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Dalton Valentim Vassallo - One of the best experts on this subject based on the ideXlab platform.
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Chronic ouabain treatment enhances cardiac Myosin ATPase activity in rats.
Clinical and experimental pharmacology & physiology, 2008Co-Authors: Alessandra Simão Padilha, Cleci Menezes Moreira, Eduardo F. Meira, Fabiana Dayse Magalhães Siman, Ivanita Stefanon, Dalton Valentim VassalloAbstract:SUMMARY 1 Chronic ouabain administration increases blood pressure and produces a positive inotropic effect. However, the temporal changes capable of affecting both arterial and ventricular pressures and Myosin ATPase activity during the induced hypertension have not been determined. 2 The aim of the present study was to investigate the time-course of the induction of hypertension to define when changes occur in Wistar rats treated with 25 mg/kg per day, s.c., ouabain for 3, 7, 15 or 30 days. 3 In anaesthetized rats, diastolic blood pressure increased after 7 days treatment with ouabain and after 15 and 30 days treatment, increases were observed in systolic blood pressure, left ventricular systolic pressure and Myosin ATPase activity. After 15 days treatment, heart rate (HR) also increased, but after 30 days treatment HR returned to control levels. However, only after 30 days treatment did the left ventricular positive and negative first derivatives of intraventricular pressure (dP/dtmax and dP/dtmin, respectively) increase. Increased arterial and left ventricular systolic pressures and Myosin ATPase activity observed after 15 days treatment maintained similar levels as those after 30 days treatment. 4 The results suggest that changes in arterial and left ventricular pressures, HR and Myosin ATPase activity induced by chronic ouabain treatment are time dependent, increasing after 15 days treatment. After 30 days treatment, the increase in systolic and diastolic arterial and ventricular pressures remained stable, as did inotropism. Normalization of HR after 30 days treatment suggests that during the period from Day 16 to Day 30 ouabain-induced hypertension is dependent, at least in part, on increased sympathetic activity.
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Lead reduces tension development and the Myosin ATPase activity of the rat right ventricular myocardium.
Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas, 2008Co-Authors: Dalton Valentim Vassallo, Cleci Menezes Moreira, E C Lebarch, Giulia Alessandra Wiggers, Ivanita StefanonAbstract:Lead (Pb2+) poisoning causes hypertension, but little is known regarding its acute effects on cardiac contractility. To evaluate these effects, force was measured in right ventricular strips that were contracting isometrically in 45 male Wistar rats (250-300 g) before and after the addition of increasing concentrations of lead acetate (3, 7, 10, 30, 70, 100, and 300 microM) to the bath. Changes in rate of stimulation (0.1-1.5 Hz), relative potentiation after pauses of 15, 30, and 60 s, effect of Ca2+ concentration (0.62, 1.25, and 2.5 mM), and the effect of isoproterenol (20 ng/mL) were determined before and after the addition of 100 microM Pb2+. Effects on contractile proteins were evaluated after caffeine treatment using tetanic stimulation (10 Hz) and measuring the activity of the Myosin ATPase. Pb2+ produced concentration-dependent force reduction, significant at concentrations greater than 30 microM. The force developed in response to increasing rates of stimulation became smaller at 0.5 and 0.8 Hz. Relative potentiation increased after 100 microM Pb2+ treatment. Extracellular Ca2+ increment and isoproterenol administration increased force development but after 100 microM Pb2+ treatment the force was significantly reduced suggesting an effect of the metal on the sarcolemmal Ca2+ influx. Concentration of 100 microM Pb2+ also reduced the peak and plateau force of tetanic contractions and reduced the activity of the Myosin ATPase. Results showed that acute Pb2+ administration, although not affecting the sarcoplasmic reticulum activity, produces a concentration-dependent negative inotropic effect and reduces Myosin ATPase activity. Results suggest that acute lead administration reduced myocardial contractility by reducing sarcolemmal calcium influx and the Myosin ATPase activity. These results also suggest that lead exposure is hazardous and has toxicological consequences affecting cardiac muscle.
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Effects of mercury on Myosin ATPase in the ventricular myocardium of the rat.
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2003Co-Authors: Cleci Menezes Moreira, Edilamar Menezes De Oliveira, Carla Denise Bonan, João José Freitas Sarkis, Dalton Valentim VassalloAbstract:Abstract Mercury reduces twitch and tetanic force development in isolated rat papillary muscles, and a putative toxic effect on the contractile machinery has been suggested. Based on that, the actions of HgCl 2 on the Myosin ATPase activity of the left ventricular myocardium were investigated. Samples for assay of Myosin ATPase activity were obtained from rats’ left ventricles. Increasing concentrations of HgCl 2 reduced dose-dependently the activity of the Myosin ATPase. This reduction was observed even at very small concentrations, 50 nM HgCl 2 . This effect was dependent on the presence of SH groups in the Myosin molecule since DTT and glutathione protected the Myosin ATPase against toxic effects of mercury; full activity being restored by using 500 nM DTT or 500 nM glutathione. Results also suggested that the metal acts as an uncompetitive inhibitor with a K i of 200 nM HgCl 2 . Our results suggest that mercury reduces the activity of the Myosin ATPase by an uncompetitive mechanism at a very low dose that does not depress force. DTT and glutathione are effective for protection against the actions of mercury suggesting that SH groups might be the sites of action of the metal on the Myosin molecule.
Cleci Menezes Moreira - One of the best experts on this subject based on the ideXlab platform.
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Chronic ouabain treatment enhances cardiac Myosin ATPase activity in rats.
Clinical and experimental pharmacology & physiology, 2008Co-Authors: Alessandra Simão Padilha, Cleci Menezes Moreira, Eduardo F. Meira, Fabiana Dayse Magalhães Siman, Ivanita Stefanon, Dalton Valentim VassalloAbstract:SUMMARY 1 Chronic ouabain administration increases blood pressure and produces a positive inotropic effect. However, the temporal changes capable of affecting both arterial and ventricular pressures and Myosin ATPase activity during the induced hypertension have not been determined. 2 The aim of the present study was to investigate the time-course of the induction of hypertension to define when changes occur in Wistar rats treated with 25 mg/kg per day, s.c., ouabain for 3, 7, 15 or 30 days. 3 In anaesthetized rats, diastolic blood pressure increased after 7 days treatment with ouabain and after 15 and 30 days treatment, increases were observed in systolic blood pressure, left ventricular systolic pressure and Myosin ATPase activity. After 15 days treatment, heart rate (HR) also increased, but after 30 days treatment HR returned to control levels. However, only after 30 days treatment did the left ventricular positive and negative first derivatives of intraventricular pressure (dP/dtmax and dP/dtmin, respectively) increase. Increased arterial and left ventricular systolic pressures and Myosin ATPase activity observed after 15 days treatment maintained similar levels as those after 30 days treatment. 4 The results suggest that changes in arterial and left ventricular pressures, HR and Myosin ATPase activity induced by chronic ouabain treatment are time dependent, increasing after 15 days treatment. After 30 days treatment, the increase in systolic and diastolic arterial and ventricular pressures remained stable, as did inotropism. Normalization of HR after 30 days treatment suggests that during the period from Day 16 to Day 30 ouabain-induced hypertension is dependent, at least in part, on increased sympathetic activity.
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Lead reduces tension development and the Myosin ATPase activity of the rat right ventricular myocardium.
Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas, 2008Co-Authors: Dalton Valentim Vassallo, Cleci Menezes Moreira, E C Lebarch, Giulia Alessandra Wiggers, Ivanita StefanonAbstract:Lead (Pb2+) poisoning causes hypertension, but little is known regarding its acute effects on cardiac contractility. To evaluate these effects, force was measured in right ventricular strips that were contracting isometrically in 45 male Wistar rats (250-300 g) before and after the addition of increasing concentrations of lead acetate (3, 7, 10, 30, 70, 100, and 300 microM) to the bath. Changes in rate of stimulation (0.1-1.5 Hz), relative potentiation after pauses of 15, 30, and 60 s, effect of Ca2+ concentration (0.62, 1.25, and 2.5 mM), and the effect of isoproterenol (20 ng/mL) were determined before and after the addition of 100 microM Pb2+. Effects on contractile proteins were evaluated after caffeine treatment using tetanic stimulation (10 Hz) and measuring the activity of the Myosin ATPase. Pb2+ produced concentration-dependent force reduction, significant at concentrations greater than 30 microM. The force developed in response to increasing rates of stimulation became smaller at 0.5 and 0.8 Hz. Relative potentiation increased after 100 microM Pb2+ treatment. Extracellular Ca2+ increment and isoproterenol administration increased force development but after 100 microM Pb2+ treatment the force was significantly reduced suggesting an effect of the metal on the sarcolemmal Ca2+ influx. Concentration of 100 microM Pb2+ also reduced the peak and plateau force of tetanic contractions and reduced the activity of the Myosin ATPase. Results showed that acute Pb2+ administration, although not affecting the sarcoplasmic reticulum activity, produces a concentration-dependent negative inotropic effect and reduces Myosin ATPase activity. Results suggest that acute lead administration reduced myocardial contractility by reducing sarcolemmal calcium influx and the Myosin ATPase activity. These results also suggest that lead exposure is hazardous and has toxicological consequences affecting cardiac muscle.
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Effects of mercury on Myosin ATPase in the ventricular myocardium of the rat.
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2003Co-Authors: Cleci Menezes Moreira, Edilamar Menezes De Oliveira, Carla Denise Bonan, João José Freitas Sarkis, Dalton Valentim VassalloAbstract:Abstract Mercury reduces twitch and tetanic force development in isolated rat papillary muscles, and a putative toxic effect on the contractile machinery has been suggested. Based on that, the actions of HgCl 2 on the Myosin ATPase activity of the left ventricular myocardium were investigated. Samples for assay of Myosin ATPase activity were obtained from rats’ left ventricles. Increasing concentrations of HgCl 2 reduced dose-dependently the activity of the Myosin ATPase. This reduction was observed even at very small concentrations, 50 nM HgCl 2 . This effect was dependent on the presence of SH groups in the Myosin molecule since DTT and glutathione protected the Myosin ATPase against toxic effects of mercury; full activity being restored by using 500 nM DTT or 500 nM glutathione. Results also suggested that the metal acts as an uncompetitive inhibitor with a K i of 200 nM HgCl 2 . Our results suggest that mercury reduces the activity of the Myosin ATPase by an uncompetitive mechanism at a very low dose that does not depress force. DTT and glutathione are effective for protection against the actions of mercury suggesting that SH groups might be the sites of action of the metal on the Myosin molecule.
Ladora V. Thompson - One of the best experts on this subject based on the ideXlab platform.
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Myofibrillar Myosin ATPase activity in hindlimb muscles from young and aged rats
Mechanisms of ageing and development, 2004Co-Authors: Dawn A. Lowe, Aimee D. Husom, Deborah A. Ferrington, Ladora V. ThompsonAbstract:We tested the hypothesis that Ca2+-activated Myosin ATPase activity is lower in muscles of aged rats relative to muscles of young rats, independent of changes in Myosin isoform expression. Myofibrils were prepared from permeabilized fibers of soleus, plantaris, and semimembranosus muscles of young (8–12 months) and aged (32–38 months) F344 × BN rats and assayed for resting Myosin ATPase, Ca2+-activated Myosin ATPase, and Myosin heavy chain (MHC) and Myosin light chain (MLC) isoform compositions. Resting Myosin ATPases were not affected by age in any muscle (P ≥ 0.42). Ca2+-activated Myosin ATPases of soleus and plantaris myofibrils were not affected by age (P ≥ 0.31) but were 16% lower in semimembranosus myofibrils from aged rats (0.448 ± 0.019 μmol Pi/min/mg) compared to young rats (0.533 ± 0.031 μmol Pi/min/mg; P = 0.03). Correspondingly, maximal unloaded shortening velocity of single semimembranosus fibers from aged rats was slow (4.6 ± 0.2 fiber lengths/s) compared with fibers from young rats (5.8 ± 0.3 fiber lengths/s; P < 0.01). No age-related changes in MHC or regulatory MLC isoforms were detected in any muscle (P ≥ 0.08) but changes in the essential MLC occurred in plantaris and semimembranosus muscles. The data indicate that Ca2+-activated Myosin ATPase activity is reduced with age in semimembranosus muscle, independent of age-related changes in MHC isoform expression, and is one mechanism contributing to age-related slowing of contraction in that muscle.
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Force generation, but not Myosin ATPase activity, declines with age in rat muscle fibers
American journal of physiology. Cell physiology, 2002Co-Authors: Dawn A. Lowe, David D. Thomas, Ladora V. ThompsonAbstract:We tested the hypothesis that age-associated decline in muscle function is related to a change in Myosin ATPase activity. Single, glycerinated semimembranosus fibers from young (8–12 mo) and aged (...
Hans Gesser - One of the best experts on this subject based on the ideXlab platform.
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Dependence of Myosin-ATPase on structure bound creatine kinase in cardiac myfibrils from rainbow trout and freshwater turtle
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2008Co-Authors: L. Haagensen, Dorthe Høj Jensen, Hans GesserAbstract:The influence of myofibrillar creatine kinase on the Myosin-ATPase activity was examined in cardiac ventricular myofibrils isolated from rainbow trout (Oncorhynchus mykiss) and freshwater turtle (Trachemys scripta). The ATPase rate was assessed by recording the rephosphorylation of ADP by the pyruvate kinase reaction alone or together with the amount of creatine formed, when myofibrillar bound creatine kinase was activated with phosphocreatine. The steady-state concentration of ADP in the solution was varied through the activity of pyruvate kinase added to the solution. For rainbow trout myofibrils at a high pyruvate kinase activity, creatine kinase competed for ADP but did not influence the total ATPase activity. When the ADP concentration was elevated within the physiological range by lowering the pyruvate kinase activity, creatine kinase competed efficiently and increased the ATPase activity twice or more for both trout and turtle. As examined for trout myofibrils, the ATPase activity was reduced about four times by inhibiting the activity of myofibril-bound creatine kinase with iodoacetamide and this reduction was only partially counteracted, when the creatine kinase activity was restored by adding creatine kinase to the solution. Hence, the results suggest that myofibril-bound creatine kinase is needed to fully activate the Myosin-ATPase activity in hearts from ectothermic vertebrates despite their low energy turn-over relative to endothermic species.
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CA2+ ACTIVATED Myosin-ATPase IN CARDIAC MYOFIBRILS OF RAINBOW TROUT, FRESHWATER TURTLE, AND RAT
The Journal of experimental zoology, 1997Co-Authors: Peter Degn, Hans GesserAbstract:The Ca(2+)-activated Myosin-ATPase and its dependence on hypoxia were assessed in freshwater turtle, rainbow trout, and in some cases rat. At 20 degrees C and pH 7.3, the maximal ATPase activity was (mean +/- SEM): turtle 0.040 +/- 0.003, trout 0.090 +/- 0.005, and rat 0.12 +/- 0.004 mmol*min-1*g-1 myofibrillar dry weight. The turnover number was about three times lower for turtle than for trout. Trout is typically active at lower temperatures than turtle, and its Myosin-ATPase activity was about three times lower at 10 degrees than at 20 degrees C. Addition of 12 mM phosphocreatine showed that the Myosin-ATPase activity covered by myofibrillar creatine kinase was 22 +/- 2% for turtle, 14 +/- 2% for trout, and 69 +/- 5% for rat. At pH 6.8 relative to 7.3, the maximal M-ATPase activity was the same, whereas the Ca(2+)-sensitivity decreased, and more so for trout than for turtle. This difference disappeared, when trout myocardium was examined at 10 degrees C. P(i) (15 mM) affected neither maximal activity nor Ca(2+)-sensitivity. ADP, however, reduced maximal Myosin-ATPase activity, and more so in trout than in turtle. In conclusion, the "slow"-type Myosin, the low sensitivity of acidification and ADP, and the high creatine kinase/Myosin-ATPase ratio in turtle relative to trout accord with the well-known ability of turtle myocardium to work during hypoxia. However, the difference in living temperature between turtle and trout obscures the situation (e.g. inclusion of rat data suggests that the creatine kinase/Myosin-ATPase ratio is related to temperature.
Kazuhiro Kohama - One of the best experts on this subject based on the ideXlab platform.
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Myosin light chain kinase stimulates smooth muscle Myosin ATPase activity by binding to the Myosin heads without phosphorylating the Myosin light chain.
Biochemical and biophysical research communications, 2003Co-Authors: Ying Gao, Kazufumi Kawano, Shinji Yoshiyama, Hozumi Kawamichi, Xiaoming Wang, Akio Nakamura, Kazuhiro KohamaAbstract:Abstract Myosin light chain kinase (MLCK) is a multifunctional regulatory protein of smooth muscle contraction [IUBMB Life 51 (2001) 337, for review]. The well-established mode for its regulation is to phosphorylate the 20 kDa Myosin light chain (MLC 20) to activate Myosin ATPase activity. MLCK exhibits Myosin-binding activity in addition to this kinase activity. The Myosin-binding activity also stimulates Myosin ATPase activity without phosphorylating MLC 20 [Proc. Natl. Acad. Sci. USA 96 (1999) 6666]. We engineered an MLCK fragment containing the Myosin-binding domain but devoid of a catalytic domain to explore how Myosin is stimulated by this non-kinase pathway. The recombinant fragment thus obtained stimulated Myosin ATPase activity by V max =5.53±0.63-fold with K m =4.22±0.58 μM ( n =4). Similar stimulation figures were obtained by measuring the ATPase activity of HMM and S1. Binding of the fragment to both HMM and S1 was also verified, indicating that the fragment exerts stimulation through the Myosin heads. Since S1 is in an active form regardless of the phosphorylated state of MLC 20, we conclude that the non-kinase stimulation is independent of the phosphorylating mode for activation of Myosin.
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A highly sensitive method for measurement of Myosin ATPase activity by reversed-phase high-performance liquid chromatography.
Analytical biochemistry, 2001Co-Authors: Koichi Samizo, Akio Nakamura, Ryoki Ishikawa, Kazuhiro KohamaAbstract:Abstract A new method for measurement of Myosin ATPase activity has been developed utilizing reversed-phase high-performance liquid chromatography (HPLC), which detects as low as 0.05 nmol of ADP hydrolyzed from ATP. After termination of the ATPase reaction by addition of perchloric acid, the hydrolysate ADP and substrate ATP were separated by reversed-phase HPLC. The absorbance of ADP was monitored at 259 nm, and the amount of ADP was quantified from its peak area on the chromatogram by use of the NIH Image computer software. Our method showed linearity over a wide range from 0.05 to 10 nmol of ADP per 20 μl with a coefficient of determination ( r 2 ) of 0.99. Myosin ATPase activities determined by the HPLC method were almost identical to those determined by the malachite green method, a widely used spectrophotometric method with range of detection from 1 to 8 nmol of phosphate. Because our method requires only a small volume of reaction solution, it will be a powerful tool for measuring ATPase activity of motor proteins, which are difficult to obtain in large amount.
