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001-es BibID:	BIBFORM049412
Első szerző:	Almássy János (élettanász, biológus, angol-magyar szakfordító)
Cím:	Miocardial infarct induced changes of skeletal type SR calcium channel (RyR1) / J. Almássy, G. Vassort, I. Jóna
Dátum:	2006
Megjegyzések:	In heart failure (HF) skeletal muscle weakness and fatigue develop that could be explained by decreased Ca2+ content of the sarcoplasmic reticulum (SR) concomitant reduction of calcium transients' amplitude, indicating the impaired balance of calcium transport mechanisms. The aim of the present study was to identify putative functional RyR1 changes contributing to the reduced Ca2+ content of the SR.Single RyR1 Ca2+-release channels from rats with HF were reconstituted into planar lipid bilayer and gating behaviour of incorporated channels was studied under voltage-clamp conditions. 1/3 of these channels showed 40% higher conductance compared to RyRs from control rats and the voltage dependency of channel conductance altered, showing still ohmic but polarity dependent conductance characterized by 785 ? 28 pS for positive and 575 ? 31 pS for negative polarity. Altered Ca2+-dependency of channel activity was also observed on RyRs from HFafflicted rats, such as enhanced calcium activation and reduced calcium inhibition.
Tárgyszavak:	Természettudományok Biológiai tudományok idézhető absztrakt calcium release
Megjelenés:	Journal of Muscle Research and Cell Motility. - 27 (2006), p. 521. -
További szerzők:	Vassort, Guy Jóna István (1948-) (élettanász, fizikus)
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001-es BibID:	BIBFORM004134
Első szerző:	Almássy János (élettanász, biológus, angol-magyar szakfordító)
Cím:	Effects of K-201 on the calcium pump and calcium release channel of rat skeletal muscle / Janos Almassy, Monika Sztretye, Balazs Lukacs, Beatrix Dienes, Laszlo Szabo, Peter Szentesi, Guy Vassort, Laszlo Csernoch, Istvan Jona
Dátum:	2008
ISSN:	0031-6768
Megjegyzések:	The benzothiazepine derivative K-201 has been suggested as a potential therapeutic agent due to its antiarrhythmogenic action. To understand how the drug alters calcium release from the sarcoplasmic reticulum (SR), we investigated its effects on the SR calcium channel and calcium pump by single channel electrophysiology, whole-cell confocal microscopy, and ATPase activity measurements on control and post-myocardial infarcted (PMI) rat skeletal muscle. In bilayers, K-201 induced two subconductance states corresponding to approximately 24% (S(1)) and approximately 13% (S(2)) of the maximum conductance. Dependence of event frequency and of time spent in S(1) and S(2) on the drug concentration was biphasic both in control and in PMI rats, with a maximum at 50 microM. At this concentration, the channel spends 26 +/- 4% and 24 +/- 4%, respectively, of the total time in these subconductance states at positive potentials, while no subconductances are observed at negative potentials. K-201 altered the frequency of elementary calcium release events: spark frequency decreased from 0.039 +/- 0.001 to 0.023 +/- 0.001 s(-1) sarcomere(-1), while the frequency of embers increased from 0.011 +/- 0.001 to 0.023 +/- 0.001 s(-1) sarcomere(-1). Embers with different amplitude levels were observed after the addition of the drug. K-201 inhibited the Ca(2+) ATPase characterized by IC(50,contr) = 119 +/- 21 muM and n (Hill,contr) = 1.84 +/- 0.48 for control and IC(50,PMI) = 122 +/- 18 microM and n (Hill,PMI) = 1.97 +/- 0.24 for PMI animals. These results suggest that although K-201 would increase the appearance of subconductance states, the overall calcium release is reduced by the drug. In addition, the effect of K-201 is identical on calcium release channels from control and PMI rats.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Pflügers Archiv. - 457 : 1 (2008), p. 171-183. -
További szerzők:	Sztretye Mónika (1981-) (élettanász, elektrofiziológus) Lukács Balázs (1978-) (élettanász) Dienes Beatrix (1972-) (élettanász, molekuláris biológus) Szabó László (Románia) Szentesi Péter (1967-) (élettanász) Vassort, Guy Csernoch László (1961-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Internet cím:	Intézményi repozitóriumban (DEA) tárolt változat DOI elektronikus változat
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001-es BibID:	BIBFORM001082
Első szerző:	Szigeti Gyula (élettanász, elektrofiziológus)
Cím:	Alterations in the calcium homeostasis of skeletal muscle from postmyocardial infarcted rats / Gyula Péter Szigeti, János Almássy, Mónika Sztretye, Beatrix Dienes, László Szabó, Péter Szentesi, Guy Vassort, Sándor Sárközi, László Csernoch, István Jóna
Dátum:	2007
ISSN:	0031-6768
Megjegyzések:	In chronic heart failure, skeletal muscles develop a weakness that is not associated to an impaired circulatory function but rather to alterations in the skeletal muscle fibers themselves. To understand these changes, the steps in excitation-contraction coupling of rats that underwent a left anterior coronary artery occlusion were studied. About 24 weeks after the myocardial infarction, neither the total amount nor the voltage dependence of intramembrane charge were altered. In contrast, calcium release from the sarcoplasmic reticulum was considerably suppressed, and its voltage dependence shifted toward more positive voltages. Elementary calcium-release events showed altered morphology as the relative proportion of embers increased. Calcium sparks were smaller in amplitude and had larger time-to-peak values. Isolated ryanodine receptors (RyR) displayed an unusual rectification with increased single-channel conductance at positive (cis vs trans) voltages. In addition, the bell-shaped calcium dependence of channel activity was broader, with a slight shift of activation to lower and a larger shift in inactivation to higher calcium concentrations. These data indicate that the number of channels that open during a calcium-release event is decreased and that RyR function is altered; thus, calcium-release is suppressed after a myocardial infarction. These observations give an explanation for the impaired skeletal muscle function in these animals.
Tárgyszavak:	Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Pflügers Archiv. - 455 : 3 (2007), p. 541-553. -
További szerzők:	Almássy János (1981-) (élettanász, biológus, angol-magyar szakfordító) Sztretye Mónika (1981-) (élettanász, elektrofiziológus) Dienes Beatrix (1972-) (élettanász, molekuláris biológus) Szabó László (orvos) Szentesi Péter (1967-) (élettanász) Vassort, Guy Sárközi Sándor (1966-) (élettanász) Csernoch László (1961-) (élettanász) Jóna István (1948-) (élettanász, fizikus)
Internet cím:	Intézményi repozitóriumban (DEA) tárolt változat DOI
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