Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Acids”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed1987

Inhibition by Salicylhydroxamic Acid, BW755C, Eicosatetraynoic Acid, and Disulfiram of Hypersensitive Resistance Elicited by Arachidonic Acid or Poly-l-Lysine in Potato Tuber.

The hypothesis that arachidonic acid (AA) induction of sesquiterpene accumulation and browning in potato (Solanum tuberosum) is mediated by a lipoxygenase metabolite of AA was tested using lipoxygenase inhibitors. Salicylhydroxamic acid (SHAM) and 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline hydrochloride (BW755C) delayed the response to AA. Inhibition by eicosatetraynoic acid (ETYA) was more persistent. These results are consistent with previous reports that SHAM and BW755C are reversible inhibitors of lipoxygenase and easily oxidized by potato while ETYA acts as an irreversible inhibitor. Disulfiram (tetraethylthiuram disulfide) also inhibited AA elicitor activity. SHAM was most effective if applied at the time of AA treatment, having no effect if applied 6 hours afterward. SHAM was effective in the presence of MES or MOPS buffers but not in acetate-buffered or unbuffered solutions; neither BW755C nor ETYA exhibited this restriction. However, SHAM, BW755C, and ETYA also were inhibitors of browning and sesquiterpene accumulation elicited in potato by poly-l-lysine, which, unlike AA, is not a lipoxygenase substrate. SHAM effectiveness also was restricted to 6 hours after treatment with poly-l-lysine. While the results with AA support a role for lipoxygenase, those with poly-l-lysine may be evidence that these compounds are having other effects in potato tissue.

Journal Article↗
PubMed2003

(+/-)-2-oxocyclohexanepropionic acid: dual conformational selection and hydrogen bonding in a delta-keto acid, and a two-phase technique for crystallizing acids by contact with aqueous solutions of their salts.

The asymmetric unit of the title compound, C(9)H(14)O(3), consists of two molecules having conformations that differ by 121.7 (4) degrees in their rotation about the equatorial substituent bond, so that the side chain extends away from the ring in different directions in the two species. The hydrogen-bonding mode is acid-to-acid dimerization. However, despite the centrosymmetric space group (P-1), the dimers are asymmetric, formed by pairing molecules of identical chirality but differing conformational type [O...O = 2.681 (2) and 2.654 (2) A, and O-H...O = 175 (3) and 176 (3) degrees ]. Two intermolecular C-H...O=C close contacts exist, involving the ketone group of one of the molecules. A two-phase technique is described for slow reforming of crystals of a water-insoluble acid by contact with an aqueous solution of its water-soluble salt.

Journal Article↗
PubMed1977

Phosphonoacetic acid-resistant mutants of herpes simplex virus: effect of phosphonoacetic acid on virus replication and in vitro deoxyribonucleic acid synthesis in isolated nuclei.

Phosphonoacetic acid (PAA) inhibits the replication of herpes simplex virus in BSC-1 cells and the in vitro synthesis of deoxyribonucleic acid (DNA) in isolated nuclei. Phosphonopropionic acid at a concentration of 100 mug/ml had no effect on herpes simplex virus replication. PAA-resistant mutants were obtained at a rate of 1 in 10(4) plaque-forming units after 5-bromodeoxyuridine mutagenization of the virus. These mutants replicate in BSC-1 cells in the presence of 100 mug of PAA per ml and induce a PAA-resistant DNA polymerase that synthesizes DNA in vitro in the presence of PAA.

Acetates↗
PubMed1995

In vitro activities of the lichen secondary metabolites vulpinic acid, (+)-usnic acid, and (-)-usnic acid against aerobic and anaerobic microorganisms.

Secondary metabolites of different species of lichen were tested for their activities against a variety of microbial species. While gram-negative rods and fungi were not inhibited by these compounds, Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium, and some anaerobic species (Bacteroides and Clostridium species) were susceptible at the concentrations tested. Vulpinic acid generally was less active than usnic acid, regardless of its stereochemistry. The susceptibility to usnic acid was not impaired in clinical isolates of S. aureus resistant to methicillin and/or mupirocin.

Anti-Bacterial Agents↗
PubMed1997

Production of 5,8,11-Eicosatrienoic Acid (Mead Acid) by a (Delta)6 Desaturation Activity-Enhanced Mutant Derived from a (Delta)12 Desaturase-Defective Mutant of an Arachidonic Acid-Producing Fungus, Mortierella alpina 1S-4.

Enhanced production of 5,8,11-eicosatrienoic acid (Mead acid, 20:3(omega)9) was attained by a mutant fungus, Mortierella alpina M209-7, derived from (Delta)12 desaturase-defective M. alpina Mut48. The 20:3(omega)9 production by M209-7 was 1.3 times greater than that by its parent strain, Mut48. This is thought to be due to its enhanced (Delta)6 desaturation activity, which was 1.4 times higher than that of Mut48. In both strains, 87 to 88% of the total lipids comprised triacylglycerol (TG) and 85% of 20:3(omega)9 was contained in TG. On optimization of the culture conditions for M209-7, earlier glucose feeding and shifting of the growth temperature from 28 to 19(deg)C on the second day were shown to be effective. Under the optimal conditions with a 10-liter jar fermentor, 20:3(omega)9 production reached 1.65 g/liter of culture medium (corresponding to 118 mg/g of dry mycelia and 28.9% of total fatty acids), which is about twice that reported previously (0.8 g/liter).

Journal Article↗
PubMed1996

Vasodilator effects of des(alpha-carboxy-3,4-dihydroxyphenethyl)lithospermic acid (8-epiblechnic acid), a derivative of lithospermic acids in salviae miltiorrhizae radix.

A potent vasodilator substance (compound III), [alpha]D +141 degrees, was isolated from salviae miltiorrhizae radix (dan-shen). This substance was determined to be des(alpha-carboxy-3,4-dihydroxyphenethyl)lithospermic acid on the basis of spectrometric and chemical evidence, and was identified with an authentic sample of 8-epiblechnic acid. However, comp. III seemed to be formed from lithospermic acid (LSA) and LSA-B during a chemical procedure to separate active ingredients. It caused a sustained, slowly developing relaxation of rat aortic strips precontracted with norepinephrine (NE) in preparations with or without endothelium. The NE-induced concentration-dependent contraction of aortic strips was significantly attenuated by pretreatment with comp. III. Concentration-response curves for Ca(2+)-induced contracture of depolarized aortic strips with isotonic high K+ (60 nM) were not affected by comp. III. Ca(2+)-induced contraction of aortic strips, preincubated with 10(-6) M NE in the presence of 10(-6) M nicardipine and 0.01 mM EGTA in Ca(2+)-free solution, was slightly inhibited by comp. III. Pretreatment of aortic strips with comp. III slightly inhibited the phorbol ester (PMA)-induced contraction. These results suggest that comp. III inhibits NE-induced contraction of the aortic strips through reduction in Ca2+ mobilization. Since comp. III inhibits NE-induced sustained contraction, this agent may be useful in the treatment of hypertension.

Animals↗
PubMedDate not supplied

Identification of thiodiglycolic acid, thiodiglycolic acid sulfoxide, and (3-carboxymethylthio)lactic acid as major human biotransformation products of S-carboxymethyl-L-cysteine.

S-Carboxymethyl-L-cysteine (CMC) is used both as an orally administered mucolytic agent and as a probe drug for uncovering polymorphic sulfoxidation of other sulfur-containing drugs in humans. However, several recent studies could not confirm the formation of significant amounts of urinary sulfoxides of CMC or its decarboxylation product S-methyl-L-cysteine. The metabolism of CMC and a 13C-labeled isotopomer was therefore reinvestigated in 11 and 14 humans, respectively, and emphasis was laid on monitoring of potential alternative metabolic pathways. Combined capillary gas chromatography/electron impact or negative-ion chemical ionization mass spectrometry employing stable isotope-labeled analogues as internal standards were used for identification and quantification of CMC metabolites in human urine. Three nitrogen-free metabolites that were identified as thiodiglycolic acid (TDGA, mean: 19.8% of the dose/24 hr), thiodiglycolic acid sulfoxide (TDGA-SO, mean: 13.3% of the dose/24 hr), and (3-carboxymethylthio)lactic acid (TLA, mean: 2.1% of the dose/8 hr), cumulatively account for about one-third of the dose during a urinary collection period of 24 hr. In addition, trace amounts of both TDGA and TLA exist as endogenous components in urine from persons not administered exogenous CMC at levels of about 5 and 1 nmol/ml, respectively. Both major metabolites TDGA and TDGA-SO, that were not considered in previous sulfoxidation phenotyping, are predominantly excreted after 8 hr. These results demonstrate the existence of a pyruvate-like metabolic pathway and suggest the necessity of a revision of the hitherto accepted biotransformation route of CMC in humans.

Biotransformation↗
PubMed1990

Synthesis and characterization of new 10-acylderivatives of the antipsoriatic agent dithranol: coupling products of dithranol with all-trans-retinoic acid, 13-cis-retinoid acid and an aromatic analogue of retinoic acid: all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl- nona-2,4,6,8-tetraenoate.

The synthesis of new 10-acylderivatives of dithranol 1 is described. Compound 1 was reacted with the acid chlorides of all-trans retinoic acid 5, 13-cis-retinoic acid 6 and all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-nona-2,4,6,8- tetraenoate 7 in toluene and collidin as a base to give the coupling products 2, 3 and 4. The different structures were confirmed by high resolution 1H- and 13C-NMR spectroscopy. Initial investigations with the enzyme glucose-6-phosphate dehydrogenase indicate that all of them are inhibitors of the protein and therefore might have antipsoriatic activity.

Acitretin↗
PubMed1985

Carcinogenicity in rats of the nitrosated bile acid conjugates N-nitrosoglycocholic acid and N-nitrosotaurocholic acid.

Two nitrosated bile acid conjugates, N-nitrosoglycocholic acid and N-nitrosotaurocholic acid, were examined for carcinogenicity in a 2-year study with male Fischer rats using a 6-week p.o. dosing protocol with a total of 300 mg compound/rat. Both compounds were approximately equally carcinogenic and induced significant levels of hepatocellular carcinoma in 54 to 70% of the animals at risk. Gastric tumors of the glandular and aglandular stomach were observed in 12 to 13% of the treated rats. Although the incidence was not significant, these levels were much higher than those in historic controls. Malignant liver and gastric tumors were not detected in vehicle control rats. Alkaline phosphatase-positive foci, putative early mucosal alterations which may precede neoplasia, were found in approximately 35% of the glandular stomachs of compound-treated rats but not in those of control rats.

Alkaline Phosphatase↗
PubMed2004

Locked nucleic acids and intercalating nucleic acids in the design of easily denaturing nucleic acids: thermal stability studies.

Intercalating nucleic acids (INA(R)s) with insertions of (R)-1-O-(1-pyrenylmethyl)glycerol were hybridized with locked nucleic acids (LNAs). INA/LNA duplexes were found to be less stable than the corresponding DNA/LNA duplexes when the INA monomer was inserted as a bulge close to the LNA monomers in the opposite strand. This property was used to make "quenched" complements that possess LNA in hairpins and in duplexes and are consequently more accessible for targeting native DNA. The duplex between a fully modified 13-mer LNA sequence and a complementary INA with six pyrene residues inserted after every second base as a bulge was found to be very unstable (Tm=30.1 degrees C) in comparison with the unmodified double-stranded DNA (Tm=48.7 degrees C) and the corresponding duplexes of LNA/DNA (Tm=81.6 degrees C) and INA/DNA (Tm=66.4 degrees C). A thermal melting experiment of a mixture of an LNA hairpin, with five LNA nucleotides in the stem, and its complementary DNA sequence gave a transition with an extremely low increase in optical density (hyperchromicity). When two INA monomers were inserted into the stem of the LNA hairpin, the same experiment resulted in a significant hyperchromicity comparable with the one obtained for the corresponding DNA/DNA duplex.

DNA↗
PubMed1990

Phase-transfer-catalyzed synthesis of aryl alpha-ketosides of N-acetylneuraminic acid. A 2-methylfluoran-6-yl glycoside of N-acetylneuraminic acid, 2-methyl-6-(5-acetamido-3,5-dideoxy-alpha-D-glycero-D-galacto- nonulopyranosylonic acid)xanthene-9-spiro-1'-isobenzofuran-3'-one, a new substrate for neuraminidase assay.

Glycosidation of N-acetylneuraminic acid by phase-transfer catalysis in chloroform-aqueous alkali gave several known and some new aryl alpha-ketosides in a short reaction time and in good yields. The 4-methylumbelliferyl alpha-ketoside, the standard substrate for neuraminidase, was prepared in a yield of up to 70%. New Neu5Ac ketosides were prepared with fluorescein and the fluorescein analog, 2-methyl-6-hydroxyfluoran (2-methyl-6-hydroxyxanthene-9-spiro-1'-isobenzofuran-3'-one) as aglycons, the latter being synthesized from 2-(2-hydroxy-5-methyl-benzoyl) benzoic acid and 3-fluorophenol. The alpha configuration was ascertained by 400-MHz 1H-n.m.r. spectroscopy and by cleavage of the ketosides with neuraminidases from Vibrio cholerae and Clostridium perfringens. The enzymic hydrolysis of the 2-methylfluoran-6-yl ketoside gave Km values of 82 microM (V. cholerae) and 96 microM (C. perfringens).

Carbohydrate Conformation↗
PubMed2006

Reduced diversity of the human erythrocyte membrane sialic acids in polycythemia vera. Absence of N-glycolylneuraminic acid and characterisation of N-acetylneuraminic acid 1,7 lactone.

Sialic acids from the erythrocyte (RBC) membrane of a patient suffering from polycythemia vera, a malignant orphan disorder of hematopoietic cells, was studied using GC/MS. We found that the sialic acid diversity of these membranes was drastically reduced since only four entities were identified: Neu5Ac (91.5%) and its 1,7 lactone Neu5Ac1,7L (7.5%) which is absent in normal RBC, Neu4,5Ac(2) (0.50%) and Neu4,5Ac(2) 9Lt (0.50%); in normal RBC, Neu5,7Ac(2), Neu5,9Ac(2), Neu5Ac9Lt, Neu5Ac8S and Neu, as well as traces of Kdn, were also present. Neu5Gc and its O-alkylated or O-acetylated derivatives, which are considered by various authors as cancer markers, were not detected.

Erythrocyte Membrane↗
PubMed2006

Gas-liquid chromatographic method for analysing complex mixtures of fatty acids including conjugated linoleic acids (cis9trans11 and trans10cis12 isomers) and long-chain (n-3 or n-6) polyunsaturated fatty acids. Application to the intramuscular fat of beef meat.

The optimisation and validation of a gas-liquid chromatographic (GLC) method using direct saponification with KOH/methanol followed by a derivatization with (trimethylsilyl)diazomethane was carried out trying to overcome all the difficulties posed by the analysis of complex mixtures of fatty acids (FAs) in animal fat tissues. The presented method allowed sensitive, selective and simultaneous determination of a wide range of different FAs, including short-chain FAs, branched-chain FAs and conjugated linoleic acid isomers in the same GLC run along with other well known saturated, monounsaturated and polyunsaturated FAs. To demonstrate the feasibility of the procedure, the total FA profile of beef meat was characterised.

Animals↗
PubMed1999

Low irradiances affect abscisic acid, indole-3-acidic acid, and cytokinin levels of wheat (Triticum aestivum L.) tissues.

Wheat (Triticum aestivum L.) plants were grown under four irradiance levels: 1,400, 400, 200, and 100 micromol m-2 s-1. Leaves and roots were sampled before, during, and after the boot stage, and levels of abscisic acid (ABA), indole-3-acetic acid (IAA), zeatin, zeatin riboside, dihydrozeatin, dihydrozeatin riboside, isopentenyl adenine, and isopentenyl adenosine were quantified using noncompetitive indirect ELISA systems. Levels of IAA in leaves and roots of plants exposed to 100 micromol m-2 s-1 of irradiance were 0.7 and 2.9 micromol kg-1 dry mass (DM), respectively. These levels were 0.2 and 1.0 micromol kg-1 DM, respectively, when plants were exposed to 1,400 micromol m-2 s-1. Levels of ABA in leaves and roots of plants exposed to 100 micromol m-2 s-1 were 0.65 and 0.55 micromol kg-1 DM, respectively. They were 0.24 micromol kg-1 DM (both leaves and roots) when plants were exposed to 1,400 micromol m-2 s-1. Levels of isopentenyl adenosine in leaves (24.3 nmol kg-1 DM) and roots (29.9 nmol kg-1 DM) were not affected by differences in the irradiance regime. Similar values were obtained in a second experiment. Other cytokinins could not be detected (<10 nmol kg 1 DM) in either experiment with the sample sizes used (150-600 mg DM for roots and shoots, respectively).

Abscisic Acid↗
PubMed2000

Effect of retinoic acid and ethanol on retinoic acid receptor beta and glial fibrillary acidic protein mRNA expression in human astrocytoma cells.

This work explores the hypothesis that perturbations caused by ethanol on the regulatory role of retinoids in brain development may be a mechanism involved in the neuropathology of fetal alcohol syndrome. The interaction of ethanol and retinoic acid (RA) on RA receptor (RAR) beta and glial fibrillary acidic protein (GFAP) mRNA expression is evaluated. In the U-373 MG astrocytoma, mRNA expression of RAR beta was increased and GFAP was decreased by RA. Ethanol decreased the expression of RAR beta mRNA, but increased that of GFAP. The RA-stimulated increase in RAR beta was not affected by the presence of ethanol. RA prevented the ethanol-induced increase in GFAP mRNA. Cycloheximide abolished only the GFAP response to ethanol. This work shows that an interrelationship between ethanol and RA exists in the astrocyte.

Astrocytoma↗
PubMed2002

Ebselen blocks the quinolinic acid-induced production of thiobarbituric acid reactive species but does not prevent the behavioral alterations produced by intra-striatal quinolinic acid administration in the rat.

Ebselen (EBS) is a seleno-organic compound with glutathione peroxidase-like activity which is neuroprotective in acute stroke ischemia. In this study, we investigated the effect of EBS on quinolinic acid (QA)-induced neurotoxicity. EBS inhibited QA-induced production of thiobarbituric acid reactive species (TBARS) by striatal homogenates in vitro with an IC(50) of 1.85 microM. Intra-striatal injection of QA (360 nmol) increased striatal content of TBARS and induced convulsions and contralateral rotational behavior. Intra-striatal pre-injection of EBS (10 nmol) 15 min before QA abolished QA-induced TBARS production but did not alter QA-induced behavioral effects. The present findings suggest that EBS acts on post-receptor events, neutralizing free radicals produced by overstimulation of N-methyl-D-aspartate receptors.

Animals↗
PubMed1999

The amino acid sequence of a lamprey (Entosphenus japonicus) liver fatty acid-binding protein identified its close relationship to cardiac fatty acid-binding proteins of Mammalia.

Fatty acid-binding proteins (FABPs) constitute a large, tissue-specific multigene family in animals. While liver FABPs of Aves, Reptilia, and Amphibia are close homologs of mammalian liver FABPs, the shark liver protein belongs to the mammalian heart FABP subfamily. We purified an FABP from the liver of lamprey, Entosphenus japonicus, by gel filtration and anion-exchange chromatography. Amino acid sequences determined for lysyl endopeptidase peptides covered nearly the entire molecule except for N- and C-terminal short segments. Examination of the phylogenetic relationship from the sequence identified the lamprey liver protein as a member of mammalian heart-type FABPs. Since livers of bony fish contain both hepatic and cardiac FABPs, expression of the FABP gene in the vertebrate liver appears to change from the heart-type to liver-type within Pisciformes, with bony fish being in a transition stage. This may be related to the evolutionary and physiological divergence of liver function and lipid metabolism of these lower vertebrates.

Amino Acid Sequence↗
PubMed2003

A general method for the synthesis of sugar 2-C-sulfonic acids by 1 --> 2 arylthio group migration in acid-sensitive thioglycosides. Direct transformation of thiotrityl ethers into C-sulfonic acids.

[reaction: see text] Fully protected triphenylmethyl 2-O-mesyl-1-thio-beta-d-gluco- (14) and -alpha-d-mannopyranoside (28) were transformed by a stereoselective intramolecular 1 --> 2 trans-arylthio migration into methyl 2-S-triphenylmethyl-alpha-d-manno- (15) and -beta-d-glucopyranoside (29), respectively, using NaOCH(3) as nucleophile. The 2-S-triphenylmethyl ethers (15 and 29) were directly oxidized to sugar 2-C-sulfonic acids by using oxone (2KHSO(5), KHSO(4), K(2)SO(4)). Compounds (21, 23, 32, and 35) are the first representatives of secondary sugar C-sulfonic acids.

Oxidation-Reduction↗