Effect of substrates of glycolysis and tricarboxylic acid cycle on the level of oxidative processes in spermatozoa of grass carp and carp

Endogenic respiration of grass carp and carp spermatozoids is rather low. Oxidation rate of metabolites is different--malate is oxidized more intensively, it is followed by lactate, pyruvate, succinate. Sperm storage lowers the respiration level and oxidation rate of metabolites.     

Effect of vitamin D3 and carbostimulin on the content of carbohydrate metabolism substrates and the tricarboxylic acid cycle in liver of rats with experimental rachitis

The development of experimental rhachitis in rats is accompanied by a decrease in the dihydroxyacetonephosphate, glyceraldehyde-phosphate concentrations and by an increase in pyruvate, lactate, alpha-ketoglutarate, glutamate, oxalacetate and malate in the liver tissue. The feeding of vitamin D3 and carbostimulin normalizes, in the main, the concentrations of these metabolites.     

Effect of exogenous succinate on the contents of tricarboxylic acid cycle metabolites of the liver

The paper deals with dynamics of tricarboxylic cycle metabolites in the liver after subcutaneous injection of succinate in a dose of 100 mg/kg to guinea pigs. Before the preparation administration the highest level was marked for succinate, malate and citrate. 3 h after the administration the succinate content increased by 57% and 6 h later it returns to the initial level. No essential changes were observed in the content of other tricarboxylic acid cycle metabolites.     

Regulation of biosynthesis of secondary metabolites. I. Biosynthesis of chlortetracycline and tricarboxylic acid cycle activity

In the course of submerged cultivation of low-production and industrial production strains of Streptomyces aureofaciens, the activity of enzymes of the tricurboxylic acid cycle was studied. The activities of citrate synthase (EC 4.1.3.7), aconitate hydratase (EC 4.2.1.3), isocitrate dehydrogenase (EC 1.1.1.42), fumarate hydratase (EC 4.2.1.2), and malate dehydrogenase (EC 1.1.1.37) were estimated spectrophotometrically in cell-free preparations. In the growth phase, mainly the initial reactions of the cycle were active with both strains. In production-phase, the activities of enzymes in the low-production strain were 2–5 × higher than in the production strain. Benzylthioeyanate, at a concentration of 5 × l0^?5M, stimulated chlortetracycline production of both strains with accompanying decrease in activity of the enzymes of the tricarboxylic acid cycle. The role of the tricarboxylic acid cycle in control of chlortetracycline biosynthesis is discussed.     

Influence of tricarboxylic acid cycle intermediates and related metabolites on the biosynthesis of aflatoxin by resting cells of Aspergillus flavus.

Resting cells of Aspergillus flavus synthesized aflatoxin from acetate as the sole carbon source after 36 h of incubation. Addition of pyruvate (5.5 mg/m) as cosubstrate to [1-14C]acetate and unlabeled acetate considerably reduced toxin production but increased the radioactivity on the tricarboxylic acid intermediates. This suggests that high tricarboxylic acid activity drastically affected toxin synthesis.     

Polymyxin B biosynthesis and tricarboxylic acid cycle enzymatic activity]

Activity of pyruvate dehydrogenase (PDG), isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase and malate dehydrogenase was found in the extracts of the cells of Bac. polymyxa 153, an organism producing polymyxin B. Dependence of the activity of the above enzymes on the carbon source in the medium, aeration conditions, strain features and culture age was shown. A low level of polymyxin B biosynthesis was observed at high activity of PDG and dehydrogenases of the tricarbonic acid cycle. Increased antibiotic production was recorded against the background of decreases values of the above enzyme activities.     

Effect of carbostimulin on indices of acid-base balance and lactate concentration in the blood of swimmer-athletes

It is studied how 10-12-day taking of carbostimulin influences the acid-base equilibrium indices and lactate content in blood of swimmer sportsmen before and after the interval anaerobic loading and in the restoration period. It is found that the preparation promotes a faster removal of the acidosis state developing in sportsmen under the effect of intensive physical exercises.     

Computer modeling of mitochondrial tricarboxylic acid cycle, oxidative phosphorylation, metabolite transport, and electrophysiology

A computational model of mitochondrial metabolism and electrophysiology is introduced and applied to analysis of data from isolated cardiac mitochondria and data on phosphate metabolites in striated muscle in vivo. This model is constructed based on detailed kinetics and thermodynamically balanced reaction mechanisms and a strict accounting of rapidly equilibrating biochemical species. Since building such a model requires introducing a large number of adjustable kinetic parameters, a correspondingly large amount of independent data from isolated mitochondria respiring on different substrates and subject to a variety of protocols is used to parameterize the model and ensure that it is challenged by a wide range of data corresponding to diverse conditions. The developed model is further validated by both in vitro data on isolated cardiac mitochondria and in vivo experimental measurements on human skeletal muscle. The validated model is used to predict the roles of NAD and ADP in regulating the tricarboxylic acid cycle dehydrogenase fluxes, demonstrating that NAD is the more important regulator. Further model predictions reveal that a decrease of cytosolic pH value results in decreases in mitochondrial membrane potential and a corresponding drop in the ability of the mitochondria to synthesize ATP at the hydrolysis potential required for cellular function.     

Sequential measurements of glycolytic and tricarboxylic acid cycle metabolites in single sample aliquots

Standard, pyridine nucleotide-linked fluorometric assays have been sequenced so that 14 glycolytic and tricarboxylic acid cycle intermediates can be measured in only two sample aliquots. This multiple assay procedure, which is based on commercially available enzymes and reagents, allows analysis on small tissue samples in relatively short times.     

Effect of organophosphorus insecticides on the oxidative processes in rat brain synaptosomes

Abstract: This paper describes the effect of four organophosphorus insecticides: Dipterex, DDVP, Ronnel and its oxygen analogue on the respiration of rat brain synaptosomes. Dipterex and DDVP in the concentrations used, 5, 50, or 500 μM, did not change the rate of oxygen uptake and oxidative phosphorylation in rat brain synaptosomes. Ronnel in the highest concentration (500 μM) inhibited respiration in state 3 conditions and abolished respiratory control by ADP. This inhibition was correlated with a change of cytochrome c oxidase activity. The oxygen analogue of Ronnel (OAR) in micromolar concentrations (50 μM) increased the rate of respiration of synaptosomes utilizing glutamate plus malate as substrate. Higher concentrations of OAR produced inhibition of respiration, cytochrome c oxidase and NADH: cytochrome c reductase activities. These observations are typical for uncouplers of oxidative phosphorylation. Noteworthy is the fact that the uncoupling activity of OAR was observed at concentrations which did not inhibit acetylcholinesterase activity. These findings seem to suggest that disturbances in oxidative processes could play an important role in the toxicity of organophosphorus insecticides. The relation between chemical structure and the ability of insecticides to affect oxidative phosphorylation is discussed.     

Influence of oxalate on the rate of the tricarboxylic acid cycle in rat hepatocytes

In hepatocytes isolated from fed rats, physiological concentrations of oxalate lower the flux through the tricarboxylic acid cycle (-48%) and reduce the steady-state levels of oxaloacetate and other Krebs cycle intermediates. All the metabolic modifications observed are explained by pyruvate carboxylase inhibition, since oxalate hardly modifies the flux through pyruvate dehydrogenase.     

Changes in the levels of glycolysis and tricarboxylic acid cycle metabolites in cat tissues during periodontosis

The predominance of restored substrates in the bone system and liver of cats under chronic parodontosis evidence for intensification of reproduction properties of NAD-pairs and causes inhibition of glycolysis and activation of gluconeogenesis. A high content of alpha-ketoglutarate and isocitrate in tissues in a result of lipogenesis inhibition. Under the lower rate of glycolysis, activation of proteolysis and transamination reactions amino acids are the major contributors to pyruvate. Under the acute course of the disease with the development of the inflammatory process the quantity of pyruvate grows sharply in the parodont tissue, as well as oxidative properties of NAD-pairs intensify and lipogenesis accelerates. This is confirmed by a decrease in the alpha-ketoglutarate and isocitrate content in the tissues.     

The interaction of glycolysis, gluconeogenesis and the tricarboxylic acid cycle in rat liver in vivo

1. The equations derived by Heath (1968) were applied to data from experiments on rats in four metabolic states: fed, post-absorptive, starved and 2hr. after an eventually lethal injury. The data used were: (a) The fractions of label injected as C1-, C2- and C3-pyruvate (where the prefix indicates the position of labelling) that are incorporated into carbon dioxide and glucose in post-absorptive and injured rats (yields). Yields could be corrected to yields on label taken up by the liver. (b) The (C5-label in glutamate)/(total label in glutamate) ratio in the liver after C2-pyruvate in rats in all four states. (c) The distribution of label within glutamate after C2-pyruvate or C2-alanine in the livers of fed, post-absorptive and starved rats. (d) The distribution of label within glucose after C2-lactate or C2-pyruvate in starved rats. (e) The relative specific radioactivities of pyruvate, aspartate, glutamate and (in two states only) of glucose 6-phosphate after injection of [U-(14)C]glucose into rats in all four states. These data were previously published, except those after (e) and some after (b) above, which are given in this paper. 2. In addition the concentrations of pyruvate, citrate, glutamate and aspartate in the livers of post-absorptive and injured rats were found. Injury decreased glutamate and citrate concentrations and to a smaller extent aspartate and pyruvate concentrations. 3. Non-steady-state theory showed that most of the data could be used without serious error in steady-state theory. Steady-state theory correlated all but one observation (the relative yields of (14)CO(2) from C2- and C3-pyruvate) listed after (a)-(e) above within the experimental errors, and gave rough estimates of the rates of pyruvate carboxylation, conversion of pyruvate and fat into acetyl-CoA and utilization of glutamate. The main conclusions were: (a) symmetrization of label in oxaloacetate both in the mitochondrion and in the cytoplasm was far from complete, because oxaloacetate did not equilibrate with fumarate in either. From this and other findings it was deduced: (b) that malate or fumarate or both left the mitochondrion, and not oxaloacetate; (c) that there was a loss from the mitochondrion of a fraction of the malate or fumarate or both formed from succinate, and (d) the resulting deficiency of oxaloacetate for the perpetuation of the tricarboxylic acid cycle was made up from pyruvate in fed and post-absorptive rats, but (e) in the starved rat could only be made up by utilization of glutamate. (f) In the fed rat the tricarboxylic acid cycle ran mostly on pyruvate, but in the post-absorptive and starved rat mostly on fat. (g) In the injured rat the tricarboxylic acid cycle was slowed, label in oxaloacetate was completely symmetrized (cf. conclusion a), and the tricarboxylic acid cycle utilized glutamate. (h) The conclusions were not invalidated by isotopic exchange, i.e. flux of label without net flux of compound, nor by interaction with lipogenic processes. (i) In the kidneys interaction between the tricarboxylic acid cycle and gluconeogenesis was different from in the liver, and was much less. The effects on the theory were roughly assessed, and were small. 4. The experiments and optimum experimental conditions required to check the theory are listed, and several predictions, open to experimental confirmation, are made.     

Effect of acetate and octanoate on tricarboxylic acid cycle metabolite disposal during propionate oxidation in the perfused rat heart

Tricarboxylic acid cycle pool size is determined by anaplerosis and metabolite disposal. The regulation of the latter during propionate metabolism was studied in isolated perfused rat hearts in the light of the characteristics of NADP-linked malic enzyme, which is inhibited by acetyl-CoA. The acetyl-CoA concentration was varied by infusions of acetate and octanoate, and the rate of metabolite disposal was calculated from a metabolic balance sheet compiled from the relevant metabolic fluxes. Propionate addition increased the tricarboxylic acid cycle pool size 4-fold and co-infusion of acetate or octanoate did not change it further. Propionate caused a decrease in the CoA-SH concentration and a 10-fold increase in the propionyl-CoA concentration. A paradoxical increase in the CoA-SH concentration was observed upon co-infusion of acetate in the presence of propionate, an effect probably caused by competitive inhibition of propionate activation. A more pronounced decline in the propionyl-CoA concentration was observed upon the co-infusion of octanoate. In a metabolic steady state, acetate and octanoate reduced propionate disposal only slightly, but did not increase the tricarboxylic acid cycle pool size. The results are in accord with the notion that the tricarboxylic acid pool size is mainly regulated by the anaplerotic mechanisms.     

Energy metabolism and alginate biosynthesis in Pseudomonas aeruginosa: role of the tricarboxylic acid cycle.

Infection with mucoid, alginate-producing strains of Pseudomonas aeruginosa is the leading cause of mortality among patients with cystic fibrosis. Alginate production by P. aeruginosa is not constitutive but is triggered by stresses such as starvation. The algR2 (also termed algQ) gene has been previously identified as being necessary for mucoidy; an algR2 mutant strain is unable to produce alginate when grown at 37 degrees C. We show here that the levels of phosphorylated succinyl coenzyme A synthetase (Scs) and nucleoside diphosphate kinase (Ndk), which form a complex in P. aeruginosa, are reduced in the algR2 mutant. We were able to correlate the lower level of phosphorylated Scs with a decrease in Scs activity. Western blots (immunoblots) also showed a decreased level of Ndk in the algR2 mutant, but the presence of another kinase activity sensitive to Tween 20 provides the missing Ndk function. The effect of AlgR2 on tricarboxylic acid (TCA) cycle enzymes appears to be specific for Scs, since none of the other TCA cycle enzymes measured showed a significant decrease in activity. Furthermore, the ability of the algR2 mutant to grow on TCA cycle intermediates, but not glucose, is impaired. These data indicate that AlgR2 is responsible for maintaining proper operation of the TCA cycle and energy metabolism.