Search PubMed⌕ Search

Biomedical subjects

A Rescigno

Publications and source records attributed to A Rescigno.

At least 37 records · Page 2Linked to original sources
PubMed1995

Autoxidation of 4-methylcatechol: a model for the study of the biosynthesis of copper amine oxidases quinonoid cofactor.

The autoxidation of 4-methylcatechol under quasi-physiological conditions, leading to 2-hydroxy-5-methyl-1,4-benzoquinone, was investigated. The effects of pH and metal ions were examined. An electrophilic attack of dioxygen to the 4-methylcatechol monoanion to form a transient peroxo species is proposed. It was concluded that such a non-enzymic conversion is likely for this model compound and for its physiological counterpart, a specific tyrosyl residue incorporated in the protein chain at the active site of copper amine oxidases.

Amine Oxidase (Copper-Containing)↗
PubMed1995

A hydroxyquinone with amine oxidase activity: preparation and properties.

The preparation and some properties of a hydroxyquinone showing an amine oxidase-like activity are described. The compound, 2-hydroxy-5-methyl-1,4-benzoquinone, oxidizes a wide range of primary amines, both benzylic and non-benzylic, at the expenses of molecular oxygen in the presence of Cu2+ ions, and reacts with hydrazine derivatives leading to stable, inactive adducts. This behaviour is similar to that of 2,4,5-trihydroxyphenylalanine quinone-containing amine oxidases and therefore the present compound could be a useful model to understand the reaction mechanism of those enzymes.

Amine Oxidase (Copper-Containing)↗
PubMed1995

Effect of NAD(P)H:quinone oxidoreductase on tyrosinase-mediated oxidation of opioid neuropeptides Leu-enkephalin and Met-enkephalin.

In vitro experiments are reported showing that NAD(P)H:(quinone acceptor) oxidoreductase (QR), purified from Glycine max seedlings, reduces Leu- and Met-enkephalin-tyrosinase oxidation products, in the presence of NADH or NADPH. QR was not capable to catalyze the reduction of N-acetyl-dopaquinone formed by the cation of mushroom tyrosinase on N-acetyl-L-tyrosine, while it was able to reduce dopachrome. The results support the hypothesis that QR can inhibit the formation of melanin-like compounds, as catalyzed by the action of tyrosinase on Leu-enkephalin and Met-enkephalin. It is proposed that, in the presence of NAD(P)H as the electron donor, the inhibition occurs by the specific conversion of the dopachrome-derivative into the reduced precursor, leucodopachrome-derivative.

Enkephalin, Leucine↗
PubMed1994

A dyed substrate for the assay of endo-1,4-beta-glucanases.

A new dyed substrate was prepared for the rapid determination of endo-1,4-beta-glucanases. Carboxymethylcellulose was coupled with Ruthenium red to obtain a violet powder, which was stable enough to allow for reproducible assays. The spontaneous reaction is based on ionic interactions between the negatively charged carboxymethylcellulose and the complex cation of the dye. The enzymic assay is based on spectrophotometric measurement at 535 nm of the enzyme-released dyed fragments with low-molecular-weight filterable through a 0.22 microns filter. The release of coloured fragments from this dyed substrate was proportional to its solubilization. The absorbance was directly proportional to the enzyme amount in the range 0.5-5.5 mU enzyme (A535 = 0.1-0.95). This enzymic assay is advantageous for both rapid time of analysis and sensitivity.

Carboxymethylcellulose Sodium↗
PubMed1994

On definition and use of the term bioavailability.

In common usage, the rate of absorption of an active ingredient or its therapeutic moiety is generally not mentioned in the context of bioavailability. In this communication it is shown that exclusion of the rate of absorption may have serious consequence on the interpretation of bioavailability depending on the underlying model for the system under study. In the case of endogenous substances, the term "bioavailability" is ambiguous unless one specifies whether it refers to availability of the exogenous substance only or the sum total of the exogenous and endogenous substances.

Absorption↗
PubMed1994

Photometric estimation of cadaverine oxidation by copper amine oxidase.

A simple method for the photometric estimation of 1-piperideine, produced by the action of copper amino oxidases on cadaverine, is described. A discussion on the formation of 1-piperideine from lysine in acidic medium is also reported, together with some observations on the nature of acid 1-piperideine-ninhydrin condensation product.

Amine Oxidase (Copper-Containing)↗
PubMed1993

Improved chromatographic purification of peroxidase and beta-glucosidase from Hordeum vulgare seedlings.

Peroxidases (E.C. 1.11.1.7., hydrogen donor oxidoreductase) utilize hydrogen peroxide or substituted peroxides for the oxidation of a large number of substrates. Peroxidases are widely distributed and have been isolated from many higher plants (1). The wide distribution of the enzyme suggests that it could be of great biological importance, but the physiological functions and metabolic control of these enzymes are still poorly understood. The simultaneous presence of amine oxidase and peroxidase in cell walls suggests that the peroxide generated on oxidation of the amines could be utilized by the peroxidase (2,3). Recently we have purified an amine oxidase from Hordeum vulgare (4) and we have attempted to purify the peroxidase in order to study in vitro the reconstituted coupled system. beta-glucosidase (beta-D-glucoside glucohydrolase E.C. 3.2.1.21.) is capable of transforming glucosides in glucose and the corresponding aglycone or disaccharides as cellobiose, sophorose, gentiobiose. This enzyme is widely distributed in plants, fungi, bacteria, yeasts and animals (5,6). In the homogenate of Hordeum vulgare seedlings we also found beta-glucosidase activity and also attempted to purify beta-glucosidase. This enzyme copurified with peroxidase up to the last step. We report here the isolation of peroxidase and beta-glucosidase from Hordeum vulgare seedlings: some molecular and kinetic properties are given.

Buffers↗
PubMed1992

Bioequivalence.

The bioequivalence of two formulations of the same drug may be determined by evaluating the similarity of their respective plasma concentration curves. The similarity of two plasma concentration functions can be measured by an index called the bioequivalence index. This paper shows how such an index may be defined and calculated.

Chemistry, Pharmaceutical↗
PubMed1992

Estimation of permanence time, exit time, dilution factor, and steady-state volume of distribution.

General solutions for exist time, permanence time, dilution factor, and volume of distribution at steady state are derived for compartmental and noncompartmental systems. These derivations require that the systems are linear and state-determined. Unique values for these parameters cannot be determined when the site of elimination is not known; in this case the parameters can be defined by a range. Interpretation of this range and its significance and use in clinical situations are illustrated with two examples.

Mathematics↗
PubMed1991

Olive milling wastewater as a medium for growth of four Pleurotus species.

Four species of Pleurotus were adapted to grow on olive milling wastewater, and in certain conditions produced high yield of fruit bodies. Some biochemical transformations were observed in the olive milling wastewater owing to the growth of Pleurotus. In particular, the fungi actively excreted large amounts of laccase in the medium, and at the same time the concentration of phenolics and other toxic compounds significantly decreased, as revealed by HPLC analysis and toxicity tests on standard cultures of human cell lines.

Culture Media↗
PubMed1990

Pharmacokinetics in patients of an anti-carcinoembryonic antigen antibody radiolabeled with indium-111 using a novel diethylenetriamine pentaacetic acid chelator.

The pharmacokinetics of the C110 anti-carcinoembryonic antigen antibody radiolabeled with 111In via a novel benzylisothiocyanate derivative of diethylenetriamine pentaacetic acid have been determined in 12 patients. The chelator was attached to the protein via a thiourea bond and in such a way that all 5 carboxymethyl arms were presumably able to participate in chelation. Patients with known or suspected colorectal carcinoma received between 5 and 20 mg of the IgG antibody labeled with 5 mCi of 111In. Individual organ radioactivity levels were quantitated, and serum and urine samples were analyzed, principally by size exclusion high-performance liquid chromatography (HPLC). Total urinary excretion averaged 0.18% of the injected dose/h with large patient to patient variation. At early times postadministration (less than 8 h) the predominant radiolabeled species in urine was free diethylenetriamine pentaacetic acid most probably administered as a small radiocontaminant in the injectate. Thereafter, radioactivity in urine was primarily present as a low molecular weight catabolic product. Analysis of serum by size exclusion HPLC occasionally showed 3 radioactivity peaks, 2 of which are due to circulating immune complexes and labeled antibody. The third peak is of low molecular weight and is due to one or more products of antibody catabolism. Transchelation of 111In to circulating transferrin was observed but at modest levels. Quantitation of organ radioactivity showed that 18 +/- 4 (SD)% of the injected dose was in the liver at 1 day postadministration and 1.4 +/- 1.1 and 1.2 +/- 0.9% was in the spleen and in both kidneys, respectively, at this time. The mean half-life for clearance of total injected radioactivity was fitted to a single exponential and was found to be 34 h (SD, 14 h; N = 13) and that for antibody alone, assessed by size exclusion HPLC analysis of serum samples, was calculated to be 22 h (SD, 8 h; N = 10). Neither of these values nor organ radioactivity levels were affected by antibody-loading dose.

Adult↗