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The effect of dietary vitamin E supplementation upon macrophage metabolism and function was examined in aged rats fed a balanced or a polyunsaturated-rich diet. The following parameters were studied: number of cells in the intraperitoneal cavity, maximal activity of hexokinase, citrate synthase, glucose-6-phosphate dehydrogenase, glutathione peroxidase and phosphate-dependent glutaminase. The consumption of glucose and the production of lactate, hydrogen peroxide and thiobarbituric reactive substances were measured in control ONCO-BCG injected rats. The results indicated that vitamin E has no significant effect on the values of the parameters studied in the macrophages of rats fed a balanced diet both for 3 (mature) or 17 months (aged). This antioxidant did not provoke any response on the changes caused by ageing the animals. However, several of the metabolic and functional alterations in macrophage induced by the polyunsaturated-rich diets were reversed by the inclusion of vitamin E in the diet. These changes were associated with macrophage migration capacity, citrate synthase and glucose-6-phosphate dehydrogenase activities and the content of lipid peroxides. The findings suggest that vitamin E has a beneficial effect for macrophage metabolism and function, but the effects are confined to particular circumstances.
Biochem Mol Biol Int 1994 Aug
PMID:Effect of dietary vitamin E supplementation on macrophage metabolism during ageing. Study in rats fed fat-rich diets during ageing. 784 17

Previous studies demonstrated that one of the most significant cellular responses of the rabbit urinary bladder to partial outlet obstruction is a 50% decrease in the activities of the mitochondrial enzymes citrate synthase and malate dehydrogenase, when calculated as either activity per unit mass or activity per mg protein. A major question arose from these studies: Are the mitochondrial enzyme activities per mitochondrion reduced, or is the number of mitochondria per unit tissue mass reduced? The current experiments were designed to study the sequential changes in the activities of mitochondrial oxidative enzymes following partial outlet obstruction. The activities of NADH-cytochrome c reductase (NCCR), cytochrome oxidase (CO), citrate synthase (CS) and malate dehydrogenase (MDH) were measured in whole tissue homogenates and in mitochondrial preparations of separated bladder mucosa and muscle, from normal bladders, and, from hypertrophied bladders at 1, 3, and 7 days following partial outlet obstruction. The results can be summarized as follows: 1) Whole tissue homogenates: Activities of all enzymes were reduced to approximately 50% of control at 1 day following partial outlet obstruction. NCCR and CO activities returned to 75 and 85% of control respectively by 7 days post-obstruction; CS activity did not show any significant recovery over the 7 day period. 2) Mucosal and smooth muscle mitochondrial preparations: Activities of all enzymes were decreased significantly by 50% or greater at 1 day following partial outlet obstruction. The cytochrome (NCCR and CO) enzyme activities returned to control levels by 7 days post-obstruction; CS activity showed only a minor recovery over this time period. These results show that mitochondrial enzyme activity is significantly impaired immediately following partial outlet outlet obstruction, and whereas the activity of the cytochrome enzymes NCCR and CO recover to control levels (in the mitochondrial preparations) within 7 days post obstruction, the Krebs cycle enzymes (CS and MD) show no significant recovery. Thus, the regulatory mechanisms for the cytochromes is significantly different from that for the enzymes of the krebs cycle.
Mol Cell Biochem 1994 Dec 07
PMID:Alterations of mitochondrial oxidative metabolism in rabbit urinary bladder after partial outlet obstruction. 787 5

A cDNA clone for glyoxysomal citrate synthase (gCS) was isolated from a lambda gt11 cDNA library prepared from etiolated pumpkin cotyledons. The cDNA of 1989 bp consisted of a 1548 bp open reading frame that encoded 516 amino acid residues. The deduced amino acid sequence of gCS did not have a typical peroxisomal targeting signal at its carboxyl terminal. A study of expression in vitro of the cDNA and an analysis of the amino-terminal sequence of the citrate synthase indicated that gCS is synthesized as a larger precursor that has a cleavable amino-terminal presequence of 43 amino acids. The predicted amino-terminal sequence of pumpkin gCS was highly homologous to those of other microbody enzymes, such as 3-ketoacyl-CoA thiolase of rat and malate dehydrogenase of watermelon that are also synthesized as precursors of higher molecular mass. Immunoblot analysis showed that the level of gCS protein increased markedly during germination and decreased rapidly during the light-induced transition of microbodies from glyoxysomes to leaf peroxisomes. By contrast, the level of mRNA for gCS reached a maximum earlier than that of the protein and declined even in darkness. The level of the mRNA was low during the microbody transition. These results indicate that the accumulation of the gCS protein does not correspond to that of the mRNA and that degradation of gCS is induced during the microbody transition, suggesting that post-transcriptional regulation plays an important role in the microbody transition.
Plant Mol Biol 1995 Jan
PMID:Molecular characterization of a glyoxysomal citrate synthase that is synthesized as a precursor of higher molecular mass in pumpkin. 788 26

The purpose of this study was to investigate whether vitamin D3 deficiency and 1,25-dihydroxyvitamin D3 treatment affect some aspects of heart metabolism in the rat. To this end, five experimental groups were studied: (1) the control group of the vitamin D3 supplemented rats (Group A); (2) rachitic rats (Group B); (3) rachitic rats treated with 1,25-dihydroxyvitamin D3 (Group C); (4) rats fed a vitamin D-deficient diet (Group D); (5) rats fed a vitamin D-deficient diet and treated with 1,25-dihydroxyvitamin D3 (Group E). The five groups were compared by checking in the heart some metabolic parameters, i.e. citrate content, and enzyme activities in cytosol and mitochondria. Citrate content was higher in the heart of treated animals when compared with the control. As regards the enzymatic activities in heart mitochondria, NAD(+)-dependent isocitrate dehydrogenase remarkably decreased in Group B rats and 1,25-dihydroxyvitamin D3 restored quite normal values. NADP(+)-dependent isocitrate dehydrogenase decreased in Group B and Group D animals, and 1,25-dihydroxyvitamin D3 treatment was effective in restoring control values. Cytochrome c oxidase activity did not change, while citrate synthase showed an increase in all the treated rats. As regards the cytosolic enzymes, fructose-6-phosphate kinase increased in the two groups of vitamin D-deplete rats in comparison with the control. Glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase showed a similar trend: an increase in all the treated animals. In heart homogenate, acylphosphatase and acid phosphatase activities were also determined. Acylphosphatase increased in the treated rats, while acid phosphatase decreased in the rats injected with 1,25-dihydroxyvitamin D3. These results support the hypothesis of a participation of 1,25-dihydroxyvitamin D3 in some aspects of heart metabolism.
J Mol Cell Cardiol 1994 Nov
PMID:Effect of vitamin D deficiency and 1,25-dihydroxyvitamin D3 on rat heart metabolism. 789 66

We have isolated the cDNA and corresponding genomic DNA encoding citrate synthase in Neurospora crassa. Analysis of the protein coding region of this gene, named cit-1, indicates that it specifies the mitochondrial form of citrate synthase. The predicted protein has 469 amino acids and a molecular mass of 52,002 Da. The gene is interrupted by four introns. Hybridization experiments show that a cit-1 probe binds to two different fragments of genomic DNA, which are located on different chromosomes. Neurospora crassa may have two isoforms of citrate synthase, one in the mitochondria and the other in microbodies.
Mol Gen Genet 1994 Jan
PMID:Characterization of the cit-1 gene from Neurospora crassa encoding the mitochondrial form of citrate synthase. 790 43

The yeast nuclear gene CIT1 encodes mitochondrial citrate synthase, which catalyses the first and rate-limiting step of the tricarboxylic acid (TCA) cycle. Transcription of CIT1 is subject to glucose repression. Mutations in HAP2, HAP3 or HAP4 block derepression of a CIT1-lacZ gene fusion. The HAP2,3,4 transcriptional activator also activates nuclear genes encoding components of the mitochondrial electron transport chain, and thus it co-ordinates derepression of two major mitochondrial functions. Two DNA sequences resembling the consensus HAP2,3,4-binding site (ACCAATNA) are located at approximately -310 and -290, upstream of the CIT1 coding sequence. Deletion and mutation analysis indicates that the -290 element is critical for activation by HAP2,3,4. Glucose-repressed expression of CIT1 is largely independent of HAP2,3,4, is repressed by glutamate, and requires a DNA sequence between -367 and -348. Evidence is presented for a second HAP2,3,4-independent activation element located just upstream and overlapping the -290 HAP2,3,4 element.
Mol Microbiol 1994 Jul
PMID:The HAP2,3,4 transcriptional activator is required for derepression of the yeast citrate synthase gene, CIT1. 798 86

Rhizobium species elicit the formation of nitrogen-fixing root nodules through a complex interaction between bacteria and plants. Various bacterial genes involved in the nodulation and nitrogen-fixation processes have been described and most have been localized on the symbiotic plasmids (pSym). We have found a gene encoding citrate synthase on the pSym plasmid of Rhizobium tropici, a species that forms nitrogen-fixing nodules on the roots of beans (Phaseolus vulgaris) and trees (Leucaena spp.). Citrate synthase is a key metabolic enzyme that incorporates carbon into the tricarboxylic acid cycle by catalysing the condensation of acetyl-CoA and oxaloacetic acid to form citrate. R. tropici pcsA (the plasmid citrate synthase gene) is closely related to the corresponding genes of Proteobacteria. pcsA inactivation by a Tn5-mob insertion causes the bacteria to form fewer nodules (30-50% of the original strain) and to have a decreased citrate synthase activity in minimal medium with sucrose. A clone carrying the pcsA gene complemented all the phenotypic alterations of the pcsA mutant, and conferred Rhizobium leguminosarum bv. phaseoli (which naturally lacks a plasmid citrate synthase gene) a higher nodulation and growth capacity in correlation with a higher citrate synthase activity. We have also found that pcsA gene expression is sensitive to iron availability, suggesting a possible role of pcsA in iron uptake.
Mol Microbiol 1994 Jan
PMID:Nodulating ability of Rhizobium tropici is conditioned by a plasmid-encoded citrate synthase. 817 Mar 93

The aim of this work was to study in the adult rat heart the effect of modifications of fatty acid (FA) supply on the content of cytoplasmic fatty acid-binding protein (H-FABPc). To modify the amount of circulating lipids, three different treatments were chosen: (i) an hypolipidemic treatment with Clofibrate, administered daily through a gastric tube at a dose of 250 mg/kg per day for one week, (ii) a continuous intravenous infusion of 20% Intralipid, a fat emulsion, for one week at a dose of 96 ml/kg per day, and (iii) a normobaric hypoxia exposure (pO2 = 10%) for three weeks. At the end of each treatment plasma lipids, myocardial H-FABPc content and the activities of three key enzymes (citrate synthase, CS, fructose-6-phosphate kinase, FPK and hydroxy-acyl CoA-dehydrogenase, HAD) were assessed. With each of the three treatments a decrease of plasma cholesterol and phospholipid levels was observed. Plasma FA concentration increased with Intralipid infusion and decreased with chronic hypoxia. The heart H-FABPc content was increased by 20% with Clofibrate, decreased by 20% with chronic hypoxia and remained unaltered upon Intralipid treatment. The induced changes in H-FABPc content were not related directly to changes in plasma lipid levels. CS activity was slightly decreased in the hypoxia group, FPK activity decreased in the Clofibrate group, and HAD activity decreased in the Intralipid group. Among the various groups heart H-FABPc content was related to HAD activity. In conclusion, the H-FABPc content of adult rat heart appears responsive to changes in plasma lipid levels.
Mol Cell Biochem
PMID:Modulation of fatty acid-binding protein content of adult rat heart in response to chronic changes in plasma lipid levels. 823 51

Since insect flight muscles are among the most active muscles in nature, their extremely high rates of fuel supply and oxidation pose interesting physiological problems. Long-distance flights of species like locusts and hawkmoths are fueled through fatty acid oxidation. The lipid substrate is transported as diacylglycerol in the blood, employing a unique and efficient lipoprotein shuttle system. Following diacyglycerol hydrolysis by a flight muscle lipoprotein lipase, the liberated fatty acids are ultimately oxidized in the mitochondria. Locusta flight muscle cytoplasm contains an abundant fatty acid-binding protein (FABP). The flight muscle FABP of Locusta migratoria is a 15 kDa protein with an isoelectric point of 5.8, binding fatty acids in a 1:1 molar stoichiometric ratio. Binding affinity of the FABP for long-chain fatty acids (apparent dissociation constant Kd = 5.21 +/- 0.16 microM) is however markedly lower than that of mammalian FABPs. The NH2-terminal amino acid sequence shares structural homologies with two insect FABPs recently purified from hawkmoth midgut, as well as with mammalian FABPs. In contrast to all other isolated FABPs, the NH2 terminus of locust flight muscle FABP appeared not to be acetylated. During development of the insect, a marked increase in fatty acid binding capacity of flight muscle homogenate was measured, along with similar increases in both fatty acid oxidation capacity and citrate synthase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem
PMID:Role of fatty acid-binding protein in lipid metabolism of insect flight muscle. 823 56

Recent studies indicate that the mucosa of the urinary bladder may play a major role in the maintenance of normal bladder function. The mucosal surface of the urinary bladder serves as a protective layer against the irritative solutes found in the urine. The integrity of this barrier can be broken by overdistension, anoxia, detergents, alcohols, bacterial infection and by contact with agents to which the mucosa has been sensitized. In view that both anoxia and ischemia can mediate a breakdown in the role of the mucosal layer as a permeability barrier, it is reasonable to assume that this function is dependent on cellular metabolism. As an initial investigation we have compared a variety of biochemical and metabolic parameters between the mucosal layer (consisting of the lamina propria, urothelium, and any connective tissue and vascular tissue within this layer); and the muscularis layer. The results of these studies demonstrated that the rate of glucose metabolism to lactic acid (LA) of the mucosa was more than three-fold greater than that of the smooth muscle. The rate of CO2 production of the mucosa was 60% greater than that of the unstimulated smooth muscle. The maximal activity of the mitochondrial enzyme citrate synthase was significantly greater in the mucosa than in the smooth muscle, however, the activity of malate dehydrogenase was similar for both tissues. The maximal activity of the cytosolic enzyme creatine kinase was more than two-fold greater in the bladder smooth muscle than in the mucosa; although the affinities of the creatine kinase isoforms of the mucosa were significantly greater than those of the muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1993 Aug 11
PMID:Metabolic studies on rabbit bladder smooth muscle and mucosa. 826 70


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