

  11. A 900-2400 MHz AC-DC Rectifier Circuit for Radio Frequency Energy Harvesting

    Directory of Open Access Journals (Sweden)

    Rosli M.A.

    2016-01-01

    Full Text Available This paper presents a 900-2400 MHz AC-DC rectifier circuit for radio frequency (RF energy harvesting. The proposed circuit consists of a rectifier and charge pump. The multi-stage NMOS RF-DC rectifier circuit is designed to convert the AC signal to DC signal while the charge pump helps to amplify the DC amplitude. The proposed circuits are designed and simulated using CMOS 0.13-μm technology. The simulation results show that the proposed circuit able to produce 2.9 V DC voltage at 10 kΩ load with an input voltage of 150 mV.

  12. Research on Passivity Based Controller of Three Phase Voltage Source PWM Rectifier

    Directory of Open Access Journals (Sweden)

    Yin Hongren

    2012-09-01

    Full Text Available Euler-Lagrange (EL model of voltage source PWM rectifier is set up based on its model in synchronous dq coordinates. Passivity based controller is designed on the basis of passivity and EL model of voltage source PWM rectifier. Three switching function are educed by passivity based controller. A switching function is only realized in engineering consequently. Voltage source PWM rectifier using passivity based controller has many advantages, such as simpler structure, low total harmonic distortion, and good disturbance rejection performance. Passivity based control law is proved feasible by simulink simulation.  

  13. Gas giant planets as dynamical barriers to inward-migrating super-Earths

    CERN Document Server

    Izidoro, Andre; Morbidelli, Alessandro; Hersant, Franck; Pierens, Arnaud

    2015-01-01

    Planets of 1-4 times Earth's size on orbits shorter than 100 days exist around 30-50% of all Sun-like stars. In fact, the Solar System is particularly outstanding in its lack of "hot super-Earths" (or "mini-Neptunes"). These planets -- or their building blocks -- may have formed on wider orbits and migrated inward due to interactions with the gaseous protoplanetary disk. Here, we use a suite of dynamical simulations to show that gas giant planets act as barriers to the inward migration of super-Earths initially placed on more distant orbits. Jupiter's early formation may have prevented Uranus and Neptune (and perhaps Saturn's core) from becoming hot super-Earths. Our model predicts that the populations of hot super-Earth systems and Jupiter-like planets should be anti-correlated: gas giants (especially if they form early) should be rare in systems with many hot super-Earths. Testing this prediction will constitute a crucial assessment of the validity of the migration hypothesis for the origin of close-in supe...

  14. Gas Giant Planets as Dynamical Barriers to Inward-Migrating Super-Earths

    Science.gov (United States)

    Morbidelli, Alessandro; Izidoro da Costa, Andre; Raymond, Sean

    2015-08-01

    Planets of 1-4 times Earth’s size on orbits shorter than 100 days exist around 30-50% of all Sun-like stars. In fact, the Solar System is particularly outstanding in its lack of “hot super-Earths” (or “mini-Neptunes”). These planets —or their building blocks—may have formed on wider orbits and migrated inward due to interactions with the gaseous protoplanetary disk. Here, we use a suite of dynamical simulations to show that gas giant planets act as barriers to the inward migration of super-Earths initially placed on more distant orbits. Jupiter’s early formation may have prevented Uranus and Neptune (and perhaps Saturn’s core) from becoming hot super-Earths. Our model predicts that the populations of hot super-Earth systems and Jupiter-like planets should be anti-correlated: gas giants (especially if they form early) should be rare in systems with many hot super-Earths. Testing this prediction will constitute a crucial assessment of the validity of the migration hypothesis for the origin of close-in super-Earths.

  15. Tuning the Outward to Inward Swelling in Lithiated Silicon Nanotubes via Surface Oxide Coating

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiangwei; Luo, Hao; Liu, Yang; He, Yang; Fan, Feifei; Zhang, Ze; Mao, Scott X.; Wang, Chongmin; Zhu, Ting

    2016-09-14

    The electrochemically-induced mechanical degradation hinders the application of Si anodes in advanced lithium-ion batteries. Hollow structures and surface coatings have been often used to mitigate the degradation of Si-based anodes. However, the structural change and degradation mechanism during lithiation/delithiation of hollow Si structures with coatings remain unclear. Here, we combine in situ TEM experiment and chemomechanical modeling to study the electrochemically induced swelling of amorphous-Si (a-Si) nanotubes with different thicknesses of surface SiOx layers. Surprisingly, we find that no inward expansion occurs at the inner surface during lithiation of a-Si nanotubes with native oxides. In contrast, inward expansion can be induced by increasing the thickness of SiOx on the outer surface. Moreover, both the sandwich lithiation mechanism and two-stage lithiation process in a-Si nanotubes remain unchanged with the increasing thickness of surface coatings. Our chemomechanical modeling reveals the mechanical confinement effects in lithiated a-Si nanotubes with and without SiOx coatings. This work not only provides insights into the degradation of nanotube anodes with surface coatings, but also sheds light onto the optimal design of hollow anodes for high-performance lithium-ion batteries.

  16. Inward foreign direct investment and industrial restructuring: micro evidence – the Slovenian firms’ growth model

    Directory of Open Access Journals (Sweden)

    Katja Zajc Kejžar

    2006-12-01

    Full Text Available We examine the impact of inward foreign direct investment (FDI on the growth of local firms in terms of employment and total factor productivity (TFP for the Slovenian manufacturing sector in the 1994-2003 period. The theoretically predicted channels through which inward FDI affects the firm dynamics in a host country prove to be in general significant. First, there is evidence of the direct impact offoreign firms through so-called direct technology transfer as foreign-owned firms have higher growth of TFP compared to domestically-owned firms after controlling for other determinants. Secondly, the entry of foreign firms stimulates the reshuffling of the resources from less to more efficient local firms. The firm selection process is, namely, characterised by the least efficient firms experiencing a drop in their employment growth upon a foreign firm’s entry. Thirdly, regarding the productivity spillover effects from foreign to local firms we provide indirect evidence that they mostly operate through vertical linkages rather than within the same industry.In general, it seems that not all firms are equally able to benefit from foreign firms’ presence and that absorptive capacity plays an important role.

  17. Inward Radial Mixing of Interstellar Water Ices in the Solar Protoplanetary Disk

    Science.gov (United States)

    Vacher, Lionel G.; Marrocchi, Yves; Verdier-Paoletti, Maximilien J.; Villeneuve, Johan; Gounelle, Matthieu

    2016-08-01

    The very wide diversity of asteroid compositions in the main belt suggests significant material transport in the solar protoplanetary disk and hints at the presence of interstellar ices in hydrated bodies. However, only a few quantitative estimations of the contribution of interstellar ice in the inner solar system have been reported, leading to considerable uncertainty about the extent of radial inward mixing in the solar protoplanetary disk 4.56 Ga ago. We show that the pristine CM chondrite Paris contains primary Ca-carbonates whose O-isotopic compositions require an 8%–35% contribution from interstellar water. The presence of interstellar water in Paris is confirmed by its bulk D/H isotopic composition that shows significant D enrichment (D/H = (167 ± 0.2) × 10‑6) relative to the mean D/H of CM chondrites ((145 ± 3) × 10‑6) and the putative D/H of local CM water ((82 ± 1.5) × 10‑6). These results imply that (i) efficient radial mixing of interstellar ices occurred from the outer zone of the solar protoplanetary disk inward and that (ii) chondrites accreted water ice grains from increasing heliocentric distances in the solar protoplanetary disk.

  18. An RF energy harvester system using UHF micropower CMOS rectifier based on a diode connected CMOS transistor.

    Science.gov (United States)

    Shokrani, Mohammad Reza; Khoddam, Mojtaba; Hamidon, Mohd Nizar B; Kamsani, Noor Ain; Rokhani, Fakhrul Zaman; Shafie, Suhaidi Bin

    2014-01-01

    This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18  μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology.

  19. Generalized space vector control for current source inverters and rectifiers

    Directory of Open Access Journals (Sweden)

    Roseline J. Anitha

    2016-06-01

    Full Text Available Current source inverters (CSI is one of the widely used converter topology in medium voltage drive applications due to its simplicity, motor friendly waveforms and reliable short circuit protection. The current source inverters are usually fed by controlled current source rectifiers (CSR with a large inductor to provide a constant supply current. A generalized control applicable for both CSI and CSR and their extension namely current source multilevel inverters (CSMLI are dealt in this paper. As space vector pulse width modulation (SVPWM features the advantages of flexible control, faster dynamic response, better DC utilization and easy digital implementation it is considered for this work. This paper generalizes SVPWM that could be applied for CSI, CSR and CSMLI. The intense computation involved in framing a generalized space vector control are discussed in detail. The algorithm includes determination of band, region, subregions and vectors. The algorithm is validated by simulation using MATLAB /SIMULINK for CSR 5, 7, 13 level CSMLI and for CSR fed CSI.

  20. Wind Solar Hybrid System Rectifier Stage Topology Simulation

    Directory of Open Access Journals (Sweden)

    Anup M. Gakare

    2014-06-01

    Full Text Available This paper presents power-control strategies of a grid-connected hybrid generation system with versatile power transfer. The hybrid system allows maximum utilization of freely available renewable sources like wind and photovoltaic energies. This paper presents a new system configuration of the multi input rectifier stage for a hybrid wind and photovoltaic energy system. This configuration allows the two sources to supply the load simultaneously depending on the availability of the energy sources maximum power from the sun when it is available. An adaptive MPPT algorithm with a standard perturbs and observed method will be used for the Photo Voltaic system. The main advantage of the hybrid system is to give continuous power supply to the load. The gating pulses to the inverter switches are implemented with conventional and fuzzy controller. This hybrid wind-photo voltaic system is modeled in MATLAB/ SIMULINK environment. Simulation circuit is analyzed and results are presented for this hybrid wind and solar energy system.

  1. Finite element modeling of electrically rectified piezoelectric energy harvesters

    Science.gov (United States)

    Wu, P. H.; Shu, Y. C.

    2015-09-01

    Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique.

  2. Graphene ballistic nano-rectifier with very high responsivity

    Science.gov (United States)

    Auton, Gregory; Zhang, Jiawei; Kumar, Roshan Krishna; Wang, Hanbin; Zhang, Xijian; Wang, Qingpu; Hill, Ernie; Song, Aimin

    2016-05-01

    Although graphene has the longest mean free path of carriers of any known electronic material, very few novel devices have been reported to harness this extraordinary property. Here we demonstrate a ballistic nano-rectifier fabricated by creating an asymmetric cross-junction in single-layer graphene sandwiched between boron nitride flakes. A mobility ~200,000 cm2 V-1 s-1 is achieved at room temperature, well beyond that required for ballistic transport. This enables a voltage responsivity as high as 23,000 mV mW-1 with a low-frequency input signal. Taking advantage of the output channels being orthogonal to the input terminals, the noise is found to be not strongly influenced by the input. Hence, the corresponding noise-equivalent power is as low as 0.64 pW Hz-1/2. Such performance is even comparable to superconducting bolometers, which however need to operate at cryogenic temperatures. Furthermore, output oscillations are observed at low temperatures, the period of which agrees with the lateral size quantization.

  3. Remote electrical stimulation by means of implanted rectifiers.

    Directory of Open Access Journals (Sweden)

    Antoni Ivorra

    Full Text Available Miniaturization of active implantable medical devices is currently compromised by the available means for electrically powering them. Most common energy supply techniques for implants--batteries and inductive couplers--comprise bulky parts which, in most cases, are significantly larger than the circuitry they feed. Here, for overcoming such miniaturization bottleneck in the case of implants for electrical stimulation, it is proposed to make those implants act as rectifiers of high frequency bursts supplied by remote electrodes. In this way, low frequency currents will be generated locally around the implant and these low frequency currents will perform stimulation of excitable tissues whereas the high frequency currents will cause only innocuous heating. The present study numerically demonstrates that low frequency currents capable of stimulation can be produced by a miniature device behaving as a diode when high frequency currents, neither capable of thermal damage nor of stimulation, flow through the tissue where the device is implanted. Moreover, experimental evidence is provided by an in vivo proof of concept model consisting of an anesthetized earthworm in which a commercial diode was implanted. With currently available microelectronic techniques, very thin stimulation capsules (diameter <500 µm deliverable by injection are easily conceivable.

  4. 2016 NOAA NGS Ortho-rectified Color Mosaic of Baton Rouge, Louisiana

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. Design and control of an LCL-filter-based three-phase active rectifier

    DEFF Research Database (Denmark)

    Liserre, Marco; Blaabjerg, Frede; Hansen, Steffan

    2005-01-01

    This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized...... by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier...... a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes....

  6. 2012 NOAA Color Ortho-rectified Mosaic of Corpus Christi to Saint Charles Bay, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2011 NOAA Ortho-rectified Mosaic of Texas: Integrated Ocean and Coastal Mapping Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2016 NOAA NGS Ortho-rectified Color Mosaic of Corpus Christi and Port Ingleside, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of St. Paul Island, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2012 NOAA Ortho-rectified Color Mosaic of Sacramento Deep Water Ship Channel, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2012 NOAA Ortho-rectified Near-Infrared Mosaic of Oregon: Lake Umatilla to Clarkson

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2016 NOAA NGS Ortho-rectified Color Mosaic of Skagway, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2016 NOAA NGS Ortho-rectified Color Mosaic of Snug Harbor, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Kenai and Nikiski, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2010 NOAA Ortho-rectified Near-infrared Mosaic of Port Arthur - Beaumont, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2013 NOAA Ortho-rectified Mean High Water Color Mosaic of Louisiana: Timbalier Islandt

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2011 NOAA Ortho-rectified Mosaic of Matagorda Ship Channel, Texas (NODC Accession 0105604(

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2011 NOAA Ortho-rectified Mosaic of Yabucoa, Puerto Rico (NODC Accession 0074381)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2016 NOAA NGS Ortho-rectified Color Mosaic of Cordova, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2012 NOAA Ortho-rectified Color Mosaic of Oregon: Columbia River - Bonneville Dam to Lake Umatilla

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2011 NOAA Ortho-rectified Near-Infrared Mosaic of Isle of Shoals, New Hampshire (MLLW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2011 NOAA Ortho-rectified Color Mosaic of Sewee Bay to Santee River, South Carolina

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. 2011 NOAA Ortho-rectified Mosaic of Colorado River, Texas (NODC Accession 0105604)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  4. 2016 NOAA NGS Ortho-rectified Color Mosaic of St. Paul Island, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Seal Rock to Lopez Rock, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Juneau and Auke Bay, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of CHOCTAWHATCHEE BAY

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of CHOCTAWHATCHEE BAY....

  8. 2011 NOAA Ortho-rectified Color Mosaic of Great Peconic Bay, New York

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2015 NOAA Ortho-rectified Color Mosaic of Delaware River: Marcus Hook to Philadelphia

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2012 NOAA Ortho-rectified Color MHW Mosaic of Washington: Seattle and Lake Washington Ship Canal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2012 NOAA Ortho-rectified Color Mosaic of Oregon: Lake Umatilla to Clarkson

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2015 NOAA NGS Ortho-rectified Mean High Water Color Mosaic of Augusta to Newcastle, Maine

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2011 NOAA Ortho-rectified Color Mosaic of Sewee Bay to Santee River, South Carolina

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2012 NOAA Color MLLW Ortho-rectified Mosaic of Sewee Bay to Santee River, South Carolina

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2011 NOAA Ortho-rectified Near-Infrared Mosaic of Isle of Shoals, New Hampshire (MLLW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of LAKE CHARLES (NODC Accession 0075827)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of LAKE CHARLES. The...

  17. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of LAKE CHARLES

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of LAKE CHARLES. The...

  18. 2012 Color NOAA Ortho-rectified Mosaic of Seadrift to Palacios, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2011 NOAA Ortho-rectified Mosaic of Brownsville Ship Channel, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2015 NOAA Ortho-rectified Color Mosaic of the port of Two Harbors, Minnesota

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Bodega Bay to Shelter Cove, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Pescadero Point to Bodega Bay, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. 2012 NOAA Ortho-rectified Color Mosaic of Sacramento Deep Water Ship Channel, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  4. 2010 NOAA Ortho-rectified Near-infrared Mosaic of Port Arthur - Beaumont, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2013 NOAA Ortho-rectified Color Mosaic of California: Port of Los Angeles and Long Beach

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2009 NOAA Near-Infrared Ortho-rectified Mosaic of Brunswick, Georgia

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2009 NOAA Ortho-rectified Infrared Mosaic of Georgia: Port of Savannah (NODC Accession 0092435)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2012 NOAA NIR Ortho-rectified Mosaic of Oregon: Ports of Longview, Kalama, Vancouver, and Portland

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2011 NOAA Ortho-rectified Mosaic of Various Ports in Penobscot Bay, Maine

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2011 NOAA Ortho-rectified Mosaic of Matagorda Ship Channel, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2014 NOAA Ortho-rectified Color Mosaic of the port of Key West, FL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2012 NOAA Ortho-rectified Color MHW Mosaic of Washington: Seattle and Lake Washington Ship Canal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Grays Harbor and Westport, Washington

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2012 NOAA Ortho-rectified Mosaic of Texas: Trinity Bay, Integrated Ocean and Coastal Mapping Product

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2012 NOAA Color Ortho-rectified Mosaic of Arroyo Colorado, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Skagway, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2009 NOAA Ortho-rectified Infrared Mosaic of Georgia: Port of Savannah

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2009 NOAA Ortho-rectified Near Infrared Mosaic of Georgia: Kings Bay and Fernandina Beach

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2013 NOAA Ortho-rectified Color Mean High Water Mosaic of North San Francisco Bay, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2011 NOAA Color MHW Ortho-rectified Mosaic of Amelia Island and Nassau River, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2011 NOAA Ortho-rectified Mosaic of Intracoastal City, Louisiana (NODC Accession 0075831)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Ketchikan Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. 2011 NOAA Color Ortho-rectified Mosaic of Eastern Lake Michigan

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  4. 2012 NOAA Color MLLW Ortho-rectified Mosaic of Fort Moultrie to Northeast Point, South Carolina

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2010 NOAA Ortho-rectified Color Mosaic of Port Arthur - Beaumont, Texas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  6. 2015 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Ashtabula, Ohio

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2013 NOAA Ortho-rectified Color Mosaic of Intercoastal Waterway - Calcasieu Lake to Vermillion Bay, Louisiana

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Baton Rouge, Louisiana

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of South Slough NERR, Oregon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2016 NOAA NGS Ortho-rectified Color Mosaic of Homer and Seldovia, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  11. 2014 NOAA Ortho-rectified Near-Infrared Mosaic of port of Key West, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2011 NOAA Ortho-rectified Mosaic of Tallaboa, Puerto Rico (NODC Accession 0074381)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Alabama: Eastern Mississippi Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2013 NOAA Ortho-rectified Color Mosaic of Florida: Lake Okeechobee

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2011 NOAA Ortho-rectified Mosaic of Isle of Shoals New Hampshire (MLLW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  16. 2015 NOAA Ortho-rectified Near-Infrared Mosaic of the port of Two Harbors, Minnesota

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2010 NOAA Ortho-rectified Mosaic of Louisiana: Mississippi River - Baton Rouge to Southwest Pass

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2012 NOAA Ortho-rectified Color Mosaic of Redwood City, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  19. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of BEAUMONT, ORANGE, PORT AUTHUR

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of BEAUMONT, ORANGE,...

  20. 2016 NOAA NGS Ortho-rectified Color Mosaic of Ketchikan Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  1. 2012 NOAA Ortho-rectified Color Mosaic of Bremerton and Manchester, Washington

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  2. 2016 NOAA NGS Ortho-rectified Near-Infrared Mosaic of Dillingham, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  3. 2016 NOAA NGS Ortho-rectified Color Mosaic of Valdez, Alaska

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  4. 2011 NOAA Ortho-rectified Mosaic of New Jersey: Cape May to Absecon Inlet

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  5. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of PORT OF GEORGETOWN - CSCAP

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of PORT OF GEORGETOWN...

  6. 2013 NOAA Ortho-rectified Color Mosaic of the port of Panama City, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  7. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Alabama: Eastern Mississippi Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  8. 2013 NOAA Ortho-rectified Color Mosaic of Virginia: Norfolk, Hampton Roads,and Newport News

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  9. 2012 NOAA Near Infrared MLLW Ortho-rectified Mosaic of Amelia Island and Nassau River, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  10. 2011 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of CHOCTAWHATCHEE BAY

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of CHOCTAWHATCHEE BAY....

  11. 2012 NOAA Ortho-rectified Color MLLW Mosaic of coastal Curry County, Oregon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  12. 2012 NOAA Ortho-rectified Color MLLW Mosaic of Lopez Rock to Pescadero Point, California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  13. 2012 NOAA Ortho-rectified Color Mosaic of Oregon: Lake Umatilla to Clarkson

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  14. 2012 NOAA Ortho-rectified Near-Infrared Mosaic of Oregon: Lake Umatilla to Clarkson

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  15. 2010 NOAA Ortho-rectified Mosaic from Color Aerial Imagery of MISSISSIPPI RIVER - LAPLACE TO VENICE

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative of MISSISSIPPI RIVER...

  16. 2011 NOAA Ortho-rectified Mosaic of Galveston, Texas (NODC Accession 0105604)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  17. 2012 NOAA Ortho-rectified Near-Infrared MLLW Mosaic of Alabama: Eastern Mississippi Sound

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  18. 2014 NOAA Ortho-rectified Mosaic of Hurricane Sandy Coastal Impact Area

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles at 0.35m GSD created for NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative in Hurricane Sandy coastal...

  19. 2016 NOAA NGS Ortho-rectified Color Mosaic of Big Carlos Pass, Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...

  20. 2009 NOAA Ortho-rectified RGB Mosaic of Savannah, Georgia (NODC Accession 0092435)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains ortho-rectified mosaic tiles, created as a product from the NOAA Integrated Ocean and Coastal Mapping (IOCM) initiative. The source imagery...