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Stefan Galler - One of the best experts on this subject based on the ideXlab platform.
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effect of ph on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
The Journal of Experimental Biology, 2006Co-Authors: Marion Christine Hopflinger, Olena Andruchova, Oleg Andruchov, Herbert Grassberger, Stefan GallerAbstract:Moderate alkalisation is known to terminate the catch state of bivalve mollusc smooth muscles such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. In the present study, we investigated the effect of moderate alkalisation (pH 7.2-7.7 vs control pH 6.7) on the myosin head detachment rate in saponin-skinned fibre bundles of ABRM in order to investigate the possible role of myosin heads in the Force maintenance during catch. The detachment rate of myosin heads was deduced from two types of experiments. (1) In stretch experiments on maximally Ca2+-activated fibre bundles (pCa 4.5), the rate of Force Decay after stepwise stretch was assessed. (2) In ATP step experiments, the rate of Force Decay from high Force rigor (pCa>8) was evaluated. The ATP step was induced by photolysis of caged ATP. We found that moderate alkalisation induces relaxation of skinned fibres in catch, thereby reducing both Force and stiffness, whereas it does not accelerate the rate of myosin head detachment. This acceleration, however, would be expected if catch would be simply due to myosin heads remaining sustainably attached to actin filaments. Thus, the myosin heads may be less involved in catch than generally assumed. Catch may possibly depend on a different kind of myofilament interconnections, which are abolished by moderate alkalisation.
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no effect of twitchin phosphorylation on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
Pflügers Archiv: European Journal of Physiology, 2005Co-Authors: Olena Andruchova, Marion Christine Hopflinger, Oleg Andruchov, Stefan GallerAbstract:Phosphorylation of twitchin is known to abolish the catch state of anterior byssus retractor muscle (ABRM) of the bivalve mollusc Mytilus edulis. To investigate the role of myosin head involvement in Force maintenance during catch, the effect of twitchin phosphorylation on myosin head detachment was studied in saponin-skinned fibre bundles of ABRM. The detachment rate of myosin heads was deduced from two types of experiments: (1) Force Decay after stepwise stretch of maximally Ca2+-activated fibre bundles (pCa 4.5) and (2) Force Decay from high-Force rigor, the former induced by a stepwise increase in ATP concentration elicited by photolysis of caged ATP (pCa<8). The rate of detachment was not affected by thiophosphorylation or phosphorylation of twitchin by 0.12 mM cAMP in the presence of the phosphatase inhibitor cyclosporine A (1 μM). Conversely, measurements of the rate of stretch-induced delayed Force increase (stretch activation) and of the Force increase following an ATP step in low-Force rigor (pCa 4.5) suggest that the rate of myosin head attachment decreases after twitchin phosphorylation. We conclude that catch is not due to myosin heads remaining attached to actin filaments, but depends on myofilament interconnections that break down when twitchin is phosphorylated.
Marion Christine Hopflinger - One of the best experts on this subject based on the ideXlab platform.
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effect of ph on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
The Journal of Experimental Biology, 2006Co-Authors: Marion Christine Hopflinger, Olena Andruchova, Oleg Andruchov, Herbert Grassberger, Stefan GallerAbstract:Moderate alkalisation is known to terminate the catch state of bivalve mollusc smooth muscles such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. In the present study, we investigated the effect of moderate alkalisation (pH 7.2-7.7 vs control pH 6.7) on the myosin head detachment rate in saponin-skinned fibre bundles of ABRM in order to investigate the possible role of myosin heads in the Force maintenance during catch. The detachment rate of myosin heads was deduced from two types of experiments. (1) In stretch experiments on maximally Ca2+-activated fibre bundles (pCa 4.5), the rate of Force Decay after stepwise stretch was assessed. (2) In ATP step experiments, the rate of Force Decay from high Force rigor (pCa>8) was evaluated. The ATP step was induced by photolysis of caged ATP. We found that moderate alkalisation induces relaxation of skinned fibres in catch, thereby reducing both Force and stiffness, whereas it does not accelerate the rate of myosin head detachment. This acceleration, however, would be expected if catch would be simply due to myosin heads remaining sustainably attached to actin filaments. Thus, the myosin heads may be less involved in catch than generally assumed. Catch may possibly depend on a different kind of myofilament interconnections, which are abolished by moderate alkalisation.
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no effect of twitchin phosphorylation on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
Pflügers Archiv: European Journal of Physiology, 2005Co-Authors: Olena Andruchova, Marion Christine Hopflinger, Oleg Andruchov, Stefan GallerAbstract:Phosphorylation of twitchin is known to abolish the catch state of anterior byssus retractor muscle (ABRM) of the bivalve mollusc Mytilus edulis. To investigate the role of myosin head involvement in Force maintenance during catch, the effect of twitchin phosphorylation on myosin head detachment was studied in saponin-skinned fibre bundles of ABRM. The detachment rate of myosin heads was deduced from two types of experiments: (1) Force Decay after stepwise stretch of maximally Ca2+-activated fibre bundles (pCa 4.5) and (2) Force Decay from high-Force rigor, the former induced by a stepwise increase in ATP concentration elicited by photolysis of caged ATP (pCa<8). The rate of detachment was not affected by thiophosphorylation or phosphorylation of twitchin by 0.12 mM cAMP in the presence of the phosphatase inhibitor cyclosporine A (1 μM). Conversely, measurements of the rate of stretch-induced delayed Force increase (stretch activation) and of the Force increase following an ATP step in low-Force rigor (pCa 4.5) suggest that the rate of myosin head attachment decreases after twitchin phosphorylation. We conclude that catch is not due to myosin heads remaining attached to actin filaments, but depends on myofilament interconnections that break down when twitchin is phosphorylated.
Olena Andruchova - One of the best experts on this subject based on the ideXlab platform.
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effect of ph on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
The Journal of Experimental Biology, 2006Co-Authors: Marion Christine Hopflinger, Olena Andruchova, Oleg Andruchov, Herbert Grassberger, Stefan GallerAbstract:Moderate alkalisation is known to terminate the catch state of bivalve mollusc smooth muscles such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. In the present study, we investigated the effect of moderate alkalisation (pH 7.2-7.7 vs control pH 6.7) on the myosin head detachment rate in saponin-skinned fibre bundles of ABRM in order to investigate the possible role of myosin heads in the Force maintenance during catch. The detachment rate of myosin heads was deduced from two types of experiments. (1) In stretch experiments on maximally Ca2+-activated fibre bundles (pCa 4.5), the rate of Force Decay after stepwise stretch was assessed. (2) In ATP step experiments, the rate of Force Decay from high Force rigor (pCa>8) was evaluated. The ATP step was induced by photolysis of caged ATP. We found that moderate alkalisation induces relaxation of skinned fibres in catch, thereby reducing both Force and stiffness, whereas it does not accelerate the rate of myosin head detachment. This acceleration, however, would be expected if catch would be simply due to myosin heads remaining sustainably attached to actin filaments. Thus, the myosin heads may be less involved in catch than generally assumed. Catch may possibly depend on a different kind of myofilament interconnections, which are abolished by moderate alkalisation.
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no effect of twitchin phosphorylation on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
Pflügers Archiv: European Journal of Physiology, 2005Co-Authors: Olena Andruchova, Marion Christine Hopflinger, Oleg Andruchov, Stefan GallerAbstract:Phosphorylation of twitchin is known to abolish the catch state of anterior byssus retractor muscle (ABRM) of the bivalve mollusc Mytilus edulis. To investigate the role of myosin head involvement in Force maintenance during catch, the effect of twitchin phosphorylation on myosin head detachment was studied in saponin-skinned fibre bundles of ABRM. The detachment rate of myosin heads was deduced from two types of experiments: (1) Force Decay after stepwise stretch of maximally Ca2+-activated fibre bundles (pCa 4.5) and (2) Force Decay from high-Force rigor, the former induced by a stepwise increase in ATP concentration elicited by photolysis of caged ATP (pCa<8). The rate of detachment was not affected by thiophosphorylation or phosphorylation of twitchin by 0.12 mM cAMP in the presence of the phosphatase inhibitor cyclosporine A (1 μM). Conversely, measurements of the rate of stretch-induced delayed Force increase (stretch activation) and of the Force increase following an ATP step in low-Force rigor (pCa 4.5) suggest that the rate of myosin head attachment decreases after twitchin phosphorylation. We conclude that catch is not due to myosin heads remaining attached to actin filaments, but depends on myofilament interconnections that break down when twitchin is phosphorylated.
Oleg Andruchov - One of the best experts on this subject based on the ideXlab platform.
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effect of ph on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
The Journal of Experimental Biology, 2006Co-Authors: Marion Christine Hopflinger, Olena Andruchova, Oleg Andruchov, Herbert Grassberger, Stefan GallerAbstract:Moderate alkalisation is known to terminate the catch state of bivalve mollusc smooth muscles such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis L. In the present study, we investigated the effect of moderate alkalisation (pH 7.2-7.7 vs control pH 6.7) on the myosin head detachment rate in saponin-skinned fibre bundles of ABRM in order to investigate the possible role of myosin heads in the Force maintenance during catch. The detachment rate of myosin heads was deduced from two types of experiments. (1) In stretch experiments on maximally Ca2+-activated fibre bundles (pCa 4.5), the rate of Force Decay after stepwise stretch was assessed. (2) In ATP step experiments, the rate of Force Decay from high Force rigor (pCa>8) was evaluated. The ATP step was induced by photolysis of caged ATP. We found that moderate alkalisation induces relaxation of skinned fibres in catch, thereby reducing both Force and stiffness, whereas it does not accelerate the rate of myosin head detachment. This acceleration, however, would be expected if catch would be simply due to myosin heads remaining sustainably attached to actin filaments. Thus, the myosin heads may be less involved in catch than generally assumed. Catch may possibly depend on a different kind of myofilament interconnections, which are abolished by moderate alkalisation.
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no effect of twitchin phosphorylation on the rate of myosin head detachment in molluscan catch muscle are myosin heads involved in the catch state
Pflügers Archiv: European Journal of Physiology, 2005Co-Authors: Olena Andruchova, Marion Christine Hopflinger, Oleg Andruchov, Stefan GallerAbstract:Phosphorylation of twitchin is known to abolish the catch state of anterior byssus retractor muscle (ABRM) of the bivalve mollusc Mytilus edulis. To investigate the role of myosin head involvement in Force maintenance during catch, the effect of twitchin phosphorylation on myosin head detachment was studied in saponin-skinned fibre bundles of ABRM. The detachment rate of myosin heads was deduced from two types of experiments: (1) Force Decay after stepwise stretch of maximally Ca2+-activated fibre bundles (pCa 4.5) and (2) Force Decay from high-Force rigor, the former induced by a stepwise increase in ATP concentration elicited by photolysis of caged ATP (pCa<8). The rate of detachment was not affected by thiophosphorylation or phosphorylation of twitchin by 0.12 mM cAMP in the presence of the phosphatase inhibitor cyclosporine A (1 μM). Conversely, measurements of the rate of stretch-induced delayed Force increase (stretch activation) and of the Force increase following an ATP step in low-Force rigor (pCa 4.5) suggest that the rate of myosin head attachment decreases after twitchin phosphorylation. We conclude that catch is not due to myosin heads remaining attached to actin filaments, but depends on myofilament interconnections that break down when twitchin is phosphorylated.
Corrado Poggesi - One of the best experts on this subject based on the ideXlab platform.
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The relation between sarcomere energetics and the rate of isometric tension relaxation in healthy and diseased cardiac muscle
Journal of Muscle Research and Cell Motility, 2019Co-Authors: Giulia Vitale, Chiara Tesi, Nicoletta Piroddi, Cecilia Ferrantini, Beatrice Scellini, Josè Manuel Pioner, Barbara Colombini, Corrado PoggesiAbstract:Full muscle relaxation happens when [Ca^2+] falls below the threshold for Force activation. Several experimental models, from whole muscle organs and intact muscle down to skinned fibers, have been used to explore the cascade of kinetic events leading to mechanical relaxation. The use of single myofibrils together with fast solution switching techniques, has provided new information about the role of cross-bridge (CB) dissociation in the time course of isometric Force Decay. Myofibril’s relaxation is biphasic starting with a slow seemingly linear phase, with a rate constant, slow k _REL, followed by a fast mono-exponential phase. Sarcomeres remain isometric during the slow Force Decay that reflects CB detachment under isometric conditions while the final fast relaxation phase begins with a sudden give of few sarcomeres and is then dominated by intersarcomere dynamics. Based on a simple two-state model of the CB cycle, myofibril slow k _REL represents the apparent forward rate with which CBs leave Force generating states ( g _app) under isometric conditions and correlates with the energy cost of tension generation (ATPase/tension ratio); in short slow k _REL ~ g _app ~ tension cost. The validation of this relationship is obtained by simultaneously measuring maximal isometric Force and ATP consumption in skinned myocardial strips that provide an unambiguous determination of the relation between contractile and energetic properties of the sarcomere. Thus, combining kinetic experiments in isolated myofibrils and mechanical and energetic measurements in multicellular cardiac strips, we are able to provide direct evidence for a positive linear correlation between myofibril isometric relaxation kinetics (slow k _REL) and the energy cost of Force production both measured in preparations from the same cardiac sample. This correlation remains true among different types of muscles with different ATPase activities and also when CB kinetics are altered by cardiomyopathy-related mutations. Sarcomeric mutations associated to hypertrophic cardiomyopathy (HCM), a primary cardiac disorder caused by mutations in genes encoding sarcomeric proteins, have been often found to accelerate CB turnover rate and increase the energy cost of myocardial contraction. Here we review data showing that faster CB detachment results in a proportional increase in the energetic cost of tension generation in heart samples from both HCM patients and mouse models of the disease.
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relaxation kinetics following sudden ca2 reduction in single myofibrils from skeletal muscle
Biophysical Journal, 2002Co-Authors: Chiara Tesi, Nicoletta Piroddi, F Colomo, Corrado PoggesiAbstract:To investigate the roles of cross-bridge dissociation and cross-bridge-induced thin filament activation in the time course of muscle relaxation, we initiated Force relaxation in single myofibrils from skeletal muscles by rapidly (approximately 10 ms) switching from high to low [Ca(2+)] solutions. Full Force Decay from maximal activation occurs in two phases: a slow one followed by a rapid one. The latter is initiated by sarcomere "give" and dominated by inter-sarcomere dynamics (see the companion paper, Stehle, R., M. Krueger, and G. Pfitzer. 2002. Biophys. J. 83:2152-2161), while the former occurs under nearly isometric conditions and is sensitive to mechanical perturbations. Decreasing the Ca(2+)-activated Force preceding the start of relaxation does not increase the rate of the slow isometric phase, suggesting that cycling Force-generating cross-bridges do not significantly sustain activation during relaxation. This conclusion is strengthened by the finding that the rate of isometric relaxation from maximum Force to any given Ca(2+)-activated Force level is similar to that of Ca(2+)-activation from rest to that given Force. It is likely, therefore, that the slow rate of Force Decay in full relaxation simply reflects the rate at which cross-bridges leave Force-generating states. Because increasing [P(i)] accelerates relaxation while increasing [MgADP] slows relaxation, both forward and backward transitions of cross-bridges from Force-generating to non-Force-generating states contribute to muscle relaxation.