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)

Physiological control of the plasma membrane sodium pump, (Na+,K+)-ATPase, is essential for proper function of eukaryotic cells. In the electric organ of the elasmobranch Narcine brasiliensis, the normal demands placed upon the pump during the process of generation of electrical currents call for large and rapid changes in activity of this enzyme, making this a good model for the study of its cellular regulation. 31P NMR spectroscopic techniques were used to study metabolic regulation of membrane pump function in resting and stimulated electric organ and in skeletal muscle of the live, intact N. brasiliensis. Because the ATP synthetic abilities of the electric organ by glycolysis or oxidative phosphorylation are extremely limited, depletion of phosphocreatinine (PCr) could be used to determine the activity of the (Na+,K+)-ATPase after the electric organ was stimulated to discharge, and to measure the net flux from PCr to ATP through the creatine phosphokinase (CPK) reaction in the electric organ. Saturation transfer, an NMR technique which measures exchange rates, was applied to determine the unidirectional flux in the forward direction through the same reaction in the electric organ and in skeletal muscle as a control. The pseudo first-order rate constant kf for the CPK reaction at 24 degrees C in resting electric organ was 0.000 +/- 0.002 s-1 (n = 10) and in skeletal muscle was 0.08 +/- 0.03 s-1 (n = 3). The results demonstrate that in resting electric organ, which is well supplied with CPK, there was no measurable flux through this reaction, although CPK when extracted is highly active. Measured and calculated levels of all substrates for the creatine kinase reaction in the electric organ are similar to those in unstimulated skeletal muscle, where the creatine phosphokinase reaction rates are high in vivo. In contrast to the resting electric organ, during stimulation of the electric organ the measured net rate constant was greater than 0.08 s-1. In addition, as shown by lack of PCr depletion, there was virtually no net turnover of ATP in the resting organ compared to the stimulated organ. The marked difference in the (Na+,K+)-ATPase activity in the resting and activated electric organ confirmed earlier results (Blum, H., Nioka, S., and Johnson, R. G., Jr. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 1247-1251). Together, these results suggest that there is a novel method of coordinate regulation of cellular enzymes of great sensitivity and rapidity.
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PMID:Coupled in vivo activity of creatine phosphokinase and the membrane-bound (Na+,K+)-ATPase in the resting and stimulated electric organ of the electric fish Narcine brasiliensis. 164 45

The effects of sepsis on skeletal muscle energetics and membrane function are poorly understood, and the time course of changes in energy metabolism are unclear. To clarify these relationships, high energy phosphate ratios, intracellular pH, and phosphocreatine breakdown rates were measured in vivo in the gastrocnemius muscle of adult male Wistar rats after cecal ligation and puncture or sham operation with 31P magnetic resonance spectroscopy. Adenosine triphosphate (ATP) concentration and Na(+)-K+ ATPase and creatine kinase activities were determined in vitro. Within 24 hours, Na(+)-K+ ATPase activity increased by 60% in rats with cecal ligation and puncture, all of which had positive bacterial cultures, as compared to none of the sham-operated controls. Phosphocreatine/ATP ratios decreased by 20% in association with a quantitatively similar increase in phosphocreatine breakdown (9.7 +/- 0.5 vs 11.9 +/- 0.5 mumoles/gm wet wt/sec; p = 0.01). ATP concentrations were maintained, and intracellular pH did not change significantly. In this model, changes in phosphocreatine breakdown were not related to total creatine kinase activity, which did not change significantly, or increases in adenosine 5'-diphosphate (ADP) concentration (62 +/- 8 vs 92 +/- 8 mumols/L; p = 0.02). Thus, in early sepsis before a measurable decrease in pH occurs, ATP is utilized at an increased rate to help maintain ionic balance and/or to support other metabolic processes. Phosphocreatine stores are used to buffer ATP concentrations.
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PMID:Sepsis alters skeletal muscle energetics and membrane function. 165 38

We have studied the effects of hypo- and hyperthyroidism on sarcolemmal (SL) and sarcoplasmic reticular (SR) ion transport processes and mitochondrial energy production in rat heart. The following conclusions were derived. 1) Compared with euthyroid state, hyperthyroidism led to increased SR Ca(2+)-accumulation. In SL, the activities of Ca(2+)-stimulated adenosine triphosphatase (ATPase), ATP-dependent Ca2+ pumping, and Na(+)-Ca2+ exchanger were not affected; but ouabain-sensitive Na(+)-K(+)-ATPase activity was enhanced. 2) Hypothyroidism resulted in depressed activities of Ca2+ pumps both in SL and SR. In SL, the Na(+)-K(+)-ATPase activity was decreased, but Na(+)-Ca2+ exchange was unaltered. 3) Thus slower relaxation of the hypothyroid myocardium may be attributed to depressed functioning of Ca2+ pumps in SR and SL, whereas faster relaxation of the hyperthyroid heart may be based on increased Ca(2+)-pumping activity of SR. 4) Hyperthyroidism and hypothyroidism, respectively, led to enhanced and decreased rates of mitochondrial phosphocreatine synthesis. The thyroid state appears to control the functional coupling between mitochondrial creatine kinase and ATP-ADP translocase: the energy of oxidative phosphorylation was transformed into phosphocreatine more effectively in mitochondria from hypothyroid hearts than in those from hyperthyroid hearts.
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PMID:Thyroid control over membrane processes in rat heart. 165 94

Recent studies indicate that in animals with marked cardiac hypertrophy, there is depressed function of Ca2+ sequestration by myocardial sarcoplasmic reticulum (SR) because of down regulation of the Ca(2+)-ATPase gene. However, in several animal models we have observed enhancement of myocardial Ca2+ sequestration in response to chronic cardiac stimulation. We tested the hypothesis that in animals with mild cardiac hypertrophy, there is enhanced Ca(2+)-cycling activity by the SR Ca2+ pump and Ca(2+)-release channel. Because creatine kinase activity is consistently decreased in cardiomyopathy, we also determined whether enhanced Ca2+ cycling was accompanied by down regulation or inhibition of the creatine kinase system. Mild cardiac hypertrophy was induced by volume overload; 2% salt was added to the diet of 2-week-old turkey poults for 4 weeks. Compared with age-matched controls, volume overload resulted in 14.3% increase in heart weight and 21.5% increase in heart-to-body weight ratios. The hypertrophied heart had approximately 20% increased activities of the SR Ca2+ pump and the SR Ca2+ channel. Net Ca2+ transport was increased by 16.5%. Compared with controls and in contrast to several other myocardial enzymes, creatine kinase activity was diminished in the hypertrophied hearts by 23% and creatine content was decreased by 8%. Differences between groups were not detected for lactate dehydrogenase, aspartate transaminase, and alanine transaminase. We concluded that an early adaptation of the myocardium undergoing hypertrophy in compensatory response to functional overload is an enhancement of Ca2+ cycling activity by the Ca2+ pump and Ca2+ channel of the SR.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of mild cardiac hypertrophy, induced by volume overload in turkeys, on myocardial sarcoplasmic reticulum calcium-pump and calcium-channel activities and on the creatine kinase system. 165 61

Fibrocytes in the lateral wall and limbus of the gerbil cochlea evidenced a capacity for ion transport activity by immunostaining for transport mediating enzymes including Na,K-ATPase, carbonic anhydrase (CA) and creatine kinase (CK). Fibrocytes of the spiral ligament unlike those in the suprastrial region and limbus decreased in abundance from base to apex. Spiral ligament fibrocytes at a given position along the cochlea varied in content of transport related enzymes, and on the basis of immunostaining, location and orientation, were classified into four types. Type I fibrocytes under the stria vascularis stained for CA isozymes II and III and CK isozyme BB. Type II fibrocytes under the outer sulcus and spiral prominence epithelium were found to contain only Na,K-ATPase. Type III fibrocytes lying adjacent to bone in the inferior region of the spiral ligament contained CA II and III and CK isozymes BB and MM. Type IV fibrocytes located more superficially in the inferior part of the spiral ligament stained variably for all the enzymes. Superficial fibrocytes in the suprastrial area disclosed Na,K-ATPase whereas the underlying fibrocytes stained for CA and CK. Limbal fibrocytes reacted with antisera to all the enzymes except CA III. Most fibrocytes in stromal plates beneath the vestibular system's neurosensory epithelium contained Na,K-ATPase and CA II but not CA III. These findings point to cooperativity in fluid and ion transport between epithelial cells and neighboring fibrocytes and demonstrate functional diversity of fibrocytes of the inner ear providing a basis for classifying those in the spiral ligament.
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PMID:Differentiation of inner ear fibrocytes according to their ion transport related activity. 166 6

1. This experiment was designed to study the effects of fasting and enforced exercise on the physiological, biochemical and physical characteristics of duck muscle. 2. Sixty 75-d-old male ducks weighing 3.0 +/- 0.2 kg were assigned to three treatments: a control, and an 8 and 24 h fast plus enforced exercise for 10 min. The ducks were then sacrificed and the carcass stored at 4 degrees C for 24 h. 3. Although the pH and serum lactate contents gradually increased with fasting time the responses were not significant. The ultimate pH was elevated and the lactate of breast and thigh muscles was lower in stressed birds. 4. The activity of lactic dehydrogenase was significantly increased by the stress, and the activities of creatine phosphokinase and alkaline phosphatase were also increased slightly. However, no effect was found on the ATPase activity of the myofibrillar protein of either breast or thigh muscle as a result of the stress. The ATPase activity of myofibrillar protein of breast muscle significantly increased with storage time. 5. The extractability of myofibrillar protein increased with storage time for all treatments. The SDS-PAGE patterns of myofibrillar proteins were also studied. 6. Consequently DFD-like muscle was observed in the breast and thigh muscles of ducks which had been stressed.
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PMID:Effect of stresses before slaughter on changes to the physiological, biochemical and physical characteristics of duck muscle. 166 82

Exercise for which a skeletal muscle is not adequately conditioned results in focal sites of injury distributed within and among the fibres. Exercise with eccentric contractions is particularly damaging. The injury process can be hypothesised to occur in several stages. First, an initial phase serves to inaugurate the sequence. Hypotheses for the initial event can be categorised as either physical or metabolic in nature. We argue that the initial event is physical, that stresses imposed on sarcolemma by sarcomere length inhomogeneities occurring during eccentric contractions cause disruption of the normal permeability barrier provided by the cell membrane and basal lamina. This structural disturbance allows Ca++ to enter the fibre down its electrochemical gradient, precipitating the Ca++ overload phase. If the breaks in the sarcolemma are relatively minor, the entering Ca++ may be adequately handled by ATPase pumps that sequester and extrude Ca++ from the cytoplasm ('reversible' injury). However, if the Ca++ influx overwhelms the Ca++ pumps and free cytosolic Ca++ concentration rises, the injury becomes 'irreversible'. Elevations in intracellular Ca++ levels activate a number of Ca(++)-dependent proteolytic and phospholipolytic pathways that are indigenous to the muscle fibres, which respectively degrade structural and contractile proteins and membrane phospholipids; for instance, it has been demonstrated that elevation of intracellular Ca++ levels with Ca++ ionophores results in loss of creatine kinase activity from the fibres through activation of phospholipase A2 and subsequent production of leukotrienes. This autogenetic phase occurs prior to arrival of phagocytic cells, and continues during the inflammatory period when macrophages and other phagocytic cells are active at the damage site. The phagocytic phase is in evidence by 2 to 6 hours after the injury, and proceeds for several days. The regenerative phase then restores the muscle fibre to its normal condition. Repair of the muscle fibres appears to be complete; the fibres adapt during this process so that future bouts of exercise of similar type, intensity, and duration cause less injury to the muscle.
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PMID:Mechanisms of exercise-induced muscle fibre injury. 178 73

Slowly progressive myopathy with tubular aggregates is rare and dominantly or recessively inherited. Three sporadic cases are reported in the present study occurring in 2 men and 1 young woman. All patients had proximal limb weakness without severe atrophy. They also complained of exercise-induced stiffening and cramps of their leg muscles. In 1 case severe cardiomyopathy caused unfavorable clinical course and death. Serum creatine kinase activity was normal and electromyogram showed only slight myopathic changes. Tubular aggregates were found to be the sale morphological abnormality. They were present in type II fibres in 1 case and in type I and type II fibres in the others. An immunocytological study with a polyclonal antibody against Ca2+ SR-ATPase showed positivity of the tubular aggregates with this antibody. A quantitative analysis (SAMBA 2000 alcatel TITN) was carried out on frozen sections stained for calcium. It showed a lower calcium content in tubular aggregates than in other part of the fibre. Slowly progressive myopathy with tubular aggregates may be distinguished from other diseases where tubular aggregates are the sale structural change, such as myopathies with myasthenic features and some neuromuscular diseases with exercise intolerance without progressive course. Usually, tubular aggregates are not a specific finding; they have been described in various disorders in association with other structural changes.
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PMID:[Slowly progressive myopathy with accumulation of tubular aggregates]. 196 68

An attempt was made to compare the toxic effects of the organochlorine insecticide 'chlordane' in man and rats. Analysis of blood for chlordane metabolites showed their presence in the descending order of trans-nonachlor, oxychlordane, heptachlorepoxide and cis-nonachlor. The total range of chlordane and its metabolites in the sera of workers was 9.84 +/- 4.47 ng/g. Serum levels of triglycerides (TG), creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) activities were also found to be higher in pest-control operators. In a simultaneous study, rats were administered 100 mg/kg body wt. of chlordane by stomach tube once a day for 4 days, whereas 50 mg/kg body wt. of chlordane was injected intraperitoneally once a day for 4 days. The data show that total cholesterol and serum TG as well as CPK and LDH activities are increased after chlordane treatment. The isoenzyme patterns suggest that an increase in CPK and LDH is related to skeletal muscle. Furthermore, the hepatotoxicity of chlordane was also studied in rats only. A significant increase in liver weight, its water content, total lipids, triglycerides and phospholipids was recorded. Chlordane induced lipid peroxidation in the liver, exhibiting a dose-response relationship. Although no appreciable effect on mitochondrial function and latent ATPase activity was observed, 2,4-dinitrophenol-stimulated ATPase activity was inhibited. Histological examination of the liver confirmed fatty infiltration induced by chlordane in rats.
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PMID:Effects of chlordane on parameters of liver and muscle toxicity in man and experimental animals. 203 78

Reperfusion of rabbit hearts after 15 min of global ischemia at 37 degrees C depressed developed pressure by 36% (myocardial stunning). Changes in myofilament function were investigated as causes of this depression. Kinetic analysis of the effects of stunning on myofibrillar catalyzed ATP hydrolysis showed that stunning lowered Michaelis constant (Km) slightly and left maximal enzyme reaction velocity unaltered in the stunned myofilaments. The myofilament end of the creatine kinase (CK) shuttle was also found to be unaffected in the stunned myofibrils. The Km ADP for myofibrillar CK from control and stunned hearts was 60.45 +/- 3.45 and 68.04 +/- 2.42 microM, respectively, and the CK activity at 100 microM ADP was 0.63 +/- 0.08 and 0.67 +/- 0.04 IU/mg myofibrillar protein from control and stunned hearts, a rate three times greater than the myofibrillar adenosinetriphosphatase (ATPase) rate and a rate sufficient to deliver ATP to the myofilaments. Myofilament Ca2+ sensitivity was assessed by measuring Ca2(+)-dependent myofibrillar Mg2(+)-ATPase activity at free [Ca2+] ranging from 10 nM to 32 microM and [Mg.ATP] of 0.8, 1.6, and 3.2 mM. The sensitivity of myofilaments to activation by Ca2+ was unaltered in the myofibrils isolated from stunned hearts. It is concluded from these analyses that the depression of pressure development observed in stunned hearts is not due to a defect in myofilament function.
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PMID:Effect of global myocardial stunning on Ca2(+)-sensitive myofibrillar ATPase activity and creatine kinase kinetics. 214 2


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