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At least 1,297 records · Page 72Linked to original sources
PubMed1999

The structure of the specific capsular polysaccharide of Rhodococcus equi serotype 4.

The specific capsular polysaccharide produced by Rhodococcus equi serotype 4 was found to be a high-molecular-weight acidic polymer composed of D-glucose, D-mannose, pyruvic acid and a previously unidentified 5-amino-3,5-dideoxynonulosonic (rhodaminic) acid in the proportions 2:1:1:1. Structural analysis, employing a combination of microanalytical methods, nuclear magnetic resonance spectroscopy, and mass spectrometric techniques, established that the polysaccharide consisted of linear repeating tetrasaccharide units having the sequence of residues shown below. In the native polysaccharide, the rhodaminic acid residues were present as their acetamido derivatives (RhoANAc) and carried 1-carboxyethylidene groups that bridged the O-7 and O-9 positions. Treatment of the capsular polysaccharide with dilute acetic acid and/or anhydrous hydrogen fluoride under hydrolytic/solvolytic conditions, resulted in the formation of four different oligosaccharide species. The 1H and 13C NMR resonances of these oligosaccharide fragments and of the native serotype 4 capsular polysaccharides were fully assigned by homo- and heteronuclear chemical shift correlation methods.

Animals↗
PubMed1978

Glycine therapy in isovaleric acidemia.

The therapeutic efficacy of oral glycine was tested in a 3-year-old girl with isovaleric acidemia. An oral leucine load (25 mg/kg) caused a rise of the blood levels of isovaleric, lactic, and pyruvic acids as well as an increase of urinary excretion of the ketone bodies. These changes did not occur when oral glycine (250 mg/kg) was given with the leucine. Glycine supplementation favored the formation of isovalerylglycine, a nontoxic conjugate of isovaleric acid which is excreted rapidly. Excretion of isovalerylglycine rose threefold when leucine and glycine were administered simultaneously. Chronic glycine therapy was tolerated well and may have prevented one episode of ketoacidosis.

Acidosis↗
PubMed1988

Role of arginine-292 in the substrate specificity of aspartate aminotransferase as examined by site-directed mutagenesis.

X-ray crystallographic data have implicated Arg-292 as the residue responsible for the preferred side-chain substrate specificity of aspartate aminotransferase. It forms a salt bridge with the beta or gamma carboxylate group of the substrate [Kirsch, J. F., Eichele, G., Ford, G. C., Vincent, M. G., Jansonius, J. N., Gehring, H., & Christen, P. (1984) J. Mol. Biol. 174, 497-525]. In order to test this proposal and, in addition, to attempt to reverse the substrate charge specificity of this enzyme, Arg-292 has been converted to Asp-292 by site-directed mutagenesis. The activity (kcat/KM) of the mutant enzyme, R292D, toward the natural anionic substrates L-aspartate, L-glutamate, and alpha-ketoglutarate is depressed by over 5 orders of magnitude, whereas the activity toward the keto acid pyruvate and a number of aromatic and other neutral amino acids is reduced by only 2-9 fold. These results confirm the proposal that Arg-292 is critical for the rapid turnover of substrates bearing anionic side chains and show further that, apart from the desired alteration, no major perturbations of the remainder of the molecule have been made. The activity of R292D toward the cationic amino acids L-arginine, L-lysine, and L-ornithine is increased by 9-16-fold over that of wild type and the ratio (kcat/KM)cationic/(kcat/KM)anionic is in the range 2-40-fold for R292D, whereas this ratio has a range of [(0.3-6) x 10(-6)]-fold for wild type. Thus, the mutation has produced an inversion of the substrate charge specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine↗
PubMed2004

GHB (gamma-hydroxybutyrate) carrier-mediated transport across the blood-brain barrier.

gamma-Hydroxybutyrate (sodium oxybate, GHB) is an approved therapeutic agent for cataplexy with narcolepsy. GHB is widely abused as an anabolic agent, euphoriant, and date rape drug. Recreational abuse or overdose of GHB (or its precursors gamma-butyrolactone or 1,4-butanediol) results in dose-dependent central nervous system (CNS) effects (respiratory depression, unconsciousness, coma, and death) as well as tolerance and withdrawal. An understanding of the CNS transport mechanisms of GHB may provide insight into overdose treatment approaches. The hypothesis that GHB undergoes carrier-mediated transport across the BBB was tested using a rat in situ brain perfusion technique. Various pharmacological agents were used to probe the pharmacological characteristics of the transporter. GHB exhibited carrier-mediated transport across the BBB consistent with a high-capacity, low-affinity transporter; averaged brain region parameters were V(max) = 709 +/- 214 nmol/min/g, K(m) = 11.0 +/- 3.56 mM, and CL(ns) = 0.019 +/- 0.003 cm(3)/min/g. Short-chain monocarboxylic acids (pyruvic, lactic, and beta-hydroxybutyric), medium-chain fatty acids (hexanoic and valproic), and organic anions (probenecid, benzoic, salicylic, and alpha-cyano-4-hydroxycinnamic acid) significantly inhibited GHB influx by 35 to 90%. Dicarboxylic acids (succinic and glutaric) and gamma-aminobutyric acid did not inhibit GHB BBB transport. Mutual inhibition was observed between GHB and benzoic acid, a well known substrate of the monocarboxylate transporter MCT1. These results are suggestive of GHB crossing the BBB via an MCT isoform. These novel findings of GHB BBB transport suggest potential therapeutic approaches in the treatment of GHB overdoses. We are currently conducting "proof-of-concept" studies involving the use of GHB brain transport inhibitors during GHB toxicity.

Adjuvants, Anesthesia↗
PubMed2006

Effects of frozen and refrigerated storage on organic acid profiles of goat milk plain soft and Monterey Jack cheeses.

The effects of 6 mo of freezing and refrigeration on organic acid profiles of 2 types of goat milk cheese [plain soft (PS) and Monterey Jack (MJ)] were studied in comparison with those of a nonfrozen control (NFC). Three lots of commercial PS cheeses were purchased, and 3 lots of MJ cheeses were manufactured at the University dairy plant. Each lot of the 2 types of cheeses was subdivided into 4 equal portions, and one subsample of each cheese was immediately stored at 4 degrees C as the NFC for 0, 14, and 28 d. The other 3 were immediately frozen (-20 degrees C) for 0, 3, and 6 mo (0MF, 3MF, and 6MF) and subsequently thawed the next day at 4 degrees C. The samples were then stored at 4 degrees C for 0, 14, and 28 d. Organic acids were quantified using an HPLC. The PS had no pyruvic acid, and MJ contained no isotartaric acid; however, several unknown large peaks appeared between propionic and butyric acids. Differences in organic acid contents between PS and MJ cheeses were significant for all acids except citric and lactic acid. Lot effect was significant for most of the known acids, indicating that variations existed in milk composition and manufacturing parameters. Effects of storage treatments (NFC, 0MF, 3MF, and 6MF) were significant for most organic acids, except for orotic and a few unidentified acids. Aging at 4 degrees C for 4 wk had little influence on all organic acids, except butyric acid. Concentrations of butyric, lactic, propionic, tartaric, and uric acids were significantly elevated as the frozen storage period advanced. At the initial stage, there were no differences in pH and acid degree values between NFC and frozen-stored groups of both cheeses. However, acid degree values gradually increased as the refrigerated storage extended up to 4 wk, indicating that lipolysis increased as the refrigeration storage at 4 degrees C advanced. Although levels of several organic acids were changed in the goat cheeses, the prolonged frozen storage, up to 6 mo, was apparently feasible for extending storage.

Acetic Acid↗
PubMed1989

Effect of dentin cleansers on the bonding efficacy of dentin adhesive.

The relation between the bonding efficacy of the dentin adhesive and the physical change of the dentin after treatment with various dentin cleansers was investigated. The dentin surface was cleaned with one of the seven experimental dentin cleansers, 5, 10, 20, 30 and 40% of the phosphoric acid, neutralized 0.5 M EDTA solution (pH 7.4) and 9.1% pyruvic acid containing 9.1% glycine, prior to the combining application of 35% hydroxyethylmethacrylate solution (HEMA) and a marketed dentin bonding agent. It was found that the bonding efficacy of the dentin bonding system employed in this study deteriorated with the degree of reduction of Vickers hardness on the dentin surface after the dentin cleaning.

Acid Etching, Dental↗
PubMed1990

[A new method of general anesthesia in pulmonary surgery using dalargin instead of narcotic analgesics].

Intraoperative and early postoperative parameters of the central hemodynamics, oxygen transport function and acid-base status of the blood, and blood lactic and pyruvic acid levels in patients under general anesthesia with dalargin were compared to those under traditional neuroleptic analgesia. The comparative evaluation allowed for a conclusion that general anaesthesia with dalargin provides for a reliable anesthesiological defence and exerts a lower deteriorating effect on the vessels of pulmonary circulation than traditional neuroleptic analgesia.

Adult↗
PubMedDate not supplied

[Effects of zinc and vitamin B 6 in experimental caries in rats].

The behaviour of caries has been studied in rats kept on a cariogenic diet enriched with zinc and vit. B6. A reduction of 16.7% in caries was observed compared to control animals fed with the cariogenic diet alone. Compared to the controls, the animals treated with Ershoff diet and zinc presented a decrease of 18.76%. The weight increase curves of the three lots of rats appeared similar. The basic role played by pyridoxal phosphate in all metabolism is recalled and the cariostatic action exerted by vit. B6 on the optimal function of two pyridoxal-phosphate-dependent systems transaminase and enzymes engaged on the synthesis of acetyl-CoA, reported. Both reduce the acid complement deriving from bacterial plaque fermentation, transaminase by deviating pyruvic acid from glycolysis to protein metabolism, acetyl-CoA synthesis by triggering Krebs cycle oxidative decarboxylation.

Animals↗
PubMed1992

Beta-oxidation as channeled reaction linked to citric acid cycle: evidence from measurements of mitochondrial pyruvate oxidation during fatty acid degradation.

1. The kinetics of mitochondrial mammalian pyruvate dehydrogenase multienzyme complex (PDHC) is studied by the formation of CO2 using tracer amounts of [1-14C]pyruvate. It is found that the Hill plot results in a (pseudo-)cooperativity with a transition of n-1----3 at a pyruvate concentration about Ks. 2. Addition of L-carnitine, octanoate, palmitoyl-CoA or palmitate + L-carnitine + fatty acid-binding protein results in a Hill coefficient of n = 2 following the kinetics of pyruvate oxidation. 3. Addition of fatty acid-binding protein to an assay system oxidizing palmitate in presence of L-carnitine alters the pattern of the kinetics in the Hill plot so that an apparently lower level of L-carnitine is necessary for the reaction course of beta-degradation. 4. It is concluded that beta-degradation is a coordinated, multienzyme-complex based mechanism tightly linked to citric acid cycle and it is proposed that L-carnitine is actively involved into the reaction and not only functioning as carrier-molecule for transmembrane transport.

Animals↗
PubMed2004

Protective effect of methionine supplementation on arsenic-induced alteration of glucose homeostasis.

Short term exposure of arsenic produces carbohydrate depletion and hypoglycemia. Dietary deficiency of methionine causes impaired biotransformation of arsenic which has been attributed to the pathogenesis of different diseases induced by arsenic. Accordingly, the effects of methionine supplementation on the altered glucose homeostasis induced by arsenic were studied. Arsenic (as sodium arsenite) treatment (i.p) of male Wistar rats (weighing 80-100 g) at a dose of 5.55 mg kg(-1) body weight (equivalent to 35% LD50) per day for a period of 21 days caused a significant diminution in blood glucose level and fall in liver glycogen and pyruvic acid contents. The free amino acid nitrogen content of liver was elevated while that of kidney was decreased after arsenic treatment. Transaminase activities in liver and kidney were not significantly altered except that glutamate-pyruvate transaminase activity of kidney decreased significantly after arsenic treatment. Methionine supplementation reversed the above changes except decreased liver glycogen due to arsenic treatment. It may be suggested that hypoglycemia with associated decreased glycolytic activity induced by arsenic treatment at the present dose and duration can be partially counteracted by dietary methionine supplementation.

Alanine Transaminase↗
PubMed1994

Protection of cytochrome c oxidase against cyanide inhibition by pyruvate and alpha-ketoglutarate: effect of aeration in vitro.

Toxicity of cyanide is related to its inhibitory action on cytochrome c oxidase (COx). The alpha-keto acids pyruvate and alpha-ketoglutarate are known to exert in vivo certain protective effect against CN- toxicity if present when the poison is administered. We characterized in vitro their protection of oxidative phosphorylation and of the activity of COx in rat testis, heart, and liver mitochondria, as well as that of the beef heart enzyme in the pure state. In all cases the keto acids proved to have a protective action, even when KCN was previously added to the incubation mixtures and inhibition had already been established. However, the extent of the protection seemed to depend upon the degree of aeration. In the presence of the alpha-keto acids, O2 succeeded with 77% efficiency in reversing CN- inhibition of [gamma-32P]ATP synthesis under high aeration, whereas only 15% was achieved if aeration was poor. In poisoned heart mitochondria (1 mM KCN) simultaneous estimations of ATP synthesis and COx activity in a closed oxygraph chamber showed a recovery of only 6% of both activities upon the addition of 12 mM pyruvate. Our results suggest that O2 displaced cyanide from the enzyme and the poison was then trapped by the keto acids to form the respective nontoxic cyanohydrin. The combination of both high oxygen concentration and the presence of either pyruvate or alpha-ketoglutarate was necessary to effectively protect COx against cyanide poisoning.

Adenosine Triphosphate↗
PubMed1989

[The role of ascorbic acid in the combined preoperative preparation of cancer patients].

Urine and blood levels of ascorbic acid (AA) were measured in healthy subjects (40), cases of cancer of the lung (74), stomach (32) and esophagus (12). AA levels were decreased in cancer patients, particularly, in those with gastric and esophageal tumors. A correlation between the decrease of AA level and the increase in blood concentrations of malonic and pyruvic acids was established. Administration of 1.5 g AA for 7 days was followed by blood-AA level returning practically to normal matched by decrease in lactate and pyruvate concentrations. Also, a correlation between postoperative complication frequency and AA deficit was shown. Correction of AA level was found to be an effective means of postoperative complication prevention.

Administration, Oral↗
PubMed2006

Fractionation of red wine polyphenols by solid-phase extraction and liquid chromatography.

A systematic method for separation of aged red wine polyphenols into various distinct fractions using combined techniques of solid-phase extraction and liquid chromatography was proposed. The aged red wine polyphenols were separated into various distinct fractions including phenolic acid fraction, monomer flavanol fraction, oligomer procyanidin fraction, anthocyanin and its pyruvic acid derivative fraction, free or non-colored proanthocyanidin fraction, fraction of direct condensation products between anthocyanins and proanthocyanidins and fraction of other pigmented complexes. The phenolic composition of each fraction was verified by HPLC with diode array detection (HPLC-DAD), thiolysis, vanillin assay, HPLC coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) and multi-stage MS fragment analysis. For the first time, anthocyanins and their pyruvic derivatives were separated from other phenolic compounds, while free or non-pigmented polymer proanthocyanidins from other pigmented complexes. The fractionation method would be of particular interest in further studying the detailed composition of polymeric polyphenols in red wine.

Chemical Fractionation↗
PubMed1999

Glucose and non-glucidic nutrients exert permissive effects on 2-keto acid regulation of pancreatic beta-cell function.

Insulin-releasing effects of straight and branched chain 2-keto acids were assessed using clonal glucose-responsive beta-cells. Pyruvic acid (PA), 2-ketovaleric acid (KV), 2-ketoisovaleric acid (KIV) or 2-keto-3-methylvaleric acid (KMV) dose-dependently promoted the stimulatory effects of D-glucose, whereas 2-ketobutyric acid (KB) did not affect insulin release. The stimulatory 2-keto acids also promoted the stimulatory activity of D-glyceraldehyde, L-leucine or L-arginine. Responses to PA, KV, KIV or KMV were significantly reduced by transport inhibition with 2-cyano-3 hydroxycinnamate, glucokinase inhibition with mannoheptulose or metabolic inhibition with sodium azide or sodium cyanide. Membrane hyperpolarisation with K+ depletion or diazoxide reduced insulin output, but failed to abolish secretory responses to KV, KIV and KMV. Secretory effects of these 2-keto acids also persisted in beta-cells depolarised with high KCl and glucose. Voltage-dependent Ca2+ channel blockade, with verapamil, or depletion of extracellular Ca2+ abolished the secretory activity of 2-keto acids. Collectively, these results indicate that glucose and metabolisable nutrients exert permissive effects on 2-keto acid-induced insulin release. In addition, KV, KIV and KMV can regulate beta-cell function at least partially independently of K+-ATP channel activity, both through their mitochondrial metabolism and regulation of Ca2+ influx.

Animals↗
PubMed1988

Production of succinic Acid from citric Acid and related acids by lactobacillus strains.

A number of Lactobacillus strains produced succinic acid in de Man-Rogosa-Sharpe broth to various extents. Among 86 fresh isolates from fermented cane molasses in Thailand, 30 strains (35%) produced succinic acid; namely, 23 of 39 Lactobacillus reuteri strains, 6 of 18 L. cellobiosus strains, and 1 of 6 unidentified strains. All of 10 L. casei subsp. casei strains, 5 L. casei subsp. rhamnosus strains, 6 L. mali strains, and 2 L. buchneri strains did not produce succinic acid. Among 58 known strains including 48 type strains of different Lactobacillus species, the strains of L. acidophilus, L. crispatus, L. jensenii, and L. parvus produced succinic acid to the same extent as the most active fresh isolates, and those of L. alimentarius, L. collinoides, L. farciminis, L. fructivorans (1 of 2 strains tested), L. malefermentans, and L. reuteri were also positive, to lesser extents. Diammonium citrate in de Man-Rogosa-Sharpe broth was determined as a precursor of the succinic acid produced. Production rates were about 70% on a molar basis with two fresh strains tested. Succinic acid was also produced from fumaric and malic acids but not from dl-isocitric, alpha-ketoglutaric, and pyruvic acids. The present study is considered to provide the first evidence on the production of succinic acid, an important flavoring substance in dairy products and fermented beverages, from citrate by lactobacilli.

Journal Article↗
PubMed2004

Interaction of the crystalline bacterial cell surface layer protein SbsB and the secondary cell wall polymer of Geobacillus stearothermophilus PV72 assessed by real-time surface plasmon resonance biosensor technology.

The interaction between S-layer protein SbsB and the secondary cell wall polymer (SCWP) of Geobacillus stearothermophilus PV72/p2 was investigated by real-time surface plasmon resonance biosensor technology. The SCWP is an acidic polysaccharide that contains N-acetylglucosamine, N-acetylmannosamine, and pyruvic acid. For interaction studies, recombinant SbsB (rSbsB) and two truncated forms consisting of either the S-layer-like homology (SLH) domain (3SLH) or the residual part of SbsB were used. Independent of the setup, the data showed that the SLH domain was exclusively responsible for SCWP binding. The interaction was found to be highly specific, since neither the peptidoglycan nor SCWPs from other organisms nor other polysaccharides were recognized. Data analysis from that setup in which 3SLH was immobilized on a sensor chip and SCWP represented the soluble analyte was done in accordance with a model that describes binding of a bivalent analyte to a fixed ligand in terms of an overall affinity for all binding sites. The measured data revealed the presence of at least two binding sites on a single SCWP molecule with a distance of about 14 nm and an overall Kd of 7.7 x 10(-7) M. Analysis of data from the inverted setup in which the SCWP was immobilized on a sensor chip was done in accordance with an extension of the heterogeneous-ligand model, which indicated the existence of three binding sites with low (Kd = 2.6 x 10(-5) M), medium (Kd = 6.1 x 10(-8) M), and high (Kd = 6.7 x 10(-11) M) affinities. Since in this setup 3SLH was the soluble analyte and the presence of small amounts of oligomers in even monomeric protein solutions cannot be excluded, the high-affinity binding site may result from avidity effects caused by binding of at least dimeric 3SLH. Solution competition assays performed with both setups confirmed the specificity of the protein-carbohydrate interaction investigated.

Bacterial Proteins↗
PubMedDate not supplied

[Role of the vitamin factor in preventing phenol poisoning].

Experiments on rats were made to examine the effect of vitamin B1, pantothenic and ascorbic acids on the acetylation system and some characteristics of protein metabolism under chronic exposure to phenol. Inhibition of phenol vapours led to inhibition of the acetylation on the 105th day of the experiment, to accumulation of pyruvic acid by the blood and diurnal urine, to elevation of cholesterol content in the blood serum. The total content of protein and protein fractions in the blood serum remained unchanged. Additional vitaminization of the animals with thiamine (150 micrograms), calcium pantothenate (650 micrograms) or with their mixture containing ascorbic acid (2 mg) resulted in normalization of the test characteristics of carbohydrate and fat metabolism. The data obtained and the clinical trials carried out by the authors suggest introduction of the physiological doses of thiamine, calcium pantothenate and ascorbic acid into the diet of the workers in order to prevent phenol poisonings more effectively.

4-Aminobenzoic Acid↗