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At least 919 records · Page 51Linked to original sources
PubMed2002

Pancreatic and extrapancreatic effects of GLP-1.

Glucagon-like peptide-1 (GLP-1), an incretin hormone which helps to regulate plasma glucose levels, is considered a potential agent for the treatment of type-2 diabetes mellitus, because of its insulinotropic capacity and insulinomimetic actions. In normal conditions, the beta-cell secretory response to GLP-1 is modulated by the extracellular concentration of D-glucose; however, the recognition of D-glucose by the beta-cell is often impaired in type-2 diabetes, and this could impede the full GLP-1 insulinotropic action. Non-glucidic substrates, such as the dimethyl ester of succinic acid, restore the effect of GLP-1 in the isolated perfused rat pancreas of normal or diabetic rats, in the absence of any other exogenous nutrient; likewise, the dimethyl ester of succinic or L-glutamic acid, and the monomethyl ester of pyruvic acid, potentiate the in vivo beta-cell secretory response to GLP-1 in normal and diabetic rats. Therefore, it was proposed that nutrients susceptible to bypass the site-specific defects of the diabetic beta-cell, could be used to potentiate and/or prolong the insulinotropic action of antidiabetic agents such as GLP-1. In vitro, GLP-1 insulin-like effects on glucose metabolism have been documented in normal and diabetic rat liver, and in rat and human skeletal muscle. In rat and human adipocytes, GLP-1 is lipolytic and/or lipogenic, and also stimulates parameters involved in the glucose metabolism. In liver, muscle and fat, GLP-1 seems to act through specific receptors, apparently different--at least in liver and muscle--in structure or signaling pathway from the pancreatic one. It is proposed that an inositolphosphoglycan might be a second messenger of GLP-1 action in extrapancreatic tissues.

Animals↗
PubMed1982

Pathways for carboxylic acid transport by rabbit renal brush border membrane vesicles.

Brush border membrane vesicles were purified from rabbit renal cortex using a calcium-precipitation procedure, and the uptake of carboxylic acids was determined by a rapid-filtration method. L-Lactate, pyruvate (monocarboxylic acids), and succinate (dicarboxylic acid) demonstrated features of Na+ cotransport: enhanced initial rate (1 s) of uptake with an inward Na+ gradient compared with the Na+ -free control condition and transient accumulation of substrate within the vesicles. Kinetic parameters derived for L-lactate and succinate show that each substrate is transported via single pathway and that the two substrates exhibit marginal cross-inhibition. A range of monocarboxylic acids including pyruvate and ketone bodies appear to interact with the monocarboxylic acid carrier. The kinetics of Nat-dependent pyruvate uptake suggest at least two transport pathways-namely, that this monocarboxylate shares both the mono- and dicarboxylic acid carriers. We conclude that isolated rabbit renal microvillus membranes possess independent transport systems for mono- and polycarboxylic acids.

Animals↗
PubMed1988

Mutants of Escherichia coli defective in acid fermentation.

Wild type E. coli ferments glucose to a mixture of ethanol and acetic, lactic, formic, and succinic acids. Mutants defective in acid production have now been isolated, including those defective in lactate dehydrogenase (LDH) or with excess alcohol dehydrogenase. These mutations had no phenotype without a pfl mutation. Novel mutants affecting acetate metabolism were isolated by insertion of the fusion vector Mudl. These aceG mutants cannot grow anaerobically on glucose or aerobically on acetate yet lack the pleiotropic growth defects of previously known pta/ack mutants. In some genetic backgrounds acetate negative mutations suppress the growth defects of adh mutations. These results are discussed in terms of redox balance.

Acetates↗
PubMed1986

The oxidation of proline by mitochondrial preparations.

The oxidation by mitochondria of various rat tissues of proline, pyrroline-5-carboxylate (P5C) and a number of aldehydes has been studied and ADP/O ratios determined for liver mitochondria. High oxidative activity for proline and P5C was found only in the liver and kidney. During the oxidation by liver and kidney mitochondria of proline and P5C; glutamate, ammonia, aspartate and some ornithine accumulated, thus suggesting that proline may normally be converted to ornithine by mitochondria. The oxidation of P5C (glutamic acid semialdehyde) by a mitochondrial dehydrogenase may be the same enzyme that oxidizes succinic acid semi-aldehyde but different from that oxidizing acetaldehyde.

Aldehyde Dehydrogenase↗
PubMed2003

Analysis of low-molecular-mass organic acids using capillary zone electrophoresis-electrospray ionization mass spectrometry.

A capillary zone electrophoresis-electrospray ionization-mass spectrometry (CZE-ESI-MS) method was developed to facilitate identification and determination of eleven low-molecular-mass (LMW) organic acids (i.e. oxalic, lactic, malonic, maleic, citric, tartaric, adipic, glutaric, gluconic, isosaccharinic and succinic acid) in different sample matrices. This CZE method was adapted to suit MS conditions. Sheath liquid, sheath flow and MS parameters were optimized to achieve high mass spectrometric sensitivity. The CZE-ESI-MS procedure showed good sensitivity (limit of detection of < 0.05-0.7 mg/l for all acids), linearity (r2 = 0.9925-0.9998) and reproducibility (2.09-5.34% RSD). The applicability of the CZE-ESI-MS was demonstrated on LMW organic acids in an ale sample. In addition the (here presented) method also provided quantification of fumaric, galacturonic and 2-ketoglutaric acid with high sensitivity.

Acids↗
PubMed1987

Short-chain fatty acids produced by anaerobic bacteria alter the physiological responses of human neutrophils to chemotactic peptide.

The effect of some short-chain fatty acids (SCFA) produced by anaerobic bacteria, namely acetic, propionic, isobutyric, butyric, isovaleric and succinic acids, on production of light and release of lysozyme by human neutrophils exposed to chemotactic peptide fMet-Leu-Phe was investigated. A short period of incubation of neutrophils with SCFA led to marked inhibition of both granulocytic chemiluminescence and degranulation (P less than 0.001). Ultrastructural studies of neutrophils, incubated with concentrations of SCFA inhibiting the chemotactic response, chemiluminescence and release of lysozyme (30 mmol/l), effected alterations in cellular morphology with formation of protrusions of varying shape. The data reported indicate that SCFA might be regarded as important pathogenicity factors. The observed effect on neutrophils could also partially explain the ability of anaerobes to inhibit their own phagocytosis and killing as well as that of the aerobic species present in mixed infections.

Bacteria, Anaerobic↗
PubMed2002

Formation of thomasidioic acid from dehydrosinapinic acid dilactone under neutral conditions, and a remaining inhibitory activity against peroxynitrite-mediated protein nitration.

Dehydrosinapinic acid dilactone (1) was converted to thomasidioic acid (3) and (E,E)-2,3-bis(3,5-dimethoxy-4-hydroxybenzylidene)succinic acid (4) via an alpha,beta-unsaturated gamma-lactone type dimer (2) in phosphate buffer (pH 7.4). A study of the reaction mechanism was accomplished by observing the reaction of methyl ester of 2. The lignans (3, 4) were also prevented the peroxynitrite-mediated protein nitration.

Benzoates↗
PubMedDate not supplied

Nitroxyl spin label contrast enhancers for magnetic resonance imaging. Studies of acute toxicity and mutagenesis.

Two nitroxyl spin label (NSL) compounds that are used experimentally as in vivo contrast enhancers in magnetic resonance (MR) imaging were tested for acute toxicity in rats and for genotoxic effects in cell cultures. These compounds, 2,2,5,5-tetramethyl-1-pyrrolidinyl-oxy-3-carboxylic acid (PCA) and 2,2,6,6-tetramethyl-1-oxido-4-piperidinyl-1-succinic acid (TES) and their hydroxylamine and amine derivatives did not induce sister chromatid exchanges or mutations in Chinese hamster ovary cells at the HGPRT or Na+/K+ ATPase loci. The acute LD50 doses in rats for PCA and TES are 15.1 mmol/kg or greater, suggesting relatively high tolerance.

Animals↗
PubMed1980

[Breeding of a biotype of Myzus persicae sulzer on a synthetic medium. V- Influence of oxalic and gentisic acids on the nutritive value of a synthetic medium].

Studies on the survival, fecundity, and food consumption by M. persicae reared on synthetic diets, have indicated: --gentisic and oxalic acids have a deleterious effect as most important as their dose is high. --succinic acid reduces, at least for the used concentrations, the deleterious effect of the oxalic acid, but not that of the gentisic acid. --gentisic acid is quickly decreasing food consumption. --the deleterious effect of oxalic and gentisic acids is not decreasing with time. The results are discussed in regard with the plant-aphid relations.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

[Optimization of energy-dependent processes in mitochondria from rat liver and brain after inhalation of negative air ions].

The effect of negative air ions (NAI) inhalation by rats on energy reactions of mitochondria in homogenates of liver and brain was studied. The influence of NAI was investigated under activation of animals by administration of physiological dose of adrenaline. Adrenaline administration induced hyperactivation of the rate of phosphorylating oxidation of succinic acid in liver and brain mitochondria which was accompanied by oxalacetate inhibition of succinate dehydrogenase (SDH) as well as excessive Ca2+ accumulation in liver mitochondria. These changes connected with a decrease of coefficient of phosphorylation efficiency ADP/O and uncoupler stimulation of respiration evidenced decrease of energy control of respiration in mitochondria. NAI inhalation diminished the rate of hyperactivated respiration and abolished excessive Ca2+ accumulation. These changes together with ADP/O coefficient and DNP stimulation increase evidence improvement of energy control of respiration which provide more moderate function of the respiratory chain under activation by adrenaline. Animals were excited by adrenaline administration. This effect was abolished by NAI inhalation, animals relaxed, some fell asleep. The data evidence sensitivity of mitochondrial processes in internal organs to inhalation of NAI and show participation of mitochondria in realization of physiological effects of NAI.

Adenosine Diphosphate↗
PubMed1975

Regulation of C3-enzymes in facultative phototrophic bacteria: the cold-labile pyruvate kinase of Rhodopseudomonas sphaeroides.

Pyruvate kinase (EC2.7.1.40) from Rhodopseudomonas sphaeroides was purified 40-fold be precipitation with protamine sulfate and ammonium sulfate followed by gel-filtration. The preparations obtained from cells grown with different carbon sources or cultural conditions differ with respect to specific activity but not with respect to molecular weight (250000 dalton) or regulatory properties. The phosphoenolpyruvate (PEP)-saturation cruve of the enzyme is sigmoidal with Hill coefficients varying from nH equals 1.8 (pH 9.2) to 2.7 (pH 6.0). The enzyme is activated by adenosinemonophosphate (AMP) and the sugarmonophosphates ribose-5-phosphate (R-5-P), glucose-6-phosphate (G-6-P), and-to a lesser extent-fructose-6-phosphate (F-6-P). Fructose-1.6-bisphosphate (FDP) has no measurable effect. Inhibitors of the enzyme are adenosinetriphosphate (ATP), inorganic phosphate (Pi) and the dicarboxylic acids succinate and fumarate. Kinetic analysis reveals that the sugar-phosphates and the dicarboxylic acids act as true allosteric ligands, whereas the effects of AMP, ATP, and Pi cannot be interpreted soley in terms of allosteric interactions. Cold-treatment of the enzymes lead to a rapid loss of activity, but does not change the regulatory properties of the enzyme. Analysis of the kinetics of cold-inactivation and its reversal at 30 percent C, together with studies on the gelfiltration behaviour of the native and the cold-treated enzyme make it likely that the cold-induced loss of activity is due to a dissociation of the enzyme.

Adenosine Monophosphate↗
PubMed1987

Monoclonal antibody modification with chelate-linked high-molecular-weight polymers: major increases in polyvalent cation binding without loss of antigen binding.

Polyethyleneimine or polylysines of differing molecular sizes were substituted with either EDTA or DTPA and then with succinic acid groups. These polymers were then reacted with the amino groups on myosin-specific monoclonal antibody or its Fab using a water soluble carbodiimide. The polymer-antibody complexes were capable of binding up to 150 di- or trivalent ions per mole (Mn++, Gd , or 111In ) without attendant loss of antigen binding. The polylysine derivatives of the intact antibody were rapidly cleared and sequestered in the liver, whereas the polylysine 14-kilodalton (kd) derivative of Fab was cleared from the circulation with minimal hepatic and kidney sequestration. This differed from the biodistribution of intact antimyosin or its Fab labeled with 111In via direct attachment of DTPA to the epsilon amino group of the lysyl residues. Applications in magnetic resonance and nuclear imaging are envisioned.

Antibodies, Monoclonal↗
PubMed1980

Biosynthesis of delta-Aminolevulinic Acid from Glutamate in Agmenellum quadruplicatum.

delta-Aminolevulinic acid accumulated in the culture medium when Agmenellum quadruplicatum strain PR-6 was incubated in the presence of levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydratase, and specifically labeled glutamate and glycine. The delta-aminolevulinic acid was purified using Dowex 50W-X8 and cleaved by periodate to yield succinic acid and formaldehyde. The distribution of radioactivity in the two fragments suggested that in blue-green algae the carbon skeleton of delta-aminolevulinic acid is derived directly from glutamate. However the possibility of the pathway of delta-aminolevulinic acid synthesis, from glycine and succinyl-coenzyme A also functioning in blue-green algae was not eliminated as uptake of glycine was minimal.

Journal Article↗
PubMed1981

Eubacterium saburreum and Veillonella parvula: a symbiotic association or oral strains.

A cocci-filament association was discovered in bacterial cultural studies of a subgingival plaque sample. Components were isolated and identified as Veillonella parvula and Eubacterium saburreum. A E. saburreum cell-associated material consisting of approximately 25% glucose and 70% protein was found which may play a role in the adherence of V. parvula to this filament. Acid end product analysis via gas liquid chromatography showed an uptake of lactic and succinic acids by V. parvula resulting in increased levels of acetic, propionic and n-butyric acids in mixed culture of the E. saburreum and the V. parvula strains. The ability of E. saburreum to adhere to nichrome wire and to glass surfaces as well as the secondary plaque forming ability of V. parvula indicates that these organisms may play a role in the maturation of human dental plaque.

Dental Plaque↗
PubMed1992

[Rapid preliminary diagnosis of anaerobic bacterial infections. II. Investigation of the presence of volatile and non-volatile fatty acids (C1-C6) in pus, purulent fluids and dressing by application of gas chromatography].

Studies were performed in the years 1986-1990 and dealing with 405 clinical materials originating from infections within the abdominal cavity, maxilla, reproductive organ, post-operative wounds as well as dressings, extremities, blood, bile and other types of material and usefulness of analysis by gas chromatography of presence of lower fatty acids in materials for rapid and preliminary diagnostics with strictly anaerobic bacteria was confirmed. Presence in chromatograms of isobutyric, butyric isovaleric, valeric, isocaproic and caproic acid, and partly of propionic acid, is a good indication of infection with strictly anaerobic bacteria. Moreover, presence of succinic acid may suggest presence of anaerobic infection, similarly as presence in chromatograms of three or more various lower fatty acids. Rapid, approximative diagnosis of anaerobic bacteria by application of gas chromatography is worth of broader application. Investigation of clinical material by this method lasts only 1-2 hours and obtained results my present a basis for preliminary diagnosis of the etiological factor and for direction of chemotherapy, which is very important in most early period of treatment of infections.

Bacteria, Anaerobic↗
PubMed1982

Effects of exercise on the histochemical changes of articular chondrocytes in adult dogs.

Effects of exercise regimens on the enzyme histochemical changes of articular chondrocytes of the humeral heads in adult shepherd-type dogs were studied. One group of 4 dogs was exercised by walking on a flat surface 5 days a week for 6 months. A 2nd group of 4 dogs was exercised under the same conditions, except that the dogs were forced to walk over platforms placed in their path. Three control dogs were exercised ad libitum in their housing area. In all dogs, the reactivity of lactic acid dehydrogenase was quite strong nicotinamide dinucleotide dehydrogenase was moderate, and glucose-6-phosphatase was week. Succinic acid dehydrogenase uridine diphosphate (UDP)-galactose-4-epimerase, and UDP-N-acetylglucosamine-4-epimerase were of weakly moderate staining reactivity. Consistent regional or laminar variability was not found among the chondrocytic populations of the exercised and control groups for the reactivity of the enzymes studied. However, regional and/or laminar variabilities in individuals of the experimental groups were identified. The weak reactivity of glucose-6-phosphatase as seemingly contradictory to the presence of intracellular lipids of adult articular chondrocytes. Lipid synthesis was suggested as a mechanism to store excessive quantities of hydrogen ions in an innocuous form, rather than in the potentially deleterious by-product of anaerobic glycolysis, lactic acid.

Animals↗
PubMed2000

Propionic acid fermentation of glycerol and glucose by Propionibacterium acidipropionici and Propionibacterium freudenreichii ssp. shermanii.

A comparative study was carried out in anaerobic batch cultures on 20 g/l of either glycerol or glucose using two propionibacteria strains, Propionibacterium acidipropionici and Propionibacterium freudenreichii ssp. shermanii. In all cases, fermentation end-products were the same and consisted of propionic acid as the major product, acetic acid as the main by-product and two minor metabolites, n-propanol and succinic acid. Evidence was provided that greater production of propionic acid by propionibacteria was obtained with glycerol as carbon and energy sources. P. acidipropionici showed higher efficiency in glycerol conversion to propionic acid with a faster substrate consumption (0.64 g l(-1) h(-1)) and a higher propionic acid production (0.42 g l(-1) h(-1) and 0.79 mol/mol). The almost exclusive production of propionic acid from glycerol by this bacterium suggested an homopropionic tendency of this fermentation. Acetic acid final concentration was two times lower on glycerol (2 g/l) than on glucose (4 g/l) for both micro-organisms. P. freudenreichii ssp. shermanii exhibited a glycerol fermentation pattern typical of non-associated glycerol-consumption-product formation. This could indicate a particular metabolism for P. freudenreichii ssp. shermanii oriented towards the production of other specific components. These results tend to show that glycerol could be an excellent alternative to conventional carbon sources such as carbohydrates for propionic acid production.

Culture Media↗
PubMed1981

Role of pH in oxidase variability of Aeromonas hydrophila.

Some strains of Aeromonas hydrophila may be oxidase negative or only weakly oxidase positive by the Kovacs method taken from the surface of a differential medium, such as MacConkey agar. Six strains of A. hydrophila, two oxidase variable, one oxidase constant, and three weakly oxidase positive on MacConkey agar, were studied to determine the cause of oxidase variability. The bacteriostatic dyes in MacConkey agar were considered possible inhibitors of the oxidase reaction. The concentration of these dyes was varied from twice the normal concentration in zero. No change in the oxidase reaction of any of the six strains was noted. Carbohydrate utilization was also studied. When lactose was deleted from the MacConkey agar formula, the oxidase-variable and weakly oxidase-positive stains become strongly oxidase positive. When glucose was substituted for lactose in the MacConkey agar formula, all strains became oxidase negative. Substitution of nonfermentable carbohydrates, such as dulcitol or raffinose, returned all strains to the oxidase-positive state. When trehalose, which is utilized by all of the strains, was substituted for lactose, the oxidase-variable strains and two of the three weakly oxidase-positive strains became oxidase negative. The other weakly oxidase-positive strain remained weakly positive and the oxidase-constant strain remained strongly oxidase positive when trehalose was substituted for lactose. Oxidase reactions were found to be negative when the pH of the medium was 5.1 or lower. Negative oxidase reactions could be reversed by raising the pH above 5.2, and positive oxidase reactions could be reversed by lowering the pH to 5.1. Therefore, the fermentation of lactose in MacConkey agar results in the inhibition of the oxidase reaction. The acid end products of the fermentation of lactose include acetic, formic, lactic, oxaloacetic, pyruvic, and succinic acids.

Aeromonas↗