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

---

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

Disuse (inactivity, bed rest, and spaceflight) may lead to a loss of muscle mass and a decrease in oxidative capacity in skeletal muscle. If such changes were to occur in hibernating animals, both locomotor and thermogenic function would be compromised. Muscle masses and oxidative capacities (as assessed by citrate synthase activity) were measured in the gastrocnemius and semitendinosus muscles, cardiac muscle (ventricle), and brown fat (axillary pad) in a group (n = 7) of prehibernating ground squirrels (Spermophilus lateralis) and after 6 mo of hibernation (n = 8). Hibernation produced significant atrophy in the gastrocnemius (14%) and semitendinosus (42%) muscles. Cardiac tissue increased (21%) in mass, as did brown adipose tissue (150%). That such changes were not due simply to fluid shifts was evidenced by similar protein concentrations between groups. In contrast to many other disuse studies, oxidative capacity was increased significantly in the gastrocnemius (65%) and semitendinosus (37%). Citrate synthase was also higher in cardiac tissue of hibernators (20%) but was not significantly different in brown fat.
...
PMID:Disuse atrophy in the hibernating golden-mantled ground squirrel, Spermophilus lateralis. 195 70

The effects of added load (20% of body mass) on the selected enzyme activities of red and white quadriceps femoris (QF), soleus, and gastrocnemius muscles of rats were studied. The rats were divided into sedentary control (SC), sedentary control with added load (SC+AL), endurance training (ET), and endurance training with added load (ET+AL) groups (n = 10 rats/group). After 6 wk, the SC+AL group had 57% higher (P less than 0.001) beta-glucuronidase (beta-GU) activity and 24% lower (P less than 0.05) citrate synthase activity in white QF than SC. Citrate synthase activity was also decreased in red QF (P less than 0.05) after the added load was used during nontraining hours. The training with added load induced similar but more pronounced changes than normal endurance training, especially in white QF. The ET+AL group demonstrated higher citrate synthase activity in white QF (P less than 0.001) and gastrocnemius (P less than 0.01) and higher malate dehydrogenase activity (P less than 0.05) and beta-GU activity (P less than 0.001) in white QF than the ET group. ET+AL rats also had higher phosphofructokinase (P less than 0.01) and lower creatine kinase (P less than 0.001) activity in white QF than ET rats. In conclusion, the added load without training had minor adaptive influences on muscles. The added load during training hours seemed to be an effective means of influencing the activation and adaptation in muscles that contain fast glycolytic fibers.
...
PMID:Muscle enzyme adaptations to added load during training and nontraining hours in rats. 202 68

This study examined the effects of a short-term sudden increment in training load on the oxidative capacity, glycogen content and tension-generating ability of rat skeletal muscle. After training on a treadmill 5 dwk-1 for 9 wk (30 m.min-1 6 degrees, 60 min.d-1), rats were randomly divided into a normal training volume (NTV) group (N = 11) and an increased training volume (ITV) group (N = 8). The NTV group were sacrificed 24 h after the last bout of exercise, while the ITV group continued to train for further 6 successive days. Training duration for this latter group was increased to 120 min.d-1 for the first 2 d; 240 min.d-1 for the next 2 d; and 360 min.d-1 for the final 2 d; speed and grade were kept constant. Respiratory capacity (QO2) and citrate synthase activity were increased (P less than 0.05) in both the soleus and plantaris muscles, with no change in the white vastus lateralis muscle of the NTV group when compared to age- matched sedentary controls. Glycogen levels were unchanged in these muscles, but liver glycogen content was greater (231.9 +/- 10.1 vs 156.8 +/- 15.3 umol.g-1 w.w. for the NTV vs age-matched sedentary controls, respectively, P less than 0.05). Peak tetanic tension in the gastrocnemius was not changed by training, or the increased training load. Citrate synthase activity (umol.min-1.g-1) was significantly greater (P less than 0.05) in the plantaris (33.3 +/- 1.0 vs 27.0 +/- 1.7) and soleus muscles (40.5 +/- 2.7 vs 28.4 +/- 1.3) in the ITV vs NTV groups.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Effects of increased training volume on the oxidative capacity, glycogen content and tension development of rat skeletal muscle. 228 88

This study investigates the effects of physiological increments in plasma thyroxine (T4) at three levels of biological organization in thyroid-intact and thyroidectomized captive western fence lizards, Sceloporus occidentalis. Two doses of T4-loaded pellets elevated plasma T4 in thyroid-intact lizards from 4.8 +/- 0.47 to 10.7 +/- 2.25 and 20.4 +/- 5.77 ng/ml (mean +/- SE). Surgical thyroidectomy reduced T4 to 1.8 +/- 0.23 ng/ml, and subsequent T4 pellet implantation raised T4 to 14.8 +/- 4.30 ng/ml. Minimal resting metabolic rate (= standard metabolic rate; SMR), a common organismal metric of thyroid perturbation, was reduced 31% (P less than 0.0001) by thyroidectomy and was restored by T4 replacement but was not stimulated by T4 supplementation in thyroid-intact lizards. In T4-replaced, thyroidectomized lizards, SMR was significantly correlated with plasma T4 (r2 = 0.626, P = 0.003, n = 11). At the organ level, liver mass was not changed by any treatment; heart mass was decreased by thyroid deficiency and restored by T4 replacement. At the molecular level, citrate synthase activity was significantly reduced by thyroidectomy and was returned to control levels by T4 replacement in liver and skeletal muscle (gastrocnemius) but was not changed in cardiac muscle. Citrate synthase was not affected in any tissue by T4 supplementation in thyroid-intact lizards. Pyruvate kinase activity was not affected by any of the treatments in any of the tissues. Cytosolic alpha-glycerophosphate dehydrogenase was significantly reduced in liver by all treatments and in skeletal muscle by T4 replacement after thyroidectomy. These results indicate that SMR and cardiac muscle mass in lizards are dependent on normal thyroid function and are expressed maximally in euthyroid animals. The stimulatory effect of T4 on SMR in thyroid-intact lizards, which has been reported previously by several investigators, is a nonphysiological response to pharmacological T4 levels, at least in these captive lizards. Molecular responses are tissue and enzyme dependent and cannot be generalized. Pellet implantation is an effective means of inducing physiological increments in plasma T4 and should replace previously used injection protocols. This new method can be used in capture-recapture experiments involving field-active lizards.
...
PMID:Thyroid regulation of resting metabolic rate and intermediary metabolic enzymes in a lizard (Sceloporus occidentalis). 229 23

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.
...
PMID:Changes in the metabolic profile of equine muscle from birth through 1 yr of age. 234 82

Citrate synthase catalyzes the slow condensation of acetyldithio-CoA [Ac(= S)CoA] with oxalacetate to form thiocitrate [Wlassics, I.D., Stille, C., & Anderson, V.E. (1988) Biochim. Biophys. Acta 952, 269]. During the transient approach to steady state an observable amount of the dithioester absorbance disappears. The amplitude of the decrease in absorbance corresponds to 0.32, 0.03, and 0.02 enzyme equiv at pH 8.3, 7.5, and 6.6, respectively. The difference spectra from before and after the transient exhibit the dithioester lambda max at 306 nm. Acid quenching of a stiochiometric reaction between Ac(= S)CoA and citrate synthase following the transient quantitatively regenerates Ac(= S)CoA, indicating carbon-carbon bond formation had not yet occurred. The apparent first-order rate constant of the transient is independent of Ac(= S)CoA concentration and increases with decreasing pH, being 0.007, 0.016, and 0.04 s-1 at pH 8.3, 7.5, and 6.6, respectively. 2-Fluoroacetyldithio-CoA is a better inhibitor of citrate synthase, Ki = 300 nM, and substrate, Vmax = 2 X 10(-3) s-1, than Ac(= S)CoA. 1H NMR experiments indicate that citrate synthase catalyzes the exchange of the alpha-hydrogens of Ac(= S)CoA with turnover numbers of 0.13 and 0.54 s-1 at pD 7.9 and 7.2, respectively. Analysis of the proton and deuterium decoupled 13C NMR spectra of [2-13C]Ac(= S)CoA that has exchanged 37% of the alpha-hydrogens in the presence of citrate synthase indicates that the relative proportions of CH3, CH2D, CHD2, and CD3 were 0.29, 0.39, 0.25, and 0.07, respectively. This statistical distribution indicates each exchange event is independent. The data indicate that citrate synthase stabilizes the ionized form of Ac(= S)CoA by 5 kcal/mol relative to the un-ionized form, that the ionized dithioester is on the reaction pathway, and that below pH 8.3 the slow carbon-carbon bond forming reaction is responsible for the 10(6) decrease in Vmax caused by substituting sulfur for oxygen in the thioester carbonyl.
...
PMID:Citrate synthase stabilizes the enethiolate of acetyldithio coenzyme A. 271 24

Cultured renal collecting duct cells from neonatal rabbit kidney were used to examine the influence of aldosterone on enzymatic activity of citrate synthase during increase in Na+ transport. Control epithelia showed citrate synthase activity of 71 +/- 3 mU/mg protein (n = 28), while after aldosterone treatment citrate synthase activity was significantly increased to 79 +/- 6 mU/mg at 1 h (n = 5), to 88 +/- 6 mU/mg at 2 h (n = 6) and to 93 +/- 8 mU/mg protein at 3 h (n = 5). Citrate synthase activity subsequently decreased to basal values. Spironolactone fully blocked the aldosterone-induced increase in citrate synthase activity. The time course of enzyme stimulation after aldosterone administration indicates that the hormone activates citrate synthase during the physiological early response phase.
...
PMID:Action of aldosterone on citrate synthase in cultured renal collecting duct cells. 276 67

Biopsies from m. quadriceps femoris from the operated leg of nine patients were taken before, and 6 weeks after, knee surgery. During the whole postoperative period the operated leg was immobilized with the knee in 40-50 degrees of flexion. Myoglobin (MYO) and the enzymes citrate synthase (CS), creatine kinase (CK) and its isozymes MB (CK-MB) and mitochondrial CK (CK-MIT), aspartate aminotransferase (ASAT), phosphofructokinase (PFK) and lactate dehydrogenase (LD) were determined on the biopsies. Citrate synthase, ASAT, CK, CK-MB, CK-MIT and LD activities were decreased (12-30%) after the postoperative leg immobilization period. Phosphofructokinase did not change, while MYO content was increased (16%). In conclusion, a different control of the synthesis of oxidative enzymes and MYO is suggested, as the induced changes following immobilization were in opposite directions. The function of the increased MYO content may be to facilitate the oxygen extraction.
...
PMID:Increase in myoglobin content and decrease in oxidative enzyme activities by leg muscle immobilization in man. 297 30

Whole-body hypokinetic-hypodynamic (H/H) suspension, unlike other models of muscle disuse, allows voluntary contractile activity. This study examined the oxidative capacity and insulin sensitivity of rat hindlimb muscles subjected to 7 days of suspension H/H conditions. Oxidative capacity was determined by measuring citrate synthase activity and cytochrome c concentration in soleus and gastrocnemius muscles. A perfused hindquarter preparation was used to measure glucose uptake rates at rest with physiological and supramaximal concentrations of insulin in the perfusate. Citrate synthase activity was 17% lower in soleus and 23% lower in gastrocnemius muscles from H/H rats. Similarly, a 29% decrease in H/H rat gastrocnemius cytochrome c concentration was observed. Rates of glucose uptake were lower in muscles from H/H rats compared with controls at physiological levels of insulin and did not increase in response to a further increase in insulin concentration. Muscles undergoing a significant loss in mass after 7 days suspension were found to have increased glycogen concentrations. In conclusion, data presented in this study suggest that hindlimb muscle disuse, brought about by whole-body suspension, results in a decreased aerobic capacity in load bearing muscles and a lowered insulin sensitivity in perfused rat hindlimb muscles.
...
PMID:Effect of hypokinesia-hypodynamia on rat muscle oxidative capacity and glucose uptake. 299 97

In the present study the effects of chronic administration of dextroamphetamine on energy metabolism in the brain of the rat were examined. The enzymes studied were: hexokinase (soluble and particulate forms), phosphofructokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase, NAD+ and NADP+-dependent isocitrate dehydrogenases, succinate dehydrogenase and malate dehydrogenase. All the activities of the enzymes were assayed in four regions of the brain of the rat (cerebellum, medulla oblongata and pons, cererbral cortex and diencephalon). Rats were injected intaperitoneally once daily with dextroamphetamine for 20 consecutive days. The initial dose was 5 mg/kg/day and the dose was then increased by 1 mg/kg/every 5 days up to a total of 8 mg/kg/day on days 16-20. In the glycolytic enzymes a reduction of the activity of phosphofructokinase was found in the diencephalon and an increase of the activity of pyruvate kinase and lactate dehydrogenase in the diencephalon and medulla oblongata and pons, respectively. Citrate synthase was the only enzyme in the Krebs' cycle affected by chronic administration of dextroamphetamine. The results presented here show that chronic administration of dextroamphetamine produced important changes in some enzymes of glycolysis and the Krebs' cycle in the brain of the rat.
...
PMID:Effects of chronic administration of dextroamphetamine on enzymes of energy metabolism in regions of the rat brain. 303 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---