Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The fundamental similarity between platelets and muscle, suggested the possiblity of a shared defect in idiopathic scoliosis, a genetic disease with lateral deformity of the spine in which there is an elevation of calicum concentration in muscles and platelets. A variety of platelet tests revealed the following abnormalities: (1) Electron microscopic x-ray analysis and x-ray fluorescence spectrometry showed a 2- to 3-fold increase in calcium and phosphorus in whole cells and in individual dense bodies. (2) Electron microscopy morphometry revealed an increase in electron-opaque bodies in air-dried cells; granules and microtubules were unchanged. There were more large cells and membranous complexes. (3) Aggregations with epinephrine and ADP were depressed in some patients. (4) Proteins (total and contractile) and myosin. ATPase activity in centrifuged fractions of platelets were decreased in the cytosol and increased in the fraction containing membranes and granules. The correlated findings suggest that platelets in idiopathic scoliosis have a mild calcium transport defect related to membrane and/or contractile protein metabolism. This investigation also shows that platelets may be used to advantage in diagnosis and research of muscle diseases.
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PMID:Platelet pathology in patients with idiopathic scoliosis: Ultrastructural morphometry, agrregations, x-ray spectrometry, and biochemical analysis. 689 14

In vertebrate striated muscle, troponin-tropomyosin is responsible, in part, not only for transducing the effect of calcium on contractile protein activation, but also for inhibiting actin and myosin interaction when calcium is absent. The regulatory troponin (Tn) complex displays several molecular and calcium binding variations in cardiac muscles of different species and undergoes genetic changes with development and in various pathologic states. Extensive reviews on the role of tropomyosin (Tm) and Tn in the regulation of striated muscle contraction have been published describing the molecular mechanisms involved in contractile protein regulation. In our studies, we have found an increase in Mg2+ ATPase activity in cardiac myofibrils from dystrophic hamsters and in rats with chronic coronary artery narrowing. The abnormalities in myofibrillar ATPase activity from cardiomyopathic hamsters were largely corrected by recombining the preparations with a TnTm complex isolated from normal hamsters indicating that the TnTm may play a major role in altered myocardial function. We have also observed down regulation of Ca2+ Mg2+ ATPase of myofibrils from hypertrophic guinea pig hearts, myocardial infarcted rats and diabetic-hypertensive rat hearts. In myosin from diabetic rats, this abnormality was substantially corrected by adding troponin-tropomyosin complex from control hearts. All of these disease models are associated with decreased ATPase activities of pure myosin and in the case of rat and hamster models, shifts of myosin heavy chain from alpha to beta predominate. In summary, there are three main troponin subunit components which might alter myofibrillar function however, very few direct links of molecular alterations in the regulatory proteins to physiologic and pathologic function have been demonstrated so far.
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PMID:Role of regulatory proteins (troponin-tropomyosin) in pathologic states. 781 55

1. U46619 (thromboxane A2 receptors; 0.002-1 microM), carbachol (muscarinic M3 receptors; 0.1-100 microM), cyclopiazonic acid (CPA; Ca(2+)-ATPase inhibitor; 0.1-30 microM) and K+ (5-100 mM) produced concentration-dependent contractions of the mouse isolated anococcygeus muscle. Equi-effective, submaximal concentrations of each agent were used in further experiments (40 nM U46619; 5 microM carbachol; 5 microM CPA; 70 mM K+). 2. Nifedipine (1 microM) totally abolished contractile responses to K+; those to U46619, carbachol and CPA were reduced by only 20-30% in the presence of nifedipine, but were greatly reduced (> 90%) by a combination of nifedipine and SKF 96365 (0.1-40 microM). 3. In Ca(2+)-free medium, contractions to K+ and CPA were abolished. Small residual responses remained to both carbachol and U46619; those to carbachol were transient, could not be repeated in the continued absence of Ca2+ and were prevented by pre-incubation with CPA, but unaffected by SKF 96365; those to U46619 were sustained, could be repeated in the absence of Ca2+, and were resistant to CPA and SKF 96365. 4. Tone induced by all four agents could be relaxed by sodium nitroprusside (SNP), but with a clear order of potency. SNP (pIC40) was most effective against U46619 (7.92), less so against carbachol (6.80) and CPA (6.68), and least potent against K+ (5.94). A similar order of potency was observed with 8Br-cyclic GMP (50 microM) and nitrergic field stimulation (1-20 Hz). 5. The relaxant potency of SNP was similar in normal Krebs solution and in high K+ (70 mM) Krebs containing 1 microM nifedipine. 6. Inclusion of SNP (0.01-1 microM) or 8Br-cyclic GMP (50 microM) in the Ca2+-free medium inhibited the transient residual response to carbachol. Inclusion of similar concentrations of SNP or 8Br-cyclic GMP,during Ca2+ re-loading, increased the subsequent residual contraction to carbachol in Ca2+-free medium.7. At higher concentrations, SNP (0.1-10 microM) produced a partial relaxation of the sustained contraction to U46619 in Ca2+-free medium.8. Thus, the relaxant potency of the nitrergic stimuli was dependent on the agent and mechanism used to induce tone in the preparation. Examination of the contractile/relaxant interactions suggests that altered Ca2+ sequestration and inhibition of contractile protein function may underlie nitrergic relaxations of this tissue.
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PMID:Variable potency of nitrergic-nitrovasodilator relaxations of the mouse anococcygeus against different forms of induced tone. 788 7

Experimentally, diabetic rat hearts are characterized by diminished responses to beta-adrenergic stimulation. Among the aberrant responses are diminished beta-adrenoceptor number and depressed contractile protein activity. In this study, intracellular Ca2+ concentration ([Ca2+]i) was determined by microfluorescence in response to beta-adrenergic stimulation to understand the basis for the changes in the beta-adrenergic pathway in diabetic myocardium. In quiescent myocytes, isoproterenol caused a decrease in [Ca2+]i, which was blocked by timolol and thapsigargin. This suggests that the beta-agonist-induced [Ca2+]i changes are mediated, in part, by sarcoplasmic reticulum Ca-adenosinetriphosphatase. Diabetic myocytes showed a blunted response to isoproterenol, which was reversed by insulin treatment. In electrically stimulated myocytes, isoproterenol and 8-bromo-adenosine 3',5'-cyclic monophosphate (cAMP) increased [Ca2+]i and contraction in a concentration-dependent manner. Electrically stimulated diabetic myocytes demonstrated a depressed maximum [Ca2+]i response to isoproterenol and 8-bromo-cAMP without a change in sensitivity. These data suggest that in addition to alterations in beta-adrenoceptor function there are postreceptor defects in diabetic myocardium that may impair the regulation of [Ca2+]i in diabetic myocardium.
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PMID:Depressed [Ca2+]i responses to isoproterenol and cAMP in isolated cardiomyocytes from experimental diabetic rats. 802 94

A previous study in intact animals assessed cardiovascular alterations in surgically thyroidectomized rats. Hemodynamic challenge via isoproterenol infusion identified abnormal left ventricular relaxation. Challenge by aortic occlusion revealed a latent deficiency in left ventricular contractility which was not apparent during beta-agonist challenge. The present study utilized left ventricular cardiac tissue obtained from the identical control and thyroidectomized animals from which intact heart hemodynamic information had been obtained. Biochemical systems were selected for evaluation based on demonstrated hemodynamic alterations, i.e., beta-adrenergic receptor number/function and contractile protein enzyme properties. The number of beta-receptors on hypothyroid cardiac membranes was significantly decreased, but receptor agonist affinity was not influenced. Basal adenylate cyclase activity in cardiac membranes from control and thyroidectomized rats was nearly identical; however, isoproterenol activation was diminished in hypothyroid cardiac membrane, particularly at the higher levels of beta-agonist stimulation. Adenylate cyclase enzyme activation by forskolin was not influenced by thyroidectomy; however, activation by sodium fluoride was reduced approximately 30% when compared with preparations from control rats. Cardiac myofibrillar enzyme activity for adenosinetriphosphatase (ATPase) was significantly lower in thyroidectomized rats. Despite reduced ATPase activity, myofibrillar calcium sensitivity was unaltered. Myofibrillar creatine kinase enzyme activity was not influenced by thyroidectomy; therefore, compartmentalized ATP regeneration potential via creatine kinase was enhanced relative to substrate utilization via ATPase. Thus hemodynamically significant cardiac influences of hypothyroidism are mediated, at least in part, via 1) reduced beta-receptor number, 2) diminished catecholamine-induced activation of adenylate cyclase, and 3) reduced myofibrillar ATPase activity.
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PMID:Beta-adrenergic receptors, adenylate cyclase activation, and myofibril enzyme activity in hypothyroid rats. 802 15

This study examined changes in contractile, biochemical, and histochemical properties of slow antigravity skeletal muscle after a 6-day spaceflight mission. Twelve male Sprague-Dawley rats were randomly divided into two groups: flight and ground-based control. Approximately 3 h after the landing, in situ contractile measurements were made on the soleus muscles of the flight animals. The control animals were studied 24 h later. The contractile measurements included force-velocity relationship, force-frequency relationship, and fatigability. Biochemical measurements focused on the myosin heavy chain (MHC) and myosin light chain profiles. Adenosine-triphosphatase histochemistry was performed to identify cross-sectional area of slow and fast muscle fibers and to determine the percent fiber type distribution. The force-velocity relationships of the flight muscles were altered such that maximal isometric tension (Po) was decreased by 24% and maximal shortening velocity was increased by 14% (P < 0.05). The force-frequency relationship of the flight muscles was shifted to the right of the control muscles. At the end of the 2-min fatigue test, the flight muscles generated only 34% of Po, whereas the control muscles generated 64% of Po. The flight muscles exhibited de novo expression of the type IIx MHC isoform as well as a slight decrease in the slow type I and fast type IIa MHC isoforms. Histochemical analyses of flight muscles demonstrated a small increase in the percentage of fast type II fibers and a greater atrophy of the slow type I fibers. The results demonstrate that contractile properties of slow antigravity skeletal muscle are sensitive to the microgravity environment and that changes begin to occur within the 1st wk. These changes were at least, in part, associated with changes in the amount and type of contractile protein expressed.
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PMID:Effect of spaceflight on skeletal muscle: mechanical properties and myosin isoform content of a slow muscle. 804 58

The myocardium is a highly adaptive tissue, as evidenced by phenotypic alterations throughout development and under conditions of altered hemodynamic load. With pressure overload, the myocardium displays adult-to-fetal transitions in expression of contractile and non-contractile proteins. Most intriguing is the fact that many of these transitions are also observed in the senescent heart. The purpose of this work was to establish if the thin filament regulatory proteins, troponin I and troponin T, exhibit reexpression of early developmental isoforms, suggestive of coordinate reprogramming of contractile protein isoform expression. As a functional index of reexpression of the early isoform of troponin I, slow skeletal troponin I, myofibrils were isolated from 12 and 24-month-old Fischer 344 rat ventricles and assayed for myofibrillar ATPase activity at pH 7.0 and 6.5. Both preparations displayed rightward shifts in Ca-ATPase relationships with no differences between groups. SDS-PAGE and Western blot analysis showed that whereas myosin heavy chain expression underwent a transition to predominance of the early development isoform, beta-myosin heavy chain, there was no reexpression of the fetal isoforms of either troponin I or troponin T in the rat heart at 24 months of age. Northern blot analysis using cDNA probes specific for cardiac or slow skeletal troponin I also confirmed the lack of slow skeletal reexpression in the 24-month ventricle. These results are significant in that they demonstrate a lack of coordinate expression of contractile protein isoforms under myocardial adaptation to the aging process.
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PMID:Discoordinate regulation of contractile protein gene expression in the senescent rat myocardium. 807 7

Our group has documented that myocardial performance is impaired in the hearts of chronically diabetic rats and rabbits. Abnormalities in the contractile proteins and regulatory proteins may be responsible for the mechanical defects in the streptozotocin (STZ)-diabetic hearts. Previously, the major focus of our research on contractile proteins in abnormal states has concentrated on myosin ATPase and its isoenzymes. Our present study is based on the overall hypothesis that regulatory proteins, in addition to contractile protein, myosin contribute to altered cardiac contractile performance in the rat model of diabetic cardiomyopathy. The purpose of our research was to define the role of cardiac regulatory proteins (troponin-tropomyosin) in the regulation of actomyosin system in diabetic cardiomyopathy. For baseline data, myofibrillar ATPase studies were conducted in the myofibrils from control and diabetic rats. To focus on the regulatory proteins (troponin and tropomyosin), individual proteins of the cardiac system were reconstituted under controlled conditions. By this approach, myosin plus actin and troponin-tropomyosin from the normal and diabetic animals could be studied enzymatically. The proteins were isolated from the cardiac muscle of control and STZ-diabetic (4 weeks) rats. Sodium dodecyl sulfate gel electrophoretic patterns demonstrate differences in the cardiac TnT and TnI regions of diabetic animals suggesting the different amounts of TnT and/or TnI or possibly different cardiac isozymes in the regulatory protein complex. Myofibrils probed with a monoclonal antibody TnI-1 (specific for adult cardiac TnI) show a downregulation of cardiac TnI in diabetics when compared to its controls. Enzymatic data confirm a diminished calcium sensitivity in the regulation of the cardiac actomyosin system when regulatory protein(s) complex was recombined from diabetic hearts. Actomyosin ATPase activity in the hearts of diabetic animals was partially reversed when myosin from diabetic rats was regulated with the regulatory protein complex isolated from control hearts. To our knowledge, this is the first study which demonstrates that the regulatory proteins from normal hearts can upregulate cardiac myosin isolated from a pathologic rat model of diabetes. This diminished calcium sensitivity along with shifts in cardiac myosin heavy chain (V1-->V3) may be partially responsible for the impaired cardiac function in the hearts of chronic diabetic rats.
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PMID:Troponin subunits contribute to altered myosin ATPase activity in diabetic cardiomyopathy. 856 62

Calponin inhibits actin-activated myosin adenosinetriphosphatase (ATPase) activity, and phosphorylation reverses this inhibition. Calponin phosphorylation has been demonstrated in reconstituted contractile protein systems, but studies using intact smooth muscle have produced mixed results. The goal of this study was to determine if vascular smooth muscle contains the necessary biochemical machinery to catalyze calponin phosphorylation. We used swine carotid homogenate, which allows access to the intracellular components and contains all endogenous proteins and enzymes in physiologically relevant concentrations. We demonstrated that calponin is phosphorylated in response to Ca2+ (0.27 +/- 0.04 mol P(i)/mol calponin) and in response to phorbol 12,13-dibutyrate in the presence or absence of Ca2+ (0.48 +/- 0.09 mol P(i)/mol calponin). Calponin phosphorylation was inhibited by the protein kinase C inhibitor staurosporine but not by the Ca(2+)- and calmodulin-dependent protein kinase II inhibitor KN-62. We conclude that Ca(2+)-dependent and -independent isoforms of protein kinase C but not the Ca(2+) -and calmodulin-dependent protein kinase II catalyze calponin phosphorylation in the swine carotid artery.
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PMID:Calcium-and phorbol ester-dependent calponin phosphorylation in homogenates of swine carotid artery. 877 Jan 22

Changes in contractile and relaxation properties of heart muscle in the cardiac hypertrophy induced by pressure overload have been attributed to alterations in intracellular Ca2+ transport as well as the phenotypic and quantitative changes in contractile protein. However, contradictory data have been reported regarding Ca2+ uptake, release and storage by the sarcoplasmic reticulum (SR). The purpose of this study was to evaluate the changes in SR Ca(2+)-ATPase, ryanodine receptor, calsequestrin and alpha-actin gene expression, and the changes in Ca2+ uptake capacity in various degrees of hypertrophied hearts due to pressure overload. Cardiac hypertrophy was produced in rats by placing a constricting clip (0.80 mm) around the suprarenal abdominal aorta for 8 days. The mRNA levels and Ca2+ uptake capacity were then measured as a function of the severity of cardiac hypertrophy. Ca(2+)-ATPase and ryanodine receptor mRNA levels were increased in mildly hypertrophied hearts but were diminished in severely hypertrophied hearts, showing a bimodal response to pressure overload, Ca2+ uptake capacity showed similar changes along with a positive correlation with Ca(2+)-ATPase mRNA level (r = 0.67, P < 0.001). In contrast, the level of calsequestrin mRNA expression was unaltered and that of alpha-actin was markedly increased over a range of severity of cardiac hypertrophy. These findings suggest that the expression of sarcoplasmic reticulum genes for Ca2+ uptake and release is up- or downregulated dependent on the degree of pressure overload. The gene for the SR Ca2+ storage protein, calsequestrin, might be under different control from these genes in pressure overload. Our findings suggest that the decrease in ratio of mRNAs encoding Ca2+ uptake and release proteins to those encoding contractile proteins could significantly contribute to the slowed contractile and relaxation properties seen in pressure-overloaded hearts.
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PMID:Sarcoplasmic reticulum genes are upregulated in mild cardiac hypertrophy but downregulated in severe cardiac hypertrophy induced by pressure overload. 887 69


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