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001-es BibID:	BIBFORM040100
035-os BibID:	PMID:3266232
Első szerző:	Csernoch László (élettanász)
Cím:	Differential effects of tetracaine on charge movements and Ca2+ signals in frog skeletal muscle / L. Csernoch, C. L.-H. Huang, G. Szűcs, L. Kovács
Dátum:	1988
ISSN:	0022-1295
Megjegyzések:	The effects of tetracaine on charge movements and on antipyrylazo III signals monitoring intracellular delta [Ca2+] were compared in cut frog semitendinosus muscle fibers in a single vaseline gap-voltage clamp. Low tetracaine concentrations (25-40 microM) markedly reduced delta [Ca2+] signals and shifted the rheobase. However, they neither influenced charge movement nor that peak delta [Ca2+] value associated with the contractile threshold. Higher tetracaine concentrations (100-200 microM) partly inhibited charge movements in cut fibers. They separated a steeply voltage-sensitive charge, some of whose features resembled 'q gamma' reported in intact fibers, and whose movement preceded delta [Ca2+] signals at threshold. These findings: (a) directly confirm an earlier suggestion that tetracaine acts on steps in excitation-contraction coupling rather than myofilament activation; (b) show that tetracaine at low concentrations can directly interfere with sarcoplasmic reticular calcium release without modifying charge movement; (c) show that the tetracaine-sensitive charge, first found in intact fibers, also exists in cut fibers; and (d) make it unlikely that tetracaine-sensitive charge transfer is a consequence of Ca2+ release as suggested on earlier occasions.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban egyetemen (Magyarországon) készült közlemény
Megjelenés:	Journal of General Physiology. - 92 : 5 (1988), p. 601-612. -
További szerzők:	Huang, C. L.-H. Szűcs Géza (1948-) (élettanász) Kovács László (1939-) (élettanász)
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001-es BibID:	BIBFORM040083
Első szerző:	Szentesi Péter (élettanász)
Cím:	Effects of Dantrolene on Steps of Excitation-Contraction Coupling in Mammalian Skeletal Muscle Fibers / Péter Szentesi, Claude Collet, Sándor Sárközi, Csaba Szegedi, István Jona, Vincent Jacquemond, László Kovács, László Csernoch
Dátum:	2001
ISSN:	0022-1295
Megjegyzések:	The effects of the muscle relaxant dantrolene on steps of excitation-contraction coupling were studied on fast twitch muscles of rodents. To identify the site of action of the drug, single fibers for voltage-clamp measurements, heavy SR vesicles for calcium efflux studies and solubilized SR calcium release channels/RYRs for lipid bilayer studies were isolated. Using the double Vaseline-gap or the silicone-clamp technique, dantrolene was found to suppress the depolarization-induced elevation in intracellular calcium concentration ([Ca2+]i) by inhibiting the release of calcium from the SR. The suppression of [Ca2+]i was dose-dependent, with no effect at or below 1 microM and a 53 +/- 8% (mean +/- SEM, n = 9, cut fibers) attenuation at 0 mV with 25 microM of extracellularly applied dantrolene. The drug was not found to be more effective if injected than if applied extracellularly. Calculating the SR calcium release revealed an equal suppression of the steady (53 +/- 8%) and of the early peak component (46 +/- 6%). The drug did not interfere with the activation of the voltage sensor in as much as the voltage dependence of both intramembrane charge movements and the L-type calcium currents (I(Ca)) were left, essentially, unaltered. However, the inactivation of I(Ca) was slowed fourfold, and the conductance was reduced from 200 +/- 16 to 143 +/- 8 SF(-1) (n = 10). Dantrolene was found to inhibit thymol-stimulated calcium efflux from heavy SR vesicles by 44 +/- 10% (n = 3) at 12 microM. On the other hand, dantrolene failed to affect the isolated RYR incorporated into lipid bilayers. The channel displayed a constant open probability for as long as 30-50 min after the application of the drug. These data locate the binding site for dantrolene to be on the SR membrane, but be distinct from the purified RYR itself.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Journal Of General Physiology. - 118 : 4 (2001), p. 355-376. -
További szerzők:	Collet, Claude Sárközi Sándor (1966-) (élettanász) Szegedi Csaba Jóna István (1948-) (élettanász, fizikus) Jacquemond, Vincent Kovács László (1939-) (élettanász) Csernoch László (1961-) (élettanász)
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001-es BibID:	BIBFORM040108
035-os BibID:	PMID:1940853
Első szerző:	Szűcs Géza (élettanász)
Cím:	Kinetic properties of intramembrane charge movement under depolarized conditions in frog skeletal muscle fibers / G. Szücs, Z. Papp, L. Csernoch, L. Kovács
Dátum:	1991
ISSN:	0022-1295
Megjegyzések:	Intramembrane charge movement was measured on skeletal muscle fibers of the frog in a single Vaseline-gap voltage clamp. Charge movements determined both under polarized conditions (holding potential, VH = -100 mV; Qmax = 30.4 +/- 4.7 nC/micro(F), V = -44.4 mV, k = 14.1 mV; charge 1) and in depolarized states (VH = 0 mV; Qmax = 50.0 +/- 6.7 nC/micro(F), V = -109.1 mV, k = 26.6 mV; charge 2) had properties as reported earlier. Linear capacitance (LC) of the polarized fibers was increased by 8.8 +/- 4.0% compared with that of the depolarized fibers. Using control pulses measured under depolarized conditions to calculate charge 1, a minor change in the voltage dependence (to V = -44.6 mV and k = 14.5 mV) and a small increase in the maximal charge (to Qmax = 31.4 +/- 5.5 nC/micro(F] were observed. While in most cases charge 1 transients seemed to decay with a single exponential time course, charge 2 currents showed a characteristic biexponential behavior at membrane potentials between -90 and -180 mV. The voltage dependence of the rate constant of the slower component was fitted with a simple constant field diffusion model (alpha m = 28.7 s-1, V = -124.0 mV, and k = 15.6 mV). The midpoint voltage (V) was similar to that obtained from the Q-V fit of charge 2, while the steepness factor (k) resembled that of charge 1. This slow component could also be isolated using a stepped OFF protocol; that is, by hyperpolarizing the membrane to -190 mV for 200 ms and then coming back to 0 mV in two steps. The faster component was identified as an ionic current insensitive to 20 mM Co2+ but blocked by large hyperpolarizing pulses. These findings are consistent with the model implying that charge 1 and the slower component of charge 2 interconvert when the holding potential is changed. They also explain the difference previously found when comparing the steepness factors of the voltage dependence of charge 1 and charge 2.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban egyetemen (Magyarországon) készült közlemény
Megjelenés:	Journal of General Physiology. - 98 : 2 (1991), p. 365-378. -
További szerzők:	Papp Zoltán (1965-) (kardiológus, élettanász) Csernoch László (1961-) (élettanász) Kovács László (1939-) (élettanász)
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001-es BibID:	BIBFORM032966
035-os BibID:	PMID:1865176 WOS:A1991FM31500003
Első szerző:	Szűcs Géza (élettanász)
Cím:	Contraction threshold and the "hump" component of charge movement in frog skeletal muscle / G. Szűcs, L. Csernoch, J. Magyar, L. Kovács
Dátum:	1991
Megjegyzések:	The delayed component of intramembranous charge movement (hump, I gamma) was studied around the contraction threshold in cut skeletal muscle fibers of the frog (Rana esculenta) in a single Vaseline-gap voltage clamp. Charges (Q) were computed as 50-ms integrals of the ON (QON) and OFF (QOFF) of the asymmetric currents after subtracting a baseline. The hump appeared in parallel with an excess of QON over QOFF by approximately 2.5 nC/mu F. Caffeine (0.75 mM) not only shifted the contraction threshold but moved both the hump and the difference between the ON and OFF charges to more negative membrane potentials. When using 10-mV voltage steps on top of different prepulse levels, the delayed component, if present, was more readily observable. The voltage dependences of the ON and OFF charges measured with these pulses were clearly different: QON had a maximum at or slightly above the contraction threshold, while QOFF increased monotonically in the voltage range examined. Caffeine (0.75 mM) shifted this voltage dependence of QON toward more negative membrane potentials, while that of QOFF was hardly influenced. These results show that the delayed component of intramembranous charge movement either is much slower during the OFF than during the ON, or returns to the OFF position during the pulse. Tetracaine (25 microM) had similar effects on the charge movement currents, shifting the voltage dependence on the ON charge in parallel with the contraction threshold, but to more positive membrane potentials, and leaving QOFF essentially unchanged. The direct difference between the charge movement measured in the presence of caffeine and in control solution was either biphasic or resembled the component isolated by tetracaine, suggesting a common site of caffeine and tetracaine action. The results can be understood if the released Ca plays a direct role in the generation of the hump, as proposed in the first paper of this series.
Tárgyszavak:	Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban egyetemen (Magyarországon) készült közlemény
Megjelenés:	The Journal of General Physiology 97 : 5 (1991), p. 897-911. -
További szerzők:	Csernoch László (1961-) (élettanász) Magyar János (1961-) (élettanász) Kovács László (1939-) (élettanász)
Internet cím:	Szerző által megadott URL Intézményi repozitóriumban (DEA) tárolt változat DOI
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