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At least 1,459 records · Page 81Linked to original sources
PubMed2005

Complex formation of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid studied by time-resolved laser-induced fluorescence spectroscopy with ultra-short laser pulses.

The complex formation of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid (vanillic acid) was studied by time-resolved laser-induced fluorescence spectroscopy with ultra-short laser pulses using the fluorescence properties of 4-hydroxy-3-methoxybenzoic acid. A 2:1 complex of neptunium(V) with 4-hydroxy-3-methoxybenzoic acid was found. The stability constant of this complex was determined to be logbeta(210) = 7.33 +/- 0.10 at an ionic strength of 0.1 mol/l (NaClO(4)) and at 21 degrees C. The determination of the stability constant required an investigation of the excited-state proton transfer of 4-hydroxy-3-methoxybenzoic acid over the whole pH range. It was realized that 4-hydroxy-3-methoxybenzoic acid undergoes excited-state reactions only at pH values below 5. At pH values above 5 stability constants can be determined without kinetic calculation of the proton transfer.

Hydrogen-Ion Concentration↗
PubMed2000

Effects of glycolic acid on light-induced skin pigmentation in Asian and caucasian subjects.

BACKGROUND: Topical use of alpha-hydroxy acid (AHA) may increase skin photosensitivity, as demonstrated by increased numbers of sunburst cells. However, effects of AHA on tanning have not been studied. OBJECTIVE: Our purpose was to study whether short-term use of glycolic acid hastens resolution of pre-existing light-induced pigmentation and whether the skin becomes tan more easily in Asian and Caucasian subjects after such treatment. METHODS: Six Asian and six Caucasian volunteers received separate irradiations of UVB and UVA to both sides of the lower back. In a double-blind fashion, patients then applied a 10% glycolic acid gel, pH 3.52, to one side of the back, including the irradiated area, and the contralateral extensor forearms once daily for 7 days and then twice daily for 2 weeks. A placebo gel, pH 5.75, was applied to the opposite sides. The subjects returned for measurement of residual tanning with a colorimeter and received additional irradiation to forearms and a second site on the back. Resulting pigmentation was measured immediately after irradiation, at 2 hours, and at 1 week. RESULTS: Increased UVB-induced skin tanning occurred on the forearm and the lower back in both races in areas pretreated with glycolic acid. UVA also caused increased tanning, but only on the extensor forearms in Asian subjects. Treatment with glycolic acid for 3 weeks had no effect on pre-existing light-induced pigmentation. CONCLUSION: Short-term topical treatment of glycolic acid caused an increase in UVB tanning as well as in UVA tanning in some subjects, even in the absence of overt irritation. The inclusion of UVB, and even UVA, sunscreen in AHA products may be warranted.

Adult↗
PubMed2003

Preparation of optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (threo-beta-phenylserine) via optical resolution.

To obtain optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (1), (2RS,3SR)-2-benzoylamino-3-hydroxy-3-phenylpropanoic acid [(2RS,3SR)-2] was first optically resolved using (1S,2S)- and (1R,2R)-2-amino-1-(4-nitrophenyl)-1,3-propanediol as the resolving agents to afford (2R,3S)- and (2S,3R)-2 in yields of 73% and 66%, based on half of the starting amount of (2RS,3SR)-2. Next, the racemic structures of ammonium and some organic ammonium salts of (2RS,3SR)-2 were examined based on melting point, solubility, and infrared spectrum, with the aim of optical resolution by preferential crystallization. The benzylammonium salt of (2RS,3SR)-2 was suggested to exist as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization of the racemic salt afforded the (2R,3S)- and (2S,3R)-salts with optical purities of 90-97%. The (2R,3S)- and (2S,3R)-2 obtained from the purified salts were hydrolyzed by reflux in hydrochloric acid to give (2R,3S)- and (2S,3R)-1.

Crystallization↗
PubMed2004

Agonist-induced internalization of leukotriene B(4) receptor 1 requires G-protein-coupled receptor kinase 2 but not arrestins.

The leukotriene B(4) (LTB(4)) receptor (BLT1) becomes desensitized upon repeated agonist stimulation. Little is known, however, about BLT1 internalization, which follows desensitization in most G-protein-coupled receptors (GPCR). In the current study, transiently expressed BLT1 readily internalized, after LTB(4) stimulation, in RBL-2H3 cells that express high levels of endogenous GPCR kinase 2 (GRK2) but did not in COS-7 or human embryonic kidney (HEK) 293 cells, which do not overexpress GRK. The internalization of BLT1 could be blocked in RBL-2H3 cells by coexpressing dominant-negative (DN) GRK2 K220R and could be promoted in HEK293 cells by coexpressing wild-type (WT) GRK2. Coexpression of WT or DN nonvisual arrestins had no effect on BLT1 internalization. Moreover, upon stimulation with LTB(4), BLT1 did not induce arrestin-green fluorescence protein redistribution in either cell type, even in the presence of overexpressed GRK2. Coimmunoprecipitation experiments confirmed that BLT1 could associate with GRK2 but not with arrestins. A C-tail-truncated mutant of BLT1 lost the capacity to internalize and associate with GRK2 upon exposure to LTB(4), suggesting that the C-tail was required for receptor internalization and association with GRK2. Taken together, our results indicate that the C terminus of BLT1 plays a pivotal role in receptor internalization and GRK2 association. Moreover, ligand-induced BLT1 internalization is dependent on GRK2 but independent of arrestins. This may allow differential, cell-type-specific signaling in response to LTB(4), depending on GRK expression levels.

Animals↗
PubMed1999

A novel trisaccharide glycolipid biosurfactant containing trehalose bears ester-linked hexanoate, succinate, and acyloxyacyl moieties: NMR and MS characterization of the underivatized structure.

A Gram-positive actinomycete growing on n-hexadecane secreted a family of anionic glycolipid surfactant homologs. The major homolog, with a molecular weight of 1210.6347, had the formula C58H98O26. Following mild alkaline saponification, 1H and 13C NMR spectroscopy were used to characterize the non-reducing trisaccharide backbone: beta-Glcp-(1-->3)-alpha-Glcp-(1<-->1)-alpha-Glcp ('laminaratrehalose'). Hexanoate, succinate, 3-hydroxyoctanoate, and 3-hydroxydecanoate were found in 3:1:1:1 molar ratio using GC-EIMS analysis of fatty acid methyl esters (FAME) prepared by transesterification. We found that the beta-hydroxy acids bore secondary hexanoate chains in 3-O-ester linkage, giving acyloxyacyl anions of appropriate m/z in FABMS and FABMS/MS spectra. COSY, HETCOR, HMBC, and HMQC NMR experiments established the acylation pattern: succinate at C-2 of the terminal alpha-glucopyranose ring; hexanoate at C-3" of the beta-glucopyranose ring; 3-hexanoyloxyoctanoate and 3-hexanoyloxydecanoate at the 2'- and 4-positions. In FABMS spectra, the homologs flanked the molecular ion by +/- 14 and +/- 28 amu, suggesting heterogeneity in acyl chain length.

Acylation↗
PubMed1996

Mutations in the Corynebacterium glutamicum proline biosynthetic pathway: a natural bypass of th proA step.

Two chromosomal loci containing the Corynebacterium glutamicum ATCC 17965 proB and proC genes were isolated by complementation of Escherichia coli proB and proC auxotrophic mutants. Together with a proA gene described earlier, these new genes describe the major C. glutamicum proline biosynthetic pathway. The proB and proA genes, closely linked in most bacteria, are in C. glutamicum separated by a 304-amino-acid open reading frame (unk) whose predicted sequence resembles that of the 2-hydroxy acid dehydrogenases. C. glutamicum mutants that carry null alleles of proB, proA, and proC were constructed or isolated from mutagenized cultures. Single proC mutants are auxotrophic for proline and secrete delta1-pyrroline-5-carboxylate, which are the expected phenotypes of bacterial proC mutants. However, the phenotypes or proB and proA mutants are unexpected. A proB mutant has a pleiotropic phenotype, being both proline auxotrophic and affected in cell morphology. Null proA alleles still grow slowly under proline starvation, which suggests that a proA-independent bypass of this metabolic step exists in C. glutamicum. Since proA mutants are complemented by a plasmid that contains the wild-type asd gene of C. glutamicum, the asd gene may play a role in this bypass.

Aldehyde Oxidoreductases↗
PubMed1990

Cerebral arteries can generate 5- and 15-hydroxyeicosatetraenoic acid from arachidonic acid.

Products of the lipoxygenase pathway have been implicated in the development of the cerebrovascular spasm that arises after subarachnoid hemorrhage. In particular the hydroperoxyeicosatetranenoic acids (HPETEs), which are unstable and break down rapidly to the corresponding 5-hydroxy acids (HETEs), are vasoconstrictor agents that mimic some aspects of cerebrovascular spasm. It is not, however, well established whether segments of cerebral artery can manufacture these products. We have studied the lipoxygenase product profile of cerebral arteries stimulated with arachidonic acid. Rings of bovine cerebral arteries were incubated in Krebs solution containing arachidonic acid. The lipoxygenase products were studied using high performance liquid chromatography. The largest peaks had the retention times of 5- and 15-HETEs, and the identity of these peaks was confirmed using specific radioimmunoassays. Stimulation with arachidonic acid resulted in a time- and dose-dependent increase in the formation of both HETEs, with 15-HETE being most abundant. The release of both HETEs was markedly reduced in the presence of AA-861, an inhibitor of lipoxygenase, but not with the cyclooxygenase inhibitor indomethacin. These data are thus consistent with our previous suggestion that the contractile activity of arachidonic acid in cerebral arteries arises, at least in part, from HPETE formation and with a possible role for these compounds in cerebral vasospasm.

Animals↗
PubMed2001

Physicians' and patients' perspectives on office-based dispensing: the central role of the physician-patient relationship.

OBJECTIVE: To describe physicians' and patients' reasons for participating in office-based sales of dermatologic products. DESIGN: Survey data on the attitudes, opinions, and beliefs of dermatologists and their patients were analyzed. SETTING: A market research study of office-based selling. PARTICIPANTS: Thirty dermatologists involved in direct selling from the office, 20 dermatologists not involved in direct selling, 22 patients who purchase products from their dermatologists' offices, and 25 office managers. MAIN OUTCOME MEASURE: The hypotheses of this study were formulated after the market research study had been done. The main outcome measure was the physicians' and patients' reported reasons for patients purchasing skin care products from dermatologists rather than from retail stores. RESULTS: "Trust" was the most frequent reason cited by physicians for patient purchases, while "physician knowledge" was the most frequent reason cited by the purchasing patients. The most common location to display the products was the waiting room (20 [67%] of the physicians). The most common types of products sold included glycolic acid products (15 [50%]), moisturizers (13 [43%]), sunscreens (12 [40%]), and alpha-hydroxy acid products other than glycolic acid (9 [30%]). CONCLUSION: The interaction between physicians who sell products in their offices and their patients is highlighted by 2 key elements of the physician-patient relationship: trust and physician knowledge.

Adult↗
PubMedDate not supplied

[Characteristics of Pseudomonas fluorescens IMV 1433 (Biovar I) lipopolysaccharide].

The lipopolysaccharide of strain Pseudomonas fluorescens IMV 1433 (biovar I) was isolated and investigated. 3-Hydroxydecanoic, 2-hydroxydodecanoic, 3-hydroxydodecanoic, dodecanoic, hexadecanoic, hexadecenoic, and octadecenoic acids were identified in the composition of lipid A. The total amount of hydroxy acids makes up 60%. In the hydrolysate of lipid A, components of the were revealed hydrophilic skeleton--glucosamine and phosphoethanolamine--were revealed. Glucose, galactose, rhamnose, glucosamine, galactosamine, alanine, phosphoethanolamine, phosphorus, and 2-keto-3-deoxyoctulosonic acid were identified in the core of the lipopolysaccharide molecule. O-specific polysaccharide chains of the lipopolysaccharide are built from repeating trisaccharide units consisting of the residues of 2-acetamido-2,6-dideoxy-L-glucose, 2-acetamido-2,6-dideoxy-D-glucose and 4-acetamido-4,6-dideoxy-D-galactose. The lipopolysaccharide studied is similar to the lipopolysaccharide of P. fluorescens IMV 1152 (biovar I) in the structure of lipid A and core oligosaccharide, and identical to it in the structure of the O-chain (this identity correlates with the high level of the serological relationship of the strains).

Carbohydrate Conformation↗
PubMedDate not supplied

Proton-transfer kinetics of photoexcited 7-hydroxy-1-naphthalenesulphonic acid in aqueous DMSO solutions.

The monoanion of 7-hydroxy-1-naphthalenesulphonic acid (HNS) undergoes pseudo-first-order dissociation and its conjugate base undergoes second-order protonation in the lowest excited singlet state. The proton transfer kinetics in water containing dimethylsulphoxide (DMSO), up to a mole fraction of about 0.4, have been evaluated as a function of DMSO concentration. At mole fractions above 0.5 of DMSO, proton-transfer does not measurably occur. At mole fractions below 0.5, steady-state and pulsed-source fluorimetries show the rate constant for dissociation to decrease exponentially with increasing mole fraction of DMSO. This is believed to be due to penetration and disruption of the aqueous solvent cage of HNS by DMSO, resulting in impairment of the Grotthus proton-transfer mechanism. The rate of neutralization of the conjugate base by hydrogen ion is found to vary only slightly with solvent composition and depends on the bulk dielectric properties of the solvent.

Dimethyl Sulfoxide↗
PubMed1992

Binding of a metabolite of triflusal (2-hydroxy-4-trifluoromethylbenzoic acid) to serum proteins in rat and man.

2-hydroxy-4-trifluoromethylbenzoic acid (HTB) is the main active metabolite of the platelet antiaggregant drug triflusal. Its binding to plasma proteins of rats and healthy volunteers in vitro and in vivo has been studied. Rats were given a single oral dose of 50 mg.kg-1 triflusal and the healthy volunteers received 300 mg as a single oral dose or a multiple dose regimen of 600 mg every 24 h and 300 mg every 8 h, both for 13 days. Protein-free HTB was obtained by ultrafiltration. Unbound and total HTB concentrations were determined by HPLC. HTB was primarily bound to albumin in plasma. The Scatchard plots suggested two types of binding sites for HTB on the albumin molecule. In rats, the binding constants (K = intrinsic affinity constant, n = number of binding sites) were K1 = 1.4 x 10(5) l.mol-1, n1 = 1.23, and K2 = 4.1 x 10(3) l.mol-1 and n2 = 3.77. The mean plasma concentration in rats after oral administration was 185 (37) micrograms.ml-1 (protein-free HTB:2.44 (0.77)%). The binding constants in human plasma were K1 = 4.7 x 10(5) l.mol-1, n1 = 1.93, K2 = 4.3 l.mol-1 and n2 = 4.28. The plasma HTB concentration in man (n = 8) was 35 micrograms.ml-1 (Cmax) after a single oral dose of triflusal 300 mg, 172.96 micrograms.ml-1 (Cmax.ss) during the multiple dosage regimen of 300 mg every 8 h, and 131 micrograms.ml-1 (Cmax.ss) during the multiple oral dose regimen of 600 mg every 24 h. Unbound HTB ranged from 0.27 to 0.43%, depending on dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1976

3-hydroxy-3-methylglutaric acid and experimental atherosclerosis in rats.

In rats 3-hydroxy-3-methylglutaric acid effectively counteracts the lipemic and atherosclerotic response of massive doses of vitamin D2. It regressed the formation of atheromatous arterial lesions. Furthermore the significant decrease in serum beta-lipoprotein levels on HMG treatment could be due to decrease in VLDL triglyceride and cholesterol levels.

Animals↗
PubMed2006

Proton-transfer kinetics of photoexcited 7-hydroxy-1-naphthalenesulfonic acid in aqueous formamide solutions.

The monoanion of 7-hydroxy-1-naphthalenesulfonic acid (HNS) undergoes pseudo-first order dissociation and its conjugate base, second order protonation in the lowest excited singlet state. The proton transfer kinetics in water containing formamide up to a mole fraction of about 0.95 have been evaluated as a function of formamide concentration. At mole fractions above 0.95 of formamide, proton-transfer does not measurably occur. At mole fractions below 0.95, steady state and pulsed-source fluorimetries show the rate constant for dissociation to decrease exponentially with increasing mole fraction of formamide. This is believed to be due to penetration and disruption of the aqueous solvent cage of the HNS by formamide, resulting in impairment of the Grotthus proton-transfer mechanism.

Formamides↗
PubMed1982

Urinary excretion of 3-hydroxy-3-methylglutaric acid in the diabetic condition.

Urinary levels of 3-hydroxy-3-methylglutaric acid (HMG) were measured by gas-liquid chromatography (GLC) after an extraction with tetrahydrofuran in normal rats, streptozotocin-diabetic rats and starved rats. The analysis was also carried out in the urine of three diabetic patients after suspending the insulin treatment. Detectable amounts of HMG are excreted in urine by normal humans and rats and such an excretion increases in the diabetic condition. Starved rats present only traces of HMG in the urine.

Acetoacetates↗
PubMed1984

The lipid-lowering effects of 3-hydroxy-3-methylglutaric acid and bile acid drainage in WHHL rabbits.

The effect of 3-hydroxy-3-methylglutaric acid (HMG) on serum cholesterol levels was investigated in Watanabe heritable hyperlipidaemic (WHHL) rabbits. Oral administration of HMG resulted in a reduction of serum cholesterol by 39%. Bile acid drainage, by means of either cholestyramine medication or partial ileal bypass (PIB) surgery, also led to significant reductions in circulating cholesterol, by 35 and 59% respectively. Intraperitoneal injection of HMG after PIB surgery further reduced serum cholesterol by 35%. Fibroblasts from the WHHL rabbits did not show high-affinity binding, uptake or degradation of 125I-labelled low density lipoprotein (LDL). The working mechanism of these lipid-lowering lowering therapies in WHHL rabbits is discussed in relation to recent literature. The significant reductions in circulating cholesterol induced by HMG warrant further investigation into the use of this compound in the management of familial hypercholesterolaemia.

Animals↗
PubMed2006

Topical anti-inflammatory activity of 2alpha-hydroxy pentacyclic triterpene acids from the leaves of Ugni molinae.

Leaf extracts of Ugni molinae Turcz. are used in the Chilean cosmetic industry on the assumption that they have decongestant, regenerative, and anti-aging properties. A bioassay-guided fractionation of this plant material showed that some extracts have potent anti-inflammatory activities. Further fractionation led to the isolation and identification of betulinic acid, a mixture of ursolic and oleanolic acids, and the 2alpha-hydroxy derivatives alphitolic, asiatic, and corosolic acids. The latter three were evaluated in vivo in the mouse ear assay for their topical anti-inflammatory activity, inducing inflammation with either arachidonic acid (AA) or 12-O-tetradecanoylphorbol-13 acetate (TPA). Only corosolic acid was active in the AA assay, with similar potency to nimesulide, but all three triterpene acids inhibited TPA-induced inflammation with potencies comparable to that of indomethacin.

Animals↗
PubMed1983

Identification of 3-hydroxy-3-ethylglutaric acid in urine of patients with propionic acidaemia.

By gas chromatographic mass spectrometric analysis, 3-hydroxy-3-ethylglutaric acid was identified in the urine of patients with propionyl CoA carboxylase deficiency. Simultaneously, large amounts of 3-hydroxyvaleric acid and 3-oxovaleric acid, as well as a number of metabolites previously well known in this disorder, were also found in the urine of the patients. It is suggested that formation of 3-oxovaleric acid and 3-hydroxyvaleric acid proceeds via 3-hydroxy-3-ethylglutaryl CoA as an intermediate by a mechanism similar to that of ketone body formation.

Carboxy-Lyases↗