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At least 253 records · Page 14Linked to original sources
PubMed2002

Mesaconitine-induced relaxation in rat aorta: involvement of Ca2+ influx and nitric-oxide synthase in the endothelium.

Aconiti tuber, roots of aconite (Aconitum japonicum), is an oriental herbal medicine used for centuries in Japan and China to improve the health of persons with a weak constitution and poor metabolism. We investigated the effects of mesaconitine, one of the aconite alkaloids in Aconiti tuber, on the contraction and free intracellular Ca2+ concentration ([Ca2+]i) level in isolated rat thoracic aorta. Mesaconitine at 30 microM inhibited 3 microM phenylephrine-induced contraction in the endothelium-intact, but not endothelium-denuded, aortic rings. The effect of mesaconitine was dependent on external Ca2+ concentrations. The relaxation induced by mesaconitine was abolished by N(omega)-nitro-L-arginine methyl ester (0.1 mM, an inhibitor of nitric-oxide synthase), as well as the relaxation induced by acetylcholine. Acetylcholine induced relaxation in two phases in our conditions; the initial phase was transient and external Ca2+ -independent, and the second phase was sustained and external Ca2+ -dependent. Treatment with 100 nM thapsigargin, which depleted intracellular Ca2+ stores, inhibited acetylcholine-induced, but not mesaconitine-induced, relaxation. Mesaconitine increased the [Ca2+]i level in endothelial cells by influx of Ca2+ from extracellular spaces. These findings suggest that mesaconitine-induced Ca2+ influx and activation of nitric-oxide synthase in endothelial cells and, thus, induced vasorelaxation in rat aorta.

Aconitine↗
PubMed1987

Determination of organic acids in sugar cane process juice by high-performance liquid chromatography: improved resolution using dual Aminex HPX-87H cation-exchange columns equilibrated to different temperatures.

The application of high-performance liquid chromatography to the quantitative analysis of organic acids in sugar cane process juice is described. Separation of these acids is achieved on Aminex HPX-87H cation-exchange columns. Resolution is improved by connecting two columns in series and equilibrating them at different temperatures. The acids in the sample are first isolated on DEAE-Sephadex A-25 anion-exchange resin equilibrated with 0.5 M isobutyric acid. They are then eluted with 0.5 M sulphuric acid and injected directly onto the HPLC column after filtration through a 0.45-micron membrane. This method allows the simultaneous determination of oxalic, cis-aconitic, citric, phosphoric, malic, trans-aconitic, succinic, glycolic, lactic, formic and acetic acids. Isobutyric acid is also separated on this system and provides a useful guide to the loading capacity of the anion-exchange resin.

Acids↗
PubMed2003

An improved reversed-phase liquid chromatographic method for the analysis of low-molecular mass organic acids in plant root exudates.

Reversed-phase column liquid chromatography (RPLC) was used for the separation and quantification of 10 low-molecular-mass organic acids (malic, malonic, lactic, acetic, maleic, citric, cis-aconitic, succinic, fumaric, and trans-aconitic) in plant root exudates. A mobile phase of 93% 25 mM KH2PO4 at pH 2.5 and 7% methanol at a flow-rate of 1 ml min(-1) resolved all 10 acids in 15 min on a C18 column. Experiments demonstrated a significant (P < 0.05) effect of sample pH on detector response, with peak heights being significantly lower at pH 6.0 compared with pH 2.5, but peak area showed no significant difference. At pH 8.0 and above, both peak height and area differed significantly from injections made at pH 2.5. Limits of detection (LOD) for the 10 acids ranged from 0.05 to 24 microM. Finally, the improved method was applied for the analysis of root exudates from soil cultured field pea, Banksia attenuata, white lupin, and chickpea.

Acids↗
PubMed1998

Transformation of monomorphic Trypanosoma brucei bloodstream form trypomastigotes into procyclic forms at 37 degrees C by removing glucose from the culture medium.

African trypanosomes have been shown previously to undergo efficient transformation from bloodstream forms to procyclic (insect dwelling) forms in vitro by adding citrate and/or cis-aconitate to the culture medium and lowering incubation temperature to 27 degrees C. In this paper, it is shown that strain 427 monomorphic bloodstream forms of Trypanosoma brucei grown in axenic culture at 37 degrees C can be transformed to procyclic forms by simply replacing the glucose carbon source in the culture medium with glycerol. The removal of glucose from the medium results in the loss of the variant surface glycoprotein, the acquisition of cell surface procyclic acidic repetitive protein, the synthesis of procyclic-specific glycosylphosphatidylinositol precursors and the acquisition of substantial resistance to salicyl hydroxamic acid and glycerol within 72 h. A procyclic-specific cytoskeletal protein, known to be a marker of the late stage of transformation, is fully expressed by 96 h but full trans-sialidase activity appears only after 18-30 days. The transformation process described here is slower and less efficient than that previously described for monomorphic trypanosomes, using citrate and/or cis-aconitate and temperature shift as triggers. However, the separation of the transformation process from these stimuli is significant and the effects of glucose deprivation described here may reflect some of the events that occur in vivo in the tsetse fly midgut, where glucose levels are known to be very low.

Animals↗
PubMed1967

Control of the citric acid cycle by glyoxylate. Mechanism of the inhibition by oxalomalate and gamma-hydroxy-alpha-oxoglutarate.

1. Hydroxyoxoglutarate was obtained by three methods: decarboxylation of oxalomalic acid, and synthesis from glyoxylate and pyruvate by using either Mg(2+) or an enzyme from rat liver as catalysts. 2. The inhibitory effects of oxalomalate and hydroxyoxoglutarate upon aconitate hydratase, isocitrate dehydrogenase (NADP) and oxoglutarate dehydrogenase were investigated. 3. Oxalomalate at low concentrations (1mm) inhibited almost completely both aconitate hydratase and isocitrate dehydrogenase. Hydroxyoxoglutarate also inhibited these enzymes, but at concentrations approximately tenfold that of oxalomalate. 4. Oxalomalate and hydroxyoxoglutarate, at the higher concentrations, inhibited oxoglutarate dehydrogenase to approximately the same extent. 5. It is suggested that the ability of glyoxylate to control reaction rates in the tricarboxylic acid cycle must in some degree be due to its condensation with oxaloacetate and pyruvate to form enzyme inhibitors.

Chemical Phenomena↗
PubMed1970

The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm.

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.

Acetates↗
PubMed2002

Identification of a novel transporter for dicarboxylates and tricarboxylates in plant mitochondria. Bacterial expression, reconstitution, functional characterization, and tissue distribution.

A cDNA from Arabidopsis thaliana and four related cDNAs from Nicotiana tabacum that we have isolated encode hitherto unidentified members of the mitochondrial carrier family. These proteins have been overexpressed in bacteria and reconstituted into phospholipid vesicles. Their transport properties demonstrate that they are orthologs/isoforms of a novel mitochondrial carrier capable of transporting both dicarboxylates (such as malate, oxaloacetate, oxoglutarate, and maleate) and tricarboxylates (such as citrate, isocitrate, cis-aconitate, and trans-aconitate). The newly identified dicarboxylate-tricarboxylate carrier accepts only the single protonated form of citrate (H-citrate2-) and the unprotonated form of malate (malate2-) and catalyzes obligatory, electroneutral exchanges. Oxoglutarate, citrate, and malate are mutually competitive inhibitors, showing K(i) close to the respective K(m). The carrier is expressed in all plant tissues examined and is largely spread in the plant kingdom. Furthermore, nitrate supply to nitrogen-starved tobacco plants leads to an increase in its mRNA in roots and leaves. The dicarboxylate-tricarboxylate carrier may play a role in important plant metabolic functions requiring organic acid flux to or from the mitochondria, such as nitrogen assimilation, export of reducing equivalents from the mitochondria, and fatty acid elongation.

Arabidopsis↗
PubMed2001

The methylcitric acid pathway in Ralstonia eutropha: new genes identified involved in propionate metabolism.

From Ralstonia eutropha HF39 null-allele mutants were created by Tn5 mutagenesis and by homologous recombination which were impaired in growth on propionic acid and levulinic acid. From the molecular, physiological and enzymic analysis of these mutants it was concluded that in this bacterium propionic acid is metabolized via the methylcitric acid pathway. The genes encoding enzymes of this pathway are organized in a cluster in the order prpR, prpB, prpC, acnM, ORF5 and prpD, with prpR transcribed divergently from the other genes. (i) prpC encodes a 2-methylcitric acid synthase (42720 Da) as shown by the measurement of the respective enzyme activity, complementation of a prpC mutant of Salmonella enterica serovar Typhimurium and high sequence similarity. (ii) For the translational product of acnM the function of a 2-methyl-cis-aconitic acid hydratase (94726 Da) is proposed. This protein and also the ORF5 translational product are essential for growth on propionic acid, as revealed by the propionic-acid-negative phenotype of Tn5-insertion mutants, and are required for the conversion of 2-methylcitric acid into 2-methylisocitric acid as shown by the accumulation of the latter, which could be purified as its calcium salt from the supernatants of these mutants. In contrast, inactivation of prpD did not block the ability of the cell to use propionic acid as carbon and energy source, as shown by the propionic acid phenotype of a null-allele mutant. It is therefore unlikely that prpD from R. eutropha encodes a 2-methyl-cis-aconitic acid dehydratase as proposed recently for the homologous prpD gene from S. enterica. (iii) The translational product of prpB encodes 2-methylisocitric acid lyase (32314 Da) as revealed by measurement of the respective enzyme activity and by demonstrating accumulation of methylisocitric acid in the supernatant of a prpB null-allele mutant. (iv) The expression of prpC and probably also of the other enzymes is regulated and is induced during cultivation on propionic acid or levulinic acid. The putative translational product of prpR (70895 Da) exhibited high similarities to PrpR of Escherichia coli and S. enterica, and might represent a transcriptional activator of the sigma-54 family involved in the regulation of the other prp genes. Since the prp locus of R. eutropha was very different from those of E. coli and S. enterica, an extensive comparison of prp loci available from databases and literature was done, revealing two different classes of prp loci.

Alleles↗
PubMed2003

Achromobacter insolitus sp. nov. and Achromobacter spanius sp. nov., from human clinical samples.

A polyphasic taxonomic study (employing whole-cell protein and fatty acid analyses, 16S rDNA sequencing, DNA-DNA hybridization, determination of DNA G+C content, antibiotic susceptibility testing and extensive phenotypic characterization) was performed on 10 isolates that appeared to be related to Alcaligenes faecalis. The isolates were recovered from diverse environments that included human clinical samples. 16S rDNA sequence analysis indicated that these isolates belonged to the genus ACHROMOBACTER: Whole-cell protein analysis distinguished two groups, which were confirmed by DNA-DNA hybridization. Based on the results of this study, the organisms were classified as two novel Achromobacter species, Achromobacter insolitus sp. nov. (type strain, LMG 6003(T)) and Achromobacter spanius sp. nov. (type strain, LMG 5911(T)). Achromobacter insolitus can be distinguished from Achromobacter spanius by its ability to grow on acetamide and to assimilate mesaconate and aconitate, and by its inability to assimilate diaminobutane. Various tests allow the differentiation of both novel species from other Achromobacter species, including growth on acetamide, denitrification and assimilation of D-glucose, D-xylose, mesaconate, aconitate and diaminobutane.

Achromobacter↗
PubMed1993

Transport of tricarballylate by intestinal brush-border membrane vesicles from steers.

Tricarballylic acid is a non-metabolizable rumen bacterial fermentation product of the naturally occurring tricarboxylic acid trans-aconitic acid. The aim of the present study was to investigate intestinal absorption of tricarballylate using brush-border membrane vesicles (BBMVs) isolated from the proximal jejunum of steers by a Ca2+ precipitation method with subsequent differential centrifugation. Transport of tricarballylate was investigated indirectly (influence of tricarballylate on the uptake of 14C-labelled citrate) as well as directly (uptake of 3H-labelled tricarballylate). Citrate as well as tricarballylate uptake (at a concentration of 0.05 mmol l-1) was strongly stimulated by an inwardly directed initial Na+ gradient. Furthermore, transport of both tricarboxylates under Na+ gradient conditions was clearly enhanced by lowering the extravesicular pH from 7.8 to 5.6. The imposition of an inwardly directed H+ gradient (pH(out)/pH(in) = 5.6/7.8) further enhanced the intravesicular accumulation of citrate as well as of tricarballylate compared with pH(out)/pH(in) = 5.6/5.6. Unequivocal evidence for a common transport site for tricarballylate and citrate was obtained from 'cis-inhibition' and 'trans-stimulation' of Na(+)-dependent citrate uptake by tricarballylate. In further experiments the influence of different substances on the uptake of 3H-labelled tricarballylate was evaluated. Unlabelled tricarballylate, citrate, succinate as well as trans- and cis-aconitate significantly inhibited the accumulation of 3H-labelled tricarballylate by BBMVs. Tricarballylate uptake as a function of the tricarballylate concentration revealed a Na(+)-dependent saturable component (apparent kinetic parameters: maximal transport capacity (Vmax) = 119 pmol (mg protein)-1 (3s)-1; affinity constant (Km) = 0.097 mmol l-1) and a Na(+)-independent diffusional component (diffusion constant: 169 nl (mg protein)-1 (3s)-1). It is concluded that tricarballylate and citrate are transported across the intestinal brush-border membrane by a common, Na(+)-dependent transport mechanism. The stimulatory influence of a low extravesicular pH most probably indicates that the protonated forms of tricarboxylates are better transported than the trivalent species.

Animals↗
PubMed1971

Citrate cycle and related metabolism of Listeria monocytogenes.

The growth response of Listeria monocytogenes strains A4413 and 9037-7 to carbohydrates was determined in a defined medium. Neither pyruvate, acetate, citrate, isocitrate, alpha-ketoglutarate, succinate, fumarate, nor malate supported growth. Furthermore, inclusion of any of these carbohydrates in the growth medium with glucose did not increase the growth of Listeria over that observed on glucose alone. Resting cell suspensions of strain A4413 oxidized pyruvate but not acetate, citrate, isocitrate, alpha-ketoglutarate, succinate, fumarate, or malate. Cell-free extracts of strain A4413 contained active citrate synthase, aconitate hydratase, isocitrate dehydrogenase, malate dehydrogenase, fumarate hydratase, fumarate reductase, pyruvate dehydrogenase system, and oxidases for reduced nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate. The alpha-ketoglutarate oxidation system, succinate dehydrogenase, isocitrate lyase, and malate synthase were not detected. Cytochromes were not detected. The data suggest that strain A4413, under these conditions, utilizes a split noncyclic citrate pathway which has an oxidative portion (citrate synthase, aconitate hydratase, and isocitrate dehydrogenase) and a reductive portion (malate dehydrogenase, fumarate hydratase, and fumarate reductase). This pathway is probably important in biosynthesis but not for a net gain in energy.

Carbohydrate Metabolism↗
PubMed1999

Bradycardia, reversible panconduction defect and syncope following self-medication with a homeopathic medicine.

Alkaloid extracts from the plant Aconitum species have been used in various forms of herbal remedies predominantly as anti-inflammatory and analgesic agents. Many of these alkaloids are extremely potent cardiotoxins and documented cases of various arrhythmias with fatal outcomes have been reported. We report a case of self-medication with 'tincture of aconite' resulting in severe bradycardia, reversible panconduction defect evidenced by sinus inactivity, atrioventricular dissociation with idiojunctional rhythm and left bundle branch block pattern resulting in hypotension and syncope. Complete reversal of ECG findings with marked improvement in symptoms was noted within a few hours. Herbal medicines containing aconite alkaloids may result in severe cardiotoxicity, and strict regulatory measures are warranted to curb unsupervised use for therapeutic purposes.

Aconitum↗
PubMed1972

An inherited defect affecting the tricarboxylic acid cycle in a patient with congenital lactic acidosis.

Cultured skin fibroblasts from a 3 yr old girl with severe, diffuse neurologic disease and persistant lactic acidosis, oxidized radioactive citrate, palmitate, and pyruvate at less than one-third the rate of control cells. Her fibroblasts oxidized isocitrate and glutamate at rates comparable with controls. In disrupted cells from this patient, the activity of aconitate hydratase appeared normal. The binding of citrate to aconitate hydratase and the activities of the NAD- and NADP-linked isocitrate dehydrogenases were also normal, while the activity of citrate synthase was slightly below control values. A significant defect was, however, apparent in the activity of the pyruvate dehydrogenase complex although not in the thiamine-dependent first enzyme of that complex. This patient appears to have a partial genetic defect affecting the tricarboxylic acid cycle.

Acidosis↗
PubMed1995

Two groups of diabetic KK-CAy mice specifically bred for high and low sensitivity to exogenous acetylcholine and beta 1-adrenergic stimulation: interaction of higenamine and aconitine on pulse rate.

Diabetic KK-CAy mice were specifically bred for high and low sensitivity to the addition of exogenous acetylcholine (ACh). The sensitivity to ACh was measured by the change in pulse rate 2 min after the administration of ACh (10 mg/kg, s.c.). The two groups of mice, with high and low sensitivity to ACh, were specially selected and mated sequentially until the 12th filial generation. Although higenamine (100 micrograms/kg, i.p.), a beta 1-adrenergic agonist (a compound derived from aconite), had no effect per se, it inhibited aconitine (another compound derived from aconite extract)-induced bradycardia within 30 s of administration in ACh-low sensitive mice but not in ACh-high sensitive mice. The effects of aconitine and higenamine alone did not differ between these two groups of mice. This demonstrates that the high muscarinic and high beta 1-adrenergic sensitive mice may be stratified into two groups based upon an antagonistic interaction between higenamine and aconitine.

Acetylcholine↗
PubMed2003

Structure identification of five unknown dilipo-alkaloids extracted from processed tuber of Aconitum Carmiechaeli by electrospray ionization tandem mass spectrometry.

The alkaloids in processed aconite tuber of Aconitum Carmiechaeli were studied, and five novel alkaloids in extract from processed aconite tuber were found. The first step involved the use of electrospray ionization mass spectrometry (ESI-MS), and then multi-stage tandem mass spectrometry (MSn) was used to provide structural information. Based on their MSn spectra, the structures of the five novel compounds were elucidated to be C3,C8-difatty acid esters of mesaconitine, aconitine and 10-hydroxyaconitine.

Aconitine↗
PubMed1983

Wheat pasture poisoning. I. An evaluation of cereal pastures as related to tetany in beef cows.

Forage samples were obtained from three wheat and rye mixed pastures (replications) from December 1979, to April 1980 (140 d), while they were being grazed by mature cows at the Southwestern Livestock and Forage Research Station, El Reno, Oklahoma. These samples were taken three times during December, twice monthly in January and February and weekly in March and April. Samples were analyzed for dry matter, ash, N, K, Ca, Mg, P, ash alkalinity, aconitic, malic and citric acids, total lipids, NO3-N, Na and total nonstructural carbohydrates (TNC). In vitro digestibility was also determined. The N:TNC ratio, estimated plasma Mg levels and K:(Ca + Mg) ratio (tetany ratio) were calculated. On d 105 (March 19), 16% (five of 32 head) of the cows developed tetany. At tetany, the forage K, protein, digestibility, ash alkalinity, aconitic acid and total lipids increased suddenly and markedly. Forage dry matter, TNC and ash decreased. Forage Ca and Mg were slightly below or equal to the animals' requirements and remained relatively constant during the period of tetany. Forage P increased about 2 wk before tetany and decreased after tetany occurred. The levels of forage NO3-N and Na did not appear to be related to the incidence of tetany. The N:TNC ratios exceeded .4 immediately before tetany and two sampling periods thereafter. The estimated plasma Mg levels were lowest at tetany and shortly thereafter and tetany ratio exceeded 2.2 during most of the study, with peaks of 3.2 in December, at tetany and in early April.

Animals↗
PubMedDate not supplied

[The effect of sodium salicylate and phenobarbital on the anti-arrhythmia properties of novocainamide and acetylnovocainamide].

CaCl2 and aconitic models of arrhythmias were reproduced in experiments with rats. Sodium salicylate was found to decrease the preventive effect of ecetylnovocainamidum and increased the effect of novocainamidum on ECG changes. Sodium salicylate diminished the preventive effect of acetyl-novocainamidum by elevating myocardial Na+ concentrations, favoured the decrease in myocardial K+ levels, eliminated the preventive effects of novocainamide and acetylnovocainamide by altering myocardial energy metabolism in CaCl2-induced arrhythmia and improved the preventive effect of acetyl-novocainamide on these parameters in aconitic arrhythmia.

Acecainide↗
PubMedDate not supplied

[Citrate and glyoxylate cycle enzyme activity in citric and isocitric acid synthesis by different strains of Candida lipolytica].

The activity of enzymes of the citrate and glyoxylate cycles was comparatively assayed in the parent strain of Candida lipolytica producing citric and isocitric acids in a medium with hexadecane and in its two mutants one of which produced citrate and the other synthesized isocitrate. The enzyme activities were determined in the dynamics of the yeast growth: (a) in the exponential growth phase (no production of the acids); (b) in the lag phase (the beginning of the acid production); and (c) in the stationary phase (active production of the acids). All of the strains had a high activity of citrate synthase. The mutant producing citrate exhibited a high activity of isocitrate lyase and a low activity of aconitate hydratase, whereas the mutant producing isocitrate manifested a high activity of aconitate hydrase and a low activity of isocitrate dehydrogenase and isocitrate lyase. The data pertinent to a change in the enzyme activities due to the growth limitation with a nitrogen source and the production of the acids are considered for explaining the mechanism of overproduction of citric and isocitric acids from n-alkanes by yeast organisms.

Alkanes↗