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)

Muscle homogenates representing slow-twitch oxidative, fast-twitch oxidative-glycolytic, fast-twitch glycolytic, and mixed fiber types were prepared from normal, diabetic, and insulin-treated diabetic rats. Diabetes was induced by injection of 80 mg . kg-1 of streptozotocin. The activities of citrate synthase, succinate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase were employed as markers of oxidative potential, whereas phosphorylase, hexokinase, and phosphofructokinase activities were used as an indication of glycolytic capacity. Diabetes was associated with a general decrement in the activity of oxidative marker enzymes for all fiber types except the fast-twitch glycolytic fiber. In contrast, the fast-twitch glycolytic fibers demonstrated the greatest decline in glycolytic enzymatic activity. Insulin-treated animals, either trained or untrained, exhibited enzyme activities similar to their normal counterparts. Exercise training of diabetic rats mimicked the effect of insulin treatment and caused a near normalization of the activity of the marker enzymes. These findings suggest that the enzymatic potential of all skeletal muscle fiber types of diabetic rats may be normalized by exercise training even in the absence of significant amounts of insulin.
...
PMID:Influence of training on skeletal muscle enzymatic adaptations in normal and diabetic rats. 293 94

Concentrations of high-energy phosphates and activities of key enzymes of energy metabolism were assessed in hearts from species with differing levels of cardiac power output. Positive correlations were found between resting power output and the total adenylate pool and between citrate synthase activity and the total adenylate pool. Maximum in vitro activity levels of enzymes from energy metabolism were compared with calculated resting cardiac power output and maximal cardiac power output (as reflected by total oligomycin-insensitive adenosine-triphosphatase activity). Three indexes of carbohydrate metabolism (hexokinase, pyruvate kinase, and L-lactate dehydrogenase) all plateau at relatively low levels of energy demand. In contrast, enzymes required for aerobic fatty acid metabolism, (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) and for tricarboxylic acid and electron transport (citrate synthase and cytochrome-c oxidase) show consistent increases as ATP demand is elevated. It appears that as capacity for power development by vertebrate hearts, increases across taxa, the elevated demand for ATP is met by expansion of fatty acid based aerobic metabolism and not carbohydrate metabolism.
...
PMID:Matching of vertebrate cardiac energy demand to energy metabolism. 295 61

The main purpose of the present study was to test the hypothesis that adrenergic stimulation of muscle fibres during exercise is a major stimulus for the training-induced enhancement of skeletal muscle respiratory capacity. Therefore, Sprague-Dawley rats either underwent bilateral surgical ablation of the adrenal medulla or were sham-operated. Furthermore, unilateral surgical extirpation of the lumbar sympathetic chain was performed. Half of the rats were then trained for 12 weeks by swimming (up to 5.5 h X day-1, 4 days X week-1) and the remaining rats were sedentary controls. In the gastrocnemius muscle, training significantly increased the mitochondrial enzymes citrate synthase, succinate dehydrogenase, cytochrome c oxidase, and 3-hydroxyacyl-CoA dehydrogenase. In sham-operated rats, the increases were 40%, 43%, 66%, and 25%, respectively, in legs with intact sympathetic innervation. The training-induced enzyme adaptation after adrenodemedullation and/or sympathectomy was not significantly lower than these control values. In sham-operated rats, training decreased resting plasma insulin and glucagon levels and increased liver glycogen content. Similar changes were induced by adrenodemedullation, but training did not augment these changes in adrenodemedullated rats. In conclusion, the data suggest that neither adrenomedullary hormones nor local sympathetic nerves are prerequisites for the training-induced increase in muscle mitochondrial enzymes. The training-induced decline in resting plasma insulin and glucagon levels in intact rats may be mediated by adrenomedullary hormones.
...
PMID:Skeletal muscle and hormonal adaptation to physical training in the rat: role of the sympatho-adrenal system. 298 95

Enzyme activities related to aerobic metabolism and cyclic nucleotides were evaluated in muscle and nonmuscle cells of rat heart. The perinatal period from weaning to adult was studied. Malate dehydrogenase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase activities of nonmuscle cells equal or exceed muscle cell activities in the weanling heart. Aerobic enzymes remain unchanged in nonmuscle cells during growth; however, muscle cell activities are enhanced. Adenylate cyclase and guanylate cyclase activities are higher in heart homogenates of weanling than adult rats. Despite elevated adenylate cyclase activity, cyclic AMP levels are identical in weanling and adult rats. Cyclic GMP levels are twofold higher in weanling than in adult rats. Muscle cell metabolism and cyclic nucleotide levels are associated with growth-related changes in heart function and cellularity, respectively.
...
PMID:Metabolic and cyclic nucleotide enzyme activities in muscle and nonmuscle cells of rat heart during perinatal development. 298 18

It has been reported that the mitochondrial cytochromes and citrate cycle enzymes occur in constant proportions to each other and increase or decrease roughly in parallel in response to various stimuli. The purpose of this study was to determine whether this proportionality is an obligatory consequence of the way in which mitochondria are assembled. Severe iron deficiency was used to bring about decreases of the iron-containing constituents of the mitochondrial respiratory chain in skeletal muscle. Cytochrome c concentration and cytochrome oxidase activity were decreased approximately 50%, while succinate dehydrogenase and NADH dehydrogenase activities were decreased by 78% in iron-deficient muscle. On electron microscopic examination, mitochondria in iron-deficient muscles had relatively sparse numbers of cristae. The iron deficiency had little or no effect on the levels of a range of mitochondrial matrix enzymes, including citrate synthase, isocitrate dehydrogenase, fumarase, aspartate aminotransferase, 3-hydroxyacyl-CoA dehydrogenase, 3-ketoacid-CoA transferase, and acetoacetyl-CoA thiolase. These results show that the usual constant proportions between the constituents of the mitochondrial respiratory chain and matrix enzymes are not obligatory; they provide evidence that mitochondrial matrix enzymes and respiratory chain constituents can be incorporated into mitochondria independently and that the ratios between them can vary within wide limits.
...
PMID:Perturbation of mitochondrial composition in muscle by iron deficiency. Implications regarding regulation of mitochondrial assembly. 302 53

Tibialis anterior (TA) muscle of mouse, rat, guinea pig, and rabbit was indirectly stimulated for 10 h/day at 10 Hz up to 28 days. Changes in the activity levels of hexokinase (HK), phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH), creatine kinase (CK), citrate synthase (CS), malate dehydrogenase (MDH), 3-hydroxyacyl-CoA dehydrogenase (HADH), and beta-hydroxybutyrate dehydrogenase (HBDH) were compared. Although the direction of changes in the enzyme activity pattern was in accordance with previous findings on rabbit TA, the magnitude of the responses varied markedly between the mammals under study. Mouse TA was almost unaffected. A major effect of chronic stimulation in rat, guinea pig and rabbit was an increase in enzyme activities of aerobic-oxidative metabolism. According to intrinsic differences of the muscles under study, the increases varied among the species and appeared to be inversely related to the basal levels of these enzymes in the unstimulated muscles. Conversely, glycolytic enzyme activities (PFK, GAPDH, LDH) markedly decreased in rat, guinea pig, and rabbit, and were only slightly reduced in mouse. Changes in HK and HBDH activities displayed the largest variations in the induced change between species. These results indicate species-specific patterns of metabolic adaptation to increased contractile activity.
...
PMID:Species-specific effects of chronic nerve stimulation upon tibialis anterior muscle in mouse, rat, guinea pig, and rabbit. 317 88

Oxygen consumption was measured before and during infusion of the catecholamine isoproterenol in age-matched spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive rats. Mass-independent rates of oxygen consumption of anesthetized 7-week-old rats were similar in the WKY and SHR rats (11.08 +/- 0.74 and 11.33 +/- 0.82 ml O2 min-1 kg-.67, respectively). Catecholamine infusion elicited increased total oxygen consumption in both WKY and SHR animals (15.0 +/- 1.0 and 14.9 +/- 1.2 ml O2 min-1 kg-.67, respectively), and the magnitude of these increases did not significantly differ. To assess whether there were changes in the metabolic state of brown adipose tissue, the major site of catecholamine-induced thermogenesis in rats, enzymes whose activity is proportional to aerobic capacity were assayed in vitro. In both the interscapular and cervical brown fat depots, maximal citrate synthase and maximal HOAD (beta-hydroxyacyl-CoA dehydrogenase) activities were similar in SHR and WKY rats. There were also no significant differences in brown fat protein content, suggesting no differential growth of this tissue in the two rat strains. Our results indicate that the nonshivering thermogenic capacity of the hypertensive SHR rats does not differ from that of the normotensive WKY animals.
...
PMID:Nonshivering thermogenesis and brown fat in spontaneously hypertensive rats. 342 Jan 7

Young rats maintained on an iron-deficient diet developed severe anemia and had large decreases in the levels of the iron-containing flavoproteins and cytochromes of the mitochondrial respiratory chain in skeletal muscle. In contrast, the levels of a number of mitochondrial matrix marker enzymes, including citrate synthase, isocitrate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase, 3-ketoacid-CoA transferase, and aspartate aminotransferase, increased in red skeletal muscle but not in white muscle. Phosphocreatine concentration was decreased and inorganic phosphate concentration was increased in soleus muscle frozen in situ. We hypothesize that the increase in mitochondrial matrix enzymes reflects a stimulus to mitochondrial biogenesis in posture-maintaining and weight-bearing red muscle fibers in severely iron-deficient rats. It is our working hypothesis that this stimulus to mitochondrial biogenesis arises from mild activity of the red fibers and is due to the same perturbation in cellular homeostasis that is normally caused by vigorous exercise or hypoxia. In iron deficiency, the stimulus to mitochondrial biogenesis can induce an increase in only those enzymes not prevented from increasing by iron deficiency, resulting in formation of mitochondria of grossly abnormal composition.
...
PMID:Induction of an increase in mitochondrial matrix enzymes in muscle of iron-deficient rats. 347 8

Old rats have a decreased hindlimb muscle respiratory capacity and whole-body maximal O2 consumption (VO2 max). The decline in spontaneous physical activity in old rats might contribute to these age-related changes. The magnitude of the age-related decline is not uniform in all skeletal muscle respiratory enzymes, and the decrease in palmitate oxidation is particularly great. This study was designed to determine if young and old rats subjected to the same exercise-training protocol would attain similar values for VO2 max and several markers of muscle respiratory capacity. Four- and 18-mo-old Fischer 344 rats underwent an identical 6-mo program of treadmill running. After training, both age groups had increased VO2 max above sedentary age-matched controls. However, the old trained rats had a lower VO2 max than identically trained young rats. In contrast to VO2 max, the two trained groups attained similar values for gastrocnemius citrate synthase, cytochrome oxidase, 3-hydroxyacyl-CoA dehydrogenase, palmitate oxidation, and total carnitine concentration. Thus, when the young and old rats performed an identical exercise protocol within the capacity of the old animals, differences in skeletal muscle respiratory capacity were eliminated. The dissimilarity in VO2 max between the identically trained groups was apparently caused by age-related differences in factors other than muscle respiratory capacity.
...
PMID:Muscle respiratory capacity and VO2 max in identically trained young and old rats. 362 29

The purpose of this study was to investigate alterations in structural and functional properties in the soleus (SOL) and extensor digitorum longus (EDL) muscles of rats after 1, 2, and 5 wk of tail suspension. Maximal O2 uptake was 19% lower after 5 wk suspension. Loss of muscle mass was greater in SOL (63%) than in EDL (22%) muscle. A reduction of type I distribution was accompanied by an increase of intermediate fiber subgroups (int I in SOL, int II in EDL). The cross-sectional area of all three fiber types was reduced by hypokinesia. The decrease in capillaries per fiber in SOL was greater than the decrease in citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities after 5 wk. No alteration in lactate dehydrogenase activity was noted. In EDL, no changes in fiber area, capillarization, and enzymatic activities occurred. Energy charge remained unchanged (0.91) whatever the muscle. These results suggest that type I fibers showed an earlier and greater susceptibility than type II fibers to suspension which is also accompanied by a decreased aerobic capacity.
...
PMID:Structural and functional responses to prolonged hindlimb suspension in rat muscle. 365 14


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

---