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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for nuclear control of amino acid transport in cultured cells (1975)
    [s.l.] : Nature Publishing Group
    Nature 255 (1975), S. 73-74 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Growth in low amino acid BME resulted in an increase in Kmax and a decrease in the apparent Km value for influx. In a typical experiment, Fmax increased from 53.51 to 70.01 pmol cm"2 s'1 and Km decreased from 2.39 to 1.24 mM. Treatment with cytochalasin B alone did not affect glycine influx and did ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/255073a0
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  • 2
    Electronic Resource
    Electronic Resource
    Is digitalis inotropy associated with enhanced slow inward calcium current? (1978)
    [s.l.] : Nature Publishing Group
    Nature 273 (1978), S. 389-392 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We studied the effects of strophanthidin on the electrical and mechanical activity of cardiac Purkinje fibres from calf hearts. The aglycone strophanthidin was preferred to cardiac glycosides such as ouabain because its effects are more readily reversible. Purkinje fibres were used because recent ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/273389a0
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  • 3
    Electronic Resource
    Electronic Resource
    CALCIUM IONS AND MEMBRANE CURRENT CHANGES INDUCED BY DIGITALIS IN CARDIAC PURKINJE FIBERS (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 307 (1978), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1978.tb41978.x
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  • 4
    Electronic Resource
    Electronic Resource
    Cardiac electrophysiology: Past, present and future Part I (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 1039-1039 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01956034
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  • 5
    Electronic Resource
    Electronic Resource
    Cell-to-cell coupling studied in isolated ventricular cell pairs (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 1091-1094 
    Details
    ISSN: 1420-9071
    Keywords: Myocytes ; electrical coupling ; cell-to-cell coupling ; nexus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cell pairs isolated from adult rat and guinea pig ventricles were used to study the electrical properties of the nexal membrane. Each cell of a pair was connected to a voltage-clamp system so as to enable whole-cell, tight-seal recording. The current-voltage relationship of the nexal membrane was found to be linear, revealing a resistance rn of 2–4 MΩ. rn was insensitive to the sarcolemmal membrane potential (range:−90 to +30 mV), and exerted no time-dependent gating behavior (range: 0.1 to 10 s). Lowering pHi yielded a small increase in rn. Vigorous elevations in [Ca2+]i gave rise to an increase in rn which was associated with a cell shortening. Uncoupling caused by aliphatic alcohols or halothane did not produce cell shortening. Cell pairs were also used to study action potential transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01956045
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  • 6
    Electronic Resource
    Electronic Resource
    Electrophysiological properties of gap junction channels in hepatocytes isolated from connexin32-deficient and wild-type mice (1999)
    Springer
    Pflügers Archiv 437 (1999), S. 846-856 
    Details
    ISSN: 1432-2013
    Keywords: Key words Connexin26 ; Connexin32 ; Electrophysiology ; Gap junction ; Gap junction channel ; Hepatocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Hepatocytes were isolated from wild-type and connexin32-deficient (Cx32-deficient) mice. Pairs of cells were chosen to study the electrical properties of gap junction channels using the dual voltage-clamp method. The total gap junction currents revealed that Cx32-deficient hepatocytes express one type of connexin (Cx26) and wild-type hepatocytes express two types of connexins (Cx26 and Cx32). The unitary gap junction currents suggest that Cx32-deficient cells have homotypic channels (Cx26–Cx26) while wild-type cells form homotypic (Cx26–Cx26, Cx32–Cx32) and heterotypic channels (Cx26–Cx32). Homotypic channels exhibited a main conductance and a residual conductance, both virtually insensitive to gap junction voltage (V j) (Cx32–Cx32: γj,main=31 pS, γj,residual=9 pS; Cx26–Cx26: γj,main=102 pS, γj,residual=17 pS). Residual states were regularly seen in Cx32–Cx32 channels, but rarely in Cx26–Cx26 channels. Heterotypic channels showed a main conductance and a residual conductance. The former was sensitive to V j (average γj,main=52 pS). The electrophysiological data suggest that Cx32 hemichannels are more abundant than Cx26 hemichannels in prenatal (ratio 4:1) and adult wild-type hepatocytes (ratio 23:1) and that the total number of gap junction channels is larger in prenatal cells than in adult cells. The diversity of the relationship g j,ss/g j,inst=f(V j) (g j,ss: gap junction conductance at steady state; g j,inst: instantaneous gap junction conductance; V j: transjunctional voltage) seen in wild-type cells suggests that the ratio Cx26/Cx32 hemichannels is variable among hepatocytes. A comparison of total and unitary conductances implies that Cx26 hemichannels are down-regulated in Cx32-deficient cells and that docking between Cx26 and Cx32 hemichannels occurs randomly. While the gap junction currents are compatible with homotypic and heterotypic channels, the presence of heteromeric channels cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050854
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  • 7
    Electronic Resource
    Electronic Resource
    Voltage gating of Cx43 gap junction channels involves fast and slow current transitions (2000)
    Springer
    Pflügers Archiv 439 (2000), S. 248-250 
    Details
    ISSN: 1432-2013
    Keywords: Connexin43 Gap junction channel RIN cells Single-channel conductance Voltage gating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. RIN cells transfected with mouse cDNA coding for connexin43 (Cx43) were used to further examine the electrical properties of single gap junction channels. The experiments involved measuring intercellular currents from cell pairs using dual whole-cell recording with the patch-clamp method. We found that the single-channel currents exhibit two types of transitions and several conductance states. Besides fast transitions between the main open state and the residual state, the channels underwent slow transitions between an open state (i.e. main open state or residual state) and a closed state. The fast transitions lasted less than 2 ms, the slow ones ranged from 3.5 to 145 ms. The incidence of slow transitions increased with increasing transjunctional voltage. These observations are consistent with the notion that Cx43 gap junction channels possess more than one mechanism of voltage gating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004249900182
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  • 8
    Electronic Resource
    Electronic Resource
    Connexin43 gap junctions exhibit asymmetrical gating properties (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 775-785 
    Details
    ISSN: 1432-2013
    Keywords: Key words Rat ; Pancreas ; RIN cells ; Gap junctions ; Connexin43 ; Biophysical properties ; Voltage gating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A communication-deficient cell line (RIN cells, derived from a rat islet tumour), stably transfected with cDNA coding for rat connexin43 (Cx43), was chosen to further assess the mechanism of voltage gating of Cx43 gap junction channels. The experiments were carried out on preformed cell pairs using a dual whole-cell, voltage-clamp method. The junctional current, I j, revealed a time- and voltage-dependent inactivation at transjunctional voltages V j 〉 ± 40mV. When an asymmetrical pulse protocol was used (in cell 1 the holding potential was maintained, in cell 2 it was altered to establish a variable V j), the channels exhibited an asymmetrical gating behaviour: V j,0 = −73.7 mV and 65.1 mV for negative and positive V j, respectively (V j at which I j is half-maximally inactivated); g j(min) = 0.34 and 0.29 (normalized minimal conductance); τ = 350 ms and 80 ms at V j = 100 mV (time constant of I j inactivation). Hence, these parameters were more sensitive to positive V j values. When a symmetrical pulse protocol was used (the holding potentials in cell 1 and cell 2 were altered simultaneously in steps of equal amplitude but of opposite polarity), the V j -dependent asymmetries were absent: V j,0 = −60.5 and 59.5; g j (min) = 0.27 and 0.29; τ = 64 ms and 47 ms at 100 mV. Putative explanations for these obervations are discussed. A possibility is that the number of channels alters with the polarity of V j.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050065
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  • 9
    Electronic Resource
    Electronic Resource
    Long-chain n-alkanols and arachidonic acid interfere with the V m-sensitive gating mechanism of gap junction channels (1997)
    Springer
    Pflügers Archiv 435 (1997), S. 310-319 
    Details
    ISSN: 1432-2013
    Keywords: Key words Insect gap junctions ; Lipophilic agents ; Chemical uncoupling ; Slow current transitions ; Vm-sensitive gating ; n-Alkanols ; Arachidonic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Experiments were carried out on preformed cell pairs and induced cell pairs of an insect cell line (mosquito Aedes albopictus, clone C6/36). The coupling conductance, g j, was determined with the dual voltage-clamp method. Exposure of preformed cell pairs to lipophilic agents, such as long-chain n-alkanols (n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol) or arachidonic acid, provoked a decrease in g j. Hyperpolarization of both cells led to a recovery of g j. Systematic studies revealed that this phenomenon is caused by a shift of the sigmoidal relationship g j(ss) = f(V m) towards more negative values of V m (where g j(ss) = conductance at steady-state; V m = membrane potential). The shift was dose dependent, it developed with time and was reversible. The longer the hydrocarbon chain of n-alkanols, the lower was the concentration required to produce a given shift. Besides shifting the function g j(ss) = f(V m), arachidonic acid decreased the maximal conductance, g j(max). Single-channel records gained from induced cell pairs revealed that the lipophilic agents interfere with the V m-sensitive slow channel gating mechanism. Application provoked slow current transitions (transition time: 5–40 ms) between an open state of the channel (i.e. main state or residual state) and the closed state; subsequently, fast channel transitions (transition time: 〈 2 ms) involving the main state and the residual state ceased completely. Hyperpolarization of V m or washout of the lipophilic agents gave rise to the inverse sequence of events. The single-channel conductances γ j(main state) and γ j(residual state) were not affected by n-heptanol. We conclude that long-chain n-alkanols and arachidonic acid interact with the V m-sensitive gating mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050517
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  • 10
    Electronic Resource
    Electronic Resource
    Cell pairs isolated from adult guinea pig and rat hearts: effects of [Ca2+]i on nexal membrane resistance (1987)
    Springer
    Pflügers Archiv 409 (1987), S. 394-402 
    Details
    ISSN: 1432-2013
    Keywords: Cardiac cell pairs ; Intercellular coupling ; Electrical uncoupling ; Intracellular calcium (or pCai)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cell pairs isolated from adult rat and guinea pig ventricles were used to study the resistance of the nexal membrane,r n. Each cell of a cell pair was connected to a voltage-clamp circuit to obtain simultaneous whole-cell, tight-seal recordings. With this technique,r n was determined under experimental conditions aimed at primarily modifying [Ca2+]i. Moderate changes in [Ca2+]i (produced by trains of depolarizing voltage-clamp pulses activating the slow inward current, or alterations in [Ca2+]o from 0.5 to 10 mM), resulted in no change inr n for normally coupled cell pairs (r n=5 MΩ), but small and reversible changes in slightly uncoupled preparations (r n≥50 MΩ). Large increases inr n developed with substantial elevations in [Ca2+]i (secondary to [Na+]o-withdrawal, exporsure to strophanthidin in conjunction withi si, or Ca2+-dialysis). Increases inr n brought about via elevation in [Ca2+]i always were accompanied by cell shortening consistent with a sustained contracture. The current-voltage relationship of the nexal membrane was ohmic regardless of whetherr n was low (control) or elevated (after increasing [Ca2+]i).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583793
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