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PubMed2000

Simultaneous determination of dihydroxybenzenes, aminophenols and phenylenediamines in hair dyes by high-performance liquid chromatography on hypercross-linked polystyrene.

The retention of polar organic molecules such as dihydroxybenzenes, aminophenols and phenylenediamines on a 250 x 4.6 mm id column packed with 5 microns hypercross-linked polystyrene Chromalite 5HGN (Purolite) was studied. The influence of separation parameters such as concentration of acetonitrile, buffer (citrate, phosphate) concentration, ionic strength and pH of the eluent on their retention was investigated. Under optimum conditions [acetonitrile-0.3 mol l-1 ammonium phosphate, pH 5.15 (30:70 v/v)], eight substances generally used as dye intermediates in hair colouring compositions could be separated within 20 min. An HPLC method with spectrophotometric detection is proposed for the simultaneous determination of pyrocatechol, resorcinol, hydroquinone, o-, m- and p-aminophenols and p-phenylenediamine in commercial haircolour products. The detection limits of these compounds are in the range 0.05-0.16 microgram ml-1. The suitability of the method is demonstrated by the analysis of three different permanent hair dyes.

Aminophenols↗
PubMed2001

Amine oxidase-like activity of polyphenols. Mechanism and properties.

Polyphenols in several oxidation systems gained amine oxidase-like activity, probably due to the formation of the corresponding quinones. In the presence of Cu(II), o- and p-phenolic compounds exhibited amine oxidase-like activity, whereas only the o-phenolic compounds showed the activity in the presence of 1,1-diphenyl-2-picrylhydrazyl radical. The activity was determined by measuring the conversion of benzylamine to benzaldehyde by HPLC. Moreover, gallic acid, chlorogenic acid, and caffeic acid, which are plant polyphenols, converted the lysine residue of bovine serum albumin to alpha-amino-adipic semialdehyde residue, indicating lysyl oxidase-like activity. We also characterized the activity of pyrocatechol, hydroquinone, and pyrogallol in the presence of Cu(II). The oxidative deamination was accelerated at a higher pH, and required O2 and transition metal ions. Furthermore, EDTA markedly inhibited the reaction but not beta-aminopropionitrile, which is a specific inhibitor of lysyl oxidase. Catalase significantly inhibited the oxidation, implying the participation of hydroxyl radical in the reaction, but superoxide dismutase stimulated the oxidation, probably due to its radical formation activity. We discussed the mechanism of the oxidative deamination by polyphenols and the possible significance of the activity for biological systems.

Amine Oxidase (Copper-Containing)↗
PubMed2001

Synthesis, free solution capillary electrophoresis separation and toxicity of seven potential impurities of dobutamine.

The seven O-methylated analogs of dobutamine [(+/-)-4-[2-[[3-(p-hydroxyphenyl)-1-methylpropyl]amino]ethyl]pyrocatechol, CAS 34368-04-2), a trihydroxy secondary amine, can be considered potential impurities of the latter, the ultimate step of the synthesis of dobutamine being the deprotection of the three phenolic groups. In order to enable the detection and the identification of such a contamination, the di- and the monomethylated derivatives of dobutamine were prepared and their mixture with dobutamine and its trimethoxy precursor completely resolved by Free Solution Capillary Electrophoresis (FSCE). Indeed, the above impurities proved to occur in dobutamine in consequence of improper demethylation conditions and to be significantly more toxic than the latter.

Adrenergic beta-Agonists↗
PubMed1975

Identification of cardiac beta-adrenergic receptors by (minus) [3H]alprenolol binding.

(Minus) [3-H] alprenolol, a potent beta-adrenergic antagonist, was used to identify binding sites in a fraction of canine cyocardium. Beta adrenergic agonists and antagonists compete for these binding sites in a manner which directly parallels their known affinity for the cardiac beta-adrenergic receptor. Thus, binding was highly stereo-specific, with the (minus) isomers of beta-adrenergic agonists or antagonists being at least two orders of magnitude more potent than were the (plus) isomers in competing for these sites. The order of potency for inhibition of binding by beta-adrenergic agonists was (minus) isoproterenol greater than (minus) epinephrine greater than (minus) norepinephrine. The dissociation constant (KD) of (minus) alprenolol for the beta-adrenergic receptors was 7-11 nM as determined independently by direct binding studies or by inhibition of isoproterenol-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]. The beta-adrenergic antagonist (minus) propranolol also had high affinity for the binding sites (KD equals 12 nM). The physiologically inactive catechol-containing compounds pyrocatechol and (plus or minus) dihydroxymandelic acid, as well as the metabolite (plus or minus) normetanephrine, and the alpha-adrenergic antagonist phentolamine did not compete for the binding sites at a concentration of 160 muM. Binding was rapid (t1/2 less than 30 sec) and was rapidly reversible (t1/2 less than 15 sec). The binding sites were saturable and bound 0.35 pmol of (minus) [3-H] alprenolol per mg of membrane protein. These characteristics suggest that these binding sites represent the cardiac beta-adrenergic receptors.

Adenylyl Cyclases↗
PubMed2002

Identification and quantification of granulocytes in caecal mucosa and submucosa of chickens experimentally infected with Eimeria tenella and Salmonella enteritidis.

1. Poultry granulocytes are not clearly distinguished from each other with haematoxylin-eosin (HE) stain; thus, histochemical techniques must be used. Three experiments were carried out using 4-week-old Leghorn chickens. 2. Three, 80-chicken groups were orally infected with (1) 10(8) colony forming units (CFUs) Salmonella enteritidis, or (2) 10(4) Eimeria tenella oocysts, or (3) 10(8) CFUs S. enteritidis + 10(4) E. tenella oocysts. Ten chickens from each group were euthanased and caecum samples obtained. Caecum samples were fixed in 10% formalin (buffered, pH 7.4) at 4, 8, 12 h, 1, 3, 5, 7, and 14 d post-inoculation (PI). 3. Samples were stained using three different staining techniques: HE for the identification of heterophils and eosinophils, Ziehl-Neelsen for mast cells, and p-phenilenediamine dihydrochloride plus pyrocatechol (PPD + PC) for eosinophils. 4. Birds from Experiment 1 showed no changes in the numbers of granulocytes. Birds from Experiments 2 and 3 showed higher numbers of heterophils in caecal mucosa and submucosa separately, on d 5 and 7. In Experiment 3, a decrease was observed in submucosal mast cells on d 3. Chickens from Experiments 2 and 3 showed increased numbers of mucosal mast cells between d 7 and 14. 5. PPD + PC positively stained eosinophils, but not heterophils. 6. Numbers of heterophils and mast cells were increased during the acute inflammatory process caused by E. tenella. Therefore, mast cells could play a role as primary inflammatory cells. Eosinophils seem not to be part of the inflammatory process caused by E. tenella.

Animals↗
PubMed1975

Isolation and characterization of collagen-synthesizing polysomes from chick embryos.

Collagen-synthesizing polysomes were isolated by low-speed centrifugation of the post-mitochondrial supernatant of chick homogenates. Electron microscopy of the fraction thus isolated shows it to be exclusively composed of ribosomes. Amino acid incorporation in vitro showed that these particles were efficient in the incorporation of proline, but not tryptophan, as opposed to ribosomes obtained from the supernatant of the low-speed centrifugation. The incorporation process was highly dependent on GTP, and exibited an optimal Mg2+concentration of 5.6mM. The reaction was inhibited by RNase, elongation inhibitors as anysomycin, sparsomycin, fusidic acid and GDPCP. It was also moderately inhibited by initiation inhibitors such as aurintricarboxilic acid and pyrocatechol violet. The product of the incorporation was characterized as collagen by its sensitivity towards purified collagenase, lack of tryptophan, chromatography in CM-cellulose and molecular sieve chromatography in Sephadex G-200.

Animals↗
PubMed2004

Effect of 3,4-dihydroxyphenylalanine on Cu(2+)-induced inactivation of HDL-associated paraoxonasel and oxidation of HDL; inactivation of paraoxonasel activity independent of HDL lipid oxidation.

Paraoxonasel (PON1), one of HDL-asssociated antioxidant proteins, is known to be sensitive to oxidative stress. Here, the effect of endogenous reducing compounds on Cu(2+)-mediated inactivation of PON1 was examined. Cu(2+)-mediated inactivation of PON1 was enhanced remarkably by catecholamines, but not by uric acid or homocysteine. Furthermore, catecholamines such as 3,4-dihydroxyphenylalanine (DOPA), dopamine or norepinephrine were more effective than caffeic acid or pyrocatechol in promoting Cu(2+)-mediated inactivation of PON1, suggesting the importance of dihydroxybenzene group as well as amino group. DOPA at relatively low concentrations showed a concentration-dependent inactivation of PON1 in a concert with Cu2+, but not Fe2+. The DOPA/Cu(2+)-induced inactivation of PON1 was prevented by catalase, but not hydroxyl radical scavengers, consistent with Cu(2+)-catalyzed oxidation. A similar result was also observed when HDL-associated PON1 (HDL-PON1) was exposed to DOPA/Cu2+. Separately, it was found that DOPA at low concentrations (1-6 microM) acted as a pro-oxidant by enhancing Cu(2+)-induced oxidation of HDL, while it exhibited an antioxidant action at > or = 10 microM. In addition, Cu(2+)-oxidized HDL lost the antioxidant action against LDL oxidation. Meanwhile, the role of DOPA/Cu(2+)-oxidized HDL differed according to DOPA concentration; HDL oxidized with Cu2+ in the presence of DOPA (60 or 120 microM) maintained antioxidant activity of native HDL, in contrast to an adverse effect of DOPA at 3 or 6 microM. These data indicate that DOPA at micromolar level may act as a pro-oxidant in Cu(2+)-induced inactivation of PON1 as well as oxidation of HDL. Also, it is proposed that the oxidative inactivation of HDL-PON1 is independent of HDL oxidation.

Aryldialkylphosphatase↗
PubMed1981

Alternate chromogens as substitutes for benzidine for myeloperoxidase cytochemistry.

Myeloperoxidase staining methods for classification of leukemias have traditionally employed benzidine dihydrochloride as the chromogen. Recent Occupational Safety and Health Administration regulations have classified benzidine as a carcinogen, which severely restricts its use in the clinical laboratory. Twenty-two specimens from normal control subjects and leukemia patients, previously classified by FAB criteria, were stained with benzidine and two alternate chromogens, diaminobenzidine and Hanker-Yates reagent (p-phenylenediamine and pyrocatechol). In a random, blind fashion, three experienced observers scored the stains from each case according to quality of smear, degree of peroxidase positivity, tinctorial distinction between nucleus and cytoplasm, and overall acceptability of the stain. All three observers rated the substitute chromogens as adequate for routine myeloperoxidase cytochemical staining. It is concluded that either of the methods studied would have clinical utility and can substitute for benzidine as a myeloperoxidase chromogen.

Benzidines↗
PubMed1975

Isolation and characterization of collagen messenger RNA*.

Chick embryo collagen-synthesizing polysomes were isolated by differential centrifugation. RNA extracted from these particles was chromatographed in oligo(dT)-cellulose solumns and the mRNA thus obtained characterized as collagen mRNA by its electrophoetical mobility in acrylamide gels (equivalent to 1.05 x 10-6 daltons) and its effect upon a cell-free system derived from Krebs ascites tumor cells. The incorporation of 3H-proline was markedly dependent upon rabbit reticulocyte initiation factors and inhibited by initiation inhibitors such as aurintricaboxilate and pyrocatechol violet. The incorporation product was characterized as collagen by its lack of tryptophan, digestibility by purified bacterial collagenase, and by its co-chromatography with unlabled chick collagen in Sephadex G-200 and CM-cellulose columns.

Animals↗
PubMed1989

Enhancement by catechols of hydroxyl-radical formation in the presence of ferric ions and hydrogen peroxide.

The effect of caffeic acid, a kind of catechol, on the Fenton reaction was examined by using the ESR spin trapping technique. Caffeic acid enhanced the formation of hydroxyl radicals in the reaction mixture, which contained caffeic acid, hydrogen peroxide, ferric chloride, EDTA, and potassium phosphate buffer. Chlorogenic acid, which is an ester of caffeic acid with quinic acid, also stimulated the formation of the hydroxyl radicals. Quinic acid did not stimulate the reaction, suggesting that the catechol moiety in chlorogenic acid is essential to the enhancement of the hydroxyl-radical formation. Indeed, other catechols and related compounds such as pyrocatechol, gallic acid, dopamine, and noradrenaline effectively stimulated the formation of the hydroxyl radicals. The above results confirm the idea that the catechol moiety is essential to the enhancement. Ferulic acid, 4-hydroxy-3-methoxybenzoic acid, and salicylic acid had no effect on the formation of the hydroxyl radicals. The results indicate that the enhancement by the catechols of the formation of hydroxyl radicals is diminished if a methyl ester is formed at the position of the hydroxyl group of the catechol. In the absence of iron chelators such as EDTA, DETAPAC, desferrioxamine, citrate, and ADP, formation of hydroxyl radicals was not detected, suggesting that chelators are essential to the reaction. The enhancement of the formation of hydroxyl radicals is presumably due to the reduction of ferric ions by the catechols. Thus, the catechols may exert deleterious effects on biological systems if chelators such as EDTA, DETAPAC, desferrioxamine, citrate, and ADP are present.

Caffeic Acids↗
PubMed1977

Degradation of benzenesulfonate to sulfite in bacterial extract.

Sulfite formation from benzenesulfonate was studied in extracts from a bacterium grown on this compound as a main carbon source. The activity of sulfite formation depended on the presence of NADH and oxygen as well as magnesium, suggesting an oxygenation-type reaction. The activity was found in a fraction precipitated by ammonium sulfate at 35-50% saturation; the specific activity was 15 times higher than that of crude extract, probably due to the elimination of inhibitory substances of low molecular weight from the preparation. In a distillate of the reaction mixture, phenol was found. Pyrocatechol as well as benzenesulfonate was oxidized in the crude extract, but phenol was not.

Aerobiosis↗
PubMed1986

Immunocytochemical localization of insulin-like immunoreactivity in mouse seminal vesicle.

Insulin-like immunoreactivity was localized in tissue sections and cell cultures of mouse seminal vesicle using the indirect technique of immunocytochemistry. Seminal vesicles were cut into fragments, fixed in 2.5% glutaraldehyde, embedded in epoxy resin, sectioned at 1 micron, and transferred to glass slides. Epithelial cell cultures of seminal vesicle were grown on coverslips in Dulbecco's Minimal Essential Medium for 4-6 days and fixed in 2.5% glutaraldehyde. Sections (etched with sodium ethanolate) or coverslips were incubated in guinea pig antiporcine insulin antiserum, in antiserum immunoabsorbed with porcine insulin, or in normal guinea pig serum. For indirect immunocytochemistry, incubation with primary antiserum was followed by treatment with rabbit anti-guinea pig immunoglobulin (Ig) G conjugated to peroxidase, or with protein A and then rabbit peroxidase anti-peroxidase (PAP). Finally, treated samples were incubated in phenylenediamine-pyrocatechol-H2O2 substrate mixture for 6-8 min at room temperature. Specific immunoreactivity to insulin antisera was confined to the epithelium of the seminal vesicle in tissue sections. No staining occurred in subepithelial connective tissue. Specific immunoreactivity was also observed in the cytoplasm of cultured seminal vesicle epithelial cells.

Animals↗
PubMed1973

Purification and some properties of two polyphenol oxidases from bartlett pears.

Two polyphenol oxidases (enzymes A and B) from Bartlett pear (Pyrus communis) peelings were purified to electrophoretic homogeneity according to polyacrylamide gel by a combination of Sephadex gel filtration, diethylaminoethyl cellulose chromatography and hydroxyl apatite chromatography. While the two enzymes differ electrophoretically at pH 9.3, chromatographically on hydroxyl apatite, and in the effect of ionic strength on activity, they are similar with respect to chromatography on diethylaminoethyl cellulose, substrate specificity, pH activity relations, inhibition by p-coumaric and benzoic acids, and heat stability. The two enzymes are o-diphenol oxidases with no detectable monophenolase or laccase activities. Pyrocatechol, 4-methyl catechol, chlorogenic acid, and d-catechin are good substrates of the enzymes with K(m) values in the range of 2 to 20 mm. Dependences of activity on oxygen and chlorogenic acid concentrations indicate a sequential mechanism for binding of these substrates to enzyme B. V(max) and K(m) values for oxygen and chlorogenic acid were 103 mumoles O(2) uptake per minute per milligram of enzyme, 0.11 mm and 7.2 mm, respectively, for enzyme B at pH 4.0. Both enzymes had maximum activity at pH 4.0 on chlorogenic acid. K(m) values for chlorogenic acid were independent of pH from 3 to 7; the V(max) values for both enzymes gave bell-shaped curves as a function of pH. p-Coumaric acid is a simple, linear noncompetitive inhibitor with respect to chlorogenic acid at pH 6.2 with K(i) values of 0.38 and 0.50 mm for enzymes A and B, respectively. Benzoic acid is a linear competitive inhibitor with respect to chlorogenic acid at pH 4.0 with K(i) values of 0.04 and 0.11 mm for enzymes A and B, respectively.

Journal Article↗
PubMed1997

Effect of tea polyphenols on histamine release from rat basophilic leukemia (RBL-2H3) cells: the structure-inhibitory activity relationship.

We studied the effect of tea polyphenols on histamine release from rat basophilic leukemia (RBL-2H3) cells. Among tea polyphenols, (-)- epigallocatechin gallate (EGCG) most strongly and dose-dependently inhibited histamine release from cells stimulated with a calcium ionophore, A23187. (-)-Epigallocatechin (EGC) and (-)-epicatechin gallate (ECG) with a triphenol residue moderately inhibited histamine release, whereas diphenolic (+)-catechin (C) and (-)-epicatechin (EC) did not. The magnitude of the inhibitory effect was in the order EGCG > ECG > EGC. Among simple polyphenols, the triphenol compounds, pyrogallol (PG) and gallic acid (GA) exerted inhibitory activity, but the diphenols, pyrocatechol, hydroquinone, and resorcinol did not. In addition, the mixture of PG and GA inhibited histamine release as strongly as EGCG with two triphenol residues. Similarly, they inhibited histamine release induced by IgE-antigen complex stimulation more efficiently than that induced by A23187 stimulation. EGCG did not inhibit the increase of intracellular Ca2+ in RBL-2H3 cells stimulated with A23187 or IgE antigen. These results indicate that the triphenol structure plays an important role in the inhibitory activity of tea polyphenols. Their activity seemed to be exerted through the metabolic events occurring after the elevation of intracellular Ca2+ concentration.

Animals↗
PubMed1977

Monitoring of the specific radioactivity of S-adenosylmethionine in kidney in vivo.

The specific radioactivity of S-adenosylmethionine was followed in the cat kidney during the infusion of L-[Me-3H]methionine into the corresponding renal artery. For this purpose 14C-labelled 4-(2-aminoethyl)pyrocatechol([14C]dopamine) as methyl acceptor was injected locally every 15 min and the 3H and 14C activity of the methylation product homovanillic acid, isolated from urine, was measured. Approximately 5% of the 14C label is excreted during the first renal passage as [14C]homovanillic acid. The specific activity of S-adenosy[Me-3H]methionine in the kidney was calculated from the known specific radioactivity of [14C]dopamine injected and the measured radioactivity ratio, 3H: 14C, of homovanillic acid isolated from urine. The specific activity of S-adenosyl[Me-3H]methionine reaches a constant value in kidney about 30-60 min after the beginning of the L-[Me-3H]methionine infusion. This plateau value was 28% +/- 14% (n = 5) lower than the specific activity of L-[Me-3H]methionine in the venous blood from the corresponding kidney. The difference between the specific radioactivity of S-adenosyl[Me-3H]methionine in kidney and of free methionine in plasma is explained by the existence of a methionine source of minor specific activity in the kidney. The average life span of S-adenosylmethionine in the kidney is 19.5 +/- 8.7 min (n = 5).

Animals↗
PubMed2005

The neurotransmitter noradrenaline rescues septal cholinergic neurons in culture from degeneration caused by low-level oxidative stress.

We have developed a model system in which rat basal forebrain cholinergic neurons degenerate progressively when maintained in culture conditions that make them susceptible to low-level oxidative stress. In this study, we showed that cholinergic neurons identified by acetylcholinesterase cytochemistry or choline acetyl transferase immunocytochemistry are rescued efficiently by the neurotransmitter noradrenaline (NA). The effect of NA required neither adrenoceptor activation nor intracellular accumulation. NA operated via a mechanism that precluded activation of a cell death pathway in which reactive oxygen species (ROS) and proapoptotic caspases were crucially involved. It is noteworthy that NA remained protective even when applied late in the degenerative process but before intracellular ROS began to increase. The high efficacy of iron chelators and catalase in preventing the death of cholinergic neurons in this model suggested that NA neutralized the effects of hydroxyl radicals produced through a Fenton-type reaction. Pyrocatechol [the diphenolic moiety of NA] was sufficient in itself to prevent ROS production and cholinergic cell demise, indicating that the catechol structure was instrumental for the neuroprotective function of NA. Therefore, the noncatecholic neurotransmitter GABA failed to prevent neurodegeneration. Nerve growth factor and brain derived neurotrophic factor, two trophic peptides for septal cholinergic neurons, did not afford protection by themselves and did not improve neuroprotection provided by NA. However, in the presence of NA, they both retained their efficacy to stimulate cholinergic parameters. These data indicate that NA-based therapeutic strategies may be of interest in such neurodegenerative conditions as Alzheimer's disease, where progressive cholinergic deficits occur.

Animals↗
PubMed2002

Activation of the mitogen-activated protein kinase (ERK(1/2)) signaling pathway by cyclic AMP potentiates the neuroprotective effect of the neurotransmitter noradrenaline on dopaminergic neurons.

We have shown previously that low concentrations of noradrenaline (NA) confer long-term but partial protection to tyrosine hydroxylase (TH(+)) dopaminergic neurons by reducing spontaneously occurring oxidative stress. We demonstrate here that the effect of NA is strongly enhanced by cAMP-elevating agents, in particular forskolin (FK), through a mechanism that does not involve activation of adrenoceptors. FK also enhanced the neuroprotective action of antioxidants that mimic the trophic effects of NA, such as trolox and pyrocatechol, but was totally ineffective by itself, suggesting that inhibition of oxidative stress was a required step to reveal the cAMP-dependent mechanism. Neuroprotection afforded by FK was rapidly reversible, optimal when the treatment was initiated in the early phase of the culture and exquisitely specific to dopaminergic neurons. FK stimulated the phosphorylation of extracellular signal-activated kinases (ERK)(1/2) in a subpopulation of dopaminergic neurons, suggesting that the mitogen-activated protein kinase (MAPK) pathway was involved in the effects of cAMP-elevating agents. Accordingly, inhibition of the upstream kinases of ERK(1/2) by 2'-amino-3'-methoxyflavone (PD98059) not only suppressed MAPK activation caused by FK but also abolished the survival promoting activity that this compound exerts on TH(+) neurons. PD98059 did not reduce, however, the trophic effects provided by NA alone. Surprisingly, the archetypal cAMP-dependent protein kinase was apparently not responsible for ERK(1/2) activation. The data suggest that the MAPK signaling pathway plays a key role in the trophic effects that cAMP elevating agents and NA cooperatively exert on TH(+) neurons.

Animals↗