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Results for “PYROCATECHOL”

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At least 253 records · Page 14Linked to original sources

PubMed1978

Effect of dobutamine, a new cardioselective sympathomimetic drug, on myocardial oxygen balance in conscious dogs.

The effects of (+/-)-4-(2-[3-(p-hydroxyphenyl)-1-methylpropyl]-amino)-ethyl-pyrocatechol hydrochloride (dobutamine) on myocardial O2 balance were investigated in healthy conscious dogs with experimental AV-block. Dobutamine, injected as a bolus of 3, 6, 10 micrograms/kg, increased myocardial contractility, coronary flow, coronary venous O2 saturation and aortic pressure, while initially decreasing SA-node rate. Following ganglionic blockade the effects of dobutamine on myocardial contractility were unchanged while those on coronary flow and coronary venous O2 saturation were reduced by 30%. Aortic pressure and heart rate showed a dose dependent, long-lasting increase. The effects of dobutamine on heart rate and myocardial contractility could be abolished by beta 1-adrenoceptor blockade with practolol (2 mg/kg) while the effects on coronary flow and myocardial O2 extraction were reduced by 40% after practolol. Following beta 1 + 2 adrenoceptor blockade with propranolol, dobutamine increased aortic pressure and coronary flow while coronary resistance and myocardial oxygen extraction were unaffected.

Animals↗

PubMedDate not supplied

[Regulation of the biosynthesis of secondary metabolites in Streptomyces galbus].

The effect of inhibiting and stimulating agents on the biosynthesis of secondary metabolites (actinomycin X and melanoid pigments) was studied in Streptomyces galbus as a function of the growth temperature. D-Valine was shown to inhibit actinomycin synthesis and to stimulate production of melanoid pigments. Tryptophan stimulated the synthesis of both actinomycin and melanoid pigments. The temperature of growth was found to regulate the biosynthesis of secondary metabolites by the culture. The organism synthesized actinomycin at 28 degrees C, but it switched to the production of melanoid pigments at 42 degrees C. This may be considered as a protective reaction of the organism to an increase in the temperature of the environment and in UV radiation which is possible under natural conditions as a consequence of temperature elevation. The paper presents a hypothetical scheme for the regulation of biosynthesis of actinomycin and melanoid pigments by temperature. According to the scheme, the culture synthesizes secondary metabolites from tryptophan to hydroxykynurenine via a general pathway which is then bifurcated: at 28 degrees C--through methylhydroxyanthranilic acid to actinocin to actinomycin; at 42 degrees C--through hydroxyanthranilic acid, o-aminophenol, pyrocatechol, and possibly, o-benzoquinone, to melanin.

Antibiosis↗

PubMed1983

The inhibition of peroxyradical-induced chemiluminescence by melanins.

Model melanins synthesized from adrenochrome, DOPA and pyrocatechol quench the peroxyradical-coupled chemiluminescence initiated by electrolysis, photolysis and redox reactions in several selected systems. Calculations of the selfadsorption (inner filter effect) of melanins that decreases chemiluminescence intensity as well as changes in absorption spectra of photolabile substrate-probes such as cytochrome c and rhodamine, lead to the conclusion that melanins scavenge peroxyradicals and inhibit chemiluminescence. The inhibition effect (beta-value) is much higher than that of most powerful antioxidants in all chemiluminescence systems excluding the luminol-hydrogen peroxide one. Donor-acceptor properties of melanins, pertinent to their antioxidizing activity, are discussed.

Antioxidants↗

PubMedDate not supplied

[Degradation of 3-chlorobenzoic acid by a Pseudomonas putida strain].

A Pseudomonas putida strain 87 capable of assimilating 3-chlorobenzoic acid as a sole source of carbon and energy (3Cba+) was isolated. Treatment with mitomycin C eliminated the 3Cba+ phenotype in 1% of cells in the population. The 3Cba+ phenotype was transferred at a low frequency in the process of conjugation to other bacteria belonging to the genus Pseudomonas. Determinants localized on the plasmid are presumed to be responsible for the capability to assimilate 3-chlorobenzoic acid. A scheme is proposed for the oxidation of 3-chlorobenzoic acid on the basis of studying the products of its degradation. Two catechol 1,2-dioxygenases are present in strains with the 3Cba+ phenotype as was shown by analysing the activity of enzymes catalysing cleavage of the aromatic cycle and by studying their induction. One of the two seems to be encoded by chromosomal genes while the other is encoded by plasmid genes and determines the capability of the culture to cleave the chlorinated pyrocatechol.

Biodegradation, Environmental↗

PubMed1982

The alleged antithiamine activity of o-diphenols: an artefact of oxygen in the thiochrome method?

1H-n. m. r. and t. l. c. measurements show that ortho-diphenols induced little or no chemical change in thiamine when co-dissolved in aqueous solution at pH 7.8. Thiamine determinations on the same solutions by the classical thiochrome method are critically susceptible to the amount of dissolved oxygen. An oxygen saturated equimolar solution of thiamine and pyrocatechol (0.03 mM), after 24 hours at pH 7.8 and at 37 degree, gives almost no thiochrome fluorescence response unless the solution is first degassed to remove all traces of oxygen. It is suggested that earlier literature reports of the pronounced anti thiamine effect of o-diphenols were erroneously based on this apparent disappearance of thiamine when oxygen is not excluded.

Caffeic Acids↗

PubMedDate not supplied

[Aniline as a single carbon, nitrogen, and energy source for Alcaligenes faecalis].

A microorganism capable of assimilating aniline as a sole source of carbon and nitrogen was isolated from soil and identified as Alcaligenes faecalis. Enzyme systems catalyzing aniline oxidation are inducible. Aniline is metabolized by A. faecalis via meta-decomposition of aromatic substances. The extracts of bacterial cells cultivated in a growth medium with aniline contain pyrocatechol 2,3-oxygenase and 2-hydroxymuconic semialdehyde hydrolyase.

Alcaligenes↗

PubMed1976

Identification of alpha-adrenergic receptors in uterine smooth muscle membranes by [3H]dihydroergocryptine binding.

[3H]Dihydroergocryptine, a potent alpha-adrenergic antagonist, was used to label smooth muscle membrane binding sites which have the characteristics expected of alpha-adrenergic receptors. Binding of [3H]dihydroergocryptine to rabbit uterine membranes was rapid and reversible with rate constants of 1.26 X 10(7) M-1 min-1 and 0.034 min-1 for the forward and reverse reactions, respectively. [3H]Dihydroergocryptine binding was of high affinity, with an equilibrium dissociation constant (KD) of 8 to 10 nM. Binding was saturable with 0.14 to 0.17 pmol of [3H]dihydroergocryptine bound/mg of protein at maximal occupancy of the sites. No cooperative interactions among the sites were detected. The specificity of the binding sites for a large number of adrenergic agonists and antagonists was identical with the specificity of alpha-adrenergic responses to these agents. The alpha-adrenergic agonist (-)-epinephrine competed for binding with a KD of 0.23 muM. The order of potencies for several adrenergic agonists in competing for the binding sites was (-)-epinephrine greater than (-)-norepinephrine greater than (-)-phenylephrine greater than (-)-isoproterenol in agreement with their alpha-adrenergic potencies. A series of 19 phenylethylamine adrenergic agonists competed for binding in a manner paralleling their potencies as alpha-adrenergic agonists. alpha-Adrenergic antagonists such as phentolamine (KD = 15 nM) and phenoxybenzamine (KD = 18 nM) potently competed for the binding sites. In contrast, beta-adrenergic antagonists such as propranolol (KD = 27,000 nM) and practolol (KD greater than 10(6) nM) did not have high affinity for the binding sites. A series of ergot alkaloids competed for [3H]dihydroergocryptine binding in a manner which paralleled their potencies as alpha-adrenergic agents. Competition for binding sites by alpha-adrenergic agonists and antagonists was a stereospecific process. The (-)-stereoi somers of epinephrine, norepinephrine, and ergotamine were at least 20- to 50-fold more potent than the corresponding (+)-stereoisomers. Compounds devoid of significant alpha-adrenergic activity, such as pyrocatechol, 3,4-dihydroxymandelic acid, normetanephrine, and D-lysergic acid, did not effectively compete for [3H]dihydroergocryptine binding sites. These rabbit uterine binding sites for [3H]dihydroergocryptine appear to have characteristics indistinguishable from those of the physiologically active alpha-adrenergic receptors.

Animals↗

PubMed1995

Oxidation of aldehydes catalyzed by pig liver flavin-containing monooxygenase.

Flavin-containing monooxygenase-1 (FMO1) purified to homogeneity from pig liver microsomes catalyzes NADPH- and oxygen-dependent oxidation of salicylaldehyde to pyrocatechol and formate. These products, formed in equimolar amounts, were the only ones detected that suggests that FMO1 catalyzes the oxidation of salicylaldehyde by Baeyer-Villiger chemistry. In addition to salicylaldehyde, 2-hydroxy-1-naphthaldehyde, 5-chlorosalicylaldehyde, 5-nitrosalicylaldehyde, ferrocene carboxaldehyde, 2-pyridine carboxaldehyde, and acetylacetone also stimulated NADPH-dependent oxygen uptake in the presence of FMO1. On the other hand, benzaldehyde, 2-methoxybenzaldehyde, 4-pyridine carboxaldehyde and 3- or 4-hydroxybenzaldehyde, and none of the alkylaldehydes tested had detectable substrate activity. Pig liver FMO1 apparently only catalyzes C-oxidation of reactive aldehydes with a hydrogen ion acceptor function adjacent to the carbonyl.

Aldehydes↗

PubMed1976

Adipocyte beta-adrenergic receptors. Identification and subcellular localization by (-)-[3H]dihydroalprenolol binding.

(--)-[3H]Dihydroalprenolol, a potent beta-adrenergic antagonist, was used to identify binding sites which have the characteristics of beta-adrenergic receptors in membranes from rat adipocytes. The subcellular distribution of the (--)-[3H]Dihydroalprenolol binding sites was examined. The binding sites were predominantly in the plasma membrane fraction, consistent with the proposal that the physiologically significant beta-adrenergic receptors are localized in the adipocyte plasma membrane. Binding of (--)-[3H]dihydroalprenolol to unfractionated adipose membranes was saturable with 0.24 pmol bound/mg of protein at saturation. Half-maximal saturation occurred at 15 nM providing an estimate of the equilibrium dissociation constant, KD, for the interaction of (--)-[3H]dihydroalprenolol with its adipocyte receptor. Kinetic analysis of (--)-[3H]dihydroalprenolol binding provided a value of 2.4 X 10(7) M-1 min-1 for the forward bimolecular rate constant, k1. Dissociation of (--)-[3H]dihydroalprenolol was a first order reaction with a rate constant, k2, of 2.94 X 10(-1) min-1. The ratio k2/k1 = 12 nM provides an independent measurement of the KD for the interaction of (--)-[3H]dihydroalprenolol with its receptor which is in good agreement with the values obtained by steady state analysis (12 to 15 nM). Beta-Adrenergic agonists and antagonists competed for the binding sites in unfractionated adipocyte membranes with a typical beta1-adrenergic specificity. The order of potency of agonists was (--)-isoproterenol greater than (--)-norepinephrine congruent to (--)-epinephrine. The beta-adrenergic antagonist, (--)-propranolol, potently competed for the binding sites with a KD of 17 nM. Compounds such as dihydroxyphenylaline, dihydroxymandelic acid, normetanephrine, pyrocatechol, and phentolamine which are structurally related to beta-adrenergic agents, but are devoid of beta-adrenergic physiologicl effects in adipocytes, did not compete for the binding sites. Binding was highly stereospecific, the (+) isomers of adrenergic agonists and antagonists requiring 23- to 330-fold higher concentrations to half-maximally inhibit binding than the corresponding (--) stereoisomers. (--)-[3H]Dihydroalprenolol binding was examined highly enriched plasma membrane, mitochondrial, and microsomal (endoplasmic reticulum) fractions of adipocytes. In the presence of 12 nM (--)-[3H]dihydroalprenolol, the specific activity of binding in the plasma membrane fraction was 5-fold higher than that of the mitochondrial fraction and 8-fold higher than that of the microsomal (endoplasmic reticulum) fraction. The specificity and affinity characteristics of the plasma membrane binding sites were found to be virtually identical with those of the unfractionated adipocyte membranes. The observation that (--)-[3H]dihydroalprenolol binding sites are predominantly localized in the plasma membrane fraction suggests the potential usefulness of this ligand as a marker for adipocyte plasma membranes.

Adenylyl Cyclases↗

PubMed1976

[Degradation of (-)-ephedrine by Arthrobacter globiformis (author's transl)].

A bacterium which grows on and completely degrades ephedrine as the only source of carbon was isolated from soil. This bacterium was identified as Arthrobacter globiformis. From the culture medium the following metabolites were isolated: 1-hydroxy-1-phenyl acetone, benzoic acid, pyrocatechol, cis-cis-muconic acid and methylamine. The mechanism of metabolism is discussed and compared with that in mammals.

Acetone↗

PubMed1950