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Sample records for eag1 channel lateral

  1. Characterization of Eag1 channel lateral mobility in rat hippocampal cultures by single-particle-tracking with quantum dots.

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    David Gómez-Varela

    2010-01-01

    Full Text Available Voltage-gated ion channels are main players involved in fast synaptic events. However, only slow intracellular mechanisms have so far been described for controlling their localization as real-time visualization of endogenous voltage-gated channels at high temporal and spatial resolution has not been achieved yet. Using a specific extracellular antibody and quantum dots we reveal and characterize lateral mobility as a faster mechanism to dynamically control the number of endogenous ether-a-go-go (Eag1 ion channels inside synapses. We visualize Eag1 entering and leaving synapses by lateral diffusion in the plasma membrane of rat hippocampal neurons. Mathematical analysis of their trajectories revealed how the motion of Eag1 gets restricted when the channels diffuse into the synapse, suggesting molecular interactions between Eag1 and synaptic components. In contrast, Eag1 channels switch to Brownian movement when they exit synapses and diffuse into extrasynaptic membranes. Furthermore, we demonstrate that the mobility of Eag1 channels is specifically regulated inside synapses by actin filaments, microtubules and electrical activity. In summary, using single-particle-tracking techniques with quantum dots nanocrystals, our study shows for the first time the lateral diffusion of an endogenous voltage-gated ion channel in neurons. The location-dependent constraints imposed by cytoskeletal elements together with the regulatory role of electrical activity strongly suggest a pivotal role for the mobility of voltage-gated ion channels in synaptic activity.

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

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    Ting-Feng Lin

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

  3. Eag1 channels as potential early-stage biomarkers of hepatocellular carcinoma

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    Chávez-López MG

    2016-09-01

    Full Text Available María de Guadalupe Chávez-López,1 Violeta Zúñiga-García,1 Julio Isael Pérez-Carreón,2 Arturo Avalos-Fuentes,3 Yesenia Escobar,4 Javier Camacho1 1Department of Pharmacology, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 2Instituto Nacional de Medicina Genómica, 3Department of Physiology, Biophysics and Neuroscience, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, 4Centro de Investigación Clínica Acelerada Sc, Mexico City, Mexico Abstract: Hepatocellular carcinoma (HCC is a major cause of cancer death worldwide. HCC is usually asymptomatic at potential curative stages, and it has very poor prognosis if detected later. Thus, the identification of early biomarkers and novel therapies is essential to improve HCC patient survival. Ion channels have been proposed as potential tumor markers and therapeutic targets for several cancers including HCC. Especially, the ether à-go-go-1 (Eag1 voltage-gated potassium channel has been suggested as an early marker for HCC. Eag1 is overexpressed during HCC development from the cirrhotic and the preneoplastic lesions preceding HCC in a rat model. The channel is also overexpressed in human HCC. Astemizole has gained great interest as a potential anticancer drug because it targets several proteins involved in cancer including Eag1. Actually, in vivo studies have shown that astemizole may have clinical utility for HCC prevention and treatment. Here, we will review first some general aspects of HCC including the current biomarkers and therapies, and then we will focus on Eag1 channels as promising tools in the early diagnosis of HCC. Keywords: ion channels, Eag1, hepatocellular carcinoma, astemizole, diethylnitrosamine

  4. External pH modulates EAG superfamily K+ channels through EAG-specific acidic residues in the voltage sensor

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    Kazmierczak, Marcin; Zhang, Xiaofei; Chen, Bihan; Mulkey, Daniel K.; Shi, Yingtang; Wagner, Paul G.; Pivaroff-Ward, Kendra; Sassic, Jessica K.; Bayliss, Douglas A.

    2013-01-01

    The Ether-a-go-go (EAG) superfamily of voltage-gated K+ channels consists of three functionally distinct gene families (Eag, Elk, and Erg) encoding a diverse set of low-threshold K+ currents that regulate excitability in neurons and muscle. Previous studies indicate that external acidification inhibits activation of three EAG superfamily K+ channels, Kv10.1 (Eag1), Kv11.1 (Erg1), and Kv12.1 (Elk1). We show here that Kv10.2, Kv12.2, and Kv12.3 are similarly inhibited by external protons, suggesting that high sensitivity to physiological pH changes is a general property of EAG superfamily channels. External acidification depolarizes the conductance–voltage (GV) curves of these channels, reducing low threshold activation. We explored the mechanism of this high pH sensitivity in Kv12.1, Kv10.2, and Kv11.1. We first examined the role of acidic voltage sensor residues that mediate divalent cation block of voltage activation in EAG superfamily channels because protons reduce the sensitivity of Kv12.1 to Zn2+. Low pH similarly reduces Mg2+ sensitivity of Kv10.1, and we found that the pH sensitivity of Kv11.1 was greatly attenuated at 1 mM Ca2+. Individual neutralizations of a pair of EAG-specific acidic residues that have previously been implicated in divalent block of diverse EAG superfamily channels greatly reduced the pH response in Kv12.1, Kv10.2, and Kv11.1. Our results therefore suggest a common mechanism for pH-sensitive voltage activation in EAG superfamily channels. The EAG-specific acidic residues may form the proton-binding site or alternatively are required to hold the voltage sensor in a pH-sensitive conformation. The high pH sensitivity of EAG superfamily channels suggests that they could contribute to pH-sensitive K+ currents observed in vivo. PMID:23712551

  5. External pH modulates EAG superfamily K+ channels through EAG-specific acidic residues in the voltage sensor.

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    Kazmierczak, Marcin; Zhang, Xiaofei; Chen, Bihan; Mulkey, Daniel K; Shi, Yingtang; Wagner, Paul G; Pivaroff-Ward, Kendra; Sassic, Jessica K; Bayliss, Douglas A; Jegla, Timothy

    2013-06-01

    The Ether-a-go-go (EAG) superfamily of voltage-gated K(+) channels consists of three functionally distinct gene families (Eag, Elk, and Erg) encoding a diverse set of low-threshold K(+) currents that regulate excitability in neurons and muscle. Previous studies indicate that external acidification inhibits activation of three EAG superfamily K(+) channels, Kv10.1 (Eag1), Kv11.1 (Erg1), and Kv12.1 (Elk1). We show here that Kv10.2, Kv12.2, and Kv12.3 are similarly inhibited by external protons, suggesting that high sensitivity to physiological pH changes is a general property of EAG superfamily channels. External acidification depolarizes the conductance-voltage (GV) curves of these channels, reducing low threshold activation. We explored the mechanism of this high pH sensitivity in Kv12.1, Kv10.2, and Kv11.1. We first examined the role of acidic voltage sensor residues that mediate divalent cation block of voltage activation in EAG superfamily channels because protons reduce the sensitivity of Kv12.1 to Zn(2+). Low pH similarly reduces Mg(2+) sensitivity of Kv10.1, and we found that the pH sensitivity of Kv11.1 was greatly attenuated at 1 mM Ca(2+). Individual neutralizations of a pair of EAG-specific acidic residues that have previously been implicated in divalent block of diverse EAG superfamily channels greatly reduced the pH response in Kv12.1, Kv10.2, and Kv11.1. Our results therefore suggest a common mechanism for pH-sensitive voltage activation in EAG superfamily channels. The EAG-specific acidic residues may form the proton-binding site or alternatively are required to hold the voltage sensor in a pH-sensitive conformation. The high pH sensitivity of EAG superfamily channels suggests that they could contribute to pH-sensitive K(+) currents observed in vivo.

  6. Expression of Eag1 K+ channel and ErbBs in human pituitary adenomas: cytoskeleton arrangement patterns in cultured cells.

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    del Pliego, Margarita González; Aguirre-Benítez, Elsa; Paisano-Cerón, Karina; Valdovinos-Ramírez, Irene; Rangel-Morales, Carlos; Rodríguez-Mata, Verónica; Solano-Agama, Carmen; Martín-Tapia, Dolores; de la Vega, María Teresa; Saldoval-Balanzario, Miguel; Camacho, Javier; Mendoza-Garrido, María Eugenia

    2013-01-01

    Pituitary adenomas can invade surrounded tissue, but the mechanism remains elusive. Ether à go-go-1 (Eag1) potassium channel and epidermal growth factor receptors (ErbB1 and ErbB2) have been associated to invasive phenotypes or poor prognosis in cancer patients. However, cells arrange their cytoskeleton in order to acquire a successful migration pattern. We have studied ErbBs and Eag1 expression, and cytoskeleton arrangements in 11 human pituitary adenomas. Eag1, ErbB1 and ErbB2 expression were studied by immunochemistry in tissue and cultured cells. The cytoskeleton arrangement was analyzed in cultured cells by immunofluorescence. Normal pituitary tissue showed ErbB2 expression and Eag1 only in few cells. However, Eag1 and ErbB2 were expressed in all the tumors analyzed. ErbB1 expression was observed variable and did not show specificity for a tumor characteristic. Cultured cells from micro- and macro-adenomas clinically functional organize their cytoskeleton suggesting a mesenchymal pattern, and a round leucocyte/amoeboid pattern from invasive clinically silent adenoma. Pituitary tumors over-express EGF receptors and the ErbB2 repeated expression suggests is a characteristic of adenomas. Eag 1 was express, in different extent, and could be a therapeutic target. The cytoskeleton arrangements observed suggest that pituitary tumor cells acquire different patterns: mesenchymal, and leucocyte/amoeboid, the last observed in the invasive adenomas. Amoeboid migration pattern has been associated with high invasion capacity.

  7. Crystallization and preliminary X-ray crystallographic characterization of a cyclic nucleotide-binding homology domain from the mouse EAG potassium channel

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    Marques-Carvalho, Maria João; Morais-Cabral, João Henrique

    2012-01-01

    The crystallization conditions and preliminary crystal characterization of the cytoplasmic cyclic nucleotide-binding homology domain from the mouse EAG potassium channel are reported. The members of the family of voltage-gated KCNH potassium channels play important roles in cardiac and neuronal repolarization, tumour proliferation and hormone secretion. These channels have a C-terminal cytoplasmic domain which is homologous to cyclic nucleotide-binding domains (CNB-homology domains), but it has been demonstrated that channel function is not affected by cyclic nucleotides and that the domain does not bind nucleotides in vitro. Here, the crystallization and preliminary crystallographic analysis of a CNB-homology domain from a member of the KCNH family, the mouse EAG channel, is reported. X-ray diffraction data were collected to 2.2 Å resolution and the crystal belonged to the hexagonal space group P3 1 21

  8. Crystallization and preliminary crystallographic characterization of the PAS domains of EAG and ELK potassium channels

    International Nuclear Information System (INIS)

    Adaixo, Ricardo; Morais-Cabral, João Henrique

    2010-01-01

    The N-terminal PAS domains from the eukaryotic EAG potassium channels are thought to have a regulatory function. Here the expression, purification, crystallization and preliminary crystallographic characterization of two of these domains are described. Per–Arnt–Sim (PAS) domains are ubiquitous in nature; they are ∼130-amino-acid protein domains that adopt a fairly conserved three-dimensional structure despite their low degree of sequence homology. These domains constitute the N-terminus or, less frequently, the C-terminus of a number of proteins, where they exert regulatory functions. PAS-containing proteins generally display two or more copies of this motif. In this work, the crystallization and preliminary analysis of the PAS domains of two eukaryotic potassium channels from the ether-à-go-go (EAG) family are reported

  9. Kv10.1 potassium channel: from the brain to the tumors.

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    Cázares-Ordoñez, V; Pardo, L A

    2017-10-01

    The KCNH1 gene encodes the Kv10.1 (Eag1) ion channel, a member of the EAG (ether-à-go-go) family of voltage-gated potassium channels. Recent studies have demonstrated that KCHN1 mutations are implicated in Temple-Baraitser and Zimmermann-Laband syndromes and other forms of developmental deficits that all present with mental retardation and epilepsy, suggesting that Kv10.1 might be important for cognitive development in humans. Although the Kv10.1 channel is mainly expressed in the mammalian brain, its ectopic expression occurs in 70% of human cancers. Cancer cells and tumors expressing Kv10.1 acquire selective advantages that favor cancer progression through molecular mechanisms that involve several cellular pathways, indicating that protein-protein interactions may be important for Kv10.1 influence in cell proliferation and tumorigenesis. Several studies on transcriptional and post-transcriptional regulation of Kv10.1 expression have shown interesting mechanistic insights about Kv10.1 role in oncogenesis, increasing the importance of identifying the cellular factors that regulate Kv10.1 expression in tumors.

  10. Ether à go-go potassium channel expression in soft tissue sarcoma patients

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    Stühmer Walter

    2006-10-01

    Full Text Available Abstract Background The expression of the human Eag1 potassium channel (Kv10.1 is normally restricted to the adult brain, but it has been detected in both tumour cell lines and primary tumours. Our purpose was to determine the frequency of expression of Eag1 in soft tissue sarcoma and its potential clinical implications. Results We used specific monoclonal antibodies to determine the expression levels of Eag1 in soft tissue sarcomas from 210 patients by immunohistochemistry. Eag1 was expressed in 71% of all tumours, with frequencies ranging from 56% (liposarcoma to 82% (rhabdomyosarcoma. We detected differences in expression levels depending on the histological type, but no association was seen between expression of this protein and sex, age, grade or tumour size. Four cell lines derived from relevant sarcoma histological types (fibrosarcoma and rhabdomyosarcoma were tested for Eag1 expression by real-time RT-PCR. We found all four lines to be positive for Eag1. In these cell lines, blockage of Eag1 by RNA interference led to a decrease in proliferation. Conclusion Eag1 is aberrantly expressed in over 70% sarcomas. In sarcoma cell lines, inhibition of Eag1 expression and/or function leads to reduced proliferation. The high frequency of expression of Eag1 in primary tumours and the restriction of normal expression of the channel to the brain, suggests the application of this protein for diagnostic or therapeutic purposes.

  11. Molecular determinants of interactions between the N-terminal domain and the transmembrane core that modulate hERG K+ channel gating.

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    Jorge Fernández-Trillo

    Full Text Available A conserved eag domain in the cytoplasmic amino terminus of the human ether-a-go-go-related gene (hERG potassium channel is critical for its slow deactivation gating. Introduction of gene fragments encoding the eag domain are able to restore normal deactivation properties of channels from which most of the amino terminus has been deleted, and also those lacking exclusively the eag domain or carrying a single point mutation in the initial residues of the N-terminus. Deactivation slowing in the presence of the recombinant domain is not observed with channels carrying a specific Y542C point mutation in the S4-S5 linker. On the other hand, mutations in some initial positions of the recombinant fragment also impair its ability to restore normal deactivation. Fluorescence resonance energy transfer (FRET analysis of fluorophore-tagged proteins under total internal reflection fluorescence (TIRF conditions revealed a substantial level of FRET between the introduced N-terminal eag fragments and the eag domain-deleted channels expressed at the membrane, but not between the recombinant eag domain and full-length channels with an intact amino terminus. The FRET signals were also minimized when the recombinant eag fragments carried single point mutations in the initial portion of their amino end, and when Y542C mutated channels were used. These data suggest that the restoration of normal deactivation gating by the N-terminal recombinant eag fragment is an intrinsic effect of this domain directed by the interaction of its N-terminal segment with the gating machinery, likely at the level of the S4-S5 linker.

  12. Calcitriol inhibits Ether-a go-go potassium channel expression and cell proliferation in human breast cancer cells

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    Garcia-Becerra, Rocio; Diaz, Lorenza; Camacho, Javier; Barrera, David; Ordaz-Rosado, David; Morales, Angelica; Ortiz, Cindy Sharon; Avila, Euclides; Bargallo, Enrique; Arrecillas, Myrna; Halhali, Ali; Larrea, Fernando

    2010-01-01

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-a-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention.

  13. Calcitriol inhibits Ether-a go-go potassium channel expression and cell proliferation in human breast cancer cells

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    Garcia-Becerra, Rocio [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Diaz, Lorenza, E-mail: lorenzadiaz@gmail.com [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Camacho, Javier [Department of Pharmacology, Centro de Investigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Av. Instituto Politecnico Nacional 2508, San Pedro Zacatenco 07360, Mexico, D.F. (Mexico); Barrera, David; Ordaz-Rosado, David; Morales, Angelica [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Ortiz, Cindy Sharon [Department of Pathology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Avila, Euclides [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Bargallo, Enrique [Department of Breast Tumors, Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Tlalpan 14080, Mexico, D.F. (Mexico); Arrecillas, Myrna [Department of Pathology, Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Tlalpan 14080, Mexico, D.F. (Mexico); Halhali, Ali; Larrea, Fernando [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico)

    2010-02-01

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-a-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention.

  14. An ERG channel inhibitor from the scorpion Buthus eupeus

    DEFF Research Database (Denmark)

    Korolkova, Y.V.; Kozlov, S.A.; Lipkin, A.V.

    2001-01-01

    and the three mutants partly inhibited the native M-like current in NG108-15 at 100 nm. The effect of the recombinant BeKm-1 on different K(+) channels was also studied. BeKm-1 inhibited hERG1 channels with an IC(50) of 3.3 nm, but had no effect at 100 nm on hEAG, hSK1, rSK2, hIK, hBK, KCNQ1/KCNE1, KCNQ2/KCNQ3......, KCNQ4 channels, and minimal effect on rELK1. Thus, BeKm-1 was shown to be a novel specific blocker of hERG1 potassium channels....

  15. Award for Distinguished Scientific Contributions: Alice H. Eagly

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    American Psychologist, 2009

    2009-01-01

    Alice H. Eagly, winner of the Award for Distinguished Scientific Contributions, is cited for her work in the field of social psychology, the psychology of gender, and the use of meta-analytic techniques. She envisions a psychology that extends from individual cognitions to societal structures. In addition to the citation, a biography and selected…

  16. Extent of Anaemia among Preschool Children in EAG States, India: A Challenge to Policy Makers

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    Singh, Rakesh Kumar; Patra, Shraboni

    2014-01-01

    Background. India is the highest contributor to child anemia. About 89 million children in India are anemic. The study determines the factors that contributed to child anemia and examines the role of the existing programs in reducing the prevalence of child anemia particularly in the EAG states. Methods. The data from the latest round of the National Family Health Survey (NFHS-3) is used. Simple bivariate and multinomial logistics regression analyses are used. Results. About 70% children are anemic in all the EAG states. The prevalence of severe anemia is the highest (6.7%) in Rajasthan followed by Uttar Pradesh (3.6%) and Madhya Pradesh (3.4%). Children aged 12 to 17 months are significantly seven times (RR = 7.99, P children of 36 to 59 months. Children of severely anemic mothers are also found to be more severely anemic (RR = 15.97, P children of not anemic mothers. Conclusions. The study reveals that the existing government program fails to control anemia among preschool children in the backward states of India. Therefore, there is an urgent need for monitoring of program in regular interval, particularly for EAG states to reduce the prevalence of anemia among preschool children. PMID:25140250

  17. C-terminal β9-strand of the cyclic nucleotide-binding homology domain stabilizes activated states of Kv11.1 channels.

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    Chai Ann Ng

    Full Text Available Kv11.1 potassium channels are important for regulation of the normal rhythm of the heartbeat. Reduced activity of Kv11.1 channels causes long QT syndrome type 2, a disorder that increases the risk of cardiac arrhythmias and sudden cardiac arrest. Kv11.1 channels are members of the KCNH subfamily of voltage-gated K(+ channels. However, they also share many similarities with the cyclic nucleotide gated ion channel family, including having a cyclic nucleotide-binding homology (cNBH domain. Kv11.1 channels, however, are not directly regulated by cyclic nucleotides. Recently, crystal structures of the cNBH domain from mEAG and zELK channels, both members of the KCNH family of voltage-gated potassium channels, revealed that a C-terminal β9-strand in the cNBH domain occupied the putative cyclic nucleotide-binding site thereby precluding binding of cyclic nucleotides. Here we show that mutations to residues in the β9-strand affect the stability of the open state relative to the closed state of Kv11.1 channels. We also show that disrupting the structure of the β9-strand reduces the stability of the inactivated state relative to the open state. Clinical mutations located in this β9-strand result in reduced trafficking efficiency, which suggests that binding of the C-terminal β9-strand to the putative cyclic nucleotide-binding pocket is also important for assembly and trafficking of Kv11.1 channels.

  18. Cost and utilisation of hospital based delivery care in Empowered Action Group (EAG) states of India.

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    Mohanty, Sanjay K; Srivastava, Akanksha

    2013-10-01

    Large scale investment in the National Rural Health Mission is expected to increase the utilization and reduce the cost of maternal care in public health centres in India. The objective of this paper is to examine recent trends in the utilization and cost of hospital based delivery care in the Empowered Action Group (EAG) states of India. The unit data from the District Level Household Survey 3, 2007-2008 is used in the analyses. The coverage and the cost of hospital based delivery at constant price is analyzed for five consecutive years preceding the survey. Descriptive and multivariate analyses are used to understand the socio-economic differentials in cost and utilization of delivery care. During 2004-2008, the utilization of delivery care from public health centres has increased in all the eight EAG states. Adjusting for inflation, the household cost of delivery care has declined for the poor, less educated and in public health centres in the EAG states. The cost of delivery care in private health centres has not shown any significant changes across the states. Results of the multivariate analyses suggest that time, state, place of residence, economic status; educational attainment and delivery characteristics of mother are significant predictors of hospital based delivery care in India. The study demonstrates the utility of public spending on health care and provides a thrust to the ongoing debate on universal health coverage in India.

  19. Health inequalities among urban children in India: a comparative assessment of Empowered Action Group (EAG) and South Indian states.

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    Arokiasamy, P; Jain, Kshipra; Goli, Srinivas; Pradhan, Jalandhar

    2013-03-01

    As India rapidly urbanizes, within urban areas socioeconomic disparities are rising and health inequality among urban children is an emerging challenge. This paper assesses the relative contribution of socioeconomic factors to child health inequalities between the less developed Empowered Action Group (EAG) states and more developed South Indian states in urban India using data from the 2005-06 National Family Health Survey. Focusing on urban health from varying regional and developmental contexts, socioeconomic inequalities in child health are examined first using Concentration Indices (CIs) and then the contributions of socioeconomic factors to the CIs of health variables are derived. The results reveal, in order of importance, pronounced contributions of household economic status, parent's illiteracy and caste to urban child health inequalities in the South Indian states. In contrast, parent's illiteracy, poor economic status, being Muslim and child birth order 3 or more are major contributors to health inequalities among urban children in the EAG states. The results suggest the need to adopt different health policy interventions in accordance with the pattern of varying contributions of socioeconomic factors to child health inequalities between the more developed South Indian states and less developed EAG states.

  20. Sedimentation rate and lateral migration of tidal channels in the Lagoon of Venice (Northern Italy)

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    Donnici, Sandra; Madricardo, Fantina; Serandrei-Barbero, Rossana

    2017-11-01

    Tidal channels are crucial for the functioning of highly valuable coastal environments, such as estuaries and lagoons. Their properties, however, are currently less understood than those of river systems. To elucidate their past behaviour, an extensive geophysical investigation was performed to reconstruct the evolution of channels and tidal surfaces in the central part of the Lagoon of Venice (Italy) over the past 5000 years. Comparing high-spatial-resolution acoustic data and sedimentary facies analyses of 41 cores, 29 of which were radiocarbon dated, revealed the sedimentation rates in different lagoonal environments and allowed the migration of two large meanders to be reconstructed. The average sedimentation rate of the study succession in the different sedimentary environments was 1.27 mm yr-1. The lateral migration rates were 13-23 m/century. This estimate is consistent with the lateral migration rates determined by comparing aerial photographs of recent channels. Comparing the buried channels with historical and current maps showed that, in general, the number of active channels is now reduced. Their morphology was sometimes simplified by artificial interventions. An understanding of the impact of the artificial interventions over time is useful for the management and conservation of tidal environments, particularly for the Lagoon of Venice, where management authorities are currently debating the possible deepening and rectification of large navigation channels.

  1. Lateral transport of solutes in microfluidic channels using electrochemically generated gradients in redox-active surfactants.

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    Liu, Xiaoyang; Abbott, Nicholas L

    2011-04-15

    We report principles for a continuous flow process that can separate solutes based on a driving force for selective transport that is generated by a lateral concentration gradient of a redox-active surfactant across a microfluidic channel. Microfluidic channels fabricated with gold electrodes lining each vertical wall were used to electrochemically generate concentration gradients of the redox-active surfactant 11-ferrocenylundecyl-trimethylammonium bromide (FTMA) in a direction perpendicular to the flow. The interactions of three solutes (a hydrophobic dye, 1-phenylazo-2-naphthylamine (yellow AB), an amphiphilic molecule, 2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine (BODIPY C(5)-HPC), and an organic salt, 1-methylpyridinium-3-sulfonate (MPS)) with the lateral gradients in surfactant/micelle concentration were shown to drive the formation of solute-specific concentration gradients. Two distinct physical mechanisms were identified to lead to the solute concentration gradients: solubilization of solutes by micelles and differential adsorption of the solutes onto the walls of the microchannels in the presence of the surfactant concentration gradient. These two mechanisms were used to demonstrate delipidation of a mixture of BODIPY C(5)-HPC (lipid) and MPS and purification of BODIPY C(5)-HPC from a mixture of BODIPY C(5)-HPC and yellow AB. Overall, the results of this study demonstrate that lateral concentration gradients of redox-active surfactants formed within microfluidic channels can be used to transport solutes across the microfluidic channels in a solute-dependent manner. The approach employs electrical potentials (solutions having high ionic strength (>0.1M), and offers the basis of continuous processes for the purification or separation of solutes in microscale systems. © 2011 American Chemical Society

  2. Acid sensing ion channel 1 in lateral hypothalamus contributes to breathing control.

    Directory of Open Access Journals (Sweden)

    Nana Song

    Full Text Available Acid-sensing ion channels (ASICs are present in neurons and may contribute to chemoreception. Among six subunits of ASICs, ASIC1 is mainly expressed in the central nervous system. Recently, multiple sites in the brain including the lateral hypothalamus (LH have been found to be sensitive to extracellular acidification. Since LH contains orexin neurons and innervates the medulla respiratory center, we hypothesize that ASIC1 is expressed on the orexin neuron and contributes to acid-induced increase in respiratory drive. To test this hypothesis, we used double immunofluorescence to determine whether ASIC1 is expressed on orexin neurons in the LH, and assessed integrated phrenic nerve discharge (iPND in intact rats in response to acidification of the LH. We found that ASIC1 was co-localized with orexinA in the LH. Microinjection of acidified artificial cerebrospinal fluid increased the amplitude of iPND by 70% (pH 7.4 v.s. pH 6.5:1.05±0.12 v.s. 1.70±0.10, n = 6, P<0.001 and increased the respiratory drive (peak amplitude of iPND/inspiratory time, PA/Ti by 40% (1.10±0.23 v.s. 1.50±0.38, P<0.05. This stimulatory effect was abolished by blocking ASIC1 with a nonselective inhibitor (amiloride 10 mM, a selective inhibitor (PcTX1, 10 nM or by damaging orexin neurons in the LH. Current results support our hypothesis that the orexin neuron in the LH can exert an excitation on respiration via ASIC1 during local acidosis. Since central acidification is involved in breathing dysfunction in a variety of pulmonary diseases, understanding its underlying mechanism may improve patient management.

  3. An aberrant vascular channel in the petrous bone: persistent lateral capital vein?

    International Nuclear Information System (INIS)

    Hermans, Robert; Rensburg, Leon J. van

    2009-01-01

    An aberrant channel was identified on CT in the petrous bone in four patients presenting with unrelated otological symptoms. These channels occurred unilaterally in each case. In two patients, the channel was seen to run between the sigmoid sinus sulcus and the superior petrosal sinus sulcus; in one of these patients, a vascular structure was identified within this channel on MRI, connecting the sigmoid sinus and the superior petrosal sinus. In the two other patients, an aberrant channel was seen between the superior petrosal sinus sulcus and the posterior genu of the facial nerve canal. There were no symptoms that could be attributed to the presence of these channels. We postulate that these aberrant vascular channels correspond to a persistent embryological vein, the lateral capital vein. (orig.)

  4. An aberrant vascular channel in the petrous bone: persistent lateral capital vein?

    Energy Technology Data Exchange (ETDEWEB)

    Hermans, Robert [University Hospitals Leuven, Department of Radiology, Leuven (Belgium); Rensburg, Leon J. van [University of the Western Cape, Department of Radiology and Diagnostics, Tygerberg (South Africa)

    2009-12-15

    An aberrant channel was identified on CT in the petrous bone in four patients presenting with unrelated otological symptoms. These channels occurred unilaterally in each case. In two patients, the channel was seen to run between the sigmoid sinus sulcus and the superior petrosal sinus sulcus; in one of these patients, a vascular structure was identified within this channel on MRI, connecting the sigmoid sinus and the superior petrosal sinus. In the two other patients, an aberrant channel was seen between the superior petrosal sinus sulcus and the posterior genu of the facial nerve canal. There were no symptoms that could be attributed to the presence of these channels. We postulate that these aberrant vascular channels correspond to a persistent embryological vein, the lateral capital vein. (orig.)

  5. Cytoplasmic Domains and Voltage-Dependent Potassium Channel Gating

    Science.gov (United States)

    Barros, Francisco; Domínguez, Pedro; de la Peña, Pilar

    2012-01-01

    The basic architecture of the voltage-dependent K+ channels (Kv channels) corresponds to a transmembrane protein core in which the permeation pore, the voltage-sensing components and the gating machinery (cytoplasmic facing gate and sensor–gate coupler) reside. Usually, large protein tails are attached to this core, hanging toward the inside of the cell. These cytoplasmic regions are essential for normal channel function and, due to their accessibility to the cytoplasmic environment, constitute obvious targets for cell-physiological control of channel behavior. Here we review the present knowledge about the molecular organization of these intracellular channel regions and their role in both setting and controlling Kv voltage-dependent gating properties. This includes the influence that they exert on Kv rapid/N-type inactivation and on activation/deactivation gating of Shaker-like and eag-type Kv channels. Some illustrative examples about the relevance of these cytoplasmic domains determining the possibilities for modulation of Kv channel gating by cellular components are also considered. PMID:22470342

  6. Instability of shallow open channel flow with lateral velocity gradients

    Energy Technology Data Exchange (ETDEWEB)

    Lima, A C; Izumi, N, E-mail: adriano@eng.hokudai.ac.jp, E-mail: nizumi@eng.hokudai.ac.jp [River and Watershed Engineering Laboratory, Hokkaido University, Sapporo, 060-8628 (Japan)

    2011-12-22

    The turbulent flow in a wide rectangular open channel partially covered with vegetation is studied using linear stability analysis. In the base state normal flow condition, the water depth is constant and the transverse velocity vanishes, while there is a lateral gradient in the streamwise velocity with an inflexion point at the boundary between the vegetated zone and the main channel. The Reynolds stress is expressed by introducing the eddy viscosity, which is obtained from assuming a logarithmic distribution of the velocity near the bed. Perturbation expansions are introduced to the streamwise and transverse velocities, as well as to the water depth. The system of governing equations was solved in order to determine the maximum growth rate of the perturbations as a function of parameters which describe physical characteristics of the channel and the flow.

  7. APETx4, a Novel Sea Anemone Toxin and a Modulator of the Cancer-Relevant Potassium Channel KV10.1

    Directory of Open Access Journals (Sweden)

    Lien Moreels

    2017-09-01

    Full Text Available The human ether-à-go-go channel (hEag1 or KV10.1 is a cancer-relevant voltage-gated potassium channel that is overexpressed in a majority of human tumors. Peptides that are able to selectively inhibit this channel can be lead compounds in the search for new anticancer drugs. Here, we report the activity-guided purification and electrophysiological characterization of a novel KV10.1 inhibitor from the sea anemone Anthopleura elegantissima. Purified sea anemone fractions were screened for inhibitory activity on KV10.1 by measuring whole-cell currents as expressed in Xenopus laevis oocytes using the two-microelectrode voltage clamp technique. Fractions that showed activity on Kv10.1 were further purified by RP-HPLC. The amino acid sequence of the peptide was determined by a combination of MALDI- LIFT-TOF/TOF MS/MS and CID-ESI-FT-ICR MS/MS and showed a high similarity with APETx1 and APETx3 and was therefore named APETx4. Subsequently, the peptide was electrophysiologically characterized on KV10.1. The selectivity of the toxin was investigated on an array of voltage-gated ion channels, including the cardiac human ether-à-go-go-related gene potassium channel (hERG or Kv11.1. The toxin inhibits KV10.1 with an IC50 value of 1.1 μM. In the presence of a similar toxin concentration, a shift of the activation curve towards more positive potentials was observed. Similar to the effect of the gating modifier toxin APETx1 on hERG, the inhibition of Kv10.1 by the isolated toxin is reduced at more positive voltages and the peptide seems to keep the channel in a closed state. Although the peptide also induces inhibitory effects on other KV and NaV channels, it exhibits no significant effect on hERG. Moreover, APETx4 induces a concentration-dependent cytotoxic and proapoptotic effect in various cancerous and noncancerous cell lines. This newly identified KV10.1 inhibitor can be used as a tool to further characterize the oncogenic channel KV10.1 or as a

  8. Astemizole synergizes calcitriol antiproliferative activity by inhibiting CYP24A1 and upregulating VDR: a novel approach for breast cancer therapy.

    Directory of Open Access Journals (Sweden)

    Janice García-Quiroz

    Full Text Available Calcitriol antiproliferative effects include inhibition of the oncogenic ether-à-go-go-1 potassium channel (Eag1 expression, which is necessary for cell cycle progression and tumorigenesis. Astemizole, a new promising antineoplastic drug, targets Eag1 by blocking ion currents. Herein, we characterized the interaction between calcitriol and astemizole as well as their conjoint antiproliferative action in SUM-229PE, T-47D and primary tumor-derived breast cancer cells.Molecular markers were studied by immunocytochemistry, Western blot and real time PCR. Inhibitory concentrations were determined by dose-response curves and metabolic activity assays. At clinically achievable drug concentrations, synergistic antiproliferative interaction was observed between calcitriol and astemizole, as calculated by combination index analysis (CI <1. Astemizole significantly enhanced calcitriol's growth-inhibitory effects (3-11 folds, P<0.01. Mean IC(20 values were 1.82 ± 2.41 nM and 1.62 ± 0.75 µM; for calcitriol (in estrogen receptor negative cells and astemizole, respectively. Real time PCR showed that both drugs alone downregulated, while simultaneous treatment further reduced Ki-67 and Eag1 gene expression (P<0.05. Astemizole inhibited basal and calcitriol-induced CYP24A1 and CYP3A4 mRNA expression (cytochromes involved in calcitriol and astemizole degradation in breast and hepatoma cancer cells, respectively, while upregulated vitamin D receptor (VDR expression.Astemizole synergized calcitriol antiproliferative effects by downregulating CYP24A1, upregulating VDR and targeting Eag1. This study provides insight into the molecular mechanisms involved in astemizole-calcitriol combined antineoplastic effect, offering scientific support to test both compounds in combination in further preclinical and clinical studies of neoplasms expressing VDR and Eag1. VDR-negative tumors might also be sensitized to calcitriol antineoplastic effects by the use of astemizole

  9. Investigating the Lateral Mixing Coefficient in a Compound Channel with Emergent Vegetation over the Floodplain

    Directory of Open Access Journals (Sweden)

    Hossein hamidifar

    2017-02-01

    asymmetric compound channel section. Three different densities of cylindrical PVC elements of 1 cm diameter were used in addition to the case without cylinders. Three-dimensional flow velocity measurements were taken using a down-looking four beam Acoustic Doppler Velcimeter (ADV. A highly concentrated solution (C0=10 g/L of red dye (KMnO4, Potassium permanganate was injected as a tracer sufficiently far downstream of the beginning of the flume such that the flow was fully developed determined by measuring velocity profiles. Variations of tracer concentration at three locations 4.00, 6.44 and 8.88 m downstream of the injection point were determined using image processing technique. In this technique, digital cameras are used at specified cross sections to capture the pixel intensity before and during the passage of the dye cloud. Using the Beer–Lambert Law, the pixel intensity is related to the dye concentration after a simple calibration. Afterward, the images could be used as input files for MATLAB’s Image Processing Toolbox. Results and Discussion: The results showed that due to the strong secondary currents and unstable vortexes in the compound channel, the tracer cloud is periodic. The transverse mixing coefficient in the main channel is also always greater than that in the floodplain and its value increases with relative depth. Another factor that was found to affect the lateral mixing coefficient was the vegetation density. The non- dimensioed transverse mixing coefficient increases with vegetation density in the main channel as well as the floodplain. As vegetation density increases from 0.26 to 0.88%, the non- dimensioned transverse mixing coefficient increased up to 40% of the flow relative depth of 0.15. For low density vegetation (0.26%, the lateral mixing coefficient in both the main channel and floodplain was increase upto 30%. Also, for the vegetation density of 0.88%, the lateral mixing coefficient increases up to 80 and 107% for the floodplain and main

  10. Developing and exploring a theory for the lateral erosion of bedrock channels for use in landscape evolution models

    Directory of Open Access Journals (Sweden)

    A. L. Langston

    2018-01-01

    Full Text Available Understanding how a bedrock river erodes its banks laterally is a frontier in geomorphology. Theories for the vertical incision of bedrock channels are widely implemented in the current generation of landscape evolution models. However, in general existing models do not seek to implement the lateral migration of bedrock channel walls. This is problematic, as modeling geomorphic processes such as terrace formation and hillslope–channel coupling depends on the accurate simulation of valley widening. We have developed and implemented a theory for the lateral migration of bedrock channel walls in a catchment-scale landscape evolution model. Two model formulations are presented, one representing the slow process of widening a bedrock canyon and the other representing undercutting, slumping, and rapid downstream sediment transport that occurs in softer bedrock. Model experiments were run with a range of values for bedrock erodibility and tendency towards transport- or detachment-limited behavior and varying magnitudes of sediment flux and water discharge in order to determine the role that each plays in the development of wide bedrock valleys. The results show that this simple, physics-based theory for the lateral erosion of bedrock channels produces bedrock valleys that are many times wider than the grid discretization scale. This theory for the lateral erosion of bedrock channel walls and the numerical implementation of the theory in a catchment-scale landscape evolution model is a significant first step towards understanding the factors that control the rates and spatial extent of wide bedrock valleys.

  11. Developing and exploring a theory for the lateral erosion of bedrock channels for use in landscape evolution models

    Science.gov (United States)

    Langston, Abigail L.; Tucker, Gregory E.

    2018-01-01

    Understanding how a bedrock river erodes its banks laterally is a frontier in geomorphology. Theories for the vertical incision of bedrock channels are widely implemented in the current generation of landscape evolution models. However, in general existing models do not seek to implement the lateral migration of bedrock channel walls. This is problematic, as modeling geomorphic processes such as terrace formation and hillslope-channel coupling depends on the accurate simulation of valley widening. We have developed and implemented a theory for the lateral migration of bedrock channel walls in a catchment-scale landscape evolution model. Two model formulations are presented, one representing the slow process of widening a bedrock canyon and the other representing undercutting, slumping, and rapid downstream sediment transport that occurs in softer bedrock. Model experiments were run with a range of values for bedrock erodibility and tendency towards transport- or detachment-limited behavior and varying magnitudes of sediment flux and water discharge in order to determine the role that each plays in the development of wide bedrock valleys. The results show that this simple, physics-based theory for the lateral erosion of bedrock channels produces bedrock valleys that are many times wider than the grid discretization scale. This theory for the lateral erosion of bedrock channel walls and the numerical implementation of the theory in a catchment-scale landscape evolution model is a significant first step towards understanding the factors that control the rates and spatial extent of wide bedrock valleys.

  12. CACNA1H missense mutations associated with amyotrophic lateral sclerosis alter Ca(v)3.2 T-type calcium channel activity and reticular thalamic neuron firing

    Czech Academy of Sciences Publication Activity Database

    Rzhepetskyy, Yuriy; Lazniewska, Joanna; Blesneac, I.; Pamphlett, R.; Weiss, Norbert

    2016-01-01

    Roč. 10, č. 6 (2016), s. 466-477 ISSN 1933-6950 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : ALS * amyotrophic lateral sclerosis * biophysics * CACNA1H * Ca(v)3 * 2 channel Subject RIV: CE - Biochemistry Impact factor: 2.042, year: 2016

  13. Determinants of Isoform-Specific Gating Kinetics of hERG1 Channel: Combined Experimental and Simulation Study

    Directory of Open Access Journals (Sweden)

    Laura L. Perissinotti

    2018-04-01

    -models. The minimization procedure presented here, allowed assessment of suitability of different Markov model topologies and the corresponding parameters that describe the channel kinetics. The kinetics modeling pointed to key differences in the gating kinetics that were linked to the full channel structure. Interactions between soluble domains and the transmembrane part of the channel appeared to be critical determinants of the gating kinetics. The structures of the full channel in the open and closed states were compared for the first time using the recent Cryo-EM resolved structure for full open hERG channel and an homology model for the closed state, based on the highly homolog EAG1 channel. Key potential interactions which emphasize the importance of electrostatic interactions between N-PAS cap, S4-S5, and C-linker are suggested based on the structural analysis. The derived kinetic parameters were later used in higher order models of cells and tissue to track down the effect of varying the ratios of hERG1a and hERG1b on cardiac action potentials and computed electrocardiograms. Simulations suggest that the recovery from inactivation of hERG1b may contribute to its physiologic role of this isoform in the action potential. Finally, the results presented here contribute to the growing body of evidence that hERG1b significantly affects the generation of the cardiac Ikr and plays an important role in cardiac electrophysiology. We highlight the importance of carefully revisiting the Markov models previously proposed in order to properly account for the relative abundance of the hERG1 a- and b- isoforms.

  14. Lateral current generation in n-AlGaAs/GaAs heterojunction channels by Schottky-barrier gate illumination

    Energy Technology Data Exchange (ETDEWEB)

    Kawazu, Takuya; Noda, Takeshi; Sakuma, Yoshiki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakaki, Hiroyuki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan)

    2015-01-12

    We observe lateral currents induced in an n-AlGaAs/GaAs heterojunction channel of Hall bar geometry, when an asymmetric position of the Schottky metal gate is locally irradiated by a near-infrared laser beam. When the left side of the Schottky gate is illuminated with the laser, the lateral current flows from left to right in the two dimensional electron gas (2DEG) channel. In contrast, the right side illumination leads to the current from right to left. The magnitude of the lateral current is almost linearly dependent on the beam position, the current reaching its maximum for the beam at the edge of the Schottky gate. The experimental findings are well explained by a theory based on the current-continuity equation, where the lateral current in the 2DEG channel is driven by the photocurrent which vertically flows from the 2DEG to the Schottky gate.

  15. Studies on diversion cross-flow between two parallel channels communicating by a lateral slot. II

    International Nuclear Information System (INIS)

    Tapucu, A.; Merilo, M.

    1977-01-01

    The axial pressure variations of two parallel channels with single phase flows communicating by a long lateral slot have been studied experimentally. Using mass and momentum conservation principles, the axial pressure variations have been derived in terms of two parameters ksub(d) and ksub(r), for donor and recipient channels, respectively. These parameters include the combined effect of fluid transferred from donor to recipient channel, and drag force brought on by the connection gap, and are functions of the velocities and slot geometry parameters. A pressure difference oscillation between channels along the slot has been detected which is sinusoidal with wave lengths which seem to be a function of the gap clearance. (Auth.)

  16. Evolutionary Psychology is Compatible with Equity Feminism, but Not with Gender Feminism: A Reply to Eagly and Wood (2011)

    OpenAIRE

    Barry X. Kuhle

    2012-01-01

    I comment on Eagly and Wood's biosocial constructionist evolutionary theory (2011; DOI: 10.1007/s11199-011-9949-9). Although this gender feminist theory allows for evolved physical differences between men and women and evolved psychological similarities for men and women, it fails to consider evolutionary accounts of psychological sex differences. I hypothesize that gender feminists' reluctance to acknowledge that evolution has left different fingerprints on men's and women's bodies and brain...

  17. A Finite Element Solution of Lateral Periodic Poisson–Boltzmann Model for Membrane Channel Proteins

    Science.gov (United States)

    Xu, Jingjie; Lu, Benzhuo

    2018-01-01

    Membrane channel proteins control the diffusion of ions across biological membranes. They are closely related to the processes of various organizational mechanisms, such as: cardiac impulse, muscle contraction and hormone secretion. Introducing a membrane region into implicit solvation models extends the ability of the Poisson–Boltzmann (PB) equation to handle membrane proteins. The use of lateral periodic boundary conditions can properly simulate the discrete distribution of membrane proteins on the membrane plane and avoid boundary effects, which are caused by the finite box size in the traditional PB calculations. In this work, we: (1) develop a first finite element solver (FEPB) to solve the PB equation with a two-dimensional periodicity for membrane channel proteins, with different numerical treatments of the singular charges distributions in the channel protein; (2) add the membrane as a dielectric slab in the PB model, and use an improved mesh construction method to automatically identify the membrane channel/pore region even with a tilt angle relative to the z-axis; and (3) add a non-polar solvation energy term to complete the estimation of the total solvation energy of a membrane protein. A mesh resolution of about 0.25 Å (cubic grid space)/0.36 Å (tetrahedron edge length) is found to be most accurate in linear finite element calculation of the PB solvation energy. Computational studies are performed on a few exemplary molecules. The results indicate that all factors, the membrane thickness, the length of periodic box, membrane dielectric constant, pore region dielectric constant, and ionic strength, have individually considerable influence on the solvation energy of a channel protein. This demonstrates the necessity to treat all of those effects in the PB model for membrane protein simulations. PMID:29495644

  18. Mechanical sensitivity of Piezo1 ion channels can be tuned by cellular membrane tension

    Science.gov (United States)

    Lewis, Amanda H; Grandl, Jörg

    2015-01-01

    Piezo1 ion channels mediate the conversion of mechanical forces into electrical signals and are critical for responsiveness to touch in metazoans. The apparent mechanical sensitivity of Piezo1 varies substantially across cellular environments, stimulating methods and protocols, raising the fundamental questions of what precise physical stimulus activates the channel and how its stimulus sensitivity is regulated. Here, we measured Piezo1 currents evoked by membrane stretch in three patch configurations, while simultaneously visualizing and measuring membrane geometry. Building on this approach, we developed protocols to minimize resting membrane curvature and tension prior to probing Piezo1 activity. We find that Piezo1 responds to lateral membrane tension with exquisite sensitivity as compared to other mechanically activated channels and that resting tension can drive channel inactivation, thereby tuning overall mechanical sensitivity of Piezo1. Our results explain how Piezo1 can function efficiently and with adaptable sensitivity as a sensor of mechanical stimulation in diverse cellular contexts. DOI: http://dx.doi.org/10.7554/eLife.12088.001 PMID:26646186

  19. Fabrication and characterization of the normally-off N-channel lateral 4H-SiC metal-oxide-semiconductor field-effect transistors

    Science.gov (United States)

    Qing-Wen, Song; Xiao-Yan, Tang; Yan-Jing, He; Guan-Nan, Tang; Yue-Hu, Wang; Yi-Meng, Zhang; Hui, Guo; Ren-Xu, Jia; Hong-Liang, Lv; Yi-Men, Zhang; Yu-Ming, Zhang

    2016-03-01

    In this paper, the normally-off N-channel lateral 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFFETs) have been fabricated and characterized. A sandwich- (nitridation-oxidation-nitridation) type process was used to grow the gate dielectric film to obtain high channel mobility. The interface properties of 4H-SiC/SiO2 were examined by the measurement of HF I-V, G-V, and C-V over a range of frequencies. The ideal C-V curve with little hysteresis and the frequency dispersion were observed. As a result, the interface state density near the conduction band edge of 4H-SiC was reduced to 2 × 1011 eV-1·cm-2, the breakdown field of the grown oxides was about 9.8 MV/cm, the median peak field-effect mobility is about 32.5 cm2·V-1·s-1, and the maximum peak field-effect mobility of 38 cm2·V-1·s-1 was achieved in fabricated lateral 4H-SiC MOSFFETs. Projcet supported by the National Natural Science Foundation of China (Grant Nos. 61404098, 61176070, and 61274079), the Doctoral Fund of Ministry of Education of China (Grant Nos. 20110203110010 and 20130203120017), the National Key Basic Research Program of China (Grant No. 2015CB759600), and the Key Specific Projects of Ministry of Education of China (Grant No. 625010101).

  20. Lateral and vertical channel movement and potential for bed-material movement on the Madison River downstream from Earthquake Lake, Montana

    Science.gov (United States)

    Chase, Katherine J.; McCarthy, Peter M.

    2012-01-01

    and to investigate the potential for bed material movement along the same reach. The purpose of this report is to present information about the lateral and vertical movement of the Madison River from 1970 to 2006 for a 1-mile reach downstream from Earthquake Lake and for Raynolds Pass Bridge, and to provide an analysis of the potential for bed-material movement so that MADTAC can evaluate the applicability of the previously determined threshold streamflow for initiation of damaging erosion. As part of this study channel cross sections originally surveyed by the USGS in 1971 were resurveyed in 2006. Incremental channel-movement distances were determined by comparing the stream centerlines from 14 aerial photographs taken between 1970 and 2006. Depths of channel incision and aggregation were determined by comparing the 2006 and 1971 cross-section and water-surface data. Particle sizes of bed and bank materials were measured in 2006 and 2008 using the pebble-count method and sieve analyses. A one-dimensional hydraulic-flow model (HEC-RAS) was used to calculate mean boundary-shear stresses for various streamflows; these calculated boundary-shear stresses were compared to calculated critical-shear stresses for the bed materials to determine the potential for bed-material movement. A comparison of lateral channel movement distances with annual peak streamflows shows that streamflows higher than the 3,500-ft3/s threshold were followed by lateral channel movement except from 1991 to 1992 and possibly from 1996 to 1997. However, it was not possible to discern whether the channel moved gradually or suddenly, or in response to one peak flow, to several peak flows, or to sustained flows. The channel moved between 2002 and 2005 even when streamflows were less than the threshold streamflow of 3,500 ft3/s. Comparisons of cross sections and aerial photographs show that the channel has moved laterally and incised and aggraded to varying degrees. The channel has developed meander bends

  1. Muddy lateral accretion and low stream power in a sub-recent confined channel belt, Rhine-Meuse delta, central Netherlands

    NARCIS (Netherlands)

    Makaske, B.; Weerts, H.J.T.

    2005-01-01

    The Hennisdijk fluvial system in the central Rhine-Meuse delta is an abandoned Rhine distributary that was active on a wide floodplain from 3800 to 3000 years BP. Cross-sectional geometry, lithological characteristics and planform patterns of the channel-belt deposits indicate lateral migration of

  2. Lateral root development in the maize (Zea mays) lateral rootless1 mutant.

    Science.gov (United States)

    Husakova, Eva; Hochholdinger, Frank; Soukup, Ales

    2013-07-01

    The maize lrt1 (lateral rootless1) mutant is impaired in its development of lateral roots during early post-embryonic development. The aim of this study was to characterize, in detail, the influences that the mutation exerts on lateral root initiation and the subsequent developments, as well as to describe the behaviour of the entire plant under variable environmental conditions. Mutant lrt1 plants were cultivated under different conditions of hydroponics, and in between sheets of moist paper. Cleared whole mounts and anatomical sections were used in combination with both selected staining procedures and histochemical tests to follow root development. Root surface permeability tests and the biochemical quantification of lignin were performed to complement the structural data. The data presented suggest a redefinition of lrt1 function in lateral roots as a promoter of later development; however, neither the complete absence of lateral roots nor the frequency of their initiation is linked to lrt1 function. The developmental effects of lrt1 are under strong environmental influences. Mutant primordia are affected in structure, growth and emergence; and the majority of primordia terminate their growth during this last step, or shortly thereafter. The lateral roots are impaired in the maintenance of the root apical meristem. The primary root shows disturbances in the organization of both epidermal and subepidermal layers. The lrt1-related cell-wall modifications include: lignification in peripheral layers, the deposition of polyphenolic substances and a higher activity of peroxidase. The present study provides novel insights into the function of the lrt1 gene in root system development. The lrt1 gene participates in the spatial distribution of initiation, but not in its frequency. Later, the development of lateral roots is strongly affected. The effect of the lrt1 mutation is not as obvious in the primary root, with no influences observed on the root apical meristem

  3. Lateral root development in the maize (Zea mays) lateral rootless1 mutant

    Science.gov (United States)

    Husakova, Eva; Hochholdinger, Frank; Soukup, Ales

    2013-01-01

    Background and Aims The maize lrt1 (lateral rootless1) mutant is impaired in its development of lateral roots during early post-embryonic development. The aim of this study was to characterize, in detail, the influences that the mutation exerts on lateral root initiation and the subsequent developments, as well as to describe the behaviour of the entire plant under variable environmental conditions. Methods Mutant lrt1 plants were cultivated under different conditions of hydroponics, and in between sheets of moist paper. Cleared whole mounts and anatomical sections were used in combination with both selected staining procedures and histochemical tests to follow root development. Root surface permeability tests and the biochemical quantification of lignin were performed to complement the structural data. Key Results The data presented suggest a redefinition of lrt1 function in lateral roots as a promoter of later development; however, neither the complete absence of lateral roots nor the frequency of their initiation is linked to lrt1 function. The developmental effects of lrt1 are under strong environmental influences. Mutant primordia are affected in structure, growth and emergence; and the majority of primordia terminate their growth during this last step, or shortly thereafter. The lateral roots are impaired in the maintenance of the root apical meristem. The primary root shows disturbances in the organization of both epidermal and subepidermal layers. The lrt1-related cell-wall modifications include: lignification in peripheral layers, the deposition of polyphenolic substances and a higher activity of peroxidase. Conclusions The present study provides novel insights into the function of the lrt1 gene in root system development. The lrt1 gene participates in the spatial distribution of initiation, but not in its frequency. Later, the development of lateral roots is strongly affected. The effect of the lrt1 mutation is not as obvious in the primary root, with no

  4. Single-channel kinetics of BK (Slo1 channels

    Directory of Open Access Journals (Sweden)

    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.

  5. Pannexin-1 channels in epilepsy.

    Science.gov (United States)

    Aquilino, Mark S; Whyte-Fagundes, Paige; Zoidl, Georg; Carlen, Peter L

    2017-09-05

    Pannexin-1 (Panx1) expression is raised in several animal seizure models and in resected human epileptic brain tissue, suggesting relevance to epilepsy. Multiple factors that are characteristic of seizures are thought to regulate Panx1 channel opening, including elevated levels of extracellular K + . Panx1, when open, 1) releases ATP, glutamate, and other metabolites into the extracellular medium, and 2) may depolarize the membrane due to a channel reversal potential around 0mV. Resultant ATP release from stimulated Panx1 can activate purinergic receptors, including P2X7 receptors. Glutamate and other signaling molecules released by Panx1 opening may have both excitatory and inhibitory actions on seizure generation. This review examines the critical and complex roles of Panx1 channels in epilepsy, which could provide a basis for future therapeutics. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Sigma-1 receptor agonists directly inhibit Nav1.2/1.4 channels.

    Directory of Open Access Journals (Sweden)

    Xiao-Fei Gao

    Full Text Available (+-SKF 10047 (N-allyl-normetazocine is a prototypic and specific sigma-1 receptor agonist that has been used extensively to study the function of sigma-1 receptors. (+-SKF 10047 inhibits K(+, Na(+ and Ca2+ channels via sigma-1 receptor activation. We found that (+-SKF 10047 inhibited Na(V1.2 and Na(V1.4 channels independently of sigma-1 receptor activation. (+-SKF 10047 equally inhibited Na(V1.2/1.4 channel currents in HEK293T cells with abundant sigma-1 receptor expression and in COS-7 cells, which barely express sigma-1 receptors. The sigma-1 receptor antagonists BD 1063,BD 1047 and NE-100 did not block the inhibitory effects of (+-SKF-10047. Blocking of the PKA, PKC and G-protein pathways did not affect (+-SKF 10047 inhibition of Na(V1.2 channel currents. The sigma-1 receptor agonists Dextromethorphan (DM and 1,3-di-o-tolyl-guanidine (DTG also inhibited Na(V1.2 currents through a sigma-1 receptor-independent pathway. The (+-SKF 10047 inhibition of Na(V1.2 currents was use- and frequency-dependent. Point mutations demonstrated the importance of Phe(1764 and Tyr(1771 in the IV-segment 6 domain of the Na(V1.2 channel and Phe(1579 in the Na(V1.4 channel for (+-SKF 10047 inhibition. In conclusion, our results suggest that sigma-1 receptor agonists directly inhibit Na(V1.2/1.4 channels and that these interactions should be given special attention for future sigma-1 receptor function studies.

  7. The subcellular distribution of T-type Ca2+ channels in interneurons of the lateral geniculate nucleus.

    Science.gov (United States)

    Allken, Vaneeda; Chepkoech, Joy-Loi; Einevoll, Gaute T; Halnes, Geir

    2014-01-01

    Inhibitory interneurons (INs) in the lateral geniculate nucleus (LGN) provide both axonal and dendritic GABA output to thalamocortical relay cells (TCs). Distal parts of the IN dendrites often enter into complex arrangements known as triadic synapses, where the IN dendrite plays a dual role as postsynaptic to retinal input and presynaptic to TC dendrites. Dendritic GABA release can be triggered by retinal input, in a highly localized process that is functionally isolated from the soma, but can also be triggered by somatically elicited Ca(2+)-spikes and possibly by backpropagating action potentials. Ca(2+)-spikes in INs are predominantly mediated by T-type Ca(2+)-channels (T-channels). Due to the complex nature of the dendritic signalling, the function of the IN is likely to depend critically on how T-channels are distributed over the somatodendritic membrane (T-distribution). To study the relationship between the T-distribution and several IN response properties, we here run a series of simulations where we vary the T-distribution in a multicompartmental IN model with a realistic morphology. We find that the somatic response to somatic current injection is facilitated by a high T-channel density in the soma-region. Conversely, a high T-channel density in the distal dendritic region is found to facilitate dendritic signalling in both the outward direction (increases the response in distal dendrites to somatic input) and the inward direction (the soma responds stronger to distal synaptic input). The real T-distribution is likely to reflect a compromise between several neural functions, involving somatic response patterns and dendritic signalling.

  8. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides

    Science.gov (United States)

    Borbiro, Istvan; Badheka, Doreen; Rohacs, Tibor

    2015-01-01

    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 PI(4)P from the plasma membrane through Ca2+-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 or 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. PMID:25670203

  9. Locating a compact odor source using a four-channel insect electroantennogram sensor

    Energy Technology Data Exchange (ETDEWEB)

    Myrick, A J; Baker, T C [Chemical Ecology Laboratory, Department of Entomology, Pennsylvania State University, University Park, PA 16802 (United States)

    2011-03-15

    Here we demonstrate the feasibility of using an array of live insects to detect concentrated packets of odor and infer the location of an odor source ({approx}15 m away) using a backward Lagrangian dispersion model based on the Langevin equation. Bayesian inference allows uncertainty to be quantified, which is useful for robotic planning. The electroantennogram (EAG) is the biopotential developed between the tissue at the tip of an insect antenna and its base, which is due to the massed response of the olfactory receptor neurons to an odor stimulus. The EAG signal can carry tens of bits per second of information with a rise time as short as 12 ms (K A Justice 2005 J. Neurophiol. 93 2233-9). Here, instrumentation including a GPS with a digital compass and an ultrasonic 2D anemometer has been integrated with an EAG odor detection scheme, allowing the location of an odor source to be estimated by collecting data at several downwind locations. Bayesian inference in conjunction with a Lagrangian dispersion model, taking into account detection errors, has been implemented resulting in an estimate of the odor source location within 0.2 m of the actual location.

  10. Locating a compact odor source using a four-channel insect electroantennogram sensor

    International Nuclear Information System (INIS)

    Myrick, A J; Baker, T C

    2011-01-01

    Here we demonstrate the feasibility of using an array of live insects to detect concentrated packets of odor and infer the location of an odor source (∼15 m away) using a backward Lagrangian dispersion model based on the Langevin equation. Bayesian inference allows uncertainty to be quantified, which is useful for robotic planning. The electroantennogram (EAG) is the biopotential developed between the tissue at the tip of an insect antenna and its base, which is due to the massed response of the olfactory receptor neurons to an odor stimulus. The EAG signal can carry tens of bits per second of information with a rise time as short as 12 ms (K A Justice 2005 J. Neurophiol. 93 2233-9). Here, instrumentation including a GPS with a digital compass and an ultrasonic 2D anemometer has been integrated with an EAG odor detection scheme, allowing the location of an odor source to be estimated by collecting data at several downwind locations. Bayesian inference in conjunction with a Lagrangian dispersion model, taking into account detection errors, has been implemented resulting in an estimate of the odor source location within 0.2 m of the actual location.

  11. The two-pore domain K+ channel TASK-1 is closely associated with brain barriers and meninges.

    Science.gov (United States)

    Kanjhan, Refik; Pow, David V; Noakes, Peter G; Bellingham, Mark C

    2010-12-01

    Impairment of the blood-brain barrier (BBB), the blood-cerebrospinal fluid (CSF) barrier and brain-CSF barrier has been implicated in neuropathology of several brain disorders, such as amyotrophic lateral sclerosis, cerebral edema, multiple sclerosis, neural inflammation, ischemia and stroke. Two-pore domain weakly inward rectifying K+ channel (TWIK)-related acid-sensitive potassium (TASK)-1 channels (K2p3.1; KCNK3) are among the targets that contribute to the development of these pathologies. For example TASK-1 activity is inhibited by acidification, ischemia, hypoxia and several signaling molecules released under pathologic conditions. We have used immuno-histochemistry to examine the distribution of the TASK-1 protein in structures associated with the BBB, blood-CSF barrier, brain-CSF barrier, and in the meninges of adult rat. Dense TASK-1 immuno-reactivity (TASK-1-IR) was observed in ependymal cells lining the fourth ventricle at the brain-CSF interface, in glial cells that ensheath the walls of blood vessels at the glio-vascular interface, and in the meninges. In these structures, TASK-1-IR often co-localized with glial fibrillary associated protein (GFAP) or vimentin. This study provides anatomical evidence for localization of TASK-1 K+ channels in cells that segregate distinct fluid compartments within and surrounding the brain. We suggest that TASK-1 channels, in coordination with other ion channels (e.g., aquaporins and chloride channels) and transporters (e.g., Na+-K+-ATPase and Na+-K+-2Cl⁻ and by virtue of its heterogeneous distribution, may differentially contribute to the varying levels of K+ vital for cellular function in these compartments. Our findings are likely to be relevant to recently reported roles of TASK-1 in cerebral ischemia, stroke and inflammatory brain disorders.

  12. The He+H¯→He p¯+e+ rearrangement

    Science.gov (United States)

    Todd, Allan C.; Armour, Edward A. G.

    2006-06-01

    In this paper, we present a summary of our work in progress on calculating cross sections for the He+H¯→He p¯+e+ rearrangement process in He H¯ scattering. This has involved a study of the system He p¯ within the Born-Oppenheimer (BO) approximation using the Rayleigh-Ritz variational method. This work has been reported in [A.C. Todd, E.A.G. Armour, J. Phys. B 38 (2005) 3367] and is summarised here. Similar calculations are in progress for the He+H¯ entrance channel. We intend to use the entrance channel and rearrangement channel wave functions to obtain the cross sections for the rearrangement using the distorted wave Born approximation T-matrix method described elsewhere in these proceedings [E.A.G. Armour, S. Jonsell, Y. Liu, A.C. Todd, these Proceedings, doi:10.1016/j.nimb.2006.01.049].

  13. The He+H-bar → Hep-bar +e+ rearrangement

    International Nuclear Information System (INIS)

    Todd, Allan C.; Armour, Edward A.G.

    2006-01-01

    In this paper, we present a summary of our work in progress on calculating cross sections for the He+H-bar ->Hep-bar +e + rearrangement process in HeH-bar scattering. This has involved a study of the system Hep-bar within the Born-Oppenheimer (BO) approximation using the Rayleigh-Ritz variational method. This work has been reported in [A.C. Todd, E.A.G. Armour, J. Phys. B 38 (2005) 3367] and is summarised here. Similar calculations are in progress for the He+H-bar entrance channel. We intend to use the entrance channel and rearrangement channel wave functions to obtain the cross sections for the rearrangement using the distorted wave Born approximation T-matrix method described elsewhere in these proceedings [E.A.G. Armour, S. Jonsell, Y. Liu, A.C. Todd, these Proceedings, doi:10.1016/j.nimb.2006.01.049

  14. An analysis of density-wave oscillations in ventilated channels

    International Nuclear Information System (INIS)

    Taleyarkhan, R.P.

    1982-01-01

    A mathematical model has been developed for the linear stability analyses of a system of ventilated parallel boiling channels. The model can accommodate phasic slip, arbitrary non-uniform axial power distributions, distributed local losses, heater wall dynamics, channel-to-channel radial power skews, discrete or continuous ventilation between the channels, turbulent mixing between the channels, various donor-cell options for the lateral transport of energy and momentum, and a transverse momentum equation, including storage and cross-flow inertia. A special matrix reduction scheme was developed to efficiently solve the system of linearized, Laplace transformed, nodal equations. The digital computer programs, MAZDA-1F, MAZDA-4S and MAZDA-4F, were written for the numerical evaluation of the mathematical model developed. MAZDA-1F is a frequency domain code which can be used for the study of linear stability of a single boiling channel. MAZDA-4S evaluates the steady-state flow and pressure fields in a system of ventilated parallel channels. The frequency domain code, MAZDA-4F, can then be used to assess the linear stability of the flow field obtained with MAZDA-4S. A parametric study using MAZDA-1F and MAZDA-4F revealed that phasic slip, axial power distribution, heater wall dynamics, local losses, lateral ventilation and radial power skew can have a significant effect on the stability characteristics of the system

  15. Rapid multiplex detection of 10 foodborne pathogens with an up-converting phosphor technology-based 10-channel lateral flow assay

    Science.gov (United States)

    Zhao, Yong; Wang, Haoran; Zhang, Pingping; Sun, Chongyun; Wang, Xiaochen; Wang, Xinrui; Yang, Ruifu; Wang, Chengbin; Zhou, Lei

    2016-01-01

    The rapid high-throughput detection of foodborne pathogens is essential in controlling food safety. In this study, a 10-channel up-converting phosphor technology-based lateral flow (TC-UPT-LF) assay was established for the rapid and simultaneous detection of 10 epidemic foodborne pathogens. Ten different single-target UPT-LF strips were developed and integrated into one TC-UPT-LF disc with optimization. Without enrichment the TC-UPT-LF assay had a detection sensitivity of 104 CFU mL−1 or 105 CFU mL−1 for each pathogen, and after sample enrichment it was 10 CFU/0.6 mg. The assay also showed good linearity, allowing quantitative detection, with a linear fitting coefficient of determination (R2) of 0.916–0.998. The 10 detection channels did not cross-react, so multiple targets could be specifically detected. When 279 real food samples were tested, the assay was highly consistent (100%) with culture-based methods. The results for 110 food samples artificially contaminated with single or multiple targets showed a high detection rate (≥80%) for most target bacteria. Overall, the TC-UPT-LF assay allows the rapid, quantitative, and simultaneous detection of 10 kinds of foodborne pathogens within 20 min, and is especially suitable for the rapid detection and surveillance of foodborne pathogens in food and water. PMID:26884128

  16. β1 subunit stabilises sodium channel Nav1.7 against mechanical stress.

    Science.gov (United States)

    Körner, Jannis; Meents, Jannis; Machtens, Jan-Philipp; Lampert, Angelika

    2018-06-01

    The voltage-gated sodium channel Nav1.7 is a key player in neuronal excitability and pain signalling. In addition to voltage sensing, the channel is also modulated by mechanical stress. Using whole-cell patch-clamp experiments, we discovered that the sodium channel subunit β1 is able to prevent the impact of mechanical stress on Nav1.7. An intramolecular disulfide bond of β1 was identified to be essential for stabilisation of inactivation, but not activation, against mechanical stress using molecular dynamics simulations, homology modelling and site-directed mutagenesis. Our results highlight the role of segment 6 of domain IV in fast inactivation. We present a candidate mechanism for sodium channel stabilisation against mechanical stress, ensuring reliable channel functionality in living systems. Voltage-gated sodium channels are key players in neuronal excitability and pain signalling. Precise gating of these channels is crucial as even small functional alterations can lead to pathological phenotypes such as pain or heart failure. Mechanical stress has been shown to affect sodium channel activation and inactivation. This suggests that stabilising components are necessary to ensure precise channel gating in living organisms. Here, we show that mechanical shear stress affects voltage dependence of activation and fast inactivation of the Nav1.7 channel. Co-expression of the β1 subunit, however, protects both gating modes of Nav1.7 against mechanical shear stress. Using molecular dynamics simulation, homology modelling and site-directed mutagenesis, we identify an intramolecular disulfide bond of β1 (Cys21-Cys43) which is partially involved in this process: the β1-C43A mutant prevents mechanical modulation of voltage dependence of activation, but not of fast inactivation. Our data emphasise the unique role of segment 6 of domain IV for sodium channel fast inactivation and confirm previous reports that the intracellular process of fast inactivation can be

  17. Lateral control strategy for a hypersonic cruise missile

    Directory of Open Access Journals (Sweden)

    Yonghua Fan

    2017-04-01

    Full Text Available Hypersonic cruise missile always adopts the configuration of waverider body with the restraint of scramjet. As a result, the lateral motion exhibits serious coupling, and the controller design of the lateral lateral system cannot be conducted separately for yaw channel and roll channel. A multiple input and multiple output optimal control method with integrators is presented to design the lateral combined control system for hypersonic cruise missile. A hypersonic cruise missile lateral model is linearized as a multiple input and multiple output plant, which is coupled by kinematics and fin deflection between yaw and roll. In lateral combined controller, the integrators are augmented, respectively, into the loop of roll angle and lateral overload to ensure that the commands are tracked with zero steady-state error. Through simulation, the proposed controller demonstrates good performance in tracking the command of roll angle and lateral overload.

  18. KCNE1 constrains the voltage sensor of Kv7.1 K+ channels.

    Directory of Open Access Journals (Sweden)

    Liora Shamgar

    Full Text Available Kv7 potassium channels whose mutations cause cardiovascular and neurological disorders are members of the superfamily of voltage-gated K(+ channels, comprising a central pore enclosed by four voltage-sensing domains (VSDs and sharing a homologous S4 sensor sequence. The Kv7.1 pore-forming subunit can interact with various KCNE auxiliary subunits to form K(+ channels with very different gating behaviors. In an attempt to characterize the nature of the promiscuous gating of Kv7.1 channels, we performed a tryptophan-scanning mutagenesis of the S4 sensor and analyzed the mutation-induced perturbations in gating free energy. Perturbing the gating energetics of Kv7.1 bias most of the mutant channels towards the closed state, while fewer mutations stabilize the open state or the inactivated state. In the absence of auxiliary subunits, mutations of specific S4 residues mimic the gating phenotypes produced by co-assembly of Kv7.1 with either KCNE1 or KCNE3. Many S4 perturbations compromise the ability of KCNE1 to properly regulate Kv7.1 channel gating. The tryptophan-induced packing perturbations and cysteine engineering studies in S4 suggest that KCNE1 lodges at the inter-VSD S4-S1 interface between two adjacent subunits, a strategic location to exert its striking action on Kv7.1 gating functions.

  19. The secret life of ion channels: Kv1.3 potassium channels and proliferation.

    Science.gov (United States)

    Pérez-García, M Teresa; Cidad, Pilar; López-López, José R

    2018-01-01

    Kv1.3 channels are involved in the switch to proliferation of normally quiescent cells, being implicated in the control of cell cycle in many different cell types and in many different ways. They modulate membrane potential controlling K + fluxes, sense changes in potential, and interact with many signaling molecules through their intracellular domains. From a mechanistic point of view, we can describe the role of Kv1.3 channels in proliferation with at least three different models. In the "membrane potential model," membrane hyperpolarization resulting from Kv1.3 activation provides the driving force for Ca 2+ influx required to activate Ca 2+ -dependent transcription. This model explains most of the data obtained from several cells from the immune system. In the "voltage sensor model," Kv1.3 channels serve mainly as sensors that transduce electrical signals into biochemical cascades, independently of their effect on membrane potential. Kv1.3-dependent proliferation of vascular smooth muscle cells (VSMCs) could fit this model. Finally, in the "channelosome balance model," the master switch determining proliferation may be related to the control of the Kv1.3 to Kv1.5 ratio, as described in glial cells and also in VSMCs. Since the three mechanisms cannot function independently, these models are obviously not exclusive. Nevertheless, they could be exploited differentially in different cells and tissues. This large functional flexibility of Kv1.3 channels surely gives a new perspective on their functions beyond their elementary role as ion channels, although a conclusive picture of the mechanisms involved in Kv1.3 signaling to proliferation is yet to be reached.

  20. The elusive character of discontinuous deep-water channels: New insights from Lucia Chica channel system, offshore California

    Science.gov (United States)

    Maier, K.L.; Fildani, A.; Paull, C.K.; Graham, S.A.; McHargue, T.R.; Caress, D.W.; McGann, M.

    2011-01-01

    New high-resolution autonomous underwater vehicle (AUV) seafloor images, with 1 m lateral resolution and 0.3 m vertical resolution, reveal unexpected seafloor rugosity and low-relief (thalwegs were interpreted originally from lower-resolution images, but newly acquired AUV data indicate that a single sinuous channel fed a series of discontinuous lower-relief channels. These discontinuous channels were created by at least four avulsion events. Channel relief, defined as the height from the thalweg to the levee crest, controls avulsions and overall stratigraphic architecture of the depositional area. Flowstripped turbidity currents separated into and reactivated multiple channels to create a distributary pattern and developed discontinuous trains of cyclic scours and megaflutes, which may be erosional precursors to continuous channels. The diverse features now imaged in the Lucia Chica channel system (offshore California) are likely common in modern and ancient systems with similar overall morphologies, but have not been previously mapped with lower-resolution detection methods in any of these systems. ?? 2011 Geological Society of America.

  1. KCNQ1 channels sense small changes in cell volume

    DEFF Research Database (Denmark)

    Grunnet, Morten; Jespersen, Thomas; MacAulay, Nanna

    2003-01-01

    Many important physiological processes involve changes in cell volume, e.g. the transport of salt and water in epithelial cells and the contraction of cardiomyocytes. In this study, we show that voltage-gated KCNQ1 channels, which are strongly expressed in epithelial cells or cardiomyocytes......, and KCNQ4 channels, expressed in hair cells and the auditory tract, are tightly regulated by small cell volume changes when co-expressed with aquaporin 1 water-channels (AQP1) in Xenopus oocytes. The KCNQ1 and KCNQ4 current amplitudes precisely reflect the volume of the oocytes. By contrast, the related...... KCNQ2 and KCNQ3 channels, which are prominently expressed in neurons, are insensitive to cell volume changes. The sensitivity of the KCNQ1 and KCNQ4 channels to cell volume changes is independent of the presence of the auxiliary KCNE1-3 subunits, although modulated by KCNE1 in the case of KCNQ1...

  2. Predictive techniques for river channel evolution and maintenance

    Science.gov (United States)

    Nelson, J.M.

    1996-01-01

    Predicting changes in alluvial channel morphology associated with anthropogenic and natural changes in flow and/or sediment supply is a critical part of the management of riverine systems. Over the past few years, advances in the understanding of the physics of sediment transport in conjunction with rapidly increasing capabilities in computational fluid dynamics have yielded now approaches to problems in river mechanics. Techniques appropriate for length scales ranging from reaches to bars and bedforms are described here. Examples of the use of these computational approaches are discussed for three cases: (1) the design of diversion scenarios that maintain channel morphology in steep cobble-bedded channels in Colorado, (2) determination of channel maintenance flows for the preservation of channel islands in the Snake River in Idaho, and (3) prediction of the temporal evolution of deposits in lateral separation zones for future assessment of the impacts of various dam release scenarios on lateral separation deposits in the Colorado River in Grand Canyon. With continued development of their scientific and technical components, the methodologies described here can provide powerful tools for the management of river environments in the future.

  3. An ALS-Associated Mutant SOD1 Rapidly Suppresses KCNT1 (Slack) Na+-Activated K+ Channels in Aplysia Neurons.

    Science.gov (United States)

    Zhang, Yalan; Ni, Weiming; Horwich, Arthur L; Kaczmarek, Leonard K

    2017-02-22

    Mutations that alter levels of Slack (KCNT1) Na + -activated K + current produce devastating effects on neuronal development and neuronal function. We now find that Slack currents are rapidly suppressed by oligomers of mutant human Cu/Zn superoxide dismutase 1 (SOD1), which are associated with motor neuron toxicity in an inherited form of amyotrophic lateral sclerosis (ALS). We recorded from bag cell neurons of Aplysia californica , a model system to study neuronal excitability. We found that injection of fluorescent wild-type SOD1 (wt SOD1YFP) or monomeric mutant G85R SOD1YFP had no effect on net ionic currents measured under voltage clamp. In contrast, outward potassium currents were significantly reduced by microinjection of mutant G85R SOD1YFP that had been preincubated at 37°C or of cross-linked dimers of G85R SOD1YFP. Reduction of potassium current was also seen with multimeric G85R SOD1YFP of ∼300 kDa or >300 kDa that had been cross-linked. In current clamp recordings, microinjection of cross-linked 300 kDa increased excitability by depolarizing the resting membrane potential, and decreasing the latency of action potentials triggered by depolarization. The effect of cross-linked 300 kDa on potassium current was reduced by removing Na + from the bath solution, or by knocking down levels of Slack using siRNA. It was also prevented by pharmacological inhibition of ASK1 (apoptosis signal-regulating kinase 1) or of c-Jun N-terminal kinase, but not by an inhibitor of p38 mitogen-activated protein kinase. These results suggest that soluble mutant SOD1 oligomers rapidly trigger a kinase pathway that regulates the activity of Na + -activated K + channels in neurons. SIGNIFICANCE STATEMENT Slack Na + -activated K + channels (KCNT1, K Na 1.1) regulate neuronal excitability but are also linked to cytoplasmic signaling pathways that control neuronal protein translation. Mutations that alter the amplitude of these currents have devastating effects on neuronal

  4. Evolutionary psychology is compatible with equity feminism, but not with gender feminism: a reply to Eagly and Wood (2011).

    Science.gov (United States)

    Kuhle, Barry X

    2012-01-11

    I comment on Eagly and Wood's biosocial constructionist evolutionary theory (2011; DOI: 10.1007/s11199-011-9949-9). Although this gender feminist theory allows for evolved physical differences between men and women and evolved psychological similarities for men and women, it fails to consider evolutionary accounts of psychological sex differences. I hypothesize that gender feminists' reluctance to acknowledge that evolution has left different fingerprints on men's and women's bodies and brains stems from two common misunderstandings of evolutionary psychology: the myth of immutability and the naturalistic fallacy. I conclude that although evolutionary psychology is eminently compatible with equity feminism, evolutionary psychology and feminist psychology will conflict as long as the latter adheres to gender feminism and its unwillingness to acknowledge the evidence for evolved psychological sex differences.  Gender feminism's dualistic view of evolution hinders the search for and understanding of the proximate and ultimate causes of inequality. Feminist psychology needs to evolve by embracing equity feminism, which has no a priori stance on the origin or existence of differences between the sexes.

  5. Evolutionary Psychology is Compatible with Equity Feminism, but Not with Gender Feminism: A Reply to Eagly and Wood (2011

    Directory of Open Access Journals (Sweden)

    Barry X. Kuhle

    2012-01-01

    Full Text Available I comment on Eagly and Wood's biosocial constructionist evolutionary theory (2011; DOI: 10.1007/s11199-011-9949-9. Although this gender feminist theory allows for evolved physical differences between men and women and evolved psychological similarities for men and women, it fails to consider evolutionary accounts of psychological sex differences. I hypothesize that gender feminists' reluctance to acknowledge that evolution has left different fingerprints on men's and women's bodies and brains stems from two common misunderstandings of evolutionary psychology: the myth of immutability and the naturalistic fallacy. I conclude that although evolutionary psychology is eminently compatible with equity feminism, evolutionary psychology and feminist psychology will conflict as long as the latter adheres to gender feminism and its unwillingness to acknowledge the evidence for evolved psychological sex differences. Gender feminism's dualistic view of evolution hinders the search for and understanding of the proximate and ultimate causes of inequality. Feminist psychology needs to evolve by embracing equity feminism, which has no a priori stance on the origin or existence of differences between the sexes.

  6. Potassium channels as drugs targets in therapy of cardiovascular diseases: 25 years later

    Directory of Open Access Journals (Sweden)

    Protić Dragana

    2013-03-01

    Full Text Available Potassium channels are the most variable ion channel group. They participate in numerous cardiovascular functions, for example regulation of vascular tone, maintenance of resting cardiac membrane potential and excitability of cardiac conduction tissue. Both drugs and endogenous ligands could modulate potassium channel function, belonging to the potassium channel blockers or openers. Modulation of potassium channels could be a therapeutic or adverse drug action. Class III antiarrhythmic agents block the potassium channels, thereby prolonging repolarization phase of action potential with resulting prolongation of effective refractory period. Their effectiveness against supraventricular and ventricular arrhythmias should be weighted against their proarrhythmogenic potential. In addition, numerous other antiarrhythmic agents could modulate potassium channels as well. Diazoxide, minoxidil and nicorandil (well known arterial vasodilators, as well as numerous newly synthesized substances with still unknown therapeutic potential, belong to the potassium channel activators/openers. Therapeutic use of such vasodilators may involve treatment of hypertension (diazoxide, minoxidil and stable angina (nicorandil. Their use might be accompanied with side effects, such as vasodilation, edema, hypotension and reflex tachycardia. Potassium channel openers have also an important role in the treatment of peripheral vascular disease and pulmonary hypertension. In the future, drugs with selective effects on the vascular or cardiac potassium channels could be useful therapeutic agents.

  7. POTASSIUM CHANNELS AS DRUGS TARGETS IN THERAPY OF CARDIOVASCULAR DESEASES: 25 YEARS LATER

    Directory of Open Access Journals (Sweden)

    Protić Dragana

    2013-01-01

    Full Text Available Potassium channels are the most variable ion channel group. They participate in numerous cardiovascular functions, for example regulation of vascular tone, maintenance of resting cardiac membrane potential and excitability of cardiac conduction tissue. Both drugs and endogenous ligands could modulate potassium channel function, belonging to the potassium channel blockers or openers. Modulation of potassium channels could be a therapeutic or adverse drug action. Class III antiarrhythmic agents block the potassium channels, thereby prolonging repolarization phase of action potential with resulting prolongation of effective refractory period. Their effectiveness against supraventricular and ventricular arrhythmias should be weighted against their proarrhythmogenic potential. In addition, numerous other antiarrhythmic agents could modulate potassium channels as well. Diazoxide, minoxidil and nicorandil (well known arterial vasodilators, as well as numerous newly synthesized substances with still unknown therapeutic potential, belong to the potassium channel activators/ openers. Therapeutic use of such vasodilators may involve treatment of hypertension (diazoxide, minoxidil and stable angina (nicorandil. Their use might be accompanied with side effects, such as vasodilation, edema, hypotension and reflex tachycardia. Potassium channel openers have also an important role in the treatment of peripheral vascular disease and pulmonary hypertension. In the future, drugs with selective effects on the vascular or cardiac potassium channels could be useful therapeutic agents.

  8. The Hv1 proton channel responds to mechanical stimuli.

    Science.gov (United States)

    Pathak, Medha M; Tran, Truc; Hong, Liang; Joós, Béla; Morris, Catherine E; Tombola, Francesco

    2016-11-01

    The voltage-gated proton channel, Hv1, is expressed in tissues throughout the body and plays important roles in pH homeostasis and regulation of NADPH oxidase. Hv1 operates in membrane compartments that experience strong mechanical forces under physiological or pathological conditions. In microglia, for example, Hv1 activity is potentiated by cell swelling and causes an increase in brain damage after stroke. The channel complex consists of two proton-permeable voltage-sensing domains (VSDs) linked by a cytoplasmic coiled-coil domain. Here, we report that these VSDs directly respond to mechanical stimuli. We find that membrane stretch facilitates Hv1 channel opening by increasing the rate of activation and shifting the steady-state activation curve to less depolarized potentials. In the presence of a transmembrane pH gradient, membrane stretch alone opens the channel without the need for strong depolarizations. The effect of membrane stretch persists for several minutes after the mechanical stimulus is turned off, suggesting that the channel switches to a "facilitated" mode in which opening occurs more readily and then slowly reverts to the normal mode observed in the absence of membrane stretch. Conductance simulations with a six-state model recapitulate all the features of the channel's response to mechanical stimulation. Hv1 mechanosensitivity thus provides a mechanistic link between channel activation in microglia and brain damage after stroke. © 2016 Pathak et al.

  9. Channel box

    International Nuclear Information System (INIS)

    Tanabe, Akira.

    1993-01-01

    In a channel box of a BWR type reactor, protruding pads are disposed in axial position on the lateral side of a channel box opposing to a control rod and facing the outer side portion of the control rod in a reactor core loaded state. In the initial loading stage of fuel assemblies, channel fasteners and spacer pads are abutted against each other in the upper portion between the channel boxes sandwiching the control rod therebetween. Further, in the lower portion, a gap as a channel for the movement of the control rod is ensured by the support of fuel support metals. If the channel box is bent toward the control rod along with reactor operation, the pads are abutted against each other to always ensure the gap through which the control rod can move easily. Further, when the pads are brought into contact with each other, the bending deformation of the channel box is corrected by urging to each other. Thus, the control rod can always be moved smoothly to attain reactor safety operation. (N.H.)

  10. Analysis of density-wave oscillations in ventilated channels

    International Nuclear Information System (INIS)

    Taleyarkhan, R.; Podowski, M.; Lahey, R.T. Jr.

    1983-03-01

    A mathematical model has been developed for the linear stability analyses of a system of ventilated parallel boiling channels. The model can accomodate phasic slip, arbitrary non-uniform axial power distributions, distributed local losses, heater wall dynamics, channel-to-channel radial power skews, discrete or continuous ventilation between the channels, turbulent mixing between the channels, various donor-cell options for the lateral transport of energy and momentum, and a transverse momentum equation, including storage and crossflow inertia. A special matrix reduction scheme was developed to efficiently solve the system of linearized, Laplace transformed , nodal equations. The digital computer programs, MAZDA-1F, MAZDA-4S and MAZDA-4F, were written for the numerical evaluation of the mathematical model developed

  11. Cardiac sodium channel NaV1.5 distribution in myocytes via interacting proteins: the multiple pool model.

    Science.gov (United States)

    Shy, Diana; Gillet, Ludovic; Abriel, Hugues

    2013-04-01

    The cardiac sodium current (INa) is responsible for the rapid depolarization of cardiac cells, thus allowing for their contraction. It is also involved in regulating the duration of the cardiac action potential (AP) and propagation of the impulse throughout the myocardium. Cardiac INa is generated by the voltage-gated Na(+) channel, NaV1.5, a 2016-residue protein which forms the pore of the channel. Over the past years, hundreds of mutations in SCN5A, the human gene coding for NaV1.5, have been linked to many cardiac electrical disorders, including the congenital and acquired long QT syndrome, Brugada syndrome, conduction slowing, sick sinus syndrome, atrial fibrillation, and dilated cardiomyopathy. Similar to many membrane proteins, NaV1.5 has been found to be regulated by several interacting proteins. In some cases, these different proteins, which reside in distinct membrane compartments (i.e. lateral membrane vs. intercalated disks), have been shown to interact with the same regulatory domain of NaV1.5, thus suggesting that several pools of NaV1.5 channels may co-exist in cardiac cells. The aim of this review article is to summarize the recent works that demonstrate its interaction with regulatory proteins and illustrate the model that the sodium channel NaV1.5 resides in distinct and different pools in cardiac cells. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Opposite effects of the S4-S5 linker and PIP2 on voltage-gated channel function: KCNQ1/KCNE1 and other channels

    Directory of Open Access Journals (Sweden)

    Frank S Choveau

    2012-07-01

    Full Text Available Voltage-gated potassium (Kv channels are tetramers, each subunit presenting six transmembrane segments (S1-S6, with each S1-S4 segments forming a voltage-sensing domain (VSD and the four S5-S6 forming both the conduction pathway and its gate. S4 segments control the opening of the intracellular activation gate in response to changes in membrane potential. Crystal structures of several voltage-gated ion channels in combination with biophysical and mutagenesis studies highlighted the critical role of the S4-S5 linker (S4S5L and of the S6 C-terminal part (S6T in the coupling between the VSD and the activation gate. Several mechanisms have been proposed to describe the coupling at a molecular scale. This review summarizes the mechanisms suggested for various voltage-gated ion channels, including a mechanism that we described for KCNQ1, in which S4S5L is acting like a ligand binding to S6T to stabilize the channel in a closed state. As discussed in this review, this mechanism may explain the reverse response to depolarization in HCN-like channels. As opposed to S4S5L, the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP2, stabilizes KCNQ1 channel in an open state. Many other ion channels (not only voltage-gated require PIP2 to function properly, confirming its crucial importance as an ion channel co-factor. This is highlighted in cases in which an altered regulation of ion channels by PIP2 leads to channelopathies, as observed for KCNQ1. This review summarizes the state of the art on the two regulatory mechanisms that are critical for KCNQ1 and other voltage-gated channels function (PIP2 and S4-S5L, and assesses their potential physiological and pathophysiological roles.

  13. Tonoplast aquaporins facilitate lateral root emergence

    DEFF Research Database (Denmark)

    Reinhardt, Hagen; Hachez, Charles; Bienert, Manuela Désirée

    2016-01-01

    Aquaporins (AQPs) are water channels allowing fast and passive diffusion of water across cell membranes. It was hypothesized that AQPs contribute to cell elongation processes by allowing water influx across the plasma membrane and the tonoplast to maintain adequate turgor pressure. Here, we report...... mutants showed no or minor reduction in growth of the main root. This phenotype was due to the retardation of LRP emergence. Live cell imaging revealed that tight spatiotemporal control of TIP abundance in the tonoplast of the different LRP cells is pivotal to mediating this developmental process. While...... lateral root emergence is correlated to a reduction of AtTIP1;1 and AtTIP1;2 protein levels in LRPs, expression of AtTIP2;1 is specifically needed in a restricted cell population at the base, then later at the flanks, of developing LRPs. Interestingly, the LRP emergence phenotype of the triple tip mutants...

  14. Genotyping of presenilin-1 polymorphism in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Panas, M; Karadima, G; Kalfakis, N; Psarrou, O; Floroskoufi, P; Kladi, A; Petersen, M B; Vassilopoulos, D

    2000-12-01

    The mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis are not fully understood. Recent studies suggest that apoptosis is involved in the abnormal neural death that occurs in this devastating disease. Presenilin-1, a transmembrane protein, seems to be implicated in apoptosis. To determine whether presenilin-1 intron 8 polymorphism has an influence in the course of amyotrophic lateral sclerosis, we examined this polymorphism genotypes in a large group of patients (n = 72) with amyotrophic lateral sclerosis and in a random sample of 213 healthy individuals. The results showed a significant difference in genotype (P < 0.04) and allele (P < 0.03) distribution between patients controls. These results suggest a possible intervention of presenilin-1 in the pathogenesis of amyotrophic lateral sclerosis.

  15. Asymmetric fluxes of water and sediments in a mesotidal mudflat channel

    Science.gov (United States)

    Mariotti, G.; Fagherazzi, S.

    2011-01-01

    The hydrodynamics of a small tributary channel and its adjacent mudflat is studied in Willapa Bay, Washington State, USA. Velocity profiles and water levels are simultaneously measured at different locations in the channel and on the mudflat for two weeks. The above tidal flat and channel hydrodynamics differ remarkably during the tidal cycle. When the water surface level is above the tidal flat elevation, the channel is inactive. At this stage, the above tidal flat flow is predominantly aligned along the Bay axis, oscillating with the tide as a standing wave with peak velocities up to 0.3 m/s. When the mudflat becomes emergent, the flow concentrates in the channel. During this stage, current velocities up to 1 m/s are measured during ebb; and up to 0.6 m/s during flood. Standard equations for open-channel flow are utilized to study the channel hydrodynamics. From the continuity equation, a lateral inflow is predicted during ebb, which likely originates from the drainage of the mudflat through the lateral runnels. Both advective acceleration and lateral discharge terms, estimated directly from the velocity profiles, play a significant role in the momentum equation. The computed drag coefficient for bottom friction is small, due to an absence of vegetation and bottom bedforms in the channel. Sediment fluxes are calculated by combining flow and suspended sediment concentration estimated using the acoustic backscatter signal of the instruments. A net export of the sediment from the channel is found during ebb, which is not balanced by the sediment import during flood. When the mudflat is submerged, ebb-flood asymmetries in suspended sediment concentration are present, leading to a net sediment flux toward the inner part of the Willapa Bay. Finally, a residual flow is detected inside the channel at high slack water, probably associated with the thermohaline circulation.

  16. Modulation of Kir4.1 and Kir4.1-Kir5.1 channels by small changes in cell volume

    DEFF Research Database (Denmark)

    Soe, Rikke; Macaulay, Nanna; Klaerke, Dan Arne

    2009-01-01

    in Kir4.1 and Kir4.1-Kir5.1 currents upon swelling of the oocytes and a reduction in the current when the oocytes were shrunk. The volume-dependent changes in channel activity were not due to changes in the kinetics of the channels. These findings implicate a putative functional interaction between...... the Kir channels and aquaporins via small, fast cell volume changes in the glial cells....... channels and aquaporins is therefore debated. To test a possible volume-sensitivity of the Kir channels, the Kir4.1 or Kir4.1-Kir5.1 channels were expressed in Xenopus oocytes with or without co-expression of aquaporins and subsequently exposed to cell volume alterations. Our results show an increase...

  17. Involvement of plasma membrane Ca2+ channels, IP3 receptors, and ryanodine receptors in the generation of spontaneous rhythmic contractions of the cricket lateral oviduct.

    Science.gov (United States)

    Tamashiro, Hirotake; Yoshino, Masami

    2014-12-01

    In the present study, the isolated cricket (Gryllus bimaculatus) lateral oviduct exhibited spontaneous rhythmic contractions (SRCs) with a frequency of 0.29±0.009 Hz (n=43) and an amplitude of 14.6±1.25 mg (n=29). SRCs completely disappeared following removal of extracellular Ca2+ using a solution containing 5mM EGTA. Application of the non-specific Ca2+ channel blockers Co2+, Ni2+, and Cd2+ also decreased both the frequency and amplitude of SRCs in dose-dependent manners, suggesting that Ca2+ entry through plasma membrane Ca2+ channels is essential for the generation of SRCs. Application of ryanodine (30 μM), which depletes intracellular Ca2+ by locking ryanodine receptor (RyR)-Ca2+ channels in an open state, gradually reduced the frequency and amplitude of SRCs. A RyR antagonist, tetracaine, reduced both the frequency and amplitude of SRCs, whereas a RyR activator, caffeine, increased the frequency of SRCs with a subsequent increase in basal tonus, indicating that RyRs are essential for generating SRCs. To further investigate the involvement of phospholipase C (PLC) and inositol 1,4,5-trisphosphate receptors (IP3Rs) in SRCs, we examined the effect of a PLC inhibitor, U73122, and an IP3R antagonist, 2-aminoethoxydiphenyl borate (2-APB), on SRCs. Separately, U73122 (10 μM) and 2-APB (30-50 μM) both significantly reduced the amplitude of SRCs with little effect on their frequency, further indicating that the PLC/IP3R signaling pathway is fundamental to the modulation of the amplitude of SRCs. A hypotonic-induced increase in the frequency and amplitude of SRCs and a hypertonic-induced decrease in the frequency and amplitude of SRCs indicated that mechanical stretch of the lateral oviduct is involved in the generation of SRCs. The sarcoplasmic reticulum Ca2+-pump ATPase inhibitors thapsigargin and cyclopiazonic acid impaired or suppressed the relaxation phase of SRCs. Taken together, the present results indicate that Ca2+ influx through plasma membrane Ca2

  18. Expression of TRPV1 channels after nerve injury provides an essential delivery tool for neuropathic pain attenuation.

    Directory of Open Access Journals (Sweden)

    Hossain Md Zakir

    Full Text Available Increased expression of the transient receptor potential vanilloid 1 (TRPV1 channels, following nerve injury, may facilitate the entry of QX-314 into nociceptive neurons in order to achieve effective and selective pain relief. In this study we hypothesized that the level of QX-314/capsaicin (QX-CAP--induced blockade of nocifensive behavior could be used as an indirect in-vivo measurement of functional expression of TRPV1 channels. We used the QX-CAP combination to monitor the functional expression of TRPV1 in regenerated neurons after inferior alveolar nerve (IAN transection in rats. We evaluated the effect of this combination on pain threshold at different time points after IAN transection by analyzing the escape thresholds to mechanical stimulation of lateral mental skin. At 2 weeks after IAN transection, there was no QX-CAP mediated block of mechanical hyperalgesia, implying that there was no functional expression of TRPV1 channels. These results were confirmed immunohistochemically by staining of regenerated trigeminal ganglion (TG neurons. This suggests that TRPV1 channel expression is an essential necessity for the QX-CAP mediated blockade. Furthermore, we show that 3 and 4 weeks after IAN transection, application of QX-CAP produced a gradual increase in escape threshold, which paralleled the increased levels of TRPV1 channels that were detected in regenerated TG neurons. Immunohistochemical analysis also revealed that non-myelinated neurons regenerated slowly compared to myelinated neurons following IAN transection. We also show that TRPV1 expression shifted towards myelinated neurons. Our findings suggest that nerve injury modulates the TRPV1 expression pattern in regenerated neurons and that the effectiveness of QX-CAP induced blockade depends on the availability of functional TRPV1 receptors in regenerated neurons. The results of this study also suggest that the QX-CAP based approach can be used as a new behavioral tool to detect

  19. Voltage-Dependent Gating: Novel Insights from KCNQ1 Channels

    Science.gov (United States)

    Cui, Jianmin

    2016-01-01

    Gating of voltage-dependent cation channels involves three general molecular processes: voltage sensor activation, sensor-pore coupling, and pore opening. KCNQ1 is a voltage-gated potassium (Kv) channel whose distinctive properties have provided novel insights on fundamental principles of voltage-dependent gating. 1) Similar to other Kv channels, KCNQ1 voltage sensor activation undergoes two resolvable steps; but, unique to KCNQ1, the pore opens at both the intermediate and activated state of voltage sensor activation. The voltage sensor-pore coupling differs in the intermediate-open and the activated-open states, resulting in changes of open pore properties during voltage sensor activation. 2) The voltage sensor-pore coupling and pore opening require the membrane lipid PIP2 and intracellular ATP, respectively, as cofactors, thus voltage-dependent gating is dependent on multiple stimuli, including the binding of intracellular signaling molecules. These mechanisms underlie the extraordinary KCNE1 subunit modification of the KCNQ1 channel and have significant physiological implications. PMID:26745405

  20. Lateral convection and diffusion of sediment in straight rivers

    DEFF Research Database (Denmark)

    Christensen, Henrik Bo; Fredsøe, Jørgen

    1998-01-01

    and a higher level of turbulence at the channel centre, than in the near bank zones, which means that the ability to support suspended sediment will decrease from the channel centre. The two turbulence models give different estimates for the lateral transport, which mainly are caused by turbulence generated......The lateral transport of suspended sediment in a straight river cross section with a parabolic shaped bed is studied be use of a k-e and a full Reynolds stress turbulence model. Due to depth variations a lateral transport of suspended sediment is generated. This is mainly caused by the slopping bed...... secondary flow cells in the Reynolds stress model. The flow cells make zones with alternately high and low sediment concentration, and thereby much higher local gradients in the lateral direction. Both models found a net inward lateral transport. The transport by convection was found more dominant than...

  1. The transverse dynamics of flow in a tidal channel within a greater strait

    Science.gov (United States)

    Khosravi, Maziar; Siadatmousavi, Seyed Mostafa; Vennell, Ross; Chegini, Vahid

    2018-02-01

    Vessel-mounted ADCP measurements were conducted to describe the transverse structure of flow between the two headland tips in Khuran Channel, south of Iran (26° 45' N), where the highest tidal velocities in spring tides were 1.8 m/s. Current profiles were obtained using a 614.4 kHz TRDI WorkHorse Broadband ADCP over nine repetitions of three cross-channel transects during one semidiurnal tidal cycle. The 2.2-km-long transects ran north/south across the channel. A least-square fit to semidiurnal, quarter-diurnal, and sixth diurnal harmonics was used to separate the tidal signals from the observed flow. Spatial gradients showed that the greatest lateral shears and convergences were found over the northern channel and near the northern headland tip due to very sharp bathymetric changes in this area. Contrary to the historical assumption, the across-channel momentum balance in the Khuran Channel was ageostrophic. The current study represents one of the few examples reported where the lateral friction influences the across-channel momentum balance.

  2. Mechanisms underlying KCNQ1channel cell volume sensitivity

    DEFF Research Database (Denmark)

    Hammami, Sofia

    Cells are constantly exposed to changes in cell volume during cell metabolism, nutrient uptake, cell proliferation, cell migration and salt and water transport. In order to cope with these perturbations, potassium channels in line with chloride channels have been shown to be likely contributors...... to the process of cell volume adjustments. A great diversity of potassium channels being members of either the 6TM, 4 TM or 2 TM K+ channel gene family have been shown to be strictly regulated by small, fast changes in cell volume. However, the precise mechanism underlying the K+ channel sensitivity to cell...... volume alterations is not yet fully understood. The KCNQ1 channel belonging to the voltage gated KCNQ family is considered a precise sensor of volume changes. The goal of this thesis was to elucidate the mechanism that induces cell volume sensitivity. Until now, a number of investigators have implicitly...

  3. Radiation-Induced Short Channel (RISCE) and Narrow Channel (RINCE) Effects in 65 and 130 nm MOSFETs

    CERN Document Server

    Faccio, F; Cornale, D; Paccagnella, A; Gerardin, S

    2015-01-01

    The behavior of transistors in commercial-grade complementary metal-oxide semiconductor technologies in the 65 and 130 nm nodes has been explored up to a total ionizing dose of 1 Grad. The large dose tolerance of the thin gate oxide is confirmed, but defects in the spacer and STI oxides have a strong effect on the performance of the transistors. A radiation-induced short channel effect is traced to charge trapping in the spacers used for drain engineering, while a radiation-induced narrow channel effect is due to defect generation in the lateral isolation oxide (STI). These strongly degrade the electrical characteristics of short and narrow channel transistors at high doses, and their magnitude depends on the applied bias and temperature during irradiation in a complex way.

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

    Science.gov (United States)

    Temme, Stephanie J.; Murphy, Geoffrey G.

    2017-01-01

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

  5. Identification of an HV 1 voltage-gated proton channel in insects.

    Science.gov (United States)

    Chaves, Gustavo; Derst, Christian; Franzen, Arne; Mashimo, Yuta; Machida, Ryuichiro; Musset, Boris

    2016-04-01

    The voltage-gated proton channel 1 (HV 1) is an important component of the cellular proton extrusion machinery and is essential for charge compensation during the respiratory burst of phagocytes. HV 1 has been identified in a wide range of eukaryotes throughout the animal kingdom, with the exception of insects. Therefore, it has been proposed that insects do not possess an HV 1 channel. In the present study, we report the existence of an HV 1-type proton channel in insects. We searched insect transcriptome shotgun assembly (TSA) sequence databases and found putative HV 1 orthologues in various polyneopteran insects. To confirm that these putative HV 1 orthologues were functional channels, we studied the HV 1 channel of Nicoletia phytophila (NpHV 1), an insect of the Zygentoma order, in more detail. NpHV 1 comprises 239 amino acids and is 33% identical to the human voltage-gated proton channel 1. Patch clamp measurements in a heterologous expression system showed proton selectivity, as well as pH- and voltage-dependent gating. Interestingly, NpHV 1 shows slightly enhanced pH-dependent gating compared to the human channel. Mutations in the first transmembrane segment at position 66 (Asp66), the presumed selectivity filter, lead to a loss of proton-selective conduction, confirming the importance of this aspartate residue in voltage-gated proton channels. Nucleotide sequence data have been deposited in the GenBank database under accession number KT780722. © 2016 Federation of European Biochemical Societies.

  6. Kv1 channels and neural processing in vestibular calyx afferents

    Directory of Open Access Journals (Sweden)

    Frances L Meredith

    2015-06-01

    Full Text Available Potassium-selective ion channels are important for accurate transmission of signals from auditory and vestibular sensory end organs to their targets in the central nervous system. During different gravity conditions, astronauts experience altered input signals from the peripheral vestibular system resulting in sensorimotor dysfunction. Adaptation to altered sensory input occurs, but it is not explicitly known whether this involves synaptic modifications within the vestibular epithelia. Future investigations of such potential plasticity require a better understanding of the electrophysiological mechanisms underlying the known heterogeneity of afferent discharge under normal conditions. This study advances this understanding by examining the role of the Kv1 potassium channel family in mediating action potentials in specialized vestibular afferent calyx endings in the gerbil crista and utricle. Pharmacological agents selective for different sub-types of Kv1 channels were tested on membrane responses in whole cell recordings in the crista. Kv1 channels sensitive to α-dendrotoxin and dendrotoxin-K were found to prevail in the central regions, whereas K+ channels sensitive to margatoxin, which blocks Kv1.3 and 1.6 channels, were more prominent in peripheral regions. Margatoxin-sensitive currents showed voltage-dependent inactivation. Dendrotoxin-sensitive currents showed no inactivation and dampened excitability in calyces in central neuroepithelial regions. The differential distribution of Kv1 potassium channels in vestibular afferents supports their importance in accurately relaying gravitational and head movement signals through specialized lines to the central nervous system. Pharmacological modulation of specific groups of K+ channels could help alleviate vestibular dysfunction on earth and in space.

  7. Kv1 channels and neural processing in vestibular calyx afferents.

    Science.gov (United States)

    Meredith, Frances L; Kirk, Matthew E; Rennie, Katherine J

    2015-01-01

    Potassium-selective ion channels are important for accurate transmission of signals from auditory and vestibular sensory end organs to their targets in the central nervous system. During different gravity conditions, astronauts experience altered input signals from the peripheral vestibular system resulting in sensorimotor dysfunction. Adaptation to altered sensory input occurs, but it is not explicitly known whether this involves synaptic modifications within the vestibular epithelia. Future investigations of such potential plasticity require a better understanding of the electrophysiological mechanisms underlying the known heterogeneity of afferent discharge under normal conditions. This study advances this understanding by examining the role of the Kv1 potassium channel family in mediating action potentials in specialized vestibular afferent calyx endings in the gerbil crista and utricle. Pharmacological agents selective for different sub-types of Kv1 channels were tested on membrane responses in whole cell recordings in the crista. Kv1 channels sensitive to α-dendrotoxin and dendrotoxin-K were found to prevail in the central regions, whereas K(+) channels sensitive to margatoxin, which blocks Kv1.3 and 1.6 channels, were more prominent in peripheral regions. Margatoxin-sensitive currents showed voltage-dependent inactivation. Dendrotoxin-sensitive currents showed no inactivation and dampened excitability in calyces in central neuroepithelial regions. The differential distribution of Kv1 potassium channels in vestibular afferents supports their importance in accurately relaying gravitational and head movement signals through specialized lines to the central nervous system. Pharmacological modulation of specific groups of K(+) channels could help alleviate vestibular dysfunction on earth and in space.

  8. Channel Control-Blade Interference Management at LaSalle 1 and 2 during 2007 and 2008

    Energy Technology Data Exchange (ETDEWEB)

    Cantonwine, Paul; Crawford, Doug; Downs, Mike [Global Nuclear Fuels, PO Box 780, Wilmington, NC 28402 (United States); Joe, Bertrum [GE-Hitachi, 1989 Little Orchard St., San Jose, CA 95125-1030 (United States); Bahensky, Ted [GE-Hitachi, PO Box 780, Wilmington, NC 28402 (United States); Reimer, John [Exelon Nuclear, 2601 North 21st Road, Marseilles, Il 61341-9757 (United States); Hoz, Carlos del la; Petersen, Ken [Exelon Nuclear, 4300 Winfield Road, Warrenville, IL 60555 (United States); Reitmeyer, Mike [Exelon Nuclear, 200 Exelon Way, Kennett Square, PA 19348 (United States); Morris, Jeff; Zbib, Ali [AREVA NP, 2101 Horn Rapids Road, Richland, WA. 99354 (United States)

    2009-06-15

    This paper provides a summary of the operational experience at LaSalle 1 and LaSalle 2 regarding channel control-blade interference that occurred in 2007 and 2008. Channel distortion data from LaSalle 1 provides a characterization of distortion in all four bundles in cells that experienced channel interference and cells that did not. Also, this paper provides a new channel distortion management strategy implemented at LaSalle 2 that avoided a mid-cycle outage. LaSalle 1 and LaSalle 2 are GE designed Boiling Water Reactors (BWR/5 Type) that generate 1195 MW electric. During 2007 and 2008, each core had 1. and 3. Cycle AREVA ATTRIUM{sup TM} 10 fuel with 100 mil Zr-2 channels and 2. Cycle GNF GE14 fuel with 120/75 mil Zr-2 channels. As a result of the channel control-blade interference observed in 2007 and 2008, two peripheral cells in LaSalle 1 and two (1 peripheral and 1 interior) cells in LaSalle 2 were declared inoperable. The first observations of channel control-blade friction occurred in September 2007 in LaSalle 1 about 6 months prior to the end of a 2-year cycle. LaSalle 2 had started up approximately 6 months earlier and had 18 months left the cycle. The initial observations (eventually seven cells with no-settle conditions were observed in LaSalle) were limited to the peripheral cells where fluence gradient-induced bow was the dominant distortion mechanism. However, near the end of cycle in LaSalle 1 in January 2008, a number of interior cells were unexpectedly found to not settle. These were later determined to be a result of shadow corrosion-induced bow. Further testing to determine the extent of condition found a total of nine interior cells that failed the no-settle criterion. These unexpected observations instigated a significant response that resulted in an extensive expansion of the work scope for the upcoming outage that began on February 4, 2008. Specifically, a large channel measurement campaign and a large re-channeling campaign were added. The

  9. AFM imaging reveals the tetrameric structure of the TRPC1 channel

    International Nuclear Information System (INIS)

    Barrera, Nelson P.; Shaifta, Yasin; McFadzean, Ian; Ward, Jeremy P.T.; Henderson, Robert M.; Edwardson, J. Michael

    2007-01-01

    We have determined the subunit stoichiometry of the transient receptor potential C1 (TRPC1) channel by imaging isolated channels using atomic force microscopy (AFM). A frequency distribution of the molecular volumes of individual channel particles had two peaks, at 170 and 720 nm 3 , corresponding with the expected sizes of TRPC1 monomers and tetramers, respectively. Complexes were formed between TRPC1 channels and antibodies against a V5 epitope tag present on each subunit. The frequency distribution of angles between pairs of bound antibodies had two peaks, at 88 o and 178 o . This result again indicates that the channel assembles as a tetramer

  10. A1C and eAG

    Science.gov (United States)

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  11. Intracellular long-chain acyl CoAs activate TRPV1 channels.

    Directory of Open Access Journals (Sweden)

    Yi Yu

    Full Text Available TRPV1 channels are an important class of membrane proteins that play an integral role in the regulation of intracellular cations such as calcium in many different tissue types. The anionic phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2 is a known positive modulator of TRPV1 channels and the negatively charged phosphate groups interact with several basic amino acid residues in the proximal C-terminal TRP domain of the TRPV1 channel. We and other groups have shown that physiological sub-micromolar levels of long-chain acyl CoAs (LC-CoAs, another ubiquitous anionic lipid, can also act as positive modulators of ion channels and exchangers. Therefore, we investigated whether TRPV1 channel activity is similarly regulated by LC-CoAs. Our results show that LC-CoAs are potent activators of the TRPV1 channel and interact with the same PIP2-binding residues in TRPV1. In contrast to PIP2, LC-CoA modulation of TRPV1 is independent of Ca2+i, acting in an acyl side-chain saturation and chain-length dependent manner. Elevation of LC-CoAs in intact Jurkat T-cells leads to significant increases in agonist-induced Ca2+i levels. Our novel findings indicate that LC-CoAs represent a new fundamental mechanism for regulation of TRPV1 channel activity that may play a role in diverse cell types under physiological and pathophysiological conditions that alter fatty acid transport and metabolism such as obesity and diabetes.

  12. Sediment and Vegetation Controls on Delta Channel Networks

    Science.gov (United States)

    Lauzon, R.; Murray, A. B.; Piliouras, A.; Kim, W.

    2016-12-01

    Numerous factors control the patterns of distributary channels formed on a delta, including water and sediment discharge, grain size, sea level rise rates, and vegetation type. In turn, these channel networks influence the shape and evolution of a delta, including what types of plant and animal life - such as humans - it can support. Previous fluvial modeling and flume experiments, outside of the delta context, have addressed how interactions between sediment and vegetation, through their influence on lateral transport of sediment, determine what type of channel networks develops. Similar interactions likely also shape delta flow patterns. Vegetation introduces cohesion, tending to reduce channel migration rates and strengthen existing channel banks, reinforcing existing channels and resulting in localized, relatively stable flow patterns. On the other hand, sediment transport processes can result in lateral migration and frequent switching of active channels, resulting in flow resembling that of a braided stream. While previous studies of deltas have indirectly explored the effects of vegetation through the introduction of cohesive sediment, we directly incorporate key effects of vegetation on flow and sediment transport into the delta-building model DeltaRCM to explore how these effects influence delta channel network formation. Model development is informed by laboratory flume experiments at UT Austin. Here we present initial results of experiments exploring the effects of sea level rise rate, sediment grain size, vegetation type, and vegetation growth rate on delta channel network morphology. These results support the hypothesis that the ability for lateral transport of sediment to occur plays a key role in determining the evolution of delta channel networks and delta morphology.

  13. Design and characterization of a laterally mounted phased-array transducer breast-specific MRgHIFU device with integrated 11-channel receiver array.

    Science.gov (United States)

    Payne, A; Merrill, R; Minalga, E; Vyas, U; de Bever, J; Todd, N; Hadley, R; Dumont, E; Neumayer, L; Christensen, D; Roemer, R; Parker, D

    2012-03-01

    This work presents the design and preliminary evaluation of a new laterally mounted phased-array MRI-guided high-intensity focused ultrasound (MRgHIFU) system with an integrated 11-channel phased-array radio frequency (RF) coil intended for breast cancer treatment. The design goals for the system included the ability to treat the majority of tumor locations, to increase the MR image's signal-to-noise ratio (SNR) throughout the treatment volume and to provide adequate comfort for the patient. In order to treat the majority of the breast volume, the device was designed such that the treated breast is suspended in a 17-cm diameter treatment cylinder. A laterally shooting 1-MHz, 256-element phased-array ultrasound transducer with flexible positioning is mounted outside the treatment cylinder. This configuration achieves a reduced water volume to minimize RF coil loading effects, to position the coils closer to the breast for increased signal sensitivity, and to reduce the MR image noise associated with using water as the coupling fluid. This design uses an 11-channel phased-array RF coil that is placed on the outer surface of the cylinder surrounding the breast. Mechanical positioning of the transducer and electronic steering of the focal spot enable placement of the ultrasound focus at arbitrary locations throughout the suspended breast. The treatment platform allows the patient to lie prone in a face-down position. The system was tested for comfort with 18 normal volunteers and SNR capabilities in one normal volunteer and for heating accuracy and stability in homogeneous phantom and inhomogeneous ex vivo porcine tissue. There was a 61% increase in mean relative SNR achieved in a homogeneous phantom using the 11-channel RF coil when compared to using only a single-loop coil around the chest wall. The repeatability of the system's energy delivery in a single location was excellent, with less than 3% variability between repeated temperature measurements at the same

  14. Sub-nanometre channels embedded in two-dimensional materials

    KAUST Repository

    Han, Yimo

    2017-12-04

    Two-dimensional (2D) materials are among the most promising candidates for next-generation electronics due to their atomic thinness, allowing for flexible transparent electronics and ultimate length scaling1. Thus far, atomically thin p–n junctions2,3,4,5,6,7,8, metal–semiconductor contacts9,10,11, and metal–insulator barriers12,13,14 have been demonstrated. Although 2D materials achieve the thinnest possible devices, precise nanoscale control over the lateral dimensions is also necessary. Here, we report the direct synthesis of sub-nanometre-wide one-dimensional (1D) MoS2 channels embedded within WSe2 monolayers, using a dislocation-catalysed approach. The 1D channels have edges free of misfit dislocations and dangling bonds, forming a coherent interface with the embedding 2D matrix. Periodic dislocation arrays produce 2D superlattices of coherent MoS2 1D channels in WSe2. Using molecular dynamics simulations, we have identified other combinations of 2D materials where 1D channels can also be formed. The electronic band structure of these 1D channels offers the promise of carrier confinement in a direct-gap material and the charge separation needed to access the ultimate length scales necessary for future electronic applications.

  15. Cholesterol modulates the cellular localization of Orai1 channels and its disposition among membrane domains.

    Science.gov (United States)

    Bohórquez-Hernández, A; Gratton, Enrico; Pacheco, Jonathan; Asanov, Alexander; Vaca, Luis

    2017-12-01

    Store Operated Calcium Entry (SOCE) is one of the most important mechanisms for calcium mobilization in to the cell. Two main proteins sustain SOCE: STIM1 that acts as the calcium sensor in the endoplasmic reticulum (ER) and Orai1 responsible for calcium influx upon depletion of ER. There are many studies indicating that SOCE is modulated by the cholesterol content of the plasma membrane (PM). However, a myriad of questions remain unanswered concerning the precise molecular mechanism by which cholesterol modulates SOCE. In the present study we found that reducing PM cholesterol results in the internalization of Orai1 channels, which can be prevented by overexpressing caveolin 1 (Cav1). Furthermore, Cav1 and Orai1 associate upon SOCE activation as revealed by FRET and coimmunoprecipitation assays. The effects of reducing cholesterol were not limited to an increased rate of Orai1 internalization, but also, affects the lateral movement of Orai1, inducing movement in a linear pattern (unobstructed diffusion) opposite to basal cholesterol conditions were most of Orai1 channels moves in a confined space, as assessed by Fluorescence Correlation Spectroscopy, Cav1 overexpression inhibited these alterations maintaining Orai1 into a confined and partially confined movement. These results not only highlight the complex effect of cholesterol regulation on SOCE, but also indicate a direct regulatory effect on Orai1 localization and compartmentalization by this lipid. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Single molecule microscopy on Store-Operated Calcium channels

    International Nuclear Information System (INIS)

    Madl, J.

    2011-01-01

    Store-Operated Calcium Entry is essential for many signaling processes in non-excitable cells. The best studied Store-Operated Calcium current is the Calcium-Release-Activated-Calcium (CRAC) current in T-cells and mast cells, with Orai1 representing the essential pore forming subunit. Functional CRAC channels in store-depleted cells are composed of four Orai1 subunits. However, the stoichiometric composition in resting cells is still discussed controversially: both a tetrameric and a dimeric stoichiometry of resting-state Orai1 have been reported for immobilized or immobile Orai1 proteins. The aim of this thesis was to design a more versatile approach that allows reliable determination of the subunit stoichiometry of mobile Orai1 channels. The motive for this approach is that mobile sub-fractions of the entire Orai1 population provide the cleanest pool of data, devoid of contributions e.g. from immobile Orai1 clusters or Orai1-loaded vesicles attached to the plasma membrane. Moreover, resting-state Orai1 is predominantly mobile, and mobility appears critical for the lateral redistribution which occurs upon store depletion. The method per se is based on single molecule fluorescence microscopy and brightness analysis. Orai1 proteins were fused to a monomeric variant of Green Fluorescent Protein (mGFP) and over-expressed in a human cell line (T24). The 1:1 labeling stoichiometry allows using the brightness of individual Orai1-mGFP channels as a direct measure of the pore stoichiometry. Due to over-expression a potential mixing with endogenous Orai1 can be neglected. However, over-expression of Orai1-mGFP results in channel densities that are too high to allow for resolving single channels using diffraction limited optical microscopy. In order to overcome this challenge, I developed an experimental strategy that allows reduction of the density of actively fluorescent Orai1-mGFP channels without altering the labeling stoichiometry. In order to reduce the surface density

  17. Complementary roles of KCa3.1 channels and β1-integrin during alveolar epithelial repair.

    Science.gov (United States)

    Girault, Alban; Chebli, Jasmine; Privé, Anik; Trinh, Nguyen Thu Ngan; Maillé, Emilie; Grygorczyk, Ryszard; Brochiero, Emmanuelle

    2015-09-04

    Extensive alveolar epithelial injury and remodelling is a common feature of acute lung injury and acute respiratory distress syndrome (ARDS) and it has been established that epithelial regeneration, and secondary lung oedema resorption, is crucial for ARDS resolution. Much evidence indicates that K(+) channels are regulating epithelial repair processes; however, involvement of the KCa3.1 channels in alveolar repair has never been investigated before. Wound-healing assays demonstrated that the repair rates were increased in primary rat alveolar cell monolayers grown on a fibronectin matrix compared to non-coated supports, whereas an anti-β1-integrin antibody reduced it. KCa3.1 inhibition/silencing impaired the fibronectin-stimulated wound-healing rates, as well as cell migration and proliferation, but had no effect in the absence of coating. We then evaluated a putative relationship between KCa3.1 channel and the migratory machinery protein β1-integrin, which is activated by fibronectin. Co-immunoprecipitation and immunofluorescence experiments indicated a link between the two proteins and revealed their cellular co-distribution. In addition, we demonstrated that KCa3.1 channel and β1-integrin membrane expressions were increased on a fibronectin matrix. We also showed increased intracellular calcium concentrations as well as enhanced expression of TRPC4, a voltage-independent calcium channel belonging to the large TRP channel family, on a fibronectin matrix. Finally, wound-healing assays showed additive effects of KCa3.1 and TRPC4 inhibitors on alveolar epithelial repair. Taken together, our data demonstrate for the first time complementary roles of KCa3.1 and TRPC4 channels with extracellular matrix and β1-integrin in the regulation of alveolar repair processes.

  18. On the mechanism of TBA block of the TRPV1 channel.

    Science.gov (United States)

    Oseguera, Andrés Jara; Islas, León D; García-Villegas, Refugio; Rosenbaum, Tamara

    2007-06-01

    The transient receptor potential vanilloid 1 (TRPV1) channel is a nonselective cation channel activated by capsaicin and responsible for thermosensation. To date, little is known about the gating characteristics of these channels. Here we used tetrabutylammonium (TBA) to determine whether this molecule behaves as an ion conduction blocker in TRPV1 channels and to gain insight into the nature of the activation gate of this protein. TBA belongs to a family of classic potassium channel blockers that have been widely used as tools for determining the localization of the activation gate and the properties of the pore of several ion channels. We found TBA to be a voltage-dependent pore blocker and that the properties of block are consistent with an open-state blocker, with the TBA molecule binding to multiple open states, each with different blocker affinities. Kinetics of channel closure and burst-length analysis in the presence of blocker are consistent with a state-dependent blocking mechanism, with TBA interfering with closing of an activation gate. This activation gate may be located cytoplasmically with respect to the binding site of TBA ions, similar to what has been observed in potassium channels. We propose an allosteric model for TRPV1 activation and block by TBA, which explains our experimental data.

  19. Laboratory Experiments on Meandering Meltwater Channels

    Science.gov (United States)

    Fernandez, R.; Berens, J.; Parker, G.; Stark, C. P.

    2017-12-01

    Meandering channels of all scales and flowing over a wide variety of media have common planform patterns. Although the analogy in planform suggests there is a common underlying framework, the constitutive relations driving planform evolution through vertical incision/deposition and lateral migration differ from medium to medium. The driving processes in alluvial and mixed bedrock-alluvial meandering channels have been studied substantially over the last decades. However, this is not the case for meandering channels in other media such as ice or soluble rock. Here we present results from experiments conducted at the Ven Te Chow Hydrosystems Laboratory of the University of Illinois at Urbana-Champaign on meltwater meandering channels. A rivulet is carved into an ice block and water is allowed to flow at a constant discharge. Planform evolution is analyzed with time lapse imaging and complemented with rubber molds of the channel once the experiment is over. These molds give us the full 3D structure of the meandering, including incisional overhang. Vertical incision rates are measured throughout the run by taking elevations along the channel, and these measurements are complemented with analysis from the molds. We show examples of meandering of intense amplitude with deep overhangs. Features resembling scroll bars document cyclically punctuated melting. We report on lateral migration rates, incision rates, sinuosity, channel depths, channel widths, reach averaged velocities, bend wavelengths and amplitudes and compare them to values reported in the literature for alluvial rivers.

  20. Phosphatidylinositol-4,5-bisphosphate is required for KCNQ1/KCNE1 channel function but not anterograde trafficking.

    Directory of Open Access Journals (Sweden)

    Alice A Royal

    Full Text Available The slow delayed-rectifier potassium current (IKs is crucial for human cardiac action potential repolarization. The formation of IKs requires co-assembly of the KCNQ1 α-subunit and KCNE1 β-subunit, and mutations in either of these subunits can lead to hereditary long QT syndrome types 1 and 5, respectively. It is widely recognised that the KCNQ1/KCNE1 (Q1/E1 channel requires phosphatidylinositol-4,5-bisphosphate (PIP2 binding for function. We previously identified a cluster of basic residues in the proximal C-terminus of KCNQ1 that form a PIP2/phosphoinositide binding site. Upon charge neutralisation of these residues we found that the channel became more retained in the endoplasmic reticulum, which raised the possibility that channel-phosphoinositide interactions could play a role in channel trafficking. To explore this further we used a chemically induced dimerization (CID system to selectively deplete PIP2 and/or phosphatidylinositol-4-phosphate (PI(4P at the plasma membrane (PM or Golgi, and we subsequently monitored the effects on both channel trafficking and function. The depletion of PIP2 and/or PI(4P at either the PM or Golgi did not alter channel cell-surface expression levels. However, channel function was extremely sensitive to the depletion of PIP2 at the PM, which is in contrast to the response of other cardiac potassium channels tested (Kir2.1 and Kv11.1. Surprisingly, when using the CID system IKs was dramatically reduced even before dimerization was induced, highlighting limitations regarding the utility of this system when studying processes highly sensitive to PIP2 depletion. In conclusion, we identify that the Q1/E1 channel does not require PIP2 or PI(4P for anterograde trafficking, but is heavily reliant on PIP2 for channel function once at the PM.

  1. Channel estimation for space-time trellis coded-OFDM systems based on nonoverlapping pilot structure

    CSIR Research Space (South Africa)

    Sokoya, O

    2008-09-01

    Full Text Available . Through the analysis, two extreme conditions that produce the largest minimum determinant for a STTC-OFDM over multiple-tap channels were pointed out. The analysis show that the performance of the STTC-OFDM under various channel condition is based on...: 1) the minimum determinant tap delay of the channel and 2) the memory order of the STTC. New STTC-OFDM schemes were later designed in [2] taking into account some of the designed criteria shown in [1]. The STTC-OFDM schemes are capable...

  2. Translating HbA1c measurements into estimated average glucose values in pregnant women with diabetes.

    Science.gov (United States)

    Law, Graham R; Gilthorpe, Mark S; Secher, Anna L; Temple, Rosemary; Bilous, Rudolf; Mathiesen, Elisabeth R; Murphy, Helen R; Scott, Eleanor M

    2017-04-01

    This study aimed to examine the relationship between average glucose levels, assessed by continuous glucose monitoring (CGM), and HbA 1c levels in pregnant women with diabetes to determine whether calculations of standard estimated average glucose (eAG) levels from HbA 1c measurements are applicable to pregnant women with diabetes. CGM data from 117 pregnant women (89 women with type 1 diabetes; 28 women with type 2 diabetes) were analysed. Average glucose levels were calculated from 5-7 day CGM profiles (mean 1275 glucose values per profile) and paired with a corresponding (±1 week) HbA 1c measure. In total, 688 average glucose-HbA 1c pairs were obtained across pregnancy (mean six pairs per participant). Average glucose level was used as the dependent variable in a regression model. Covariates were gestational week, study centre and HbA 1c . There was a strong association between HbA 1c and average glucose values in pregnancy (coefficient 0.67 [95% CI 0.57, 0.78]), i.e. a 1% (11 mmol/mol) difference in HbA 1c corresponded to a 0.67 mmol/l difference in average glucose. The random effects model that included gestational week as a curvilinear (quadratic) covariate fitted best, allowing calculation of a pregnancy-specific eAG (PeAG). This showed that an HbA 1c of 8.0% (64 mmol/mol) gave a PeAG of 7.4-7.7 mmol/l (depending on gestational week), compared with a standard eAG of 10.2 mmol/l. The PeAG associated with maintaining an HbA 1c level of 6.0% (42 mmol/mol) during pregnancy was between 6.4 and 6.7 mmol/l, depending on gestational week. The HbA 1c -average glucose relationship is altered by pregnancy. Routinely generated standard eAG values do not account for this difference between pregnant and non-pregnant individuals and, thus, should not be used during pregnancy. Instead, the PeAG values deduced in the current study are recommended for antenatal clinical care.

  3. Sub-Nanometer Channels Embedded in Two-Dimensional Materials

    KAUST Repository

    Han, Yimo

    2017-07-31

    Two-dimensional (2D) materials are among the most promising candidates for next-generation electronics due to their atomic thinness, allowing for flexible transparent electronics and ultimate length scaling1. Thus far, atomically-thin p-n junctions2-7, metal-semiconductor contacts8-10, and metal-insulator barriers11-13 have been demonstrated. While 2D materials achieve the thinnest possible devices, precise nanoscale control over the lateral dimensions are also necessary. Although external one-dimensional (1D) carbon nanotubes14 can be used to locally gate 2D materials, this adds a non-trivial third dimension, complicating device integration and flexibility. Here, we report the direct synthesis of sub-nanometer 1D MoS2 channels embedded within WSe2 monolayers, using a dislocation-catalyzed approach. The 1D channels have edges free of misfit dislocations and dangling bonds, forming a coherent interface with the embedding 2D matrix. Periodic dislocation arrays produce 2D superlattices of coherent MoS2 1D channels in WSe2. Molecular dynamics (MD) simulations have identified other combinations of 2D materials that could form 1D channels. Density function theory (DFT) calculation predicts these 1D channels display type II band alignment needed for carrier confinement and charge separation to access the ultimate length scales necessary for future electronic applications.

  4. TRPA1 expression levels and excitability brake by KV channels influence cold sensitivity of TRPA1-expressing neurons.

    Science.gov (United States)

    Memon, Tosifa; Chase, Kevin; Leavitt, Lee S; Olivera, Baldomero M; Teichert, Russell W

    2017-06-14

    The molecular sensor of innocuous (painless) cold sensation is well-established to be transient receptor potential cation channel, subfamily M, member 8 (TRPM8). However, the role of transient receptor potential cation channel, subfamily A, member 1 (TRPA1) in noxious (painful) cold sensation has been controversial. We find that TRPA1 channels contribute to the noxious cold sensitivity of mouse somatosensory neurons, independent of TRPM8 channels, and that TRPA1-expressing neurons are largely non-overlapping with TRPM8-expressing neurons in mouse dorsal-root ganglia (DRG). However, relatively few TRPA1-expressing neurons (e.g., responsive to allyl isothiocyanate or AITC, a selective TRPA1 agonist) respond overtly to cold temperature in vitro, unlike TRPM8-expressing neurons, which almost all respond to cold. Using somatosensory neurons from TRPM8-/- mice and subtype-selective blockers of TRPM8 and TRPA1 channels, we demonstrate that responses to cold temperatures from TRPA1-expressing neurons are mediated by TRPA1 channels. We also identify two factors that affect the cold-sensitivity of TRPA1-expressing neurons: (1) cold-sensitive AITC-sensitive neurons express relatively more TRPA1 transcripts than cold-insensitive AITC-sensitive neurons and (2) voltage-gated potassium (K V ) channels attenuate the cold-sensitivity of some TRPA1-expressing neurons. The combination of these two factors, combined with the relatively weak agonist-like activity of cold temperature on TRPA1 channels, partially explains why few TRPA1-expressing neurons respond to cold. Blocking K V channels also reveals another subclass of noxious cold-sensitive DRG neurons that do not express TRPM8 or TRPA1 channels. Altogether, the results of this study provide novel insights into the cold-sensitivity of different subclasses of somatosensory neurons. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

  5. Further development of a facility for channeling studies: application to lattice location

    International Nuclear Information System (INIS)

    Lopes, D.R.

    1984-08-01

    Equipment modifications at the Lawrence Berkeley Laboratory (LBL) Rutherford backscattering facility, including the addition of a high precision goniometer, have been made to enhance the performance of channeling experiments. The angular divergence of the alpha particle beam was also reduced to 0 by improving the collimation. To demonstrate improved channeling capability angular scans were performed about the [100], [110], and [111] axial channels of a 3400 A (100) silicon membrane. Both the minimum yield, chi/sub min/, and the critical angle, psi/sub 1/2/, were consistent with accepted values. A preliminary investigation of the lattice location of cobalt on the (100) silicon surface was undertaken. Approximately 4.5 x 10 15 Co atoms/cm 2 were electron beam deposited on a 3900 A, HF etched silicon membrane in a system using oilless pumps. Preliminary channeling data taken approximately one month later indicated a preferred site for approximately 16% of the cobalt atoms. Channeling data obtained six months later with the new goniometer showed no evidence for a preferred site. Room temperature oxidation between experiments was observed and is thought to have affected the location of the cobalt atoms. 33 references, 15 figures

  6. Reservoir architecture patterns of sandy gravel braided distributary channel

    Directory of Open Access Journals (Sweden)

    Senlin Yin

    2016-06-01

    Full Text Available The purpose of this study was to discuss shape, scale and superimposed types of sandy gravel bodies in sandy-gravel braided distributary channel. Lithofacies analysis, hierarchy bounding surface analysis and subsurface dense well pattern combining with outcrops method were used to examine reservoir architecture patterns of sandy gravel braided distributary channel based on cores, well logging, and outcrops data, and the reservoir architecture patterns of sandy gravel braided distributary channels in different grades have been established. The study shows: (1 The main reservoir architecture elements for sandy gravel braided channel delta are distributary channel and overbank sand, while reservoir flow barrier elements are interchannel and lacustrine mudstone. (2 The compound sand bodies in the sandy gravel braided delta distributary channel take on three shapes: sheet-like distributary channel sand body, interweave strip distributary channel sand body, single strip distributary channel sand body. (3 Identification marks of single distributary channel include: elevation of sand body top, lateral overlaying, “thick-thin-thick” feature of sand bodies, interchannel mudstone and overbank sand between distributary channels and the differences in well log curve shape of sand bodies. (4 Nine lithofacies types were distinguished in distributary channel unit interior, different channel units have different lithofacies association sequence.

  7. Channel planform evolution: Spatial and temporal aspect

    Science.gov (United States)

    Rusnák, M.; Frandofer, M.; Lehotský, M.

    2012-04-01

    The recent period is characterized by impacts of climate change. Increasing magnitude and frequency of flood events results in morphological and morphodynamical changes of river channels. It is a challenge for the fluvial geomorphology to highlight the morphological response to these events, because the knowledge of the morphological-sedimentological attributes of the river channel is the first step in pursue of a comprehensive knowledge of the riverine landscape and impact on its sustainable management. Research of the spatial variability of landforms and the regime of processes creates an appropriate knowledge base for other sciences interested in the riverine as well as terrestrial systems. The contribution deals with the morphological changes of the channel pattern of the River Topľa (115 km in total length, 1506 km2 of catchment area, average annual discharge 8.08 m3.s-1 in mouth). The 72.5 km long segment has been studied (Strahler ord. 4-7). It represents a transient from the mountain cobble-bed to the basin fine gravel-bed river. The Topľa is a less regulated and laterally partly confined river in northeastern Slovakia, with flysch geology. Three time horizons of the remote sensing imagery (1987, 2002 and 2009) have been analyzed using the GIS, with the reference time horizon of 1987. The analysis consists of identification and delimitation of an active channel bank line and the delimitation of the channel bars in the mentioned series of imageries. The active channel width, area of channel bars, lateral channel shift and area stricken by bank erosion were studied via overlaying layers. The last attribute showed a significant increase: during the 1987-2002 period the area of 32.6 ha was eroded, whereas during the following period (2002-2009) of frequent and intensive floods up to 70.0 ha was eroded. Likewise, the maximum channel shift was 260 m and 443 m in 1987-2002 and in 2002-2009 respectively. The key results are not only the values of these parameters

  8. Results of the examination of channel H12/1

    International Nuclear Information System (INIS)

    Bauer, E.

    1983-01-01

    Channel H12/1 is one part of the channel unit of the High-Flux Reactor that has been affected by corrosion attack. It was disassembled after the appearance of a heavy water leak and examined in a hot cell. Results of the examination are presented

  9. Differential distribution of the sodium‐activated potassium channels slick and slack in mouse brain

    Science.gov (United States)

    Knaus, Hans‐Günther; Schwarzer, Christoph

    2015-01-01

    ABSTRACT The sodium‐activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are high‐conductance potassium channels of the Slo family. In neurons, Slick and Slack channels are involved in the generation of slow afterhyperpolarization, in the regulation of firing patterns, and in setting and stabilizing the resting membrane potential. The distribution and subcellular localization of Slick and Slack channels in the mouse brain have not yet been established in detail. The present study addresses this issue through in situ hybridization and immunohistochemistry. Both channels were widely distributed and exhibited distinct distribution patterns. However, in some brain regions, their expression overlapped. Intense Slick channel immunoreactivity was observed in processes, varicosities, and neuronal cell bodies of the olfactory bulb, granular zones of cortical regions, hippocampus, amygdala, lateral septal nuclei, certain hypothalamic and midbrain nuclei, and several regions of the brainstem. The Slack channel showed primarily a diffuse immunostaining pattern, and labeling of cell somata and processes was observed only occasionally. The highest Slack channel expression was detected in the olfactory bulb, lateral septal nuclei, basal ganglia, and distinct areas of the midbrain, brainstem, and cerebellar cortex. In addition, comparing our data obtained from mouse brain with a previously published study on rat brain revealed some differences in the expression and distribution of Slick and Slack channels in these species. J. Comp. Neurol. 524:2093–2116, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. PMID:26587966

  10. Differential distribution of the sodium-activated potassium channels slick and slack in mouse brain.

    Science.gov (United States)

    Rizzi, Sandra; Knaus, Hans-Günther; Schwarzer, Christoph

    2016-07-01

    The sodium-activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are high-conductance potassium channels of the Slo family. In neurons, Slick and Slack channels are involved in the generation of slow afterhyperpolarization, in the regulation of firing patterns, and in setting and stabilizing the resting membrane potential. The distribution and subcellular localization of Slick and Slack channels in the mouse brain have not yet been established in detail. The present study addresses this issue through in situ hybridization and immunohistochemistry. Both channels were widely distributed and exhibited distinct distribution patterns. However, in some brain regions, their expression overlapped. Intense Slick channel immunoreactivity was observed in processes, varicosities, and neuronal cell bodies of the olfactory bulb, granular zones of cortical regions, hippocampus, amygdala, lateral septal nuclei, certain hypothalamic and midbrain nuclei, and several regions of the brainstem. The Slack channel showed primarily a diffuse immunostaining pattern, and labeling of cell somata and processes was observed only occasionally. The highest Slack channel expression was detected in the olfactory bulb, lateral septal nuclei, basal ganglia, and distinct areas of the midbrain, brainstem, and cerebellar cortex. In addition, comparing our data obtained from mouse brain with a previously published study on rat brain revealed some differences in the expression and distribution of Slick and Slack channels in these species. J. Comp. Neurol. 524:2093-2116, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc.

  11. Punctuated sediment record resulting from channel migration in a shallow sand-dominated micro-tidal lagoon, Northern Wadden Sea, Denmark

    DEFF Research Database (Denmark)

    Fruergaard, M.; Andersen, T.J.; Nielsen, L.H.

    2011-01-01

    depositional environment, but tidal channel sediments dominate in the five sediment cores, making up 56% of the 15 mof sediment core. Sedimentation in the lagoon alternated between slow vertical aggradation of sand flats (1.5–2 mm yr-1) and very fast lateral progradation of point bars in tidal channels, which...... caused the formation of a punctuated lagoonal fill. Frequent and comprehensive reworking of the sand flat sediments by tidal channel migration entails loss of sedimentary structures and bioturbation related to sand flat deposits, and old sand flat sediments are only very sparsely preserved. We further...... conclude that long-term (millennial timescale) sediment accumulation in the lagoon was controlled by rising sea-level, whereas short-term (centurial timescale) sediment accumulation was controlled by local erosion and depositional events caused by lateral migration of channels. Records of short-term sea...

  12. Sigma-1 Receptor Plays a Negative Modulation on N-type Calcium Channel

    Directory of Open Access Journals (Sweden)

    Kang Zhang

    2017-05-01

    Full Text Available The sigma-1 receptor is a 223 amino acids molecular chaperone with a single transmembrane domain. It is resident to eukaryotic mitochondrial-associated endoplasmic reticulum and plasma membranes. By chaperone-mediated interactions with ion channels, G-protein coupled receptors and cell-signaling molecules, the sigma-1 receptor performs broad physiological and pharmacological functions. Despite sigma-1 receptors have been confirmed to regulate various types of ion channels, the relationship between the sigma-1 receptor and N-type Ca2+ channel is still unclear. Considering both sigma-1 receptors and N-type Ca2+ channels are involved in intracellular calcium homeostasis and neurotransmission, we undertake studies to explore the possible interaction between these two proteins. In the experiment, we confirmed the expression of the sigma-1 receptors and the N-type calcium channels in the cholinergic interneurons (ChIs in rat striatum by using single-cell reverse transcription-polymerase chain reaction (scRT-PCR and immunofluorescence staining. N-type Ca2+ currents recorded from ChIs in the brain slice of rat striatum was depressed when sigma-1 receptor agonists (SKF-10047 and Pre-084 were administrated. The inhibition was completely abolished by sigma-1 receptor antagonist (BD-1063. Co-expression of the sigma-1 receptors and the N-type calcium channels in Xenopus oocytes presented a decrease of N-type Ca2+ current amplitude with an increase of sigma-1 receptor expression. SKF-10047 could further depress N-type Ca2+ currents recorded from oocytes. The fluorescence resonance energy transfer (FRET assays and co-immunoprecipitation (Co-IP demonstrated that sigma-1 receptors and N-type Ca2+ channels formed a protein complex when they were co-expressed in HEK-293T (Human Embryonic Kidney -293T cells. Our results revealed that the sigma-1 receptors played a negative modulation on N-type Ca2+ channels. The mechanism for the inhibition of sigma-1 receptors on

  13. Structure of the CLC-1 chloride channel from Homo sapiens.

    Science.gov (United States)

    Park, Eunyong; MacKinnon, Roderick

    2018-05-29

    CLC channels mediate passive Cl - conduction, while CLC transporters mediate active Cl - transport coupled to H + transport in the opposite direction. The distinction between CLC-0/1/2 channels and CLC transporters seems undetectable by amino acid sequence. To understand why they are different functionally we determined the structure of the human CLC-1 channel. Its 'glutamate gate' residue, known to mediate proton transfer in CLC transporters, adopts a location in the structure that appears to preclude it from its transport function. Furthermore, smaller side chains produce a wider pore near the intracellular surface, potentially reducing a kinetic barrier for Cl - conduction. When the corresponding residues are mutated in a transporter, it is converted to a channel. Finally, Cl - at key sites in the pore appear to interact with reduced affinity compared to transporters. Thus, subtle differences in glutamate gate conformation, internal pore diameter and Cl - affinity distinguish CLC channels and transporters. © 2018, Park & MacKinnon.

  14. A Soluble Fluorescent Binding Assay Reveals PIP2 Antagonism of TREK-1 Channels

    Directory of Open Access Journals (Sweden)

    Cerrone Cabanos

    2017-08-01

    Full Text Available Lipid regulation of ion channels by low-abundance signaling lipids phosphatidylinositol 4,5-bisphosphate (PIP2 and phosphatidic acid (PA has emerged as a central cellular mechanism for controlling ion channels and the excitability of nerves. A lack of robust assays suitable for facile detection of a lipid bound to a channel has hampered the probing of the lipid binding sites and measuring the pharmacology of putative lipid agonists for ion channels. Here, we show a fluorescent PIP2 competition assay for detergent-purified potassium channels, including TWIK-1-related K+-channel (TREK-1. Anionic lipids PA and phosphatidylglycerol (PG bind dose dependently (9.1 and 96 μM, respectively and agonize the channel. Our assay shows PIP2 binds with high affinity (0.87 μM but surprisingly can directly antagonize TREK-1 in liposomes. We propose a model for TREK-1 lipid regulation where PIP2 can compete with PA and PG agonism based on the affinity of the lipid for a site within the channel.

  15. Inferior Olive HCN1 Channels Coordinate Synaptic Integration and Complex Spike Timing

    Directory of Open Access Journals (Sweden)

    Derek L.F. Garden

    2018-02-01

    Full Text Available Cerebellar climbing-fiber-mediated complex spikes originate from neurons in the inferior olive (IO, are critical for motor coordination, and are central to theories of cerebellar learning. Hyperpolarization-activated cyclic-nucleotide-gated (HCN channels expressed by IO neurons have been considered as pacemaker currents important for oscillatory and resonant dynamics. Here, we demonstrate that in vitro, network actions of HCN1 channels enable bidirectional glutamatergic synaptic responses, while local actions of HCN1 channels determine the timing and waveform of synaptically driven action potentials. These roles are distinct from, and may complement, proposed pacemaker functions of HCN channels. We find that in behaving animals HCN1 channels reduce variability in the timing of cerebellar complex spikes, which serve as a readout of IO spiking. Our results suggest that spatially distributed actions of HCN1 channels enable the IO to implement network-wide rules for synaptic integration that modulate the timing of cerebellar climbing fiber signals.

  16. Axonal excitability properties in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Vucic, Steve; Kiernan, Matthew C

    2006-07-01

    To investigate axolemmal ion channel function in patients diagnosed with sporadic amyotrophic lateral sclerosis (ALS). A recently described threshold tracking protocol was implemented to measure multiple indices of axonal excitability in 26 ALS patients by stimulating the median motor nerve at the wrist. The excitability indices studied included: stimulus-response curve (SR); strength-duration time constant (tauSD); current/threshold relationship; threshold electrotonus to a 100 ms polarizing current; and recovery curves to a supramaximal stimulus. Compound muscle action potential (CMAP) amplitudes were significantly reduced in ALS patients (ALS, 2.84+/-1.17 mV; controls, 8.27+/-1.09 mV, P<0.0005) and the SR curves for both 0.2 and 1 ms pulse widths were shifted in a hyperpolarized direction. Threshold electrotonus revealed a greater threshold change to both depolarizing and hyperpolarizing conditioning stimuli, similar to the 'fanned out' appearance that occurs with membrane hyperpolarization. The tauSD was significantly increased in ALS patients (ALS, 0.50+/-0.03 ms; controls, 0.42+/-0.02 ms, P<0.05). The recovery cycle of excitability following a conditioning supramaximal stimulus revealed increased superexcitability in ALS patients (ALS, 29.63+/-1.25%; controls, 25.11+/-1.01%, P<0.01). Threshold tracking studies revealed changes indicative of widespread dysfunction in axonal ion channel conduction, including increased persistent Na+ channel conduction, and abnormalities of fast paranodal K+ and internodal slow K+ channel function, in ALS patients. An increase in persistent Na+ conductances coupled with reduction in K+ currents would predispose axons of ALS patients to generation of fasciculations and cramps. Axonal excitability studies may provide insight into mechanisms responsible for motor neuron loss in ALS.

  17. The Nav1.2 channel is regulated by GSK3

    Science.gov (United States)

    James, Thomas F.; Nenov, Miroslav N.; Wildburger, Norelle C.; Lichti, Cheryl; Luisi, Jonathan; Vergara, Fernanda; Panova-Electronova, Neli I.; Nilsson, Carol L.; Rudra, Jai; Green, Thomas A.; Labate, Demetrio; Laezza, Fernanda

    2015-01-01

    Background Phosphorylation plays an essential role in regulating the voltage-gated sodium (Nav) channels and excitability. Yet, a surprisingly limited number of kinases have been identified as regulators of Nav channels. Herein, we posited that glycogen synthase kinase 3 (GSK3), a critical kinase found associated with numerous brain disorders, might directly regulate neuronal Nav channels. Methods We used patch-clamp electrophysiology to record sodium currents from Nav1.2 channels stably expressed in HEK-293 cells. mRNA and protein levels were quantified with RT-PCR, Western blot, or confocal microscopy, and in vitro phosphorylation and mass spectrometry to identify phosphorylated residues. Results We found that exposure of cells to GSK3 inhibitor XIII significantly potentiates the peak current density of Nav1.2, a phenotype reproduced by silencing GSK3 with siRNA. Contrarily, overexpression of GSK3β suppressed Nav1.2-encoded currents. Neither mRNA nor total protein expression were changed upon GSK3 inhibition. Cell surface labeling of CD4-chimeric constructs expressing intracellular domains of the Nav1.2 channel indicates that cell surface expression of CD4-Nav1.2-Ctail was up-regulated upon pharmacological inhibition of GSK3, resulting in an increase of surface puncta at the plasma membrane. Finally, using in vitro phosphorylation in combination with high resolution mass spectrometry, we further demonstrate that GSK3β phosphorylates T1966 at the C-terminal tail of Nav1.2. Conclusion These findings provide evidence for a new mechanism by which GSK3 modulate Nav channel function via its C-terminal tail. General Significance These findings provide fundamental knowledge in understanding signaling dysfunction common in several neuropsychiatric disorders. PMID:25615535

  18. Design of boron carbide-shielded irradiation channel of the outer irradiation channel of the Ghana Research Reactor-1 using MCNP.

    Science.gov (United States)

    Abrefah, R G; Sogbadji, R B M; Ampomah-Amoako, E; Birikorang, S A; Odoi, H C; Nyarko, B J B

    2011-01-01

    The MCNP model for the Ghana Research Reactor-1 was redesigned to incorporate a boron carbide-shielded irradiation channel in one of the outer irradiation channels. Extensive investigations were made before arriving at the final design of only one boron carbide covered outer irradiation channel; as all the other designs that were considered did not give desirable results of neutronic performance. The concept of redesigning a new MCNP model, which has a boron carbide-shielded channel is to equip the Ghana Research Reactor-1 with the means of performing efficient epithermal neutron activation analysis. After the simulation, a comparison of the results from the original MCNP model for the Ghana Research Reactor-1 and the new redesigned model of the boron carbide shielded channel was made. The final effective criticality of the original MCNP model for the GHARR-1 was recorded as 1.00402 while that of the new boron carbide designed model was recorded as 1.00282. Also, a final prompt neutron lifetime of 1.5245 × 10(-4)s was recorded for the new boron carbide designed model while a value of 1.5571 × 10(-7)s was recorded for the original MCNP design of the GHARR-1. Copyright © 2010 Elsevier Ltd. All rights reserved.

  19. Expression and function of Kv1.1 potassium channels in human atria from patients with atrial fibrillation.

    Science.gov (United States)

    Glasscock, Edward; Voigt, Niels; McCauley, Mark D; Sun, Qiang; Li, Na; Chiang, David Y; Zhou, Xiao-Bo; Molina, Cristina E; Thomas, Dierk; Schmidt, Constanze; Skapura, Darlene G; Noebels, Jeffrey L; Dobrev, Dobromir; Wehrens, Xander H T

    2015-09-01

    Voltage-gated Kv1.1 channels encoded by the Kcna1 gene are traditionally regarded as being neural-specific with no known expression or intrinsic functional role in the heart. However, recent studies in mice reveal low-level Kv1.1 expression in heart and cardiac abnormalities associated with Kv1.1-deficiency suggesting that the channel may have a previously unrecognized cardiac role. Therefore, this study tests the hypothesis that Kv1.1 channels are associated with arrhythmogenesis and contribute to intrinsic cardiac function. In intra-atrial burst pacing experiments, Kcna1-null mice exhibited increased susceptibility to atrial fibrillation (AF). The atria of Kcna1-null mice showed minimal Kv1 family ion channel remodeling and fibrosis as measured by qRT-PCR and Masson's trichrome histology, respectively. Using RT-PCR, immunocytochemistry, and immunoblotting, KCNA1 mRNA and protein were detected in isolated mouse cardiomyocytes and human atria for the first time. Patients with chronic AF (cAF) showed no changes in KCNA1 mRNA levels relative to controls; however, they exhibited increases in atrial Kv1.1 protein levels, not seen in paroxysmal AF patients. Patch-clamp recordings of isolated human atrial myocytes revealed significant dendrotoxin-K (DTX-K)-sensitive outward current components that were significantly increased in cAF patients, reflecting a contribution by Kv1.1 channels. The concomitant increases in Kv1.1 protein and DTX-K-sensitive currents in atria of cAF patients suggest that the channel contributes to the pathological mechanisms of persistent AF. These findings provide evidence of an intrinsic cardiac role of Kv1.1 channels and indicate that they may contribute to atrial repolarization and AF susceptibility.

  20. Reliability assessment of PARR-1 renovated I and C system startup channel-b

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, M.A.; Habib, M.A.; Iqbal, M.

    1991-11-20

    The report covers the reliability assessment of the startup channel-B of the PARR-1 renovated instrumentation and Control. For startup channel-A, a separate report (DNSRP-10(7)/88) was prepared in 1988. As the modules are of different origins in both the channels, a separate calculation was necessary. In the report the overall unreliability of the startup channel has been calculated by considering 1 out of 2 operation mode. In the assessment, the reliability calculations for the channel has been performed using similar assumptions as used in the authors' report on startup channel-A. For the analysis the Component Count Method (CCM) was applied. Comparison of results for channel-A and channel-B were made.

  1. The calmodulin-binding, short linear motif, NSCaTE is conserved in L-type channel ancestors of vertebrate Cav1.2 and Cav1.3 channels.

    Directory of Open Access Journals (Sweden)

    Valentina Taiakina

    Full Text Available NSCaTE is a short linear motif of (xWxxx(I or Lxxxx, composed of residues with a high helix-forming propensity within a mostly disordered N-terminus that is conserved in L-type calcium channels from protostome invertebrates to humans. NSCaTE is an optional, lower affinity and calcium-sensitive binding site for calmodulin (CaM which competes for CaM binding with a more ancient, C-terminal IQ domain on L-type channels. CaM bound to N- and C- terminal tails serve as dual detectors to changing intracellular Ca(2+ concentrations, promoting calcium-dependent inactivation of L-type calcium channels. NSCaTE is absent in some arthropod species, and is also lacking in vertebrate L-type isoforms, Cav1.1 and Cav1.4 channels. The pervasiveness of a methionine just downstream from NSCaTE suggests that L-type channels could generate alternative N-termini lacking NSCaTE through the choice of translational start sites. Long N-terminus with an NSCaTE motif in L-type calcium channel homolog LCav1 from pond snail Lymnaea stagnalis has a faster calcium-dependent inactivation than a shortened N-termini lacking NSCaTE. NSCaTE effects are present in low concentrations of internal buffer (0.5 mM EGTA, but disappears in high buffer conditions (10 mM EGTA. Snail and mammalian NSCaTE have an alpha-helical propensity upon binding Ca(2+-CaM and can saturate both CaM N-terminal and C-terminal domains in the absence of a competing IQ motif. NSCaTE evolved in ancestors of the first animals with internal organs for promoting a more rapid, calcium-sensitive inactivation of L-type channels.

  2. Kir2.1 channels set two levels of resting membrane potential with inward rectification.

    Science.gov (United States)

    Chen, Kuihao; Zuo, Dongchuan; Liu, Zheng; Chen, Haijun

    2018-04-01

    Strong inward rectifier K + channels (Kir2.1) mediate background K + currents primarily responsible for maintenance of resting membrane potential. Multiple types of cells exhibit two levels of resting membrane potential. Kir2.1 and K2P1 currents counterbalance, partially accounting for the phenomenon of human cardiomyocytes in subphysiological extracellular K + concentrations or pathological hypokalemic conditions. The mechanism of how Kir2.1 channels contribute to the two levels of resting membrane potential in different types of cells is not well understood. Here we test the hypothesis that Kir2.1 channels set two levels of resting membrane potential with inward rectification. Under hypokalemic conditions, Kir2.1 currents counterbalance HCN2 or HCN4 cation currents in CHO cells that heterologously express both channels, generating N-shaped current-voltage relationships that cross the voltage axis three times and reconstituting two levels of resting membrane potential. Blockade of HCN channels eliminated the phenomenon in K2P1-deficient Kir2.1-expressing human cardiomyocytes derived from induced pluripotent stem cells or CHO cells expressing both Kir2.1 and HCN2 channels. Weakly inward rectifier Kir4.1 or inward rectification-deficient Kir2.1•E224G mutant channels do not set such two levels of resting membrane potential when co-expressed with HCN2 channels in CHO cells or when overexpressed in human cardiomyocytes derived from induced pluripotent stem cells. These findings demonstrate a common mechanism that Kir2.1 channels set two levels of resting membrane potential with inward rectification by balancing inward currents through different cation channels such as hyperpolarization-activated HCN channels or hypokalemia-induced K2P1 leak channels.

  3. Experimental effect of flow depth on ratio discharge in lateral intakes in river bend

    International Nuclear Information System (INIS)

    Masjedi, A; Foroushani, E P

    2012-01-01

    Open-channel dividing flow is characterized by the inflow and outflow discharges, the upstream and downstream water depths, and the recirculation flow in the branch channel. In general, diversion flow can be categorized as natural and artificial flow. Natural flow diversion usually occurs as braiding or cut-off in bend rivers, while artificial flow is man-made to divert flow by lateral intake channels for water supply. This study presents the results of a laboratory research into effect intake flow depth on ratio discharge in lateral intakes in 180 degree bend. Investigation on lateral intake and determination of intake flow depth is among the most important issues in lateral intake on ratio discharge with model intake flow depth were measured in a laboratory flume under clear-water. Experiments were conducted for various intake flow depths and with different discharges. It was found that by increasing the flow depth at 180 degree flume bend, ratio discharge increases.

  4. Ionic Selectivity and Permeation Properties of Human PIEZO1 Channels.

    Directory of Open Access Journals (Sweden)

    Radhakrishnan Gnanasambandam

    Full Text Available Members of the eukaryotic PIEZO family (the human orthologs are noted hPIEZO1 and hPIEZO2 form cation-selective mechanically-gated channels. We characterized the selectivity of human PIEZO1 (hPIEZO1 for alkali ions: K+, Na+, Cs+ and Li+; organic cations: TMA and TEA, and divalents: Ba2+, Ca2+, Mg2+ and Mn2+. All monovalent ions permeated the channel. At a membrane potential of -100 mV, Cs+, Na+ and K+ had chord conductances in the range of 35-55 pS with the exception of Li+, which had a significantly lower conductance of ~ 23 pS. The divalents decreased the single-channel permeability of K+, presumably because the divalents permeated slowly and occupied the open channel for a significant fraction of the time. In cell-attached mode, 90 mM extracellular divalents had a conductance for inward currents carried by the divalents of: 25 pS for Ba2+ and 15 pS for Ca2+ at -80 mV and 10 pS for Mg2+ at -50 mV. The organic cations, TMA and TEA, permeated slowly and attenuated K+ currents much like the divalents. As expected, the channel K+ conductance increased with K+ concentration saturating at ~ 45 pS and the KD of K+ for the channel was 32 mM. Pure divalent ion currents were of lower amplitude than those with alkali ions and the channel opening rate was lower in the presence of divalents than in the presence of monovalents. Exposing cells to the actin disrupting reagent cytochalasin D increased the frequency of openings in cell-attached patches probably by reducing mechanoprotection.

  5. Osteopontin activates the diabetes-associated potassium channel TALK-1 in pancreatic β-cells.

    Directory of Open Access Journals (Sweden)

    Matthew T Dickerson

    Full Text Available Glucose-stimulated insulin secretion (GSIS relies on β-cell Ca2+ influx, which is modulated by the two-pore-domain K+ (K2P channel, TALK-1. A gain-of-function polymorphism in KCNK16, the gene encoding TALK-1, increases risk for developing type-2 diabetes. While TALK-1 serves an important role in modulating GSIS, the regulatory mechanism(s that control β-cell TALK-1 channels are unknown. Therefore, we employed a membrane-specific yeast two-hybrid (MYTH assay to identify TALK-1-interacting proteins in human islets, which will assist in determining signaling modalities that modulate TALK-1 function. Twenty-one proteins from a human islet cDNA library interacted with TALK-1. Some of these interactions increased TALK-1 activity, including intracellular osteopontin (iOPN. Intracellular OPN is highly expressed in β-cells and is upregulated under pre-diabetic conditions to help maintain normal β-cell function; however, the functional role of iOPN in β-cells is poorly understood. We found that iOPN colocalized with TALK-1 in pancreatic sections and coimmunoprecipitated with human islet TALK-1 channels. As human β-cells express two K+ channel-forming variants of TALK-1, regulation of these TALK-1 variants by iOPN was assessed. At physiological voltages iOPN activated TALK-1 transcript variant 3 channels but not TALK-1 transcript variant 2 channels. Activation of TALK-1 channels by iOPN also hyperpolarized resting membrane potential (Vm in HEK293 cells and in primary mouse β-cells. Intracellular OPN was also knocked down in β-cells to test its effect on β-cell TALK-1 channel activity. Reducing β-cell iOPN significantly decreased TALK-1 K+ currents and increased glucose-stimulated Ca2+ influx. Importantly, iOPN did not affect the function of other K2P channels or alter Ca2+ influx into TALK-1 deficient β-cells. These results reveal the first protein interactions with the TALK-1 channel and found that an interaction with iOPN increased

  6. Mechanisms underlying stage-1 TRPL channel translocation in Drosophila photoreceptors.

    Directory of Open Access Journals (Sweden)

    Minh-Ha Lieu

    Full Text Available TRP channels function as key mediators of sensory transduction and other cellular signaling pathways. In Drosophila, TRP and TRPL are the light-activated channels in photoreceptors. While TRP is statically localized in the signaling compartment of the cell (the rhabdomere, TRPL localization is regulated by light. TRPL channels translocate out of the rhabdomere in two distinct stages, returning to the rhabdomere with dark-incubation. Translocation of TRPL channels regulates their availability, and thereby the gain of the signal. Little, however, is known about the mechanisms underlying this trafficking of TRPL channels.We first examine the involvement of de novo protein synthesis in TRPL translocation. We feed flies cycloheximide, verify inhibition of protein synthesis, and test for TRPL translocation in photoreceptors. We find that protein synthesis is not involved in either stage of TRPL translocation out of the rhabdomere, but that re-localization to the rhabdomere from stage-1, but not stage-2, depends on protein synthesis. We also characterize an ex vivo eye preparation that is amenable to biochemical and genetic manipulation. We use this preparation to examine mechanisms of stage-1 TRPL translocation. We find that stage-1 translocation is: induced with ATP depletion, unaltered with perturbation of the actin cytoskeleton or inhibition of endocytosis, and slowed with increased membrane sterol content.Our results indicate that translocation of TRPL out of the rhabdomere is likely due to protein transport, and not degradation/re-synthesis. Re-localization from each stage to the rhabdomere likely involves different strategies. Since TRPL channels can translocate to stage-1 in the absence of ATP, with no major requirement of the cytoskeleton, we suggest that stage-1 translocation involves simple diffusion through the apical membrane, which may be regulated by release of a light-dependent anchor in the rhabdomere.

  7. Purification of the functional plant membrane channel KAT1

    International Nuclear Information System (INIS)

    Hibi, Takao; Aoki, Shiho; Oda, Keisuke; Munemasa, Shintaro; Ozaki, Shunsuke; Shirai, Osamu; Murata, Yoshiyuki; Uozumi, Nobuyuki

    2008-01-01

    The inward-rectifying K + channel KAT1 is expressed mainly in Arabidopsis thaliana guard cells. The purification of functional KAT1 has never been reported. We investigated the extraction of the plant K + channel KAT1 with different detergents, as an example for how to select detergents for purifying a eukaryotic membrane protein. A KAT1-GFP fusion protein was used to screen a library of 46 detergents for the effective solubilization of intact KAT1. Then, a 'test set' of three detergents was picked for further analysis, based on their biochemical characteristics and availability. The combination use of the selected detergents enabled the effective purification of functional KAT1 with affinity and gel-filtration chromatography

  8. The RCK1 high-affinity Ca2+ sensor confers carbon monoxide sensitivity to Slo1 BK channels.

    Science.gov (United States)

    Hou, Shangwei; Xu, Rong; Heinemann, Stefan H; Hoshi, Toshinori

    2008-03-11

    Carbon monoxide (CO) is a lethal gas, but it is also increasingly recognized as a physiological signaling molecule capable of regulating a variety of proteins. Among them, large-conductance Ca(2+)- and voltage-gated K(+) (Slo1 BK) channels, important in vasodilation and neuronal firing, have been suggested to be directly stimulated by CO. However, the molecular mechanism of the stimulatory action of CO on the Slo1 BK channel has not been clearly elucidated. We report here that CO reliably and repeatedly activates Slo1 BK channels in excised membrane patches in the absence of Ca(2+) in a voltage-sensor-independent manner. The stimulatory action of CO on the Slo1 BK channel requires an aspartic acid and two histidine residues located in the cytoplasmic RCK1 domain, and the effect persists under the conditions known to inhibit the conventional interaction between CO and heme in other proteins. We propose that CO acts as a partial agonist for the high-affinity divalent cation sensor in the RCK1 domain of the Slo1 BK channel.

  9. Heteromeric ASIC channels composed of ASIC2b and ASIC1a display novel channel properties and contribute to acidosis-induced neuronal death

    Science.gov (United States)

    Sherwood, Thomas W.; Lee, Kirsten G.; Gormley, Matthew G.; Askwith, Candice C.

    2011-01-01

    Acid-sensing ion channel (ASIC) subunits associate to form homomeric or heteromeric proton-gated ion channels in neurons throughout the nervous system. The ASIC1a subunit plays an important role in establishing the kinetics of proton-gated currents in the central nervous system and activation of ASIC1a homomeric channels induces neuronal death following local acidosis that accompanies cerebral ischemia. The ASIC2b subunit is expressed in the brain in a pattern that overlaps ASIC1a, yet the contribution of ASIC2b has remained elusive. We find that co-expression of ASIC2b with ASIC1a in Xenopus oocytes results in novel proton-gated currents with properties distinct from ASIC1a homomeric channels. In particular, ASIC2b/1a heteromeric channels are inhibited by the non-selective potassium channel blockers tetraethylammonium (TEA) and barium. In addition, steady-state desensitization is induced at more basic pH values and Big Dynorphin sensitivity is enhanced in these unique heteromeric channels. Cultured hippocampal neurons show proton-gated currents consistent with ASIC2b contribution and these currents are lacking in neurons from mice with an ACCN1 (ASIC2) gene disruption. Finally, we find that these ASIC2b/1a heteromeric channels contribute to acidosis-induced neuronal death. Together, our results show that ASIC2b confers unique properties to heteromeric channels in central neurons. Further, these data indicate that ASIC2, like ASIC1, plays a role in acidosis-induced neuronal death and implicate the ASIC2b/1a subtype as a novel pharmacological target to prevent neuronal injury following stroke. PMID:21715637

  10. Classification of EA1-box proteins and new insights into their role during reproduction in grasses.

    Science.gov (United States)

    Uebler, Susanne; Márton, Mihaela L; Dresselhaus, Thomas

    2015-12-01

    EA1-box protein classification. Success in reproduction and vegetative development in flowering plants strongly depends on precise cell-to-cell signaling events mediated by secreted peptides.A small peptide family named as EA1-like (EAL) has been first described 10 years ago and includes EA1 involved in pollen tubes attraction by the female gametophyte and EAL1-regulating germ cell identity in maize. EALs consist of an N-terminal endoplasmic reticulum-targeting motif, the highly conserved EA1-box and a short C-terminal alanine-rich domain. Whereas EAL peptides are exclusively found in the Gramineae, the EA1-box is widely distributed throughout the plant kingdom. Based on in silico analysis and subcellular localization studies, we report here a new classification of EA1-box proteins in flowering plants. They can be distinguished into three protein classes: the already defined EAL proteins, the EAG (EA1-box glycine-rich) proteins and the EAC (EA1-box containing)proteins. While fusion proteins of EAL and EAC classes locate to the secretory pathway, EAGs are cytoplasmic and locate also to the nucleus. Moreover, we further show that the third EAL protein of Zea mays, EAL2, appears to be also involved in processes related to late embryogenic development as its peptide level increases after formation of leaf primordia. Immunohistochemical studies indicate its presence in the scutellar parenchyma and around the vasculature, where it is secreted to the extracellular space. In conclusion, the members of the maize EAL family possess very diverse functions during reproduction and it will now be exciting to elucidate the functions of EAGs and EACs in plants.

  11. Behavior of instantaneous lateral velocity and flow pulsation in duct flow with cylindrical rod

    International Nuclear Information System (INIS)

    Lee, Chi Young; Shin, Chang Hwan; Park, Ju Yong; Oh, Dong Seok; Chun, Tae Hyun; In, Wang Kee

    2012-01-01

    Recently, KAERI (Korea Atomic Energy Research Institute) has examined and developed a dual cooled annular fuel. Dual cooled annular fuel allows the coolant to flow through the inner channel as well as the outer channel. Due to inner channel, the outer diameter of dual cooled annular fuel (15.9 mm) is larger than that of conventional cylindrical solid fuel (9.5 mm). Hence, dual cooled annular fuel assembly becomes a tight lattice fuel bundle configuration to maintain the same array size and guide tube locations as cylindrical solid fuel assembly. P/Ds (pitch between rods to rod diameter ratio) of dual cooled annular and cylindrical solid fuel assemblies are 1.08 and 1.35, respectively. This difference of P/D could change the behavior of turbulent flow in rod bundle. Our research group has investigated a turbulent flow parallel to the fuel rods using two kinds of simulated 3x3 rod bundles. To measure the turbulent rod bundle flow, PIV (Particle Image Velocimetry) and MIR (Matching Index of Refraction) techniques were used. In a simulated dual cooled annular fuel bundle (i.e., P/D=1.08), the quasi periodic oscillating flow motion in the lateral direction, called the flow pulsation, was observed, which significantly increased the lateral turbulence intensity at the rod gap center. The flow pulsation was visualized and measured clearly and successfully by PIV and MIR techniques. Such a flow motion may have influence on the fluid induced vibration, heat transfer, CHF (Critical Heat Flux), and flow mixing between subchannels in rod bundle flow. On the other hand, in a simulated cylindrical solid fuel bundle (i.e., P/D=1.35), the peak of turbulence intensity at the gap center was not measured due to an irregular motion of the lateral flow. This study implies that the behavior of lateral velocity in rod bundle flow is greatly influenced by the P/D (i.e., gap distance). In this work, the influence of gap distance on behavior of instantaneous lateral velocity and flow

  12. A Gradually Varied Approach to Model Turbidity Currents in Submarine Channels

    Science.gov (United States)

    Bolla Pittaluga, M.; Frascati, A.; Falivene, O.

    2018-01-01

    We develop a one-dimensional model to describe the dynamics of turbidity current flowing in submarine channels. We consider the flow as a steady state polydisperse suspension accounting for water detrainment from the clear water-turbid interface, for spatial variations of the channel width and for water and sediment lateral overspill from the channel levees. Moreover, we account for sediment exchange with the bed extending the model to deal with situations where the current meets a nonerodible bed. Results show that when water detrainment is accounted for, the flow thickness becomes approximately constant proceeding downstream. Similarly, in the presence of channel levees, the flow tends to adjust to channel relief through the lateral loss of water and sediment. As more mud is spilled above the levees relative to sand, the flow becomes more sand rich proceeding downstream when lateral overspill is present. Velocity and flow thickness predicted by the model are then validated by showing good agreement with laboratory observations. Finally, the model is applied to the Monterey Canyon bathymetric data matching satisfactorily the December 2002 event field measurements and predicting a runout length consistent with observations.

  13. Mutation I136V alters electrophysiological properties of the NaV1.7 channel in a family with onset of erythromelalgia in the second decade

    Directory of Open Access Journals (Sweden)

    Dib-Hajj Sulayman D

    2008-01-01

    Full Text Available Abstract Background Primary erythromelalgia is an autosomal dominant pain disorder characterized by burning pain and skin redness in the extremities, with onset of symptoms during the first decade in the families whose mutations have been physiologically studied to date. Several mutations of voltage-gated Na+ channel NaV1.7 have been linked with primary erythromelalgia. Recently, a new substitution NaV1.7/I136V has been reported in a Taiwanese family, in which pain appeared at later ages (9–22 years, with onset at 17 years of age or later in 5 of 7 family members, with relatively slow progression (8–10 years to involvement of the hands. The proband reported onset of symptoms first in his feet at the age of 11, which then progressed to his hands at the age of 19. The new mutation is located in transmembrane segment 1 (S1 of domain I (DI in contrast to all NaV1.7 mutations reported to date, which have been localized in the voltage sensor S4, the linker joining segments S4 and S5 or pore-lining segments S5 and S6 in DI, II and III. Results In this study, we characterized the gating and kinetic properties of I136V mutant channels in HEK293 cells using whole-cell patch clamp. I136V shifts the voltage-dependence of activation by -5.7 mV, a smaller shift in activation than the other erythromelalgia mutations that have been characterized. I136V also decreases the deactivation rate, and generates larger ramp currents. Conclusion The I136V substitution in NaV1.7 alters channel gating and kinetic properties. Each of these changes may contribute to increased excitability of nociceptive dorsal root ganglion neurons, which underlies pain in erythromelalgia. The smaller shift in voltage-dependence of activation of NaV1.7, compared to the other reported cases of inherited erythromelalgia, may contribute to the later age of onset and slower progression of the symptoms reported in association with this mutation.

  14. Functional analysis of Kv1.2 and paddle chimera Kv channels in planar lipid bilayers

    Science.gov (United States)

    Tao, Xiao; MacKinnon, Roderick

    2010-01-01

    Summary Voltage-dependent K+ channels play key roles in shaping electrical signaling in both excitable as well as non-excitable cells. These channels open and close in response to the voltage changes across the cell membrane. Many studies have been carried out in order to understand the voltage sensing mechanism. Our laboratory recently determined the atomic structures of a mammalian voltage-dependent K+ channel Kv1.2 and a mutant of Kv1.2 named the ‘paddle-chimera’ channel, in which the voltage sensor paddle was transferred from Kv2.1 to Kv1.2. These two structures provide atomic descriptions of voltage-dependent channels with unprecedented clarity. Until now the functional integrity of these two channels biosynthesized in yeast cells have not been assessed. Here we report the electrophysiological and pharmacological properties of Kv1.2 and the paddle chimera channels in planar lipid bilayers. We demonstrate that Pichia yeast produce ‘normally functioning’ mammalian voltage-dependent K+ channels with qualitatively similar features to the Shaker K+ channel in the absence of the N-terminal inactivation gate, and that the paddle chimera mutant channel functions as well as Kv1.2. We find, however, that in several respects the Kv1.2 channel exhibits functional properties that are distinct from Kv1.2 channels reported in the literature. PMID:18638484

  15. Channel Bottom Morphology in the Deltaic Reach of the Song Hau (mekong) River Channel in Vietnam

    Science.gov (United States)

    Allison, M. A.; Weathers, H. D., III; Meselhe, E. A.

    2016-02-01

    Boat-based, channel bathymetry and bankline elevation studies were conducted in the tidal and estuarine Mekong River channel using multibeam bathymetry and LIDAR corrected for elevation by RTK satellite positioning. Two mapping campaigns, one at high discharge in October 2014 and one at low discharge in March 2015, were conducted in the lower 100 km reach of the Song Hau distributary channel to (1) examine bottom morphology and its relationship to sediment transport, and (2) to provide information to setup the grid for a multi-dimensional and reduced complexity models of channel hydrodynamics and sediment dynamics. Sand fields were identified in multibeam data by the presence of dunes that were as large as 2-4 m high and 40-80 m wavelength and by clean sands in bottom grabs. Extensive areas of sand at the head and toe of mid-channel islands displayed 10-25 m diameter circular pits that could be correlated with bucket dredge, sand mining activities observed at some of the sites. Large areas of the channel floor were relict (containing little or no modern sediment) in the high discharge campaign, identifiable by the presence of along channel erosional furrows and terraced outcrops along the channel floor and margins. Laterally extensive flat areas were also observed in the channel thalweg. Both these and the relict areas were sampled by bottom grab as stiff silty clays. Complex cross-channel combinations of these morphologies were observed in some transects, suggesting strong bottom steering of tidal and riverine currents. Relative to high discharge, transects above and below the salt penetration limit showed evidence of shallowing in the thalweg and adjacent sloping areas at low discharge in March 2015. This shallowing, combined with the reduced extent of sand fields and furrowed areas, and soft muds in grabs, suggests seasonal trapping of fine grained sediment is occurring by estuarine and tidal circulation.

  16. miR-1 is increased in pulmonary hypertension and downregulates Kv1.5 channels in rat pulmonary arteries.

    Science.gov (United States)

    Mondejar-Parreño, Gema; Callejo, María; Barreira, Bianca; Morales-Cano, Daniel; Esquivel-Ruiz, Sergio; Moreno, Laura; Cogolludo, Angel; Perez-Vizcaino, Francisco

    2018-05-02

    ■The expression of miR-1 is increased in lungs from the Hyp/Su5416 PAH rat model. ■PASMC from this animal model are more depolarised and show decreased expression and activity of Kv1.5. ■miR-1 directly targets Kv1.5 channels, reduces Kv1.5 activity and induces membrane depolarization. ■Antagomir-1 prevents Kv1.5 channel downregulation and the depolarization induced by hypoxia/Su5416 exposition. Impairment of voltage-dependent potassium channel (Kv) plays a central role in the development of cardiovascular diseases, including pulmonary arterial hypertension (PAH). MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression by binding to the 3'-UTR region of specific mRNAs. The aim of this study was to analyze the effects of miR-1 on Kv channel function in pulmonary arteries (PA). Kv channel activity was studied in PA from healthy animals transfected with miR-1 or scrambled-miR. Kv currents were studied using the whole-cell configuration of patch-clamp technique. The characterization of the Kv1.5 currents was performed with the selective inhibitor DPO-1. miR-1 expression was increased and Kv1.5 channels were decreased in lungs from a rat model of PAH induced by hypoxia and Su5416. miR-1 transfection increased cell capacitance, reduced Kv1.5 currents and induced membrane depolarization in isolated pulmonary artery smooth muscle cells (PASMCs). Luciferase reporter assay indicated that KCNA5, which encodes Kv1.5 channels, is a direct target gene of miR-1. Incubation of PA with Su5416 and hypoxia (3% O 2 ) increased miR-1 and induced a decline in Kv1.5 currents, which was prevented by antagomiR-1. In conclusion, these data indicate that miR-1 induces PASMC hypertrophy and reduces the activity and expression of Kv channels, suggesting a pathophysiological role in PAH. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  17. Selective spider toxins reveal a role for Nav1.1 channel in mechanical pain

    OpenAIRE

    Osteen, Jeremiah D.; Herzig, Volker; Gilchrist, John; Emrick, Joshua J.; Zhang, Chuchu; Wang, Xidao; Castro, Joel; Garcia-Caraballo, Sonia; Grundy, Luke; Rychkov, Grigori Y.; Weyer, Andy D.; Dekan, Zoltan; Undheim, Eivind A. B.; Alewood, Paul; Stucky, Cheryl L.

    2016-01-01

    Voltage-gated sodium (Nav) channels initiate action potentials in most neurons, including primary afferent nerve fibers of the pain pathway. Local anesthetics block pain through non-specific actions at all Nav channels, but the discovery of selective modulators would facilitate the analysis of individual subtypes and their contributions to chemical, mechanical, or thermal pain. Here, we identify and characterize spider toxins that selectively activate the Nav1.1 subtype, whose role in nocicep...

  18. The voltage-gated potassium channel subunit, Kv1.3, is expressed in epithelia

    DEFF Research Database (Denmark)

    Grunnet, Morten; Rasmussen, Hanne B; Hay-Schmidt, Anders

    2003-01-01

    The Shaker-type voltage-gated potassium channel, Kv1.3, is believed to be restricted in distribution to lymphocytes and neurons. In lymphocytes, this channel has gained intense attention since it has been proven that inhibition of Kv1.3 channels compromise T lymphocyte activation. To investigate...

  19. Investigation of the transient receptor potential vanilloid 1 (TRPV1) ion channel

    OpenAIRE

    Winter Zoltán

    2013-01-01

    The aims of this research were to determine sensory modalities that may be lost after the RTX treatment of newborn or adult mice, to dissect potential side-effect(s) of molecular neurosurgery, to gather information about the structure and function of the channel by investigating the effects of M2+ on the TRPV1 and by collecting the literature data on the functionally important point mutations of the channel for prospective in silico modeling. The findings of the research work can be summa...

  20. Subthreshold Current and Swing Modeling of Gate Underlap DG MOSFETs with a Source/Drain Lateral Gaussian Doping Profile

    Science.gov (United States)

    Singh, Kunal; Kumar, Sanjay; Goel, Ekta; Singh, Balraj; Kumar, Mirgender; Dubey, Sarvesh; Jit, Satyabrata

    2017-01-01

    This paper proposes a new model for the subthreshold current and swing of the short-channel symmetric underlap ultrathin double gate metal oxide field effect transistors with a source/drain lateral Gaussian doping profile. The channel potential model already reported earlier has been utilized to formulate the closed form expression for the subthreshold current and swing of the device. The effects of the lateral straggle and geometrical parameters such as the channel length, channel thickness, and oxide thickness on the off current and subthreshold slope have been demonstrated. The devices with source/drain lateral Gaussian doping profiles in the underlap structure are observed to be highly resistant to short channel effects while improving the current drive. The proposed model is validated by comparing the results with the numerical simulation data obtained by using the commercially available ATLAS™, a two-dimensional (2-D) device simulator from SILVACO.

  1. Translating HbA1c measurements into estimated average glucose values in pregnant women with diabetes

    DEFF Research Database (Denmark)

    Law, Graham R; Gilthorpe, Mark S; Secher, Anna L

    2017-01-01

    AIMS/HYPOTHESIS: This study aimed to examine the relationship between average glucose levels, assessed by continuous glucose monitoring (CGM), and HbA1c levels in pregnant women with diabetes to determine whether calculations of standard estimated average glucose (eAG) levels from HbA1c measureme...

  2. Morphology of channels and channel-sand bodies in the Glauconitic sandstone member (Upper Mannville), Little Bow area, Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, J.C.; Hermanson, S.W.; Lawton, D.C.

    1982-12-01

    Large channels in the Glauconitic sandstone member of southern Alberta have proved to be difficult exploration targets because of an irregular distribution of reservoir sands within the channels. In the Little Bow area, two channels are present in the lower part of the Glauconitic member and have cut into the underlying Calcareous member. The channels can be recognized where they truncate regional markers of the Calcareous member -- the Bantry shale and Ostracod limestone, and where channel-fill deposits exhibit uniform geophysical log characters, indicating sandstone- or mudstone-filled reaches. Sediments of the Glauconitic member adjacent to the channels comprise a series of splay sandstones and mudstones that prograded into interdistributary bays of the lower delta plain. The two channels associated with these deposits are interpreted as distributary channels. Sand bodies within the channels formed as lateral bars and are isolated by mudstones which mark the abandoned stream course. Geological exploration for these discontinuous channel sandstones is difficult, and high-resolutio seismic data integrated with sound geologic modelling are critical for successful prospect delineation.

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

    DEFF Research Database (Denmark)

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

    2006-01-01

    Voltage-dependent Ca2+ channels Cav1.2 (L type) and Cav2.1 (P/Q type) are expressed in vascular smooth muscle cells (VSMCs) and are important for the contraction of renal resistance vessels. In the present study we examined whether native renal VSMCs coexpress L-, P-, and Q-type Ca2+ currents...... microscopy revealed expression of both channels in all of the smooth muscle cells. Whole-cell patch clamp on single preglomerular VSMCs from mice showed L-, P-, and Q-type currents. Blockade of the L-type currents by calciseptine (20 nmol/L) inhibited 35.6+/-3.9% of the voltage-dependent Ca2+ current......-type and P-type channels inhibited 58.0+/-11.8%, and simultaneous inhibition of L-, P-, and Q-type channels led to blockade (88.7+/-5.6%) of the Ca2+ current. We conclude that aortic and renal preglomerular smooth muscle cells express L-, P-, and Q-type voltage-dependent Ca2+ channels in the rat and mouse....

  4. Experimental study of the IPR-R1 TRIGA reactor power channels responses

    International Nuclear Information System (INIS)

    Mesquita, Henrique F.A.; Ferreira, Andrea V.

    2015-01-01

    The IPR-R1 nuclear reactor installed at Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Belo Horizonte, Brazil, is a Mark I TRIGA reactor (Training, Research, Isotopes, General Atomics) and became operational on November of 1960. The reactor has four irradiation devices: a rotary specimen rack with 40 irradiation channels, the central tube, and two pneumatic transfer tubes. The nuclear reactor is operated in a power range between zero and 100 kW. The instrumentation for IPR-R1 operation is mainly composed of four neutronic channels for power measurements. The aim of this work is to investigate the responses of neutronic channels of IPR-R1, Linear, Log N and Percent Power channels, and to check their linearity. Gold foils were activated at low powers (0.125-1.000 kW), and cobalt foils were activated at high powers (10-100kW). For each sample irradiated at rotary specimen rack, another one was irradiated at the same time at the pneumatic transfer tube-2. The obtained results allowed evaluating the linearity of the neutronic channels responses. (author)

  5. Structure of the TRPV1 ion channel determined by electron cryo-microscopy.

    Science.gov (United States)

    Liao, Maofu; Cao, Erhu; Julius, David; Cheng, Yifan

    2013-12-05

    Transient receptor potential (TRP) channels are sensors for a wide range of cellular and environmental signals, but elucidating how these channels respond to physical and chemical stimuli has been hampered by a lack of detailed structural information. Here we exploit advances in electron cryo-microscopy to determine the structure of a mammalian TRP channel, TRPV1, at 3.4 Å resolution, breaking the side-chain resolution barrier for membrane proteins without crystallization. Like voltage-gated channels, TRPV1 exhibits four-fold symmetry around a central ion pathway formed by transmembrane segments 5-6 (S5-S6) and the intervening pore loop, which is flanked by S1-S4 voltage-sensor-like domains. TRPV1 has a wide extracellular 'mouth' with a short selectivity filter. The conserved 'TRP domain' interacts with the S4-S5 linker, consistent with its contribution to allosteric modulation. Subunit organization is facilitated by interactions among cytoplasmic domains, including amino-terminal ankyrin repeats. These observations provide a structural blueprint for understanding unique aspects of TRP channel function.

  6. Role of TRPV1 channels in ischemia/reperfusion-induced acute kidney injury.

    Directory of Open Access Journals (Sweden)

    Lan Chen

    Full Text Available OBJECTIVES: Transient receptor potential vanilloid 1 (TRPV1 -positive sensory nerves are widely distributed in the kidney, suggesting that TRPV1-mediated action may participate in the regulation of renal function under pathophysiological conditions. Stimulation of TRPV1 channels protects against ischemia/reperfusion (I/R-induced acute kidney injury (AKI. However, it is unknown whether inhibition of these channels is detrimental in AKI or not. We tested the role of TRPV1 channels in I/R-induced AKI by modulating these channels with capsaicin (TRPV1 agonist, capsazepine (TRPV1 antagonist and using Trpv1-/- mice. METHODS AND RESULTS: Anesthetized C57BL/6 mice were subjected to 25 min of renal ischemia and 24 hrs of reperfusion. Mice were pretreated with capsaicin (0.3 mg/kg body weight or capsazepine (50 mg/kg body weight. Capsaicin ameliorated the outcome of AKI, as measured by serum creatinine levels, tubular damage,neutrophil gelatinase-associated lipocalin (NGAL abundance and Ly-6B.2 positive polymorphonuclear inflammatory cells in injured kidneys. Neither capsazepine nor deficiency of TRPV1 did deteriorate renal function or histology after AKI. Measurements of endovanilloids in kidney tissue indicate that 20-hydroxyeicosatetraeonic acid (20-HETE or epoxyeicosatrienoic acids (EETs are unlikely involved in the beneficial effects of capsaicin on I/R-induced AKI. CONCLUSIONS: Activation of TRPV1 channels ameliorates I/R-induced AKI, but inhibition of these channels does not affect the outcome of AKI. Our results may have clinical implications for long-term safety of renal denervation to treat resistant hypertension in man, with respect to the function of primary sensory nerves in the response of the kidney to ischemic stimuli.

  7. Synthesis and characterisation of NS13558: a new important tool for addressing KCa1.1 channel function ex vivo

    DEFF Research Database (Denmark)

    Bentzen, Bo Hjorth; Andersen, Rune Wederkinck; Olesen, Søren-Peter

    2009-01-01

    Pharmacological activation of the large-conductance Ca(2+)-activated K(+) channel (KCa1.1) in the cardiac inner mitochondrial membrane has been found to protect the heart against ischemia reperfusion injuries. However, there are concerns about the selectivity of the pharmacological tools used...... to modulate the channel. Here, we address this issue by synthesising a methylated analogue of the tool KCa1.1 channel activator NS11021. The compound (NS13558) is designed as a structurally closely related and biologically inactive analogue of NS11021. NS13558 did not elicit any significant opening of cloned...... human KCa1.1 channels, but maintained comparable biological activity towards other cardiac ion channels as compared to NS11021. In isolated perfused rat hearts subjected to ischemia-reperfusion, infarct size was reduced from 29% in control to 7% in NS11021 treated hearts. In comparison, the inactive...

  8. Glycosylation of alpha(2)delta(1) subunit: a sweet talk with Ca(v)1.2 channels

    Czech Academy of Sciences Publication Activity Database

    Lazniewska, Joanna; Weiss, Norbert

    2016-01-01

    Roč. 35, č. 3 (2016), s. 239-242 ISSN 0231-5882 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channel * Ca(v)1.2 channel * ancillary subunit * alpha(2)delta(1) subunit * glycosylation * trafficking Subject RIV: CE - Biochemistry Impact factor: 1.170, year: 2016

  9. Pannexin-1 channels show distinct morphology and no gap junction characteristics in mammalian cells.

    Science.gov (United States)

    Beckmann, Anja; Grissmer, Alexander; Krause, Elmar; Tschernig, Thomas; Meier, Carola

    2016-03-01

    Pannexins (Panx) are proteins with a similar membrane topology to connexins, the integral membrane protein of gap junctions. Panx1 channels are generally of major importance in a large number of system and cellular processes and their function has been thoroughly characterized. In contrast, little is known about channel structure and subcellular distribution. We therefore determine the subcellular localization of Panx1 channels in cultured cells and aim at the identification of channel morphology in vitro. Using freeze-fracture replica immunolabeling on EYFP-Panx1-overexpressing HEK 293 cells, large particles were identified in plasma membranes, which were immunogold-labeled using either GFP or Panx1 antibodies. There was no labeling or particles in the nuclear membranes of these cells, pointing to plasma membrane localization of Panx1-EYFP channels. The assembly of particles was irregular, this being in contrast to the regular pattern of gap junctions. The fact that no counterparts were identified on apposing cells, which would have been indicative of intercellular signaling, supported the idea of Panx1 channels within one membrane. Control cells (transfected with EYFP only, non-transfected) were devoid of both particles and immunogold labeling. Altogether, this study provides the first demonstration of Panx1 channel morphology and assembly in intact cells. The identification of Panx1 channels as large particles within the plasma membrane provides the knowledge required to enable recognition of Panx1 channels in tissues in future studies. Thus, these results open up new avenues for the detailed analysis of the subcellular localization of Panx1 and of its nearest neighbors such as purinergic receptors in vivo.

  10. Spontaneous laterality in mouse Crl:CD1.

    Science.gov (United States)

    Maciejewska, Maria; Zięba, Katarzyna; Szymańska, Justyna; Warońska, Magdalena

    2016-01-01

    Lateralization developed very early in evolution and it is a characteristic of a wide range of representatives from the animal kingdom. The aim of the present study was to examine the spontaneous laterality in mice (Mus musculus) with the T-maze test. We wanted to check if this kind of functional asymmetry occurs at a population level, and also if there are gender differences in this regard. The study involved 40 mice Crl:CD1. The research procedure was simple: mice had to choose one arm of the T-shaped apparatus to find the exit. The animals performed the 10 trails one after another. We took into account only the animals' fist reactions while preparing results. Most of the animals (68%) chose the right arm of the maze. The lateralization was stronger among females--75% of them had preferences for the right side. The majority of animals, which preferred the right side, were from the food deprivation group. However, the results did not unequivocally resolve whether mice evince the functional asymmetry at the population level, or whether there are gender differences in this area. Further research with a larger group and multiple observations for each animal are required to answer these questions.

  11. Channel coincidence counter: version 1

    International Nuclear Information System (INIS)

    Krick, M.S.; Menlove, H.O.

    1980-06-01

    A thermal neutron coincidence counter has been designed for the assay of fast critical assembly fuel drawers and plutonium-bearing fuel rods. The principal feature of the detector is a 7-cm by 7-cm by 97-cm detector channel, which provides a uniform neutron detection efficiency of 16% along the central 40 cm of the channel. The electronics system is identical to that used for the High-Level Neutron Coincidence Counter

  12. Safety and surgical techniques of C1 lateral mass screws

    International Nuclear Information System (INIS)

    Kubo, Shinichiro; Kuroki, Hiroshi; Hanado, Shoji; Hamanaka, Hideaki; Inomata, Naoki; Kuroki, Shuji; Chosa, Etsuo

    2010-01-01

    The objectives of this study were to evaluate the proper insertion techniques of C1 lateral mass screws. Eighteen consecutive patients were examined after upper cervical fusion using twenty-nine C1 lateral mass screws. Screws were placed by three different techniques; Goel's technique (4), Tan's technique (20), Notching technique (5). Pre and post-operative CT scans with multiplanar reconstruction were used to detect cortical breaches and direction of screws. No transverse foramen and vertebral groove violation was found in CT scans. Three had breached superior articular facet of the atlas. However, the range of motion (R.O.M) of atlanto-occipital joints had not changed postoperatively. Theses screws were inserted with Tan's technique and two of three were directed medially. It is feasible to safely insert C1 lateral mass screws when correct insertion point and direction are considered preoperatively. However, care should be taken because screws can violate the atlanto-occipital joint especially with Tan's technique. (author)

  13. Hypotonic stimuli enhance proton-gated currents of acid-sensing ion channel-1b

    International Nuclear Information System (INIS)

    Ugawa, Shinya; Ishida, Yusuke; Ueda, Takashi; Yu, Yong; Shimada, Shoichi

    2008-01-01

    Acid-sensing ion channels (ASICs) are strong candidates for mammalian mechanoreceptors. We investigated whether mouse acid-sensing ion channel-1b (ASIC1b) is sensitive to mechanical stimuli using oocyte electrophysiology, because ASIC1b is located in the mechanosensory stereocilia of cochlear hair cells. Hypotonic stimuli that induced membrane stretch of oocytes evoked no significant current in ASIC1b-expressing oocytes at pH 7.5. However, acid (pH 4.0 or 5.0)-evoked currents in the oocytes were substantially enhanced by the hypotonicity, showing mechanosensitivity of ASIC1b and possible mechanogating of the channel in the presence of other components. Interestingly, the ASIC1b channel was permeable to K + (a principal charge carrier for cochlear sensory transduction) and the affinity of the channel for amiloride (IC 50 (inhibition constant) = approximately 48.3 μM) was quite similar to that described for the mouse hair cell mechanotransducer current. Taken together, these data raise the possibility that ASIC1b participates in cochlear mechanoelectrical transduction

  14. Functionalized Fullerene Targeting Human Voltage-Gated Sodium Channel, hNav1.7.

    Science.gov (United States)

    Hilder, Tamsyn A; Robinson, Anna; Chung, Shin-Ho

    2017-08-16

    Mutations of hNa v 1.7 that cause its activities to be enhanced contribute to severe neuropathic pain. Only a small number of hNa v 1.7 specific inhibitors have been identified, most of which interact with the voltage-sensing domain of the voltage-activated sodium ion channel. In our previous computational study, we demonstrated that a [Lys 6 ]-C 84 fullerene binds tightly (affinity of 46 nM) to Na v Ab, the voltage-gated sodium channel from the bacterium Arcobacter butzleri. Here, we extend this work and, using molecular dynamics simulations, demonstrate that the same [Lys 6 ]-C 84 fullerene binds strongly (2.7 nM) to the pore of a modeled human sodium ion channel hNa v 1.7. In contrast, the fullerene binds only weakly to a mutated model of hNa v 1.7 (I1399D) (14.5 mM) and a model of the skeletal muscle hNa v 1.4 (3.7 mM). Comparison of one representative sequence from each of the nine human sodium channel isoforms shows that only hNa v 1.7 possesses residues that are critical for binding the fullerene derivative and blocking the channel pore.

  15. Large spin-valve effect in a lateral spin-valve device based on ferromagnetic semiconductor GaMnAs

    Science.gov (United States)

    Asahara, Hirokatsu; Kanaki, Toshiki; Ohya, Shinobu; Tanaka, Masaaki

    2018-03-01

    We investigate the spin-dependent transport properties of a lateral spin-valve device based on the ferromagnetic semiconductor GaMnAs. This device is composed of a GaMnAs channel layer grown on GaAs with a narrow trench across the channel. Its current-voltage characteristics show tunneling behavior. Large magnetoresistance (MR) ratios of more than ˜10% are obtained. These values are much larger than those (˜0.1%) reported for lateral-type spin metal-oxide-semiconductor field-effect transistors. The magnetic field direction dependence of the MR curve differs from that of the anisotropic magnetoresistance of GaMnAs, which confirms that the MR signal originates from the spin-valve effect between the GaMnAs electrodes.

  16. 16-channel DWDM based on 1D defect mode nonlinear photonic crystal

    Science.gov (United States)

    Kalhan, Abhishek; Sharma, Sanjeev; Kumar, Arun

    2018-05-01

    We propose a sixteen-channel Dense Wavelength Division Multiplexer (DWDM), using the 1-D defect mode nonlinear photonic crystal which is a function of intensity as well as wavelength. Here, we consider an alternate layer of two semiconductor materials in which we found the bandgap of materials when defect layer is introduced then 16-channel dense wavelength division multiplexer is obtained within bandgap. From the theoretical analysis, we can achieve average quality factor of 7800.4, the uniform spectral line-width of 0.2 nm, crosstalk of -31.4 dB, central wavelength changes 0.07 nm/(1GW/cm2) and 100% transmission efficiency. Thus, Sixteen-channel DWDM has very high quality factor, low crosstalk, near 100% power transmission efficiency and small channel spacing (1.44 nm).

  17. Cartap hydrolysis relative to its action at the insect nicotinic channel.

    Science.gov (United States)

    Lee, Seog-Jong; Caboni, Pierluigi; Tomizawa, Motohiro; Casida, John E

    2004-01-14

    The insecticide cartap is the bis(thiocarbamate) derivative of 2-(dimethylamino)propane-1,3-dithiol, which on oxidation forms the natural toxicant nereistoxin (NTX) [4-(dimethylamino)-1,2-dithiolane]. Both cartap and NTX are ion channel blockers of the nicotinic acetylcholine receptor (nAChR). Cartap was originally proposed to act only after metabolic conversion to NTX and later suggested to block directly without activation. The present study uses a new approach to differentiate these hypotheses, that is, pH effects on channel-blocking activity and hydrolysis rates. As controls, mecamylamine (the classic channel blocker) and NTX are stable and similar in channel-blocking potency ([(3)H]thienylcyclohexylpiperidine binding assay, honeybee nAChR) at pH 6.1-8.4. In contrast, cartap is >200-fold more effective at pH 7.4 than at pH 6.1, indicating that it undergoes hydrolytic activation. Cartap slowly hydrolyzes to cartap monothiol at pH 6.1 but quickly forms the dithiol and some NTX at pH 7.4. The relationship between potency and hydrolysis products at various pH ranges suggests that cartap dithiol is the most plausible blocking agent.

  18. Biophysical characterization of Vpu from HIV-1 suggests a channel-pore dualism.

    Science.gov (United States)

    Mehnert, T; Routh, A; Judge, P J; Lam, Y H; Fischer, D; Watts, A; Fischer, W B

    2008-03-01

    Vpu from HIV-1 is an 81 amino acid type I integral membrane protein which consists of a cytoplasmic and a transmembrane (TM) domain. The TM domain is known to alter membrane permeability for ions and substrates when inserted into artificial membranes. Peptides corresponding to the TM domain of Vpu (Vpu(1-32)) and mutant peptides (Vpu(1-32)-W23L, Vpu(1-32)-R31V, Vpu(1-32)-S24L) have been synthesized and reconstituted into artificial lipid bilayers. All peptides show channel activity with a main conductance level of around 20 pS. Vpu(1-32)-W23L has a considerable flickering pattern in the recordings and longer open times than Vpu(1-32). Whilst recordings for Vpu(1-32)-R31V are almost indistinguishable from those of the WT peptide, recordings for Vpu(1-32)-S24L do not exhibit any noticeable channel activity. Recordings of WT peptide and Vpu(1-32)-W23L indicate Michaelis-Menten behavior when the salt concentration is increased. Both peptide channels follow the Eisenman series I, indicative for a weak ion channel with almost pore like characteristics. 2007 Wiley-Liss, Inc.

  19. Structural Changes and Lack of HCN1 Channels in the Binaural Auditory Brainstem of the Naked Mole-Rat (Heterocephalus glaber).

    Science.gov (United States)

    Gessele, Nikodemus; Garcia-Pino, Elisabet; Omerbašić, Damir; Park, Thomas J; Koch, Ursula

    2016-01-01

    Naked mole-rats (Heterocephalus glaber) live in large eu-social, underground colonies in narrow burrows and are exposed to a large repertoire of communication signals but negligible binaural sound localization cues, such as interaural time and intensity differences. We therefore asked whether monaural and binaural auditory brainstem nuclei in the naked mole-rat are differentially adjusted to this acoustic environment. Using antibody stainings against excitatory and inhibitory presynaptic structures, namely the vesicular glutamate transporter VGluT1 and the glycine transporter GlyT2 we identified all major auditory brainstem nuclei except the superior paraolivary nucleus in these animals. Naked mole-rats possess a well structured medial superior olive, with a similar synaptic arrangement to interaural-time-difference encoding animals. The neighboring lateral superior olive, which analyzes interaural intensity differences, is large and elongated, whereas the medial nucleus of the trapezoid body, which provides the contralateral inhibitory input to these binaural nuclei, is reduced in size. In contrast, the cochlear nucleus, the nuclei of the lateral lemniscus and the inferior colliculus are not considerably different when compared to other rodent species. Most interestingly, binaural auditory brainstem nuclei lack the membrane-bound hyperpolarization-activated channel HCN1, a voltage-gated ion channel that greatly contributes to the fast integration times in binaural nuclei of the superior olivary complex in other species. This suggests substantially lengthened membrane time constants and thus prolonged temporal integration of inputs in binaural auditory brainstem neurons and might be linked to the severely degenerated sound localization abilities in these animals.

  20. Structural Changes and Lack of HCN1 Channels in the Binaural Auditory Brainstem of the Naked Mole-Rat (Heterocephalus glaber.

    Directory of Open Access Journals (Sweden)

    Nikodemus Gessele

    Full Text Available Naked mole-rats (Heterocephalus glaber live in large eu-social, underground colonies in narrow burrows and are exposed to a large repertoire of communication signals but negligible binaural sound localization cues, such as interaural time and intensity differences. We therefore asked whether monaural and binaural auditory brainstem nuclei in the naked mole-rat are differentially adjusted to this acoustic environment. Using antibody stainings against excitatory and inhibitory presynaptic structures, namely the vesicular glutamate transporter VGluT1 and the glycine transporter GlyT2 we identified all major auditory brainstem nuclei except the superior paraolivary nucleus in these animals. Naked mole-rats possess a well structured medial superior olive, with a similar synaptic arrangement to interaural-time-difference encoding animals. The neighboring lateral superior olive, which analyzes interaural intensity differences, is large and elongated, whereas the medial nucleus of the trapezoid body, which provides the contralateral inhibitory input to these binaural nuclei, is reduced in size. In contrast, the cochlear nucleus, the nuclei of the lateral lemniscus and the inferior colliculus are not considerably different when compared to other rodent species. Most interestingly, binaural auditory brainstem nuclei lack the membrane-bound hyperpolarization-activated channel HCN1, a voltage-gated ion channel that greatly contributes to the fast integration times in binaural nuclei of the superior olivary complex in other species. This suggests substantially lengthened membrane time constants and thus prolonged temporal integration of inputs in binaural auditory brainstem neurons and might be linked to the severely degenerated sound localization abilities in these animals.

  1. Seismic stochastic inversion identify river channel sand body

    Science.gov (United States)

    He, Z.

    2015-12-01

    The technology of seismic inversion is regarded as one of the most important part of geophysics. By using the technology of seismic inversion and the theory of stochastic simulation, the concept of seismic stochastic inversion is proposed.Seismic stochastic inversion can play an significant role in the identifying river channel sand body. Accurate sand body description is a crucial parameter to measure oilfield development and oilfield stimulation during the middle and later periods. Besides, rational well spacing density is an essential condition for efficient production. Based on the geological knowledge of a certain oilfield, in line with the use of seismic stochastic inversion, the river channel sand body in the work area is identified. In this paper, firstly, the single river channel body from the composite river channel body is subdivided. Secondly, the distribution of river channel body is ascertained in order to ascertain the direction of rivers. Morever, the superimposed relationship among the sand body is analyzed, especially among the inter-well sand body. The last but not at the least, via the analysis of inversion results of first vacuating the wells and continuous infilling later, it is meeted the most needs well spacing density that can obtain the optimal inversion result. It would serve effective guidance for oilfield stimulation.

  2. Divergent biophysical properties, gating mechanisms, and possible functions of the two skeletal muscle Ca(V)1.1 calcium channel splice variants.

    Science.gov (United States)

    Tuluc, Petronel; Flucher, Bernhard E

    2011-12-01

    Voltage-gated calcium channels are multi-subunit protein complexes that specifically allow calcium ions to enter the cell in response to membrane depolarization. But, for many years it seemed that the skeletal muscle calcium channel Ca(V)1.1 is the exception. The classical splice variant Ca(V)1.1a activates slowly, has a very small current amplitude and poor voltage sensitivity. In fact adult muscle fibers work perfectly well even in the absence of calcium influx. Recently a new splice variant of the skeletal muscle calcium channel Ca(V)1.1e has been characterized. The lack of the 19 amino acid exon 29 in this splice variant results in a rapidly activating calcium channel with high current amplitude and good voltage sensitivity. Ca(V)1.1e is the dominant channel in embryonic muscle, where the expression of this high calcium-conducting Ca(V)1.1 isoform readily explains developmental processes depending on L-type calcium currents. Moreover, the availability of these two structurally similar but functionally distinct channel variants facilitates the analysis of the molecular mechanisms underlying the unique current properties of the classical Ca(V)1.1a channel.

  3. Non-equivalent role of TM2 gating hinges in heteromeric Kir4.1/Kir5.1 potassium channels.

    Science.gov (United States)

    Shang, Lijun; Tucker, Stephen J

    2008-02-01

    Comparison of the crystal structures of the KcsA and MthK potassium channels suggests that the process of opening a K(+) channel involves pivoted bending of the inner pore-lining helices at a highly conserved glycine residue. This bending motion is proposed to splay the transmembrane domains outwards to widen the gate at the "helix-bundle crossing". However, in the inwardly rectifying (Kir) potassium channel family, the role of this "hinge" residue in the second transmembrane domain (TM2) and that of another putative glycine gating hinge at the base of TM2 remain controversial. We investigated the role of these two positions in heteromeric Kir4.1/Kir5.1 channels, which are unique amongst Kir channels in that both subunits lack a conserved glycine at the upper hinge position. Contrary to the effect seen in other channels, increasing the potential flexibility of TM2 by glycine substitutions at the upper hinge position decreases channel opening. Furthermore, the contribution of the Kir4.1 subunit to this process is dominant compared to Kir5.1, demonstrating a non-equivalent contribution of these two subunits to the gating process. A homology model of heteromeric Kir4.1/Kir5.1 shows that these upper "hinge" residues are in close contact with the base of the pore alpha-helix that supports the selectivity filter. Our results also indicate that the highly conserved glycine at the "lower" gating hinge position is required for tight packing of the TM2 helices at the helix-bundle crossing, rather than acting as a hinge residue.

  4. Emerging role of the KCNT1 Slack channel in intellectual disability.

    Science.gov (United States)

    Kim, Grace E; Kaczmarek, Leonard K

    2014-01-01

    The sodium-activated potassium KNa channels Slack and Slick are encoded by KCNT1 and KCNT2, respectively. These channels are found in neurons throughout the brain, and are responsible for a delayed outward current termed I KNa. These currents integrate into shaping neuronal excitability, as well as adaptation in response to maintained stimulation. Abnormal Slack channel activity may play a role in Fragile X syndrome, the most common cause for intellectual disability and inherited autism. Slack channels interact directly with the fragile X mental retardation protein (FMRP) and I KNa is reduced in animal models of Fragile X syndrome that lack FMRP. Human Slack mutations that alter channel activity can also lead to intellectual disability, as has been found for several childhood epileptic disorders. Ongoing research is elucidating the relationship between mutant Slack channel activity, development of early onset epilepsies and intellectual impairment. This review describes the emerging role of Slack channels in intellectual disability, coupled with an overview of the physiological role of neuronal I KNa currents.

  5. Inward rectifier potassium (Kir2.1) channels as end‐stage boosters of endothelium‐dependent vasodilators

    Science.gov (United States)

    Dalsgaard, Thomas; Bonev, Adrian D.; Nelson, Mark T.

    2016-01-01

    Key points Increase in endothelial cell (EC) calcium activates calcium‐sensitive intermediate and small conductance potassium (IK and SK) channels, thereby causing hyperpolarization and endothelium‐dependent vasodilatation.Endothelial cells express inward rectifier potassium (Kir) channels, but their role in endothelium‐dependent vasodilatation is not clear.In the mesenteric arteries, only ECs, but not smooth muscle cells, displayed Kir currents that were predominantly mediated by the Kir2.1 isoform.Endothelium‐dependent vasodilatations in response to muscarinic receptor, TRPV4 (transient receptor potential vanilloid 4) channel and IK/SK channel agonists were highly attenuated by Kir channel inhibitors and by Kir2.1 channel knockdown.These results point to EC Kir channels as amplifiers of vasodilatation in response to increases in EC calcium and IK/SK channel activation and suggest that EC Kir channels could be targeted to treat endothelial dysfunction, which is a hallmark of vascular disorders. Abstract Endothelium‐dependent vasodilators, such as acetylcholine, increase intracellular Ca2+ through activation of transient receptor potential vanilloid 4 (TRPV4) channels in the plasma membrane and inositol trisphosphate receptors in the endoplasmic reticulum, leading to stimulation of Ca2+‐sensitive intermediate and small conductance K+ (IK and SK, respectively) channels. Although strong inward rectifier K+ (Kir) channels have been reported in the native endothelial cells (ECs) their role in EC‐dependent vasodilatation is not clear. Here, we test the idea that Kir channels boost the EC‐dependent vasodilatation of resistance‐sized arteries. We show that ECs, but not smooth muscle cells, of small mesenteric arteries have Kir currents, which are substantially reduced in EC‐specific Kir2.1 knockdown (EC‐Kir2.1 −/−) mice. Elevation of extracellular K+ to 14 mm caused vasodilatation of pressurized arteries, which was prevented by endothelial

  6. Inward rectifier potassium (Kir2.1) channels as end-stage boosters of endothelium-dependent vasodilators.

    Science.gov (United States)

    Sonkusare, Swapnil K; Dalsgaard, Thomas; Bonev, Adrian D; Nelson, Mark T

    2016-06-15

    Increase in endothelial cell (EC) calcium activates calcium-sensitive intermediate and small conductance potassium (IK and SK) channels, thereby causing hyperpolarization and endothelium-dependent vasodilatation. Endothelial cells express inward rectifier potassium (Kir) channels, but their role in endothelium-dependent vasodilatation is not clear. In the mesenteric arteries, only ECs, but not smooth muscle cells, displayed Kir currents that were predominantly mediated by the Kir2.1 isoform. Endothelium-dependent vasodilatations in response to muscarinic receptor, TRPV4 (transient receptor potential vanilloid 4) channel and IK/SK channel agonists were highly attenuated by Kir channel inhibitors and by Kir2.1 channel knockdown. These results point to EC Kir channels as amplifiers of vasodilatation in response to increases in EC calcium and IK/SK channel activation and suggest that EC Kir channels could be targeted to treat endothelial dysfunction, which is a hallmark of vascular disorders. Endothelium-dependent vasodilators, such as acetylcholine, increase intracellular Ca(2+) through activation of transient receptor potential vanilloid 4 (TRPV4) channels in the plasma membrane and inositol trisphosphate receptors in the endoplasmic reticulum, leading to stimulation of Ca(2+) -sensitive intermediate and small conductance K(+) (IK and SK, respectively) channels. Although strong inward rectifier K(+) (Kir) channels have been reported in the native endothelial cells (ECs) their role in EC-dependent vasodilatation is not clear. Here, we test the idea that Kir channels boost the EC-dependent vasodilatation of resistance-sized arteries. We show that ECs, but not smooth muscle cells, of small mesenteric arteries have Kir currents, which are substantially reduced in EC-specific Kir2.1 knockdown (EC-Kir2.1(-/-) ) mice. Elevation of extracellular K(+) to 14 mm caused vasodilatation of pressurized arteries, which was prevented by endothelial denudation and Kir channel

  7. S1 constrains S4 in the voltage sensor domain of Kv7.1 K+ channels.

    Directory of Open Access Journals (Sweden)

    Yoni Haitin

    Full Text Available Voltage-gated K(+ channels comprise a central pore enclosed by four voltage-sensing domains (VSDs. While movement of the S4 helix is known to couple to channel gate opening and closing, the nature of S4 motion is unclear. Here, we substituted S4 residues of Kv7.1 channels by cysteine and recorded whole-cell mutant channel currents in Xenopus oocytes using the two-electrode voltage-clamp technique. In the closed state, disulfide and metal bridges constrain residue S225 (S4 nearby C136 (S1 within the same VSD. In the open state, two neighboring I227 (S4 are constrained at proximity while residue R228 (S4 is confined close to C136 (S1 of an adjacent VSD. Structural modeling predicts that in the closed to open transition, an axial rotation (approximately 190 degrees and outward translation of S4 (approximately 12 A is accompanied by VSD rocking. This large sensor motion changes the intra-VSD S1-S4 interaction to an inter-VSD S1-S4 interaction. These constraints provide a ground for cooperative subunit interactions and suggest a key role of the S1 segment in steering S4 motion during Kv7.1 gating.

  8. Strained Si channel NMOSFETs using a stress field with Si1-yC y source and drain stressors

    International Nuclear Information System (INIS)

    Chang, S.T.; Tasi, H.-S.; Kung, C.Y.

    2006-01-01

    The strain field in the silicon channel of a metal-oxide-semiconductor transistor with silicon-carbon alloy source and drain stressors was evaluated using the commercial process simulator FLOOPS-ISE TM . The physical origin of the strain components in the transistor channel region was explained. The magnitude and distribution of the strain components, and their dependence on device design parameters such as the spacing L G between the silicon-carbon alloy stressors, the carbon mole fraction in the stressors and stressor depth were investigated. Reducing the stressor spacing L G or increasing the carbon mole fraction in the stressors and stressor depth increases the magnitude of the vertical compressive stress and the lateral tensile stress in the portion of the N channel region where the inversion charge resides. This is beneficial for improving the electron mobility in n-channel metal-oxide-semiconductor transistors. A simple guiding principle for an optimum combination of the above-mentioned device design parameters in terms of mobility enhancement, drain current enhancement and the tradeoff consideration for junction leakage current degradation

  9. [An autopsy case of amyotrophic lateral sclerosis with prominent muscle cramps, fasciculation, and high titer of anti-voltage gated potassium channel (VGKC) complex antibody].

    Science.gov (United States)

    Sato, Aki; Sakai, Naoko; Shinbo, Junsuke; Hashidate, Hideki; Igarashi, Shuichi; Kakita, Akiyoshi; Yamazaki, Motoyoshi

    2014-01-01

    The patient was a 55-year-old male who had prominent fasciculation and muscle cramps. Muscle weakness and atrophy of the trunk, respiratory system, and extremities gradually progressed. On the basis of these features, we diagnosed this patient as having amyotrophic lateral sclerosis (ALS), however, the upper motor neuron signs were not significant. Following the detection of the anti-voltage gated potassium channel (VGKC) complex antibody at 907.5 pM (normal VGKC complex antibody in the development of cramp-fasciculation syndrome has been speculated. In this ALS patient, the antibodies might be associated with pathomechanisms underlying the characteristic symptoms.

  10. Structural changes in the cytoplasmic pore of the Kir1.1 channel during pHi-gating probed by FRET.

    Science.gov (United States)

    Lee, Jay-Ron; Shieh, Ru-Chi

    2009-03-06

    Kir1.1 channels are important in maintaining K+ homeostasis in the kidney. Intracellular acidification reversibly closes the Kir1.1 channel and thus decreases K+ secretion. In this study, we used Foster resonance energy transfer (FRET) to determine whether the conformation of the cytoplasmic pore changes in response to intracellular pH (pHi)-gating in Kir1.1 channels fused with enhanced cyan fluorescent protein (ECFP) and enhanced yellow fluorescent protein (EYFP) (ECFP-Kir1.1-EYFP). Because the fluorescence intensities of ECFP and EYFP were affected at pHi pHi-gating occurs in the ECFP-Kir1.1-EYFP construct, we examined the FRET efficiencies of an ECFP-S219R-EYFP mutant, which is completed closed at pHi 7.4 and open at pHi 10.0. FRET efficiency was increased from 25% to 40% when the pHi was decreased from 10.0 to 7.4. These results suggest that the conformation of the cytoplasmic pore in the Kir1.1 channel changes in response to pHi gating such that the N- and C-termini move apart from each other at pHi 7.4, when the channel is open.

  11. C-terminus-mediated voltage gating of Arabidopsis guard cell anion channel QUAC1.

    Science.gov (United States)

    Mumm, Patrick; Imes, Dennis; Martinoia, Enrico; Al-Rasheid, Khaled A S; Geiger, Dietmar; Marten, Irene; Hedrich, Rainer

    2013-09-01

    Anion transporters in plants play a fundamental role in volume regulation and signaling. Currently, two plasma membrane-located anion channel families—SLAC/SLAH and ALMT—are known. Among the ALMT family, the root-expressed ALuminium-activated Malate Transporter 1 was identified by comparison of aluminum-tolerant and Al(3+)-sensitive wheat cultivars and was subsequently shown to mediate voltage-independent malate currents. In contrast, ALMT12/QUAC1 (QUickly activating Anion Channel1) is expressed in guard cells transporting malate in an Al(3+)-insensitive and highly voltage-dependent manner. So far, no information is available about the structure and mechanism of voltage-dependent gating with the QUAC1 channel protein. Here, we analyzed gating of QUAC1-type currents in the plasma membrane of guard cells and QUAC1-expressing oocytes revealing similar voltage dependencies and activation–deactivation kinetics. In the heterologous expression system, QUAC1 was electrophysiologically characterized at increasing extra- and intracellular malate concentrations. Thereby, malate additively stimulated the voltage-dependent QUAC1 activity. In search of structural determinants of the gating process, we could not identify transmembrane domains common for voltage-sensitive channels. However, site-directed mutations and deletions at the C-terminus of QUAC1 resulted in altered voltage-dependent channel activity. Interestingly, the replacement of a single glutamate residue, which is conserved in ALMT channels from different clades, by an alanine disrupted QUAC1 activity. Together with C- and N-terminal tagging, these results indicate that the cytosolic C-terminus is involved in the voltage-dependent gating mechanism of QUAC1.

  12. Physiological role of Kv1.3 channel in T lymphocyte cell investigated quantitatively by kinetic modeling.

    Directory of Open Access Journals (Sweden)

    Panpan Hou

    Full Text Available Kv1.3 channel is a delayed rectifier channel abundant in human T lymphocytes. Chronic inflammatory and autoimmune disorders lead to the over-expression of Kv1.3 in T cells. To quantitatively study the regulatory mechanism and physiological function of Kv1.3 in T cells, it is necessary to have a precise kinetic model of Kv1.3. In this study, we firstly established a kinetic model capable to precisely replicate all the kinetic features for Kv1.3 channels, and then constructed a T-cell model composed of ion channels including Ca2+-release activated calcium (CRAC channel, intermediate K+ (IK channel, TASK channel and Kv1.3 channel for quantitatively simulating the changes in membrane potentials and local Ca2+ signaling messengers during activation of T cells. Based on the experimental data from current-clamp recordings, we successfully demonstrated that Kv1.3 dominated the membrane potential of T cells to manipulate the Ca2+ influx via CRAC channel. Our results revealed that the deficient expression of Kv1.3 channel would cause the less Ca2+ signal, leading to the less efficiency in secretion. This was the first successful attempt to simulate membrane potential in non-excitable cells, which laid a solid basis for quantitatively studying the regulatory mechanism and physiological role of channels in non-excitable cells.

  13. Fluoxetine Blocks Nav1.5 Channels via a Mechanism Similar to That of Class 1 Antiarrhythmics

    Science.gov (United States)

    Poulin, Hugo; Bruhova, Iva; Timour, Quadiri; Theriault, Olivier; Beaulieu, Jean-Martin; Frassati, Dominique

    2014-01-01

    The voltage-gated Nav1.5 channel is essential for the propagation of action potentials in the heart. Malfunctions of this channel are known to cause hereditary diseases. It is a prime target for class 1 antiarrhythmic drugs and a number of antidepressants. Our study investigated the Nav1.5 blocking properties of fluoxetine, a selective serotonin reuptake inhibitor. Nav1.5 channels were expressed in HEK-293 cells, and Na+ currents were recorded using the patch-clamp technique. Dose-response curves of racemic fluoxetine (IC50 = 39 μM) and its optical isomers had a similar IC50 [40 and 47 μM for the (+) and (−) isomers, respectively]. Norfluoxetine, a fluoxetine metabolite, had a higher affinity than fluoxetine, with an IC50 of 29 μM. Fluoxetine inhibited currents in a frequency-dependent manner, shifted steady-state inactivation to more hyperpolarized potentials, and slowed the recovery of Nav1.5 from inactivation. Mutating a phenylalanine (F1760) and a tyrosine (Y1767) in the S6 segment of domain (D) IV (DIVS6) significantly reduced the affinity of fluoxetine and its frequency-dependent inhibition. We used a noninactivating Nav1.5 mutant to show that fluoxetine displays open-channel block behavior. The molecular model of fluoxetine in Nav1.5 was in agreement with mutational experiments in which F1760 and Y1767 were found to be the key residues in binding fluoxetine. We concluded that fluoxetine blocks Nav1.5 by binding to the class 1 antiarrhythmic site. The blocking of cardiac Na+ channels should be taken into consideration when prescribing fluoxetine alone or in association with other drugs that may be cardiotoxic or for patients with conduction disorders. PMID:25028482

  14. Silicon Waveguide with Lateral p-i-n Diode for Nonlinearity Compensation by On-Chip Optical Phase Conjugation

    DEFF Research Database (Denmark)

    Gajda, A.; Da Ros, Francesco; Porto da Silva, Edson

    2018-01-01

    A 1-dB Q-factor improvement through optical phase conjugation in a silicon waveguide with a lateral p-i-n diode enables BERchannels of a 5xWDM 16-QAM single-polarization signal...

  15. Topology of transmembrane channel-like gene 1 protein.

    Science.gov (United States)

    Labay, Valentina; Weichert, Rachel M; Makishima, Tomoko; Griffith, Andrew J

    2010-10-05

    Mutations of transmembrane channel-like gene 1 (TMC1) cause hearing loss in humans and mice. TMC1 is the founding member of a family of genes encoding proteins of unknown function that are predicted to contain multiple transmembrane domains. The goal of our study was to define the topology of mouse TMC1 expressed heterologously in tissue culture cells. TMC1 was retained in the endoplasmic reticulum (ER) membrane of five tissue culture cell lines that we tested. We used anti-TMC1 and anti-HA antibodies to probe the topologic orientation of three native epitopes and seven HA epitope tags along full-length TMC1 after selective or complete permeabilization of transfected cells with digitonin or Triton X-100, respectively. TMC1 was present within the ER as an integral membrane protein containing six transmembrane domains and cytosolic N- and C-termini. There is a large cytoplasmic loop, between the fourth and fifth transmembrane domains, with two highly conserved hydrophobic regions that might associate with or penetrate, but do not span, the plasma membrane. Our study is the first to demonstrate that TMC1 is a transmembrane protein. The topologic organization revealed by this study shares some features with that of the shaker-TRP superfamily of ion channels.

  16. PRRT2 controls neuronal excitability by negatively modulating Na+ channel 1.2/1.6 activity.

    Science.gov (United States)

    Fruscione, Floriana; Valente, Pierluigi; Sterlini, Bruno; Romei, Alessandra; Baldassari, Simona; Fadda, Manuela; Prestigio, Cosimo; Giansante, Giorgia; Sartorelli, Jacopo; Rossi, Pia; Rubio, Alicia; Gambardella, Antonio; Nieus, Thierry; Broccoli, Vania; Fassio, Anna; Baldelli, Pietro; Corradi, Anna; Zara, Federico; Benfenati, Fabio

    2018-04-01

    See Lerche (doi:10.1093/brain/awy073) for a scientific commentary on this article.Proline-rich transmembrane protein 2 (PRRT2) is the causative gene for a heterogeneous group of familial paroxysmal neurological disorders that include seizures with onset in the first year of life (benign familial infantile seizures), paroxysmal kinesigenic dyskinesia or a combination of both. Most of the PRRT2 mutations are loss-of-function leading to haploinsufficiency and 80% of the patients carry the same frameshift mutation (c.649dupC; p.Arg217Profs*8), which leads to a premature stop codon. To model the disease and dissect the physiological role of PRRT2, we studied the phenotype of neurons differentiated from induced pluripotent stem cells from previously described heterozygous and homozygous siblings carrying the c.649dupC mutation. Single-cell patch-clamp experiments on induced pluripotent stem cell-derived neurons from homozygous patients showed increased Na+ currents that were fully rescued by expression of wild-type PRRT2. Closely similar electrophysiological features were observed in primary neurons obtained from the recently characterized PRRT2 knockout mouse. This phenotype was associated with an increased length of the axon initial segment and with markedly augmented spontaneous and evoked firing and bursting activities evaluated, at the network level, by multi-electrode array electrophysiology. Using HEK-293 cells stably expressing Nav channel subtypes, we demonstrated that the expression of PRRT2 decreases the membrane exposure and Na+ current of Nav1.2/Nav1.6, but not Nav1.1, channels. Moreover, PRRT2 directly interacted with Nav1.2/Nav1.6 channels and induced a negative shift in the voltage-dependence of inactivation and a slow-down in the recovery from inactivation. In addition, by co-immunoprecipitation assays, we showed that the PRRT2-Nav interaction also occurs in brain tissue. The study demonstrates that the lack of PRRT2 leads to a hyperactivity of voltage

  17. PRRT2 controls neuronal excitability by negatively modulating Na+ channel 1.2/1.6 activity

    Science.gov (United States)

    Fruscione, Floriana; Valente, Pierluigi; Sterlini, Bruno; Romei, Alessandra; Baldassari, Simona; Fadda, Manuela; Prestigio, Cosimo; Giansante, Giorgia; Sartorelli, Jacopo; Rossi, Pia; Rubio, Alicia; Gambardella, Antonio; Nieus, Thierry; Broccoli, Vania; Fassio, Anna; Baldelli, Pietro; Corradi, Anna; Zara, Federico

    2018-01-01

    Abstract See Lerche (doi:10.1093/brain/awy073) for a scientific commentary on this article. Proline-rich transmembrane protein 2 (PRRT2) is the causative gene for a heterogeneous group of familial paroxysmal neurological disorders that include seizures with onset in the first year of life (benign familial infantile seizures), paroxysmal kinesigenic dyskinesia or a combination of both. Most of the PRRT2 mutations are loss-of-function leading to haploinsufficiency and 80% of the patients carry the same frameshift mutation (c.649dupC; p.Arg217Profs*8), which leads to a premature stop codon. To model the disease and dissect the physiological role of PRRT2, we studied the phenotype of neurons differentiated from induced pluripotent stem cells from previously described heterozygous and homozygous siblings carrying the c.649dupC mutation. Single-cell patch-clamp experiments on induced pluripotent stem cell-derived neurons from homozygous patients showed increased Na+ currents that were fully rescued by expression of wild-type PRRT2. Closely similar electrophysiological features were observed in primary neurons obtained from the recently characterized PRRT2 knockout mouse. This phenotype was associated with an increased length of the axon initial segment and with markedly augmented spontaneous and evoked firing and bursting activities evaluated, at the network level, by multi-electrode array electrophysiology. Using HEK-293 cells stably expressing Nav channel subtypes, we demonstrated that the expression of PRRT2 decreases the membrane exposure and Na+ current of Nav1.2/Nav1.6, but not Nav1.1, channels. Moreover, PRRT2 directly interacted with Nav1.2/Nav1.6 channels and induced a negative shift in the voltage-dependence of inactivation and a slow-down in the recovery from inactivation. In addition, by co-immunoprecipitation assays, we showed that the PRRT2-Nav interaction also occurs in brain tissue. The study demonstrates that the lack of PRRT2 leads to a hyperactivity of

  18. Genesis and sedimentary record of blind channel and islands of the anabranching river: An evolution model

    Science.gov (United States)

    Leli, Isabel T.; Stevaux, José C.; Assine, Mário L.

    2018-02-01

    Blind channel (BC) is a fluvial feature formed by attachment of a lateral sand bar to an island or riverbank. It consists of a 10- to 20-m wide and hundreds to thousands meters long channel, parallel to the island or bank, closed at its upstream end by accretion to the island. It is an important feature in anabranching rivers that plays an important role in both the island formation and river ecology. This paper discusses the formation processes, functioning, evolution, and the sedimentary record of a blind channel, related landforms, and its context on island development in the Upper Paraná River. The evolution of this morphologic feature involves (1) formation of a lateral or attachment bar beside an island with the development of a channel in between; (2) vertical accretion of mud deposits during the flood and vegetal development on the bar; (3) the upstream channel closure that generates the blind channel; and (4) annexation of the blind channel to the island. A blind channel is semilotic to lentic, that is not totally integrated to the dynamics of the main active channel and that acts as a nursery for fingerlings and macrophytes. The sedimentary facies succession of BCs are relatively simple and characterized by cross-stratified sand covered by organic muddy sediments. Based on facies analysis of 12 cores, we identified a succession of environments that contribute to the formation of islands: channel bar, blind channel, pond, and swamp. Blind channel formation and its related bar-island attachment are relevant processes associated with the growing of large island evolution in some anabranching rivers.

  19. Large Object Irradiation Facility In The Tangential Channel Of The JSI TRIGA Reactor

    CERN Document Server

    Radulovic, Vladimir; Kaiba, Tanja; Kavsek, Darko; Cindro, Vladimir; Mikuz, Marko; Snoj, Luka

    2017-01-01

    This paper presents the design and installation of a new irradiation device in the Tangential Channel of the JSI TRIGA reactor in Ljubljana, Slovenia. The purpose of the device is to enable on-line irradiation testing of electronic components considerably larger in size (of lateral dimensions of at least 12 cm) than currently possible in the irradiation channels located in the reactor core, in a relatively high neutron flux (exceeding 10^12 n cm^-2 s^-1) and to provide adequate neutron and gamma radiation shielding.

  20. Differential expression of the Kv1 voltage-gated potassium channel family in the rat nephron.

    Science.gov (United States)

    Carrisoza-Gaytán, Rolando; Salvador, Carolina; Diaz-Bello, Beatriz; Escobar, Laura I

    2014-10-01

    Several potassium (K(+)) channels contribute to maintaining the resting membrane potential of renal epithelial cells. Apart from buffering the cell membrane potential and cell volume, K(+) channels allow sodium reabsorption in the proximal tubule (PT), K(+) recycling and K(+) reabsorption in the thick ascending limb (TAL) and K(+) secretion and K(+) reabsorption in the distal convoluted tubule (DCT), connecting tubule (CNT) and collecting duct. Previously, we identified Kv.1.1, Kv1.3 and Kv1.6 channels in collecting ducts of the rat inner medulla. We also detected intracellular Kv1.3 channel in the acid secretory intercalated cells, which is trafficked to the apical membrane in response to dietary K(+) to function as a secretory K(+) channel. In this work we sought to characterize the expression of all members of the Kv1 family in the rat nephron. mRNA and protein expression were detected for all Kv1 channels. Immunoblots identified differential expression of each Kv1 in the cortex, outer and inner medulla. Immunofluorescence labeling detected Kv1.5 in Bowman´s capsule and endothelial cells and Kv1.7 in podocytes, endothelial cells and macula densa in glomeruli; Kv1.4, Kv1.5 and Kv1.7 in PT; Kv1.2, Kv1.4 and Kv1.6 in TAL; Kv1.1, Kv1.4 and Kv1.6 in DCT and CNT and Kv1.3 in DCT, and all the Kv1 family in the cortical and medullary collecting ducts. Recently, some hereditary renal syndromes have been attributed to mutations in K(+) channels. Our results expand the repertoire of K(+) channels that contribute to K(+) homeostasis to include the Kv1 family.

  1. Pharmacological dissection of K(v)7.1 channels in systemic and pulmonary arteries

    DEFF Research Database (Denmark)

    Chadha, Preet S; Zunke, Friederike; Davis, Alison J

    2012-01-01

    The aim of this study was to characterize the functional impact of KCNQ1-encoded voltage-dependent potassium channels (K(v)7.1) in the vasculature.......The aim of this study was to characterize the functional impact of KCNQ1-encoded voltage-dependent potassium channels (K(v)7.1) in the vasculature....

  2. The jasmonate receptor COI1 plays a role in jasmonate-induced lateral root formation and lateral root positioning in Arabidopsis thaliana.

    Science.gov (United States)

    Raya-González, Javier; Pelagio-Flores, Ramón; López-Bucio, José

    2012-09-15

    Jasmonic acid (JA) regulates a broad range of plant defense and developmental responses. COI1 has been recently found to act as JA receptor. In this report, we show that low micromolar concentrations of JA inhibited primary root (PR) growth and promoted lateral root (LR) formation in Arabidopsis wild-type (WT) seedlings. It was observed that the coi1-1 mutant was less sensitive to JA on pericycle cell activation to induce lateral root primordia (LRP) formation and presented alterations in lateral root positioning and lateral root emergence on bends. To investigate JA-auxin interactions important for remodeling of root system (RS) architecture, we tested the expression of auxin-inducible markers DR5:uidA and BA3:uidA in WT and coi1-1 seedlings in response to indole-3-acetic acid (IAA) and JA and analyzed the RS architecture of a suite of auxin-related mutants under JA treatments. We found that JA did not affect DR5:uidA and BA3:uidA expression in WT and coi1-1 seedlings. Our data also showed that PR growth inhibition in response to JA was likely independent of auxin signaling and that the induction of LRP required ARF7, ARF19, SLR, TIR1, AFB2, AFB3 and AXR1 loci. We conclude that JA regulation of postembryonic root development involves both auxin-dependent and independent mechanisms. Copyright © 2012 Elsevier GmbH. All rights reserved.

  3. Identification (GC and GC-MS) of unsaturated acetates in Elasmopalpus lignosellus and their biological activity (GC-EAD and EAG).

    Science.gov (United States)

    Jham, Gulab N; da Silva, Alexsandro A; Lima, Eraldo R; Viana, Paulo

    2005-02-01

    Two insect colonies of Elasmopalpus lignosellus were reared in our laboratory, the first being initiated from pupae obtained from a cornfield in the region of Sete Lagoas, Minas Gerais and the second from a cornfield in the region of Goiânia, Goiás. From the two colonies, two extracts were prepared from the pheromone glands of virgin E. lignosellus females. The extract obtained from the first colony was designated as extract 1 while the extract obtained from the second colony was designated as extract 2. Extract 1 was analyzed by gas chromatography-mass spectrometry (GC-MS) with (Z)-9-hexadecenyl acetate [(Z)-9-HDA] and (Z)-11-hexadecenyl acetate [(Z)-11-HDA] being identified and confirmed by the formation of DMDS derivatives. In addition, a third acetate, which could be either (E)-8-hexadecenyl acetate [(E)-8-HDA] or (E)-9-hexadecenyl acetate [(E)-9-HDA] was detected by GC-MS. Extract 2 was analyzed by gas chromatography (GC) and gas chromatography-electroannetography (GC-EAD) revealing the presence of (Z)-11-HDA and (Z)-9-TDA. In addition, the same compounds elicited a response with the E. lignosellus male antenna obtained from the second insect colony. Electroantennography (EAG) screening with the male E. lignosellus antenna (obtained from the second insect colony) was conducted with the 23 possible tetradecenyl acetates (TDA) and 22 hexadecenyl acetates (HDA) as standards. Out of the 23 TDA isomers evaluated, only (Z)-9-TDA elicited a response and out of the 22 HDA [(Z) and (E) isomers gamma2 to delta13] evaluated only (Z)-11-HDA elicited a response. The acetate compositions of two extracts obtained from insects originating from the two states (Minas Gerais and Goiás) of Brazil were different from one another as well as from that obtained from insects in Tifton, GA, USA. The bioactivity data (GC-EAD) of the extract 2 differed from those reported for the Tifton, GA, USA population. These data suggest polymorphism in relation to the insect populations found in

  4. Proton channel HVCN1 is required for effector functions of mouse eosinophils

    Science.gov (United States)

    2013-01-01

    Background Proton currents are required for optimal respiratory burst in phagocytes. Recently, HVCN1 was identified as the molecule required for the voltage-gated proton channel activity associated with the respiratory burst in neutrophils. Although there are similarities between eosinophils and neutrophils regarding their mechanism for respiratory burst, the role of proton channels in eosinophil functions has not been fully understood. Results In the present study, we first identified the expression of the proton channel HVCN1 in mouse eosinophils. Furthermore, using HVCN1-deficient eosinophils, we demonstrated important cell-specific effector functions for HVCN1. Similar to HVCN1-deficient neutrophils, HVCN1-deficient eosinophils produced significantly less reactive oxygen species (ROS) upon phorbol myristate acetate (PMA) stimulation compared with WT eosinophils. In contrast to HVCN1-deficient neutrophils, HVCN1-deficient eosinophils did not show impaired calcium mobilization or migration ability compared with wild-type (WT) cells. Uniquely, HVCN1-deficient eosinophils underwent significantly increased cell death induced by PMA stimulation compared with WT eosinophils. The increased cell death was dependent on NADPH oxidase activation, and correlated with the failure of HVCN1-deficient cells to maintain membrane polarization and intracellular pH in the physiological range upon activation. Conclusions Eosinophils require proton channel HVCN1 for optimal ROS generation and prevention of activation-induced cell death. PMID:23705768

  5. CB3PMF - Thermohidraulic analysis using the open lateral boundary method

    International Nuclear Information System (INIS)

    Borges, R.C.; Andrade, G.G. de

    1985-01-01

    A calculation method for the thermohydraulic analysis of a nuclear reator having a large number of sub-channels is presented. The method uses the open lateral boundary which mantains the influence of the external boundaries of the channel under study and adds to the external face of the channel physical model important characteristcs that other computational models identify only at the sub-channel level. This permits to keep the mixture characteristics that exist between the channel under analysis and the neighboring ones from the previous step. This method is shown be valid, reliable and applicable to the steady state thermohydraulic analysis and permits greater flexibility in the application of coefficients and correlations. The additional computing time is negligible compared to the information obtained. (F.E.) [pt

  6. Quasi-double-blind screening of semiochemicals for reducing navel orangeworm oviposition on almonds.

    Directory of Open Access Journals (Sweden)

    Kevin Cloonan

    Full Text Available A three-step, quasi-double-bind approach was used as a proof-of-concept study to screen twenty compounds for their ability to reduce oviposition of gravid female navel orangeworm(NOW, Ameylois transitella (Lepidoptera: Pyralidae. First, the panel of compounds, whose identity was unknown to the experimenters, was tested by electroantennogram (EAG using antennae of two-day old gravid females as the sensing element. Of the twenty compounds tested three showed significant EAG responses. These three EAG-active compounds and a negative control were then analyzed for their ability to reduce oviposition via small-cage, two-choice laboratory assays. Two of the three compounds significantly reduced oviposition under laboratory conditions. Lastly, these two compounds were deployed in a field setting in an organic almond orchard in Arbuckle, CA using black egg traps to monitor NOW oviposition. One of these two compounds significantly reduced oviposition on black egg traps under these field conditions. Compound 9 (later identified as isophorone showed a significant reduction in oviposition in field assays and thus has a potential as a tool to control the navel orangeworm as a pest of almonds.

  7. Structural mechanism underlying capsaicin binding and activation of TRPV1 ion channel

    OpenAIRE

    Yang, Fan; Xiao, Xian; Cheng, Wei; Yang, Wei; Yu, Peilin; Song, Zhenzhen; Yarov-Yarovoy, Vladimir; Zheng, Jie

    2015-01-01

    Capsaicin bestows spiciness by activating TRPV1 channel with exquisite potency and selectivity. Capsaicin-bound channel structure was previously resolved by cryo-EM at 4.2-to-4.5 ? resolution, however important details required for mechanistic understandings are unavailable: capsaicin was registered as a small electron density, reflecting neither its chemical structure nor specific ligand-channel interactions. We obtained the missing atomic-level details by iterative computation, which were c...

  8. Pannexin 1 channels: new actors in the regulation of catecholamine release from adrenal chromaffin cells

    Directory of Open Access Journals (Sweden)

    Fanny eMomboisse

    2014-09-01

    Full Text Available Chromaffin cells of the adrenal gland medulla synthesize and store hormones and peptides, which are released into the blood circulation in response to stress. Among them, adrenaline is critical for the fight-or-flight response. This neurosecretory process is highly regulated and depends on cytosolic [Ca2+]. By forming channels at the plasma membrane, pannexin-1 (Panx1 is a protein involved in many physiological and pathological processes amplifying ATP release and/or Ca2+ signals. Here, we show that Panx1 is expressed in the adrenal gland where it plays a role by regulating the release of catecholamines. In fact, inhibitors of Panx1 channels, such as carbenoxolone (Cbx and probenecid, reduced the secretory activity induced with the nicotinic agonist 1,1-dimethyl-4-phenyl-piperazinium (DMPP, 50 µM in whole adrenal glands. A similar inhibitory effect was observed in single chromaffin cells using Cbx or 10Panx1 peptide, another Panx1 channel inhibitors. Given that the secretory response depends on cytosolic [Ca2+] and Panx1 channels are permeable to Ca2+, we studied the possible implication of Panx1 channels in the Ca2+ signaling occurring during the secretory process. In support of this possibility, Panx1 channel inhibitors significantly reduced the Ca2+ signals evoked by DMPP in single chromaffin cells. However, the Ca2+ signals induced by caffeine in the absence of extracellular Ca2+ was not affected by Panx1 channel inhibitors, suggesting that this mechanism does not involve Ca2+ release from the endoplasmic reticulum. Conversely, Panx1 inhibitors significantly blocked the DMPP-induce dye uptake, supporting the idea that Panx1 forms functional channels at the plasma membrane. These findings indicate that Panx1 channels participate in the control the Ca2+ signal that triggers the secretory response of adrenal chromaffin cells. This mechanism could have physiological implications during the response to stress.

  9. Phosphorylation of Lbx1 controls lateral myoblast migration into the limb.

    Science.gov (United States)

    Masselink, Wouter; Masaki, Megumi; Sieiro, Daniel; Marcelle, Christophe; Currie, Peter D

    2017-10-15

    The migration of limb myogenic precursors from limb level somites to their ultimate site of differentiation in the limb is a paradigmatic example of a set of dynamic and orchestrated migratory cell behaviours. The homeobox containing transcription factor ladybird homeobox 1 (Lbx1) is a central regulator of limb myoblast migration, null mutations of Lbx1 result in severe disruptions to limb muscle formation, particularly in the distal region of the limb in mice (Gross et al., 2000). As such Lbx1 has been hypothesized to control lateral migration of myoblasts into the distal limb anlage. It acts as a core regulator of the limb myoblast migration machinery, controlled by Pax3. A secondary role for Lbx1 in the differentiation and commitment of limb musculature has also been proposed (Brohmann et al., 2000; Uchiyama et al., 2000). Here we show that lateral migration, but not differentiation or commitment of limb myoblasts, is controlled by the phosphorylation of three adjacent serine residues of LBX1. Electroporation of limb level somites in the chick embryo with a dephosphomimetic form of Lbx1 results in a specific defect in the lateral migration of limb myoblasts. Although the initial delamination and migration of myoblasts is unaffected, migration into the distal limb bud is severely disrupted. Interestingly, myoblasts undergo normal differentiation independent of their migratory status, suggesting that the differentiation potential of hypaxial muscle is not regulated by the phosphorylation state of LBX1. Furthermore, we show that FGF8 and ERK mediated signal transduction, both critical regulators of the developing limb bud, have the capacity to induce the phosphorylation of LBX1 at these residues. Overall, this suggests a mechanism whereby the phosphorylation of LBX1, potentially through FGF8 and ERK signalling, controls the lateral migration of myoblasts into the distal limb bud. Copyright © 2017. Published by Elsevier Inc.

  10. KCNQ1 channel modulation by KCNE proteins via the voltage-sensing domain.

    Science.gov (United States)

    Nakajo, Koichi; Kubo, Yoshihiro

    2015-06-15

    The gating of the KCNQ1 potassium channel is drastically regulated by auxiliary subunit KCNE proteins. KCNE1, for example, slows the activation kinetics of KCNQ1 by two orders of magnitude. Like other voltage-gated ion channels, the opening of KCNQ1 is regulated by the voltage-sensing domain (VSD; S1-S4 segments). Although it has been known that KCNE proteins interact with KCNQ1 via the pore domain, some recent reports suggest that the VSD movement may be altered by KCNE. The altered VSD movement of KCNQ1 by KCNE proteins has been examined by site-directed mutagenesis, the scanning cysteine accessibility method (SCAM), voltage clamp fluorometry (VCF) and gating charge measurements. These accumulated data support the idea that KCNE proteins interact with the VSDs of KCNQ1 and modulate the gating of the KCNQ1 channel. In this review, we will summarize recent findings and current views of the KCNQ1 modulation by KCNE via the VSD. In this context, we discuss our recent findings that KCNE1 may alter physical interactions between the S4 segment (VSD) and the S5 segment (pore domain) of KCNQ1. Based on these findings from ourselves and others, we propose a hypothetical mechanism for how KCNE1 binding alters the VSD movement and the gating of the channel. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

  11. Cholesterol regulates HERG K+ channel activation by increasing phospholipase C β1 expression.

    Science.gov (United States)

    Chun, Yoon Sun; Oh, Hyun Geun; Park, Myoung Kyu; Cho, Hana; Chung, Sungkwon

    2013-01-01

    Human ether-a-go-go-related gene (HERG) K(+) channel underlies the rapidly activating delayed rectifier K(+) conductance (IKr) during normal cardiac repolarization. Also, it may regulate excitability in many neuronal cells. Recently, we showed that enrichment of cell membrane with cholesterol inhibits HERG channels by reducing the levels of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] due to the activation of phospholipase C (PLC). In this study, we further explored the effect of cholesterol enrichment on HERG channel kinetics. When membrane cholesterol level was mildly increased in human embryonic kidney (HEK) 293 cells expressing HERG channel, the inactivation and deactivation kinetics of HERG current were not affected, but the activation rate was significantly decelerated at all voltages tested. The application of PtdIns(4,5)P2 or inhibitor for PLC prevented the effect of cholesterol enrichment, while the presence of antibody against PtdIns(4,5)P2 in pipette solution mimicked the effect of cholesterol enrichment. These results indicate that the effect of cholesterol enrichment on HERG channel is due to the depletion of PtdIns(4,5)P2. We also found that cholesterol enrichment significantly increases the expression of β1 and β3 isoforms of PLC (PLCβ1, PLCβ3) in the membrane. Since the effects of cholesterol enrichment on HERG channel were prevented by inhibiting transcription or by inhibiting PLCβ1 expression, we conclude that increased PLCβ1 expression leads to the deceleration of HERG channel activation rate via downregulation of PtdIns(4,5)P2. These results confirm a crosstalk between two plasma membrane-enriched lipids, cholesterol and PtdIns(4,5)P2, in the regulation of HERG channels.

  12. [Open lateral clavicle resection in acromioclavicular osteoarthritis: favourable results after 1 year].

    NARCIS (Netherlands)

    Stroet, M.A.J. te; Schreurs, B.W.; Waal Malefijt, M.C. de

    2010-01-01

    OBJECTIVE: To determine the follow-up outcomes of open lateral clavicle resection 1 year postoperatively in patients with acromioclavicular osteoarthritis. The operation involves resection of a small part of the lateral clavicle. DESIGN: Prospective descriptive. METHOD: Data were collected from all

  13. Localized iron supply triggers lateral root elongation in Arabidopsis by altering the AUX1-mediated auxin distribution.

    Science.gov (United States)

    Giehl, Ricardo F H; Lima, Joni E; von Wirén, Nicolaus

    2012-01-01

    Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-29

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

  15. One channel bolometric diagnostic for TBR-1 tokamak

    International Nuclear Information System (INIS)

    Silveira, R.M.; Vannucci, A.; Silva, R.P. da; Machida, M.

    1993-01-01

    One channel bolometric diagnostic has been designed and built for the TBR-1 tokamak to measure the machine radiation power loss. The detector, a thinistor, was calibrated and its characteristics experimentally determined. In this work the first results obtained with the bolometer are presented and discussed. (author)

  16. Correcting lateral response artifacts from flatbed scanners for radiochromic film dosimetry

    International Nuclear Information System (INIS)

    Lewis, David; Chan, Maria F.

    2015-01-01

    Purpose: A known factor affecting the accuracy of radiochromic film dosimetry is the lateral response artifact (LRA) induced by nonuniform response of a flatbed scanner in the direction perpendicular to the scan direction. This work reports a practical solution to eliminate such artifacts for all forms of dose QA. Methods: EBT3 films from a single production lot (02181401) cut into rectangular 4 × 5 cm 2 pieces, with the long dimension parallel to the long dimension of the original 20.3 × 25.4 cm 2 sheets, were exposed at a depth of 5 cm on a Varian Trilogy at the center of a 20 × 20 cm 2 open field at seven doses between 50 and 1600 cGy using 6 MV photons. These films together with an unexposed film from the same production lot were lined one next to the other on an Epson 10000XL or 11000XL scanner in portrait orientation with their long dimension parallel to the scan direction. Scanned images were then obtained with the line of films positioned at seven discrete lateral locations perpendicular to the scan direction. The process was repeated in landscape orientation and on three other Epson scanners. Data were also collected for three additional production lots of EBT3 film (11051302, 03031401, and 03171403). From measurements at the various lateral positions, the scanner response was determined as a function of the lateral position of the scanned film. For a given color channel X, the response at any lateral position L is related to the response at the center, C, of the scanner by Response(C, D, X) = A L,X + B L,X ⋅Response(L, D, X), where D is dose and the coefficients A L,X and B L,X are determined from the film measurements at the center of the scanner and six other discrete lateral positions. The values at intermediate lateral positions were obtained by linear interpolation. The coefficients were determined for the red, green, and blue color channels, preserving the ability to apply triple-channel dosimetry once corrections were applied to compensate for

  17. Correcting lateral response artifacts from flatbed scanners for radiochromic film dosimetry.

    Science.gov (United States)

    Lewis, David; Chan, Maria F

    2015-01-01

    A known factor affecting the accuracy of radiochromic film dosimetry is the lateral response artifact (LRA) induced by nonuniform response of a flatbed scanner in the direction perpendicular to the scan direction. This work reports a practical solution to eliminate such artifacts for all forms of dose QA. EBT3 films from a single production lot (02181401) cut into rectangular 4 × 5 cm(2) pieces, with the long dimension parallel to the long dimension of the original 20.3 × 25.4 cm(2) sheets, were exposed at a depth of 5 cm on a Varian Trilogy at the center of a 20 × 20 cm(2) open field at seven doses between 50 and 1600 cGy using 6 MV photons. These films together with an unexposed film from the same production lot were lined one next to the other on an Epson 10000 XL or 11000 XL scanner in portrait orientation with their long dimension parallel to the scan direction. Scanned images were then obtained with the line of films positioned at seven discrete lateral locations perpendicular to the scan direction. The process was repeated in landscape orientation and on three other Epson scanners. Data were also collected for three additional production lots of EBT3 film (11051302, 03031401, and 03171403). From measurements at the various lateral positions, the scanner response was determined as a function of the lateral position of the scanned film. For a given color channel X, the response at any lateral position L is related to the response at the center, C, of the scanner by Response(C, D, X) = A(L,X) + B(L,X) ⋅ Response(L, D, X), where D is dose and the coefficients A(L,X) and B(L,X) are determined from the film measurements at the center of the scanner and six other discrete lateral positions. The values at intermediate lateral positions were obtained by linear interpolation. The coefficients were determined for the red, green, and blue color channels, preserving the ability to apply triple-channel dosimetry once corrections were applied to compensate for the

  18. Correcting lateral response artifacts from flatbed scanners for radiochromic film dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, David [RCF Consulting, LLC, 54 Benedict Road, Monroe, Connecticut 06468 (United States); Chan, Maria F., E-mail: chanm@mskcc.org [Memorial Sloan-Kettering Cancer Center, 136 Mountain View Boulevard, Basking Ridge, New Jersey 07920 (United States)

    2015-01-15

    Purpose: A known factor affecting the accuracy of radiochromic film dosimetry is the lateral response artifact (LRA) induced by nonuniform response of a flatbed scanner in the direction perpendicular to the scan direction. This work reports a practical solution to eliminate such artifacts for all forms of dose QA. Methods: EBT3 films from a single production lot (02181401) cut into rectangular 4 × 5 cm{sup 2} pieces, with the long dimension parallel to the long dimension of the original 20.3 × 25.4 cm{sup 2} sheets, were exposed at a depth of 5 cm on a Varian Trilogy at the center of a 20 × 20 cm{sup 2} open field at seven doses between 50 and 1600 cGy using 6 MV photons. These films together with an unexposed film from the same production lot were lined one next to the other on an Epson 10000XL or 11000XL scanner in portrait orientation with their long dimension parallel to the scan direction. Scanned images were then obtained with the line of films positioned at seven discrete lateral locations perpendicular to the scan direction. The process was repeated in landscape orientation and on three other Epson scanners. Data were also collected for three additional production lots of EBT3 film (11051302, 03031401, and 03171403). From measurements at the various lateral positions, the scanner response was determined as a function of the lateral position of the scanned film. For a given color channel X, the response at any lateral position L is related to the response at the center, C, of the scanner by Response(C, D, X) = A{sub L,X} + B{sub L,X}⋅Response(L, D, X), where D is dose and the coefficients A{sub L,X} and B{sub L,X} are determined from the film measurements at the center of the scanner and six other discrete lateral positions. The values at intermediate lateral positions were obtained by linear interpolation. The coefficients were determined for the red, green, and blue color channels, preserving the ability to apply triple-channel dosimetry once

  19. Large-conductance Ca2+-activated K+ channel β1-subunit knockout mice are not hypertensive

    Science.gov (United States)

    Garver, Hannah; Galligan, James J.; Fink, Gregory D.

    2011-01-01

    Large-conductance Ca2+-activated K+ (BK) channels are composed of pore-forming α-subunits and accessory β1-subunits that modulate Ca2+ sensitivity. BK channels regulate arterial myogenic tone and renal Na+ clearance/K+ reabsorption. Previous studies using indirect or short-term blood pressure measurements found that BK channel β1-subunit knockout (BK β1-KO) mice were hypertensive. We evaluated 24-h mean arterial pressure (MAP) and heart rate in BK β1-KO mice using radiotelemetry. BK β1-KO mice did not have a higher 24-h average MAP when compared with wild-type (WT) mice, although MAP was ∼10 mmHg higher at night. The dose-dependent peak declines in MAP by nifedipine were only slightly larger in BK β1-KO mice. In BK β1-KO mice, giving 1% NaCl to mice to drink for 7 days caused a transient (5 days) elevation of MAP (∼5 mmHg); MAP returned to pre-saline levels by day 6. BK β1-KO mesenteric arteries in vitro demonstrated diminished contractile responses to paxilline, increased reactivity to Bay K 8644 and norepinephrine (NE), and maintained relaxation to isoproterenol. Paxilline and Bay K 8644 did not constrict WT or BK β1-KO mesenteric veins (MV). BK β1-subunits are not expressed in MV. The results indicate that BK β1-KO mice are not hypertensive on normal or high-salt intake. BK channel deficiency increases arterial reactivity to NE and L-type Ca2+ channel function in vitro, but the L-type Ca2+ channel modulation of MAP is not altered in BK β1-KO mice. BK and L-type Ca2+ channels do not modulate murine venous tone. It appears that selective loss of BK channel function in arteries only is not sufficient to cause sustained hypertension. PMID:21131476

  20. Rate estimates for lateral bedrock erosion based on radiocarbon ages, Duck River, Tennessee

    International Nuclear Information System (INIS)

    Brakenridge, G.R.

    1985-01-01

    Rates of bedrock erosion in ingrown meandering rivers can be inferred from the location of buried relict flood-plain and river-bank surfaces, associated paleosols, and radiocarbon dates. Two independent methods are used to evaluate the long-term rates of limestone bedrock erosion by the Duck River. Radiocarbon dates on samples retrieved from buried Holocene flood-plain and bank surfaces indicate lateral migration of the river bank at average rates of 0.6-1.9 m/100 yr. Such rates agree with lateral bedrock cliff erosion rates of 0.5-1.4 m/100 yr, as determined from a comparison of late Pleistocene and modern bedrock cliff and terrace scarp positions. These results show that lateral bedrock erosion by this river could have occurred coevally with flood-plain and terrace formation and that the resulting evolution of valley meander bends carved into bedrock is similar in many respects to that of channel meanders cut into alluvium. 11 references, 5 figures

  1. Selective spider toxins reveal a role for Nav1.1 channel in mechanical pain

    Science.gov (United States)

    Osteen, Jeremiah D.; Herzig, Volker; Gilchrist, John; Emrick, Joshua J.; Zhang, Chuchu; Wang, Xidao; Castro, Joel; Garcia-Caraballo, Sonia; Grundy, Luke; Rychkov, Grigori Y.; Weyer, Andy D.; Dekan, Zoltan; Undheim, Eivind A. B.; Alewood, Paul; Stucky, Cheryl L.; Brierley, Stuart M.; Basbaum, Allan I.; Bosmans, Frank; King, Glenn F.; Julius, David

    2016-01-01

    Voltage-gated sodium (Nav) channels initiate action potentials in most neurons, including primary afferent nerve fibers of the pain pathway. Local anesthetics block pain through non-specific actions at all Nav channels, but the discovery of selective modulators would facilitate the analysis of individual subtypes and their contributions to chemical, mechanical, or thermal pain. Here, we identify and characterize spider toxins that selectively activate the Nav1.1 subtype, whose role in nociception and pain has not been explored. We exploit these probes to demonstrate that Nav1.1-expressing fibers are modality-specific nociceptors: their activation elicits robust pain behaviors without neurogenic inflammation and produces profound hypersensitivity to mechanical, but not thermal, stimuli. In the gut, high-threshold mechanosensitive fibers also express Nav1.1 and show enhanced toxin sensitivity in a model of irritable bowel syndrome. Altogether, these findings establish an unexpected role for Nav1.1 in regulating the excitability of sensory nerve fibers that underlie mechanical pain. PMID:27281198

  2. Surface dynamics of voltage-gated ion channels

    Science.gov (United States)

    Heine, Martin; Ciuraszkiewicz, Anna; Voigt, Andreas; Heck, Jennifer; Bikbaev, Arthur

    2016-01-01

    ABSTRACT Neurons encode information in fast changes of the membrane potential, and thus electrical membrane properties are critically important for the integration and processing of synaptic inputs by a neuron. These electrical properties are largely determined by ion channels embedded in the membrane. The distribution of most ion channels in the membrane is not spatially uniform: they undergo activity-driven changes in the range of minutes to days. Even in the range of milliseconds, the composition and topology of ion channels are not static but engage in highly dynamic processes including stochastic or activity-dependent transient association of the pore-forming and auxiliary subunits, lateral diffusion, as well as clustering of different channels. In this review we briefly discuss the potential impact of mobile sodium, calcium and potassium ion channels and the functional significance of this for individual neurons and neuronal networks. PMID:26891382

  3. Structural basis for KV7.1/KCNEx interactions in the IKs channel complex

    DEFF Research Database (Denmark)

    Lundby, Alicia; Tseng, Gea-Ny; Schmitt, Nicole

    2010-01-01

    The cardiac I(Ks) current is involved in action potential repolarization, where its primary function is to limit action potential prolongation during sympathetic stimulation. The I(Ks) channel is mainly composed of K(V)7.1 ion channels associated with KCNE1 auxiliary subunits. The availability of...

  4. A novel PKD2L1 C-terminal domain critical for trimerization and channel function.

    Science.gov (United States)

    Zheng, Wang; Hussein, Shaimaa; Yang, JungWoo; Huang, Jun; Zhang, Fan; Hernandez-Anzaldo, Samuel; Fernandez-Patron, Carlos; Cao, Ying; Zeng, Hongbo; Tang, Jingfeng; Chen, Xing-Zhen

    2015-03-30

    As a transient receptor potential (TRP) superfamily member, polycystic kidney disease 2-like-1 (PKD2L1) is also called TRPP3 and has similar membrane topology as voltage-gated cation channels. PKD2L1 is involved in hedgehog signaling, intestinal development, and sour tasting. PKD2L1 and PKD1L3 form heterotetramers with 3:1 stoichiometry. C-terminal coiled-coil-2 (CC2) domain (G699-W743) of PKD2L1 was reported to be important for its trimerization but independent studies showed that CC2 does not affect PKD2L1 channel function. It thus remains unclear how PKD2L1 proteins oligomerize into a functional channel. By SDS-PAGE, blue native PAGE and mutagenesis we here identified a novel C-terminal domain called C1 (K575-T622) involved in stronger homotrimerization than the non-overlapping CC2, and found that the PKD2L1 N-terminus is critical for dimerization. By electrophysiology and Xenopus oocyte expression, we found that C1, but not CC2, is critical for PKD2L1 channel function. Our co-immunoprecipitation and dynamic light scattering experiments further supported involvement of C1 in trimerization. Further, C1 acted as a blocking peptide that inhibits PKD2L1 trimerization as well as PKD2L1 and PKD2L1/PKD1L3 channel function. Thus, our study identified C1 as the first PKD2L1 domain essential for both PKD2L1 trimerization and channel function, and suggest that PKD2L1 and PKD2L1/PKD1L3 channels share the PKD2L1 trimerization process.

  5. Excitation of fluorescent nanoparticles by channel plasmon polaritons propagating in V-grooves

    DEFF Research Database (Denmark)

    Cuesta, Irene Fernandez; Nielsen, Rasmus Bundgaard; Boltasseva, Alexandra

    2009-01-01

    Recently, it has been proven that light can be squeezed into metallic channels with subwavelength lateral dimensions. Here, we present the study of the propagation of channel plasmon polaritons confined in gold V-grooves, filled with fluorescent particles. In this way, channel plasmon polaritons......-diameter beads, we show the possibility of individual excitation, what may have applications to develop very sensitive biosensors....

  6. Inward rectifier potassium channels in the HL-1 cardiomyocyte-derived cell line.

    Science.gov (United States)

    Goldoni, Dana; Zhao, YouYou; Green, Brian D; McDermott, Barbara J; Collins, Anthony

    2010-11-01

    HL-1 is a line of immortalized cells of cardiomyocyte origin that are a useful complement to native cardiomyocytes in studies of cardiac gene regulation. Several types of ion channel have been identified in these cells, but not the physiologically important inward rectifier K(+) channels. Our aim was to identify and characterize inward rectifier K(+) channels in HL-1 cells. External Ba(2+) (100 µM) inhibited 44 ± 0.05% (mean ± s.e.m., n = 11) of inward current in whole-cell patch-clamp recordings. The reversal potential of the Ba(2+)-sensitive current shifted with external [K(+)] as expected for K(+)-selective channels. The slope conductance of the inward Ba(2+)-sensitive current increased with external [K(+)]. The apparent Kd for Ba(2+) was voltage dependent, ranging from 15 µM at -150  mV to 148 µM at -75  mV in 120  mM external K(+). This current was insensitive to 10 µM glybenclamide. A component of whole-cell current was sensitive to 150 µM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), although it did not correspond to the Ba(2+)-sensitive component. The effect of external 1 mM Cs(+) was similar to that of Ba(2+). Polymerase chain reaction using HL-1 cDNA as template and primers specific for the cardiac inward rectifier K(ir)2.1 produced a fragment of the expected size that was confirmed to be K(ir)2.1 by DNA sequencing. In conclusion, HL-1 cells express a current that is characteristic of cardiac inward rectifier K(+) channels, and express K(ir)2.1 mRNA. This cell line may have use as a system for studying inward rectifier gene regulation in a cardiomyocyte phenotype. © 2010 Wiley-Liss, Inc.

  7. 1,4,2-Benzo/pyridodithiazine 1,1-dioxides structurally related to the ATP-sensitive potassium channel openers 1,2,4-Benzo/pyridothiadiazine 1,1-dioxides exert a myorelaxant activity linked to a distinct mechanism of action.

    Science.gov (United States)

    Pirotte, Bernard; de Tullio, Pascal; Florence, Xavier; Goffin, Eric; Somers, Fabian; Boverie, Stéphane; Lebrun, Philippe

    2013-04-25

    The synthesis of diversely substituted 3-alkyl/aralkyl/arylamino-1,4,2-benzodithiazine 1,1-dioxides and 3-alkylaminopyrido[4,3-e]-1,4,2-dithiazine 1,1-dioxides is described. Their biological activities on pancreatic β-cells and on smooth muscle cells were compared to those of the reference ATP-sensitive potassium channel (KATP channel) openers diazoxide and 7-chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide. The aim was to assess the impact on biological activities of the replacement of the 1,2,4-thiadiazine ring by an isosteric 1,4,2-dithiazine ring. Most of the dithiazine analogues were found to be inactive on the pancreatic tissue, although some compounds bearing a 1-phenylethylamino side chain at the 3-position exerted a marked myorelaxant activity. Such an effect did not appear to be related to the opening of KATP channels but rather reflected a mechanism of action similar to that of calcium channel blockers. Tightly related 3-(1-phenylethyl)sulfanyl-4H-1,2,4-benzothiadiazine 1,1-dioxides were also found to exert a pronounced myorelaxant activity, resulting from both a KATP channel activation and a calcium channel blocker mechanism. The present work highlights the critical importance of an intracyclic NH group at the 4-position, as well as an exocyclic NH group linked to the 3-position of the benzo- and pyridothiadiazine dioxides, for activity on KATP channels.

  8. 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.

  9. Direct proton conductance through the TRPV1 pore and multimerization of TRPV channel subunits

    OpenAIRE

    Hellwig, Nicole Barbara

    2010-01-01

    TRPV1-induced intracellular acidification: The vanilloid receptor-related transient receptor potential channels (TRPV) belong to the superfamily of hexahelical cation channels and are integral components of thermosensation, pain perception and Ca2+-reabsorption in kidney and intestine. The vanilloid receptor (TRPV1), a poorly selective cation channel, is expressed in dorsal root ganglion (DRG) neurons and is regulated by diverse stimuli including capsaicin, endovanilloids and heat. Since a...

  10. Properties of electroantennograms in flies

    NARCIS (Netherlands)

    Kelling, FJ; den Otter, CJ

    1999-01-01

    By varying the positions of electrodes on the antenna, it was revealed that EAGs from globular antennae measure the summated receptor potentials over the cuticula of olfactory receptor neurons near the electrode. Two effects of acids were found: 1. Using low doses of acids, EAGs reflect the

  11. 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...

  12. Anti-calmodulins and tricyclic adjuvants in pain therapy block the TRPV1 channel.

    Directory of Open Access Journals (Sweden)

    Zoltán Oláh

    2007-06-01

    Full Text Available Ca(2+-loaded calmodulin normally inhibits multiple Ca(2+-channels upon dangerous elevation of intracellular Ca(2+ and protects cells from Ca(2+-cytotoxicity, so blocking of calmodulin should theoretically lead to uncontrolled elevation of intracellular Ca(2+. Paradoxically, classical anti-psychotic, anti-calmodulin drugs were noted here to inhibit Ca(2+-uptake via the vanilloid inducible Ca(2+-channel/inflamatory pain receptor 1 (TRPV1, which suggests that calmodulin inhibitors may block pore formation and Ca(2+ entry. Functional assays on TRPV1 expressing cells support direct, dose-dependent inhibition of vanilloid-induced (45Ca(2+-uptake at microM concentrations: calmidazolium (broad range > or = trifluoperazine (narrow range chlorpromazine/amitriptyline>fluphenazine>>W-7 and W-13 (only partially. Most likely a short acidic domain at the pore loop of the channel orifice functions as binding site either for Ca(2+ or anti-calmodulin drugs. Camstatin, a selective peptide blocker of calmodulin, inhibits vanilloid-induced Ca(2+-uptake in intact TRPV1(+ cells, and suggests an extracellular site of inhibition. TRPV1(+, inflammatory pain-conferring nociceptive neurons from sensory ganglia, were blocked by various anti-psychotic and anti-calmodulin drugs. Among them, calmidazolium, the most effective calmodulin agonist, blocked Ca(2+-entry by a non-competitive kinetics, affecting the TRPV1 at a different site than the vanilloid binding pocket. Data suggest that various calmodulin antagonists dock to an extracellular site, not found in other Ca(2+-channels. Calmodulin antagonist-evoked inhibition of TRPV1 and NMDA receptors/Ca(2+-channels was validated by microiontophoresis of calmidazolium to laminectomised rat monitored with extracellular single unit recordings in vivo. These unexpected findings may explain empirically noted efficacy of clinical pain adjuvant therapy that justify efforts to develop hits into painkillers, selective to sensory Ca(2

  13. TRPV1 channels and the progesterone receptor Sig-1R interact to regulate pain.

    Science.gov (United States)

    Ortíz-Rentería, Miguel; Juárez-Contreras, Rebeca; González-Ramírez, Ricardo; Islas, León D; Sierra-Ramírez, Félix; Llorente, Itzel; Simon, Sidney A; Hiriart, Marcia; Rosenbaum, Tamara; Morales-Lázaro, Sara L

    2018-02-13

    The Transient Receptor Potential Vanilloid 1 (TRPV1) ion channel is expressed in nociceptors where, when activated by chemical or thermal stimuli, it functions as an important transducer of painful and itch-related stimuli. Although the interaction of TRPV1 with proteins that regulate its function has been previously explored, their modulation by chaperones has not been elucidated, as is the case for other mammalian TRP channels. Here we show that TRPV1 physically interacts with the Sigma 1 Receptor (Sig-1R), a chaperone that binds progesterone, an antagonist of Sig-1R and an important neurosteroid associated to the modulation of pain. Antagonism of Sig-1R by progesterone results in the down-regulation of TRPV1 expression in the plasma membrane of sensory neurons and, consequently, a decrease in capsaicin-induced nociceptive responses. This is observed both in males treated with a synthetic antagonist of Sig-1R and in pregnant females where progesterone levels are elevated. This constitutes a previously undescribed mechanism by which TRPV1-dependent nociception and pain can be regulated.

  14. Zinc release in the lateral nucleus of the amygdala by stimulation of the entorhinal cortex.

    Science.gov (United States)

    Takeda, Atsushi; Imano, Sachie; Itoh, Hiromasa; Oku, Naoto

    2006-11-06

    Zinc release in the lateral nucleus of the amygdala was examined using rat brain slices. The lateral and basolateral nuclei in the amygdala were evidently stained by Timm's sulfide-silver staining method. When the amygdala including both the nuclei was stimulated with 100 mM KCl by means of in vivo microdialysis, extracellular zinc concentration was increased significantly. Zinc release in the lateral nucleus of the amygdala innervated by the entorhinal cortex was next examined in brain slices double-stained with zinc and calcium indicators. Extracellular zinc signal (ZnAF-2) in the lateral nucleus was increased with intracellular calcium signal (calcium orange) during delivery of tetanic stimuli to the entorhinal cortex. Both the increases were completely inhibited by addition of 1 micro M tetrodotoxin, a sodium channel blocker. Furthermore, calcium signal in the lateral nucleus during delivery of tetanic stimuli to the entorhinal cortex was increased in the presence of 10 micro M CNQX, an AMPA/KA receptor antagonist, and this increase was facilitated by addition of 1 mM CaEDTA, a membrane-impermeable zinc chelator. The present study suggested that zinc is released in the lateral nucleus of the amygdala by depolarization of the entorhinal neurons. In the lateral nucleus, zinc released may suppress the increase in presynaptic calcium signal.

  15. Regimes of Two-Phase Flow in Short Rectangular Channel

    Science.gov (United States)

    Chinnov, Evgeny A.; Guzanov, Vladimir V.; Cheverda, Vyacheslav; Markovich, Dmitry M.; Kabov, Oleg A.

    2009-08-01

    Experimental study of two-phase flow in the short rectangular horizontal channel with height 440 μm has been performed. Characteristics of liquid motion inside the channel have been registered and measured by the Laser Induced Fluorescence technique. New information has allowed determining more precisely the characteristics of churn regime and boundaries between different regimes of two-phase flow. It was shown that formation of some two-phase flow regimes and transitions between them are determined by instability of the flow in the lateral parts of the channel.

  16. TRPV1 channels in human skeletal muscle feed arteries: implications for vascular function.

    Science.gov (United States)

    Ives, Stephen J; Park, Song Young; Kwon, Oh Sung; Gifford, Jayson R; Andtbacka, Robert H I; Hyngstrom, John R; Richardson, Russell S

    2017-09-01

    What is the central question of this study? We sought to determine whether human skeletal muscle feed arteries (SFMAs) express TRPV 1 channels and what role they play in modulating vascular function. What is the main finding and its importance? Human SMFAs do express functional TRPV 1 channels that modulate vascular function, specifically opposing α-adrenergic receptor-mediated vasocontraction and potentiating vasorelaxation, in an endothelium-dependent manner, as evidenced by the α 1 -receptor-mediated responses. Thus, the vasodilatory role of TRPV 1 channels, and their ligand capsaicin, could be a potential therapeutic target for improving vascular function. Additionally, given the 'sympatholytic' effect of TRPV 1 activation and known endogenous activators (anandamide, reactive oxygen species, H + , etc.), TRPV 1 channels might contribute to functional sympatholysis during exercise. To examine the role of the transient receptor potential vanilloid type 1 (TRPV 1 ) ion channel in the vascular function of human skeletal muscle feed arteries (SMFAs) and whether activation of this heat-sensitive receptor could be involved in modulating vascular function, SMFAs from 16 humans (63 ± 5 years old, range 41-89 years) were studied using wire myography with capsaicin (TRPV 1 agonist) and without (control). Specifically, phenylephrine (α 1 -adrenergic receptor agonist), dexmedetomidine (α 2 -adrenergic receptor agonist), ACh and sodium nitroprusside concentration-response curves were established to assess the role of TRPV 1 channels in α-receptor-mediated vasocontraction as well as endothelium-dependent and -independent vasorelaxation, respectively. Compared with control conditions, capsaicin significantly attenuated maximal vasocontraction in response to phenylephrine [control, 52 ± 8% length-tension max (LT max ) and capsaicin, 21 ± 5%LT max ] and dexmedetomidine (control, 29 ± 12%LT max and capsaicin, 2 ± 3%LT max ), while robustly enhancing maximal

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

    Directory of Open Access Journals (Sweden)

    Locke Emily

    2004-11-01

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

  18. Point mutations in the transmembrane region of the clic1 ion channel selectively modify its biophysical properties.

    Directory of Open Access Journals (Sweden)

    Stefania Averaimo

    Full Text Available Chloride intracellular Channel 1 (CLIC1 is a metamorphic protein that changes from a soluble cytoplasmic protein into a transmembrane protein. Once inserted into membranes, CLIC1 multimerises and is able to form chloride selective ion channels. Whilst CLIC1 behaves as an ion channel both in cells and in artificial lipid bilayers, its structure in the soluble form has led to some uncertainty as to whether it really is an ion channel protein. CLIC1 has a single putative transmembrane region that contains only two charged residues: arginine 29 (Arg29 and lysine 37 (Lys37. As charged residues are likely to have a key role in ion channel function, we hypothesized that mutating them to neutral alanine to generate K37A and R29A CLIC1 would alter the electrophysiological characteristics of CLIC1. By using three different electrophysiological approaches: i single channel Tip-Dip in artificial bilayers using soluble recombinant CLIC1, ii cell-attached and iii whole-cell patch clamp recordings in transiently transfected HEK cells, we determined that the K37A mutation altered the single-channel conductance while the R29A mutation affected the single-channel open probability in response to variation in membrane potential. Our results show that mutation of the two charged amino acids (K37 and R29 in the putative transmembrane region of CLIC1 alters the biophysical properties of the ion channel in both artificial bilayers and cells. Hence these charged residues are directly involved in regulating its ion channel activity. This strongly suggests that, despite its unusual structure, CLIC1 itself is able to form a chloride ion channel.

  19. NEK1 variants confer susceptibility to amyotrophic lateral sclerosis

    NARCIS (Netherlands)

    Kenna, Kevin P.; van Doormaal, Perry T. C.; Dekker, Annelot M.; Ticozzi, Nicola; Kenna, Brendan J.; Diekstra, Frank P.; van Rheenen, Wouter; van Eijk, Kristel R.; Jones, Ashley R.; Keagle, Pamela; Shatunov, Aleksey; Sproviero, William; Smith, Bradley N.; van Es, Michael A.; Topp, Simon D.; Kenna, Aoife; Miller, Jack W.; Fallini, Claudia; Tiloca, Cinzia; McLaughlin, Russell L.; Vance, Caroline; Troakes, Claire; Colombrita, Claudia; Mora, Gabriele; Calvo, Andrea; Verde, Federico; Al-Sarraj, Safa; King, Andrew; Calini, Daniela; de Belleroche, Jacqueline; Baas, Frank; van der Kooi, Anneke J.; de Visser, Marianne; ten Asbroek, Anneloor L. M. A.; Sapp, Peter C.; McKenna-Yasek, Diane; Polak, Meraida; Asress, Seneshaw; Muñoz-Blanco, José Luis; Strom, Tim M.; Meitinger, Thomas; Morrison, Karen E.; Lauria, Giuseppe; Williams, Kelly L.; Leigh, P. Nigel; Nicholson, Garth A.; Blair, Ian P.; Leblond, Claire S.; Dion, Patrick A.; Rouleau, Guy A.

    2016-01-01

    To identify genetic factors contributing to amyotrophic lateral sclerosis (ALS), we conducted whole-exome analyses of 1,022 index familial ALS (FALS) cases and 7,315 controls. In a new screening strategy, we performed gene-burden analyses trained with established ALS genes and identified a

  20. Distinct roles of the DmNav and DSC1 channels in the action of DDT and pyrethroids.

    Science.gov (United States)

    Rinkevich, Frank D; Du, Yuzhe; Tolinski, Josh; Ueda, Atsushi; Wu, Chun-Fang; Zhorov, Boris S; Dong, Ke

    2015-03-01

    Voltage-gated sodium channels (Nav channels) are critical for electrical signaling in the nervous system and are the primary targets of the insecticides DDT and pyrethroids. In Drosophila melanogaster, besides the canonical Nav channel, Para (also called DmNav), there is a sodium channel-like cation channel called DSC1 (Drosophila sodium channel 1). Temperature-sensitive paralytic mutations in DmNav (para(ts)) confer resistance to DDT and pyrethroids, whereas DSC1 knockout flies exhibit enhanced sensitivity to pyrethroids. To further define the roles and interaction of DmNav and DSC1 channels in DDT and pyrethroid neurotoxicology, we generated a DmNav/DSC1 double mutant line by introducing a para(ts1) allele (carrying the I265N mutation) into a DSC1 knockout line. We confirmed that the I265N mutation reduced the sensitivity to two pyrethroids, permethrin and deltamethrin of a DmNav variant expressed in Xenopus oocytes. Computer modeling predicts that the I265N mutation confers pyrethroid resistance by allosterically altering the second pyrethroid receptor site on the DmNav channel. Furthermore, we found that I265N-mediated pyrethroid resistance in para(ts1) mutant flies was almost completely abolished in para(ts1);DSC1(-/-) double mutant flies. Unexpectedly, however, the DSC1 knockout flies were less sensitive to DDT, compared to the control flies (w(1118A)), and the para(ts1);DSC1(-/-) double mutant flies were even more resistant to DDT compared to the DSC1 knockout or para(ts1) mutant. Our findings revealed distinct roles of the DmNav and DSC1 channels in the neurotoxicology of DDT vs. pyrethroids and implicate the exciting possibility of using DSC1 channel blockers or modifiers in the management of pyrethroid resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. A possible CO2 conducting and concentrating mechanism in plant stomata SLAC1 channel.

    Directory of Open Access Journals (Sweden)

    Qi-Shi Du

    Full Text Available BACKGROUND: The plant SLAC1 is a slow anion channel in the membrane of stomatal guard cells, which controls the turgor pressure in the aperture-defining guard cells, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals such as drought, high levels of carbon dioxide, and bacterial invasion. Recent study demonstrated that bicarbonate is a small-molecule activator of SLAC1. Higher CO(2 and HCO(3(- concentration activates S-type anion channel currents in wild-type Arabidopsis guard cells. Based on the SLAC1 structure a theoretical model is derived to illustrate the activation of bicarbonate to SLAC1 channel. Meanwhile a possible CO(2 conducting and concentrating mechanism of the SLAC1 is proposed. METHODOLOGY: The homology structure of Arabidopsis thaliana SLAC1 (AtSLAC1 provides the structural basis for study of the conducting and concentrating mechanism of carbon dioxide in SLAC1 channels. The pK(a values of ionizable amino acid side chains in AtSLAC1 are calculated using software PROPKA3.0, and the concentration of CO(2 and anion HCO(3(- are computed based on the chemical equilibrium theory. CONCLUSIONS: The AtSLAC1 is modeled as a five-region channel with different pH values. The top and bottom layers of channel are the alkaline residue-dominated regions, and in the middle of channel there is the acidic region surrounding acidic residues His332. The CO(2 concentration is enhanced around 10(4 times by the pH difference between these regions, and CO(2 is stored in the hydrophobic region, which is a CO(2 pool. The pH driven CO(2 conduction from outside to inside balances the back electromotive force and maintain the influx of anions (e.g. Cl(- and NO(3(- from inside to outside. SLAC1 may be a pathway providing CO(2 for photosynthesis in the guard cells.

  2. The development of a laterally confined laboratory fan delta under sediment supply reduction

    Science.gov (United States)

    Zhang, Xiaofeng; Wang, Siqiang; Wu, Xi; Xu, Shun; Li, Zhangyong

    2016-03-01

    In previous fan delta experiments, the effect of lateral confinement was generally ignored as these fans were usually unconfined with semiconical geometries. However, in gorge areas, fan development is usually laterally confined by valley walls. This study investigates autogenic processes of fan deltas in a laterally confined experimental tank. The experiment is divided into three phases. The sediment supply is held constant within each phase, so the autogenic processes of the fan are separated from the allogenic forcings. Results indicate that laterally confined fan deltas have higher progradation and aggradation potential, more regular channel braiding, and more even transverse sedimentation than unconfined fans. Besides, responses of fan deltas to sediment supply reduction are investigated in this research. At the initiation of the second and third phases, sediment feed rates are instantaneously reduced so that the allogenic forcings are predominant. Observations show that under sediment supply reduction, channelization on fan deltas are more pronounced and durations of the fluvial cycles are longer. The adjustment of fan morphology becomes slower as the self-regulation capacity of the fan decreases with reduced sediment supply.

  3. 1 D analysis of Radiative Shock damping by lateral radiative losses

    Science.gov (United States)

    Busquet, Michel; Audit, Edouard

    2008-11-01

    We have demonstrated the effect of the lateral radiative losses in radiative shocks propagative in layered quasi-planar atmospheres.[1,2] The damping of the precursor is sensitive to the fraction of self-emitted radiation reflected by the walls (called albedo) We have given recently an experimental determination of the wall albedo.[2] For parametric analysis of this effect, we implement lateral losses in the 1D hydro-rad code MULTI [3] and compared results with 2D simulations. [1] S.Leygnac, et al., Phys. Plasmas 13, 113301 (2006) [2] M.Busquet, et al, High Energy Density Plasmas 3, 8-11 (2007); M.Gonzalez, et al, Laser Part. Beams 24, 1-6 (2006) [3] Ramis et al, Comp. Phys. Comm., 49, 475 (1988)

  4. The Function of the Novel Mechanical Activated Ion Channel Piezo1 in the Human Osteosarcoma Cells

    OpenAIRE

    Jiang, Long; Zhao, Yi-ding; Chen, Wei-xiang

    2017-01-01

    Background The Piezo1 protein ion channel is a novel mechanical activated ion channel which is related to mechanical signal transduction. However, the function of the mechanically activated ion channel Piezo1 had not been explored. In this study, we explored the function of the Piezo1 ion channel in human osteosarcoma (OS) cells related to apoptosis, invasion, and the cell proliferation. Material/Methods Reverse transcription polymerase chain reaction (RT-PCR) and western-blotting were used t...

  5. A negative charge in transmembrane segment 1 of domain II of the cockroach sodium channel is critical for channel gating and action of pyrethroid insecticides

    International Nuclear Information System (INIS)

    Du Yuzhe; Song Weizhong; Groome, James R.; Nomura, Yoshiko; Luo Ningguang; Dong Ke

    2010-01-01

    Voltage-gated sodium channels are the primary target of pyrethroids, an important class of synthetic insecticides. Pyrethroids bind to a distinct receptor site on sodium channels and prolong the open state by inhibiting channel deactivation and inactivation. Recent studies have begun to reveal sodium channel residues important for pyrethroid binding. However, how pyrethroid binding leads to inhibition of sodium channel deactivation and inactivation remains elusive. In this study, we show that a negatively charged aspartic acid residue at position 802 (D802) located in the extracellular end of transmembrane segment 1 of domain II (IIS1) is critical for both the action of pyrethroids and the voltage dependence of channel activation. Charge-reversing or -neutralizing substitutions (K, G, or A) of D802 shifted the voltage dependence of activation in the depolarizing direction and reduced channel sensitivity to deltamethrin, a pyrethroid insecticide. The charge-reversing mutation D802K also accelerated open-state deactivation, which may have counteracted the inhibition of sodium channel deactivation by deltamethrin. In contrast, the D802G substitution slowed open-state deactivation, suggesting an additional mechanism for neutralizing the action of deltamethrin. Importantly, Schild analysis showed that D802 is not involved in pyrethroid binding. Thus, we have identified a sodium channel residue that is critical for regulating the action of pyrethroids on the sodium channel without affecting the receptor site of pyrethroids.

  6. ATP Release Channels

    Directory of Open Access Journals (Sweden)

    Akiyuki Taruno

    2018-03-01

    Full Text Available Adenosine triphosphate (ATP has been well established as an important extracellular ligand of autocrine signaling, intercellular communication, and neurotransmission with numerous physiological and pathophysiological roles. In addition to the classical exocytosis, non-vesicular mechanisms of cellular ATP release have been demonstrated in many cell types. Although large and negatively charged ATP molecules cannot diffuse across the lipid bilayer of the plasma membrane, conductive ATP release from the cytosol into the extracellular space is possible through ATP-permeable channels. Such channels must possess two minimum qualifications for ATP permeation: anion permeability and a large ion-conducting pore. Currently, five groups of channels are acknowledged as ATP-release channels: connexin hemichannels, pannexin 1, calcium homeostasis modulator 1 (CALHM1, volume-regulated anion channels (VRACs, also known as volume-sensitive outwardly rectifying (VSOR anion channels, and maxi-anion channels (MACs. Recently, major breakthroughs have been made in the field by molecular identification of CALHM1 as the action potential-dependent ATP-release channel in taste bud cells, LRRC8s as components of VRACs, and SLCO2A1 as a core subunit of MACs. Here, the function and physiological roles of these five groups of ATP-release channels are summarized, along with a discussion on the future implications of understanding these channels.

  7. Structure of Voltage-gated Two-pore Channel TPC1 from Arabidopsis thaliana

    Science.gov (United States)

    Guo, Jiangtao; Zeng, Weizhong; Chen, Qingfeng; Lee, Changkeun; Chen, Liping; Yang, Yi; Cang, Chunlei; Ren, Dejian; Jiang, Youxing

    2015-01-01

    Two-pore channels (TPCs) contain two copies of a Shaker-like six-transmembrane (6-TM) domain in each subunit and are ubiquitously expressed in both animals and plants as organellar cation channels. Here, we present the first crystal structure of a vacuolar two-pore channel from Arabidopsis thaliana, AtTPC1, which functions as a homodimer. AtTPC1 activation requires both voltage and cytosolic Ca2+. Ca2+ binding to the cytosolic EF-hand domain triggers conformational changes coupled to the pair of pore-lining inner helices (IS6 helices) from the first 6-TM domains, whereas membrane potential only activates the second voltage-sensing domain (VSD2) whose conformational changes are coupled to the pair of inner helices (IIS6 helices) from the second 6-TM domains. Luminal Ca2+ or Ba2+ can modulate voltage activation by stabilizing VSD2 in the resting state and shifts voltage activation towards more positive potentials. Our Ba2+ bound AtTPC1 structure reveals a voltage sensor in the resting state, providing hitherto unseen structural insight into the general voltage-gating mechanism among voltage-gated channels. PMID:26689363

  8. Voltage-Gated Potassium Channels Kv1.3--Potentially New Molecular Target in Cancer Diagnostics and Therapy.

    Science.gov (United States)

    Teisseyre, Andrzej; Gąsiorowska, Justyna; Michalak, Krystyna

    2015-01-01

    Voltage-gated potassium channels, Kv1.3, which were discovered in 1984, are integral membrane proteins which are activated ("open") upon change of the cell membrane potential, enabling a passive flux of potassium ions across the cell membrane. The channels are expressed in many different tissues, both normal and cancer. Since 2005 it has been known that the channels are expressed not only in the plasma membrane, but also in the inner mitochondrial membrane. The activity of Kv1.3 channels plays an important role, among others, in setting the cell resting membrane potential, cell proliferation, apoptosis and volume regulation. For some years, these channels have been considered a potentially new molecular target in both the diagnostics and therapy of some cancer diseases. This review article focuses on: 1) changes of expression of the channels in cancer disorders with special regard to correlations between the channels' expression and stage of the disease, 2) influence of inhibitors of Kv1.3 channels on proliferation and apoptosis of cancer cells, 3) possible future applications of Kv1.3 channels' inhibitors in therapy of some cancer diseases. In the last section, the results of studies performed in our Laboratory of Bioelectricity on the influence of selected biologically active plant-derived compounds from the groups of flavonoids and stilbenes and their natural and synthetic derivatives on the activity of Kv1.3 channels in normal and cancer cells are reviewed. A possible application of some compounds from these groups to support therapy of cancer diseases, such as breast, colon and lymph node cancer, and melanoma or chronic lymphocytic leukemia (B-CLL), is announced.

  9. Testosterone-mediated upregulation of delayed rectifier potassium channel in cardiomyocytes causes abbreviation of QT intervals in rats.

    Science.gov (United States)

    Masuda, Kimiko; Takanari, Hiroki; Morishima, Masaki; Ma, FangFang; Wang, Yan; Takahashi, Naohiko; Ono, Katsushige

    2018-01-13

    Men have shorter rate-corrected QT intervals (QTc) than women, especially at the period of adolescence or later. The aim of this study was to elucidate the long-term effects of testosterone on cardiac excitability parameters including electrocardiogram (ECG) and potassium channel current. Testosterone shortened QT intervals in ECG in castrated male rats, not immediately after, but on day 2 or later. Expression of Kv7.1 (KCNQ1) mRNA was significantly upregulated by testosterone in cardiomyocytes of male and female rats. Short-term application of testosterone was without effect on delayed rectifier potassium channel current (I Ks ), whereas I Ks was significantly increased in cardiomyocytes treated with dihydrotestosterone for 24 h, which was mimicked by isoproterenol (24 h). Gene-selective inhibitors of a transcription factor SP1, mithramycin, abolished the effects of testosterone on Kv7.1. Testosterone increases Kv7.1-I Ks possibly through a pathway related to a transcription factor SP1, suggesting a genomic effect of testosterone as an active factor for cardiac excitability.

  10. Neuron-specific antioxidant OXR1 extends survival of a mouse model of amyotrophic lateral sclerosis.

    Science.gov (United States)

    Liu, Kevin X; Edwards, Benjamin; Lee, Sheena; Finelli, Mattéa J; Davies, Ben; Davies, Kay E; Oliver, Peter L

    2015-05-01

    Amyotrophic lateral sclerosis is a devastating neurodegenerative disorder characterized by the progressive loss of spinal motor neurons. While the aetiological mechanisms underlying the disease remain poorly understood, oxidative stress is a central component of amyotrophic lateral sclerosis and contributes to motor neuron injury. Recently, oxidation resistance 1 (OXR1) has emerged as a critical regulator of neuronal survival in response to oxidative stress, and is upregulated in the spinal cord of patients with amyotrophic lateral sclerosis. Here, we tested the hypothesis that OXR1 is a key neuroprotective factor during amyotrophic lateral sclerosis pathogenesis by crossing a new transgenic mouse line that overexpresses OXR1 in neurons with the SOD1(G93A) mouse model of amyotrophic lateral sclerosis. Interestingly, we report that overexpression of OXR1 significantly extends survival, improves motor deficits, and delays pathology in the spinal cord and in muscles of SOD1(G93A) mice. Furthermore, we find that overexpression of OXR1 in neurons significantly delays non-cell-autonomous neuroinflammatory response, classic complement system activation, and STAT3 activation through transcriptomic analysis of spinal cords of SOD1(G93A) mice. Taken together, these data identify OXR1 as the first neuron-specific antioxidant modulator of pathogenesis and disease progression in SOD1-mediated amyotrophic lateral sclerosis, and suggest that OXR1 may serve as a novel target for future therapeutic strategies. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain.

  11. Padrões de identidade e qualidade de fermentados acéticos comerciais de frutas e vegetais Quality pattern and identity of commercial fruit and vegetable vinegar (Acetic acid fermentation

    Directory of Open Access Journals (Sweden)

    Fabíola Pedrosa Peixoto Marques

    2010-05-01

    Full Text Available Este trabalho objetivou identificar padrões de identidade e qualidade de vinagres e quantificar a presença de compostos fenólicos totais em vinagres produzidos a partir de frutas e vegetais. Analisaram-se, em triplicata, vinagres de cana-de-açúcar, cana-de-açúcar com milho, kiwi, laranja, laranja com mel, maçã, arroz, manga, maracujá, milho, tangerina, tangerina com milho, vinagre de vinho tinto e vinagre de vinho branco. Foram realizadas análises de extrato seco, densidade, acidez volátil, pH, cinzas, grau alcoólico, açúcares redutores e polifenóis totais. Os resultados foram submetidos à ANOVA e as médias destes ao teste de Tukey ao nível de 5%. Houve correlação estatística entre extrato seco e densidade. Todas as amostras apresentaram valores de 0% de álcool. A presença do mel na formulação do vinagre de laranja com mel (43,27 mg EAG 100.mL-1 contribuiu para o aumento do conteúdo de polifenóis totais em relação ao de laranja (28,83 mg EAG.100 mL-1 em 50%. O fermentado de laranja com mel apresentou teor de polifenóis totais (43,27 mg EAG.100 mL-1 maior que o vinagre de vinho tinto (31,86 mg EAG.100 mL-1, assim como os de laranja e tangerina (34,36 mg EAG.100 mL-1. Conclui-se que houve diferenças entre as amostras para os parâmetros analisados e que os fermentados acéticos de laranja com mel, laranja e tangerina apresentam maior conteúdo de polifenóis totais que o de vinho tinto.This work aimed to identify the patterns of identity and quality of vinegars and quantify the presence of total phenolics compounds in fruit and vegetable vinegars, Vinegars made from sugar cane, sugar cane and corn, kiwi, orange, orange and honey, apple, rice, mango, passion fruit, corn, tangerine, tangerine and corn, red wine, and white wine were analyzed in triplicates. Analyses of dry extract, density, volatile acidity, pH, ashes, alcoholic content, reducing sugars, and total polyphenols were performed. The results were submitted

  12. A radiolabeled peptide ligand of the hERG channel, [125I]-BeKm-1

    DEFF Research Database (Denmark)

    Angelo, Kamilla; Korolkova, Yuliya V; Grunnet, Morten

    2003-01-01

    The wild-type scorpion toxin BeKm-1, which selectively blocks human ether-a-go-go related (hERG) channels, was radiolabeled with iodine at tyrosine 11. Both the mono- and di-iodinated derivatives were found to be biologically active. In electrophysiological patch-clamp recordings mono-[127I]-BeKm-1...... had a concentration of half-maximal inhibition (IC50 value) of 27 nM, while wild-type BeKm-1 inhibited hERG channels with an IC50 value of 7 nM. Mono-[125I]-BeKm-1 was found to bind in a concentration-dependent manner and with picomolar affinity to hERG channel protein in purified membrane vesicles...... of [125I]-BeKm-1 to the hERG channel to an IC50 of 7 nM. In autoradiographic studies on rat hearts, binding of [125I]-BeKm-1 was dose-dependent and could partially be displaced by the addition of excess amounts of non-radioactive BeKm-1. The density of the radioactive signal was equally distributed...

  13. Functional diversity of potassium channel voltage-sensing domains.

    Science.gov (United States)

    Islas, León D

    2016-01-01

    Voltage-gated potassium channels or Kv's are membrane proteins with fundamental physiological roles. They are composed of 2 main functional protein domains, the pore domain, which regulates ion permeation, and the voltage-sensing domain, which is in charge of sensing voltage and undergoing a conformational change that is later transduced into pore opening. The voltage-sensing domain or VSD is a highly conserved structural motif found in all voltage-gated ion channels and can also exist as an independent feature, giving rise to voltage sensitive enzymes and also sustaining proton fluxes in proton-permeable channels. In spite of the structural conservation of VSDs in potassium channels, there are several differences in the details of VSD function found across variants of Kvs. These differences are mainly reflected in variations in the electrostatic energy needed to open different potassium channels. In turn, the differences in detailed VSD functioning among voltage-gated potassium channels might have physiological consequences that have not been explored and which might reflect evolutionary adaptations to the different roles played by Kv channels in cell physiology.

  14. Ligand binding and conformational changes of SUR1 subunit in pancreatic ATP-sensitive potassium channels.

    Science.gov (United States)

    Wu, Jing-Xiang; Ding, Dian; Wang, Mengmeng; Kang, Yunlu; Zeng, Xin; Chen, Lei

    2018-06-01

    ATP-sensitive potassium channels (K ATP ) are energy sensors on the plasma membrane. By sensing the intracellular ADP/ATP ratio of β-cells, pancreatic K ATP channels control insulin release and regulate metabolism at the whole body level. They are implicated in many metabolic disorders and diseases and are therefore important drug targets. Here, we present three structures of pancreatic K ATP channels solved by cryo-electron microscopy (cryo-EM), at resolutions ranging from 4.1 to 4.5 Å. These structures depict the binding site of the antidiabetic drug glibenclamide, indicate how Kir6.2 (inward-rectifying potassium channel 6.2) N-terminus participates in the coupling between the peripheral SUR1 (sulfonylurea receptor 1) subunit and the central Kir6.2 channel, reveal the binding mode of activating nucleotides, and suggest the mechanism of how Mg-ADP binding on nucleotide binding domains (NBDs) drives a conformational change of the SUR1 subunit.

  15. PKC and AMPK regulation of Kv1.5 potassium channels

    DEFF Research Database (Denmark)

    Andersen, Martin Nybo; Skibsbye, Lasse; Tang, Chuyi

    2015-01-01

    The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid rectifier K(+) current (IKur), is regulated through several pathways. Here we investigate if Kv1.5 surface expression is controlled by the 2 kinases PKC and AMPK, using Xenopus oocytes, MDCK cells and atrial derived HL-1 cells....

  16. Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage.

    Science.gov (United States)

    Zaika, Oleg; Palygin, Oleg; Tomilin, Viktor; Mamenko, Mykola; Staruschenko, Alexander; Pochynyuk, Oleh

    2016-02-15

    Potassium Kir4.1/5.1 channels are abundantly expressed at the basolateral membrane of principal cells in the cortical collecting duct (CCD), where they are thought to modulate transport rates by controlling transepithelial voltage. Insulin and insulin-like growth factor-1 (IGF-1) stimulate apically localized epithelial sodium channels (ENaC) to augment sodium reabsorption in the CCD. However, little is known about their actions on potassium channels localized at the basolateral membrane. In this study, we implemented patch-clamp analysis in freshly isolated murine CCD to assess the effect of these hormones on Kir4.1/5.1 at both single channel and cellular levels. We demonstrated that K(+)-selective conductance via Kir4.1/5.1 is the major contributor to the macroscopic current recorded from the basolateral side in principal cells. Acute treatment with 10 μM amiloride (ENaC blocker), 100 nM tertiapin-Q (TPNQ; ROMK inhibitor), and 100 μM ouabain (Na(+)-K(+)-ATPase blocker) failed to produce a measurable effect on the macroscopic current. In contrast, Kir4.1 inhibitor nortriptyline (100 μM), but not fluoxetine (100 μM), virtually abolished whole cell K(+)-selective conductance. Insulin (100 nM) markedly increased the open probability of Kir4.1/5.1 and nortriptyline-sensitive whole cell current, leading to significant hyperpolarization of the basolateral membrane. Inhibition of the phosphatidylinositol 3-kinase cascade with LY294002 (20 μM) abolished action of insulin on Kir4.1/5.1. IGF-1 had similar stimulatory actions on Kir4.1/5.1-mediated conductance only when applied at a higher (500 nM) concentration and was ineffective at 100 nM. We concluded that both insulin and, to a lesser extent, IGF-1 activate Kir4.1/5.1 channel activity and open probability to hyperpolarize the basolateral membrane, thereby facilitating Na(+) reabsorption in the CCD. Copyright © 2016 the American Physiological Society.

  17. Verification of the linearity of the IPR-R1 TRIGA reactor power channels

    International Nuclear Information System (INIS)

    Souza, Rose Mary Gomes do Prado; Campolina, Daniel de Almeida Magalhaes

    2013-01-01

    The aim of this paper is to verify the linearity of the three power channels of the IPR-R1 TRIGA reactor. Located at Nuclear Technology Development Center-CDTN in Belo Horizonte, the IPR-R1 reactor is a typical 100 kW Mark I light-water reactor cooled by natural convection. When the experiments were performed, the reactor core had 59 fuel elements, containing 8% by weight of uranium enriched to 20% in 235 U. The core has cylindrical configuration with an annular graphite reflector. The responses of the detectors of the Linear, Log N and Percent Power channels were compared with the responses of detectors which only depend on the overall neutron flux within the reactor. Gold and cobalt foils were activated at low and high powers, respectively, and the specific count results were compared with measurements performed, simultaneously, with a fission chamber, and with the power registered by the three channels. The results show that the Linear channel responds linearly up to 100 kW, and the Log N channel responses are linear at low powers. In the range of high power, the Log N and the Percent Power channels exhibit linearity only from 10 kW to 50 kW. (author)

  18. Tratamento de Classe II, Divisão 1, com ausência congênita de incisivo lateral superior Treatment of Class II Division 1 with congenitally absent maxillary lateral incisor

    Directory of Open Access Journals (Sweden)

    Roberto M. A. Lima Filho

    2004-10-01

    Full Text Available Este relato mostra tratamento Ortodôntico efetuado em paciente portador de Classe II, Divisão 1, de Angle, com sobremordida profunda e agenesia do incisivo lateral superior esquerdo, em que o espaço foi fechado ortodonticamente e o canino ocupou o lugar do incisivo lateral. Os procedimentos adotados possibilitaram a obtenção de estética agradável e relação oclusal normal. A linha mediana não apresentou desvio ao término do tratamento e a discrepância vertical foi devidamente corrigida.This case report demonstrates the orthodontic treatment of a patient who presented a Class II Division 1 malocclusion, deep overbite and congenitally absent maxillary left lateral incisor. The space was closed orthodontically and maxillary cuspid was positioned in the place of the maxillary lateral incisor. The treatment applied resulted in a pleasant esthetics and normal occlusal relationship. The midline was coincident at the end of treatment and vertical discrepancy was properly corrected.

  19. Cav1.2 channels mediate persistent chronic stress-induced behavioral deficits that are associated with prefrontal cortex activation of the p25/Cdk5-glucocorticoid receptor pathway

    Directory of Open Access Journals (Sweden)

    Charlotte C. Bavley

    2017-12-01

    Full Text Available Chronic stress is known to precipitate and exacerbate neuropsychiatric symptoms, and exposure to stress is particularly pathological in individuals with certain genetic predispositions. Recent genome wide association studies have identified single nucleotide polymorphisms (SNPs in the gene CACNA1C, which codes for the Cav1.2 subunit of the L-type calcium channel (LTCC, as a common risk variant for multiple neuropsychiatric conditions. Cav1.2 channels mediate experience-dependent changes in gene expression and long-term synaptic plasticity through activation of downstream calcium signaling pathways. Previous studies have found an association between stress and altered Cav1.2 expression in the brain, however the contribution of Cav1.2 channels to chronic stress-induced behaviors, and the precise Cav1.2 signaling mechanisms activated are currently unknown. Here we report that chronic stress leads to a delayed increase in Cav1.2 expression selectively within the prefrontal cortex (PFC, but not in other stress-sensitive brain regions such as the hippocampus or amygdala. Further, we demonstrate that while Cav1.2 heterozygous (Cav1.2+/− mice show chronic stress-induced depressive-like behavior, anxiety-like behavior, and deficits in working memory 1–2 days following stress, they are resilient to the effects of chronic stress when tested 5–7 days later. Lastly, molecular studies find a delayed upregulation of the p25/Cdk5-glucocorticoid receptor (GR pathway in the PFC when examined 8 days post-stress that is absent in Cav1.2+/− mice. Our findings reveal a novel Cav1.2-mediated molecular mechanism associated with the persistent behavioral effects of chronic stress and provide new insight into potential Cav1.2 channel mechanisms that may contribute to CACNA1C-linked neuropsychiatric phenotypes.

  20. Activation of the chemosensing transient receptor potential channel A1 (TRPA1) by alkylating agents.

    Science.gov (United States)

    Stenger, Bernhard; Zehfuss, Franziska; Mückter, Harald; Schmidt, Annette; Balszuweit, Frank; Schäfer, Eva; Büch, Thomas; Gudermann, Thomas; Thiermann, Horst; Steinritz, Dirk

    2015-09-01

    The transient receptor potential ankyrin 1 (TRPA1) cation channel is expressed in different tissues including skin, lung and neuronal tissue. Recent reports identified TRPA1 as a sensor for noxious substances, implicating a functional role in the molecular toxicology. TRPA1 is activated by various potentially harmful electrophilic substances. The chemical warfare agent sulfur mustard (SM) is a highly reactive alkylating agent that binds to numerous biological targets. Although SM is known for almost 200 years, detailed knowledge about the pathophysiology resulting from exposure is lacking. A specific therapy is not available. In this study, we investigated whether the alkylating agent 2-chloroethyl-ethylsulfide (CEES, a model substance for SM-promoted effects) and SM are able to activate TRPA1 channels. CEES induced a marked increase in the intracellular calcium concentration ([Ca(2+)]i) in TRPA1-expressing but not in TRPA1-negative cells. The TRP-channel blocker AP18 diminished the CEES-induced calcium influx. HEK293 cells permanently expressing TRPA1 were more sensitive toward cytotoxic effects of CEES compared with wild-type cells. At low CEES concentrations, CEES-induced cytotoxicity was prevented by AP18. Proof-of-concept experiments using SM resulted in a pronounced increase in [Ca(2+)]i in HEK293-A1-E cells. Human A549 lung epithelial cells, which express TRPA1 endogenously, reacted with a transient calcium influx in response to CEES exposure. The CEES-dependent calcium response was diminished by AP18. In summary, our results demonstrate that alkylating agents are able to activate TRPA1. Inhibition of TRPA1 counteracted cellular toxicity and could thus represent a feasible approach to mitigate SM-induced cell damage.

  1. Bi-allelic Mutations in PKD1L1 Are Associated with Laterality Defects in Humans.

    Science.gov (United States)

    Vetrini, Francesco; D'Alessandro, Lisa C A; Akdemir, Zeynep C; Braxton, Alicia; Azamian, Mahshid S; Eldomery, Mohammad K; Miller, Kathryn; Kois, Chelsea; Sack, Virginia; Shur, Natasha; Rijhsinghani, Asha; Chandarana, Jignesh; Ding, Yan; Holtzman, Judy; Jhangiani, Shalini N; Muzny, Donna M; Gibbs, Richard A; Eng, Christine M; Hanchard, Neil A; Harel, Tamar; Rosenfeld, Jill A; Belmont, John W; Lupski, James R; Yang, Yaping

    2016-10-06

    Disruption of the establishment of left-right (L-R) asymmetry leads to situs anomalies ranging from situs inversus totalis (SIT) to situs ambiguus (heterotaxy). The genetic causes of laterality defects in humans are highly heterogeneous. Via whole-exome sequencing (WES), we identified homozygous mutations in PKD1L1 from three affected individuals in two unrelated families. PKD1L1 encodes a polycystin-1-like protein and its loss of function is known to cause laterality defects in mouse and medaka fish models. Family 1 had one fetus and one deceased child with heterotaxy and complex congenital heart malformations. WES identified a homozygous splicing mutation, c.6473+2_6473+3delTG, which disrupts the invariant splice donor site in intron 42, in both affected individuals. In the second family, a homozygous c.5072G>C (p.Cys1691Ser) missense mutation was detected in an individual with SIT and congenital heart disease. The p.Cys1691Ser substitution affects a highly conserved cysteine residue and is predicted by molecular modeling to disrupt a disulfide bridge essential for the proper folding of the G protein-coupled receptor proteolytic site (GPS) motif. Damaging effects associated with substitutions of this conserved cysteine residue in the GPS motif have also been reported in other genes, namely GPR56, BAI3, and PKD1 in human and lat-1 in C. elegans, further supporting the likely pathogenicity of p.Cys1691Ser in PKD1L1. The identification of bi-allelic PKD1L1 mutations recapitulates previous findings regarding phenotypic consequences of loss of function of the orthologous genes in mice and medaka fish and further expands our understanding of genetic contributions to laterality defects in humans. Copyright © 2016 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  2. Evidence for Dual Binding Sites for 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in Insect Sodium Channels*

    Science.gov (United States)

    Du, Yuzhe; Nomura, Yoshiko; Zhorov, Boris S.; Dong, Ke

    2016-01-01

    1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), the first organochlorine insecticide, and pyrethroid insecticides are sodium channel agonists. Although the use of DDT is banned in most of the world due to its detrimental impact on the ecosystem, indoor residual spraying of DDT is still recommended for malaria control in Africa. Development of resistance to DDT and pyrethroids is a serious global obstacle for managing disease vectors. Mapping DDT binding sites is necessary for understanding mechanisms of resistance and modulation of sodium channels by structurally different ligands. The pioneering model of the housefly sodium channel visualized the first receptor for pyrethroids, PyR1, in the II/III domain interface and suggested that DDT binds within PyR1. Previously, we proposed the second pyrethroid receptor, PyR2, at the I/II domain interface. However, whether DDT binds to both pyrethroid receptor sites remains unknown. Here, using computational docking of DDT into the Kv1.2-based mosquito sodium channel model, we predict that two DDT molecules can bind simultaneously within PyR1 and PyR2. The bulky trichloromethyl group of each DDT molecule fits snugly between four helices in the bent domain interface, whereas two p-chlorophenyl rings extend into two wings of the interface. Model-driven mutagenesis and electrophysiological analysis confirmed these propositions and revealed 10 previously unknown DDT-sensing residues within PyR1 and PyR2. Our study proposes a dual DDT-receptor model and provides a structural background for rational development of new insecticides. PMID:26637352

  3. Acid-sensing ion channel (ASIC) 1a/2a heteromers have a flexible 2:1/1:2 stoichiometry.

    Science.gov (United States)

    Bartoi, Tudor; Augustinowski, Katrin; Polleichtner, Georg; Gründer, Stefan; Ulbrich, Maximilian H

    2014-06-03

    Acid-sensing ion channels (ASICs) are widely expressed proton-gated Na(+) channels playing a role in tissue acidosis and pain. A trimeric composition of ASICs has been suggested by crystallization. Upon coexpression of ASIC1a and ASIC2a in Xenopus oocytes, we observed the formation of heteromers and their coexistence with homomers by electrophysiology, but could not determine whether heteromeric complexes have a fixed subunit stoichiometry or whether certain stoichiometries are preferred over others. We therefore imaged ASICs labeled with green and red fluorescent proteins on a single-molecule level, counted bleaching steps from GFP and colocalized them with red tandem tetrameric mCherry for many individual complexes. Combinatorial analysis suggests a model of random mixing of ASIC1a and ASIC2a subunits to yield both 2:1 and 1:2 ASIC1a:ASIC2a heteromers together with ASIC1a and ASIC2a homomers.

  4. Differentiating submarine channel-related thin-bedded turbidite facies: Outcrop examples from the Rosario Formation, Mexico

    Science.gov (United States)

    Hansen, Larissa; Callow, Richard; Kane, Ian; Kneller, Ben

    2017-08-01

    Thin-bedded turbidites deposited by sediment gravity flows that spill from submarine channels often contain significant volumes of sand in laterally continuous beds. These can make up over 50% of the channel-belt fill volume, and can thus form commercially important hydrocarbon reservoirs. Thin-bedded turbidites can be deposited in environments that include levees and depositional terraces, which are distinguished on the basis of their external morphology and internal architecture. Levees have a distinctive wedge shaped morphology, thinning away from the channel, and confine both channels (internal levees) and channel-belts (external levees). Terraces are flat-lying features that are elevated above the active channel within a broad channel-belt. Despite the ubiquity of terraces and levees in modern submarine channel systems, the recognition of these environments in outcrop and in the subsurface is challenging. In this outcrop study of the Upper Cretaceous Rosario Formation (Baja California, Mexico), lateral transects based on multiple logged sections of thin-bedded turbidites reveal systematic differences in sandstone layer thicknesses, sandstone proportion, palaeocurrents, sedimentary structures and ichnology between channel-belt and external levee thin-bedded turbidites. Depositional terrace deposits have a larger standard deviation in sandstone layer thicknesses than external levees because they are topographically lower, and experience a wider range of turbidity current sizes overspilling from different parts of the channel-belt. The thickness of sandstone layers within external levees decreases away from the channel-belt while those in depositional terraces are less laterally variable. Depositional terrace environments of the channel-belt are characterized by high bioturbation intensities, and contain distinctive trace fossil assemblages, often dominated by ichnofabrics of the echinoid trace fossil Scolicia. These assemblages contrast with the lower

  5. 5-HT1A receptors modulate small-conductance Ca2+-activated K+ channels

    DEFF Research Database (Denmark)

    Grunnet, Morten; Jespersen, Thomas; Perrier, Jean-François

    2004-01-01

    Small-conductance calcium-activated potassium channels (SK) are responsible for the medium afterhyperpolarisation (mAHP) following action potentials in neurons. Here we tested the ability of serotonin (5-HT) to modulate the activity of SK channels by coexpressing 5-HT1A receptors with different...

  6. Evidence for functional diversity between the voltage-gated proton channel Hv1 and its closest related protein HVRP1.

    Directory of Open Access Journals (Sweden)

    Iris H Kim

    Full Text Available The Hv1 channel and voltage-sensitive phosphatases share with voltage-gated sodium, potassium, and calcium channels the ability to detect changes in membrane potential through voltage-sensing domains (VSDs. However, they lack the pore domain typical of these other channels. NaV, KV, and CaV proteins can be found in neurons and muscles, where they play important roles in electrical excitability. In contrast, VSD-containing proteins lacking a pore domain are found in non-excitable cells and are not involved in neuronal signaling. Here, we report the identification of HVRP1, a protein related to the Hv1 channel (from which the name Hv1 Related Protein 1 is derived, which we find to be expressed primarily in the central nervous system, and particularly in the cerebellum. Within the cerebellar tissue, HVRP1 is specifically expressed in granule neurons, as determined by in situ hybridization and immunohistochemistry. Analysis of subcellular distribution via electron microscopy and immunogold labeling reveals that the protein localizes on the post-synaptic side of contacts between glutamatergic mossy fibers and the granule cells. We also find that, despite the similarities in amino acid sequence and structural organization between Hv1 and HVRP1, the two proteins have distinct functional properties. The high conservation of HVRP1 in vertebrates and its cellular and subcellular localizations suggest an important function in the nervous system.

  7. Properties of the intracellular transient receptor potential (TRP) channel in yeast, Yvc1.

    Science.gov (United States)

    Chang, Yiming; Schlenstedt, Gabriel; Flockerzi, Veit; Beck, Andreas

    2010-05-17

    Transient receptor potential (TRP) channels are found among mammals, flies, worms, ciliates, Chlamydomonas, and yeast but are absent in plants. These channels are believed to be tetramers of proteins containing six transmembrane domains (TMs). Their primary structures are diverse with sequence similarities only in some short amino acid sequence motifs mainly within sequences covering TM5, TM6, and adjacent domains. In the yeast genome, there is one gene encoding a TRP-like sequence. This protein forms an ion channel in the vacuolar membrane and is therefore called Yvc1 for yeast vacuolar conductance 1. In the following we summarize its prominent features. Copyright 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  8. Results of a prospective randomized controlled trial of early ambulation for patients with lower extremity autografts.

    Science.gov (United States)

    Lorello, David John; Peck, Michael; Albrecht, Marlene; Richey, Karen J; Pressman, Melissa A

    2014-01-01

    It is common practice to keep those patients with lower extremity autografts immobile until post-operative day (POD) 5. There is however inherent risks associated with even short periods of immobility. As of now there are no randomized controlled trials looking at early ambulation of patients with lower extremity autografts in the burn community.The objective of this study was to show that patients who begin ambulation within 24 hours of lower extremity autografting will have no increased risk of graft failure than those patients who remain immobile until POD 5. Thirty-one subjects who received autografts to the lower extremity were randomized after surgery into either the early ambulation group (EAG;17 subjects) or the standard treatment group (STG;14 subjects). Those subjects randomized to the EAG began ambulating with physical therapy on POD 1. Subjects in the STG maintained bed rest until POD 5. There was no difference in the number of patients with graft loss in either the EAG or STG on POD 5, and during any of the follow-up visits. No subjects required regrafting. There was a significant difference in the mean minutes of ambulation, with the EAG ambulating longer than the STG (EAG 23.4 minutes [SD 12.03], STG 14.1 [SD 9.00], P=.0235) on POD 5. Burn patients with lower extremity autografts can safely ambulate on POD 1 without fear of graft failure compared with those patients that remain on bed rest for 5 days.

  9. Channel estimation for physical layer network coding systems

    CERN Document Server

    Gao, Feifei; Wang, Gongpu

    2014-01-01

    This SpringerBrief presents channel estimation strategies for the physical later network coding (PLNC) systems. Along with a review of PLNC architectures, this brief examines new challenges brought by the special structure of bi-directional two-hop transmissions that are different from the traditional point-to-point systems and unidirectional relay systems. The authors discuss the channel estimation strategies over typical fading scenarios, including frequency flat fading, frequency selective fading and time selective fading, as well as future research directions. Chapters explore the performa

  10. Acoustic programming in step-split-flow lateral-transport thin fractionation.

    Science.gov (United States)

    Ratier, Claire; Hoyos, Mauricio

    2010-02-15

    We propose a new separation scheme for micrometer-sized particles combining acoustic forces and gravitational field in split-flow lateral-transport thin (SPLITT)-like fractionation channels. Acoustic forces are generated by ultrasonic standing waves set up in the channel thickness. We report on the separation of latex particles of two different sizes in a preliminary experiment using this proposed hydrodynamic acoustic sorter, HAS. Total binary separation of 5 and 10 microm diameter particles has been achieved. Numerical simulations of trajectories of particles flowing through a step-SPLITT under the conditions which combine acoustic standing waves and gravity show a very good agreement with the experiment. Calculations in order to compare separations obtained by the acoustic programming s-SPLITT fractionation and the conventional SPLITT fractionation show that the improvement in separation time is around 1 order of magnitude and could still be improved; this is the major finding of this work. This separation technique can be extended to biomimetic particles and blood cells.

  11. Cell volume changes regulate slick (Slo2.1), but not slack (Slo2.2) K+ channels.

    Science.gov (United States)

    Tejada, Maria A; Stople, Kathleen; Hammami Bomholtz, Sofia; Meinild, Anne-Kristine; Poulsen, Asser Nyander; Klaerke, Dan A

    2014-01-01

    Slick (Slo2.1) and Slack (Slo2.2) channels belong to the family of high-conductance K+ channels and have been found widely distributed in the CNS. Both channels are activated by Na+ and Cl- and, in addition, Slick channels are regulated by ATP. Therefore, the roles of these channels in regulation of cell excitability as well as ion transport processes, like regulation of cell volume, have been hypothesized. It is the aim of this work to evaluate the sensitivity of Slick and Slack channels to small, fast changes in cell volume and to explore mechanisms, which may explain this type of regulation. For this purpose Slick and Slack channels were co-expressed with aquaporin 1 in Xenopus laevis oocytes and cell volume changes of around 5% were induced by exposure to hypotonic or hypertonic media. Whole-cell currents were measured by two electrode voltage clamp. Our results show that Slick channels are dramatically stimulated (196% of control) by cell swelling and inhibited (57% of control) by a decrease in cell volume. In contrast, Slack channels are totally insensitive to similar cell volume changes. The mechanism underlining the strong volume sensitivity of Slick channels needs to be further explored, however we were able to show that it does not depend on an intact actin cytoskeleton, ATP release or vesicle fusion. In conclusion, Slick channels, in contrast to the similar Slack channels, are the only high-conductance K+ channels strongly sensitive to small changes in cell volume.

  12. Rearrangement of potassium ions and Kv1.1/Kv1.2 potassium channels in regenerating axons following end-to-end neurorrhaphy: ionic images from TOF-SIMS.

    Science.gov (United States)

    Liu, Chiung-Hui; Chang, Hung-Ming; Wu, Tsung-Huan; Chen, Li-You; Yang, Yin-Shuo; Tseng, To-Jung; Liao, Wen-Chieh

    2017-10-01

    The voltage-gated potassium channels Kv1.1 and Kv1.2 that cluster at juxtaparanodal (JXP) regions are essential in the regulation of nerve excitability and play a critical role in axonal conduction. When demyelination occurs, Kv1.1/Kv1.2 activity increases, suppressing the membrane potential nearly to the equilibrium potential of K + , which results in an axonal conduction blockade. The recovery of K + -dependent communication signals and proper clustering of Kv1.1/Kv1.2 channels at JXP regions may directly reflect nerve regeneration following peripheral nerve injury. However, little is known about potassium channel expression and its relationship with the dynamic potassium ion distribution at the node of Ranvier during the regenerative process of peripheral nerve injury (PNI). In the present study, end-to-end neurorrhaphy (EEN) was performed using an in vivo model of PNI. The distribution of K + at regenerating axons following EEN was detected by time-of-flight secondary-ion mass spectrometry. The specific localization and expression of Kv1.1/Kv1.2 channels were examined by confocal microscopy and western blotting. Our data showed that the re-establishment of K + distribution and intensity was correlated with the functional recovery of compound muscle action potential morphology in EEN rats. Furthermore, the re-clustering of Kv1.1/1.2 channels 1 and 3 months after EEN at the nodal region of the regenerating nerve corresponded to changes in the K + distribution. This study provided direct evidence of K + distribution in regenerating axons for the first time. We proposed that the Kv1.1/Kv1.2 channels re-clustered at the JXP regions of regenerating axons are essential for modulating the proper patterns of K + distribution in axons for maintaining membrane potential stability after EEN.

  13. Functional expression of TRPM8 and TRPA1 channels in rat odontoblasts.

    Directory of Open Access Journals (Sweden)

    Maki Tsumura

    Full Text Available Odontoblasts produce dentin during development, throughout life, and in response to pathological conditions by sensing stimulation of exposed dentin. The functional properties and localization patterns of transient receptor potential (TRP melastatin subfamily member 8 (TRPM8 and ankyrin subfamily member 1 (TRPA1 channels in odontoblasts remain to be clarified. We investigated the localization and the pharmacological, biophysical, and mechano-sensitive properties of TRPM8 and TRPA1 channels in rat odontoblasts. Menthol and icilin increased the intracellular free Ca(2+ concentration ([Ca(2+]i. Icilin-, WS3-, or WS12-induced [Ca(2+]i increases were inhibited by capsazepine or 5-benzyloxytriptamine. The increase in [Ca(2+]i elicited by allyl isothiocyanate (AITC was inhibited by HC030031. WS12 and AITC exerted a desensitizing effect on [Ca(2+]i increase. Low-temperature stimuli elicited [Ca(2+]i increases that are sensitive to both 5-benzyloxytriptamine and HC030031. Hypotonic stimulation-induced membrane stretch increased [Ca(2+]i; HC030031 but not 5-benzyloxytriptamine inhibited the effect. The results suggest that TRPM8 channels in rat odontoblasts play a role in detecting low-temperature stimulation of the dentin surface and that TRPA1 channels are involved in sensing membrane stretching and low-temperature stimulation. The results also indicate that odontoblasts act as mechanical and thermal receptor cells, detecting the stimulation of exposed dentin to drive multiple cellular functions, such as sensory transduction.

  14. Tungstate-targeting of BKαβ1 channels tunes ERK phosphorylation and cell proliferation in human vascular smooth muscle.

    Directory of Open Access Journals (Sweden)

    Ana Isabel Fernández-Mariño

    Full Text Available Despite the substantial knowledge on the antidiabetic, antiobesity and antihypertensive actions of tungstate, information on its primary target/s is scarce. Tungstate activates both the ERK1/2 pathway and the vascular voltage- and Ca2+-dependent large-conductance BKαβ1 potassium channel, which modulates vascular smooth muscle cell (VSMC proliferation and function, respectively. Here, we have assessed the possible involvement of BKαβ1 channels in the tungstate-induced ERK phosphorylation and its relevance for VSMC proliferation. Western blot analysis in HEK cell lines showed that expression of vascular BKαβ1 channels potentiates the tungstate-induced ERK1/2 phosphorylation in a Gi/o protein-dependent manner. Tungstate activated BKαβ1 channels upstream of G proteins as channel activation was not altered by the inhibition of G proteins with GDPβS or pertussis toxin. Moreover, analysis of Gi/o protein activation measuring the FRET among heterologously expressed Gi protein subunits suggested that tungstate-targeting of BKαβ1 channels promotes G protein activation. Single channel recordings on VSMCs from wild-type and β1-knockout mice indicated that the presence of the regulatory β1 subunit was essential for the tungstate-mediated activation of BK channels in VSMCs. Moreover, the specific BK channel blocker iberiotoxin lowered tungstate-induced ERK phosphorylation by 55% and partially reverted (by 51% the tungstate-produced reduction of platelet-derived growth factor (PDGF-induced proliferation in human VSMCs. Our observations indicate that tungstate-targeting of BKαβ1 channels promotes activation of PTX-sensitive Gi proteins to enhance the tungstate-induced phosphorylation of ERK, and inhibits PDGF-stimulated cell proliferation in human vascular smooth muscle.

  15. Laser--Doppler anemometry technique applied to two-phase dispersed flows in a rectangular channel

    International Nuclear Information System (INIS)

    Lee, S.L.; Srinivasan, J.

    1979-01-01

    A new optical technique using Laser--Doppler anemometry has been applied to the local measurement of turbulent upward flow of a dilute water droplet--air two-phase dispersion in a vertical rectangular channel. Individually examined were over 20,000 droplet signals coming from each of a total of ten transversely placed measuring points, the closest of which to the channel wall was 250 μ away from the wall. Two flows of different patterns due to different imposed flow conditions were investigated, one with and the other without a liquid film formed on the channel wall. Reported are the size and number density distribution and the axial and lateral velocity distributions for the droplets as well as the axial and lateral velocity distributions for the air

  16. El Tor hemolysin of Vibrio cholerae O1 forms channels in planar lipid bilayer membranes.

    Science.gov (United States)

    Ikigai, H; Ono, T; Iwata, M; Nakae, T; Shimamura, T

    1997-05-15

    We investigated the channel formation by El Tor hemolysin (molecular mass, 65 kDa) of Vibrio cholerae O1 biotype El Tor in planar lipid bilayers. The El Tor hemolysin channel exhibited asymmetric and hyperbolic membrane current with increasing membrane potential, meaning that the channel is voltage dependent. The zero-current membrane potential measured in KCI solution showed that permeability ratio PK+/PCl- was 0.16, indicating that the channel is 6-fold more anion selective over cation. The hemolysin channel frequently flickered in the presence of divalent cations, suggesting that the channel spontaneously opens and closes. These data imply that the El Tor hemolysin damages target cells by the formation of transmembrane channels and, consequently, is the cause of osmotic cytolysis.

  17. Reduced Sodium Current in the Lateral Ventricular Wall Induces Inferolateral J-Waves.

    Science.gov (United States)

    Meijborg, Veronique M F; Potse, Mark; Conrath, Chantal E; Belterman, Charly N W; De Bakker, Jacques M T; Coronel, Ruben

    2016-01-01

    J-waves in inferolateral leads are associated with a higher risk for idiopathic ventricular fibrillation. We aimed to test potential mechanisms (depolarization or repolarization dependent) responsible for inferolateral J-waves. We hypothesized that inferolateral J-waves can be caused by regional delayed activation of myocardium that is activated late during normal conditions. Computer simulations were performed to evaluate how J-point elevation is influenced by reducing sodium current conductivity (GNa), increasing transient outward current conductivity (Gto), or cellular uncoupling in three predefined ventricular regions (lateral, anterior, or septal). Two pig hearts were Langendorff-perfused with selective perfusion with a sodium channel blocker of lateral or anterior/septal regions. Volume-conducted pseudo-electrocardiograms (ECG) were recorded to detect the presence of J-waves. Epicardial unipolar electrograms were simultaneously recorded to obtain activation times (AT). Simulation data showed that conduction slowing, caused by reduced sodium current, in lateral, but not in other regions induced inferolateral J-waves. An increase in transient outward potassium current or cellular uncoupling in the lateral zone elicited slight J-point elevations which did not meet J-wave criteria. Additional conduction slowing in the entire heart attenuated J-waves and J-point elevations on the ECG, because of masking by the QRS. Experimental data confirmed that conduction slowing attributed to sodium channel blockade in the left lateral but not in the anterior/septal ventricular region induced inferolateral J-waves. J-waves coincided with the delayed activation. Reduced sodium current in the left lateral ventricular myocardium can cause inferolateral J-waves on the ECG.

  18. Experimental test results of multi-channel test rig of T1 test section, 5

    International Nuclear Information System (INIS)

    Hino, Ryutaro; Takase, Kazuyuki; Miyamoto, Yoshiaki

    1990-09-01

    Channel blockage test on a fuel column of the high temperature engineering test reactor (HTTR) has been performed under the helium gas atmosphere at a high temperature and a high pressure in order to obtain safety data on flow rate and temperature distributions in the fuel column with the multi-channel test rig of the fuel stack test section (T 1 ) in HENDEL. In the test, one of 12 fuel channels was blockaded to 90% of flow area at the channel inlet. Experimental results showed that the helium gas flow rate in the blockaded channel was 28%∼33% lower than the average flow rate for Reynolds number from 2300 to 14000 in isothermal flow. When simulated fuel rods were heated, the flow rate in the blockaded channel did not decrease down in comparison with the isothermal flow. This is due to that the heat generated in the fuel rods conducts to the other fuel channels in graphite fuel blocks, so that accelerated pressure losses in the fuel channels change with helium gas temperatures. (author)

  19. Characterization of hERG1a and hERG1b potassium channels-a possible role for hERG1b in the I (Kr) current

    DEFF Research Database (Denmark)

    Larsen, Anders Peter; Olesen, Søren-Peter; Grunnet, Morten

    2008-01-01

    I (Kr) is the fast component of the delayed rectifier potassium currents responsible for the repolarization of the cardiac muscle. The molecular correlate underlying the I (Kr) current has been identified as the hERG1 channel. Recently, two splice variants of the hERG1 alpha-subunit, hERG1a and hERG......1b, have been shown to be co-expressed in human cardiomyocytes. In this paper, we present the electrophysiological characterization of hERG1a, hERG1b, and co-expressed hERG1a/b channels in a mammalian expression system using the whole-cell patch clamp technique. We also quantified the messenger RNA...... (mRNA) levels of hERG1a and hERG1b in human cardiac tissue, and based on the expressed ratios, we evaluated the resulting currents in Xenopus laevis oocytes. Compared to hERG1a channels, activation was faster for both hERG1b and hERG1a/b channels. The deactivation kinetics was greatly accelerated...

  20. Cav1.3 channels control D2-autoreceptor responses via NCS-1 in substantia nigra dopamine neurons

    Science.gov (United States)

    Dragicevic, Elena; Poetschke, Christina; Duda, Johanna; Schlaudraff, Falk; Lammel, Stephan; Schiemann, Julia; Fauler, Michael; Hetzel, Andrea; Watanabe, Masahiko; Lujan, Rafael; Malenka, Robert C.; Striessnig, Joerg

    2014-01-01

    Dopamine midbrain neurons within the substantia nigra are particularly prone to degeneration in Parkinson’s disease. Their selective loss causes the major motor symptoms of Parkinson’s disease, but the causes for the high vulnerability of SN DA neurons, compared to neighbouring, more resistant ventral tegmental area dopamine neurons, are still unclear. Consequently, there is still no cure available for Parkinson’s disease. Current therapies compensate the progressive loss of dopamine by administering its precursor l-DOPA and/or dopamine D2-receptor agonists. D2-autoreceptors and Cav1.3-containing L-type Ca2+ channels both contribute to Parkinson’s disease pathology. L-type Ca2+ channel blockers protect SN DA neurons from degeneration in Parkinson’s disease and its mouse models, and they are in clinical trials for neuroprotective Parkinson’s disease therapy. However, their physiological functions in SN DA neurons remain unclear. D2-autoreceptors tune firing rates and dopamine release of SN DA neurons in a negative feedback loop through activation of G-protein coupled potassium channels (GIRK2, or KCNJ6). Mature SN DA neurons display prominent, non-desensitizing somatodendritic D2-autoreceptor responses that show pronounced desensitization in PARK-gene Parkinson’s disease mouse models. We analysed surviving human SN DA neurons from patients with Parkinson’s disease and from controls, and detected elevated messenger RNA levels of D2-autoreceptors and GIRK2 in Parkinson’s disease. By electrophysiological analysis of postnatal juvenile and adult mouse SN DA neurons in in vitro brain-slices, we observed that D2-autoreceptor desensitization is reduced with postnatal maturation. Furthermore, a transient high-dopamine state in vivo, caused by one injection of either l-DOPA or cocaine, induced adult-like, non-desensitizing D2-autoreceptor responses, selectively in juvenile SN DA neurons, but not ventral tegmental area dopamine neurons. With pharmacological

  1. Twenty-four-hour exposure to altered blood flow modifies endothelial Ca2+-activated K+ channels in rat mesenteric arteries

    DEFF Research Database (Denmark)

    Hilgers, Rob H P; Janssen, Ger M J; Fazzi, Gregorio E

    2010-01-01

    We tested the hypothesis that changes in arterial blood flow modify the function of endothelial Ca2+-activated K+ channels [calcium-activated K+ channel (K(Ca)), small-conductance calcium-activated K+ channel (SK3), and intermediate calcium-activated K+ channel (IK1)] before arterial structural...... remodeling. In rats, mesenteric arteries were exposed to increased [+90%, high flow (HF)] or reduced blood flow [-90%, low flow (LF)] and analyzed 24 h later. There were no detectable changes in arterial structure or in expression level of endothelial nitric-oxide synthase, SK3, or IK1. Arterial relaxing...... arteries, the balance between the NO/prostanoid versus EDHF response was unaltered. However, the contribution of IK1 to the EDHF response was enhanced, as indicated by a larger effect of TRAM-34 and a larger residual NS309-induced relaxation in the presence of UCL 1684. Reduction of blood flow selectively...

  2. Evidence for Dual Binding Sites for 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in Insect Sodium Channels.

    Science.gov (United States)

    Du, Yuzhe; Nomura, Yoshiko; Zhorov, Boris S; Dong, Ke

    2016-02-26

    1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), the first organochlorine insecticide, and pyrethroid insecticides are sodium channel agonists. Although the use of DDT is banned in most of the world due to its detrimental impact on the ecosystem, indoor residual spraying of DDT is still recommended for malaria control in Africa. Development of resistance to DDT and pyrethroids is a serious global obstacle for managing disease vectors. Mapping DDT binding sites is necessary for understanding mechanisms of resistance and modulation of sodium channels by structurally different ligands. The pioneering model of the housefly sodium channel visualized the first receptor for pyrethroids, PyR1, in the II/III domain interface and suggested that DDT binds within PyR1. Previously, we proposed the second pyrethroid receptor, PyR2, at the I/II domain interface. However, whether DDT binds to both pyrethroid receptor sites remains unknown. Here, using computational docking of DDT into the Kv1.2-based mosquito sodium channel model, we predict that two DDT molecules can bind simultaneously within PyR1 and PyR2. The bulky trichloromethyl group of each DDT molecule fits snugly between four helices in the bent domain interface, whereas two p-chlorophenyl rings extend into two wings of the interface. Model-driven mutagenesis and electrophysiological analysis confirmed these propositions and revealed 10 previously unknown DDT-sensing residues within PyR1 and PyR2. Our study proposes a dual DDT-receptor model and provides a structural background for rational development of new insecticides. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. Electroantennogram Responses to Plant Volatiles Associated with Fenvalerate Resistance in the Diamondback Moth, Plutella xylostella (Lepidoptera: Plutellidae).

    Science.gov (United States)

    Houjun, Tian; Lin, Shuo; Chen, Yong; Chen, Yixin; Zhao, Jianwei; Gu, Xiaojun; Wei, Hui

    2018-05-28

    The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is the main destructive insect pest of brassica vegetables around the world, and has developed resistance to numerous insecticides. Although host plant volatiles are important in pest control, the mechanism of low-level insecticide resistance in P. xylostella due to plant volatiles has not been examined. Here, electroantennograms (EAGs) were used to compare the responses of adult male and female DBMs of a susceptible strain (S-strain) and a derived resistant strain, Fen-R-strain (6.52-fold more resistant than the S-strain), to different concentrations of nine plant volatiles. We found significantly different relative EAG responses between S-strain and Fen-R-strain males to different concentrations of methyl jasmonate, methyl salicylate, and octanal. The relative EAG responses of S-strain and Fen-R-strain females to different concentrations of β-myrcene, methyl jasmonate, methyl salicylate, and allyl isothiocyanate were significantly different. Fen-R-strain females showed lower EAG responses to most of the tested plant volatiles (at concentrations of 1:10) than males, except for allyl isothiocyanate. A larger difference in relative EAG response to α-farnesene and β-myrcene was found between S-strain and Fen-R-strain females than between males of the two strains. A larger difference in relative EAG response to octanal, nonanal, and octan-1-ol was found between S-strain and Fen-R-strain males than between females of the two strains. These results illustrate the relationship between the function of plant volatiles and resistance in an insect pest species, and provide a scientific basis for resistance evolutionary theory in pest management research.

  4. Loss of Transient Receptor Potential Ankyrin 1 Channel Deregulates Emotion, Learning and Memory, Cognition, and Social Behavior in Mice.

    Science.gov (United States)

    Lee, Kuan-I; Lin, Hui-Ching; Lee, Hsueh-Te; Tsai, Feng-Chuan; Lee, Tzong-Shyuan

    2017-07-01

    The transient receptor potential ankyrin 1 (TRPA1) channel is a non-selective cation channel that helps regulate inflammatory pain sensation and nociception and the development of inflammatory diseases. However, the potential role of the TRPA1 channel and the underlying mechanism in brain functions are not fully resolved. In this study, we demonstrated that genetic deletion of the TRPA1 channel in mice or pharmacological inhibition of its activity increased neurite outgrowth. In vivo study in mice provided evidence of the TRPA1 channel as a negative regulator in hippocampal functions; functional ablation of the TRPA1 channel in mice enhanced hippocampal functions, as evidenced by less anxiety-like behavior, and enhanced fear-related or spatial learning and memory, and novel location recognition as well as social interactions. However, the TRPA1 channel appears to be a prerequisite for motor function; functional loss of the TRPA1 channel in mice led to axonal bundle fragmentation, downregulation of myelin basic protein, and decreased mature oligodendrocyte population in the brain, for impaired motor function. The TRPA1 channel may play a crucial role in neuronal development and oligodendrocyte maturation and be a potential regulator in emotion, cognition, learning and memory, and social behavior.

  5. Nimbus-7 Earth radiation budget calibration history. Part 1: The solar channels

    Science.gov (United States)

    Kyle, H. Lee; Hoyt, Douglas V.; Hickey, John R.; Maschhoff, Robert H.; Vallette, Brenda J.

    1993-01-01

    The Earth Radiation Budget (ERB) experiment on the Nimbus-7 satellite measured the total solar irradiance plus broadband spectral components on a nearly daily basis from 16 Nov. 1978, until 16 June 1992. Months of additional observations were taken in late 1992 and in 1993. The emphasis is on the electrically self calibrating cavity radiometer, channel 10c, which recorded accurate total solar irradiance measurements over the whole period. The spectral channels did not have inflight calibration adjustment capabilities. These channels can, with some additional corrections, be used for short-term studies (one or two solar rotations - 27 to 60 days), but not for long-term trend analysis. For channel 10c, changing radiometer pointing, the zero offsets, the stability of the gain, the temperature sensitivity, and the influences of other platform instruments are all examined and their effects on the measurements considered. Only the question of relative accuracy (not absolute) is examined. The final channel 10c product is also compared with solar measurements made by independent experiments on other satellites. The Nimbus experiment showed that the mean solar energy was about 0.1 percent (1.4 W/sqm) higher in the excited Sun years of 1979 and 1991 than in the quiet Sun years of 1985 and 1986. The error analysis indicated that the measured long-term trends may be as accurate as +/- 0.005 percent. The worse-case error estimate is +/- 0.03 percent.

  6. Coarse architecture of the transient receptor potential vanilloid 1 (TRPV1) ion channel determined by fluorescence resonance energy transfer.

    Science.gov (United States)

    De-la-Rosa, Víctor; Rangel-Yescas, Gisela E; Ladrón-de-Guevara, Ernesto; Rosenbaum, Tamara; Islas, León D

    2013-10-11

    The transient receptor potential vanilloid 1 ion channel is responsible for the perception of high temperatures and low extracellular pH, and it is also involved in the response to some pungent compounds. Importantly, it is also associated with the perception of pain and noxious stimuli. Here, we attempt to discern the molecular organization and location of the N and C termini of the transient receptor potential vanilloid 1 ion channel by measuring FRET between genetically attached enhanced yellow and cyan fluorescent protein to the N or C terminus of the channel protein, expressed in transfected HEK 293 cells or Xenopus laevis oocytes. The static measurements of the domain organization were mapped into an available cryo-electron microscopy density of the channel with good agreement. These measurements also provide novel insights into the organization of terminal domains and their proximity to the plasma membrane.

  7. Channel properties of Nax expressed in neurons.

    Directory of Open Access Journals (Sweden)

    Masahito Matsumoto

    Full Text Available Nax is a sodium-concentration ([Na+]-sensitive Na channel with a gating threshold of ~150 mM for extracellular [Na+] ([Na+]o in vitro. We previously reported that Nax was preferentially expressed in the glial cells of sensory circumventricular organs including the subfornical organ, and was involved in [Na+] sensing for the control of salt-intake behavior. Although Nax was also suggested to be expressed in the neurons of some brain regions including the amygdala and cerebral cortex, the channel properties of Nax have not yet been adequately characterized in neurons. We herein verified that Nax was expressed in neurons in the lateral amygdala of mice using an antibody that was newly generated against mouse Nax. To investigate the channel properties of Nax expressed in neurons, we established an inducible cell line of Nax using the mouse neuroblastoma cell line, Neuro-2a, which is endogenously devoid of the expression of Nax. Functional analyses of this cell line revealed that the [Na+]-sensitivity of Nax in neuronal cells was similar to that expressed in glial cells. The cation selectivity sequence of the Nax channel in cations was revealed to be Na+ ≈ Li+ > Rb+ > Cs+ for the first time. Furthermore, we demonstrated that Nax bound to postsynaptic density protein 95 (PSD95 through its PSD95/Disc-large/ZO-1 (PDZ-binding motif at the C-terminus in neurons. The interaction between Nax and PSD95 may be involved in promoting the surface expression of Nax channels because the depletion of endogenous PSD95 resulted in a decrease in Nax at the plasma membrane. These results indicated, for the first time, that Nax functions as a [Na+]-sensitive Na channel in neurons as well as in glial cells.

  8. KCNE4 is an inhibitory subunit to Kv1.1 and Kv1.3 potassium channels

    DEFF Research Database (Denmark)

    Grunnet, Morten; Rasmussen, Hannne B; Hay-Schmidt, Anders

    2003-01-01

    is detected in the heart and in five different parts of the brain. Having the broad distribution of Kv1 channels in mind, the demonstrated inhibitory property of KCNE4-subunits could locally and/or transiently have a dramatic influence on cellular excitability and on setting resting membrane potentials....

  9. Cell volume changes regulate slick (Slo2.1, but not slack (Slo2.2 K+ channels.

    Directory of Open Access Journals (Sweden)

    Maria A Tejada

    Full Text Available Slick (Slo2.1 and Slack (Slo2.2 channels belong to the family of high-conductance K+ channels and have been found widely distributed in the CNS. Both channels are activated by Na+ and Cl- and, in addition, Slick channels are regulated by ATP. Therefore, the roles of these channels in regulation of cell excitability as well as ion transport processes, like regulation of cell volume, have been hypothesized. It is the aim of this work to evaluate the sensitivity of Slick and Slack channels to small, fast changes in cell volume and to explore mechanisms, which may explain this type of regulation. For this purpose Slick and Slack channels were co-expressed with aquaporin 1 in Xenopus laevis oocytes and cell volume changes of around 5% were induced by exposure to hypotonic or hypertonic media. Whole-cell currents were measured by two electrode voltage clamp. Our results show that Slick channels are dramatically stimulated (196% of control by cell swelling and inhibited (57% of control by a decrease in cell volume. In contrast, Slack channels are totally insensitive to similar cell volume changes. The mechanism underlining the strong volume sensitivity of Slick channels needs to be further explored, however we were able to show that it does not depend on an intact actin cytoskeleton, ATP release or vesicle fusion. In conclusion, Slick channels, in contrast to the similar Slack channels, are the only high-conductance K+ channels strongly sensitive to small changes in cell volume.

  10. A three-dimensional stratigraphic model for aggrading submarine channels based on laboratory experiments, numerical modeling, and sediment cores

    Science.gov (United States)

    Limaye, A. B.; Komatsu, Y.; Suzuki, K.; Paola, C.

    2017-12-01

    Turbidity currents deliver clastic sediment from continental margins to the deep ocean, and are the main driver of landscape and stratigraphic evolution in many low-relief, submarine environments. The sedimentary architecture of turbidites—including the spatial organization of coarse and fine sediments—is closely related to the aggradation, scour, and lateral shifting of channels. Seismic stratigraphy indicates that submarine, meandering channels often aggrade rapidly relative to lateral shifting, and develop channel sand bodies with high vertical connectivity. In comparison, the stratigraphic architecture developed by submarine, braided is relatively uncertain. We present a new stratigraphic model for submarine braided channels that integrates predictions from laboratory experiments and flow modeling with constraints from sediment cores. In the laboratory experiments, a saline density current developed subaqueous channels in plastic sediment. The channels aggraded to form a deposit with a vertical scale of approximately five channel depths. We collected topography data during aggradation to (1) establish relative stratigraphic age, and (2) estimate the sorting patterns of a hypothetical grain size distribution. We applied a numerical flow model to each topographic surface and used modeled flow depth as a proxy for relative grain size. We then conditioned the resulting stratigraphic model to observed grain size distributions using sediment core data from the Nankai Trough, offshore Japan. Using this stratigraphic model, we establish new, quantitative predictions for the two- and three-dimensional connectivity of coarse sediment as a function of fine-sediment fraction. Using this case study as an example, we will highlight outstanding challenges in relating the evolution of low-relief landscapes to the stratigraphic record.

  11. Olfactory antennal responses of the black vine weevil (Otiorhynchus sulcatus) to plant volatiles

    NARCIS (Netherlands)

    Tol, van R.W.H.M.; Visser, J.H.

    2002-01-01

    Electroantennograms (EAGs) were recorded from the vine weevil, Otiorhynchus sulcatus F. (Coleoptera: Curculionidae) to a broad range of volatile plant compounds. The response profile is restricted to a small number of volatiles that evoke substantial EAGs. Large EAG responses were particularly found

  12. The role of hERG1 ion channels in epithelial-mesenchymal transition and the capacity of riluzole to reduce cisplatin resistance in colorectal cancer cells.

    Science.gov (United States)

    Fortunato, Angelo

    2017-08-01

    The transition of cells from the epithelial to the mesenchymal state (EMT) plays an important role in tumor progression. EMT allows cells to acquire mobility, stem-like behavior and resistance to apoptosis and drug treatment. These features turn EMT into a central process in tumor biology. Ion channels are attractive targets for the treatment of cancer since they play critical roles in controlling a wide range of physiological processes that are frequently deregulated in cancer. Here, we investigated the role of ether-a-go-go-related 1 (hERG1) ion channels in the EMT of colorectal cancer cells. We studied the epithelial-mesenchymal profile of different colorectal cancer-derived cell lines and the expression of hERG1 potassium channels in these cell lines using real-time PCR. Next, we knocked down hERG1 expression in HCT116 cells using lentivirus mediated RNA interference and characterized the hERG1 silenced cells in vitro and in vivo. Finally, we investigated the capacity of riluzole, an ion channel-modulating drug used in humans to treat amyotrophic lateral sclerosis, to reduce the resistance of the respective colorectal cancer cells to the chemotherapeutic drug cisplatin. We found that of the colorectal cancer-derived cell lines tested, HCT116 showed the highest mesenchymal profile and a high hERG1 expression. Subsequent hERG1 expression knockdown induced a change in cell morphology, which was accompanied by a reduction in the proliferative and tumorigenic capacities of the cells. Notably, we found that hERG1expression knockdown elicited a reversion of the EMT profile in HCT116 cells with a reacquisition of the epithelial-like profile. We also found that riluzole increased the sensitivity of HCT116 cisplatin-resistant cells to cisplatin. Our data indicate that hERG1 plays a role in the EMT of colorectal cancer cells and that its knockdown reduces the proliferative and tumorigenic capacities of these cells. In addition, we conclude that riluzole may be used in

  13. Pannexin 1 channels mediate 'find-me' signal release and membrane permeability during apoptosis.

    Science.gov (United States)

    Chekeni, Faraaz B; Elliott, Michael R; Sandilos, Joanna K; Walk, Scott F; Kinchen, Jason M; Lazarowski, Eduardo R; Armstrong, Allison J; Penuela, Silvia; Laird, Dale W; Salvesen, Guy S; Isakson, Brant E; Bayliss, Douglas A; Ravichandran, Kodi S

    2010-10-14

    Apoptotic cells release 'find-me' signals at the earliest stages of death to recruit phagocytes. The nucleotides ATP and UTP represent one class of find-me signals, but their mechanism of release is not known. Here, we identify the plasma membrane channel pannexin 1 (PANX1) as a mediator of find-me signal/nucleotide release from apoptotic cells. Pharmacological inhibition and siRNA-mediated knockdown of PANX1 led to decreased nucleotide release and monocyte recruitment by apoptotic cells. Conversely, PANX1 overexpression enhanced nucleotide release from apoptotic cells and phagocyte recruitment. Patch-clamp recordings showed that PANX1 was basally inactive, and that induction of PANX1 currents occurred only during apoptosis. Mechanistically, PANX1 itself was a target of effector caspases (caspases 3 and 7), and a specific caspase-cleavage site within PANX1 was essential for PANX1 function during apoptosis. Expression of truncated PANX1 (at the putative caspase cleavage site) resulted in a constitutively open channel. PANX1 was also important for the 'selective' plasma membrane permeability of early apoptotic cells to specific dyes. Collectively, these data identify PANX1 as a plasma membrane channel mediating the regulated release of find-me signals and selective plasma membrane permeability during apoptosis, and a new mechanism of PANX1 activation by caspases.

  14. Genome-wide analysis of mechanosensitive channel of small ...

    African Journals Online (AJOL)

    Mechanosensitive (MS) ion channels are transmembrane proteins that open and close in response to mechanical forces produced by osmotic pressure, sound, touch and gravity. In plants, MS have an important role in different biological processes like gravity detection, maintenance of plastid shape and size, lateral root ...

  15. TRPA1 channels in Drosophila and honey bee ectoparasitic mites share heat sensitivity and temperature-related physiological functions

    Directory of Open Access Journals (Sweden)

    Guangda Peng

    2016-10-01

    Full Text Available The transient receptor potential cation channel, subfamily A, member 1 (TRPA1 is conserved between many arthropods, and in some has been shown to function as a chemosensor for noxious compounds. Activation of arthropod TRPA1 channels by temperature fluctuations has been tested in only a few insect species, and all of them were shown to be activated by heat. The recent identification of chemosensitive TRPA1 channels from two honey bee ectoparasitic mite species (VdTRPA1 and TmTRPA1 have provided an opportunity to study the temperature-dependent activation and the temperature-associated physiological functions of TRPA1 channels in non-insect arthropods. We found that both mite TRPA1 channels are heat sensitive and capable of rescuing the temperature-related behavioral defects of a Drosophila melanogaster trpA1 mutant. These results suggest that heat-sensitivity of TRPA1 could be conserved between many arthropods despite its amino acid sequence diversity. Nevertheless, the ankyrin repeats (ARs 6 and 7 are well-conserved between six heat-sensitive arthropod TRPA1 channels and have critical roles for the heat activation of VdTRPA1.

  16. Voltage-Gated Sodium Channel β11B Subunits Regulate Cardiac Physiology and Pathophysiology

    Directory of Open Access Journals (Sweden)

    Nnamdi Edokobi

    2018-04-01

    Full Text Available Cardiac myocyte contraction is initiated by a set of intricately orchestrated electrical impulses, collectively known as action potentials (APs. Voltage-gated sodium channels (NaVs are responsible for the upstroke and propagation of APs in excitable cells, including cardiomyocytes. NaVs consist of a single, pore-forming α subunit and two different β subunits. The β subunits are multifunctional cell adhesion molecules and channel modulators that have cell type and subcellular domain specific functional effects. Variants in SCN1B, the gene encoding the Nav-β1 and -β1B subunits, are linked to atrial and ventricular arrhythmias, e.g., Brugada syndrome, as well as to the early infantile epileptic encephalopathy Dravet syndrome, all of which put patients at risk for sudden death. Evidence over the past two decades has demonstrated that Nav-β11B subunits play critical roles in cardiac myocyte physiology, in which they regulate tetrodotoxin-resistant and -sensitive sodium currents, potassium currents, and calcium handling, and that Nav-β11B subunit dysfunction generates substrates for arrhythmias. This review will highlight the role of Nav-β11B subunits in cardiac physiology and pathophysiology.

  17. Identification of a tetrameric assembly domain in the C terminus of heat-activated TRPV1 channels.

    Science.gov (United States)

    Zhang, Feng; Liu, Shuang; Yang, Fan; Zheng, Jie; Wang, KeWei

    2011-04-29

    Transient receptor potential (TRP) channels as cellular sensors are thought to function as tetramers. Yet, the molecular determinants governing channel multimerization remain largely elusive. Here we report the identification of a segment comprising 21 amino acids (residues 752-772 of mouse TRPV1) after the known TRP-like domain in the channel C terminus that functions as a tetrameric assembly domain (TAD). Purified recombinant C-terminal proteins of TRPV1-4, but not the N terminus, mediated the protein-protein interaction in an in vitro pulldown assay. Western blot analysis combined with electrophysiology and calcium imaging demonstrated that TAD exerted a robust dominant-negative effect on wild-type TRPV1. When fused with the membrane-tethered peptide Gap43, the TAD blocked the formation of stable homomultimers. Calcium imaging and current recordings showed that deletion of the TAD in a poreless TRPV1 mutant subunit suppressed its dominant-negative phenotype, confirming the involvement of the TAD in assembly of functional channels. Our findings suggest that the C-terminal TAD in TRPV1 channels functions as a domain that is conserved among TRPV1-4 and mediates a direct subunit-subunit interaction for tetrameric assembly.

  18. TRANTHAC-1: transient thermal-hydraulic analysis code for HTGR core of multi-channel model

    International Nuclear Information System (INIS)

    Sato, Sadao; Miyamoto, Yoshiaki

    1980-08-01

    The computer program TRANTHAC-1 is for predicting thermal-hydraulic transient behavior in HTGR's core of pin-in-block type fuel elements, taking into consideration of the core flow distribution. The program treats a multi-channel model, each single channel representing the respective column composed of fuel elements. The fuel columns are grouped in flow control regions; each region is provided with an orifice assembly. In the region, all channels are of the same shape except one channel. Core heat is removed by downward flow of the control through the channel. In any transients, for given time-dependent power, total core flow, inlet coolant temperature and coolant pressure, the thermal response of the core can be determined. In the respective channels, the heat conduction in radial and axial direction are represented. And the temperature distribution in each channel with the components is calculated. The model and usage of the program are described. The program is written in FORTRAN-IV for computer FACOM 230-75 and it is composed of about 4,000 cards. The required core memory is about 75 kilowords. (author)

  19. Rate of displacement for Jakob Type 1 lateral condyle fractures treated with a cast.

    Science.gov (United States)

    Zale, C; Winthrop, Z A; Hennrikus, W

    2018-04-01

    The aim of this retrospective study is to report the rate of displacement of Jakob Type 1 lateral condyle fractures that were initially treated in a cast. We performed a retrospective review of all patients that were treated for a non-displaced (Jakob Type 1 displaced and were converted to a closed pinning treatment plan with a conversion rate of 8.5%. There was a mean of 13.2 days (4 to 21) between treatment by initial casting and closed pinning. This study demonstrates an 8.5% displacement and conversion rate from cast treatment to closed pinning for initially non-displaced Jakob Type 1 lateral condyle fractures of the humerus. The internal oblique radiograph is most accurate to determine displacement. We recommend obtaining an internal oblique view at initial evaluation and at follow-up in the cast for lateral condyle fractures. To minimize movement at the fracture site, we recommend treating Jakob Type 1 lateral condyle fractures with a long arm cast with the elbow at 90° and the forearm in the supine position with a sling-loop design. IV - retrospective therapeutic study.

  20. hERG1 channels are overexpressed in glioblastoma multiforme and modulate VEGF secretion in glioblastoma cell lines

    Science.gov (United States)

    Masi, A; Becchetti, A; Restano-Cassulini, R; Polvani, S; Hofmann, G; Buccoliero, A M; Paglierani, M; Pollo, B; Taddei, G L; Gallina, P; Di Lorenzo, N; Franceschetti, S; Wanke, E; Arcangeli, A

    2005-01-01

    Recent studies have led to considerable advancement in our understanding of the molecular mechanisms that underlie the relentless cell growth and invasiveness of human gliomas. Partial understanding of these mechanisms has (1) improved the classification for gliomas, by identifying prognostic subgroups, and (2) pointed to novel potential therapeutic targets. Some classes of ion channels have turned out to be involved in the pathogenesis and malignancy of gliomas. We studied the expression and properties of K+ channels in primary cultures obtained from surgical specimens: human ether a gò-gò related (hERG)1 voltage-dependent K+ channels, which have been found to be overexpressed in various human cancers, and human ether a gò-gò-like 2 channels, that share many of hERG1's biophysical features. The expression pattern of these two channels was compared to that of the classical inward rectifying K+ channels, IRK, that are widely expressed in astrocytic cells and classically considered a marker of astrocytic differentiation. In our study, hERG1 was found to be specifically overexpressed in high-grade astrocytomas, that is, glioblastoma multiforme (GBM). In addition, we present evidence that, in GBM cell lines, hERG1 channel activity actively contributes to malignancy by promoting vascular endothelial growth factor secretion, thus stimulating the neoangiogenesis typical of high-grade gliomas. Our data provide important confirmation for studies proposing the hERG1 channel as a molecular marker of tumour progression and a possible target for novel anticancer therapies. PMID:16175187

  1. Voltage-gated potassium channel (K(v) 1) autoantibodies in patients with chagasic gut dysmotility and distribution of K(v) 1 channels in human enteric neuromusculature (autoantibodies in GI dysmotility).

    Science.gov (United States)

    Hubball, A W; Lang, B; Souza, M A N; Curran, O D; Martin, J E; Knowles, C H

    2012-08-01

    Autoantibodies directed against specific neuronal antigens are found in a significant number of patients with gastrointestinal neuromuscular diseases (GINMDs) secondary to neoplasia. This study examined the presence of antineuronal antibodies in idiopathic GINMD and GINMD secondary to South American Trypanosomiasis. The GI distribution of voltage-gated potassium channels (VGKCs) was also investigated. Seventy-three patients were included in the study with diagnoses of primary achalasia, enteric dysmotility, chronic intestinal pseudo-obstruction, esophageal or colonic dysmotility secondary to Chagas' disease. Sera were screened for specific antibodies to glutamic acid decarboxylase, voltage-gated calcium channels (VGCCs; P/Q subtype), nicotinic acetylcholine receptors (nAChRs; α3 subtype), and voltage-gated potassium channels (VGKCs, K(V) 1 subtype) using validated immunoprecipitation assays. The distribution of six VGKC subunits (K(V) 1.1-1.6), including those known to be antigenic targets of anti-VGKC antibodies was immunohistochemically investigated in all main human GI tract regions. Three patients (14%) with chagasic GI dysmotility were found to have positive anti-VGKC antibody titers. No antibodies were detected in patients with idiopathic GINMD. The VGKCs were found in enteric neurons at every level of the gut in unique yet overlapping distributions. The VGKC expression in GI smooth muscle was found to be limited to the esophagus. A small proportion of patients with GI dysfunction secondary to Chagas' disease have antibodies against VGKCs. The presence of these channels in the human enteric nervous system may have pathological relevance to the growing number of GINMDs with which anti-VGKC antibodies have been associated. © 2012 Blackwell Publishing Ltd.

  2. 47 CFR 27.6 - Service areas.

    Science.gov (United States)

    2010-10-01

    ... the United States Virgin Islands, American Samoa, and the Gulf of Mexico, which have been assigned...) 173. 10 (Puerto Rico and U.S. Virgin Islands) 50 (Puerto Rico and U.S. Virgin Islands) 174. 11... Northeast 1-11, 54. EAG002 Mid-Atlantic 12-26, 41, 42, 44-53, 70. EAG003 Southeast 27-40, 43, 69, 71-86, 88...

  3. Ion channeling

    International Nuclear Information System (INIS)

    Erramli, H.; Blondiaux, G.

    1994-01-01

    Channeling phenomenon was predicted, many years ago, by stark. The first channeling experiments were performed in 1963 by Davies and his coworkers. Parallely Robinson and Oen have investigated this process by simulating trajectories of ions in monocrystals. This technique has been combined with many methods like Rutherford Backscattering Spectrometry (R.B.S.), Particles Induced X-rays Emission (P.I.X.E) and online Nuclear Reaction (N.R.A.) to localize trace elements in the crystal or to determine crystalline quality. To use channeling for material characterization we need data about the stopping power of the incident particle in the channeled direction. The ratios of channeled to random stopping powers of silicon for irradiation in the direction have been investigated and compared to the available theoretical results. We describe few applications of ion channeling in the field of materials characterization. Special attention is given to ion channeling combined with Charged Particle Activation Analysis (C.P.A.A.) for studying the behaviour of oxygen atoms in Czochralski silicon lattices under the influence of internal gettering and in different gaseous atmospheres. Association between ion channeling and C.P.A.A was also utilised for studying the influence of the growing conditions on concentration and position of carbon atoms at trace levels in the MOVPE Ga sub (1-x) Al sub x lattice. 6 figs., 1 tab., 32 refs. (author)

  4. Seismic patterns and migration history of submarine fan channels in deep-water area, Niger Delta, West Africa

    Science.gov (United States)

    Zhang, Guotao; Zhang, Shangfeng; Li, Yuan

    2015-04-01

    The channels of deep-water submarine fan under Niger delta slope are characterized by large dimensions special deposition positions and complex formation processes, its geographical location and sedimentary environment also hinder the research and exploration development. According to the strata slicing, RMS amplitude attribute and other techniques, we exhibit the platforms patterns of channels at different period, and based on the analysis of internal architecture and deformation history of channel-leveed systems, migration and evolution process of channel systems could be understood accurately. A great quantity of isolated channels develop in middle Miocene and aggrading streams in late Miocene, which generating because of large scale of turbidity caused by the drop of second order sea-level, which characterized by vertical accretion at smooth channel, while vertical accretion and lateral migration at bend. Evolution of channel systems can be divided into three stages: the initial erosion, erosion and filling alternately, and abandoned stage. With these three stages, the sinuosity of channel change from moderate to high, then decrease. Incision and filling of channels, being during the three development phases, is the driving force of meander-loops migration, which promote three kinds of migration patterns: lateral, down-system and combination migration. The research provides theoretical basis for high-precision prediction and evaluation of deep-water reservoir.

  5. Localized Iron Supply Triggers Lateral Root Elongation in Arabidopsis by Altering the AUX1-Mediated Auxin Distribution[C][W][OA

    Science.gov (United States)

    Giehl, Ricardo F.H.; Lima, Joni E.; von Wirén, Nicolaus

    2012-01-01

    Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-β-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation. PMID:22234997

  6. Integrated 1 GHz 4-channel InP phasar based WDM-receiver with Si bipolar frontend array

    NARCIS (Netherlands)

    Steenbergen, C.A.M.; Vreede, de L.C.N.; Dam, van C.; Scholtes, T.L.M.; Smit, M.K.; Tauritz, J.L.; Pedersen, J.W.; Moerman, I.; Verbeek, B.H.; Baets, R.G.F.

    1995-01-01

    An integrated 4-channel WDM-receiver frontend with 1 GHz channel bandwidth is described. The receiver consists of an integrated wavelength demultiplexer with photodiodes in InP technology connected through bond wires with a 4 channel Si bipolar transimpedance amplifier mounted on an epoxy board. The

  7. Morphological resilience to flow fluctuations of fine sediment deposits in bank lateral cavities

    Science.gov (United States)

    Juez, C.; Thalmann, M.; Schleiss, A. J.; Franca, M. J.

    2018-05-01

    Lateral cavities are built in the banks of rivers for several purposes: to create harbors, to capture sediment, to keep a central navigable channel (i.e., Casiers de Girardon in the Rhone river) or to promote the formation of aquatic habitats if a limited amount of sediment is captured, providing hydraulic and morphologic diversity (i.e., the case of Japanese Wandos). This work is focused on this latter purpose: promotion of hydraulic and morphologic diversity. In these scenarios, an increase in the flow discharge in the main channel may, however, re-mobilize the deposit of sediment inside these lateral embayments and cause a sudden increase of the sediment concentration and turbidity in the main channel. It is thus of interest to characterize the resistance and resilience of these sedimentary deposits when the main channel is subjected to high flow or flushing events. Laboratory tests were carried out for five different normalized geometries of the cavities installed in the banks of an open channel and for five hydrographs with different levels of unsteadiness. Water depth, sediment deposit mass, sediment concentration and area covered by the settled sediments were recorded throughout each experiment. Although sediment deposits established at equilibrium before the flushing events are different depending on the geometry of the cavities, generally, they are recovered after being flushed by the high flow events. It is shown that the resistance and resilience of the sediment deposits are strongly dependent on the flow field and the mass exchange between the main channel and the cavities. This mass exchange is governed by the geometry of the cavities and the magnitude of the hydrographs applied.

  8. Properties and function of KCNQ1 K+ channels isolated from the rectal gland of Squalus acanthias.

    Science.gov (United States)

    Kerst, G; Beschorner, U; Unsöld, B; von Hahn, T; Schreiber, R; Greger, R; Gerlach, U; Lang, H J; Kunzelmann, K; Bleich, M

    2001-10-01

    KCNQ1 (KVLQT1) K+ channels play an important role during electrolyte secretion in airways and colon. KCNQ1 was cloned recently from NaCl-secreting shark rectal glands. Here we study the properties and regulation of the cloned sKVLQT1 expressed in Xenopus oocytes and Chinese hamster ovary (CHO) cells and compare the results with those obtained from in vitro perfused rectal gland tubules (RGT). The expression of sKCNQ1 induced voltage-dependent, delayed activated K+ currents, which were augmented by an increase in intracellular cAMP and Ca2+. The chromanol derivatives 293B and 526B potently inhibited sKCNQ1 expressed in oocytes and CHO cells, but had little effect on RGT electrolyte transport. Short-circuit currents in RGT were activated by alkalinization and were decreased by acidification. In CHO cells an alkaline pH activated and an acidic pH inhibited 293B-sensitive KCNQ1 currents. Noise analysis of the cell-attached basolateral membrane of RGT indicated the presence of low-conductance (<3 pS) K+ channels, in parallel with other K+ channels. sKCNQ1 generated similar small-conductance K+ channels upon expression in CHO cells and Xenopus oocytes. The results suggest the presence of low-conductance KCNQ1 K+ channels in RGT, which are probably regulated by changes in intracellular cAMP, Ca2+ and pH.

  9. Mechanism of μ-conotoxin PIIIA binding to the voltage-gated Na+ channel NaV1.4.

    Directory of Open Access Journals (Sweden)

    Rong Chen

    Full Text Available Several subtypes of voltage-gated Na+ (NaV channels are important targets for pain management. μ-Conotoxins isolated from venoms of cone snails are potent and specific blockers of different NaV channel isoforms. The inhibitory effect of μ-conotoxins on NaV channels has been examined extensively, but the mechanism of toxin specificity has not been understood in detail. Here the known structure of μ-conotoxin PIIIA and a model of the skeletal muscle channel NaV1.4 are used to elucidate elements that contribute to the structural basis of μ-conotoxin binding and specificity. The model of NaV1.4 is constructed based on the crystal structure of the bacterial NaV channel, NaVAb. Six different binding modes, in which the side chain of each of the basic residues carried by the toxin protrudes into the selectivity filter of NaV1.4, are examined in atomic detail using molecular dynamics simulations with explicit solvent. The dissociation constants (Kd computed for two selected binding modes in which Lys9 or Arg14 from the toxin protrudes into the filter of the channel are within 2 fold; both values in close proximity to those determined from dose response data for the block of NaV currents. To explore the mechanism of PIIIA specificity, a double mutant of NaV1.4 mimicking NaV channels resistant to μ-conotoxins and tetrodotoxin is constructed and the binding of PIIIA to this mutant channel examined. The double mutation causes the affinity of PIIIA to reduce by two orders of magnitude.

  10. Gravity currents in rotating channels. Part 1. Steady-state theory

    Science.gov (United States)

    Hacker, J. N.; Linden, P. F.

    2002-04-01

    A theory is developed for the speed and structure of steady-state non-dissipative gravity currents in rotating channels. The theory is an extension of that of Benjamin (1968) for non-rotating gravity currents, and in a similar way makes use of the steady-state and perfect-fluid (incompressible, inviscid and immiscible) approximations, and supposes the existence of a hydrostatic ‘control point’ in the current some distance away from the nose. The model allows for fully non-hydrostatic and ageostrophic motion in a control volume V ahead of the control point, with the solution being determined by the requirements, consistent with the perfect-fluid approximation, of energy and momentum conservation in V, as expressed by Bernoulli's theorem and a generalized flow-force balance. The governing parameter in the problem, which expresses the strength of the background rotation, is the ratio W = B/R, where B is the channel width and R = (g[prime prime or minute]H)1/2/f is the internal Rossby radius of deformation based on the total depth of the ambient fluid H. Analytic solutions are determined for the particular case of zero front-relative flow within the gravity current. For each value of W there is a unique non-dissipative two-layer solution, and a non-dissipative one-layer solution which is specified by the value of the wall-depth h0. In the two-layer case, the non-dimensional propagation speed c = cf(g[prime prime or minute]H)[minus sign]1/2 increases smoothly from the non-rotating value of 0.5 as W increases, asymptoting to unity for W [rightward arrow] [infty infinity]. The gravity current separates from the left-hand wall of the channel at W = 0.67 and thereafter has decreasing width. The depth of the current at the right-hand wall, h0, increases, reaching the full depth at W = 1.90, after which point the interface outcrops on both the upper and lower boundaries, with the distance over which the interface slopes being 0.881R. In the one-layer case, the wall

  11. Imaging an optogenetic pH sensor reveals that protons mediate lateral inhibition in the retina.

    Science.gov (United States)

    Wang, Tzu-Ming; Holzhausen, Lars C; Kramer, Richard H

    2014-02-01

    The reciprocal synapse between photoreceptors and horizontal cells underlies lateral inhibition and establishes the antagonistic center-surround receptive fields of retinal neurons to enhance visual contrast. Despite decades of study, the signal mediating the negative feedback from horizontal cells to cones has remained under debate because the small, invaginated synaptic cleft has precluded measurement. Using zebrafish retinas, we show that light elicits a change in synaptic proton concentration with the correct magnitude, kinetics and spatial dependence to account for lateral inhibition. Light, which hyperpolarizes horizontal cells, causes synaptic alkalinization, whereas activating an exogenously expressed ligand-gated Na(+) channel, which depolarizes horizontal cells, causes synaptic acidification. Whereas acidification was prevented by blocking a proton pump, re-alkalinization was prevented by blocking proton-permeant ion channels, suggesting that distinct mechanisms underlie proton efflux and influx. These findings reveal that protons mediate lateral inhibition in the retina, raising the possibility that protons are unrecognized retrograde messengers elsewhere in the nervous system.

  12. Increased transient receptor potential vanilloid type 1 (TRPV1) channel expression in hypertrophic heart

    DEFF Research Database (Denmark)

    Thilo, Florian; Liu, Ying; Schulz, Nico

    2010-01-01

    The aim of this study was to compare the expression of transient receptor potential vanilloid type 1 (TRPV1) channels in hypertrophic hearts from transgenic mice showing overexpression of the catalytic subunit alpha of protein phosphatase 2A alpha (PP2Ac alpha) with wild-type mice and with TRPV1-...... alpha transgenic mice compared to wild-type mice and TRPV1-/- mice (8.6±1.3mg/g; 5.4±0.3mg/g; and 5.4±0.4mg/g; respectively; p...

  13. Uranium in tertiary stream channels, Lake Frome area, South Australia

    International Nuclear Information System (INIS)

    Brunt, D.A.

    1978-01-01

    Uranium exploration over a wide area of the Southern Frome Embayment, South Australia, has defined a number of Lower Tertiary fluvial palacochannels incised in older rocks. The buried channels contain similar stratigraphic sequences of interbedded sand, silt, and clay, probably derived from the adjacent uranium-rich Olary Province. Uranium mineralization is pervasive within two major palacochannels, and four small uranium deposits have been found in the basal sands of these channel sequences, at the margins of extensive tongues of limonitic sand. A genetic model is proposed suggesting formation by a uraniferous geochemical cell which migrated down the stream gradient and concentrated uranium on its lateral margins adjacent to the channel bank

  14. Positive Feedback Regulation of Agonist-Stimulated Endothelial Ca2+ Dynamics by KCa3.1 Channels in Mouse Mesenteric Arteries

    DEFF Research Database (Denmark)

    Qian, Xun; Francis, Michael; Köhler, Ralf

    2014-01-01

    Intermediate and small conductance KCa channels IK1 (KCa3.1) and SK3 (KCa2.3) are primary targets of endothelial Ca(2+) signals in the arterial vasculature, and their ablation results in increased arterial tone and hypertension. Activation of IK1 channels by local Ca(2+) transients from internal ...... stores or plasma membrane channels promotes arterial hyperpolarization and vasodilation. Here, we assess arteries from genetically altered IK1 knockout mice (IK1(-/-)) to determine whether IK1 channels exert a positive feedback influence on endothelial Ca(2+) dynamics....

  15. The role and mechanism of KCa3.1 channels in human monocyte migration induced by palmitic acid.

    Science.gov (United States)

    Ma, Xiao-Zhen; Pang, Zheng-Da; Wang, Jun-Hong; Song, Zheng; Zhao, Li-Mei; Du, Xiao-Jun; Deng, Xiu-Ling

    2018-05-21

    Monocyte migration into diseased tissues contributes to the pathogenesis of diseases. Intermediate-conductance Ca 2+ -activated K + (K Ca 3.1) channels play an important role in cell migration. However, the role of K Ca 3.1 channels in mediating monocyte migration induced by palmitic acid (PA) is still unclear. Using cultured THP-1 cells and peripheral blood mononuclear cells from healthy subjects, we investigated the role and signaling mechanisms of K Ca 3.1 channels in mediating the migration induced by PA. Using methods of Western blotting analysis, RNA interference, cell migration assay and ELISA, we found that PA-treated monocytes exhibited increment of the protein levels of K Ca 3.1 channel and monocyte chemoattractant protein-1 (MCP-1), and the effects were reversed by co-incubation of PA with anti-TLR2/4 antibodies or by specific inhibitors of p38-MAPK, or NF-κB. In addition, PA increased monocyte migration, which was abolished by a specific K Ca 3.1 channel blocker, TRAM-34, or K Ca 3.1 small interfering RNA (siRNA). The expression and secretion of MCP-1 induced by PA was also similarly prevented by TRAM-34 and K Ca 3.1 siRNA. These results demonstrate for the first time that PA upregulates K Ca 3.1 channels through TLR2/4, p38-MAPK and NF-κB pathway to promote the expression of MCP-1, and then induce the trans-endothelial migration of monocytes. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Ion channels in plants.

    Science.gov (United States)

    Hedrich, Rainer

    2012-10-01

    Since the first recordings of single potassium channel activities in the plasma membrane of guard cells more than 25 years ago, patch-clamp studies discovered a variety of ion channels in all cell types and plant species under inspection. Their properties differed in a cell type- and cell membrane-dependent manner. Guard cells, for which the existence of plant potassium channels was initially documented, advanced to a versatile model system for studying plant ion channel structure, function, and physiology. Interestingly, one of the first identified potassium-channel genes encoding the Shaker-type channel KAT1 was shown to be highly expressed in guard cells. KAT1-type channels from Arabidopsis thaliana and its homologs from other species were found to encode the K(+)-selective inward rectifiers that had already been recorded in early patch-clamp studies with guard cells. Within the genome era, additional Arabidopsis Shaker-type channels appeared. All nine members of the Arabidopsis Shaker family are localized at the plasma membrane, where they either operate as inward rectifiers, outward rectifiers, weak voltage-dependent channels, or electrically silent, but modulatory subunits. The vacuole membrane, in contrast, harbors a set of two-pore K(+) channels. Just very recently, two plant anion channel families of the SLAC/SLAH and ALMT/QUAC type were identified. SLAC1/SLAH3 and QUAC1 are expressed in guard cells and mediate Slow- and Rapid-type anion currents, respectively, that are involved in volume and turgor regulation. Anion channels in guard cells and other plant cells are key targets within often complex signaling networks. Here, the present knowledge is reviewed for the plant ion channel biology. Special emphasis is drawn to the molecular mechanisms of channel regulation, in the context of model systems and in the light of evolution.

  17. Lateral Pancreaticojejunostomy for Chronic Pancreatitis and Pancreatic Ductal Dilation in Children.

    Science.gov (United States)

    Shah, Adil A; Petrosyan, Mikael; Kane, Timothy D

    2018-06-06

    Pancreatic ductal obstruction leading to ductal dilation and recurrent pancreatitis is uncommon in children. Treatment is dependent upon etiology but consists of decompression of the pancreatic duct (PD) proximally, if possible, by endoscopic retrograde cholangiopancreatography (ERCP) intervention or surgical decompression with pancreaticojejunal anastomosis. After institutional review board approval, we retrospectively reviewed the records for 2 children who underwent lateral pancreaticojejunostomy for pancreatic ductal dilation. Data, including demographics, diagnostic studies, operative details, complications, outcomes, and follow-up, were analyzed. Case 1 was a 4-year-old female with pancreatic ductal obstruction with multiple episodes of recurrent pancreatitis and failure of ERCP to clear her PD of stones. She underwent a laparoscopic cholecystectomy with a lateral pancreaticojejunostomy (Puestow procedure). She recovered well with no further episodes of pancreatitis and normal pancreatic function 4 years later. Case 2 was a 2-year-old female who developed recurrent pancreatitis and was found to have papillary stenosis and long common bile-PD channel. Despite multiple sphincterotomies, laparoscopic cholecystectomy, and laparoscopic hepaticoduodenostomy, she continued to experience episodes of pancreatitis. She underwent a laparoscopy converted to open lateral pancreaticojejunostomy. Her recovery was also smooth having had no episodes of pancreatitis or hospital admissions for over 2 years following the Puestow. Indication for lateral pancreaticojejunostomy or Puestow procedure is rare in children and even less often performed using laparoscopy. In our small experience, both patients with pancreatic ductal obstruction managed with Puestow's procedure enjoy durable symptom and pain relief in the long term.

  18. Sequential grouping constraints on across-channel auditory processing

    DEFF Research Database (Denmark)

    Oxenham, Andrew J.; Dau, Torsten

    2005-01-01

    Søren Buus was one of the pioneers in the study of across-channel auditory processing. His influential 1985 paper showed that introducing slow fluctuations to a low-frequency masker could reduce the detection thresholds of a high-frequency signal by as much as 25 dB [S. Buus, J. Acoust. Soc. Am. 78......, 1958–1965 (1985)]. Søren explained this surprising result in terms of the spread of masker excitation and across-channel processing of envelope fluctuations. A later study [S. Buus and C. Pan, J. Acoust. Soc. Am. 96, 1445–1457 (1994)] pioneered the use of the same stimuli in tasks where across......-channel processing could either help or hinder performance. In the present set of studies we also use paradigms in which across-channel processing can lead to either improvement or deterioration in performance. We show that sequential grouping constraints can affect both types of paradigm. In particular...

  19. Channel Evolution Following Avulsion: an Example from the Yellow River Delta

    Science.gov (United States)

    Zheng, S.

    2017-12-01

    Long-term field observation of morphological adjustments of rivers following avulsions is lacked when studying the evolution of avulsive channel on deltas. Avulsion at the Yellow River Delta (YRD) is frequent with average lifespan of channels of only about a decade. The Qing-shui-gou channel, the recent lobe on the YRD, provides a rare opportunity for investigating channel evolution following artificial avulsion. The reasons for its longer lifespan also needs investigation of the channel evolution. In this study, we comprehensively analyzed the geomorphic adjustment of the channel based on filed survey data during 1976-2014. The evolution of the channel was impacted by anthropogenic activities, including artificial avulsion at the downstream channel reaches in 1996, alteration of runoff and sediment load through Water and Sediment Regulation Scheme (WSRS), construction of levees and dikes. Analysis on channel geometry showed that avulsions in 1976 and in 1996 both caused short-term (1 2 years) erosion at the upstream channel reaches. Following the avulsion in 1976, massive aggradation occurred at the channel reaches at the downstream of the avulsion point. A single-thread channel gradually formed, widened and enlarged as channel bed under-cut on the deposition material. As delta extended seaward and the longitudinal slope decreased with time, aggradation occurred and an alluvial ridge formed. The ratio of lateral slope to the longitudinal slope (i.e. gradient advantage) and the relative super-elevation of the channel were calculated to estimate the possibility of avulsion at the channel in the late 1990. Results showed that the slope ratio was greater than 20 locally and super-elevation near its critical value for avulsion. The fact, that natural avulsion did not occurred despite of high values of gradient advantage and super elevation, may indicate that they are not sufficient conditions for avulsion at highly human-controlled rivers, where channel boundaries are

  20. Inhibition of Inwardly Rectifying Potassium (Kir 4.1 Channels Facilitates Brain-Derived Neurotrophic Factor (BDNF Expression in Astrocytes

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    Masato Kinboshi

    2017-12-01

    Full Text Available Inwardly rectifying potassium (Kir 4.1 channels in astrocytes regulate neuronal excitability by mediating spatial potassium buffering. Although dysfunction of astrocytic Kir4.1 channels is implicated in the development of epileptic seizures, the functional mechanisms of Kir4.1 channels in modulating epileptogenesis remain unknown. We herein evaluated the effects of Kir4.1 inhibition (blockade and knockdown on expression of brain-derived neurotrophic factor (BDNF, a key modulator of epileptogenesis, in the primary cultures of mouse astrocytes. For blockade of Kir4.1 channels, we tested several antidepressant agents which reportedly bound to and blocked Kir4.1 channels in a subunit-specific manner. Treatment of astrocytes with fluoxetine enhanced BDNF mRNA expression in a concentration-dependent manner and increased the BDNF protein level. Other antidepressants (e.g., sertraline and imipramine also increased the expression of BDNF mRNA with relative potencies similar to those for inhibition of Kir4.1 channels. In addition, suppression of Kir4.1 expression by the transfection of small interfering RNA (siRNA targeting Kir4.1 significantly increased the mRNA and protein levels of BDNF. The BDNF induction by Kir4.1 siRNA transfection was suppressed by the MEK1/2 inhibitor U0126, but not by the p38 MAPK inhibitor SB202190 or the JNK inhibitor SP600125. The present results demonstrated that inhibition of Kir4.1 channels facilitates BDNF expression in astrocytes primarily by activating the Ras/Raf/MEK/ERK pathway, which may be linked to the development of epilepsy and other neuropsychiatric disorders.

  1. Lateral Erosion Encourages Vertical Incision in a Bimodal Alluvial River

    Science.gov (United States)

    Gran, K. B.

    2015-12-01

    Sand can have a strong impact on gravel transport, increasing gravel transport rates by orders of magnitude as sand content increases. Recent experimental work by others indicates that adding sand to an armored bed can even cause armor to break-up and mobilize. These two elements together help explain observations from a bimodal sand and gravel-bedded river, where lateral migration into sand-rich alluvium breaks up the armor layer, encouraging further incision into the bed. Detailed bedload measurements were coupled with surface and subsurface grain size analyses and cross-sectional surveys in a seasonally-incised channel carved into the upper alluvial fan of the Pasig-Potrero River at Mount Pinatubo, Philippines. Pinatubo erupted in 1991, filling valleys draining the flanks of the volcano with primarily sand-sized pyroclastic flow debris. Twenty years after the eruption, sand-rich sediment inputs are strongly seasonal, with most sediment input to the channel during the rainy season. During the dry season, flow condenses from a wide braided planform to a single-thread channel in most of the upper basin, extending several km onto the alluvial fan. This change in planform creates similar unit discharge ranges in summer and winter. Lower sediment loads in the dry season drive vertical incision until the bed is sufficiently armored. Incision proceeds downstream in a wave, with increasing sediment transport rates and decreasing grain size with distance downstream, eventually reaching a gravel-sand transition and return to a braided planform. Incision depths in the gravel-bedded section exceeded 3 meters in parts of a 4 km-long study reach, a depth too great to be explained by predictions from simple winnowing during incision. Instead, lateral migration into sand-rich alluvium provides sufficient fine sediment to break up the armor surface, allowing incision to start anew and increasing the total depth of the seasonally-incised valley. Lateral migration is recorded in a

  2. Choline Modulation of the Aβ P1-40 Channel Reconstituted into a Model Lipid Membrane

    Directory of Open Access Journals (Sweden)

    Daniela Meleleo

    2010-01-01

    Full Text Available Nicotinic acetylcholine receptors (AChRs, implicated in memory and learning, in subjects affected by Alzheimer's disease result altered. Stimulation of α7-nAChRs inhibits amyloid plaques and increases ACh release. β-amyloid peptide (AβP forms ion channels in the cell and model phospholipid membranes that are retained responsible in Alzheimer disease. We tested if choline, precursor of ACh, could affect the AβP1-40 channels in oxidized cholesterol (OxCh and in palmitoyl-oleoyl-phosphatidylcholine (POPC:Ch lipid bilayers. Choline concentrations of 5 × 10−11 M–1.5 × 10−8 M added to the cis- or trans-side of membrane quickly increased AβP1-40 ion channel frequency (events/min and ion conductance in OxCh membranes, but not in POPC:Ch membranes. Circular Dichroism (CD spectroscopy shows that after 24 and 48 hours of incubation with AβP1-40, choline stabilizes the random coil conformation of the peptide, making it less prone to fibrillate. These actions seem to be specific in that ACh is ineffective either in solution or on AβP1-40 channel incorporated into PLMs.

  3. Tx1, from Phoneutria nigriventer spider venom, interacts with dihydropyridine sensitive-calcium channels in GH3 cells

    International Nuclear Information System (INIS)

    Gouvea dos Santos, R.; Soares, M.A.; Pimenta, A.M.; De Lima, M.E.; ICB, UFMG, Belo Horizonte

    2006-01-01

    The aim of this work was to use the binding assay of tritiated-dihydropyridine and radioiodinated Tx1, isolated from the Phoneutria nigriventer venom, in order to show the presence of Ca v 1 calcium channels on pituitary tumour cell (GH3). We showed that GH3 cells have specific sites for 125 I-Tx1, which are sensitive to nifedipine (∼20%). Reverse competition assay with 3 H-PN200-110 (40% inhibition) and electrophysiological data (50% inhibition) suggest that Ca v 1 calcium channels are target sites for this toxin. To summarize, Tx1 binds to specific sites on GH3 cells and this interaction results in Ca v 1 calcium channel blockade. 3 H-PN200-110 and 125 I-Tx1 binding assays proved to be useful tools to show the presence of calcium channels on GH3 cells. (author)

  4. Effect of Potassium Channel Modulators on Morphine Withdrawal in Mice

    Directory of Open Access Journals (Sweden)

    Vikas Seth

    2010-01-01

    Full Text Available The present study was conducted to investigate the effect of potassium channel openers and blockers on morphine withdrawal syndrome. Mice were rendered dependent on morphine by subcutaneous injection of morphine; four hours later, withdrawal was induced by using an opioid antagonist, naloxone. Mice were observed for 30 minutes for the withdrawal signs ie, the characteristic jumping, hyperactivity, urination and diarrhea. ATP-dependent potassium (K + ATP channel modulators were injected intraperitoneally (i.p. 30 minutes before the naloxone. It was found that a K + ATP channel opener, minoxidil (12.5–50 mg/kg i.p., suppressed the morphine withdrawal significantly. On the other hand, the K + ATP channel blocker glibenclamide (12.5–50 mg/kg i.p. caused a significant facilitation of the withdrawal. Glibenclamide was also found to abolish the minoxidil's inhibitory effect on morphine withdrawal. The study concludes that K + ATP channels play an important role in the genesis of morphine withdrawal and K + ATP channel openers could be useful in the management of opioid withdrawal. As morphine opens K + ATP channels in neurons, the channel openers possibly act by mimicking the effects of morphine on neuronal K + currents.

  5. Inward rectifier K+ channel and T-type Ca2+ channel contribute to enhancement of GABAergic transmission induced by β1-adrenoceptor in the prefrontal cortex.

    Science.gov (United States)

    Luo, Fei; Zheng, Jian; Sun, Xuan; Tang, Hua

    2017-02-01

    The functions of prefrontal cortex (PFC) are sensitive to norepinephrine (NE). Endogenously released NE influences synaptic transmission through activation of different subtypes of adrenergic receptors in PFC including α 1 , α 2 , β 1 or β 2 -adrenoceptor. Our recent study has revealed that β 1 -adrenoceptor (β 1 -AR) activation modulates glutamatergic transmission in the PFC, whereas the roles of β 1 -AR in GABAergic transmission are elusive. In the current study, we probed the effects of the β 1 -AR agonist dobutamine (Dobu) on GABAergic transmission onto pyramidal neurons in the PFC of juvenile rats. Dobu increased both the frequency and amplitude of miniature IPSCs (mIPSCs). Ca 2+ influx through T-type voltage-gated Ca 2+ channel was required for Dobu-enhanced mIPSC frequency. We also found that Dobu facilitated GABA release probability and the number of releasable vesicles through regulating T-type Ca 2+ channel. Dobu depolarized GABAergic fast-spiking (FS) interneurons with no effects on the firing rate of action potentials (APs) of interneurons. Dobu-induced depolarization of FS interneurons required inward rectifier K + channel (Kir). Our results suggest that Dobu increase GABA release via inhibition of Kir, which further depolarizes FS interneurons resulting in Ca 2+ influx via T-type Ca 2+ channel. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. OSR1 regulates a subset of inward rectifier potassium channels via a binding motif variant.

    Science.gov (United States)

    Taylor, Clinton A; An, Sung-Wan; Kankanamalage, Sachith Gallolu; Stippec, Steve; Earnest, Svetlana; Trivedi, Ashesh T; Yang, Jonathan Zijiang; Mirzaei, Hamid; Huang, Chou-Long; Cobb, Melanie H

    2018-04-10

    The with-no-lysine (K) (WNK) signaling pathway to STE20/SPS1-related proline- and alanine-rich kinase (SPAK) and oxidative stress-responsive 1 (OSR1) kinase is an important mediator of cell volume and ion transport. SPAK and OSR1 associate with upstream kinases WNK 1-4, substrates, and other proteins through their C-terminal domains which interact with linear R-F-x-V/I sequence motifs. In this study we find that SPAK and OSR1 also interact with similar affinity with a motif variant, R-x-F-x-V/I. Eight of 16 human inward rectifier K + channels have an R-x-F-x-V motif. We demonstrate that two of these channels, Kir2.1 and Kir2.3, are activated by OSR1, while Kir4.1, which does not contain the motif, is not sensitive to changes in OSR1 or WNK activity. Mutation of the motif prevents activation of Kir2.3 by OSR1. Both siRNA knockdown of OSR1 and chemical inhibition of WNK activity disrupt NaCl-induced plasma membrane localization of Kir2.3. Our results suggest a mechanism by which WNK-OSR1 enhance Kir2.1 and Kir2.3 channel activity by increasing their plasma membrane localization. Regulation of members of the inward rectifier K + channel family adds functional and mechanistic insight into the physiological impact of the WNK pathway.

  7. Synthetic Ciguatoxins Selectively Activate Nav1.8-derived Chimeric Sodium Channels Expressed in HEK293 Cells*

    Science.gov (United States)

    Yamaoka, Kaoru; Inoue, Masayuki; Miyazaki, Keisuke; Hirama, Masahiro; Kondo, Chie; Kinoshita, Eiji; Miyoshi, Hiroshi; Seyama, Issei

    2009-01-01

    The synthetic ciguatoxin CTX3C has been shown to activate tetrodotoxin (TTX)-sensitive sodium channels (Nav1.2, Nav1.4, and Nav1.5) by accelerating activation kinetics and shifting the activation curve toward hyperpolarization (Yamaoka, K., Inoue, M., Miyahara, H., Miyazaki, K., and Hirama, M. (2004) Br. J. Pharmacol. 142, 879–889). In this study, we further explored the effects of CTX3C on the TTX-resistant sodium channel Nav1.8. TTX-resistant channels have been shown to be involved in transducing pain and related sensations (Akopian, A. N., Sivilotti, L., and Wood, J. N. (1996) Nature 379, 257–262). Thus, we hypothesized that ciguatoxin-induced activation of the Nav1.8 current would account for the neurological symptoms of ciguatera poisoning. We found that 0.1 μm CTX3C preferentially affected the activation process of the Nav1.8 channel compared with those of the Nav1.2 and Nav1.4 channels. Importantly, without stimulation, 0.1 μm CTX3C induced a large leakage current (IL). The conductance of the IL calculated relative to the maximum conductance (Gmax) was 10 times larger than that of Nav1.2 or Nav1.4. To determine the molecular domain of Nav1.8 responsible for conferring higher sensitivity to CTX3C, we made two chimeric constructs from Nav1.4 and Nav1.8. Chimeras containing the N-terminal half of Nav1.8 exhibited a large response similar to wild-type Nav1.8, indicating that the region conferring high sensitivity to ciguatoxin action is located in the D1 or D2 domains. PMID:19164297

  8. Insights from investigating the interactions of adamantane-based drugs with the M2 proton channel from the H1N1 swine virus

    International Nuclear Information System (INIS)

    Wang, Jing-Fang; Wei, Dong-Qing; Chou, Kuo-Chen

    2009-01-01

    The M2 proton channel is one of indispensable components for the influenza A virus that plays a vital role in its life cycle and hence is an important target for drug design against the virus. In view of this, the three-dimensional structure of the H1N1-M2 channel was developed based on the primary sequence taken from a patient recently infected by the H1N1 (swine flu) virus. With an explicit water-membrane environment, molecular docking studies were performed for amantadine and rimantadine, the two commercial drugs generally used to treat influenza A infection. It was found that their binding affinity to the H1N1-M2 channel is significantly lower than that to the H5N1-M2 channel, fully consistent with the recent report that the H1N1 swine virus was resistant to the two drugs. The findings and the relevant analysis reported here might provide useful structural insights for developing effective drugs against the new swine flu virus.

  9. The electrically silent Kv6.4 subunit confers hyperpolarized gating charge movement in Kv2.1/Kv6.4 heterotetrameric channels.

    Directory of Open Access Journals (Sweden)

    Elke Bocksteins

    Full Text Available The voltage-gated K(+ (Kv channel subunit Kv6.4 does not form functional homotetrameric channels but co-assembles with Kv2.1 to form functional Kv2.1/Kv6.4 heterotetrameric channels. Compared to Kv2.1 homotetramers, Kv6.4 exerts a ~40 mV hyperpolarizing shift in the voltage-dependence of Kv2.1/Kv6.4 channel inactivation, without a significant effect on activation gating. However, the underlying mechanism of this Kv6.4-induced modulation of Kv2.1 channel inactivation, and whether the Kv6.4 subunit participates in the voltage-dependent gating of heterotetrameric channels is not well understood. Here we report distinct gating charge movement of Kv2.1/Kv6.4 heterotetrameric channels, compared to Kv2.1 homotetramers, as revealed by gating current recordings from mammalian cells expressing these channels. The gating charge movement of Kv2.1/Kv6.4 heterotetrameric channels displayed an extra component around the physiological K(+ equilibrium potential, characterized by a second sigmoidal relationship of the voltage-dependence of gating charge movement. This distinct gating charge displacement reflects movement of the Kv6.4 voltage-sensing domain and has a voltage-dependency that matches the hyperpolarizing shift in Kv2.1/Kv6.4 channel inactivation. These results provide a mechanistic basis for the modulation of Kv2.1 channel inactivation gating kinetics by silent Kv6.4 subunits.

  10. Zebrafish CaV2.1 Calcium Channels Are Tailored for Fast Synchronous Neuromuscular Transmission

    Science.gov (United States)

    Naranjo, David; Wen, Hua; Brehm, Paul

    2015-01-01

    The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925

  11. Systematic Study of Binding of μ-Conotoxins to the Sodium Channel NaV1.4

    Directory of Open Access Journals (Sweden)

    Somayeh Mahdavi

    2014-12-01

    Full Text Available Voltage-gated sodium channels (NaV are fundamental components of the nervous system. Their dysfunction is implicated in a number of neurological disorders, such as chronic pain, making them potential targets for the treatment of such disorders. The prominence of the NaV channels in the nervous system has been exploited by venomous animals for preying purposes, which have developed toxins that can block the NaV channels, thereby disabling their function. Because of their potency, such toxins could provide drug leads for the treatment of neurological disorders associated with NaV channels. However, most toxins lack selectivity for a given target NaV channel, and improving their selectivity profile among the NaV1 isoforms is essential for their development as drug leads. Computational methods will be very useful in the solution of such design problems, provided accurate models of the protein-ligand complex can be constructed. Using docking and molecular dynamics simulations, we have recently constructed a model for the NaV1.4-μ-conotoxin-GIIIA complex and validated it with the ample mutational data available for this complex. Here, we use the validated NaV1.4 model in a systematic study of binding other μ-conotoxins (PIIIA, KIIIA and BuIIIB to NaV1.4. The binding mode obtained for each complex is shown to be consistent with the available mutation data and binding constants. We compare the binding modes of PIIIA, KIIIA and BuIIIB to that of GIIIA and point out the similarities and differences among them. The detailed information about NaV1.4-μ-conotoxin interactions provided here will be useful in the design of new NaV channel blocking peptides.

  12. Independent and cooperative motions of the Kv1.2 channel: voltage sensing and gating.

    Science.gov (United States)

    Yeheskel, Adva; Haliloglu, Turkan; Ben-Tal, Nir

    2010-05-19

    Voltage-gated potassium (Kv) channels, such as Kv1.2, are involved in the generation and propagation of action potentials. The Kv channel is a homotetramer, and each monomer is composed of a voltage-sensing domain (VSD) and a pore domain (PD). We analyzed the fluctuations of a model structure of Kv1.2 using elastic network models. The analysis suggested a network of coupled fluctuations of eight rigid structural units and seven hinges that may control the transition between the active and inactive states of the channel. For the most part, the network is composed of amino acids that are known to affect channel activity. The results suggested allosteric interactions and cooperativity between the subunits in the coupling between the motion of the VSD and the selectivity filter of the PD, in accordance with recent empirical data. There are no direct contacts between the VSDs of the four subunits, and the contacts between these and the PDs are loose, suggesting that the VSDs are capable of functioning independently. Indeed, they manifest many inherent fluctuations that are decoupled from the rest of the structure. In general, the analysis suggests that the two domains contribute to the channel function both individually and cooperatively. Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  13. Expression-dependent pharmacology of transient receptor potential vanilloid subtype 1 channels in Xenopus laevis oocytes

    DEFF Research Database (Denmark)

    Rivera-Acevedo, Ricardo E; Pless, Stephan Alexander; Schwarz, Stephan K W

    2013-01-01

    Transient receptor potential vanilloid subfamily member 1 channels are polymodal sensors of noxious stimuli and integral players in thermosensation, inflammation and pain signaling. It has been shown previously that under prolonged stimulation, these channels show dynamic pore dilation, providing...

  14. Enhancing interaural-delay-based extents of laterality at high frequencies by using ``transposed stimuli''

    Science.gov (United States)

    Bernstein, Leslie R.; Trahiotis, Constantine

    2003-06-01

    An acoustic pointing task was used to determine whether interaural temporal disparities (ITDs) conveyed by high-frequency ``transposed'' stimuli would produce larger extents of laterality than ITDs conveyed by bands of high-frequency Gaussian noise. The envelopes of transposed stimuli are designed to provide high-frequency channels with information similar to that conveyed by the waveforms of low-frequency stimuli. Lateralization was measured for low-frequency Gaussian noises, the same noises transposed to 4 kHz, and high-frequency Gaussian bands of noise centered at 4 kHz. Extents of laterality obtained with the transposed stimuli were greater than those obtained with bands of Gaussian noise centered at 4 kHz and, in some cases, were equivalent to those obtained with low-frequency stimuli. In a second experiment, the general effects on lateral position produced by imposed combinations of bandwidth, ITD, and interaural phase disparities (IPDs) on low-frequency stimuli remained when those stimuli were transposed to 4 kHz. Overall, the data were fairly well accounted for by a model that computes the cross-correlation subsequent to known stages of peripheral auditory processing augmented by low-pass filtering of the envelopes within the high-frequency channels of each ear.

  15. Trafficking of Kv2.1 Channels to the Axon Initial Segment by a Novel Nonconventional Secretory Pathway

    DEFF Research Database (Denmark)

    Jensen, Camilla Stampe; Watanabe, Shoji; Stas, Jeroen Ingrid

    2017-01-01

    the localization of Kv2.1 in these two different membrane compartments in cultured rat hippocampal neurons of mixed sex. Our data uncover a unique ability of Kv2.1 channels to use two molecularly distinct trafficking pathways to accomplish this. Somatodendritic Kv2.1 channels are targeted by the conventional...... secretory pathway, whereas axonal Kv2.1 channels are targeted by a nonconventional trafficking pathway independent of the Golgi apparatus. We further identified a new AIS trafficking motif in the C-terminus of Kv2.1, and show that putative phosphorylation sites in this region are critical for the restricted.......SIGNIFICANCE STATEMENT Our study uncovered a novel mechanism that targets the Kv2.1 voltage-gated potassium channel to two distinct trafficking pathways and two distinct subcellular destinations: the somatodendritic plasma membrane and that of the axon initial segment. We also identified a distinct motif, including...

  16. The AKAP Cypher/Zasp contributes to β-adrenergic/PKA stimulation of cardiac CaV1.2 calcium channels.

    Science.gov (United States)

    Yu, Haijie; Yuan, Can; Westenbroek, Ruth E; Catterall, William A

    2018-06-04

    Stimulation of the L-type Ca 2+ current conducted by Ca V 1.2 channels in cardiac myocytes by the β-adrenergic/protein kinase A (PKA) signaling pathway requires anchoring of PKA to the Ca V 1.2 channel by an A-kinase anchoring protein (AKAP). However, the AKAP(s) responsible for regulation in vivo remain unknown. Here, we test the role of the AKAP Cypher/Zasp in β-adrenergic regulation of Ca V 1.2 channels using physiological studies of cardiac ventricular myocytes from young-adult mice lacking the long form of Cypher/Zasp (LCyphKO mice). These myocytes have increased protein levels of Ca V 1.2, PKA, and calcineurin. In contrast, the cell surface density of Ca V 1.2 channels and the basal Ca 2+ current conducted by Ca V 1.2 channels are significantly reduced without substantial changes to kinetics or voltage dependence. β-adrenergic regulation of these L-type Ca 2+ currents is also significantly reduced in myocytes from LCyphKO mice, whether calculated as a stimulation ratio or as net-stimulated Ca 2+ current. At 100 nM isoproterenol, the net β-adrenergic-Ca 2+ current conducted by Ca V 1.2 channels was reduced to 39 ± 12% of wild type. However, concentration-response curves for β-adrenergic stimulation of myocytes from LCyphKO mice have concentrations that give a half-maximal response similar to those for wild-type mice. These results identify Cypher/Zasp as an important AKAP for β-adrenergic regulation of cardiac Ca V 1.2 channels. Other AKAPs may work cooperatively with Cypher/Zasp to give the full magnitude of β-adrenergic regulation of Ca V 1.2 channels observed in vivo. This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may apply.

  17. A Case of Morvan Syndrome Mimicking Amyotrophic Lateral Sclerosis With Frontotemporal Dementia.

    Science.gov (United States)

    Freund, Brin; Maddali, Manoj; Lloyd, Thomas E

    2016-06-01

    Morvan syndrome is a rare autoimmune/paraneoplastic disorder involving antibodies to the voltage-gated potassium channel complex. It is defined by subacute encephalopathy, neuromuscular hyperexcitability, dysautonomia, and sleep disturbance. It may present a diagnostic dilemma when trying to differentiate from amyotrophic lateral sclerosis with frontotemporal dementia. A 76-year-old man with a history of untreated prostate adenocarcinoma was evaluated for subacute cognitive decline, diffuse muscle cramps, and hyponatremia. MRI demonstrated atrophy most prominent in the frontal and temporal regions. Electromyography (EMG) demonstrated diffuse myokymia/neuromyotonia. Polysomnography lacked REM and N3 sleep. Paraneoplastic panel detected antibodies to voltage-gated potassium channel complex (CASPR2 subtype). It is difficult to differentiate between Morvan syndrome and amyotrophic lateral sclerosis with frontotemporal dementia with examination and neuroimaging alone. There may be a link between Morvan syndrome and prostate adenocarcinoma which could help with screening/diagnosis. The authors found that laboratory and neurophysiological tests are indispensable in diagnosing and treating Morvan syndrome.

  18. Cooperative endocytosis of the endosomal SNARE protein syntaxin-8 and the potassium channel TASK-1

    Science.gov (United States)

    Renigunta, Vijay; Fischer, Thomas; Zuzarte, Marylou; Kling, Stefan; Zou, Xinle; Siebert, Kai; Limberg, Maren M.; Rinné, Susanne; Decher, Niels; Schlichthörl, Günter; Daut, Jürgen

    2014-01-01

    The endosomal SNARE protein syntaxin-8 interacts with the acid-sensitive potassium channel TASK-1. The functional relevance of this interaction was studied by heterologous expression of these proteins (and mutants thereof) in Xenopus oocytes and in mammalian cell lines. Coexpression of syntaxin-8 caused a fourfold reduction in TASK-1 current, a corresponding reduction in the expression of TASK-1 at the cell surface, and a marked increase in the rate of endocytosis of the channel. TASK-1 and syntaxin-8 colocalized in the early endosomal compartment, as indicated by the endosomal markers 2xFYVE and rab5. The stimulatory effect of the SNARE protein on the endocytosis of the channel was abolished when both an endocytosis signal in TASK-1 and an endocytosis signal in syntaxin-8 were mutated. A syntaxin-8 mutant that cannot assemble with other SNARE proteins had virtually the same effect as wild-type syntaxin-8. Total internal reflection fluorescence microscopy showed formation and endocytosis of vesicles containing fluorescence-tagged clathrin, TASK-1, and/or syntaxin-8. Our results suggest that the unassembled form of syntaxin-8 and the potassium channel TASK-1 are internalized via clathrin-mediated endocytosis in a cooperative manner. This implies that syntaxin-8 regulates the endocytosis of TASK-1. Our study supports the idea that endosomal SNARE proteins can have functions unrelated to membrane fusion. PMID:24743596

  19. Inertial manipulation of bubbles in rectangular microfluidic channels.

    Science.gov (United States)

    Hadikhani, Pooria; Hashemi, S Mohammad H; Balestra, Gioele; Zhu, Lailai; Modestino, Miguel A; Gallaire, François; Psaltis, Demetri

    2018-03-27

    Inertial microfluidics is an active field of research that deals with crossflow positioning of the suspended entities in microflows. Until now, the majority of the studies have focused on the behavior of rigid particles in order to provide guidelines for microfluidic applications such as sorting and filtering. Deformable entities such as bubbles and droplets are considered in fewer studies despite their importance in multiphase microflows. In this paper, we show that the trajectory of bubbles flowing in rectangular and square microchannels can be controlled by tuning the balance of forces acting on them. A T-junction geometry is employed to introduce bubbles into a microchannel and analyze their lateral equilibrium position in a range of Reynolds (1 < Re < 40) and capillary numbers (0.1 < Ca < 1). We find that the Reynolds number (Re), the capillary number (Ca), the diameter of the bubble (D[combining macron]), and the aspect ratio of the channel are the influential parameters in this phenomenon. For instance, at high Re, the flow pushes the bubble towards the wall while large Ca or D[combining macron] moves the bubble towards the center. Moreover, in the shallow channels, having aspect ratios higher than one, the bubble moves towards the narrower sidewalls. One important outcome of this study is that the equilibrium position of bubbles in rectangular channels is different from that of solid particles. The experimental observations are in good agreement with the performed numerical simulations and provide insights into the dynamics of bubbles in laminar flows which can be utilized in the design of flow based multiphase flow reactors.

  20. Cervical myelography via C1/C2 lateral puncture

    International Nuclear Information System (INIS)

    Grange, B.

    1981-01-01

    The use of the water soluble, tri-iodinated contrast medium, metrizamide, in cervical myelography via C1/C2 lateral puncture is described. Details of the tomographic apparatus and the technique employed are given. The advantages of water soluble myelography using metrizamide are overwhelming due to its miscibility with CSF, improved anatomical demonstration, radiographic visualisation and diagnostic accuracy and advantageous pharmacological properties with reduced toxicity. This technique provided successful diagnoses in a series of 104 patients. (U.K.)

  1. Functional characterization of Kv11.1 (hERG) potassium channels split in the voltage-sensing domain.

    Science.gov (United States)

    de la Peña, Pilar; Domínguez, Pedro; Barros, Francisco

    2018-03-23

    Voltage-dependent KCNH family potassium channel functionality can be reconstructed using non-covalently linked voltage-sensing domain (VSD) and pore modules (split channels). However, the necessity of a covalent continuity for channel function has not been evaluated at other points within the two functionally independent channel modules. We find here that by cutting Kv11.1 (hERG, KCNH2) channels at the different loops linking the transmembrane spans of the channel core, not only channels split at the S4-S5 linker level, but also those split at the intracellular S2-S3 and the extracellular S3-S4 loops, yield fully functional channel proteins. Our data indicate that albeit less markedly, channels split after residue 482 in the S2-S3 linker resemble the uncoupled gating phenotype of those split at the C-terminal end of the VSD S4 transmembrane segment. Channels split after residues 514 and 518 in the S3-S4 linker show gating characteristics similar to those of the continuous wild-type channel. However, breaking the covalent link at this level strongly accelerates the voltage-dependent accessibility of a membrane impermeable methanethiosulfonate reagent to an engineered cysteine at the N-terminal region of the S4 transmembrane helix. Thus, besides that of the S4-S5 linker, structural integrity of the intracellular S2-S3 linker seems to constitute an important factor for proper transduction of VSD rearrangements to opening and closing the cytoplasmic gate. Furthermore, our data suggest that the short and probably rigid characteristics of the extracellular S3-S4 linker are not an essential component of the Kv11.1 voltage sensing machinery.

  2. Processes Leading to Beaded Channels Formation in Central Yakutia

    Science.gov (United States)

    Tarbeeva, A. M.; Lebedeva, L.; Efremov, V. S.; Krylenko, I. V.; Surkov, V. V.

    2017-12-01

    Beaded channels, consisting of deepened and widened pools and connecting narrow runs, are common fluvial forms in permafrost regions. Recent studies have shown that beaded channels are very important for connecting alluvial rivers with headwater lakes allowing fish passage and foraging habitats, as well as regulating river runoff. Beaded channels are known as typical thermokarst landforms; however, there is no evidence of their origin and formative processes. Geomorphological analyzes of beaded channels have been completed in several permafrost regions including field observations of Shestakovka River in Central Yakutia. The study aims to recognize the modern exogenic processes and formative mechanisms of beaded river channels. We show that beaded channel of Shestakovka River form in the perennially frozen sand with low ice content, leading us to hypothesize that thermokarst is not the main process of formation. Due to the significant volume of water, the pools don't freeze over entirely during winters, even under harsh climatic conditions. As a result, lenses of pressurized water remain under surface ice underlain by perennially thawed sediments. The presence of thawed sediments under the pools and frozen sediments under the runs leads to uneven thermoerosion of the riverbed during floods, providing the beaded form of the channel. In addition, freezing of pools during winter leads to pressure increasing under ice cover and formation of ice mounds, which crack several times during winter leading to disturbance of riverbanks. Many 1st to 3rd order streams have a specific transitional meandering-to-beaded form resembling the shape of unconfined meandering rivers, but consisting of pools and runs. However, such channels exhibit no evidences of present-day erosion of concave banks and sediment accumulation at the convex banks as typically being observed in normally meandering rivers. Such forms of channels indicates that their formation occurred by the greater channel

  3. Fluid velocity in outer channels of tube bundle of PGV-1 steam generator prototype

    International Nuclear Information System (INIS)

    Salgo, C.

    1979-01-01

    This paper deals with the determination of the fluid velocity and pressure in every channel outside the tube bundle of the prototype model of the steam generator PGV-1, designed jointly by CNEN and NIRA. The results are obtained by the numerical solution of a system of algebraic and differential equations deduced by a mathematical ''channel'' model. Such results agree with the experiments performed on a model of the prototype PGV-1 by Alsthom Technique des Fluides

  4. Lateral supraorbital approach to ipsilateral PCA-P1 and ICA-PCoA aneurysms.

    Science.gov (United States)

    Goehre, Felix; Jahromi, Behnam Rezai; Elsharkawy, Ahmed; Lehto, Hanna; Shekhtman, Oleg; Andrade-Barazarte, Hugo; Munoz, Francisco; Hijazy, Ferzat; Makhkamov, Makhkam; Hernesniemi, Juha

    2015-01-01

    Aneurysms of the posterior cerebral artery (PCA) are rare and often associated with anterior circulation aneurysms. The lateral supraorbital approach allows for a very fast and safe approach to the ipsilateral lesions Circle of Willis. A technical note on the successful clip occlusion of two aneurysms in the anterior and posterior Circle of Willis via this less invasive approach has not been published before. The objective of this technical note is to describe the simultaneous microsurgical clip occlusion of an ipsilateral PCA-P1 and an internal carotid artery - posterior communicating artery (ICA-PCoA) aneurysm via the lateral supraorbital approach. The authors present a technical report of successful clip occlusions of ipsilateral located PCA-P1 and ICA-PCoA aneurysms. A 59-year-old female patient was diagnosed with a PCA-P1 and an ipsilateral ICA-PCoA aneurysm by computed tomography angiography (CTA) after an ischemic stroke secondary to a contralateral ICA dissection. The patient underwent microsurgical clipping after a lateral supraorbital craniotomy. The intraoperative indocyanine green (ICG) videoangiography and the postoperative CTA showed a complete occlusion of both aneurysms; the parent vessels (ICA and PCA) were patent. The patient presents postoperative no new neurologic deficit. The lateral supraorbital approach is suitable for the simultaneous microsurgical treatment of proximal anterior circulation and ipsilateral proximal PCA aneurysms. Compared to endovascular treatment, direct visual control of brainstem perforators is possible.

  5. Expression of the transient receptor potential channels TRPV1, TRPA1 and TRPM8 in mouse trigeminal primary afferent neurons innervating the dura

    Science.gov (United States)

    2012-01-01

    Background Migraine and other headache disorders affect a large percentage of the population and cause debilitating pain. Activation and sensitization of the trigeminal primary afferent neurons innervating the dura and cerebral vessels is a crucial step in the “headache circuit”. Many dural afferent neurons respond to algesic and inflammatory agents. Given the clear role of the transient receptor potential (TRP) family of channels in both sensing chemical stimulants and mediating inflammatory pain, we investigated the expression of TRP channels in dural afferent neurons. Methods We used two fluorescent tracers to retrogradely label dural afferent neurons in adult mice and quantified the abundance of peptidergic and non-peptidergic neuron populations using calcitonin gene-related peptide immunoreactivity (CGRP-ir) and isolectin B4 (IB4) binding as markers, respectively. Using immunohistochemistry, we compared the expression of TRPV1 and TRPA1 channels in dural afferent neurons with the expression in total trigeminal ganglion (TG) neurons. To examine the distribution of TRPM8 channels, we labeled dural afferent neurons in mice expressing farnesylated enhanced green fluorescent protein (EGFPf) from a TRPM8 locus. We used nearest-neighbor measurement to predict the spatial association between dural afferent neurons and neurons expressing TRPA1 or TRPM8 channels in the TG. Results and conclusions We report that the size of dural afferent neurons is significantly larger than that of total TG neurons and facial skin afferents. Approximately 40% of dural afferent neurons exhibit IB4 binding. Surprisingly, the percentage of dural afferent neurons containing CGRP-ir is significantly lower than those of total TG neurons and facial skin afferents. Both TRPV1 and TRPA1 channels are expressed in dural afferent neurons. Furthermore, nearest-neighbor measurement indicates that TRPA1-expressing neurons are clustered around a subset of dural afferent neurons. Interestingly, TRPM

  6. Phosphatidylinositol (4,5)Bisphosphate Inhibits K+-Efflux Channel Activity in NT1 Tobacco Cultured Cells1[W][OA

    Science.gov (United States)

    Ma, Xiaohong; Shor, Oded; Diminshtein, Sofia; Yu, Ling; Im, Yang Ju; Perera, Imara; Lomax, Aaron; Boss, Wendy F.; Moran, Nava

    2009-01-01

    In the animal world, the regulation of ion channels by phosphoinositides (PIs) has been investigated extensively, demonstrating a wide range of channels controlled by phosphatidylinositol (4,5)bisphosphate (PtdInsP2). To understand PI regulation of plant ion channels, we examined the in planta effect of PtdInsP2 on the K+-efflux channel of tobacco (Nicotiana tabacum), NtORK (outward-rectifying K channel). We applied a patch clamp in the whole-cell configuration (with fixed “cytosolic” Ca2+ concentration and pH) to protoplasts isolated from cultured tobacco cells with genetically manipulated plasma membrane levels of PtdInsP2 and cellular inositol (1,4,5)trisphosphate: “Low PIs” had depressed levels of these PIs, and “High PIs” had elevated levels relative to controls. In all of these cells, K channel activity, reflected in the net, steady-state outward K+ currents (IK), was inversely related to the plasma membrane PtdInsP2 level. Consistent with this, short-term manipulations decreasing PtdInsP2 levels in the High PIs, such as pretreatment with the phytohormone abscisic acid (25 μm) or neutralizing the bath solution from pH 5.6 to pH 7, increased IK (i.e. NtORK activity). Moreover, increasing PtdInsP2 levels in controls or in abscisic acid-treated high-PI cells, using the specific PI-phospholipase C inhibitor U73122 (2.5–4 μm), decreased NtORK activity. In all cases, IK decreases stemmed largely from decreased maximum attainable NtORK channel conductance and partly from shifted voltage dependence of channel gating to more positive potentials, making it more difficult to activate the channels. These results are consistent with NtORK inhibition by the negatively charged PtdInsP2 in the internal plasma membrane leaflet. Such effects are likely to underlie PI signaling in intact plant cells. PMID:19052153

  7. Two distinct voltage-sensing domains control voltage sensitivity and kinetics of current activation in CaV1.1 calcium channels.

    Science.gov (United States)

    Tuluc, Petronel; Benedetti, Bruno; Coste de Bagneaux, Pierre; Grabner, Manfred; Flucher, Bernhard E

    2016-06-01

    Alternative splicing of the skeletal muscle CaV1.1 voltage-gated calcium channel gives rise to two channel variants with very different gating properties. The currents of both channels activate slowly; however, insertion of exon 29 in the adult splice variant CaV1.1a causes an ∼30-mV right shift in the voltage dependence of activation. Existing evidence suggests that the S3-S4 linker in repeat IV (containing exon 29) regulates voltage sensitivity in this voltage-sensing domain (VSD) by modulating interactions between the adjacent transmembrane segments IVS3 and IVS4. However, activation kinetics are thought to be determined by corresponding structures in repeat I. Here, we use patch-clamp analysis of dysgenic (CaV1.1 null) myotubes reconstituted with CaV1.1 mutants and chimeras to identify the specific roles of these regions in regulating channel gating properties. Using site-directed mutagenesis, we demonstrate that the structure and/or hydrophobicity of the IVS3-S4 linker is critical for regulating voltage sensitivity in the IV VSD, but by itself cannot modulate voltage sensitivity in the I VSD. Swapping sequence domains between the I and the IV VSDs reveals that IVS4 plus the IVS3-S4 linker is sufficient to confer CaV1.1a-like voltage dependence to the I VSD and that the IS3-S4 linker plus IS4 is sufficient to transfer CaV1.1e-like voltage dependence to the IV VSD. Any mismatch of transmembrane helices S3 and S4 from the I and IV VSDs causes a right shift of voltage sensitivity, indicating that regulation of voltage sensitivity by the IVS3-S4 linker requires specific interaction of IVS4 with its corresponding IVS3 segment. In contrast, slow current kinetics are perturbed by any heterologous sequences inserted into the I VSD and cannot be transferred by moving VSD I sequences to VSD IV. Thus, CaV1.1 calcium channels are organized in a modular manner, and control of voltage sensitivity and activation kinetics is accomplished by specific molecular mechanisms

  8. Synthetic ciguatoxins selectively activate Nav1.8-derived chimeric sodium channels expressed in HEK293 cells.

    Science.gov (United States)

    Yamaoka, Kaoru; Inoue, Masayuki; Miyazaki, Keisuke; Hirama, Masahiro; Kondo, Chie; Kinoshita, Eiji; Miyoshi, Hiroshi; Seyama, Issei

    2009-03-20

    The synthetic ciguatoxin CTX3C has been shown to activate tetrodotoxin (TTX)-sensitive sodium channels (Na(v)1.2, Na(v)1.4, and Na(v)1.5) by accelerating activation kinetics and shifting the activation curve toward hyperpolarization (Yamaoka, K., Inoue, M., Miyahara, H., Miyazaki, K., and Hirama, M. (2004) Br. J. Pharmacol. 142, 879-889). In this study, we further explored the effects of CTX3C on the TTX-resistant sodium channel Na(v)1.8. TTX-resistant channels have been shown to be involved in transducing pain and related sensations (Akopian, A. N., Sivilotti, L., and Wood, J. N. (1996) Nature 379, 257-262). Thus, we hypothesized that ciguatoxin-induced activation of the Na(v)1.8 current would account for the neurological symptoms of ciguatera poisoning. We found that 0.1 mum CTX3C preferentially affected the activation process of the Na(v)1.8 channel compared with those of the Na(v)1.2 and Na(v)1.4 channels. Importantly, without stimulation, 0.1 mum CTX3C induced a large leakage current (I (L)). The conductance of the I (L) calculated relative to the maximum conductance (G (max)) was 10 times larger than that of Na(v)1.2 or Na(v)1.4. To determine the molecular domain of Na(v)1.8 responsible for conferring higher sensitivity to CTX3C, we made two chimeric constructs from Na(v)1.4 and Na(v)1.8. Chimeras containing the N-terminal half of Na(v)1.8 exhibited a large response similar to wild-type Na(v)1.8, indicating that the region conferring high sensitivity to ciguatoxin action is located in the D1 or D2 domains.

  9. Voltage-sensing domain of voltage-gated proton channel Hv1 shares mechanism of block with pore domains.

    Science.gov (United States)

    Hong, Liang; Pathak, Medha M; Kim, Iris H; Ta, Dennis; Tombola, Francesco

    2013-01-23

    Voltage-gated sodium, potassium, and calcium channels are made of a pore domain (PD) controlled by four voltage-sensing domains (VSDs). The PD contains the ion permeation pathway and the activation gate located on the intracellular side of the membrane. A large number of small molecules are known to inhibit the PD by acting as open channel blockers. The voltage-gated proton channel Hv1 is made of two VSDs and lacks the PD. The location of the activation gate in the VSD is unknown and open channel blockers for VSDs have not yet been identified. Here, we describe a class of small molecules which act as open channel blockers on the Hv1 VSD and find that a highly conserved phenylalanine in the charge transfer center of the VSD plays a key role in blocker binding. We then use one of the blockers to show that Hv1 contains two intracellular and allosterically coupled gates. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Elementary properties of CaV1.3 Ca2+ channels expressed in mouse cochlear inner hair cells

    Science.gov (United States)

    Zampini, Valeria; Johnson, Stuart L; Franz, Christoph; Lawrence, Neil D; Münkner, Stefan; Engel, Jutta; Knipper, Marlies; Magistretti, Jacopo; Masetto, Sergio; Marcotti, Walter

    2010-01-01

    Mammalian cochlear inner hair cells (IHCs) are specialized to process developmental signals during immature stages and sound stimuli in adult animals. These signals are conveyed onto auditory afferent nerve fibres. Neurotransmitter release at IHC ribbon synapses is controlled by L-type CaV1.3 Ca2+ channels, the biophysics of which are still unknown in native mammalian cells. We have investigated the localization and elementary properties of Ca2+ channels in immature mouse IHCs under near-physiological recording conditions. CaV1.3 Ca2+ channels at the cell pre-synaptic site co-localize with about half of the total number of ribbons present in immature IHCs. These channels activated at about −70 mV, showed a relatively short first latency and weak inactivation, which would allow IHCs to generate and accurately encode spontaneous Ca2+ action potential activity characteristic of these immature cells. The CaV1.3 Ca2+ channels showed a very low open probability (about 0.15 at −20 mV: near the peak of an action potential). Comparison of elementary and macroscopic Ca2+ currents indicated that very few Ca2+ channels are associated with each docked vesicle at IHC ribbon synapses. Finally, we found that the open probability of Ca2+ channels, but not their opening time, was voltage dependent. This finding provides a possible correlation between presynaptic Ca2+ channel properties and the characteristic frequency/amplitude of EPSCs in auditory afferent fibres. PMID:19917569

  11. Elementary properties of CaV1.3 Ca(2+) channels expressed in mouse cochlear inner hair cells.

    Science.gov (United States)

    Zampini, Valeria; Johnson, Stuart L; Franz, Christoph; Lawrence, Neil D; Münkner, Stefan; Engel, Jutta; Knipper, Marlies; Magistretti, Jacopo; Masetto, Sergio; Marcotti, Walter

    2010-01-01

    Mammalian cochlear inner hair cells (IHCs) are specialized to process developmental signals during immature stages and sound stimuli in adult animals. These signals are conveyed onto auditory afferent nerve fibres. Neurotransmitter release at IHC ribbon synapses is controlled by L-type Ca(V)1.3 Ca(2+) channels, the biophysics of which are still unknown in native mammalian cells. We have investigated the localization and elementary properties of Ca(2+) channels in immature mouse IHCs under near-physiological recording conditions. Ca(V)1.3 Ca(2+) channels at the cell pre-synaptic site co-localize with about half of the total number of ribbons present in immature IHCs. These channels activated at about 70 mV, showed a relatively short first latency and weak inactivation, which would allow IHCs to generate and accurately encode spontaneous Ca(2+) action potential activity characteristic of these immature cells. The Ca(V)1.3 Ca(2+) channels showed a very low open probability (about 0.15 at 20 mV: near the peak of an action potential). Comparison of elementary and macroscopic Ca(2+) currents indicated that very few Ca(2+) channels are associated with each docked vesicle at IHC ribbon synapses. Finally, we found that the open probability of Ca(2+) channels, but not their opening time, was voltage dependent. This finding provides a possible correlation between presynaptic Ca(2+) channel properties and the characteristic frequency/amplitude of EPSCs in auditory afferent fibres.

  12. Multiserver Queue with Guard Channel for Priority and Retrial Customers

    Directory of Open Access Journals (Sweden)

    Kazuki Kajiwara

    2016-01-01

    Full Text Available This paper considers a retrial queueing model where a group of guard channels is reserved for priority and retrial customers. Priority and normal customers arrive at the system according to two distinct Poisson processes. Priority customers are accepted if there is an idle channel upon arrival while normal customers are accepted if and only if the number of idle channels is larger than the number of guard channels. Blocked customers (priority or normal join a virtual orbit and repeat their attempts in a later time. Customers from the orbit (retrial customers are accepted if there is an idle channel available upon arrival. We formulate the queueing system using a level dependent quasi-birth-and-death (QBD process. We obtain a Taylor series expansion for the nonzero elements of the rate matrices of the level dependent QBD process. Using the expansion results, we obtain an asymptotic upper bound for the joint stationary distribution of the number of busy channels and that of customers in the orbit. Furthermore, we develop an efficient numerical algorithm to calculate the joint stationary distribution.

  13. Martian channels and valleys - Their characteristics, distribution, and age

    Science.gov (United States)

    Carr, M. H.; Clow, G. D.

    1981-01-01

    The distribution and ages of Martian channels and valleys, which are generally believed to have been cut by running water, are examined with particular emphasis on the small branching networks referred to as runoff channels or valley networks. Valleys at latitudes from 65 deg S to 65 deg N were surveyed on Viking images at resolutions between 125 and 300 m. Almost all of the valleys are found in the old cratered terrain, in areas characterized by high elevations, low albedos and low violet/red ratios. The networks are deduced to have formed early in the history of the planet, with a formation rate declining rapidly shortly after the decline of the cratering rate 3.9 billion years ago. Two types of outflow channels are distinguished: unconfined, in which broad swaths of terrain are scoured, and confined, in which flow is restricted to discrete channels. Both types start at local sources, and have formed episodically throughout Martian history. Fretted channels, found mainly in two latitude belts characterized by relatively rapid erosion along escarpments, are explained by the lateral enlargement of other channels by mass wasting.

  14. Oestrogen directly inhibits the cardiovascular L-type Ca2+ channel Cav1.2

    International Nuclear Information System (INIS)

    Ullrich, Nina D.; Koschak, Alexandra; MacLeod, Kenneth T.

    2007-01-01

    Oestrogen can modify the contractile function of vascular smooth muscle and cardiomyocytes. The negative inotropic actions of oestrogen on the heart and coronary vasculature appear to be mediated by L-type Ca 2+ channel (Ca v 1.2) inhibition, but the underlying mechanisms remain elusive. We tested the hypothesis that oestrogen directly inhibits the cardiovascular L-type Ca 2+ current, I CaL . The effect of oestrogen on I CaL was measured in Ca v 1.2-transfected HEK-293 cells using the whole-cell patch-clamp technique. The current revealed typical activation and inactivation profiles of nifedipine- and cadmium-sensitive I CaL . Oestrogen (50 μM) rapidly reduced I CaL by 50% and shifted voltage-dependent activation and availability to more negative potentials. Furthermore, oestrogen blocked the Ca 2+ channel in a rate-dependent way, exhibiting higher efficiency of block at higher stimulation frequencies. Our data suggest that oestrogen inhibits I CaL through direct interaction of the steroid with the channel protein

  15. Membrane-tethered peptides patterned after the TRP domain (TRPducins) selectively inhibit TRPV1 channel activity.

    Science.gov (United States)

    Valente, Pierluigi; Fernández-Carvajal, Asia; Camprubí-Robles, María; Gomis, Ana; Quirce, Susana; Viana, Félix; Fernández-Ballester, Gregorio; González-Ros, José M; Belmonte, Carlos; Planells-Cases, Rosa; Ferrer-Montiel, Antonio

    2011-05-01

    The transient receptor potential vanilloid 1 (TRPV1) channel is a thermosensory receptor implicated in diverse physiological and pathological processes. The TRP domain, a highly conserved region in the C terminus adjacent to the internal channel gate, is critical for subunit tetramerization and channel gating. Here, we show that cell-penetrating, membrane-anchored peptides patterned after this protein domain are moderate and selective TRPV1 antagonists both in vitro and in vivo, blocking receptor activity in intact rat primary sensory neurons and their peripheral axons with mean decline time of 30 min. The most potent lipopeptide, TRP-p5, blocked all modes of TRPV1 gating with micromolar efficacy (IC(50)100 μM). TRP-p5 did not affect the capsaicin sensitivity of the vanilloid receptor. Our data suggest that TRP-p5 interferes with protein-protein interactions at the level of the TRP domain that are essential for the "conformational" change that leads to gate opening. Therefore, these palmitoylated peptides, which we termed TRPducins, are noncompetitive, voltage-independent, sequence-specific TRPV1 blockers. Our findings indicate that TRPducin-like peptides may embody a novel molecular strategy that can be exploited to generate a selective pharmacological arsenal for the TRP superfamily of ion channels.

  16. The bifunctional abiotic stress signalling regulator and endogenous RNA silencing suppressor FIERY1 is required for lateral root formation

    KAUST Repository

    Chen, Hao

    2010-09-28

    The Arabidopsis FIERY1 (FRY1) locus was originally identified as a negative regulator of stress-responsive gene expression and later shown to be required for suppression of RNA silencing. In this study we discovered that the FRY1 locus also regulates lateral root formation. Compared with the wild type, fry1 mutant seedlings generated significantly fewer lateral roots under normal growth conditions and also exhibited a dramatically reduced sensitivity to auxin in inducing lateral root initiation. Using transgenic plants that overexpress a yeast homolog of FRY1 that possesses only the 3\\', 5\\'-bisphosphate nucleotidase activity but not the inositol 1-phosphatase activity, we demonstrated that the lateral root phenotypes in fry1 result from loss of the nucleotidase activity. Furthermore, a T-DNA insertion mutant of another RNA silencing suppressor, XRN4 (but not XRN2 or XRN3), which is an exoribonuclease that is inhibited by the substrate of the FRY1 3\\', 5\\'-bisphosphate nucleotidase, exhibits similar lateral root defects. Although fry1 and xrn4 exhibited reduced sensitivity to ethylene, our experiments demonstrated that restoration of ethylene sensitivity in the fry1 mutant is not sufficient to rescue the lateral root phenotypes of fry1. Our results indicate that RNA silencing modulated by FRY1 and XRN4 plays an important role in shaping root architecture. © 2010 Blackwell Publishing Ltd.

  17. Renal effects of renal x irradiation and induced autoallergic glomerulonephritis

    International Nuclear Information System (INIS)

    Rappaport, D.S.

    1977-01-01

    This study was conducted to determine what, if any, influence a single large x-ray exposure of kidney has on the development and course of an experimental autoallergic glomerulonephritis (EAG) in rats. The EAG was induced by immunization with B. pertussis vaccine and homogenate of homologous kidney tissue and Freund's complete adjuvant. Rats were either immunized, sham-immunized, irradiated (1500 R to right kidney temporarily exteriorized), sham-irradiated, or both immunized and irradiated. Immunized-irradiated animals were irradiated either 4 or 2 weeks prior to, concurrently with, or 1 or 2 weeks after immunization, and were sacrificed at 2, 4, 6, 10, or 14 weeks post-immunization. Immunized-only and sham-immunized-only animals were sacrificed at corresponding post-immunization times, and irradiated-only and sham-irradiated-only animals were sacrificed at corresponding post-irradiation times. Progressive arteriolonephrosclerosis (ANA) was observed in right (irradiated) kidneys following x irradiation. The experimental autoallergic glomerulonephritis (EAG) was observed in both kidneys following immunization. The histopathological changes associated with EAG were distinct from those associated with ANS

  18. Effects of the β1 auxiliary subunit on modification of Rat Na{sub v}1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin

    Energy Technology Data Exchange (ETDEWEB)

    He, Bingjun [College of Life Sciences, Nankai University, Tianjin 300071 (China); Soderlund, David M., E-mail: dms6@cornell.edu [Department of Entomology, Cornell University, Geneva, NY 14456 (United States)

    2016-01-15

    We expressed rat Na{sub v}1.6 sodium channels with or without the rat β1 subunit in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on whole-cell sodium currents. In assays with the Na{sub v}1.6 α subunit alone, both pyrethroids prolonged channel inactivation and deactivation and shifted the voltage dependence of channel activation and steady-state inactivation toward hyperpolarization. Maximal shifts in activation were ~ 18 mV for tefluthrin and ~ 24 mV for deltamethrin. These compounds also caused hyperpolarizing shifts of ~ 10–14 mV in the voltage dependence of steady-state inactivation and increased in the fraction of sodium current that was resistant to inactivation. The effects of pyrethroids on the voltage-dependent gating greatly increased the size of sodium window currents compared to unmodified channels; modified channels exhibited increased probability of spontaneous opening at membrane potentials more negative than the normal threshold for channel activation and incomplete channel inactivation. Coexpression of Na{sub v}1.6 with the β1 subunit had no effect on the kinetic behavior of pyrethroid-modified channels but had divergent effects on the voltage-dependent gating of tefluthrin- or deltamethrin-modified channels, increasing the size of tefluthrin-induced window currents but decreasing the size of corresponding deltamethrin-induced currents. Unexpectedly, the β1 subunit did not confer sensitivity to use-dependent channel modification by either tefluthrin or deltamethrin. We conclude from these results that functional reconstitution of channels in vitro requires careful attention to the subunit composition of channel complexes to ensure that channels in vitro are faithful functional and pharmacological models of channels in neurons. - Highlights: • We expressed Na{sub v}1.6 sodium channels with or without β1 subunits in HEK293 cells. • Tefluthrin and deltamethrin

  19. Reliable lateral manipulation of a single Ag adatom on a Ag(1 1 1) surface with a trimer-apex tip

    International Nuclear Information System (INIS)

    Xie Yiqun; Shi Wangzhou; Du Guoping

    2009-01-01

    We study the reliability of the lateral manipulation of a single Ag adatom on a Ag(1 1 1) surface with the single-atom and trimer-apex tips based on molecular statics simulations using surface embedded-atom-method potential. The dependence of the manipulation reliability on tip height and orientation is investigated. For the single-atom tip the manipulation reliability increases monotonically with decreasing tip height, which is owing to the strengthened lateral tip-adatom interaction as the tip height lowers. For the trimer-apex tip, the manipulation reliability is sensitive to the tip orientation in the lower tip-height range, while in the higher tip-height range the manipulation reliability is independent of the tip orientation and moreover can be greatly improved due to the strong vertical attraction of the tip on the adatom as compared to the single-atom tip. We also compare these results to those for manipulating single Cu adatoms on the Cu(1 1 1) surface, reveal the underlying physics, and propose the method to improve the manipulation reliability for different systems.

  20. Lateral release of proteins from the TOM complex into the outer membrane of mitochondria.

    Science.gov (United States)

    Harner, Max; Neupert, Walter; Deponte, Marcel

    2011-07-15

    The TOM complex of the outer membrane of mitochondria is the entry gate for the vast majority of precursor proteins that are imported into the mitochondria. It is made up by receptors and a protein conducting channel. Although precursor proteins of all subcompartments of mitochondria use the TOM complex, it is not known whether its channel can only mediate passage across the outer membrane or also lateral release into the outer membrane. To study this, we have generated fusion proteins of GFP and Tim23 which are inserted into the inner membrane and, at the same time, are spanning either the TOM complex or are integrated into the outer membrane. Our results demonstrate that the TOM complex, depending on sequence determinants in the precursors, can act both as a protein conducting pore and as an insertase mediating lateral release into the outer membrane.

  1. Resolving vorticity-driven lateral fire spread using the WRF-Fire coupled atmosphere–fire numerical model

    OpenAIRE

    Simpson, C. C.; Sharples, J. J.; Evans, J. P.

    2014-01-01

    Fire channelling is a form of dynamic fire behaviour, during which a wildland fire spreads rapidly across a steep lee-facing slope in a direction transverse to the background winds, and is often accompanied by a downwind extension of the active flaming region and extreme pyro-convection. Recent work using the WRF-Fire coupled atmosphere-fire model has demonstrated that fire channelling can be characterised as vorticity-driven lateral fire spread (VDLS). In t...

  2. Channel and Floodplain Change Analysis over a 100-Year Period: Lower Yuba River, California

    Directory of Open Access Journals (Sweden)

    Rolf Aalto

    2010-07-01

    Full Text Available Hydraulic gold mining in the Sierra Nevada, California (1853–1884 displaced ~1.1 billion m3 of sediment from upland placer gravels that were deposited along piedmont rivers below dams where floods can remobilize them. This study uses topographic and planimetric data from detailed 1906 topographic maps, 1999 photogrammetric data, and pre- and post-flood aerial photographs to document historic sediment erosion and deposition along the lower Yuba River due to individual floods at the reach scale. Differencing of 3 × 3-m topographic data indicates substantial changes in channel morphology and documents 12.6 × 106 m3 of erosion and 5.8 × 106 m3 of deposition in these reaches since 1906. Planimetric and volumetric measurements document spatial and temporal variations of channel enlargement and lateral migration. Over the last century, channels incised up to ~13 m into mining sediments, which dramatically decreased local flood frequencies and increased flood conveyance. These adjustments were punctuated by event-scale geomorphic changes that redistributed sediment and associated contaminants to downstream lowlands.

  3. Quantum Channeling Effects for 1 MeV Positrons

    International Nuclear Information System (INIS)

    Haakenaasen, R.; Vestergaard Hau, L.; Golovchenko, J.A.; Palathingal, J.C.; Peng, J.P.; Asoka-Kumar, P.; Lynn, K.G.

    1995-01-01

    A high resolution angular study of positrons transmitted through a thin single crystal of Si clearly reveals a detailed fine structure due to strong quantum channeling effects. The beam transmitted in the forward direction displays many features associated with dynamical diffraction effects and long coherence lengths. Calculations are presented showing that in flight annihilation of channeled positrons can serve as a solid state probe of electron and spin densities in thin crystals

  4. Cholesterol modulates Orai1 channel function

    Czech Academy of Sciences Publication Activity Database

    Derler, I.; Jardin, I.; Stathopulos, P.B.; Muik, M.; Fahrner, M.; Zayats, Vasilina; Pandey, Saurabh Kumar; Poteser, M.; Lackner, B.; Absolonova, M.; Schindl, R.; Groschner, K.; Ettrich, Rüdiger; Ikura, M.; Romanin, Ch.

    2016-01-01

    Roč. 9, č. 412 (2016), ra10 ISSN 1945-0877 R&D Projects: GA ČR GA13-21053S Institutional support: RVO:61388971 Keywords : ACTIVATES CRAC CHANNELS * OPERATED CA2+ ENTRY * PLASMA-MEMBRANE Subject RIV: CE - Biochemistry Impact factor: 6.494, year: 2016

  5. Pore Polarity and Charge Determine Differential Block of Kir1.1 and Kir7.1 Potassium Channels by Small-Molecule Inhibitor VU590.

    Science.gov (United States)

    Kharade, Sujay V; Sheehan, Jonathan H; Figueroa, Eric E; Meiler, Jens; Denton, Jerod S

    2017-09-01

    VU590 was the first publicly disclosed, submicromolar-affinity (IC 50 = 0.2 μ M), small-molecule inhibitor of the inward rectifier potassium (Kir) channel and diuretic target, Kir1.1. VU590 also inhibits Kir7.1 (IC 50 ∼ 8 μ M), and has been used to reveal new roles for Kir7.1 in regulation of myometrial contractility and melanocortin signaling. Here, we employed molecular modeling, mutagenesis, and patch clamp electrophysiology to elucidate the molecular mechanisms underlying VU590 inhibition of Kir1.1 and Kir7.1. Block of both channels is voltage- and K + -dependent, suggesting the VU590 binding site is located within the pore. Mutagenesis analysis in Kir1.1 revealed that asparagine 171 (N171) is the only pore-lining residue required for high-affinity block, and that substituting negatively charged residues (N171D, N171E) at this position dramatically weakens block. In contrast, substituting a negatively charged residue at the equivalent position in Kir7.1 enhances block by VU590, suggesting the VU590 binding mode is different. Interestingly, mutations of threonine 153 (T153) in Kir7.1 that reduce constrained polarity at this site (T153C, T153V, T153S) make wild-type and binding-site mutants (E149Q, A150S) more sensitive to block by VU590. The Kir7.1-T153C mutation enhances block by the structurally unrelated inhibitor VU714 but not by a higher-affinity analog ML418, suggesting that the polar side chain of T153 creates a barrier to low-affinity ligands that interact with E149 and A150. Reverse mutations in Kir1.1 suggest that this mechanism is conserved in other Kir channels. This study reveals a previously unappreciated role of membrane pore polarity in determination of Kir channel inhibitor pharmacology. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

  6. Cardiac sodium channel Na(v)1.5 interacts with and is regulated by the protein tyrosine phosphatase PTPH1

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Gavillet, Bruno; van Bemmelen, Miguel X

    2006-01-01

    In order to identify proteins interacting with the cardiac voltage-gated sodium channel Na(v)1.5, we used the last 66 amino acids of the C-terminus of the channel as bait to screen a human cardiac cDNA library. We identified the protein tyrosine phosphatase PTPH1 as an interacting protein. Pull......-down experiments confirmed the interaction, and indicated that it depends on the PDZ-domain binding motif of Na(v)1.5. Co-expression experiments in HEK293 cells showed that PTPH1 shifts the Na(v)1.5 availability relationship toward hyperpolarized potentials, whereas an inactive PTPH1 or the tyrosine kinase Fyn...... does the opposite. The results of this study suggest that tyrosine phosphorylation destabilizes the inactivated state of Na(v)1.5....

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

    Directory of Open Access Journals (Sweden)

    Alan eNeely

    2014-06-01

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

  8. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels

    Science.gov (United States)

    Neely, Alan; Hidalgo, Patricia

    2014-01-01

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

  9. Ciguatoxins Evoke Potent CGRP Release by Activation of Voltage-Gated Sodium Channel Subtypes NaV1.9, NaV1.7 and NaV1.1

    Directory of Open Access Journals (Sweden)

    Filip Touska

    2017-08-01

    Full Text Available Ciguatoxins (CTXs are marine toxins that cause ciguatera fish poisoning, a debilitating disease dominated by sensory and neurological disturbances that include cold allodynia and various painful symptoms as well as long-lasting pruritus. Although CTXs are known as the most potent mammalian sodium channel activator toxins, the etiology of many of its neurosensory symptoms remains unresolved. We recently described that local application of 1 nM Pacific Ciguatoxin-1 (P-CTX-1 into the skin of human subjects induces a long-lasting, painful axon reflex flare and that CTXs are particularly effective in releasing calcitonin-gene related peptide (CGRP from nerve terminals. In this study, we used mouse and rat skin preparations and enzyme-linked immunosorbent assays (ELISA to study the molecular mechanism by which P-CTX-1 induces CGRP release. We show that P-CTX-1 induces CGRP release more effectively in mouse as compared to rat skin, exhibiting EC50 concentrations in the low nanomolar range. P-CTX-1-induced CGRP release from skin is dependent on extracellular calcium and sodium, but independent from the activation of various thermosensory transient receptor potential (TRP ion channels. In contrast, lidocaine and tetrodotoxin (TTX reduce CGRP release by 53–75%, with the remaining fraction involving L-type and T-type voltage-gated calcium channels (VGCC. Using transgenic mice, we revealed that the TTX-resistant voltage-gated sodium channel (VGSC NaV1.9, but not NaV1.8 or NaV1.7 alone and the combined activation of the TTX-sensitive VGSC subtypes NaV1.7 and NaV1.1 carry the largest part of the P-CTX-1-caused CGRP release of 42% and 34%, respectively. Given the contribution of CGRP to nociceptive and itch sensing pathways, our findings contribute to a better understanding of sensory symptoms of acute and chronic ciguatera that may help in the identification of potential therapeutics.

  10. Ciguatoxins Evoke Potent CGRP Release by Activation of Voltage-Gated Sodium Channel Subtypes NaV1.9, NaV1.7 and NaV1.1

    Science.gov (United States)

    Touska, Filip; Sattler, Simon; Malsch, Philipp; Lewis, Richard J.; Zimmermann, Katharina

    2017-01-01

    Ciguatoxins (CTXs) are marine toxins that cause ciguatera fish poisoning, a debilitating disease dominated by sensory and neurological disturbances that include cold allodynia and various painful symptoms as well as long-lasting pruritus. Although CTXs are known as the most potent mammalian sodium channel activator toxins, the etiology of many of its neurosensory symptoms remains unresolved. We recently described that local application of 1 nM Pacific Ciguatoxin-1 (P-CTX-1) into the skin of human subjects induces a long-lasting, painful axon reflex flare and that CTXs are particularly effective in releasing calcitonin-gene related peptide (CGRP) from nerve terminals. In this study, we used mouse and rat skin preparations and enzyme-linked immunosorbent assays (ELISA) to study the molecular mechanism by which P-CTX-1 induces CGRP release. We show that P-CTX-1 induces CGRP release more effectively in mouse as compared to rat skin, exhibiting EC50 concentrations in the low nanomolar range. P-CTX-1-induced CGRP release from skin is dependent on extracellular calcium and sodium, but independent from the activation of various thermosensory transient receptor potential (TRP) ion channels. In contrast, lidocaine and tetrodotoxin (TTX) reduce CGRP release by 53–75%, with the remaining fraction involving L-type and T-type voltage-gated calcium channels (VGCC). Using transgenic mice, we revealed that the TTX-resistant voltage-gated sodium channel (VGSC) NaV1.9, but not NaV1.8 or NaV1.7 alone and the combined activation of the TTX-sensitive VGSC subtypes NaV1.7 and NaV1.1 carry the largest part of the P-CTX-1-caused CGRP release of 42% and 34%, respectively. Given the contribution of CGRP to nociceptive and itch sensing pathways, our findings contribute to a better understanding of sensory symptoms of acute and chronic ciguatera that may help in the identification of potential therapeutics. PMID:28867800

  11. Clofazimine inhibits human Kv1.3 potassium channel by perturbing calcium oscillation in T lymphocytes.

    Directory of Open Access Journals (Sweden)

    Yunzhao R Ren

    Full Text Available The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders.

  12. Single amino acids in the carboxyl terminal domain of aquaporin-1 contribute to cGMP-dependent ion channel activation

    Directory of Open Access Journals (Sweden)

    Yool Andrea J

    2003-10-01

    Full Text Available Abstract Background Aquaporin-1 (AQP1 functions as an osmotic water channel and a gated cation channel. Activation of the AQP1 ion conductance by intracellular cGMP was hypothesized to involve the carboxyl (C- terminus, based on amino acid sequence alignments with cyclic-nucleotide-gated channels and cGMP-selective phosphodiesterases. Results Voltage clamp analyses of human AQP1 channels expressed in Xenopus oocytes demonstrated that the nitric oxide donor, sodium nitroprusside (SNP; 3–14 mM activated the ionic conductance response in a dose-dependent manner. Block of soluble guanylate cyclase prevented the response. Enzyme immunoassays confirmed a linear dose-dependent relationship between SNP and the resulting intracellular cGMP levels (up to 1700 fmol cGMP /oocyte at 14 mM SNP. Results here are the first to show that the efficacy of ion channel activation is decreased by mutations of AQP1 at conserved residues in the C-terminal domain (aspartate D237 and lysine K243. Conclusions These data support the idea that the limited amino acid sequence similarities found between three diverse classes of cGMP-binding proteins are significant to the function of AQP1 as a cGMP-gated ion channel, and provide direct evidence for the involvement of the AQP1 C-terminal domain in cGMP-mediated ion channel activation.

  13. Migration of finite sized particles in a laminar square channel flow from low to high Reynolds numbers

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, M., E-mail: micheline.abbas@ensiacet.fr [Laboratoire de Génie Chimique, Université de Toulouse INPT-UPS, 31030, Toulouse (France); CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Magaud, P. [CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Institut Clément Ader, Université de Toulouse UPS-INSA-ISAE-Mines Albi, 31400, Toulouse (France); Gao, Y. [Institut Clément Ader, Université de Toulouse UPS-INSA-ISAE-Mines Albi, 31400, Toulouse (France); Geoffroy, S. [CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Laboratoire Matériaux et Durabilité des Constructions, Université de Toulouse (France); UPS, INSA, 31077, Toulouse (France)

    2014-12-15

    The migration of neutrally buoyant finite sized particles in a Newtonian square channel flow is investigated in the limit of very low solid volumetric concentration, within a wide range of channel Reynolds numbers Re = [0.07-120]. In situ microscope measurements of particle distributions, taken far from the channel inlet (at a distance several thousand times the channel height), revealed that particles are preferentially located near the channel walls at Re > 10 and near the channel center at Re < 1. Whereas the cross-streamline particle motion is governed by inertia-induced lift forces at high inertia, it seems to be controlled by shear-induced particle interactions at low (but finite) Reynolds numbers, despite the low solid volume fraction (<1%). The transition between both regimes is observed in the range Re = [1-10]. In order to exclude the effect of multi-body interactions, the trajectories of single freely moving particles are calculated thanks to numerical simulations based on the force coupling method. With the deployed numerical tool, the complete particle trajectories are accessible within a reasonable computational time only in the inertial regime (Re > 10). In this regime, we show that (i) the particle undergoes cross-streamline migration followed by a cross-lateral migration (parallel to the wall) in agreement with previous observations, and (ii) the stable equilibrium positions are located at the midline of the channel faces while the diagonal equilibrium positions are unstable. At low flow inertia, the first instants of the numerical simulations (carried at Re = O(1)) reveal that the cross-streamline migration of a single particle is oriented towards the channel wall, suggesting that the particle preferential positions around the channel center, observed in the experiments, are rather due to multi-body interactions.

  14. Migration of finite sized particles in a laminar square channel flow from low to high Reynolds numbers

    International Nuclear Information System (INIS)

    Abbas, M.; Magaud, P.; Gao, Y.; Geoffroy, S.

    2014-01-01

    The migration of neutrally buoyant finite sized particles in a Newtonian square channel flow is investigated in the limit of very low solid volumetric concentration, within a wide range of channel Reynolds numbers Re = [0.07-120]. In situ microscope measurements of particle distributions, taken far from the channel inlet (at a distance several thousand times the channel height), revealed that particles are preferentially located near the channel walls at Re > 10 and near the channel center at Re < 1. Whereas the cross-streamline particle motion is governed by inertia-induced lift forces at high inertia, it seems to be controlled by shear-induced particle interactions at low (but finite) Reynolds numbers, despite the low solid volume fraction (<1%). The transition between both regimes is observed in the range Re = [1-10]. In order to exclude the effect of multi-body interactions, the trajectories of single freely moving particles are calculated thanks to numerical simulations based on the force coupling method. With the deployed numerical tool, the complete particle trajectories are accessible within a reasonable computational time only in the inertial regime (Re > 10). In this regime, we show that (i) the particle undergoes cross-streamline migration followed by a cross-lateral migration (parallel to the wall) in agreement with previous observations, and (ii) the stable equilibrium positions are located at the midline of the channel faces while the diagonal equilibrium positions are unstable. At low flow inertia, the first instants of the numerical simulations (carried at Re = O(1)) reveal that the cross-streamline migration of a single particle is oriented towards the channel wall, suggesting that the particle preferential positions around the channel center, observed in the experiments, are rather due to multi-body interactions

  15. The K+ channel KCa3.1 as a novel target for idiopathic pulmonary fibrosis.

    Directory of Open Access Journals (Sweden)

    Katy M Roach

    Full Text Available Idiopathic pulmonary fibrosis (IPF is a common, progressive and invariably lethal interstitial lung disease with no effective therapy. We hypothesised that K(Ca3.1 K(+ channel-dependent cell processes contribute to IPF pathophysiology.K(Ca3.1 expression in primary human lung myofibroblasts was examined using RT-PCR, western blot, immunofluorescence and patch-clamp electrophysiology. The role of K(Ca3.1 channels in myofibroblast proliferation, wound healing, collagen secretion and contraction was examined using two specific and distinct K(Ca3.1 blockers (TRAM-34 and ICA-17043 [Senicapoc].Both healthy non fibrotic control and IPF-derived human lung myofibroblasts expressed K(Ca3.1 channel mRNA and protein. K(Ca3.1 ion currents were elicited more frequently and were larger in IPF-derived myofibroblasts compared to controls. K(Ca3.1 currents were increased in myofibroblasts by TGFβ1 and basic FGF. K(Ca3.1 was expressed strongly in IPF tissue. K(Ca3.1 pharmacological blockade attenuated human myofibroblast proliferation, wound healing, collagen secretion and contractility in vitro, and this was associated with inhibition of TGFβ1-dependent increases in intracellular free Ca(2+.K(Ca3.1 activity promotes pro-fibrotic human lung myofibroblast function. Blocking K(Ca3.1 may offer a novel approach to treating IPF with the potential for rapid translation to the clinic.

  16. The stress protein heat shock cognate 70 (Hsc70) inhibits the Transient Receptor Potential Vanilloid type 1 (TRPV1) channel.

    Science.gov (United States)

    Iftinca, Mircea; Flynn, Robyn; Basso, Lilian; Melo, Helvira; Aboushousha, Reem; Taylor, Lauren; Altier, Christophe

    2016-01-01

    Specialized cellular defense mechanisms prevent damage from chemical, biological, and physical hazards. The heat shock proteins have been recognized as key chaperones that maintain cell survival against a variety of exogenous and endogenous stress signals including noxious temperature. However, the role of heat shock proteins in nociception remains poorly understood. We carried out an expression analysis of the constitutively expressed 70 kDa heat-shock cognate protein, a member of the stress-induced HSP70 family in lumbar dorsal root ganglia from a mouse model of Complete Freund's Adjuvant-induced chronic inflammatory pain. We used immunolabeling of dorsal root ganglion neurons, behavioral analysis and patch clamp electrophysiology in both dorsal root ganglion neurons and HEK cells transfected with Hsc70 and Transient Receptor Potential Channels to examine their functional interaction in heat shock stress condition. We report an increase in protein levels of Hsc70 in mouse dorsal root ganglia, 3 days post Complete Freund's Adjuvant injection in the hind paw. Immunostaining of Hsc70 was observed in most of the dorsal root ganglion neurons, including the small size nociceptors immunoreactive to the TRPV1 channel. Standard whole-cell patch-clamp technique was used to record Transient Receptor Potential Vanilloid type 1 current after exposure to heat shock. We found that capsaicin-evoked currents are inhibited by heat shock in dorsal root ganglion neurons and transfected HEK cells expressing Hsc70 and TRPV1. Blocking Hsc70 with matrine or spergualin compounds prevented heat shock-induced inhibition of the channel. We also found that, in contrast to TRPV1, both the cold sensor channels TRPA1 and TRPM8 were unresponsive to heat shock stress. Finally, we show that inhibition of TRPV1 depends on the ATPase activity of Hsc70 and involves the rho-associated protein kinase. Our work identified Hsc70 and its ATPase activity as a central cofactor of TRPV1 channel function

  17. The PSI web interface to the EPICS channel archiver

    International Nuclear Information System (INIS)

    Gaudenz Jud; Luedeke, A.; Portmann, W.

    2012-01-01

    the EPICS (Experimental Physics and Industrial Control System) channel archiver is used at different facilities at PSI (Paul Scherrer Institute) like the Swiss Light Source or the medical cyclotron. The EPICS channel archiver is a powerful tool to collect control system data of thousands of EPICS process variables with rates of many Hertz each to an archive for later retrieval. Within the package of the channel archiver version 2 you get a Java application for graphical data retrieval and a command line tool for data extraction into different file formats. For the Paul Scherrer Institute (PSI) we wanted a possibility to retrieve the archived data from a web interface. It was desired to have flexible retrieval functions and to allow interchanging data references by e-mail. This web interface has been implemented by the PSI controls group and has now been in operation for several years. This paper will highlight the special features of the PSI web interface to the EPICS channel archiver

  18. Remodeling of Kv1.5 channel in right atria from Han Chinese patients with atrial fibrillation.

    Science.gov (United States)

    Ou, Xian-hong; Li, Miao-ling; Liu, Rui; Fan, Xin-rong; Mao, Liang; Fan, Xue-hui; Yang, Yan; Zeng, Xiao-rong

    2015-04-28

    The incidence of atrial fibrillation (AF) in rheumatic heart diseases (RHD) is very high and increases with age. Occurrence and maintenance of AF are very complicated process accompanied by many different mechanisms. Ion-channel remodeling, including the voltage-gated potassium channel Kv1.5, plays an important role in the pathophysiology of AF. However, the changes of Kv1.5 channel expression in Han Chinese patients with RHD and AF remain poorly understood. The aim of the present study was to investigate whether the Kv1.5 channels of the right atria may be altered with RHD, age, and sex to contribute to AF. Right atrial appendages were obtained from 20 patients with normal cardiac functions who had undergone surgery, and 26 patients with AF. Subjects were picked from 4 groups: adult and aged patients in normal sinus rhythm (SR) and AF. Patients were divided into non-RHD and RHD groups or men and women groups in normal SR and AF, respectively. The expression of Kv1.5 protein and messenger RNA (mRNA) were measured using Western blotting and polymerase chain reaction (PCR) method, respectively. Compared with the SR group, the expression of Kv1.5 protein decreased significantly in the AF group. However, neither Kv1.5 protein nor KCNA5 mRNA had significant differences in adult and aged groups, non-RHD and RHD group, and men and women group of AF. The expression of Kv1.5 channel protein changes with AF but not with age, RHD, and sex in AF.

  19. Tris-hydroxymethyl-aminomethane enhances capsaicin-induced intracellular Ca2+ influx through transient receptor potential V1 (TRPV1 channels

    Directory of Open Access Journals (Sweden)

    Satoshi Murakami

    2016-02-01

    Full Text Available Non-selective transient receptor potential vanilloid (TRPV cation channels are activated by various insults, including exposure to heat, acidity, and the compound capsaicin, resulting in sensations of pain in the skin, visceral organs, and oral cavity. Recently, TRPV1 activation was also demonstrated in response to basic pH elicited by ammonia and intracellular alkalization. Tris-hydroxymethyl aminomethane (THAM is widely used as an alkalizing agent; however, the effects of THAM on TRPV1 channels have not been defined. In this study, we characterized the effects of THAM-induced TRPV1 channel activation in baby hamster kidney cells expressing human TRPV1 (hTRPV1 and the Ca2+-sensitive fluorescent sensor GCaMP2 by real-time confocal microscopy. Notably, both capsaicin (1 μM and pH 6.5 buffer elicited steep increases in the intracellular Ca2+ concentration ([Ca2+]i, while treatment with THAM (pH 8.5 alone had no effect. However, treatment with THAM (pH 8.5 following capsaicin application elicited a profound, long-lasting increase in [Ca2+]i that was completely inhibited by the TRPV1 antagonist capsazepine. Taken together, these results suggest that hTRPV1 pre-activation is required to provoke enhanced, THAM-induced [Ca2+]i increases, which could be a mechanism underlying pain induced by basic pH.

  20. Improvement in the thermostability of chitosanase from Bacillus ehimensis by introducing artificial disulfide bonds.

    Science.gov (United States)

    Sheng, Jun; Ji, Xiaofeng; Zheng, Yuan; Wang, Zhipeng; Sun, Mi

    2016-10-01

    To determine the effects of artificial disulfide bridges on the thermostability and catalytic efficiency of chitosanase EAG1. Five artificial disulfide bridges were designed based on the structural information derived from the three-dimensional (3-D) model of chitosanase EAG1. Two beneficial mutants (G113C/D116C, A207C-L286C) were located in the flexible surface loop region, whereas the similar substitutions introduced in α-helices regions had a negligible effect. Mut5, the most active mutant, had a longer half-life at 50 °C (from 10.5 to 69.3 min) and a 200 % higher catalytic efficiency (K cat/K m) than that of the original EAG1. The contribution of disulfide bridges to enzyme thermostability is mainly dependent on its location within the polypeptide chain. Strategical placement of a disulfide bridge in flexible regions provides a rigid support and creation of a protected microenvironment, which is effective in improving enzyme's thermostability and catalytic efficiency.

  1. Rapid internalization of the oncogenic K+ channel K(V10.1.

    Directory of Open Access Journals (Sweden)

    Tobias Kohl

    Full Text Available K(V10.1 is a mammalian brain voltage-gated potassium channel whose ectopic expression outside of the brain has been proven relevant for tumor biology. Promotion of cancer cell proliferation by K(V10.1 depends largely on ion flow, but some oncogenic properties remain in the absence of ion permeation. Additionally, K(V10.1 surface populations are small compared to large intracellular pools. Control of protein turnover within cells is key to both cellular plasticity and homeostasis, and therefore we set out to analyze how endocytic trafficking participates in controlling K(V10.1 intracellular distribution and life cycle. To follow plasma membrane K(V10.1 selectively, we generated a modified channel of displaying an extracellular affinity tag for surface labeling by α-bungarotoxin. This modification only minimally affected K(V10.1 electrophysiological properties. Using a combination of microscopy and biochemistry techniques, we show that K(V10.1 is constitutively internalized involving at least two distinct pathways of endocytosis and mainly sorted to lysosomes. This occurs at a relatively fast rate. Simultaneously, recycling seems to contribute to maintain basal K(V10.1 surface levels. Brief K(V10.1 surface half-life and rapid lysosomal targeting is a relevant factor to be taken into account for potential drug delivery and targeting strategies directed against K(V10.1 on tumor cells.

  2. Physical mechanism for gating and mechanosensitivity of the human TRAAK K+ channel

    Science.gov (United States)

    Brohawn, Stephen G.; Campbell, Ernest B.; MacKinnon, Roderick

    2015-01-01

    Summary Activation of mechanosensitive ion channels by physical force underlies many physiological processes including the sensation of touch, hearing and pain1–5. TRAAK ion channels are neuronally expressed members of the two-pore domain K+ (K2P) channel family and are mechanosensitive6. They are involved in controlling mechanical and temperature nociception in mice7. Mechanosensitivity of TRAAK is mediated directly through the lipid bilayer: it is a membrane tension gated channel8. However, the molecular mechanism of TRAAK channel gating and mechanosensitivity is unknown. Here we present crystal structures of TRAAK in conductive and nonconductive conformations defined by the presence of permeant ions along the conduction pathway. In the nonconductive state, a lipid acyl chain accesses the channel cavity through a 5 Å-wide lateral opening in the membrane inner leaflet and physically blocks ion passage. In the conductive state, rotation of a transmembrane helix (TM4) about a central hinge seals the intramembrane opening, preventing lipid block of the cavity and permitting ion entry. Additional rotation of a membrane interacting TM2-TM3 segment, unique to mechanosensitive K2Ps, against TM4 may further stabilize the conductive conformation. Comparison of the structures reveals a biophysical explanation for TRAAK mechanosensitivity: an expansion in cross sectional area up to 2.7 nm2 in the conductive state is expected to create a membrane tension-dependent energy difference between conformations that promotes force activation. Our results show how tension of the lipid bilayer can be harnessed to control gating and mechanosensitivity of a eukaryotic ion channel. PMID:25471887

  3. Regulation of 1, 4, 5-triphosphate receptor channel gating dynamics by mutant presenilin in Alzheimer's disease cells

    Science.gov (United States)

    Wei, Fang; Li, Xiang; Cai, Meichun; Liu, Yanping; Jung, Peter; Shuai, Jianwei

    2017-06-01

    In neurons of patients with Alzheimer's disease, the intracellular Ca2+ concentration is increased by its release from the endoplasmic reticulum via the inositol 1, 4, 5-triphosphate receptor (IP3R). In this paper, we discuss the IP3R gating dynamics in familial Alzheimer's disease (FAD) cells induced with presenilin mutation PS1. By fitting the parameters of an IP3R channel model to experimental data of the open probability, the mean open time and the mean closed time of IP3R channels, in control cells and FAD mutant cells, we suggest that the interaction of presenilin mutation PS1 with IP3R channels leads the decrease in the unbinding rates of IP3 and the activating Ca2+ from IP3Rs. As a result, the increased affinities of IP3 and activating Ca2+ for IP3R channels induce the increase in the Ca2+ signal in FAD mutant cells. Specifically, the PS1 mutation decreases the IP3 dissociation rate of IP3R channels significantly in FAD mutant cells. Our results suggest possible novel targets for FAD therapeutic intervention.

  4. Trafficking and intracellular regulation of Kv7.1 potassium channels in the heart

    DEFF Research Database (Denmark)

    Nielsen, Nathalie Hélix

    identified. About 100 of these mutations are located in the N- or the C-terminal parts of the channel. The aim of the present work was to gain a better understanding of the Kv7.1 channel protein function. In the first study we identified a Kv7.1 missense mutation in a German family with Long QT Syndrome......The electrical activity of the heart, measured by application of surface body electrodes and recorded as an electrocardiogram, is the result of a finely tuned balance of ion movement (K+, Na+, Ca2+). The ionic currents collectively constitute the cardiac action potential created in the cell...

  5. The C-terminus SH3-binding domain of Kv1.3 is required for the actin-mediated immobilization of the channel via cortactin

    Science.gov (United States)

    Hajdu, Peter; Martin, Geoffrey V.; Chimote, Ameet A.; Szilagyi, Orsolya; Takimoto, Koichi; Conforti, Laura

    2015-01-01

    Kv1.3 channels play a pivotal role in the activation and migration of T-lymphocytes. These functions are accompanied by the channels' polarization, which is essential for associated downstream events. However, the mechanisms that govern the membrane movement of Kv1.3 channels remain unclear. F-actin polymerization occurs concomitantly to channel polarization, implicating the actin cytoskeleton in this process. Here we show that cortactin, a factor initiating the actin network, controls the membrane mobilization of Kv1.3 channels. FRAP with EGFP-tagged Kv1.3 channels demonstrates that knocking down cortactin decreases the actin-based immobilization of the channels. Using various deletion and mutation constructs, we show that the SH3 motif of Kv1.3 mediates the channel immobilization. Proximity ligation assays indicate that deletion or mutation of the SH3 motif also disrupts interaction of the channel with cortactin. In T-lymphocytes, the interaction between HS1 (the cortactin homologue) and Kv1.3 occurs at the immune synapse and requires the channel's C-terminal domain. These results show that actin dynamics regulates the membrane motility of Kv1.3 channels. They also provide evidence that the SH3 motif of the channel and cortactin plays key roles in this process. PMID:25739456

  6. System performance of a 4-channel PHASAR WDM receiver operating at 1.2 Gbit/s

    NARCIS (Netherlands)

    Steenbergen, C.A.M.; van Deventer, M.O.; Vreede, de L.C.N.; Dam, van C.; Smit, M.K.; Verbeek, B.H.

    1996-01-01

    Phased arrays are important key components in wavelength-division multiplexing (WDM) systems. We have realized a 4-channel WDM receiver combining a phased array with photodetectors on InP with a Si bipolar transimpedance amplifier. The channels are spaced at 2.0 nm with a 1.0-nm flat passband. On

  7. Genetic interaction of two abscisic acid signaling regulators, HY5 and FIERY1, in mediating lateral root formation

    KAUST Repository

    Chen, Hao

    2011-01-01

    Root architecture is continuously shaped in a manner that helps plants to better adapt to the environment. Gene regulation at the transcriptional or post-transcriptional levels largely controls this environmental response. Recently, RNA silencing has emerged as an important player in gene regulation and is involved in many aspects of plant development, including lateral root formation. In a recent study, we found that FIERY1, a bifunctional abiotic stress and abscisic acid (ABA) signaling regulator and an endogenous RNA silencing suppressor, mediates auxin response during lateral root formation in Arabidopsis. We proposed that FRY1 regulates lateral root development through its activity on adenosine 3,5-bisphosphate (PAP), a strong inhibitor of exoribonucleases (XRNs). Interestingly, some of the phenotypes of fry1, such as enhanced response to light in repressing hypocotyl elongation and hypersensitivity to ABA in lateral root growth, are opposite to those of another light- and ABA-signaling mutant, hy5. Here we analyzed the hy5 fry1 double mutant for root and hypocotyl growth. We found that the hy5 mutation can suppress the enhanced light sensitivity in fry1 hypocotyl elongation and restore the lateral root formation. The genetic interaction between HY5 and FRY1 indicates that HY5 and FRY1 may act in overlapping pathways that mediate light signaling and lateral root development. © 2011 Landes Bioscience.

  8. A Hot Knife Through Ice-Cream: Earthflow Response to Channel Incision (Or Channel Response to Earthflows?), Eel River Canyon, California

    Science.gov (United States)

    Mackey, B. H.; Roering, J. J.; McKean, J. A.

    2007-12-01

    Abundant glacier-like earthflow features are recognized as a primary erosional process in the highly erodable Franciscan Melange of the Eel River Basin, CA. Despite their prominence in this "melting ice-cream" topography, many questions regarding their effects on the long term sediment flux from this rapidly eroding basin remain unresolved. For example, does an earthflow's basal shear zone propagate vertically downwards with vertical river incision? What controls the upslope and lateral extent of individual earthflows? How does the erosive power of a river influence the rate of earthflow movement, or conversely do earthflow toe deposits regulate the rate of river incision? Here we present preliminary findings derived from study of 200km2 of lidar data (1m resolution) covering hillslopes adjacent to 30km of the Eel River. Lidar allows detailed analysis of the interaction between earthflows and the drainage network, and we document how inferred changes in local base level are propagated throughout adjacent hillslopes via earthflow movement. The most active earthflows (determined by field surveying and analysis of aerial photos rectified using lidar- generated digital topography) coincide with locally steep sections of channel, while downstream of the most active flows we frequently observe less-active or dormant earthflows. This observation supports the idea that the locations of the most active earthflows coincide with headward propagating knickpoints in the channel. The rate of earthflow movement appears to slow when an earthflow exhausts the upslope area of easily mobilized sediment. Earthflow toes can protrude directly into the channel, causing the channel to narrow and steepen, and even undercut the opposite bank. Large resistant boulders (>2m diameter) transported by the earthflow accumulate in the streambed and appear to both act as a check on further channel incision and earthflow movement. In contrast, areas adjacent to active earthflows exhibit smooth

  9. The first transmembrane domain (TM1) of β2-subunit binds to the transmembrane domain S1 of α-subunit in BK potassium channels

    Science.gov (United States)

    Morera, Francisco J.; Alioua, Abderrahmane; Kundu, Pallob; Salazar, Marcelo; Gonzalez, Carlos; Martinez, Agustin D.; Stefani, Enrico; Toro, Ligia; Latorre, Ramon

    2012-01-01

    The BK channel is one of the most broadly expressed ion channels in mammals. In many tissues, the BK channel pore-forming α-subunit is associated to an auxiliary β-subunit that modulates the voltage- and Ca2+-dependent activation of the channel. Structural components present in β-subunits that are important for the physical association with the α-subunit are yet unknown. Here, we show through co-immunoprecipitation that the intracellular C-terminus, the second transmembrane domain (TM2) and the extracellular loop of the β2-subunit are dispensable for association with the α-subunit pointing transmembrane domain 1 (TM1) as responsible for the interaction. Indeed, the TOXCAT assay for transmembrane protein–protein interactions demonstrated for the first time that TM1 of the β2-subunit physically binds to the transmembrane S1 domain of the α-subunit. PMID:22710124

  10. Blockade of the voltage-gated potassium channel Kv1.3 inhibits immune responses in vivo.

    Science.gov (United States)

    Koo, G C; Blake, J T; Talento, A; Nguyen, M; Lin, S; Sirotina, A; Shah, K; Mulvany, K; Hora, D; Cunningham, P; Wunderler, D L; McManus, O B; Slaughter, R; Bugianesi, R; Felix, J; Garcia, M; Williamson, J; Kaczorowski, G; Sigal, N H; Springer, M S; Feeney, W

    1997-06-01

    The voltage activated K+ channel (Kv1.3) has recently been identified as the molecule that sets the resting membrane potential of peripheral human T lymphoid cells. In vitro studies indicate that blockage of Kv1.3 inhibits T cell activation, suggesting that Kv1.3 may be a target for immunosuppression. However, despite the in vitro evidence, there has been no in vivo demonstration that blockade of Kv1.3 will attenuate an immune response. The difficulty is due to species differences, as the channel does not set the membrane potential in rodent peripheral T cells. In this study, we show that the channel is present on peripheral T cells of miniswine. Using the peptidyl Kv1.3 inhibitor, margatoxin, we demonstrate that Kv1.3 also regulates the resting membrane potential, and that blockade of Kv1.3 inhibits, in vivo, both a delayed-type hypersensitivity reaction and an Ab response to an allogeneic challenge. In addition, prolonged Kv1.3 blockade causes reduced thymic cellularity and inhibits the thymic development of T cell subsets. These results provide in vivo evidence that Kv1.3 is a novel target for immunomodulation.

  11. Channel catfish response to ultraviolet-B radiation

    Science.gov (United States)

    Ewing, M.S.; Blazer, V.S.; Fabacher, D.L.; Little, E.E.; Kocan, K.M.

    1999-01-01

    Fingerling channel catfish Ictalurus punctatus exposed to simulated ultraviolet-B radiation at an average daily dose of 2.9 J/cm2 were quite sensitive to the radiation. After a 24-h exposure, thinning of the most dorsal epidermis frequently was accompanied by edema. Compared with epidermis of unexposed fish, mucous cells in exposed fish were less superficial and club cells were less numerous both dorsally and high on the lateral surface of the body. Sunburn cells with pyknotic nuclei were evident in the epidermis of exposed fish. Among fish exposed for 48 h, focal necrosis and sloughing of the outer epidermal layer were widespread. A methanol-extractable skin substance that is associated with resistance to sunburn in other fish species was not detected in channel catfish.

  12. Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France

    Science.gov (United States)

    Piégay, H.; Hupp, C.R.; Citterio, A.; Dufour, S.; Moulin, B.; Walling, D.E.

    2008-01-01

    Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides 137Cs and unsupported 210Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a−1 over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and 137Cs approaches are cross validated for estimating the sedimentation rate within a channel infill.

  13. AdE-1, a new inotropic Na(+) channel toxin from Aiptasia diaphana, is similar to, yet distinct from, known anemone Na(+) channel toxins.

    Science.gov (United States)

    Nesher, Nir; Shapira, Eli; Sher, Daniel; Moran, Yehu; Tsveyer, Liora; Turchetti-Maia, Ana Luiza; Horowitz, Michal; Hochner, Binyamin; Zlotkin, Eliahu

    2013-04-01

    Heart failure is one of the most prevalent causes of death in the western world. Sea anemone contains a myriad of short peptide neurotoxins affecting many pharmacological targets, several of which possess cardiotonic activity. In the present study we describe the isolation and characterization of AdE-1 (ion channel modifier), a novel cardiotonic peptide from the sea anemone Aiptasia diaphana, which differs from other cnidarian toxins. Although AdE-1 has the same cysteine residue arrangement as sea anemone type 1 and 2 Na(+) channel toxins, its sequence contains many substitutions in conserved and essential sites and its overall homology to other toxins identified to date is low (Anemonia viridis toxin II), AdE-1 markedly inhibits Na(+) current inactivation with no significant effect on current activation, suggesting a similar mechanism of action. However, its effects on twitch relaxation velocity, action potential amplitude and on the time to peak suggest that this novel toxin affects cardiomyocyte function via a more complex mechanism. Additionally, Av2's characteristic delayed and early after-depolarizations were not observed. Despite its structural differences, AdE-1 physiologic effectiveness is comparable with Av2 with a similar ED(50) value to blowfly larvae. This finding raises questions regarding the extent of the universality of structure-function in sea anemone Na(+) channel toxins.

  14. Brain-derived neurotrophic factor modulation of Kv1.3 channel is disregulated by adaptor proteins Grb10 and nShc

    Directory of Open Access Journals (Sweden)

    Marks David R

    2009-01-01

    Full Text Available Abstract Background Neurotrophins are important regulators of growth and regeneration, and acutely, they can modulate the activity of voltage-gated ion channels. Previously we have shown that acute brain-derived neurotrophic factor (BDNF activation of neurotrophin receptor tyrosine kinase B (TrkB suppresses the Shaker voltage-gated potassium channel (Kv1.3 via phosphorylation of multiple tyrosine residues in the N and C terminal aspects of the channel protein. It is not known how adaptor proteins, which lack catalytic activity, but interact with members of the neurotrophic signaling pathway, might scaffold with ion channels or modulate channel activity. Results We report the co-localization of two adaptor proteins, neuronal Src homology and collagen (nShc and growth factor receptor-binding protein 10 (Grb10, with Kv1.3 channel as demonstrated through immunocytochemical approaches in the olfactory bulb (OB neural lamina. To further explore the specificity and functional ramification of adaptor/channel co-localization, we performed immunoprecipitation and Western analysis of channel, kinase, and adaptor transfected human embryonic kidney 293 cells (HEK 293. nShc formed a direct protein-protein interaction with Kv1.3 that was independent of BDNF-induced phosphorylation of Kv1.3, whereas Grb10 did not complex with Kv1.3 in HEK 293 cells. Both adaptors, however, co-immunoprecipitated with Kv1.3 in native OB. Grb10 was interestingly able to decrease the total expression of Kv1.3, particularly at the membrane surface, and subsequently eliminated the BDNF-induced phosphorylation of Kv1.3. To examine the possibility that the Src homology 2 (SH2 domains of Grb10 were directly binding to basally phosphorylated tyrosines in Kv1.3, we utilized point mutations to substitute multiple tyrosine residues with phenylalanine. Removal of the tyrosines 111–113 and 449 prevented Grb10 from decreasing Kv1.3 expression. In the absence of either adaptor protein

  15. Polycystin-1 Is a Cardiomyocyte Mechanosensor That Governs L-Type Ca2+ Channel Protein Stability.

    Science.gov (United States)

    Pedrozo, Zully; Criollo, Alfredo; Battiprolu, Pavan K; Morales, Cyndi R; Contreras-Ferrat, Ariel; Fernández, Carolina; Jiang, Nan; Luo, Xiang; Caplan, Michael J; Somlo, Stefan; Rothermel, Beverly A; Gillette, Thomas G; Lavandero, Sergio; Hill, Joseph A

    2015-06-16

    L-type calcium channel activity is critical to afterload-induced hypertrophic growth of the heart. However, the mechanisms governing mechanical stress-induced activation of L-type calcium channel activity are obscure. Polycystin-1 (PC-1) is a G protein-coupled receptor-like protein that functions as a mechanosensor in a variety of cell types and is present in cardiomyocytes. We subjected neonatal rat ventricular myocytes to mechanical stretch by exposing them to hypo-osmotic medium or cyclic mechanical stretch, triggering cell growth in a manner dependent on L-type calcium channel activity. RNAi-dependent knockdown of PC-1 blocked this hypertrophy. Overexpression of a C-terminal fragment of PC-1 was sufficient to trigger neonatal rat ventricular myocyte hypertrophy. Exposing neonatal rat ventricular myocytes to hypo-osmotic medium resulted in an increase in α1C protein levels, a response that was prevented by PC-1 knockdown. MG132, a proteasomal inhibitor, rescued PC-1 knockdown-dependent declines in α1C protein. To test this in vivo, we engineered mice harboring conditional silencing of PC-1 selectively in cardiomyocytes (PC-1 knockout) and subjected them to mechanical stress in vivo (transverse aortic constriction). At baseline, PC-1 knockout mice manifested decreased cardiac function relative to littermate controls, and α1C L-type calcium channel protein levels were significantly lower in PC-1 knockout hearts. Whereas control mice manifested robust transverse aortic constriction-induced increases in cardiac mass, PC-1 knockout mice showed no significant growth. Likewise, transverse aortic constriction-elicited increases in hypertrophic markers and interstitial fibrosis were blunted in the knockout animals PC-1 is a cardiomyocyte mechanosensor that is required for cardiac hypertrophy through a mechanism that involves stabilization of α1C protein. © 2015 American Heart Association, Inc.

  16. The inward rectifier potassium channel Kir2.1 is expressed in mouse neutrophils from bone marrow and liver.

    Science.gov (United States)

    Masia, Ricard; Krause, Daniela S; Yellen, Gary

    2015-02-01

    Neutrophils are phagocytic cells that play a critical role in innate immunity by destroying bacterial pathogens. Channels belonging to the inward rectifier potassium channel subfamily 2 (Kir2 channels) have been described in other phagocytes (monocytes/macrophages and eosinophils) and in hematopoietic precursors of phagocytes. Their physiological function in these cells remains unclear, but some evidence suggests a role in growth factor-dependent proliferation and development. Expression of functional Kir2 channels has not been definitively demonstrated in mammalian neutrophils. Here, we show by RT-PCR that neutrophils from mouse bone marrow and liver express mRNA for the Kir2 subunit Kir2.1 but not for other subunits (Kir2.2, Kir2.3, and Kir2.4). In electrophysiological experiments, resting (unstimulated) neutrophils from mouse bone marrow and liver exhibit a constitutively active, external K(+)-dependent, strong inwardly rectifying current that constitutes the dominant current. The reversal potential is dependent on the external K(+) concentration in a Nernstian fashion, as expected for a K(+)-selective current. The current is not altered by changes in external or internal pH, and it is blocked by Ba(2+), Cs(+), and the Kir2-selective inhibitor ML133. The single-channel conductance is in agreement with previously reported values for Kir2.1 channels. These properties are characteristic of homomeric Kir2.1 channels. Current density in short-term cultures of bone marrow neutrophils is decreased in the absence of growth factors that are important for neutrophil proliferation [granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF)]. These results demonstrate that mouse neutrophils express functional Kir2.1 channels and suggest that these channels may be important for neutrophil function, possibly in a growth factor-dependent manner. Copyright © 2015 the American Physiological Society.

  17. Heparin/heparan sulfates bind to and modulate neuronal L-type (Cav1.2) voltage-dependent Ca2+ channels

    DEFF Research Database (Denmark)

    Garau, Gianpiero; Magotti, Paola; Heine, Martin

    2015-01-01

    Our previous studies revealed that L-type voltage-dependent Ca2+ channels (Cav1.2 L-VDCCs) are modulated by the neural extracellular matrix backbone, polyanionic glycan hyaluronic acid. Here we used isothermal titration calorimetry and screened a set of peptides derived from the extracellular......M), integrating their enthalpic and entropic binding contributions. Interaction between heparin and recombinant as well as native full-length neuronal Cav1.2α1 channels was confirmed using the heparin–agarose pull down assay. Whole cell patch clamp recordings in HEK293 cells transfected with neuronal Cav1.......2 channels revealed that enzymatic digestion of highly sulfated heparan sulfates with heparinase 1 affects neither voltage-dependence of channel activation nor the level of steady state inactivation, but did speed up channel inactivation. Treatment of hippocampal cultures with heparinase 1 reduced the firing...

  18. Functional Properties of a Newly Identified C-terminal Splice Variant of Cav1.3 L-type Ca2+ Channels*

    Science.gov (United States)

    Bock, Gabriella; Gebhart, Mathias; Scharinger, Anja; Jangsangthong, Wanchana; Busquet, Perrine; Poggiani, Chiara; Sartori, Simone; Mangoni, Matteo E.; Sinnegger-Brauns, Martina J.; Herzig, Stefan; Striessnig, Jörg; Koschak, Alexandra

    2011-01-01

    An intramolecular interaction between a distal (DCRD) and a proximal regulatory domain (PCRD) within the C terminus of long Cav1.3 L-type Ca2+ channels (Cav1.3L) is a major determinant of their voltage- and Ca2+-dependent gating kinetics. Removal of these regulatory domains by alternative splicing generates Cav1.342A channels that activate at a more negative voltage range and exhibit more pronounced Ca2+-dependent inactivation. Here we describe the discovery of a novel short splice variant (Cav1.343S) that is expressed at high levels in the brain but not in the heart. It lacks the DCRD but, in contrast to Cav1.342A, still contains PCRD. When expressed together with α2δ1 and β3 subunits in tsA-201 cells, Cav1.343S also activated at more negative voltages like Cav1.342A but Ca2+-dependent inactivation was less pronounced. Single channel recordings revealed much higher channel open probabilities for both short splice variants as compared with Cav1.3L. The presence of the proximal C terminus in Cav1.343S channels preserved their modulation by distal C terminus-containing Cav1.3- and Cav1.2-derived C-terminal peptides. Removal of the C-terminal modulation by alternative splicing also induced a faster decay of Ca2+ influx during electrical activities mimicking trains of neuronal action potentials. Our findings extend the spectrum of functionally diverse Cav1.3 L-type channels produced by tissue-specific alternative splicing. This diversity may help to fine tune Ca2+ channel signaling and, in the case of short variants lacking a functional C-terminal modulation, prevent excessive Ca2+ accumulation during burst firing in neurons. This may be especially important in neurons that are affected by Ca2+-induced neurodegenerative processes. PMID:21998310

  19. Transient Receptor Potential Canonical (TRPC)/Orai1-dependent Store-operated Ca2+ Channels

    Science.gov (United States)

    Sabourin, Jessica; Bartoli, Fiona; Antigny, Fabrice; Gomez, Ana Maria; Benitah, Jean-Pierre

    2016-01-01

    Store-operated Ca2+ entry (SOCE) has emerged as an important mechanism in cardiac pathology. However, the signals that up-regulate SOCE in the heart remain unexplored. Clinical trials have emphasized the beneficial role of mineralocorticoid receptor (MR) signaling blockade in heart failure and associated arrhythmias. Accumulated evidence suggests that the mineralocorticoid hormone aldosterone, through activation of its receptor, MR, might be a key regulator of Ca2+ influx in cardiomyocytes. We thus assessed whether and how SOCE involving transient receptor potential canonical (TRPC) and Orai1 channels are regulated by aldosterone/MR in neonatal rat ventricular cardiomyocytes. Molecular screening using qRT-PCR and Western blotting demonstrated that aldosterone treatment for 24 h specifically increased the mRNA and/or protein levels of Orai1, TRPC1, -C4, -C5, and stromal interaction molecule 1 through MR activation. These effects were correlated with a specific enhancement of SOCE activities sensitive to store-operated channel inhibitors (SKF-96365 and BTP2) and to a potent Orai1 blocker (S66) and were prevented by TRPC1, -C4, and Orai1 dominant negative mutants or TRPC5 siRNA. A mechanistic approach showed that up-regulation of serum- and glucocorticoid-regulated kinase 1 mRNA expression by aldosterone is involved in enhanced SOCE. Functionally, 24-h aldosterone-enhanced SOCE is associated with increased diastolic [Ca2+]i, which is blunted by store-operated channel inhibitors. Our study provides the first evidence that aldosterone promotes TRPC1-, -C4-, -C5-, and Orai1-mediated SOCE in cardiomyocytes through an MR and serum- and glucocorticoid-regulated kinase 1 pathway. PMID:27129253

  20. Polychronicity and its Impact on Leader-Member Exchange and Outcome Behaviors

    Science.gov (United States)

    2008-05-01

    of gender differences (Eagly, Karau, & Makhijani, 1995; Eagly, Johannesen-Schmidt & van Engen , 2003), just to name a few. While certainly not a new...Bulletin, 111, 3-22. Eagly, A. H., Johannesen-Schmidt, M. C., & van Engen , M. L. (2003). Transformational, transactional, and laissez-faire...1984). Type A behavior and faculty research productivity: What are the mechanisms . Organizational Behavior and Human Performance, 34,402-418. Vardi, Y

  1. A Novel KCNJ2 Mutation Identified in an Autistic Proband Affects the Single Channel Properties of Kir2.1

    Directory of Open Access Journals (Sweden)

    Anna Binda

    2018-03-01

    Full Text Available Inwardly rectifying potassium channels (Kir have been historically associated to several cardiovascular disorders. In particular, loss-of-function mutations in the Kir2.1 channel have been reported in cases affected by Andersen-Tawil syndrome while gain-of-function mutations in the same channel cause the short QT3 syndrome. Recently, a missense mutation in Kir2.1, as well as mutations in the Kir4.1, were reported to be involved in autism spectrum disorders (ASDs suggesting a role of potassium channels in these diseases and introducing the idea of the existence of K+ channel ASDs. Here, we report the identification in an Italian affected family of a novel missense mutation (p.Phe58Ser in the KCNJ2 gene detected in heterozygosity in a proband affected by autism and borderline for short QT syndrome type 3. The mutation is located in the N-terminal region of the gene coding for the Kir2.1 channel and in particular in a very conserved domain. In vitro assays demonstrated that this mutation results in an increase of the channel conductance and in its open probability. This gain-of-function of the protein is consistent with the autistic phenotype, which is normally associated to an altered neuronal excitability.

  2. The correlation of the Cs 137 lateral and radial migration in the Sozh valley soil

    International Nuclear Information System (INIS)

    Ryabova, L.N; Kuznetsov, V.A.; Glaz, A.S.

    2002-01-01

    Radiocesium distribution in soils of four geochemical landscapes: eluvial - watershed, transeluvial - terrace slope upper part, transaccumulative - slope lower part, accumulative - flood plain is discussed. Maximum concentration of Cs 137 (2,961...3,280 Bq/kg) was noted in the soil of eluvial landscapes, with a depth of the isotope migration being 26 cm. Its accumulation is associated with the biogeochemical and sorption geochemical barriers. Fe, Ca, Pb, Mn, Ni, Cr and Cu are accumulated simultaneously with Cs 137. The maximum concentration of Cs 137 is confined to the humus horizon of buried soils in the transition landscapes and in the upper part of relict horizons (geochemical barrier), where the Cs 137, Fe, Ca and Mn penetration increases. The lower part of the buried humus horizon is impermeable for Cs 137 migration and partly permeable for Fe, Ca, Mg, that migrate in soluble forms. Cs 137 is accumulated in the humus horizon of buried soils, that occur in the lower parts of slopes and are overlain by light deposits. Radiocesium is accumulated with Al, Fe, Ti, Ca, Mg and trace elements. By the value of a coefficient R9 the buried humus horizon is divided into the upper and lower parts. In the soils of accumulative landscapes radiocesium is accumulated in the sod of the central flood plain lows. In the elevated parts the radial migration is dominant and Cs-137 is accumulated in the humus horizons. Radiocesium is accumulated under the influence of different barriers in the river channel flood plain. A system of watershed - flood plain for Cs 137 is as follows: central flood plain low (6,045...1,955 Bq/kg) > watershed (2,961...3,280) > slope upper part (1,436) > central flood plain elevation (870...4,844), river channel flood plain (381 Bq/kg). Its accumulation in the humus horizons follows the pattern: central flood plain elevation (302...429 Bq/kg) > buried soils (1,055...1,941) > slope upper part (1,628) > river channel flood plain (424) > > watershed (52

  3. Structural basis of dual Ca2+/pH regulation of the endolysosomal TRPML1 channel

    Energy Technology Data Exchange (ETDEWEB)

    Li, Minghui; Zhang, Wei K.; Benvin, Nicole M.; Zhou, Xiaoyuan; Su, Deyuan; Li, Huan; Wang, Shu; Michailidis, Ioannis E.; Tong, Liang; Li, Xueming; Yang, Jian

    2017-01-23

    The activities of organellar ion channels are often regulated by Ca2+ and H+, which are present in high concentrations in many organelles. Here we report a structural element critical for dual Ca2+/pH regulation of TRPML1, a Ca2+-release channel crucial for endolysosomal function. TRPML1 mutations cause mucolipidosis type IV (MLIV), a severe lysosomal storage disorder characterized by neurodegeneration, mental retardation and blindness. We obtained crystal structures of the 213-residue luminal domain of human TRPML1 containing three missense MLIV-causing mutations. This domain forms a tetramer with a highly electronegative central pore formed by a novel luminal pore loop. Cysteine cross-linking and cryo-EM analyses confirmed that this architecture occurs in the full-length channel. Structure–function studies demonstrated that Ca2+ and H+ interact with the luminal pore and exert physiologically important regulation. The MLIV-causing mutations disrupt the luminal-domain structure and cause TRPML1 mislocalization. Our study reveals the structural underpinnings of TRPML1's regulation, assembly and pathogenesis.

  4. Function and expression of the epithelial Ca(2+) channel family: comparison of mammalian ECaC1 and 2.

    NARCIS (Netherlands)

    Hoenderop, J.G.J.; Vennekens, R.; Müller, D.G.; Prenen, J.; Droogmans, G.; Bindels, R.J.M.; Nilius, B.

    2001-01-01

    1. The epithelial Ca(2+) channel (ECaC) family represents a unique group of Ca(2+)-selective channels that share limited homology to the ligand-gated capsaicin receptors, the osmolarity-sensitive channel OTRPC4, as well as the transient receptor potential family. Southern blot analysis demonstrated

  5. CANDU channel flow verification

    International Nuclear Information System (INIS)

    Mazalu, N.; Negut, Gh.

    1997-01-01

    The purpose of this evaluation was to obtain accurate information on each channel flow that enables us to assess precisely the level of reactor thermal power and, for reasons of safety, to establish which channel is boiling. In order to assess the channel flow parameters, computer simulations were done with the NUCIRC code and the results were checked by measurements. The complete channel flow measurements were made in the zero power cold condition. In hot conditions there were made flow measurements using the Shut Down System 1 (SDS 1) flow devices from 0.1 % F.P. up to 100 % F.P. The NUCIRC prediction for CANDU channel flows and the measurements by Ultrasonic Flow Meter at zero power cold conditions and SDS 1 flow channel measurements at different reactor power levels showed an acceptable agreement. The 100 % F.P. average errors for channel flow of R, shows that suitable NUCIRC flow assessment can be made. So, it can be done a fair prediction of the reactor power distribution. NUCIRC can predict accurately the onset of boiling and helps to warn at the possible power instabilities at high powers or it can detect the flow blockages. The thermal hydraulic analyst has in NUCIRC a suitable tool to do accurate predictions for the thermal hydraulic parameters for different steady state power levels which subsequently leads to an optimal CANDU reactor operation. (authors)

  6. New binding site on common molecular scaffold provides HERG channel specificity of scorpion toxin BeKm-1

    DEFF Research Database (Denmark)

    Korolkova, Yuliya V; Bocharov, Eduard V; Angelo, Kamilla

    2002-01-01

    The scorpion toxin BeKm-1 is unique among a variety of known short scorpion toxins affecting potassium channels in its selective action on ether-a-go-go-related gene (ERG)-type channels. BeKm-1 shares the common molecular scaffold with other short scorpion toxins. The toxin spatial structure...... resolved by NMR consists of a short alpha-helix and a triple-stranded antiparallel beta-sheet. By toxin mutagenesis study we identified the residues that are important for the binding of BeKm-1 to the human ERG K+ (HERG) channel. The most critical residues (Tyr-11, Lys-18, Arg-20, Lys-23) are located...

  7. Spark Channels

    Energy Technology Data Exchange (ETDEWEB)

    Haydon, S. C. [Department of Physics, University of New England, Armidale, NSW (Australia)

    1968-04-15

    A brief summary is given of the principal methods used for initiating spark channels and the various highly time-resolved techniques developed recently for studies with nanosecond resolution. The importance of the percentage overvoltage in determining the early history and subsequent development of the various phases of the growth of the spark channel is discussed. An account is then given of the recent photographic, oscillographic and spectroscopic investigations of spark channels initiated by co-axial cable discharges of spark gaps at low [{approx} 1%] overvoltages. The phenomena observed in the development of the immediate post-breakdown phase, the diffuse glow structure, the growth of the luminous filament and the final formation of the spark channel in hydrogen are described. A brief account is also given of the salient features emerging from corresponding studies of highly overvolted spark gaps in which the spark channel develops from single avalanche conditions. The essential differences between the two types of channel formation are summarized and possible explanations of the general features are indicated. (author)

  8. Oxidation promotes insertion of the CLIC1 chloride intracellular channel into the membrane.

    Science.gov (United States)

    Goodchild, Sophia C; Howell, Michael W; Cordina, Nicole M; Littler, Dene R; Breit, Samuel N; Curmi, Paul M G; Brown, Louise Jennifer

    2009-12-01

    Members of the chloride intracellular channel (CLIC) family exist primarily as soluble proteins but can also auto-insert into cellular membranes to form ion channels. While little is known about the process of CLIC membrane insertion, a unique feature of mammalian CLIC1 is its ability to undergo a dramatic structural metamorphosis between a monomeric glutathione-S-transferase homolog and an all-helical dimer upon oxidation in solution. Whether this oxidation-induced metamorphosis facilitates CLIC1 membrane insertion is unclear. In this work, we have sought to characterise the role of oxidation in the process of CLIC1 membrane insertion. We examined how redox conditions modify the ability of CLIC1 to associate with and insert into the membrane using fluorescence quenching studies and a sucrose-loaded vesicle sedimentation assay to measure membrane binding. Our results suggest that oxidation of monomeric CLIC1, in the presence of membranes, promotes insertion into the bilayer more effectively than the oxidised CLIC1 dimer.

  9. A lateral chromatic aberration correction system for ultrahigh-definition color video camera

    Science.gov (United States)

    Yamashita, Takayuki; Shimamoto, Hiroshi; Funatsu, Ryohei; Mitani, Kohji; Nojiri, Yuji

    2006-02-01

    We have developed color camera for an 8k x 4k-pixel ultrahigh-definition video system, which is called Super Hi- Vision, with a 5x zoom lens and a signal-processing system incorporating a function for real-time lateral chromatic aberration correction. The chromatic aberration of the lens degrades color image resolution. So in order to develop a compact zoom lens consistent with ultrahigh-resolution characteristics, we incorporated a real-time correction function in the signal-processing system. The signal-processing system has eight memory tables to store the correction data at eight focal length points on the blue and red channels. When the focal length data is inputted from the lens control units, the relevant correction data are interpolated from two of eights correction data tables. This system performs geometrical conversion on both channels using this correction data. This paper describes that the correction function can successfully reduce the lateral chromatic aberration, to an amount small enough to ensure the desired image resolution was achieved over the entire range of the lens in real time.

  10. Involvement of transient receptor potential A1 channel in algesic and analgesic actions of the organic compound limonene.

    Science.gov (United States)

    Kaimoto, T; Hatakeyama, Y; Takahashi, K; Imagawa, T; Tominaga, M; Ohta, T

    2016-08-01

    TRPA1 is a Ca-permeable nonselective cation channel expressed in sensory neurons and acts as a nocisensor. Recent reports show that some monoterpenes, a group of naturally occurring organic compounds, modulate TRP channel activity. Here, we report that limonene, being contained in citrus fruits and mushrooms, shows a unique bimodal action on TRPA1 channel. We examine the effects of limonene on sensory neurons from wild-type, TRPV1- and TRPA1-gene-deficient mice and on heterologously expressed channels in vitro. Molecular determinants were identified with using mutated channels. Cellular excitability is monitored with ratiometric Ca imaging. Nociceptive and analgesic actions of limonene are also examined in vivo. In wild-type mouse sensory neurons, limonene increased the intracellular Ca(2+) concentration ([Ca(2+) ]i ), which was inhibited by selective inhibitors of TRPA1 but not TRPV1. Limonene-responsive neurons highly corresponded to TRPA1 agonist-sensitive ones. Limonene failed to stimulate sensory neurons from the TRPA1 (-/-) mouse. Heterologously expressed mouse TRPA1 was activated by limonene. Intraplantar injection of limonene elicited acute pain, which was significantly less in TRPA1 (-/-) mice. Systemic administration of limonene reduced nociceptive behaviours evoked by H2 O2 . In both heterologously and endogenously expressed TRPA1, a low concentration of limonene significantly inhibited H2 O2 -induced TRPA1 activation. TRPA1 activation by limonene was abolished in H2 O2 -insensitive cysteine-mutated channels. Topically applied limonene stimulates TRPA1, resulting in elicitation of acute pain, but its systemic application inhibits nociception induced by oxidative stress. Because limonene is a safe compound, it may be utilized for pain control due to its inhibition of TRPA1 channels. What does this study add: Limonene, a monoterpene in essential oils of various plants, has been known for its antitumor and anti-inflammatory properties. However, molecular

  11. Pore helix domain is critical to camphor sensitivity of transient receptor potential vanilloid 1 channel.

    Science.gov (United States)

    Marsakova, Lenka; Touska, Filip; Krusek, Jan; Vlachova, Viktorie

    2012-04-01

    The recent discovery that camphor activates and strongly desensitizes the capsaicin-sensitive and noxious heat-sensitive channel transient receptor potential vanilloid subfamily member 1 (TRPV1) has provided new insights and opened up new research paths toward understanding why this naturally occurring monoterpene is widely used in human medicine for its local counter-irritant, antipruritic, and anesthetic properties. However, the molecular basis for camphor sensitivity remains mostly unknown. The authors attempt to explore the nature of the activation pathways evoked by camphor and narrow down a putative interaction site at TRPV1. The authors transiently expressed wild-type or specifically mutated recombinant TRPV1 channels in human embryonic kidney cells HEK293T and recorded cation currents with the whole cell, patch clamp technique. To monitor changes in the spatial distribution of phosphatidylinositol 4,5-bisphosphate, they used fluorescence resonance energy transfer measurements from cells transfected with the fluorescent protein-tagged pleckstrin homology domains of phospholipase C. The results revealed that camphor modulates TRPV1 channel through the outer pore helix domain by affecting its overall gating equilibrium. In addition, camphor, which generally is known to decrease the fluidity of cell plasma membranes, may also regulate the activity of TRPV1 by inducing changes in the spatial distribution of phosphatidylinositol-4,5-bisphosphate on the inner leaflet of the plasma membrane. The findings of this study provide novel insights into the structural basis for the modulation of TRPV1 channel by camphor and may provide an explanation for the mechanism by which camphor modulates thermal sensation in vivo.

  12. Neutron Spectrum Parameters In Inner Irradiation Channel Of The Nigeria Research Reactor-1 (NIRR-1) For Use In Absolute And KO-NAA Methods

    International Nuclear Information System (INIS)

    Jonah, S.A; Balogun, G.I; Mayaki, M.C.

    2004-01-01

    In Nigeria, the first Nuclear Reactor achieved critically on February 03, 2004 at about 11:35 GMT and has been commissioned or training and research. It is a Miniature Neutron Source Reactor (MNSR), code-named Nigeria Research Reactor-1 (NIRR-1). NIRR-1 has a tan-in-pool structural configuration and a nominal thermal power rating of 30 Kw. With a built-in clean old core excess reactivity of 3.77 mk determined during the on-site zero and critically experimental, the reactor can operate for a n.cm-2 .s-1 in the inner irradiation channels). Under these conditions, the reactor can operate with the same fuel loading for over ten years with a burn-up of <1%. A detailed description of operating characteristics for NIRR-1, measured during the on-site zero-power and criticality experiments has been given elsewhere. In order to extend its utilization to include absolute and ko-NAA methods, the neutron spectrum parameters in the irradiation channels: power and critically experiments has been given elsewhere. In order to extend it's the irradiation channels: thermal-to-epithermal flux ration, F; and epithermal flux shape factor, a in both the inner and outer irradiation channels must be determined experimentally. In this work, we have developed and experimental procedure for monitoring the neutron spectrum parameters in an inner irradiation channel based on irradiation and gamma-ray counting of detector foils via (n,y), (n,p) and (n,a) dosimetry reactions. Results obtained indicate that a thermal neutron flux of (5.14+-0.02) x 1011 n/c m2.s determined by foil activation method in the inner irradiation channel, B2, at a power level of 15.5 kw corresponds to the flux indicators on the control console and the micro-computer control system respectively. Other parameters of the neutron spectrum determined for inner irradiation channel B2, are: a -0.0502+0.003; 18.92+-0.14; F = 3.87=0.23. The method was validated through the comparison of our result with published neutron spectrum

  13. Six-channel adaptive fibre-optic interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Romashko, R V; Bezruk, M N; Kamshilin, A A; Kulchin, Yurii N

    2012-06-30

    We have proposed and analysed a scheme for the multiplexing of orthogonal dynamic holograms in photorefractive crystals which ensures almost zero cross talk between the holographic channels upon phase demodulation. A six-channel adaptive fibre-optic interferometer was built, and the detection limit for small phase fluctuations in the channels of the interferometer was determined to be 2.1 Multiplication-Sign 10{sup -8} rad W{sup 1/2} Hz{sup -1/2}. The channel multiplexing capacity of the interferometer was estimated. The formation of 70 channels such that their optical fields completely overlap in the crystal reduces the relative detection limit in the working channel by just 10 %. We found conditions under which the maximum cross talk between the channels was within the intrinsic noise level in the channels (-47 dB).

  14. Effect of channel-protein interaction on translocation of a protein-like chain through a finite channel

    International Nuclear Information System (INIS)

    Sun Ting-Ting; Ma Hai-Zhu; Jiang Zhou-Ting

    2012-01-01

    We study the translocation of a protein-like chain through a finite cylindrical channel using the pruned-enriched Rosenbluth method (PERM) and the modified orientation-dependent monomer-monomer interaction (ODI) model. Attractive channels (in cp = −2.0, −1.0, −0.5), repulsive channels (in cp = 0.5, 1.0, 2.0), and a neutral channel (in cp = 0) are discussed. The results of the chain dimension and the energy show that Z 0 = 1.0 is an important case to distinguish the types of the channels. For the strong attractive channel, more contacts form during the process of translocation. It is also found that an external force is needed to drive the chain outside of the channel with the strong attraction. While for the neutral, the repulsive, and the weak attractive channels, the translocation is spontaneous. (interdisciplinary physics and related areas of science and technology)

  15. The proapoptotic influenza A virus protein PB1-F2 forms a nonselective ion channel.

    Directory of Open Access Journals (Sweden)

    Michael Henkel

    2010-06-01

    Full Text Available PB1-F2 is a proapoptotic influenza A virus protein of approximately 90 amino acids in length that is located in the nucleus, cytosol and in the mitochondria membrane of infected cells. Previous studies indicated that the molecule destabilizes planar lipid bilayers and has a strong inherent tendency for multimerization. This may be correlate with its capacity to induce mitochondrial membrane depolarization.Here, we investigated whether PB1-F2 is able to form ion channels within planar lipid bilayers and microsomes. For that purpose, a set of biologically active synthetic versions of PB1-F2 (sPB1-F2 derived from the IAV isolates A/Puerto Rico/8/34(H1N1 (IAV(PR8, from A/Brevig Mission/1/1918(H1N1 (IAV(SF2 or the H5N1 consensus sequence (IAV(BF2 were used. Electrical and fluorimetric measurements show that all three peptides generate in planar lipid bilayers or in liposomes, respectively, a barely selective conductance that is associated with stochastic channel type fluctuations between a closed state and at least two defined open states. Unitary channel fluctuations were also generated when a truncated protein comprising only the 37 c-terminal amino acids of sPB1-F2 was reconstituted in bilayers. Experiments were complemented by extensive molecular dynamics simulations of the truncated fragment in a lipid bilayer. The results indicate that the c-terminal region exhibits a slightly bent helical fold, which is stable and remains embedded in the bilayer for over 180 ns.The data support the idea that PB1-F2 is able to form protein channel pores with no appreciable selectivity in membranes and that the c-terminus is important for this function. This information could be important for drug development.

  16. Ion channeling in NbC/sub 1-c/: Determination of local atomic displacements around carbon vacancies

    International Nuclear Information System (INIS)

    Kaufmann, R.; Meyer, O.

    1983-01-01

    The results of channeling experiments on NbC/sub 1-c/ single crystals as a function of the vacancy concentration (0.02 1 = 0.12 +- 0.025 A and of the second Nb neighbors of u 2 1 = 0.09 +- 0.007 A and of the second neighbors to values of u 2 < or =0.02 +- 0.007 A. The static displacements determined with the channeling method were in good agreement with the results of x-ray diffraction experiments

  17. Multi-channel amplitude analyzer CMA-1 and CMA-2

    International Nuclear Information System (INIS)

    Czermak, A.; Jablonski, J.; Ostrowicz, A.

    1977-01-01

    Analyzer CMA is implemented in the CAMAC system. A single crate contains the required modules and is controlled by the PDP-11/10 minicomputer with 8k 16 bit word memory. Spectra can be accumulated in full 4k, 2k 1k or 0,5k. System provides: display of stored data in the form of full memory, very accurate representation of any part (44 channels) on alphanumeric display, readout of the data by paper tape punch or printing. (author)

  18. Defueled channel experiments in ZED-2 in support of ACR-1000 ROP analysis

    International Nuclear Information System (INIS)

    LaFontaine, M.W.R.; Zeller, M.B.; McPhee, G.P.

    2011-01-01

    Defueled channel experiments were performed in ZED-2 to help resolve discrepancies between calculated flux detector response during refueling in ACR-1000 according the reactor codes RFSP and MCNP. The data produced from these experiments was later used in a separate Regional-Over-Power (ROP) analysis to verify MCNP and RFSP neutron response predictions during refueling. These experiments provided information on thermal flux distributions interior and exterior to a fueled and defueled channel; and on epithermal absolute flux distributions exterior to the same channel. Critical height and moderator temperature data for fueled and defueled channel conditions were also measured. In addition, standard platinum-clad Inconel Self-Powered Detector (SPD) performance data was obtained. The following reactor physics and SPD parameters were measured in these experiments: C Radial flux distribution inside the channel of interest (fueled and defueled), C Radial flux distribution outside the channel of interest (fueled and defueled), C Epithermal radial flux distribution outside the channel of interest (fueled and defueled), and C SPD response parallel to and normal to the channel of interest (fueled and defueled).

  19. Defueled channel experiments in ZED-2 in support of ACR-1000 ROP analysis

    Energy Technology Data Exchange (ETDEWEB)

    LaFontaine, M.W.R.; Zeller, M.B.; McPhee, G.P. [Atomic Energy of Canada Limited (Canada)

    2011-07-01

    Defueled channel experiments were performed in ZED-2 to help resolve discrepancies between calculated flux detector response during refueling in ACR-1000 according the reactor codes RFSP and MCNP. The data produced from these experiments was later used in a separate Regional-Over-Power (ROP) analysis to verify MCNP and RFSP neutron response predictions during refueling. These experiments provided information on thermal flux distributions interior and exterior to a fueled and defueled channel; and on epithermal absolute flux distributions exterior to the same channel. Critical height and moderator temperature data for fueled and defueled channel conditions were also measured. In addition, standard platinum-clad Inconel Self-Powered Detector (SPD) performance data was obtained. The following reactor physics and SPD parameters were measured in these experiments: C Radial flux distribution inside the channel of interest (fueled and defueled), C Radial flux distribution outside the channel of interest (fueled and defueled), C Epithermal radial flux distribution outside the channel of interest (fueled and defueled), and C SPD response parallel to and normal to the channel of interest (fueled and defueled).

  20. The role of entropic potential in voltage activation and K+ transport through Kv 1.2 channels

    Science.gov (United States)

    Wawrzkiewicz-Jałowiecka, Agata; Grzywna, Zbigniew J.

    2018-03-01

    We analyze the entropic effects of inner pore geometry changes of Kv 1.2 channel during membrane depolarization and their implications for the rate of transmembrane transport of potassium ions. We base this on the idea that spatial confinements within the channel pore give rise to entropic barriers which can both effectively affect the stability of open macroconformation and influence channel's ability to conduct the potassium ions through the membrane. First, we calculate the differences in entropy between voltage-activated and resting states of the channel. As a template, we take a set of structures of channel pore in an open state at different membrane potentials generated in our previous research. The obtained results indicate that tendency to occupy open states at membrane depolarization is entropy facilitated. Second, we describe the differences in rates of K+ transport through the channel pore at different voltages based on the results of appropriate random walk simulations in entropic and electric potentials. The simulated single channel currents (I) suggest that the geometry changes during membrane depolarization are an important factor contributing to the observed flow of potassium ions through the channel. Nevertheless, the charge distribution within the channel pore (especially at the extracellular entrance) seems most prominent for the observed I/Imax relation at a qualitative level at analyzed voltages.

  1. Motor laterality as an indicator of speech laterality.

    Science.gov (United States)

    Flowers, Kenneth A; Hudson, John M

    2013-03-01

    The determination of speech laterality, especially where it is anomalous, is both a theoretical issue and a practical problem for brain surgery. Handedness is commonly thought to be related to speech representation, but exactly how is not clearly understood. This investigation analyzed handedness by preference rating and performance on a reliable task of motor laterality in 34 patients undergoing a Wada test, to see if they could provide an indicator of speech laterality. Hand usage preference ratings divided patients into left, right, and mixed in preference. Between-hand differences in movement time on a pegboard task determined motor laterality. Results were correlated (χ2) with speech representation as determined by a standard Wada test. It was found that patients whose between-hand difference in speed on the motor task was small or inconsistent were the ones whose Wada test speech representation was likely to be ambiguous or anomalous, whereas all those with a consistently large between-hand difference showed clear unilateral speech representation in the hemisphere controlling the better hand (χ2 = 10.45, df = 1, p laterality are related where they both involve a central control of motor output sequencing and that a measure of that aspect of the former will indicate the likely representation of the latter. A between-hand measure of motor laterality based on such a measure may indicate the possibility of anomalous speech representation. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  2. Biophysical and Pharmacological Characterization of Nav1.9 Voltage Dependent Sodium Channels Stably Expressed in HEK-293 Cells.

    Directory of Open Access Journals (Sweden)

    Zhixin Lin

    Full Text Available The voltage dependent sodium channel Nav1.9, is expressed preferentially in peripheral sensory neurons and has been linked to human genetic pain disorders, which makes it target of interest for the development of new pain therapeutics. However, characterization of Nav1.9 pharmacology has been limited due in part to the historical difficulty of functionally expressing recombinant channels. Here we report the successful generation and characterization of human, mouse and rat Nav1.9 stably expressed in human HEK-293 cells. These cells exhibit slowly activating and inactivating inward sodium channel currents that have characteristics of native Nav1.9. Optimal functional expression was achieved by coexpression of Nav1.9 with β1/β2 subunits. While recombinantly expressed Nav1.9 was found to be sensitive to sodium channel inhibitors TC-N 1752 and tetracaine, potency was up to 100-fold less than reported for other Nav channel subtypes despite evidence to support an interaction with the canonical local anesthetic (LA binding region on Domain 4 S6. Nav1.9 Domain 2 S6 pore domain contains a unique lysine residue (K799 which is predicted to be spatially near the local anesthetic interaction site. Mutation of this residue to the consensus asparagine (K799N resulted in an increase in potency for tetracaine, but a decrease for TC-N 1752, suggesting that this residue can influence interaction of inhibitors with the Nav1.9 pore. In summary, we have shown that stable functional expression of Nav1.9 in the widely used HEK-293 cells is possible, which opens up opportunities to better understand channel properties and may potentially aid identification of novel Nav1.9 based pharmacotherapies.

  3. Function Lateralization via Measuring Coherence Laterality

    Science.gov (United States)

    Wang, Ze; Mechanic-Hamilton, Dawn; Pluta, John; Glynn, Simon; Detre, John A.

    2009-01-01

    A data-driven approach for lateralization of brain function based on the spatial coherence difference of functional MRI (fMRI) data in homologous regions-of-interest (ROI) in each hemisphere is proposed. The utility of using coherence laterality (CL) to determine function laterality was assessed first by examining motor laterality using normal subjects’ data acquired both at rest and with a simple unilateral motor task and subsequently by examining mesial temporal lobe memory laterality in normal subjects and patients with temporal lobe epilepsy. The motor task was used to demonstrate that CL within motor ROI correctly lateralized functional stimulation. In patients with unilateral epilepsy studied during a scene-encoding task, CL in a hippocampus-parahippocampus-fusiform (HPF) ROI was concordant with lateralization based on task activation, and the CL index (CLI) significantly differentiated the right side group to the left side group. By contrast, normal controls showed a symmetric HPF CLI distribution. Additionally, similar memory laterality prediction results were still observed using CL in epilepsy patients with unilateral seizures after the memory encoding effect was removed from the data, suggesting the potential for lateralization of pathological brain function based on resting fMRI data. A better lateralization was further achieved via a combination of the proposed approach and the standard activation based approach, demonstrating that assessment of spatial coherence changes provides a complementary approach to quantifying task-correlated activity for lateralizing brain function. PMID:19345736

  4. Sella turcica measurements on lateral cephalograms of patients with neurofibromatosis type 1

    Directory of Open Access Journals (Sweden)

    Friedrich, Reinhard E.

    2017-03-01

    Full Text Available The aim of this study was to measure line segments and areas of sella turcica on lateral cephalograms with respect to the clinical diagnosis of facial phenotype of patients with neurofibromatosis type 1 (NF1. Special attention was given to correlate the measured values with certain tumour types that are typical for this disease.Material and methods: Lateral cephalograms of 194 individuals were investigated. Patients with NF1 were further divided according to the detection and topography of facial plexiform neurofibromas (PNF taking into account the distribution pattern of the trigeminal nerve. All patients with PNF showed unilateral tumour localisation. Patients without any facial PNF constituted a separate group. Healthy volunteers with ideal occlusion and no history of any intervention in the maxillofacial region served as a control group. The following items were determined on the radiographs: sella entrance, sella width, sella depths, sella diagonal, and sella area.Results: Patients with PNF of the first and second trigeminal nerve branch or affected in all branches showed highly statistically significant enlarged sella tucica measurement values. On the other hand, patients with PNF restricted to one branch only or simultaneously in the second and third branches showed measurement values that were not different to those obtained in NF1 patients devoid of facial PNF. The latter group also showed no difference of sella turcica parameters obtained in the control group.Conclusion: This study provides evidence for the association of a certain NF1 phenotype with distinct skeletal alterations of the skull base, shown here using the example of the representation of the sella turcica in the lateral radiograph. These findings are also relevant in the discussion of NF1 as a disease of bones and in the assessment of brain development in NF1. Both items are discussed in relationship to a facial plexiform neurofibroma. Furthermore, the knowledge of this

  5. Mechanism of inhibition of mouse Slo3 (KCa 5.1) potassium channels by quinine, quinidine and barium.

    Science.gov (United States)

    Wrighton, David C; Muench, Stephen P; Lippiat, Jonathan D

    2015-09-01

    The Slo3 (KCa 5.1) channel is a major component of mammalian KSper (sperm potassium conductance) channels and inhibition of these channels by quinine and barium alters sperm motility. The aim of this investigation was to determine the mechanism by which these drugs inhibit Slo3 channels. Mouse (m) Slo3 (KCa 5.1) channels or mutant forms were expressed in Xenopus oocytes and currents recorded with 2-electrode voltage-clamp. Gain-of-function mSlo3 mutations were used to explore the state-dependence of the inhibition. The interaction between quinidine and mSlo3 channels was modelled by in silico docking. Several drugs known to block KSper also affected mSlo3 channels with similar levels of inhibition. The inhibition induced by extracellular barium was prevented by increasing the extracellular potassium concentration. R196Q and F304Y mutations in the mSlo3 voltage sensor and pore, respectively, both increased channel activity. The F304Y mutation did not alter the effects of barium, but increased the potency of inhibition by both quinine and quinidine approximately 10-fold; this effect was not observed with the R196Q mutation. Block of mSlo3 channels by quinine, quinidine and barium is not state-dependent. Barium inhibits mSlo3 outside the cell by interacting with the selectivity filter, whereas quinine and quinidine act from the inside, by binding in a hydrophobic pocket formed by the S6 segment of each subunit. Furthermore, we propose that the Slo3 channel activation gate lies deep within the pore between F304 in the S6 segment and the selectivity filter. © 2015 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of The British Pharmacological Society.

  6. Environmental regulation of lateral root emergence in Medicago truncatula requires the HD-Zip I transcription factor HB1.

    Science.gov (United States)

    Ariel, Federico; Diet, Anouck; Verdenaud, Marion; Gruber, Véronique; Frugier, Florian; Chan, Raquel; Crespi, Martin

    2010-07-01

    The adaptation of root architecture to environmental constraints is a major agricultural trait, notably in legumes, the third main crop worldwide. This root developmental plasticity depends on the formation of lateral roots (LRs) emerging from primary roots. In the model legume Medicago truncatula, the HD-Zip I transcription factor HB1 is expressed in primary and lateral root meristems and induced by salt stress. Constitutive expression of HB1 in M. truncatula roots alters their architecture, whereas hb1 TILLING mutants showed increased lateral root emergence. Electrophoretic mobility shift assay, promoter mutagenesis, and chromatin immunoprecipitation-PCR assays revealed that HB1 directly recognizes a CAATAATTG cis-element present in the promoter of a LOB-like (for Lateral Organ Boundaries) gene, LBD1, transcriptionally regulated by auxin. Expression of these genes in response to abscisic acid and auxin and their behavior in hb1 mutants revealed an HB1-mediated repression of LBD1 acting during LR emergence. M. truncatula HB1 regulates an adaptive developmental response to minimize the root surface exposed to adverse environmental stresses.

  7. Properties of Single K+ and Cl− Channels in Asclepias tuberosa Protoplasts 1

    Science.gov (United States)

    Schauf, Charles L.; Wilson, Kathryn J.

    1987-01-01

    Potassium and chloride channels were characterized in Asclepias tuberosa suspension cell derived protoplasts by patch voltage-clamp. Whole-cell currents and single channels in excised patches had linear instantaneous current-voltage relations, reversing at the Nernst potentials for K+ and Cl−, respectively. Whole cell K+ currents activated exponentially during step depolarizations, while voltage-dependent Cl− channels were activated by hyperpolarizations. Single K+ channel conductance was 40 ± 5 pS with a mean open time of 4.5 milliseconds at 100 millivolts. Potassium channels were blocked by Cs+ and tetraethylammonium, but were insensitive to 4-aminopyridine. Chloride channels had a single-channel conductance of 100 ± 17 picosiemens, mean open time of 8.8 milliseconds, and were blocked by Zn2+ and ethacrynic acid. Whole-cell Cl− currents were inhibited by abscisic acid, and were unaffected by indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid. Since internal and external composition can be controlled, patch-clamped protoplasts are ideal systems for studying the role of ion channels in plant physiology and development. Images Fig. 5 PMID:16665712

  8. Homologue Structure of the SLAC1 Anion Channel for Closing Stomata in Leaves

    Energy Technology Data Exchange (ETDEWEB)

    Y Chen; L Hu; M Punta; R Bruni; B Hillerich; B Kloss; B Rost; J Love; S Siegelbaum; W Hendrickson

    2011-12-31

    The plant SLAC1 anion channel controls turgor pressure in the aperture-defining guard cells of plant stomata, thereby regulating the exchange of water vapour and photosynthetic gases in response to environmental signals such as drought or high levels of carbon dioxide. Here we determine the crystal structure of a bacterial homologue (Haemophilus influenzae) of SLAC1 at 1.20 {angstrom} resolution, and use structure-inspired mutagenesis to analyse the conductance properties of SLAC1 channels. SLAC1 is a symmetrical trimer composed from quasi-symmetrical subunits, each having ten transmembrane helices arranged from helical hairpin pairs to form a central five-helix transmembrane pore that is gated by an extremely conserved phenylalanine residue. Conformational features indicate a mechanism for control of gating by kinase activation, and electrostatic features of the pore coupled with electrophysiological characteristics indicate that selectivity among different anions is largely a function of the energetic cost of ion dehydration.

  9. Receptor model for the molecular basis of tissue selectivity of 1,4-dihydropyridine calcium channel drugs

    Science.gov (United States)

    Langs, David A.; Strong, Phyllis D.; Triggle, David J.

    1990-09-01

    Our analysis of the solid state conformations of nifedipine [dimethyl 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinecarboxylate] and its 1,4-dihydropyridine (1,4-DHP) analogues produced a cartoon description of the important interactions between these drugs and their voltage-dependent calcium channel receptor. In the present study a molecular-level detailed model of the 1,4-DHP receptor binding site has been built from the published amino acid sequence of the 215-1 subunit of the voltage-dependent calcium channel isolated from rabbit skeletal muscle transverse tubule membranes. The voltage-sensing component of the channel described in this work differs from others reported for the homologous sodium channel in that it incorporates a water structure and a staggered, rather than eclipsed, hydrogen bonded S4 helix conformation. The major recognition surfaces of the receptor lie in helical grooves on the S4 or voltagesensing α-helix that is positioned in the center of the bundle of transmembrane helices that define each of the four calcium channel domains. Multiple binding clefts defined by Arg-X-X-Arg-P-X-X-S `reading frames' exist on the S4 strand. The tissue selectivity of nifedipine and its analogues may arise, in part, from conservative changes in the amino acid residues at the P and S positions of the reading frame that define the ester-binding regions of receptors from different tissues. The crystal structures of two tissue-selective nifedipine analogues, nimodipine [isopropyl (2-methoxyethyl) 1,4-dihydro-2,6- dimethyl-4-(3-nitrophenyl)-3,5-pyridinecarboxylate] and nitrendipine [ethyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinecarboxylate] are reported. Nimodipine was observed to have an unusual ester side chain conformation that enhances the fit to the proposed ester-sensing region of the receptor.

  10. Electroantennogram measurement of the olfactory response of Daphnia spp. and its impairment by waterborne copper.

    Science.gov (United States)

    Simbeya, Christy K; Csuzdi, Catherine E; Dew, William A; Pyle, Greg G

    2012-08-01

    In this study an electroantennogram (EAG) method was developed for use on live daphniids. The EAG response of Daphnia magna and Daphnia pulex to a variety of amino acids was measured. The strongest response measured was elicited by L-arginine and was shown to induce a concentration-dependent response indicating the response is olfactory in nature. Subsequent exposures of D. magna to a low, ecologically-relevant concentration of copper (7.5 μg/L) showed a disruption in EAG function. This study utilizes the development of an EAG method for measuring olfactory acuity of live daphniids and demonstrates that at ecologically-relevant concentrations, the olfactory dysfunction caused by copper can be detected. The EAG technique is a useful tool for investigating the olfactory response of daphniids to odourants at the cellular level and detecting the effects of toxicants on the olfactory acuity of daphniids. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. Laboratory Modeling of Self-Formed Leveed Channels From Sediment-Laden Flows Entering Still Water

    Science.gov (United States)

    Rowland, J. C.; Dietrich, W. E.

    2004-12-01

    Self-formed leveed channels constructed by deposition of suspended sediment from sediment-laden flows entering still water are common features in nature. Such channels drive delta progradation, develop at tidal inlets and occur where mainstem river flows empty into oxbows and blocked valley lakes. Presently there is no theory for the formation of such channels. This lack of theory is partly due to a lack of field or laboratory studies that provide insight about the mechanism controlling these self-formed, propagating channels. The creation of such features in the laboratory, have proved illusive to date. Our ongoing experiments aimed at modeling the formation of floodplain tie channels provide insight into the necessary conditions for levee formation and channel growth. Under conditions of steady water discharge, constant sediment feed rate, unimodal sediment distribution and invariant basin stage we are able to create subaqueous lateral bars (submerged levees) along the margins of a sediment laden jet. Our results highlight the sensitivity of channel formation to issues of scaling and experimental design. In the laboratory, levee formation has only been possible with the use of plastic particles (specific gravity ~1.5); complete bed alluviation and dune formation results from the use of particles with specific gravities of ~ 2.65 across a range grain diameters and shapes. We hypothesize this effect is related to high entrainment thresholds relative to suspension thresholds of small (< 100 mm) natural particles under conditions of reduced turbulence in laboratory scaled flows. Additionally, both the width to depth ratio and the form of the outlet channel introducing the sediment laden flow into the experimental basin exert a strong control on sedimentation pattern and levee growth. Continuing experiments are focused on generating emergent channel levees and a basin ward propagation of the channel by adjusting the form of the feed channel, varying basin stage, and

  12. Sar1-GTPase-dependent ER exit of KATP channels revealed by a mutation causing congenital hyperinsulinism

    DEFF Research Database (Denmark)

    Taneja, Tarvinder K; Mankouri, Jamel; Karnik, Rucha

    2009-01-01

    The ATP-sensitive potassium (K(ATP)) channel controls insulin secretion by coupling glucose metabolism to excitability of the pancreatic beta-cell membrane. The channel comprises four subunits each of Kir6.2 and the sulphonylurea receptor (SUR1), encoded by KCNJ11 and ABCC8, respectively. Mutatio...

  13. 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

  14. The Vein Patterning 1 (VEP1 gene family laterally spread through an ecological network.

    Directory of Open Access Journals (Sweden)

    Rosa Tarrío

    Full Text Available Lateral gene transfer (LGT is a major evolutionary mechanism in prokaryotes. Knowledge about LGT--particularly, multicellular--eukaryotes has only recently started to accumulate. A widespread assumption sees the gene as the unit of LGT, largely because little is yet known about how LGT chances are affected by structural/functional features at the subgenic level. Here we trace the evolutionary trajectory of VEin Patterning 1, a novel gene family known to be essential for plant development and defense. At the subgenic level VEP1 encodes a dinucleotide-binding Rossmann-fold domain, in common with members of the short-chain dehydrogenase/reductase (SDR protein family. We found: i VEP1 likely originated in an aerobic, mesophilic and chemoorganotrophic α-proteobacterium, and was laterally propagated through nets of ecological interactions, including multiple LGTs between phylogenetically distant green plant/fungi-associated bacteria, and five independent LGTs to eukaryotes. Of these latest five transfers, three are ancient LGTs, implicating an ancestral fungus, the last common ancestor of land plants and an ancestral trebouxiophyte green alga, and two are recent LGTs to modern embryophytes. ii VEP1's rampant LGT behavior was enabled by the robustness and broad utility of the dinucleotide-binding Rossmann-fold, which provided a platform for the evolution of two unprecedented departures from the canonical SDR catalytic triad. iii The fate of VEP1 in eukaryotes has been different in different lineages, being ubiquitous and highly conserved in land plants, whereas fungi underwent multiple losses. And iv VEP1-harboring bacteria include non-phytopathogenic and phytopathogenic symbionts which are non-randomly distributed with respect to the type of harbored VEP1 gene. Our findings suggest that VEP1 may have been instrumental for the evolutionary transition of green plants to land, and point to a LGT-mediated 'Trojan Horse' mechanism for the evolution of

  15. Effects of large floods on channel width: recent insights from Italian rivers

    Science.gov (United States)

    Scorpio, Vittoria; Righini, Margherita; Amponsah, William; Crema, Stefano; Ciccarese, Giuseppe; Nardi, Laura; Zoccatelli, Davide; Borga, Marco; Cavalli, Marco; Comiti, Francesco; Corsini, Alessandro; Marchi, Lorenzo; Rinaldi, Massimo; Surian, Nicola

    2017-04-01

    Variations of channel morphology occurring during large flood events (recurrence interval > 50-100 years.) are very often the cause of damages to buildings and infrastructures, as well as of casualties. However, our knowledge of such processes remains poor, as is our capability to predict them. Post-event campaigns documenting channel changes and linking them to hydrological and morphological factors thus bear an enormous value for both the scientific community and river management agencies. We present the results of an analysis on the geomorphic response associated to 4 large floods that occurred between October 2011 and September 2015, affecting several catchments in Northern Italy (Magra-Vara, Trebbia, Nure rivers) and Sardinia (Posada and Mannu di Bitti rivers), characterized by different climatic, lithological and geomorphological settings. The analysis considered more than 400 channel reaches characterized by a drainage area ranging from 39 to 1,100 km2 and featuring a wide range of lateral confinement, mostly within the partly- and unconfined conditions. The approach to flood analysis encompassed: (i) hydrological and hydraulic analysis; (ii) analysis of sediment delivery by landslides to the channel network; (iii) GIS-based and field assessment of morphological channel modifications. For the Nure River flood event (September 2015) a quantitative assessment on average bed level variations was also carried out. Return period for maximum hourly rainfall intensities and peak water discharges exceeded in all basins 100 yr, in some cases even 300 yr. Very high unit peak discharges were estimated, reaching 8.8 m3 s-1km-2 in the Nure River (205 km2) and up to 30 m3 s-1km-2in few Magra River tributaries (5-10 km2). Notable channel widening (post-flood width / pre-flood width > 1.1) occurred in 83% of studied reaches, and it was found more relevant in the channels with narrower initial width, i.e. along the relatively steep tributaries. For these tributaries, the

  16. The challenges of molecular nutrition research 1- Linking genotype to healthy nutrition

    Science.gov (United States)

    Nutrition science finds itself at a major crossroad. On one hand we can continue the current path that along several decades has resulted in substantial advances but surrounded by conflicting messages and unsubstantiated claims that have been crumbling the trust of the general population, always eag...

  17. A role for corticotropin-releasing factor signaling in the lateral habenula and its modulation by early-life stress.

    Science.gov (United States)

    Authement, Michael E; Langlois, Ludovic D; Shepard, Ryan D; Browne, Caroline A; Lucki, Irwin; Kassis, Haifa; Nugent, Fereshteh S

    2018-03-06

    Centrally released corticotropin-releasing factor or hormone (extrahypothalamic CRF or CRH) in the brain is involved in the behavioral and emotional responses to stress. The lateral habenula (LHb) is an epithalamic brain region involved in value-based decision-making and stress evasion. Through its inhibition of dopamine-mediated reward circuitry, the increased activity of the LHb is associated with addiction, depression, schizophrenia, and behavioral disorders. We found that extrahypothalamic CRF neurotransmission increased neuronal excitability in the LHb. Through its receptor CRFR1 and subsequently protein kinase A (PKA), CRF application increased the intrinsic excitability of LHb neurons by affecting changes in small-conductance SK-type and large-conductance BK-type K + channels. CRF also reduced inhibitory γ-aminobutyric acid-containing (GABAergic) synaptic transmission onto LHb neurons through endocannabinoid-mediated retrograde signaling. Maternal deprivation is a severe early-life stress that alters CRF neural circuitry and is likewise associated with abnormal mental health later in life. LHb neurons from pups deprived of maternal care exhibited increased intrinsic excitability, reduced GABAergic transmission, decreased abundance of SK2 channel protein, and increased activity of PKA, without any substantial changes in Crh or Crhr1 expression. Furthermore, maternal deprivation blunted the response of LHb neurons to subsequent, acute CRF exposure. Activating SK channels or inhibiting postsynaptic PKA activity prevented the effects of both CRF and maternal deprivation on LHb intrinsic excitability, thus identifying potential pharmacological targets to reverse central CRF circuit dysregulation in patients with associated disorders. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  18. Secondary electron emission induced by channeled relativistic electrons in a (1 1 0) Si crystal

    International Nuclear Information System (INIS)

    Korotchenko, K.B.; Kunashenko, Yu P.; Tukhfatullin, T.A.

    2012-01-01

    A new effect that accompanies electrons channeled in a crystal is considered. This phenomenon was previously predicted was called channeling secondary electron emission (CSEE). The exact CSEE cross-section on the basis of using the exact Bloch wave function of electron channeled in a crystal is obtained. The detailed investigation of CSEE cross-section is performed. It is shown that angular distribution of electrons emitted due to CSEE has a complex form.

  19. Intrinsic Membrane Hyperexcitability of Amyotrophic Lateral Sclerosis Patient-Derived Motor Neurons

    Directory of Open Access Journals (Sweden)

    Brian J. Wainger

    2014-04-01

    Full Text Available Amyotrophic lateral sclerosis (ALS is a fatal neurodegenerative disease of the motor nervous system. We show using multielectrode array and patch-clamp recordings that hyperexcitability detected by clinical neurophysiological studies of ALS patients is recapitulated in induced pluripotent stem cell-derived motor neurons from ALS patients harboring superoxide dismutase 1 (SOD1, C9orf72, and fused-in-sarcoma mutations. Motor neurons produced from a genetically corrected but otherwise isogenic SOD1+/+ stem cell line do not display the hyperexcitability phenotype. SOD1A4V/+ ALS patient-derived motor neurons have reduced delayed-rectifier potassium current amplitudes relative to control-derived motor neurons, a deficit that may underlie their hyperexcitability. The Kv7 channel activator retigabine both blocks the hyperexcitability and improves motor neuron survival in vitro when tested in SOD1 mutant ALS cases. Therefore, electrophysiological characterization of human stem cell-derived neurons can reveal disease-related mechanisms and identify therapeutic candidates.

  20. Historical perspectives on channel pattern in the Clark Fork River, Montana and implications for post-dam removal restoration

    Science.gov (United States)

    Woelfle-Erskine, C. A.; Wilcox, A. C.

    2009-12-01

    Active restoration approaches such as channel reconstruction have moved beyond the realm of small streams and are being applied to larger rivers. Uncertainties arising from limited knowledge, fluvial and ecosystem variability, and contaminants are especially significant in restoration of large rivers, where project costs and the social, infrastructural, and ecological costs of failure are high. We use the case of Milltown Dam removal on the Clark Fork River, Montana and subsequent channel reconstruction in the former reservoir to examine the use of historical research and uncertainty analysis in river restoration. At a cost of approximately $120 million, the Milltown Dam removal involves the mechanical removal of approximately 2 million cubic meters of sediments contaminated by upstream mining, followed by restoration of the former reservoir reach in which a single-thread meandering channel is being constructed. Historical maps, surveys, photographs, and accounts suggest a conceptual model of a multi-thread, anastomosing river in the reach targeted for channel reconstruction, upstream of the confluence of the Clark Fork and Blackfoot Rivers. We supplemented historical research with analysis of aerial photographs, topographic data, and USGS stage-discharge measurements in a lotic but reservoir-influenced reach of the Clark Fork River within our study area to estimate avulsion frequency (0.8 avulsions/year over a 70-year period) and average rates of lateral migration and aggradation. These were used to calculate the mobility number, a dimensionless relationship between channel filling and lateral migration timescales that can be used to predict whether a river’s planform is single or multi-threaded. The mobility number within our study reach ranged from 0.6 (multi-thread channel) to 1.7 (transitional channel). We predict that, in the absence of active channel reconstruction, the post-dam channel pattern would evolve to one that alternates between single and multi

  1. Structural and functional analysis of the putative pH sensor in the Kir1.1 (ROMK) potassium channel.

    Science.gov (United States)

    Rapedius, Markus; Haider, Shozeb; Browne, Katharine F; Shang, Lijun; Sansom, Mark S P; Baukrowitz, Thomas; Tucker, Stephen J

    2006-06-01

    The pH-sensitive renal potassium channel Kir1.1 is important for K+ homeostasis. Disruption of the pH-sensing mechanism causes type II Bartter syndrome. The pH sensor is thought to be an anomalously titrated lysine residue (K80) that interacts with two arginine residues as part of an 'RKR triad'. We show that a Kir1.1 orthologue from Fugu rubripes lacks this lysine and yet is still highly pH sensitive, indicating that K80 is not the H+ sensor. Instead, K80 functionally interacts with A177 on transmembrane domain 2 at the 'helix-bundle crossing' and controls the ability of pH-dependent conformational changes to induce pore closure. Although not required for pH inhibition, K80 is indispensable for the coupling of pH gating to the extracellular K+ concentration, explaining its conservation in most Kir1.1 orthologues. Furthermore, we demonstrate that instead of interacting with K80, the RKR arginine residues form highly conserved inter- and intra-subunit interactions that are important for Kir channel gating and influence pH sensitivity indirectly.

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

    Directory of Open Access Journals (Sweden)

    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.

  3. Wandering gravel-bed rivers and high-constructive stable channel sandy fluvial systems in the Ross River area, Yukon Territory, Canada

    Directory of Open Access Journals (Sweden)

    Darrel G.F. Long

    2011-07-01

    Gravel-dominated strata, inter-bedded with, and overlying coal-bearing units, are interpreted as deposits of wandering gravel-bed rivers, with sinuosity approaching 1.4. In most exposures they appear to be dominated by massive and thin planar-bedded granule to small pebble conglomerates, which would traditionally be interpreted as sheet-flood or longitudinal bar deposits of a high-gradient braided stream or alluvial fan. Architectural analysis of exposures in an open-pit shows that the predominance of flat bedding is an artefact of the geometry of the roadside exposures. In the pit the conglomerates are dominated by large scale cross stratification on a scale of 1–5.5 m. These appear to have developed as downstream and lateral accretion elements on side-bars and on in-channel bars in water depths of 2–12 m. Stacking of strata on domed 3rd order surfaces suggests development of longitudinal in-channel bar complexes similar to those observed in parts of the modern Rhône River system. Mudstone preserved in some of the channels reflects intervals of channel abandonment or avulsion. Minimum channel width is from 70 to 450 m.

  4. Oxidized/misfolded superoxide dismutase-1: the cause of all amyotrophic lateral sclerosis?

    Science.gov (United States)

    Kabashi, Edor; Valdmanis, Paul N; Dion, Patrick; Rouleau, Guy A

    2007-12-01

    The identification in 1993 of superoxide dismutase-1 (SOD1) mutations as the cause of 10 to 20% of familial amyotrophic lateral sclerosis cases, which represents 1 to 2% of all amyotrophic lateral sclerosis (ALS) cases, prompted a substantial amount of research into the mechanisms of SOD1-mediated toxicity. Recent experiments have demonstrated that oxidation of wild-type SOD1 leads to its misfolding, causing it to gain many of the same toxic properties as mutant SOD1. In vitro studies of oxidized/misfolded SOD1 and in vivo studies of misfolded SOD1 have indicated that these protein species are selectively toxic to motor neurons, suggesting that oxidized/misfolded SOD1 could lead to ALS even in individuals who do not carry an SOD1 mutation. It has also been reported that glial cells secrete oxidized/misfolded mutant SOD1 to the extracellular environment, where it can trigger the selective death of motor neurons, offering a possible explanation for the noncell autonomous nature of mutant SOD1 toxicity and the rapid progression of disease once the first symptoms develop. Therefore, considering that sporadic (SALS) and familial ALS (FALS) cases are clinically indistinguishable, the toxic properties of mutated SOD1 are similar to that of oxidized/misfolded wild-type SOD1 (wtSOD1), and secreted/extracellular misfolded SOD1 is selectively toxic to motor neurons, we propose that oxidized/misfolded SOD1 is the cause of most forms of classic ALS and should be a prime target for the design of ALS treatments.

  5. A Subjective Evaluation of the Minimum Audible Channel Separation in Binaural Reproduction Systems Through Loudspeakers

    DEFF Research Database (Denmark)

    Lacouture Parodi, Yesenia; Rubak, Per

    2010-01-01

    To evaluate the performance of crosstalk cancellation systems the channel separation is usually used as parameter.  However, no systematic evaluation of the minimum audible channel separation has been found in the literature known by the authors.  This paper describes a set of subjective experime......To evaluate the performance of crosstalk cancellation systems the channel separation is usually used as parameter.  However, no systematic evaluation of the minimum audible channel separation has been found in the literature known by the authors.  This paper describes a set of subjective...... simulated.  Results indicate that  in order to avoid lateralization the  channel separation should be below -15dB for most of the stimuli and around -20dB for broad-band noise....

  6. Structural mechanism underlying capsaicin binding and activation of TRPV1 ion channel

    Science.gov (United States)

    Cheng, Wei; Yang, Wei; Yu, Peilin; Song, Zhenzhen; Yarov-Yarovoy, Vladimir; Zheng, Jie

    2015-01-01

    Capsaicin bestows spiciness by activating TRPV1 channel with exquisite potency and selectivity. Capsaicin-bound channel structure was previously resolved by cryo-EM at 4.2-to-4.5 Å resolution, however important details required for mechanistic understandings are unavailable: capsaicin was registered as a small electron density, reflecting neither its chemical structure nor specific ligand-channel interactions. We obtained the missing atomic-level details by iterative computation, which were confirmed by systematic site-specific functional tests. We observed that the bound capsaicin takes “tail-up, head-down” configurations. The vanillyl and amide groups form specific interactions to anchor its bound position, while the aliphatic tail may sample a range of conformations, making it invisible in cryo-EM images. Capsaicin stabilizes the open state by “pull-and-contact” interactions between the vanillyl group and the S4-S5 linker. Our study provided a structural mechanism for the agonistic function of capsaicin and its analogs, and demonstrated an effective approach to obtain atomic level information from cryo-EM structures. PMID:26053297

  7. Functional properties of a newly identified C-terminal splice variant of Cav1.3 L-type Ca2+ channels.

    Science.gov (United States)

    Bock, Gabriella; Gebhart, Mathias; Scharinger, Anja; Jangsangthong, Wanchana; Busquet, Perrine; Poggiani, Chiara; Sartori, Simone; Mangoni, Matteo E; Sinnegger-Brauns, Martina J; Herzig, Stefan; Striessnig, Jörg; Koschak, Alexandra

    2011-12-09

    An intramolecular interaction between a distal (DCRD) and a proximal regulatory domain (PCRD) within the C terminus of long Ca(v)1.3 L-type Ca(2+) channels (Ca(v)1.3(L)) is a major determinant of their voltage- and Ca(2+)-dependent gating kinetics. Removal of these regulatory domains by alternative splicing generates Ca(v)1.3(42A) channels that activate at a more negative voltage range and exhibit more pronounced Ca(2+)-dependent inactivation. Here we describe the discovery of a novel short splice variant (Ca(v)1.3(43S)) that is expressed at high levels in the brain but not in the heart. It lacks the DCRD but, in contrast to Ca(v)1.3(42A), still contains PCRD. When expressed together with α2δ1 and β3 subunits in tsA-201 cells, Ca(v)1.3(43S) also activated at more negative voltages like Ca(v)1.3(42A) but Ca(2+)-dependent inactivation was less pronounced. Single channel recordings revealed much higher channel open probabilities for both short splice variants as compared with Ca(v)1.3(L). The presence of the proximal C terminus in Ca(v)1.3(43S) channels preserved their modulation by distal C terminus-containing Ca(v)1.3- and Ca(v)1.2-derived C-terminal peptides. Removal of the C-terminal modulation by alternative splicing also induced a faster decay of Ca(2+) influx during electrical activities mimicking trains of neuronal action potentials. Our findings extend the spectrum of functionally diverse Ca(v)1.3 L-type channels produced by tissue-specific alternative splicing. This diversity may help to fine tune Ca(2+) channel signaling and, in the case of short variants lacking a functional C-terminal modulation, prevent excessive Ca(2+) accumulation during burst firing in neurons. This may be especially important in neurons that are affected by Ca(2+)-induced neurodegenerative processes.

  8. Calcium homeostasis modulator (CALHM) ion channels.

    Science.gov (United States)

    Ma, Zhongming; Tanis, Jessica E; Taruno, Akiyuki; Foskett, J Kevin

    2016-03-01

    Calcium homeostasis modulator 1 (CALHM1), formerly known as FAM26C, was recently identified as a physiologically important plasma membrane ion channel. CALHM1 and its Caenorhabditis elegans homolog, CLHM-1, are regulated by membrane voltage and extracellular Ca(2+) concentration ([Ca(2+)]o). In the presence of physiological [Ca(2+)]o (∼1.5 mM), CALHM1 and CLHM-1 are closed at resting membrane potentials but can be opened by strong depolarizations. Reducing [Ca(2+)]o increases channel open probability, enabling channel activation at negative membrane potentials. Together, voltage and Ca(2+) o allosterically regulate CALHM channel gating. Through convergent evolution, CALHM has structural features that are reminiscent of connexins and pannexins/innexins/LRRC8 (volume-regulated anion channel (VRAC)) gene families, including four transmembrane helices with cytoplasmic amino and carboxyl termini. A CALHM1 channel is a hexamer of CALHM1 monomers with a functional pore diameter of ∼14 Å. CALHM channels discriminate poorly among cations and anions, with signaling molecules including Ca(2+) and ATP able to permeate through its pore. CALHM1 is expressed in the brain where it plays an important role in cortical neuron excitability induced by low [Ca(2+)]o and in type II taste bud cells in the tongue that sense sweet, bitter, and umami tastes where it functions as an essential ATP release channel to mediate nonsynaptic neurotransmitter release. CLHM-1 is expressed in C. elegans sensory neurons and body wall muscles, and its genetic deletion causes locomotion defects. Thus, CALHM is a voltage- and Ca(2+) o-gated ion channel, permeable to large cations and anions, that plays important roles in physiology.

  9. Structural domains required for channel function of the mouse transient receptor potential protein homologue TRP1beta.

    Science.gov (United States)

    Engelke, Michael; Friedrich, Olaf; Budde, Petra; Schäfer, Christina; Niemann, Ursula; Zitt, Christof; Jüngling, Eberhard; Rocks, Oliver; Lückhoff, Andreas; Frey, Jürgen

    2002-07-17

    Transient receptor potential proteins (TRP) are supposed to participate in the formation of store-operated Ca(2+) influx channels by co-assembly. However, little is known which domains facilitate the interaction of subunits. Contribution of the N-terminal coiled-coil domain and ankyrin-like repeats and the putative pore region of the mouse TRP1beta (mTRP1beta) variant to the formation of functional cation channels were analyzed following overexpression in HEK293 (human embryonic kidney) cells. MTRP1beta expressing cells exhibited enhanced Ca(2+) influx and enhanced whole-cell membrane currents compared to mTRP1beta deletion mutants. Using a yeast two-hybrid assay only the coiled-coil domain facilitated homodimerization of the N-terminus. These results suggest that the N-terminus of mTRP1beta is required for structural organization thus forming functional channels.

  10. Biphasic voltage-dependent inactivation of human NaV 1.3, 1.6 and 1.7 Na+ channels expressed in rodent insulin-secreting cells.

    Science.gov (United States)

    Godazgar, Mahdieh; Zhang, Quan; Chibalina, Margarita V; Rorsman, Patrik

    2018-05-01

    Na + current inactivation is biphasic in insulin-secreting cells, proceeding with two voltage dependences that are half-maximal at ∼-100 mV and -60 mV. Inactivation of voltage-gated Na + (Na V ) channels occurs at ∼30 mV more negative voltages in insulin-secreting Ins1 and primary β-cells than in HEK, CHO or glucagon-secreting αTC1-6 cells. The difference in inactivation between Ins1 and non-β-cells persists in the inside-out patch configuration, discounting an involvement of a diffusible factor. In Ins1 cells and primary β-cells, but not in HEK cells, inactivation of a single Na V subtype is biphasic and follows two voltage dependences separated by 30-40 mV. We propose that Na V channels adopt different inactivation behaviours depending on the local membrane environment. Pancreatic β-cells are equipped with voltage-gated Na + channels that undergo biphasic voltage-dependent steady-state inactivation. A small Na + current component (10-15%) inactivates over physiological membrane potentials and contributes to action potential firing. However, the major Na + channel component is completely inactivated at -90 to -80 mV and is therefore inactive in the β-cell. It has been proposed that the biphasic inactivation reflects the contribution of different Na V α-subunits. We tested this possibility by expression of TTX-resistant variants of the Na V subunits found in β-cells (Na V 1.3, Na V 1.6 and Na V 1.7) in insulin-secreting Ins1 cells and in non-β-cells (including HEK and CHO cells). We found that all Na V subunits inactivated at 20-30 mV more negative membrane potentials in Ins1 cells than in HEK or CHO cells. The more negative inactivation in Ins1 cells does not involve a diffusible intracellular factor because the difference between Ins1 and CHO persisted after excision of the membrane. Na V 1.7 inactivated at 15--20 mV more negative membrane potentials than Na V 1.3 and Na V 1.6 in Ins1 cells but this small difference is insufficient to solely

  11. Molecular basis of inhibition of acid sensing ion channel 1A by diminazene.

    Directory of Open Access Journals (Sweden)

    Aram J Krauson

    Full Text Available Acid-sensing ion channels (ASICs are trimeric proton-gated cation permeable ion channels expressed primarily in neurons. Here we employed site-directed mutagenesis and electrophysiology to investigate the mechanism of inhibition of ASIC1a by diminazene. This compound inhibits mouse ASIC1a with a half-maximal inhibitory concentration (IC50 of 2.4 μM. At first, we examined whether neutralizing mutations of Glu79 and Glu416 alter diminazene block. These residues form a hexagonal array in the lower palm domain that was previously shown to contribute to pore opening in response to extracellular acidification. Significantly, single Gln substitutions at positions 79 and 416 in ASIC1a reduced diminazene apparent affinity by 6-7 fold. This result suggests that diminazene inhibits ASIC1a in part by limiting conformational rearrangement in the lower palm domain. Because diminazene is charged at physiological pHs, we assessed whether it inhibits ASIC1a by blocking the ion channel pore. Consistent with the notion that diminazene binds to a site within the membrane electric field, diminazene block showed a strong dependence with the membrane potential. Moreover, a Gly to Ala mutation at position 438, in the ion conduction pathway of ASIC1a, increased diminazene IC50 by one order of magnitude and eliminated the voltage dependence of block. Taken together, our results indicate that the inhibition of ASIC1a by diminazene involves both allosteric modulation and blocking of ion flow through the conduction pathway. Our findings provide a foundation for the development of more selective and potent ASIC pore blockers.

  12. Kv7.1 ion channels require a lipid to couple voltage sensing to pore opening.

    Science.gov (United States)

    Zaydman, Mark A; Silva, Jonathan R; Delaloye, Kelli; Li, Yang; Liang, Hongwu; Larsson, H Peter; Shi, Jingyi; Cui, Jianmin

    2013-08-06

    Voltage-gated ion channels generate dynamic ionic currents that are vital to the physiological functions of many tissues. These proteins contain separate voltage-sensing domains, which detect changes in transmembrane voltage, and pore domains, which conduct ions. Coupling of voltage sensing and pore opening is critical to the channel function and has been modeled as a protein-protein interaction between the two domains. Here, we show that coupling in Kv7.1 channels requires the lipid phosphatidylinositol 4,5-bisphosphate (PIP2). We found that voltage-sensing domain activation failed to open the pore in the absence of PIP2. This result is due to loss of coupling because PIP2 was also required for pore opening to affect voltage-sensing domain activation. We identified a critical site for PIP2-dependent coupling at the interface between the voltage-sensing domain and the pore domain. This site is actually a conserved lipid-binding site among different K(+) channels, suggesting that lipids play an important role in coupling in many ion channels.

  13. The quaternary lidocaine derivative, QX-314, exerts biphasic effects on transient receptor potential vanilloid subtype 1 channels in vitro

    DEFF Research Database (Denmark)

    Rivera-Acevedo, Ricardo E; Pless, Stephan Alexander; Ahern, Christopher A

    2011-01-01

    concentrations (less than 1 mM), QX-314 potently inhibited capsaicin-evoked TRPV1 currents with an IC₅₀ of 8.0 ± 0.6 μM. CONCLUSIONS: The results of this study show that the quaternary lidocaine derivative QX-314 exerts biphasic effects on TRPV1 channels, inhibiting capsaicin-evoked TRPV1 currents at lower...... channels. METHODS: The authors conducted an in vitro laboratory study in which they expressed TRPV1 and TRPV4 channels in Xenopus laevis oocytes and recorded cation currents with the two-electrode voltage clamp method. They used confocal microscopy for Ca²⁺ imaging in TRPV1 transient transfected tsA201...

  14. Lateral and vertical manipulations of single atoms on the Ag(1 1 1) surface with the copper single-atom and trimer-apex tips

    International Nuclear Information System (INIS)

    Xie Yiqun; Yang Tianx