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  • 1
    Electronic Resource
    Electronic Resource
    Voltage dependent calcium channels in cerebellar granule cell primary cultures (1991)
    Springer
    European biophysics journal 20 (1991), S. 157-164 
    Details
    ISSN: 1432-1017
    Keywords: Calcium channels ; Cerebellar granule cells ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Voltage activated calcium channels were studied in rat cerebellar granule cells in primary culture. Macroscopic currents, carried by 20 mM Ba2+, were measured in the whole-cell configuration. Slowly inactivating macroscopic currents, with a maximum value at a membrane potential around 5 mV were recorded between the 1st and the 4th day in culture. These currents were completely blocked by 5 mM Co2+ , partially blocked by 10 μM nifedipine, and increased by 2 to 5 μM BAY K-8644. Two types of channels, in the presence of 80 mM Ba2+, were identified by single channel recording in cell-attached patches. The first type, which was dihydropyridine agonist sensitive, had a conductance of 18 pS, a half activation potential of more than 10 mV and did not inactivate. This type of channel was the only type found during the first four days in culture, although it was also present up to the 11th day. The second type of channel was dihydropyridine insensitive, had a conductance of 10 pS, a half activation potential less than −15 mV and displayed voltage dependent inactivation. This second type of channel was found in cells for more than four days in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01561138
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  • 2
    Electronic Resource
    Electronic Resource
    Physical characterization of the pore forming cytolysine from Gardnerella vaginalis (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 105 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The cytolytic toxin (CTox) produced by Gardnerella vaginalis is able to form voltage-dependent cationic channels when incorporated in lipid membranes (Moran et al, 1991) FEBS Lett. 283, 317–320). Osmotic protection experiments show that toxin incorporated in human erythrocytes forms pores between 18 Å and 28 Å in diameter. A hypothesis of pore formation as a primary event to produce cytolysis is proposed. The CTox activity increases when cells are depolarized by increasing the extracellular K+ concentration, probably reflecting the voltage dependent character of CTox formed channels. The cytolytic effect of the toxin was prevented by low temperatures and was a function of the extracellular Ca2+ concentration, suggesting a Ca2+ influx as part of the lytic mechanism. Binding of CTox to erythrocytes was dependent on external Ca2+ and was less temperature-dependent. Dose-response analysis suggests cooperativity of the toxin for the lytic activity, although no direct evidence of oligomerization has been found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb05888.x
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  • 3
    Electronic Resource
    Electronic Resource
    Voltage-dependent cationic channels formed by a cytolytic toxin produced by Gardnerella vaginalis
    Amsterdam : Elsevier
    FEBS Letters 283 (1991), S. 317-320 
    Details
    ISSN: 0014-5793
    Keywords: Cytolytic toxin ; Gardnerella vaginalis ; Ionic channel ; Patch clamp
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(91)80617-C
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  • 4
    Electronic Resource
    Electronic Resource
    Properties of the transient potassium currents in cerebellar granule cells (1994)
    Springer
    Experimental brain research 98 (1994), S. 298-304 
    Details
    ISSN: 1432-1106
    Keywords: Potassium channels ; Patch clamp ; Cerebellar granule cells ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Macroscopic potassium currents were studied in cell-attached and inside-out patches from rat cerebellar granule cells. They were related with transient IA type potassium channels. Currents activated rapidly at potentials higher than -40 mV and did not inactivate completely. The magnitude of the current diminished when the membrane patches were excised. No differences in the activation and inactivation properties were found between patches in the integral cells and cell free membrane patches. A biophysical description of the currents is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228417
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  • 5
    Electronic Resource
    Electronic Resource
    Cl− Currents Activated by Extracellular Nucleotides in Human Bronchial Cells (1997)
    Springer
    The journal of membrane biology 156 (1997), S. 297 -305 
    Details
    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
    URL: http://dx.doi.org/10.1007/s002329900209
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  • 6
    Electronic Resource
    Electronic Resource
    Biophysical Characteristics of Swelling-Activated Cl− Channels in Human Tracheal 9HTEo-Cells (1998)
    Springer
    The journal of membrane biology 165 (1998), S. 255-264 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Cl− channels — Patch clamp — Swelling-activated Cl− currents — Single channels — Human tracheal cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The question of whether a single molecule can account for every observed swelling-activated Cl− current deserves to be addressed and biophysical description seems to be an adequate criterion to classify these channels. We studied the biophysical properties of swelling-activated Cl− currents in 9HTEo-cells using whole-cell and outside-out patch clamp recordings. Hypotonic shock activated outwardly rectifying currents that inactivated at potentials higher than 20 mV. The decay phase of the current was well fitted by two exponential functions and both time constants were voltage-dependent. Two voltage-dependent time constants were also necessary to describe reactivation. The midpoint of current inactivation was 54 mV. The voltage dependence of kinetics did not significantly change by modifying the extracellular NaCl concentration while the inactivation midpoint slightly shifted. In conclusion, our results indicate that the voltage-dependent properties of the swelling-activated Cl− currents in 9HTEo- cells are largely independent from the extracellular ionic strength and the extracellular Cl− concentration. Excised patches from cells exposed to hypotonic shock showed single channel currents that inactivated at positive membrane potentials and displayed chord conductance of ∼60 pS at 100 mV and of ∼20 pS at −80 mV. The permeability sequence for the single channel was I− 〉 Br− 〉 Cl− 〉 gluconate and currents were blocked by Reactive blue 2. These properties indicate that intermediate conductance outwardly rectifying channels are responsible for the macroscopic swelling-activated current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900439
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  • 7
    Electronic Resource
    Electronic Resource
    Accumulation of long-lasting inactivation in rat brain K+-channels (1996)
    Springer
    Experimental brain research 110 (1996), S. 401-412 
    Details
    ISSN: 1432-1106
    Keywords: Potassium channel ; Long-lastinginactivation ; Kv1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the phenomenon of cumulative inactivation in the voltage-dependent K+ channels of the Shaker-related subfamily Kv1 cloned from rat brain and expressed in Xenopus oocytes. In Kv1.4, repetitive stimulations at intervals shorter than 20 s produce cumulative inactivation even for brief stimuli that elicit K+ currents which do not show any significant decline during the depolarising pulse. These effects are absent or greatly reduced in the clones Kv1.1, Kv1.3, Kv1.5 and Kv1.6, and in the deletion mutant Kv1.4-Δ-110, characterised by lack of “fast” (N-type) inactivation. We find that the inactivation caused by a single pulse increases after the pulse while the channels deactivate, and subsides with two time constants, indicating the existence of (at least) two inactivated states: IS, with a slow recovery kinetics and IF, with faster kinetics. In the simplest kinetic scheme accounting for our observations, IF is coupled sequentially to the open state O, while IS can be reached at a fast rate both from IF and from a pre-open, activated state, A, that is in fast equilibrium with O. The accumulation of long-lasting inactivation during the repolarisation is favoured by the prolongation of the lifetime of activated states due to the presence of IF. This explains the smaller accumulation effect observed in channels lacking fast inactivation. The physiological implications of these findings suggest how different channels of the Kv1 subfamily can affect differently the firing behaviour of neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229140
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  • 8
    Electronic Resource
    Electronic Resource
    Sodium ionic and gating currents in mammalian cells (1990)
    Springer
    European biophysics journal 18 (1990), S. 25-32 
    Details
    ISSN: 1432-1017
    Keywords: Sodium channel ; Gating currents ; Mammalian cells ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ionic and gating currents from voltage-gated sodium channels were recorded in mouse neuroblastoma cells using the path-clamp technique. Displacement currents were measured from whole-cell recordings. The gating charge displaced during step depolarizations increased with the applied membrane potential and reached saturating levels above 20 mV Prolonged large depolarizations produced partial immobilization of the gating charge, and only about one third of the displaced charge was quickly reversed upon return to negative holding potentials. The activation and inactivation properties of macroscopic sodium currents were characterized by voltage-clamp analysis of large outside-out patches and the single-channel conductance was estimated from nonstationary noise analysis. The general properties of the sodium channels in mouse neuroblastoma cells are very similar to those previously reported for various preparations of invertebrate and vertebrate nerve cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185417
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  • 9
    Electronic Resource
    Electronic Resource
    Inward rectifier potassium channels in plants differ from their animal counterparts in response to voltage and channel modulators (1995)
    Springer
    European biophysics journal 24 (1995), S. 107-115 
    Details
    ISSN: 1432-1017
    Keywords: Potassium channel ; KAT1 ; Voltage dependence ; Cesium block ; pH dependence ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have investigated the electrophysiological basis of potassium inward rectification of the KAT1 gene product from Arabidopsis thaliana expressed in Xenopus oocytes and of functionally related K+ channels in the plasma membrane of guard and root cells from Vicia faba and Zea mays. The whole-cell currents passed by these channels activate, following steps to membrane potentials more negative than −100 mV, with half activation times of tens of milliseconds. This voltage dependence was unaffected by the removal of cytoplasmic magnesium. Consequently, unlike inward rectifier channels of animals, inward rectification of plant potassium channels is an intrinsic property of the channel protein itself. We also found that the activation kinetics of KAT1 were modulated by external pH. Decreasing the pH in the range 8.5 to 4.5 hastened activation and shifted the steady state activation curve by 19 mV per pH unit. This indicates that the activity of these K+ channels and the activity of the plasma membrane H+-ATPase may not only be coordinated by membrane potential but also by pH. The instantaneous current-voltage relationship, on the other hand, did not depend on pH, indicating that H+ do not block the channel. In addition to sensitivity towards protons, the channels showed a high affinity voltage dependent block in the presence of cesium, but were less sensitive to barium. Recordings from membrane patches of KAT1 injected oocytes in symmetric, Mg2+-free, 100 mM-K+, solutions allowed measurements of the current-voltage relation of single open KAT1 channels with a unitary conductance of 5 pS. We conclude that the inward rectification of the currents mediated by the KAT1 gene product, or the related endogenous channels of plant cells, results from voltage-modulated structural changes within the channel proteins. The voltage-sensing or the gating-structures appear to interact with a titratable acidic residue exposed to the extracellular medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211406
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  • 10
    Electronic Resource
    Electronic Resource
    Interaction between dihydropyridines and phospholipid bilayers: a molecular dynamics simulation (1998)
    Springer
    European biophysics journal 27 (1998), S. 211-218 
    Details
    ISSN: 1432-1017
    Keywords: Key words Molecular dynamics ; Lipid bilayer ; Dihydropyridine ; Membrane ; Molecular modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Interaction of the calcium-channel antagonist dihydropyridines (DHPs), lacidipine and nifedipine, with a phospholipid bilayer was studied using 600 ps molecular dynamic simulations. We have constructed a double layer membrane model composed of 42 dimirystoyl-phosphatidylcholine molecules. The DHP molecules locate at about 7 Å from the centre of the membrane, inducing an asymmetry in the bilayer. While lacidipine did not induce significant local perturbations as judged by the gauche-trans isomerisation rate, nifedipine significantly decreased this rate, probably by producing a local rigidity of the membrane in the vicinity of the DHP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050127
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