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)

An assumed link between red cell hypervolaemia, an excessive amount of training and impaired performance of hypervolaemic horses has led to a theory that the muscle fibres could be affected. Myosin heavy chain (MHC)-based fibre type composition in gluteus medius muscle of red blood cell normo- (NV) and hypervolaemic (HV) Standardbred trotters was evaluated using immunohistochemistry. Muscle biopsies were obtained from 13 NV and 16 HV horses. Serial transverse sections were cut and reacted with antibodies against different isoforms of the myosin heavy chains MHCI, MHCIIA and MHCIIX. Sections were also stained for myofibrillar ATPase pH 4,6 to identify types I, IIA and IIB, and NADH tetrazolium reductase to evaluate the oxidative capacity. The results show that types I and IIA fibres corresponded between staining methods, whereas IIB fibres in the ATPase stains were more numerous than pure MHCIIX fibres from immunohistochemistry. Many fibres identified histochemically as type IIB fibres contained both MHC isoforms IIA and IIX (MHCIIAX). Most fibres had a high oxidative capacity, but among the fibres within a section, the lowest was seen subjectively in pure MHCIIX fibres. Immunohistochemical stains make it possible to detect differences in fibre type composition that are not observed with myosin ATPase stainings, as it was found that HV horses had a lower percentage of MHCIIX fibres than NV horses. Immunohistochemical methods are, therefore, valuable for use in further research and clinical studies concerning muscle adaptations.
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PMID:Myosin heavy chain-based fibre types in red cell hyper- and normovolaemic Standardbred trotters. 1240 1

This short review discusses changes in the fibre type distribution, myosin heavy chain isoform composition and histological appearance of the very elderly human skeletal muscle. Point of origin of the discussion comes from data that we have obtained from muscle biopsies from the vastus lateralis muscle of a group of frail very elderly subjects (age: 88 +/- 3 years, range 85-97). Myosin heavy chain composition of muscle homogenates and single fibres, fibre type distribution, fibre size and capillary density were examined and compared with muscle biopsies from the young vastus lateralis muscle. Histological preparations of the muscle biopsies from our elderly subjects showed extended "grouping" (Nygaard & Sanchez, Anat Rec 1992: 202: 451-459) of the fibre types as well as significant changes in the appearance and size of the individual muscle fibres. On average, the fibre type composition of our very elderly subjects do not seem to be different to what is observed in a corresponding young group when examined with ATPase histochemistry. Likewise, the MHC composition of the muscle homogenates is comparable to what is observed in young subjects. Nevertheless, a detailed examination of the MHC composition of single fibres from the old subjects revealed that the most prominent phenotype was fibres co-expressing MHC I and MHC IIA. This is very different from what is observed in the young muscle. Detailed investigation of longitudinally cut fibres indicated that some fibres in the very old muscle, in contrast to the young muscle, switch fibre type along the length of the fibre or contain areas or nuclear domains in which the MHC expression is different from the remaining part of the fibre.
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PMID:Muscle fibre type adaptation in the elderly human muscle. 1253 16

A histochemical assay for myofibrillar adenosine triphosphatase (mATPase) activity is routinely utilized in the delineation of fiber types in healthy human skeletal muscle. Each fiber type has a specific pH range of mATPase stability (activation). Outside of this pH range, mATPase activity is labile (inactivated), no reaction product is formed, and the fibers remain unstained. The aim of the present study was to carefully investigate the pH stability/lability of mATPase in postmortem muscles. To this end, vastus lateralis muscle samples were obtained approximately 0.5, 1, 2, 3, and 4 days after death, as well as control samples from a healthy young man and woman. Serial cross sections of the muscle samples were assayed for mATPase activity throughout preincubation pH ranges of 4.15-4.7 and 10.2-10.5 in increments of 0.05 pH units. Myosin heavy chain analysis (as well as a regression analysis comparing fiber type area and relative myosin heavy chain content) verified the mATPase-based fiber types. The pH ranges of mATPase stability/lability for the control samples were as previously reported, and support the use of preincubation pH values of 4.3, 4.6, and 10.4 for the delineation of fiber types in normal human muscle. For the postmortem samples, both quantitative and qualitative changes altered the pH ranges of mATPase activation/inactivation. Quantitative changes consisted of a time-dependent loss of mATPase activity that was inhibited in all fibers outside the pH range of 4.15-10.50. In addition, qualitative changes caused "shifts to the left" in mATPase stability within the fast fiber types (IIA and IIB). As such, complete inhibition of mATPase activity did not occur until preincubation at pH 4.45 and pH 4.30 for fiber types IIA and IIB, respectively. For the postmortem vastus lateralis muscle samples, optimal preincubation pH values for mATPase-based fiber type delineation were pH 4.30, 4.45, and 10.35. The reason for these qualitative changes in mATPase stability is not known. However, postmortem changes such as increased lactate production and marked acidification may play a role.
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PMID:Postmortem alterations in the pH range of myofibrillar ATPase activation/inactivation. 1261 Jul 35

The present study tests the hypothesis that endurance exercise training (ETr) reverses age-associated alterations in expression of Na+-K+-ATPase subunit isoforms in rat skeletal muscles. Expression of the isoforms was examined in 16-mo-old sedentary middle-aged, 29-mo-old sedentary senescent, and 29-mo-old treadmill exercise-trained senescent Fischer 344 x Brown Norway rats. Levels of the alpha1-isoform increased with age in red gastrocnemius (GR), white gastrocnemius (GW), and extensor digitorum longus (EDL) muscles, and ETr further increased its levels. Levels of the alpha2-isoform were unchanged in GR, had a strong trend for a decrease in GW, and decreased significantly in EDL. ETr increased expression of the alpha2-isoform in all three muscle groups. There was no increase in expression of the beta1-isoform in GR, GW, or EDL with age, whereas ETr markedly increased its levels in the muscles. There was a marked decrease with age in expression of the beta2-isoform in the muscle groups that was not reversed by ETr. By contrast, beta3-isoform levels increased with age in GR and GW, and ETr was able to reverse this increase. Na+-K+-ATPase enzyme activity was unchanged with age in GR and GW but increased in EDL. ETr increased enzyme activity in GR and GW and did not change in EDL. Myosin heavy chain isoforms in the muscle groups did not change significantly with age; ETr caused a general shift toward more oxidative fibers. Thus ETr differentially modifies age-associated alterations in expression of Na+-K+-ATPase subunit isoforms, and a mechanism(s) other than physical inactivity appears to play significant role in some of the age-associated changes.
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PMID:Exercise training differentially modifies age-associated alteration in expression of Na+-K+-ATPase subunit isoforms in rat skeletal muscles. 1295 16

Myosin heavy chain (MHC) isoforms alpha and beta have intrinsically different ATP hydrolysis activities (ATPase) and therefore cross-bridge cycling rates in solution. There is considerable evidence of altered MHC expression in rodent cardiac disease models; however, the effect of incremental beta-MHC expression over a wide range on the rate of high-strain, isometric cross-bridge cycling is yet to be ascertained. We treated male rats with 6-propyl-2-thiouracil (PTU; 0.8 g/l in drinking water) for short intervals (6, 11, 16, and 21 days) to generate cardiac MHC patterns in transition from predominantly alpha-MHC to predominantly beta-MHC. Steady-state calcium-dependent tension development and tension-dependent ATP consumption (tension cost; proportional to cross-bridge cycling) were measured in chemically permeabilized (skinned) right ventricular muscles at 20 degrees C. To assess dynamic cross-bridge cycling kinetics, the rate of force redevelopment (ktr) was determined after rapid release-restretch of fully activated muscles. MHC isoform content in each experimental muscle was measured by SDS-PAGE and densitometry. alpha-MHC content decreased significantly and progressively with length of PTU treatment [68 +/- 5%, 58 +/- 4%, 37 +/- 4%, and 27 +/- 6% for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA)]. Tension cost decreased, linearly, with decreased alpha-MHC content [6.7 +/- 0.4, 5.6 +/- 0.5, 4.0 +/- 0.4, and 3.9 +/- 0.3 ATPase/tension for 6, 11, 16, and 21 days, respectively; P < 0.001 (ANOVA)]. Likewise, ktr was significantly and progressively depressed with length of PTU treatment [11.1 +/- 0.6, 9.1 +/- 0.5, 8.2 +/- 0.7, and 6.2 +/- 0.3 s(-1) for 6, 11, 16, and 21 days, respectively; P < 0.05 (ANOVA)] Thus cross-bridge cycling, under high strain, for alpha-MHC is three times higher than for beta-MHC. Furthermore, under isometric conditions, alpha-MHC and beta-MHC cross bridges hydrolyze ATP independently of one another.
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PMID:Impact of beta-myosin heavy chain isoform expression on cross-bridge cycling kinetics. 1547 82

Hypothyroid heart displays a phenotype of cardioprotection against ischemia and this study investigated whether administration of dronedarone, an amiodarone-like compound that has been shown to preferentially antagonize thyroid hormone binding to thyroid hormone receptor alpha1 (TRalpha1), results in a similar effect. Dronedarone was given in Wistar rats (90 mg/kg, once daily (od) for 2 weeks) (DRON), while untreated animals served as controls (CONT). Hypothyroidism (HYPO) was induced by propylthiouracil administration. Isolated rat hearts were perfused in Langendorff mode and subjected to 20 minutes of zero-flow global ischemia (I) followed by 45 minutes of reperfusion (R). 3,5,3' Triiodothyronine remained unchanged while body weight and food intake were reduced. alpha-Myosin heavy chain (alpha-MHC) decreased in DRON while beta-myosin heavy chain (beta-MHC) and sarcoplasmic reticulum Ca2+ adenosine triphosphatase (ATPase) expression (SERCA) was similar to CONT. In HYPO, alpha-MHC and SERCA were decreased while beta-MHC was increased. Myocardial glycogen content was increased in both DRON and HYPO. In DRON, resting heart rate and contractility were reduced and ischemic contracture was significantly suppressed while postischemic left ventricular end-diastolic pressure and lactate dehydrogenase release (IU/L min) after I/R were significantly decreased. In conclusion, dronedarone treatment results in cardioprotection by selectively mimicking hypothyroidism. This is accompanied by a reduction in body weight because of the suppression of food intake. TRs might prove novel pharmacologic targets for the treatment of cardiovascular illnesses.
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PMID:Dronedarone administration prevents body weight gain and increases tolerance of the heart to ischemic stress: a possible involvement of thyroid hormone receptor alpha1. 1568 16

Myosin heavy chain isoforms (MHC) of adult skeletal muscles are codified by four genes named: slow, or type 1, and fast types 2A, 2X and 2B. The slow, 2A and 2X isoforms have been found expressed in all mammalian species studied so far whereas there is a large inter-species variability in the expression of MHC-2B. In this study histochemistry (m-ATPase), immunohistochemistry with the use of specific monoclonal antibodies and RT-PCR were combined together to assess whether the MHC-2B gene is expressed in bovine muscles. ATPase staining and RT-PCR experiments showed that three MHC isoforms (1, 2A, 2X) were expressed in trunk and limb muscles. Slow or type 1 expression was confirmed using a specific antibody (BA-F8) whereas the detection of fast MHC isoforms were validate by means of BF-35 antibody although not by the SC-71 antibody. MHC-2B was absent in limb and trunk muscles, but was present in specialized eye muscles (rectus lateralis and retractor bulbi) as consistently showed by RT-PCR and reactivity with a specific antibody (BF-F3). Interestingly, a cardiac isoform, MHC-a-cardiac was found to be expressed not only in extraocular muscles but also in masticatory muscles as masseter.
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PMID:Myosin heavy chain 2B isoform is expressed in specialized eye muscles but not in trunk and limb muscles of cattle. 1571 1

Sarcomeric protein abnormalities have been recognized for many years in heart failure due to dilated cardiomyopathy (DCM). In contrast, virtually nothing is known about myofilament abnormalities in heart failure occurring in association with diastolic dysfunction. With the exception of sarcomeric protein mutations that cause DCM, the most important mechanism of myofilament dysfunction in DCM is probably altered post-translational modification, in particular the phosphorylation state of troponins I and T and possibly myosin light chain. Other modifications, including oxidation and glycation, may also play a role. Myosin heavy chain isoform switching occurs in human heart failure, but its functional significance is uncertain. Myofilament abnormalities contribute significantly to myocardial dysfunction in DCM, although their relative importance compared with abnormal calcium handling is debated. One consistent functional abnormality in DCM is increased myofilament calcium sensitivity of tension generation, which contributes to slowed or incomplete relaxation. More recently, decreases in the optimal frequency of myofilament work and power generation have been recognized. These changes may contribute to depression of the force-frequency relation in DCM. Altered mechanoenergetics constitute one of the most important manifestations of myofilament dysfunction in heart failure. DCM and hemodynamic overload are associated with more economical and efficient energy utilization by the contractile machinery, which may be protective of the myocardium. This change is strongly associated with depressed myofibrillar ATPase activity. We speculate that the effectiveness of mechanical therapies such as resynchronization may at least in part be related to improved mechanical function without loss of this mechanoenergetic advantage.
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PMID:Functional consequences of sarcomeric protein abnormalities in failing myocardium. 1641 47

The left and right ventricles are muscular chambers of the heart that differ significantly in the extent of pressure work-load. The regional and differential distribution of gene expression patterns is critical not only for heart development, but, also in the establishment of cardiac hypertrophy phenotypes. the cells of the myocardium employ elaborate regulatory mechanisms to establish changes in chromatin structure and function, yet, the role of epigenetic modifications and specific gene expression patterns in cardiac ventricles remains poorly understood. We have examined gene expression changes and studied histone H3 and H4 acetylation as well as dimethylation of lysine 4 on histone H3 on promoters of alpha-Myosin heavy chain gene (alpha-MHC), beta-Myosin heavy chain gene (beta-MHC), Atrial natriuretic peptide gene (ANp), B-type natriuretic peptide gene (BNP) and Sarcoplasmic reticulum Ca(2+) ATPase gene (SERCA2a). The recruitment of histone acetyltransferase (HAT) enzyme p300, which is a transcriptional coactivator, was also studied on the hyperacetylated promoters using immunopurification of soluble chromatin in the left and right ventricles of the mouse. We present evidence for the first time that the pattern of gene expression is closely linked with histone modifications and propose the left and right chambers of the heart are epigenetically distinguishable.
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PMID:Cardiac ventricular chambers are epigenetically distinguishable. 2009 Apr 19

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a highly prevalent disorder that is characterized by recurrent sleep-induced collapse of the upper airway. Genioglossus is an important pharyngeal dilator muscle that helps to maintain the patency of the upper airway. The effect of female hormones on pharyngeal dilator muscle activity may be one possible explanation for the differences observed in the prevalence of OSAHS between genders. The aim of this research was to investigate the influence of estrogen on genioglossus activity in rats exposed to chronic intermittent hypoxia (CIH). Eight-wk-old female rats were ovariectomized or sham-operated, received 5-wk of estrogen replacement therapy, and/or were exposed to CIH. The contractile properties of the genioglossus were measured. ATPase staining was performed to determine the per cent fiber-type distribution and to measure the cross-sectional area (CSA) of muscle fibers. Myosin heavy chain phenotypes were determined by gel electrophoresis. Chronic intermittent hypoxia reduced the contractile properties of the genioglossus muscle, decreased the CSA of type IIA fibers, and decreased the proportion of myosin heavy chain IIA, and ovariectomy exacerbated this effect. However, estrogen replacement can partially reverse the effect of CIH in ovariectomized rats. It is concluded that a low female hormone level and CIH may increase fatigue and alter genioglossus structure and function, and may compromise the maintenance of upper airway patency, while estrogen may help to reverse this effect.
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PMID:Effects of estrogen on genioglossal muscle contractile properties and fiber-type distribution in chronic intermittent hypoxia rats. 2012 31


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