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:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relationships between the carnitine concentration and enzyme activities representative of different metabolic pathways, glycogenolysis, glycolysis, beta-oxidation of fatty acids, citric acid cycle, and respiratory chain were studied in skeletal muscle tissue from 18 volunteering subjects. In addition, the in vitro incorporation rates of glucose-carbon and palmitate-carbon into different metabolites, and the concentration of glycogen, triglycerides, and phospholipids were determined in the same tissue specimen. The carnitine concentration correlated positively and statistically significantly with the activities of 3-OH-acyl-CoA dehydrogenase and citrate synthase, with the incorporation rate of palmitate-carbon into CO2, and the incorporation rate of glucose-carbon into lactate in the muscle tissue. The results indicate a coupling between the concentration of carnitine and the capacity for long-chained fatty acid oxidation in human skeletal muscles.
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PMID:Carnitine concentration in relation to enzyme activities and substrate utilization in human skeletal muscles. 13 18

The effects of chronic "steady-state" and high-speed interval running were investigated on time-course changes in certain biochemical properties of cardiac and skeletal muscle fiber types of rats. Nine weeks of the interval program resulted in significant increased (15%) in both cardiac enlargement and ATPase activity of myofibrils; whereas increases in these parameters were only transient and not significant at the termination of the program involving steady-state running. Neither program induced appreciable alterations in citrate synthase and phosphofructokinase activity in cardiac muscle. In fast-twitch white fibers, "steady-state" training induced only a transient 45% increase in citrate synthase activity in contrast to a progressive twofold change with interval training. Both programs resulted in similar increases (45-50%) in citrate synthase activity in fast-twitch and slow-twitch red fibers. However, the patterns of increase for both fiber types differed between the two programs. These findings suggest that training programs incorporating elements of both "steady-state" incline and high-speed interval running can potentially induce respiratory enzyme adaptations in the greatest spectrum of rodent skeletal muscle fibers in addition to inducing adaptations to enhance contractile potential in cardiac muscle.
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PMID:Time course adaptations in cardiac and skeletal muscle to different running programs. 13 67

The effects of bilateral functional overload on enzyme changes in fast-twitch plantaris muscles were studied on different groups of rats: 1) normal-control; 2) normal-exercise; 3) overload-control; and 4) overload-exercise. Overload was accomplished by surgical elimination of synergists. Exercising groups walked up a 65% grade, 3 m/min, 2 h/day. Peak muscle enlargement of the overload groups was reached after 5 wk. Citrate synthase, phosphofructokinase, and myofibril ATPase activities were consistantly depressed by approximately 30%, 40%, and 18%, respectively, in overload as compared to normal groups. Daily exercise prevented the decrease in only citrate synthase activity. Unilateral overload of medial gastrocnemius muscle indicated that both fast-twitch oxidative-glycogenolytic and fast-twitch glycogenolytic fiber types undergo enzyme changes in response to the functional stress. However, changes in the former were in closer agreement with the net changes seen in the plantaris than the latter. Soleus muscle responded to overload primarily with marked reductions in respiratory capacity. These findings suggest that certain enzyme systems are altered with functional overload in different fiber types. However, the alterations in certain enzyme systems may, in part, be independent of the process of hypertrophy.
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PMID:Effect of functional overload on enzyme levels in different types of skeletal muscle. 13 68

Fifty-seven isolated, blood perfused, continuously weighed canine hearts have been utilized to study the development of abnormal myocardial fluid retention during early myocardial ischemic injury. Inflatable balloon catheters were positioned around the left anterior descending coronary arteries (LAD) of 54 hearts or the proximal left circumflex coronary arteries of three hearts for study of the following intervals of coronary occlusion: a) 10 minutes followed by 20 minutes of reflow, b) 40 minutes followed by either no reflow or by 20 minutes of reflow, and c) 60 minutes without reflow. After 60 minutes of fixed coronary occlusion, histologic and ultrastructural examination revealed mild swelling of many ischemic cardiac muscle cells in the absence of interstitial edema, cardiac weight gain, and obvious structural defects in cell membrane integrity. After 40 minutes of coronary occlusion and 20 minutes of reflow, significant cardiac weight gain occurred in association with characteristic alterations in the ischemic region, including widespread interstitial edema and focal vascular congestion and hemorrhage and swelling of cardiac muscle cells. Focal structural defects in cell membrane integrity were also noted. The development of abnormal myocardial fluid retention after 40 minutes of LAD occlusion occurred in association with a significant reduction in sodium-potassium-ATPase activity in the ischemic area, but with no significant alteration in either creatine phosphokinase or citrate synthase activity in the same region. Despite the abnormal myocardial fluid retention in these hearts, it was possible pharmacologically to vasodilate coronary vessels with adenosine and nitroglycerin infusion to maintain a consistently high coronary flow following release of the coronary occlusion after 40 minutes and to even exceed initial hyperemic flow values following release of the occlusion when adenosine and nitroglycerin infusion was delayed until 15 minutes after reflow. Thus, the data indicate that impaired cell volume regulation and interstitial fluid accumulation and focal structural defects in cell membrane integrity are early manifestations of ischemic injury followed by reflow, but fail to establish a major role for the abnormal fluid retention in altering coronary blood flow prior to the development of extensive myocardial necrosis. In contrast, fixed coronary occlusion for 60 minutes results in mild intracellular swelling but no significant interstitial edema and no obvious structural defects in cell membrane integrity.
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PMID:Abnormal myocardial fluid retention as an early manifestation of ischemic injury. 13 29

1. Percutaneous needle biopsies were obtained from six limb muscles in six horses before and during a training programme of 10 or 15 weeks designed to involve both aerobic and anaerobic work. In a subsequent detraining period, biopsies were also taken after 5 and 10 weeks. 2. Samples were analysed biochemically for enzyme activity of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aldolase (ALD), citrate synthase (CS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) and for glycogen content. Fibre typing was carried out histochemically before and 10 weeks after commencement of training. 3. There was a significant increase in the percentage of high myosin ATPase activity pH 9-4/high oxidative (FTH) fibres with a corresponding decrease in high myosin ATPase activity pH 9-4/low oxidative (FT) fibres and low myosin ATPase activity pH 9-4/high oxidative (ST) fibres after 10 weeks training. 4. During training, enzyme activities increased progressively but at different rates with an approximate twofold increase in all of the enzymes except CPK by the end of the training period. Changes in all the muscles studied were similar. Glycogen content increased by approximately 33% which was significant when all the muscles were considered together. 5. A decrease in enzyme activity occurred after 5 weeks detraining. However at 10 weeks a consistent but inexplicable increase in all enzyme levels, except CS again occurred. 6. It is concluded that training increased greatly the activity of enzymes involved in both aerobic and anaerobic metabolism.
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PMID:The effect of training and detraining on muscle composition in the horse. 14 28

The effect of prolonged digoxin treatment (1 mg/kg day for 8 days) on the activity levels of some enzymes of energy metabolism (phosphofructokinase, lactate dehydrogenase, citrate synthase, succinate dehydrogenase) in rat myocardium was studied. In the control animals receiving the solvent mixture (glycerol:ethanol:water in 1:1:1) a transient decrease in the lactate dehydrogenase and citrate synthase activity levels was observed. In the hearts of digoxin treated rats the level of activity of phosphofructokinase was permanently lowered by the fourth day and the level of activity of citrate synthase permanently increased after the first day of treatment. A transient increase in the activity level of succinate dehydrogenase in the myocardium of digoxin treated animals was seen between days 1 and 6. In this study a permanent decrease in phosphofructokinase and an increase in citrate synthase activity levels in rat heart muscle was noted during prolonged digoxin treatment.
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PMID:Enzyme activities of myocardial energy metabolism during prolonged digoxin treatment in rats. 14 96

The activities of phosphofructokinase, pyruvate kinase, citrate synthase and creatine kinase were determined in blastocysts from rabbits at 144 h post coitum and in similar blastocysts cultured for 24 h with or without oestradiol-17beta (1 microgrm/ml). There was a significant increase in all the enzymes during the 24-h culture period but oestradiol had no effect.
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PMID:Regulatory enzymes of carbohydrate and energy metabolism in the rabbit blastocyst. 14 40

This study was undertaken to evaluate the relationship between physical performance capacity and the mitochondrial content of skeletal muscle. Four groups of rats were trained by means of treadmill running 5 days/wk for 13 wk. One group ran 10 min/day, a second group ran 30 min/day, a third group ran 60 min/day, and a fourth group ran 120 min/day. The magnitude of the exercise-induced adaptive increase in gastrocnemius muscle respiratory capacity varied over a twofold range in the four groups. There were significant correlations between the levels of three mitochondrial markers (cytochrome c, citrate synthase, respiratory capacity) in the animals' gastrocnemius muscles and the duration of a run to exhaustion. There was also a significant correlation between the amounts of glycogen remaining in liver and skeletal muscle after a 30-min-long exercise test and the respiratory capacity of the animal's leg muscles. These findings are compatible with the interpretation that a close relationshiop exists between skeletal muscle mitochondrial content and the capacity to perform endurance exercise.
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PMID:Skeletal muscle respiratory capacity, endurance, and glycogen utilization. 1816 Apr 57

The effects of thyroid hormone administration on the levels of a number of mitochondrial markers were measured in skeletal muscle and liver of normal rats. Injection of 18 mug of L-thyroxine (T4) per 100 g body wt every 4th day for 3 wk had no effect on the concentrations of cytochrome c, on citrate synthase activity, or on respiratory capacity of skeletal muscle. Injection of 200 mug of L-triiodothyronine (T3) daily for 5 days, or feeding 23 mg T4 and 7 mg T3/kg of diet for 2 wk, resulted in thyrotoxicosis and large increases in the activity of hepatic alpha-glycerophosphate dehydrogenase and other mitochondrial markers; however, the levels of activity of mitochondrial marker enzymes in gastrocnemius and quadriceps muscles were not significantly changed. Only when rats were fed 3 mg T4 and 1 mg T3/kg diet for a 6-wk period did we observe an increase in skeletal muscle mitochondrial markers. Thus, thyroxine treatment must be sufficiently prolonged if it is to be used as a tool for studying skeletal muscle mitochondrial biogenesis.
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PMID:Effects of thyroid hormone administration on skeletal muscle mitochondria. 16 30

The activities (Vmax) of hexokinase, glycogen phosphorylase, glucose-6-phosphate dehydrogenase, phosphofructokinase, lactate dehydrogenase, citrate synthase, cytochrome c oxidase, and 3-OH-acyl-CoA dehydrogenase in human skeletal muscles were compared with the in vitro utilization of glucose and palmitic acid assessed under optimal conditions. Statistically significant correlations between substrate fluxes and enzyme activities were found suggesting that the substrate incorporation rate in vitro in some way reflects the capacity of metabolic pathways. The incorporation rate of leucine into muscle proteins was also statistically significantly correlated to the RNA concentration in the muscle tissue. Glycolytic and glycogenolytic enzymes correlated significantly to each other and correlations were also found between aerobic enzymes supporting the validity of constant proportions between certain key enzymes in human skeletal muscles.
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PMID:Incorporation rate of glucose carbon, palmitate carbon and leucine carbon into metabolites in relation to enzyme activities and RNA levels in human skeletal muscles. 17 28


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