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PubMed1969

Structural studies on colanic acid, the common exopolysaccharide found in the enterobacteriaceae, by partial acid hydrolysis. Oligosaccharides from colanic acid.

The exopolysaccharide slime colanic acid has been isolated from representative strains of Escherichia coli, Salmonella typhimurium and Aerobacter cloacae. Analysis showed that each polymer contained glucose, galactose, fucose and glucuronic acid, together with acetate and pyruvate. The molar proportions of these components were 1:1.8:1.9:1:1:1 approximately. On the basis of periodate oxidation of the natural and deacetylated polysaccharide, glucose is proposed as the site of the acetyl groups. The pyruvate is attached to galactose. Three neutral oligosaccharides and ten electrophoretically mobile oligosaccharides were isolated and partially characterized. Four of the fragments were esters of pyruvic acid. Most oligosaccharides were isolated from all three polysaccharide preparations. Three further oligosaccharides were isolated from carboxyl-reduced colanic acid and sodium borotritide was used to label the glucose derived from glucuronic acid in these fragments. One trisaccharide was obtained from periodate-oxidized polysaccharide. On the basis of these oligosaccharides a repeating hexasaccharide unit of the following structure is proposed: [Formula: see text] The significance of this structure in colanic acid biosynthesis is discussed.

Acetates↗

PubMed1982

[Dependence of intestinal excretion of amino acids on the amino acid content of animal feed. 2. Intestinal excretion of amino acids feeding soybean oil meal].

In an experiment with 20 15N-labelled growing rats the excretion of amino acids and the excretion of metabolic faecal amino acids were investigated after the feeding of soybean oil meal as sole protein source. A low, yet statistically significant increase of the excretion of amino acids and metabolic faecal amino acids was ascertained in accordance with a growing quota of soybean oil meal in the ration. The true digestibility of amino acids ascertained according to conventional methods is above 90% and, under consideration of the increase of metabolic faecal amino acids, on average increases by 3.5 digestibility units (1.4 to 6.2).

Amino Acids↗

PubMed1970

Dicarboxylic amino acid influx across brush border of rabbit ileum. Effects of amino acid charge on the sodium-amino acid interaction.

Glutamate and aspartate influxes across the brush border of rabbit intestine are saturable processes that are subject to competitive inhibition and are markedly influenced by the Na concentration in the mucosal solution. Lowering the Na concentration increases the amino acid concentration needed to elicit a half-maximal influx but does not significantly affect the maximal influx. The interaction between Na and anionic amino acid influx can be described by the same kinetic model that has been applied to the influxes of neutral amino acids and lysine. Comparison of the kinetic parameters for anionic, neutral, and cationic amino acids suggests that amino acid charge influences (a) the stability of the binary (amino acid-site) complex and (b) the affinity of this binary complex for the subsequent binding of Na. A mechanistic interpretation of these interactions is proposed.

Animals↗

PubMed1993

Biosynthesis and metabolism of retinoic acid: roles of CRBP and CRABP in retinoic acid: roles of CRBP and CRABP in retinoic acid homeostasis.

The enzymes that constitute the pathway of retinoic acid biosynthesis and metabolism may recognize retinoid binding proteins as effectors and substrates. Apocellular retinol-binding protein (CRBP) stimulates a bile-salt independent membrane-bound retinyl ester hydrolase resulting in the hydrolysis of endogenous retinyl esters and the formation of holoCRBP. HoloCRBP delivers retinol to a microsomal nicotin-amide-adenine dinucleotide phosphate-dependent dehydrogenase, protects it from artifactual oxidation and denies enzymes that cannot recognize the binding protein access to retinol. The retinal synthesized may be transferred from the microsomes to the cytosol by CRBP. A cytosolic retinal dehydrogenase has been purified that produces retinoic acid from retinal generated by microsomes in the presence of CRBP and from the complex CRBP-retinal itself. Thus, CRBP(type I) seems to channel retinoids through the reactions of retinoic acid synthesis via a series of protein-protein interactions. Cellular retinoic acid-binding protein (type I) facilitates retinoic acid metabolism by sequestering it and by acting as a low Km substrate, thereby also modulating the steady-state concentrations of retinoic acid.

Animals↗

PubMed1975

Patho-physiological studies on lactic acid-induced pulmonary thrombosis in rat. I. Effect of heparin, acetylsalicylic acid, urokinase and tranexamic acid.

The role of platelet aggregation and coagulo-fibrinolytic systems in thrombogenesis of lactic acid-induced pulmonary thrombosis in rat were studied using an anti-coagulant, platelet aggregation inhibitor, fibrinolytic or anti-fibrinolytic agents. In normal rat, heparin (2.5 mg/kg), acetylsalicylic acid (30 mg/kg) and tranexamic acid (100 mg/kg) suppressed specifically coagulation, platelet aggregation induced by collagen or thrombin and fibrinolysis respectively. Urokinase (10,000 units/kg) activated powerfully fibrinolytic system in addition to suppressing slightly platelet aggregation. The pretreatment with heparin, acetylsalicylic acid or urokinase markedly prevented the formation of thrombus initiated by the infusion of lactic acid at the doses used. Additive effect was also obtained by combined administration of these agents. On the other hand, it was interesting to note that tranexamic acid (100 mg/kg) did not affect the thrombus formation at all despite a potent anti-fibrinolytic effect of this agent. These results indicate that both platelet aggregation and enhancement of coagulation activity are important factors responsible for the formation of thrombi in DIC, while the fibrinolytic activity in blood seems not to be involved in it. On the basis of the findings, mechanism for triggering activation of coagulation and platelet aggregation is also discussed here.

Animals↗

PubMed1987

Direct concurrent measurement of urinary vanillylmandelic acid, 5-hydroxyindoleacetic acid and homovanillic acid by HPLC. Three methodologies compared.

Three different direct HPLC methods for the determination of 3-methoxy-4-hydroxymandelic acid (VMA, vanillylmandelic acid), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylacetic acid (HVA, homovanillic acid) in urine were compared: two spectrofluorometric methods, applying discontinuous gradients, and one serial coulometric linear gradient method. The imprecision study (n = 6) revealed comparable coefficients of variation (CV), intra-assay ranging 1.4-11.1%, and inter-assay ranging 5.9-11.8% for physiological and moderately elevated levels of VMA, 5-HIAA and HVA. All methods showed good linearities up to 100 mumol/L for each of the three compounds studied. Analytical recoveries were 97-114% for VMA, 87-103% for 5-HIAA, and 80-95% for HVA. Recoveries were not dependent on urinary relative densities in the range 1.010-1.030 kg/L or on protein content (prior to acidification) in the range 0.1-3 g/L, or on the pH of conservation in the range 2-5 or on storage temperature in the range -20 - +22 degrees C for three weeks. The distributed-sample comparison revealed acceptable correlations and clinically unimportant accuracy differences between the methods. It is concluded that direct fluorometric and electrochemical HPLC methods can be used in the determination of major catecholamine and serotonin metabolites in human urine for clinical diagnosis and follow-up of neural crest and carcinoid tumours.

Chromatography, High Pressure Liquid↗

PubMed1996

Production of hydroxy fatty acid (10-hydroxy-12(Z)-octadecenoic acid) by Lactobacillus plantarum from linoleic acid and its cardiac effects to guinea pig papillary muscles.

Lactobacillus plantarum produced 10-hydroxy-12(Z)-octadecenoic acid (10-OHODA) from linoleic acid. It was suspected that 10-OHODA might be closely related to leukotoxin (9,10-epoxy-12-octa-decenoic acid (LTx)) which was regarded as a toxic and/or defensive substance in living beings. The cardiac effect of 10-OHODA, which was biosynthesized by Lactobacillus plantarum, on an isolated guinea-pig papillary muscle was determined. Its effect on the contractile force of the tissue preparations was examined both in terms of its concentration and the time of exposure. A decrease in muscular tension was observed immediately after administration of 10-OHODA at concentrations of 30, 100, and 300 microM. We also compared the effect of 10-OHODA on muscle tension with that of LTx and its isomer 12,13-epoxy-9-octadecenoic acid (LTx'). Each inhibitory effect on the contractile force of the papillary muscle was statistically significant in the concentration of 300 microM 5 min after administration compared to the control in the absence of each fatty acid, suggesting that 10-OHODA is likely to exert some influence on the circulatory system together with LTx and LTx'.

Animals↗

PubMed1982

Electrophysiological analysis of rat renal sugar and amino acid transport. V. Acidic amino acids.

We have used electrophysiological techniques to study various aspects of the transport of glutamate and aspartate in proximal tubules of the rat kidney in vivo. Single tubular cells were punctured with microelectrodes and the response of the cell membrane potential to sudden luminal or peritubular applications of these amino acids was measured. The experiments indicated that a specific transport system exists for L-glutamate and L-aspartate in the brushborder membrane, which does not transport neutral or basic amino acids. The uptake of both L-amino acids from the lumen into the cell was found to be rheogenic, probably reflecting the cotransport of two Na+ ions together with one amino acid molecule. The transport system has a slightly greater affinity for L-glutamate, but transports the smaller L-aspartate somewhat faster. Besides the L-isomers also D-glutamate and D-aspartate were found to depolarize the tubular cells which suggests that also the D-isomers are absorbed in the tubule, however they do not seem to use the same transport system as the L-isomers. In addition to the transport system in the brushborder, a similar Na+-dependent, rheogenic transport system for L-glutamate and L-aspartate was also found in the peritubular cell membrane, as deduced from cell cell depolarizations in response to these substrates applied peritubularly. The simultaneous presence of Na-driven transport systems in the apical and basal cell membrane which is not found with other amino acids, may explain the high intracellular accumulation of L-glutamate and L-aspartate in the kidney and provides a rational basis for explaining clinically observed cases of dicarboxylic aminoacidurias.

Amino Acids↗

PubMed1978

Reduction in medium chain acids and monoenoic acids in livers and plasma of rats fed eicosa-5,8,11, 14-tetraynoic acid.

Male Sprague-Dawley rats were fed for 8 weeks a corn oil (CO) diet or a hydrogenated coconut oil (HCNO) diet. These diets were fed in the absence or presence of eicosa-5,8,11,14-tetraynoic acid (TYA). The inclusion of TYA in the HCNO diet reduced the levels of 12:0 and 14:0 in the total fatty acids of livers and plasma. With either diet, the presence of TYA caused an alteration in the fatty acid composition of these tissues so as to reduce the values of the ratios: 16:1/16:0, 18:1/18:0. and 20:4/18:2. These results suggest that dietary TYA can influence the hepatic metabolism of medium chain fatty acids and that it may inhibit the desaturase enzyme involved in the synthesis of not only 20:4 but also of monoenoic fatty acids.

5,8,11,14-Eicosatetraynoic Acid↗

PubMed2000

Increased alpha-linolenic acid intake increases tissue alpha-linolenic acid content and apparent oxidation with little effect on tissue docosahexaenoic acid in the guinea pig.

The essential fatty acids do not have identical roles in nutrition. Linoleic acid (LA) accumulates throughout the body of most mammals, whereas alpha-linolenic acid (ALA) is rarely found in tissue lipids to the same extent as LA. It has been argued that this is the result of metabolism of ALA to docosahexaenoic acid (DHA) or that ALA is rapidly beta-oxidized to acetyl CoA and CO2. In this study, we consider the effect of high and low ALA levels on the tissue distribution of ALA and other n-3 polyunsaturated fatty acids (PUFA) in all tissues. Guinea pigs were fed one of two defined diets for 3 wk from weaning with both diets containing 1.8% (by weight) of LA and either 1.7% ALA or 0.03% ALA. The high ALA diet was associated with significantly increased ALA levels in all tissues except the brain and significantly increased levels of long-chain n-3 PUFA in all tissues except intestines, brain, carcass, and skin. The long-chain n-3 PUFA content of the whole body was less than 5% of that of the ALA content in both diet groups, and the major long-chain n-3 PUFA (>66% of total) in the body was 22:5n-3. The brain was the only tissue where the DHA content exceeded that of 22:5n-3. On the low ALA diet, there appeared to be conservation of ALA based on a comparison of the ratio of LA to ALA in the tissues compared with that in the diet. On the high ALA diet there was a loss of ALA relative to LA in the tissues compared with the diet. These studies suggest that the low levels of tissue ALA in the guinea pig are likely the result of beta-oxidation or excretion via the skin and fur rather than metabolism to DHA.

Animals↗

PubMed1992

Effect in vitro of arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid on the hepatic activation of dietary genotoxins by rat post-mitochondrial fractions.

The effect of arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid on the conversion of the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) to its genotoxic metabolites was investigated using a modified bacterial mutation assay. The assay used Salmonella typhimurium TA98 as an indicator of the mutagenicity and hepatic post-mitochondrial fractions (S-9) from male Sprague-Dawley rats as the activating system. All three fatty acids inhibited the mutagenicity of IQ without effect on the uptake of the active metabolites and/or on the DNA repair processes within the bacterial cell. The activation of three other food mutagens, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and aflatoxin B1 (AFB1) was also inhibited by these fatty acids.

Animals↗

PubMed2006

Simultaneous voltammetric measurement of ascorbic acid, epinephrine and uric acid at a glassy carbon electrode modified with caffeic acid.

A stable electroactive thin film of poly(caffeic acid) has been deposited on the surface of a glassy carbon electrode by potentiostatic technique in an aqueous solution containing caffeic acid. Poly(caffeic acid) was used as a modified electrode for the detection of ascorbic acid (AA), epinephrine (EP), uric acid (UA) and their mixture by cyclic voltammetry. This modified electrode exhibits potent and persistent electron-mediating behavior followed by well-separated oxidation peaks towards AA, EP and UA with activation overpotential. For the ternary mixture containing AA, EP and UA, the three compounds can well separate from each other at the scan rate of 20 mVs(-1) with a potential difference of 156, 132 and 288 mV between AA and EP, EP and UA and AA and UA, respectively, which was large enough to determine AA, EP and UA individually and simultaneously. The catalytic peak current obtained, was linearly dependent on the AA, EP and UA concentrations in the range of 2.0 x 10(-5) to 1.0 x 10(-3) mol l(-1), 2.0 x 10(-6) to 8.0 x 10(-5) mol l(-1) and 5.0 x 10(-6) to 3.0 x 10(-4) mol l(-1), and the detection limits for AA, EP and UA were 7.0 x 10(-6), 2.0 x 10(-7) and 6.0 x 10(-7) mol l(-1), respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of EP in practical injection samples and that of EP, UA and AA simultaneously with satisfactory results.

Ascorbic Acid↗

PubMed2004

Solid-liquid phase behavior of binary fatty acid mixtures. 1. Oleic acid/stearic acid and oleic acid/behenic acid mixtures.

Solid-liquid phase behavior of binary fatty acid mixtures was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) for the mixture composed of oleic acid (OA) and stearic acid (SA) and that composed of OA and behenic acid (BA). The DSC results provided a monotectic type T-X phase diagram for these mixtures, from which it was suggested that the two fatty acid species are completely immiscible in a solid phase regardless of the two polymorphs of OA, i.e., alpha-form or gamma-form. The solid phase immiscibility was confirmed by the FT-IR observation that the spectra obtained for the mixtures correspond to the superposition of the two spectra for respective components. Thermodynamic analysis of liquidus line demonstrated that OA and SA form an ideal mixture in a liquid phase, whereas the mixing of OA and BA in a liquid phase is slightly non-ideal.

Calorimetry, Differential Scanning↗

PubMed2003

Determination of chloride and sulfate in semiconductor-grade etchants comprised of acetic acid, nitric acid and phosphoric acid.

The variable-capacity Dionex Cryptand A1 column was used for the determination of low-ppm levels of chloride and sulfate in etchants comprised of acetic acid, nitric acid and phosphoric acid. All possible ratios of the three acids could be analyzed for chloride and sulfate, if the samples were first diluted 1:100. However, a suitable eluent program was found to be needed for each mixture. A proprietary formulation was chosen to undergo this suitability determination. The resulting gradient was 10 mM KOH with a step to 30 mM NaOH at 15 min, flow-rate=0.5 ml/min; column temperature=29 degrees C; sample loop=7.5 microl. Under these conditions, a low-ppm calibration study (using the proprietary mix as the matrix) was performed and the associated prediction intervals were determined. At 50 ppm (in the original etchant), the +/- prediction interval was +/- 7 ppm for chloride and +/- 20 ppm for sulfate, both at the 95% confidence level. This step gradient was found to be a good starting place for separating the five components in all other ratios of these three acids.

Acetic Acid↗

PubMed2000

Inhibition of apple 1-aminocyclopropane-1-carboxylic acid oxidase, by cyclopropane-1,1-dicarboxylic acid and trans-2-phenylcyclopropane-1-carboxylic acid.

Cyclopropane-1,1-dicarboxylic acid (CDA) and trans-2-phenylcyclopropane-1-carboxylic acid (PCCA) are the main representatives of a group of compounds that are structural analogues of 1-aminocyclopropane-1-carboxylic acid (ACC) and have been proved to have an inhibitory effect on the wound ethylene produced by Lycopersicum esculentum fruit discs. During the experiments, that were carried out in this work the inhibition pattern of PCCA and CDA were studied when tested on partially purified apple ACO and their Ki values were determined. A mechanistic proposal was given, in order to explain the kinetic behaviour of the inhibitors. The common feature of these molecules is their cyclopropane ring, with different substitutes mainly at the positions C1 and C2. Two other compounds with similar structure where also tested as inhibitors, in order to clarify the relationship between structure and activity. These compounds are: 2-methyl cyclopropanecarboxylic acid (MCA), and cyclopropanecarboxylic acid (CCA).

Amino Acid Oxidoreductases↗

PubMed1998

Rat D-amino-acid oxidase cDNA: rat D-amino-acid oxidase as an intermediate form between mouse and other mammalian D-amino-acid oxidases.

Nucleotide sequence of cDNA encoding rat D-amino-acid oxidase (DAO) was determined. Two species of DAO mRNA were present in rat kidney, liver, and brain. They were probably produced by alternative splicing. Rat DAO cDNA encodes 346 amino acid residues, indicating that rat DAO is an intermediate form between mouse DAO (345 amino acids) and DAOs (347 amino acids) of human, rabbit, and pig. Deduced amino acid sequence indicates 93% identity between rat and mouse DAO. Northern hybridization and western blotting supported the sequence data.

Amino Acid Sequence↗

PubMed1976

Preparation of the 3-monosulphates of cholic acid, chenodeoxycholic acid and deoxycholic acid.

1. The 3-sulphates of cholic, chenodeoxycholic and deoxycholic acids were prepared as crystalline disodium salts. 2. The method described shows that it is possible to prepare specific sulphate esters of polyhydroxy bile acids and to remove protecting acyl groups without removing the sulphate. 3. A study of bile acid sulphate solvolysis showed that none of the usual methods give the original bile acid in major yield in a single step. 4. An understanding of the preparation, properties and methods of solvolysis of bile acid sulphates is basic for investigations of cholestasis and liver disease.

Acetylation↗

PubMed1995

Thermodynamics of fatty acid binding to fatty acid-binding proteins and fatty acid partition between water and membranes measured using the fluorescent probe ADIFAB.

Using the fluorescent probe ADIFAB (acrylodan-derivatized intestinal fatty acid-binding protein) to determine the equilibrium concentration of the free (unbound) fatty acid (FFA), dissociation constants were measured between 10 and 50 degrees C for the interaction of five different long chain fatty acids (FA) with fatty acid-binding proteins (FABP) from adipocyte, intestine, and heart. Gibbs free energies (delta G) determined from the dissociation constants were between about -9 and -11 kcal/mol at 25 degrees C. Thermodynamic parameters for binding were determined using van't Hoff plots of the dissociation constants, which range, over the entire temperature region, between 2 and 3000 nM. For all the unlabeled FABPs, free energies of binding were dominated by large negative enthalpies that ranged from -7 to -12 kcal/mol, and the enthalpies tended to decrease with increasing FA unsaturation. The entropic contributions (-T detla S) at 25 degrees C between -4 and +2 kcal/mol and tended to increase with increasing FA unsaturation. To assess the role of FA aqueous solubility in FABP binding, measurements of the partition of FA between unilamellar lipid vesicles and water were also done using ADIFAB; the lipid/water partition coefficients (Kp) determined from these measurements were found to be independent of temperature. The binding of FA to FABP is governed by the sum of contributions of various interactions between FA, water, and FABP. An analysis of the individual contributions suggests that the net free energy of binding results from the canceling in part of a number of separate quite large contributions. The entropic contributions sum almost to zero for most FA and FABPs as a result of the canceling of a large increase in bulk solvent entropy by decreases in configurational entropy upon FA binding to FABP. The net, approximately -10 kcal/mol enthalpy of binding, probably results from an increase in FA configurational enthalpy upon binding to FABP plus a large negative enthalpy from the interaction between the FA and the FABP. This large enthalpy of the FA-FABP interaction suggests that in addition to previously identified specific interactions between the carboxylate portion of the FA and charged amino acids within the binding cavity, other significantly larger enthalpic interactions, presumably involving the hydrocarbon portion of the FA, must contribute to the binding energy.

Adipocytes↗