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001-es BibID:	BIBFORM040606
Első szerző:	Velden, Jolanda, van der
Cím:	Calcium sensitivity of force in human ventricular cardiomyocytes from donor and failing hearts / van der Velden J., Boontje N. M., Papp Z., Klein L. J., Visser F. C., de Jong J. W., Owen V. J., Burton P. B., Stienen G. J.
Dátum:	2002
ISSN:	0300-8428
Megjegyzések:	In failing human myocardium changes occur, in particular, in isoform composition and phosphorylation level of the troponin T (TnT) and troponin I (TnI) subunits of the actin filament and the myosin light chains (MLC-1 and -2), but it is unclear to what extent they influence cardiac performance. This overview concentrates on the relation between contractile function, contractile protein composition and phosphorylation levels in small biopsies from control (donor) hearts, from biopsies obtained during open heart surgery (NYHA Class I-IV) and from end-stage failing (explanted, NYHA class IV) hearts. Furthermore, attention is paid to the effect of the catalytic subunit of protein kinase A on isometric force development in single Triton-skinned human cardiomyocytes isolated from donor and end-stage failing left ventricular myocardium at different resting sarcomere lengths. A reduction in sarcomere length from 2.2 to 1.8 microm caused reductions in maximum isometric force by approximately 35% both in donor and in failing cardiomyocytes. The midpoints of the calcium sensitivity curves (pCa50) of donor and end-stage failing hearts differed markedly at all sarcomere lengths (mean delta pCa50 = 0.22). Our findings indicate that 1) TnI phosphorylation contributes to the differences in calcium sensitivity between donor and end-stage failing hearts, 2) human ventricular myocardium is heterogeneous with respect of the phosphorylation of TnT, MLC-2 and the isoform distribution of MLC-1 and MLC-2, and 3) the Frank-Starling mechanism is preserved in end-stage failing myocardium.
Tárgyszavak:	Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:	Basic Research In Cardiology. - 97 : Suppl.1 (2002), p. 118-126. -
További szerzők:	Boontje, Nicky M. Papp Zoltán (1965-) (kardiológus, élettanász) Klein, L. J. Visser, F. C. de Jong, J. W. Owen, V. J. Burton, P. B. Stienen, Ger J. M.
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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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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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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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