Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alterations of cardiac contractility caused by thiamine deficiency were studied on three groups of 2 month old male Wistar rats: B1, fed a thiamine deficient diet, PF pair fed, which received an amount of thiamine free diet determined on the daily consumption of B1 animals, supplemented with appropriate thiamine supply, C ad libitum fed controls. The animals were studied after 35 days of dietary treatment. Force-velocity curves were determined in right ventricle papillary muscles. Shortening velocity was significantly lower in B1 and PF than in C muscles and in B1 than in PF muscles. The ability to develop tension was not altered. Myosin ATPase activity was assayed in preparations of myofibrils and in preparations of purified myosin. Both Ca-Mg activated myofibrillar ATPase activity and Ca-activated myosin ATPase activity were significantly reduced in B1 and PF compared to C myocardium. Furthermore Ca-activated ATPase activity was lower in B1 than in PF myocardium. Myosin isoenzyme distribution was determined by pyrophosphate gel electrophoresis of purified myosin preparations. When compared to C animals both B1 and PF animals showed a myosin electrophoretic pattern shifted towards the slow isoform V3; such a shift was more pronounced in B1 animals. Information concerning excitation-contraction coupling was obtained by determining the steady state and transient force-interval relation and by recording transmembrane action potential. B1 and PF myocardium exhibited, when compared to C, a less sensitivity to a reduction of the interval of stimulation, a faster mechanical restitution, a prolonged action potential duration. Such alterations were generally more pronounced in B1 than in PF myocardium. The results support the view that in the rat cardiac contractility is deeply affected by thiamine deficiency. The alterations of cardiac contractility seem to be caused by adaptive mechanisms rather than by cardiac failure and seem to be attributable for a big part to the reduction of food supply.
J Mol Cell Cardiol 1990 Oct
PMID:Altered contractile properties of rat cardiac muscle during experimental thiamine deficiency and food deprivation. 215 36

The aim of this study was to determine whether variations of isomyosin expression occurred during doxorubicin-induced cardiomyopathy. A suitable experimental model in which pure delayed cardiotoxic effects could be easily studied was adopted. Young adult female Sprague Dawley rats received 9 mg/kg of doxorubicin (DXR) i.v. divided into three subdoses of 3 mg/kg every third day. Control animals received equal volumes of saline. The animals were examined 9 weeks after treatment. At this time the animals treated with DXR showed ECG alterations, reduction of body weight and a marked decrease of both atrial and ventricular mass, but were still fully hemodynamically compensated. Loss of myofibrillar material could be documented by the reduced recovery of myofibril and myosin. The contractile response of papillary muscles isolated from the right ventricle of treated animals was markedly impaired. Ca-Mg-activated and Mg-activated myofibrillar ATPase activity and Ca-activated myosin ATPase activity were determined on ventricular myocardium of control and treated animals. Both myofibrillar and myosin ATPase activities were found to be significantly reduced. Pyrophosphate gel electrophoresis of purified myosin was carried out. The isomyosin pattern of DXR-treated animals showed a pronounced shift towards V3, the percent of alpha heavy chains being 54.6% in treated rats (80.5% in control rats). This isomyosin shift can explain the reduced myofibrillar and myosin ATPase activity found in treated animals.
J Mol Cell Cardiol 1989 Jan
PMID:Reduction of myofibrillar ATPase activity and isomyosin shift in delayed doxorubicin cardiotoxicity. 252 75

The pathogenesis of reduced systolic left ventricular function in dilated cardiomyopathy is yet unclear. To analyze a possible involvement of contractile protein, function and structure of left ventricular myofibrils were examined in hearts of patients with advanced cardiomyopathy undergoing heart transplantation and in normal control hearts (from renal transplant donors). Myosin and actin content of the left ventricular myocardium was slightly reduced in cardiomyopathic hearts. Myofibrillar polypeptide composition was determined using two-dimensional electrophoresis and immunoblotting. No differences in constituting polypeptides were apparent, including Z-line proteins and proteins of the endosarcomeric lattice. M-line-bound creatine kinase was identical in both groups. Further, basal and maximal myofibrillar adenosine triphosphatase (ATPase) activities were unaltered in dilated cardiomyopathy. The structure of purified myosin was identical in both groups by the following criteria: electrophoretic mobility of native myosin, identical pattern of light chains after isoelectric focusing, identical cleavage peptides of myosin's heavy chain, and identical patterns after immunoblotting of heavy chain cleavage peptides using polyclonal antibodies generated against myosin from normal and cardiomyopathic ventricles. Ca2+-activated, K+-EDTA-activated and actin-activated myosin ATPase activities were identical in control and cardiomyopathic hearts. A structural alteration or functional defect of myofibrils does not seem to be primarily involved in the pathogenesis of reduced myocardial contractility in dilated cardiomyopathy.
Clin Cardiol 1989 Nov
PMID:Structure and function of contractile proteins in human dilated cardiomyopathy. 258 58

Calcium-independent regulation of the contractile proteins of cardiac muscle has been studied using hyperpermeable cells from rat ventricles and sections of quickly-frozen rat hearts. These preparations have been used to study maximum Ca-activated force, myosin ATPase activity and the maximum velocity of unloaded shortening. Beta adrenergic activity increases the amount of force and the ATPase activity in accordance with the concentration of the V1 isozyme of myosin. V3 activity is decreased at the same time. In tissues containing only V1, there is no change in maximum velocity in response to beta adrenergic stimulation. These results indicate that beta adrenergic stimulation recruits V1 force generators and probably regulates the transition between a Ca unresponsive and a Ca responsive force generator. This type of regulation provides the cell with the ability to operate along many different force-velocity relations.
Basic Res Cardiol 1987
PMID:Ca-independent regulation of cardiac myosin. 282 83

We measured the interrelationships between ventricular muscle myosin mass, myosin ATPase activity and collagen in cats with varying degrees of hypertrophy from left ventricular (LV) pressure-overload produced by either aortic banding or renal hypertension. In order to compare two models of LV pressure-overload with different time courses of progression, the results were analyzed as a function of LV mass or LV weight/body weight (LV/BW) ratio. Myosin was quantitated by SDS-polyacrylamide gel electrophoresis and hydroxyproline was measured as an index of collagen. Myosin concentration was positively correlated with increasing LV mass in control cats. However, in pressure-overloaded LV, myosin concentration was elevated and nearly constant for LV less than 9.0 g, but decreased in LV greater than 9.0 g. Myosin concentration in pressure-overloaded LV was greatest before a significant increase in LV/BW ratio. Hydroxyproline concentration was inversely related to myosin concentration in both LV pressure-overload models and increased with the severity of hypertrophy. Actomyosin ATPase activity in pressure-overloaded LV, was not significantly different from control over a wide range of LV/BW ratios. However, absolute myosin ATP hydrolysis in pressure-overloaded LV, increased by as much as 40%, relative to control, due primarily to increased myosin. The changing spectrum and interrelationships of myosin and collagen were independent of the mechanism of pressure-overload, but were correlated with the severity of hypertrophy.
J Mol Cell Cardiol 1987 Jan
PMID:Myocardial changes during the progression of left ventricular pressure-overload by renal hypertension or aortic constriction: myosin, myosin ATPase and collagen. 295 26

A non-failing hypertrophy of the left ventricle was produced in the pig heart by supravalvular banding of aorta for 4, 8 and 12 weeks and the myosin and myofibrillar adenosine triphosphatase activities were measured. A significant increase in myosin Ca2+-ATPase activity was seen at 4 weeks of hypertrophy, but at 8 and 12 weeks this activity was significantly decreased compared to sham control. Similar changes were also seen in actin-activated myosin ATPase activities at 4, 8 and 12 weeks of hypertrophy. There were no changes in the K+- and NH4+-EDTA-stimulated ATPAse activities of myosin. Basal ATPase activities of myofibrils were decreased at 4 and 8 weeks of hypertrophy and there was no change in this activity at 12 weeks of hypertrophy. Ca2+ stimulated ATPase activity of myofibrils was significantly increased at 4 weeks, normal at 8 weeks and significantly reduced at 12 weeks of hypertrophy. The changes in ATPase activities were not due to any alterations of proteins by high concentrations of salts during the purification of myosin. The non-hypertrophied right ventricle from the banded animals did not show any change in the basal or Ca2+ stimulated myofibrillar ATPase activities. It is suggested that hypertrophy of the myocardium is accompanied by specific changes in the enzyme activities of the contractile proteins and the biphasic responses may correlate with the functional state of the myocardium subjected to a chronic increase in pressure.
Basic Res Cardiol
PMID:A biphasic change in contractile proteins during the development of cardiac hypertrophy in pigs. 295 33

The energy output of a cardiac contraction can be divided into several phenomenologically measured components, although it must be emphasized that such subdivisions are often thermodynamically misleading. There is an activation term that relates to Ca++ release and retrieval, a work term and a stress or load-dependent heat term. The work and load-dependent energy terms presumably have their origin in the actin-activated myosin ATPase. It can be shown that the enthalpy: load relationship has a similar format across both mammalian and amphibian hearts: the scaling of both the energy and load axes is however altered by changes in contractility. The fact that enthalpy production is so clearly load-dependent indicates that there is a Fenn effect in cardiac muscle, although the discovery that energy output is greatest in an isometric contraction clearly contradicts one of the two central findings of Fenn's skeletal muscle investigations. Cardiac oxygen consumption per beat can be linearly correlated with ventricular systolic pressure--volume area (PVA) which is defined in terms of stroke work and potential energy components. If the basal and activation components are subtracted out cardiac muscle can be shown to operate at a constant PVA efficiency. The existing myothermic and polarographic data can be reconciled with the PVA concept.
Basic Res Cardiol 1987
PMID:Cardiac energetics and the Fenn effect. 295 66

Heterotopic cardiac transplants are vascularly perfused organs that can be used to study the regulation of myocardial protein content. Prior studies have demonstrated that cardiac isografts undergo marked atrophy with a decrease in weight and myosin content. In the present studies we have investigated the changes in size, myosin content and myosin isoenzyme distribution in the heterotopic cardiac allografts. Six days after transplantation allograft hearts were not spontaneously beating and histologically showed evidence of necrosis and cellular infiltration. Total heart weight (816 +/- 16 mg) and protein content (117 +/- 7 mg) were significantly greater in the allografts compared to in situ hearts (471 +/- 11 and 90 +/- 5 mg respectively, (P less than 0.01). In contrast to the increase in weight there was a simultaneous decrease in myosin ATPase (26%), the V1 isoform of the myosin isoenzyme (43%), and myosin content (53%) in the allograft heart. These studies demonstrate that similar to cardiac isografts, allograft hearts undergo a decrease in myosin content and a shift in myosin isoenzymes. In contrast to the marked atrophy of the cardiac isograft, the allograft heart weight is increased most likely due to rejection with cellular infiltration and an increased water content.
J Mol Cell Cardiol 1987 Sep
PMID:Myosin content and myosin isoenzyme distribution in the heterotopic rat heart allograft. 296 35

The change in the isomyosin complement of avian and mammalian hearts was examined during the embryonic period in primary cultures of embryonic myocytes and in the cross-section of the adult ventricular wall. The type of myosin was determined by immunofluorescence using Abs specific for heavy chains of V1 and V3 isomyosins and by cytochemical staining for Ca2+ activated myosin ATPase. Our analysis indicates that the first isomyosin to appear in both chambers of avian heart is of the V3 type (HC beta). With advancing development, however, the atria initiate the expression of HC alpha and repress that of HC beta while the ventricle retains HC beta. In cultured myocytes derived from rat embryos cellular heterogeneity was detected in response to thyroid hormone. The cells are not synchronized in their response. Two populations are discernible with the minor one being thyroid hormone insensitive. Heterogeneity of the cellular populations was also seen in the left ventricle of adult rabbits. Myocytes with a similar isomyosin complement appear clustered with a predominance of V1 in the epicardium. Heterogeneous myocytes are, however, also frequently seen connected by an intercalated disc.
Basic Res Cardiol 1985
PMID:Developmental aspects of cardiac contractile proteins. 299 29

The influence of hyper- and hypothyroidism on atrial and ventricular myosin structure and Ca2+-activated ATPase activity has been analyzed in adult mini-pigs. Whereas no difference could be demonstrated between hypo- and euthyroid ventricular myocardium, Ca2+-activated ATPase activity was significantly higher in the hyperthyroid than in the hypo- or euthyroid state. Using pyrophosphate electrophoresis and isoelectric focusing of subfragment 1 this could be ascribed to an additional ventricular myosin in the hyperthyroid myocardium. Atrial myosin ATPase activity and structure were not influenced by the thyroid state of the animals. These results present evidence that thyreotoxicosis induces an additional isomyosin in the pig ventricular myocardium, albeit to a lesser degree than in the rodent heart. The lacking difference between the hypothyroid and the euthyroid states indicates that a myosin with a lower enzymatic activity than the normal ventricular myosin is not synthesized in the heart of higher mammals.
Basic Res Cardiol
PMID:Influence of the thyroid state on myocardial myosin in the adult pig heart. 315 68


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