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T Severin

Publications and source records attributed to T Severin.

At least 19 recordsLinked to original sources
PubMed2001

Formation of a novel colored product during the Maillard reaction of D-glucose.

Reactions between reducing sugars and proteins or amino acids (Maillard reaction) lead to the formation of yellow to brown products (melanoidins) that are important for food preparation and processing, such as baking, roasting, or malt production. Thus far, the structures of the melanoidins have not been elucidated, although some structural insights have been gained from model reactions. In this study, D-glucose was heated with an amine and two colored compounds were detected by HPLC/UV--vis. After purification, the main product was identified as [(4aS,6R,7S,8R,8aR)-4,4a,6,7,8,8a-hexahydro-7,8-dihydroxy-6-hydroxymethyl-1,4-dipropyl-1H-pyrano[2,3-b]pyrazine-2-yl]-1-hydroxy-3-buten-2-one (1a). For the minor compound (2a), some spectral data were obtained, but the structure was not fully characterized. 1a and 2a are the main colored compounds when the reaction is performed in alcoholic solution or on a cellulose surface. Thus, it was concluded that products with an analogous structure are important for the color formation of foodstuffs with low water activity.

Chromatography, High Pressure Liquid↗
PubMed2001

Heparin-induced thrombocytopenia in pediatrics.

As in adult patients, heparin is used for prophylaxis and treatment of thromboembolism in newborns, children, and adolescents. Patients receiving heparin are potentially at risk to develop heparin-induced thrombocytopenia (HIT). HIT type II has been extensively described in the adult population; only a few reports address HIT type II in pediatric patients (total of 15 neonates, 4 young children, 12 older children and adolescents). The available data are discussed, and the case of a patient with recurrent thrombosis and HIT type II without thrombocytopenia is presented. The review of the literature reveals that HIT type II occurs especially in neonates and adolescents, corresponding to the two age peaks of thrombosis in pediatric patients. Risk factors for thrombosis include hereditary factors, immobilization, and surgery. HIT complications are severe and partly lead to life-threatening thromboembolism. In three patients, an increasing heparin demand was found. In five cases, thrombocytopenia was absent. Heparin was replaced mostly by danaparoid sodium; in three patients hirudin was used as an alternative anticoagulant. HIT type II represents a potentially dangerous complication of heparin therapy in pediatric patients and should be taken into consideration whenever heparin is given for prophylactic or therapeutic use in newborns, children, or adolescents.

Adolescent↗
PubMed2000

Formation of tetrahydro-beta-carbolines and beta-carbolines during the reaction of L-tryptophan with D-glucose.

The reaction of L-tryptophan (Trp) with D-glucose under conditions that can occur during food processing and preparation was studied by high-performance liquid chromatography with diode array detection (HPLC/DAD). Besides the well-established glucose-tryptophan Amadori product (AP), (1R,3S)-1-(D-gluco-1,2,3,4,5-pentahydroxypentyl)-1,2,3, 4-tetrahydro-beta-carboline-3-carboxylic acid (PHP-THbetaC) was identified as an important product of this reaction. For preparation, PHP-THbetaC was obtained in high yields when Trp and D-glucose were reacted under strongly acidic conditions after heating in methanol. At elevated reaction temperatures (150 degrees C) 1-acetyl-beta-carboline (acetyl-betaC), was detected in significant concentrations. The mixtures were heated under variations of reaction time and temperature, and AP, PHP-THbetaC, and acetyl-betaC were quantified. In the presence of air oxygen or mild, food relevant oxidants, such as L-dehydroascorbic acid, PHP-THbetaC was readily oxidized to a product that was identified as the previously unknown 1-(D-gluco-1,2,3,4,5-pentahydroxypentyl)-beta-carboline (PHP-betaC). Formation of PHP-THbetaC and PHP-betaC in foodstuffs would deserve particular interest because multiple physiological activity of THbetaC and betaC derivatives has been shown previously.

Carbolines↗
PubMed2000

DDAVP (desmopressin; 1-deamino-cys-8-D-arginine-vasopressin) treatment in children with haemophilia B.

We tested the response to desmopressin (1-deamino-cys-8-D-arginine-vasopressin; DDAVP) in four patients with haemophilia B [factor IX (F IX) at diagnosis 1.4-5%]. The activated partial thromboplastin time (aPTT) was significantly shortened in all patients. Although there was an up to 1.4-fold increase in F IX levels in three patients, maximal F IX activity remained below 10%. Much more prominent were the increases in F VIII (three- to fourfold), in von Willebrand factor antigen (VWF:Ag; 2.5-fold) and particularly in VWF collagen-binding activity (VWF:CBA; fivefold). These changes were reflected by the prophylactic efficacy of DDAVP for dental surgery. After pretesting, DDAVP could be a useful drug for reducing the need for plasma products for prevention of minor surgical bleeding in patients with mild to moderate haemophilia B.

Adolescent↗
PubMed1998

Cross-linking of proteins by Maillard processes--model reactions of D-glucose or methylglyoxal with butylamine and guanidine derivatives.

Advanced Maillard reaction in proteins leads to formation of covalently cross-linked aggregates the chemical nature of which is largely unknown. From model reactions of methylglyoxal and butylamine with creatine or alpha-N-acetyl-L-arginine, one main product each was isolated. These two compounds were identified, on the basis of unequivocal spectroscopic evidence, as 2-[(5-butylimino-4-methyl-4,5-dihydro-1H-2-imidazolyl)(methyl)amin o]acetic acid and 2-acetylamino-5-[(5-butylimino-4-methyl-4,5-dihydro-1H-2-imidazoly l)amino]pentanoic acid, respectively. Using D-glucose instead of methylglyoxal, two main products each were obtained from reaction with the respective guanidine derivative. The spectroscopic data definitively establish the formation of the diastereoisomeric 2-[(4-butyl-6,7-dihydroxy-4,5,6,7,8,8a-hexahydroimidazo[4,5-b]a zepin-2-yl)(methyl)amino]acetic acid from the reaction with creatine, and of the diastereoisomeric 2-acetylamino-5-[(4-butyl-6,7-dihydroxy-4,5,6,7,8,8a-hexahydroimidazo [4,5-b]azepin-2-yl)amino]pentanoic acid from the reaction with alpha-N-acetyl-L-arginine. All products were isolated in fairly good yield and represent 1:1:1 adducts of the respective reaction partners. Formation of these compounds thus constitutes an efficient reaction pathway for linking primary amines to guanidine derivatives. It seems justified, therefore, to expect cross-linking of proteins by action of reducing carbohydrates to proceed analogously.

Butylamines↗
PubMed1994

pH-dependent LAK cell cytotoxicity.

In the microenvironment of many solid tumors the pH is considerably lower (mean pH between 6.6 to 7.2) than the pH in normal tissue (pH 7.0-7.5). Therefore, the influence of acidic pH on the cytotoxic activity of lymphokine-activated killer cells (LAK cells) after different culture periods was tested. K-562 human erythroleukemia cells were selected as target cells. Cell killing was measured using a two-color flow cytometric method. At physiological pH of 7.4, LAK cell-mediated cytotoxicity ranged from 15 to 48% (E:T ratio = 50:1). The specific lysis of target cells was considerably reduced (up to 70% inhibition of specific lysis) under acidic conditions (pH 6.8, 6.3, 5.8). This effect was independent of donors, duration of the culture period, and the E:T ratio in the cytotoxic assay. As pH gradients surrounding tumor cells may reach values below pH 6.0 at the cell surface, the pH-dependence of LAK cell cytotoxicity could at least partially explain the inhibition of the natural immune response in solid tumors. Therapeutic immunological strategies concerning the enhancement of the natural immune response like LAK cell and IL-2 immunotherapy including IL-2 gene therapy may only be successful if a simultaneous inhibition of the acidification process and an elevation of tumor pH is achieved.

Cell Line↗
PubMed1990

Formation of acids, lactones and esters through the Maillard reaction.

From a glucose/glycine reaction mixture acids, esters and lactones were isolated and identified. Sugar degradation products could also be determined as benzimidazole derivatives after reaction with o-phenylenediamine. Results derived from model systems suggested possible reaction pathways leading to some of the isolated substances. A lactic acid ester is formed as a product of an unstable beta-pyranone intermediate. A 3-deoxyhexosone serves as a precursor of two furanolactones.

Acids↗
PubMed1989

[Maillard reaction of bovine serum albumin with glucose. Determination of 2-formyl-5-(hydroxymethyl)pyrrole-1-norleucine by high-performance liquid chromatography after alkaline hydrolysis].

Reactions between glucose and bovine serum albumin proceed predominantly at the side chain amino groups of lysine residues. Among other products, protein-bound 2-formyl-5-(hydroxymethyl)pyrrole-1-norleucine is formed. After alkaline hydrolysis and fractionation of the protein hydrolysate on RP-18 material this substance can be separated by high-performance liquid chromatography. The identity of the norleucine derivative with a synthesized compound can be determined with fast atom bombardment-mass spectrometry spectral data. A colour reaction with thiobarbituric acid is also suitable for detection.

Chromatography, High Pressure Liquid↗
PubMed1989

Chemical pathways of the Maillard reaction.

From reaction mixtures of reducing sugars with primary and secondary amines many heterocyclic and carbocyclic compounds have been separated. From the structures of these substances together with the knowledge about reactive intermediates some degradation pathways can be proposed. Caused by the nature of the sugar (pentose, mono- or disaccharide) and the amine (primary or secondary) differences in the pathways are observed. An attempt is made to present some reactions with emphasis to the Maillard reaction in mammalians.

Chemical Phenomena↗