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Sample records for bk channel localization

  1. An alpha-catulin homologue controls neuromuscular function through localization of the dystrophin complex and BK channels in Caenorhabditis elegans.

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    Linu S Abraham

    2010-08-01

    Full Text Available The large conductance, voltage- and calcium-dependent potassium (BK channel serves as a major negative feedback regulator of calcium-mediated physiological processes and has been implicated in muscle dysfunction and neurological disorders. In addition to membrane depolarization, activation of the BK channel requires a rise in cytosolic calcium. Localization of the BK channel near calcium channels is therefore critical for its function. In a genetic screen designed to isolate novel regulators of the Caenorhabditis elegans BK channel, SLO-1, we identified ctn-1, which encodes an α-catulin homologue with homology to the cytoskeletal proteins α-catenin and vinculin. ctn-1 Mutants resemble slo-1 loss-of-function mutants, as well as mutants with a compromised dystrophin complex. We determined that CTN-1 uses two distinct mechanisms to localize SLO-1 in muscles and neurons. In muscles, CTN-1 utilizes the dystrophin complex to localize SLO-1 channels near L-type calcium channels. In neurons, CTN-1 is involved in localizing SLO-1 to a specific domain independent of the dystrophin complex. Our results demonstrate that CTN-1 ensures the localization of SLO-1 within calcium nanodomains, thereby playing a crucial role in muscles and neurons.

  2. BK channel modulators: a comprehensive overview

    DEFF Research Database (Denmark)

    Nardi, Antonio; Olesen, Søren-Peter

    2008-01-01

    channels as a potentially attractive target, the design and synthesis of potent and selective BK modulators continue based on novel chemical ideas. A comprehensive overview of BK channel modulators is therefore timely and important to the current medicinal chemist for review, summary, and classification...... and blockers 4) Marketed and/or investigational drugs with BK-modulating side properties and structural analogues 5) Naturally-occurring BK channel openers and structural analogues 6) Synthetic BK channel openers. This review is intended to provide readers with current opinion on the BK channel as a drug...

  3. BK channel activators and their therapeutic perspectives

    DEFF Research Database (Denmark)

    Bentzen, Bo Hjorth; Olesen, Søren-Peter; Rønn, Lars C B;

    2014-01-01

    The large conductance calcium- and voltage-activated K(+) channel (KCa1.1, BK, MaxiK) is ubiquitously expressed in the body, and holds the ability to integrate changes in intracellular calcium and membrane potential. This makes the BK channel an important negative feedback system linking increases...

  4. Downregulation of BK channel expression in the pilocarpine model of temporal lobe epilepsy

    OpenAIRE

    Pacheco Otalora, Luis F.; Hernandez, Eder F.; Arshadmansab, Massoud F.; rancisco, Sebastian F; Willis, Michael; Ermolinsky, Boris; Zarei, Masoud; Knaus, Hans-Guenther; Garrido-Sanabria, Emilio R.

    2008-01-01

    In the hippocampus, BK channels are preferentially localized in presynaptic glutamatergic terminals including mossy fibers where they are thought to play an important role regulating excessive glutamate release during hyperactive states. Large conductance calcium-activated potassium channels (BK, MaxiK, Slo) have recently been implicated in the pathogenesis of genetic epilepsy. However, the role of BK channels in acquired mesial temporal lobe epilepsy (MTLE) remains unknown. Here we used immu...

  5. BK channels regulate sinoatrial node firing rate and cardiac pacing in vivo.

    Science.gov (United States)

    Lai, Michael H; Wu, Yuejin; Gao, Zhan; Anderson, Mark E; Dalziel, Julie E; Meredith, Andrea L

    2014-11-01

    Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels play prominent roles in shaping muscle and neuronal excitability. In the cardiovascular system, BK channels promote vascular relaxation and protect against ischemic injury. Recently, inhibition of BK channels has been shown to lower heart rate in intact rodents and isolated hearts, suggesting a novel role in heart function. However, the underlying mechanism is unclear. In the present study, we recorded ECGs from mice injected with paxilline (PAX), a membrane-permeable BK channel antagonist, and examined changes in cardiac conduction. ECGs revealed a 19 ± 4% PAX-induced reduction in heart rate in wild-type but not BK channel knockout (Kcnma1(-/-)) mice. The heart rate decrease was associated with slowed cardiac pacing due to elongation of the sinus interval. Action potential firing recorded from isolated sinoatrial node cells (SANCs) was reduced by 55 ± 15% and 28 ± 9% by application of PAX (3 μM) and iberiotoxin (230 nM), respectively. Furthermore, baseline firing rates from Kcnma1(-/-) SANCs were 33% lower than wild-type SANCs. The slowed firing upon BK current inhibition or genetic deletion was due to lengthening of the diastolic depolarization phase of the SANC action potential. Finally, BK channel immunoreactivity and PAX-sensitive currents were identified in SANCs with HCN4 expression and pacemaker current, respectively, and BK channels cloned from SANCs recapitulated similar activation as the PAX-sensitive current. Together, these data localize BK channels to SANCs and demonstrate that loss of BK current decreases SANC automaticity, consistent with slowed sinus pacing after PAX injection in vivo. Furthermore, these findings suggest BK channels are potential therapeutic targets for disorders of heart rate.

  6. Regulation of BK channels by auxiliary γ subunits

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    Jiyuan eZhang

    2014-10-01

    Full Text Available The large-conductance, calcium- and voltage-activated potassium (BK channel has the largest single-channel conductance among potassium channels and can be activated by both membrane depolarization and increases in intracellular calcium concentration. BK channels consist of pore-forming, voltage- and calcium-sensing α subunits, either alone or in association with regulatory subunits. BK channels are widely expressed in various tissues and cells including both excitable and non-excitable cells and display diverse biophysical and pharmacological characteristics. This diversity can be explained in part by posttranslational modifications and alternative splicing of the α subunit, which is encoded by a single gene, KCNMA1, as well as by tissue-specific β subunit modulation. Recently, a leucine-rich repeat-containing membrane protein, LRRC26, was found to interact with BK channels and cause an unprecedented large negative shift (~-140 mV in the voltage dependence of the BK channel activation. LRRC26 allows BK channels to open even at near-physiological calcium concentration and membrane voltage in non-excitable cells. Three LRRC26-related proteins, LRRC52, LRRC55, and LRRC38, were subsequently identified as BK channel modulators. These LRRC proteins are structurally and functionally distinct from the BK channel β subunits and were designated as γ subunits. The discovery of the γ subunits adds a new dimension to BK channel regulation and improves our understanding of the physiological functions of BK channels in various tissues and cell types. Unlike BK channel β subunits, which have been intensively investigated both mechanistically and physiologically, our understanding of the γ subunits is very limited at this stage. This article reviews the structure, modulatory mechanisms, physiological relevance, and potential therapeutic implications of γ subunits as they are currently understood.

  7. Down-regulation of BK channel expression in the pilocarpine model of temporal lobe epilepsy.

    Science.gov (United States)

    Pacheco Otalora, Luis F; Hernandez, Eder F; Arshadmansab, Massoud F; Francisco, Sebastian; Willis, Michael; Ermolinsky, Boris; Zarei, Masoud; Knaus, Hans-Guenther; Garrido-Sanabria, Emilio R

    2008-03-20

    In the hippocampus, BK channels are preferentially localized in presynaptic glutamatergic terminals including mossy fibers where they are thought to play an important role regulating excessive glutamate release during hyperactive states. Large conductance calcium-activated potassium channels (BK, MaxiK, Slo) have recently been implicated in the pathogenesis of genetic epilepsy. However, the role of BK channels in acquired mesial temporal lobe epilepsy (MTLE) remains unknown. Here we used immunohistochemistry, laser scanning confocal microscopy (LSCM), Western immunoblotting and RT-PCR to investigate the expression pattern of the alpha-pore-forming subunit of BK channels in the hippocampus and cortex of chronically epileptic rats obtained by the pilocarpine model of MTLE. All epileptic rats experiencing recurrent spontaneous seizures exhibited a significant down-regulation of BK channel immunostaining in the mossy fibers at the hilus and stratum lucidum of the CA3 area. Quantitative analysis of immunofluorescence signals by LSCM revealed a significant 47% reduction in BK channel immunofluorescent signals in epileptic rats when compared to age-matched non-epileptic control rats. These data correlate with a similar reduction in BK channel protein levels and transcripts in the cortex and hippocampus. Our data indicate a seizure-related down-regulation of BK channels in chronically epileptic rats. Further functional assays are necessary to determine whether altered BK channel expression is an acquired channelopathy or a compensatory mechanism affecting the network excitability in MTLE. Moreover, seizure-mediated BK down-regulation may disturb neuronal excitability and presynaptic control at glutamatergic terminals triggering exaggerated glutamate release and seizures.

  8. Single-channel kinetics of BK (Slo1 channels

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    Yanyan eGeng

    2015-01-01

    Full Text Available Single-channel kinetics has proven a powerful tool to reveal information about the gating mechanisms that control the opening and closing of ion channels. This introductory review focuses on the gating of large conductance Ca2+- and voltage-activated K+ (BK or Slo1 channels at the single-channel level. It starts with single-channel current records and progresses to presentation and analysis of single-channel data and the development of gating mechanisms in terms of discrete state Markov (DSM models. The DSM models are formulated in terms of the tetrameric modular structure of BK channels, consisting of a central transmembrane pore-gate domain (PGD attached to four surrounding transmembrane voltage sensing domains (VSD and a large intracellular cytosolic domain (CTD, also referred to as the gating ring. The modular structure and data analysis shows that the Ca2+ and voltage dependent gating considered separately can each be approximated by 10-state two-tiered models with 5 closed states on the upper tier and 5 open states on the lower tier. The modular structure and joint Ca2+ and voltage dependent gating are consistent with a 50 state two-tiered model with 25 closed states on the upper tier and 25 open states on the lower tier. Adding an additional tier of brief closed (flicker states to the 10-state or 50-state models improved the description of the gating. For fixed experimental conditions a channel would gate in only a subset of the potential number of states. The detected number of states and the correlations between adjacent interval durations are consistent with the tiered models. The examined models can account for the single-channel kinetics and the bursting behavior of gating. Ca2+ and voltage activate BK channels by predominantly increasing the effective opening rate of the channel with a smaller decrease in the effective closing rate. Ca2+ and depolarization thus activate by mainly destabilizing the closed states.

  9. TRPV1 channels are functionally coupled with BK(mSlo1 channels in rat dorsal root ganglion (DRG neurons.

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    Ying Wu

    Full Text Available The transient receptor potential vanilloid receptor 1 (TRPV1 channel is a nonselective cation channel activated by a variety of exogenous and endogenous physical and chemical stimuli, such as temperature (≥42 °C, capsaicin, a pungent compound in hot chili peppers, and allyl isothiocyanate. Large-conductance calcium- and voltage-activated potassium (BK channels regulate the electric activities and neurotransmitter releases in excitable cells, responding to changes in membrane potentials and elevation of cytosolic calcium ions (Ca(2+. However, it is unknown whether the TRPV1 channels are coupled with the BK channels. Using patch-clamp recording combined with an infrared laser device, we found that BK channels could be activated at 0 mV by a Ca(2+ influx through TRPV1 channels not the intracellular calcium stores in submilliseconds. The local calcium concentration around BK is estimated over 10 μM. The crosstalk could be affected by 10 mM BAPTA, whereas 5 mM EGTA was ineffectual. Fluorescence and co-immunoprecipitation experiments also showed that BK and TRPV1 were able to form a TRPV1-BK complex. Furthermore, we demonstrated that the TRPV1-BK coupling also occurs in dosal root ganglion (DRG cells, which plays a critical physiological role in regulating the "pain" signal transduction pathway in the peripheral nervous system.

  10. TRPV1 channels are functionally coupled with BK(mSlo1) channels in rat dorsal root ganglion (DRG) neurons.

    Science.gov (United States)

    Wu, Ying; Liu, Yongfeng; Hou, Panpan; Yan, Zonghe; Kong, Wenjuan; Liu, Beiying; Li, Xia; Yao, Jing; Zhang, Yuexuan; Qin, Feng; Ding, Jiuping

    2013-01-01

    The transient receptor potential vanilloid receptor 1 (TRPV1) channel is a nonselective cation channel activated by a variety of exogenous and endogenous physical and chemical stimuli, such as temperature (≥42 °C), capsaicin, a pungent compound in hot chili peppers, and allyl isothiocyanate. Large-conductance calcium- and voltage-activated potassium (BK) channels regulate the electric activities and neurotransmitter releases in excitable cells, responding to changes in membrane potentials and elevation of cytosolic calcium ions (Ca(2+)). However, it is unknown whether the TRPV1 channels are coupled with the BK channels. Using patch-clamp recording combined with an infrared laser device, we found that BK channels could be activated at 0 mV by a Ca(2+) influx through TRPV1 channels not the intracellular calcium stores in submilliseconds. The local calcium concentration around BK is estimated over 10 μM. The crosstalk could be affected by 10 mM BAPTA, whereas 5 mM EGTA was ineffectual. Fluorescence and co-immunoprecipitation experiments also showed that BK and TRPV1 were able to form a TRPV1-BK complex. Furthermore, we demonstrated that the TRPV1-BK coupling also occurs in dosal root ganglion (DRG) cells, which plays a critical physiological role in regulating the "pain" signal transduction pathway in the peripheral nervous system.

  11. The brain-specific Beta4 subunit downregulates BK channel cell surface expression.

    Science.gov (United States)

    Shruti, Sonal; Urban-Ciecko, Joanna; Fitzpatrick, James A; Brenner, Robert; Bruchez, Marcel P; Barth, Alison L

    2012-01-01

    The large-conductance K(+) channel (BK channel) can control neural excitability, and enhanced channel currents facilitate high firing rates in cortical neurons. The brain-specific auxiliary subunit β4 alters channel Ca(++)- and voltage-sensitivity, and β4 knock-out animals exhibit spontaneous seizures. Here we investigate β4's effect on BK channel trafficking to the plasma membrane. Using a novel genetic tag to track the cellular location of the pore-forming BKα subunit in living cells, we find that β4 expression profoundly reduces surface localization of BK channels via a C-terminal ER retention sequence. In hippocampal CA3 neurons from C57BL/6 mice with endogenously high β4 expression, whole-cell BK channel currents display none of the characteristic properties of BKα+β4 channels observed in heterologous cells. Finally, β4 knock-out animals exhibit a 2.5-fold increase in whole-cell BK channel current, indicating that β4 also regulates current magnitude in vivo. Thus, we propose that a major function of the brain-specific β4 subunit in CA3 neurons is control of surface trafficking.

  12. The brain-specific Beta4 subunit downregulates BK channel cell surface expression.

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    Sonal Shruti

    Full Text Available The large-conductance K(+ channel (BK channel can control neural excitability, and enhanced channel currents facilitate high firing rates in cortical neurons. The brain-specific auxiliary subunit β4 alters channel Ca(++- and voltage-sensitivity, and β4 knock-out animals exhibit spontaneous seizures. Here we investigate β4's effect on BK channel trafficking to the plasma membrane. Using a novel genetic tag to track the cellular location of the pore-forming BKα subunit in living cells, we find that β4 expression profoundly reduces surface localization of BK channels via a C-terminal ER retention sequence. In hippocampal CA3 neurons from C57BL/6 mice with endogenously high β4 expression, whole-cell BK channel currents display none of the characteristic properties of BKα+β4 channels observed in heterologous cells. Finally, β4 knock-out animals exhibit a 2.5-fold increase in whole-cell BK channel current, indicating that β4 also regulates current magnitude in vivo. Thus, we propose that a major function of the brain-specific β4 subunit in CA3 neurons is control of surface trafficking.

  13. BK channels reveal novel phosphate sensitivity in SNr neurons.

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    Juan Juan Ji

    Full Text Available Whether large conductance Ca(2+-activated potassium (BK channels are present in the substantia nigra pars reticulata (SNr is a matter of debate. Using the patch-clamp technique, we examined the functional expression of BK channels in neurons of the SNr and showed that the channels were activated or inhibited by internal high-energy phosphates (IHEPs at positive and negative membrane potentials, respectively. SNr neurons showed membrane potential hyperpolarization under glucose-deprivation conditions which was attenuated by paxilline, a specific BK channel blocker. In addition, Fluo-3 fluorescence recording detected an increase in the level of internal free calcium ([Ca(2+](i during ischemic hyperpolarization. These results confirm that BK channels are present in SNr neurons and indicate that their unique IHEP sensitivity is requisite in neuronal ischemic responses. Bearing in mind that the K(ATP channel blocker tolbutamide also attenuated the hyperpolarization, we suggest that BK channels may play a protective role in the basal ganglia by modulating the excitability of SNr neurons along with K(ATP channels under ischemic stresses.

  14. SHAPING OF ACTION POTENTIALS BY TYPE I AND TYPE II BK CHANNELS

    OpenAIRE

    Jaffe, David B.; Wang, Bin; Brenner, Robert

    2011-01-01

    The BK channel is a Ca2+ and voltage-gated conductance responsible for shaping action potential waveforms in many types of neurons. Type II BK channels are differentiated from type I channels by their pharmacology and slow gating kinetics. The β4 accessory subunit confers type II properties on BK α subunits. Empirically derived properties of BK channels, with and without the β4 accessory subunit, were obtained using a heterologous expression system under physiological ionic conditions. These ...

  15. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification.

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    Alqadah, Amel; Hsieh, Yi-Wen; Schumacher, Jennifer A; Wang, Xiaohong; Merrill, Sean A; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.

  16. Oxidative Stress and Maxi Calcium-Activated Potassium (BK Channels

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    Anton Hermann

    2015-08-01

    Full Text Available All cells contain ion channels in their outer (plasma and inner (organelle membranes. Ion channels, similar to other proteins, are targets of oxidative impact, which modulates ion fluxes across membranes. Subsequently, these ion currents affect electrical excitability, such as action potential discharge (in neurons, muscle, and receptor cells, alteration of the membrane resting potential, synaptic transmission, hormone secretion, muscle contraction or coordination of the cell cycle. In this chapter we summarize effects of oxidative stress and redox mechanisms on some ion channels, in particular on maxi calcium-activated potassium (BK channels which play an outstanding role in a plethora of physiological and pathophysiological functions in almost all cells and tissues. We first elaborate on some general features of ion channel structure and function and then summarize effects of oxidative alterations of ion channels and their functional consequences.

  17. A role for BK channels in heart rate regulation in rodents.

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    Wendy L Imlach

    Full Text Available The heart generates and propagates action potentials through synchronized activation of ion channels allowing inward Na(+ and Ca(2+ and outward K(+ currents. There are a number of K(+ channel types expressed in the heart that play key roles in regulating the cardiac cycle. Large conductance calcium-activated potassium (BK ion channels are not thought to be directly involved in heart function. Here we present evidence that heart rate can be significantly reduced by inhibiting the activity of BK channels. Agents that specifically inhibit BK channel activity, including paxilline and lolitrem B, slowed heart rate in conscious wild-type mice by 30% and 42%, respectively. Heart rate of BK channel knock-out mice (Kcnma1(-/- was not affected by these BK channel inhibitors, suggesting that the changes to heart rate were specifically mediated through BK channels. The possibility that these effects were mediated through BK channels peripheral to the heart was ruled out with experiments using isolated, perfused rat hearts, which showed a significant reduction in heart rate when treated with the BK channel inhibitors paxilline (1 microM, lolitrem B (1 microM, and iberiotoxin (0.23 microM, of 34%, 60%, and 42%, respectively. Furthermore, paxilline was shown to decrease heart rate in a dose-dependent manner. These results implicate BK channels located in the heart to be directly involved in the regulation of heart rate.

  18. A novel BK channel-targeted peptide suppresses sound evoked activity in the mouse inferior colliculus

    Science.gov (United States)

    Scott, L. L.; Brecht, E. J.; Philpo, A.; Iyer, S.; Wu, N. S.; Mihic, S. J.; Aldrich, R. W.; Pierce, J.; Walton, J. P.

    2017-01-01

    Large conductance calcium-activated (BK) channels are broadly expressed in neurons and muscle where they modulate cellular activity. Decades of research support an interest in pharmaceutical applications for modulating BK channel function. Here we report a novel BK channel-targeted peptide with functional activity in vitro and in vivo. This 9-amino acid peptide, LS3, has a unique action, suppressing channel gating rather than blocking the pore of heterologously expressed human BK channels. With an IC50 in the high picomolar range, the apparent affinity is higher than known high affinity BK channel toxins. LS3 suppresses locomotor activity via a BK channel-specific mechanism in wild-type or BK channel-humanized Caenorhabditis elegans. Topical application on the dural surface of the auditory midbrain in mouse suppresses sound evoked neural activity, similar to a well-characterized pore blocker of the BK channel. Moreover, this novel ion channel-targeted peptide rapidly crosses the BBB after systemic delivery to modulate auditory processing. Thus, a potent BK channel peptide modulator is open to neurological applications, such as preventing audiogenic seizures that originate in the auditory midbrain. PMID:28195225

  19. Conserved BK channel-protein interactions reveal signals relevant to cell death and survival.

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    Bernd Sokolowski

    Full Text Available The large-conductance Ca(2+-activated K(+ (BK channel and its β-subunit underlie tuning in non-mammalian sensory or hair cells, whereas in mammals its function is less clear. To gain insights into species differences and to reveal putative BK functions, we undertook a systems analysis of BK and BK-Associated Proteins (BKAPS in the chicken cochlea and compared these results to other species. We identified 110 putative partners from cytoplasmic and membrane/cytoskeletal fractions, using a combination of coimmunoprecipitation, 2-D gel, and LC-MS/MS. Partners included 14-3-3γ, valosin-containing protein (VCP, stathmin (STMN, cortactin (CTTN, and prohibitin (PHB, of which 16 partners were verified by reciprocal coimmunoprecipitation. Bioinformatics revealed binary partners, the resultant interactome, subcellular localization, and cellular processes. The interactome contained 193 proteins involved in 190 binary interactions in subcellular compartments such as the ER, mitochondria, and nucleus. Comparisons with mice showed shared hub proteins that included N-methyl-D-aspartate receptor (NMDAR and ATP-synthase. Ortholog analyses across six species revealed conserved interactions involving apoptosis, Ca(2+ binding, and trafficking, in chicks, mice, and humans. Functional studies using recombinant BK and RNAi in a heterologous expression system revealed that proteins important to cell death/survival, such as annexinA5, γ-actin, lamin, superoxide dismutase, and VCP, caused a decrease in BK expression. This revelation led to an examination of specific kinases and their effectors relevant to cell viability. Sequence analyses of the BK C-terminus across 10 species showed putative binding sites for 14-3-3, RAC-α serine/threonine-protein kinase 1 (Akt, glycogen synthase kinase-3β (GSK3β and phosphoinositide-dependent kinase-1 (PDK1. Knockdown of 14-3-3 and Akt caused an increase in BK expression, whereas silencing of GSK3β and PDK1 had the opposite

  20. Big Potassium (BK) ion channels in biology, disease and possible targets for cancer immunotherapy.

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    Ge, Lisheng; Hoa, Neil T; Wilson, Zechariah; Arismendi-Morillo, Gabriel; Kong, Xiao-Tang; Tajhya, Rajeev B; Beeton, Christine; Jadus, Martin R

    2014-10-01

    The Big Potassium (BK) ion channel is commonly known by a variety of names (Maxi-K, KCNMA1, slo, stretch-activated potassium channel, KCa1.1). Each name reflects a different physical property displayed by this single ion channel. This transmembrane channel is found on nearly every cell type of the body and has its own distinctive roles for that tissue type. The BKα channel contains the pore that releases potassium ions from intracellular stores. This ion channel is found on the cell membrane, endoplasmic reticulum, Golgi and mitochondria. Complex splicing pathways produce different isoforms. The BKα channels can be phosphorylated, palmitoylated and myristylated. BK is composed of a homo-tetramer that interacts with β and γ chains. These accessory proteins provide a further modulating effect on the functions of BKα channels. BK channels play important roles in cell division and migration. In this review, we will focus on the biology of the BK channel, especially its role, and its immune response towards cancer. Recent proteomic studies have linked BK channels with various proteins. Some of these interactions offer further insight into the role that BK channels have with cancers, especially with brain tumors. This review shows that BK channels have a complex interplay with intracellular components of cancer cells and still have plenty of secrets to be discovered.

  1. Cochlear function in mice lacking the BK channel alpha, beta1, or beta4 subunits

    NARCIS (Netherlands)

    Pyott, Sonja J; Meredith, Andrea L; Fodor, Anthony A; Vázquez, Ana E; Yamoah, Ebenezer N; Aldrich, Richard W

    2007-01-01

    Large conductance voltage- and calcium-activated potassium (BK) channels are important for regulating many essential cellular functions, from neuronal action potential shape and firing rate to smooth muscle contractility. In amphibians, reptiles, and birds, BK channels mediate the intrinsic frequenc

  2. BK channels regulate spontaneous action potential rhythmicity in the suprachiasmatic nucleus.

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    Jack Kent

    Full Text Available BACKGROUND: Circadian ( approximately 24 hr rhythms are generated by the central pacemaker localized to the suprachiasmatic nucleus (SCN of the hypothalamus. Although the basis for intrinsic rhythmicity is generally understood to rely on transcription factors encoded by "clock genes", less is known about the daily regulation of SCN neuronal activity patterns that communicate a circadian time signal to downstream behaviors and physiological systems. Action potentials in the SCN are necessary for the circadian timing of behavior, and individual SCN neurons modulate their spontaneous firing rate (SFR over the daily cycle, suggesting that the circadian patterning of neuronal activity is necessary for normal behavioral rhythm expression. The BK K(+ channel plays an important role in suppressing spontaneous firing at night in SCN neurons. Deletion of the Kcnma1 gene, encoding the BK channel, causes degradation of circadian behavioral and physiological rhythms. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that loss of robust behavioral rhythmicity in Kcnma1(-/- mice is due to the disruption of SFR rhythms in the SCN, we used multi-electrode arrays to record extracellular action potentials from acute wild-type (WT and Kcnma1(-/- slices. Patterns of activity in the SCN were tracked simultaneously for up to 3 days, and the phase, period, and synchronization of SFR rhythms were examined. Loss of BK channels increased arrhythmicity but also altered the amplitude and period of rhythmic activity. Unexpectedly, Kcnma1(-/- SCNs showed increased variability in the timing of the daily SFR peak. CONCLUSIONS/SIGNIFICANCE: These results suggest that BK channels regulate multiple aspects of the circadian patterning of neuronal activity in the SCN. In addition, these data illustrate the characteristics of a disrupted SCN rhythm downstream of clock gene-mediated timekeeping and its relationship to behavioral rhythms.

  3. Interacting influence of diuretics and diet on BK channel-regulated K homeostasis

    Science.gov (United States)

    Wen, Donghai; Cornelius, Ryan J.; Sansom, Steven C.

    2014-01-01

    Large conductance, Ca-activated K channels are abundantly located in cells of vasculature, glomerulus and distal nephron, where they are involved in maintaining blood volume, blood pressure and K homeostasis. In mesangial cells and smooth muscle cells of vessels, the BK-α pore associates with BK-β1 subunits and regulates contraction in a Ca-mediated feedback manner. The BK-β1 also resides in connecting tubule cells of the nephron. BK-β1 knockout mice (β1KO) exhibit fluid retention, hypertension, and compromised K handling. The BK-α/β4resides in acid/base transporting intercalated cells (IC) of the distal nephron, where they mediate K secretion in mammals on a high K, alkaline diet. BK-α expression in IC is increased by a high K diet via aldosterone. The BK-β4 subunit and alkaline urine are necessary for the luminal expression and function of BK-α in mouse IC. In distal nephron cells, membrane BK-α expression is inhibited by WNK4 in in vitro expression systems, indicating a role in the hyperkalemic phenotype in patients with familial hyperkalemic hypertension type 2 (FHHt2). β1KO and BK-β4 knockout mice (β4KO) are hypertensive because of exaggerated ENaC-mediated Na retention in an effort to secrete K via only ROMK. BK hypertension is resistant to thiazides and furosemide, and would be more amenable to ENaC and aldosterone inhibiting drugs. Activators of BK-α/β1 or BK-α/β4 might be effective blood pressure lowering agents for a subset of hypertensive patients. Inhibitors of renal BK would effectively spare K in patients with Bartter Syndrome, a renal K wasting disease. PMID:24721651

  4. Current understanding of iberiotoxin-resistant BK channels in the nervous system.

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    Wang, Bin; Jaffe, David B; Brenner, Robert

    2014-01-01

    While most large-conductance, calcium-, and voltage-activated potassium channels (BK or Maxi-K type) are blocked by the scorpion venom iberiotoxin, the so-called "type II" subtype has the property of toxin resistance. This property is uniquely mediated by channel assembly with one member of the BK accessory β subunit family, the neuron-enriched β4 subunit. This review will focus on current understanding of iberiotoxin-resistant, β4-containing BK channel properties and their function in the CNS. Studies have shown that β4 dramatically promotes BK channel opening by shifting voltage sensor activation to more negative voltage ranges, but also slows activation to timescales that theoretically preclude BK ability to shape action potentials (APs). In addition, β4 membrane trafficking is regulated through an endoplasmic retention signal and palmitoylation. More recently, the challenge has been to understand the functional role of the iberiotoxin-resistant BK subtype utilizing computational modeling of neurons and neurophysiological approaches. Utilizing iberiotoxin-resistance as a footprint for these channels, they have been identified in dentate gyrus granule neurons and in purkinje neurons of the cerebellum. In these neurons, the role of these channels is largely consistent with slow-gated channels that reduce excitability either through an interspike conductance, such as in purkinje neurons, or by replacing fast-gating BK channels that otherwise facilitate high frequency AP firing, such as in dentate gyrus neurons. They are also observed in presynaptic mossy fiber terminals of the dentate gyrus and posterior pituitary terminals. More recent studies suggest that β4 subunits may also be expressed in some neurons lacking iberiotoxin-resistant BK channels, such as in CA3 hippocampus neurons. Ongoing research using novel, specific blockers and agonists of BK/β4, and β4 knockout mice, will continue to move the field forward in understanding the function of these

  5. Current understanding of iberiotoxin-resistant BK channels in the nervous system

    Directory of Open Access Journals (Sweden)

    Bin eWang

    2014-10-01

    Full Text Available While most large-conductance, calcium- and voltage-activated potassium channels (BK or Maxi-K type are blocked by the scorpion venom iberiotoxin, the so-called type II subtype has the property of toxin resistance. This property is uniquely mediated by channel assembly with one member of the BK accessory β subunit family, the neuron-enriched β4 subunit. This review will focus on current understanding of iberiotoxin-resistant, β4-containing BK channel properties and their function in the CNS. Studies have shown that β4 dramatically promotes BK channel opening by shifting voltage sensor activation to more negative voltage ranges, but also slows activation to timescales that theoretically preclude BK ability to shape action potentials (APs. In addition, β4 membrane trafficking is regulated through an endoplasmic retention signal and palmitoylation. More recently, the challenge has been to understand the functional role of the iberiotoxin-resistant BK subtype utilizing computational modeling of neurons and neurophysiological approaches. Utilizing iberiotoxin-resistance as a footprint for these channels, they have been identified in dentate gyrus granule neurons and in purkinje neurons of the cerebellum. In these neurons, the role of these channels is largely consistent with slow-gated channels that reduce excitability either through an interspike conductance, such as in purkinje neurons, or by replacing fast-gating BK channels that otherwise facilitate high frequency AP firing, such as in dentate gyrus neurons. They are also observed in presynaptic mossy fiber terminals of the dentate gyrus and posterior pituitary terminals. More recent studies suggest that β4 subunits may also be expressed in some neurons lacking iberiotoxin-resistant BK channels, such as in CA3 hippocampus neurons. Ongoing research using novel, specific blockers and agonists of BK/β4, and β4 knockout mice, will continue to move the field forward in understanding the

  6. Current understanding of iberiotoxin-resistant BK channels in the nervous system

    OpenAIRE

    Bin eWang; Jaffe, David B.; Robert eBrenner

    2014-01-01

    While most large-conductance, calcium- and voltage-activated potassium channels (BK or Maxi-K type) are blocked by the scorpion venom iberiotoxin, the so-called type II subtype has the property of toxin resistance. This property is uniquely mediated by channel assembly with one member of the BK accessory β subunit family, the neuron-enriched β4 subunit. This review will focus on current understanding of iberiotoxin-resistant, β4-containing BK channel properties and their function in the CNS. ...

  7. 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...

  8. Hair cell BK channels interact with RACK1, and PKC increases its expression on the cell surface by indirect phosphorylation

    OpenAIRE

    Surguchev, Alexei; Bai, Jun-Ping; Joshi, Powrnima; Navaratnam, Dhasakumar

    2012-01-01

    Large conductance (BK) calcium activated potassium channels (Slo) are ubiquitous and implicated in a number of human diseases including hypertension and epilepsy. BK channels consist of a pore forming α-subunit (Slo) and a number of accessory subunits. In hair cells of nonmammalian vertebrates these channels play a critical role in electrical resonance, a mechanism of frequency selectivity. Hair cell BK channel clusters on the surface and currents increase along the tonotopic axis and contrib...

  9. Adrenaline-induced colonic K+ secretion is mediated by KCa1.1 (BK) channels

    DEFF Research Database (Denmark)

    Sørensen, Mads Vaarby; Sausbier, Matthias; Ruth, Peter

    2010-01-01

    secretory K(+) channel in the apical membrane of the murine distal colon. The BK channel is responsible for both resting and Ca(2+)-activated colonic K(+) secretion and is up-regulated by aldosterone. Agonists (e.g. adrenaline) that elevate cAMP are potent activators of distal colonic K(+) secretion....... However, the secretory K(+) channel responsible for cAMP-induced K(+) secretion remains to be defined. In this study we used the Ussing chamber to identify adrenaline-induced electrogenic K(+) secretion. We found that the adrenaline-induced electrogenic ion secretion is a compound effect dominated...... by anion secretion and a smaller electrically opposing K(+) secretion. Using tissue from (i) BK wildtype (BK(+/+)) and knockout (BK(/)) and (ii) cystic fibrosis transmembrane regulator (CFTR) wildtype (CFTR(+/+)) and knockout (CFTR(/)) mice we were able to isolate the adrenaline-induced K(+) secretion. We...

  10. Tuning the mechanosensitivity of a BK channel by changing the linker length

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Some large-conductance Ca2+ and voltage-activated K+ (BK) channels are activated by membrane stretch. However, the mechanism of mechano-gating of the BK channels is still not well understood. Previous studies have led to the proposal that the tinker-gating ring complex functions as a passive spring, transducing the force generated by intraceilular Ca2+ to the gate to open the channel. This raises the question as to whether membrane stretch is also transmitted to the gate of mechanosensitive (MS) BK channels via the tinker-gating complex. To study this, we changed the linker length in the stretch-activated BK channel (SAKCaC), and examined the effect of membrane stretch on the gating of the resultant mutant channels. Shortening the tinker increased, whereas extending the tinker reduced, the channel mechanosensitivity both in the presence and in the absence of intracellular Ca2+. However, the voltage and Ca2+ sensitivities were not significantly altered by membrane stretch. Furthermore, the SAKCaC became less sensitive to membrane stretch at relatively high intracellular Ca2+ concentrations or membrane depolarization. These observations suggest that once the channel is in the open-state conformation, tension on the spring is partially released and membrane stretch is less effective. Our results are consistent with the idea that membrane stretch is transferred to the gate via the tinker-gating ring complex of the MS BK channels.

  11. The Brain-Specific Beta4 Subunit Downregulates BK Channel Cell Surface Expression

    OpenAIRE

    Sonal Shruti; Joanna Urban-Ciecko; Fitzpatrick, James A.; Robert Brenner; Bruchez, Marcel P.; Alison L Barth

    2012-01-01

    The large-conductance K(+) channel (BK channel) can control neural excitability, and enhanced channel currents facilitate high firing rates in cortical neurons. The brain-specific auxiliary subunit β4 alters channel Ca(++)- and voltage-sensitivity, and β4 knock-out animals exhibit spontaneous seizures. Here we investigate β4's effect on BK channel trafficking to the plasma membrane. Using a novel genetic tag to track the cellular location of the pore-forming BKα subunit in living cells, we fi...

  12. BK potassium channels control transmitter release at CA3-CA3 synapses in the rat hippocampus.

    Science.gov (United States)

    Raffaelli, Giacomo; Saviane, Chiara; Mohajerani, Majid H; Pedarzani, Paola; Cherubini, Enrico

    2004-05-15

    Large conductance calcium- and voltage-activated potassium channels (BK channels) activate in response to calcium influx during action potentials and contribute to the spike repolarization and fast afterhyperpolarization. BK channels targeted to active zones in presynaptic nerve terminals have been shown to limit calcium entry and transmitter release by reducing the duration of the presynaptic spike at neurosecretory nerve terminals and at the frog neuromuscular junction. However, their functional role in central synapses is still uncertain. In the hippocampus, BK channels have been proposed to act as an 'emergency brake' that would control transmitter release only under conditions of excessive depolarization and accumulation of intracellular calcium. Here we demonstrate that in the CA3 region of hippocampal slice cultures, under basal experimental conditions, the selective BK channel blockers paxilline (10 microM) and iberiotoxin (100 nM) increase the frequency, but not the amplitude, of spontaneously occurring action potential-dependent EPSCs. These drugs did not affect miniature currents recorded in the presence of tetrodotoxin, suggesting that their action was dependent on action potential firing. Moreover, in double patch-clamp recordings from monosynaptically interconnected CA3 pyramidal neurones, blockade of BK channels enhanced the probability of transmitter release, as revealed by the increase in success rate, EPSC amplitude and the concomitant decrease in paired-pulse ratio in response to pairs of presynaptic action potentials delivered at a frequency of 0.05 Hz. BK channel blockers also enhanced the appearance of delayed responses, particularly following the second action potential in the paired-pulse protocol. These results are consistent with the hypothesis that BK channels are powerful modulators of transmitter release and synaptic efficacy in central neurones.

  13. Molecular mechanism underlying β1 regulation in voltage- and calcium-activated potassium (BK) channels.

    Science.gov (United States)

    Castillo, Karen; Contreras, Gustavo F; Pupo, Amaury; Torres, Yolima P; Neely, Alan; González, Carlos; Latorre, Ramon

    2015-04-14

    Being activated by depolarizing voltages and increases in cytoplasmic Ca(2+), voltage- and calcium-activated potassium (BK) channels and their modulatory β-subunits are able to dampen or stop excitatory stimuli in a wide range of cellular types, including both neuronal and nonneuronal tissues. Minimal alterations in BK channel function may contribute to the pathophysiology of several diseases, including hypertension, asthma, cancer, epilepsy, and diabetes. Several gating processes, allosterically coupled to each other, control BK channel activity and are potential targets for regulation by auxiliary β-subunits that are expressed together with the α (BK)-subunit in almost every tissue type where they are found. By measuring gating currents in BK channels coexpressed with chimeras between β1 and β3 or β2 auxiliary subunits, we were able to identify that the cytoplasmic regions of β1 are responsible for the modulation of the voltage sensors. In addition, we narrowed down the structural determinants to the N terminus of β1, which contains two lysine residues (i.e., K3 and K4), which upon substitution virtually abolished the effects of β1 on charge movement. The mechanism by which K3 and K4 stabilize the voltage sensor is not electrostatic but specific, and the α (BK)-residues involved remain to be identified. This is the first report, to our knowledge, where the regulatory effects of the β1-subunit have been clearly assigned to a particular segment, with two pivotal amino acids being responsible for this modulation.

  14. CRL4A(CRBN) E3 ubiquitin ligase restricts BK channel activity and prevents epileptogenesis.

    Science.gov (United States)

    Liu, Jiye; Ye, Jia; Zou, Xiaolong; Xu, Zhenghao; Feng, Yan; Zou, Xianxian; Chen, Zhong; Li, Yuezhou; Cang, Yong

    2014-05-21

    Ion channels regulate membrane excitation, and mutations of ion channels often cause serious neurological disorders including epilepsy. Compared with extensive analyses of channel protein structure and function, much less is known about the fine tuning of channel activity by post-translational modification. Here we report that the large conductance, Ca(2+)- and voltage-activated K(+) (BK) channels are targeted by the E3 ubiquitin ligase CRL4A(CRBN) for polyubiquitination and retained in the endoplasmic reticulum (ER). Inactivation of CRL4A(CRBN) releases deubiquitinated BK channels from the ER to the plasma membrane, leading to markedly enhanced channel activity. Mice with CRL4A(CRBN) mutation in the brain or treated with a CRL4A(CRBN) inhibitor are very sensitive to seizure induction, which can be attenuated by blocking BK channels. Finally, the mutant mice develop spontaneous epilepsy when aged. Therefore, ubiquitination of BK channels before their cell surface expression is an important step to prevent systemic neuronal excitability and epileptogenesis.

  15. KCNMA1 encoded cardiac BK channels afford protection against ischemia-reperfusion injury

    DEFF Research Database (Denmark)

    Soltysinska, Ewa; Bentzen, Bo Hjorth; Barthmes, Maria;

    2014-01-01

    Mitochondrial potassium channels have been implicated in myocardial protection mediated through pre-/postconditioning. Compounds that open the Ca2+- and voltage-activated potassium channel of big-conductance (BK) have a pre-conditioning-like effect on survival of cardiomyocytes after ischemia/rep...

  16. Role of BK channels in the apoptotic volume decrease in native eel intestinal cells

    DEFF Research Database (Denmark)

    Lionetto, Maria Giulia; Giordano, Maria Elena; Calisi, Antonio

    2010-01-01

    of these channels in the Apoptotic Volume Decrease (AVD) of isolated eel enterocytes, and the possible interaction between BK channels and the progression of apoptosis. The detection of apoptosis was performed by confocal microscopy and annexin V and propidium iodide labelling; cell volume changes were monitored...

  17. Ca(2+)-BK channel clusters in olfactory receptor neurons and their role in odour coding.

    Science.gov (United States)

    Bao, Guobin; de Jong, Daniëlle; Alevra, Mihai; Schild, Detlev

    2015-12-01

    Olfactory receptor neurons (ORNs) have high-voltage-gated Ca(2+) channels whose physiological impact has remained enigmatic since the voltage-gated conductances in this cell type were first described in the 1980s. Here we show that in ORN somata of Xenopus laevis tadpoles these channels are clustered and co-expressed with large-conductance potassium (BK) channels. We found approximately five clusters per ORN and twelve Ca(2+) channels per cluster. The action potential-triggered activation of BK channels accelerates the repolarization of action potentials and shortens interspike intervals during odour responses. This increases the sensitivity of individual ORNs to odorants. At the level of mitral cells of the olfactory bulb, odour qualities have been shown to be coded by first-spike-latency patterns. The system of Ca(2+) and BK channels in ORNs appears to be important for correct odour coding because the blockage of BK channels not only affects ORN spiking patterns but also changes the latency pattern representation of odours in the olfactory bulb.

  18. Renovascular BK(Ca) channels are not activated in vivo under resting conditions and during agonist stimulation

    DEFF Research Database (Denmark)

    Magnusson, Linda; Sørensen, Charlotte Mehlin; Braunstein, Thomas Hartig;

    2006-01-01

    of renal vascular BK(Ca) channels by cAMP was investigated by infusing forskolin. Renal blood flow (RBF) was measured in vivo using electromagnetic flowmetry or ultrasonic Doppler. Renal preinfusion of tetraethylammonium (TEA; 3.0 mumol/min) caused a small reduction of baseline RBF, but iberiotoxin (IBT; 0......, but it attenuated the response to ANG II. Coadministration of NS-1619 with TEA or IBT abolished this effect. Forskolin caused renal vasodilation that was not inhibited by IBT. The presence of BK(Ca) channels in the preglomerular vessels was confirmed by immunohistochemistry. Despite their presence......, there is no indication for a major role for BK(Ca) channels in the control of basal renal tone in vivo. Furthermore, BK(Ca) channels do not have a buffering effect on the rat renal vascular responses to ANG II and NE. The fact that NS-1619 attenuates the ANG II response indicates that the renal vascular BK(Ca) channels...

  19. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation.

    Science.gov (United States)

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

    2015-07-01

    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca(2+) bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca(2+) bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action.

  20. Deletion of cytosolic gating ring decreases gate and voltage sensor coupling in BK channels.

    Science.gov (United States)

    Zhang, Guohui; Geng, Yanyan; Jin, Yakang; Shi, Jingyi; McFarland, Kelli; Magleby, Karl L; Salkoff, Lawrence; Cui, Jianmin

    2017-03-06

    Large conductance Ca(2+)-activated K(+) channels (BK channels) gate open in response to both membrane voltage and intracellular Ca(2+) The channel is formed by a central pore-gate domain (PGD), which spans the membrane, plus transmembrane voltage sensors and a cytoplasmic gating ring that acts as a Ca(2+) sensor. How these voltage and Ca(2+) sensors influence the common activation gate, and interact with each other, is unclear. A previous study showed that a BK channel core lacking the entire cytoplasmic gating ring (Core-MT) was devoid of Ca(2+) activation but retained voltage sensitivity (Budelli et al. 2013. Proc. Natl. Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1313433110). In this study, we measure voltage sensor activation and pore opening in this Core-MT channel over a wide range of voltages. We record gating currents and find that voltage sensor activation in this truncated channel is similar to WT but that the coupling between voltage sensor activation and gating of the pore is reduced. These results suggest that the gating ring, in addition to being the Ca(2+) sensor, enhances the effective coupling between voltage sensors and the PGD. We also find that removal of the gating ring alters modulation of the channels by the BK channel's β1 and β2 subunits.

  1. BK Channels Alleviate Lysosomal Storage Diseases by Providing Positive Feedback Regulation of Lysosomal Ca2+ Release.

    Science.gov (United States)

    Cao, Qi; Zhong, Xi Zoë; Zou, Yuanjie; Zhang, Zhu; Toro, Ligia; Dong, Xian-Ping

    2015-05-26

    Promoting lysosomal trafficking represents a promising therapeutic approach for lysosome storage diseases. Efficient Ca(2+) mobilization from lysosomes is important for lysosomal trafficking. Ca(2+) release from lysosomes could generate a negative potential in the lumen to disturb subsequent Ca(2+) release in the absence of counter ion flux. Here we report that lysosomes express big-conductance Ca(2+)-activated potassium (BK) channels that form physical and functional coupling with the lysosomal Ca(2+) release channel, TRPML1. Ca(2+) release via TRPML1 causes BK activation, which in turn facilitates further lysosomal Ca(2+) release and membrane trafficking. Importantly, BK overexpression rescues the impaired TRPML1-mediated Ca(2+) release and abnormal lysosomal storage in cells from Niemann-Pick C1 patients. Therefore, we have identified a lysosomal K(+) channel that provides a positive feedback mechanism to facilitate TRPML1-mediated Ca(2+) release and membrane trafficking. Our findings suggest that upregulating BK may be a potential therapeutic strategy for certain lysosomal storage diseases and common neurodegenerative disorders.

  2. Bimane fluorescence scanning suggests secondary structure near the S3-S4 linker of BK channels.

    Science.gov (United States)

    Semenova, Nina P; Abarca-Heidemann, Karin; Loranc, Eva; Rothberg, Brad S

    2009-04-17

    Gating of large conductance Ca(2+)-activated K(+) channels (BK or maxi-K channels) is controlled by a Ca(2+)-sensor, formed by the channel cytoplasmic C-terminal domain, and a voltage sensor, formed by its S0-S4 transmembrane helices. Here we analyze structural properties of a portion of the BK channel voltage sensing domain, the S3-S4 linker, using fluorescence lifetime spectroscopy. Single residues in the S3-S4 linker region were substituted with cysteine, and the cysteine-substituted mutants were expressed in CHO cells and covalently labeled with the sulfhydryl-reactive fluorophore monobromo-trimethylammonio-bimane (qBBr). qBBr fluorescence is quenched by tryptophan and, to a lesser extent, tyrosine side chains. We found that qBBr fluorescence in several of the labeled cysteine-substituted channels shows position-specific quenching, as indicated by increase of the brief lifetime component of the qBBr fluorescence decay. Quenching was reduced with the mutation W203F (in the S4 segment), suggesting that Trp-203 acts as a quenching group. Our results suggest a working hypothesis for the secondary structure of the BK channel S3-S4 region, and places residues Leu-204, Gly-205, and Leu-206 within the extracellular end of the S4 helix.

  3. Localization of large conductance calcium-activated potassium channels and their effect on calcitonin gene-related peptide release in the rat trigemino-neuronal pathway

    DEFF Research Database (Denmark)

    Wulf-Johansson, H.; Amrutkar, D.V.; Hay-Schmidt, Anders;

    2010-01-01

    pathophysiology. Here we study the expression and localization of BK(Ca) channels and CGRP in the rat trigeminal ganglion (TG) and the trigeminal nucleus caudalis (TNC) as these structures are involved in migraine pain. Also the effect of the BK(Ca) channel blocker iberiotoxin and the BK(Ca) channel opener NS......Large conductance calcium-activated potassium (BK(Ca)) channels are membrane proteins contributing to electrical propagation through neurons. Calcitonin gene-related peptide (CGRP) is a neuropeptide found in the trigeminovascular system (TGVS). Both BK(Ca) channels and CGRP are involved in migraine...

  4. Habituation of reflexive and motivated behaviour in mice with deficient BK channel function

    Directory of Open Access Journals (Sweden)

    Marei eTyplt

    2013-11-01

    Full Text Available Habituation is considered the most basic form of learning. It describes the decrease of a behavioural response to a repeated non-threatening sensory stimulus and therefore provides an important sensory filtering mechanism. While some neuronal pathways mediating habituation are well described, underlying cellular/molecular mechanisms are not yet fully understood. In general, there is an agreement that short-term and long-term habituation are based on different mechanisms. Historically, a distinction has also been made between habituation of motivated versus reflexive behaviour. In recent studies in invertebrates the large conductance voltage- and calcium-activated potassium (BK channel has been implicated to be a key player in habituation by regulating synaptic transmission. Here, we tested mice deficient for the pore forming α-subunit of the BK channel for short-term and long-term habituation of the acoustic startle reflex (reflexive behaviour and of the exploratory locomotor behaviour in the open field box (motivated behaviour. Short-term habituation of startle was completely abolished in the BK knock-out mice, whereas neither long-term habituation of startle nor habituation of motivated behaviour was affected by the BK deficiency. Our results support a highly preserved mechanism for short-term habituation of startle across species that is distinct from long-term habituation mechanisms. It also supports the notion that there are different mechanisms underlying habituation of motivated behaviour versus reflexive behaviour.

  5. Activation of big conductance Ca(2+)-activated K (+) channels (BK) protects the heart against ischemia-reperfusion injury

    DEFF Research Database (Denmark)

    Bentzen, Bo Hjorth; Osadchii, Oleg; Jespersen, Thomas;

    2009-01-01

    complexes, while producing no effect on cardiac K(ATP) channels. The cardioprotective effects of NS11021-induced BK channel activation were studied in isolated, perfused rat hearts subjected to 35 min of global ischemia followed by 120 min of reperfusion. 3 microM NS11021 applied prior to ischemia...... (3 microM) antagonized the protective effect. These findings suggest that tissue damage induced by ischemia and reperfusion can be reduced by activation of cardiac BK channels.......Activation of the large-conductance Ca(2+)-activated K(+) channel (BK) in the cardiac inner mitochondrial membrane has been suggested to protect the heart against ischemic injury. However, these findings are limited by the low selectivity profile and potency of the BK channel activator (NS1619...

  6. A non-cardiomyocyte autonomous mechanism of cardioprotection involving the SLO1 BK channel

    Directory of Open Access Journals (Sweden)

    Andrew P. Wojtovich

    2013-03-01

    Full Text Available Opening of BK-type Ca2+ activated K+ channels protects the heart against ischemia-reperfusion (IR injury. However, the location of BK channels responsible for cardioprotection is debated. Herein we confirmed that openers of the SLO1 BK channel, NS1619 and NS11021, were protective in a mouse perfused heart model of IR injury. As anticipated, deletion of the Slo1 gene blocked this protection. However, in an isolated cardiomyocyte model of IR injury, protection by NS1619 and NS11021 was insensitive to Slo1 deletion. These data suggest that protection in intact hearts occurs by a non-cardiomyocyte autonomous, SLO1-dependent, mechanism. In this regard, an in-situ assay of intrinsic cardiac neuronal function (tachycardic response to nicotine revealed that NS1619 preserved cardiac neurons following IR injury. Furthermore, blockade of synaptic transmission by hexamethonium suppressed cardioprotection by NS1619 in intact hearts. These results suggest that opening SLO1 protects the heart during IR injury, via a mechanism that involves intrinsic cardiac neurons. Cardiac neuronal ion channels may be useful therapeutic targets for eliciting cardioprotection.

  7. NS19504: a novel BK channel activator with relaxing effect on bladder smooth muscle spontaneous phasic contractions.

    Science.gov (United States)

    Nausch, Bernhard; Rode, Frederik; Jørgensen, Susanne; Nardi, Antonio; Korsgaard, Mads P G; Hougaard, Charlotte; Bonev, Adrian D; Brown, William D; Dyhring, Tino; Strøbæk, Dorte; Olesen, Søren-Peter; Christophersen, Palle; Grunnet, Morten; Nelson, Mark T; Rønn, Lars C B

    2014-09-01

    Large-conductance Ca(2+)-activated K(+) channels (BK, KCa1.1, MaxiK) are important regulators of urinary bladder function and may be an attractive therapeutic target in bladder disorders. In this study, we established a high-throughput fluorometric imaging plate reader-based screening assay for BK channel activators and identified a small-molecule positive modulator, NS19504 (5-[(4-bromophenyl)methyl]-1,3-thiazol-2-amine), which activated the BK channel with an EC50 value of 11.0 ± 1.4 µM. Hit validation was performed using high-throughput electrophysiology (QPatch), and further characterization was achieved in manual whole-cell and inside-out patch-clamp studies in human embryonic kidney 293 cells expressing hBK channels: NS19504 caused distinct activation from a concentration of 0.3 and 10 µM NS19504 left-shifted the voltage activation curve by 60 mV. Furthermore, whole-cell recording showed that NS19504 activated BK channels in native smooth muscle cells from guinea pig urinary bladder. In guinea pig urinary bladder strips, NS19504 (1 µM) reduced spontaneous phasic contractions, an effect that was significantly inhibited by the specific BK channel blocker iberiotoxin. In contrast, NS19504 (1 µM) only modestly inhibited nerve-evoked contractions and had no effect on contractions induced by a high K(+) concentration consistent with a K(+) channel-mediated action. Collectively, these results show that NS19504 is a positive modulator of BK channels and provide support for the role of BK channels in urinary bladder function. The pharmacologic profile of NS19504 indicates that this compound may have the potential to reduce nonvoiding contractions associated with spontaneous bladder overactivity while having a minimal effect on normal voiding.

  8. Localization of Ca2+ -activated big-conductance K+ channels in rabbit distal colon

    DEFF Research Database (Denmark)

    Hay-Schmidt, Anders; Grunnet, Morten; Abrahamse, Salomon L

    2003-01-01

    Big-conductance Ca(2+)-activated K(+) channels (BK channels) may play an important role in the regulation of epithelial salt and water transport, but little is known about the expression level and the precise localization of BK channels in epithelia. The aim of the present study was to quantify...... cells. In conclusion, the significant and distinct expression of BK channels in epithelia, combined with their strict regulation, indicate that these channels may play an important role in the overall regulation of salt and water transport....

  9. FMRP regulates neurotransmitter release and synaptic information transmission by modulating action potential duration via BK channels.

    Science.gov (United States)

    Deng, Pan-Yue; Rotman, Ziv; Blundon, Jay A; Cho, Yongcheol; Cui, Jianmin; Cavalli, Valeria; Zakharenko, Stanislav S; Klyachko, Vitaly A

    2013-02-20

    Loss of FMRP causes fragile X syndrome (FXS), but the physiological functions of FMRP remain highly debatable. Here we show that FMRP regulates neurotransmitter release in CA3 pyramidal neurons by modulating action potential (AP) duration. Loss of FMRP leads to excessive AP broadening during repetitive activity, enhanced presynaptic calcium influx, and elevated neurotransmitter release. The AP broadening defects caused by FMRP loss have a cell-autonomous presynaptic origin and can be acutely rescued in postnatal neurons. These presynaptic actions of FMRP are translation independent and are mediated selectively by BK channels via interaction of FMRP with BK channel's regulatory β4 subunits. Information-theoretical analysis demonstrates that loss of these FMRP functions causes marked dysregulation of synaptic information transmission. FMRP-dependent AP broadening is not limited to the hippocampus, but also occurs in cortical pyramidal neurons. Our results thus suggest major translation-independent presynaptic functions of FMRP that may have important implications for understanding FXS neuropathology.

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

    Directory of Open Access Journals (Sweden)

    Michael J Shipston

    2014-08-01

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

  11. BK channel activation by NS11021 decreases excitability and contractility of urinary bladder smooth muscle

    DEFF Research Database (Denmark)

    Layne, Jeffrey J; Nausch, Bernhard; Olesen, Søren-Peter

    2009-01-01

    (o)) and whole cell BK channel currents. The frequency of spontaneous action potentials in UBSM strips was reduced by NS11021 from a control value of 20.9 + or - 5.9 to 10.9 + or - 3.7 per minute. NS11021 also reduced the force of UBSM spontaneous phasic contractions by approximately 50%, and this force...... the frequency of spontaneous action potentials....

  12. Expression of BK Ca channels and the modulatory beta-subunits in the rat and porcine trigeminal ganglion

    DEFF Research Database (Denmark)

    Johansson, Helle Wulf; Hay-Schmidt, Anders; Poulsen, Asser Nyander;

    2009-01-01

    Large conductance calcium-activated potassium (BK(Ca)) channels contribute to electrical impulses, proper signal transmission of information and regulation of neurotransmitter release. Migraine has been proposed to be a trigeminovascular disease involving the sensory trigeminal pathways and the c......Large conductance calcium-activated potassium (BK(Ca)) channels contribute to electrical impulses, proper signal transmission of information and regulation of neurotransmitter release. Migraine has been proposed to be a trigeminovascular disease involving the sensory trigeminal pathways...... and the cerebral arteries. We hypothesize that BK(Ca) channel alpha- and beta-subunits are present in the rat and porcine trigeminal ganglion (TG) thus enabling a role in migraine. BK(Ca) channel mRNA was detected using reverse transcription polymerase chain reaction (RT-PCR) and in situ hybridization. BK(Ca...... revealed beta2- and beta 4-subunit proteins in rat and porcine TG. The present study showed BK(Ca) channel expression in rat and porcine TG. The main modulatory beta-subunits detected in TG of both species were beta2- and beta 4-subunits....

  13. The coupling of acetylcholine-induced BK channel and calcium channel in guinea pig saccular type II vestibular hair cells.

    Science.gov (United States)

    Kong, Wei-Jia; Guo, Chang-Kai; Zhang, Xiao-Wen; Chen, Xiong; Zhang, Song; Li, Guan-Qiao; Li, Zhi-Wang; Van Cauwenberge, Paul

    2007-01-19

    Molecular biological studies and electrophysiological data have demonstrated that acetylcholine (ACh) is the principal cochlear and vestibular efferent neurotransmitter among mammalians. However, the functional roles of ACh in type II vestibular hair cells (VHCs II) among mammalians are still unclear, with the exception of the well-known alpha9-containing nicotinic ACh receptor (alpha9-containing nAChR)-activated small conductance, calcium-dependent potassium current (SK) in cochlear hair cells and frog saccular hair cells. The activation of SK current was necessary for the calcium influx through the alpha9-containing nAChR. Recently, we have demonstrated that ACh-induced big conductance, calcium-dependent potassium current (BK) was present in VHCs II of the vestibular end-organ of guinea pig. In this study, the nature of calcium influx for the activation of ACh-induced BK current in saccular VHCs II of guinea pig was investigated. Following extracellular perfusion of ACh, saccular VHCs II displayed a sustained outward current, which was sensitive to iberiotoxin (IBTX). High concentration of apamin failed to inhibit the current amplitude of ACh-induced outward current. Intracellular application of Cs(+) completely abolished the current evoked by ACh. ACh-induced current was potently inhibited by nifedipine, nimodipine, Cd(2+) and Ni(2+), respectively. The inhibition potency of these four calcium channel antagonists was nimodipine>nifedipine>cadmium>nickel. The L-type Ca(2+) channels agonist, (-)-Bay-K 8644 mimicked the effect of ACh and activated an IBTX-sensitive current. In addition, partial VHCs II displayed a biphasic waveform. In conclusion, the present data showed that in the guinea pig saccular VHCs II, ACh-induced BK channel was coupled with the calcium channel, but not the receptor. The perfusion of ACh will drive the opening of calcium channels; the influx of calcium ions will then activate the BK current.

  14. Neuronal fast activating and meningeal silent modulatory BK channel splice variants cloned from rat

    DEFF Research Database (Denmark)

    Poulsen, Asser Nyander; Jansen-Olesen, Inger; Olesen, Jes

    2011-01-01

    The big conductance calcium-activated K(+) channel (BK) is involved in regulating neuron and smooth muscle cell excitability. Functional diversity of BK is generated by alpha-subunit splice variation and co-expression with beta subunits. Here, we present six different splice combinations cloned...... from rat brain or cerebral vascular/meningeal tissues, of which at least three variants were previously uncharacterized (X1, X2(92), and X2(188)). An additional variant was identified by polymerase chain reaction but not cloned. Expression in Xenopus oocytes showed that the brain-specific X1 variant...... displays reduced current, faster activation, and less voltage sensitivity than the insert-less Zero variant. Other cloned variants Strex and Slo27,3 showed slower activation than Zero. The X1 variant contains sequence inserts in the S1-S2 extracellular loop (8 aa), between intracellular domains RCK1...

  15. BK channel activity determines the extent of cell degeneration after oxygen and glucose deprivation: a study in organotypical hippocampal slice cultures.

    Science.gov (United States)

    Rundén-Pran, E; Haug, F M; Storm, J F; Ottersen, O P

    2002-01-01

    BK channels are voltage- and calcium-dependent potassium channels whose activation tends to reduce cellular excitability. In hippocampal pyramidal cells, BK channels repolarize somatic action potentials, and recent immunogold and electrophysiological analyses have revealed a presynaptic pool of BK channels that can regulate glutamate release. Agents that modulate BK channel activity would therefore be expected to affect cell excitability and neurotransmitter release also under pathological conditions. We have investigated the role of BK potassium channels in a model of ischemia-induced nerve cell degeneration. Organotypical slice cultures of rat hippocampus were exposed to oxygen and glucose deprivation (OGD), and cell death was assessed by the fluorescent dye propidium iodide. OGD induced cell death in the CA1 region and to a lesser extent in CA3. Treatment with the BK channel blockers, paxilline and iberiotoxin, during and after OGD induced increased cell death in CA1 and CA3. Both BK channel blockers also sensitized the relatively resistant granule cells in fascia dentata to OGD. The effect of paxilline and iberiotoxin was evident from 3 h after OGD, indicating a role of BK channels early in the post-ischemic phase or during OGD itself. The BK channel opener, NS1619, turned out to be gliotoxic, and this effect was not counteracted by paxilline and iberiotoxin. Our data show that blockade of BK channels aggravates OGD-induced cell damage and suggest that BK channels act as a kind of 'emergency brake' during and/or after ischemia. Accordingly, the BK channel is a potential molecular target for neuroprotective therapy in stroke.

  16. Phosphorylation of BK channels modulates the sensitivity to hydrogen sulfide (H2S

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    Guzel F. Sitdikova

    2014-11-01

    Full Text Available Introduction: Gases, such as nitric oxide (NO, carbon monoxide (CO or hydrogen sulfide (H2S, termed gasotransmitters, play an increasingly important role in understanding of how electrical signaling of cells is modulated. H2S is well known to act on various ion channels and receptors. In a previous study we reported that H2S increased calcium-activated potassium (BK channel activity. Aims: The goal of the present study is to investigate the modulatory effect of BK channel phosphorylation on the action of H2S on the channel as well as to recalculate and determine the H2S concentrations in aqueous sodium hydrogen sulfide (NaHS solutions.Methods: Single channel recordings of GH3, GH4 and GH4 STREX cells were used to analyze channel open probability, amplitude and open dwell times. H2S was measured with ananion selective electrode. Results: The concentration of H2S produced from NaHS was recalculated taking pH, temperature salinity of the perfusate and evaporation of H2S into account. The results indicate that from a concentration of 300 µM NaHS, only11-13%, i.e. 34-41 µM is effective as H2S in solution. GH3, GH4 and GH4 STREX cells respond differently to phosphorylation. BK channel open probability (Po of all cells lines used was increased by H2S in ATP containing solutions. PKA prevented the action of H2S on channel Po in GH4 and GH4 STREX, but not in GH3 cells. H2S, high significantly increased Po of all PKG pretreated cells. In the presence of PKC, which lowers channel activity, H2S increased channel Po of GH4 and GH4 STREX, but not those of GH3 cells. H2S increased open dwell times of GH3 cells in the absence of ATP significantly. A significant increase of dwell times with H2S was also observed in the presence of okadaic acid.Conclusions: Our results suggest that phosphorylation by PKG primes the channels for H2S activation and indicate that channel phosphorylation plays an important role in the response to H2S.

  17. Functional coupling of TRPV4 channels and BK channels in regulating spontaneous contractions of the guinea pig urinary bladder.

    Science.gov (United States)

    Isogai, Ayu; Lee, Ken; Mitsui, Retsu; Hashitani, Hikaru

    2016-09-01

    We investigated the role of TRPV4 channels (TRPV4) in regulating the contractility of detrusor smooth muscle (DSM) and muscularis mucosae (MM) of the urinary bladder. Distribution of TRPV4 in DSM and MM of guinea-pig bladders was examined by fluorescence immunohistochemistry. Changes in the contractility of DSM and MM bundles were measured using isometric tension recording. Intracellular Ca(2+) dynamics were visualized by Cal-520 fluorescent Ca(2+) imaging, while membrane potential changes were recorded using intracellular microelectrode technique. DSM and MM expressed TRPV4 immunoreactivity. GSK1016790A (GSK, 1 nM), a TRPV4 agonist, evoked a sustained contraction in both DSM and MM associated with a cessation of spontaneous phasic contractions in a manner sensitive to HC-067047 (10 μM), a TRPV4 antagonist. Iberiotoxin (100 nM) and paxilline (1 μM), large conductance Ca(2+)-activated K(+) (BK) channel blockers restored the spontaneous contractions in GSK. The sustained contractions in DSM and MM were reduced by nifedipine (10 μM), a blocker of L-type voltage-dependent Ca(2+) channels (LVDCCs) by about 40 % and by nominally Ca(2+)-free solution by some 90 %. GSK (1 nM) abolished spontaneous Ca(2+) transients, increased basal Ca(2+) levels and also prevented spontaneous action potential discharge associated with DSM membrane hyperpolarization. In conclusion, Ca(2+) influx through TRPV4 appears to activate BK channels to suppress spontaneous contractions and thus a functional coupling of TRPV4 with BK channels may act as a self-limiting mechanism for bladder contractility during its storage phase. Despite the membrane hyperpolarization in GSK, Ca(2+) entry mainly through TRPV4 develops the tonic contraction.

  18. Recombinant Expression and Functional Characterization of Martentoxin: A Selective Inhibitor for BK Channel (α + β4

    Directory of Open Access Journals (Sweden)

    Jie Tao

    2014-04-01

    Full Text Available Martentoxin (MarTX, a 37-residue peptide purified from the venom of East-Asian scorpion (Buthus martensi Karsch, was capable of blocking large-conductance Ca2+-activated K+ (BK channels. Here, we report an effective expression and purification approach for this toxin. The cDNA encoding martentoxin was expressed by the prokaryotic expression system pGEX-4T-3 which was added an enterokinase cleavage site by PCR. The fusion protein (GST-rMarTX was digested by enterokinase to release hetero-expressed toxin and further purified via reverse-phase HPLC. The molecular weight of the hetero-expressed rMarTX was 4059.06 Da, which is identical to that of the natural peptide isolated from scorpion venom. Functional characterization through whole-cell patch clamp showed that rMarTX selectively and potently inhibited the currents of neuronal BK channels (α + β4 (IC50 = 186 nM, partly inhibited mKv1.3, but hardly having any significant effect on hKv4.2 and hKv3.1a even at 10 μM. Successful expression of martentoxin lays basis for further studies of structure-function relationship underlying martentoxin or other potassium-channel specific blockers.

  19. Ethanol modulation of mammalian BK channels in excitable tissues: molecular targets and their possible contribution to alcohol-induced altered behavior

    Directory of Open Access Journals (Sweden)

    Alex M. Dopico

    2014-12-01

    Full Text Available In most tissues, the function of calcium- and voltage-gated potassium (BK channels is modified in response to ethanol concentrations reached in human blood during alcohol intoxication. In general, modification of BK current from ethanol-naïve preparations in response to brief ethanol exposure results from changes in channel open probability without modification of unitary conductance or change in BK protein levels in the membrane. Protracted and/or repeated ethanol exposure, however, may evoke changes in BK expression. The final ethanol effect on BK open probability leading to either BK current potentiation or BK current reduction is determined by an orchestration of molecular factors, including levels of activating ligand (cytosolic calcium, BK subunit composition and posttranslational modifications, and the channel’s lipid microenvironment. These factors seem to allosterically regulate a direct interaction between ethanol and a recognition pocket of discrete dimensions recently mapped to the channel-forming (slo1 subunit. Type of ethanol exposure also plays a role in the final BK response to the drug: in several central nervous system regions (e.g., striatum, primary sensory neurons, and supraoptic nucleus, acute exposure to ethanol reduces neuronal excitability by enhancing BK activity. In contrast, protracted or repetitive ethanol administration may alter BK subunit composition and membrane expression, rendering the BK complex insensitive to further ethanol exposure. In neurohypophysial axon terminals, ethanol potentiation of BK channel activity leads to a reduction in neuropeptide release. In vascular smooth muscle, however, ethanol inhibition of BK current leads to cell contraction and vascular constriction.

  20. Intracellular segment between transmembrane helices S0 and S1 of BK channel α subunit contains two amphipathic helices connected by a flexible loop.

    Science.gov (United States)

    Shi, Pan; Li, Dong; Lai, Chaohua; Zhang, Longhua; Tian, Changlin

    2013-08-02

    The BK channel, a tetrameric potassium channel with very high conductance, has a central role in numerous physiological functions. The BK channel can be activated by intracellular Ca(2+) and Mg(2+), as well as by membrane depolarization. Unlike other tetrameric potassium channels, the BK channel has seven transmembrane helices (S0-S6) including an extra helix S0. The intracellular segment between S0 and S1 (BK-IS1) is essential to BK channel functions and Asp99 in BK-IS1 is reported to be responsible for Mg(2+) coordination. In this study, BK-IS1 (44-113) was over-expressed using a bacterial system and purified in the presence of detergent micelles for multidimensional heteronuclear nuclear magnetic resonance (NMR) structural studies. Backbone resonance assignment and secondary structure analysis showed that BK-IS1 contains two amphipathic helices connected by a 36-residue loop. Amide (1)H-(15)N heteronuclear NOE analysis indicated that the loop is very flexible, while the two amphipathic helices are possibly stabilized through interaction with the membrane. A solution NMR-based titration assay of BK-IS1 was performed with various concentrations of Mg(2+). Two residues (Thr45 and Leu46) with chemical shift changes were observed but no, or very minor, chemical shift difference was observed for Asp99, indicating a possible site for binding divalent ions or other modulation partners.

  1. BKCa and KV channels limit conducted vasomotor responses in rat mesenteric terminal arterioles

    DEFF Research Database (Denmark)

    Hald, Bjørn Olav; Jacobsen, Jens Christian Brings; Braunstein, Thomas Hartig

    2012-01-01

    and inhibition of BK(Ca) channel current in silico increased ¿ by 34% and 32%, respectively. Similarly, inhibition of K(V) channels in vitro (4-aminopyridine, 1 mM) or in silico increased ¿ by 41% and 21%, respectively. Immunofluorescence microscopy demonstrated expression of BK(Ca), Kv1.5, Kv2.1, but not Kv1...

  2. FMRP Regulates Neurotransmitter Release and Synaptic Information Transmission by Modulating Action Potential Duration via BK channels

    Science.gov (United States)

    Deng, Pan-Yue; Rotman, Ziv; Blundon, Jay A.; Cho, Yongcheol; Cui, Jianmin; Cavalli, Valeria; Zakharenko, Stanislav S.; Klyachko, Vitaly A.

    2013-01-01

    SUMMARY Loss of FMRP causes Fragile X syndrome (FXS), but the physiological functions of FMRP remain highly debatable. Here we show that FMRP regulates neurotransmitter release in CA3 pyramidal neurons by modulating action potential (AP) duration. Loss of FMRP leads to excessive AP broadening during repetitive activity, enhanced presynaptic calcium influx and elevated neurotransmitter release. The AP broadening defects caused by FMRP loss have a cell-autonomous presynaptic origin and can be acutely rescued in postnatal neurons. These presynaptic actions of FMRP are translation-independent and are mediated selectively by BK channels via interaction of FMRP with BK channel’s regulatory β4 subunits. Information-theoretical analysis demonstrates that loss of these FMRP functions causes marked dysregulation of synaptic information transmission. FMRP-dependent AP broadening is not limited to the hippocampus, but also occurs in cortical pyramidal neurons. Our results thus suggest major translation-independent presynaptic functions of FMRP that may have important implications for understanding FXS neuropathology. PMID:23439122

  3. BK and Kv3.1 potassium channels control different aspects of deep cerebellar nuclear neurons action potentials and spiking activity.

    Science.gov (United States)

    Pedroarena, Christine M

    2011-12-01

    Deep cerebellar nuclear neurons (DCNs) display characteristic electrical properties, including spontaneous spiking and the ability to discharge narrow spikes at high frequency. These properties are thought to be relevant to processing inhibitory Purkinje cell input and transferring well-timed signals to cerebellar targets. Yet, the underlying ionic mechanisms are not completely understood. BK and Kv3.1 potassium channels subserve similar functions in spike repolarization and fast firing in many neurons and are both highly expressed in DCNs. Here, their role in the abovementioned spiking characteristics was addressed using whole-cell recordings of large and small putative-glutamatergic DCNs. Selective BK channel block depolarized DCNs of both groups and increased spontaneous firing rate but scarcely affected evoked activity. After adjusting the membrane potential to control levels, the spike waveforms under BK channel block were indistinguishable from control ones, indicating no significant BK channel involvement in spike repolarization. The increased firing rate suggests that lack of DCN-BK channels may have contributed to the ataxic phenotype previously found in BK channel-deficient mice. On the other hand, block of Kv3.1 channels with low doses of 4-aminopyridine (20 μM) hindered spike repolarization and severely depressed evoked fast firing. Therefore, I propose that despite similar characteristics of BK and Kv3.1 channels, they play different roles in DCNs: BK channels control almost exclusively spontaneous firing rate, whereas DCN-Kv3.1 channels dominate the spike repolarization and enable fast firing. Interestingly, after Kv3.1 channel block, BK channels gained a role in spike repolarization, demonstrating how the different function of each of the two channels is determined in part by their co-expression and interplay.

  4. Hair cell BK channels interact with RACK1, and PKC increases its expression on the cell surface by indirect phosphorylation.

    Science.gov (United States)

    Surguchev, Alexei; Bai, Jun-Ping; Joshi, Powrnima; Navaratnam, Dhasakumar

    2012-07-15

    Large conductance (BK) calcium activated potassium channels (Slo) are ubiquitous and implicated in a number of human diseases including hypertension and epilepsy. BK channels consist of a pore forming α-subunit (Slo) and a number of accessory subunits. In hair cells of nonmammalian vertebrates these channels play a critical role in electrical resonance, a mechanism of frequency selectivity. Hair cell BK channel clusters on the surface and currents increase along the tonotopic axis and contribute significantly to the responsiveness of these hair cells to sounds of high frequency. In contrast, messenger RNA levels encoding the Slo gene show an opposite decrease in high frequency hair cells. To understand the molecular events underlying this paradox, we used a yeast two-hybrid screen to isolate binding partners of Slo. We identified Rack1 as a Slo binding partner and demonstrate that PKC activation increases Slo surface expression. We also establish that increased Slo recycling of endocytosed Slo is at least partially responsible for the increased surface expression of Slo. Moreover, analysis of several PKC phosphorylation site mutants confirms that the effects of PKC on Slo surface expression are likely indirect. Finally, we show that Slo clusters on the surface of hair cells are also increased by increased PKC activity and may contribute to the increasing amounts of channel clusters on the surface of high-frequency hair cells.

  5. Mice with deficient BK channel function show impaired prepulse inhibition and spatial learning, but normal working and spatial reference memory.

    Directory of Open Access Journals (Sweden)

    Marei Typlt

    Full Text Available Genetic variations in the large-conductance, voltage- and calcium activated potassium channels (BK channels have been recently implicated in mental retardation, autism and schizophrenia which all come along with severe cognitive impairments. In the present study we investigate the effects of functional BK channel deletion on cognition using a genetic mouse model with a knock-out of the gene for the pore forming α-subunit of the channel. We tested the F1 generation of a hybrid SV129/C57BL6 mouse line in which the slo1 gene was deleted in both parent strains. We first evaluated hearing and motor function to establish the suitability of this model for cognitive testing. Auditory brain stem responses to click stimuli showed no threshold differences between knockout mice and their wild-type littermates. Despite of muscular tremor, reduced grip force, and impaired gait, knockout mice exhibited normal locomotion. These findings allowed for testing of sensorimotor gating using the acoustic startle reflex, as well as of working memory, spatial learning and memory in the Y-maze and the Morris water maze, respectively. Prepulse inhibition on the first day of testing was normal, but the knockout mice did not improve over the days of testing as their wild-type littermates did. Spontaneous alternation in the y-maze was normal as well, suggesting that the BK channel knock-out does not impair working memory. In the Morris water maze knock-out mice showed significantly slower acquisition of the task, but normal memory once the task was learned. Thus, we propose a crucial role of the BK channels in learning, but not in memory storage or recollection.

  6. Differential expression of BK channel isoforms and beta-subunits in rat neuro-vascular tissues

    DEFF Research Database (Denmark)

    Poulsen, Asser Nyander; Johansson, Helle Wulf; Hay-Schmidt, Anders;

    2009-01-01

    We investigated the expression of splice variants and beta-subunits of the BK channel (big conductance Ca(2+)-activated K(+) channel, Slo1, MaxiK, K(Ca)1.1) in rat cerebral blood vessels, meninges, trigeminal ganglion among other tissues. An alpha-subunit splice variant X1(+24) was found expressed...... (RT-PCR) in nervous tissue only where also the SS4(+81) variant was dominating with little expression of the short form SS4(0). SS4(+81) was present in some cerebral vessels too. The SS2(+174) variant (STREX) was found in both blood vessels and in nervous tissue. In situ hybridization data supported...... the finding of SS4(+81) and SS2(+174) in vascular smooth muscle and trigeminal ganglion. beta-subunits beta2 and beta4 showed high expression in brain and trigeminal ganglion and some in cerebral vessels while beta1 showed highest expression in blood vessels. beta3 was found only in testis and possibly brain...

  7. Ca2+-activated K+ (BK) channel inactivation contributes to spike broadening during repetitive firing in the rat lateral amygdala.

    Science.gov (United States)

    Faber, E S Louise; Sah, Pankaj

    2003-10-15

    In many neurons, trains of action potentials show frequency-dependent broadening. This broadening results from the voltage-dependent inactivation of K+ currents that contribute to action potential repolarisation. In different neuronal cell types these K+ currents have been shown to be either slowly inactivating delayed rectifier type currents or rapidly inactivating A-type voltage-gated K+ currents. Recent findings show that inactivation of a Ca2+-dependent K+ current, mediated by large conductance BK-type channels, also contributes to spike broadening. Here, using whole-cell recordings in acute slices, we examine spike broadening in lateral amygdala projection neurons. Spike broadening is frequency dependent and is reversed by brief hyperpolarisations. This broadening is reduced by blockade of voltage-gated Ca2+ channels and BK channels. In contrast, broadening is not blocked by high concentrations of 4-aminopyridine (4-AP) or alpha-dendrotoxin. We conclude that while inactivation of BK-type Ca2+-activated K+ channels contributes to spike broadening in lateral amygdala neurons, inactivation of another as yet unidentified outward current also plays a role.

  8. Role of BKCa channels in cephalic vasodilation induced by CGRP, NO and transcranial electrical stimulation in the rat

    DEFF Research Database (Denmark)

    Gozalov, A.; Jansen-Olesen, I.; Klærke, Dan Arne;

    2007-01-01

    by the NO donor glyceryltrinitrate (GTN) or by CGRP is partially mediated via large conductance calcium-activated potassium (BK(Ca)) channels. The effects of the BK(Ca) channel selective inhibitor iberiotoxin on dural and pial vasodilation induced by CGRP, GTN and endogenously released CGRP by transcranial...... electrical stimulation (TES) were examined. Iberiotoxin significantly attenuated GTN-induced dural and pial artery dilation in vivo and in vitro, but had no effect on vasodilation induced by CGRP and TES. Our results show that GTN- but not CGRP-induced dural and pial vasodilation involves opening of BK...

  9. Expression of BKCa channels and the modulatory ß-subunits in the rat and porcine trigeminal ganglion

    DEFF Research Database (Denmark)

    Wulf-Johansson, Helle; Hay-Schmidt, Anders; Poulsen, Asser Nyander;

    2009-01-01

    Large conductance calcium-activated potassium (BK(Ca)) channels contribute to electrical impulses, proper signal transmission of information and regulation of neurotransmitter release. Migraine has been proposed to be a trigeminovascular disease involving the sensory trigeminal pathways and the c......Large conductance calcium-activated potassium (BK(Ca)) channels contribute to electrical impulses, proper signal transmission of information and regulation of neurotransmitter release. Migraine has been proposed to be a trigeminovascular disease involving the sensory trigeminal pathways...

  10. Overexpression of the Large-Conductance, Ca2+-Activated K+ (BK) Channel Shortens Action Potential Duration in HL-1 Cardiomyocytes.

    Science.gov (United States)

    Stimers, Joseph R; Song, Li; Rusch, Nancy J; Rhee, Sung W

    2015-01-01

    Long QT syndrome is characterized by a prolongation of the interval between the Q wave and the T wave on the electrocardiogram. This abnormality reflects a prolongation of the ventricular action potential caused by a number of genetic mutations or a variety of drugs. Since effective treatments are unavailable, we explored the possibility of using cardiac expression of the large-conductance, Ca2+-activated K+ (BK) channel to shorten action potential duration (APD). We hypothesized that expression of the pore-forming α subunit of human BK channels (hBKα) in HL-1 cells would shorten action potential duration in this mouse atrial cell line. Expression of hBKα had minimal effects on expression levels of other ion channels with the exception of a small but significant reduction in Kv11.1. Patch-clamped hBKα expressing HL-1 cells exhibited an outward voltage- and Ca2+-sensitive K+ current, which was inhibited by the BK channel blocker iberiotoxin (100 nM). This BK current phenotype was not detected in untransfected HL-1 cells or in HL-1 null cells sham-transfected with an empty vector. Importantly, APD in hBKα-expressing HL-1 cells averaged 14.3 ± 2.8 ms (n = 10), which represented a 53% reduction in APD compared to HL-1 null cells lacking BKα expression. APD in the latter cells averaged 31.0 ± 5.1 ms (n = 13). The shortened APD in hBKα-expressing cells was restored to normal duration by 100 nM iberiotoxin, suggesting that a repolarizing K+ current attributed to BK channels accounted for action potential shortening. These findings provide initial proof-of-concept that the introduction of hBKα channels into a cardiac cell line can shorten APD, and raise the possibility that gene-based interventions to increase hBKα channels in cardiac cells may hold promise as a therapeutic strategy for long QT syndrome.

  11. Localization of large conductance calcium-activated potassium channels and their effect on calcitonin gene-related peptide release in the rat trigemino-neuronal pathway.

    Science.gov (United States)

    Wulf-Johansson, H; Amrutkar, D V; Hay-Schmidt, A; Poulsen, A N; Klaerke, D A; Olesen, J; Jansen-Olesen, I

    2010-06-02

    Large conductance calcium-activated potassium (BK(Ca)) channels are membrane proteins contributing to electrical propagation through neurons. Calcitonin gene-related peptide (CGRP) is a neuropeptide found in the trigeminovascular system (TGVS). Both BK(Ca) channels and CGRP are involved in migraine pathophysiology. Here we study the expression and localization of BK(Ca) channels and CGRP in the rat trigeminal ganglion (TG) and the trigeminal nucleus caudalis (TNC) as these structures are involved in migraine pain. Also the effect of the BK(Ca) channel blocker iberiotoxin and the BK(Ca) channel opener NS11021 on CGRP release from isolated TG and TNC was investigated. By RT-PCR, BK(Ca) channel mRNA was detected in the TG and the TNC. A significant difference in BK(Ca) channel mRNA transcript levels were found using qPCR between the TNC as compared to the TG. The BK(Ca) channel protein was more expressed in the TNC as compared to the TG shown by western blotting. Immunohistochemistry identified BK(Ca) channels in the nerve cell bodies of the TG and the TNC. The beta2- and beta4-subunit proteins were found in the TG and the TNC. They were both more expressed in the TNC as compared to TG shown by western blotting. In isolated TNC, the BK(Ca) channel blocker iberiotoxin induced a concentration-dependent release of CGRP that was attenuated by the BK(Ca) channel opener NS11021. No effect on basal CGRP release was found by NS11021 in isolated TG or TNC or by iberiotoxin in TG. In conclusion, we found both BK(Ca) channel mRNA and protein expression in the TG and the TNC. The BK(Ca) channel protein and the modulatory beta2- and beta4-subunt proteins were more expressed in the TNC than in the TG. Iberiotoxin induced an increase in CGRP release from the TNC that was attenuated by NS11021. Thus, BK(Ca) channels might have a role in trigeminovascular pain transmission.

  12. Biophysical studies of the membrane location of the voltage-gated sensors in the HsapBK and KvAP K(+) channels.

    Science.gov (United States)

    Biverståhl, Henrik; Lind, Jesper; Bodor, Andrea; Mäler, Lena

    2009-09-01

    The membrane location of two fragments in two different K(+)-channels, the KvAP (from Aeropyrum pernix) and the HsapBK (human) corresponding to the putative "paddle" domains, has been investigated by CD, fluorescence and NMR spectroscopy. Both domains interact with q = 0.5 phospholipid bicelles, DHPC micelles and with POPC vesicles. CD spectra demonstrate that both peptides become largely helical in the presence of phospholipid bicelles. Fluorescence quenching studies using soluble acrylamide or lipid-attached doxyl-groups show that the arginine-rich domains are located within the bilayered region in phospholipid bicelles. Nuclear magnetic relaxation parameters, T(1) and (13)C-(1)H NOE, for DMPC in DMPC/DHPC bicelles and for DHPC in micelles showed that the lipid acyl chains in the bicelles become less flexible in the presence of either of the fragments. An even more pronounced effect is seen on the glycerol carbons. (2)H NMR spectra of magnetically aligned bicelles showed that the peptide derived from KvAP had no or little effect on bilayer order, while the peptide derived from HsapBK had the effect of lowering the order of the bilayer. The present study demonstrates that the fragments derived from the full-length proteins interact with the bilayered interior of model membranes, and that they affect both the local mobility and lipid order of model membrane systems.

  13. Functional insights into modulation of BKCa channel activity to alter myometrial contractility

    Directory of Open Access Journals (Sweden)

    Ramón A Lorca

    2014-07-01

    Full Text Available The large-conductance voltage- and Ca2+-activated K+ channel (BKCa is an important regulator of membrane excitability in a wide variety of cells and tissues. In myometrial smooth muscle, activation of BKCa plays essential roles in buffering contractility to maintain uterine quiescence during pregnancy and in the transition to a more contractile state at the onset of labor. Multiple mechanisms of modulation have been described to alter BKCa channel activity, expression, and cellular localization. In the myometrium, BKCa is regulated by alternative splicing, protein targeting to the plasma membrane, compartmentation in membrane microdomains, and posttranslational modifications. In addition, interaction with auxiliary proteins (i.e., β1- and β2-subunits, association with G-protein coupled receptor signaling pathways, such as those activated by adrenergic and oxytocin receptors, and hormonal regulation provide further mechanisms of variable modulation of BKCa channel function in myometrial smooth muscle. Here, we provide an overview of these mechanisms of BKCa channel modulation and provide a context for them in relation to myometrial function.

  14. Astaxanthin and Docosahexaenoic Acid Reverse the Toxicity of the Maxi-K (BK Channel Antagonist Mycotoxin Penitrem A

    Directory of Open Access Journals (Sweden)

    Amira A. Goda

    2016-11-01

    Full Text Available Penitrem A (PA is a food mycotoxin produced by several terrestrial and few marine Penicillium species. PA is a potent tremorgen through selective antagonism of the calcium-dependent potassium BK (Maxi-K channels. Discovery of natural products that can prevent the toxic effects of PA is important for food safety. Astaxanthin (AST is a marine natural xanthophyll carotenoid with documented antioxidant activity. Unlike other common antioxidants, AST can cross blood brain barriers (BBBs, inducing neuroprotective effects. Docosahexaenoic acid (DHA is polyunsaturated ω-3 fatty acid naturally occurring in fish and algae. DHA is essential for normal neurological and cellular development. This study evaluated the protective activity of AST and DHA against PA-induced toxicity, in vitro on Schwann cells CRL-2765 and in vivo in the worm Caenorhbitidis elegans and Sprague Dawley rat models. PA inhibited the viability of Schwann cells, with an IC50 of 22.6 μM. Dose-dependent treatments with 10–100 μM DHA significantly reversed the PA toxicity at its IC50 dose, and improved the survival of Schwann cells to 70.5%–98.8%. Similarly, dose-dependent treatments with 10–20 μM AST reversed the PA toxicity at its IC50 dose and raised these cells’ survival to 61.7%–70.5%. BK channel inhibition in the nematode C. elegans is associated with abnormal reversal locomotion. DHA and AST counteracted the in vivo PA BK channel antagonistic activity in the C. elegans model. Rats fed a PA-contaminated diet showed high levels of glutamate (GLU, aspartate (ASP, and gamma amino butyric acid (GABA, with observed necrosis or absence of Purkinjie neurons, typical of PA-induced neurotoxicity. Dopamine (DA, serotonin (5-HT, and norepinephrine (NE levels were abnormal, Nitric Oxide (NO and Malondialdehyde (MDA levels were significantly increased, and total antioxidant capacity (TAC level in serum and brain homogenates was significantly decreased in PA-treated rats. DHA and AST

  15. Astaxanthin and Docosahexaenoic Acid Reverse the Toxicity of the Maxi-K (BK) Channel Antagonist Mycotoxin Penitrem A

    Science.gov (United States)

    Goda, Amira A.; Naguib, Khayria M.; Mohamed, Magdy M.; Amra, Hassan A.; Nada, Somaia A.; Abdel-Ghaffar, Abdel-Rahman B.; Gissendanner, Chris R.; El Sayed, Khalid A.

    2016-01-01

    Penitrem A (PA) is a food mycotoxin produced by several terrestrial and few marine Penicillium species. PA is a potent tremorgen through selective antagonism of the calcium-dependent potassium BK (Maxi-K) channels. Discovery of natural products that can prevent the toxic effects of PA is important for food safety. Astaxanthin (AST) is a marine natural xanthophyll carotenoid with documented antioxidant activity. Unlike other common antioxidants, AST can cross blood brain barriers (BBBs), inducing neuroprotective effects. Docosahexaenoic acid (DHA) is polyunsaturated ω-3 fatty acid naturally occurring in fish and algae. DHA is essential for normal neurological and cellular development. This study evaluated the protective activity of AST and DHA against PA-induced toxicity, in vitro on Schwann cells CRL-2765 and in vivo in the worm Caenorhbitidis elegans and Sprague Dawley rat models. PA inhibited the viability of Schwann cells, with an IC50 of 22.6 μM. Dose-dependent treatments with 10–100 μM DHA significantly reversed the PA toxicity at its IC50 dose, and improved the survival of Schwann cells to 70.5%–98.8%. Similarly, dose-dependent treatments with 10–20 μM AST reversed the PA toxicity at its IC50 dose and raised these cells’ survival to 61.7%–70.5%. BK channel inhibition in the nematode C. elegans is associated with abnormal reversal locomotion. DHA and AST counteracted the in vivo PA BK channel antagonistic activity in the C. elegans model. Rats fed a PA-contaminated diet showed high levels of glutamate (GLU), aspartate (ASP), and gamma amino butyric acid (GABA), with observed necrosis or absence of Purkinjie neurons, typical of PA-induced neurotoxicity. Dopamine (DA), serotonin (5-HT), and norepinephrine (NE) levels were abnormal, Nitric Oxide (NO) and Malondialdehyde (MDA) levels were significantly increased, and total antioxidant capacity (TAC) level in serum and brain homogenates was significantly decreased in PA-treated rats. DHA and AST

  16. Novel mechanism of hydrogen sulfide-induced guinea pig urinary bladder smooth muscle contraction: role of BK channels and cholinergic neurotransmission.

    Science.gov (United States)

    Fernandes, Vítor S; Xin, Wenkuan; Petkov, Georgi V

    2015-07-15

    Hydrogen sulfide (H2S) is a key signaling molecule regulating important physiological processes, including smooth muscle function. However, the mechanisms underlying H2S-induced detrusor smooth muscle (DSM) contractions are not well understood. This study investigates the cellular and tissue mechanisms by which H2S regulates DSM contractility, excitatory neurotransmission, and large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels in freshly isolated guinea pig DSM. We used a multidisciplinary experimental approach including isometric DSM tension recordings, colorimetric ACh measurement, Ca(2+) imaging, and patch-clamp electrophysiology. In isolated DSM strips, the novel slow release H2S donor, P-(4-methoxyphenyl)-p-4-morpholinylphosphinodithioic acid morpholine salt (GYY4137), significantly increased the spontaneous phasic and nerve-evoked DSM contractions. The blockade of neuronal voltage-gated Na(+) channels or muscarinic ACh receptors with tetrodotoxin or atropine, respectively, reduced the stimulatory effect of GYY4137 on DSM contractility. GYY4137 increased ACh release from bladder nerves, which was inhibited upon blockade of L-type voltage-gated Ca(2+) channels with nifedipine. Furthermore, GYY4137 increased the amplitude of the Ca(2+) transients and basal Ca(2+) levels in isolated DSM strips. GYY4137 reduced the DSM relaxation induced by the BK channel opener, NS11021. In freshly isolated DSM cells, GYY4137 decreased the amplitude and frequency of transient BK currents recorded in a perforated whole cell configuration and reduced the single BK channel open probability measured in excised inside-out patches. GYY4137 inhibited spontaneous transient hyperpolarizations and depolarized the DSM cell membrane potential. Our results reveal the novel findings that H2S increases spontaneous phasic and nerve-evoked DSM contractions by activating ACh release from bladder nerves in combination with a direct inhibition of DSM BK channels.

  17. Membrane-perturbing properties of two Arg-rich paddle domains from voltage-gated sensors in the KvAP and HsapBK K(+) channels.

    Science.gov (United States)

    Unnerståle, Sofia; Madani, Fatemeh; Gräslund, Astrid; Mäler, Lena

    2012-05-15

    Voltage-gated K(+) channels are gated by displacement of basic residues located in the S4 helix that together with a part of the S3 helix, S3b, forms a "paddle" domain, whose position is altered by changes in the membrane potential modulating the open probability of the channel. Here, interactions between two paddle domains, KvAPp from the K(v) channel from Aeropyrum pernix and HsapBKp from the BK channel from Homo sapiens, and membrane models have been studied by spectroscopy. We show that both paddle domains induce calcein leakage in large unilamellar vesicles, and we suggest that this leakage represents a general thinning of the bilayer, making movement of the whole paddle domain plausible. The fact that HsapBKp induces more leakage than KvAPp may be explained by the presence of a Trp residue in HsapBKp. Trp residues generally promote localization to the hydrophilic-hydrophobic interface and disturb tight packing. In magnetically aligned bicelles, KvAPp increases the level of order along the whole acyl chain, while HsapBKp affects the morphology, also indicating that KvAPp adapts more to the lipid environment. Nuclear magnetic resonance (NMR) relaxation measurements for HsapBKp show that overall the sequence has anisotropic motions. The S4 helix is well-structured with restricted local motion, while the turn between S4 and S3b is more flexible and undergoes slow local motion. Our results indicate that the calcein leakage is related to the flexibility in this turn region. A possibility by which HsapBKp can undergo structural transitions is also shown by relaxation NMR, which may be important for the gating mechanism.

  18. Functional BK channels facilitate the β3-adrenoceptor agonist-mediated relaxation of nerve-evoked contractions in rat urinary bladder smooth muscle isolated strips.

    Science.gov (United States)

    Afeli, Serge A Y; Petkov, Georgi V

    2013-07-05

    The large-conductance voltage- and Ca(2+)-activated K(+) (BK) channel is a major regulator of detrusor smooth muscle (DSM) contractility thus facilitating urinary bladder function. Recent findings suggest that activation of β3-adrenoceptors causes DSM relaxation. However, it is unknown whether the β3-adrenoceptor-mediated DSM relaxation is BK channel-dependent during nerve-evoked contractions. To test this hypothesis, we induced nerve-evoked contractions in rat DSM isolated strips by using a tissue bath system equipped with platinum electrodes for electrical field stimulation (EFS). (±)-(R(*),R(*))-[4-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]amino]propyl]phenoxy] acetic acid sodium hydrate (BRL37344), a β3-adrenoceptor agonist, significantly decreased the amplitude and muscle force of the 20 Hz EFS-induced DSM contractions in a concentration-dependent manner. The BRL37344 inhibitory effect was significantly antagonized by 1-(2-ethylphenoxy)-3-[[(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]-(2S)-2-propanol hydrochloride (SR59230A), a β3-adrenoceptor antagonist. We further isolated the cholinergic from the purinergic component of the 0.5-50 Hz EFS-induced DSM contractions by using selective inhibitors, atropine as well as suramin and α,β-methylene-ATP. We found that BRL37344 inhibited both the purinergic and cholinergic components of the nerve-evoked contractions in rat DSM isolated strips. The pharmacological blockade of the BK channels with iberiotoxin, a selective BK channel inhibitor, increased the amplitude and muscle force of the 20 Hz EFS-induced contractions in rat DSM isolated strips. In the presence of iberiotoxin, there was a significant reduction in the BRL37344-induced inhibition of the 20 Hz EFS-induced contractions in rat DSM isolated strips. These latter findings suggest that BK channels play a critical role in the β3-adrenoceptor-mediated inhibition of rat DSM nerve-evoked contractions.

  19. Martentoxin: A unique ligand of BK channels%Martentoxin:一种大电导钙激活钾离子通道的独有配体

    Institute of Scientific and Technical Information of China (English)

    陶杰; 施健; 刘志睿; 吉永华

    2012-01-01

    The large-conductance calcium-activated potassium (BK) channels distributed in both excitable and non-excitable cells are key participants in a variety of physiological functions.By employing numerous high-affinity natural toxins originated from scorpion venoms the pharmacological and structural characteristics of these channels tend to be approached A 37-residue short-chain peptide,named as martentoxin,arising from the venom of the East-Asian scorpion (Buthus martensi Karsch) has been investigated with a comparatively higher preference for BK channels over other voltage-gated potassium (Kv) channels.Up to now,since the specific drug tool probing for clarifying structure-function of BK channel subtypes and related pathology remain scarce,it is of importance to illuminate the underlying mechanism of molecular interaction between martentoxin and BK channels.As for it,the current review will address the recent progress on the studies of pharmacological characterizations and molecular determinants of martentoxin targeting on BK channels.%大电导钙激活钾离子(BK)通道广泛分布于可兴奋细胞与非兴奋细胞中,行使着一系列重要的生理功能.以源于蝎粗毒的高亲和性毒素作为研究工具,使BK通道的药理学和结构性质正逐步被揭示.Martentoxin是一种分离提取自东亚短钳蝎(Buthus martensi Karsch)粗毒的短链多肽,由37个氨基酸残基构成.研究表明,其对BK通道的特异性远高于其它各类型的电压门控钾通道(Kv).迄今为止,由于用以探明BK通道亚型结构与功能及相关病理的特异性药物工具仍然稀缺,因此阐明martentoxin与BK通道间的相互作用模式就显得至关重要了.鉴于此原因,本综述将针对martentoxin的药理性质和其与BK通道相互作用的分子机制做进一步阐明.

  20. Gentamicin Blocks the ACh-Induced BK Current in Guinea Pig Type II Vestibular Hair Cells by Competing with Ca2+ at the l-Type Calcium Channel

    Directory of Open Access Journals (Sweden)

    Hong Yu

    2014-04-01

    Full Text Available Type II vestibular hair cells (VHCs II contain big-conductance Ca2+-dependent K+ channels (BK and L-type calcium channels. Our previous studies in guinea pig VHCs II indicated that acetylcholine (ACh evoked the BK current by triggering the influx of Ca2+ ions through l-type Ca2+ channels, which was mediated by M2 muscarinic ACh receptor (mAChRs. Aminoglycoside antibiotics, such as gentamicin (GM, are known to have vestibulotoxicity, including damaging effects on the efferent nerve endings on VHCs II. This study used the whole-cell patch clamp technique to determine whether GM affects the vestibular efferent system at postsynaptic M2-mAChRs or the membrane ion channels. We found that GM could block the ACh-induced BK current and that inhibition was reversible, voltage-independent, and dose-dependent with an IC50 value of 36.3 ± 7.8 µM. Increasing the ACh concentration had little influence on GM blocking effect, but increasing the extracellular Ca2+ concentration ([Ca2+]o could antagonize it. Moreover, 50 µM GM potently blocked Ca2+ currents activated by (--Bay-K8644, but did not block BK currents induced by NS1619. These observations indicate that GM most likely blocks the M2 mAChR-mediated response by competing with Ca2+ at the l-type calcium channel. These results provide insights into the vestibulotoxicity of aminoglycoside antibiotics on mammalian VHCs II.

  1. WNK4 kinase-mediated inhibitory effect on expression of BK channel via lysosomal pathway%WNK4激酶通过溶酶体途径抑制BK通道表达

    Institute of Scientific and Technical Information of China (English)

    庄捷秋; 王德选; 张益前; 牛伟辉; 陈方旋; 施珍; 潘殊方; 谷定英

    2012-01-01

    Objective To investigate the mechanism underlying the WNK4 kinasemediated inhibitory effect on BK channel. Methods Cos-7 cells were cotransfected with BK in combination with either CD4 (control group) or wild type WNK4 (WNK4-WT).Immunostaining and confocal microscopy,chemiluminescence,Western blotting analysis were then employed to determine the BK localization in cells,BK surface expression and total protein level,respectively.To further investigate whether the reduction of BK protein expression is due to an increase in degradation through a lysosomal pathway,BK protein level was determined after treated with bafilomycin A1(Baf A1),a proton pump inhibitor affecting lysosomal degradation. Results Immunostaining and confocal microscopic study showed that BK was localized both in plasma membrane and cytosol in the control group.After cells transfected with WNK4-WT,BK expression was markedly reduced.Chemiluminescent assay found that BK surface expression level was 299.9±18.6 in the control group,whereas it was significantly reduced (148.4±13.7,P<0.01) in the WNK4-WT group.Western blotting analysis showed that total BK protein level was markedly reduced in the presence of WNK4-WT compared to the control group.WNK4-WT was shown to significantly reduce the BK total protein level (42.3%±15.2%) compared to the control group (100%) (P<0.01).When the cells was treated with Bafilomycin A1 (Baf A1,0.5 μmol/L),WNK4-mediated reduction in BK protein was reversed (82.2%±12.1%,P<0.05). Conclusions WNK4 inhibits total and surface protein expression of BK in Cos-7 cells whick is likely due to an increase in BK degradation through a lysosomal pathway.%目的 研究WNK4激酶对BK通道的调节作用及机制.方法 将BK和WNK4野生型(WNK4-WT)或CD4(对照)质粒DNA共同转染进Cos-7细胞中,采用免疫染色-共聚焦激光显微镜、化学发光法、Western印迹法检测BK在细胞上的分布、细胞膜表面蛋白和总蛋

  2. Molecular mechanisms underlying the effect of the novel BK channel opener GoSlo: involvement of the S4/S5 linker and the S6 segment.

    Science.gov (United States)

    Webb, Timothy I; Kshatri, Aravind Singh; Large, Roddy J; Akande, Adebola Morayo; Roy, Subhrangsu; Sergeant, Gerard P; McHale, Noel G; Thornbury, Keith D; Hollywood, Mark A

    2015-02-17

    GoSlo-SR-5-6 is a novel large-conductance Ca(2+)-activated K(+) (BK) channel agonist that shifts the activation V1/2 of these channels in excess of -100 mV when applied at a concentration of 10 μM. Although the structure-activity relationship of this family of molecules has been established, little is known about how they open BK channels. To help address this, we used a combination of electrophysiology, mutagenesis, and mathematical modeling to investigate the molecular mechanisms underlying the effect of GoSlo-SR-5-6. Our data demonstrate that the effects of this agonist are practically abolished when three point mutations are made: L227A in the S4/S5 linker in combination with S317R and I326A in the S6C region. Our data suggest that GoSlo-SR-5-6 interacts with the transmembrane domain of the channel to enhance pore opening. The Horrigan-Aldrich model suggests that GoSlo-SR-5-6 works by stabilizing the open conformation of the channel and the activated state of the voltage sensors, yet decouples the voltage sensors from the pore gate.

  3. Local Transfer Coefficient, Smooth Channel

    Directory of Open Access Journals (Sweden)

    R. T. Kukreja

    1998-01-01

    Full Text Available Naphthalene sublimation technique and the heat/mass transfer analogy are used to determine the detailed local heat/mass transfer distributions on the leading and trailing walls of a twopass square channel with smooth walls that rotates about a perpendicular axis. Since the variation of density is small in the flow through the channel, buoyancy effect is negligible. Results show that, in both the stationary and rotating channel cases, very large spanwise variations of the mass transfer exist in he turn and in the region immediately downstream of the turn in the second straight pass. In the first straight pass, the rotation-induced Coriolis forces reduce the mass transfer on the leading wall and increase the mass transfer on the trailing wall. In the turn, rotation significantly increases the mass transfer on the leading wall, especially in the upstream half of the turn. Rotation also increases the mass transfer on the trailing wall, more in the downstream half of the turn than in the upstream half of the turn. Immediately downstream of the turn, rotation causes the mass transfer to be much higher on the trailing wall near the downstream corner of the tip of the inner wall than on the opposite leading wall. The mass transfer in the second pass is higher on the leading wall than on the trailing wall. A slower flow causes higher mass transfer enhancement in the turn on both the leading and trailing walls.

  4. Role of the BK channel (KCa1.1) during activation of electrogenic K+ secretion in guinea pig distal colon.

    Science.gov (United States)

    Zhang, Jin; Halm, Susan T; Halm, Dan R

    2012-12-15

    Secretagogues acting at a variety of receptor types activate electrogenic K(+) secretion in guinea pig distal colon, often accompanied by Cl(-) secretion. Distinct blockers of K(Ca)1.1 (BK, Kcnma1), iberiotoxin (IbTx), and paxilline inhibited the negative short-circuit current (I(sc)) associated with K(+) secretion. Mucosal addition of IbTx inhibited epinephrine-activated I(sc) ((epi)I(sc)) and transepithelial conductance ((epi)G(t)) consistent with K(+) secretion occurring via apical membrane K(Ca)1.1. The concentration dependence of IbTx inhibition of (epi)I(sc) yielded an IC(50) of 193 nM, with a maximal inhibition of 51%. Similarly, IbTx inhibited (epi)G(t) with an IC(50) of 220 nM and maximal inhibition of 48%. Mucosally added paxilline (10 μM) inhibited (epi)I(sc) and (epi)G(t) by ∼50%. IbTx and paxilline also inhibited I(sc) activated by mucosal ATP, supporting apical K(Ca)1.1 as a requirement for this K(+) secretagogue. Responses to IbTx and paxilline indicated that a component of K(+) secretion occurred during activation of Cl(-) secretion by prostaglandin-E(2) and cholinergic stimulation. Analysis of K(Ca)1.1α mRNA expression in distal colonic epithelial cells indicated the presence of the ZERO splice variant and three splice variants for the COOH terminus. The presence of the regulatory β-subunits K(Ca)β1 and K(Ca)β4 also was demonstrated. Immunolocalization supported the presence of K(Ca)1.1α in apical and basolateral membranes of surface and crypt cells. Together these results support a cellular mechanism for electrogenic K(+) secretion involving apical membrane K(Ca)1.1 during activation by several secretagogue types, but the observed K(+) secretion likely required the activity of additional K(+) channel types in the apical membrane.

  5. The role of potassium BK channels in anticonvulsant effect of cannabidiol in pentylenetetrazole and maximal electroshock models of seizure in mice.

    Science.gov (United States)

    Shirazi-zand, Zahra; Ahmad-Molaei, Leila; Motamedi, Fereshteh; Naderi, Nima

    2013-07-01

    Cannabidiol is a nonpsychoactive member of phytocannabinoids that produces various pharmacological effects that are not mediated through putative CB1/CB2 cannabinoid receptors and their related effectors. In this study, we examined the effect of the i.c.v. administration of potassium BK channel blocker paxilline alone and in combination with cannabidiol in protection against pentylenetetrazol (PTZ)- and maximal electroshock (MES)-induced seizure in mice. In the PTZ-induced seizure model, i.c.v. administration of cannabidiol caused a significant increase in seizure threshold compared with the control group. Moreover, while i.c.v. administration of various doses of paxilline did not produce significant change in the PTZ-induced seizure threshold in mice, coadministration of cannabidiol and paxilline attenuated the antiseizure effect of cannabidiol in PTZ-induced tonic seizures. In the MES model of seizure, both cannabidiol and paxilline per se produced significant increase in percent protection against electroshock-induced seizure. However, coadministration of cannabidiol and paxilline did not produce significant interaction in their antiseizure effect in the MES test. The results of the present study showed a protective effect of cannabidiol in both PTZ and MES models of seizure. These results suggested a BK channel-mediated antiseizure action of cannabidiol in PTZ model of seizure. However, such an interaction might not exist in MES-induced convulsion.

  6. Cell volume and membrane stretch independently control K+ channel activity

    DEFF Research Database (Denmark)

    Bomholtz, Sofia Hammami; Willumsen, Niels J; Olsen, Hervør L;

    2009-01-01

    A number of potassium channels including members of the KCNQ family and the Ca(2+) activated IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch....... To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in Xenopus oocytes. Results from cell-attached patch clamp studies (approximately 50 microm(2) macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume-insensitive BK current...... was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude...

  7. Orientations and proximities of the extracellular ends of transmembrane helices S0 and S4 in open and closed BK potassium channels.

    Directory of Open Access Journals (Sweden)

    Xiaowei Niu

    Full Text Available The large-conductance potassium channel (BK α subunit contains a transmembrane (TM helix S0 preceding the canonical TM helices S1 through S6. S0 lies between S4 and the TM2 helix of the regulatory β1 subunit. Pairs of Cys were substituted in the first helical turns in the membrane of BK α S0 and S4 and in β1 TM2. One such pair, W22C in S0 and W203C in S4, was 95% crosslinked endogenously. Under voltage-clamp conditions in outside-out patches, this crosslink was reduced by DTT and reoxidized by a membrane-impermeant bis-quaternary ammonium derivative of diamide. The rate constants for this reoxidation were not significantly different in the open and closed states of the channel. Thus, these two residues are approximately equally close in the two states. In addition, 90% crosslinking of a second pair, R20C in S0 and W203C in S4, had no effect on the V50 for opening. Taken together, these findings indicate that separation between residues at the extracellular ends of S0 and S4 is not required for voltage-sensor activation. On the contrary, even though W22C and W203C were equally likely to form a disulfide in the activated and deactivated states, relative immobilization by crosslinking of these two residues favored the activated state. Furthermore, the efficiency of recrosslinking of W22C and W203C on the cell surface was greater in the presence of the β1 subunit than in its absence, consistent with β1 acting through S0 to stabilize its immobilization relative to α S4.

  8. Archaerhodopsin voltage imaging: synaptic calcium and BK channels stabilize action potential repolarization at the Drosophila neuromuscular junction.

    Science.gov (United States)

    Ford, Kevin J; Davis, Graeme W

    2014-10-29

    The strength and dynamics of synaptic transmission are determined, in part, by the presynaptic action potential (AP) waveform at the nerve terminal. The ion channels that shape the synaptic AP waveform remain essentially unknown for all but a few large synapses amenable to electrophysiological interrogation. The Drosophila neuromuscular junction (NMJ) is a powerful system for studying synaptic biology, but it is not amenable to presynaptic electrophysiology. Here, we demonstrate that Archaerhodopsin can be used to quantitatively image AP waveforms at the Drosophila NMJ without disrupting baseline synaptic transmission or neuromuscular development. It is established that Shaker mutations cause a dramatic increase in neurotransmitter release, suggesting that Shaker is predominantly responsible for AP repolarization. Here we demonstrate that this effect is caused by a concomitant loss of both Shaker and slowpoke (slo) channel activity because of the low extracellular calcium concentrations (0.2-0.5 mM) used typically to assess synaptic transmission in Shaker. In contrast, at physiological extracellular calcium (1.5 mM), the role of Shaker during AP repolarization is limited. We then provide evidence that calcium influx through synaptic CaV2.1 channels and subsequent recruitment of Slo channel activity is important, in concert with Shaker, to ensure proper AP repolarization. Finally, we show that Slo assumes a dominant repolarizing role during repetitive nerve stimulation. During repetitive stimulation, Slo effectively compensates for Shaker channel inactivation, stabilizing AP repolarization and limiting neurotransmitter release. Thus, we have defined an essential role for Slo channels during synaptic AP repolarization and have revised our understanding of Shaker channels at this model synapse.

  9. Presynaptic Ca2+-activated K+ channels in glutamatergic hippocampal terminals and their role in spike repolarization and regulation of transmitter release.

    Science.gov (United States)

    Hu, H; Shao, L R; Chavoshy, S; Gu, N; Trieb, M; Behrens, R; Laake, P; Pongs, O; Knaus, H G; Ottersen, O P; Storm, J F

    2001-12-15

    Large-conductance Ca(2+)-activated K(+) channels (BK, also called Maxi-K or Slo channels) are widespread in the vertebrate nervous system, but their functional roles in synaptic transmission in the mammalian brain are largely unknown. By combining electrophysiology and immunogold cytochemistry, we demonstrate the existence of functional BK channels in presynaptic terminals in the hippocampus and compare their functional roles in somata and terminals of CA3 pyramidal cells. Double-labeling immunogold analysis with BK channel and glutamate receptor antibodies indicated that BK channels are targeted to the presynaptic membrane facing the synaptic cleft in terminals of Schaffer collaterals in stratum radiatum. Whole-cell, intracellular, and field-potential recordings from CA1 pyramidal cells showed that the presynaptic BK channels are activated by calcium influx and can contribute to repolarization of the presynaptic action potential (AP) and negative feedback control of Ca(2+) influx and transmitter release. This was observed in the presence of 4-aminopyridine (4-AP, 40-100 microm), which broadened the presynaptic compound action potential. In contrast, the presynaptic BK channels did not contribute significantly to regulation of action potentials or transmitter release under basal experimental conditions, i.e., without 4-AP, even at high stimulation frequencies. This is unlike the situation in the parent cell bodies (CA3 pyramidal cells), where BK channels contribute strongly to action potential repolarization. These results indicate that the functional role of BK channels depends on their subcellular localization.

  10. Contribution of SK and BK channels in the control of catecholamine release by electrical stimulation of the cat adrenal gland.

    Science.gov (United States)

    Montiel, C; López, M G; Sánchez-García, P; Maroto, R; Zapater, P; García, A G

    1995-01-01

    on catecholamine release induced by electrical stimulation was observed at low but not at high [Ca2+]o. 6. Simultaneous release of acetylcholine and catecholamines upon electrical stimulation was achieved in glands in which the endogenous acetylcholine stores in the splanchnic nerve terminals had been prelabelled by perfusion with [3H]choline. While apamin enhanced more than 2-fold the postsynaptic release of catecholamines, the presynaptic release of acetylcholine remained unaffected. 7. The results are compatible with the hypothesis that, under physiological conditions, Ca(2+)-activated SK channels present in chromaffin cells control the firing patterns of action potentials induced by the acetylcholine released from splanchnic nerves during stress.(ABSTRACT TRUNCATED AT 400 WORDS) Images Figure 3 Figure 4 Figure 6 PMID:7473208

  11. Contribution of SK and BK channels in the control of catecholamine release by electrical stimulation of the cat adrenal gland.

    Science.gov (United States)

    Montiel, C; López, M G; Sánchez-García, P; Maroto, R; Zapater, P; García, A G

    1995-07-15

    on catecholamine release induced by electrical stimulation was observed at low but not at high [Ca2+]o. 6. Simultaneous release of acetylcholine and catecholamines upon electrical stimulation was achieved in glands in which the endogenous acetylcholine stores in the splanchnic nerve terminals had been prelabelled by perfusion with [3H]choline. While apamin enhanced more than 2-fold the postsynaptic release of catecholamines, the presynaptic release of acetylcholine remained unaffected. 7. The results are compatible with the hypothesis that, under physiological conditions, Ca(2+)-activated SK channels present in chromaffin cells control the firing patterns of action potentials induced by the acetylcholine released from splanchnic nerves during stress.(ABSTRACT TRUNCATED AT 400 WORDS)

  12. Molecular and functional expression of high conductance Ca 2+ activated K+ channels in the eel intestinal epithelium

    DEFF Research Database (Denmark)

    Lionetto, Maria G; Rizzello, Antonia; Giordano, Maria E;

    2008-01-01

    Several types of K(+) channels have been identified in epithelial cells. Among them high conductance Ca(2+)-activated K(+) channels (BK channels) are of relevant importance for their involvement in regulatory volume decrease (RVD) response following hypotonic stress. The aim of the present work...... and morphometric analysis on the intact tissue. BK(Ca) channels appeared to be localized along all the plasma membrane of the enterocytes; the apical part of the villi showed the most intense immunostaining. These channels were silent in basal condition, but were activated on both membranes (apical and basolateral......) by increasing intracellular Ca(2+) concentration with the Ca(2+) ionophore ionomycin (1 microM). BK(Ca) channels were also activated on both membranes by hypotonic swelling of the epithelium and their inhibition by 100 nM iberiotoxin (specific BK(Ca) inhibitor) abolished the Regulatory Volume Decrease (RVD...

  13. Genetic activation of BK currents in vivo generates bidirectional effects on neuronal excitability.

    Science.gov (United States)

    Montgomery, Jenna R; Meredith, Andrea L

    2012-11-13

    Large-conductance calcium-activated potassium channels (BK) are potent negative regulators of excitability in neurons and muscle, and increasing BK current is a novel therapeutic strategy for neuro- and cardioprotection, disorders of smooth muscle hyperactivity, and several psychiatric diseases. However, in some neurons, enhanced BK current is linked with seizures and paradoxical increases in excitability, potentially complicating the clinical use of agonists. The mechanisms that switch BK influence from inhibitory to excitatory are not well defined. Here we investigate this dichotomy using a gain-of-function subunit (BK(R207Q)) to enhance BK currents. Heterologous expression of BK(R207Q) generated currents that activated at physiologically relevant voltages in lower intracellular Ca(2+), activated faster, and deactivated slower than wild-type currents. We then used BK(R207Q) expression to broadly augment endogenous BK currents in vivo, generating a transgenic mouse from a circadian clock-controlled Period1 gene fragment (Tg-BK(R207Q)). The specific impact on excitability was assessed in neurons of the suprachiasmatic nucleus (SCN) in the hypothalamus, a cell type where BK currents regulate spontaneous firing under distinct day and night conditions that are defined by different complements of ionic currents. In the SCN, Tg-BK(R207Q) expression converted the endogenous BK current to fast-activating, while maintaining similar current-voltage properties between day and night. Alteration of BK currents in Tg-BK(R207Q) SCN neurons increased firing at night but decreased firing during the day, demonstrating that BK currents generate bidirectional effects on neuronal firing under distinct conditions.

  14. On Capacity Regions of Interference Channels with Mismatched Local Views

    CERN Document Server

    Kao, David T -H

    2011-01-01

    We study the capacity regions of two-user interference channels where transmitters base their transmission decisions on local views of the channel state. Under the local view model, each transmitter knows only a subset of the four channel gains, which may be mismatched from the other transmitter. We consider a set of seven local views, and find that for five out of the seven local views, TDMA is sufficient to achieve the capacity region of the deterministic interference channel. Conversely for these five views, no policy can achieve a rate point outside the TDMA region without inducing a corner case of sub-TDMA performance in another channel state. The common trait shared by the two remaining local views - those with the potential to outperform TDMA - is transmitter knowledge of the outgoing interference link, emphasizing its importance in creating opportunities to use more advanced schemes. Our conclusions are extended to bounded gap characterizations of the capacity region for the Gaussian interference chan...

  15. Localized Algorithm for Channel Assignment in Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Harpreet Kaur

    2015-12-01

    Full Text Available Cognitive Radio has been emerged as a revolutionary solution to migrate the current shortage of spectrum allocation in wireless networks. In this paper, an improved localized channel allocation algorithm based on channel weight is proposed. A factor of channel stability is introduced based on link environment, which efficiently assigns the best channels to the links. Based on the framework, a conflict resolution strategy is used to make the scheme adaptable to different network conditions. Calculations indicate that this algorithm can reduce the conflicts, increase the delivery rate and link assignment rate compared with the basic channel assignment algorithm.

  16. Effects of sodium metabisulfite on the expression of BK(Ca), K(ATP), and L-Ca(2+) channels in rat aortas in vivo and in vitro.

    Science.gov (United States)

    Zhang, Quanxi; Bai, Yunlong; Tian, Jingjing; Lei, Xiaodong; Li, Mei; Yang, Zhenhua; Meng, Ziqiang

    2015-03-01

    Sodium metabisulfite (SMB) is most commonly used as the preservative in many food preparations and drugs. So far, few studies about its negative effects were reported. The purpose of this study was to investigate the effect of SMB on the expression of big-conductance Ca(2+)-activated K(+) (BKCa), ATP-sensitive K(+) (KATP), and L-type calcium (L-Ca(2+)) channels in rat aorta in vivo and in vitro. The results showed that the mRNA and protein levels of the BKCa channel subunits α and β1 of aorta in rats were increased by SMB in vivo and in vitro. Similarly, the expression of the KATP channel subunits Kir6.1, Kir6.2, and SUR2B were increased by SMB. However, SMB at the highest concentration significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. These results suggest that SMB can activate BKCa and KATP channels by increasing the expression of α, β1, and Kir6.1, Kir6.2, SUR2B respectively, while also inhibit L-Ca(2+) channels by decreasing the expression of Cav1.2 and Cav1.3 of aorta in rats. The molecular mechanism of SMB-induced vasorelaxant effect might be related to the expression changes of BKCa, KATP, and L-Ca(2+) channels subunits. Further work is needed to determine the relative contribution of each channel in SMB-mediated vasorelaxant effect.

  17. Robust Source Localization in a Random Shallow Water Channel

    CERN Document Server

    Sazontov, Alexander; Matveyev, Alexander

    2014-01-01

    This paper addresses source localization problem in a random shallow water channel. We present an extension of the generalized MUSIC method to the case, %in which when the signal correlation matrix is imprecisely known. The algorithm is validated by %simulations and its application to the experimental data observed in the Barents Sea. It has been found that the approach proposed demonstrates its excellent performance.

  18. 豚鼠Ⅱ型前庭毛细胞乙酰胆碱敏感性大电导钙依赖性钾通道与L型钙通道共存%Co-location of Ach-sensitive BK channels and L-type calcium channels in type Ⅱ vestibular hair cells of guinea pig

    Institute of Scientific and Technical Information of China (English)

    郭长凯; 李冠乔; 孔维佳; 张松; 吴婷婷; 李家荔; 李擎天

    2008-01-01

    Objective To explore the mechanisms of the influx of calcium ions during the activation of Ach-sensitive BK channel(big conductance,calcium-dependent potassium channel)in type Ⅱ vestibular hair cells of guinea pigs. Methods Type Ⅱ vestibular hair cells were isolated by collagenase type IA.Under the whole-cell patch mode,the sensitivity of Ach-sensitive BK current to the calcium channels blockers was investigated,the pharmacological property of L-type calcium channel activator-sensitive current and Ach-sensitive BK current was compared. Results Following application of Ach, type Ⅱ vestibular hair cells displayed a sustained outward potassium current,with a reversal potential of(-70.5±10.6)mV(-x±s,n=10). At the holding potential of -50 mV, the current amplitude of Ach-sensitive potassium current activated by 100 μmol/L Ach was(267±106) pA(n=11). Ach-sensitive potassium current was potently sensitive to the BK current blocker, IBTX(iberiotoxin, 200 nmol/L). Apamin,the well-known small conductance, calcium-dependent potassium current blocker, failed to inhibit the amplitude of Ach-sensitive potassium current at a dose of 1 μmol/L. Ach-sensitive BK current was sensitive to NiCl2 and potently inhibited by CdCl2. NiCl2 and CdCl2 showed a dose-dependent blocking effect with a half inhibitionmaximal response of(135.5±18.5)μmol/L(n=7) and (23.4±2.6) μmol/L(n=7). The L-type calcium channel activator,(-)-Bay-K 8644(10 μmol/L),mimicked the role of Ach and activated the IBTX-sensitive outward current. Conclusion Ach-sensitive BK and L-type calcium channels are co-located in type Ⅱ vestibular hair cells of guinea pigs.%目的 研究豚鼠Ⅱ型前庭毛细胞乙酰胆碱(acetylcholine,ACh)敏感性大电导钙依赖性钾通道(big conductance,calcium-dependent potassium channel,BK)激活过程中的钙离子内流机制.方法 健康杂色豚鼠52只,断头后取出前庭终器,经胶原酶IA消化后获取Ⅱ型前庭毛细胞.采用全细胞膜片钳技术

  19. The sodium channel as a target for local anesthetic drugs

    Directory of Open Access Journals (Sweden)

    Harry A Fozzard

    2011-11-01

    Full Text Available Na channels are the source of excitatory currents for the nervous system and muscle. They are the target for a class of drugs called local anesthetics (LA, which have been used for local and regional anesthesia and for excitatory dysfunction problems such as epilepsy and cardiac arrhythmia. LA drugs are prototypes for new analgesic drugs. The LA drug binding site has been localized to the inner pore of the channel, where drugs interact mainly with a phenylalanine in domain IV S6. Drug affinity is both voltage- and use-dependent. Voltage-dependency is the result of changes in the conformation of the inner pore during channel activation and opening, allowing high energy interaction of drugs with the phenylalanine. LA drugs also reduce the gating current of Na channels, which represents the movement of charged residues in the voltage sensors. Specifically, drug binding to phenylalanine locks the domain III S4 in its outward (activated position, and slows recovery of the domain IV S4. Although strongly affecting gating, LA drugs almost certainly also block by steric occlusion of the pore. Molecular definition of the binding and blocking interactions may help in new drug development.

  20. Role of BK(Ca) Potassium Channels in the Mechanisms of Modulatory Effects of IL-10 on Hypoxia-Induced Changes in Activity of Hippocampal Neurons.

    Science.gov (United States)

    Levin, S G; Konakov, M V; Godukhin, O V

    2016-03-01

    We studied the contribution of large conductance Ca(2+)-activated potassium channels (BKCa) in the mechanisms of neuromodulatory effects of anti-inflammatory cytokine IL-10 on hypoxiainduced changes in activity of CA1 pyramidal neurons in rat hippocampus. We used the method of registration of population spikes from CA1 pyramidal neurons in hippocampal slices before, during, and after exposure to short-term episodes of hypoxia. Selective blocker (iberiotoxin) and selective activator of BKCa (BMS-191011) were used to evaluate the contribution of these channels in the mechanisms of suppressive effects of IL-10 on changes in neuronal activity during hypoxia and development of post-hypoxic hyperexcitability. It was shown that BKCa are involved in the modulatory effects of IL-10 on hypoxia-induced suppression of activity of CA1 pyramidal neurons in the hippocampus and development of post-hypoxic hyperexcitability in these neurons.

  1. Localization in chaotic systems with a single-channel opening.

    Science.gov (United States)

    Lippolis, Domenico; Ryu, Jung-Wan; Kim, Sang Wook

    2015-07-01

    We introduce a single-channel opening in a random Hamiltonian and a quantized chaotic map: localization on the opening occurs as a sensible deviation of the wave-function statistics from the predictions of random matrix theory, even in the semiclassical limit. Increasing the coupling to the open channel in the quantum model, we observe a similar picture to resonance trapping, made of a few fast-decaying states, whose left (right) eigenfunctions are entirely localized on the (preimage of the) opening, and plentiful long-lived states, whose probability density is instead suppressed at the opening. For the latter, we derive and test a linear relation between the wave-function intensities and the decay rates, similar to the Breit-Wigner law. We then analyze the statistics of the eigenfunctions of the corresponding (discretized) classical propagator, finding a similar behavior to the quantum system only in the weak-coupling regime.

  2. Niflumic acid hyperpolarizes the smooth muscle cells by opening BK(Ca) channels through ryanodine-sensitive Ca(2+) release in spiral modiolar artery.

    Science.gov (United States)

    Li, Li; Ma, Ke-Tao; Zhao, Lei; Si, Jun-Qiang

    2008-12-25

    The mechanism by which niflumic acid (NFA), a Cl(-) channel antagonist, hyperpolarizes the smooth muscle cells (SMCs) of cochlear spiral modiolar artery (SMA) was explored. Guinea pigs were used as subjects and perforated patch clamp and intracellular recording technique were used to observe NFA-induced response of SMC in the acutely isolated SMA preparation. The results showed that bath application of NFA, indanyloxyacetic acid 94 (IAA-94) and disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS) caused hyperpolarization and evoked outward currents in all cells at low resting potential (RP), but had no effects in cells at high RP. In the low RP SMCs, the average RP was about (-42.47+/-1.38) mV (n=24). Application of NFA (100 mumol/L), IAA-94 (10 mumol/L) and DIDS (200 mumol/L) shifted the RP to (13.7+/-4.3) mV (n=9, P<0.01), (11.4+/-4.2) mV (n=7, P<0.01) and (12.3+/-3.7) mV (n=8, P<0.01), respectively. These drug-induced responses were in a concentration-dependent manner. NFA-induced hyperpolarization and outward current were almost blocked by charybdotoxin (100 nmol/L), iberiotoxin (100 nmol/L), tetraethylammonium (10 mmol/L), BAPTA-AM (50 mumol/L), ryanodine (10 mumol/L) and caffeine (0.1-10 mmol/L), respectively, but not by nifedipine (100 mumol/L), CdCl2 (100 mumol/L) and Ca(2+)-free medium. It is concluded that NFA induces a release of intracellular calcium from the Ca(2+) stores and the released intracellular calcium in turn causes concentration-dependent and reversible hyperpolarization and evokes outward currents in the SMCs of the cochlear SMA via activation of the Ca(2+)-activated potassium channels.

  3. Intrarenal localization of the plasma membrane ATP channel pannexin1.

    Science.gov (United States)

    Hanner, Fiona; Lam, Lisa; Nguyen, Mien T X; Yu, Alan; Peti-Peterdi, János

    2012-11-15

    In the renal tubules, ATP released from epithelial cells stimulates purinergic receptors, regulating salt and water reabsorption. However, the mechanisms by which ATP is released into the tubular lumen are multifaceted. Pannexin1 (Panx1) is a newly identified. ubiquitously expressed protein that forms connexin-like channels in the plasma membrane, which have been demonstrated to function as a mechanosensitive ATP conduit. Here, we report on the localization of Panx1 in the mouse kidney. Using immunofluorescence, strong Panx1 expression was observed in renal tubules, including proximal tubules, thin descending limbs, and collecting ducts, along their apical cell membranes. In the renal vasculature, Panx1 expression was localized to vascular smooth muscle cells in renal arteries, including the afferent and efferent arterioles. Additionally, we tested whether Panx1 channels expressed in renal epithelial cells facilitate luminal ATP release by measuring the ATP content of urine samples freshly collected from wild-type and Panx1(-/-) mice. Urinary ATP levels were reduced by 30% in Panx1(-/-) compared with wild-type mice. These results suggest that Panx1 channels in the kidney may regulate ATP release and via purinergic signaling may participate in the control of renal epithelial fluid and electrolyte transport and vascular functions.

  4. Streamwise decay of localized states in channel flow

    CERN Document Server

    Zammert, Stefan

    2016-01-01

    Channel flow, the pressure driven flow between parallel plates, has exact coherent structures that show various degrees of localization. For states which are localized in streamwise direction but extended in spanwise direction, we show that they are exponentially localized, with decay constants that are different on the upstream and downstream side. We extend the analysis of Brand and Gibson, J. Fluid Mech. 750, R1 (2014), for stationary states to the case of advected structures that is needed here, and derive expressions for the decay in terms of eigenvalues and eigenfunctions of certain second order differential equations. The results are in very good agreement with observations on exact coherent structures of different transversal wave length.

  5. Functional characterization of three ethylene response factor genes from Bupleurum kaoi indicates that BkERFs mediate resistance to Botrytis cinerea.

    Science.gov (United States)

    Liu, Wen-Yu; Chiou, Shu-Jiau; Ko, Chia-Yun; Lin, Tsai-Yun

    2011-03-01

    Three novel ethylene response factor (ERF) genes, BkERF1, BkERF2.1 and BkERF2.2, were isolated from a medicinal plant, Bupleurum kaoi. The deduced BkERFs contain a canonical nuclear localization signal and an ERF/AP2 DNA binding domain. RNA gel blot analysis revealed that BkERF1 and BkERF2.1 were ubiquitously expressed at low levels in all parts of mature plants, and that BkERF2.2 was expressed at moderate levels in vegetative tissues. Exogenous application of methyl jasmonate induced BkERF1/2.1/2.2 transcripts. BkERF2.2 transcript levels were slightly increased by addition of ethephon and salicylic acid. BkERFs were localized in the plant nucleus and functioned as transcriptional activators. In B. kaoi cells overexpressing BKERFs, inoculation with Botrytis cinerea increased expression of some defense genes which are associated with enhanced disease resistance. Similarly, overexpression of BkERFs in transgenic Arabidopsis thaliana resulted in elevated mRNA levels of the defense gene PDF1.2, and in enhanced resistance to B. cinerea. Collectively, these results provide evidence that BkERFs mediate the expression of defense-related genes in plants.

  6. A Case of BK Nephropathy without Detectable Viremia or Viruria

    OpenAIRE

    Kamel, Mahmoud; Kadian, Manish; Salazar, Maria Nieva; Mohan, Prince; Self, Sally; Srinivas, Titte; Salas, Maria Aurora Posadas

    2015-01-01

    Patient: Male, 49 Final Diagnosis: BK nephropathy without detectable viremia or viruria Symptoms: — Medication: — Clinical Procedure: Kidney biopsy Specialty: Nephrology Objective: Unusual clinical course Background: BK nephropathy is an evolving challenge among kidney transplant recipients. Diagnosis of BK nephropathy depends on the presence of BK viral inclusions on renal biopsy. Most cases of BK nephropathy are preceded by BK viremia or viruria. Case Report: We report a case of BK nephropa...

  7. Median-plane sound localization as a function of the number of spectral channels using a channel vocoder.

    Science.gov (United States)

    Goupell, Matthew J; Majdak, Piotr; Laback, Bernhard

    2010-02-01

    Using a vocoder, median-plane sound localization performance was measured in eight normal-hearing listeners as a function of the number of spectral channels. The channels were contiguous and logarithmically spaced in the range from 0.3 to 16 kHz. Acutely testing vocoded stimuli showed significantly worse localization compared to noises and 100 pulses click trains, both of which were tested after feedback training. However, localization for the vocoded stimuli was better than chance. A second experiment was performed using two different 12-channel spacings for the vocoded stimuli, now including feedback training. One spacing was from experiment 1. The second spacing (called the speech-localization spacing) assigned more channels to the frequency range associated with speech. There was no significant difference in localization between the two spacings. However, even with training, localizing 12-channel vocoded stimuli remained worse than localizing virtual wideband noises by 4.8 degrees in local root-mean-square error and 5.2% in quadrant error rate. Speech understanding for the speech-localization spacing was not significantly different from that for a typical spacing used by cochlear-implant users. These experiments suggest that current cochlear implants have a sufficient number of spectral channels for some vertical-plane sound localization capabilities, albeit worse than normal-hearing listeners, without loss of speech understanding.

  8. Cholesterol tuning of BK ethanol response is enantioselective, and is a function of accompanying lipids.

    Directory of Open Access Journals (Sweden)

    Chunbo Yuan

    Full Text Available In the search to uncover ethanol's molecular mechanisms, the calcium and voltage activated, large conductance potassium channel (BK has emerged as an important molecule. We examine how cholesterol content in bilayers of 1,2-dioleoyl-3-phosphatidylethanolamine (DOPE/sphingomyelin (SPM and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine (POPE/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS affect the function and ethanol sensitivity of BK. In addition, we examine how manipulation of cholesterol in biological membranes modulates ethanol's actions on BK. We report that cholesterol levels regulate the change in BK channel open probability elicited by 50 mM ethanol. Low levels of cholesterol (<20%, molar ratio supports ethanol activation, while high levels of cholesterol leads to ethanol inhibition of BK. To determine if cholesterol affects BK and its sensitivity to ethanol through a direct cholesterol-protein interaction or via an indirect action on the lipid bilayer, we used the synthetic enantiomer of cholesterol (ent-CHS. We found that 20% and 40% ent-CHS had little effect on the ethanol sensitivity of BK, when compared with the same concentration of nat-CHS. We accessed the effects of ent-CHS and nat-CHS on the molecular organization of DOPE/SPM monolayers at the air/water interface. The isotherm data showed that ent-CHS condensed DOPE/SPM monolayer equivalently to nat-CHS at a 20% concentration, but slightly less at a 40% concentration. Atomic force microscopy (AFM images of DOPE/SPM membranes in the presence of ent-CHS or nat-CHS prepared with LB technique or vesicle deposition showed no significant difference in topographies, supporting the interpretation that the differences in actions of nat-CHS and ent-CHS on BK channel are not likely from a generalized action on bilayers. We conclude that membrane cholesterol influences ethanol's modulation of BK in a complex manner, including an interaction with the channel protein

  9. Theory of Stochastic Local Area Channel Modeling for Wireless Communications

    OpenAIRE

    Durgin, Gregory David

    2000-01-01

    This dissertation outlines work accomplished in the pursuit of this degree. This report is also designed to be a general introduction to the concepts and techniques of small-scale radio channel modeling. At the present time, there does not exist a comprehensive introduction and overview of basic concepts in this field. Furthermore, as the wireless industry continues to mature and develop technology, the need is now greater than ever for more sophisticated channel modeling research. Eac...

  10. Up-Regulatory Effects of Curcumin on Large Conductance Ca2+-Activated K+ Channels.

    Directory of Open Access Journals (Sweden)

    Qijing Chen

    Full Text Available Large conductance Ca2+-activated potassium channels (BK are targets for research that explores therapeutic means to various diseases, owing to the roles of the channels in mediating multiple physiological processes in various cells and tissues. We investigated the pharmacological effects of curcumin, a compound isolated from the herb Curcuma longa, on BK channels. As recorded by whole-cell patch-clamp, curcumin increased BK (α and BK (α+β1 currents in transfected HEK293 cells as well as the current density of BK in A7r5 smooth muscle cells in a dose-dependent manner. By incubating with curcumin for 24 hours, the current density of exogenous BK (α in HEK293 cells and the endogenous BK in A7r5 cells were both enhanced notably, though the steady-state activation of the channels did not shift significantly, except for BK (α+β1. Curcumin up-regulated the BK protein expression without changing its mRNA level in A7r5 cells. The surface expression and the half-life of BK channels were also increased by curcumin in HEK293 cells. These effects of curcumin were abolished by MG-132, a proteasome inhibitor. Curcumin also increased ERK 1/2 phosphorylation, while inhibiting ERK by U0126 attenuated the curcumin-induced up-regulation of BK protein expression. We also observed that the curcumin-induced relaxation in the isolated rat aortic rings was significantly attenuated by paxilline, a BK channel specific blocker. These results show that curcumin enhances the activity of the BK channels by interacting with BK directly as well as enhancing BK protein expression through inhibiting proteasomal degradation and activating ERK signaling pathway. The findings suggest that curcumin is a potential BK channel activator and provide novel insight into its complicated pharmacological effects and the underlying mechanisms.

  11. AN ANALYSIS OF MARKETING CHANNELS OF LOCAL FOOD IN SCOTLAND

    OpenAIRE

    Revoredo-Giha, Cesar; Watts, D.; Leat, Philip M.K.

    2010-01-01

    Local food and its possibilities for addressing sustainable regional growth, food availability, accessibility and affordability has received considerable attention in the discussion on and development of the National Food Policy in Scotland. In terms of methodology, the paper continues the analysis of the local food database for Scotland constructed in Watts et al (2010) by exploring the marketing outlets used by the local food enterprises. This subject is important because it may provide inf...

  12. Soft Matter-Regulated Active Nanovalves Locally Self-Assembled in Femtoliter Nanofluidic Channels.

    Science.gov (United States)

    Xu, Yan; Shinomiya, Misato; Harada, Atsushi

    2016-03-16

    Well-tailored thermoresponsive polymer brushes locally self-assembled in tiny nanofluidic channels enable the active regulation of femtoliter-scale fluids. Such soft-matter-regulated active nanovalves within nanofluidic channels can be extended to build well-controlled functional nanofluidic systems, allowing complex fluidic processes to be performed at the nanometer scales.

  13. The minimum entropy output of a quantum channel is locally additive

    CERN Document Server

    Gour, Gilad

    2011-01-01

    We show that the minimum von-Neumann entropy output of a quantum channel is locally additive. Hasting's counterexample for the additivity conjecture, makes this result quite surprising. In particular, it indicates that the non-additivity of the minimum entropy output is a global effect of quantum channels.

  14. 78 FR 19155 - Special Local Regulations; Marine Events, Wrightsville Channel; Wrightsville Beach, NC

    Science.gov (United States)

    2013-03-29

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulations; Marine Events, Wrightsville... Channel Sprint'' swim event, to be held on the waters adjacent to and surrounding Harbor Island in... Channel Sprint'' on the waters adjacent to and surrounding Harbor Island in Wrightsville Beach,...

  15. Localization and function of ATP-sensitive potassium channels in human skeletal muscle

    DEFF Research Database (Denmark)

    Nielsen, Jens Jung; Kristensen, Michael; Hellsten, Ylva

    2003-01-01

    The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique...

  16. Identification and functional characterization of cereblon as a binding protein for large-conductance calcium-activated potassium channel in rat brain.

    Science.gov (United States)

    Jo, Sooyeon; Lee, Kwang-Hee; Song, Sungmin; Jung, Yong-Keun; Park, Chul-Seung

    2005-09-01

    Large-conductance Ca2+-activated K+ (BK(Ca)) channels are activated by membrane depolarization and modulated by intracellular Ca2+. Here, we report the direct interaction of cereblon (CRBN) with the cytosolic carboxy-terminus of the BK(Ca) channel alpha subunit (Slo). Rat CRBN contained the N-terminal domain of the Lon protease, a 'regulators of G protein-signaling' (RGS)-like domain, a leucine zipper (LZ) motif, and four putative protein kinase C (PKC) phosphorylation sites. RNA messages of rat cereblon (rCRBN) were widely distributed in different tissues with especially high-levels of expression in the brain. Direct association of rCRBN with the BK(Ca) channel was confirmed by immunoprecipitation in brain lysate, and the two proteins were co-localized in cultured rat hippocampal neurons. Ionic currents evoked by the rSlo channel were dramatically suppressed upon coexpression of rCRBN. rCRBN decreased the formation of the tetrameric rSlo complex thus reducing the surface expression of functional channels. Therefore, we suggest that CRBN may play an important role in assembly and surface expression of functional BK(Ca) channels by direct interaction with the cytosolic C-terminus of its alpha-subunit.

  17. Neuronal Ca2+-activated K+ channels limit brain infarction and promote survival.

    Directory of Open Access Journals (Sweden)

    Yiliu Liao

    Full Text Available Neuronal calcium-activated potassium channels of the BK type are activated by membrane depolarization and intracellular Ca(2+ ions. It has been suggested that these channels may play a key neuroprotective role during and after brain ischemia, but this hypothesis has so far not been tested by selective BK-channel manipulations in vivo. To elucidate the in vivo contribution of neuronal BK channels in acute focal cerebral ischemia, we performed middle cerebral artery occlusion (MCAO in mice lacking BK channels (homozygous mice lacking the BK channel alpha subunit, BK(-/-. MCAO was performed in BK(-/- and WT mice for 90 minutes followed by a 7-hour-reperfusion period. Coronal 1 mm thick sections were stained with 2,3,5-triphenyltetrazolium chloride to reveal the infarction area. We found that transient focal cerebral ischemia by MCAO produced larger infarct volume, more severe neurological deficits, and higher post-ischemic mortality in BK(-/- mice compared to WT littermates. However, the regional cerebral blood flow was not significantly different between genotypes as measured by Laser Doppler (LD flowmetry pre-ischemically, intra-ischemically, and post-ischemically, suggesting that the different impact of MCAO in BK(-/- vs. WT was not due to vascular BK channels. Furthermore, when NMDA was injected intracerebrally in non-ischemic mice, NMDA-induced neurotoxicity was found to be larger in BK(-/- mice compared to WT. Whole-cell patch clamp recordings from CA1 pyramidal cells in organotypic hippocampal slice cultures revealed that BK channels contribute to rapid action potential repolarization, as previously found in acute slices. When these cultures were exposed to ischemia-like conditions this induced significantly more neuronal death in BK(-/- than in WT cultures. These results indicate that neuronal BK channels are important for protection against ischemic brain damage.

  18. Neuronal Ca2+-activated K+ channels limit brain infarction and promote survival.

    Science.gov (United States)

    Liao, Yiliu; Kristiansen, Ase-Marit; Oksvold, Cecilie P; Tuvnes, Frode A; Gu, Ning; Rundén-Pran, Elise; Ruth, Peter; Sausbier, Matthias; Storm, Johan F

    2010-12-30

    Neuronal calcium-activated potassium channels of the BK type are activated by membrane depolarization and intracellular Ca(2+) ions. It has been suggested that these channels may play a key neuroprotective role during and after brain ischemia, but this hypothesis has so far not been tested by selective BK-channel manipulations in vivo. To elucidate the in vivo contribution of neuronal BK channels in acute focal cerebral ischemia, we performed middle cerebral artery occlusion (MCAO) in mice lacking BK channels (homozygous mice lacking the BK channel alpha subunit, BK(-/-)). MCAO was performed in BK(-/-) and WT mice for 90 minutes followed by a 7-hour-reperfusion period. Coronal 1 mm thick sections were stained with 2,3,5-triphenyltetrazolium chloride to reveal the infarction area. We found that transient focal cerebral ischemia by MCAO produced larger infarct volume, more severe neurological deficits, and higher post-ischemic mortality in BK(-/-) mice compared to WT littermates. However, the regional cerebral blood flow was not significantly different between genotypes as measured by Laser Doppler (LD) flowmetry pre-ischemically, intra-ischemically, and post-ischemically, suggesting that the different impact of MCAO in BK(-/-) vs. WT was not due to vascular BK channels. Furthermore, when NMDA was injected intracerebrally in non-ischemic mice, NMDA-induced neurotoxicity was found to be larger in BK(-/-) mice compared to WT. Whole-cell patch clamp recordings from CA1 pyramidal cells in organotypic hippocampal slice cultures revealed that BK channels contribute to rapid action potential repolarization, as previously found in acute slices. When these cultures were exposed to ischemia-like conditions this induced significantly more neuronal death in BK(-/-) than in WT cultures. These results indicate that neuronal BK channels are important for protection against ischemic brain damage.

  19. 78 FR 34881 - Special Local Regulations; Marine Events, Wrightsville Channel; Wrightsville Beach, NC

    Science.gov (United States)

    2013-06-11

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulations; Marine Events, Wrightsville... Guard is establishing a Special Local Regulation for the ``Swim the Loop/Motts Channel Sprint'' swim... Sprint'' on the waters adjacent to and surrounding Harbor Island in Wrightsville Beach, North...

  20. Apical Ca2+-activated potassium channels in mouse parotid acinar cells.

    Science.gov (United States)

    Almassy, Janos; Won, Jong Hak; Begenisich, Ted B; Yule, David I

    2012-02-01

    Ca(2+) activation of Cl and K channels is a key event underlying stimulated fluid secretion from parotid salivary glands. Cl channels are exclusively present on the apical plasma membrane (PM), whereas the localization of K channels has not been established. Mathematical models have suggested that localization of some K channels to the apical PM is optimum for fluid secretion. A combination of whole cell electrophysiology and temporally resolved digital imaging with local manipulation of intracellular [Ca(2+)] was used to investigate if Ca(2+)-activated K channels are present in the apical PM of parotid acinar cells. Initial experiments established Ca(2+)-buffering conditions that produced brief, localized increases in [Ca(2+)] after focal laser photolysis of caged Ca(2+). Conditions were used to isolate K(+) and Cl(-) conductances. Photolysis at the apical PM resulted in a robust increase in K(+) and Cl(-) currents. A localized reduction in [Ca(2+)] at the apical PM after photolysis of Diazo-2, a caged Ca(2+) chelator, resulted in a decrease in both K(+) and Cl(-) currents. The K(+) currents evoked by apical photolysis were partially blocked by both paxilline and TRAM-34, specific blockers of large-conductance "maxi-K" (BK) and intermediate K (IK), respectively, and almost abolished by incubation with both antagonists. Apical TRAM-34-sensitive K(+) currents were also observed in BK-null parotid acini. In contrast, when the [Ca(2+)] was increased at the basal or lateral PM, no increase in either K(+) or Cl(-) currents was evoked. These data provide strong evidence that K and Cl channels are similarly distributed in the apical PM. Furthermore, both IK and BK channels are present in this domain, and the density of these channels appears higher in the apical versus basolateral PM. Collectively, this study provides support for a model in which fluid secretion is optimized after expression of K channels specifically in the apical PM.

  1. General Approach to Quantum Channel Impossibility by Local Operations and Classical Communication

    Science.gov (United States)

    Cohen, Scott M.

    2017-01-01

    We describe a general approach to proving the impossibility of implementing a quantum channel by local operations and classical communication (LOCC), even with an infinite number of rounds, and find that this can often be demonstrated by solving a set of linear equations. The method also allows one to design a LOCC protocol to implement the channel whenever such a protocol exists in any finite number of rounds. Perhaps surprisingly, the computational expense for analyzing LOCC channels is not much greater than that for LOCC measurements. We apply the method to several examples, two of which provide numerical evidence that the set of quantum channels that are not LOCC is not closed and that there exist channels that can be implemented by LOCC either in one round or in three rounds that are on the boundary of the set of all LOCC channels. Although every LOCC protocol must implement a separable quantum channel, it is a very difficult task to determine whether or not a given channel is separable. Fortunately, prior knowledge that the channel is separable is not required for application of our method.

  2. Shaping of action potentials by type I and type II large-conductance Ca²+-activated K+ channels.

    Science.gov (United States)

    Jaffe, D B; Wang, B; Brenner, R

    2011-09-29

    The BK channel is a Ca(2+) and voltage-gated conductance responsible for shaping action potential waveforms in many types of neurons. Type II BK channels are differentiated from type I channels by their pharmacology and slow gating kinetics. The β4 accessory subunit confers type II properties on BK α subunits. Empirically derived properties of BK channels, with and without the β4 accessory subunit, were obtained using a heterologous expression system under physiological ionic conditions. These data were then used to study how BK channels alone (type I) and with the accessory β4 subunit (type II) modulate action potential properties in biophysical neuron models. Overall, the models support the hypothesis that it is the slower kinetics provided by the β4 subunit that endows the BK channel with type II properties, which leads to broadening of action potentials and, secondarily, to greater recruitment of SK channels reducing neuronal excitability. Two regions of parameter space distinguished type II and type I effects; one where the range of BK-activating Ca(2+) was high (>20 μM) and the other where BK-activating Ca(2+) was low (∼0.4-1.2 μM). The latter required an elevated BK channel density, possibly beyond a likely physiological range. BK-mediated sharpening of the spike waveform associated with the lack of the β4 subunit was sensitive to the properties of voltage-gated Ca(2+) channels due to electrogenic effects on spike duration. We also found that depending on Ca(2+) dynamics, type II BK channels may have the ability to contribute to the medium AHP, a property not generally ascribed to BK channels, influencing the frequency-current relationship. Finally, we show how the broadening of action potentials conferred by type II BK channels can also indirectly increase the recruitment of SK-type channels decreasing the excitability of the neuron.

  3. A theory of local learning, the learning channel, and the optimality of backpropagation.

    Science.gov (United States)

    Baldi, Pierre; Sadowski, Peter

    2016-11-01

    In a physical neural system, where storage and processing are intimately intertwined, the rules for adjusting the synaptic weights can only depend on variables that are available locally, such as the activity of the pre- and post-synaptic neurons, resulting in local learning rules. A systematic framework for studying the space of local learning rules is obtained by first specifying the nature of the local variables, and then the functional form that ties them together into each learning rule. Such a framework enables also the systematic discovery of new learning rules and exploration of relationships between learning rules and group symmetries. We study polynomial local learning rules stratified by their degree and analyze their behavior and capabilities in both linear and non-linear units and networks. Stacking local learning rules in deep feedforward networks leads to deep local learning. While deep local learning can learn interesting representations, it cannot learn complex input-output functions, even when targets are available for the top layer. Learning complex input-output functions requires local deep learning where target information is communicated to the deep layers through a backward learning channel. The nature of the communicated information about the targets and the structure of the learning channel partition the space of learning algorithms. For any learning algorithm, the capacity of the learning channel can be defined as the number of bits provided about the error gradient per weight, divided by the number of required operations per weight. We estimate the capacity associated with several learning algorithms and show that backpropagation outperforms them by simultaneously maximizing the information rate and minimizing the computational cost. This result is also shown to be true for recurrent networks, by unfolding them in time. The theory clarifies the concept of Hebbian learning, establishes the power and limitations of local learning rules

  4. The Use of Inhibitors of Mechanosensitive Ion Channels as Local Inhibitors of Peripheral Pain

    Science.gov (United States)

    2015-01-01

    type currents are more closely associated with  nociception .  Although the current associated with the two main types of  pain  are not restricted to a...Award Number: W81XWH-11-2-0125 TITLE: The Use of Inhibitors of Mechanosensitive Ion Channels as Local Inhibitors of Peripheral Pain PRINCIPAL...2011 - 24 Oct 2014 4. TITLE AND SUBTITLE The Use of Inhibitors of Mechanosensitive Ion Channels as Local Inhibitors of Peripheral Pain 5a. CONTRACT

  5. Polyoma BK Virus: An Oncogenic Virus?

    Directory of Open Access Journals (Sweden)

    Syed Hassan

    2013-01-01

    Full Text Available We report a case of a 65-year-old gentleman with a history of end stage renal disease who underwent a successful cadaveric donor kidney transplant four years ago. He subsequently developed BK virus nephropathy related to chronic immunosuppressant therapy. Three years later, misfortune struck again, and he developed adenocarcinoma of the bladder.

  6. Evaluating the BK 21 Program. Research Brief

    Science.gov (United States)

    Seong, Somi; Popper, Steven W.; Goldman, Charles A.; Evans, David K.; Grammich, Clifford A.

    2008-01-01

    The Brain Korea 21 program (BK21), an effort to improve Korean universities and research, has attracted a great deal of attention in Korea, producing the need to understand how well the program is meeting its goals. RAND developed a logic model for identifying program goals and dynamics, suggested quantitative and qualitative evaluation methods,…

  7. Influence of Global and Local Membrane Curvature on Mechanosensitive Ion Channels: A Finite Element Approach

    Directory of Open Access Journals (Sweden)

    Omid Bavi

    2016-02-01

    Full Text Available Mechanosensitive (MS channels are ubiquitous molecular force sensors that respond to a number of different mechanical stimuli including tensile, compressive and shear stress. MS channels are also proposed to be molecular curvature sensors gating in response to bending in their local environment. One of the main mechanisms to functionally study these channels is the patch clamp technique. However, the patch of membrane surveyed using this methodology is far from physiological. Here we use continuum mechanics to probe the question of how curvature, in a standard patch clamp experiment, at different length scales (global and local affects a model MS channel. Firstly, to increase the accuracy of the Laplace’s equation in tension estimation in a patch membrane and to be able to more precisely describe the transient phenomena happening during patch clamping, we propose a modified Laplace’s equation. Most importantly, we unambiguously show that the global curvature of a patch, which is visible under the microscope during patch clamp experiments, is of negligible energetic consequence for activation of an MS channel in a model membrane. However, the local curvature (RL < 50 and the direction of bending are able to cause considerable changes in the stress distribution through the thickness of the membrane. Not only does local bending, in the order of physiologically relevant curvatures, cause a substantial change in the pressure profile but it also significantly modifies the stress distribution in response to force application. Understanding these stress variations in regions of high local bending is essential for a complete understanding of the effects of curvature on MS channels.

  8. Distributed Channel Selection in CRAHNs with Heterogeneous Spectrum Opportunities: A Local Congestion Game Approach

    Science.gov (United States)

    Xu, Yuhua; Wu, Qihui; Wang, Jinlong; Min, Neng; Anpalagan, Alagan

    This letter investigates the problem of distributed channel selection in cognitive radio ad hoc networks (CRAHNs) with heterogeneous spectrum opportunities. Firstly, we formulate this problem as a local congestion game, which is proved to be an exact potential game. Then, we propose a spatial best response dynamic (SBRD) to rapidly achieve Nash equilibrium via local information exchange. Moreover, the potential function of the game reflects the network collision level and can be used to achieve higher throughput.

  9. 78 FR 33219 - Special Local Regulations; Swim Across the Potomac, Potomac River; National Harbor Access Channel...

    Science.gov (United States)

    2013-06-04

    ... INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice of Proposed... Access Channel, MD'' in the Federal Register (78 FR 67). We received no comments on the proposed rule. No... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulations; Swim Across the...

  10. Quantification and distribution of big conductance Ca2+-activated K+ channels in kidney epithelia

    DEFF Research Database (Denmark)

    Grunnet, Morten; Hay-Schmidt, Anders; Klaerke, Dan A

    2005-01-01

    and immunohistochemical studies. In cortical collecting ducts, BK channels were exclusively located in principal cells while no channels could be found in intercalated cells. The abundant and distinct distribution in kidney epithelia talks in favor for BK channels being important contributors in maintaining salt...

  11. The use of kernel local Fisher discriminant analysis for the channelization of the Hotelling model observer

    Science.gov (United States)

    Wen, Gezheng; Markey, Mia K.

    2015-03-01

    It is resource-intensive to conduct human studies for task-based assessment of medical image quality and system optimization. Thus, numerical model observers have been developed as a surrogate for human observers. The Hotelling observer (HO) is the optimal linear observer for signal-detection tasks, but the high dimensionality of imaging data results in a heavy computational burden. Channelization is often used to approximate the HO through a dimensionality reduction step, but how to produce channelized images without losing significant image information remains a key challenge. Kernel local Fisher discriminant analysis (KLFDA) uses kernel techniques to perform supervised dimensionality reduction, which finds an embedding transformation that maximizes betweenclass separability and preserves within-class local structure in the low-dimensional manifold. It is powerful for classification tasks, especially when the distribution of a class is multimodal. Such multimodality could be observed in many practical clinical tasks. For example, primary and metastatic lesions may both appear in medical imaging studies, but the distributions of their typical characteristics (e.g., size) may be very different. In this study, we propose to use KLFDA as a novel channelization method. The dimension of the embedded manifold (i.e., the result of KLFDA) is a counterpart to the number of channels in the state-of-art linear channelization. We present a simulation study to demonstrate the potential usefulness of KLFDA for building the channelized HOs (CHOs) and generating reliable decision statistics for clinical tasks. We show that the performance of the CHO with KLFDA channels is comparable to that of the benchmark CHOs.

  12. Experimental demonstration of tunable homodyne detection of WDM and dual-polarization PSK channels by automatically locking the channels to a local pump laser using nonlinear mixing.

    Science.gov (United States)

    Almaiman, Ahmed; Ziyadi, Morteza; Mohajerin-Ariaei, Amirhossein; Cao, Yinwen; Chitgarha, Mohammad Reza; Liao, Peicheng; Bao, Changjing; Shamee, Bishara; Ahmed, Nisar; Alishahi, Fatemeh; Fallahpour, Ahmad; Akasaka, Youichi; Yang, Jeng-Yuan; Sekiya, Motoyoshi; Touch, Joseph D; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

    2016-06-15

    This Letter proposes a method for tunable automatically locked homodyne detection of wavelength-division multiplexing (WDM) dual-polarization (DP) phase-shift keyed (PSK) channels using nonlinear mixing. Two stages of periodically poled lithium niobate (PPLN) waveguides and an LCoS filter enable automatic phase locking of the channels to a local laser.

  13. BK Virus Nephropathy in Heart Transplant Recipients.

    Science.gov (United States)

    Joseph, Alin; Pilichowska, Monika; Boucher, Helen; Kiernan, Michael; DeNofrio, David; Inker, Lesley A

    2015-06-01

    Polyomavirus-associated nephropathy (PVAN) has become an important cause of kidney failure in kidney transplant recipients. PVAN is reported to affect 1% to 7% of kidney transplant recipients, leading to premature transplant loss in approximately 30% to 50% of diagnosed cases. PVAN occurring in the native kidneys of solid-organ transplant recipients other than kidney only recently has been noted. We report 2 cases of PVAN in heart transplant recipients, which brings the total of reported cases to 7. We briefly review the literature on the hypothesized causes of PVAN in kidney transplant recipients and comment on whether these same mechanisms also may cause PVAN in other solid-organ transplant recipients. PVAN should be considered in the differential diagnosis when evaluating worsening kidney function. BK viremia surveillance studies of nonkidney solid-organ recipients should be conducted to provide data to assist the transplantation community in deciding whether regular monitoring of nonkidney transplant recipients for BK viremia is indicated.

  14. A monosaccharide transporter is localized to sieve plate and plasmodesmal channel in developing apple fruit

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lingyun; PENG Changcao; ZOU Keqin; WANG Xiuling; FAN Renchun; YU Xiangchun; ZHANG Xiaoyan; SHEN Yuanyue; ZHANG Dapeng

    2005-01-01

    Two major classes of plant sugar transporters, sucrose and monosaccharide transporters, may be localized to tonoplast or plasma membrane. The monosaccharide transporters may also be localized in plastid. However, whether these transporters reside in other subcellular compartments remains unclear. We recently detected in apple fruit a 52 kD plasma membrane-localized monosaccharide transporter, and showed that this transporter may be functional in phloem unloading in the fruit. In this paper, we report that this monosaccharide transporter is also localized to sieve plate and plasmodesmal channel in apple fruit. The amount of this sieve plate- and plasmodesma-associated transporter changes during fruit development. This amount of the transporter expression may be altered in the phloem sieve elements but not in the parenchyma cells by a photoassimilate deficiency applied by the shoot girdling treatment, suggesting that the monosaccharide transporter of the special sub-cellular localization may be of biological significance.

  15. Exposing the Molecular Machinery of BK Polyomavirus.

    Science.gov (United States)

    Buck, Christopher B

    2016-04-05

    BK polyomavirus (BKV) is an opportunistic pathogen that poses a serious threat to organ transplant recipients. In this issue of Structure, Hurdiss and colleagues' (Hurdiss et al., 2016) beautiful new high-resolution cryo-EM reconstruction of BKV provides a structural roadmap for the ongoing development of therapeutic antibodies and vaccines targeting this potentially deadly virus. The study also serves as a platform for exploring the basic biology of virion assembly and infectious entry.

  16. Dual channel rank-based intensity weighting for quantitative co-localization of microscopy images

    LENUS (Irish Health Repository)

    Singan, Vasanth R

    2011-10-21

    Abstract Background Accurate quantitative co-localization is a key parameter in the context of understanding the spatial co-ordination of molecules and therefore their function in cells. Existing co-localization algorithms consider either the presence of co-occurring pixels or correlations of intensity in regions of interest. Depending on the image source, and the algorithm selected, the co-localization coefficients determined can be highly variable, and often inaccurate. Furthermore, this choice of whether co-occurrence or correlation is the best approach for quantifying co-localization remains controversial. Results We have developed a novel algorithm to quantify co-localization that improves on and addresses the major shortcomings of existing co-localization measures. This algorithm uses a non-parametric ranking of pixel intensities in each channel, and the difference in ranks of co-localizing pixel positions in the two channels is used to weight the coefficient. This weighting is applied to co-occurring pixels thereby efficiently combining both co-occurrence and correlation. Tests with synthetic data sets show that the algorithm is sensitive to both co-occurrence and correlation at varying levels of intensity. Analysis of biological data sets demonstrate that this new algorithm offers high sensitivity, and that it is capable of detecting subtle changes in co-localization, exemplified by studies on a well characterized cargo protein that moves through the secretory pathway of cells. Conclusions This algorithm provides a novel way to efficiently combine co-occurrence and correlation components in biological images, thereby generating an accurate measure of co-localization. This approach of rank weighting of intensities also eliminates the need for manual thresholding of the image, which is often a cause of error in co-localization quantification. We envisage that this tool will facilitate the quantitative analysis of a wide range of biological data sets

  17. Three-dimensional Sound Source Localization Using Inter-channel Time Difference Trajectory

    Directory of Open Access Journals (Sweden)

    Sangmoon Lee

    2015-12-01

    Full Text Available Sound source localization is one of the basic and essential techniques for intelligent robots in terms of human-robot interaction and has been utilized in various engineering fields. This paper suggests a new localization method using an inter-channel time difference trajectory, which is a new localization cue for efficient 3-D localization. As one of the ways to realize the proposed cue, a two-channel rotating array is employed. Two microphones are attached on the left and right sides of the spherical head. One microphone is in a circular motion on the right side, while the other is fixed on the left side. According to the rotating motion of the array, the (source direction-dependent characteristics of the trajectories are analysed using the Ray-Tracing formula extended for 3-D models. In simulation, the synthesized signals generated by the fixed and rotating microphone signal models were used as the output signals of the two microphones. The simulation showed that the localization performance is strongly dependent on the azimuthal position of a source, which is caused by the asymmetry of the trajectory amplitude. Additionally, the experimental results of the two experiments carried out in the room environment demonstrated that the proposed system can localize a Gaussian noise source and a voice source in 3-D space.

  18. Progression from Sustained BK Viruria to Sustained BK Viremia with Immunosuppression Reduction Is Not Associated with Changes in the Noncoding Control Region of the BK Virus Genome

    Science.gov (United States)

    Memon, Imran A.; Parikh, Bijal A.; Gaudreault-Keener, Monique; Skelton, Rebecca; Storch, Gregory A.; Brennan, Daniel C.

    2012-01-01

    Changes in the BK virus archetypal noncoding control region (NCCR) have been associated with BK-virus-associated nephropathy (BKVAN). Whether sustained viremia, a surrogate for BKVAN, is associated with significant changes in the BK-NCCR is unknown. We performed PCR amplification and sequencing of (1) stored urine and (2) plasma samples from the time of peak viremia from 11 patients with sustained viremia who participated in a 200-patient clinical trial. The antimetabolite was withdrawn for BK viremia and reduction of the calcineurin inhibitor for sustained BK viremia. DNA sequencing from the 11 patients with sustained viremia revealed 8 insertions, 16 transversions, 3 deletions, and 17 transitions. None were deemed significant. No patient developed clinically evident BKVAN. Our data support, at a genomic level, the effectiveness of reduction of immunosuppression for prevention of progression from viremia to BKVAN. PMID:22701777

  19. Bedform migration in steep channels: from local avalanches to large scale changes

    Science.gov (United States)

    Mettra, F.; Heyman, J.; Ancey, C.

    2013-12-01

    flume angles and produced intense solid discharge pulses. Moreover, small avalanches occurred on the steep lee sides of antidunes. From these results, we infer a mechanism of steep channel evolution. The time- and space-averaged profile of the bed in the streamwise direction depends on the experimental parameters. Variations in the profile result mainly from bedform migration. The instantaneous global state of the bed (which can be characterized by the global channel slope) controls the growth of bedforms, which can be seen as local instabilities. When the global channel slope approaches its critical value, local instabilities of higher amplitude can develop and create intense bedload transport pulses, leading to a less steep, but more stable bed profile.

  20. Strain localization associated with channelized melt migration in upper mantle lithosphere: Insights from the Twin Sisters ultramafic complex, Washington, USA

    Science.gov (United States)

    Kruckenberg, Seth C.; Tikoff, Basil; Toy, Virginia G.; Newman, Julie; Young, Laura I.

    2013-05-01

    We present results of field, microstructural, and textural studies in the Twin Sisters ultramafic complex (Washington State) that document localized deformation associated with the formation of dunite channels in naturally deformed upper mantle. The Twin Sisters complex is a well-exposed, virtually unaltered section of upper mantle lithosphere comprised largely of dunite and harzburgite (in cm- to m-scale primary compositional layers), and variably deformed orthopyroxenite and clinopyroxenite dikes. A series of ˜N-S striking, m-scale dunite bands (typically with porphyroclastic texture) occur throughout the study area and crosscut both the primary compositional layers and older orthopyroxenite dikes. Structural relationships suggest that these dunite bands represent former zones of channelized melt migration (i.e., dunite channels), and that strain localization was associated with melt migration. Early formed orthopyroxenite dikes are either absent within cross-cutting dunite channels, or have been displaced within channels relative to their position in the adjacent host rocks. These pre-existing orthopyroxenite dikes provide strain markers illustrating that displacement was localized primarily along channel margins, which have opposite senses of shear. In all cases where offsets were noted, the center of the channel was moved southward relative to its margins. Material flow and strain was, therefore, partitioned within channels during melt migration, and dunite channels did not accommodate net shear displacement of the adjacent host peridotites. Primary compositional layers adjacent to dunite channels document opposite rotation of olivine [100] crystallographic axes on either side of channel margins, consistent with the kinematic reversal inferred from offset markers at the outcrop scale, suggesting that the formation of dunite channels also induced host rock deformation proximal to channels. Strain localization that was focused at the margin of the bands was

  1. Synaptic Ribbons Require Ribeye for Electron Density, Proper Synaptic Localization, and Recruitment of Calcium Channels

    Directory of Open Access Journals (Sweden)

    Caixia Lv

    2016-06-01

    Full Text Available Synaptic ribbons are structures made largely of the protein Ribeye that hold synaptic vesicles near release sites in non-spiking cells in some sensory systems. Here, we introduce frameshift mutations in the two zebrafish genes encoding for Ribeye and thus remove Ribeye protein from neuromast hair cells. Despite Ribeye depletion, vesicles collect around ribbon-like structures that lack electron density, which we term “ghost ribbons.” Ghost ribbons are smaller in size but possess a similar number of smaller vesicles and are poorly localized to synapses and calcium channels. These hair cells exhibit enhanced exocytosis, as measured by capacitance, and recordings from afferent neurons post-synaptic to hair cells show no significant difference in spike rates. Our results suggest that Ribeye makes up most of the synaptic ribbon density in neuromast hair cells and is necessary for proper localization of calcium channels and synaptic ribbons.

  2. Fusion and quasifission dynamics in the reactions 48Ca+249Bk and 50Ti+249Bk using a time-dependent Hartree-Fock approach

    Science.gov (United States)

    Umar, A. S.; Oberacker, V. E.; Simenel, C.

    2016-08-01

    Background: Synthesis of superheavy elements (SHEs) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHEs have been recently produced with doubly-magic 48Ca beams. However, SHE synthesis experiments with single-magic 50Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for Z =117 ,119 superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in 48Ca,50Ti+249Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleus-nucleus potentials, nuclear contact times, masses and charges of the fragments, as well as their kinetic and excitation energies strongly depend on the orientation of the prolate 249Bk nucleus. Long contact times associated with fusion are observed in collisions of both projectiles with the side of the 249Bk nucleus, but not on collisions with its tip. The energy and impact parameter dependencies of the fragment properties, as well as their mass-angle and mass-total kinetic energy correlations are investigated. Conclusions: Entrance channel reaction dynamics are similar with both 48Ca and 50Ti projectiles. Both are expected to lead to the formation of a compound nucleus by fusion if they have enough energy to get in contact with the side of the 249Bk target.

  3. Regulation of Guinea Pig Detrusor Smooth Muscle Excitability by 17β-Estradiol: The Role of the Large Conductance Voltage- and Ca2+-Activated K+ Channels.

    Science.gov (United States)

    Provence, Aaron; Hristov, Kiril L; Parajuli, Shankar P; Petkov, Georgi V

    2015-01-01

    Estrogen replacement therapies have been suggested to be beneficial in alleviating symptoms of overactive bladder. However, the precise regulatory mechanisms of estrogen in urinary bladder smooth muscle (UBSM) at the cellular level remain unknown. Large conductance voltage- and Ca2+-activated K+ (BK) channels, which are key regulators of UBSM function, are suggested to be non-genomic targets of estrogens. This study provides an electrophysiological investigation into the role of UBSM BK channels as direct targets for 17β-estradiol, the principle estrogen in human circulation. Single BK channel recordings on inside-out excised membrane patches and perforated whole cell patch-clamp were applied in combination with the BK channel selective inhibitor paxilline to elucidate the mechanism of regulation of BK channel activity by 17β-estradiol in freshly-isolated guinea pig UBSM cells. 17β-Estradiol (100 nM) significantly increased the amplitude of depolarization-induced whole cell steady-state BK currents and the frequency of spontaneous transient BK currents in freshly-isolated UBSM cells. The increase in whole cell BK currents by 17β-estradiol was eliminated upon blocking BK channels with paxilline. 17β-Estradiol (100 nM) significantly increased (~3-fold) the single BK channel open probability, indicating direct 17β-estradiol-BK channel interactions. 17β-Estradiol (100 nM) caused a significant hyperpolarization of the membrane potential of UBSM cells, and this hyperpolarization was reversed by blocking the BK channels with paxilline. 17β-Estradiol (100 nM) had no effects on L-type voltage-gated Ca2+ channel currents recorded under perforated patch-clamp conditions. This study reveals a new regulatory mechanism in the urinary bladder whereby BK channels are directly activated by 17β-estradiol to reduce UBSM cell excitability.

  4. Twist decomposition of proton structure from BFKL and BK amplitudes

    CERN Document Server

    Motyka, Leszek

    2014-01-01

    An analysis of twist composition of Balitsky-Kovchegov (BK) amplitude is performed in the double logarithmic limit. In this limit the BK evolution of color dipole -- proton scattering is equivalent to BFKL evolution which follows from vanishing of the Bartels vertex in the collinear limit. We perform twist decomposition of the BFKL/BK amplitude for proton structure functions and find compact analytic expressions that provide accurate approximations for higher twist amplitudes. The BFKL/BK higher twist amplitudes are much smaller than those following from eikonal saturation models.

  5. Comparison between Two Local Thermal Non Equilibrium Criteria in Forced Convection through a Porous Channel

    Directory of Open Access Journals (Sweden)

    azzedine ABDEDOU

    2015-01-01

    Full Text Available Two criteria are used and compared to investigate the local thermal equilibrium assumption in a forced convection through a porous channel. The first criterion is based on the maximum local temperature difference between the solid and fluid phases, while the second is based on the average of the local differences between the temperature of the solid phase and the fluid phase. For this purpose, the momentum and energy equations based on the Darcy-Brinkman-Forchheimer and the local thermal non equilibrium models are solved numerically using the finite volume method. The analysis focused on searching thermophysical parameters ranges which validate local thermal equilibrium hypothesis. Thus, by using the two criteria, the obtained results mainly revealed that this local thermal equilibrium assumption is verified for low thermal conductivity ratio and Reynolds number values and for high interstitial Biot number and porosity, while it is unfavorably affected by the high values of Prandtl number. However, it is also found that the parameters ranges corresponding to the local equilibrium validity depends on the selected local thermal non equilibrium criterion.

  6. Single-thread channels resulting from a localization process driven by vegetation

    Science.gov (United States)

    Narteau, C.; Tal, M.

    2009-12-01

    The unpredictable manner in which braided rivers evolve is in stark contrast to the orderly migration pattern of meandering rivers driven by erosion along outer bends and deposition along inner banks. Braided channels are the default pattern that develops when an unbounded water flow interacts with noncohesive sediment. A series of laboratory experiments demonstrated that plants alone are able to achieve the two key mechanisms to developing meandering: slowing the rate of widening and discouraging channel cutoffs. Plants initially colonized braid-bars that were emergent during low flow. By adding cohesion to the sediment and increasing roughness, vegetation deterred the flow from reoccupying areas which were colonized. By decreasing erosion rates, plants made it possible for deposition along the inner bank to match the rate of erosion along the outer bank. This enabled the channel to develop sinuosity and migrate laterally while suppressing channel splitting and the creation of new channel width. Areas with established vegetation provided stable conditions which promoted new seedling establishment and expansion of the vegetated area. A generic mechanism of width production in the braided state is the opportunistic creation of new channels. As existing flow paths become slightly less favorable, for example by bar deposition or an increase in sinuosity, new ones are readily created in areas that are not currently occupied by flow. By making it more difficult for flow to occupy vegetated areas, plants in effect decouple the transition between wet and dry areas, making it harder for areas that are dry (vegetated) to turn wet (reoccupied by flow) and less likely for areas that are wet to become dry. The net effect is localization of the flow into a single-thread channel with transitions between wet and dry occurring predominantly along the channel margin and driving lateral migration while a single-thread channel remains intact. We are using a 1D cellular automata model

  7. Strain localization in a fossilized subduction channel: Insights from the Cycladic Blueschist Unit (Syros, Greece)

    Science.gov (United States)

    Laurent, Valentin; Jolivet, Laurent; Roche, Vincent; Augier, Romain; Scaillet, Stéphane; Cardello, Giovanni Luca

    2016-03-01

    Syros Island is worldwide known for its preservation of HP-LT parageneses in the Cycladic Blueschist Unit (CBU) providing one of the best case-studies to understand the tectonometamorphic evolution of a subduction channel. Conflicting structural interpretations have been proposed to explain the geological architecture of Syros, in part reflecting a lack of consensus about the tectonic structure of the CBU. In this study, the geological and tectonometamorphic maps of Syros have been entirely redrawn in order to decipher the structure of a fossilized subduction channel. Based on structural and petrological observations, the CBU has been subdivided into three subunits separated by major ductile shear zones. New observations of the Vari Unit confirm that it rests on top of the CBU through a detachment or exhumation fault. While retrograde top-to-the E/NE shearing overprinting prograde deformation is widespread across the island, the prograde deformation has been only locally preserved within the less retrograded units. We show that after the prograde top-to-the S/SW shearing deformation, the CBU was exhumed by an overall top-to-the E/NE shearing from the depth of the eclogite-facies all the way to the depth of the greenschist-facies and finally, to the brittle crust. The exhumation process encompassed the syn-orogenic stage (contemporaneous of subduction, within the subduction channel - Eocene) to the post-orogenic stage (contemporaneous with the formation of the Aegean Sea - Oligocene to Miocene). From syn-orogenic to post-orogenic exhumation, deformation progressively localized toward the base of the CBU, along large-scale ductile shear zones, allowing the preservation of earlier HP-LT structures and HP-LT metamorphic parageneses. Finally, this study brings new insights on the tectonometamorphic evolution of a subduction channel showing how strain localizes during the history of an accretionary complex, both during the prograde and retrograde history.

  8. Single Channel Recordings Reveal Differential β2 Subunit Modulations Between Mammalian and Drosophila BKCa(β2) Channels

    Science.gov (United States)

    Zhong, Ling; Guo, Xiying; Weng, Anxi; Xiao, Feng; Zeng, Wenping; Zhang, Yan; Ding, Jiuping; Hou, Panpan

    2016-01-01

    Large-conductance Ca2+- and voltage-activated potassium (BK) channels are widely expressed in tissues. As a voltage and calcium sensor, BK channels play significant roles in regulating the action potential frequency, neurotransmitter release, and smooth muscle contraction. After associating with the auxiliary β2 subunit, mammalian BK(β2) channels (mouse or human Slo1/β2) exhibit enhanced activation and complete inactivation. However, how the β2 subunit modulates the Drosophila Slo1 channel remains elusive. In this study, by comparing the different functional effects on heterogeneous BK(β2) channel, we found that Drosophila Slo1/β2 channel exhibits “paralyzed”-like and incomplete inactivation as well as slow activation. Further, we determined three different modulations between mammalian and Drosophila BK(β2) channels: 1) dSlo1/β2 doesn’t have complete inactivation. 2) β2(K33,R34,K35) delays the dSlo1/Δ3-β2 channel activation. 3) dSlo1/β2 channel has enhanced pre-inactivation than mSlo1/β2 channel. The results in our study provide insights into the different modulations of β2 subunit between mammalian and Drosophila Slo1/β2 channels and structural basis underlie the activation and pre-inactivation of other BK(β) complexes. PMID:27755549

  9. Sum-capacity of Interference Channels with a Local View: Impact of Distributed Decisions

    CERN Document Server

    Aggarwal, Vaneet; Sabharwal, Ashutosh

    2009-01-01

    Due to the large size of wireless networks, it is often impractical for nodes to track changes in the complete network state. As a result, nodes have to make distributed decisions about their transmission and reception parameters based on their local view of the network. In this paper, we characterize the impact of distributed decisions on the global network performance in terms of achievable sum-rates. We first formalize the concept of local view by proposing a protocol abstraction using the concept of local message passing. In the proposed protocol, nodes forward information about the network state to other neighboring nodes, thereby allowing network state information to trickle to all the nodes. The protocol proceeds in rounds, where all transmitters send a message followed by a message by all receivers. The number of rounds then provides a natural metric to quantify the extent of local information at each node. We next study three network connectivities, Z-channel, a three-user double Z-channel and a redu...

  10. Multi-Channel Three-Dimensional SOLA Inversion for Local Helioseismology

    CERN Document Server

    Jackiewicz, J; Gizon, L; Hanasoge, S M; Hohage, T; Ruffio, J -B; Svanda, M

    2011-01-01

    Inversions for local helioseismology are an important and necessary step for obtaining three-dimensional maps of various physical quantities in the solar interior. Frequently, the full inverse problems that one would like to solve prove intractable because of computational constraints. Due to the enormous seismic data sets that already exist and those forthcoming, this is a problem that needs to be addressed. To this end, we present a very efficient linear inversion algorithm for local helioseismology. It is based on a subtractive optimally localized averaging (SOLA) scheme in the Fourier domain, utilizing the horizontal-translation invariance of the sensitivity kernels. In Fourier space the problem decouples into many small problems, one for each horizontal wave vector. This multi-channel SOLA method is demonstrated for an example problem in time-distance helioseismology that is small enough to be solved both in real and Fourier space. We find that both approaches are successful in solving the inverse proble...

  11. Carbon monoxide stimulates the Ca2(+)-activated big conductance k channels in cultured human endothelial cells.

    Science.gov (United States)

    Dong, De-Li; Zhang, Yan; Lin, Dao-Hong; Chen, Jun; Patschan, Susann; Goligorsky, Michael S; Nasjletti, Alberto; Yang, Bao-Feng; Wang, Wen-Hui

    2007-10-01

    We used the whole-cell patch-clamp technique to study K channels in the human umbilical vein endothelial cells and identified a 201 pS K channel, which was blocked by tetraethylammonium and iberiotoxin but not by TRAM34 and apamin. This suggests that the Ca(2+)-activated big-conductance K channel (BK) is expressed in endothelial cells. Application of carbon monoxide (CO) or tricarbonylchloro(glycinato)ruthenium(II), a water soluble CO donor, stimulated the BK channels. Moreover, application of hemin, a substrate of heme oxygenase, mimicked the effect of CO and increased the BK channel activity. The stimulatory effect of hemin was significantly diminished by tin mesoporphyrin, an inhibitor of heme oxygenase. To determine whether the stimulatory effect of CO on the BK channel was mediated by NO and the cGMP-dependent pathway, we examined the effect of CO on BK channels in cells treated with, N(G)-nitro-l-arginine methyl ester, 1H(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one, an inhibitor of soluble guanylate cyclase, or KT5823, an inhibitor of protein kinase G. Addition of either diethylamine NONOate or sodium nitroprusside significantly increased BK channel activity. Inhibition of endogenous NO synthesis with N(G)-nitro-l-arginine methyl ester, blocking soluble guanylate cyclase or protein kinase G, delayed but did not prevent the CO-induced activation of BK channels. Finally, application of an antioxidant agent, ebselen, had no effect on CO-mediated stimulation of BK channels in human umbilical vein endothelial cells. We conclude that BK channels are expressed in human umbilical vein endothelial cells and that they are activated by both CO and NO. CO activates BK channels directly, as well as via a mechanism involving NO or the cGMP-dependent pathway.

  12. BK Virus in Recipients of Kidney Transplants.

    Science.gov (United States)

    Hendrix, Kelly M

    2014-01-01

    Since its discovery in 1971, the BK virus, a human polyomavirus, has emerged as a significant cause of renal dysfunction and transplant graft loss in kidney transplant recipients. Improved screening methods have been effective in assisting in the early identification of the virus, and thus, prompt intervention to prevent the progression of the disease. Treatment options for the virus are limited; therefore, lowering immunosuppressive medications should be considered the first line of treatment. Current adjunctive therapies are not guaranteed to control the viral activity and may have limited therapeutic value.

  13. Studying of Membrane Localization of Recombinant Potassium Channels in E.coli

    Science.gov (United States)

    Tagway, A.; Ignatova, A.; Feofanov, A.; Kirpichnikov, M.

    2009-01-01

    The effective expression of recombinant membrane proteins in E.coli depends upon the targeting and insertion of proteins into the cellular membrane, as well as on those proteins adopting the correct spatial structure. A significant technological problem involves the design of approaches for detecting the location of target proteins within a host cell. Using a hybrid potassium channel KcsA-Kv1.3 as a model, we developed a technological scheme which is suitable for the study of membrane localization in E.coli cells of recombinant proteins containing voltage-gated eukaryotic potassium channels as the functional active site. The scheme involves both biochemical and fluorescent methods for detecting target proteins in the cytoplasmic membrane of E.coli, as well as the study of the ligand-binding activity of membrane-embedded proteins. PMID:22649591

  14. Bisphenol A binds to the local anesthetic receptor site to block the human cardiac sodium channel.

    Directory of Open Access Journals (Sweden)

    Andrias O O'Reilly

    Full Text Available Bisphenol A (BPA has attracted considerable public attention as it leaches from plastic used in food containers, is detectable in human fluids and recent epidemiologic studies link BPA exposure with diseases including cardiovascular disorders. As heart-toxicity may derive from modified cardiac electrophysiology, we investigated the interaction between BPA and hNav1.5, the predominant voltage-gated sodium channel subtype expressed in the human heart. Electrophysiology studies of heterologously-expressed hNav1.5 determined that BPA blocks the channel with a K(d of 25.4±1.3 µM. By comparing the effects of BPA and the local anesthetic mexiletine on wild type hNav1.5 and the F1760A mutant, we demonstrate that both compounds share an overlapping binding site. With a key binding determinant thus identified, an homology model of hNav1.5 was generated based on the recently-reported crystal structure of the bacterial voltage-gated sodium channel NavAb. Docking predictions position both ligands in a cavity delimited by F1760 and contiguous with the DIII-IV pore fenestration. Steered molecular dynamics simulations used to assess routes of ligand ingress indicate that the DIII-IV pore fenestration is a viable access pathway. Therefore BPA block of the human heart sodium channel involves the local anesthetic receptor and both BPA and mexiletine may enter the closed-state pore via membrane-located side fenestrations.

  15. Characteristics of single large-conductance Ca2+-activated K+ channels and their regulation of action potentials and excitability in parasympathetic cardiac motoneurons in the nucleus ambiguus.

    Science.gov (United States)

    Lin, Min; Hatcher, Jeff T; Wurster, Robert D; Chen, Qin-Hui; Cheng, Zixi Jack

    2014-01-15

    Large-conductance Ca2(+)-activated K+ channels (BK) regulate action potential (AP) properties and excitability in many central neurons. However, the properties and functional roles of BK channels in parasympathetic cardiac motoneurons (PCMNs) in the nucleus ambiguus (NA) have not yet been well characterized. In this study, the tracer X-rhodamine-5 (and 6)-isothiocyanate (XRITC) was injected into the pericardial sac to retrogradely label PCMNs in FVB mice at postnatal 7-9 days. Two days later, XRITC-labeled PCMNs in brain stem slices were identified. Using excised patch single-channel recordings, we identified voltage-gated and Ca(2+)-dependent BK channels in PCMNs. The majority of BK channels exhibited persistent channel opening during voltage holding. These BK channels had a conductance of 237 pS and a 50% opening probability at +27.9 mV, the channel open time constant was 3.37 ms at +20 mV, and dwell time increased exponentially as the membrane potential depolarized. At the +20-mV holding potential, the [Ca2+]50 was 15.2 μM with a P0.5 of 0.4. Occasionally, some BK channels showed a transient channel opening and fast inactivation. Using whole cell voltage clamp, we found that BK channel mediated outward currents and afterhyperpolarization currents (IAHP). Using whole cell current clamp, we found that application of BK channel blocker iberiotoxin (IBTX) increased spike half-width and suppressed fast afterhyperpolarization (fAHP) amplitude following single APs. In addition, IBTX application increased spike half-width and reduced the spike frequency-dependent AP broadening in trains and spike frequency adaption (SFA). Furthermore, BK channel blockade decreased spike frequency. Collectively, these results demonstrate that PCMNs have BK channels that significantly regulate AP repolarization, fAHP, SFA, and spike frequency. We conclude that activation of BK channels underlies one of the mechanisms for facilitation of PCMN excitability.

  16. Subcellular localization of the delayed rectifier K(+) channels KCNQ1 and ERG1 in the rat heart

    DEFF Research Database (Denmark)

    Rasmussen, Hanne Borger; Møller, Morten; Knaus, Hans-Günther

    2003-01-01

    In the heart, several K(+) channels are responsible for the repolarization of the cardiac action potential, including transient outward and delayed rectifier K(+) currents. In the present study, the cellular and subcellular localization of the two delayed rectifier K(+) channels, KCNQ1 and ether...

  17. Molecular mechanisms of diabetic coronary dysfunction due to large conductance Ca2+-activated K+ channel impairment

    Institute of Scientific and Technical Information of China (English)

    WANG Ru-xing; ZHENG Jie; GUO Su-xia; LI Xiao-rong; LU Tong; SHI Hai-feng; CHAI Qiang; WU Ying; SUN Wei; JI Yuan; YAO Yong; LI Ku-lin; ZHANG Chang-ying

    2012-01-01

    Background Diabetes mellitus is associated with coronary dysfunction,contributing to a 2- to 4-fold increase in the risk of coronary heart diseases.The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus.The purpose of this study is to determine the role of vascular large conductance Ca2+-activated K+ (BK) channel activities in coronary dysfunction in streptozotocin-induced diabetic rats.Methods Using videomicroscopy,immunoblotting,fluorescent assay and patch clamp techniques,we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats.Results BK currents (defined as the iberiotoxin-sensitive K+ component) contribute (65±4)% of the total K+ currents in freshly isolated coronary smooth muscle cells and >50% of the contraction of the inner diameter of coronary arteries from normal rats.However,BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats,leading to an increase in coronary artery tension.BK channel activity in response to free Ca2+ is impaired in diabetic rats.Moreover,cytoplasmic application of DHS-1 (a specific BK channel β1 subunit activator) robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats.In diabetic rats,the DHS-1 effect was diminished in the presence of 200 nmol/L Ca2+ and was significantly attenuated in the presence of high free calcium concentration,i.e.,1 μmol/L Ca2+.Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-β1 protein expression in diabetic vessels,without altering the BK channel α-subunit expression.Although the cytosolic Ca2+ concentration of coronary arterial smooth muscle cells was increased from (103±23)nmol/L (n=5) of control rats to (193±22) nmol/L (n=6,P<0.05) of STZ-induced diabetic rats,reduced BK

  18. Systematic study of spatiotemporal dynamics of intense femtosecond laser pulses in BK-7 glass

    Indian Academy of Sciences (India)

    Ram Gopal; V Deepak; S Sivaramakrishnan

    2007-04-01

    In this paper we present a systematic study of the spatial and temporal effects of intense femtosecond laser pulses in BK-7 over a broad range of input powers, 1–1000 times the critical power for self-focusing (cr) by numerically solving the nonlinear Schrödinger equation (NLS). Most numerical studies have not been extended to such high powers. A clear-cut classification of spatio-temporal dynamics up to very high powers into three regimes – the group-velocity dispersion (GVD) regime, the ionization regime and the dominant plasma regime – as done here, is a significant step towards a better understanding. Further, we examine in detail the role of GVD in channel formation by comparing BK-7 to an `artificial' medium. Our investigations bring forth the important observation that diffraction plays a minimal role in the formation of multiple cones and that plasma plays a diffraction-like role at very high powers. A detailed study of the spatio-temporal dynamics in any condensed medium over this range of powers has not been reported hitherto, to the best of our knowledge. We also suggest appropriate operational powers for various applications employing BK-7 on the basis of our results.

  19. Numerical study of cell performance and local transport phenomena in PEM fuel cells with various flow channel area ratios

    Science.gov (United States)

    Wang, Xiao-Dong; Duan, Yuan-Yuan; Yan, Wei-Mon

    Three-dimensional models of proton exchange membrane fuel cells (PEMFCs) with parallel and interdigitated flow channel designs were developed including the effects of liquid water formation on the reactant gas transport. The models were used to investigate the effects of the flow channel area ratio and the cathode flow rate on the cell performance and local transport characteristics. The results reveal that at high operating voltages, the cell performance is independent of the flow channel designs and operating parameters, while at low operating voltages, both significantly affect cell performance. For the parallel flow channel design, as the flow channel area ratio increases the cell performance improves because fuel is transported into the diffusion layer and the catalyst layer mainly by diffusion. A larger flow channel area ratio increases the contact area between the fuel and the diffusion layer, which allows more fuel to directly diffuse into the porous layers to participate in the electrochemical reaction which enhances the reaction rates. For the interdigitated flow channel design, the baffle forces more fuel to enter the cell and participate in the electrochemical reaction, so the flow channel area ratio has less effect. Forced convection not only increases the fuel transport rates but also enhances the liquid water removal, thus interdigitated flow channel design has higher performance than the parallel flow channel design. The optimal performance for the interdigitated flow channel design occurs for a flow channel area ratio of 0.4. The cell performance also improves as the cathode flow rate increases. The effects of the flow channel area ratio and the cathode flow rate on cell performance are analyzed based on the local current densities, oxygen flow rates and liquid water concentrations inside the cell.

  20. Numerical study of cell performance and local transport phenomena in PEM fuel cells with various flow channel area ratios

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiao-Dong [Department of Thermal Engineering, School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Duan, Yuan-Yuan [Key Laboratory of Thermal Science and Power Engineering of MOE, Tsinghua University, Beijing 100084 (China); Yan, Wei-Mon [Department of Mechatronic Engineering, Huafan University, Shih-Ting 22305 (China)

    2007-10-11

    Three-dimensional models of proton exchange membrane fuel cells (PEMFCs) with parallel and interdigitated flow channel designs were developed including the effects of liquid water formation on the reactant gas transport. The models were used to investigate the effects of the flow channel area ratio and the cathode flow rate on the cell performance and local transport characteristics. The results reveal that at high operating voltages, the cell performance is independent of the flow channel designs and operating parameters, while at low operating voltages, both significantly affect cell performance. For the parallel flow channel design, as the flow channel area ratio increases the cell performance improves because fuel is transported into the diffusion layer and the catalyst layer mainly by diffusion. A larger flow channel area ratio increases the contact area between the fuel and the diffusion layer, which allows more fuel to directly diffuse into the porous layers to participate in the electrochemical reaction which enhances the reaction rates. For the interdigitated flow channel design, the baffle forces more fuel to enter the cell and participate in the electrochemical reaction, so the flow channel area ratio has less effect. Forced convection not only increases the fuel transport rates but also enhances the liquid water removal, thus interdigitated flow channel design has higher performance than the parallel flow channel design. The optimal performance for the interdigitated flow channel design occurs for a flow channel area ratio of 0.4. The cell performance also improves as the cathode flow rate increases. The effects of the flow channel area ratio and the cathode flow rate on cell performance are analyzed based on the local current densities, oxygen flow rates and liquid water concentrations inside the cell. (author)

  1. Requirement of subunit co-assembly and ankyrin-G for M-channel localization at the axon initial segment

    DEFF Research Database (Denmark)

    Rasmussen, Hanne B; Frøkjaer-Jensen, Christian; Jensen, Camilla Stampe;

    2007-01-01

    The potassium channel subunits KCNQ2 and KCNQ3 are believed to underlie the M current of hippocampal neurons. The M-type potassium current plays a key role in the regulation of neuronal excitability; however, the subcellular location of the ion channels underlying this regulation has been...... controversial. We report here that KCNQ2 and KCNQ3 subunits are localized to the axon initial segment of pyramidal neurons of adult rat hippocampus and in cultured hippocampal neurons. We demonstrate that the localization of the KCNQ2/3 channel complex to the axon initial segment is favored by co......-expression of the two channel subunits. Deletion of the ankyrin-G-binding motif in both the KCNQ2 and KCNQ3 C-terminals leads to the disappearance of the complex from the axon initial segment, albeit the channel complex remains functional and still reaches the plasma membrane. We further show that although heteromeric...

  2. Molecular Networks Involved in the Immune Control of BK Polyomavirus

    Directory of Open Access Journals (Sweden)

    Eva Girmanova

    2012-01-01

    Full Text Available BK polyomavirus infection is the important cause of virus-related nephropathy following kidney transplantation. BK virus reactivates in 30%–80% of kidney transplant recipients resulting in BK virus-related nephropathy in 1%–10% of cases. Currently, the molecular processes associated with asymptomatic infections in transplant patients infected with BK virus remain unclear. In this study we evaluate intrarenal molecular processes during different stages of BKV infection. The gene expression profiles of 90 target genes known to be associated with immune response were evaluated in kidney graft biopsy material using TaqMan low density array. Three patient groups were examined: control patients with no evidence of BK virus reactivation (n=11, infected asymptomatic patients (n=9, and patients with BK virus nephropathy (n=10. Analysis of biopsies from asymptomatic viruria patients resulted in the identification of 5 differentially expressed genes (CD3E, CD68, CCR2, ICAM-1, and SKI (P<0.05, and functional analysis showed a significantly heightened presence of costimulatory signals (e.g., CD40/CD40L; P<0.05. Gene ontology analysis revealed several biological networks associated with BKV immune control in comparison to the control group. This study demonstrated that asymptomatic BK viruria is associated with a different intrarenal regulation of several genes implicating in antiviral immune response.

  3. Molecular networks involved in the immune control of BK polyomavirus.

    Science.gov (United States)

    Girmanova, Eva; Brabcova, Irena; Klema, Jiri; Hribova, Petra; Wohlfartova, Mariana; Skibova, Jelena; Viklicky, Ondrej

    2012-01-01

    BK polyomavirus infection is the important cause of virus-related nephropathy following kidney transplantation. BK virus reactivates in 30%-80% of kidney transplant recipients resulting in BK virus-related nephropathy in 1%-10% of cases. Currently, the molecular processes associated with asymptomatic infections in transplant patients infected with BK virus remain unclear. In this study we evaluate intrarenal molecular processes during different stages of BKV infection. The gene expression profiles of 90 target genes known to be associated with immune response were evaluated in kidney graft biopsy material using TaqMan low density array. Three patient groups were examined: control patients with no evidence of BK virus reactivation (n = 11), infected asymptomatic patients (n = 9), and patients with BK virus nephropathy (n = 10). Analysis of biopsies from asymptomatic viruria patients resulted in the identification of 5 differentially expressed genes (CD3E, CD68, CCR2, ICAM-1, and SKI) (P < 0.05), and functional analysis showed a significantly heightened presence of costimulatory signals (e.g., CD40/CD40L; P < 0.05). Gene ontology analysis revealed several biological networks associated with BKV immune control in comparison to the control group. This study demonstrated that asymptomatic BK viruria is associated with a different intrarenal regulation of several genes implicating in antiviral immune response.

  4. Local indigenous knowledge about some medicinal plants in and around Kakamega forest in western Kenya [v2; ref status: indexed, http://f1000r.es/UDNyBK

    Directory of Open Access Journals (Sweden)

    Nickson Erick Otieno

    2012-12-01

    Full Text Available Kakamega forest is Kenya’s only rainforest and is distinguishably rich in biodiversity but threatened by agricultural encroachment and other forms of human activity. It is also one of Kenya’s Important Bird Areas and a significant source of natural products to neighboring rural communities, such as medicinal plants, food, wood and other fibers. By using structured questionnaires for direct interviews, local indigenous knowledge was tapped through involvement of a focal group of elderly key informants in three blocks of the forest. Forty key species of medicinal plants used by local people were identified and recorded. Fifty-five percent of these were shrubs, thirty-two percent trees, seven-and-a-half percent lower plants such as herbs or forbs while five percent were climbers. About seventy percent of the medicinal plants occurred inside the forest itself and thirty percent around the edge and the immediate surroundings outside the forest. Thirty-eight (95% of the plants were indigenous to Kenya and two (5% exotic. Such extensive indigenous knowledge of the medicinal uses of the plants, including their distribution trends in the forest, may be tapped for decision support in rural health service planning, policy formulation for conserving the forest, tracking and mitigation of climate change impacts.

  5. Ion-exchanged tapered-waveguide laser in neodymium-doped BK7 glass.

    Science.gov (United States)

    Hettrick, S J; Mackenzie, J I; Harris, R D; Wilkinson, J S; Shepherd, D P; Tropper, A C

    2000-10-01

    We report what is to our knowledge the first operation of a planar dielectric tapered-waveguide laser. The waveguide laser is fabricated by potassium-ion exchange in Nd(3+) -doped BK7 glass and consists of a single-mode channel waveguide of a few micrometers' width followed by a linear taper up to a broad region with a width of ~180microm . A slope efficiency of 42% is found both in the tapers and in standard channel waveguides fabricated upon the same substrate, indicating that the tapers and the channels have similar internal losses; hence the low-loss nature of the tapered beam expansion. The output from either end of the tapered structure is found to be nearly diffraction limited.

  6. A study of the low-luminosity Type II-Plateau supernova 2008bk

    CERN Document Server

    Lisakov, Sergey; Hillier, D John; Waldman, Roni; Livne, Eli

    2016-01-01

    Supernova (SN) 2008bk is a well observed low-luminosity Type II event visually associated with a low-mass red-supergiant progenitor. To model SN 2008bk, we evolve a 12Msun star from the main sequence until core collapse, when it has a total mass of 9.88Msun, a He-core mass of 3.22Msun, and a radius of 502Rsun. We then artificially trigger an explosion that produces 8.29Msun of ejecta with a total energy of 2.5x10^50erg and ~0.009Msun of 56Ni. We model the subsequent evolution of the ejecta with non-Local-Thermodynamic-Equilibrium time-dependent radiative transfer. Although somewhat too luminous and energetic, this model reproduces satisfactorily the multi-band light curves and multi-epoch spectra of SN 2008bk, confirming the suitability of a low-mass massive star progenitor. As in other low-luminosity SNe II, the structured Halpha profile at the end of the plateau phase is probably caused by BaII 6496.9A rather than asphericity. We discuss the sensitivity of our results to changes in progenitor radius and mas...

  7. dTULP, the Drosophila melanogaster homolog of tubby, regulates transient receptor potential channel localization in cilia.

    Directory of Open Access Journals (Sweden)

    Jina Park

    Full Text Available Mechanically gated ion channels convert sound into an electrical signal for the sense of hearing. In Drosophila melanogaster, several transient receptor potential (TRP channels have been implicated to be involved in this process. TRPN (NompC and TRPV (Inactive channels are localized in the distal and proximal ciliary zones of auditory receptor neurons, respectively. This segregated ciliary localization suggests distinct roles in auditory transduction. However, the regulation of this localization is not fully understood. Here we show that the Drosophila Tubby homolog, King tubby (hereafter called dTULP regulates ciliary localization of TRPs. dTULP-deficient flies show uncoordinated movement and complete loss of sound-evoked action potentials. Inactive and NompC are mislocalized in the cilia of auditory receptor neurons in the dTulp mutants, indicating that dTULP is required for proper cilia membrane protein localization. This is the first demonstration that dTULP regulates TRP channel localization in cilia, and suggests that dTULP is a protein that regulates ciliary neurosensory functions.

  8. Polyomavirus specific cellular immunity: from BK-virus-specific cellular immunity to BK-virus-associated nephropathy ?

    Directory of Open Access Journals (Sweden)

    manon edekeyser

    2015-06-01

    Full Text Available In renal transplantation, BK-virus-associated nephropathy has emerged as a major complication, with a prevalence of 5–10% and graft loss in >50% of cases. BK-virus is a member of the Polyomavirus family and rarely induces apparent clinical disease in the general population. However, replication of polyomaviruses, associated with significant organ disease, is observed in patients with acquired immunosuppression, which suggests a critical role for virus-specific cellular immunity to control virus replication and prevent chronic disease. Monitoring of specific immunity combined with viral load could be used to individually assess the risk of viral reactivation and virus control. We review the current knowledge on BK-virus specific cellular immunity and, more specifically, in immunocompromised patients. In the future, immune-based therapies could allow us to treat and prevent BK-virus-associated nephropathy.

  9. Local and global stability analysis of compressible channel flow over wall impedance

    Science.gov (United States)

    Rahbari, Iman; Scalo, Carlo

    2016-11-01

    The stability properties of compressible channel flow over porous walls is investigated via Local (LSA) and Global Stability Analysis (GSA) for laminar and turbulent base flows at Reb = 6900 and Mb = 0 . 85 , 1 . 5 , 3 . 5 . Linearized Navier-Stokes equations are discretized via a sixth-order fully collocated Padé scheme leading to a Generalized Eigenvalue Problem (GEVP) solved using a parallel sparse eigenvalue solver based on the shift-invert Arnoldi method. The adopted discretization guarantees spectral-like spatial resolution. Fully sparsity of the system is retained via implicit calculation of the numerical derivatives ensuring computational efficiency on multi-processor platforms. The global eigen-spectrum exhibits various sets of modes grouped by streamwise wave-numbers, which are captured via LSA, as well as global acoustic modes. Consistently with the findings of C. Scalo et al., two unstable local modes are found for sufficiently high wall permeability: one standing-wave-like and one representing a bulk pressure mode, both generating additional Reynolds shear stresses concentrated in the viscous sublayer region. Stability properties of the flow over non-modal streamwise impedance distributions are also discussed.

  10. Localization of transient receptor potential ion channels in primary and motile cilia of the female murine reproductive organs

    DEFF Research Database (Denmark)

    Teilmann, Stefan C.; Byskov, Anne Grete; Pedersen, Per Amstrup;

    2005-01-01

    We have examined the subcellular localization of transient receptor potential (TRP) ion channels and the potential sensory role of cilia in murine female reproductive organs using confocal laser scanning microscopy analysis on ovary and oviduct tissue sections as well as on primary cultures...... intensity in proximal invaginations of the epithelial folds. These observations are the first to demonstrate ciliary localization of TRP ion channels and their possible receptor function in the female reproductive organs. We suggest that polycystins 1 and 2 play an important role in granulosa cell...

  11. Progression from Sustained BK Viruria to Sustained BK Viremia with Immunosuppression Reduction Is Not Associated with Changes in the Noncoding Control Region of the BK Virus Genome

    Directory of Open Access Journals (Sweden)

    Imran A. Memon

    2012-01-01

    We performed PCR amplification and sequencing of (1 stored urine and (2 plasma samples from the time of peak viremia from 11 patients with sustained viremia who participated in a 200-patient clinical trial. The antimetabolite was withdrawn for BK viremia and reduction of the calcineurin inhibitor for sustained BK viremia. DNA sequencing from the 11 patients with sustained viremia revealed 8 insertions, 16 transversions, 3 deletions, and 17 transitions. None were deemed significant. No patient developed clinically evident BKVAN. Our data support, at a genomic level, the effectiveness of reduction of immunosuppression for prevention of progression from viremia to BKVAN.

  12. Localization of the nucleic acid channel regulatory subunit, cytosolic malate dehydrogenase.

    Science.gov (United States)

    Hanss, Basil; Leal-Pinto, Edgar; Teixeira, Avelino; Tran, Baohuong; Lee, Chun-Hui; Henderson, Scott C; Klotman, Paul E

    2008-01-01

    NACh is a nucleic acid-conducting channel found in apical membrane of rat kidney proximal tubules. It is a heteromultimeric complex consisting of at least two proteins: a 45-kDa pore-forming subunit and a 36-kDa regulatory subunit. The regulatory subunit confers ion selectivity and influences gating kinetics. The regulatory subunit has been identified as cytosolic malate dehydrogenase (cMDH). cMDH is described in the literature as a soluble protein that is not associated with plasma membrane. Yet a role for cMDH as the regulatory subunit of NACh requires that it be present at the plasma membrane. To resolve this conflict, studies were initiated to determine whether cMDH could be found at the plasma membrane. Before performing localization studies, a suitable model system that expressed NACh was identified. A channel was identified in LLC-PK(1) cells, a line derived from pig proximal tubule, that is selective for nucleic acid and has a conductance of approximately 10 pS. It exhibits dose-dependent blockade by heparan sulfate or L-malate. These characteristics are similar to what has been reported for NACh from rat kidney and indicate that NACh is present in LLC-PK(1) cells. LLC-PK(1) cells were therefore used as a model system for immunolocalization of cMDH. Both immunofluorescence and immunoelectron microscopy demonstrated cMDH at the plasma membrane of LLC-PK(1) cells. This finding supports prior functional data that describe a role for cMDH as the regulatory subunit of NACh.

  13. Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle.

    Science.gov (United States)

    Hristov, Kiril L; Smith, Amy C; Parajuli, Shankar P; Malysz, John; Petkov, Georgi V

    2014-03-01

    Large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca(2+) imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca(2+) sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca(2+) levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca(2+)-dependent mechanism, thus increasing DSM contractility.

  14. T-type Ca(2+) channels and Autoregulation of Local Blood Flow

    DEFF Research Database (Denmark)

    Jensen, Lars Jørn; Nielsen, Morten Schak; Salomonsson, Max;

    2017-01-01

    L-type voltage gated Ca(2+) channels are considered to be the primary source of calcium influx during the myogenic response. However, many vascular beds also express T-type voltage gated Ca(2+) channels. Recent studies suggest that these channels may also play a role in autoregulation. At low pre...

  15. Phospholipase D2 specifically regulates TREK potassium channels via direct interaction and local production of phosphatidic acid.

    Science.gov (United States)

    Comoglio, Yannick; Levitz, Joshua; Kienzler, Michael A; Lesage, Florian; Isacoff, Ehud Y; Sandoz, Guillaume

    2014-09-16

    Membrane lipids serve as second messengers and docking sites for proteins and play central roles in cell signaling. A major question about lipid signaling is whether diffusible lipids can selectively target specific proteins. One family of lipid-regulated membrane proteins is the TWIK-related K channel (TREK) subfamily of K2P channels: TREK1, TREK2, and TWIK-related arachdonic acid stimulated K(+) channel (TRAAK). We investigated the regulation of TREK channels by phosphatidic acid (PA), which is generated by phospholipase D (PLD) via hydrolysis of phosphatidylcholine. Even though all three of the channels are sensitive to PA, we found that only TREK1 and TREK2 are potentiated by PLD2 and that none of these channels is modulated by PLD1, indicating surprising selectivity. We found that PLD2, but not PLD1, directly binds to the C terminus of TREK1 and TREK2, but not to TRAAK. The results have led to a model for selective lipid regulation by localization of phospholipid enzymes to specific effector proteins. Finally, we show that regulation of TREK channels by PLD2 occurs natively in hippocampal neurons.

  16. Bio-fabrication of nanomesh channels of single-walled carbon nanotubes for locally gated field-effect transistors

    Science.gov (United States)

    Byeon, Hye-Hyeon; Lee, Woo Chul; Kim, Wonbin; Kim, Seong Keun; Kim, Woong; Yi, Hyunjung

    2017-01-01

    Single-walled carbon nanotubes (SWNTs) are one of the promising electronic components for nanoscale electronic devices such as field-effect transistors (FETs) owing to their excellent device characteristics such as high conductivity, high carrier mobility and mechanical flexibility. Localized gating gemometry of FETs enables individual addressing of active channels and allows for better electrostatics via thinner dielectric layer of high k-value. For localized gating of SWNTs, it becomes critical to define SWNTs of controlled nanostructures and functionality onto desired locations in high precision. Here, we demonstrate that a biologically templated approach in combination of microfabrication processes can successfully produce a nanostructured channels of SWNTs for localized active devices such as local bottom-gated FETs. A large-scale nanostructured network, nanomesh, of SWNTs were assembled in solution using an M13 phage with strong binding affinity toward SWNTs and micrometer-scale nanomesh channels were defined using negative photolithography and plasma-etching processes. The bio-fabrication approach produced local bottom-gated FETs with remarkably controllable nanostructures and successfully enabled semiconducting behavior out of unsorted SWNTs. In addition, the localized gating scheme enhanced the device performances such as operation voltage and I on/I off ratio. We believe that our approach provides a useful and integrative method for fabricating electronic devices out of nanoscale electronic materials for applications in which tunable electrical properties, mechanical flexibility, ambient stability, and chemical stability are of crucial importance.

  17. Membrane-localized β-subunits alter the PIP2 regulation of high-voltage activated Ca2+ channels.

    Science.gov (United States)

    Suh, Byung-Chang; Kim, Dong-Il; Falkenburger, Björn H; Hille, Bertil

    2012-02-21

    The β-subunits of voltage-gated Ca(2+) (Ca(V)) channels regulate the functional expression and several biophysical properties of high-voltage-activated Ca(V) channels. We find that Ca(V) β-subunits also determine channel regulation by the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP(2)). When Ca(V)1.3, -2.1, or -2.2 channels are cotransfected with the β3-subunit, a cytosolic protein, they can be inhibited by activating a voltage-sensitive lipid phosphatase to deplete PIP(2). When these channels are coexpressed with a β2a-subunit, a palmitoylated peripheral membrane protein, the inhibition is much smaller. PIP(2) sensitivity could be increased by disabling the two palmitoylation sites in the β2a-subunit. To further test effects of membrane targeting of Ca(V) β-subunits on PIP(2) regulation, the N terminus of Lyn was ligated onto the cytosolic β3-subunit to confer lipidation. This chimera, like the Ca(V) β2a-subunit, displayed plasma membrane localization, slowed the inactivation of Ca(V)2.2 channels, and increased the current density. In addition, the Lyn-β3 subunit significantly decreased Ca(V) channel inhibition by PIP(2) depletion. Evidently lipidation and membrane anchoring of Ca(V) β-subunits compete with the PIP(2) regulation of high-voltage-activated Ca(V) channels. Compared with expression with Ca(V) β3-subunits alone, inhibition of Ca(V)2.2 channels by PIP(2) depletion could be significantly attenuated when β2a was coexpressed with β3. Our data suggest that the Ca(V) currents in neurons would be regulated by membrane PIP(2) to a degree that depends on their endogenous β-subunit combinations.

  18. BIN1 localizes the L-type calcium channel to cardiac T-tubules.

    Directory of Open Access Journals (Sweden)

    Ting-Ting Hong

    2010-02-01

    Full Text Available The BAR domain protein superfamily is involved in membrane invagination and endocytosis, but its role in organizing membrane proteins has not been explored. In particular, the membrane scaffolding protein BIN1 functions to initiate T-tubule genesis in skeletal muscle cells. Constitutive knockdown of BIN1 in mice is perinatal lethal, which is associated with an induced dilated hypertrophic cardiomyopathy. However, the functional role of BIN1 in cardiomyocytes is not known. An important function of cardiac T-tubules is to allow L-type calcium channels (Cav1.2 to be in close proximity to sarcoplasmic reticulum-based ryanodine receptors to initiate the intracellular calcium transient. Efficient excitation-contraction (EC coupling and normal cardiac contractility depend upon Cav1.2 localization to T-tubules. We hypothesized that BIN1 not only exists at cardiac T-tubules, but it also localizes Cav1.2 to these membrane structures. We report that BIN1 localizes to cardiac T-tubules and clusters there with Cav1.2. Studies involve freshly acquired human and mouse adult cardiomyocytes using complementary immunocytochemistry, electron microscopy with dual immunogold labeling, and co-immunoprecipitation. Furthermore, we use surface biotinylation and live cell confocal and total internal fluorescence microscopy imaging in cardiomyocytes and cell lines to explore delivery of Cav1.2 to BIN1 structures. We find visually and quantitatively that dynamic microtubules are tethered to membrane scaffolded by BIN1, allowing targeted delivery of Cav1.2 from the microtubules to the associated membrane. Since Cav1.2 delivery to BIN1 occurs in reductionist non-myocyte cell lines, we find that other myocyte-specific structures are not essential and there is an intrinsic relationship between microtubule-based Cav1.2 delivery and its BIN1 scaffold. In differentiated mouse cardiomyocytes, knockdown of BIN1 reduces surface Cav1.2 and delays development of the calcium transient

  19. Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina.

    Science.gov (United States)

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

    2015-07-01

    High-voltage-activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes, including the influx of extracellular Ca(2+), neurotransmitter release, gene transcription, and synaptic plasticity. These channels consist of a primary α(1) pore-forming subunit, which is associated with an extracellular α(2)δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α(2)δ(3) subunit in the mouse and rat retina is unknown. In this study using RT-PCR, a single band at ∼ 305 bp corresponding to the predicted size of the α(2)δ(3) subunit fragment was found in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123-kDa band. Immunohistochemistry with an affinity-purified antibody to the α(2)δ(3) subunit revealed immunoreactive cell bodies in the ganglion cell layer and inner nuclear layer and immunoreactive processes in the inner plexiform layer and the outer plexiform layer. α(2)δ(3) immunoreactivity was localized to multiple cell types, including ganglion, amacrine, and bipolar cells and photoreceptors, but not horizontal cells. The expression of the α(2)δ(3) calcium channel subunit to multiple cell types suggests that this subunit participates widely in Ca-channel-mediated signaling in the retina.

  20. Data of evolutionary structure change: 1BK9A-2QOGD [Confc[Archive

    Lifescience Database Archive (English)

    Full Text Available 1BK9A-2QOGD 1BK9 2QOG A D SLIQFETLIMKVAKKSGMFWYSNYGCYCGWGGQGRPQDA...TDRCCFVHDCCYGKVTGCDPKMDVYSFSEENGDIVCGGDDPCKKEICECDRAAAICFRDNLTLYNDKKYWAFGAKNCPQEESEPC SLLQFNKMI.../pdbChain> 2QOGD LSTYK-NEYMF

  1. Localized Calcineurin Confers Ca2+-Dependent Inactivation Upon Neuronal L-Type Ca2+ Channels

    OpenAIRE

    2012-01-01

    Excitation-driven entry of Ca2+ through L-type voltage-gated Ca2+ channels controls gene expression in neurons and a variety of fundamental activities in other kinds of excitable cells. The probability of opening of CaV1.2 L-type channels is subject to pronounced enhancement by cAMP-dependent protein kinase (PKA), which is scaffolded to CaV1.2 channels by A-kinase anchoring proteins (AKAPs). CaV1.2 channels also undergo negative autoregulation via Ca2+-dependent inactivation (CDI), which stro...

  2. BK virus in solid organ transplant recipients: an emerging syndrome.

    Science.gov (United States)

    Mylonakis, E; Goes, N; Rubin, R H; Cosimi, A B; Colvin, R B; Fishman, J A

    2001-11-27

    BK virus is a human polyomavirus associated with a range of clinical presentations from asymptomatic viruria with pyuria to ureteral ulceration with ureteral stenosis in renal transplant patients or hemorrhagic cystitis in bone marrow transplant recipients. Infection of renal allografts has been associated with diminished graft function in some individuals. Fortunately, however, the majority of patients with BK virus infections are asymptomatic. The type, duration, and intensity of immunosuppression are major contributors to susceptibility to the activation of BK virus infection. Histopathology is required for the demonstration of renal parenchymal involvement; urine cytology and viral polymerase chain reaction methods are useful adjunctive diagnostic tools. Current, treatment of immunosuppressed patients with polyomavirus viruria is largely supportive and directed toward minimizing immunosuppression. Improved diagnostic tools and antiviral therapies are needed for polyomavirus infections.

  3. Internalisasi Mind Skills Mahasiswa Bimbingan Konseling (BK Melalui Experiential Learning

    Directory of Open Access Journals (Sweden)

    Ribut Purwaningrum

    2014-06-01

    Full Text Available Tujuan penelitian ini adalah mengetahui bagaimana menerapkan model pembelajaran experi-ential learning untuk internalisasi mind skills mahasiswa jurusan BK. Rancangan penelitian ini menggunakan penelitian tindakan kelas. Subjek penelitian adalah mahasiswa BK offering C angkatan 2011 peserta matakuliah Konseling Individual. Penelitian dilakukan selama tiga siklus dengan jabaran siklus I sebanyak 6 pertemuan, siklus II sebanyak 6 pertemuan, dan siklus III sebanyak 3 pertemuan. Pengumpulan data dilakukan menggunakan metode kuantitatif dan kualitatif. Data kuantitatif diolah menggunakan statistik dan diinterpretasi secara kualitatif. Analisis data dilakukan secara kualitatif merujuk pada Miles dan Huberman, meliputi reduksi data, penyajian data, dan pengambilan simpulan. Hasil penelitian menunjukkan bahwa model pembelajaran experiential learning mampu digunakan sebagai strategi internalisasi mind skills mahasiswa BK adalah experiential learning yang dilakukan secara berkesinambungan dalam tahapnya, sehingga mampu menyentuh aspek ‘feeling’,‘watching or describing’,‘thinking’ dan ‘doing’. Kata kunci: internalisasi, mind skills, experiential learning

  4. Valley and channel networks extraction based on local topographic curvature and k-means clustering of contours

    Science.gov (United States)

    Hooshyar, Milad; Wang, Dingbao; Kim, Seoyoung; Medeiros, Stephen C.; Hagen, Scott C.

    2016-10-01

    A method for automatic extraction of valley and channel networks from high-resolution digital elevation models (DEMs) is presented. This method utilizes both positive (i.e., convergent topography) and negative (i.e., divergent topography) curvature to delineate the valley network. The valley and ridge skeletons are extracted using the pixels' curvature and the local terrain conditions. The valley network is generated by checking the terrain for the existence of at least one ridge between two intersecting valleys. The transition from unchannelized to channelized sections (i.e., channel head) in each first-order valley tributary is identified independently by categorizing the corresponding contours using an unsupervised approach based on k-means clustering. The method does not require a spatially constant channel initiation threshold (e.g., curvature or contributing area). Moreover, instead of a point attribute (e.g., curvature), the proposed clustering method utilizes the shape of contours, which reflects the entire cross-sectional profile including possible banks. The method was applied to three catchments: Indian Creek and Mid Bailey Run in Ohio and Feather River in California. The accuracy of channel head extraction from the proposed method is comparable to state-of-the-art channel extraction methods.

  5. Transient receptor potential ankyrin 1 channel localized to non-neuronal airway cells promotes non-neurogenic inflammation

    DEFF Research Database (Denmark)

    Nassini, Romina; Pedretti, Pamela; Moretto, Nadia;

    2012-01-01

    The transient receptor potential ankyrin 1 (TRPA1) channel, localized to airway sensory nerves, has been proposed to mediate airway inflammation evoked by allergen and cigarette smoke (CS) in rodents, via a neurogenic mechanism. However the limited clinical evidence for the role of neurogenic...... and fibroblasts, acrolein and CS extract evoked IL-8 release, a response selectively reduced by TRPA1 antagonists. Capsaicin, agonist of the transient receptor potential vanilloid 1 (TRPV1), a channel co-expressed with TRPA1 by airway sensory nerves, and acrolein or CS (TRPA1 agonists), or the neuropeptide...

  6. Molecular insights into the local anesthetic receptor within voltage-gated sodium channels using hydroxylated analogues of mexiletine

    Directory of Open Access Journals (Sweden)

    Jean-François eDesaphy

    2012-02-01

    Full Text Available We previously showed that the β-adrenoceptor modulators, clenbuterol and propranolol, directly blocked voltage-gated sodium channels, whereas salbutamol and nadolol did not (Desaphy et al., 2003, suggesting the presence of two hydroxyl groups on the aromatic moiety of the drugs as a molecular requisite for impeding sodium channel block. To verify such an hypothesis, we synthesized five new mexiletine analogues by adding one or two hydroxyl groups to the aryl moiety of the sodium channel blocker and tested these compounds on hNav1.4 channels expressed in HEK293 cells. Concentration-response relationships were constructed using an holding potential of -120 mV at 0.1 Hz (tonic block and 10 Hz (use-dependent block stimulation frequencies. The half-maximum inhibitory concentrations (IC50 were linearly correlated to drug lipophilicity: the less lipophilic the drug, minor was the block. The same compounds were also tested on F1586C and Y1593C hNav1.4 channel mutants, to gain further information on the molecular interactions of mexiletine with its receptor within the sodium channel pore. Alteration of tonic block suggests that the aryl moiety of mexiletine may interact either directly or indirectly with Phe1586 in the closed sodium channel to produce low-affinity binding block, and that this interaction depends on the electrostatic potential of the drug aromatic tail. Alteration of use-dependent block suggests that addition of hydroxyl groups to the aryl moiety may modify high-affinity binding of the drug ammine terminal to Phe1586 through cooperativity between the two pharmacophores, this effect being mainly related to drug lipophilicity. Mutation of Tyr1593 further impaired such cooperativity. In conclusion, these results confirm our former hypothesis showing that the presence of hydroxyl groups to the aryl moiety of mexiletine greatly reduced sodium channel block, and provide molecular insights into the intimate interaction of local anesthetics with

  7. Drosophila TRPN(=NOMPC channel localizes to the distal end of mechanosensory cilia.

    Directory of Open Access Journals (Sweden)

    Jeongmi Lee

    Full Text Available BACKGROUND: A TRPN channel protein is essential for sensory transduction in insect mechanosensory neurons and in vertebrate hair cells. The Drosophila TRPN homolog, NOMPC, is required to generate mechanoreceptor potentials and currents in tactile bristles. NOMPC is also required, together with a TRPV channel, for transduction by chordotonal neurons of the fly's antennal ear, but the TRPN or TRPV channels have distinct roles in transduction and in regulating active antennal mechanics. The evidence suggests that NOMPC is a primary mechanotransducer channel, but its subcellular location-key for understanding its exact role in transduction-has not yet been established. METHODOLOGY/PRINCIPAL FINDINGS: Here, by immunostaining, we locate NOMPC at the tips of mechanosensory cilia in both external and chordotonal sensory neurons, as predicted for a mechanotransducer channel. In chordotonal neurons, the TRPN and TRPV channels are respectively segregated into distal and proximal ciliary zones. This zonal separation is demarcated by and requires the ciliary dilation, an intraciliary assembly of intraflagellar transport (IFT proteins. CONCLUSIONS: Our results provide a strong evidence for NOMPC as a primary transduction channel in Drosophila mechansensory organs. The data also reveals a structural basis for the model of auditory chordotonal transduction in which the TRPN and TRPV channels play sequential roles in generating and amplifying the receptor potential, but have opposing roles in regulating active ciliary motility.

  8. Zero-error channel capacity and simulation assisted by non-local correlations

    CERN Document Server

    Cubitt, Toby S; Matthews, William; Winter, Andreas

    2010-01-01

    Shannon's theory of zero-error communication is re-examined in the broader setting of using one classical channel to simulate another exactly, and in the presence of various resources that are all classes of non-signalling correlations: Shared randomness, shared entanglement and arbitrary non-signalling correlations. Specifically, when the channel being simulated is noiseless, this reduces to the zero-error capacity of the channel, assisted by the various classes of non-signalling correlations. When the resource channel is noiseless, it results in the "reverse" problem of simulating a noisy channel exactly by a noiseless one, assisted by correlations. In both cases, 'one-shot' separations between the power of the different assisting correlations are exhibited. The most striking result of this kind is that entanglement can assist in zero-error communication, in stark contrast to the standard setting of communicaton with asymptotically vanishing error in which entanglement does not help at all. In the asymptoti...

  9. Study of the properties of the superheavy nuclei Z = 117 produced in the 249Bk + 48Ca reaction

    Science.gov (United States)

    Oganessian, Yu. Ts.; Abdullin, F. Sh.; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Utyonkov, V. K.; Voinov, A. A.; Vostokin, G. K.

    2014-03-01

    The reaction of 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of element 117 on a larger number of events. The experiments were performed at five projectile energies and with a total beam dose of 48Ca of about 4.6×1019. Two isotopes 293,294117 were synthesized in the 249Bk+48Ca reaction, providing excitation functions and α-decay spectra of the produced isotopes that establishes these nuclei to be the products of the 4n- and 3n-evaporation channels, respectively. Decay properties of 293,294117 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time in 2010. The new 289115 events, populated by α decay of 293117, demonstrate the same decay properties as those observed for 289115 produced in the 243Am(48Ca,2n) reaction thus providing crossbombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf - a result of the in-growth of 249Cf in the 249Bk target.

  10. Study of the properties of the superheavy nuclei Z = 117 produced in the 249Bk + 48Ca reaction

    Directory of Open Access Journals (Sweden)

    Oganessian Yu. Ts.

    2014-03-01

    Full Text Available The reaction of 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of element 117 on a larger number of events. The experiments were performed at five projectile energies and with a total beam dose of 48Ca of about 4.6×1019. Two isotopes 293,294117 were synthesized in the 249Bk+48Ca reaction, providing excitation functions and α-decay spectra of the produced isotopes that establishes these nuclei to be the products of the 4n- and 3n-evaporation channels, respectively. Decay properties of 293,294117 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time in 2010. The new 289115 events, populated by α decay of 293117, demonstrate the same decay properties as those observed for 289115 produced in the 243Am(48Ca,2n reaction thus providing crossbombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf – a result of the in-growth of 249Cf in the 249Bk target.

  11. A study of the low-luminosity Type II-Plateau supernova 2008bk

    Science.gov (United States)

    Lisakov, S. M.; Dessart, Luc; Hillier, D. John; Waldman, Roni; Livne, Eli

    2017-04-01

    Supernova (SN) 2008bk is a well-observed low-luminosity Type II event visually associated with a low-mass red-supergiant progenitor. To model SN 2008bk, we evolve a 12 M⊙ star from the main sequence until core collapse, when it has a total mass of 9.88 M⊙, a He-core mass of 3.22 M⊙ and a radius of 502 R⊙. We then artificially trigger an explosion that produces 8.29 M⊙ of ejecta with a total energy of 2.5 × 1050 erg and ∼0.009 M⊙ of 56Ni. We model the subsequent evolution of the ejecta with non-local thermodynamic equilibrium time-dependent radiative transfer. Although somewhat too luminous and energetic, this model reproduces satisfactorily the multiband light curves and multi-epoch spectra of SN 2008bk, confirming the suitability of a low-mass massive star progenitor. As in other low-luminosity SNe II, the structured Hα profile at the end of the plateau phase is probably caused by Ba II 6496.9 Å rather than asphericity. We discuss the sensitivity of our results to changes in progenitor radius and mass, as well as chemical mixing. A 15 per cent increase in progenitor radius causes a 15 per cent increase in luminosity and a 0.2 mag V-band brightening of the plateau but leaves its length unaffected. An increase in ejecta mass by 10 per cent lengthens the plateau by ∼10 d. Chemical mixing introduces slight changes to the bolometric light curve, limited to the end of the plateau, but has a large impact on colours and spectra at nebular times.

  12. [BK virus infection in a pediatric renal transplant recipient].

    Science.gov (United States)

    Bonaventura, R; Vázquez, A; Exeni, A; Rivero, K; Freire, M C

    2005-01-01

    BK Human Polyomavirus causes an asymptomatic primary infection in children, then establishing latency mainly in the urinary tratt. Viral reactivation can lead to renal pathology in individuals with impaired cellular immune response. This is particularly important in pediatric transplant recipients, who can suffer a primary infection when immunosupressed. We followed up the case of a 5 years old patient who received a renal transplant in October 2003, and presented damaged graft 45 days after the intervention. The patient suffered 3 episodes of renal function failure between October 2003 and June 2004. Blood, urine, renal biopsy and lymphocele liquid samples were analyzed. A differential diagnosis between acute rejection and infectious causes was established by testing for BK, CMV and ADV viruses, and the cytological study of renal tissue. Laboratory findings together with clinical signs suggest the patient was infected by BK virus. As a final consideration, the great importance of differentiating between acute rejection and BK infection is emphasized, since immunosuppressant management is opposite in each case.

  13. WNK1 Activates Large-Conductance Ca2+-Activated K+ Channels through Modulation of ERK1/2 Signaling

    OpenAIRE

    Liu, Yingli; Song, Xiang; Shi, Yanling; Shi, Zhen; Niu, Weihui; Feng, Xiuyan; Gu, Dingying; Bao, Hui-Fang; Ma, He-Ping; Eaton, Douglas C.; Zhuang, Jieqiu; Cai, Hui

    2014-01-01

    With no lysine (WNK) kinases are members of the serine/threonine kinase family. We previously showed that WNK4 inhibits renal large-conductance Ca2+-activated K+ (BK) channel activity by enhancing its degradation through a lysosomal pathway. In this study, we investigated the effect of WNK1 on BK channel activity. In HEK293 cells stably expressing the α subunit of BK (HEK-BKα cells), siRNA-mediated knockdown of WNK1 expression significantly inhibited both BKα channel activity and open probabi...

  14. L-type calcium channel gating is modulated by bradykinin with a PKC-dependent mechanism in NG108-15 cells.

    Science.gov (United States)

    Toselli, Mauro; Taglietti, Vanni

    2005-05-01

    Bradykinin (BK) excites dorsal root ganglion cells, leading to the sensation of pain. The actions of BK are thought to be mediated by heterotrimeric G protein-regulated pathways. Indeed there is strong evidence that in different cell types BK is involved in phosphoinositide breakdown following activation of G(q/11). In the present study we show that the Ca(2+) current flowing through L-type voltage-gated Ca(2+) channels in NG108-15 cells (differentiated in vitro to acquire a neuronal phenotype), measured using the whole-cell patch clamp configuration, is reversibly inhibited by BK in a voltage-independent fashion, suggesting a cascade process where a second messenger system is involved. This inhibitory action of BK is mimicked by the application of 1,2-oleoyl-acetyl glycerol (OAG), an analog of diacylglycerol that activates PKC. Interestingly, OAG occluded the effects of BK and both effects were blocked by selective PKC inhibitors. The down modulation of single L-type Ca(2+) channels by BK and OAG was also investigated in cell-attached patches. Our results indicate that the inhibitory action of BK involves activation of PKC and mainly shows up in a significant reduction of the probability of channel opening, caused by an increase and clustering of null sweeps in response to BK.

  15. Specific functions of synaptically localized potassium channels in synaptic transmission at the neocortical GABAergic fast-spiking cell synapse.

    Science.gov (United States)

    Goldberg, Ethan M; Watanabe, Shigeo; Chang, Su Ying; Joho, Rolf H; Huang, Z Josh; Leonard, Christopher S; Rudy, Bernardo

    2005-05-25

    Potassium (K+) channel subunits of the Kv3 subfamily (Kv3.1-Kv3.4) display a positively shifted voltage dependence of activation and fast activation/deactivation kinetics when compared with other voltage-gated K+ channels, features that confer on Kv3 channels the ability to accelerate the repolarization of the action potential (AP) efficiently and specifically. In the cortex, the Kv3.1 and Kv3.2 proteins are expressed prominently in a subset of GABAergic interneurons known as fast-spiking (FS) cells and in fact are a significant determinant of the fast-spiking discharge pattern. However, in addition to expression at FS cell somata, Kv3.1 and Kv3.2 proteins also are expressed prominently at FS cell terminals, suggesting roles for Kv3 channels in neurotransmitter release. We investigated the effect of 1.0 mM tetraethylammonium (TEA; which blocks Kv3 channels) on inhibitory synaptic currents recorded in layer II/III neocortical pyramidal cells. Spike-evoked GABA release by FS cells was enhanced nearly twofold by 1.0 mM TEA, with a decrease in the paired pulse ratio (PPR), effects not reproduced by blockade of the non-Kv3 subfamily K+ channels also blocked by low concentrations of TEA. Moreover, in Kv3.1/Kv3.2 double knock-out (DKO) mice, the large effects of TEA were absent, spike-evoked GABA release was larger, and the PPR was lower than in wild-type mice. Together, these results suggest specific roles for Kv3 channels at FS cell terminals that are distinct from those of Kv1 and large-conductance Ca2+-activated K+ channels (also present at the FS cell synapse). We propose that at FS cell terminals synaptically localized Kv3 channels keep APs brief, limiting Ca2+ influx and hence release probability, thereby influencing synaptic depression at a synapse designed for sustained high-frequency synaptic transmission.

  16. Localized calcineurin confers Ca2+-dependent inactivation on neuronal L-type Ca2+ channels.

    Science.gov (United States)

    Oliveria, Seth F; Dittmer, Philip J; Youn, Dong-ho; Dell'Acqua, Mark L; Sather, William A

    2012-10-31

    Excitation-driven entry of Ca(2+) through L-type voltage-gated Ca(2+) channels controls gene expression in neurons and a variety of fundamental activities in other kinds of excitable cells. The probability of opening of Ca(V)1.2 L-type channels is subject to pronounced enhancement by cAMP-dependent protein kinase (PKA), which is scaffolded to Ca(V)1.2 channels by A-kinase anchoring proteins (AKAPs). Ca(V)1.2 channels also undergo negative autoregulation via Ca(2+)-dependent inactivation (CDI), which strongly limits Ca(2+) entry. An abundance of evidence indicates that CDI relies upon binding of Ca(2+)/calmodulin (CaM) to an isoleucine-glutamine motif in the carboxy tail of Ca(V)1.2 L-type channels, a molecular mechanism seemingly unrelated to phosphorylation-mediated channel enhancement. But our work reveals, in cultured hippocampal neurons and a heterologous expression system, that the Ca(2+)/CaM-activated phosphatase calcineurin (CaN) is scaffolded to Ca(V)1.2 channels by the neuronal anchoring protein AKAP79/150, and that overexpression of an AKAP79/150 mutant incapable of binding CaN (ΔPIX; CaN-binding PXIXIT motif deleted) impedes CDI. Interventions that suppress CaN activity-mutation in its catalytic site, antagonism with cyclosporine A or FK506, or intracellular perfusion with a peptide mimicking the sequence of the phosphatase's autoinhibitory domain-interfere with normal CDI. In cultured hippocampal neurons from a ΔPIX knock-in mouse, CDI is absent. Results of experiments with the adenylyl cyclase stimulator forskolin and with the PKA inhibitor PKI suggest that Ca(2+)/CaM-activated CaN promotes CDI by reversing channel enhancement effectuated by kinases such as PKA. Hence, our investigation of AKAP79/150-anchored CaN reconciles the CaM-based model of CDI with an earlier, seemingly contradictory model based on dephosphorylation signaling.

  17. TEMPERATURE PROFILES OF LOCAL THERMAL NONEQUILIBRIUM FOR THERMAL DEVELOPING FORCED CONVECTION IN POROUS MEDIUM PARALLEL PLATE CHANNEL

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao; LIU Xue-mei

    2006-01-01

    Based on the two-energy equation model, taking into account viscous dissipation due to the interaction between solid skeleton and pore fluid flow, temperature expressions of the solid skeleton and pore fluid flow are obtained analytically for the thermally developing forced convection in a saturated porous medium parallel plate channel,with walls being at constant temperature. It is proved that the temperatures of the two phases for the local thermal nonequilibrium approach to the temperature derived from the one-energy equation model for the local thermal equilibrium when the heat exchange coefficient goes to infinite. The temperature profiles are shown in figures for different dimensionless parameters and the effects of the parameters on the local thermal nonequilibrium are revealed by parameter study.

  18. Cholesterol binding to ion channels

    Directory of Open Access Journals (Sweden)

    Irena eLevitan

    2014-02-01

    Full Text Available Numerous studies demonstrated that membrane cholesterol is a major regulator of ion channel function. The goal of this review is to discuss significant advances that have been recently achieved in elucidating the mechanisms responsible for cholesterol regulation of ion channels. The first major insight that comes from growing number of studies that based on the sterol specificity of cholesterol effects, show that several types of ion channels (nAChR, Kir, BK, TRPV are regulated by specific sterol-protein interactions. This conclusion is supported by demonstrating direct saturable binding of cholesterol to a bacterial Kir channel. The second major advance in the field is the identification of putative cholesterol binding sites in several types of ion channels. These include sites at locations associated with the well-known cholesterol binding motif CRAC and its reversed form CARC in nAChR, BK, and TRPV, as well as novel cholesterol binding regions in Kir channels. Notably, in the majority of these channels, cholesterol is suggested to interact mainly with hydrophobic residues in non-annular regions of the channels being embedded in between transmembrane protein helices. We also discuss how identification of putative cholesterol binding sites is an essential step to understand the mechanistic basis of cholesterol-induced channel regulation. Clearly, however, these are only the first few steps in obtaining a general understanding of cholesterol-ion channels interactions and their roles in cellular and organ functions.

  19. Local anesthetic interaction with human ether-a-go-go-related gene (HERG) channels: role of aromatic amino acids Y652 and F656

    DEFF Research Database (Denmark)

    Siebrands, Cornelia C; Schmitt, Nicole; Friederich, Patrick

    2005-01-01

    : wild-type IC50 = 22 +/- 2 microm, n = 38; Y652A IC50 = 95 +/- 5 microm, n = 31). The mutations resulted in a change of the stereoselectivity of HERG channel block by ropivacaine. The potency of the local anesthetics to inhibit wild-type and mutant channels correlated with the lipophilicity of the drug...

  20. Intra- and Inter-Channel Competition in Local-Service Sectors

    NARCIS (Netherlands)

    K. Cleeren; M.G. Dekimpe (Marnik); F. Verboven

    2005-01-01

    textabstractAlthough economically very important, local-service sectors have received little attention in the extensive literature on competitive interactions. Detailed data gathering in these sectors is hard, not only because of the multitude of local players, but also because key service dimensio

  1. A 32-channel waveform sampling FASTBUS module with local DSP processing

    Energy Technology Data Exchange (ETDEWEB)

    Wixted, R.L. [Princeton Univ., NJ (United States). Dept. of Physics; Chidzik, S. [Princeton Univ., NJ (United States). Dept. of Physics; Marlow, D.R. [Princeton Univ., NJ (United States). Dept. of Physics; Mindas, C.R. [Princeton Univ., NJ (United States). Dept. of Physics; Sekikawa, S. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan); Arai, I. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan); Suzuki, A. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan); Watanabe, A. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan); Kuno, Y. [Department of Physics, National Laboratory for High Energy Physics (KEK), Tsukuba, Ibaraki 305 (Japan)

    1997-02-21

    A 32-channel FASTBUS module that uses switched-capacitor arrays to sample and store input waveforms at rates up to 30 MHz is described. The captured data are digitized using commercial 12-bit analog-to-digital converters and are routed to an array of dual port memories. The data in the dual port memories can be readout directly over the FASTBUS backplane or can be subjected to further processing by a digital signal processor mounted on the FASTBUS auxiliary card. (orig.).

  2. Pannexin2 oligomers localize into endosomal vesicles in mammalian cells while Pannexin1 channels traffic to the plasma membrane

    Directory of Open Access Journals (Sweden)

    Daniela eBoassa

    2015-02-01

    Full Text Available Pannexin2 (Panx2 is the largest of three members of the pannexin proteins. Pannexins are topologically related to connexins and innexins, but serve different functional roles than forming gap junctions. We previously showed that pannexins form oligomeric channels but unlike connexins and innexins, they form only single membrane channels. High levels of Panx2 mRNA and protein in the Central Nervous System (CNS have been documented. Whereas Pannexin1 (Panx1 is fairly ubiquitous and Pannexin3 (Panx3 is found in skin and connective tissue, both are fully glycosylated, traffic to the plasma membrane and have functions correlated with extracellular ATP release. Here, we describe trafficking and subcellular localizations of exogenous Panx2 and Panx1 protein expression in MDCK, HeLa and HEK293T cells as well as endogenous Panx1 and Panx2 patterns in the CNS. Panx2 was found in intracellular localizations, was partially N-glycosylated, and localizations were non-overlapping with Panx1. Confocal images of hippocampal sections immunolabeled for the astrocytic protein GFAP, Panx1 and Panx2 demonstrated that the two isoforms, Panx1 and Panx2, localized at different subcellular compartments in both astrocytes and neurons. Using recombinant fusions of Panx2 with appended genetic tags developed for correlated light and electron microscopy and then expressed in different cell lines, we determined that Panx2 is localized in the membrane of intracellular vesicles and not in the endoplasmic reticulum as initially indicated by calnexin colocalization experiments. Dual immunofluorescence imaging with protein markers for specific vesicle compartments showed that Panx2 vesicles are early endosomal in origin. In electron tomographic volumes, cross-sections of these vesicles displayed fine structural details and close proximity to actin filaments. Thus, pannexins expressed at different subcellular compartments likely exert distinct functional roles, particularly in the

  3. Large-conductance calcium-activated potassium channels facilitate transmitter release in salamander rod synapse.

    Science.gov (United States)

    Xu, Jian Wei; Slaughter, Malcolm M

    2005-08-17

    Large-conductance calcium-activated potassium (BK) channels are colocalized with calcium channels at sites of exocytosis at the presynaptic terminals throughout the nervous system. It is expected that their activation would provide negative feedback to transmitter release, but the opposite is sometimes observed. Attempts to resolve this apparent paradox based on alterations in action potential waveform have been ambiguous. In an alternative approach, we investigated the influence of this channel on neurotransmitter release in a nonspiking neuron, the salamander rod photoreceptors. Surprisingly, the BK channel facilitates calcium-mediated transmitter release from rods. The two presynaptic channels form a positive coupled loop. Calcium influx activates the BK channel current, leading to potassium efflux that increases the calcium current. The normal physiological voltage range of the rod is well matched to the dynamics of this positive loop. When the rod is further depolarized, then the hyperpolarizing BK channel current exceeds its facilitatory effect, causing truncation of transmitter release. Thus, the calcium channel-BK channel linkage performs two functions at the synapse: nonlinear potentiator and safety brake.

  4. Effect of rib angle on local heat/mass transfer distribution in a two-pass rib-roughened channel

    Science.gov (United States)

    Chandra, P. R.; Han, J. C.; Lau, S. C.

    1987-01-01

    The naphthalene sublimation technique is used to investigate the heat transfer characteristics of turbulent air flow in a two-pass channel. A test section that resembles the internal cooling passages of gas turbine airfoils is employed. The local Sherwood numbers on the ribbed walls were found to be 1.5-6.5 times those for a fully developed flow in a smooth square duct. Depending on the rib angle-of-attack and the Reynolds number, the average ribbed-wall Sherwood numbers were 2.5-3.5 times higher than the fully developed values.

  5. Supernova 2008bk and Its Red Supergiant Progenitor

    CERN Document Server

    Van Dyk, Schuyler D; Elias-Rosa, Nancy; Taubenberger, Stefan; Li, Weidong; Howerton, Stanley; Pignata, Giuliano; Morrell, Nidia; Hamuy, Mario; Filippenko, Alexei V

    2010-01-01

    We have observed Supernova (SN) 2008bk in NGC 7793, both photometrically and spectroscopically, primarily at late times. We find that it is a Type II-Plateau (II-P) SN, which most closely resembles the low-luminosity SN 1999br in NGC 4900. Given the overall similarity between the observed light curves and colors of SNe 2008bk and 1999br, we infer that the total visual extinction to SN 2008bk must be almost entirely due to the Galactic foreground, similar to that for SN 1999br: A_V=0.065 mag, which is substantially less than the 1.0 +/- 0.5 mag assumed by Mattila et al. (2008). Furthermore, we confirm the identification of the putative red supergiant progenitor star of the SN in high-quality g'r'i' Gemini-South images from 2007. Little ambiguity exists in this progenitor identification; besides the connection between the star Sk -69 202 and SN 1987A, it qualifies as one of the best SN progenitor identifications to date. From a combination of the Gemini images with archival, pre-SN, Very Large Telescope JHK_s i...

  6. Subcellular localization of the K+ channel subunit Kv3.1b in selected rat CNS neurons.

    Science.gov (United States)

    Sekirnjak, C; Martone, M E; Weiser, M; Deerinck, T; Bueno, E; Rudy, B; Ellisman, M

    1997-08-22

    Voltage-gated potassium channels constitute the largest group of heteromeric ion channels discovered to date. Over 20 genes have been isolated, encoding different channel subunit proteins which form functional tetrameric K+ channels. We have analyzed the subcellular localization of subunit Kv3.1b, a member of the Kv3 (Shaw-like) subfamily, in rat brain at the light and electron microscopic level, using immunocytochemical detection. Detailed localization was carried out in specific neurons of the neocortex, hippocampus and cerebellum. The identity of Kv3.1b-positive neurons was established using double labeling with markers for specific neuronal populations. In the neocortex, the Kv3.1b subunit was expressed in most parvalbumin-containing bipolar, basket or chandelier cells, and in some bipolar or double bouquet neurons containing calbindin. In the hippocampus, Kv3.1b was expressed in many parvalbumin-containing basket cells, as well as in calbindin-positive neurons in the stratum oriens, and in a small number of interneurons that did not stain for either parvalbumin or calbindin. Kv3.1b protein was not present in pyramidal cells in the neocortex and the hippocampus, but these cells were outlined by labeled presynaptic terminals from interneuron axons that surround the postsynaptic cell. In the cerebellar cortex, granule cells were the only population expressing the channel protein. Careful examination of individual granule cells revealed a non-uniform distribution of Kv3.1 staining on the somata: circular bands of labeling were present in the vicinity of the axon hillock. In cortical and hippocampal interneurons, as well as in cerebellar granule cells, the Kv3.1b subunit was present in somatic and unmyelinated axonal membranes and adjacent cytoplasm, as well as in the most proximal portion of dendritic processes, but not throughout most of the dendrite. Labeling was also seen in the terminals of labeled axons, but not at a higher concentration than in other parts

  7. Reactivation of BK polyomavirus in patients with multiple sclerosis receiving natalizumab therapy.

    LENUS (Irish Health Repository)

    Lonergan, Roisin M

    2012-02-01

    Natalizumab therapy in multiple sclerosis has been associated with JC polyomavirus-induced progressive multifocal leucoencephalopathy. We hypothesized that natalizumab may also lead to reactivation of BK, a related human polyomavirus capable of causing morbidity in immunosuppressed groups. Patients with relapsing remitting multiple sclerosis treated with natalizumab were prospectively monitored for reactivation of BK virus in blood and urine samples, and for evidence of associated renal dysfunction. In this cohort, JC and BK DNA in blood and urine; cytomegalovirus (CMV) DNA in blood and urine; CD4 and CD8 T-lymphocyte counts and ratios in peripheral blood; and renal function were monitored at regular intervals. BK subtyping and noncoding control region sequencing was performed on samples demonstrating reactivation. Prior to commencement of natalizumab therapy, 3 of 36 patients with multiple sclerosis (8.3%) had BK viruria and BK reactivation occurred in 12 of 54 patients (22.2%). BK viruria was transient in 7, continuous in 2 patients, and persistent viruria was associated with transient viremia. Concomitant JC and CMV viral loads were undetectable. CD4:CD8 ratios fluctuated, but absolute CD4 counts did not fall below normal limits. In four of seven patients with BK virus reactivation, transient reductions in CD4 counts were observed at onset of BK viruria: these resolved in three of four patients on resuppression of BK replication. No renal dysfunction was observed in the cohort. BK virus reactivation can occur during natalizumab therapy; however, the significance in the absence of renal dysfunction is unclear. We propose regular monitoring for BK reactivation or at least for evidence of renal dysfunction in patients receiving natalizumab.

  8. BIOPSY-PROVEN BK VIRUS NEPHROPATHY WITHOUT DETECTABLE BK VIREMIA IN A ONE-YEAR POST-KIDNEY TRANSPLANT RECIPIENT.

    Science.gov (United States)

    Ruangkanchanasetr, Prajej; Pumchandh, Norawee; Satirapoj, Bancha; Termmathurapoj, Sumeth; Pongthanapisith, Viroj

    2015-07-01

    BK virus nephropathy (BKVN) is an important clinical problem in kidney transplant (KT) recipients. The sequence of disease is usually viruria, viremia and then nephropathy. Diagnosis of BK virus (BKV) infection includes checking BKV DNA in the urine, in the plasma and histology on renal biopsy. This last method is used to diagnose BKVN. We describe a KT patient with BKVN without detectable BK viremia. A 62-year-old female with hypertensive nephropathy underwent renal transplant from a living relative donor in December 2011. Fourteen months after transplantation, her serum creatinine(SCr) rose up from 1.2 to 1.6 mg/dl with biopsy-proven acute antibody-mediated and cellular rejection. After pulse methylprednisolone, plasmapheresis and intravenous immunoglobulin, her SCr decreased to baseline but she subsequently developed cytomegalovirus infection with pancytopenia and transaminitis. The SCr rose to 1.9 mg/dl despite ganciclovir treatment. Renal ultrasound and antegrade pyelogram showed partial obstruction of the proximal ureter with moderate hydronephrosis. A quantitative polymerase chain reaction (PCR) assay for BKV DNA was negative (less than 10 copies/ml). A renal biopsy was performed and the pathology revealed viral cytopathic changes in the tubular epithelium with interstitial inflammation. The renal biopsy also showed BKV nucleic acid sequences by in-situ hybridization confirming BKVN. Immunosuppression regimen was changed to cyclosporine, low-dose prednisolone and leflunomide. A temporary percutaneous nephrostomy was performed. Her renal function improved within one week. The diagnosis of BKVN should be considered in a KT recipient with a rising SCr with or without BK viremia and should be made by renal biopsy.

  9. Presynaptic Localization and Possible Function of Calcium-Activated Chloride Channel Anoctamin 1 in the Mammalian Retina.

    Directory of Open Access Journals (Sweden)

    Ji Hyun Jeon

    Full Text Available Calcium (Ca(2+-activated chloride (Cl(- channels (CaCCs play a role in the modulation of action potentials and synaptic responses in the somatodendritic regions of central neurons. In the vertebrate retina, large Ca(2+-activated Cl(- currents (ICl(Ca regulate synaptic transmission at photoreceptor terminals; however, the molecular identity of CaCCs that mediate ICl(Ca remains unclear. The transmembrane protein, TMEM16A, also called anoctamin 1 (ANO1, has been recently validated as a CaCC and is widely expressed in various secretory epithelia and nervous tissues. Despite the fact that tmem16a was first cloned in the retina, there is little information on its cellular localization and function in the mammalian retina. In this study, we found that ANO1 was abundantly expressed as puncta in 2 synaptic layers. More specifically, ANO1 immunoreactivity was observed in the presynaptic terminals of various retinal neurons, including photoreceptors. ICl(Ca was first detected in dissociated rod bipolar cells expressing ANO1. ICl(Ca was abolished by treatment with the Ca(2+ channel blocker Co(2+, the L-type Ca(2+ channel blocker nifedipine, and the Cl(- channel blockers 5-nitro-2-(3-phenylpropylamino benzoic acid (NPPB and niflumic acid (NFA. More specifically, a recently discovered ANO1-selective inhibitor, T16Ainh-A01, and a neutralizing antibody against ANO1 inhibited ICl(Ca in rod bipolar cells. Under a current-clamping mode, the suppression of ICl(Ca by using NPPB and T16Ainh-A01 caused a prolonged Ca(2+ spike-like depolarization evoked by current injection in dissociated rod bipolar cells. These results suggest that ANO1 confers ICl(Ca in retinal neurons and acts as an intrinsic regulator of the presynaptic membrane potential during synaptic transmission.

  10. Regulation of cloned, Ca2+-activated K+ channels by cell volume changes

    DEFF Research Database (Denmark)

    Grunnet, Morten; MacAulay, Nanna; Jorgensen, Nanna K;

    2002-01-01

    Ca2+-activated K+ channels of big (hBK), intermediate (hIK) or small (rSK3) conductance were co-expressed with aquaporin 1 (AQP1) in Xenopus laevis oocytes. hBK channels were activated by depolarization, whereas hIK and rSK3 channels were activated by direct injection of Ca2+ or Cd2+ into the ooc......Ca2+-activated K+ channels of big (hBK), intermediate (hIK) or small (rSK3) conductance were co-expressed with aquaporin 1 (AQP1) in Xenopus laevis oocytes. hBK channels were activated by depolarization, whereas hIK and rSK3 channels were activated by direct injection of Ca2+ or Cd2......+ into the oocyte cytoplasm, before the oocytes were subjected to hyperosmolar or hypoosmolar (+/-50 mOsm mannitol) challenges. In all cases, the oocytes responded rapidly to the osmotic changes with shrinkage or swelling and the effects on the K+ currents were measured. hIK and rSK3 currents were highly sensitive......IK/rSK3 and hBK channels suggest that the significant stimulation of hIK and rSK3 channels during swelling is not mediated by changes in intracellular Ca2+, but rather through interactions with the cytoskeleton, provided that a sufficient basal concentration of intracellular Ca2+ or Cd2+ is present....

  11. A novel potassium channel in skeletal muscle mitochondria.

    Science.gov (United States)

    Skalska, Jolanta; Piwońska, Marta; Wyroba, Elzbieta; Surmacz, Liliana; Wieczorek, Rafal; Koszela-Piotrowska, Izabela; Zielińska, Joanna; Bednarczyk, Piotr; Dołowy, Krzysztof; Wilczynski, Grzegorz M; Szewczyk, Adam; Kunz, Wolfram S

    2008-01-01

    In this work we provide evidence for the potential presence of a potassium channel in skeletal muscle mitochondria. In isolated rat skeletal muscle mitochondria, Ca(2+) was able to depolarize the mitochondrial inner membrane and stimulate respiration in a strictly potassium-dependent manner. These potassium-specific effects of Ca(2+) were completely abolished by 200 nM charybdotoxin or 50 nM iberiotoxin, which are well-known inhibitors of large conductance, calcium-activated potassium channels (BK(Ca) channel). Furthermore, NS1619, a BK(Ca)-channel opener, mimicked the potassium-specific effects of calcium on respiration and mitochondrial membrane potential. In agreement with these functional data, light and electron microscopy, planar lipid bilayer reconstruction and immunological studies identified the BK(Ca) channel to be preferentially located in the inner mitochondrial membrane of rat skeletal muscle fibers. We propose that activation of mitochondrial K(+) transport by opening of the BK(Ca) channel may be important for myoprotection since the channel opener NS1619 protected the myoblast cell line C2C12 against oxidative injury.

  12. Inhalation of the BK(Ca-opener NS1619 attenuates right ventricular pressure and improves oxygenation in the rat monocrotaline model of pulmonary hypertension.

    Directory of Open Access Journals (Sweden)

    Marc Revermann

    Full Text Available BACKGROUND: Right heart failure is a fatal consequence of chronic pulmonary hypertension (PH. The development of PH is characterized by increased proliferation of vascular cells, in particular pulmonary artery smooth muscle cells (PASMCs and pulmonary artery endothelial cells. In the course of PH, an escalated right ventricular (RV afterload occurs, which leads to increased perioperative morbidity and mortality. BK(Ca channels are ubiquitously expressed in vascular smooth muscle cells and their opening induces cell membrane hyperpolarization followed by vasodilation. Moreover, BK activation induces anti-proliferative effects in a multitude of cell types. On this basis, we hypothesized that treatment with the nebulized BK channel opener NS1619 might be a therapy option for pulmonary hypertension and tested this in rats. METHODS: (1 Rats received monocrotaline injection for PH induction. Twenty-four days later, rats were anesthetized and NS1619 or the solvent was administered by inhalation. Systemic hemodynamic parameters, RV hemodynamic parameters, and blood gas analyses were measured before as well as 30 and 120 minutes after inhalation. (2 Rat PASMCs were stimulated with PDGF-BB in the presence and absence of NS1619. AKT, ERK1 and ERK2 activation were investigated by western blot analyses, and relative cell number was determined 48 hours after stimulation. RESULTS: Inhalation of a 12 µM and 100 µM NS1619 solution significantly reduced RV pressure without affecting systemic arterial pressure. Blood gas analyses demonstrated significantly reduced carbon dioxide and improved oxygenation in NS1619-treated animals pointing towards a considerable pulmonary shunt-reducing effect. In PASMC's, NS1619 (100 µM significantly attenuated PASMC proliferation by a pathway independent of AKT and ERK1/2 activation. CONCLUSION: NS1619 inhalation reduces RV pressure and improves oxygen supply and its application inhibits PASMC proliferation in vitro. Hence, BK

  13. On locality of Generalized Reed-Muller codes over the broadcast erasure channel

    KAUST Repository

    Alloum, Amira

    2016-07-28

    One to Many communications are expected to be among the killer applications for the currently discussed 5G standard. The usage of coding mechanisms is impacting broadcasting standard quality, as coding is involved at several levels of the stack, and more specifically at the application layer where Rateless, LDPC, Reed Slomon codes and network coding schemes have been extensively studied, optimized and standardized in the past. Beyond reusing, extending or adapting existing application layer packet coding mechanisms based on previous schemes and designed for the foregoing LTE or other broadcasting standards; our purpose is to investigate the use of Generalized Reed Muller codes and the value of their locality property in their progressive decoding for Broadcast/Multicast communication schemes with real time video delivery. Our results are meant to bring insight into the use of locally decodable codes in Broadcasting. © 2016 IEEE.

  14. Transient receptor potential ankyrin 1 channel localized to non-neuronal airway cells promotes non-neurogenic inflammation.

    Directory of Open Access Journals (Sweden)

    Romina Nassini

    Full Text Available BACKGROUND: The transient receptor potential ankyrin 1 (TRPA1 channel, localized to airway sensory nerves, has been proposed to mediate airway inflammation evoked by allergen and cigarette smoke (CS in rodents, via a neurogenic mechanism. However the limited clinical evidence for the role of neurogenic inflammation in asthma or chronic obstructive pulmonary disease raises an alternative possibility that airway inflammation is promoted by non-neuronal TRPA1. METHODOLOGY/PRINCIPAL FINDINGS: By using Real-Time PCR and calcium imaging, we found that cultured human airway cells, including fibroblasts, epithelial and smooth muscle cells express functional TRPA1 channels. By using immunohistochemistry, TRPA1 staining was observed in airway epithelial and smooth muscle cells in sections taken from human airways and lung, and from airways and lung of wild-type, but not TRPA1-deficient mice. In cultured human airway epithelial and smooth muscle cells and fibroblasts, acrolein and CS extract evoked IL-8 release, a response selectively reduced by TRPA1 antagonists. Capsaicin, agonist of the transient receptor potential vanilloid 1 (TRPV1, a channel co-expressed with TRPA1 by airway sensory nerves, and acrolein or CS (TRPA1 agonists, or the neuropeptide substance P (SP, which is released from sensory nerve terminals by capsaicin, acrolein or CS, produced neurogenic inflammation in mouse airways. However, only acrolein and CS, but not capsaicin or SP, released the keratinocyte chemoattractant (CXCL-1/KC, IL-8 analogue in bronchoalveolar lavage (BAL fluid of wild-type mice. This effect of TRPA1 agonists was attenuated by TRPA1 antagonism or in TRPA1-deficient mice, but not by pharmacological ablation of sensory nerves. CONCLUSIONS: Our results demonstrate that, although either TRPV1 or TRPA1 activation causes airway neurogenic inflammation, solely TRPA1 activation orchestrates an additional inflammatory response which is not neurogenic. This finding suggests

  15. Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks

    Science.gov (United States)

    Zhang, Jie; Han, Guangjie; Qian, Yujie

    2016-01-01

    Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today’s high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users’ behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs. PMID:27563896

  16. Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks.

    Science.gov (United States)

    Zhang, Jie; Han, Guangjie; Qian, Yujie

    2016-08-23

    Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today's high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users' behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs.

  17. Channel access schemes and fiber optic configurations for integrated-services local area networks. Ph.D. Thesis

    Science.gov (United States)

    Nassehi, M. Mehdi

    1987-01-01

    Local Area Networks are in common use for data communications and have enjoyed great success. Recently, there is a growing interest in using a single network to support many applications in addition to traditional data traffic. These additional applications introduce new requirements in terms of volume of traffic and real-time delivery of data which are not met by existing networks. To satisfy these requirements, a high-bandwidth tranmission medium, such as fiber optics, and a distributed channel access scheme for the efficient sharing of the bandwidth among the various applications are needed. As far as the throughput-delay requirements of the various application are concerned, a network structure along with a distributed channel access are proposed which incorporate appropriate scheduling policies for the transmission of outstanding messages on the network. A dynamic scheduling policy was devised which outperforms all existing policies in terms of minimizing the expected cost per message. A broadcast mechanism was devised for the efficient dissemination of all relevant information. Fiber optic technology is considered for the high-bandwidth transmisison medium.

  18. Nanobubble Fragmentation and Bubble-Free-Channel Shear Localization in Helium-Irradiated Submicron-Sized Copper.

    Science.gov (United States)

    Ding, Ming-Shuai; Tian, Lin; Han, Wei-Zhong; Li, Ju; Ma, Evan; Shan, Zhi-Wei

    2016-11-18

    Helium bubbles are one of the typical radiation microstructures in metals and alloys, significantly influencing their deformation behavior. However, the dynamic evolution of helium bubbles under straining is less explored so far. Here, by using in situ micromechanical testing inside a transmission electron microscope, we discover that the helium bubble not only can coalesce with adjacent bubbles, but also can split into several nanoscale bubbles under tension. Alignment of the splittings along a slip line can create a bubble-free channel, which appears softer, promotes shear localization, and accelerates the failure in the shearing-off mode. Detailed analyses unveil that the unexpected bubble fragmentation is mediated by the combination of dislocation cutting and internal surface diffusion, which is an alternative microdamage mechanism of helium irradiated copper besides the bubble coalescence.

  19. Hillslope-channel connectivity and local sediment budget in a Himalayan Valley (Kali Gandaki, Nepal)

    Science.gov (United States)

    Fort, Monique; Etienne, Cossart; Gilles, Arnaud-Fassetta

    2010-05-01

    In the confined Himalayan valleys and in a context of monsoon, contrasted climate, landslides interact with rivers immediately, causing channel diversions, short-lived dams and sediment traps. Yet, remnants of ancient landslides may play an important role in the location of present instabilities and sediment fluxes. We document here debris storages and interaction patterns with fluvial activity observed in the Middle Kali Gandaki river (Myagdi District, Nepal Himalayas). We focus on the Pairothapla-Talbagar landslide (about 10 x 10 exponent 6 m3) that dammed the Kali Gandaki probably a few centuries ago. On the basis of diachronic (1974-2000-2008) geomorphic surveys and mapping, and thanks to DEM facilities, we reconstructed the extent of the landslide deposits, characterized the material (debris avalanche, including >350 m3 blocks), estimated the volume of the resulting lake (9-14 x 10 exponent 6 m3), and of sedimentary wedges resulting from later superficial reworking and downstream redistribution of debris. We assess the recent evolution of the landslide mass. Current instabilities (rainfall triggered shallow landslides) are large enough to supply debris to the river and increase the density hence the transport capacity of the flow downstream; in turn armouring boulders may be set into motion again, hence accelerating erosion of the Talbagar landslide mass in a positive feedback. We estimate the volume of debris eroded and exported by the Kali Gandaki during the last three decades. We end up with the sedimentary budget related to this event. Comparison with other features, either older or more recent, observed along the middle Kali Gandaki valley suggests that landsliding plays the major role in the overall process of denudation and sediment transfer of the Higher Himalaya. When coupled with high fluvial activity, it considerably reduces the residence time of sediments in the temporary, spatially limited traps of the valley bottom and highly influences sediment

  20. Inhibitory Interactions between BK and JC Virus among Kidney Transplant Recipients

    Science.gov (United States)

    Cheng, Xingxing S.; Bohl, Daniel L.; Storch, Gregory A.; Ryschkewitsch, Caroline; Gaudreault-Keener, Monique; Major, Eugene O.; Randhawa, Parmjeet; Hardinger, Karen L.

    2011-01-01

    BK and JC polyomaviruses can reactivate after transplantation, causing renal dysfunction and graft loss. The incidence of JC reactivation after renal transplant is not well understood. Here, we characterized JC reactivation using samples collected during the first year after transplantation from 200 kidney recipients. We detected BK and JC viruses in the urine of 35 and 16% of transplant recipients, respectively. The median viral load in the urine was 400 times higher for BK virus than JC virus. The presence of BK viruria made concurrent JC viruria less likely: JC viruria was detected in 22% of non-BK viruric recipients compared with 4% of BK viruric recipients (P = 0.001). The co-detection rate was 1.5%, which is less than the expected 5.6% if reactivation of each virus was independent (P = 0.001). We did not observe JC viremia, JC nephropathy, or progressive multifocal leukoencephalopathy. The onset of JC viruria was associated with donor, but not recipient, JC-specific antibody in a titer-dependent fashion and inversely associated with donor and recipient BK-specific antibody. Donor and recipient JC seropositivity did not predict BK viruria or viremia. In conclusion, among renal transplant recipients, infection with one polyomavirus inversely associates with infection with the other. PMID:21511831

  1. Atomic determinants of state-dependent block of sodium channels by charged local anesthetics and benzocaine.

    Science.gov (United States)

    Tikhonov, Denis B; Bruhova, Iva; Zhorov, Boris S

    2006-11-13

    Molecular modeling predicts that a local anesthetic (LA) lidocaine binds to the resting and open Na(v)1.5 in different modes, interacting with LA-sensing residues known from experiments. Besides the major pathway via the open activation gate, LAs can reach the inner pore via a "sidewalk" between D3S6, D4S6, and D3P. The ammonium group of a cationic LA binds in the focus of the pore-helices macrodipoles, which also stabilize a Na(+) ion chelated by two benzocaine molecules. The LA's cationic group and a Na(+) ion in the selectivity filter repel each other suggesting that the Na(+) depletion upon slow inactivation would stabilize a LA, while a LA would stabilize slow-inactivated states.

  2. Water Channels Aquaporin 4 and -1 Expression in Subependymoma Depends on the Localization of the Tumors.

    Directory of Open Access Journals (Sweden)

    Susan Noell

    Full Text Available We analyzed aquaporin 4 and -1 expression in subependymomas, benign and slow growing brain tumors WHO grade I. Ten subependymoma cases were investigated, five of the fossa inferior and five of the fossa superior.Using immunohistochemistry, we observed different aquaporin expression patterns depending on localization: aquaporin 4 and -1 were detected in infratentorial subependymomas in the entire tumor tissue. In contrast, supratentorial subependymomas revealed aquaporin 4 and -1 expression only in border areas of the tumor. PCR analyses however showed no difference in aquaporin 4 expression between all subependymomas independent of localization but at higher levels than in normal brain. In contrast, aquaporin 1 RNA levels were found to be higher only in infratentorial samples compared to supratentorial and normal brain samples. The reason for the different distribution pattern of aquaporin 4 in subependymomas still remains unclear. On the cellular level, aquaporin 4 was redistributed on the surface of the tumor cells, and in freeze fracture replicas no orthogonal arrays of particles were found. This was similar to our previous findings in malignant glioblastomas. From these studies, we know that extracellular matrix molecules within the tumor like agrin and its receptor alpha-dystroglycan are involved in forming orthogonal arrays of particles. In subependymomas neither agrin nor alpha-dystroglycan were detected around blood vessels.Taken together, we show in this study that in the benign subependymomas aquaporins 1 and 4 are dramatically redistributed and upregulated. We speculate that extracellular environments of infra- and supratentorial subependymomas are different and lead to different distribution patterns of aquaporin 4 and -1.

  3. Numerical and experimental analysis of local flow phenomena in laminar Taylor flow in a square mini-channel

    Science.gov (United States)

    Falconi, C. J.; Lehrenfeld, C.; Marschall, H.; Meyer, C.; Abiev, R.; Bothe, D.; Reusken, A.; Schlüter, M.; Wörner, M.

    2016-01-01

    The vertically upward Taylor flow in a small square channel (side length 2 mm) is one of the guiding measures within the priority program "Transport Processes at Fluidic Interfaces" (SPP 1506) of the German Research Foundation (DFG). This paper presents the results of coordinated experiments and three-dimensional numerical simulations (with three different academic computer codes) for typical local flow parameters (bubble shape, thickness of the liquid film, and velocity profiles) in different cutting planes (lateral and diagonal) for a specific co-current Taylor flow. For most quantities, the differences between the three simulation results and also between the numerical and experimental results are below a few percent. The experimental and computational results consistently show interesting three-dimensional flow effects in the rear part of the liquid film. There, a local back flow of liquid occurs in the fixed frame of reference which leads to a temporary reversal of the direction of the wall shear stress during the passage of a Taylor bubble. Notably, the axial positions of the region with local backflow and those of the minimum vertical velocity differ in the lateral and the diagonal liquid films. By a thorough analysis of the fully resolved simulation results, this previously unknown phenomenon is explained in detail and, moreover, approximate criteria for its occurrence in practical applications are given. It is the different magnitude of the velocity in the lateral film and in the corner region which leads to azimuthal pressure differences in the lateral and diagonal liquid films and causes a slight deviation of the bubble from the rotational symmetry. This deviation is opposite in the front and rear parts of the bubble and has the mentioned significant effects on the local flow field in the rear part of the liquid film.

  4. Conformal Barrier and Hidden Local Symmetry Constraints: Walking Technirhos in LHC Diboson Channels

    CERN Document Server

    Fukano, Hidenori S; Terashi, Koji; Yamawaki, Koichi

    2015-01-01

    We expand the previous analyses of the conformal barrier on the walking technirho for the 2 TeV diboson excesses reported by the ATLAS collaboration, with a special emphasis on the hidden local symmetry (HLS) constraints. The scale symmetry forbids the new vector boson decay to the 125 GeV Higgs plus $W/Z$ boson, in sharp contrast to the conventional "equivalence theorem" which is invalidated by the conformality. The HLS forbids mixing between the iso-triplet technirho's, $\\rho_{\\Pi}$ and $\\rho_{P}$, of the one-family walking technicolor (with four doublets $N_D=N_F/2=4$), which, without the HLS, would be generated when switching on the standard model gauging. We also present updated analyses of the walking technrho's for the diboson excesses by fully incorporating the constraints from the conformal barrier and the HLS as well as possible higher order effects: still characteristic of the one-family walking technirho is its smallness of the decay width, roughly of order $\\Gamma/M_\\rho \\sim [3/N_C\\times 1/N_D] ...

  5. Collinearly-improved BK evolution meets the HERA data

    Directory of Open Access Journals (Sweden)

    E. Iancu

    2015-11-01

    Full Text Available In a previous publication, we have established a collinearly-improved version of the Balitsky–Kovchegov (BK equation, which resums to all orders the radiative corrections enhanced by large double transverse logarithms. Here, we study the relevance of this equation as a tool for phenomenology, by confronting it to the HERA data. To that aim, we first improve the perturbative accuracy of our resummation, by including two classes of single-logarithmic corrections: those generated by the first non-singular terms in the DGLAP splitting functions and those expressing the one-loop running of the QCD coupling. The equation thus obtained includes all the next-to-leading order corrections to the BK equation which are enhanced by (single or double collinear logarithms. We then use numerical solutions to this equation to fit the HERA data for the electron–proton reduced cross-section at small Bjorken x. We obtain good quality fits for physically acceptable initial conditions. Our best fit, which shows a good stability up to virtualities as large as Q2=400 GeV2 for the exchanged photon, uses as an initial condition the running-coupling version of the McLerran–Venugopalan model, with the QCD coupling running according to the smallest dipole prescription.

  6. Mechanisms of sustained high firing rates in two classes of vestibular nucleus neurons: differential contributions of resurgent Na, Kv3, and BK currents.

    Science.gov (United States)

    Gittis, Aryn H; Moghadam, Setareh H; du Lac, Sascha

    2010-09-01

    To fire at high rates, neurons express ionic currents that work together to minimize refractory periods by ensuring that sodium channels are available for activation shortly after each action potential. Vestibular nucleus neurons operate around high baseline firing rates and encode information with bidirectional modulation of firing rates up to several hundred Hz. To determine the mechanisms that enable these neurons to sustain firing at high rates, ionic currents were measured during firing by using the action potential clamp technique in vestibular nucleus neurons acutely dissociated from transgenic mice. Although neurons from the YFP-16 line fire at rates higher than those from the GIN line, both classes of neurons express Kv3 and BK currents as well as both transient and resurgent Na currents. In the fastest firing neurons, Kv3 currents dominated repolarization at all firing rates and minimized Na channel inactivation by rapidly transitioning Na channels from the open to the closed state. In slower firing neurons, BK currents dominated repolarization at the highest firing rates and sodium channel availability was protected by a resurgent blocking mechanism. Quantitative differences in Kv3 current density across neurons and qualitative differences in immunohistochemically detected expression of Kv3 subunits could account for the difference in firing range within and across cell classes. These results demonstrate how divergent firing properties of two neuronal populations arise through the interplay of at least three ionic currents.

  7. Conformal barrier and hidden local symmetry constraints: Walking technirhos in LHC diboson channels

    Directory of Open Access Journals (Sweden)

    Hidenori S. Fukano

    2016-03-01

    Full Text Available We expand the previous analyses of the conformal barrier on the walking technirho for the 2 TeV diboson excesses reported by the ATLAS Collaboration, with a special emphasis on the hidden local symmetry (HLS constraints. We first show that the Standard Model (SM Higgs Lagrangian is equivalent to the scale-invariant nonlinear chiral Lagrangian, which is further gauge equivalent to the scale-invariant HLS model, with the scale symmetry realized nonlinearly via SM Higgs as a (pseudo-dilaton. The scale symmetry forbids the new vector boson decay to the 125 GeV Higgs plus W/Z boson, in sharp contrast to the conventional “equivalence theorem” which is invalidated by the conformality. The HLS forbids mixing between the iso-triplet technirho's, ρΠ and ρP, of the one-family walking technicolor (with four doublets ND=NF/2=4, which, without the HLS, would be generated when switching on the standard model gauging. We also present updated analyses of the walking technirho's for the diboson excesses by fully incorporating the constraints from the conformal barrier and the HLS as well as possible higher order effects: still characteristic of the one-family walking technirho is its smallness of the decay width, roughly of order Γ/Mρ∼[3/NC×1/ND]×[Γ/Mρ]QCD≃70 GeV/2 TeV (ND=NC=4, in perfect agreement with the expected diboson resonance with Γ<100 GeV. The model is so sharply distinguishable from other massive spin 1 models without the conformality and HLS that it is clearly testable at the LHC Run II. If the 2 TeV boson decay to WH/ZH is not observed in the ongoing Run II, then the conformality is operative on the 125 GeV Higgs, strongly suggesting that the 2 TeV excess events are responsible for the walking technirhos and the 125 GeV Higgs is the technidilaton.

  8. OSR1 and SPAK Sensitivity of Large-Conductance Ca2+ Activated K+ Channel

    Directory of Open Access Journals (Sweden)

    Bernat Elvira

    2016-04-01

    Full Text Available Background/Aims: The oxidative stress-responsive kinase 1 (OSR1 and the serine/threonine kinases SPAK (SPS1-related proline/alanine-rich kinase are under the control of WNK (with-no-K [Lys] kinases. OSR1 and SPAK participate in diverse functions including cell volume regulation and neuronal excitability. Cell volume and neuronal excitation are further modified by the large conductance Ca2+-activated K+ channels (maxi K+ channel or BK channels. An influence of OSR1 and/or SPAK on BK channel activity has, however, never been shown. The present study thus explored whether OSR1 and/or SPAK modify the activity of BK channels. Methods: cRNA encoding the Ca2+ insensitive BK channel mutant BKM513I+Δ899-903 was injected into Xenopus laevis oocytes without or with additional injection of cRNA encoding wild-type OSR1 or wild-type SPAK, constitutively active T185EOSR1, catalytically inactive D164AOSR1, constitutively active T233ESPAK or catalytically inactive D212ASPAK. K+ channel activity was measured utilizing dual electrode voltage clamp. Results: BK channel activity in BKM513I+Δ899-903 expressing oocytes was significantly decreased by co-expression of OSR1 or SPAK. The effect of wild-type OSR1/SPAK was mimicked by T185EOSR1 and T233ESPAK, but not by D164AOSR1 or D212ASPAK. Conclusions: OSR1 and SPAK suppress BK channels, an effect possibly contributing to cell volume regulation and neuroexcitability.

  9. Interaction of local anesthetics with a peptide encompassing the IV/S4-S5 linker of the Na+ channel.

    Science.gov (United States)

    Fraceto, Leonardo F; Oyama, Sérgio; Nakaie, Clóvis R; Spisni, Alberto; de Paula, Eneida; Pertinhez, Thelma A

    2006-08-20

    The peptide pIV/S4-S5 encompasses the cytoplasmic linker between helices S4-S5 in domain IV of the voltage-gated Na+ channel, residues 1644-1664. The interaction of two local anesthetics (LA), lidocaine and benzocaine, with pIV/S4-S5 has been studied by DOSY, heteronuclear NMR 1H-15N-HSQC spectroscopy and computational methods. DOSY indicates that benzocaine, a neutral ester, exhibits stronger interaction with pIV/S4-S5 than lidocaine, a charged amine-amide. Weighted average chemical shifts, Deltadelta(1H-15N), show that benzocaine affects residues L1653, M1655 and S1656 while lidocaine slightly perturbs residues I1646, L1649 and A1659, L1660, near the N- and C-terminus, respectively. Computational methods confirmed the stability of the benzocaine binding and the existence of two binding sites for lidocaine. Even considering that the approach of studying the peptide in the presence of a co-solvent (TFE/H2O, 30%/70% v/v) has an inherently limited implication, our data strongly support the existence of multiple LA binding sites in the IV/S4-S5 linker, as suggested in the literature. In addition, we consider that LA can bind to the S4-S5 linker with diverse binding modes and strength since this linker is part of the receptor for the "inactivation gate particle". Conditions for devising new functional studies, aiming to better understand Na+ channel functionality as well as the various facets of LA pharmacological activity are proposed in this work.

  10. Ca2+ Channel Re-localization to Plasma-Membrane Microdomains Strengthens Activation of Ca2+-Dependent Nuclear Gene Expression

    Directory of Open Access Journals (Sweden)

    Krishna Samanta

    2015-07-01

    Full Text Available In polarized cells or cells with complex geometry, clustering of plasma-membrane (PM ion channels is an effective mechanism for eliciting spatially restricted signals. However, channel clustering is also seen in cells with relatively simple topology, suggesting it fulfills a more fundamental role in cell biology than simply orchestrating compartmentalized responses. Here, we have compared the ability of store-operated Ca2+ release-activated Ca2+ (CRAC channels confined to PM microdomains with a similar number of dispersed CRAC channels to activate transcription factors, which subsequently increase nuclear gene expression. For similar levels of channel activity, we find that channel confinement is considerably more effective in stimulating gene expression. Our results identify a long-range signaling advantage to the tight evolutionary conservation of channel clustering and reveal that CRAC channel aggregation increases the strength, fidelity, and reliability of the general process of excitation-transcription coupling.

  11. Effect of blockers of Kv and BKCa channels on muscle tension of rabbit oddi sphincter in vivo and th e regulatory effect of paeoniflorin%Kv 和 BK Ca通道阻断剂对家兔离体 Oddi括约肌肌环张力的作用及芍药甙的调控作用

    Institute of Scientific and Technical Information of China (English)

    雒建瑞; 王芳; 冯骅; 王长淼

    2014-01-01

    Objective It is to investigate the effect of blockers of voltage-gated potassium channels ( Kv) , large-conduct-ance calcium-activated potassium channel ( BKCa) on sphincter of Oddi ( sphincter of Oddi , SO) from rabbits muscle ten-sion rings, and to explore the regulatory effect of the active ingredients of traditional Chinese medicine paeoniflorin on them . Methods Isolated rabbit sphincter of Oddi muscle rings specimens were prepared and placed on the smooth muscle perfusion bath temperature to observe the contraction effect of Kv channel blocker 4-aminopyridine (4-AP), BKCa channel blocker tetraethylammonium chloride( TEA) on isolated rabbit SO muscle rings and the effects of paeoniflorin on the contraction effects induced by 4-AP and TEA.Resul ts 4-AP and TEA both could cause contraction of SO muscle rings , with the the concen-trations increased , the contraction degrees increased .The contraction effects induced by 4-AP and TEA could be inhibited by paeoniflorin .Conclusion In vitro condition , Kv channel and BKCa channel play a major role in the maintenance of sphincter of Oddi resting membrane potential of cells .Paeoniflorin may influence the relaxant responses of SO cells possibly through the regulation of Kv and BKCa channels .%目的:探讨电压依赖性钾通道( Kv)、大电导钙激活钾通道( BKCa )阻断剂对家兔离体Oddi 括约肌( SO)肌环张力的作用及中药芍药的有效成分芍药甙对其调控作用。方法制备离体兔Oddi 括约肌肌环标本,放置于平滑肌恒温灌流浴槽中,观察Kv通道阻断剂4-aminopyridine (4-AP)、BKCa通道阻断剂tetraethylammonium chloride ( TEA)对家兔离体SO肌环的收缩作用;观察芍药甙对4-AP和TEA引起的收缩作用的影响。结果4-AP、TEA均可以引起SO肌环收缩,且随4-AP、TEA浓度增加,收缩程度也在增强。4-AP和TEA对SO肌环的收缩作用可以被芍药甙抑制。结论在离体条件下,Kv通道和BKCa通道

  12. Large-conductance Ca2+-activated potassium channels in secretory neurons.

    Science.gov (United States)

    Lara, J; Acevedo, J J; Onetti, C G

    1999-09-01

    Large-conductance Ca2+-activated K+ channels (BK) are believed to underlie interburst intervals and contribute to the control of hormone release in several secretory cells. In crustacean neurosecretory cells, Ca2+ entry associated with electrical activity could act as a modulator of membrane K+ conductance. Therefore we studied the contribution of BK channels to the macroscopic outward current in the X-organ of crayfish, and their participation in electrophysiological activity, as well as their sensitivity toward intracellular Ca2+, ATP, and voltage, by using the patch-clamp technique. The BK channels had a conductance of 223 pS and rectified inwardly in symmetrical K+. These channels were highly selective to K+ ions; potassium permeability (PK) value was 2.3 x 10(-13) cm(3) s(-1). The BK channels were sensitive to internal Ca2+ concentration, voltage dependent, and activated by intracellular MgATP. Voltage sensitivity (k) was approximately 13 mV, and the half-activation membrane potentials depended on the internal Ca2+ concentration. Calcium ions (0.3-3 microM) applied to the internal membrane surface caused an enhancement of the channel activity. This activation of BK channels by internal calcium had a KD(0) of 0.22 microM and was probably due to the binding of only one or two Ca2+ ions to the channel. Addition of MgATP (0.01-3 mM) to the internal solution increased steady state-open probability. The dissociation constant for MgATP (KD) was 119 microM, and the Hill coefficient (h) was 0.6, according to the Hill analysis. Ca2+-activated K+ currents recorded from whole cells were suppressed by either adding Cd2+ (0.4 mM) or removing Ca2+ ions from the external solution. TEA (1 mM) or charybdotoxin (100 nM) blocked these currents. Our results showed that both BK and K(ATP) channels are present in the same cell. Even when BK and K(ATP) channels were voltage dependent and modulated by internal Ca2+ and ATP, the profile of sensitivity was quite different for each kind

  13. Neurogenic detrusor overactivity is associated with decreased expression and function of the large conductance voltage- and Ca(2+-activated K(+ channels.

    Directory of Open Access Journals (Sweden)

    Kiril L Hristov

    Full Text Available Patients suffering from a variety of neurological diseases such as spinal cord injury, Parkinson's disease, and multiple sclerosis often develop neurogenic detrusor overactivity (NDO, which currently lacks a universally effective therapy. Here, we tested the hypothesis that NDO is associated with changes in detrusor smooth muscle (DSM large conductance Ca(2+-activated K(+ (BK channel expression and function. DSM tissue samples from 33 patients were obtained during open bladder surgeries. NDO patients were clinically characterized preoperatively with pressure-flow urodynamics demonstrating detrusor overactivity, in the setting of a clinically relevant neurological condition. Control patients did not have overactive bladder and did not have a clinically relevant neurological disease. We conducted quantitative polymerase chain reactions (qPCR, perforated patch-clamp electrophysiology on freshly-isolated DSM cells, and functional studies on DSM contractility. qPCR experiments revealed that DSM samples from NDO patients showed decreased BK channel mRNA expression in comparison to controls. Patch-clamp experiments demonstrated reduced whole cell and transient BK currents (TBKCs in freshly-isolated DSM cells from NDO patients. Functional studies on DSM contractility showed that spontaneous phasic contractions had a decreased sensitivity to iberiotoxin, a selective BK channel inhibitor, in DSM strips isolated from NDO patients. These results reveal the novel finding that NDO is associated with decreased DSM BK channel expression and function leading to increased DSM excitability and contractility. BK channel openers or BK channel gene transfer could be an alternative strategy to control NDO. Future clinical trials are needed to evaluate the value of BK channel opening drugs or gene therapies for NDO treatment and to identify any possible adverse effects.

  14. The Role of L- and T-Type Calcium Channels in Local and Remote Calcium Responses in Rat Mesenteric Terminal Arterioles

    DEFF Research Database (Denmark)

    Braunstein, Thomas Hartig; Inoue, Ryuji; Cribbs, Leanne;

    2009-01-01

    Background/Aims: The roles of intercellular communication and T-type versus L-type voltage-dependent Ca(2+) channels (VDCCs) in conducted vasoconstriction to local KCl-induced depolarization were investigated in mesenteric arterioles. Methods: Ratiometric Ca(2+) imaging (R) using Fura-PE3...

  15. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation.

    Directory of Open Access Journals (Sweden)

    Domenico Tricarico

    Full Text Available Emerging evidences suggest that Ca(2+activated-K(+-(BK channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L or hypokalemia (0.55 mEq/L conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293 in the presence or absence of BK channel modulators. The BK channel openers(10(-11-10(-3M were: acetazolamide(ACTZ, Dichlorphenamide(DCP, methazolamide(MTZ, bendroflumethiazide(BFT, ethoxzolamide(ETX, hydrochlorthiazide(HCT, quercetin(QUERC, resveratrol(RESV and NS1619; and the BK channel blockers(2 x 10(-7M-5 x 10(-3M were: tetraethylammonium(TEA, iberiotoxin(IbTx and charybdotoxin(ChTX. Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing the

  16. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation.

    Science.gov (United States)

    Tricarico, Domenico; Mele, Antonietta; Calzolaro, Sara; Cannone, Gianluigi; Camerino, Giulia Maria; Dinardo, Maria Maddalena; Latorre, Ramon; Conte Camerino, Diana

    2013-01-01

    Emerging evidences suggest that Ca(2+)activated-K(+)-(BK) channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L) or hypokalemia (0.55 mEq/L) conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293) in the presence or absence of BK channel modulators. The BK channel openers(10(-11)-10(-3)M) were: acetazolamide(ACTZ), Dichlorphenamide(DCP), methazolamide(MTZ), bendroflumethiazide(BFT), ethoxzolamide(ETX), hydrochlorthiazide(HCT), quercetin(QUERC), resveratrol(RESV) and NS1619; and the BK channel blockers(2 x 10(-7)M-5 x 10(-3)M) were: tetraethylammonium(TEA), iberiotoxin(IbTx) and charybdotoxin(ChTX). Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm) was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing

  17. 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.

  18. Search for the Decay B+-->K+ tau-/+ mu+/-.

    Science.gov (United States)

    Aubert, B; Bona, M; Boutigny, D; Karyotakis, Y; Lees, J P; Poireau, V; Prudent, X; Tisserand, V; Zghiche, A; Garra Tico, J; Grauges, E; Lopez, L; Palano, A; Pappagallo, M; Eigen, G; Stugu, B; Sun, L; Abrams, G S; Battaglia, M; Brown, D N; Button-Shafer, J; Cahn, R N; Groysman, Y; Jacobsen, R G; Kadyk, J A; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lopes Pegna, D; Lynch, G; Mir, L M; Orimoto, T J; Osipenkov, I L; Ronan, M T; Tackmann, K; Tanabe, T; Wenzel, W A; del Amo Sanchez, P; Hawkes, C M; Watson, A T; Held, T; Koch, H; Pelizaeus, M; Schroeder, T; Steinke, M; Walker, D; Asgeirsson, D J; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Mattison, T S; McKenna, J A; Khan, A; Saleem, M; Teodorescu, L; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Bondioli, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Martin, E C; Stoker, D P; Abachi, S; Buchanan, C; Foulkes, S D; Gary, J W; Liu, F; Long, O; Shen, B C; Zhang, L; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Kovalskyi, D; Richman, J D; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Schalk, T; Schumm, B A; Seiden, A; Wilson, M G; Winstrom, L O; Chen, E; Cheng, C H; Fang, F; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Andreassen, R; Mancinelli, G; Meadows, B T; Mishra, K; Sokoloff, M D; Blanc, F; Bloom, P C; Chen, S; Ford, W T; Hirschauer, J F; Kreisel, A; Nagel, M; Nauenberg, U; Olivas, A; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Gabareen, A M; Soffer, A; Toki, W H; Wilson, R J; Winklmeier, F; Altenburg, D D; Feltresi, E; Hauke, A; Jasper, H; Merkel, J; Petzold, A; Spaan, B; Wacker, K; Klose, V; Kobel, M J; Lacker, H M; Mader, W F; Nogowski, R; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Volk, A; Bernard, D; Bonneaud, G R; Latour, E; Lombardo, V; Thiebaux, Ch; Verderi, M; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Robertson, A I; Watson, J E; Xie, Y; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cecchi, A; Cibinetto, G; Franchini, P; Luppi, E; Negrini, M; Petrella, A; Piemontese, L; Prencipe, E; Santoro, V; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Pacetti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Buzzo, A; Contri, R; Lo Vetere, M; Macri, M M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Chaisanguanthum, K S; Morii, M; Wu, J; Dubitzky, R S; Marks, J; Schenk, S; Uwer, U; Bard, D J; Dauncey, P D; Flack, R L; Nash, J A; Panduro Vazquez, W; Tibbetts, M; Behera, P K; Chai, X; Charles, M J; Mallik, U; Ziegler, V; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Gao, Y Y; Gritsan, A V; Guo, Z J; Lae, C K; Denig, A G; Fritsch, M; Schott, G; Arnaud, N; Béquilleux, J; D'Orazio, A; Davier, M; Grosdidier, G; Höcker, A; Lepeltier, V; Le Diberder, F; Lutz, A M; Pruvot, S; Rodier, S; Roudeau, P; Schune, M H; Serrano, J; Sordini, V; Stocchi, A; Wang, W F; Wormser, G; Lange, D J; Wright, D M; Bingham, I; Burke, J P; Chavez, C A; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; Hutchcroft, D E; Payne, D J; Schofield, K C; Touramanis, C; Bevan, A J; George, K A; Di Lodovico, F; Menges, W; Sacco, R; Cowan, G; Flaecher, H U; Hopkins, D A; Paramesvaran, S; Salvatore, F; Wren, A C; Brown, D N; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Chia, Y M; Edgar, C L; Lafferty, G D; West, T J; Yi, J I; Anderson, J; Chen, C; Jawahery, A; Roberts, D A; Simi, G; Tuggle, J M; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Li, X; Moore, T B; Salvati, E; Saremi, S; Cowan, R; Dujmic, D; Fisher, P H; Koeneke, K; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Zhao, M; Zheng, Y; Mclachlin, S E; Patel, P M; Robertson, S H; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Simard, M; Taras, P; Viaud, F B; Nicholson, H; De Nardo, G; Fabozzi, F; Lista, L; Monorchio, D; Sciacca, C; Baak, M A; Raven, G; Snoek, H L; Jessop, C P; Knoepfel, K J; LoSecco, J M; Benelli, G; Corwin, L A; Honscheid, K; Kagan, H; Kass, R; Morris, J P; Rahimi, A M; Regensburger, J J; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Kolb, J A; Lu, M; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Gagliardi, N; Gaz, A; Margoni, M; Morandin, M; Pompili, A; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Ben-Haim, E; Briand, H; Calderini, G; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; Leruste, Ph; Malclès, J; Ocariz, J; Perez, A; Prendki, J; Gladney, L; Biasini, M; Covarelli, R; Manoni, E; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Cenci, R; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Mazur, M A; Morganti, M; Neri, N; Paoloni, E; Rizzo, G; Walsh, J J; Haire, M; Biesiada, J; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Baracchini, E; Bellini, F; Cavoto, G; del Re, D; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Jackson, P D; Gioi, L Li; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Renga, F; Voena, C; Ebert, M; Hartmann, T; Schröder, H; Waldi, R; Adye, T; Castelli, G; Franek, B; Olaiya, E O; Ricciardi, S; Roethel, W; Wilson, F F; Emery, S; Escalier, M; Gaidot, A; Ganzhur, S F; Hamel de Monchenault, G; Kozanecki, W; Vasseur, G; Yèche, Ch; Zito, M; Chen, X R; Liu, H; Park, W; Purohit, M V; Wilson, J R; Allen, M T; Aston, D; Bartoldus, R; Bechtle, P; Berger, N; Claus, R; Coleman, J P; Convery, M R; Dingfelder, J C; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Graham, M T; Grenier, P; Hast, C; Hryn'ova, T; Innes, W R; Kaminski, J; Kelsey, M H; Kim, H; Kim, P; Kocian, M L; Leith, D W G S; Li, S; Luitz, S; Luth, V; Lynch, H L; MacFarlane, D B; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ofte, I; Perazzo, A; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S K; Thompson, J M; Va'vra, J; van Bakel, N; Wagner, A P; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Wilden, L; Ahmed, S; Alam, M S; Bula, R; Ernst, J A; Jain, V; Pan, B; Saeed, M A; Wappler, F R; Zain, S B; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Ruland, A M; Schilling, C J; Schwitters, R F; Izen, J M; Lou, X C; Ye, S; Bianchi, F; Gallo, F; Gamba, D; Pelliccioni, M; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Lanceri, L; Vitale, L; Azzolini, V; Lopez-March, N; Martinez-Vidal, F; Milanes, D A; Oyanguren, A; Albert, J; Banerjee, Sw; Bhuyan, B; Hamano, K; Kowalewski, R; Nugent, I M; Roney, J M; Sobie, R J; Harrison, P F; Ilic, J; Latham, T E; Mohanty, G B; Band, H R; Chen, X; Dasu, S; Flood, K T; Hollar, J J; Kutter, P E; Pan, Y; Pierini, M; Prepost, R; Wu, S L; Neal, H

    2007-11-16

    We present a search for the lepton flavor violating decay B+-->K+ tau-/+ mu+/- using 383 x 10;{6} BB[over ] events collected by the BABAR experiment. The branching fraction for this decay can be substantially enhanced in new physics models. The kinematics of the tau from the signal B decay are inferred from the K+, mu, and other B in the event, which is fully reconstructed in one of a variety of hadronic decay modes, allowing the signal B candidate to be fully reconstructed. We observe no excess of events over the expected background and set a limit of B(B+-->K+ tau mu)<7.7 x 10(-5) at 90% confidence level, where the branching fraction is for the sum of the K+ tau- mu+ and K+ tau+mu- final states. We use this result to improve a model-independent bound on the energy scale of flavor-changing new physics.

  19. Covariance fitting of highly correlated $B_K$ data

    CERN Document Server

    Yoon, Boram; Jung, Chulwoo; Lee, Weonjong

    2011-01-01

    We present the reason why we use the diagonal approximation (uncorrelated fitting) when we perform the data analysis of highly correlated $B_K$ data on the basis of the SU(2) staggered chiral perturbation theory. Basically, the essence of the problem is that we do not have enough statistics to determine the small eigenvalues of the covariance matrix with a high precision. As a result, we have the smallest eigenvalue, which is smaller than the statistical error of the covariance matrix, corresponding to an unphysical eigenmode. We have applied a number of prescriptions available in the market such as the cutoff method and modified covariance matrix method. It turns out that the cutoff method is not a good prescription and the modified covariance matrix method is an even worse one. The diagonal approximation turns out to be a good prescription if the data points are somehow correlated and the statistics are relatively poor.

  20. Troponin T3 regulates nuclear localization of the calcium channel Cavβ1a subunit in skeletal muscle.

    Science.gov (United States)

    Zhang, Tan; Taylor, Jackson; Jiang, Yang; Pereyra, Andrea S; Messi, Maria Laura; Wang, Zhong-Min; Hereñú, Claudia; Delbono, Osvaldo

    2015-08-15

    The voltage-gated calcium channel (Cav) β1a subunit (Cavβ1a) plays an important role in excitation-contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Cavβ1a subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160-244 aa) and Cavβ1a NH2-terminus (1-99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Cavβ1a/YFP shows that TnT3 facilitates Cavβ1a nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation.

  1. Production and decay of the heaviest odd-Z nuclei in the 249Bk + 48Ca reaction

    Science.gov (United States)

    Oganessian, Yu Ts; Abdullin, F. Sh; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu S.; Utyonkov, V. K.; Voinov, A. A.; Vostokin, G. K.

    2015-02-01

    The reaction of 249Bk with 48Ca has been investigated with an aim of synthesizing and studying the decay properties of isotopes of the new element 117. The experiments were performed at five projectile energies (in two runs, in 2009-2010 and 2012) and with a total beam dose of 48Ca ions of about 9x1019 The experiments yielded data on a-decay characteristics and excitation functions of the produced nuclei that establish these to be 293117 and 294117 - the products of the 4n- and 3n-evaporation channels, respectively. In total, we have observed 20 decay chains of Z=117 nuclides. The cross sections were measured to be 1.1 pb for the 3n and 2.4 pb for the 4n-reaction channel. The new 289115 events, populated by α decay of 117, demonstrate the same decay properties as those observed for 115 produced in the 243Am(48Ca,2n) reaction thus providing cross-bombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf - a result of the in-growth of 249Cf in the 249Bk target. The observed decay chain of 294118 is in good agreement with decay properties obtained in 2002-2005 in the experiments with the reaction 249Cf(48Ca,3n)294118. The energies and half-lives of the odd-Z isotopes observed in the 117 decay chains together with the results obtained for lower-Z superheavy nuclei demonstrate enhancement of nuclear stability with increasing neutron number towards the predicted new magic number N=184.

  2. Point mutations at the local anesthetic receptor site modulate the state-dependent block of rat Na v1.4 sodium channels by pyrazoline-type insecticides.

    Science.gov (United States)

    Silver, Kristopher S; Soderlund, David M

    2007-05-01

    Pyrazoline-type insecticides (PTIs) selectively block sodium channels at membrane potentials that promote slow sodium channel inactivation and are proposed to interact with a site that overlaps the local anesthetic (LA) receptor site. Mutagenesis studies identified two amino acid residues in the S6 segment of homology domain IV (Phe-1579 and Tyr-1586 in the rat Na(v)1.4 sodium channel) as principal elements of the LA receptor. To test the hypothesis that PTIs bind to the LA receptor, we constructed mutated Na(v)1.4/F1579A and Na(v)1.4/Y1586A cDNAs, expressed native and mutated channels in Xenopus oocytes, and examined the effects of these mutations on channel block by three PTIs (indoxacarb, its bioactivation product DCJW, and RH3421) by two-electrode voltage clamp. DCJW and RH3421 had no effect on Na(v)1.4 channels held at -120mV but caused a slowly developing block upon depolarization to -30mV. Estimated IC(50) values following 15min of exposure were 1 and 4muM for DCJW and RH3421, respectively. Indoxacarb failed to block Na(v)1.4 channels under all experimental conditions. Sensitivity to block by DCJW and RH3421 at -30mV was significantly reduced in Na(v)1.4/F1579A channels, a finding that is consistent with the impact of this mutation on drug binding. In contrast to its effect on drug binding, the Y1586A mutation increased the sensitivity of Na(v)1.4 channels held at -30mV to all three compounds, conferring modest sensitivity to indoxacarb and increasing sensitivity to DCJW and RH3421 by 58- and 16-fold, respectively. These results provide direct evidence for the action of PTIs at the LA receptor.

  3. Hydralazine-induced vasodilation involves opening of high conductance Ca2+-activated K+ channels

    DEFF Research Database (Denmark)

    Bang, Lone; Nielsen-Kudsk, J E; Gruhn, N;

    1998-01-01

    The purpose of this study was to investigate whether high conductance Ca2+-activated K+ channels (BK(Ca)) are mediating the vasodilator action of hydralazine. In isolated porcine coronary arteries, hydralazine (1-300 microM), like the K+ channel opener levcromakalim, preferentially relaxed...

  4. Fusion and quasifission dynamics in the reactions $^{48}$Ca+$^{249}$Bk and $^{50}$Ti+$^{249}$Bk using TDHF

    CERN Document Server

    Umar, A S; Simenel, C

    2016-01-01

    Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHE have been recently produced with doubly-magic $^{48}$Ca beams. However, SHE synthesis experiments with single-magic $^{50}$Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for $Z=117,119$ superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in $^{48}$Ca,$^{50}$Ti+$^{249}$Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleu...

  5. 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

  6. A Novel Case of Symptomatic BK Viraemia in a Patient Undergoing Treatment for Hodgkin Lymphoma

    Directory of Open Access Journals (Sweden)

    Jacinta Perram

    2014-01-01

    Full Text Available Symptomatic BK viral infection in the immunocompromised host is well described, most commonly seen in renal transplant recipients, bone marrow transplant recipients, and HIV positive patients. The present case describes a novel clinical scenario of symptomatic urological BK virus infection in a patient receiving treatment for Hodgkin lymphoma. This case highlights the importance of casting a wide diagnostic net for adverse events encountered with novel therapeutic agents or regimens.

  7. Kv3.3 Channels Bind Hax-1 and Arp2/3 to Assemble a Stable Local Actin Network that Regulates Channel Gating.

    Science.gov (United States)

    Zhang, Yalan; Zhang, Xiao-Feng; Fleming, Matthew R; Amiri, Anahita; El-Hassar, Lynda; Surguchev, Alexei A; Hyland, Callen; Jenkins, David P; Desai, Rooma; Brown, Maile R; Gazula, Valeswara-Rao; Waters, Michael F; Large, Charles H; Horvath, Tamas L; Navaratnam, Dhasakumar; Vaccarino, Flora M; Forscher, Paul; Kaczmarek, Leonard K

    2016-04-07

    Mutations in the Kv3.3 potassium channel (KCNC3) cause cerebellar neurodegeneration and impair auditory processing. The cytoplasmic C terminus of Kv3.3 contains a proline-rich domain conserved in proteins that activate actin nucleation through Arp2/3. We found that Kv3.3 recruits Arp2/3 to the plasma membrane, resulting in formation of a relatively stable cortical actin filament network resistant to cytochalasin D that inhibits fast barbed end actin assembly. These Kv3.3-associated actin structures are required to prevent very rapid N-type channel inactivation during short depolarizations of the plasma membrane. The effects of Kv3.3 on the actin cytoskeleton are mediated by the binding of the cytoplasmic C terminus of Kv3.3 to Hax-1, an anti-apoptotic protein that regulates actin nucleation through Arp2/3. A human Kv3.3 mutation within a conserved proline-rich domain produces channels that bind Hax-1 but are impaired in recruiting Arp2/3 to the plasma membrane, resulting in growth cones with deficient actin veils in stem cell-derived neurons.

  8. From complex B(1) mapping to local SAR estimation for human brain MR imaging using multi-channel transceiver coil at 7T.

    Science.gov (United States)

    Zhang, Xiaotong; Schmitter, Sebastian; Van de Moortele, Pierre-Francois; Liu, Jiaen; He, Bin

    2013-06-01

    Elevated specific absorption rate (SAR) associated with increased main magnetic field strength remains a major safety concern in ultra-high-field (UHF) magnetic resonance imaging (MRI) applications. The calculation of local SAR requires the knowledge of the electric field induced by radio-frequency (RF) excitation, and the local electrical properties of tissues. Since electric field distribution cannot be directly mapped in conventional MR measurements, SAR estimation is usually performed using numerical model-based electromagnetic simulations which, however, are highly time consuming and cannot account for the specific anatomy and tissue properties of the subject undergoing a scan. In the present study, starting from the measurable RF magnetic fields (B1) in MRI, we conducted a series of mathematical deduction to estimate the local, voxel-wise and subject-specific SAR for each single coil element using a multi-channel transceiver array coil. We first evaluated the feasibility of this approach in numerical simulations including two different human head models. We further conducted experimental study in a physical phantom and in two human subjects at 7T using a multi-channel transceiver head coil. Accuracy of the results is discussed in the context of predicting local SAR in the human brain at UHF MRI using multi-channel RF transmission.

  9. Ion channels generating complex spikes in cartwheel cells of the dorsal cochlear nucleus.

    Science.gov (United States)

    Kim, Yuil; Trussell, Laurence O

    2007-02-01

    Cartwheel cells are glycinergic interneurons that modify somatosensory input to the dorsal cochlear nucleus. They are characterized by firing of mixtures of both simple and complex action potentials. To understand what ion channels determine the generation of these two types of spike waveforms, we recorded from cartwheel cells using the gramicidin perforated-patch technique in brain slices of mouse dorsal cochlear nucleus and applied channel-selective blockers. Complex spikes were distinguished by whether they arose directly from a negative membrane potential or later during a long depolarization. Ca(2+) channels and Ca(2+)-dependent K(+) channels were major determinants of complex spikes. Onset complex spikes required T-type and possibly R-type Ca(2+) channels and were shaped by BK and SK K(+) channels. Complex spikes arising later in a depolarization were dependent on P/Q- and L-type Ca(2+) channels as well as BK and SK channels. BK channels also contributed to fast repolarization of simple spikes. Simple spikes featured an afterdepolarization that is probably the trigger for complex spiking and is shaped by T/R-type Ca(2+) and SK channels. Fast spikes were dependent on Na(+) channels; a large persistent Na(+) current may provide a depolarizing drive for spontaneous activity in cartwheel cells. Thus the diverse electrical behavior of cartwheel cells is determined by the interaction of a wide variety of ion channels with a prominent role played by Ca(2+).

  10. Co-localization of putative calcium channels (phenylalkylamine-binding sites) on oil bodies in protoplasts from dark-grown sunflower seedling cotyledons.

    Science.gov (United States)

    Vandana, Shweta; Bhatla, Satish C

    2009-07-01

    Oil bodies are spherical entities containing a triacylglycerol (TAG) matrix encased by a phospholipid monolayer, which is stabilized by oil body-specific proteins, principally oleosins. Biochemical investigations in the recent past have also demonstrated the expression of calcium-binding proteins, called caleosins, as a component of oil body membranes during seed germination. Using DM-Bodipy-phenylalkylamine (PAA; a fluorescent derivative of phenylalkylamine)-a fluorescent probe known to bind L-type calcium channel proteins, present investigations provide the first report on the localization and preferential accumulation of putative calcium channel proteins on/around oil bodies during peak lipolytic phase in protoplasts derived from dark-grown sunflower (Helianthus annuus L. cv Morden) seedling cotyledons. Specificity of DM-Bodipy-PAA labeling was confirmed by using bepridil, a non-fluorescent competitor of PAA while non-specific dye accumulation has been ruled out by using Bodipy-FL as control. Co-localization of fluorescence from DM-Bodipy-PAA binding sites (ex: 504 nm; em: 511 nm) and nile red fluorescing oil bodies (ex: 552 nm; em: 636 nm) has been undertaken by epifluorescence and confocal laser scanning microscopy (CLSM). It revealed the affinity of PAA-sensitive ion channels for the oil body surface. Findings from the current investigations highlight the significance of calcium and calcium channel proteins during oil body mobilization in sunflower.

  11. Ultrastructural evidence for pre- and postsynaptic localization of Cav1.2 L-type Ca2+ channels in the rat hippocampus.

    Science.gov (United States)

    Tippens, Alyssa L; Pare, Jean-Francois; Langwieser, Nicole; Moosmang, Sven; Milner, Teresa A; Smith, Yoland; Lee, Amy

    2008-02-01

    In the hippocampal formation, Ca(v)1.2 (L-type) voltage-gated Ca(2+) channels mediate Ca(2+) signals that can trigger long-term alterations in synaptic efficacy underlying learning and memory. Immunocytochemical studies indicate that Ca(v)1.2 channels are localized mainly in the soma and proximal dendrites of hippocampal pyramidal neurons, but electrophysiological data suggest a broader distribution of these channels. To define the subcellular substrates underlying Ca(v)1.2 Ca(2+) signals, we analyzed the localization of Ca(v)1.2 in the hippocampal formation by using antibodies against the pore-forming alpha(1)-subunit of Ca(v)1.2 (alpha(1)1.2). By light microscopy, alpha(1)1.2-like immunoreactivity (alpha(1)1.2-IR) was detected in pyramidal cell soma and dendritic fields of areas CA1-CA3 and in granule cell soma and fibers in the dentate gyrus. At the electron microscopic level, alpha(1)1.2-IR was localized in dendrites, but also in axons, axon terminals, and glial processes in all hippocampal subfields. Plasmalemmal immunogold particles representing alpha(1)1.2-IR were more significant for small- than large-caliber dendrites and were largely associated with extrasynaptic regions in dendritic spines and axon terminals. These findings provide the first detailed ultrastructural analysis of Ca(v)1.2 localization in the brain and support functionally diverse roles of these channels in the hippocampal formation.

  12. Mitochondrial changes in cidofovir therapy for BK virus nephropathy.

    Science.gov (United States)

    Talmon, G; Cornell, L D; Lager, D J

    2010-06-01

    Polyoma (BK) virus nephropathy (BKVN) is often treated with the nucleotide analog cidofovir. An adverse effect of this drug class is proximal tubular toxicity, and ultrastructural abnormalities in proximal tubular mitochondria have been observed in patients treated with similar drugs for other viral infections. We report similar changes in biopsies from BKVN treated with cidofovir. Renal allograft biopsies showing BKVN, on which electron microscopy was performed, were categorized into 3 groups: initial diagnosis (BD), postcidofovir treatment (CT), and posttreatment with immunosuppression reduction (IR). Nineteen cases from each group were randomly selected. Mitochondrial changes were present in 6 biopsies from patients receiving CT therapy (31.5%), ranging from diffuse mitochondrial swelling to profound morphologic changes. No similar abnormalities were seen in other groups. In those with atypical mitochondria, the mean number of cidofovir doses was 2.67, with an average interval between last dose and biopsy of 2.17 weeks. CT patients without mitochondrial changes had a mean of 4.6 doses and an average interval between last dose and biopsy of 27.2 weeks. Some renal transplant patients treated with cidofovir display alterations in proximal tubular mitochondria akin to those seen with similar drugs. The findings support the mitochondrial toxicity of nucleotide analogs.

  13. A BK inequality for randomly drawn subsets of fixed size

    CERN Document Server

    Berg, J van den

    2011-01-01

    The BK inequality, proved by van den Berg and Kesten \\cite{BeKe85}, says that, for product measures on $\\Om := \\{0,1\\}^n$, the probability that two increasing events $A$ and $B$ 'occur disjointly' is smaller than or equal to the product of the two individual probabilities. Their conjecture that this holds for {\\em all} events was proved by Reimer \\cite{Re00}. In spite of Reimer's work, several fundamental problems in this area remained open. For instance, although it is easy to see that non-product measures can not satisfy the above inequality for all events, there are several such measures on $\\Om$ which, intuitively, should satisfy the inequality for all increasing events. One of the most 'natural' candidates is what we call here the $k$-out-of-$n$ measure, the measure assigning equal probabilities to all elements of $\\Om$ with exactly $k$ 1's (and probability 0 to all other elements). The main contribution of this paper is a proof for these measures. Remarkably, although the $k$-out-of-$n$ measures are not...

  14. BK virus infection in human immunodeficiency virus-infected patients.

    Science.gov (United States)

    Ledesma, J; Muñoz, P; Garcia de Viedma, D; Cabrero, I; Loeches, B; Montilla, P; Gijon, P; Rodriguez-Sanchez, B; Bouza, E

    2012-07-01

    The aim of this study is to evaluate the prevalence of BK virus (BKV) infection in HIV-positive patients receiving highly active antiretroviral therapy (HAART) in our hospital. The presence of BKV was analysed in urine and plasma samples from 78 non-selected HIV-infected patients. Clinical data were recorded using a pre-established protocol. We used a nested PCR to amplify a specific region of the BKV T-large antigen. Positive samples were quantified using real-time PCR. Mean CD4 count in HIV-infected patients was 472 cells/mm3 and median HIV viral load was 500 cells/mm3 (74.3% vs 25.7%; p=0.007). Viruria was present in 21.7% of healthy controls (5 out of 23 samples, p=0.02). All viral loads were low (<100 copies/mL), and we could not find any association between BKV infection and renal or neurological manifestations. We provide an update on the prevalence of BKV in HIV-infected patients treated with HAART. BKV viruria was more common in HIV-infected patients; however, no role for BKV has been demonstrated in this population.

  15. Inhibition of human two-pore domain K+ channel TREK1 by local anesthetic lidocaine: negative cooperativity and half-of-sites saturation kinetics.

    Science.gov (United States)

    Nayak, Tapan K; Harinath, S; Nama, S; Somasundaram, K; Sikdar, S K

    2009-10-01

    TWIK-related K+ channel TREK1, a background leak K+ channel, has been strongly implicated as the target of several general and local anesthetics. Here, using the whole-cell and single-channel patch-clamp technique, we investigated the effect of lidocaine, a local anesthetic, on the human (h)TREK1 channel heterologously expressed in human embryonic kidney 293 cells by an adenoviral-mediated expression system. Lidocaine, at clinical concentrations, produced reversible, concentration-dependent inhibition of hTREK1 current, with IC(50) value of 180 muM, by reducing the single-channel open probability and stabilizing the closed state. We have identified a strategically placed unique aromatic couplet (Tyr352 and Phe355) in the vicinity of the protein kinase A phosphorylation site, Ser348, in the C-terminal domain (CTD) of hTREK1, that is critical for the action of lidocaine. Furthermore, the phosphorylation state of Ser348 was found to have a regulatory role in lidocaine-mediated inhibition of hTREK1. It is interesting that we observed strong intersubunit negative cooperativity (Hill coefficient = 0.49) and half-of-sites saturation binding stoichiometry (half-reaction order) for the binding of lidocaine to hTREK1. Studies with the heterodimer of wild-type (wt)-hTREK1 and Delta119 C-terminal deletion mutant (hTREK1(wt)-Delta119) revealed that single CTD of hTREK1 was capable of mediating partial inhibition by lidocaine, but complete inhibition necessitates the cooperative interaction between both the CTDs upon binding of lidocaine. Based on our observations, we propose a model that explains the unique kinetics and provides a plausible paradigm for the inhibitory action of lidocaine on hTREK1.

  16. Local heat/mass transfer and pressure drop in a two-pass rib-roughened channel for turbine airfoil cooling

    Science.gov (United States)

    Han, J. C.; Chandra, P. R.

    1987-01-01

    The heat transfer characteristics of turbulent air flow in a multipass channel were studied via the naphthalene sublimation technique. The naphthalene-coated test section, consisting of two straight, square channels joined by a 180 deg turn, resembled the internal cooling passages of gas turbine airfoils. The top and bottom surfaces of the test channel were roughened by rib turbulators. The rib height-to-hydraulic diameter ratio (e/D) were 0.063 and 0.094, and the rib pitch-to-height ratio (P/e) were 10 and 20. The local heat/mass transfer coefficients on the roughened top wall and on the smooth divider and side walls of the test channel were determined for three Reynolds numbers of 15, 30, and 60, thousand, and for three angles of attack (alpha) of 90, 60, and 45 deg. Results showed that the local Sherwood numbers on the ribbed walls were 1.5 to 6.5 times those for a fully developed flow in a smooth square duct. The average ribbed-wall Sherwood numbers were 2.5 to 3.5 times higher than the fully developed values, depending on the rib angle of attack and the Reynolds number. The results also indicated that, before the turn, the heat/mass transfer coefficients in the cases of alpha = 60 and 45 deg were higher than those in the case of alpha=90 deg. However, after the turn, the heat/mass transfer coefficients in the oblique-rib cases were lower than those in the transverse rib case. Correlations for the average Sherwood number ratios for individual channel surfaces and for the overall Sherwood number ratios are reported. Correlations for the fully developed friction factors and for the loss coefficients are also provided.

  17. Tetrodotoxin-sensitive α-subunits of voltage-gated sodium channels are relevant for inhibition of cardiac sodium currents by local anesthetics.

    Science.gov (United States)

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

    2016-06-01

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

  18. Exploring the structure of the voltage-gated Na+ channel by an engineered drug access pathway to the receptor site for local anesthetics.

    Science.gov (United States)

    Lukacs, Peter; Gawali, Vaibhavkumar S; Cervenka, Rene; Ke, Song; Koenig, Xaver; Rubi, Lena; Zarrabi, Touran; Hilber, Karlheinz; Stary-Weinzinger, Anna; Todt, Hannes

    2014-08-01

    Despite the availability of several crystal structures of bacterial voltage-gated Na(+) channels, the structure of eukaryotic Na(+) channels is still undefined. We used predictions from available homology models and crystal structures to modulate an external access pathway for the membrane-impermeant local anesthetic derivative QX-222 into the internal vestibule of the mammalian rNaV1.4 channel. Potassium channel-based homology models predict amino acid Ile-1575 in domain IV segment 6 to be in close proximity to Lys-1237 of the domain III pore-loop selectivity filter. The mutation K1237E has been shown previously to increase the diameter of the selectivity filter. We found that an access pathway for external QX-222 created by mutations of Ile-1575 was abolished by the additional mutation K1237E, supporting the notion of a close spatial relationship between sites 1237 and 1575. Crystal structures of bacterial voltage-gated Na(+) channels predict that the side chain of rNaV1.4 Trp-1531 of the domain IV pore-loop projects into the space between domain IV segment 6 and domain III pore-loop and, therefore, should obstruct the putative external access pathway. Indeed, mutations W1531A and W1531G allowed for exceptionally rapid access of QX-222. In addition, W1531G created a second non-selective ion-conducting pore, bypassing the outer vestibule but probably merging into the internal vestibule, allowing for control by the activation gate. These data suggest a strong structural similarity between bacterial and eukaryotic voltage-gated Na(+) channels.

  19. Impact of two different commercial DNA extraction methods on BK virus viral load

    Directory of Open Access Journals (Sweden)

    Massimiliano Bergallo

    2016-03-01

    Full Text Available Background and aim: BK virus, a member of human polyomavirus family, is a worldwide distributed virus characterized by a seroprevalence rate of 70-90% in adult population. Monitoring of viral replication is made by evaluation of BK DNA by quantitative polymerase chain reaction. Many different methods can be applied for extraction of nucleic acid from several specimens. The aim of this study was to assess the impact of two different DNA extraction procedure on BK viral load. Materials and methods: DNA extraction procedure including the Nuclisens easyMAG platform (bioMerieux, Marcy l’Etoile, France and manual QIAGEN extraction (QIAGEN Hilden, Germany. BK DNA quantification was performed by Real Time TaqMan PCR using a commercial kit. Result and discussion: The samples capacity, cost and time spent were compared for both systems. In conclusion our results demonstrate that automated nucleic acid extraction method using Nuclisense easyMAG was superior to manual protocol (QIAGEN Blood Mini kit, for the extraction of BK virus from serum and urine specimens.

  20. Immunocytochemical Identification and Localization of Diffuse Neuroendocrine System (DNES) Cells in Gastrointestinal Tract of Channel Catfish (Ictalurus punctatus)

    Institute of Scientific and Technical Information of China (English)

    HE Min; WANG Kai-yu; ZHANG Yu

    2009-01-01

    To detect distribution and relative frequency of diffuse neuroendocrine system (DNES) cells in the gastrointestinal tract of channel catfish (Ictalurus punctatus), the intestinal tract of channel catfish was divided into seven portions from proximal to distal: the enlarged area after oesophagus, cardia, fundus, pylorus, and anterior, middle, and posterior intestine. Immunohistochemical method using the strept avidin-biotin-complex (SABC) was employed. All antisera between seven portions of the channel catfish were compared statistically using statistical package for the social science (SPSS). Five types of DNES cells were determined: neuropeptide Y-immunoreactive (NPY-IR) cells were demonstrated in both anterior and middle intestine; serotonin (5-HT) immunoreactive cells were detected throughout the whole gastrointestinal tract; vasoactive intestinal peptide (VIP) positive cells were at the highest frequency in pylorus; glucagon-immunoreactive (GLU-IR) cells were moderate in number in the fundus and anterior, middle intestine, and no immunoreactivity was determined in the other portions; somatostatin (SOM) positive cells were more abundant in the anterior and middle intestine. The regional distribution and relative frequency of immunoreactive cells in the channel catfish, Ictalurus punctatus, are essentially similar to those of other fish. However, some characteristics are observed in this species, which further proved that the diversity of the physiological function of DNES cells was based on their morphology.

  1. PACSINs bind to the TRPV4 cation channel. PACSIN 3 modulates the subcellular localization of TRPV4.

    NARCIS (Netherlands)

    Cuajungco, M.P.; Grimm, C.; Oshima, K.; D'hoedt, D.; Nilius, B.; Mensenkamp, A.R.; Bindels, R.J.M.; Plomann, M.; Heller, S.

    2006-01-01

    TRPV4 is a cation channel that responds to a variety of stimuli including mechanical forces, temperature, and ligand binding. We set out to identify TRPV4-interacting proteins by performing yeast two-hybrid screens, and we isolated with the avian TRPV4 amino terminus the chicken orthologues of mamma

  2. Expression and localization of voltage dependent potassium channel Kv4.2 in epilepsy associated focal lesions

    NARCIS (Netherlands)

    Aronica, E.; Boer, K.; Doorn, K.J.; Zurolo, E.; Spliet, W.G.M.; van Rijen, P.C.; Baayen, J.C.; Gorter, J.A.; Jeromin, A.

    2009-01-01

    An increasing number of observations suggest an important role for voltage-gated potassium (Kv) channels in epilepsy. We studied the cell-specific distribution of Kv4.2, phosphorylated (p) Kv4.2 and the Kv4.2 interacting protein NCS-1 using immunocytochemistry in different epilepsy-associated focal

  3. The Effect of Inclination Angle on Critical Heat Flux in a Locally Heated Liquid Film Moving Under the Action of Gas Flow in a Mini-Channel

    Directory of Open Access Journals (Sweden)

    Tkachenko Egor M.

    2016-01-01

    Full Text Available Intensively evaporating liquid films moving under the action of the cocurrent gas flow in a microchannel are promising for the use in modern cooling systems of semiconductor devices with high local heat release. This work has studied the dependence of the critical heat flux on the inclination angle of the channel. It has been found that the inclination angle in the plane parallel to the flow has no significant effect on the critical heat flux. Whereas the inclination angle in the plane perpendicular to the flow, on the contrary, significantly changes the value of the critical heat flux. However, for a given flow rate of fluid there is a threshold gas velocity at which the critical heat flux does not differ from the case of zero inclination of the channel. Thus, it can be concluded that the cooling system based on shear-driven liquid films can be potentially used when direction of the gravity changes.

  4. Kidney retransplantation for BK virus nephropathy with active viremia without allograft nephrectomy.

    Science.gov (United States)

    Huang, Jingbo; Danovitch, Gabriel; Pham, Phuong-Thu; Bunnapradist, Suphamai; Huang, Edmund

    2015-12-01

    BK virus nephropathy is an important cause of kidney allograft failure. Retransplantation has been successfully performed for patients with previous allograft loss due to BK virus nephropathy; however, whether allograft nephrectomy and viral clearance are required prior to retransplantation is controversial. Some recent studies have suggested that retransplantion can be successfully achieved without allograft nephrectomy if viremia is cleared prior to retransplant. The only published experience of successful retransplantation in the presence of active viremia occurred in the presence of concomitant allograft nephrectomy of the failing kidney. In this report, we describe a case of successful repeat kidney transplant in a patient with high-grade BK viremia and fulminant hepatic failure without concomitant allograft nephrectomy performed under the setting of a simultaneous liver-kidney transplant.

  5. FMRP Regulates Neurotransmitter Release and Synaptic Information Transmission by Modulating Action Potential Duration via BK channels

    OpenAIRE

    Deng, Pan-Yue; Rotman, Ziv; Blundon, Jay A.; Cho, Yongcheol; Cui, Jianmin; Cavalli, Valeria; Zakharenko, Stanislav S; Klyachko, Vitaly A.

    2013-01-01

    Loss of FMRP causes Fragile X syndrome (FXS), but the physiological functions of FMRP remain highly debatable. Here we show that FMRP regulates neurotransmitter release in CA3 pyramidal neurons by modulating action potential (AP) duration. Loss of FMRP leads to excessive AP broadening during repetitive activity, enhanced presynaptic calcium influx and elevated neurotransmitter release. The AP broadening defects caused by FMRP loss have a cell-autonomous presynaptic origin and can be acutely r...

  6. Stimulation of large-conductance calcium-activated potassium channels inhibits neurogenic contraction of human bladder from patients with urinary symptoms and reverses acetic acid-induced bladder hyperactivity in rats.

    Science.gov (United States)

    La Fuente, José M; Fernández, Argentina; Cuevas, Pedro; González-Corrochano, Rocío; Chen, Mao Xiang; Angulo, Javier

    2014-07-15

    We have analysed the effects of large-conductance calcium-activated potassium channel (BK) stimulation on neurogenic and myogenic contraction of human bladder from healthy subjects and patients with urinary symptoms and evaluated the efficacy of activating BK to relief bladder hyperactivity in rats. Bladder specimens were obtained from organ donors and from men with benign prostatic hyperplasia (BPH). Contractions elicited by electrical field stimulation (EFS) and carbachol (CCh) were evaluated in isolated bladder strips. in vivo cystometric recordings were obtained in anesthetized rats under control and acetic acid-induced hyperactive conditions. Neurogenic contractions of human bladder were potentiated by blockade of BK and small-conductance calcium-activated potassium channels (SK) but were unaffected by the blockade of intermediate calcium-activated potassium channels (IK). EFS-induced contractions were inhibited by BK stimulation with NS-8 or NS1619 or by SK/IK stimulation with NS309 (3µM). CCh-induced contractions were not modified by blockade or stimulation of BK, IK or SK. The anti-cholinergic agent, oxybutynin (0.3µM) inhibited either neurogenic or CCh-induced contractions. Neurogenic contractions of bladders from BPH patients were less sensitive to BK inhibition and more sensitive to BK activation than healthy bladders. The BK activator, NS-8 (5mg/kg; i.v.), reversed bladder hyperactivity induced by acetic acid in rats, while oxybutynin was ineffective. NS-8 did not significantly impact blood pressure or heart rate. BK stimulation specifically inhibits neurogenic contractions in patients with urinary symptoms and relieves bladder hyperactivity in vivo without compromising bladder contractile capacity or cardiovascular safety, supporting its potential therapeutic use for relieving bladder overactivity.

  7. 75 FR 48617 - Airworthiness Directives; Eurocopter Deutschland GmbH (ECD) Model MBB-BK 117 C-2 Helicopters

    Science.gov (United States)

    2010-08-11

    ... vibration, and subsequent loss of control of the helicopter. Actions and Compliance (e) Before further... Deutschland GmbH (ECD) Model MBB-BK 117 C-2 Helicopters AGENCY: Federal Aviation Administration (FAA), DOT... directive (AD) for ECD Model MBB-BK 117 C-2 helicopters. This proposed AD results from a...

  8. 75 FR 66657 - Airworthiness Directives; Eurocopter Deutschland GmbH Model MBB-BK 117 C-2 Helicopters

    Science.gov (United States)

    2010-10-29

    ... separation of dynamic weights, severe vibration, and subsequent loss of control of the helicopter. Actions... Deutschland GmbH Model MBB- BK 117 C-2 Helicopters AGENCY: Federal Aviation Administration, DOT. ACTION: Final... Deutschland GmbH (ECD) Model MBB BK 117 C-2 helicopters. This amendment results from a mandatory...

  9. Mutation in the kv3.3 voltage-gated potassium channel causing spinocerebellar ataxia 13 disrupts sound-localization mechanisms.

    Science.gov (United States)

    Middlebrooks, John C; Nick, Harry S; Subramony, S H; Advincula, Joel; Rosales, Raymond L; Lee, Lillian V; Ashizawa, Tetsuo; Waters, Michael F

    2013-01-01

    Normal sound localization requires precise comparisons of sound timing and pressure levels between the two ears. The primary localization cues are interaural time differences, ITD, and interaural level differences, ILD. Voltage-gated potassium channels, including Kv3.3, are highly expressed in the auditory brainstem and are thought to underlie the exquisite temporal precision and rapid spike rates that characterize brainstem binaural pathways. An autosomal dominant mutation in the gene encoding Kv3.3 has been demonstrated in a large Filipino kindred manifesting as spinocerebellar ataxia type 13 (SCA13). This kindred provides a rare opportunity to test in vivo the importance of a specific channel subunit for human hearing. Here, we demonstrate psychophysically that individuals with the mutant allele exhibit profound deficits in both ITD and ILD sensitivity, despite showing no obvious impairment in pure-tone sensitivity with either ear. Surprisingly, several individuals exhibited the auditory deficits even though they were pre-symptomatic for SCA13. We would expect that impairments of binaural processing as great as those observed in this family would result in prominent deficits in localization of sound sources and in loss of the "spatial release from masking" that aids in understanding speech in the presence of competing sounds.

  10. 78 FR 25572 - Special Local Regulation; Wy-Hi Rowing Regatta, Trenton Channel; Detroit River, Wyandotte, MI

    Science.gov (United States)

    2013-05-02

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation; Wy-Hi Rowing Regatta, Trenton... navigable waters immediately prior to, during, and immediately after the Wy-Hi Rowing Regatta. This special... to read as follows: Sec. 100.T09-0287 Special Local Regulation; Wy-Hi Rowing Regatta, Wyandotte,...

  11. 77 FR 25077 - Special Local Regulation; Wy-Hi Rowing Regatta, Trenton Channel; Detroit River, Wyandotte, MI

    Science.gov (United States)

    2012-04-27

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation; Wy-Hi Rowing Regatta, Trenton... navigable waters immediately prior to, during, and immediately after the Wy-Hi Rowing Regatta. This special....35T09-0342 Special Local Regulation; Wy-Hi Rowing Regatta, Wyandotte, MI. (a) Regulated Area....

  12. Increased function of the TRPV1 channel in small sensory neurons after local inflammation or in vitro exposure to the pro-inflammatory cytokine GRO/KC

    Institute of Scientific and Technical Information of China (English)

    Fei Dong; Yi-Ru Du; Wenrui Xie; Judith A.Strong; Xi-Jing He; Jun-Ming Zhang

    2012-01-01

    Objective Inflammation at the level of the sensory dorsal root ganglia (DRGs) leads to robust mechanical pain behavior and the local inflammation has direct excitatory effects on sensory neurons including small,primarily nociceptive,neurons.These neurons express the transient receptor potential vanilloid-1 (TRPV 1) channel,which integrates multiple signals of pain and inflammation.The aim of this study was to characterize the regulation of the TRPV1 channel by local DRG inflammation and by growth-related oncogene (GRO/KC,systemic name:CXCL1),a cytokine known to be upregulated in inflamed DRGs.Methods Activation of the TRPV1 receptor with capsaicin was studied with patch clamp methods in acutely isolated small-diameter rat sensory neurons in primary culture.In vivo,behavioral effects of TRPV1 and GRO/KC were examined by paw injections.Results Neurons isolated from lumbar DRGs 3 days after local inflammation showed enhanced TRPV1 function:tachyphylaxis (the decline in response to repeated applications of capsaicin) was significantly reduced.A similar effect on tachyphylaxis was observed in neurons pre-treated for 4 h in vitro with GRO/KC.This effect was blocked by H-89,a protein kinase A inhibitor.Consistent with the in vitro results,in vivo behavioral responses to paw injection of capsaicin were enhanced and prolonged by pre-injecting the paw with GRO/KC 4 h before the capsaicin injection.GRO/KC paw injections alone did not elicit pain behaviors.Conclusion Function of the TRPV 1 channel is enhanced by DRG inflammation and these effects are preserved in vitro during short-term culture.The effects (decreased tachyphylaxis) are mimicked by incubation with GRO/KC,which has previously been found to be strongly upregulated in this and other pain models.

  13. Pannexin2 oligomers localize in the membranes of endosomal vesicles in mammalian cells while Pannexin1 channels traffic to the plasma membrane.

    Science.gov (United States)

    Boassa, Daniela; Nguyen, Phuong; Hu, Junru; Ellisman, Mark H; Sosinsky, Gina E

    2014-01-01

    Pannexin2 (Panx2) is the largest of three members of the pannexin proteins. Pannexins are topologically related to connexins and innexins, but serve different functional roles than forming gap junctions. We previously showed that pannexins form oligomeric channels but unlike connexins and innexins, they form only single membrane channels. High levels of Panx2 mRNA and protein in the Central Nervous System (CNS) have been documented. Whereas Pannexin1 (Panx1) is fairly ubiquitous and Pannexin3 (Panx3) is found in skin and connective tissue, both are fully glycosylated, traffic to the plasma membrane and have functions correlated with extracellular ATP release. Here, we describe trafficking and subcellular localizations of exogenous Panx2 and Panx1 protein expression in MDCK, HeLa, and HEK 293T cells as well as endogenous Panx1 and Panx2 patterns in the CNS. Panx2 was found in intracellular localizations, was partially N-glycosylated, and localizations were non-overlapping with Panx1. Confocal images of hippocampal sections immunolabeled for the astrocytic protein GFAP, Panx1 and Panx2 demonstrated that the two isoforms, Panx1 and Panx2, localized at different subcellular compartments in both astrocytes and neurons. Using recombinant fusions of Panx2 with appended genetic tags developed for correlated light and electron microscopy and then expressed in different cell lines, we determined that Panx2 is localized in the membrane of intracellular vesicles and not in the endoplasmic reticulum as initially indicated by calnexin colocalization experiments. Dual immunofluorescence imaging with protein markers for specific vesicle compartments showed that Panx2 vesicles are early endosomal in origin. In electron tomographic volumes, cross-sections of these vesicles displayed fine structural details and close proximity to actin filaments. Thus, pannexins expressed at different subcellular compartments likely exert distinct functional roles, particularly in the nervous system.

  14. Degrees of Freedom (DoF) of Locally Connected Interference Channels with Coordinated Multi-Point (CoMP) Transmission

    CERN Document Server

    Gamal, Aly El; Veeravalli, Venugopal V

    2011-01-01

    The degrees of freedom (DoF) available for communication provides an analytically tractable way to characterize the information-theoretic capacity of interference channels. In this paper, the DoF of a K-user interference channel is studied under the assumption that the transmitters can cooperate via coordinated multi-point (CoMP) transmission. In [1], the authors considered the linear asymmetric model of Wyner, where each transmitter is connected to its own receiver and its successor, and is aware of its own message as well as M-1 preceding messages. The per user DoF was shown to go to M/(M+1) as the number of users increases to infinity. In this work, the same model of channel connectivity is considered, with a relaxed cooperation constraint that bounds the maximum number of transmitters at which each message can be available, by a cooperation order M. We show that the relaxation of the cooperation constraint, while maintaining the same load imposed on a backhaul link needed to distribute the messages, resul...

  15. Karakterisasi Enzim Kitinase dari Bacillus sp. BK17, Isolat Potensial Pengendali Hayati Jamur Patogen Tanaman

    OpenAIRE

    Maimunah, Siti

    2016-01-01

    Characterization of chitinase of including pH and temperature, Km and Vmax of Bacillus sp. BK 17 has been conducted. Crude extract of Bacillus sp. BK17 growing in minimum salt medium with colloidal chitin for 5 days was precipited with ammonium sulphate. Optimum chitinase activity was found in 50% ammonium sulphate precipitation with specific activity of 0.545 Units. Chitinase activity in homogenated mycelia of Sclerotium rolfsii was 0.0012 U/ml. The Km and Vmax of the enzyme was 0.46 μg and ...

  16. Pengaruh pH dan Perubahan Temperatur Terhadap Pembentukan Spora Bacillus sp. BK17

    OpenAIRE

    2014-01-01

    Bacterial spores are the surviving structure under unfavourable physical and chemical conditions. Bacillus sp. BK17 is a spore forming bacteria that has been reported to have an ability to inhibit the growth of various pathogenic fungi.This study aims to determine the best pH and temperature for the formation of spore. The result showed that Bacillus sp. BK17 has the highest spore formation at the initial pH of media of 5,0 and at a heat shock of 70° C for 60 minutes. 090805025

  17. Comparison of Topas cyclic olefin copolymers to BK7 glass in night vision goggle objectives

    Science.gov (United States)

    Stevens, James S.

    2004-09-01

    The objective of this study was to determine the suitability of Topas cyclic olefin copolymers (COC) as an optical plastic for use in military-grade night vision goggle (NVG) lens objectives. Test objective lenses that could include either a Topas COC window element or BK7 glass window element were manufactured. The test objectives were evaluated for low light resolution, MTF, off-axis veiling glare, and on-axis stray light. Additionally, the spectral transmittance of the individual windows elements was measured. This paper compares the evaluation results of test objectives containing Topas COC with test objectives containing BK7 glass.

  18. Hydronephrosis Resulting from Bilateral Ureteral Stenosis: A Late Complication of Polyoma BK Virus Cystitis?

    Directory of Open Access Journals (Sweden)

    N. Basara

    2010-01-01

    Full Text Available We report here a case of acute lymphoblastic leukemia in remission presenting a late-onset bilateral hydronephrosis probably due to polyoma BK virus-induced proliferation of bladder endothelium on both ostii. The diagnosis was made virologically by BK virus Polymerase Chain Reaction (PCR detection in the absence of any other bladder disease. Awareness of this late complication is necessary not only in patients after renal transplantation but also in patients after hematopoietic stem cell transplantation from matched unrelated donor.

  19. Polyoma (BK) virus associated urothelial carcinoma originating within a renal allograft five years following resolution of polyoma virus nephropathy.

    Science.gov (United States)

    Salvatore, Steven P; Myers-Gurevitch, Patricia M; Chu, Stacy; Robinson, Brian D; Dadhania, Darshana; Seshan, Surya V

    2016-03-01

    A direct role for BK polyomavirus infection in malignant tumors of renal allografts and urinary tract is emerging. Case reports suggest a link between BK virus (BKV) reactivation and development of malignancy in renal allograft recipients. Herein we describe the first case of BKV positive invasive urothelial carcinoma within the renal allograft, presenting with chronic diarrhea and weight loss 5 years following resolution of BK viremia/nephropathy (BKVN). Unique to our case was the remote history of BK viremia/BKVN, rising titer of anti-HLA antibody and presence of renal limited urothelial carcinoma with microinvasion of malignant cells staining positive for SV40 large T antigen (T-Ag). These findings suggest that persistence of subclinical BKV infection within the renal allograft may play a role in the malignant transformation of epithelial cells. Patients with history of BKVN may be at risk for kidney and urinary tract malignancy despite resolution of BK viremia/BKVN.

  20. P2Y2 and P2Y4 receptors regulate pancreatic Ca²+-activated K+ channels differently

    DEFF Research Database (Denmark)

    Klærke, Susanne Edeling Hede; Amstrup, Jan; Klærke, Dan Arne;

    2005-01-01

    Extracellular ATP is an important regulator of transepithelial transport in a number of tissues. In pancreatic ducts, we have shown that ATP modulates epithelial K+ channels via purinergic receptors, most likely the P2Y2 and P2Y4 receptors, but the identity of the involved K+ channels was not clear....... In this study, we show by RT-PCR analysis that rat pancreatic ducts express Ca(2+)-activated K+ channels of intermediate conductance (IK) and big conductance (BK), but not small conductance (SK). Possible interactions between P2Y receptors and these Ca(2+)-activated K+ channels were examined in co......-expression experiments in Xenopus laevis oocytes. K+ channel activity was measured electrophysiologically in oocytes stimulated with UTP (0.1 mM). UTP stimulation of oocytes expressing P2Y4 receptors and BK channels resulted in a 30% increase in the current through the expressed channels. In contrast, stimulation of P2Y...

  1. Electrophysiological characterisation of KCNQ channel modulators

    DEFF Research Database (Denmark)

    Schrøder, R.L

    -cell configuration by the patch-clamp technique. Voltage-activated KCNQ currents were enhanced by extracellular application of retigabine, and also by the novel BK channel opener Compound 1 (( )-(5-chloro-2-metoxyphenyl)-1.3-didydroxy-3-fluoro-6-(trifluoromethyl)-2H-indol-2-one) (Gribkoff et al. 2001). The effects......, was sensitive to linopirdine and XE991, and had a nearly linear I-V relationship. Moreover, development of the voltage-independent current did not require a preceding voltage-dependent activation of the channel. This effect of Compound 1 may have profound hyperpolarising actions on cells expressing the KCNQ4......Potassium (K+) ion channels are ubiquitously expressed in mammalian cells, and each channel serves a precise physiological role due to its specific biophysical characteristics and expression pattern. A few K+ channels are targets for certain drugs, and in this thesis it is suggested that the KCNQ K...

  2. Large-conductance K+ channel openers NS1619 and NS004 as inhibitors of mitochondrial function in glioma cells.

    Science.gov (United States)

    Debska, Grazyna; Kicinska, Anna; Dobrucki, Jerzy; Dworakowska, Beata; Nurowska, Ewa; Skalska, Jolanta; Dolowy, Krzysztof; Szewczyk, Adam

    2003-06-01

    Recently, it has been reported that large-conductance Ca(2+)-activated potassium channels, also known as BK(Ca)-type potassium channels, are present in the inner mitochondrial membrane of the human glioma LN229 cell line. Hence, in the present study, we have investigated whether BK(Ca)-channel openers (BK(Ca)COs), such as the benzimidazolone derivatives NS004 (5-trifluoromethyl-1-(5-chloro-2-hydroxyphenyl)-1,3-dihydro-2H-benzimidazole-2-one) and NS1619 (1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one), affect the functioning of LN229 glioma cell mitochondria in situ. We examined the effect of BK(Ca)COs on mitochondrial membrane potential, mitochondrial respiration and plasma membrane potassium current in human glioma cell line LN229. We found that BK(Ca)COs decrease the mitochondrial membrane potential with an EC(50) value of 3.6+/-0.4 microM for NS1619 and 5.4+/-0.8 microM for NS004. This mitochondrial depolarization was accompanied by an inhibition of the mitochondrial respiratory chain. Both BK(Ca)COs induced whole-cell potassium current blocked by charybdotoxin, as measured by the patch-clamp technique. The BK(Ca)COs had no effect on membrane bilayer conductance. Moreover, the inhibition of mitochondrial function by NS004 and NS1619 was without effect on cell survival, as measured by lactate dehydrogenase release from the cells.

  3. Experimental Evaluation of the Local Packing Distributed Dynamic Channel Allocation Strategy Application for AI-Madar Telephone Telecommunication Network in Libya

    Directory of Open Access Journals (Sweden)

    Mohamed Yousef Ahmed Abou-Hussein

    2014-06-01

    Full Text Available The great challenge of the remarkably growing demand for personal communication mobile service in Libya has actively motivated Al-Madar Telephone Telecommunication Company to adopt various techniques in order to substantially improve its network capacity. An efficient allocation strategy of communication channels that could ensure good performance of the cellular network is critically needed, given the limited spectrum currently available that uses the Fixed Channel Allocation (FCA strategy. In this study, experimental investigations were conducted to improve Al-Madar Company network by proposing the evaluation of the adoption of the Local Packing Distributed Dynamic Channel Allocation (LP-DDCA strategy. The main reasons for proposing the adoption of the LP-DDCA strategy are; to minimize the call blocking probability, enhancing the network performance and increasing the number of network subscribers. This work has been done by applying actual data from an existing cellular network of Al-Madar Company in to the experimental simulation program. The results demonstrated clearly the superiority of the proposed the LP-DDCA strategy in the investigated locations (cells compared with the currently used FCA strategy. Conclusion: Application of the LP-DDCA strategy could give rise to substantial improvement in Al-Madar telecommunication mobile network performance and it will considerably increase the number of network subscribers.

  4. Stress channelling in extreme couple-stress materials Part II: Localized folding vs faulting of a continuum in single and cross geometries

    Science.gov (United States)

    Gourgiotis, Panos A.; Bigoni, Davide

    2016-03-01

    The antiplane strain Green's functions for an applied concentrated force and moment are obtained for Cosserat elastic solids with extreme anisotropy, which can be tailored to bring the material in a state close to an instability threshold such as failure of ellipticity. It is shown that the wave propagation condition (and not ellipticity) governs the behaviour of the antiplane strain Green's functions. These Green's functions are used as perturbing agents to demonstrate in an extreme material the emergence of localized (single and cross) stress channelling and the emergence of antiplane localized folding (or creasing, or weak elastostatic shock) and faulting (or elastostatic shock) of a Cosserat continuum, phenomena which remain excluded for a Cauchy elastic material. During folding some components of the displacement gradient suffer a finite jump, whereas during faulting the displacement itself displays a finite discontinuity.

  5. Transient receptor potential ankyrin 1 channel localized to non-neuronal airway cells promotes non-neurogenic inflammation

    DEFF Research Database (Denmark)

    Nassini, Romina; Pedretti, Pamela; Moretto, Nadia

    2012-01-01

    and fibroblasts, acrolein and CS extract evoked IL-8 release, a response selectively reduced by TRPA1 antagonists. Capsaicin, agonist of the transient receptor potential vanilloid 1 (TRPV1), a channel co-expressed with TRPA1 by airway sensory nerves, and acrolein or CS (TRPA1 agonists), or the neuropeptide...... substance P (SP), which is released from sensory nerve terminals by capsaicin, acrolein or CS), produced neurogenic inflammation in mouse airways. However, only acrolein and CS, but not capsaicin or SP, released the keratinocyte chemoattractant (CXCL-1/KC, IL-8 analogue) in bronchoalveolar lavage (BAL...

  6. New Marketing Channel for Special Local Agricultural Products in Anhui Province%安徽省特色农产品营销渠道创新

    Institute of Scientific and Technical Information of China (English)

    王亮; 雷勋平

    2012-01-01

    In Anhui Province, special local agricultural products represent local brands and play an importanl and leading role in forming the agricultural product structure and in increasing farmers' income. The marketing channels for thesc products have been basically formed, but there arc still some problems. We have conducted extensive researches in major areas of the province and in this paper we put forward new strategies concerning marketing channels of these products in the hope to promote development of agricultural businesses and further increase farmers' income.%特色农产品在安徽省整个农产品结构中发挥着重要的引领作用,是地方农产品品牌的代表,其产业发展对于农民增收具有重要的推动作用。安徽省特色农产品营销渠道虽已初步形成,但尚存在一些问题。本课题组通过对安徽省典型地区进行广泛调研,提出安徽省特色农产品渠道创新策略,希望促进农民的增收和农业企业的发展。

  7. The cystic fibrosis transmembrane conductance regulator (CFTR): three-dimensional structure and localization of a channel gate.

    Science.gov (United States)

    Rosenberg, Mark F; O'Ryan, Liam P; Hughes, Guy; Zhao, Zhefeng; Aleksandrov, Luba A; Riordan, John R; Ford, Robert C

    2011-12-09

    Cystic fibrosis affects about 1 in 2500 live births and involves loss of transmembrane chloride flux due to a lack of a membrane protein channel termed the cystic fibrosis transmembrane conductance regulator (CFTR). We have studied CFTR structure by electron crystallography. The data were compared with existing structures of other ATP-binding cassette transporters. The protein was crystallized in the outward facing state and resembled the well characterized Sav1866 transporter. We identified regions in the CFTR map, not accounted for by Sav1866, which were potential locations for the regulatory region as well as the channel gate. In this analysis, we were aided by the fact that the unit cell was composed of two molecules not related by crystallographic symmetry. We also identified regions in the fitted Sav1866 model that were missing from the map, hence regions that were either disordered in CFTR or differently organized compared with Sav1866. Apart from the N and C termini, this indicated that in CFTR, the cytoplasmic end of transmembrane helix 5/11 and its associated loop could be partly disordered (or alternatively located).

  8. Effects of large conductance Ca(2+)-activated K(+) channels on nitroglycerin-mediated vasorelaxation in humans

    DEFF Research Database (Denmark)

    Gruhn, Nicolai; Boesgaard, Søren; Eiberg, Jonas;

    2002-01-01

    /kg/min). Iberiotoxin reduced the vasorelaxant effect of nitroglycerin (E(max)) by 60% in endothelium-intact arteries and 13% in endothelium-denuded arteries (P0.05) and (compared to arterial segments) veins were less sensitive to BK(Ca) channel blockade (30% reduction in E(max)) or endothelial removal. The results...

  9. The amiodarone derivative 2-methyl-3-(3,5-diiodo-4-carboxymethoxybenzyl)benzofuran (KB130015) opens large-conductance Ca2+-activated K+ channels and relaxes vascular smooth muscle.

    Science.gov (United States)

    Gessner, Guido; Heller, Regine; Hoshi, Toshinori; Heinemann, Stefan H

    2007-01-26

    2-methyl-3-(3,5-diiodo-4-carboxymethoxybenzyl)benzofuran (KB130015) has been developed to retain the antiarrhythmic properties of the parent molecule amiodarone but to eliminate its undesired side effects. In patch-clamp experiments, KB130015 activated large-conductance, Ca2+-activated BK(Ca) channels formed by hSlo1 (alpha) subunits in HEK 293 cells. Channels were reversibly activated by shifting the open-probability/voltage (P(o)/V) relationship by about -60 mV in 3 muM intracellular free Ca2+ ([Ca2+]in). No effect on the single-channel conductance was observed. KB130015-mediated activation of BK(Ca) channels was half-maximal at 20 microM with a Hill coefficient of 2.8. BK(Ca) activation by KB130015 did not require the presence of Ca2+ and still occurred with saturating (100 microM) [Ca2+]in. Effects of the prototypic BK(Ca) activator NS1619 (1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one) and those of KB130015 were not additive suggesting that both activators may at least partially share a common mechanism of action. KB130015-mediated activation was observed also for BK(Ca) channels from insects and for human BK(Ca) channels with already profoundly left-shifted voltage-dependence. In contrast, human intermediate conductance Ca2+-activated channels were inhibited by KB130015. Using segments of porcine pulmonary arteries, KB130015 induced endothelium-independent vasorelaxation, half-maximal at 43 microM KB130015. Relaxation was inhibited by 1 mM tetraethylammonium, suggesting that KB130015 can activate vascular smooth muscle type BK(Ca) channels under physiological conditions. Interestingly, the shift in the P(o)/V relationship was considerably stronger (-90 mV in 3 microM [Ca2+]in) for BK(Ca) channels containing Slo-beta1 subunits. Thus, KB130015 belongs to a novel class of BK(Ca) channel openers that exert an effect depending on the subunit composition of the channel complex.

  10. Bilirubin oxidation end products directly alter K+ channels important in the regulation of vascular tone.

    Science.gov (United States)

    Hou, Shangwei; Xu, Rong; Clark, Joseph F; Wurster, William L; Heinemann, Stefan H; Hoshi, Toshinori

    2011-01-01

    The exact etiology of delayed cerebral vasospasm following cerebral hemorrhage is not clear, but a family of compounds termed 'bilirubin oxidation end products (BOXes)' derived from heme has been implicated. As proper regulation of vascular smooth muscle tone involves large-conductance Ca(2+)- and voltage-dependent Slo1 K(+) (BK, maxiK, K(Ca)1.1) channels, we examined whether BOXes altered functional properties of the channel. Electrophysiological measurements of Slo1 channels heterologously expressed in a human cell line and of native mouse BK channels in isolated cerebral myocytes showed that BOXes markedly diminished open probability. Biophysically, BOXes specifically stabilized the conformations of the channel with its ion conduction gate closed. The results of chemical amino-acid modifications and molecular mutagenesis together suggest that two specific lysine residues in the structural element linking the transmembrane ion-permeation domain to the carboxyl cytosolic domain of the Slo1 channel are critical in determining the sensitivity of the channel to BOXes. Inhibition of Slo1 BK channels by BOXes may contribute to the development of delayed cerebral vasospasm following brain hemorrhage.

  11. Basolateral potassium channels of rabbit colon epithelium: role in sodium absorption and chloride secretion.

    Science.gov (United States)

    Turnheim, Klaus; Plass, Herbert; Wyskovsky, Wolfgang

    2002-02-18

    In order to assess the role of different classes of K(+) channels in recirculation of K(+) across the basolateral membrane of rabbit distal colon epithelium, the effects of various K(+) channel inhibitors were tested on the activity of single K(+) channels from the basolateral membrane, on macroscopic basolateral K(+) conductance, and on the rate of Na(+) absorption and Cl(-) secretion. In single-channel measurements using the lipid bilayer reconstitution system, high-conductance (236 pS), Ca(2+)-activated K(+) (BK(Ca)) channels were most frequently detected; the second most abundant channel was a low-conductance K(+) channel (31 pS) that exhibited channel rundown. In addition to Ba(2+) and charybdotoxin (ChTX), the BK(Ca) channels were inhibited by quinidine, verapamil and tetraethylammonium (TEA), the latter only when present on the side of the channel from which K(+) flow originates. Macroscopic basolateral K(+) conductance, determined in amphotericin-permeabilised epithelia, was also markedly reduced by quinidine and verapamil, TEA inhibited only from the lumen side, and serosal ChTX was without effect. The chromanol 293B and the sulphonylurea tolbutamide did not affect BK(Ca) channels and had no or only a small inhibitory effect on macroscopic basolateral K(+) conductance. Transepithelial Na(+) absorption was partly inhibited by Ba(2+), quinidine and verapamil, suggesting that BK(Ca) channels are involved in basolateral recirculation of K(+) during Na(+) absorption in rabbit colon. The BK(Ca) channel inhibitors TEA and ChTX did not reduce Na(+) absorption, probably because TEA does not enter intact cells and ChTX is 'knocked off' its extracellular binding site by K(+) outflow from the cell interior. Transepithelial Cl(-) secretion was inhibited completely by Ba(2+) and 293B, partly by quinidine but not by the other K(+) channel blockers, indicating that the small (<3 pS) K(V)LQT1 channels are responsible for basolateral K(+) exit during Cl(-) secretion. Hence

  12. Test du Module BECKHOFF (BK7420) Entrées/Sorties deportees sur FIPIO de SCHNEIDER

    CERN Document Server

    Palluel, J; CERN. Geneva. AB Department

    2004-01-01

    Cette note présente le test du nouveau coupleur I/O déporté sur FIPIO de Beckhoff référencé BK7420 (voir photo ci-dessous), et notamment son évaluation sur différentes longueurs par rapport à un module semblable de Schneider (Momentum 170 FNT 110 01).

  13. Application of fibrin glue to damaged bladder mucosa in a case of BK viral hemorrhagic cystitis.

    Science.gov (United States)

    Purves, J Todd; Graham, Michael L; Ramakumar, Sanjay

    2005-09-01

    BK virus is a common cause of severe hemorrhagic cystitis refractory to standard treatment. We describe a technique to achieve hemostasis after failed conservative therapy using fibrin glue applied suprapubically while visualizing and insufflating the bladder through a cystoscope. Long-term hemostasis was achieved using this novel procedure.

  14. New properties of BK-spaces defined by using regular matrix of Fibonacci numbers

    Science.gov (United States)

    Ercan, Sinan; Bektaş, ćiǧdem A.

    2016-06-01

    In the present paper, we studied the new properties of BK-spaces which were defined using regular matrix of Fibonacci numbers in [1]. We computed alpha-, beta-, gamma- duals of these spaces and obtained Schauder basis. We also derived some topological properties of these spaces.

  15. Influence of BK7 Substrate Solarization on the Performance of Hafnia and Silica Multilayer Mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Stolz, C J; Menapace, J A; Genin, F; Ehrmann, P; Miller, P; Rogowski, G

    2002-11-26

    Transport mirrors within the National Ignition Facility, a 192-beam 4-MJ fusion laser at 1053 nm, will be exposed to backscattered light from plasmas created from fusion targets and backlighters. This backscattered light covers the UV and visible spectrum from 351-600 nm. The transport mirror BK7 substrates will be intentionally solarized to absorb >95% of the backscattered light to prevent damage to the metallic mechanical support hardware. Solarization has minimal impact on the 351- and 1053-nm laser-induced damage threshold or the reflected wavefront of the multilayer hafnia silica coating. Radiation sources of various energies were examined for BK7 darkening efficiency within the UV and visible region with 1.1 MeV gamma rays from a Cobalt 60 source ultimately being selected. Finally, bleaching rates were measured at elevated temperatures to generate a model for predicting the lifetime at ambient conditions (20 C), before solarized BK7 substrates exceed 5% transmission in the UV and visible region. Over a 30-mm thickness, BK7 glass will bleach in 10 years to 5% transmission at 600 nm, the most transmissive wavelengths over the 351-600 nm regions.

  16. Combination of Leflunomide and Everolimus for treatment of BK virus nephropathy.

    Science.gov (United States)

    Jaw, Juli; Hill, Prue; Goodman, David

    2017-04-01

    BK nephropathy (BKN) is a common cause of graft dysfunction following kidney transplantation. Minimization of immunosuppressive therapy remains the first line of therapy, but this may lead to rejection and graft loss. In some cases, despite lowering immunosuppression, BK infection can persist, leading to chronic damage and kidney failure. Currently, there is no specific anti-BK viral therapy. Recent in vitro experiments have demonstrated a reduction in BK viral replication when infected cells are treated with the combination of Leflunomide and Everolimus. This study aims to explore the effect of this drugs combination on viral clearance and graft function in patients with persistent disease despite reduction in immunosuppression. We treated three patients with combination Leflunomide and Everolimus. Data on medical history, biochemical parameters and viral loads were collected. Significant improvement in viral loads was observed in two cases with resolution of viremia in another (Table 1). Two recipients had preserved allograft function. The remaining graft was lost because of combination of obstruction and BKN. No adverse reactions such as bone marrow toxicity were observed. Combination of Leflunomide and Everolimus is safe and should be considered as a rescue therapy in treatment of BKN, especially in those who fail to clear this infection despite reduction of immunosuppressive therapy.

  17. Anti-metastatic Potential of Amide-linked Local Anesthetics: Inhibition of Lung Adenocarcinoma Cell Migration and Inflammatory Src Signaling Independent of Sodium Channel Blockade

    Science.gov (United States)

    Piegeler, Tobias; Votta-Velis, E. Gina; Liu, Guoquan; Place, Aaron T.; Schwartz, David E.; Beck-Schimmer, Beatrice; Minshall, Richard D.; Borgeat, Alain

    2012-01-01

    Background Retrospective analysis of patients undergoing cancer surgery suggests the use of regional anesthesia may reduce cancer recurrence and improve survival. Amide-linked local anesthetics have anti-inflammatory properties, although the mechanism of action in this regard is unclear. As inflammatory processes involving Src tyrosine protein kinase and intercellular adhesion molecule-1 are important in tumor growth and metastasis, we hypothesized that amide-linked local anesthetics may inhibit inflammatory Src-signaling involved in migration of adenocarcinoma cells. Methods NCI-H838 lung cancer cells were incubated with Tumor Necrosis Factor-α in absence/presence of ropivacaine, lidocaine, or chloroprocaine (1nM-100μM). Cell migration and total cell lysate Src-activation and Intercellular Adhesion Molecule-1 phosphorylation were assessed. The role of voltage-gated sodium-channels in the mechanism of local anesthetic effects was also evaluated. Results Ropivacaine treatment (100μM) of H838 cells for 20 minutes decreased basal Src activity by 62% (p=0.003), and both ropivacaine and lidocaine co-administered with Tumor Necrosis Factor-α statistically significantly decreased Src-activation and Intercellular Adhesion Molecule-1 phosphorylation, whereas chloroprocaine had no such effect. Migration of these cells at 4 hours was inhibited by 26% (p=0.005) in presence of 1μM ropivacaine and 21% by 1μM lidocaine (p=0.004). These effects of ropivacaine and lidocaine were independent of voltage-gated sodium-channel inhibition. Conclusions This study indicates that amide-, but not ester-linked local anesthetics may provide beneficial anti-metastatic effects. The observed inhibition of NCI-H838 cell migration by lidocaine and ropivacaine was associated with the inhibition of Tumor Necrosis Factor-α-induced Src-activation and Intercellular Adhesion Molecule-1 phosphorylation, providing the first evidence of a molecular mechanism which appears to be independent of their

  18. Surveillance of polyomavirus BK in relation to immunosuppressive therapy in kidney transplantation

    Directory of Open Access Journals (Sweden)

    Cristina Costa

    2012-03-01

    Full Text Available Introduction. Reactivation of polyomavirus BK in kidney transplant recipients has been associated to the development of nephropathy (polyomavirus-associated nephropathy, PVAN, possibly leading to the loss of the transplanted organ. Immunosuppression is the condicio sine qua non for the onset of PVAN; however, a lower incidence of BK viremia has been reported with low-level tacrolimus based immunosuppressive protocols in comparison to cyclosporine A.Aim of this study was to compare the two immunosuppressive protocols. Methods. Virological monitoring of BK was performed in 468 consecutive renal transplant patients over a period of 3 years (2370 urine e 2370 serum specimens: in particular, 1780 specimens from 362 patients treated with tacrolimus and 590 from 106 treated with cyclosporine A. Results. BK viremia was evidenced in 124 (7.0% and 12 (2.0% specimens from 40 (11.0% and 11 (10.4% patients treated with tacrolimus and cyclosporine A, respectively; similarly, BK viruria in 289 (16.2% and 58 (9.8% specimens from 67 (18.5% and 27 (25.5% patients, being the difference of incidence highly significant (p <0.0001 for both viremia and viruria at comparison between specimens and not significant for patients. No case of PVAN was diagnosed at histophatology evaluation. Conclusions. The incidence of viremia and viruria was similar to that previously reported. Our results evidenced that with low-level tacrolimus-based protocols the overall incidence of reactivation in renal transplant patients is not significantly different and there is no increased risk of PVAN, nevertheless the higher incidence of episodes of reactivation.

  19. Positions of the cytoplasmic end of BK α S0 helix relative to S1-S6 and of β1 TM1 and TM2 relative to S0-S6.

    Science.gov (United States)

    Liu, Guoxia; Zakharov, Sergey I; Yao, Yongneng; Marx, Steven O; Karlin, Arthur

    2015-03-01

    The large-conductance, voltage- and Ca(2+)-gated K(+) (BK) channel consists of four α subunits, which form a voltage- and Ca(2+)-gated channel, and up to four modulatory β subunits. The β1 subunit is expressed in smooth muscle, where it slows BK channel kinetics and shifts the conductance-voltage (G-V) curve to the left at [Ca(2+)] > 2 µM. In addition to the six transmembrane (TM) helices, S1-S6, conserved in all voltage-dependent K(+) channels, BK α has a unique seventh TM helix, S0, which may contribute to the unusual rightward shift in the G-V curve of BK α in the absence of β1 and to a leftward shift in its presence. Such a role is supported by the close proximity of S0 to S3 and S4 in the voltage-sensing domain. Furthermore, on the extracellular side of the membrane, one of the two TM helices of β1, TM2, is adjacent to S0. We have now analyzed induced disulfide bond formation between substituted Cys residues on the cytoplasmic side of the membrane. There, in contrast, S0 is closest to the S2-S3 loop, from which position it is displaced on the addition of β1. The cytoplasmic ends of β1 TM1 and TM2 are adjacent and are located between the S2-S3 loop of one α subunit and S1 of a neighboring α subunit and are not adjacent to S0; i.e., S0 and TM2 have different trajectories through the membrane. In the absence of β1, 70% of disulfide bonding of W43C (S0) and L175C (S2-S3) has no effect on V50 for activation, implying that the cytoplasmic end of S0 and the S2-S3 loop move in concert, if at all, during activation. Otherwise, linking them together in one state would obstruct the transition to the other state, which would certainly change V50.

  20. N-terminal arginines modulate plasma-membrane localization of Kv7.1/KCNE1 channel complexes.

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    Zenawit Girmatsion

    Full Text Available BACKGROUND AND OBJECTIVE: The slow delayed rectifier current (I(Ks is important for cardiac action potential termination. The underlying channel is composed of Kv7.1 α-subunits and KCNE1 β-subunits. While most evidence suggests a role of KCNE1 transmembrane domain and C-terminus for the interaction, the N-terminal KCNE1 polymorphism 38G is associated with reduced I(Ks and atrial fibrillation (a human arrhythmia. Structure-function relationship of the KCNE1 N-terminus for I(Ks modulation is poorly understood and was subject of this study. METHODS: We studied N-terminal KCNE1 constructs disrupting structurally important positively charged amino-acids (arginines at positions 32, 33, 36 as well as KCNE1 constructs that modify position 38 including an N-terminal truncation mutation. Experimental procedures included molecular cloning, patch-clamp recording, protein biochemistry, real-time-PCR and confocal microscopy. RESULTS: All KCNE1 constructs physically interacted with Kv7.1. I(Ks resulting from co-expression of Kv7.1 with non-atrial fibrillation '38S' was greater than with any other construct. Ionic currents resulting from co-transfection of a KCNE1 mutant with arginine substitutions ('38G-3xA' were comparable to currents evoked from cells transfected with an N-terminally truncated KCNE1-construct ('Δ1-38'. Western-blots from plasma-membrane preparations and confocal images consistently showed a greater amount of Kv7.1 protein at the plasma-membrane in cells co-transfected with the non-atrial fibrillation KCNE1-38S than with any other construct. CONCLUSIONS: The results of our study indicate that N-terminal arginines in positions 32, 33, 36 of KCNE1 are important for reconstitution of I(Ks. Furthermore, our results hint towards a role of these N-terminal amino-acids in membrane representation of the delayed rectifier channel complex.

  1. Neuropatía por virus BK post trasplante renal diagnostico y seguimiento por PCR en tiempo real BK virus nephropathy after renal transplantation: Diagnosis and prognosis by real time PCR

    Directory of Open Access Journals (Sweden)

    Marcela Echavarria

    2007-12-01

    Full Text Available La nefropatía producida por el virus BK puede llevar a la pérdida del trasplante renal. El diagnóstico etiológico es importante debido a que la clínica no permite diferenciar entre nefropatía por virus BK y rechazo agudo, en donde los tratamientos de estas dos entidades son diametralmente opuestos. El desarrollo reciente de métodos moleculares muy sensibles y específicos como PCR y PCR en tiempo real para virus BK permiten un diagnóstico de certeza en forma rápida y cuantificar la carga viral presente. El diagnóstico de nefropatía por virus BK se realiza por inmunohistoquímica en una biopsia renal, pero dada la naturaleza multifocal de las lesiones, la sensibilidad no siempre es del 100%. Los nuevos métodos de PCR para detectar virus BK en sangre y orina contribuyen al diagnóstico de nefropatía de una manera más normatizada y menos invasiva. Más aún, la cuantificación del virus BK en sangre por PCR en tiempo real, ha demostrado ser útil en el diagnóstico y monitoreo de esta enfermedad. En este trabajo se presenta el caso de una paciente transplantada renal con nefropatía por virus BK y el desarrollo de un método de PCR en tiempo real para la detección de virus BK en sangre y orina. Esta nueva metodología confirmó el diagnóstico de nefropatía por virus BK lo que permitió un cambio en el esquema de inmunosupresión y la instauración de un tratamiento que pudo ser monitorizado utilizando la carga viral.BK virus nephropathy may lead to kidney transplant failure. BK infection and acute rejection are clinically undistinguishable, therefore diagnosis of these entities is critical to establish the correct treatment. The new molecular methods using PCR and real time PCR have significantly contributed to the rapid and sensitive diagnosis of BK virus. Furthermore, viral load determination in plasma has significantly been associated with BK virus nephropathy. Definite diagnosis of nephropathy requires renal biopsy, although

  2. Molecular cloning of a K+ channel from the malaria parasite Plasmodium falciparum

    DEFF Research Database (Denmark)

    Ellekvist, Peter; Ricke, Christina Høier; Litman, Thomas

    2004-01-01

    concentrations of K(+) when inside the erythrocyte and low concentrations when in plasma. In the recently published genome of P. falciparum, we have identified a gene, pfkch1, encoding a potential K(+) channel, which to some extent resembles the big-conductance (BK) K(+) channel. We have cloned the approximately...... 6000 nucleotide (nt) fragment from cDNA, studied the pattern of expression of pfkch1 throughout the intraerythrocytic part of the parasite's life-cyclus, and characterized the channel on the basis of similarity to other K(+) channels from pro- and eukaryotic organisms. This P. falciparum K(+) channel...

  3. Encoding of rat working memory by power of multi-channel local field potentials via sparse non-negative matrix factorization.

    Science.gov (United States)

    Liu, Xu; Liu, Tiao-Tiao; Bai, Wen-Wen; Yi, Hu; Li, Shuang-Yan; Tian, Xin

    2013-06-01

    Working memory plays an important role in human cognition. This study investigated how working memory was encoded by the power of multi-channel local field potentials (LFPs) based on sparse nonnegative matrix factorization (SNMF). SNMF was used to extract features from LFPs recorded from the prefrontal cortex of four Sprague-Dawley rats during a memory task in a Y maze, with 10 trials for each rat. Then the power-increased LFP components were selected as working memory-related features and the other components were removed. After that, the inverse operation of SNMF was used to study the encoding of working memory in the time-frequency domain. We demonstrated that theta and gamma power increased significantly during the working memory task. The results suggested that postsynaptic activity was simulated well by the sparse activity model. The theta and gamma bands were meaningful for encoding working memory.

  4. The large conductance calcium-activated K(+) channel interacts with the small GTPase Rab11b.

    Science.gov (United States)

    Sokolowski, Sophia; Harvey, Margaret; Sakai, Yoshihisa; Jordan, Amy; Sokolowski, Bernd

    2012-09-21

    The transduction of sound by the receptor or hair cells of the cochlea leads to the activation of ion channels found in the basal and lateral regions of these cells. Thus, the processing of these transduced signals to the central nervous system is tied to the regulation of baso-lateral ion channels. The large conductance calcium-activated potassium or BK channel was revealed to interact with the small GTPase, Rab11b, which is one of many Rabs found in various endosomal pathways. Immunoelectron microscopy showed the colocalization of these two proteins in receptor cells and auditory neurons. Using Chinese hamster ovary cells as a heterologous expression system, Rab11b increased or decreased BK expression, depending on the overexpression or RNAi knockdown of Rab, respectively. Additional mutation analyses, using a yeast two-hybrid assay, suggested that this GTPase moderately interacts within a region of BK exclusive of the N- or C-terminal tails. These data suggest that this small GTPase regulates BK in a slow recycling process through the endocytic compartment and to the plasmalemma.

  5. Isospin dependence of reactions $^{48}$Ca+$^{243-251}$Bk

    CERN Document Server

    Shen, Caiwan; Boilley, Davoid; Kosenko, Grigory; Zhao, Enguang

    2008-01-01

    The fusion process of $^{48}$Ca induced reactions is studied with the two-step model. In this model, the fusion process is devided into two stages: first, the sticking stage where projectile and target come to the touching point over the Coulomb barrier from infinite distance, and second, the formation stage where the di-nucleus formed with projectile and target evolve to form the spherical compound nucleus from the touching point. By the use of the statistical evaporation model, the residue cross sections for different neutron evaporation channels are analyzed. From the results, optimum reactions are given to synthesize $Z$ = 117 element with $^{48}$Ca induced reactions.

  6. Inhibition of Ca2+-activated large-conductance K+ channel activity alters synaptic AMPA receptor phenotype in mouse cerebellar stellate cells.

    Science.gov (United States)

    Liu, Yu; Savtchouk, Iaroslav; Acharjee, Shoana; Liu, Siqiong June

    2011-07-01

    Many fast-spiking inhibitory interneurons, including cerebellar stellate cells, fire brief action potentials and express α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors (AMPAR) that are permeable to Ca(2+) and do not contain the GluR2 subunit. In a recent study, we found that increasing action potential duration promotes GluR2 gene transcription in stellate cells. We have now tested the prediction that activation of potassium channels that control the duration of action potentials can suppress the expression of GluR2-containing AMPARs at stellate cell synapses. We find that large-conductance Ca(2+)-activated potassium (BK) channels mediate a large proportion of the depolarization-evoked noninactivating potassium current in stellate cells. Pharmacological blockade of BK channels prolonged the action potential duration in postsynaptic stellate cells and altered synaptic AMPAR subtype from GluR2-lacking to GluR2-containing Ca(2+)-impermeable AMPARs. An L-type channel blocker abolished an increase in Ca(2+) entry that was associated with spike broadening and also prevented the BK channel blocker-induced switch in AMPAR phenotype. Thus blocking BK potassium channels prolongs the action potential duration and increases the expression of GluR2-containing receptors at the synapse by enhancing Ca(2+) entry in cerebellar stellate cells.

  7. CNTF-Treated Astrocyte Conditioned Medium Enhances Large-Conductance Calcium-Activated Potassium Channel Activity in Rat Cortical Neurons.

    Science.gov (United States)

    Sun, Meiqun; Liu, Hongli; Xu, Huanbai; Wang, Hongtao; Wang, Xiaojing

    2016-08-01

    Seizure activity is linked to astrocyte activation as well as dysfunctional cortical neuron excitability produced from changes in calcium-activated potassium (KCa) channel function. Ciliary neurotrophic factor-treated astrocyte conditioned medium (CNTF-ACM) can be used to investigate the peripheral effects of activated astrocytes upon cortical neurons. However, CNTF-ACM's effect upon KCa channel activity in cultured cortical neurons has not yet been investigated. Whole-cell patch clamp recordings were performed in rat cortical neurons to evaluate CNTF-ACM's effects upon charybdotoxin-sensitive large-conductance KCa (BK) channel currents and apamin-sensitive small-conductance KCa (SK) channel current. Biotinylation and RT-PCR were applied to assess CNTF-ACM's effects upon the protein and mRNA expression, respectively, of the SK channel subunits SK2 and SK3 and the BK channel subunits BKα1 and BKβ3. An anti-fibroblast growth factor-2 (FGF-2) monoclonal neutralizing antibody was used to assess the effects of the FGF-2 component of CNTF-ACM. CNTF-ACM significantly increased KCa channel current density, which was predominantly attributable to gains in BK channel activity (p ACM produced a significant increase in BKα1 and BKβ3 expression (p  0.05). Blocking FGF-2 produced significant reductions in KCa channel current density (p > 0.05) as well as BKα1 and BKβ3 expression in CNTF-ACM-treated neurons (p > 0.05). CNTF-ACM significantly enhances BK channel activity in rat cortical neurons and that FGF-2 is partially responsible for these effects. CNTF-induced astrocyte activation results in secretion of neuroactive factors which may affect neuronal excitability and resultant seizure activity in mammalian cortical neurons.

  8. BK/TD models for analyzing in vitro impedance data on cytotoxicity.

    Science.gov (United States)

    Teng, S; Barcellini-Couget, S; Beaudouin, R; Brochot, C; Desousa, G; Rahmani, R; Pery, A R R

    2015-06-01

    The ban of animal testing has enhanced the development of new in vitro technologies for cosmetics safety assessment. Impedance metrics is one such technology which enables monitoring of cell viability in real time. However, analyzing real time data requires moving from static to dynamic toxicity assessment. In the present study, we built mechanistic biokinetic/toxicodynamic (BK/TD) models to analyze the time course of cell viability in cytotoxicity assay using impedance. These models account for the fate of the tested compounds during the assay. BK/TD models were applied to analyze HepaRG cell viability, after single (48 h) and repeated (4 weeks) exposures to three hepatotoxic compounds (coumarin, isoeugenol and benzophenone-2). The BK/TD models properly fit the data used for their calibration that was obtained for single or repeated exposure. Only for one out of the three compounds, the models calibrated with a single exposure were able to predict repeated exposure data. We therefore recommend the use of long-term exposure in vitro data in order to adequately account for chronic hepatotoxic effects. The models we propose here are capable of being coupled with human biokinetic models in order to relate dose exposure and human hepatotoxicity.

  9. Caracterização da virulência da cepa de Escherichia coli - BK99

    Directory of Open Access Journals (Sweden)

    Brito Benito Guimarães de

    2001-01-01

    Full Text Available Com o objetivo de identificar a patogenicidade e resistência a antimicrobianos da cepa de E. coli BK99, foram utilizados alguns testes: aglutinação em lâmina para detecção da fímbria F5, produção de STa, ensaios para hemolisinas e colicinas, patogenicidade em leitões e antibiograma. A cepa BK99 apresentou o seguinte perfil: F1+, F5+, STa+, Col V+, Hly-, ST R, KA R, NO R, TT R SF R e foi capaz de provocar a doença clínica e morte em leitões inoculados; também foi possível o resgate dessa cepa de fezes diarréicas e do conteúdo intestinal dos leitões revelando, assim, alto índice de recuperação de colônias portadoras da fímbria F5+. Os resultados permitem concluir que a cepa de E. coli BK99 é produtora de fatores de virulência e reproduz experimentalmente a colibacilose suína neonatal.

  10. BK virus as a potential oncovirus for bladder cancer in a renal transplant patient.

    Science.gov (United States)

    Yin, Wen-Yao; Lee, Ming-Che; Lai, Ning-Sheng; Lu, Ming-Chi

    2015-04-01

    Renal transplant patients have high risk for bladder cancer. The reactivation of BK virus is common in renal transplant patients especially in the urinary tract. There was some evidence suggesting that the reactivation of BK virus (BKV) in renal transplant patients may associate with the development of bladder cancer. Here we demonstrated that a patient that had persistent elevated BKV viruria (urine BKV DNA concentration more than 10(11) copies/ml) after renal transplantation. Then, bladder cancer was found in 13 months after kidney transplantation. The urine BKV DNA concentration was detected by real-time PCR and the BKV DNA in the bladder tumor was detected by PCR. BKV DNA was found in the marginal and central part of the bladder tumor. After removal of the bladder cancer, the urine BKV viral load in this patients dropped dramatically to <10(2) copies/ml. However, the urine viral load had increased modestly to 10(6) copies/ml in 3 months after surgery. Since there is a close correlation between the urine BK viral load and the presence of bladder cancer, we suggested that there might be a causal relationship between the reactivation of BKV and the development of bladder cancer in renal transplant patient.

  11. Dysregulation of large-conductance Ca2+-activated K+ channel expression in nonsyndromal mental retardation due to a cereblon p.R419X mutation.

    Science.gov (United States)

    Higgins, Joseph J; Hao, Jin; Kosofsky, Barry E; Rajadhyaksha, Anjali M

    2008-07-01

    A nonsense mutation (R419X) in the human cereblon gene [mutation (mut) CRBN] causes a mild type of autosomal recessive nonsyndromal mental retardation (ARNSMR). CRBN, a cytosolic protein, regulates the assembly and neuronal surface expression of large-conductance Ca(2+)-activated K(+) channels (BK(Ca)) in brain regions involved in memory and learning. Using the real-time quantitative polymerase chain reaction, we show that mut CRBN disturbs the development of adult brain BK(Ca) isoforms. These changes are predicted to result in BK(Ca) channels with a higher intracellular Ca(2+) sensitivity, faster activation, and slower deactivation kinetics. Such alterations may contribute to cognitive impairments in patients with mild ARNSMR.

  12. [The characteristics and oxidative modulation of large-conductance calcium-activated potassium channels in guinea-pig colon smooth muscle cells.].

    Science.gov (United States)

    Huang, Wei-Feng; Ouyang, Shou; Zhang, Hui

    2009-06-25

    To investigate the characteristics of large-conductance calcium-activated potassium channels (BK(Ca)) and the effect of hydrogen peroxide (H2O2) on BK(Ca) in guinea-pig proximal colon smooth muscle cells, single smooth muscle cells of guinea-pig colon were enzymatically isolated in low calcium solution containing papain (3 mg/mL), DTT (2 mg/mL), and bovine serum albumin (BSA, 2 mg/mL). Tissues were incubated at 36 degrees C in enzyme solution for 15 min and were then suspended in enzyme-free low calcium solution. Inside-out single channel recording technique was used to record BK(Ca) current. The intracellular (bath) and microelectrode solution both contained symmetrical high potassium. The BK(Ca) in guinea-pig colon smooth muscle cell possesses: 1) voltage-dependence, 2) high selectivity for potassium ion, 3) large conductance (223.7 pS+/-9.2 pS), 4) dependence of [Ca(2+)](i). Intracellular application of H2O2 decreased the open probability (P(o)) of BK(Ca) at low concentration (Ca) at high concentration (5 mmol/L), without affecting the unitary conductance. The effects of H2O2 were reversed by reducing agent dithiothreitol (DTT). Similarly, cysteine specific oxidizing agent, DTNB, also increased or decreased P(o) of BK(Ca) and DTT partially reversed the effect of DTNB. It is thus suggested that H2O2 and DTNB may modulate P(o) of BK(Ca) via the oxidation of cysteine residue.

  13. Apelin-13 inhibits large-conductance Ca2+-activated K+ channels in cerebral artery smooth muscle cells via a PI3-kinase dependent mechanism.

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    Amit Modgil

    Full Text Available Apelin-13 causes vasoconstriction by acting directly on APJ receptors in vascular smooth muscle (VSM cells; however, the ionic mechanisms underlying this action at the cellular level remain unclear. Large-conductance Ca(2+-activated K(+ (BKCa channels in VSM cells are critical regulators of membrane potential and vascular tone. In the present study, we examined the effect of apelin-13 on BK(Ca channel activity in VSM cells, freshly isolated from rat middle cerebral arteries. In whole-cell patch clamp mode, apelin-13 (0.001-1 μM caused concentration-dependent inhibition of BK(Ca in VSM cells. Apelin-13 (0.1 µM significantly decreased BK(Ca current density from 71.25 ± 8.14 pA/pF to 44.52 ± 7.10 pA/pF (n=14 cells, P<0.05. This inhibitory effect of apelin-13 was confirmed by single channel recording in cell-attached patches, in which extracellular application of apelin-13 (0.1 µM decreased the open-state probability (NPo of BK(Ca channels in freshly isolated VSM cells. However, in inside-out patches, extracellular application of apelin-13 (0.1 µM did not alter the NPo of BK(Ca channels, suggesting that the inhibitory effect of apelin-13 on BKCa is not mediated by a direct action on BK(Ca. In whole cell patches, pretreatment of VSM cells with LY-294002, a PI3-kinase inhibitor, markedly attenuated the apelin-13-induced decrease in BK(Ca current density. In addition, treatment of arteries with apelin-13 (0.1 µM significantly increased the ratio of phosphorylated-Akt/total Akt, indicating that apelin-13 significantly increases PI3-kinase activity. Taken together, the data suggest that apelin-13 inhibits BK(Ca channel via a PI3-kinase-dependent signaling pathway in cerebral artery VSM cells, which may contribute to its regulatory action in the control of vascular tone.

  14. Efficient uptake of blood-borne BK and JC polyomavirus-like particles in endothelial cells of liver sinusoids and renal vasa recta.

    Directory of Open Access Journals (Sweden)

    Jaione Simon-Santamaria

    Full Text Available Liver sinusoidal endothelial cells (LSECs are specialized scavenger cells that mediate high-capacity clearance of soluble waste macromolecules and colloid material, including blood-borne adenovirus. To explore if LSECs function as a sink for other viruses in blood, we studied the fate of virus-like particles (VLPs of two ubiquitous human DNA viruses, BK and JC polyomavirus, in mice. Like complete virions, VLPs specifically bind to receptors and enter cells, but unlike complete virions, they cannot replicate. 125I-labeled VLPs were used to assess blood decay, organ-, and hepatocellular distribution of ligand, and non-labeled VLPs to examine cellular uptake by immunohisto- and -cytochemistry. BK- and JC-VLPs rapidly distributed to liver, with lesser uptake in kidney and spleen. Liver uptake was predominantly in LSECs. Blood half-life (∼1 min, and tissue distribution of JC-VLPs and two JC-VLP-mutants (L55F and S269F that lack sialic acid binding affinity, were similar, indicating involvement of non-sialic acid receptors in cellular uptake. Liver uptake was not mediated by scavenger receptors. In spleen, the VLPs localized to the red pulp marginal zone reticuloendothelium, and in kidney to the endothelial lining of vasa recta segments, and the transitional epithelium of renal pelvis. Most VLP-positive vessels in renal medulla did not express PV-1/Meca 32, suggesting location to the non-fenestrated part of vasa recta. The endothelial cells of these vessels also efficiently endocytosed a scavenger receptor ligand, formaldehyde-denatured albumin, suggesting high endocytic activity compared to other renal endothelia. We conclude that LSECs very effectively cleared a large fraction of blood-borne BK- and JC-VLPs, indicating a central role of these cells in early removal of polyomavirus from the circulation. In addition, we report the novel finding that a subpopulation of endothelial cells in kidney, the main organ of polyomavirus persistence, showed

  15. BK polyoma virus infection and renal disease in non-renal solid organ transplantation.

    Science.gov (United States)

    Kuppachi, Sarat; Kaur, Deepkamal; Holanda, Danniele G; Thomas, Christie P

    2016-04-01

    BK virus (BKV) is a non-enveloped DNA virus of the polyomaviridae family that causes an interstitial nephritis in immunosuppressed patients. BKV nephropathy is now a leading cause of chronic kidney disease and early allograft failure following kidney transplantation. It is also known to cause renal disease with a progressive decline in kidney function in non-renal solid organ transplant (NRSOT) recipients, although the disease may not be recognized nor its impact appreciated in this patient population. In this report, we review the existing literature to highlight our current understanding of its incidence in NRSOT populations, the approaches to diagnosis and the potential treatment options.

  16. Nephritic-nephrotic syndrome as a presentation of BK virus infection

    Directory of Open Access Journals (Sweden)

    Nima Derakhshan

    2011-01-01

    Full Text Available BK virus (BKV is increasingly found as an important cause of allograft nephro-pathy. Nephrotic syndrome is not a usual manifestation of BKV nephropathy. Here, we report a 12-year-old boy, a case of end-stage renal disease due to nephronophthisis, who got the kidney trans-planted from a 16-year-old cadaver, and after 18 months of uneventful transplantation on triple immunosuppressive therapy (Mycophenolate mofetil (MMF, cyclosporin and prednisolone, pre-sented with nephrotic feature (edema, heavy proteinuria, hypoalbuminemia and hyperlipidema. Kidney biopsy was in favor of BKV infection and eventually ended in graft failure.

  17. Low-loss waveguides fabricated in BK7 glass by high repetition rate femtosecond fiber laser.

    Science.gov (United States)

    Eaton, Shane M; Ng, Mi Li; Bonse, Jörn; Mermillod-Blondin, Alexandre; Zhang, Haibin; Rosenfeld, Arkadi; Herman, Peter R

    2008-04-20

    For the first time femtosecond-laser writing has inscribed low-loss optical waveguides in Schott BK7 glass, a commercially important type of borosilicate widely used in optical applications. The use of a variable repetition rate laser enabled the identification of a narrow processing window at 1 MHz repetition rate with optimal waveguides exhibiting propagation losses of 0.3 dB/cm and efficient mode matching to standard optical fibers at a 1550 nm wavelength. The waveguides were characterized by complementary phase contrast and optical transmission microscopy, identifying a micrometer-sized guiding region within a larger complex structure of both positive and negative refractive index variations.

  18. Interaction of hydrogen sulfide with ion channels.

    Science.gov (United States)

    Tang, Guanghua; Wu, Lingyun; Wang, Rui

    2010-07-01

    1. Hydrogen sulfide (H(2)S) is a signalling gasotransmitter. It targets different ion channels and receptors, and fulfils its various roles in modulating the functions of different systems. However, the interaction of H(2)S with different types of ion channels and underlying molecular mechanisms has not been reviewed systematically. 2. H(2)S is the first identified endogenous gaseous opener of ATP-sensitive K(+) channels in vascular smooth muscle cells. Through the activation of ATP-sensitive K(+) channels, H(2)S lowers blood pressure, protects the heart from ischemia and reperfusion injury, inhibits insulin secretion in pancreatic beta cells, and exerts anti-inflammatory, anti-nociceptive and anti-apoptotic effects. 3. H(2)S inhibited L-type Ca(2+) channels in cardiomyocytes but stimulated the same channels in neurons, thus regulating intracellular Ca(2+) levels. H(2)S activated small and medium conductance K(Ca) channels but its effect on BK(Ca) channels has not been consistent. 4. H(2)S-induced hyperalgesia and pro-nociception seems to be related to the sensitization of both T-type Ca(2+) channels and TRPV(1) channels. The activation of TRPV(1) and TRPA(1) by H(2)S is believed to result in contraction of nonvascular smooth muscles and increased colonic mucosal Cl(-) secretion. 5. The activation of Cl(-) channel by H(2)S has been shown as a protective mechanism for neurons from oxytosis. H(2)S also potentiates N-methyl-d-aspartic acid receptor-mediated currents that are involved in regulating synaptic plasticity for learning and memory. 6. Given the important modulatory effects of H(2)S on different ion channels, many cellular functions and disease conditions related to homeostatic control of ion fluxes across cell membrane should be re-evaluated.

  19. Towards saturation of the electron-capture delayed fission probability: The new isotopes 240Es and 236Bk

    Directory of Open Access Journals (Sweden)

    J. Konki

    2017-01-01

    Full Text Available The new neutron-deficient nuclei 240Es and 236Bk were synthesised at the gas-filled recoil separator RITU. They were identified by their radioactive decay chains starting from 240Es produced in the fusion–evaporation reaction 209Bi(34S,3n240Es. Half-lives of 6(2s and 22−6+13s were obtained for 240Es and 236Bk, respectively. Two groups of α particles with energies Eα=8.19(3MeV and 8.09(3MeV were unambiguously assigned to 240Es. Electron-capture delayed fission branches with probabilities of 0.16(6 and 0.04(2 were measured for 240Es and 236Bk, respectively. These new data show a continuation of the exponential increase of ECDF probabilities in more neutron-deficient isotopes.

  20. T-current related effects of antiepileptic drugs and a Ca2+ channel antagonist on thalamic relay and local circuit interneurons in a rat model of absence epilepsy.

    Science.gov (United States)

    Broicher, Tilman; Seidenbecher, Thomas; Meuth, Patrick; Munsch, Thomas; Meuth, Sven G; Kanyshkova, Tatyana; Pape, Hans-Christian; Budde, Thomas

    2007-09-01

    Channel blocking, anti-oscillatory, and anti-epileptic effects of clinically used anti-absence substances (ethosuximide, valproate) and the T-type Ca2+ current (IT) blocker mibefradil were tested by analyzing membrane currents in acutely isolated local circuit interneurons and thalamocortical relay (TC) neurons, slow intrathalamic oscillations in brain slices, and spike and wave discharges (SWDs) occurring in vivo in Wistar Albino Glaxo rats from Rijswijk (WAG/Rij). Substance effects in vitro were compared between WAG/Rij and a non-epileptic control strain, the ACI rats. Ethosuximide (ETX) and valproate were found to block IT in acutely isolated thalamic neurons. Block of IT by therapeutically relevant ETX concentrations (0.25-0.75 mM) was stronger in WAG/Rij, although the maximal effect at saturating concentrations (>or=10 mM) was stronger in ACI. Ethosuximide delayed the onset of the low threshold Ca2+ spike (LTS) of neurons recorded in slice preparations. Mibefradil (>or=2 microM) completely blocked IT and the LTS, dampened evoked thalamic oscillations, and attenuated SWDs in vivo. Computational modeling demonstrated that the complete effect of ETX can be replicated by a sole reduction of IT. However, the necessary degree of IT reduction was not induced by therapeutically relevant ETX concentrations. A combined reduction of IT, the persistent sodium current, and the Ca2+ activated K+ current resulted in an LTS alteration resembling the experimental observations. In summary, these results support the hypothesis of IT reduction as part of the mechanism of action of anti-absence drugs and demonstrate the ability of a specific IT antagonist to attenuate rhythmic burst firing and SWDs.

  1. Rapid incision of the Colorado River in Glen Canyon - insights from channel profiles, local incision rates, and modeling of lithologic controls

    Science.gov (United States)

    Cook, K.L.; Whipple, K.X.; Heimsath, A.M.; Hanks, T.C.

    2009-01-01

    The Colorado River system in southern Utah and northern Arizona is continuing to adjust to the baselevel fall responsible for the carving of the Grand Canyon. Estimates of bedrock incision rates in this area vary widely, hinting at the transient state of the Colorado and its tributaries. In conjunction with these data, we use longitudinal profiles of the Colorado and tributaries between Marble Canyon and Cataract Canyon to investigate the incision history of the Colorado in this region. We find that almost all of the tributaries in this region steepen as they enter the Colorado River. The consistent presence of oversteepened reaches with similar elevation drops in the lower section of these channels, and their coincidence within a corridor of high local relief along the Colorado, suggest that the tributaries are steepening in response to an episode of increased incision rate on the mainstem. This analysis makes testable predictions about spatial variations in incision rates; these predictions are consistent with existing rate estimates and can be used to guide further studies. We also present cosmogenic nuclide data from the Henry Mountains of southern Utah. We measured in situ 10Be concentrations on four gravel-covered strath surfaces elevated from 1 m to 110 m above Trachyte Creek. The surfaces yield exposure ages that range from approximately 2??5 ka to 267 ka and suggest incision rates that vary between 350 and 600 m/my. These incision rates are similar to other rates determined within the high-relief corridor. Available data thus support the interpretation that tributaries of the Colorado River upstream of the Grand Canyon are responding to a recent pulse of rapid incision on the Colorado. Numerical modeling of detachment-limited bedrock incision suggests that this incision pulse is likely related to the upstream-dipping lithologic boundary at the northern edge of the Kaibab upwarp. ?? 2009 John Wiley & Sons, Ltd.

  2. 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

  3. A single-center epidemiological study of BK virus infection and analysis of risk factors in patients with renal transplantation

    Directory of Open Access Journals (Sweden)

    Ji-gang LI

    2014-10-01

    Full Text Available Objective To investigate the epidemiological characteristics of BK virus (BKV infection in living renal transplantation patients, and analyze the risk factors of BKV infection and BKV nephropathy (BKVN. Methods The BKV DNA load in urine and blood samples of 43 renal transplant recipients, who had received renal transplantation in 309 Hospital from Feb. 2012 to Feb. 2013, was determined at preoperative period and 0.5, 1, 3, 6, 9, 12 and 15 months after transplantation. Meanwhile, the biopsy of grafted kidney was performed in those patients with continuously elevated serum creatinine and those with higher BKV DNA load. Patients were divided into 3 groups as follows according to the test results: BK viruria group, BK viremia group and pathologically diagnosed BKVN group. Data of each group were then recorded, including gender, age, postoperative diabetes (PTDM, acute rejection (AR, delayed recovery of graft function (DGF, postoperative pulmonary infection, preoperative immune induction therapy, postoperative immunosuppressive regimen, and other information. The risk factors for postoperative BKV infection and BKVN were analyzed. Results After an average of 15-month follow-up, it was found that the incidence of BKV viruria was 46.5%, that of BKV viremia was 14.0%, and that of BKVN was 2.3%. Sixth month after transplantation was found to be the peak time of viruria and viremia. FK506 was significantly associated with viremia in living donor renal transplantation. The immunosuppressive regimen was the immune related independent risk factor for BK viremia developing BKVN after living renal transplantation. Conclusion The incidence of BK viremia and BKVN is lower in living donor renal transplantation than in cadaver renal transplantation, but that of viruria is similar in both groups. Immunosuppressive scheme based on FK506 is an immune related independent risk factor leading to BK viremia proceeding to BKVN in living donor kidney

  4. Local heat/mass transfer distributions around sharp 180 deg turns in two-pass smooth and rib-roughened channels

    Science.gov (United States)

    Han, J. C.; Chandra, P. R.; Lau, S. C.

    1988-01-01

    The napthalene sublimation technique was employed to study the detailed mass transfer distributions around the sharp 180 deg turns in a two-pass, square, smooth channel and in an identical channel with two rib-roughened opposite walls. Experiments conducted for Reynolds numbers of 15,000, 30,000, and 60,000 indicate that the Sherwood numbers on the top, outer, and inner walls around the turn in the rib-roughened channel are higher than the corresponding Sherwood numbers around the turn in the smooth channel. Sherwood numbers after the sharp turn are found to be higher than those before the turn for both the smooth and the ribbed channels.

  5. Physical mapping of BK virus DNA with SacI, MboII, and AluI restriction endonucleases.

    Science.gov (United States)

    Yang, R C; Wu, R

    1978-12-01

    A new restriction endonuclease, SacI from Streptomyces achromogenes cleaves BK virus (strain MM) DNA into 3 fragments, whereas MboII from Moraxella bovis and AluI from Arthrobacter luteus give 22 and 30 fragments, respectively. All these specific DNA fragments were ordered and mapped on the viral genome by two methods first, by the reciprocal digestion method using uniformly 32P-labeled DNA; and second, by the partial digestion technique using the single-end 32P-labeled DNA. This study, together with those reported earlier, defined the location of 90 cleavage sites on the BK virus DNA.

  6. Adjuvant Ciprofloxacin for Persistent BK Polyomavirus Infection in Kidney Transplant Recipients

    Directory of Open Access Journals (Sweden)

    David Arroyo

    2014-01-01

    Full Text Available Background. BK virus (BKV infection is a common complication following kidney transplantation. Immunosuppression reduction is the cornerstone of treatment while adjuvant drugs have been tried in small uncontrolled studies. We sought to examine our center’s experience with the use of ciprofloxacin in patients with persistent BKV infection. Methods. Retrospective evaluation of the effect of a 30-day ciprofloxacin course (250 mg twice daily on BKV infection in kidney transplant recipients who had been diagnosed with BK viruria ≥106 copies/mL and viremia ≥500 copies/mL and in whom the infection did not resolve after immunosuppression reduction and/or treatment with other adjuvant agents. BKV in plasma and urine was evaluated after 3 months following treatment with ciprofloxacin. Results. Nine kidney transplant recipients received ciprofloxacin at a median of 130 days following the initial reduction in immunosuppression. Three patients showed complete viral clearance and another 3 had a ≥50% decrease in plasma viral load. No serious adverse events secondary to ciprofloxacin were reported and no grafts were lost due to BKV up to 1 year after treatment. Conclusion. Ciprofloxacin may be a useful therapy for persistent BKV infection despite conventional treatment. Randomized trials are required to evaluate the potential benefit of this adjuvant therapy.

  7. Intermediate dose cidofovir does not cause additive nephrotoxicity in BK virus allograft nephropathy.

    Science.gov (United States)

    Araya, Carlos E; Lew, Judy F; Fennell, Robert S; Neiberger, Richard E; Dharnidharka, Vikas R

    2008-11-01

    BKVAN has emerged as a major morbidity in kidney transplant recipients. Among treatment options is cidofovir, which can be nephrotoxic. We previously reported that intermediate dose cidofovir could be used without significant nephrotoxicity. We present extended results of the same treatment protocol in a larger cohort and with longer follow up. Diagnosis of BKVAN was based on detection of BK viral DNA from plasma and renal allograft biopsy tissue. All patients received cidofovir (0.25-1 mg/kg/dose) every 2-3 wk. Total number of cidofovir doses ranged from 1 to 18 (mean 8). This report includes eight patients, aged 5-21 yr, treated with intermediate dose cidofovir. Median follow-up was 11 months (range 4-32). Mean fall in reciprocal of serum creatinine (1/sCr) from baseline at BKVAN diagnosis was 64% (range 28-120%). A time-series plot of plasma BK virus PCR and 1/sCr showed marked reduction in viral loads without significant deterioration in 1/sCr from the initial value at BKVAN diagnosis. In this larger series with extended follow up, intermediate dose cidofovir without probenecid for the treatment of BKVAN continues to show stabilization of renal function without progression to renal failure.

  8. A new precise mass for the progenitor of the Type IIP SN 2008bk

    CERN Document Server

    Maund, J R; Ramirez-Ruiz, E; Eldridge, J J

    2013-01-01

    The progenitor of the Type IIP SN 2008bk was discovered in pre-explosion g'r'i'IYJHKs images, acquired with European Southern Observatory Very Large Telescope FORS, HAWK-I and ISAAC instruments and the Gemini GMOS-S instrument. The wealth of pre-explosion observations makes the progenitor of this SN one of the best studied, since the detection of the progenitor of SN1987A. Previous analyses of the properties of the progenitor were hampered by the limited quality of the photometric calibration of the pre-explosion images and the crowded nature of the field containing the SN. We present new late-time observations of the site of SN2008bk acquired with identical instrument and filter configurations as the pre-explosion observations, and confirm that the previously identified red supergiant star was the progenitor of this SN and has now disappeared. Image subtraction techniques were used to conduct precise photometry of the now missing progenitor, independently of blending from any nearby stars. The nature of the ...

  9. BK Lyncis: The Oldest Old Nova?... And a Bellwether for Cataclysmic-Variable Evolution

    CERN Document Server

    Patterson, Joseph; Kemp, Jonathan; de Miguel, Enrique; Krajci, Thomas; Foote, Jerry; Hambsch, Franz-Josef; Campbell, Tut; Roberts, George; Cejudo, David; Dvorak, Shawn; Vanmunster, Tonny; Koff, Robert; Skillman, David; Harvey, David; Martin, Brian; Rock, John; Boyd, David; Oksanen, Arto; Morelle, Etienne; Ulowetz, Joseph; Kroes, Anthony; Sabo, Richard; Jensen, Lasse

    2012-01-01

    We summarize the results of a 20-year campaign to study the light curves of BK Lyncis, a nova-like star strangely located below the 2-3 hour orbital period gap in the family of cataclysmic variables. Two apparent "superhumps" dominate the nightly light curves - with periods 4.6% longer, and 3.0% shorter, than P_orb. The first appears to be associated with the star's brighter states (V~14), while the second appears to be present throughout and becomes very dominant in the low state (V~15.7). Starting in the year 2005, the star's light curve became indistinguishable from that of a dwarf nova - in particular, that of the ER UMa subclass. Reviewing all the star's oddities, we speculate: (a) BK Lyn is the remnant of the probable nova on 30 December 101, and (b) it has been fading ever since, but has taken ~2000 years for the accretion rate to drop sufficiently to permit dwarf-nova eruptions. If such behavior is common, it can explain other puzzles of CV evolution. One: why the ER UMa class even exists (because all...

  10. Troponin T3 regulates nuclear localization of the calcium channel Ca{sub v}β{sub 1a} subunit in skeletal muscle

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tan; Taylor, Jackson; Jiang, Yang [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Pereyra, Andrea S. [Department of Histology, National University of La Plata, 1900 La Plata (Argentina); Messi, Maria Laura; Wang, Zhong-Min [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Hereñú, Claudia [Department of Histology, National University of La Plata, 1900 La Plata (Argentina); Delbono, Osvaldo, E-mail: odelbono@wakehealth.edu [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States)

    2015-08-15

    The voltage-gated calcium channel (Ca{sub v}) β{sub 1a} subunit (Ca{sub v}β{sub 1a}) plays an important role in excitation–contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Ca{sub v}β{sub 1a} subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160–244 aa) and Ca{sub v}β{sub 1a} NH{sub 2}-terminus (1–99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Ca{sub v}β{sub 1a}/YFP shows that TnT3 facilitates Ca{sub v}β{sub 1a} nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation. - Highlights: • Previously, we demonstrated that Ca{sub v}β{sub 1a} is a gene transcription regulator. • Here, we show that TnT3 interacts with Ca{sub v}β{sub 1a}. • We mapped TnT3 and Ca{sub v}β{sub 1a} interaction domain. • TnT3 facilitates Ca{sub v}β{sub 1a} nuclear enrichment. • The two proteins play a heretofore unknown role during early muscle differentiation.

  11. Functional coupling between heterologously expressed dopamine D(2) receptors and KCNQ channels

    DEFF Research Database (Denmark)

    Ljungstrom, Trine; Grunnet, Morten; Jensen, Bo Skaaning

    2003-01-01

    Activation of KCNQ potassium channels by stimulation of co-expressed dopamine D(2) receptors was studied electrophysiologically in Xenopus laevis oocytes and in mammalian cells. To address the specificity of the interaction between D(2)-like receptors and KCNQ channels, combinations of KCNQ1...... activation of the KCNQ channels was confirmed by co-expression of other neuronal K(+) channels (BK, K(V)1.1, and K(V)4.3) with the D(2L) receptor in Xenopus oocytes. None of these K(+) channels responded to stimulation of the D(2L) receptor. In the mammalian brain, dopamine D(2) receptors and KCNQ channels...... co-localise postsynaptically in several brain regions, so modulation of neuronal excitability by dopamine release could in part be mediated via an effect on KCNQ channels....

  12. Draft Genome Sequence of an Invasive Multidrug-Resistant Strain, Pseudomonas aeruginosa BK1, Isolated from a Keratitis Patient

    KAUST Repository

    Jeganathan, Lakshmi Priya

    2014-03-27

    Pseudomonas aeruginosa infections are difficult to treat due to the presence of a multitude of virulence factors and antibiotic resistance. Here, we report the draft genome sequence of P. aeruginosa BK1, an invasive and multidrug-resistant strain, isolated from a bacterial keratitis patient in southern India.

  13. BK virus-hemorrhagic cystitis following allogeneic stem cell transplantation: Clinical characteristics and utility of leflunomide treatment.

    Science.gov (United States)

    Park, Young Hoon; Lim, Joo Han; Yi, Hyeon Gyu; Lee, Moon Hee; Kim, Chul Soo

    2016-04-18

    BK virus-hemorrhagic cystitis (BKV-HC) is a potential cause of morbidity and mortality in patients having undergone allogeneic stem cell transplantation (Allo-SCT). We analyzed the clinical features of BKV-HC following Allo-SCT and reported the utility of leflunomide therapy for BKV-HC.

  14. APE1/Ref-1 promotes the effect of angiotensin II on Ca2+ -activated K+ channel in human endothelial cells via suppression of NADPH oxidase.

    Science.gov (United States)

    Park, Won Sun; Ko, Eun A; Jung, In Duk; Son, Youn Kyoung; Kim, Hyoung Kyu; Kim, Nari; Park, So Youn; Hong, Ki Whan; Park, Yeong-Min; Choi, Tae-Hoon; Han, Jin

    2008-10-01

    The effects of angiotensin II (Ang II) on whole-cell large conductance Ca(2+)-activated K(+) (BK(Ca)) currents was investigated in control and Apurinic/apyrimidinic endonuclease1/redox factor 1 (APE1/Ref-1)-overexpressing human umbilical vein endothelial cells (HUVECs). Ang II blocked the BK(Ca) current in a dose-dependent fashion, and this inhibition was greater in APE1/Ref-1-overexpressing HUVECs than in control HUVECs (half-inhibition values of 102.81+/-9.54 nM and 11.34+/-0.39 nM in control and APE1/Ref-1-overexpressing HUVECs, respectively). Pretreatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) or knock down of NADPH oxidase (p22 phox) using siRNA increased the inhibitory effect of Ang II on the BK(Ca) currents, similar to the effect of APE1/Ref-1 overexpression. In addition, application of Ang II increased the superoxide and hydrogen peroxide levels in the control HUVECs but not in APE1/Ref-1-overexpressing HUVECs. Furthermore, direct application of hydrogen peroxide increased BK(Ca) channel activity. Finally, the inhibitory effect of Ang II on the BK(Ca) current was blocked by an antagonist of the Ang II type 1 (AT(1)) receptor in both control and APE1/Ref-1-overexpressing HUVECs. From these results, we conclude that the inhibitory effect of Ang II on BK(Ca) channel function is NADPH oxidase-dependent and may be promoted by APE1/Ref-1.

  15. Improving the specific activity of β-mannanase from Aspergillus niger BK01 by structure-based rational design.

    Science.gov (United States)

    Huang, Jian-Wen; Chen, Chun-Chi; Huang, Chun-Hsiang; Huang, Ting-Yung; Wu, Tzu-Hui; Cheng, Ya-Shan; Ko, Tzu-Ping; Lin, Cheng-Yen; Liu, Je-Ruei; Guo, Rey-Ting

    2014-03-01

    β-Mannanase has found various biotechnological applications because it is capable of degrading mannans into smaller sugar components. A highly potent example is the thermophilic β-mannanase from Aspergillus niger BK01 (ManBK), which can be efficiently expressed in industrial yeast strains and is thus an attractive candidate for commercial utilizations. In order to understand the molecular mechanism, which helps in strategies to improve the enzyme's performance that would meet industrial demands, 3D-structural information is a great asset. Here, we present the 1.57Å crystal structure of ManBK. The protein adopts a typical (β/α)8 fold that resembles the other GH5 family members. Polysaccharides were subsequently modeled into the substrate binding groove to identify the residues and structural features that may be involved in the catalytic reaction. Based on the structure, rational design was conducted to engineer ManBK in an attempt to enhance its enzymatic activity. Among the 23 mutants that we constructed, the most promising Y216W showed an 18±2.7% increase in specific activity by comparison with the wild type enzyme. The optimal temperature and heat tolerance profiles of Y216W were similar to those of the wild type, manifesting a preserved thermostability. Kinetic studies showed that Y216W has higher kcat values than the wild type enzyme, suggesting a faster turnover rate of catalysis. In this study we applied rational design to ManBK by using its crystal structure as a basis and identified the Y216W mutant that shows great potentials in industrial applications.

  16. Progressive renal failure due to renal infiltration by BK polyomavirus and leukaemic cells: which is the culprit?

    Science.gov (United States)

    Sangala, Nicholas; Dewdney, Alex; Marley, Nicholas; Cranfield, Tanya; Venkat-Raman, Gopalakrishnan

    2011-02-01

    Renal infiltration with leukaemic cells is a common finding in patients suffering with chronic lymphocytic leukaemia (CLL) but rarely does it lead to significant renal dysfunction. Similarly, BK nephropathy is a recognized cause of graft failure in renal transplant recipients but rarely causes significant disease in native kidneys. In the few reports where leukaemic infiltration of the kidney has led to significant renal impairment, the pathological process causing renal dysfunction is not identified on biopsy. In these cases, it is unclear whether BK polyomavirus (BKV) nephropathy has been excluded. We describe a case of dual pathologies in a patient with Binet stage C CLL and deteriorating renal function where renal biopsy reveals leukaemic infiltration of the kidney occurring alongside BKV nephropathy. The relative importance of each pathology in relation to the rapid decline to end-stage renal failure remains unclear, but the presence of both pathologies appears to impart a poor prognosis. Additionally, we describe the novel histological finding of loss of tubular integrity resulting in tubular infiltration and occlusion by leukaemic cells. It is possible that the patient with advanced CLL is at particular risk of BK activation, and the presence of BK nephropathy may compromise tubular integrity allowing leukaemic cell infiltration and obstruction of tubules. This case bares remarkable resemblance to the first and only other report of its kind in the literature. It is not clear how available immunocytochemistry for polyoma infection is outside transplant centres, and it is possible that BK nephropathy is being under-diagnosed in patients with CLL in the context of declining renal function. At present, the combination of BKV nephropathy and leukaemic infiltration represents a management conundrum and the prognosis is poor. Further research is required in order to better understand the pathological process and therefore develop management strategies.

  17. Hemorrhagic Cystitis due to BK Reactivation in a Young Female Treated for Hodgkin-Disease

    Directory of Open Access Journals (Sweden)

    R. Le Calloch

    2011-01-01

    Full Text Available Hodgkin's lymphoma is a disease with a high rate of curability under classic chemo-radiotherapy regimes. Complications due to chemotherapy could include viral reactivation due to chronic lymphopenia. BK virus (BKV is a polyoma virus belonging to the Papovaviridae family with antibody seroprevalences in healthy populations varying from 60% to 80%. Initial infections are asymptomatic usually occur in early childhood, after which the viruses remain latent in the kidneys or urothelium. Reactivation of BKV occurs in individuals with severe immunosuppression during HIV infections, transplantation or, exceptionally, after classical chemotherapy. BKV incidence is approximately 0% to 5% in immunocompetent individuals. Reactivation is associated with nephropathy and haemorrhagic cystitis. Herein, we present a case of a haemorrhagic cystitis due to BKV reactivation in a patient with Hodgkin's disease treated with chemotherapy.

  18. Resummation of double collinear logs in BK evolution versus HERA data

    CERN Document Server

    Albacete, Javier L

    2015-01-01

    We present a global fit to HERA data on the reduced cross section measured in electron-proton collisions in the region of small Bjorken-$x$: $x\\le x_0=10^{-2}$ and moderate to high values of the virtuality $Q^2BK equations for the description of the small-$x$ evolution of the dipole scattering amplitude. These two new equations provide an all-order resummation of double collinear logarithms that arise beyond leading logarithmic accuracy. We show that a very good description of data is possible in both cases, provided the parent dipole or smallest dipole prescriptions are employed for the running of the coupling.

  19. Measurement of B-->K{*}(892)gamma branching fractions and CP and Isospin asymmetries.

    Science.gov (United States)

    Aubert, B; Karyotakis, Y; Lees, J P; Poireau, V; Prencipe, E; Prudent, X; Tisserand, V; Garra Tico, J; Grauges, E; Martinelli, M; Palano, A; Pappagallo, M; Eigen, G; Stugu, B; Sun, L; Battaglia, M; Brown, D N; Kerth, L T; Kolomensky, Yu G; Lynch, G; Osipenkov, I L; Tackmann, K; Tanabe, T; Hawkes, C M; Soni, N; Watson, A T; Koch, H; Schroeder, T; Asgeirsson, D J; Fulsom, B G; Hearty, C; Mattison, T S; McKenna, J A; Barrett, M; Khan, A; Randle-Conde, A; Blinov, V E; Bukin, A D; Buzykaev, A R; Druzhinin, V P; Golubev, V B; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Bondioli, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Martin, E C; Stoker, D P; Atmacan, H; Gary, J W; Liu, F; Long, O; Vitug, G M; Yasin, Z; Zhang, L; Sharma, V; Campagnari, C; Hong, T M; Kovalskyi, D; Mazur, M A; Richman, J D; Beck, T W; Eisner, A M; Heusch, C A; Kroseberg, J; Lockman, W S; Martinez, A J; Schalk, T; Schumm, B A; Seiden, A; Wang, L; Winstrom, L O; Cheng, C H; Doll, D A; Echenard, B; Fang, F; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Andreassen, R; Mancinelli, G; Meadows, B T; Mishra, K; Sokoloff, M D; Bloom, P C; Ford, W T; Gaz, A; Hirschauer, J F; Nagel, M; Nauenberg, U; Smith, J G; Wagner, S R; Ayad, R; Toki, W H; Wilson, R J; Feltresi, E; Hauke, A; Jasper, H; Karbach, T M; Merkel, J; Petzold, A; Spaan, B; Wacker, K; Kobel, M J; Nogowski, R; Schubert, K R; Schwierz, R; Volk, A; Bernard, D; Latour, E; Verderi, M; Clark, P J; Playfer, S; Watson, J E; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cecchi, A; Cibinetto, G; Fioravanti, E; Franchini, P; Luppi, E; Munerato, M; Negrini, M; Petrella, A; Piemontese, L; Santoro, V; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Pacetti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Contri, R; Guido, E; Lo Vetere, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Tosi, S; Chaisanguanthum, K S; Morii, M; Adametz, A; Marks, J; Schenk, S; Uwer, U; Bernlochner, F U; Klose, V; Lacker, H M; Bard, D J; Dauncey, P D; Tibbetts, M; Behera, P K; Charles, M J; Mallik, U; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Gao, Y Y; Gritsan, A V; Guo, Z J; Arnaud, N; Béquilleux, J; D'Orazio, A; Davier, M; Derkach, D; Firmino da Costa, J; Grosdidier, G; Le Diberder, F; Lepeltier, V; Lutz, A M; Malaescu, B; Pruvot, S; Roudeau, P; Schune, M H; Serrano, J; Sordini, V; Stocchi, A; Wormser, G; Lange, D J; Wright, D M; Bingham, I; Burke, J P; Chavez, C A; Fry, J R; Gabathuler, E; Gamet, R; Hutchcroft, D E; Payne, D J; Touramanis, C; Bevan, A J; Clarke, C K; Di Lodovico, F; Sacco, R; Sigamani, M; Cowan, G; Paramesvaran, S; Wren, A C; Brown, D N; Davis, C L; Denig, A G; Fritsch, M; Gradl, W; Hafner, A; Alwyn, K E; Bailey, D; Barlow, R J; Jackson, G; Lafferty, G D; West, T J; Yi, J I; Anderson, J; Chen, C; Jawahery, A; Roberts, D A; Simi, G; Tuggle, J M; Dallapiccola, C; Salvati, E; Saremi, S; Cowan, R; Dujmic, D; Fisher, P H; Henderson, S W; Sciolla, G; Spitznagel, M; Yamamoto, R K; Zhao, M; Patel, P M; Robertson, S H; Schram, M; Lazzaro, A; Lombardo, V; Palombo, F; Stracka, S; Bauer, J M; Cremaldi, L; Godang, R; Kroeger, R; Sonnek, P; Summers, D J; Zhao, H W; Simard, M; Taras, P; Nicholson, H; De Nardo, G; Lista, L; Monorchio, D; Onorato, G; Sciacca, C; Raven, G; Snoek, H L; Jessop, C P; Knoepfel, K J; Losecco, J M; Wang, W F; Corwin, L A; Honscheid, K; Kagan, H; Kass, R; Morris, J P; Rahimi, A M; Regensburger, J J; Sekula, S J; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Kolb, J A; Lu, M; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Castelli, G; Gagliardi, N; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Del Amo Sanchez, P; Ben-Haim, E; Bonneaud, G R; Briand, H; Chauveau, J; Hamon, O; Leruste, Ph; Marchiori, G; Ocariz, J; Perez, A; Prendki, J; Sitt, S; Gladney, L; Biasini, M; Manoni, E; Angelini, C; Batignani, G; Bettarini, S; Calderini, G; Carpinelli, M; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Morganti, M; Neri, N; Paoloni, E; Rizzo, G; Walsh, J J; Lopes Pegna, D; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Anulli, F; Baracchini, E; Cavoto, G; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Jackson, P D; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Renga, F; Voena, C; Ebert, M; Hartmann, T; Schröder, H; Waldi, R; Adye, T; Franek, B; Olaiya, E O; Wilson, F F; Emery, S; Esteve, L; Hamel de Monchenault, G; Kozanecki, W; Vasseur, G; Yèche, Ch; Zito, M; Allen, M T; Aston, D; Bartoldus, R; Benitez, J F; Cenci, R; Coleman, J P; Convery, M R; Dingfelder, J C; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Field, R C; Franco Sevilla, M; Gabareen, A M; Graham, M T; Grenier, P; Hast, C; Innes, W R; Kaminski, J; Kelsey, M H; Kim, H; Kim, P; Kocian, M L

    2009-11-20

    We present an analysis of the decays B{0}-->K{*0}(892)gamma and B{+}-->K{*+}(892)gamma using a sample of about 383 x 10{6} BB[-over ] events collected with the BABAR detector at the PEP-II asymmetric energy B factory. We measure the branching fractions B(B{0}-->K{*0}gamma)=(4.47+/-0.10+/-0.16) x 10{-5} and B(B{+}-->K{*+}gamma)=(4.22+/-0.14+/-0.16) x 10{-5}. We constrain the direct CP asymmetry to be -0.033K{*}gamma)<0.028 and the isospin asymmetry to be 0.017

  20. Simultaneous BK Polyomavirus (BKPyV)-associated nephropathy and hemorrhagic cystitis after living donor kidney transplantation.

    Science.gov (United States)

    Helanterä, Ilkka; Hirsch, Hans H; Wernli, Marion; Ortiz, Fernanda; Lempinen, Marko; Räisänen-Sokolowski, Anne; Auvinen, Eeva; Mannonen, Laura; Lautenschlager, Irmeli

    2016-03-01

    BK polyomavirus (BKPyV) commonly reactivates after kidney transplantation, and can cause polyomavirus-associated nephropathy (PyVAN), whereas after allogeneic stem cell transplantation the most frequent manifestation of BKPyV is polyomavirus-associated hemorrhagic cystitis (PyVHC). Despite high-level BKPyV replication in both, the pathogenesis and manifestation of both BKPyV entities appears to differ substantially. We describe an unusual case of simultaneous PyVAN and PyVHC presenting with acute symptoms in a BKPyV-IgG positive recipient eight months after kidney transplantation from a haploidentical living donor, who was BKPyV-IgG negative. Symptoms of cystitis and viremia subsided rapidly after reduction of immunosuppression.

  1. N-terminal isoforms of the large-conductance Ca²⁺-activated K⁺ channel are differentially modulated by the auxiliary β1-subunit.

    Science.gov (United States)

    Lorca, Ramón A; Stamnes, Susan J; Pillai, Meghan K; Hsiao, Jordy J; Wright, Michael E; England, Sarah K

    2014-04-04

    The large-conductance Ca(2+)-activated K(+) (BK(Ca)) channel is essential for maintaining the membrane in a hyperpolarized state, thereby regulating neuronal excitability, smooth muscle contraction, and secretion. The BK(Ca) α-subunit has three predicted initiation codons that generate proteins with N-terminal ends starting with the amino acid sequences MANG, MSSN, or MDAL. Because the N-terminal region and first transmembrane domain of the α-subunit are required for modulation by auxiliary β1-subunits, we examined whether β1 differentially modulates the N-terminal BK(Ca) α-subunit isoforms. In the absence of β1, all isoforms had similar single-channel conductances and voltage-dependent activation. However, whereas β1 did not modulate the voltage-activation curve of MSSN, β1 induced a significant leftward shift of the voltage activation curves of both the MDAL and MANG isoforms. These shifts, of which the MDAL was larger, occurred at both 10 μM and 100 μM Ca(2+). The β1-subunit increased the open dwell times of all three isoforms and decreased the closed dwell times of MANG and MDAL but increased the closed dwell times of MSSN. The distinct modulation of voltage activation by the β1-subunit may be due to the differential effect of β1 on burst duration and interburst intervals observed among these isoforms. Additionally, we observed that the related β2-subunit induced comparable leftward shifts in the voltage-activation curves of all three isoforms, indicating that the differential modulation of these isoforms was specific to β1. These findings suggest that the relative expression of the N-terminal isoforms can fine-tune BK(Ca) channel activity in cells, highlighting a novel mechanism of BK(Ca) channel regulation.

  2. Mutation in the myelin proteolipid protein gene alters BK and SK channel function in the caudal medulla

    OpenAIRE

    Mayer, Catherine A.; Macklin, Wendy B.; Avishai, Nanthawan; Balan, Kannan; Wilson, Christopher G.; Miller, Martha J.

    2009-01-01

    Proteolipid protein (Plp) gene mutation in rodents causes severe CNS dysmyelination, early death, and lethal hypoxic ventilatory depression (Miller et al. 2004). To determine if Plp mutation alters neuronal function critical for control of breathing, the nucleus tractus solitarii (nTS) of four rodent strains were studied: myelin deficient rats (MD), myelin synthesis deficient (Plpmsd), and Plpnull mice, as well as shiverer (Mbpshi) mice, a myelin basic protein mutant. Current-voltage relation...

  3. Altered expression and localization of hippocampal A-type potassium channel subunits in the pilocarpine-induced model of temporal lobe epilepsy.

    Science.gov (United States)

    Monaghan, M M; Menegola, M; Vacher, H; Rhodes, K J; Trimmer, J S

    2008-10-15

    Altered ion channel expression and/or function may contribute to the development of certain human epilepsies. In rats, systemic administration of pilocarpine induces a model of human temporal lobe epilepsy, wherein a brief period of status epilepticus (SE) triggers development of spontaneous recurrent seizures that appear after a latency of 2-3 weeks. Here we investigate changes in expression of A-type voltage-gated potassium (Kv) channels, which control neuronal excitability and regulate action potential propagation and neurotransmitter release, in the pilocarpine model of epilepsy. Using immunohistochemistry, we examined the expression of component subunits of somatodendritic (Kv4.2, Kv4.3, KChIPl and KChIP2) and axonal (Kv1.4) A-type Kv channels in hippocampi of pilocarpine-treated rats that entered SE. We found that Kv4.2, Kv4.3 and KChIP2 staining in the molecular layer of the dentate gyrus changes from being uniformly distributed across the molecular layer to concentrated in just the outer two-thirds. We also observed a loss of KChIP1 immunoreactive interneurons, and a reduction of Kv4.2 and KChIP2 staining in stratum radiatum of CA1. These changes begin to appear 1 week after pilocarpine treatment and persist or are enhanced at 4 and 12 weeks. As such, these changes in Kv channel distribution parallel the acquisition of recurrent spontaneous seizures as observed in this model. We also found temporal changes in Kv1.4 immunoreactivity matching those in Timm's stain, being expanded in stratum lucidum of CA3 and in the inner third of the dentate molecular layer. Among pilocarpine-treated rats, changes were only observed in those that entered SE. These changes in A-type Kv channel expression may contribute to hyperexcitability of dendrites in the associated hippocampal circuits as observed in previous studies of the effects of pilocarpine-induced SE.

  4. Intravesical cidofovir to treat BK virus-associated hemorrhagic cystitis in children after hematopoietic stem cell transplantation.

    Science.gov (United States)

    Rascon, Jelena; Verkauskas, Gilvydas; Pasauliene, Ramune; Zubka, Vytautas; Bilius, Vytautas; Rageliene, Lina

    2015-06-01

    HC related to BK virus replication might be a severe complication following allogeneic HSCT. There are no clearly defined treatment guidelines in pediatric population. The data on the effectiveness of ICI to manage severe bleeding in children are very limited. We report our experience of intravesical cidofovir in four children, 6-15 yr of age, to manage grade III-IV BK virus-associated HC. Three of four children had high CSA serum level prior to developing cystitis. Intravesical instillations of cidofovir resulted only in temporal relief of bleeding. After immune suppression was withdrawn or tapered, intravesical instillations of formalin solution had to be undertaken to abort severe bleeding. We concluded that intravesical cidofovir alone did not appear to be sufficiently effective in case of severe HC, necessitating complimentary procedures to stop macrohematuria.

  5. BK Virus Nephropathy in Kidney Transplantation: An Approach Proposal and Update on Risk Factors, Diagnosis, and Treatment.

    Science.gov (United States)

    Gonzalez, S; Escobar-Serna, D P; Suarez, O; Benavides, X; Escobar-Serna, J F; Lozano, E

    2015-01-01

    BK virus belongs to Polyomaviridae family; it causes 95% of nephropathy cases related to polyomavirus, with the other 5% caused by JC virus. Nephropathy jeopardizes graft function, causing a premature failure of the graft in 1%-10% of patients with kidney transplants. Nowadays, antiviral effective treatment is unknown, which is why blood and urine screening of renal transplantation patients has become the most important recommendation to guide the decrease of immunosuppression, and the only proven method to decrease poor outcomes. Different interventions, such as cidofovir, leflunomide, fluoroquinolones, and intravenous immunoglobulin, have been attempted with no improvement at all. This review aims to summarize the most relevant features of BK virus, historical issues, transmission mechanisms, risk factors, and therapeutic interventions.

  6. Development of Energy Efficient, Multi-Channel, Pulsed Plasma Generator for High-Speed Flow Control by Localized Arc Filament Plasma Actuators Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The research team at The Ohio State University has been developing technologies to suppress jet noise using localized arc filament plasma actuators and are in the...

  7. Clearance of BK Virus Nephropathy by Combination Antiviral Therapy With Intravenous Immunoglobulin

    Science.gov (United States)

    Kable, Kathy; Davies, Carmen D.; O'connell, Philip J.; Chapman, Jeremy R.; Nankivell, Brian John

    2017-01-01

    Background Reactivation of BK polyoma virus causes a destructive virus allograft nephropathy (BKVAN) with graft loss in 46%. Treatment options are limited to reduced immunosuppression and largely ineffective antiviral agents. Some studies suggest benefit from intravenous immunoglobulin (IVIG). Methods We evaluated effectiveness of adjuvant IVIG to eliminate virus from blood and tissue, in a retrospective, single-center cohort study, against standard-of-care controls. Both groups underwent reduced immunosuppression; conversion of tacrolimus to cyclosporine; and mycophenolate to leflunomide, oral ciprofloxacin, and intravenous cidofovir. Results Biopsy-proven BKVAN occurred in 50 kidneys at 7 (median interquartile range, 3-12) months after transplantation, predominantly as histological stage B (92%), diagnosed following by dysfunction in 46%, screening viremia in 20%, and protocol biopsy in 34%. After treatment, mean viral loads fell from 1581 ± 4220 × 103 copies at diagnosis to 1434 ± 70 639 midtreatment, and 0.138 ± 0.331 after 3 months (P < 0.001). IVIG at 1.01 ± 0.18 g/kg was given to 22 (44%) patients. The IVIG group more effectively cleared viremia (hazard ratio, 3.68; 95% confidence interval, 1.56-8.68; P = 0.003) and BK immunohistochemistry from repeated tissue sampling (hazard ratio, 2.24; 95% confidence interval, 1.09-4.58; P = 0.028), and resulted in faster (11.3 ± 10.4 months vs 29.1 ± 31.8 months, P = 0.015) and more complete resolution of viremia (33.3% vs 77.3%, P = 0.044). Numerically, fewer graft losses occurred with IVIG (27.3% vs 53.6% for control, P = 0.06), although graft and patient survivals were not statistically different. Acute renal dysfunction requiring pulse corticosteroid was common (59.1% vs 78.6%, P = 0.09), respectively, after immunosuppression reduction. Conclusions Combination treatment incorporating adjuvant IVIG was more effective eliminating virus from BKVAN, compared with conventional therapy. Validation by multicenter

  8. Temporal and spatial mouse brain expression of cereblon, an ionic channel regulator involved in human intelligence.

    Science.gov (United States)

    Higgins, Joseph J; Tal, Adit L; Sun, Xiaowei; Hauck, Stefanie C R; Hao, Jin; Kosofosky, Barry E; Rajadhyaksha, Anjali M

    2010-03-01

    A mild form of autosomal recessive, nonsyndromal intellectual disability (ARNSID) in humans is caused by a homozygous nonsense mutation in the cereblon gene (mutCRBN). Rodent crbn protein binds to the intracellular C-terminus of the large conductance Ca(2+)-activated K(+)channel (BK(Ca)). An mRNA variant (human SITE 2 INSERT or mouse strex) of the BK(Ca) gene (KCNMA1) that is normally expressed during embryonic development is aberrantly expressed in mutCRBN human lymphoblastoid cell lines (LCLs) as compared to wild-type (wt) LCLs. The present study analyzes the temporal and spatial distribution of crbn and kcnma1 mRNAs in the mouse brain by the quantitative real-time reverse transcriptase-polymerase chain reaction (qPCR). The spatial expression pattern of endogenous and exogenous crbn proteins is characterized by immunostaining. The results show that neocortical (CTX) crbn and kcnma1 mRNA expression increases from embryonic stages to adulthood. The strex mRNA variant is >3.5-fold higher in embryos and decreases rapidly postnatally. Mouse crbn mRNA is abundant in the cerebellum (CRBM), with less expression in the CTX, hippocampus (HC), and striatum (Str) in adult mice. The intracytoplasmic distribution of endogenous crbn protein in the mouse CRBM, CTX, HC, and Str is similar to the immunostaining pattern described previously for the BK(Ca) channel. Exogenous hemagglutinin (HA) epitope-tagged human wt- and mutCRBN proteins using cDNA transfection in HEK293T cell lines showed the same intracellular expression distribution as endogenous mouse crbn protein. The results suggest that mutCRBN may cause ARNSID by disrupting the developmental regulation of BK(Ca) in brain regions that are critical for memory and learning.

  9. NRA-2, a nicalin homolog, regulates neuronal death by controlling surface localization of toxic Caenorhabditis elegans DEG/ENaC channels.

    Science.gov (United States)

    Kamat, Shaunak; Yeola, Shrutika; Zhang, Wenying; Bianchi, Laura; Driscoll, Monica

    2014-04-25

    Hyperactivated DEG/ENaCs induce neuronal death through excessive cation influx and disruption of intracellular calcium homeostasis. Caenorhabditis elegans DEG/ENaC MEC-4 is hyperactivated by the (d) mutation and induces death of touch neurons. The analogous substitution in MEC-10 (MEC-10(d)) co-expressed in the same neurons is only mildly neurotoxic. We exploited the lower toxicity of MEC-10(d) to identify RNAi knockdowns that enhance neuronal death. We report here that knock-out of the C. elegans nicalin homolog NRA-2 enhances MEC-10(d)-induced neuronal death. Cell biological assays in C. elegans neurons show that NRA-2 controls the distribution of MEC-10(d) between the endoplasmic reticulum and the cell surface. Electrophysiological experiments in Xenopus oocytes support this notion and suggest that control of channel distribution by NRA-2 is dependent on the subunit composition. We propose that nicalin/NRA-2 functions in a quality control mechanism to retain mutant channels in the endoplasmic reticulum, influencing the extent of neuronal death. Mammalian nicalin may have a similar role in DEG/ENaC biology, therefore influencing pathological conditions like ischemia.

  10. NRA-2, a Nicalin Homolog, Regulates Neuronal Death by Controlling Surface Localization of Toxic Caenorhabditis elegans DEG/ENaC Channels*

    Science.gov (United States)

    Kamat, Shaunak; Yeola, Shrutika; Zhang, Wenying; Bianchi, Laura; Driscoll, Monica

    2014-01-01

    Hyperactivated DEG/ENaCs induce neuronal death through excessive cation influx and disruption of intracellular calcium homeostasis. Caenorhabditis elegans DEG/ENaC MEC-4 is hyperactivated by the (d) mutation and induces death of touch neurons. The analogous substitution in MEC-10 (MEC-10(d)) co-expressed in the same neurons is only mildly neurotoxic. We exploited the lower toxicity of MEC-10(d) to identify RNAi knockdowns that enhance neuronal death. We report here that knock-out of the C. elegans nicalin homolog NRA-2 enhances MEC-10(d)-induced neuronal death. Cell biological assays in C. elegans neurons show that NRA-2 controls the distribution of MEC-10(d) between the endoplasmic reticulum and the cell surface. Electrophysiological experiments in Xenopus oocytes support this notion and suggest that control of channel distribution by NRA-2 is dependent on the subunit composition. We propose that nicalin/NRA-2 functions in a quality control mechanism to retain mutant channels in the endoplasmic reticulum, influencing the extent of neuronal death. Mammalian nicalin may have a similar role in DEG/ENaC biology, therefore influencing pathological conditions like ischemia. PMID:24567339

  11. Precise localization of the voltage-gated potassium channel subunits Kv3.1b and Kv3.3 revealed in the molecular layer of the rat cerebellar cortex by a pre-embedding immunogold method.

    Science.gov (United States)

    Puente, Nagore; Mendizabal-Zubiaga, Juan; Elezgarai, Izaskun; Reguero, Leire; Buceta, Ianire; Grandes, Pedro

    2010-10-01

    A proper motor activity relies on a correct cerebellar function. The Kv3.1 and Kv3.3 voltage-gated potassium channels are key proteins involved in cerebellar function and dysfunction, as the lack of these causes severe motor deficits. Both channel subunits are coexpressed in granule cells and are rapidly activated at relatively positive potentials to support the generation of fast action potentials. However, the contribution of each subunit to the molecular architecture of the parallel fibers, the granule cell axons, is so far unknown. The goal of this study was to elucidate the relative distribution of Kv3.1b and Kv3.3 in specific compartments of the rat parallel fibers by using a pre-embedding immunocytochemical method for electron microscopy. Numerous Kv3.1b and Kv3.3 silver-intensified gold particles were associated with membranes of parallel fiber synaptic terminals and their intervaricose segments. Kv3.1b was found in about 85% of parallel fiber synaptic terminals and in about 47% of their intervaricose portions. However, only 28% of intervaricosities and 23% of parallel fiber presynaptic boutons were Kv3.3 immunopositive. The analysis also revealed that 54% of Purkinje cell dendritic spines localized Kv3.3. Although both potassium channel subunits share localization in the same presynaptic parallel fiber compartments, the present results with the method used indicate that there are a higher percentage of parallel fibers labeled for Kv3.1b than for Kv3.3, and that the labeling intensity for each subunit is higher in specific subcompartments analyzed than in others.

  12. Ultra-precision ductile grinding of BK7 using super abrasive diamond wheel

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qingliang; Brinksmeier Ekkard; Riemer Oltmann; Rickens Kai

    2007-01-01

    In this paper,a novel conditioning technique using copper bonded diamond grinding wheels of 91 μm grain size and electrolytic in-process dressing (ELID) is first developed to precisely and effectively condition a nickelelectroplated monolayer coarse-grained diamond grinding wheel of 151 μm grain size.Under optimised conditioning parameters,the super abrasive diamond wheel was well conditioned in terms of a minimized run-out error and flattened diamond grain surfaces of constant peripheral envelope.The conditioning force was monitored by a force transducer,while the modified wheel surface status was in-situ monitored by a coaxial optical distance measurement system.Finally,the grinding experiment on BK7 was conducted using the well-conditioned wheel with the corresponding surface morphology and subsurface damage measured by atomic force microscope (AFM) and scanning electric microscope (SEM),respectively.The experimental result shows that the newly developed conditioning technique is applicable and feasible to ductile grinding optical glass featuring nano scale surface roughness,indicating the potential of super abrasive diamond wheels in ductile machining brittle materials.

  13. BK polyomavirus reactivation after reduced-intensity double umbilical cord blood cell transplantation.

    Science.gov (United States)

    Satyanarayana, Gowri; Hammond, Sarah P; Broge, Thomas A; Mackenzie, Matthew R; Viscidi, Raphael; Politikos, Ioannis; Koralnik, Igor J; Cutler, Corey S; Ballen, Karen; Boussiotis, Vassiliki; Marty, Francisco M; Tan, Chen Sabrina

    2015-03-01

    Serial serum samples from 27 patients who underwent double umbilical cord blood transplantation (dUCBT) were analyzed for BK polyomavirus (BKPyV) DNA by real-time PCR and BKPyV-specific immune globulin by ELISA. Clinical data were collected on all patients. All pre-transplant sera had detectable anti-BKPyV IgG. Fifteen patients (56%) had detectable serum BKPyV DNA (median 8.9 × 10(4) copies/ml; range 4.1 × 10(3)-7.9 × 10(6) copies/ml) a median of 40 days (range, 27-733 days) after dUCBT, with highest viral loads on Day 100 assessment. The cumulative probability of developing BKPyV viremia by Day 100 was 0.52 (95% CI, 0.33-0.71). Six of 15 patients with BKPyV viremia experienced hemorrhagic cystitis by Day 100. By Day 100, there was a trend towards higher BKPyV viral loads in sera of patients with hemorrhagic cystitis than in those BKPyV viremic patients without hemorrhagic cystitis (p = 0.06). BKPyV viremia was associated with significantly higher anti-BKPyV IgM values at 6 months post-dUCBT (P = 0.003). BKPyV viremia occurs early after dUBCT and is associated with a detectable humoral immune response by 6 months post-dUBCT.

  14. Human BK Polyomavirus—The Potential for Head and Neck Malignancy and Disease

    Directory of Open Access Journals (Sweden)

    Raquel Burger-Calderon

    2015-07-01

    Full Text Available Members of the human Polyomaviridae family are ubiquitous and pathogenic among immune-compromised individuals. While only Merkel cell polyomavirus (MCPyV has conclusively been linked to human cancer, all members of the polyomavirus (PyV family encode the oncoprotein T antigen and may be potentially carcinogenic. Studies focusing on PyV pathogenesis in humans have become more abundant as the number of PyV family members and the list of associated diseases has expanded. BK polyomavirus (BKPyV in particular has emerged as a new opportunistic pathogen among HIV positive individuals, carrying harmful implications. Increasing evidence links BKPyV to HIV-associated salivary gland disease (HIVSGD. HIVSGD is associated with elevated risk of lymphoma formation and its prevalence has increased among HIV/AIDS patients. Determining the relationship between BKPyV, disease and tumorigenesis among immunosuppressed individuals is necessary and will allow for expanding effective anti-viral treatment and prevention options in the future.

  15. Impact of combined acute rejection on BK virus-associated nephropathy in kidney transplantation.

    Science.gov (United States)

    Kim, Yoon Jung; Jeong, Jong Cheol; Koo, Tai Yeon; Kwon, Hyuk Yong; Han, Miyeun; Jeon, Hee Jung; Ahn, Curie; Yang, Jaeseok

    2013-12-01

    BK virus-associated nephropathy (BKVAN) is one of the major causes of allograft dysfunction in kidney transplant (KT) patients. We compared BKVAN combined with acute rejection (BKVAN/AR) with BKVAN alone in KT patients. We retrospectively analyzed biopsy-proven BKVAN in KT patients from 2000 to 2011 at Seoul National University Hospital. Among 414 biopsies from 951 patients, biopsy-proven BKVAN was found in 14 patients. Nine patients had BKVAN alone, while 5 patients had both BKVAN and acute cellular rejection. BKVAN in the BKVAN alone group was detected later than in BKVAN/AR group (21.77 vs 6.39 months after transplantation, P=0.03). Serum creatinine at diagnosis was similar (2.09 vs 2.00 mg/dL). Histological grade was more advanced in the BKVAN/AR group (P=0.034). Serum load of BKV, dose of immunosuppressants, and tacrolimus level showed a higher tendency in the BKVAN alone group; however it was not statistically significant. After anti-rejection therapy, immunosuppression was reduced in the BKVAN/AR group. Renal functional deterioration over 1 yr after BKVAN diagnosis was similar between the two groups (P=0.665). These findings suggest that the prognosis of BKVAN/AR after anti-rejection therapy followed by anti-BKV therapy might be similar to that of BKVAN alone after anti-BKV therapy.

  16. Optimization, purification, and characterization of L-asparaginase from Actinomycetales bacterium BkSoiiA.

    Science.gov (United States)

    Dash, Chitrangada; Mohapatra, Sukanti Bala; Maiti, Prasanta Kumar

    2016-01-01

    Actinobacteria are promising source of a wide range of important enzymes, some of which are produced in industrial scale, with others yet to be harnessed. L-Asparaginase is used as an antineoplastic agent. The present work deals with the production and optimization of L-asparaginase from Actinomycetales bacterium BkSoiiA using submerged fermentation in M9 medium. Production optimization resulted in a modified M9 medium with yeast extract and fructose as carbon and nitrogen sources, respectively, at pH 8.0, incubated for 120 hr at 30 ± 2 °C. The crude enzyme was purified to near homogeneity by ammonium sulfate precipitation following dialysis, ion-exchange column chromatography, and finally gel filtration. The sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) revealed an apparent molecular weight of 57 kD. The enzyme was purified 95.06-fold and showed a final specific activity of 204.37 U/mg with 3.49% yield. The purified enzyme showed maximum activity at a pH 10.0 and was stable at pH 7.0 to 9.0. The enzyme was activated by Mn(2+) and strongly inhibited by Ba(2+). All these preliminary characterization suggests that the L-asparaginase from the source may be a tool useful to pharmaceutical industries after further research.

  17. Characterization of Immunodominant BK Polyomavirus 9mer Epitope T Cell Responses

    Science.gov (United States)

    Cioni, M.; Leboeuf, C.; Comoli, P.; Ginevri, F.

    2016-01-01

    Uncontrolled BK polyomavirus (BKPyV) replication in kidney transplant recipients (KTRs) causes polyomavirus‐associated nephropathy and allograft loss. Reducing immunosuppression is associated with clearing viremia and nephropathy and increasing BKPyV‐specific T cell responses in most patients; however, current immunoassays have limited sensitivity, target mostly CD4+ T cells, and largely fail to predict onset and clearance of BKPyV replication. To characterize BKPyV‐specific CD8+ T cells, bioinformatics were used to predict 9mer epitopes in the early viral gene region (EVGR) presented by 14 common HLAs in Europe and North America. Thirty‐nine EVGR epitopes were experimentally confirmed by interferon‐γ enzyme‐linked immunospot assays in at least 30% of BKPyV IgG–seropositive healthy participants. Most 9mers clustered in domains, and some were presented by more than one HLA class I, as typically seen for immunodominant epitopes. Specific T cell binding using MHC class I streptamers was demonstrated for 21 of 39 (54%) epitopes. In a prospective cohort of 118 pediatric KTRs, 19 patients protected or recovering from BKPyV viremia were experimentally tested, and 13 epitopes were validated. Single HLA mismatches were not associated with viremia, suggesting that failing immune control likely involves multiple factors including maintenance immunosuppression. Combining BKPyV load and T cell assays using immunodominant epitopes may help in evaluating risk and reducing immunosuppression and may lead to safe adoptive T cell transfer. PMID:26663765

  18. Carbon monoxide: an emerging regulator of ion channels.

    Science.gov (United States)

    Wilkinson, William J; Kemp, Paul J

    2011-07-01

    Carbon monoxide is rapidly emerging as an important cellular messenger, regulating a wide range of physiological processes. Crucial to its role in both physiology and disease is its ability differentially to regulate several classes of ion channels, including examples from calcium-activated K(+) (BK(Ca)), voltage-activated K(+) (K(v)) and Ca(2+) channel (L-type) families, ligand-gated P2X receptors (P2X2 and P2X4), tandem P domain K(+) channels (TREK1) and the epithelial Na(+) channel (ENaC). The mechanisms by which CO regulates these ion channels are still unclear and remain somewhat controversial. However, available structure-function studies suggest that a limited range of amino acid residues confer CO sensitivity, either directly or indirectly, to particular ion channels and that cellular redox state appears to be important to the final integrated response. Whatever the molecular mechanism by which CO regulates ion channels, endogenous production of this gasotransmitter has physiologically important roles and is currently being explored as a potential therapeutic.

  19. 结合Gabor纹理特征的局域化多通道水平集分割方法%Localized Multi-Channel Level Set Segmentation Combined with Gabor Texture Feature

    Institute of Scientific and Technical Information of China (English)

    张立和; 朱莉莉; 米晓莉

    2011-01-01

    本文提出了一种局域化多通道主动轮廓模型的图像分割算法.针对纹理特征比较明显的图像,通过Gabor滤波提取纹理特征,与图像灰度信息构成多通道.考虑到演化过程中曲线内部和外部特征属性不均匀,引入局域化思想,通过计算各像素在局部区域的最小能量得到图像分割结果.最后算法结合先验形状对有遮挡目标进行分割,并能得到理想结果.大量实验验证了该方法具有良好的分割性能,优于同类算法.%An new algorithm based on localized Multi-Channel active contour model is proposed for image segmentation. For the images with obvious texture, Gabor texture features ate constituted multiple channels of active contour model together with image intensity information. Considering that intensity and texture characteristics are inconsistent in the interior and exterior of the evolution curve, localized energy idea is introduced, the minimum energy is calculated in the specific local area around each pixel on the evolution curve. Our model combined with the shape prior is used to segment the shadowed objects. The proposed algorithm is exemplified on various images objects and its superiority over state of the art variations] segmentation techniques is demonstrated.

  20. The effects of some carbamate local anaesthetics on the guinea-pig ileum.

    Science.gov (United States)

    Bezeková, M; Bauer, V

    1986-01-01

    The action of some carbamate local anaesthetics, pentacaine, BK-52 and heptacaine, was compared in the guinea-pig ileum with that of classic local anaesthetics, procaine and trimecaine. Contractions of the ileum were evoked by transmural stimulation, nicotine, acetylcholine, noradrenaline, histamine, K+ and Ba++. Although the evoked contractions were inhibited by all the local anaesthetics, there was a marked difference in their ability to influence the smooth muscle activation induced by different stimuli. The differences among the IC50 values were slight in the case of pentacaine, moderate in the case of trimecaine and BK-52 and large in the case of procaine and heptacaine. It is suggested that besides their effects on the unmyelinated autonomic nerves, the carbamate local anaesthetics studied can also affect the smooth muscle membrane, similarly to the classic agents. The mechanism of their direct effect is discussed.

  1. Cell Cycle-dependent Changes in Localization and Phosphorylation of the Plasma Membrane Kv2.1 K+ Channel Impact Endoplasmic Reticulum Membrane Contact Sites in COS-1 Cells.

    Science.gov (United States)

    Cobb, Melanie M; Austin, Daniel C; Sack, Jon T; Trimmer, James S

    2015-12-04

    The plasma membrane (PM) comprises distinct subcellular domains with diverse functions that need to be dynamically coordinated with intracellular events, one of the most impactful being mitosis. The Kv2.1 voltage-gated potassium channel is conditionally localized to large PM clusters that represent specialized PM:endoplasmic reticulum membrane contact sites (PM:ER MCS), and overexpression of Kv2.1 induces more exuberant PM:ER MCS in neurons and in certain heterologous cell types. Localization of Kv2.1 at these contact sites is dynamically regulated by changes in phosphorylation at one or more sites located on its large cytoplasmic C terminus. Here, we show that Kv2.1 expressed in COS-1 cells undergoes dramatic cell cycle-dependent changes in its PM localization, having diffuse localization in interphase cells, and robust clustering during M phase. The mitosis-specific clusters of Kv2.1 are localized to PM:ER MCS, and M phase clustering of Kv2.1 induces more extensive PM:ER MCS. These cell cycle-dependent changes in Kv2.1 localization and the induction of PM:ER MCS are accompanied by increased mitotic Kv2.1 phosphorylation at several C-terminal phosphorylation sites. Phosphorylation of exogenously expressed Kv2.1 is significantly increased upon metaphase arrest in COS-1 and CHO cells, and in a pancreatic β cell line that express endogenous Kv2.1. The M phase clustering of Kv2.1 at PM:ER MCS in COS-1 cells requires the same C-terminal targeting motif needed for conditional Kv2.1 clustering in neurons. The cell cycle-dependent changes in localization and phosphorylation of Kv2.1 were not accompanied by changes in the electrophysiological properties of Kv2.1 expressed in CHO cells. Together, these results provide novel insights into the cell cycle-dependent changes in PM protein localization and phosphorylation.

  2. A simultaneous liver-kidney transplant recipient with IgA nephropathy limited to native kidneys and BK virus nephropathy limited to the transplant kidney.

    Science.gov (United States)

    Ujire, Manasa P; Curry, Michael P; Stillman, Isaac E; Hanto, Douglas W; Mandelbrot, Didier A

    2013-08-01

    Immunoglobulin A (IgA) deposition in the native kidneys of patients with liver disease is well described. Secondary IgA nephropathy usually is thought to be benign, but hematuria, proteinuria, and loss of kidney function have been reported in this context. BK virus nephropathy is an important cause of kidney transplant loss; however, BK virus nephropathy is rare in the native kidneys of patients who underwent transplantation of other organs. We report the case of a patient with alcohol-related end-stage liver disease and chronic kidney disease with hematuria who underwent simultaneous liver-kidney transplantation. His kidney function decreased over the course of several weeks posttransplantation. Biopsy of the transplant kidney showed BK virus nephropathy, but no IgA deposits. In contrast, biopsy of the native kidneys showed IgA deposits, but no BK virus nephropathy. To our knowledge, this is the first reported case of a simultaneous liver-kidney transplantation wherein both the native and transplant kidneys were biopsied posttransplantation and showed exclusively different pathologies. These findings confirm the predilection of BK virus nephropathy for transplant rather than native kidneys.

  3. MEMS in microfluidic channels.

    Energy Technology Data Exchange (ETDEWEB)

    Ashby, Carol Iris Hill; Okandan, Murat; Michalske, Terry A.; Sounart, Thomas L.; Matzke, Carolyn M.

    2004-03-01

    Microelectromechanical systems (MEMS) comprise a new class of devices that include various forms of sensors and actuators. Recent studies have shown that microscale cantilever structures are able to detect a wide range of chemicals, biomolecules or even single bacterial cells. In this approach, cantilever deflection replaces optical fluorescence detection thereby eliminating complex chemical tagging steps that are difficult to achieve with chip-based architectures. A key challenge to utilizing this new detection scheme is the incorporation of functionalized MEMS structures within complex microfluidic channel architectures. The ability to accomplish this integration is currently limited by the processing approaches used to seal lids on pre-etched microfluidic channels. This report describes Sandia's first construction of MEMS instrumented microfluidic chips, which were fabricated by combining our leading capabilities in MEMS processing with our low-temperature photolithographic method for fabricating microfluidic channels. We have explored in-situ cantilevers and other similar passive MEMS devices as a new approach to directly sense fluid transport, and have successfully monitored local flow rates and viscosities within microfluidic channels. Actuated MEMS structures have also been incorporated into microfluidic channels, and the electrical requirements for actuation in liquids have been quantified with an elegant theory. Electrostatic actuation in water has been accomplished, and a novel technique for monitoring local electrical conductivities has been invented.

  4. Conserved archetypal configuration of the transcriptional control region during the course of BK polyomavirus evolution.

    Science.gov (United States)

    Yogo, Yoshiaki; Zhong, Shan; Xu, Yawei; Zhu, Mengyun; Chao, Yuegen; Sugimoto, Chie; Ikegaya, Hiroshi; Shibuya, Ayako; Kitamura, Tadaichi

    2008-08-01

    BK polyomavirus (BKV) is widespread among humans, asymptomatically infecting children and then persisting in renal tissue. The transcriptional control region (TCR) of the BKV genome is variable among clinical isolates. Thus, archetypal TCRs with a common basic configuration generally occur in BKV isolates from the urine of immunocompromised patients, but rearranged TCRs that possibly arise from the archetypal configuration have also been detected in clinical specimens. To examine the hypothesis that archetypal strains represent wild-type strains circulating in the human population (the archetype hypothesis), we analysed 145 complete viral genomes amplified directly from the urine of non-immunocompromised individuals worldwide. These genomes included 82, three, two and 58 sequences classified as belonging to subtypes I, II, III and IV, respectively. Rearranged TCRs with long duplications or deletions were detected from two subtype I and two subtype IV genomes, but not from the other 141 genomes (thus, the TCRs of these genomes were judged to be archetypal). The variations in the archetypal TCRs were nucleotide substitutions and single-nucleotide deletions, most of which were unique to particular subtypes or subgroups. We confirmed that the four complete BKV genomes with rearranged TCRs did not form a unique lineage on a phylogenetic tree. Collectively, the findings demonstrate that the archetypal TCR configuration has been conserved during the evolution of BKV, providing support for the archetype hypothesis. Additionally, we suggest that 'archetype' should be used as a conceptual term that denotes a prototypical structure that can generate various rearranged TCRs during viral growth in vivo and in vitro.

  5. Geometric pumping in autophoretic channels

    CERN Document Server

    Michelin, Sebastien; De Canio, Gabriele; Lobato-Dauzier, Nicolas; Lauga, Eric

    2015-01-01

    Many microfluidic devices use macroscopic pressure differentials to overcome viscous friction and generate flows in microchannels. In this work, we investigate how the chemical and geometric properties of the channel walls can drive a net flow by exploiting the autophoretic slip flows induced along active walls by local concentration gradients of a solute species. We show that chemical patterning of the wall is not required to generate and control a net flux within the channel, rather channel geometry alone is sufficient. Using numerical simulations, we determine how geometric characteristics of the wall influence channel flow rate, and confirm our results analytically in the asymptotic limit of lubrication theory.

  6. Fracture channel waves

    Science.gov (United States)

    Nihei, Kurt T.; Yi, Weidong; Myer, Larry R.; Cook, Neville G. W.; Schoenberg, Michael

    1999-03-01

    The properties of guided waves which propagate between two parallel fractures are examined. Plane wave analysis is used to obtain a dispersion equation for the velocities of fracture channel waves. Analysis of this equation demonstrates that parallel fractures form an elastic waveguide that supports two symmetric and two antisymmetric dispersive Rayleigh channel waves, each with particle motions and velocities that are sensitive to the normal and tangential stiffnesses of the fractures. These fracture channel waves degenerate to shear waves when the fracture stiffnesses are large, to Rayleigh waves and Rayleigh-Lamb plate waves when the fracture stiffnesses are low, and to fracture interface waves when the fractures are either very closely spaced or widely separated. For intermediate fracture stiffnesses typical of fractured rock masses, fracture channel waves are dispersive and exhibit moderate to strong localization of guided wave energy between the fractures. The existence of these waves is examined using laboratory acoustic measurements on a fractured marble plate. This experiment confirms the distinct particle motion of the fundamental antisymmetric fracture channel wave (A0 mode) and demonstrates the ease with which a fracture channel wave can be generated and detected.

  7. Drosophila TRPA1 channel is required to avoid the naturally occurring insect repellent citronellal.

    Science.gov (United States)

    Kwon, Young; Kim, Sang Hoon; Ronderos, David S; Lee, Youngseok; Akitake, Bradley; Woodward, Owen M; Guggino, William B; Smith, Dean P; Montell, Craig

    2010-09-28

    Plants produce insect repellents, such as citronellal, which is the main component of citronellal oil. However, the molecular pathways through which insects sense botanical repellents are unknown. Here, we show that Drosophila use two pathways for direct avoidance of citronellal. The olfactory coreceptor OR83b contributes to citronellal repulsion and is essential for citronellal-evoked action potentials. Mutations affecting the Ca(2+)-permeable cation channel TRPA1 result in a comparable defect in avoiding citronellal vapor. The TRPA1-dependent aversion to citronellal relies on a G protein (Gq)/phospholipase C (PLC) signaling cascade rather than direct detection of citronellal by TRPA1. Loss of TRPA1, Gq, or PLC causes an increase in the frequency of citronellal-evoked action potentials in olfactory receptor neurons. Absence of the Ca(2+)-activated K(+) channel (BK channel) Slowpoke results in a similar impairment in citronellal avoidance and an increase in the frequency of action potentials. These results suggest that TRPA1 is required for activation of a BK channel to modulate citronellal-evoked action potentials and for aversion to citronellal. In contrast to Drosophila TRPA1, Anopheles gambiae TRPA1 is directly and potently activated by citronellal, thereby raising the possibility that mosquito TRPA1 may be a target for developing improved repellents to reduce insect-borne diseases such as malaria.

  8. Pharmacodynamics of potassium channel openers in cultured neuronal networks.

    Science.gov (United States)

    Wu, Calvin; V Gopal, Kamakshi; Lukas, Thomas J; Gross, Guenter W; Moore, Ernest J

    2014-06-01

    A novel class of drugs - potassium (K(+)) channel openers or activators - has recently been shown to cause anticonvulsive and neuroprotective effects by activating hyperpolarizing K(+) currents, and therefore, may show efficacy for treating tinnitus. This study presents measurements of the modulatory effects of four K(+) channel openers on the spontaneous activity and action potential waveforms of neuronal networks. The networks were derived from mouse embryonic auditory cortices and grown on microelectrode arrays. Pentylenetetrazol was used to create hyperactivity states in the neuronal networks as a first approximation for mimicking tinnitus or tinnitus-like activity. We then compared the pharmacodynamics of the four channel activators, retigabine and flupirtine (voltage-gated K(+) channel KV7 activators), NS1619 and isopimaric acid ("big potassium" BK channel activators). The EC50 of retigabine, flupirtine, NS1619, and isopimaric acid were 8.0, 4.0, 5.8, and 7.8µM, respectively. The reduction of hyperactivity compared to the reference activity was significant. The present results highlight the notion of re-purposing the K(+) channel activators for reducing hyperactivity of spontaneously active auditory networks, serving as a platform for these drugs to show efficacy toward target identification, prevention, as well as treatment of tinnitus.

  9. Isospin Symmetry Breaking in B->K^* \\gamma Decay due to an Extra Generation of Vector Quarks

    CERN Document Server

    Ahmady, M R; Ahmady, Mohammad R.; Chishtie, Farrukh

    2005-01-01

    The extra contributions due to an extra generation of vector-like quarks to the isospin symmetry breaking observable associated with the radiative B->K^* \\gamma decay is obtained. It is shown that this additional contribution is sensitive to the nonunitarity parameter U^{sb}, which is a measure of the the strength of the non-zero tree-level flavor changing neutral current in this model. The significance of this result is that, once accurate experimental resultson the isospin asymmetry becomes available, one can constrain the U^{sb} independent of the mass of the extra quarks and so a much more stringent acceptablemodel parameter space could be obtained.

  10. Mechanosensitive Channels

    Science.gov (United States)

    Martinac, Boris

    Living cells are exposed to a variety of mechanical stimuli acting throughout the biosphere. The range of the stimuli extends from thermal molecular agitation to potentially destructive cell swelling caused by osmotic pressure gradients. Cellular membranes present a major target for these stimuli. To detect mechanical forces acting upon them cell membranes are equipped with mechanosensitive (MS) ion channels. Functioning as molecular mechanoelectrical transducers of mechanical forces into electrical and/or chemical intracellular signals these channels play a critical role in the physiology of mechanotransduction. Studies of prokaryotic MS channels and recent work on MS channels of eukaryotes have significantly increased our understanding of their gating mechanism, physiological functions, and evolutionary origins as well as their role in the pathology of disease.

  11. Semi-contact-writing of polymer molds for prototyping PDMS chips with low surface roughness, sharp edges and locally varying channel heights

    Science.gov (United States)

    Gutzweiler, Ludwig; Stumpf, Fabian; Tanguy, Laurent; Roth, Guenter; Koltay, Peter; Zengerle, Roland; Riegger, Lutz

    2016-04-01

    Microfluidic systems fabricated in polydimethylsiloxane (PDMS) enable a broad variety of applications and are widespread in the field of Lab-on-a-Chip. Here we demonstrate semi-contact-writing, a novel method for fabrication of polymer based molds for casting microfluidic PDMS chips in a highly flexible, time and cost-efficient manner. The method is related to direct-writing of an aqueous polymer solution on a planar glass substrate and substitutes conventional, time- and cost-consuming UV-lithography. This technique facilitates on-demand prototyping in a low-cost manner and is therefore ideally suited for rapid chip layout iterations. No cleanroom facilities and less expertise are required. Fabrication time from scratch to ready-to-use PDMS-chip is less than 5 h. This polymer writing method enables structure widths down to 140 μm and controllable structure heights ranging from 5.5 μm for writing single layers up to 98 μm by stacking. As a unique property, freely selectable height variations across a substrate can be achieved by application of local stacking. Furthermore, the molds exhibit low surface roughness (R a   =  24 nm, R RMS  =  28 nm) and high fidelity edge sharpness. We validated the method by fabrication of molds to cast PDMS chips for droplet based flow-through PCR with single-cell sensitivity.

  12. Influence of salinity on the localization and expression of the CFTR chloride channel in the ionocytes of Dicentrarchus labrax during ontogeny.

    Science.gov (United States)

    Bodinier, Charlotte; Boulo, Viviane; Lorin-Nebel, Catherine; Charmantier, Guy

    2009-03-01

    The expression and localization of the cystic fibrosis transmembrane conductance regulator (CFTR) were determined in four osmoregulatory tissues during the ontogeny of the sea-bass Dicentrarchus labrax acclimated to fresh water and sea water. At hatch in sea water, immunolocalization showed an apical CFTR in the digestive tract and integumental ionocytes. During the ontogeny, although CFTR was consistently detected in the digestive tract, it shifted from the integument to the gills. In fresh water, CFTR was not present in the integument and the gills, suggesting the absence of chloride secretion. In the kidney, the CFTR expression was brief from D4 to D35, prior to the larva-juvenile transition. CFTR was apical in the renal tubules, suggesting a chloride secretion at both salinities, and it was basolateral only in sea water in the collecting ducts, suggesting chloride absorption. In the posterior intestine, CFTR was located differently from D4 depending on salinity. In sea water, the basolateral CFTR may facilitate ionic absorption, perhaps in relation to water uptake. In fresh water, CFTR was apical in the gut, suggesting chloride secretion. Increased osmoregulatory ability was acquired just before metamorphosis, which is followed by the sea-lagoon migration.

  13. 肾移植术后BK病毒相关性肾病的研究现状%Study on BK virus-associated nephropathy after renal transplantation

    Institute of Scientific and Technical Information of China (English)

    肖荆; 田野

    2008-01-01

    BACKGROUND: BK viral infection after renal transplantation influences the prognosis of BK virus-associated nephropathy in renal transplant recipients. The disease has been widely studied in foreign countries.OBJECTIVE: This study was designed to sum up the diagnosis and treatment of BK virus-associated nephropathy after renal transplantation.RETRIVAL STRATEGY: Using the terms "renal transplantation; BK virus" in the English language, manuscripts responsible for BK virus-associated nephropathy after renal transplantation that were published from January 2000 to January 2007 were retrieved from the PubMed database. A total of 206 manuscripts were obtained and primarily screened. Inclusion criteria: studies addressing BK virus-associated nephropathy after renal transplantation. Exclusion criteria: repetitive studies.LITERATURE EVALUATION: The included manuscripts were primarily from PubMed database. Manuscripts were primarily original and review studies.DATA SYNTHESIS: BK virus can be found in the urine of 3%-40% of adult renal transplant recipients. BK virus reactivation rate is very high, but the histological manifestations of BK virus associated nephropathy are found only in a small number of renal transplant recipients. The prognosis of BK virus associated nephropathy is very poor. BK virus associated nephropathy develops into renal failure, leading to transplant loss, in 30%-50% patients. BK virus-caused renal transplant disease must be diagnosed according to histological manifestations. Viral infection should be primarily confirmed, but serological measurements have no predominant effects. Electron microscopy should be involved in the assessment of renal graft biopsy, especially when renal failure factors are unknown, as through the use of electron microscope, viral particles in the nucleus, cytoplasm and outside of the cells could be detectable. Viral antigen in the urine sample of patients with BK viruria can be detected by nucleic acid hybridization method

  14. The secretory KCa1.1 channel localises to crypts of distal mouse colon: functional and molecular evidence

    DEFF Research Database (Denmark)

    Sørensen, Mads Vaarby; Strandsby, Anne Bystrup; Larsen, Casper Kornbech;

    2011-01-01

    Na+ absorption is mediated by epithelial Na+ channel (ENaC) in surface cells. Previously, we identified the large conductance Ca2+-activated K+ channel, KCa1.1 or big potassium (BK) channel, as the only relevant K+ secretory pathway in mouse distal colon. The exact localisation of K(Ca)1.1 channels...... along the crypt axis is, however, still controversial. The aim of this project was to further define the localisation of the K(Ca)1.1 channel in mouse distal colonic epithelium. Through quantification of mRNA extracted from micro-dissected surface and crypt cells, we confirmed that Na+/K+/2Cl- (NKCC1......The colonic epithelium absorbs and secretes electrolytes and water. Ion and water absorption occurs primarily in surface cells, whereas crypt cells perform secretion. Ion transport in distal colon is regulated by aldosterone, which stimulates both Na+ absorption and K+ secretion. The electrogenic...

  15. The Berry-Keating Hamiltonian and the local Riemann hypothesis

    Science.gov (United States)

    Srednicki, Mark

    2011-07-01

    The local Riemann hypothesis states that the zeros of the Mellin transform of a harmonic-oscillator eigenfunction (on a real or p-adic configuration space) have a real part 1/2. For the real case, we show that the imaginary parts of these zeros are the eigenvalues of the Berry-Keating Hamiltonian \\hat{H}_BK=(\\hat{x}\\hat{p}+\\hat{p}\\hat{x})/2 projected onto the subspace of oscillator eigenfunctions of a lower level. This gives a spectral proof of the local Riemann hypothesis for the reals, in the spirit of the Hilbert-Pólya conjecture. The p-adic case is also discussed.

  16. Angioedema attacks in patients with hereditary angioedema: Local manifestations of a systemic activation process.

    Science.gov (United States)

    Hofman, Zonne L M; Relan, Anurag; Zeerleder, Sacha; Drouet, Christian; Zuraw, Bruce; Hack, C Erik

    2016-08-01

    Hereditary angioedema (HAE) caused by a deficiency of functional C1-inhibitor (C1INH) becomes clinically manifest as attacks of angioedema. C1INH is the main inhibitor of the contact system. Poor control of a local activation process of this system at the site of the attack is believed to lead to the formation of bradykinin (BK), which increases local vasopermeability and mediates angioedema on interaction with BK receptor 2 on the endothelium. However, several observations in patients with HAE are difficult to explain from a pathogenic model claiming a local activation process at the site of the angioedema attack. Therefore we postulate an alternative model for angioedema attacks in patients with HAE, which assumes a systemic, fluid-phase activation of the contact system to generate BK and its breakdown products. Interaction of these peptides with endothelial receptors that are locally expressed in the affected tissues rather than with receptors constitutively expressed by the endothelium throughout the whole body explains that such a systemic activation process results in local manifestations of an attack. In particular, BK receptor 1, which is induced on the endothelium by inflammatory stimuli, such as kinins and cytokines, meets the specifications of the involved receptor. The pathogenic model discussed here also provides an explanation for why angioedema can occur at multiple sites during an attack and why HAE attacks respond well to modest increases of circulating C1INH activity levels because inhibition of fluid-phase Factor XIIa and kallikrein requires lower C1INH levels than inhibition of activator-bound factors.

  17. Littoral steering of deltaic channels

    Science.gov (United States)

    Nienhuis, Jaap H.; Ashton, Andrew D.; Giosan, Liviu

    2016-11-01

    The typically single-threaded channels on wave-influenced deltas show striking differences in their orientations, with some channels oriented into the incoming waves (e.g., Ombrone, Krishna), and others oriented away from the waves (e.g., Godavari, Sao Francisco). Understanding the controls on channel orientation is important as the channel location greatly influences deltaic morphology and sedimentology, both subaerially and subaqueously. Here, we explore channel orientation and consequent feedbacks with local shoreline dynamics using a plan-form numerical model of delta evolution. The model treats fluvial sediment delivery to a wave-dominated coast in two ways: 1) channels are assumed to prograde in a direction perpendicular to the local shoreline orientation and 2) a controlled fraction of littoral sediment transport can bypass the river mouth. Model results suggest that channels migrate downdrift when there is a significant net littoral transport and alongshore transport bypassing of the river mouth is limited. In contrast, river channels tend to orient themselves into the waves when fluvial sediment flux is relatively large, causing the shoreline of the downdrift delta flank to attain the orientation of maximum potential sediment transport for the incoming wave climate. Using model results, we develop a framework to estimate channel orientations for wave-influenced deltas that shows good agreement with natural examples. An increase in fluvial sediment input can cause a channel to reorient itself into incoming waves, behavior observed, for example, in the Ombrone delta in Italy. Our results can inform paleoclimate studies by linking channel orientation to fluvial sediment flux and wave energy. In particular, our approach provides a means to quantify past wave directions, which are notoriously difficult to constrain.

  18. Simultaneous pancreas and kidney transplantation with concurrent allograft nephrectomy for recipients with prior renal transplants lost to BK virus nephropathy: two case reports.

    Science.gov (United States)

    Kubal, S; Powelson, J A; Taber, T E; Goble, M L; Fridell, J A

    2010-01-01

    Candidacy for retransplantation after allograft loss due to BK virus-associated nephropathy (BKVN) with or without allograft nephrectomy is controversial. This report describes 2 renal transplant recipients who lost their grafts to BKVN and subsequently underwent simultaneous kidney and pancreas transplantation with allograft nephrectomy.

  19. New Results for Elements 115, 117, and 118 Produced in the Reactions 243Am+48Ca and 249BK/249Cf+48Ca

    Science.gov (United States)

    Utyonkov, V. K.; Oganessian, Yu. Ts.; Abdullin, F. Sh.; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Voinov, A. A.; Vostokin, G. K.

    2014-09-01

    The reactions of 243Am and 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of elements 113, 115, and 117. Three isotopes 287-289115 were synthesized in the 243Am+48Ca reactions at five projectile energies, providing excitation functions and α-decay spectra of the produced isotopes. Decay properties of 287,288115 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time. The new 289115 events demonstrate the same decay properties as those observed for 289115 populated by a decay of 293117 produced in the 249Bk+48Ca reaction to provide cross-bombardment evidence. Results of recent experiments at the Dubna gas-filled recoil separator aimed at studying production crosssections, excitation functions, and nuclear decay properties for isotopes 293,294117 synthesized in the 249Bk+48Ca reaction at five projectile energies are presented. In addition, a single decay of 294118 was observed from the reaction with 249Cf - a result of the in-growth of 249Cf in the 249Bk target.

  20. Relationship between clinical and BK virological response in patients with late hemorrhagic cystitis treated with cidofovir: a retrospective study from the European Group for Blood and Marrow Transplantation.

    Science.gov (United States)

    Cesaro, S; Pillon, M; Tridello, G; Aljurf, M; Martino, R; Schroyens, W; Nozzoli, C; Barba, P; Faraci, M; Fagioli, F; Cappelli, B; Cordonnier, C; Al-Mohareb, F; Floisand, Y; Greil, J; Panizzolo, I S; Santarone, S

    2013-06-01

    To investigate the relationship between clinical response and modification of BK viremia, we assessed retrospectively 32 cases of hemorrhagic cystitis (HC) after allogeneic hematopoietic SCT that were treated with i.v. cidofovir (CDV). They were 22 men (69%) and 10 women (31%) with a median age of 24 years, range 3-62. The median number of CDV doses was 3, range 1-8, and the treatment lasted for a median of 3 weeks, range 1-10. Clinical improvement of HC was observed in 27 patients (84%). In 12 of 32 episodes (37.5%), BK viremia was determined before every CDV administration and a complete clinical response was observed in 10 of 12 patients (83%), the reduction of BK viremia load being 1 log by 2 weeks after starting CDV. Nephrotoxicity related to CDV was observed in nine patients. Among 26 patients with 100-day follow-up, 4 of 4 patients who had a complete clinical response by 30 days were alive vs 16 of 22 (73%) who did not have the resolution of HC in this time frame. We conclude that in patients with HC, the response to CDV treatment is usually associated with a significant reduction of BK viremia load.

  1. Brands & Channels

    Institute of Scientific and Technical Information of China (English)

    Alice Yang

    2009-01-01

    @@ "Brands" and "Channels" are the two most important things in Ku-Hai Chen's eyes when doing business with Main-land China. Ku-Hai Chen, Executive Director of the International Trade Institute of Taiwan External Trade Development Council (TAITRA), flies frequently between Chinese Taipei and Mainland China, and was in Beijing earlier this month for his seminar.

  2. Positron Channeling

    CERN Document Server

    Badikyan, Karen

    2016-01-01

    The possibility of channeling the low-energy relativistic positrons around separate crystallographic axes with coaxial symmetry of negative ions in some types of crystals is shown. The process of annihilation of positrons with electrons of medium was studied in detail.

  3. Quantum channel capacities - multiparty communication

    CERN Document Server

    Demianowicz, M; Demianowicz, Maciej; Horodecki, Pawel

    2006-01-01

    We analyze different aspects of multiparty communication over quantum memoryless channels and generalize some of key results known from bipartite channels to that of multiparty scenario. In particular, we introduce multiparty versions of minimal subspace transmission fidelity and entanglement transmission fidelity. We also provide alternative, local, versions of fidelities and show their equivalence to the global ones in context of capacity regions defined. The equivalence of two different capacity notions with respect to two types of the fidelities is proven. In analogy to bipartite case it is shown, via sufficiency of isometric encoding theorem, that additional classical forward side channel does not increase capacity region of any quantum channel with $k$ senders and $m$ receivers which represents a compact unit of general quantum networks theory. The result proves that recently provided capacity region of multiple access channel ([M. Horodecki et al, Nature {\\bf 436} 673 (2005)], [J.Yard et al, quant-ph/0...

  4. 铜离子交换单步掩埋BK7玻璃波导的制备与表征%Characterization of Single Step Buried Waveguides on BK7 Glass by Copper Ion Exchange

    Institute of Scientific and Technical Information of China (English)

    王鹏飞; 郑杰; 鄂书林; G.C.Righini

    2004-01-01

    利用Cu离子交换技术制备了BK7玻璃平面光波导,在632.8 nm波长下,用棱镜耦合技术测量出所制备波导的有效折射率,利用反WKB方法计算并确定了平面光波导的折射率分布,通过对折射率分布进行函数拟合,发现离子交换后的样品折射率分布近似符合改进后的高斯分布,样品的折射率分布似乎是一个掩埋波导的折射率分布,求出所制备玻璃平面光波导在570℃的扩散系数De≈1.2133×10-14m2/s.同时,对所制备波导进行了电子显微镜(EMS)和次级离子质谱(SIMS)测试,得到了铜离子在玻璃表面的浓度分布,从而证明了实验所得到的BK7玻璃平面光波导是掩埋波导.这种掩埋平面波导是由单步Cu离子交换技术得到的.

  5. 江苏卫视高清频道本地上星平台设计和运行%Jiangsu Satelite TV HD Channel Local Broadcasting Platform’SDesign and Operation

    Institute of Scientific and Technical Information of China (English)

    李嘉; 胡振光

    2016-01-01

    With the realization of remote encryption technology,Consider the economy and security,The JiangSu Broadcasting Corporation decided that the Jiangsu satellite channel in local broadcast. They design and construction to the principle of safety and practical innovation.The Project contains Broadcast system、Operation supervision system、P& E Supervision System and Visual system for operation and maintenance management.%随着远程加密技术得以解决,江苏省广播电视台从经济和安全性等方面考虑,决定江苏卫视高清频道转为本地上星,并开展了高清频道上星平台的项目设计施工。项目设计施工以安全、实用、创新为基本原则,分别开展播出系统、上星运行监管系统、机房及环境保障系统、运维可视化等分系统的建设。

  6. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key compon

  7. Transcriptome analysis of the role of GlnD/GlnBK in nitrogen stress adaptation by Sinorhizobium meliloti Rm1021.

    Directory of Open Access Journals (Sweden)

    Svetlana N Yurgel

    Full Text Available Transcriptional changes in the nitrogen stress response (NSR of wild type S. meliloti Rm1021, and isogenic strains missing both PII proteins, GlnB and GlnK, or carrying a ΔglnD-sm2 mutation were analyzed using whole-genome microarrays. This approach allowed us to identify a number of new genes involved in the NSR and showed that the response of these bacteria to nitrogen stress overlaps with other stress responses, including induction of the fixK2 transcriptional activator and genes that are part of the phosphate stress response. Our data also show that GlnD and GlnBK proteins may regulate many genes that are not part of the NSR. Analysis of transcriptome profiles of the Rm1021 ΔglnD-sm2 strain allowed us to identify several genes that appear to be regulated by GlnD without the participation of the PII proteins.

  8. Persistence of DNA sequences of BK virus and JC virus in normal human tissues and in diseased tissues.

    Science.gov (United States)

    Chesters, P M; Heritage, J; McCance, D J

    1983-04-01

    Available evidence suggests that BK virus (BKV) and JC virus (JCV) persist in the kidneys of healthy individuals after primary infection and may reactivate when the host's immune response is impaired. Data supporting this hypothesis are presented. A previous study had shown BKV to be present in the kidneys of eight (57%) of 14 subjects. In the present study, which extended the investigation to a total of 30 subjects, BKV DNA was found in the renal tissues of 10 (33%) subjects, and JCV DNA was found in the renal tissues of three (10%) subjects. The viral DNA detected appeared not to be integrated with host DNA and to be isolated in foci. Investigation of normal and diseased brain tissue, including tissue from six subjects with multiple sclerosis, failed to reveal the presence of either JCV DNA or BKV DNA.

  9. A comparison of HK-CONWIP and BK-CONWIP control strategies in a multi-product manufacturing system

    Directory of Open Access Journals (Sweden)

    Chukwunonyelum Emmanuel Onyeocha

    2015-12-01

    Full Text Available This paper evaluates the performance of the Hybrid Kanban Constant Work-In-Process control strategy and Basestock Kanban Constant Work-In-Process control strategy operating Shared Kanban Allocation Policy (S-KAP and Dedicated Kanban Allocation Policy (D-KAP in a multi-product serial flow line. We explored the effect of an increase of product types on the WIP inventory in the system. A simulation-based optimisation technique was used in determining the optimal settings for the strategies. The strategies were compared via pairwise comparison technique and Nelson’s ranking and selection procedure. S-KAP responds quicker to demand than D-KAP. BK-CONWIP outperforms HK-CONWIP in a serial manufacturing system. It was shown that an increase in the number of product-type increases the number of PAC and WIP inventory.

  10. Ion channels in inflammation.

    Science.gov (United States)

    Eisenhut, Michael; Wallace, Helen

    2011-04-01

    Most physical illness in vertebrates involves inflammation. Inflammation causes disease by fluid shifts across cell membranes and cell layers, changes in muscle function and generation of pain. These disease processes can be explained by changes in numbers or function of ion channels. Changes in ion channels have been detected in diarrhoeal illnesses, pyelonephritis, allergy, acute lung injury and systemic inflammatory response syndromes involving septic shock. The key role played by changes in ion transport is directly evident in inflammation-induced pain. Expression or function of all major categories of ion channels like sodium, chloride, calcium, potassium, transient receptor potential, purinergic receptor and acid-sensing ion channels can be influenced by cyto- and chemokines, prostaglandins, leukotrienes, histamine, ATP, reactive oxygen species and protons released in inflammation. Key pathways in this interaction are cyclic nucleotide, phosphoinositide and mitogen-activated protein kinase-mediated signalling, direct modification by reactive oxygen species like nitric oxide, ATP or protons and disruption of the cytoskeleton. Therapeutic interventions to modulate the adverse and overlapping effects of the numerous different inflammatory mediators on each ion transport system need to target adversely affected ion transport systems directly and locally.

  11. A fast BK-type KCa current acts as a postsynaptic modulator of temporal selectivity for communication signals

    Directory of Open Access Journals (Sweden)

    Tsunehiko eKohashi

    2014-09-01

    Full Text Available Temporal patterns of spiking often convey behaviorally relevant information. Various synaptic mechanisms and intrinsic membrane properties can influence neuronal selectivity to temporal patterns of input. However, little is known about how synaptic mechanisms and intrinsic properties together determine the temporal selectivity of neuronal output. We tackled this question by recording from midbrain electrosensory neurons in mormyrid fish, in which the processing of temporal intervals between communication signals can be studied in a reduced in vitro preparation. Mormyrids communicate by varying interpulse intervals (IPIs between electric pulses. Within the midbrain posterior exterolateral nucleus (ELp, the temporal patterns of afferent spike trains are filtered to establish single-neuron IPI tuning. We performed whole-cell recording from ELp neurons in a whole-brain preparation and examined the relationship between intrinsic excitability and IPI tuning. We found that spike frequency adaptation of ELp neurons was highly variable. Postsynaptic potentials (PSPs of strongly adapting (phasic neurons were more sharply tuned to IPIs than weakly adapting (tonic neurons. Further, the synaptic filtering of IPIs by tonic neurons was more faithfully converted into variation in spiking output, particularly at short IPIs. Pharmacological manipulation under current- and voltage-clamp revealed that tonic firing is mediated by a fast, large-conductance Ca2+-activated K+ (KCa current (BK that speeds up action potential repolarization. These results suggest that BK currents can shape the temporal filtering of sensory inputs by modifying both synaptic responses and PSP-to-spike conversion. Slow SK-type KCa currents have previously been implicated in temporal processing. Thus, both fast and slow KCa currents can fine-tune temporal selectivity.

  12. Nonlinear channelizer

    Science.gov (United States)

    In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio

    2012-12-01

    The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.

  13. 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.

  14. Shaker-type Kv1 channel blockers increase the peristaltic activity of guinea-pig ileum by stimulating acetylcholine and tachykinins release by the enteric nervous system.

    Science.gov (United States)

    Vianna-Jorge, Rosane; Oliveira, Cyntia F; Garcia, Maria L; Kaczorowski, Gregory J; Suarez-Kurtz, Guilherme

    2003-01-01

    1 A constant intraluminal pressure system was used to evaluate the effects of Kv1 channel blockers on the peristaltic activity of guinea-pig ileum. 2 The nortriterpene correolide, a non-selective inhibitor of all Kv1 sub-types, causes progressive and sustained reduction of the pressure threshold for eliciting peristaltic contractions. 3 Margatoxin (MgTX), alpha-dendrotoxin (alpha-DTX) and dendrotoxin-K (DTX-K), highly selective peptidyl inhibitors of certain Kv1 sub-types, cause immediate reduction of the pressure threshold. This effect subsides with time, irrespective of the peptides' concentration in the bath. In preparations pretreated with saturating concentrations of MgTX, correolide further stimulates the peristaltic activity. 4 Iberiotoxin (IbTX), a selective inhibitor of the high-conductance Ca(2+)-activated K(+) (BK) channels, and charybdotoxin (ChTX), which inhibits Kv1.2 and Kv1.3 as well as BK channels, fail to stimulate the peristaltic activity. 5 Blockade of muscarinic receptors by atropine reduces, and occasionally suppresses the peristaltic activity of guinea-pig ileum. In atropine-treated preparations, correolide and MgTX retain their abilities to reduce the pressure threshold and are able to restore the peristaltic reflex in the preparations where this reflex was suppressed by atropine. 6 The stimulatory effect of correolide and MgTX in atropine-treated preparations is abolished by subsequent addition of selective antagonists of both NK1 and NK2 receptors. 7 In conclusion, blockade of Kv1, particularly Kv1.1 channels, increases the peristaltic activity of guinea-pig ileum by enhancing the release of neurotransmitters at the enteric nervous system. In contrast, stimulation of the myogenic motility by blockade of BK channels does not affect the threshold for the peristaltic reflex.

  15. Analysis of the action of lidocaine on insect sodium channels

    OpenAIRE

    Song, Weizhong; Silver, Kristopher S.; Du, Yuzhe; Liu, Zhiqi; Dong, Ke

    2010-01-01

    A new class of sodium channel blocker insecticides (SCBIs), which include indoxacarb, its active metabolite, DCJW, and metaflumizone, preferably block inactivated states of both insect and mammalian sodium channels in a manner similar to that by which local anesthetic (LA) drugs block mammalian sodium channels. A recent study showed that two residues in the cockroach sodium channel, F1817 and Y1824, corresponding to two key LA-interacting residues identified in mammalian sodium channels are n...

  16. Regulation of Voltage-Activated K(+) Channel Gating by Transmembrane β Subunits.

    Science.gov (United States)

    Sun, Xiaohui; Zaydman, Mark A; Cui, Jianmin

    2012-01-01

    Voltage-activated K(+) (K(V)) channels are important for shaping action potentials and maintaining resting membrane potential in excitable cells. K(V) channels contain a central pore-gate domain (PGD) surrounded by four voltage-sensing domains (VSDs). The VSDs will change conformation in response to alterations of the membrane potential thereby inducing the opening of the PGD. Many K(V) 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 K(V) β subunits that contain transmembrane (TM) segments including the KCNE family and the β subunits of large conductance, Ca(2+)- and voltage-activated K(+) (BK) channels. These TM β subunits affect the voltage-dependent activation of K(V) 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 K(V) channel modulation by TM β subunits.

  17. 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.

  18. The secretory KCa1.1 channel localises to crypts of distal mouse colon: functional and molecular evidence.

    Science.gov (United States)

    Sørensen, Mads V; Strandsby, Anne B; Larsen, Casper K; Praetorius, Helle A; Leipziger, Jens

    2011-11-01

    The colonic epithelium absorbs and secretes electrolytes and water. Ion and water absorption occurs primarily in surface cells, whereas crypt cells perform secretion. Ion transport in distal colon is regulated by aldosterone, which stimulates both Na(+) absorption and K(+) secretion. The electrogenic Na(+) absorption is mediated by epithelial Na(+) channel (ENaC) in surface cells. Previously, we identified the large conductance Ca(2+)-activated K(+) channel, K(Ca)1.1 or big potassium (BK) channel, as the only relevant K(+) secretory pathway in mouse distal colon. The exact localisation of K(Ca)1.1 channels along the crypt axis is, however, still controversial. The aim of this project was to further define the localisation of the K(Ca)1.1 channel in mouse distal colonic epithelium. Through quantification of mRNA extracted from micro-dissected surface and crypt cells, we confirmed that Na(+)/K(+)/2Cl(-) (NKCC1) is expressed primarily in the crypts and γ-ENaC primarily in the surface cells. The K(Ca)1.1 α-subunit mRNA was like NKCC1, mainly expressed in the crypts. The crypt to surface expression pattern of the channels and transporters was not altered when plasma aldosterone was elevated. The mRNA levels for NKCC1, γ-ENaC and K(Ca)1.1 α-subunit were, however, under these circumstances substantially augmented (K(Ca)1.1 α-subunit, twofold; NKCC1, twofold and ENaC, tenfold). Functionally, we show that ENaC-mediated Na(+) absorption and BK channel-mediated K(+) secretion are two independent processes. These findings show that K(Ca)1.1-mediated K(+) secretion mainly occurs in the crypts of the murine distal colon. This is in agreement with the general model of ion secretion being preferentially located to the crypt and not surface enterocytes.

  19. Regulated trafficking of the CFTR chloride channel

    NARCIS (Netherlands)

    Braakman, L.J.; Kleizen, B.; Jonge, H.R. de

    2000-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR), the ABC transporter encoded by the cystic fibrosis gene, is localized in the apical membrane of epithelial cells where it functions as a cyclic AMP-regulated chloride channel and as a regulator of other ion channels and transporters. Wh

  20. Detection of BK virus DNA in nasopharyngeal aspirates from children with respiratory infections but not in saliva from immunodeficient and immunocompetent adult patients.

    OpenAIRE

    SUNDSFJORD, A.; Spein, A R; Lucht, E.; Flaegstad, T; Seternes, O M; Traavik, T.

    1994-01-01

    Our understanding of important stages in the pathogenesis of the human polyomavirus BK virus (BKV) and JC virus (JCV) infections is limited. In this context, nasopharyngeal aspirates from 201 children with respiratory diseases and saliva from 60 human immunodeficiency virus type 1-infected adults and 10 healthy adult controls were collected and analyzed for the presence of BKV and JCV DNA by PCR. Neither BKV nor JCV DNA was detected in the saliva specimens. We demonstrated BKV DNA, but no inf...

  1. Evaluation of the Genetic Variation of Non Coding Control Region of BK Virus Using Nested-PCR Sequencing Method in Renal Graft Patients

    Directory of Open Access Journals (Sweden)

    A Emami

    2015-05-01

    Full Text Available Background & aim: Polyomaviruses (BK is a comprehensive infection with more than of 80% prevalence in the world. One of the most important reasons of BK virus nephropathy is in the renal transplant recipients and rejection of transplanted tissue between them. Non Coding region of this virus play a regulatory role in replication and amplification of the virus. The aim of this study was to evaluate the genetic patterns of this area in renal graft at Namazi Transplantation Center, Shiraz, Iran. Methods: In the present experimental study, 380 renal allograft serums were collected. DNAs of 129 eligible samples were extracted and evaluated using a virus genome. The presence of the virus was determined by qualitative and sequencing. Of these, 129 samples were tested for the presence of virus according to the condition study, using quantitative, qualitative genomic amplification and sequencing. Results: The study showed symptoms of nephropathy, 76 (58.9% of them were males and 46 (35.7% were females with the mean age 38.0±.089 years of age. In general, 46 patients (35.7% percent were positive for BK Polyomaviruses. After comparing the genomic sequence with applications of molecular they were categorized in three groups and then recorded in gene bank. Conclusion: About 35% of renal transplant recipients with high creatinine levels were positive for the presence of BK virus. Non-coding region of respondents in the sample survey revealed that among patients with the most common genotypes were rearranged the entire transplant patients were observed at this tranplant center. Examination of these sequences indicated that this rearrangments had a specific pattern, different from the standard strain of archaea type.

  2. The Activation Effect of Hainantoxin-I, a Peptide Toxin from the Chinese Spider, Ornithoctonus hainana, on Intermediate-Conductance Ca2+-Activated K+ Channels

    Directory of Open Access Journals (Sweden)

    Pengfei Huang

    2014-08-01

    Full Text Available Intermediate-conductance Ca2+-activated K+ (IK channels are calcium/calmodulin-regulated voltage-independent K+ channels. Activation of IK currents is important in vessel and respiratory tissues, rendering the channels potential drug targets. A variety of small organic molecules have been synthesized and found to be potent activators of IK channels. However, the poor selectivity of these molecules limits their therapeutic value. Venom-derived peptides usually block their targets with high specificity. Therefore, we searched for novel peptide activators of IK channels by testing a series of toxins from spiders. Using electrophysiological experiments, we identified hainantoxin-I (HNTX-I as an IK-channel activator. HNTX-I has little effect on voltage-gated Na+ and Ca2+ channels from rat dorsal root ganglion neurons and on the heterologous expression of voltage-gated rapidly activating delayed rectifier K+ channels (human ether-à-go-go-related gene; human ERG in HEK293T cells. Only 35.2% ± 0.4% of the currents were activated in SK channels, and there was no effect on BK channels. We demonstrated that HNTX-I was not a phrenic nerve conduction blocker or acutely toxic. This is believed to be the first report of a peptide activator effect on IK channels. Our study suggests that the activity and selectivity of HNTX-I on IK channels make HNTX-I a promising template for designing new drugs for cardiovascular diseases.

  3. Channeling Frustration

    Institute of Scientific and Technical Information of China (English)

    LiLi

    2013-01-01

    Transparency and inclusiveness should guide local governments to defuse NIMBY protests China's largest oil and natural gas producer Petro China published a report on the environmental impact assessment it submitted to the government for its controversial refinery in Kunming,capital of southwest China's Yunnan Province.According to

  4. New localized excitations and cross-like fractal structures to the (2+1)-dimensional Broer–Kaup system

    Indian Academy of Sciences (India)

    Zitian Li

    2014-09-01

    A broad general variable separation solution with two arbitrary lower-dimensional functions of the (2+1)-dimensional Broer–Kaup (BK) equations was derived by means of a projective equation method and a variable separation hypothesis. Based on the derived variable separation excitation, some new special types of localized solutions such as oscillating solitons, instantonlike and cross-like fractal structures are revealed by selecting appropriate functions of the general variable separation solution.

  5. Urological management (medical and surgical of BK-virus associated haemorrhagic cystitis in children following haematopoietic stem cell transplantation

    Directory of Open Access Journals (Sweden)

    Nikhil Vasdev

    2013-10-01

    Full Text Available Aim: Haemorrhagic cystitis (HC is uncommon and in its severe form potentially life threatening complication of Haematopoietic stem cell transplantation (HSCT in children. We present our single centre experience in the urological management of this clinically challenging condition. Patients and Methods: Fourteen patients were diagnosed with BK-Virus HC in our centre. The mean age at diagnosis was 8.8 years (range, 3.2-18.4 years. The mean number of days post-BMT until onset of HC was 20.8 (range, 1 – 51. While all patients tested urine positive for BKV at the clinical onset of HC, only four patients had viral quantification, with viral loads ranging from 97,000 to >1 billion/ml. 8 patients had clinical HC. Ten patients experienced acute GVHD (grade I: 6 patients, grade II: 3 patients, grade 4: 1 patient.Results: Four patients received medical management for their HC. Treatments included hyperhydration, MESNA, blood and platelet transfusion, premarin and oxybutynin (Table 6.  Two patients received both medical and surgical management which included cystoscopy with clot evacuation, bladder irrigation and supra-pubic catheter insertion. One patient received exclusive surgical management. Seven patients were treated conservatively. Conclusion: There is limited available evidence for other potential therapeutic strategies highlighting the need for more research into the pathophysiology of HSCT-associated HC. Commonly used interventions with possible clinical benefit (e.g. cidofovir, ciprofloxacin still require to be evaluated in multi-centre, high-quality studies. Potential future preventative and therapeutic options, such as modulation of conditioning, immunosuppression and engraftment, new antiviral and anti-inflammatory and less nephrotoxic agents need to be assessed.---------------------------Cite this article as:Vasdev N, Davidson A, Harkensee C, Slatter M, Gennery A, Willetts I, Thorpe A.Urological management (medical and surgical of BK

  6. Growth of bultfonteinite and hydrogarnet in metasomatized basalt xenoliths in the B/K9 kimberlite, Damtshaa, Botswana: insights into hydrothermal metamorphism in kimberlite pipes

    Science.gov (United States)

    Buse, Ben; Schumacher, John C.; Sparks, R. Stephen J.; Field, Matthew

    2010-10-01

    Metamorphic assemblages within Karoo basalt xenoliths, found within volcaniclastic kimberlite of the B/K9 pipe, Damtshaa, Botswana, constrain conditions of kimberlite alteration. Bultfonteinite and chlorite partially replace the original augite-plagioclase assemblage, driven by the serpentinisation of the kimberlite creating strong chemical potential gradients for Si and Mg. Hydrogarnet and serpentine replace these earlier metamorphic assemblages as the deposits cool. The bultfonteinite (ideally Ca2SiO2[OH,F]4) and hydrogarnet assemblages require a water-rich fluid containing F-, and imply hydrothermal alteration dominated by external fluids rather than autometamorphism from deuteric fluids. Bultfonteinite and hydrogarnet are estimated to form at temperatures of ca. 350-250°C, which are similar to those for serpentinisation. Alteration within the B/K9 kimberlite predominantly occurs between 250 and 400°C. We attribute these conditions to increased efficiency of mass transfer and chemical reactions below the critical point of water and a consequence of volume-increasing serpentinisation and metasomatic reactions that take place over this temperature range. A comparison of the B/K9 kimberlite with kimberlites from Venetia, South Africa suggests that the composition and mineralogy of included xenoliths affects the alteration assemblages within kimberlite deposits.

  7. Development of a clone from established Bovine Kidney (BK cell line and evaluation of its sensitivity to Parainfluenza type 3 and Herpes Simplex type 1 viruses.

    Directory of Open Access Journals (Sweden)

    Yashar Mohammadzadeh sedigh

    2009-09-01

    Full Text Available Background: Application of continuous cell lines has got a special place in the virological researches. These cells are immortal and their chromosomes are aneuploid. Therefore, they can be passage without any limitation. The aim of this research was to choose the best way of producing clone of cells. Methods: in this study, Bovine Kidney (BK cell line was used to be cloned through limiting dilution method in which Vero cells were used as feeder layer. Vero cells were first cultured in DMEM supplimented with 7% heat inactivated calf serum and after a monolayer were formed, their growth was arrested by Mitomycin C. The cloned cells after incubation were separated and cultured in a new flask. After several experiments different clones were obtained and cultured for further studies. Results: Karyotype of clone cells were determined and compared with original cells. It was shown that cloned cells were more homogenous in early passages and their karyotypes showed less variability than original ones. Cloned and original cells were inoculated with HSV-1 and Parainfluenza virus 3 in order to evaluate its biological abilities. Tissue culture of infectious dose 50 (TCID50 of each virus was calculated and it was shown that there was no significant different between the HSV-1 titers before and after cloning whereas the titer of the Parainfluenza virus 3 was significantly higher in the original cells. Conclusions: Cloned cells of BK showed more stable karyotype and were less sensitive to parainfluenza type-3 virus infection than original BK cells.

  8. Dynamic changes of mechanically activated channels and K~+ channels at injury site of peripheral nerve in rat

    Institute of Scientific and Technical Information of China (English)

    凌琰; 谢益宽

    1996-01-01

    Ectopic ion channels developed locally at the injury site after nerve damage by light ligation around common sciatic nerve of the rats. Different channel types have different processes of formation, accumulation and degeneration. During the first three days after injury, mechanically activated channels that are modulated by Ca++ channel activities first appeared. As the nerve fibers begin to be excited by TEA, a blocker of K+ channels, suggesting that the accumulation of K+ channels, the responsibility of mechanically activated channels was declining. Onset of K+ channels was from the 3rd postoperative day and lasted up to the fiftieth day. This time course of K+ channel development was closely related to allodynia and hyperalgesia of neuropathic animal behaviour. The results suggest that chronic contraction injury induces a dynamic change in the ectopic mechanically activated channels and K+ channels at the injury site of nerve and there is an interchange in the development time courses of the mechanic

  9. Subcellular localization of the voltage-gated potassium channels Kv3.1b and Kv3.3 in the cerebellar dentate nucleus of glutamic acid decarboxylase 67-green fluorescent protein transgenic mice.

    Science.gov (United States)

    Alonso-Espinaco, V; Elezgarai, I; Díez-García, J; Puente, N; Knöpfel, T; Grandes, P

    2008-09-09

    Deep cerebellar dentate nuclei are in a key position to control motor planning as a result of an integration of cerebropontine inputs and hemispheric Purkinje neurons signals, and their influence through synaptic outputs onto extracerebellar hubs. GABAergic dentate neurons exhibit broader action potentials and slower afterhyperpolarization than non-GABAergic (presumably glutamatergic) neurons. Specific potassium channels may be involved in these distinct firing profiles, particularly, Kv3.1 and Kv3.3 subunits which rapidly activate at relatively positive potentials to support the generation of fast action potentials. To investigate the subcellular localization of Kv3.1b and Kv3.3 in GAD- and GAD+ dentate neurons of glutamic acid decarboxylase 67-green fluorescent protein (GAD67-GFP) knock-in mice a preembedding immunocytochemical method for electron microscopy was used. Kv3.1b and Kv3.3 were in membranes of cell somata, dendrites, axons and synaptic terminals of both GAD- and GAD+ dentate neurons. The vast majority of GAD- somatodendritic membrane segments domains labeled for Kv3.1b and Kv3.3 (96.1% and 84.7%, respectively) whereas 56.2% and 69.8% of GAD- axonal membrane segments were immunopositive for these subunits. Furthermore, density of Kv3.1b immunoparticles was much higher in GAD- somatodendritic than axonal domains. As to GAD+ neurons, only 70.6% and 50% of somatodendritic membrane segments, and 53.3% and 59.5% of axonal membranes exhibited Kv3.1b and Kv3.3 labeling, respectively. In contrast to GAD- cells, GAD+ cells exhibited a higher density labeling for both Kv3 subunits at their axonal than at their somatodendritic membranes. Taken together, Kv3.1b and Kv3.3 potassium subunits are expressed in both GAD- and GAD+ cells, albeit at different densities and distribution. They likely contribute to the distinct biophysical properties of both GAD- and GAD+ neurons in the dentate nucleus.

  10. Impact of mTORC1 inhibition on keratinocyte proliferation during skin tumor promotion in wild-type and BK5.AktWT mice.

    Science.gov (United States)

    Rho, Okkyung; Kiguchi, Kaoru; Jiang, Guiyu; DiGiovanni, John

    2014-11-01

    In this study, we examined the impact of rapamycin on mTORC1 signaling during 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced keratinocyte proliferation and skin tumor promotion in both wild-type (FVB/N) and BK5.Akt(WT) mice. TPA activated mTORC1 signaling in a time-dependent manner in cultured primary mouse keratinocytes and a mouse keratinocyte cell line. Early activation (15-30 min) of mTORC1 signaling induced by TPA was mediated in part by PKC activation, whereas later activation (2-4 h) was mediated by activation of EGFR and Akt. BK5.Akt(WT) transgenic mice, where Akt1 is overexpressed in basal epidermis, are highly sensitive to TPA-induced epidermal proliferation and two-stage skin carcinogenesis. Targeting mTORC1 with rapamycin effectively inhibited TPA-induced epidermal hyperplasia and hyperproliferation as well as tumor promotion in a dose-dependent manner in both wild-type and BK5.Akt(WT) mice. A significant expansion (∼threefold) of the label retaining cell (LRC) population per hair follicle was observed in BK5.Akt(WT) mice compared to FVB/N mice. There was also a significant increase in K15 expressing cells in the hair follicle of transgenic mice that coincided with expression of phospho-Akt, phospho-S6K, and phospho-PRAS40, suggesting an important role of mTORC1 signaling in bulge-region keratinocyte stem cell (KSC) homeostasis. After 2 weeks of TPA treatment, LRCs had moved upward into the interfollicular epidermis from the bulge region of both wild-type and BK5.Akt(WT) mice. TPA-mediated LRC proliferation and migration was significantly inhibited by rapamycin. Collectively, the current data indicate that signaling through mTORC1 contributes significantly to the process of skin tumor promotion through effects on proliferation of the target cells for tumor development.

  11. High-frequency vibration effects on hole entrance chipping in rotary ultrasonic drilling of BK7 glass.

    Science.gov (United States)

    Lv, Dongxi; Zhang, Yuanming; Peng, Yunfeng

    2016-12-01

    This present investigation exhibited some fundamental information about the influence of the high-frequency vibration on the hole entrance chipping formation involved in rotary ultrasonic drilling (RUD) of BK7 glass process. The entrance chipping morphologies, produced with and without ultrasonic, were observed and evaluated with respect to the fracture mechanics of brittle material. Giving consideration to the variation characteristics of the plastic deformation region in the interior material induced by the specific kinematics principles of the abrasive, the ultrasonic effects on the chipping formation mechanisms were investigated by assessing the groove morphologies obtained in the scratching experiment utilizing the formation mechanisms of the lateral cracking. Furthermore, the formal confirmatory tests with and without ultrasonic were performed to validate these chipping formation mechanisms. It was found that the plastic deformed region reached its maximum at the trajectory bottom. Moreover, the propagation of the lateral cracking initially nucleated at the bottom of the ductile deformation zone resulted in the formation of the entrance chipping in formal RUD process. The slight deformation of the material at the two terminals of each groove produced with ultrasonic would provide the inhibitory effects to the further extending of the lateral cracks, which would shrink with the increased spindle speed, and the inhibitory effect dominated in determining the improvement effects on the hole entrance quality. Additionally, a theoretical relationship between the nucleation depth and the propagation length of the lateral cracking was developed for the conventional drilling (CD) process.

  12. Quantum teleportation without classical channel

    Science.gov (United States)

    Al Amri, M.; Li, Zheng-Hong; Zubairy, M. Suhail

    2016-11-01

    For the first time, we show how quantum teleportation can be achieved without the assistance of classical channels. Our protocol does not need any pre-established entangled photon pairs beforehand. Just by utilizing quantum Zeno effect and couterfactual communication idea, we can achieve two goals; entangling a photon and an atom and also disentangling them by non-local interaction. Information is completely transferred from atom to photon with controllable disentanglement processes. More importantly, there is no need to confirm teleportation results via classical channels.

  13. Business Models for Local Foods

    DEFF Research Database (Denmark)

    Esbjerg, Lars; Pedersen, Maja; Pederson, Robert

    2014-01-01

    sales of food products (and vice versa) and therefore have to develop alternative marketing channels. The purpose of this paper is to investigate the practices of different small and medium-sized Danish producers of locally grown and/or processed foods in relation to developing marketing channels......Interest in local foods is growing, but there has been limited research on who and why producers of local foods thrive or struggle. A particularly important problem for local food producers is how to reach end consumers, as they often find it difficult to work with the retail chains that dominate...

  14. Activation of BK and SK channels by efferent synapses on outer hair cells in high-frequency regions of the rodent cochlea

    NARCIS (Netherlands)

    Rohmann, Kevin N; Wersinger, Eric; Braude, Jeremy P; Pyott, Sonja J; Fuchs, Paul Albert

    2015-01-01

    Cholinergic neurons of the brainstem olivary complex project to and inhibit outer hair cells (OHCs), refining acoustic sensitivity of the mammalian cochlea. In all vertebrate hair cells studied to date, cholinergic inhibition results from the combined action of ionotropic acetylcholine receptors and

  15. Information geometry of Gaussian channels

    CERN Document Server

    Monras, Alex

    2009-01-01

    We define a local Riemannian metric tensor in the manifold of Gaussian channels and the distance that it induces. We adopt an information-geometric approach and define a metric derived from the Bures-Fisher metric for quantum states. The resulting metric inherits several desirable properties from the Bures-Fisher metric and is operationally motivated from distinguishability considerations: It serves as an upper bound to the attainable quantum Fisher information for the channel parameters using Gaussian states, under some restriction on the available resources. We prove that optimal states are always pure and bounded in the number of ancillary modes that are needed. This has experimental and computational advantages: It limits the complexity of optimal experimental setups for channel estimation and reduces the computational requirements for the evaluation of the metric. Indeed, we construct a converging algorithm for computing the metric. We provide explicit formulae for computing the multiparametric quantum F...

  16. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  17. Co-Localization of Sodium Channel Na[v]1.6 and the Sodium--Calcium Exchanger at Sites of Axonal Injury in the Spinal Cord in EAE

    Science.gov (United States)

    Craner, Matthew J.; Hains, Bryan C.; Lo, Albert C.; Black, Joel A.; Waxman, Stephen G.

    2004-01-01

    Axonal degeneration contributes to the development of non-remitting neurological deficits and disability in multiple sclerosis, but the molecular mechanisms that underlie axonal loss in multiple sclerosis are not clearly understood. Studies of white matter axonal injury have demonstrated that voltage-gated sodium channels can provide a route for…

  18. Effects of manipulating slowpoke calcium-dependent potassium channel expression on rhythmic locomotor activity in Drosophila larvae

    Directory of Open Access Journals (Sweden)

    Erin C. McKiernan

    2013-03-01

    Full Text Available Rhythmic motor behaviors are generated by networks of neurons. The sequence and timing of muscle contractions depends on both synaptic connections between neurons and the neurons’ intrinsic properties. In particular, motor neuron ion currents may contribute significantly to motor output. Large conductance Ca2+-dependent K+ (BK currents play a role in action potential repolarization, interspike interval, repetitive and burst firing, burst termination and interburst interval in neurons. Mutations in slowpoke (slo genes encoding BK channels result in motor disturbances. This study examined the effects of manipulating slo channel expression on rhythmic motor activity using Drosophila larva as a model system. Dual intracellular recordings from adjacent body wall muscles were made during spontaneous crawling-related activity in larvae expressing a slo mutation or a slo RNA interference construct. The incidence and duration of rhythmic activity in slo mutants were similar to wild-type control animals, while the timing of the motor pattern was altered. slo mutants showed decreased burst durations, cycle durations, and quiescence intervals, and increased duty cycles, relative to wild-type. Expressing slo RNAi in identified motor neurons phenocopied many of the effects observed in the mutant, including decreases in quiescence interval and cycle duration. Overall, these results show that altering slo expression in the whole larva, and specifically in motor neurons, changes the frequency of crawling activity. These results suggest an important role for motor neuron intrinsic properties in shaping the timing of motor output.

  19. Specific IgG Antibodies React to Mimotopes of BK Polyomavirus, a Small DNA Tumor Virus, in Healthy Adult Sera

    Science.gov (United States)

    Pietrobon, Silvia; Bononi, Ilaria; Mazzoni, Elisa; Lotito, Francesca; Manfrini, Marco; Puozzo, Andrea; Destro, Federica; Guerra, Giovanni; Nocini, Pier Francesco; Martini, Fernanda; Tognon, Mauro G.

    2017-01-01

    BK polyomavirus (BKPyV) was isolated in 1971 from the urine of a kidney transplant patient. Soon after its identification, BKPyV was characterized as a kidney-tropic virus, which is responsible of a significant fraction of the rejection of transplant kidney in the host. Moreover, in experimental conditions, BKPyV is able to transform different types of animal and human cells and to induce tumors of different histotypes in experimental animals. BKPyV DNA sequences have been detected in healthy individuals and cancer patients using polymerase chain reaction/Shouthern blot hybridization methods. Serum antibodies against this polyomavirus were revealed using immunological techniques, which, however, cross-react with other polyomaviruses such as JC (JCPyV) and Simian Virus 40. These non-specific data indicate the need of novel immunological methods and new investigations to check in a specific manner, BKPyV spread in humans. To this aim, mimotopes from BKPyV structural capsid protein 1 (VP1) were employed for specific immunological reactions to IgG antibodies of human serum samples. An indirect enzyme-linked immunosorbent assay with synthetic peptides mimicking immunogenic epitopes of BKPyV VP1 was set up and employed to test sera of healthy adult subjects. Data from this innovative immunological assay indicate that serum antibodies against BKPyV VP1 mimotopes are detectable in healthy subjects ranging from 18 to 90 years old. The overall prevalence of serum samples that reacted to BKPyV VP1 mimotopes was 72%. The strong points from this investigation are the novelty of the immunological method, its simplicity of the approach, and the specificity of BKPyV antibody reaction to VP1 mimotopes. PMID:28321224

  20. 1-O-hexadecyloxypropyl cidofovir (CMX001) effectively inhibits polyomavirus BK replication in primary human renal tubular epithelial cells.

    Science.gov (United States)

    Rinaldo, Christine Hanssen; Gosert, Rainer; Bernhoff, Eva; Finstad, Solrun; Hirsch, Hans H

    2010-11-01

    Antiviral drugs for treating polyomavirus BK (BKV) replication in polyomavirus-associated nephropathy or hemorrhagic cystitis are of considerable clinical interest. Unlike cidofovir, the lipid conjugate 1-O-hexadecyloxypropyl cidofovir (CMX001) is orally available and has not caused detectable nephrotoxicity in rodent models or human studies to date. Primary human renal proximal tubular epithelial cells were infected with BKV-Dunlop, and CMX001 was added 2 h postinfection (hpi). The intracellular and extracellular BKV DNA load was determined by quantitative PCR. Viral gene expression was examined by quantitative reverse transcription-PCR, Western blotting, and immunofluorescence microscopy. We also examined host cell viability, proliferation, metabolic activity, and DNA replication. The titration of CMX001 identified 0.31 μM as the 90% effective concentration (EC(90)) for reducing the extracellular BKV load at 72 hpi. BKV large T antigen mRNA and protein expression was unaffected at 24 hpi, but the intracellular BKV genome was reduced by 90% at 48 hpi. Late gene expression was reduced by 70 and 90% at 48 and 72 hpi, respectively. Comparisons of CMX001 and cidofovir EC(90)s from 24 to 96 hpi demonstrated that CMX001 had a more rapid and enduring effect on BKV DNA and infectious progeny at 96 hpi than cidofovir. CMX001 at 0.31 μM had little effect on overall cell metabolism but reduced bromodeoxyuridine incorporation and host cell proliferation by 20 to 30%, while BKV infection increased cell proliferation in both rapidly dividing and near-confluent cultures. We conclude that CMX001 inhibits BKV replication with a longer-lasting effect than cidofovir at 400× lower levels, with fewer side effects on relevant host cells in vitro.

  1. Clinical Pharmacokinetic Monitoring of Leflunomide in Renal Transplant Recipients with BK Virus Reactivation: A Review of the Literature.

    Science.gov (United States)

    Ng, Joan C Y; Leung, Marianna; Wright, Alissa J; Ensom, Mary H H

    2017-02-28

    Leflunomide is an immunosuppressive drug with in vitro and initial observational evidence of antiviral activity against BK virus (BKV), a pathogen that causes opportunistic infection upon reactivation in renal transplant recipients. Leflunomide is considered an ancillary option to immunosuppression reduction in the management of BKV reactivation. Plasma or blood concentrations of teriflunomide, the active metabolite of leflunomide, are commonly monitored because of high leflunomide doses being used, known inter-individual variability in pharmacokinetics, and hepatotoxicity risk. However, the utility of clinical pharmacokinetic monitoring for leflunomide is as yet unclear. A literature search of MEDLINE (1946-December 2016), EMBASE (1974-December 2016), the CENTRAL database, and Google Scholar was performed to identify relevant English-language articles. Further articles were identified from references in relevant literature. A previously published 9-step decision-making algorithm was used to assess the available literature and determine the utility of clinical pharmacokinetic monitoring for leflunomide. Teriflunomide is readily measurable in the plasma or blood, but a clear relationship between concentration and efficacy or toxicity is lacking, and its therapeutic range is not well-established. Efficacy and toxicity endpoints such as renal function and BKV clearance can be readily assessed without measuring teriflunomide concentrations. Pharmacokinetic parameters are affected by genetic polymorphisms in cytochrome P450 CYP2C19 and ABCG2 genes. Therefore, routine clinical pharmacokinetic monitoring of leflunomide cannot be recommended based on current available evidence. However, it may provide clinical benefit in difficult situations when patients demonstrate a lack of therapeutic response or exhibit signs of drug toxicity.

  2. Computed Tomography Findings of Human Polyomavirus BK (BKV)-Associated Cystitis in Allogeneic Hematopoietic Stem Cell Transplant Recipients

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, M.; Beck, R.; Igney, A.; Vogel, M.; Maksimovic, O.; Claussen, C.D.; Faul, C.; Horger, M. [Dept. of Diagnostic Radiology, Dept. of Internal Medicine-Oncology, and Inst. of Medical Virology, Eberhard-Karls Univ., Tbingen (Germany)

    2008-12-15

    Background: Over 70% of the general population worldwide is positive for antibodies against polyomavirus hominis type 1 (BKV). Polyomavirus can be reactivated in immunocompromised patients and thereby induce urogenital tract infection, including cystitis. Purpose: To describe the computed tomography (CT) findings of human polyomavirus-induced cystitis in adult patients after allogeneic hematopoietic stem cell transplantation (allogeneic HCT). Material and Methods: The study population was a retrospective cohort of 11 consecutive adult patients (eight men, three women; age range 22-59 years, mean 42.9 years) who received allogeneic HCT between December 2003 and December 2007 and were tested positive for urinary BKV infection. All CT scans were evaluated with regard to bladder wall thickness, mucosal enhancement, distinct layering of thickened bladder wall, and presence of intravesical clots, perivesical stranding as well as attenuation values of intravesical urine. Clinical data concerning transplant and conditioning regimen variables and laboratory parameters were correlated with degree and extent of imaging findings. Results: All patients had clinical signs of cystitis with different degrees of thickening of the urinary bladder wall. Well-delineated urinary bladder layers were present in six patients. Thickening of the urinary bladder wall was continuous in nine of 11 patients. Increased attenuation of intravesical urine was found in seven patients with hemorrhagic cystitis. Four patients had intraluminal clots. Perivesical stranding was not a major CT finding, occurring in a mild fashion in three of 11 patients. The clinical classification of hemorrhagic cystitis did not correlate with the analyzed imaging parameters. Patient outcome was not influenced by this infectious complication. Conclusion: CT findings in patients with polyomavirus BK cystitis consist of different degrees of bladder wall thickening usually with good delineation of all mural layers and

  3. Computed Tomography Findings of Human Polyomavirus BK (BKV)-Associated Cystitis in Allogeneic Hematopoietic Stem Cell Transplant Recipients

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, M.; Beck, R.; Igney, A.; Vogel, M.; Maksimovic, O.; Claussen, C.D.; Faul, C.; Horger, M. (Dept. of Diagnostic Radiology, Dept. of Internal Medicine-Oncology, and Inst. of Medical Virology, Eberhard-Karls Univ., Tbingen (Germany))

    2008-12-15

    Background: Over 70% of the general population worldwide is positive for antibodies against polyomavirus hominis type 1 (BKV). Polyomavirus can be reactivated in immunocompromised patients and thereby induce urogenital tract infection, including cystitis. Purpose: To describe the computed tomography (CT) findings of human polyomavirus-induced cystitis in adult patients after allogeneic hematopoietic stem cell transplantation (allogeneic HCT). Material and Methods: The study population was a retrospective cohort of 11 consecutive adult patients (eight men, three women; age range 22-59 years, mean 42.9 years) who received allogeneic HCT between December 2003 and December 2007 and were tested positive for urinary BKV infection. All CT scans were evaluated with regard to bladder wall thickness, mucosal enhancement, distinct layering of thickened bladder wall, and presence of intravesical clots, perivesical stranding as well as attenuation values of intravesical urine. Clinical data concerning transplant and conditioning regimen variables and laboratory parameters were correlated with degree and extent of imaging findings. Results: All patients had clinical signs of cystitis with different degrees of thickening of the urinary bladder wall. Well-delineated urinary bladder layers were present in six patients. Thickening of the urinary bladder wall was continuous in nine of 11 patients. Increased attenuation of intravesical urine was found in seven patients with hemorrhagic cystitis. Four patients had intraluminal clots. Perivesical stranding was not a major CT finding, occurring in a mild fashion in three of 11 patients. The clinical classification of hemorrhagic cystitis did not correlate with the analyzed imaging parameters. Patient outcome was not influenced by this infectious complication. Conclusion: CT findings in patients with polyomavirus BK cystitis consist of different degrees of bladder wall thickening usually with good delineation of all mural layers and

  4. Vascular potassium channels in NVC.

    Science.gov (United States)

    Yamada, K

    2016-01-01

    It has long been proposed that the external potassium ion ([K(+)]0) works as a potent vasodilator in the dynamic regulation of local cerebral blood flow. Astrocytes may play a central role for producing K(+) outflow possibly through calcium-activated potassium channels on the end feet, responding to a rise in the intracellular Ca(2+) concentration, which might well reflect local neuronal activity. A mild elevation of [K(+)]0 in the end feet/vascular smooth muscle space could activate Na(+)/K(+)-ATPase concomitant with inwardly rectifying potassium (Kir) channels in vascular smooth muscle cells, leading to a hyperpolarization of vascular smooth muscle and relaxation of smooth muscle actin-positive vessels. Also proposed notion is endothelial calcium-activated potassium channels and/or inwardly rectifying potassium channel-mediated hyperpolarization of vascular smooth muscle. A larger elevation of [K(+)]0, which may occur pathophysiologically in such as spreading depression or stroke, can trigger a depolarization of vascular smooth muscle cells and vasoconstriction instead.

  5. Anestésicos locais: interação com membranas biológicas e com o canal de sódio voltagem-dependente Local anesthetics: interaction with biological membranes and with the voltage-gated sodium channel

    Directory of Open Access Journals (Sweden)

    Daniele Ribeiro de Araujo

    2008-01-01

    Full Text Available Many theories about the mechanism of action of local anesthetics (LA are described in the literature. Two types of theories can be distinguished: those that focus on the direct effects of LA on their target protein in the axon membranes, i.e. the voltage-gated sodium channel and the ones that take into account the interaction of anesthetic molecules with the lipid membrane phase for the reversible nerve blockage. Since there is a direct correlation between LA hydrophobicity and potency, it is crucial to take this physico-chemical property into account to understand the mechanism of action of LA, be it on the sodium channel protein, lipid(s, or on the whole membrane phase.

  6. Study on resistance coefficient in compound channels

    Institute of Scientific and Technical Information of China (English)

    Kejun Yang; Shuyou Cao; Xingnian Liu; Ron Marshall

    2005-01-01

    This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the lateral distribution of depth mean velocity and local boundary shear stress in compound channels. The relationships between the local, zonal and overall resistance coefficients, and a wide range of geometries and different roughness between the main channel and the flood plain are established by analyzing a vast amount of experimental data from a British Science and Engineering Research Council Flood Channel Facility (SERC-FCF). And the experimental results also show that the overall Darcy-Weisbach resistance coefficient for a compound channel is the function of Reynolds number, but the function relationship is different from that for a single channel. By comparing and analyzing the conventional methods with the experimental data to predict composite roughness in compound channels, it is found that these methods are not suitable for compound channels. Moreover, the reason why the conventional methods cannot assess correctly the conveyance capacity of com pound channels is also analyzed in this paper.

  7. Mobile radio channels

    CERN Document Server

    Pätzold, Matthias

    2011-01-01

    Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta

  8. Characterization of Kbot21 Reveals Novel Side Chain Interactions of Scorpion Toxins Inhibiting Voltage-Gated Potassium Channels.

    Directory of Open Access Journals (Sweden)

    Rym ElFessi-Magouri

    Full Text Available Scorpion toxins are important pharmacological tools for probing the physiological roles of ion channels which are involved in many physiological processes and as such have significant therapeutic potential. The discovery of new scorpion toxins with different specificities and affinities is needed to further characterize the physiology of ion channels. In this regard, a new short polypeptide called Kbot21 has been purified to homogeneity from the venom of Buthus occitanus tunetanus scorpion. Kbot21 is structurally related to BmBKTx1 from the venom of the Asian scorpion Buthus martensii Karsch. These two toxins differ by only two residues at position 13 (R /V and 24 (D/N.Despite their very similar sequences, Kbot21 and BmBKTx1 differ in their electrophysiological activities. Kbot21 targets KV channel subtypes whereas BmBKTx1 is active on both big conductance (BK and small conductance (SK Ca2+-activated K+ channel subtypes, but has no effects on Kv channel subtypes. The docking model of Kbot21 with the Kv1.2 channel shows that the D24 and R13 side-chain of Kbot21 are critical for its interaction with KV channels.

  9. Characterization of Kbot21 Reveals Novel Side Chain Interactions of Scorpion Toxins Inhibiting Voltage-Gated Potassium Channels.

    Science.gov (United States)

    ElFessi-Magouri, Rym; Peigneur, Steve; Othman, Houcemeddine; Srairi-Abid, Najet; ElAyeb, Mohamed; Tytgat, Jan; Kharrat, Riadh

    2015-01-01

    Scorpion toxins are important pharmacological tools for probing the physiological roles of ion channels which are involved in many physiological processes and as such have significant therapeutic potential. The discovery of new scorpion toxins with different specificities and affinities is needed to further characterize the physiology of ion channels. In this regard, a new short polypeptide called Kbot21 has been purified to homogeneity from the venom of Buthus occitanus tunetanus scorpion. Kbot21 is structurally related to BmBKTx1 from the venom of the Asian scorpion Buthus martensii Karsch. These two toxins differ by only two residues at position 13 (R /V) and 24 (D/N).Despite their very similar sequences, Kbot21 and BmBKTx1 differ in their electrophysiological activities. Kbot21 targets KV channel subtypes whereas BmBKTx1 is active on both big conductance (BK) and small conductance (SK) Ca2+-activated K+ channel subtypes, but has no effects on Kv channel subtypes. The docking model of Kbot21 with the Kv1.2 channel shows that the D24 and R13 side-chain of Kbot21 are critical for its interaction with KV channels.

  10. Channel nut tool

    Energy Technology Data Exchange (ETDEWEB)

    Olson, Marvin

    2016-01-12

    A method, system, and apparatus for installing channel nuts includes a shank, a handle formed on a first end of a shank, and an end piece with a threaded shaft configured to receive a channel nut formed on the second end of the shaft. The tool can be used to insert or remove a channel nut in a channel framing system and then removed from the channel nut.

  11. Eleven new heaviest isotopes of elements Z = 105 to Z = 117 identified among the products of 249Bk+48Ca reactions

    Energy Technology Data Exchange (ETDEWEB)

    Oganessian, Yuri Ts. [FLNR-JINR, Russia; Abdullin, F. Sh. [Joint Institute for Nuclear Research, Dubna, Russia; Bailey, P. D. [Oak Ridge National Laboratory (ORNL); Benker, D. E. [Oak Ridge National Laboratory (ORNL); Bennett, M. E. [University of Nevada, Las Vegas; Dmitriev, S. [FLNR-JINR, Russia; Ezold, Julie G. [Oak Ridge National Laboratory (ORNL); Hamilton, J. H. [Vanderbilt University; Henderson, R. [Lawrence Livermore National Laboratory (LLNL); Itkis, M. G. [FLNR-JINR, Russia; Lobanov, Yu. V. [Joint Institute for Nuclear Research, Dubna, Russia; Mezentsev, A. N. [Joint Institute for Nuclear Research, Dubna, Russia; Moody, K. [Lawrence Livermore National Laboratory (LLNL); Nelson, S. L. [Lawrence Livermore National Laboratory (LLNL); Polyakov, A. N. [Joint Institute for Nuclear Research, Dubna, Russia; Porter, C. E. [Oak Ridge National Laboratory (ORNL); Ramayya, A. V. [Vanderbilt University; Riley, F. D. [Oak Ridge National Laboratory (ORNL); Roberto, James B [ORNL; Ryabinin, M. A. [Research Institute of Atomic Reactors, Dimitrovgrad, Russia; Rykaczewski, Krzysztof Piotr [ORNL; Taylor, R [Oak Ridge National Laboratory (ORNL); Tsyganov, Yu. S. [Joint Institute for Nuclear Research, Dubna, Russia; Utyonkov, V. [FLNR-JINR, Russia; Voinov, A. A. [Joint Institute for Nuclear Research, Dubna, Russia; Vostokin, G. K. [Joint Institute for Nuclear Research, Dubna, Russia; Wilk, P. A. [Lawrence Livermore National Laboratory (LLNL)

    2011-01-01

    The heaviest isotopes of elements Z = 117 to Z = 105, 294117, 293117, 290115, 289115, 286113, 285113, 282Rg, 281Rg, 278Mt, 274Bh, and 270Db, were identified by means of the Dubna gas-filled recoil separator among the products of the 249Bk + 48Ca reaction. The details of the observed six decay chains, indicating the production and decay of isotopes 293117 and 294117, are presented and discussed. The decay energies and resulting half-lives of these new nuclei show a strong rise of stability with increasing neutron number, validating the concept of the island of enhanced stability for superheavy nuclei.

  12. River channel adjustments in Southern Italy over the past 150 years and implications for channel recovery

    Science.gov (United States)

    Scorpio, Vittoria; Aucelli, Pietro P. C.; Giano, Salvatore I.; Pisano, Luca; Robustelli, Gaetano; Rosskopf, Carmen M.; Schiattarella, Marcello

    2015-12-01

    Multi-temporal GIS analysis of topographic maps and aerial photographs along with topographic and geomorphological surveys are used to assess evolutionary trends and key control factors of channel adjustments for five major rivers in southern Italy (the Trigno, Biferno, Volturno, Sinni and Crati rivers) to support assessment of channel recovery and river restoration. Three distinct phases of channel adjustment are identified over the past 150 years primarily driven by human disturbances. Firstly, slight channel widening dominated from the last decades of the nineteenth century to the 1950s. Secondly, from the 1950s to the end of the 1990s, altered sediment fluxes induced by in-channel mining and channel works brought about moderate to very intense incision (up to 6-7 m) accompanied by strong channel narrowing (up to 96%) and changes in channel configuration from multi-threaded to single-threaded patterns. Thirdly, the period from around 2000 to 2015 has been characterized by channel stabilization and local widening. Evolutionary trajectories of the rivers studied are quite similar to those reconstructed for other Italian rivers, particularly regarding the second phase of channel adjustments and ongoing transitions towards channel recovery in some reaches. Analyses of river dynamics, recovery potential and connectivity with sediment sources of the study reaches, framed in their catchment context, can be used as part of a wider interdisciplinary approach that views effective river restoration alongside sustainable and risk-reduced river management.

  13. Pore dimensions and the role of occupancy in unitary conductance of Shaker K channels

    Science.gov (United States)

    Díaz-Franulic, Ignacio; Sepúlveda, Romina V.; Navarro-Quezada, Nieves; González-Nilo, Fernando

    2015-01-01

    conductance of the large conductance K (BK) channel (the K channel of highest conductance), reducing the energy gap between their K+ transport rates to ∼1 kT. Thus, although Shaker’s pore sustains ion translocation as the BK channel’s does, higher energetic costs of ion stabilization or higher friction with the ion’s rigid hydration cage in its narrower aqueous cavity may entail higher resistance. PMID:26216859

  14. Closure of multiple types of K+ channels is necessar to induce changes in renal vascular resistance in vivo in rats

    DEFF Research Database (Denmark)

    Sørensen, Charlotte Mehlin; Giese, Isaiah; Braunstein, Thomas Hartig

    2011-01-01

    flow (RBF) in vivo in anesthetized Sprague-Dawley rats. Test agents were infused directly into the renal artery to avoid systemic effects. Inhibition of BK(Ca) and K(ir) channels (with TEA and Ba(2+), respectively) caused small and transient reductions in RBF (to 93¿±¿2% and 95¿±¿1% of baseline...... the vasoconstriction induced by bolus injections of norepinephrine or angiotensin II (by 33¿±¿5% and 60¿±¿5%, respectively). Our results indicate that closure of numerous types of K(+) channels could participate in the mediation of agonist-induced renal vasoconstriction. Our results also suggest that renal...

  15. Multi-Channel Retailing

    Directory of Open Access Journals (Sweden)

    Dirk Morschett, Dr.,

    2005-01-01

    Full Text Available Multi-channel retailing entails the parallel use by retailing enterprises of several sales channels. The results of an online buyer survey which has been conducted to investigate the impact of multi-channel retailing (i.e. the use of several retail channels by one retail company on consumer behaviour show that the frequently expressed concern that the application of multi-channel systems in retailing would be associated with cannibalization effects, has proven unfounded. Indeed, the appropriate degree of similarity, consistency, integration and agreement achieves the exact opposite. Different channels create different advantages for consumers. Therefore the total benefit an enterprise which has a multi-channel system can offer to its consumers is larger, the greater the number of available channels. The use of multi-channel systems is associated with additional purchases in the different channels. Such systems are thus superior to those offering only one sales channel to their customers. Furthermore, multi-channel systems with integrated channels are superior to those in which the channels are essentially autonomous and independent of one another. In integrated systems, consumers can achieve synergy effects in the use of sales-channel systems. Accordingly, when appropriately formulated, multi-channel systems in retailing impact positively on consumers. They use the channels more frequently, buy more from them and there is a positive customer-loyalty impact. Multi-channel systems are strategic options for achieving customer loyalty, exploiting customer potential and for winning new customers. They are thus well suited for approaching differing and varied target groups.

  16. Acid-Sensing Ion Channels and Pain

    Directory of Open Access Journals (Sweden)

    Qihai Gu

    2010-05-01

    Full Text Available Pathophysiological conditions such as inflammation, ischemia, infection and tissue injury can all evoke pain, and each is accompanied by local acidosis. Acid sensing ion channels (ASICs are proton-gated cation channels expressed in both central and peripheral nervous systems. Increasing evidence suggests that ASICs represent essential sensors for tissue acidosis-related pain. This review provides an update on the role of ASICs in pain sensation and discusses their therapeutic potential for pain management.

  17. What controls sediment flux in dryland channels?

    Science.gov (United States)

    Michaelides, K.; Singer, M. B.

    2010-12-01

    Theories for the development of longitudinal and grain size profiles in perennial fluvial systems are well developed, allowing for generalization of sediment flux and sorting in these fluvial systems over decadal to millennial time scales under different forcings (e.g., sediment supply, climate changes, etc). However, such theoretical frameworks are inadequate for understanding sediment flux in dryland channels subject to spatially and temporally discontinuous streamflow, where transport capacity is usually much lower than sediment supply. In such fluvial systems, channel beds are poorly sorted with weak vertical layering, poorly defined bar forms, minimal downstream fining, and straight longitudinal profiles. Previous work in dryland channels has documented sediment flux at higher rates than their humid counterparts once significant channel flow develops, pulsations in bed material transport under constant discharge, and oscillations in dryland channel width that govern longitudinal patterns in erosion and deposition. These factors point to less well appreciated controls on sediment flux in dryland valley floors that invite further study. This paper investigates the relative roles of hydrology, bed material grain size, and channel width on sediment flux rates in the Rambla de Nogalte in southeastern Spain. Topographic valley cross sections and hillslope and channel particle sizes were collected from an ephemeral-river reach. Longitudinal grain-size variation on the hillslopes and on the channel bed were analysed in order to determine the relationship between hillslope supply characteristics and channel grain-size distribution and longitudinal changes. Local fractional estimates of bed-material transport in the channel were calculated using a range of channel discharge scenarios in order to examine the effect of channel hydrology on sediment transport. Numerical modelling was conducted to investigate runoff connectivity from hillslopes to channel and to examine the

  18. Neuronal trafficking of voltage-gated potassium channels

    DEFF Research Database (Denmark)

    Jensen, Camilla S; Rasmussen, Hanne Borger; Misonou, Hiroaki

    2011-01-01

    The computational ability of CNS neurons depends critically on the specific localization of ion channels in the somatodendritic and axonal membranes. Neuronal dendrites receive synaptic inputs at numerous spines and integrate them in time and space. The integration of synaptic potentials....... The physiological significance of proper Kv channel localization is emphasized by the fact that defects in the trafficking of Kv channels are observed in several neurological disorders including epilepsy. In this review, we will summarize the current understanding of the mechanisms of Kv channel trafficking...... is regulated by voltage-gated potassium (Kv) channels, such as Kv4.2, which are specifically localized in the dendritic membrane. The synaptic potentials eventually depolarize the membrane of the axon initial segment, thereby activating voltage-gated sodium channels to generate action potentials. Specific Kv...

  19. Cidofovir in the Treatment of BK Virus-Associated Hemorrhagic Cystitis after Allogeneic Hematopoietic Stem Cell Transplantation.

    Science.gov (United States)

    Philippe, Michael; Ranchon, Florence; Gilis, Lila; Schwiertz, Vérane; Vantard, Nicolas; Ader, Florence; Labussiere-Wallet, Hélène; Thomas, Xavier; Nicolini, Franck-Emmanuel; Wattel, Eric; Ducastelle-Leprêtre, Sophie; Barraco, Fiorenza; Lebras, Laure; Salles, Gilles; Michallet, Mauricette; Rioufol, Catherine

    2016-04-01

    After allogeneic hematopoietic stem cell transplantation (HSCT), BK virus-associated hemorrhagic cystitis (BKV-HC) is a common complication. Although supportive measures have been the standard of care for many years, several studies suggested the efficacy of cidofovir. The aim of this study was to assess the safety profile and efficacy of cidofovir. A retrospective study was conducted on all patients treated with cidofovir in our HSCT unit between March 2011 and May 2013. Data for efficacy (partial [PR] or complete response [CR]), prescription (dose, frequency, number of doses, and administration route), and toxicity were collected from published reports and medical files. Renal toxicity was evaluated using creatinine clearance calculated with the Cockcroft and Gault formula. A parallel literature search using PubMed (last search, May 2015) was performed. From March 2011 to June 2013, 27 of 181 patients undergoing allogeneic HSCT in our department received cidofovir for BKV-HC: 24 (88.9%) intravenously, 1 intravesically, and 2 via both routes. Mean dose was 5 mg/kg per administration, for a median of 4 injections (range, 1 to 11), from twice a week to once every 2 weeks. CR was achieved in 22 patients (81.5%), PR in 2, and no response in 2 patients. Eight patients presented renal failure (29.6%): 6 moderate (creatinine clearance cidofovir was 27% (35 mL/min; range, 2 to 159). In 3 cases renal insufficiency and hematologic toxicity led to discontinuation of treatment or switch to intravesical instillation. For 3 patients cidofovir dose was reduced because of nephrotoxicity. Thirteen studies have reported on the use of cidofovir for BKV-HC (204 patients) since 2005. Intravenous cidofovir was used for 91.3% of patients, with doses ranging from .5 to 5 mg/kg. The main toxicity reported was renal failure (9% to 50% in 9 studies). Between 60% and 100% of CRs were observed independently of cidofovir dose or administration route. Cidofovir is an effective therapy for

  20. Synchronization of P Systems with Simplex Channels

    CERN Document Server

    Ipate, Florentin; Niculescu, Ionut-Mihai; Stefan, Cristian

    2011-01-01

    We solve the Firing Squad Synchronization Problem (FSSP), for P systems based on digraphs with simplex channels, where communication is restricted by the direction of structural arcs. Previous work on FSSP for P systems focused exclusively on P systems with duplex channels, where communication between parents and children is bidirectional. Our P solution, the first for simplex channels, requires cell IDs, strongly connected digraphs and some awareness of the local topology (such as each cell's outdegree)---we argue that these requirements are necessary. Compared to the known solutions for cellular automata, our solution is substantially simpler and faster.

  1. High prevalence of the simultaneous excretion of polyomaviruses JC and BK in the urine of HIV-infected patients without neurological symptoms in São Paulo, Brazil

    Directory of Open Access Journals (Sweden)

    Luiz Henrique da Silva Nali

    2012-08-01

    Full Text Available OBJECTIVE: To evaluate the prevalence of the urinary excretion of BKV and JCV in HIV-infected patients without neurological symptoms. METHODS: Urine samples from HIV-infected patients without neurological symptoms were tested for JC virus and BK virus by PCR. Samples were screened for the presence of polyomavirus with sets of primers complementary to the early region of JCV and BKV genome (AgT. The presence of JC virus or BK virus were confirmed by two other PCR assays using sets of primers complementary to the VP1 gene of each virus. Analysis of the data was performed by the Kruskal-Wallis test for numerical data and Pearson or Yates for categorical variables. RESULTS: A total of 75 patients were included in the study. The overall prevalence of polyomavirus DNA urinary shedding was 67/75 (89.3%. Only BKV DNA was detected in 14/75 (18.7% urine samples, and only JCV DNA was detected in 11/75 (14.7% samples. Both BKV and JCV DNA were present in 42/75 (56.0% samples. CONCLUSION: In this study we found high rates of excretion of JCV, BKV, and simultaneous excretion in HIV+ patients. Also these results differ from the others available on the literature.

  2. Determination of ion-exchanged channel waveguide profile parameters by mode-index measurements.

    Science.gov (United States)

    Weiss, M N; Srivastava, R

    1995-01-20

    We report a method for characterizing ion-exchanged channel waveguides in terms of the diffusion depth, width, and surface-index change from mode-index measurements. The method is then used to study the effect of the diffusion time and the mask width on these parameters in K(+)-Na(+)-exchanged guides in BK7 glass. It is observed that the mask width affects the waveguide dimensions in ways not reported in earlier studies. Our results reveal that the diffusion depth depends on the mask opening and saturates with time to a maximum value for a given mask width. The lateral-diffusion rate and the side diffusion beneath the mask are independent of the mask width, which indicates that the lateral electric field associated with the metallic mask plays an important role in such diffusion. We discuss the implications of this behavior to modeling and fabricating integrated optical devices.

  3. Channel Floor Yardangs

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] Released 19 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth. Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms. The yardangs in this image are forming in channel floor deposits. The channel itself is funneling the wind to cause the erosion. Image information: VIS instrument. Latitude 4.5, Longitude 229.7 East (133.3 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from

  4. USACE Navigation Channels 2012

    Data.gov (United States)

    California Department of Resources — This dataset represents both San Francisco and Los Angeles District navigation channel lines. All San Francisco District channel lines were digitized from CAD files...

  5. Function of specific K(+) channels in sustained high-frequency firing of fast-spiking neocortical interneurons.

    Science.gov (United States)

    Erisir, A; Lau, D; Rudy, B; Leonard, C S

    1999-11-01

    Fast-spiking GABAergic interneurons of the neocortex and hippocampus fire high-frequency trains of brief action potentials with little spike-frequency adaptation. How these striking properties arise is unclear, although recent evidence suggests K(+) channels containing Kv3.1-Kv3.2 proteins play an important role. We investigated the role of these channels in the firing properties of fast-spiking neocortical interneurons from mouse somatosensory cortex using a pharmacological and modeling approach. Low tetraethylammonium (TEA) concentrations (BK Ca(2+)-activated K(+) channels, which also have high TEA sensitivity, produced opposite or no effects. Voltage-clamp experiments confirmed the presence of a Kv3.1-Kv3.2-like current in fast-spiking neurons, but not in other interneurons. Analysis of spike shape changes during the spike trains suggested that Na(+) channel inactivation plays a significant role in the firing-rate slowdown produced by TEA, a conclusion that was supported by computer simulations. These findings indicate that the unique properties of Kv3.1-Kv3.2 channels enable sustained high-frequency firing by facilitating the recovery of Na(+) channel inactivation and by minimizing the duration of the afterhyperpolarization in neocortical interneurons.

  6. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  7. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  8. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...

  9. Analysis of the action of lidocaine on insect sodium channels.

    Science.gov (United States)

    Song, Weizhong; Silver, Kristopher S; Du, Yuzhe; Liu, Zhiqi; Dong, Ke

    2011-01-01

    A new class of sodium channel blocker insecticides (SCBIs), which include indoxacarb, its active metabolite, DCJW, and metaflumizone, preferably block inactivated states of both insect and mammalian sodium channels in a manner similar to that by which local anesthetic (LA) drugs block mammalian sodium channels. A recent study showed that two residues in the cockroach sodium channel, F1817 and Y1824, corresponding to two key LA-interacting residues identified in mammalian sodium channels are not important for the action of SCBIs on insect sodium channels, suggesting unique interactions of SCBIs with insect sodium channels. However, the mechanism of action of LAs on insect sodium channels has not been investigated. In this study, we examined the effects of lidocaine on a cockroach sodium channel variant, BgNa(v)1-1a, and determined whether F1817 and Y1824 are also critical for the action of LAs on insect sodium channels. Lidocaine blocked BgNa(v)1-1a channels in the resting state with potency similar to that observed in mammalian sodium channels. Lidocaine also stabilized both fast-inactivated and slow-inactivated states of BgNa(v)1-1a channels, and caused a limited degree of use- and frequency-dependent block, major characteristics of LA action on mammalian sodium channels. Alanine substitutions of F1817 and Y1824 reduced the sensitivity of the BgNa(v)1-1a channel to the use-dependent block by lidocaine, but not to tonic blocking and inactivation stabilizing effects of lidocaine. Thus, similar to those on mammalian sodium channels, F1817 and Y1824 are important for the action of lidocaine on cockroach sodium channels. Our results suggest that the receptor sites for lidocaine and SCBIs are different on insect sodium channels.

  10. Protocol channels as a new design alternative of covert channels

    CERN Document Server

    Wendzel, Steffen

    2008-01-01

    Covert channel techniques are used by attackers to transfer hidden data. There are two main categories of covert channels: timing channels and storage channels. This paper introduces a third category called protocol channels. A protocol channel switches one of at least two protocols to send a bit combination to a destination while sent packets include no hidden information themselves.

  11. Surface vacancy channels through ion channeling

    Energy Technology Data Exchange (ETDEWEB)

    Redinger, Alex; Standop, Sebastian; Michely, Thomas [II. Physikalisches Institut, Universitaet Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Rosandi, Yudi; Urbassek, Herbert M. [Fachbereich Physik, Technische Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)

    2009-07-01

    Damage patterns of single ion impacts on Pt(111) have been studied by scanning tunneling microscopy (STM) and molecular dynamics simulations (MD). Low temperature experiments, where surface diffusion is absent, have been performed for argon and xenon ions with energies between 1 keV and 15 keV at an angle of incidence of 86 {sup circle} measured with respect to the surface normal. Ions hitting preexisting illuminated step edges penetrate into the crystal and are guided in open crystallographic directions, one or more layers underneath the surface (subsurface channeling). In the case of argon channeling the resulting surface damage consists of adatom and vacancy pairs aligned in ion beam direction. After xenon channeling thin surface vacancy trenches along the ion trajectories - surface vacancy channels - are observed. They result from very efficient sputtering and adatom production along the ion trajectory. This phenomena is well reproduced in molecular dynamics simulations of single ion impacts at 0 K. The damage patterns of Argon and Xenon impacts can be traced back to the different energy losses of the particles in the channel. Channeling distances exceeding 1000 A for 15 keV xenon impacts are observed.

  12. The Research Progress of BK Virus Infection After Renal Transplantation%肾移植术后BK病毒感染研究进展

    Institute of Scientific and Technical Information of China (English)

    范宇(综述); 石炳毅; 钱叶勇(审校)

    2014-01-01

    BK病毒是一种隶属于多瘤病毒种属的DNA病毒,在正常人群中的感染率高达90%。然而,仅在免疫功能受损的个体中引发相关疾病,以接受移植手术后服用免疫抑制药物的患者最为显著。 BK病毒的持续复制被认为是导致肾移植受者移植肾功能受损的重要因素,而由其引发的BK病毒性肾病( BKVN)则已成为肾移植失败的重要原因之一。应用尿细胞学染色和检测尿液或血液中BK病毒DNA载量等方法可对BK病毒感染和BKVN进行监测并早期诊断,增加了早期治疗的成功率。然而,由于缺乏特异性的抗病毒药物,BKVN的治疗仍然是非常困难。该文即针对肾移植术后BK病毒感染的流行病学、发病机制、实验室检测方法以及治疗策略的研究予以综述。%The BK virus,a DNA virus from the polyomavirus group,infects up to 90% of the general population. However,significant clinical manifestations are rare and limited to individuals with impaired im-mune functions,especially in the renal transplant recipients who recepted immunosuppressor. Persistent BK virus replication in patients with renal allografts was identified as an important cause of progressive graft dys-function,and the BK virus nephritis ( BKVN) has emerged as an important cause of renal transplant failure. Diagnostic strategies using urine cytology and BKV load measurements in urine or plasma have led to earlier diagnosis of BKV infection and BKVN,which increased the success rate of intervention. But due to the lack of specific antiviral drugs,the treatment of BKVN is difficult. In this review,we discuss the epidemiology,patho-genesis,detction method and current treatment protocols.

  13. Inmunoterapia local Local immunotherapy

    Directory of Open Access Journals (Sweden)

    E. Lasa

    2003-01-01

    Full Text Available La inmunoterapia específica, junto con la evitación del alergeno y el tratamiento sintomático, forma parte del tratamiento de la patología alérgica. La modalidad más antigua, más conocida y mejor estudiada es la inmunoterapia subcutánea (ITSC, cuya eficacia tanto a corto como a largo plazo, ha sido ampliamente demostrada en numerosos estudios. Sin embargo, a pesar de haberse demostrado segura, no está exenta de efectos adversos y precisa ser administrada bajo supervisión de personal médico. Esto ha animado a buscar nuevas vías de administración de eficacia similar, con un buen perfil de seguridad, y de buena cumplimentación por parte del paciente. De las distintas alternativas estudiadas la más relevante es la inmunoterapia sublingual (ITSL. En ésta, se administra el antígeno en forma de gotas debajo de la lengua. Existen diferentes pautas de administración en función del alergeno implicado. La dosis óptima de tratamiento está aún sin determinar, hallándose en este momento en un rango amplio de dosis respecto a la inmunoterapia subcutánea. Su mecanismo de acción es poco conocido aunque en diversos estudios se han observado cambios inmunológicos. La ITSL ha mostrado un buen perfil de seguridad con escasos efectos secundarios, habitualmente de carácter local. Asimismo se han realizado distintos ensayos clínicos en los que se ha demostrado su eficacia en el tratamiento de la alergia respiratoria tanto en niños como en adultos. Por ello, aunque aún existen datos sin resolver respecto a esta vía de administración de inmunoterapia, ha sido propuesta por la OMS como una alternativa válida a la ITSC.Specific immunotherapy, together with avoidance of the allergen and symptomatic treatment, forms part of the treatment of allergic pathology. The oldest, best known and most studied form is subcutaneous immunotherapy (SCIT, whose efficacy, both in the short and the long term, has been widely demonstrated in numerous studies

  14. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides.

    Science.gov (United States)

    Borbiro, Istvan; Badheka, Doreen; Rohacs, Tibor

    2015-02-10

    Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor phosphatidylinositol 4-phosphate [PI(4)P] from the plasma membrane through Ca(2+)-induced phospholipase Cδ (PLCδ) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLCβ indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 and PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin.

  15. Documenting localities

    CERN Document Server

    Cox, Richard J

    1996-01-01

    Now in paperback! Documenting Localities is the first effort to summarize the past decade of renewed discussion about archival appraisal theory and methodology and to provide a practical guide for the documentation of localities.This book discusses the continuing importance of the locality in American historical research and archival practice, traditional methods archivists have used to document localities, and case studies in documenting localities. These chapters draw on a wide range of writings from archivists, historians, material culture specialists, historic preservationists

  16. Electrokinetic inversion of ion screening charges in nano-channels

    CERN Document Server

    Zhu, Xin; Ni, Sheng; Zhang, Xingye; Liu, Yang

    2016-01-01

    This work studies a counter-intuitive but basic process of ionic screening in nano-fluidic channels. Numerical simulations and perturbation analysis reveal that, under significant electrokinetic transport, the ion screening charges can be locally inverted in the channels: their charge sign becomes the same as that of the channel surface charges. The process is identified to originate from the coupling of longitudinal transport and junction electrostatics. This finding may revise the common understanding of ionic screening in nano-channels and indicates that their ion selectivity can be locally changed by transport. Furthermore, the charge inversion process results in a body force torque on channel fluids, which is a possible mechanism for vortex generation in the channels.

  17. Measuring Method for Lightning Channel Temperature

    Science.gov (United States)

    Li, X.; Zhang, J.; Chen, L.; Xue, Q.; Zhu, R.

    2016-09-01

    In this paper, we demonstrate the temperature of lightning channel utilizing the theory of lightning spectra and the model of local thermodynamic equilibrium (LTE). The impulse current generator platform (ICGS) was used to simulate the lightning discharge channel, and the spectral energy of infrared spectroscopy (930 nm) and the visible spectroscopy (648.2 nm) of the simulated lightning has been calculated. Results indicate that the peaks of luminous intensity of both infrared and visible spectra increase with the lightning current intensity in range of 5-50 kA. Based on the results, the temperature of the lightning channel is derived to be 6140.8-10424 K. Moreover, the temperature of the channel is approximately exponential to the lightning current intensity, which shows good agreement with that of the natural lightning cases.

  18. Nonperturbative approach to relativistic quantum communication channels

    Science.gov (United States)

    Landulfo, André G. S.

    2016-05-01

    We investigate the transmission of both classical and quantum information between two arbitrary observers in globally hyperbolic spacetimes using a quantum field as a communication channel. The field is supposed to be in some arbitrary quasifree state and no choice of representation of its canonical commutation relations is made. Both sender and receiver possess some localized two-level quantum system with which they can interact with the quantum field to prepare the input and receive the output of the channel, respectively. The interaction between the two-level systems and the quantum field is such that one can trace out the field degrees of freedom exactly and thus obtain the quantum channel in a nonperturbative way. We end the paper determining the unassisted as well as the entanglement-assisted classical and quantum channel capacities.

  19. Measuring Method for Lightning Channel Temperature

    Science.gov (United States)

    Li, X.; Zhang, J.; Chen, L.; Xue, Q.; Zhu, R.

    2016-01-01

    In this paper, we demonstrate the temperature of lightning channel utilizing the theory of lightning spectra and the model of local thermodynamic equilibrium (LTE). The impulse current generator platform (ICGS) was used to simulate the lightning discharge channel, and the spectral energy of infrared spectroscopy (930 nm) and the visible spectroscopy (648.2 nm) of the simulated lightning has been calculated. Results indicate that the peaks of luminous intensity of both infrared and visible spectra increase with the lightning current intensity in range of 5–50 kA. Based on the results, the temperature of the lightning channel is derived to be 6140.8–10424 K. Moreover, the temperature of the channel is approximately exponential to the lightning current intensity, which shows good agreement with that of the natural lightning cases. PMID:27665937

  20. Channel estimation for MIMO-OFDM systems in wireless mobile channels

    Institute of Scientific and Technical Information of China (English)

    Lu Zhen; Ge Jianhua

    2008-01-01

    New training sequences and frame structure are proposed to estimate time-varying channel for multiple-input multiple-output and orthogonal frequency division multiplexing (MIMO-OFDM) systems. The training sequences are modulatable orthogonal polyphase sequences, which have both good autocorrelations and cross-correlations. The channel impulse response (CIR) can be obtained by measuring the correlation between the received training sequence and the locally generated training sequence. The training sequences are used as guard interval instead of cyclic prefix, which not only improve the transmission efficiency but also enable the channel estimator to track time-varying channel. The simulation results show that the proposed method has about 2dB SNR gain over conventional methods in fast time-varying channel.

  1. Observation of a resonance-like structure in the pi^+- psi' mass distribution in exclusive B-->K pi^+- psi' decays

    CERN Document Server

    Abe, K; Aihara, H; Arinstein, K; Aso, T; Aulchenko, V; Aushev, T; Aziz, T; Bahinipati, S; Bakich, A M; Balagura, V; Ban, Y; Banerjee, S; Barberio, E; Bay, A; Bedny, I; Belous, K S; Bhardwaj, V; Bitenc, U; Blyth, S; Bondar, A; Bozek, A; Bracko, M; Brodzicka, J; Browder, T E; Chang, M C; Chang, P; Chao, Y; Chen, A; Chen, K F; Chen, W T; Cheon, B G; Chiang, C C; Chistov, R; Cho, I S; Choi, S K; Choi, Y; Choi, Y K; Cole, S; Dalseno, J; Danilov, M; Das, A; Dash, M; Dragic, J; Drutskoy, A; Eidelman, S; Epifanov, D; Fratina, S; Fujii, H; Fujikawa, M; Gabyshev, N; Garmash, A; Go, A; Gokhroo, G; Goldenzweig, P; Golob, B; Grosse-Perdekamp, M; Guler, H; Ha, H; Haba, J; Hara, K; Hara, T; Hasegawa, Y; Hastings, N C; Hayasaka, K; Hayashii, H; Hazumi, M; Heffernan, D; Higuchi, T; Hinz, L; Hoedlmoser, H; Hokuue, T; Horii, Y; Hoshi, Y; Hoshina, K; Hou, S; Hou, W S; Hsiung, Y B; Hyun, H J; Igarashi, Y; Iijima, T; Ikado, K; Inami, K; Ishikawa, A; Ishino, H; Itoh, R; Iwabuchi, M; Iwasaki, M; Iwasaki, Y; Jacoby, C; Joshi, N J; Kaga, M; Kah, D H; Kaji, H; Kajiwara, S; Kakuno, H; Kang, J H; Kapusta, P; Kataoka, S U; Katayama, N; Kawai, H; Kawasaki, T; Kibayashi, A; Kichimi, H; Kim, H J; Kim, H O; Kim, J H; Kim, S K; Kim, Y J; Kinoshita, K; Korpar, S; Kozakai, Y; Krizan, P; Krokovny, P; Kumar, R; Kurihara, E; Kusaka, A; Kuzmin, A; Kwon, Y J; Lange, J S; Leder, G; Lee, J; Lee, J S; Lee, M J; Lee, S E; Lesiak, T; Li, J; Limosani, A; Lin, S W; Liu, Y; Liventsev, D; MacNaughton, J; Majumder, G; Mandl, F; Marlow, D; Matsumura, T; Matyja, A; McOnie, S; Medvedeva, T; Mikami, Y; Mitaroff, W A; Miyabayashi, K; Miyake, H; Miyata, H; Miyazaki, Y; Mizuk, R; Moloney, G R; Mori, T; Müller, J; Murakami, A; Nagamine, T; Nagasaka, Y; Nakahama, Y; Nakamura, I; Nakano, E; Nakao, M; Nakayama, H; Nakazawa, H; Natkaniec, Z; Neichi, K; Nishida, S; Nishimura, K; Nishio, Y; Nishizawa, I; Nitoh, O; Noguchi, S; Nozaki, T; Ogawa, A; Ogawa, S; Ohshima, T; Okuno, S; Olsen, S L; Ono, S; Ostrowicz, W; Ozaki, H; Pakhlov, P; Pakhlova, G; Palka, H; Park, C W; Park, H; Park, K S; Parslow, N; Peak, L S; Pernicka, M; Pestotnik, R; Peters, M; Piilonen, L E; Poluektov, A; Rorie, J; Rózanska, M; Sahoo, H; Sakai, Y; Sakamoto, H; Sakaue, H; Sarangi, T R; Satoyama, N; Sayeed, K; Schietinger, T; Schneider, O; Schonmeier, P; Schümann, J; Schwanda, C; Schwartz, A J; Seidl, R; Sekiya, A; Senyo, K; Sevior, M E; Shang, L; Shapkin, M; Shen, C P; Shibuya, H; Shinomiya, S; Shiu, J G; Shwartz, B; Singh, J B; Sokolov, A; Solovieva, E; Somov, A; Stanic, S; Staric, M; Stypula, J; Sugiyama, A; Sumisawa, K; Sumiyoshi, T; Suzuki, S; Suzuki, S Y; Tajima, O; Takasaki, F; Tamai, K; Tamura, N; Tanaka, M; Taniguchi, N; Taylor, G N; Teramoto, Y; Tikhomirov, I; Trabelsi, K; Tse, Y F; Tsuboyama, T; Uchida, K; Uchida, Y; Uehara, S; Ueno, K; Uglov, T; Unno, Y; Uno, S; Urquijo, P; Ushiroda, Y; Usov, Yu; Varner, G; Varvell, K E; Vervink, K; Villa, S; Vinokurova, A; Wang, C C; Wang, C H; Wang, J; Wang, M Z; Wang, P; Wang, X L; Watanabe, M; Watanabe, Y; Wedd, R; Wicht, J; Widhalm, L; Wiechczynski, J; Won, E; Yabsley, B D; Yamaguchi, A; Yamamoto, H; Yamaoka, M; Yamashita, Y; Yamauchi, M; Yuan, C Z; Yusa, Y; Zhang, C C; Zhang, L M; Zhang, Z P; Zhilich, V; Zhulanov, V; Zupanc, A; Zwahlen, N

    2007-01-01

    A distinct peak is observed in the pi^+/- psi' invariant mass distribution near 4.43 GeV in B->K pi^+/- psi' decays. A fit using a Breit Wigner resonance shape yields a peak mass and width of 4433+-4(stat)+-1(syst) MeV and Gamma = 44^+17_-13(stat) ^+30_-11 MeV. The product branching fraction is determined to be Bf(B-->KZ(4430))xBf(Z(4430)-->pi^+psi') = (4.1+-1.0(stat)+-1.3(syst))x10^{-5), where Z(4430) is used to designate the observed structure. The statistical significance of the observed peak is greater than 7sigma. These results are obtained from a 605 fb-1 data sample that contains 657 million BBbar pairs collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider.

  2. Human endothelial cells allow passage of an archetypal BK virus (BKV) strain--a tool for cultivation and functional studies of natural BKV strains.

    Science.gov (United States)

    Hanssen Rinaldo, C; Hansen, H; Traavik, T

    2005-07-01

    The ubiquitous human polyomavirus BK (BKV) causes the serious condition BKV-nephropathy in an increasing number of renal-transplant patients. The lack of authentic cell cultures for multiplication of naturally occurring strains has hampered cultivation and functional studies of BKV. Here we demonstrate that the most common urine shed BKV strain, the archetype, multiplies in the human endothelial cell line HUV-EC-C. Additional variants with deletions in the non-coding control region (NCCR) appear upon prolonged propagation. Although the titer produced was low, at the present HUV-EC-C is the only cell line shown to allow propagation of archetypal BKV. HUV-EC-C may therefore be a useful tool for BKV cultivation as well as functional studies.

  3. Quantum broadcast channels

    CERN Document Server

    Yard, J; Devetak, I; Yard, Jon; Hayden, Patrick; Devetak, Igor

    2006-01-01

    We analyze quantum broadcast channels, which are quantum channels with a single sender and many receivers. Focusing on channels with two receivers for simplicity, we generalize a number of results from the network Shannon theory literature which give the rates at which two senders can receive a common message, while a personalized one is sent to one of them. Our first collection of results applies to channels with a classical input and quantum outputs. The second class of theorems we prove concern sending a common classical message over a quantum broadcast channel, while sending quantum information to one of the receivers. The third group of results we obtain concern communication over an isometry, giving the rates at quantum information can be sent to one receiver, while common quantum information is sent to both, in the sense that tripartite GHZ entanglement is established. For each scenario, we provide an additivity proof for an appropriate class of channels, yielding single-letter characterizations of the...

  4. Influence of salinity on the localization of Na+/K +-ATPase, Na+/K+/2Cl- cotransporter (NKCC) and CFTR anion channel in chloride cells of the Hawaiian goby (Stenogobius hawaiiensis)

    Science.gov (United States)

    McCormick, S.D.; Sundell, K.; Bjornsson, Bjorn Thrandur; Brown, C.L.; Hiroi, J.

    2003-01-01

    Na+/K+-ATPase, Na+/K+/2Cl- cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR) are the three major transport proteins thought to be involved in chloride secretion in teleost fish. If this is the case, the levels of these transporters should be high in chloride cells of seawater-acclimated fish. We therefore examined the influence of salinity on immunolocalization of Na +/K+-ATPase, NKCC and CFTR in the gills of the Hawaiian goby (Stenogobius hawaiiensis). Fish were acclimated to freshwater and 20??? and 30??? seawater for 10 days. Na+/K +-ATPase and NKCC were localized specifically to chloride cells and stained throughout most of the cell except for the nucleus and the most apical region, indicating a basolateral/tubular distribution. All Na+/K +-ATPase-positive chloride cells were also positive for NKCC in all salinities. Salinity caused a slight increase in chloride cell number and size and a slight decrease in staining intensity for Na+/K +-ATPase and NKCC, but the basic pattern of localization was not altered. Gill Na+/K+-ATPase activity was also not affected by salinity. CFTR was localized to the apical surface of chloride cells, and only cells staining positive for Na+/K+-ATPase were CFTR-positive. CFTR-positive cells greatly increased in number (5-fold), area stained (53%) and intensity (29%) after seawater acclimation. In freshwater, CFTR immunoreactivity was light and occurred over a broad apical surface on chloride cells, whereas in seawater there was intense immunoreactivity around the apical pit (which was often punctate in appearance) and a light subapical staining. The results indicate that Na+/K +-ATPase, NKCC and CFTR are all present in chloride cells and support current models that all three are responsible for chloride secretion by chloride cells of teleost fish.

  5. Intra-membrane molecular interactions of K+ channel proteins :

    Energy Technology Data Exchange (ETDEWEB)

    Moczydlowski, Edward G.

    2013-07-01

    Ion channel proteins regulate complex patterns of cellular electrical activity and ionic signaling. Certain K+ channels play an important role in immunological biodefense mechanisms of adaptive and innate immunity. Most ion channel proteins are oligomeric complexes with the conductive pore located at the central subunit interface. The long-term activity of many K+ channel proteins is dependent on the concentration of extracellular K+; however, the mechanism is unclear. Thus, this project focused on mechanisms underlying structural stability of tetrameric K+ channels. Using KcsA of Streptomyces lividans as a model K+ channel of known structure, the molecular basis of tetramer stability was investigated by: 1. Bioinformatic analysis of the tetramer interface. 2. Effect of two local anesthetics (lidocaine, tetracaine) on tetramer stability. 3. Molecular simulation of drug docking to the ion conduction pore. The results provide new insights regarding the structural stability of K+ channels and its possible role in cell physiology.

  6. Multi-channel support for DMAC in WSNs

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Currently most wireless sensor network applications assume the presence of single-channel medium access control (MAC) protocols. However, lower sensing range result in dense networks, single-channel MAC protocols may be inadequate due to higher demand for the limited bandwidth. In this paper we proposed a method of multi-channel support for DMAC in Wireless sensor networks (WSNs). The channel assignment method is based on local information of nodes. Our multi-channel DMAC protocol implement channel distribution before message collecting from source nodes to sink node and made broadcasting possible in DMAC. Analysis and simulation result displays this multi-channel protocol obviously decreases the latency without increasing energy consumption.

  7. Quantum feedback channels

    CERN Document Server

    Bowen, G

    2002-01-01

    In classical information theory the capacity of a noisy communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum information cannot be achieved. In this paper, quantum feedback is defined as the unlimited use of a noiseless quantum channel from receiver to sender. Given such quantum feedback, it is shown to provide no increase in the entanglement-assisted capacities of a noisy quantum channel, in direct analogy to the classical case. It is also shown that in various cases of non-assisted capacities, feedback can increase the capacity of many quantum channels.

  8. Ion channels in asthma.

    Science.gov (United States)

    Valverde, Miguel A; Cantero-Recasens, Gerard; Garcia-Elias, Anna; Jung, Carole; Carreras-Sureda, Amado; Vicente, Rubén

    2011-09-23

    Ion channels are specialized transmembrane proteins that permit the passive flow of ions following their electrochemical gradients. In the airways, ion channels participate in the production of epithelium-based hydroelectrolytic secretions and in the control of intracellular Ca(2+) levels that will ultimately activate almost all lung cells, either resident or circulating. Thus, ion channels have been the center of many studies aiming to understand asthma pathophysiological mechanisms or to identify therapeutic targets for better control of the disease. In this minireview, we focus on molecular, genetic, and animal model studies associating ion channels with asthma.

  9. TRP channels in schistosomes

    Directory of Open Access Journals (Sweden)

    Swarna Bais

    2016-12-01

    Full Text Available Praziquantel (PZQ is effectively the only drug currently available for treatment and control of schistosomiasis, a disease affecting hundreds of millions of people worldwide. Many anthelmintics, likely including PZQ, target ion channels, membrane protein complexes essential for normal functioning of the neuromusculature and other tissues. Despite this fact, only a few classes of parasitic helminth ion channels have been assessed for their pharmacological properties or for their roles in parasite physiology. One such overlooked group of ion channels is the transient receptor potential (TRP channel superfamily. TRP channels share a common core structure, but are widely diverse in their activation mechanisms and ion selectivity. They are critical to transducing sensory signals, responding to a wide range of external stimuli. They are also involved in other functions, such as regulating intracellular calcium and organellar ion homeostasis and trafficking. Here, we review current literature on parasitic helminth TRP channels, focusing on those in schistosomes. We discuss the likely roles of these channels in sensory and locomotor activity, including the possible significance of a class of TRP channels (TRPV that is absent in schistosomes. We also focus on evidence indicating that at least one schistosome TRP channel (SmTRPA has atypical, TRPV1-like pharmacological sensitivities that could potentially be exploited for future therapeutic targeting.

  10. Local architecture

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Local architecture refers to structures built in the countryside,such as temples,memorial halls,residences, stores,pavilions, bridges,decorated archways, and wells. Because these structures were all built by focal craftsmen and villagers in the traditional local style, they are generally called local architecture.

  11. A linearization of quantum channels

    Science.gov (United States)

    Crowder, Tanner

    2015-06-01

    Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.

  12. Morphological dynamics of an englacial channel

    Directory of Open Access Journals (Sweden)

    G. Vatne

    2015-08-01

    Full Text Available Despite an interest in the hydraulic functioning of supraglacial and englacial channels over the last four decades, the processes and forms of such ice-bounded streams have remained poorly documented. Recent glaciological research has demonstrated the potential significance of so-called "cut and closure" streams, where englacial or subglacial flowpaths are created from the long-term incision of supraglacial channels. These flowpaths are reported to exhibit step-pool morphology, comprising knickpoints and/or knickzones, albeit exaggerated in dimensions in comparison to their supraglacial channel counterparts. However, little is known of the development of such channels' morphology. Here, we examine the spatial organization of step-pools and the upstream migration of steps, many of which form knickzones, with repeated surveys over a 10 year period in an englacial conduit in cold-based Austre Brøggerbreen, Svalbard. The observations show upstream knickpoint recession to be the dominant process for channel evolution. This is paralleled by an increase in average step height and conduit gradient over time. Characteristic channel reach types and step-riser forms are consistently observed in each of the morphological surveys reported. We suggest that the formation of steps has a hydrodynamic origin, where step-pool geometry is more efficient for energy dissipation than meanders, and that the englacial channel system is one in rapid transition rather than in dynamic equilibrium. The evolution and recession of knickzones reported here result in the formation of a 37 m moulin, suggesting over time the englacial channel may evolve towards a stable end-point characterised by a singular vertical descent to the local hydraulic base level. In light of this, our observations highlight the need to further examine the adjustment processes in cut-and-closure channels to better understand their coupling to supraglacial meltwater sources and role and potential

  13. Ion channels in toxicology.

    Science.gov (United States)

    Restrepo-Angulo, Iván; De Vizcaya-Ruiz, Andrea; Camacho, Javier

    2010-08-01

    Ion channels play essential roles in human physiology and toxicology. Cardiac contraction, neural transmission, temperature sensing, insulin release, regulation of apoptosis, cellular pH and oxidative stress, as well as detection of active compounds from chilli, are some of the processes in which ion channels have an important role. Regulation of ion channels by several chemicals including those found in air, water and soil represents an interesting potential link between environmental pollution and human diseases; for instance, de novo expression of ion channels in response to exposure to carcinogens is being considered as a potential tool for cancer diagnosis and therapy. Non-specific binding of several drugs to ion channels is responsible for a huge number of undesirable side-effects, and testing guidelines for several drugs now require ion channel screening for pharmaceutical safety. Animal toxins targeting human ion channels have serious effects on the population and have also provided a remarkable tool to study the molecular structure and function of ion channels. In this review, we will summarize the participation of ion channels in biological processes extensively used in toxicological studies, including cardiac function, apoptosis and cell proliferation. Major findings on the adverse effects of drugs on ion channels as well as the regulation of these proteins by different chemicals, including some pesticides, are also reviewed. Association of ion channels and toxicology in several biological processes strongly suggests these proteins to be excellent candidates to follow the toxic effects of xenobiotics, and as potential early indicators of life-threatening situations including chronic degenerative diseases.

  14. Residue Phe266 in S5-S6 loop is not critical for Charybdotoxin binding to Ca2+-activated K+ (mSlo1) channels

    Institute of Scientific and Technical Information of China (English)

    Jing YAO; Hui LI; Ge-liang GAN; Ying WU; Jiu-ping DING

    2006-01-01

    Aim: To gain insight into the interaction between the Charybdotoxin (ChTX) and BK channels. Methods: Site-directed mutagenesis was used to make two mutants: mSlo1-F266L and mSlo1-F266A. The two mutants were then expressed in Xeno-pus oocytes and their effects were tested on ChTX by electrophysiology experiments. Results: We demonstrate an equilibrium dissociation constant Kd= 3.1-4.2 nmol/L for both the mutants mSlo1-F266L and mSlo1-F266A similar to that of the wild-type mSlo1 Kd=3.9 nmol/L. Conclusion: The residue Phe266 does not play a crucial role in binding to ChTX, which is opposed to the result arising from the simulation of peptide-channel interaction.

  15. BK Virus-Hemorrhagic Cystitis Following Allogeneic Stem Cell Transplantation: Clinical Characteristics and Utility of Leflunomide Treatment

    Directory of Open Access Journals (Sweden)

    Young Hoon Park

    2016-08-01

    Full Text Available Objective: BK virus-hemorrhagic cystitis (BKV-HC is a potential cause of morbidity and mortality in patients having undergone allogeneic stem cell transplantation (Allo-SCT. We analyzed the clinical features of BKV-HC following Allo-SCT and reported the utility of leflunomide therapy for BKV-HC. Materials and methods: From January 2005 to June 2014, among the 69 patients underwent Allo-SCT in our institution, the patients who experienced BKV-HC were investigated retrospectively. Results: Hemorrhagic cystitis (HC was observed in 30 patients (43.5%, and among them, 18 patients (26.1% were identified as BKV-HC. The median age of the patients (12 males and 6 females was 45 years (range, 13-63. Patients received Allo-SCT from acute myeloid leukemia (n=11, aplastic anemia (n=4, myelodysplastic syndrome (n=2, and non-Hodgkin lymphoma (n=1.The donor types were a HLA-matched sibling donor for 6 patients, HLA-matched unrelated donor for 9, and a haploidentical familial donor for 2. The median onset and duration of BKV-HC was on day 21 (range, 7-97 after transplantation and 22 days (range, 6-107. Eleven patients (62.1% had grade I-II HC and seven patients (38.9% had grade III-IV (high-grade HC. Among the seven patients who had high-grade HC, one had complete response (CR, one partial response (PR, and five no response (NR. Among the five non-responders, one died of BKV-HC associated complications. The remaining four patients were treated with leflunomide, with achieving CR (n=2 and PR (n=2. The median duration from the start of leflunomide therapy to response was 13 days (range, 8–17 days. All patients tolerated the leflunomide treatment well, with three patients having mild gastrointestinal symptoms, including anorexia and abdominal bloating. Conclusion: BKV-HC was commonly observed in patients with HC following Allo-SCT. In high-grade BKV-HC patients who fail supportive care, leflunomide may be a feasible option without significant toxicity. Materials

  16. Effect of large conductance Ca2+-activated K+ channel current and cytosolic calcium concentrations in retinal artery smooth muscle cells on diabetic retinal artery tension%视网膜动脉平滑肌细胞中大电导钙离子激活钾通道电流和钙离子浓度变化对糖尿病视网膜动脉收缩的影响

    Institute of Scientific and Technical Information of China (English)

    邵珺; 姚勇; 孙尉; 王如兴

    2016-01-01

    Background Diabetic retinopathy (DR) is a common microvascular complications of the retina,retinal vascular smooth muscle cells of large conductance calcium-activated potassium channels (BK) is a major factor in regulating vasomotor and hemodynamic.Currently,functional changes of BK channel in retinal artery smooth muscle cells (RASMCs) and its role in DR were rarely reported.Objective This study was to investigate the early vascular damage mechanisms in DR by detecting the changes of BK channels current,calcium concentration and open probability (NP0) of BK channel with different calcium concentration in RASMCs of normal and diabetic rats.Method Fifty SPF SD 8-12 weeks old rats were randomly divided into normal control group and diabetic model group.Forty diabetic rats was intraperitoneally injected with 60 mg/kg streptozotocin to form type 1 diabetic model,10 rats (the normal control group) were injected sodium citrate solution with the same manner.Fluorescent probe was applied to detect calcium concentration in rat RASMCs;RASMCs were isolated by using enzyme digestion,and BK-channel electric currents and calcium concentrations in the RASMCs were measured by whole-cell patch clamp technique and fluorescence assay,respectively.The NP0 of BK channel was measured by single patch clamp technique.Results Diabetic models were successfully established in 36 rats with the success rate 90%.When stimulation voltage is greater than 60 mV,the current density of BK channel in RASMCs of diabetic model group decreased;when stimulating voltage was 100 mV,the BK channel currents of RASMCs in the normal control group and diabetic model group were (100±23) PA/PF and (50 ± 7) PA/PF,the difference was statistically significant (t =19.80,P < 0.05).After adding specific BK channel blocker African scorpion toxin 100 nmol,the BK channel current in the normal control group significantly reduced,and that in the diabetes model group was not significantly changed;the calcium ion

  17. River channel patterns: Braided, meandering, and straight

    Science.gov (United States)

    Leopold, Luna B.; Wolman, M. Gordon

    1957-01-01

    Channel pattern is used to describe the plan view of a reach of river as seen from an airplane, and includes meandering, braiding, or relatively straight channels. Natural channels characteristically exhibit alternating pools or deep reaches and riffles or shallow reaches, regardless of the type of pattern. The length of the pool or distance between riffles in a straight channel equals the straight line distance between successive points of inflection in the wave pattern of a meandering river of the same width. The points of inflection are also shallow points and correspond to riffles in the straight channel. This distance, which is half the wavelength of the meander, varies approximately as a linear function of channel width. In the data we analysed the meander wavelength, or twice the distance between successive riffles, is from 7 to 12 times the channel width. It is concluded that the mechanics which may lead to meandering operate in straight channels. River braiding is characterized by channel division around alluvial islands. The growth of an island begins as the deposition of a central bar which results from sorting and deposition of the coarser fractions of the load which locally cannot be transported. The bar grows downstream and in height by continued deposition on its surface, forcing the water into the flanking channels, which, to carry the flow, deepen and cut laterally into the origin