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  • 1
    Electronic Resource
    Electronic Resource
    EXCITATION-CONTRACTION COUPLING IN GASTROINTESTINAL AND OTHER SMOOTH MUSCLES (1999)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 61 (1999), S. 85-115 
    Details
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Notes: Abstract The main contributors to increases in [Ca2+]i and tension are the entry of Ca2+ through voltage-dependent channels opened by depolarization or during action potential (AP) or slow-wave discharge, and Ca2+ release from store sites in the cell by the action of IP3 or by Ca2+-induced Ca2+-release (CICR). The entry of Ca2+ during an AP triggers CICR from up to 20 or more subplasmalemmal store sites (seen as hot spots, using fluorescent indicators); Ca2+ waves then spread from these hot spots, which results in a rise in [Ca2+]i throughout the cell. Spontaneous transient releases of store Ca2+, previously detected as spontaneous transient outward currents (STOCs), are seen as sparks when fluorescent indicators are used. Sparks occur at certain preferred locations-frequent discharge sites (FDSs)-and these and hot spots may represent aggregations of sarcoplasmic reticulum scattered throughout the cytoplasm. Activation of receptors for excitatory signal molecules generally depolarizes the cell while it increases the production of IP3 (causing calcium store release) and diacylglycerols (which activate protein kinases). Activation of receptors for inhibitory signal molecules increases the activity of protein kinases through increases in cAMP or cGMP and often hyperpolarizes the cell. Other receptors link to tyrosine kinases, which trigger signal cascades interacting with trimeric G-protein systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.physiol.61.1.85
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  • 2
    Electronic Resource
    Electronic Resource
    The action of caffeine on inward barium current through voltage-dependent calcium channels in single rabbit ear artery cells (1990)
    Springer
    Pflügers Archiv 416 (1990), S. 462-466 
    Details
    ISSN: 1432-2013
    Keywords: Caffeine ; Methylxanthine ; Smooth muscle ; Calcium channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of caffeine on inward current carried by barium ions through voltage-dependent calcium channels has been investigated in single rabbit ear artery cells using whole-cell voltage-clamp techniques. Caffeine (1 –30 mM) caused a rapid and reversible concentration-dependent blockade of barium current and a related compound, 3-isobutyl-1-methylxanthine (IBMX), was a more potent inhibitor of barium current. Caffeine-induced inhibition of barium current showed no voltage- or usedependence and caffeine did not alter the steady-state inactivation of barium current. The effect of caffeine was not blocked by extracellular or by intracellular ryanodine or inclusion of both 5 mM 1,2-bis(2-aminophenoxy)-ethane N,N,N′,N′,-tetraacetic acid (BAPTA) and 2 mM ethylene glycol-bis(β-amino ethyl ether) N,N,N′,N′,-tetraacetic acid (EGTA) in the intracellular solution. Rolipram and M&B 22984, non-xanthine inhibitors of phosphodiesterase, did not diminish inward barium current. The data indicate that caffeine and IBMX block voltage-operated calcium channels and it is suggested that this is due to a direct interaction of methylxanthines with the calcium channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370755
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  • 3
    Electronic Resource
    Electronic Resource
    Inositol trisphosphate releases stored calcium to block voltage-dependent calcium channels in single smooth muscle cells (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 437-441 
    Details
    ISSN: 1432-2013
    Keywords: Inositol trisphosphate ; Caged InsP 3 ; Caged ATP ; Heparin ; Calcium current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In single cells obtained by enzymic treatment of rabbit small-intestinal smooth muscle, and held under voltage clamp by patch pipette in the whole-cell recording mode, release of inositol trisphosphate (InsP 3) from its caged precursor by flash photolysis caused complete inhibition of the voltage-dependent calcium current. No inhibition was seen in control experiments where the cage (2-nitrosoacetophenone) was released by flash photolysis from caged ATP. The inhibition by InsP 3 of the calcium current was prevented if 10 mM EGTA or 2 mg/ml heparin was included in the pipette solution. Heparin is known to block InsP 3 receptors. These results suggest that release of calcium stores by InsP 3 raises Cai and that calcium ions inhibit the calcium current by acting either directly or otherwise on the internal mouth of the calcium channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00497770
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  • 4
    Electronic Resource
    Electronic Resource
    Oscillations of receptor-operated cationic current and internal calcium in single guinea-pig ileal smooth muscle cells (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 431-438 
    Details
    ISSN: 1432-2013
    Keywords: Calcium oscillations ; Muscarinic receptor ; Calcium stores ; G protein ; Heparin ; Ryanodine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In single cells isolated from guinea-pig ileal smooth muscle, held under voltage clamp at −40 mV or −50 mV by patch pipette in the whole-cell recording mode, carbachol (CCh) evoked an oscillatory inward cationic current. The frequency of current oscillations increased with increasing CCh concentration. CCh-evoked current oscillations were followed very closely by oscillations in intracellular free Ca2+ estimated from the Indo-1 signal, and were abolished by inclusion of EGTA in the pipette solution. Ryanodine and heparin, but not nifedipine, blocked the generation of current oscillations. CCh-evoked current oscillations were abolished upon withdrawal of extracellular calcium and restored upon its reintroduction. Inclusion of GTP[γS] in the pipette solution caused the generation of an oscillatory inward current, which was blocked by ryanodine. The present results are consistent with the hypothesis that CChevoked cationic current is gated by activation of a G protein and is steeply dependent on [Ca2+]i, fluctuations in the release of Ca2+ from stores during carbachol's action produce oscillations in [Ca2+]i which cause similar oscillations in the cationic current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374905
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of the strange quark content of the nucleon from a next-to-leading-order QCD analysis of neutrino charm production (1995)
    Springer
    The European physical journal 65 (1995), S. 189-198 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the first next-to-leading-order QCD analysis of neutrino charm production, using a sample of 6090ν μ − and $$\bar \nu _\mu $$ -induced opposite-sign dimuon events observed in the CCFR detector at the Fermilab Tevatron. We find that the nucleon strange quark content is suppressed with respect to the non-strange sea quarks by a factor κ=0.477 −0.053 +0.063 , where the error includes statistical, systematic and QCD scale uncertainties. In contrast to previous leading order analyses, we find that the strange seax-dependence is similar to that of the non-strange sea, and that the measured charm quark mass,m c =1.70±0.19 GeV/c2, is larger and consistent with that determined in other processes. Further analysis finds that the difference inx-distributions betweenxs(x) and $$x\bar s{\text{(}}x{\text{)}}$$ is small. A measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V cd |=0.232 −0.020 +0.018 is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571875
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