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See detailOverexpression of the sarcolemmal calcium pump in the myocardium of transgenic rats.
Hammes, A.; Oberdorf-Maass, S.; Rother, T. et al

in Circulation Research (1998), 83(9), 877-88

The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme controlling Ca2+ homeostasis in nonexcitable cells. However, its function in the myocardium is unclear because ... [more ▼]

The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme controlling Ca2+ homeostasis in nonexcitable cells. However, its function in the myocardium is unclear because of the presence of the Na+/Ca2+ exchanger. We approached the question of the physiological function of the calcium pump using a transgenic "gain of function" model. Transgenic rat lines carrying the human PMCA 4 cDNA under control of the ventricle-specific myosin light chain-2 promoter were established, and expression in the myocardium was ascertained at the mRNA, protein, and functional levels. In vivo hemodynamic measurements in adult homozygous animals showed no differences in baseline and increased cardiac performance recruited by volume overload compared with controls. No differences between transgenic and control cardiomyocytes were found in patch clamp voltage dependence, activation/inactivation behavior of the L-type Ca2+ current, or fast [Ca2+]i transients (assessed by the Fura-2 method). To test whether the PMCA might be involved in processes other than beat-to-beat regulation of contraction/relaxation, we compared growth processes of neonatal transgenic and control cardiomyocytes. A 1.6- and 2.3-fold higher synthesis rate of total protein was seen in cells from transgenic animals compared with controls on incubation with 2% FCS for 24 hours and 36 hours, respectively. An effect of similar magnitude was observed using 20 micromol/L phenylephrine. A 1.4-fold- and 2.0-fold-higher protein synthesis peak was seen in PMCA-overexpressing cardiomyocytes after stimulation with isoproterenol for 12 hours and 24 hours, respectively. Because pivotal parts of the alpha- and beta-adrenergic signal transduction pathways recently have been localized to caveolae, we tested the hypothesis that the PMCA might alter the amplitude of alpha- and beta-adrenergic growth signals by virtue of its localization in caveolae. Biochemical as well as immunocytochemical studies suggested that the PMCA in large part was colocalized with caveolin 3 in caveolae of cardiomyocytes. These results indicate that the sarcolemmal Ca2+-pump has little relevance for beat-to-beat regulation of contraction/relaxation in adult animals but likely plays a role in regulating myocardial growth, possibly through modulation of caveolar signal transduction. [less ▲]

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See detailExpression of the plasma membrane Ca2+-ATPase in myogenic cells.
Hammes, A.; Oberdorf-Maass, S.; Jenatschke, S. et al

in The Journal of biological chemistry (1996), 271(48), 30816-22

To study the physiological function of the plasma membrane calmodulin-dependent calcium ATPase (PMCA) in intact cells, L6 myogenic cell lines stably overexpressing the human PMCA isoform 4CI (= human PMCA ... [more ▼]

To study the physiological function of the plasma membrane calmodulin-dependent calcium ATPase (PMCA) in intact cells, L6 myogenic cell lines stably overexpressing the human PMCA isoform 4CI (= human PMCA isoform 4b) were generated. Several independent L6 clones and controls stably transfected with the empty expression vector were analyzed in detail. The resting cytosolic calcium level in hPMCA4CI-overexpressing muscle cells (measured by the Fura-2 method) was significantly reduced by 20-30% compared with controls. This was shown in a cytosolic window of 1322 single cells (p < 0.01). Furthermore, the differentiation process of these cells was remarkably accelerated compared with control myoblasts and parental nontransfected L6 cells as assessed by multinucleated myotube formation and creatine phosphokinase activity elevation. After 4 and 6 days of differentiation, PMCA-overexpressing L6 cells from four independent clones displayed a 3- and 4-fold higher creatine phosphokinase activity compared with controls (n = 5, p < 0.02). These results may extend the concept of the function of the PMCA from simple prevention of calcium overload to an active involvement in intracellular calcium regulation with potentially important consequences for cellular functions. [less ▲]

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See detailImmediate-early gene induction by repetitive mechanical but not electrical activity in adult rat cardiomyocytes.
Kubisch, C.; Wollnik, B.; Maass, A. et al

in FEBS letters (1993), 335(1), 37-40

Mechanical factors are thought to play an important role in the induction of myocardial hypertrophy. Yet, it is not known whether active contraction induces genes that probably represent initial steps in ... [more ▼]

Mechanical factors are thought to play an important role in the induction of myocardial hypertrophy. Yet, it is not known whether active contraction induces genes that probably represent initial steps in the hypertrophic response in the adult myocardium--and if so, whether the mechanical or the electrical component of the twitch governs this response. We therefore investigated whether electrical stimulation of contraction was able to induce the immediate-early genes (IEGs) egr-1 and c-fos in adult rat cardiomyocytes. Cyclical contraction led to an increase in egr-1 and c-fos mRNA levels within 30 min. Full inhibition of contraction during electrostimulation by the Ca(2+)-desensitizer 2,3-butanedione monoxime (BDM) totally blocked this IEG-response without altering membrane potential. These data suggest that in adult myocardium, the mechanical rather than the electrical activity is responsible for the IEG-response during active twitch. [less ▲]

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See detailOptimization of Strained Ga1-xInxAs/InP Heterostructures Towards High Channel Conductivity for HEMT Application
Meyer, R.; Hardtdegen, H.; Leuther, A. et al

in Proceedings of the 5th International Conference on InP and Related Compounds, Paris, France (1993)

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See detailA Novel InGaAs Schottky-2DEG Diode
Marso, Michel UL; Kordoš, P.; Fox, A. et al

in Proceedings of the 5th International Conference on InP and Related Compounds, Paris, France (1993)

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See detailSchottky Contacts on n-In0.53Ga0.47As with Enhanced Barriers by Counter-Doped Interfacial Layers,
Kordoš, P.; Marso, Michel UL; Meyer, R. et al

in IEEE Transactions on Electron Devices (1992), 39(1992), 1970-1972

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See detailSchottky Barrier Height Enhancement on n-In0.53Ga0.47As
Kordoš, P.; Marso, Michel UL; Meyer, R. et al

in Journal of Applied Physics (1992), 72(1992), 2347-2355

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See detailEnhanced Schottky Barriers on n-In.53Ga.47As Using pInGaAs, GaAs, InP and InGaP Surface layers
Kordoš, P.; Marso, Michel UL; Meyer, R. et al

in Proceedings of the 4th International Conference on InP and Related Compounds, Newport, Rhode Island, USA (1992)

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See detailQuasi-Schottky Diodes on (n)In.53Ga.47As With Barrier Heights of 0.6eV
Marso, Michel UL; Kordoš, P.; Meyer, R. et al

in Proceedings of the the MRS Fall Meeting, Symposium E, Boston, MA, USA (1991)

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See detailBarrier Height Enhancement of n-In0.53Ga0.47As Schottky Diodes Grown by MOCVD Technique
Kordoš, P.; Marso, Michel UL; Meyer, R. et al

in Electronics Letters (1991), 27(1991), 1759-1760

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