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 purpose was to determine the biochemical and hemodynamic adaptations of the myocardium to chronic tachycardia. Cardiac pacemakers were implanted in Yorkshire pigs and set at a rate of 180 beats/min for a period of 35-42 days. Animals were then anesthetized with pentobarbital sodium. Myocardial blood flow and hemodynamics were determined at three different heart rates (i.e., 120, 180, and 220 beats/min). Tissue samples were then taken for microsphere and biochemical analyses. Chronically paced hearts maintained better cardiac function and had consistently higher left ventricular blood flow with a higher endocardial-to-epicardial ratio. The activities of citrate synthase and 3-hydroxyacyl-CoA dehydrogenase were 23 and 45% greater in the paced hearts, respectively. The sarcoplasmic reticulum adenosinetriphosphatase activity was 55% greater in the paced hearts, whereas the myosin adenosinetriphosphatase was the same as in the control hearts. Polyacrylamide gels of the ventricular myosin isoforms showed only the V3 type to be present in both the control and paced hearts. These findings show that the heart of a large mammal adapts to chronic tachycardia (i.e., 180 beats/min) by elevating the aerobic and calcium-sequestering capacities without altering its myosin type.
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PMID:Myocardial biochemical and hemodynamic adaptations to chronic tachycardia. 182 10

The purpose of this study was to determine whether cardiac biochemical adaptations are induced by chronic exercise training (ET) of miniature swine. Female Yucatan miniature swine were trained on a treadmill or were cage confined (C) for 16-22 wk. After training, the ET pigs had increased exercise tolerance, lower heart rates during exercise at submaximal intensities, moderate cardiac hypertrophy, increased coronary blood flow capacity, and increased oxidative capacity of skeletal muscle. Myosin from both the C and ET hearts was 100% of the V3 isozyme, and there were no differences between the myosin adenosine triphosphatase (ATPase) or myofibrillar ATPase activities of C and ET hearts. Also, the sarcoplasmic reticulum Ca(2+)-ATPase activity and Na(+)-Ca2+ exchange activity of sarcolemmal vesicles were the same in cardiac muscle of C and ET hearts. Finally, the glycolytic and oxidative capacity of ET cardiac muscle was not different from control, since phosphofructokinase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase activities were the same in cardiac tissue from ET and C pigs. We conclude that endurance exercise training does not provide sufficient stress on the heart of a large mammal to induce changes in any of the three major cardiac biochemical systems of the porcine myocardium: the contractile system, the Ca2+ regulatory systems, or the metabolic system.
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PMID:Biochemical characterization of exercise-trained porcine myocardium. 183 67

This study was conducted to obtain additional information about the adaptations after 12 wk of high-fat diet (HFD) per se or HFD combined with endurance training in the rat using a two [diet: carbohydrate (CHO) or HFD] by two (training: sedentary or trained) by two (condition at death: rested or exercised) factorial design. Adaptation to prolonged HFD increases maximal O2 uptake (VO2max; 13%, P less than 0.05) and submaximal running endurance (+64%, P less than 0.05). This enhancement in exercise capacity could be attributed to 1) an increase in skeletal muscle aerobic enzyme activities (3-hydroxyacyl-CoA dehydrogenase and citrate synthase in soleus and red quadriceps) or 2) a decrease in liver glycogen breakdown in response to 1 h exercise at 80% VO2max. When training is superimposed to HFD, the most prominent finding provided by this study is that the diet-induced effects are cumulative with the well-known training effect on VO2max, exercise endurance, oxidative capacity of red muscle, and metabolic responses to exercise, with a further reduction in liver glycogen breakdown.
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PMID:Additive effects of training and high-fat diet on energy metabolism during exercise. 191 43

Fast-twitch tibialis anterior muscle of the rabbit was subjected to chronic low-frequency (10 Hz, 10 h/day) stimulation for different time periods up to 28 days. Total cellular activities of carnitine:palmitoyl-CoA transferase, crotonase, 3-hydroxyacyl-CoA dehydrogenase, 3-keto-acyl-CoA thiolase, citrate synthase, NADH:cytochrome c oxidoreductase, succinate: cytochrome c oxidoreductase, and cytochrome c oxidase were measured in contralateral and stimulated muscles at various times. With the exception of crotonase, which increased only 1.6-fold after 28 days of stimulation, the other enzymes increased in parallel displaying 3-fold elevated absolute activities. These results, by supporting and extending our previous findings, indicate that the expression of the enzymes of the main metabolic systems of aerobic substrate oxidation, i.e. the citric acid cycle, the fatty acid oxidation and the respiratory chain, is regulated in a coordinate manner.
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PMID:Enzyme activities of fatty acid oxidation and the respiratory chain in chronically stimulated fast-twitch muscle of the rabbit. 194 50

The purpose of this study was to determine the extent to which functional demand regulates the biochemical character and enzyme capacities of the rat myocardium. Hearts from donor rats were heterotopically transplanted onto the abdominal aorta and inferior vena cava of isogenic recipients. The procedure results in a perfused but nonpumping heart that has a reduced heart rate (HR) and performs essentially no stroke work (SW). After 30 days, metabolic enzyme activities (phosphorylase, 6-phosphofructokinase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase) were significantly lower (40-60%) in the nonworking heart. Specific sarcoplasmic reticulum Ca2(+)-adenosinetriphosphatase (ATPase) activity was unchanged, but activity per gram of heart was 41% lower. Myosin isozymes were 58% V1, 21% V2, and 21% V3 in the nonworking heart compared with 100% V1 in the working heart. Myosin and myofibrillar ATPase activities each decreased by 28%. These findings suggest that both HR and SW play major and specific roles in regulating myocardial biochemical capacities and determining the myosin phenotype.
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PMID:Role of cardiac work in regulating myocardial biochemical characteristics. 214 21

Skeletal muscle has an inherent biochemical phenotypic plasticity that provides the possibility for it to be remodeled into a "heart-like" muscle for use in cardiac-assist devices. The purpose of this study was to chronically stimulate skeletal muscle electrically to transform the biochemical capacities of the three major subcellular systems (i.e., metabolic, calcium regulating, and contractile) to resemble those of heart muscle. The latissimus dorsi muscle (LDM) of mongrel dogs weighing 22-27 kg was stimulated via the thoracodorsal nerve at 2 Hz for 6-8 wk. This stimulation protocol reduced the phosphorylase (glycogenolytic) and phosphofructokinase (glycolytic) activities by 70%. The aerobic (citrate synthase activity) and fatty acid oxidative (3-hydroxyacyl-CoA dehydrogenase activity) capacities were not significantly increased by chronic stimulation and remained at about one-fourth those in the canine heart. The calcium-dependent sarcoplasmic reticulum adenosinetriphosphatase (ATPase) activity in the microsomal fraction, which was sixfold greater in the nonstimulated LDM than in the heart, was reduced by electrical stimulation to a level similar to that of the dog heart. The contractile capacity was evaluated by determining the percentage of types I and II fibers, the myofibrillar ATPase activity, and the proportion of myosin isoforms. The transformed muscle was comprised of 93 +/- 2% type I fibers, a myofibrillar ATPase activity similar to that in heart with primarily a slow-twitch muscle myosin isoform. In conclusion, electrical stimulation of canine LDM at 2 Hz for 6-8 wk resulted in two of the three biochemical systems, which confer physiological expression and fatigue resistance to muscle being transformed to resemble those of the myocardium.
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PMID:Biochemical transformation of canine skeletal muscle for use in cardiac-assist devices. 214 Aug 28

Nine bodybuilders performed heavy-resistance exercise activating the quadriceps femoris muscle. Intermittent 30-s exhaustive exercise bouts comprising 6-12 repetitions were interspersed with 60-s periods for 30 min. Venous blood samples were taken repeatedly during and after exercise for analyses of plasma free fatty acid (FFA) and glycerol concentration. Muscle biopsies were obtained from the vastus lateralis muscle before and after exercise and assayed for glycogen, glycerol-3-phosphate, lactate and triglyceride (TG) content. The activities of citrate synthase (CS), lactate dehydrogenase, hexokinase (HK), myokinase, creatine kinase and 3-hydroxyacyl-CoA dehydrogenase (HAD), were analysed. Histochemical staining procedures were used to assess fibre type composition, fibre area and capillary density. TG content before and after exercise averaged (SD) 23.9 (13.3) and 16.7 (6.4) mmol kg-1 dry wt. The basal triglyceride content varied sixfold among individuals and the higher the levels the greater was the change during exercise. The glycogen content decreased (P less than 0.001) from 690 (82) to 495 (95) mmol kg-1 dry wt. and lactate and glycerol-3-phosphate increased (P less than 0.001) to 79.5 (5.5) and 14.5 (7.3) mmol kg-1 dry wt., respectively, after exercise. The HK and HAD/CS content respectively correlated with glycogen or TG content at rest and with changes in these metabolites during exercise. FFA and glycerol concentrations increased slightly (P less than 0.001) during exercise. Lipolysis may, therefore, provide energy during heavy-resistance exercise of relatively short duration. Also, storage and utilization of intramuscular substrates appear to be influenced by the metabolic profile of muscle.
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PMID:Glycogen and triglyceride utilization in relation to muscle metabolic characteristics in men performing heavy-resistance exercise. 228 98

The histochemical, biochemical, and electrophysiological properties of selected muscles were evaluated in spontaneously hypertensive rats (SHR) and compared with their normotensive Wistar-Kyoto (WKY) counterparts. As early as 4 wk of age, slow muscles (soleus) of SHR displayed a significant alteration in fiber type distribution with a decrease of slow-twitch fibers (from 64 to 53%) and a simultaneous increase of type IIA-fibers (from 19 to 39%). In addition, soleus from young SHR had a significant enhancement of both oxidative (citrate synthase, 3-hydroxyacyl-CoA dehydrogenase) and glycolytic [lactate dehydrogenase (LDH)] capacities, which could be partly related to a capillary rarefaction. During development (from the 4th to the 12-14th wk), in the soleus muscle the histochemical differences between SHR and WKY were amplified, whereas most of the enzymatic differences between strains were abolished, except for a significantly higher LDH activity. These histochemical changes had only marginal repercussions on soleus electrophysiological properties. SHR animals had a significantly higher basal metabolic rate, which could not be accounted for by elevation of thyroid hormones. The origin of the slow-to-fast fiber type transition in slow muscle remains unclear but could be related to the increased level of plasma catecholamines in SHR. Indeed, chronic treatment of rats with a beta 2-receptor agonist has been reported to cause slow-to-fast muscle fiber transition [R. J. Zeman, R. Ludemann, T. G. Easton, and J. D. Etlinger. Am. J. Physiol. 254 (Endocrinol. Metab. 17): E726-E732, 1988].
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PMID:Evidence of a slow-to-fast fiber type transition in skeletal muscle from spontaneously hypertensive rats. 230 28

The purpose of this study was to investigate metabolic changes in equine muscle from birth to 1 yr of age. Duplicate biopsies from the middle portion of the gluteus medius were obtained from a depth of 2 cm beneath the superficial fascia at 1 day, 7 days, 1 mo, 3 mo, 6 mo, and 1 yr of age in 11 quarter horses and at 1 day, 3 mo, 6 mo, and 1 yr of age in 5 Standardbreds. Muscle enzyme activities determined were citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, phosphorylase, and lactate dehydrogenase. Percent fast-twitch, fast-twitch high oxidative, and slow-twitch oxidative fiber types were determined using succinate dehydrogenase and myosin adenosinetriphosphatase (pH 9.4) histochemical stains. Histochemically determined muscle fiber-type percents did not change dramatically with increasing age. However, lactate dehydrogenase activity increased threefold in quarter horses and twofold in Standardbreds, and phosphorylase activity increased sixfold in quarter horses and sevenfold in Standardbreds from 1 day to 6 mo of age. Citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities decreased during the first 3 mo of age in quarter horses.
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PMID:Changes in the metabolic profile of equine muscle from birth through 1 yr of age. 234 82

To study the metabolic and functional changes that occur during training with inspiratory flow resistive loads, a chronically instrumented unanesthetized sheep preparation was used. Sheep were exposed to resistances ranging from 50 to 100 cmH2O.l-1.s, for 2-4 h/day, 5-6 days/wk, for a total of 3 wk. Load intensity was adjusted to maintain arterial Po2 (PaO2) above 60 Torr and arterial PCO2 (PaCO2) below 45 Torr. Training produced significant (P less than 0.05) increases in citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, and cytochrome oxidase in the costal and crural diaphragm of the trained sheep (n = 9) compared with control sheep (n = 7). Phosphofructokinase did not increase. In the quadriceps, citrate synthase, 3-hydroxyacyl-CoA dehydrogenase, and phosphofructokinase did not change with training but cytochrome oxidase increased significantly (P less than 0.01). Function of the diaphragm was assessed in a subset of five sheep exposed to the same severe load 1 wk before and 2 days after the final training session. After training, sheep had a lower PaCO2 (10-40%), generated a higher transdiaphragmatic pressure (20-40%), and could sustain this level of transdiaphragmatic pressure for 0.5-2 h longer. The respiratory duty cycle was 10-15% lower, whereas minute ventilation and tidal volume were 20-30% higher in the posttraining test. We conclude that 1) training with inspiratory flow resistive loads improves the performance of the respiratory neuromuscular system and 2) the shift in enzyme profile of the diaphragm is at least in part responsible for this improvement.
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PMID:Metabolic and functional adaptation of the diaphragm to training with resistive loads. 254 Jan 38


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