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  • Key words: Bronchial epithelial cells — Cl− currents — Cl− channels — Patch-clamp — Intracellular Ca2+— ATP — UTP  (1)
  • Transport properties  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 156 (1997), S. 297 -305 
    ISSN: 1432-1424
    Keywords: Key words: Bronchial epithelial cells — Cl− currents — Cl− channels — Patch-clamp — Intracellular Ca2+— ATP — UTP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The perforated-patch technique was used to study the response of human bronchial cells to extracellular nucleotides. ATP or UTP (100 μm) elicited a complex response consisting of a large transient membrane current increase followed by a relatively small sustained level. These two phases were characterized by different current kinetics. Throughout the transient phase (2–3 min) the membrane current (I p ) displayed slow activation and deactivation kinetics at depolarizing and hyperpolarizing potentials respectively. At steady-state (I s ) the relaxation at hyperpolarizing potential disappeared whereas at positive membrane potentials the current became slightly deactivating. The I s amplitude was dependent on the extracellular Ca2+ concentration, being completely inhibited in Ca2+-free medium. Cell pre-incubation with the membrane-permeable chelating agent BAPTA/AM prevented completely the response to nucleotides, thus suggesting that both I p and I s were dependent on intracellular Ca2+. The presence of a hypertonic medium during nucleotide stimulation abolished I s leaving I p unchanged. On the contrary, niflumic acid, a blocker of Ca2+-activated Cl− channels, prevented completely I p without reducing significantly I s . 1,9-dideoxyforskolin fully inhibited I s but also reduced I p . Replacement of extracellular Cl− with aspartate demonstrated that the currents activated by nucleotides were Cl− selective. I p resulted five times more Cl− selective than I s with respect to aspartate. Taken together, our results indicate that ATP and UTP activate two types of Cl− currents through a Ca2+-dependent mechanism.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 12 (1999), S. 631-639 
    ISSN: 1572-9605
    Keywords: Transport properties ; flux pinning ; flux creep ; flux line lattice dynamices ; Bi-based cuprates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electrical transport of a superconducting BSCCO-2223 Ag-sheathed tape is studied as a function of temperature T, current I, and magnetic field H. In a range of current and field, covering two orders of magnitude, the resistance R(T) is described by R = R o exp{−b[(T m −T)/(T −T o )]0.5}, where T o and T m are the limits of the non-ohmic and field dependent behavior. The threshold T o is a decreasing function of I and H, whereas T m depends only on H. The isothermal R(I) and the R(H) trends confirm the previous function, suggesting that, within the examined ranges, the dissipation may be attributed to a process in which the temperature has a prevalent role, whereas I and H change the limits of the process. The experimental data are consistent with a process in which the dynamics of thermally generated vortices is current and field controlled.
    Type of Medium: Electronic Resource
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