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1.

001-es BibID:BIBFORM040598
Első szerző:Ebus, J.
Cím:Effects of MgATP on ATP utilization and force under normal and simulated ischaemic conditions in rat cardiac trabeculae / J. Ebus, Z. Papp, R. Zaremba, G. J. Stienen
Dátum:2001
ISSN:0031-6768
Megjegyzések:The dependency of ATP utilization and isometric force on [MgATP] was studied in skinned rat trabeculae under normal (pH 7.0) and simulated ischaemic (pH 6.2, 30 mM added Pi) conditions at 20+/-1 degrees C. At saturating [Ca2+], mean (+/-SEM) ATP utilization at 5 mM MgATP (A0) was 0.48+/-0.03 mM/s and force (F0) was 37+/-2 kN/m2. At 10 microM MgATP under normal conditions ATP utilization decreased gradually to 66+/-3% of A0, and force increased to 169+/-7% of F0. Under ischaemic conditions at 10 microM MgATP, ATP utilization decreased from 30+/-5% to 11+/-2% of A0 whereas force increased eightfold from 12+/-4% to 97+/-7% of F0. The [MgATP] at half-maximal ATP utilization (Km) under ischaemic conditions was 21+/-3 microM. At pH 7.0, Km was estimated to be less than 10 microM. These results show that tension cost decreases markedly with decreasing MgATP. Under ischaemic conditions parallel changes in Ca2+ sensitivity of force and ATP utilization were observed, corresponding to 1.3 pCa units. Reducing [MgATP] from 0.5 to 0.05 mM caused a modest reversal of this change in Ca2+ sensitivity. These changes in Ca2+ sensitivity are consistent with a marked reduction in active force and force-related ATP utilization during ischaemia but are insufficient to explain the ischaemic contracture on the basis of active force development.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Pflugers Archiv-European Journal Of Physiology. - 443 : 1 (2001), p. 102-111. -
További szerzők:Papp Zoltán (1965-) (kardiológus, élettanász) Zaremba, Ruud Stienen, Ger J. M.
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2.

001-es BibID:BIBFORM040576
Első szerző:Stienen, Ger J. M.
Cím:Influence of inorganic phosphate and pH on sarcoplasmic reticular ATPase in skinned muscle fibres of Xenopus laevis / Stienen G. J., Papp Z., Zaremba R.
Dátum:1999
Megjegyzések:1. The influence of 30 mM inorganic phosphate (Pi) and pH (6.2-7.4) on the rate of ATP utilization was determined in mechanically skinned bundles of myofibrils from the iliofibularis muscle of Xenopus laevis at approximately 5 C. 2. BDM (2,3-butanedione monoxime; 10 mM) depressed isometric force production and actomyosin (AM) ATPase activity equally. Therefore sarcoplasmic reticular (SR) ATPase activity could be determined by extrapolation of the total ATPase activity to zero force. 3. The SR ATPase activity without added Pi at pH 7.1 was 42 +/- 2 % of the total ATPase activity. Addition of 30 mM Pi reduced SR ATPase activity slightly, by 9 +/- 5 %, and depressed force by 62 +/- 2 % and AM ATPase activity by 21 +/- 6 %. 4. At pH 6.2, force, SR ATPase activity and AM ATPase activity were reduced by 21 +/- 5, 61 +/- 5 and 10 +/- 4 % of their respective values at pH 7.1. 5. The SR ATPase activity at 30 mM Pi and pH 6.2 was reduced markedly to 20 +/- 6 % of the value under control conditions, suggesting that the maximum rate of Ca2+ uptake during muscle fatigue was strongly depressed. This reduction was larger than expected on the basis of the effects of Pi and pH alone.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Journal of Physiology. - 518 : Pt3 (1999), p. 735-744. -
További szerzők:Papp Zoltán (1965-) (kardiológus, élettanász) Zaremba, Ruud
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3.

001-es BibID:BIBFORM040584
Első szerző:Velden, Jolanda, van der
Cím:The effect of myosin light chain 2 dephosphorylation on Ca2+ -sensitivity of force is enhanced in failing human hearts / van der Velden J., Papp Z., Boontje N. M., Zaremba R., de Jong J. W., Janssen P. M., Hasenfuss G., Stienen G. J.
Dátum:2003
ISSN:0008-6363
Megjegyzések:OBJECTIVE: Phosphorylation of the myosin light chain 2 (MLC-2) isoform expressed as a percentage of total MLC-2 was decreased in failing (21.1+/-2.0%) compared to donor (31.9+/-4.8%) hearts. To assess the functional implications of this change, we compared the effects of MLC-2 dephosphorylation on force development in failing and non-failing (donor) human hearts. METHODS: Cooperative effects in isometric force and rate of force redevelopment (K(tr)) were studied in single Triton-skinned human cardiomyocytes at various [Ca(2+)] before and after protein phosphatase-1 (PP-1) incubation. RESULTS: Maximum force and K(tr) values did not differ between failing and donor hearts, but Ca(2+)-sensitivity of force (pCa(50)) was significantly higher in failing myocardium (Deltap Ca(50)=0.17). K(tr) decreased with decreasing [Ca(2+)], although this decrease was less in failing than in donor hearts. Incubation of the myocytes with PP-1 (0.5 U/ml; 60 min) decreased pCa(50) to a larger extent in failing (0.20 pCa units) than in donor cardiomyocytes (0.10 pCa units). A decrease in absolute K(tr) values was found after PP-1 in failing and donor myocytes, while the shape of the K(tr)-Ca(2+) relationships remained unaltered. CONCLUSIONS: Surprisingly, the contractile response to MLC-2 dephosphorylation is enhanced in failing hearts, despite the reduced level of basal MLC-2 phosphorylation. The enhanced response to MLC-2 dephosphorylation in failing myocytes might result from differences in basal phosphorylation of other thin and thick filament proteins between donor and failing hearts. Regulation of Ca(2+)-sensitivity via MLC-2 phosphorylation may be a potential compensatory mechanism to reverse the detrimental effects of increased Ca(2+)-sensitivity and impaired Ca(2+)-handling on diastolic function in human heart failure.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Cardiovascular Research. - 57 : 2 (2003), p. 505-514. -
További szerzők:Papp Zoltán (1965-) (kardiológus, élettanász) Boontje, Nicky M. Zaremba, Ruud de Jong, J. W. Janssen, P. M. L. Hasenfuß, Gerd Stienen, Ger J. M.
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4.

001-es BibID:BIBFORM040583
Első szerző:Velden, Jolanda, van der
Cím:Myosin light chain composition in non-failing donor and end-stage failing human ventricular myocardium / van der Velden J., Papp Z., Boontje N. M., Zaremba R., de Jong J. W., Janssen P. M. L., Hasenfuss G., Stienen G. J. M.
Dátum:2003
ISSN:0065-2598
Megjegyzések:The increased Ca(2+)-responsiveness in end-stage human heart failure cannot be attributed to contractile protein isoform changes, but rather is the complex resultant of changes in degree of phosphorylation of VLC-2 and TnI. Despite the decreased basal level of VLC-2 phosphorylation the response to VLC-2 dephosphorylation is enhanced in failing myocytes, which might result from differences in endogenous phosphorylation of thin and thick filament proteins between donor and failing hearts. Taken together decreased VLC-2 phosphorylation in end-stage human heart failure might represent a compensatory process leading to an improvement of myocardial contractility by opposing the detrimental effects of increased Ca(2+)-responsiveness of force and impaired Ca(2+)-handling on diastolic function.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Advances in Experimental Medicine and Biology. - 538 (2003), p. 3-15. -
További szerzők:Papp Zoltán (1965-) (kardiológus, élettanász) Boontje, Nicky M. Zaremba, Ruud de Jong, J. W. Janssen, P. M. L. Hasenfuß, Gerd Stienen, Ger J. M.
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5.

001-es BibID:BIBFORM040582
Első szerző:Velden, Jolanda, van der
Cím:Increased Ca2+-sensitivity of the contractile apparatus in end-stage human heart failure results from altered phosphorylation of contractile proteins / van der Velden J., Papp Z., Zaremba R., Boontje N. M., de Jong J. W., Owen V. J., Burton P. B., Goldmann P., Jaquet K., Stienen G. J.
Dátum:2003
ISSN:0008-6363
Megjegyzések:OBJECTIVE: The alterations in contractile proteins underlying enhanced Ca(2+)-sensitivity of the contractile apparatus in end-stage failing human myocardium are still not resolved. In the present study an attempt was made to reveal to what extent protein alterations contribute to the increased Ca(2+)-responsiveness in human heart failure. METHODS: Isometric force and its Ca(2+)-sensitivity were studied in single left ventricular myocytes from non-failing donor (n=6) and end-stage failing (n=10) hearts. To elucidate which protein alterations contribute to the increased Ca(2+)-responsiveness isoform composition and phosphorylation status of contractile proteins were analysed by one- and two-dimensional gel electrophoresis and Western immunoblotting. RESULTS: Maximal tension did not differ between myocytes obtained from donor and failing hearts, while Ca(2+)-sensitivity of the contractile apparatus (pCa(50)) was significantly higher in failing myocardium (deltapCa(50)=0.17). Protein analysis indicated that neither re-expression of atrial light chain 1 and fetal troponin T (TnT) nor degradation of myosin light chains and troponin I (TnI) are responsible for the observed increase in Ca(2+)-responsiveness. An inverse correlation was found between pCa(50) and percentage of phosphorylated myosin light chain 2 (MLC-2), while phosphorylation of MLC-1 and TnT did not differ between donor and failing hearts. Incubation of myocytes with protein kinase A decreased Ca(2+)-sensitivity to a larger extent in failing (deltapCa(50)=0.20) than in donor (deltapCa(50)=0.03) myocytes, abolishing the difference in Ca(2+)-responsiveness. An increased percentage of dephosphorylated TnI was found in failing hearts, which significantly correlated with the enhanced Ca(2+)-responsiveness.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Cardiovascular Research. - 57 : 1 (2003), p. 37-47. -
További szerzők:Papp Zoltán (1965-) (kardiológus, élettanász) Zaremba, Ruud Boontje, Nicky M. de Jong, J. W. Owen, V. J. Burton, P. B. Goldmann, P. Jaquet, Kai Stienen, Ger J. M.
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6.

001-es BibID:BIBFORM015092
Első szerző:Velden, Jolanda, van der
Cím:Functional effects of protein kinase C-mediated myofilament phosphorylation in human myocardium / van der Velden J., Narolska N. A., Lamberts R. R., Boontje N. M., Borbély A., Zaremba R., Bronzwaer J. G. F., Papp Z., Jaquet K., Paulus W. J., Stienen G. J.
Dátum:2006
ISSN:0008-6363
Megjegyzések:In human heart failure beta-adrenergic-mediated protein kinase A (PKA) activity is down-regulated, while protein kinase C (PKC) activity is up-regulated. PKC-mediated myofilament protein phosphorylation might be detrimental for contractile function in cardiomyopathy. This study was designed to reveal the effects of PKC on myofilament function in human myocardium under basal conditions and upon modulation of protein phosphorylation by PKA and phosphatases.METHODS: Isometric force was measured at different [Ca(2+)] in single permeabilized cardiomyocytes from non-failing and failing human left ventricular tissue. Basal phosphorylation of myofilament proteins and the influence of PKC, PKA, and phosphatase treatments were analyzed by one- and two-dimensional gel electrophoresis, Western immunoblotting, and ELISA.RESULTS: Troponin I (TnI) phosphorylation at the PKA sites was decreased in failing compared to non-failing hearts and correlated well with myofilament Ca(2+) sensitivity (pCa(50)). Incubation with the catalytic domain of PKC slightly decreased maximal force under basal conditions, but not following PKA and phosphatase pretreatments. PKC reduced Ca(2+) sensitivity to a larger extent in failing (DeltapCa(50)=0.19+/-0.03) than in non-failing (DeltapCa(50)=0.08+/-0.01) cardiomyocytes. This shift was reduced, though still significant, when PKC was preceded by PKA, while PKA following PKC did not further decrease pCa(50). Protein analysis indicated that PKC phosphorylated PKA sites in human TnI and increased phosphorylation of troponin T, while myosin light chain phosphorylation remained unaltered.CONCLUSION: In human myocardium PKC-mediated myofilament protein phosphorylation only has a minor effect on maximal force development. The PKC-mediated decrease in Ca(2+) sensitivity may serve to improve diastolic function in failing human myocardium in which PKA-mediated TnI phosphorylation is decreased.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Cardiovascular Research. - 69 : 4 (2006), p. 876-887. -
További szerzők:Narolska, Nadiya A. Lamberts, Regis Boontje, Nicky M. Borbély Attila (1978-) (kardiológus) Zaremba, Ruud Bronzwaer, Jean G. F. Papp Zoltán (1965-) (kardiológus, élettanász) Jaquet, Kornelia Paulus, Walter J. Stienen, Ger J. M.
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