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Biomedical subjects

A Vetere

Publications and source records attributed to A Vetere.

At least 19 recordsLinked to original sources
PubMed2005

The aggregation of pig articular chondrocyte and synthesis of extracellular matrix by a lactose-modified chitosan.

A reductive amination reaction (N-alkylation) obtained exploiting the aldheyde group of lactose and the amino group of the glucosamine residues of chitosan (d.a. 89%) afforded a highly soluble engineered polysaccharide (chitlac) for a potential application in the repair of the articular cartilage. Chitosan derivatives with 9% and 64% of side chain groups introduced have been prepared and characterized by means of potentiometric titration, (1)H-NMR and intrinsic viscosity. Both polymers, with respect to the unmodified chitosan, induce cell aggregation when in contact with a primary culture of pig chondrocytes, leading to the formation of nodules of considerable dimensions (up to 0.5-1 mm in diameter). The nodules obtained from chondrocytes treated with chitlac with the higher degree of substitution have been studied by means of optical and electron microscopy (SEM, TEM) and the production of glycosaminoglycans (GAGs) and collagen has been measured by means of colorimetric assays. The chondro-specificity of GAG and collagen was determined by RT-PCR. The results show that the lactose-modified chitosan is non-toxic and stimulates the production of aggrecan and type II collagen.

Animals↗
PubMed2000

Regiospecific transglycolytic synthesis and structural characterization of 6-O-alpha-glucopyranosyl-glucopyranose (isomaltose).

The enzymatic synthesis of 6-O-alpha-glucopyranosyl-glucopyranose (isomaltose) was achieved. The regiospecific transglycosylation reaction was catalyzed by a crude preparation of alpha-D-glucosidase from Aspergillus niger, using p-nitrophenyl alpha-D-glucopyranose as the donor and glucopyranose as the acceptor. The yield of the reaction was 59% on a molar basis with respect to the donor. The structural identity of the product was fully determined by HPLC, HPAEC-PAD, ionspray mass spectrometry and (13)C NMR.

Aspergillus niger↗
PubMed2000

Selective upregulation of cardiac endothelin system in patients with ischemic but not idiopathic dilated cardiomyopathy: endothelin-1 system in the human failing heart.

Only scarce information is available on the activity and modifications of the cardiac endothelin (ET)-1 system in heart failure due to ischemic (ICM) or idiopathic dilated (DCM) cardiomyopathy. The activity of the ET-1 system was investigated by measuring cardiac ET-1 and big ET-1 formation and quantifying cardiac mRNA for prepro-ET-1 (ppET-1), ET-converting enzyme-1, and ET(A) and ET(B) receptors both in myocardium and in isolated myocytes using Northern blot, reverse transcription-polymerase chain reaction, and in situ hybridization in 22 patients with DCM and 20 with ICM who underwent cardiac transplantation and in 7 potential heart transplant donors (nonfailing hearts). Notwithstanding a similar increase of plasma ET-1 in the 2 groups, cardiac ET formation, mRNA levels for ppET-1, and ET(A) and ET(B) receptors were higher on both the myocardium and isolated myocytes from ICM than on those from DCM hearts (P<0.001 for all). ppET-1 and ET-converting enzyme-1 mRNAs were expressed on myocytes and endothelial and interstitial cells in ICM, whereas in DCM and nonfailing hearts they were mainly expressed on nonmyocyte cells. In both ICM and DCM, the ET(A) mRNA signal was expressed on both myocytes and nonmyocyte cells, whereas ET(B) mRNA was almost exclusively localized on nonmyocyte cells. ET(A)- and ET(B)-specific receptor binding was increased on both myocytes and cardiac membranes, showing a positive correlation with left ventricular ejection fraction in ICM (r=0.78 and 0.70) but not in DCM patients. The present results show that human ventricular myocytes express all of the components of the ET-1 system, which is selectively upregulated in ICM patients and appears to be functionally important in the maintenance of cardiac function.

Adult↗
PubMed2000

Regiospecific glycosidase-assisted synthesis of lacto-N-biose I (Galbeta1-3GlcNAc) and 3'-sialyl-lacto-N-biose I (NeuAcalpha2-3Galbeta1-3GlcNAc).

The all-transglycolytic synthesis of lacto-N-biose I (Galbeta1-3GlcNAc) and 3'-sialyl-lacto-N-biose I (NeuAcalpha2-3Galbeta1-3GlcNAc) was performed. The disaccharide lacto-N-biose I was obtained by use of p-nitrophenyl beta-D-galactopyranoside as the donor, 2-acetamido-2-deoxy-D-glucopyranose as the acceptor and Xanthomonas manihotis beta-D-galactosidase as the catalyst. The reaction was shown to be regiospecific, with a high molar yield (about 55%) with respect to the donor. Lacto-N-biose I obtained by this method was used as the acceptor for a subsequent enzymatic reaction catalyzed by Trypanosoma cruzi trans-sialidase in which 2'-(4-methylumbellyferyl)-alpha-D-N-acetylneuraminic was used as the donor of the N-acetylneuraminil moiety. The reaction generated the product, 3'-sialyl-lacto-N-biose I, regiospecifically and with a molar yield of about 35%.

Acetylglucosamine↗
PubMed1999

Thermodynamics of the conformational transition of biopolyelectrolytes: the case of specific affinity of counterions.

A formal development of the Counterion Condensation theory (CC) of linear polyelectrolytes has been performed to include specific (chemical) affinity of condensed counterions, for polyelectrolyte charge density values larger than the critical value of condensation. It has been conventionally assumed that each condensed counterion exhibits an affinity free-energy difference for the polymer, (DeltaG(aff)). Moreover, the model assumes that the enthalpic and entropic contributions to DeltaG(aff), i.e., DeltaH(aff) and DeltaS(aff), are both independent of temperature, ionic strength and polymer concentration. Equations have been derived relative to the case of the thermally induced, ionic strength dependent, conformational transition of a biopolyelectrolyte between two conformations for which chemical affinity is supposed to take place. The experimental data of the intramolecular conformational transition of the ionic polysaccharide kappa-carrageenan in dimethylsulfoxide (DMSO) have been successfully compared with the theoretical predictions. This novel approach provides the enthalpic and entropic affinity values for both conformations, together with the corresponding thermodynamic functions of nonpolyelectrolytic origin pertaining to the biopolymer backbone change per se, i.e., DeltaH(n.pol) and DeltaS(n.pol), according to a treatment previously shown to be successful for lower values of the biopolyelectrolyte linear charge density. The ratio of DeltaH(n.pol) to DeltaS(n.pol) was found to be remarkably constant independent of the value of the dielectric constant of the solvent, from formamide to water to DMSO, pointing to the identity of the underlying conformational process.

Biopolymers↗
PubMed1998

Separation and characterization of three beta-galactosidases from Bacillus circulans.

Crude preparation of Bacillus circulans beta-galactosidase is known to have a good transglycolytic activity. Two isoforms of the enzyme have been described so far in the literature. Aiming at separating these two forms to assess their relative contribution to the regioselectivity of transglycosylation, we observed the presence of a third isoform never described before. This paper deals with the isolation procedures of the three enzymes and a re-consideration of their properties. The estimated molecular weight for the isoforms were 212 kDa (I), 145 kDa (II) and 86 kDa (III), respectively. Kinetic parameters were determined towards the hydrolysis of o-nitrophenyl-beta-d-galactopyranoside (ONPG) and lactose. For ONPG the following values of Km were found: 3.6, 5.0 and 3.3 mM for I, II and III, respectively, whereas for lactose the values were 3.7, 2.94 and 2.71 mM, respectively.

Bacillus↗
PubMed1998

Enzymatic synthesis and characterization of 6-O-Beta-D-xylopyranosyl-2-acetamido-2-deoxy-D-glucopyranose, a structural analog of primeverose.

The synthesis of the disaccharide 6-O-beta-D-xylopyranosyl-2-acetamido-2-deoxy-D-glucopyranose (N-acetylprimeverosamine), structurally related to the natural disaccharide 6-O-beta-D-xylopyranosyl-D-glycopyranose (primeverose), was obtained via a transglycosylation reaction catalyzed by a crude preparation of beta-D-xylosidase from Aspergillus niger, using p-nitrophenyl beta-D-xylopyranoside as the donor and 2-acetamido-2-deoxy-D-glucopyranose as the acceptor. The yield of the reaction was 36% on a molar basis with respect to the donor. The chemical identity of the product was assessed by HPLC, ionspray mass spectrometry and NMR spectroscopy.

Aspergillus niger↗
PubMed1997

All-transglycolytic synthesis and characterization of sialyl(alpha2-3)galactosyl(beta1-4)xylosyl-p-nitrophenyl(beta1-), an oligosaccharide derivative related to glycosaminoglycan biosynthesis.

Beta-D-Xylopyranosides, such as p-nitrophenyl-beta-D-xylopyranoside (Xyl-Np) or 4-methylumbelliferyl-beta-D-xylopyranoside (Xyl-MeUmb), when added to the culture medium of human skin fibroblasts have previously been shown to produce some Np- or MeUmb-oligosaccharides related to the regulation of glycosaminoglycan biosynthesis. Among these oligosaccharide derivatives, we synthesized the trisaccharide derivative NeuAc(alpha2-3)Gal(beta1-4)Xyl-Np(beta1- as a potential inhibitor of human skin fibroblast glycosaminoglycan biosynthesis. This synthesis was achieved by sequential use of transglycosylating activities of Escherichia coli beta-galactosidase and Trypanosoma cruzi trans-sialidase. The structure of the oligosaccharide obtained was determined by HPLC, ion-spray mass spectrometry, and NMR.

Carbohydrate Conformation↗
PubMed1997

All-aqueous, regiospecific transglycosylation synthesis of 3-O-alpha-L-fucopyranosyl-2-acetamido-2-deoxy-D-glucopyranose, a building block for the synthesis of branched oligosaccharides.

A transglycosylation reaction, carried out in an aqueous medium and catalyzed by a crude preparation of alpha-fucosidase (E.C. 3.2.1.51) from Aspergillus niger, allowed for the regiospecific synthesis of the disaccharide 3-O-alpha-L-fucopyranosyl-2-acetamido-2-deoxy-D-glucopyranose using p-nitrophenyl-alpha-L-fucopyranose as the donor and 2-acetamido-2-deoxy-D-glucopyranose as the acceptor. The chemical identity of the product obtained was demonstrated by HPLC, ion spray mass spectrometry and NMR spectroscopy. Further transglycosylation using a beta-galactosidase (E.C. 3.2.1.23) yielded the branched oligosaccharide 2-acetamido-2-deoxy-3-O-(alpha-L-fucopyranosyl)-4-O-(beta-D-galactopyran osyl)-D-glucopyranose, i.e., the Lewis(x) antigen.

Aspergillus niger↗
PubMed1996

Complete synthesis of 3'-sialyl-N-acetyllactosamine by regioselective transglycosylation.

Transglycolytic synthesis of 3'-sialyl-N-acetyllactosamine by sequential use of beta-galactosidase from Bacillus circulans and trans-sialidase from Trypanosoma cruzi was described. These reactions depicted the first complete synthesis of a biologically important oligosaccharide with high regioselectivity avoiding use of glycosyltransferases and NDP sugars.

Amino Sugars↗
PubMed1996

High-yield synthesis of N-acetyllactosamine by regioselective transglycosylation.

The synthesis of N-acetyllactosamine (D-Galp beta 1-4D-GlcpNAc) with very low contamination of its isomer N-acetyllactosamine (D-Galp beta 1-6D-GlcpNAc) was obtained by use of regioselective transglycosylation activity of beta-galactosidase from Bacillus circulans using lactose as the donor of D-Galp and D-GlcpNAc as the acceptor. The reaction was conducted at 15 degrees C and at pH 5.0. The incubation time was considerably reduced and the yield improved 100% with respect to the best results so far described in the literature.

Amino Sugars↗
PubMed1995

Sleep disruption in young children. The influence of temperament on the sleep patterns of pre-school children.

Sleep problems are a common concern of parents with toddlers. Various reasons have been put forward as to the possible causes and maintenance of sleep disruption. These have included neurophysical differences in the child, perinatal differences such as a long labour and depression and anxiety in the parents themselves resulting in adverse effects on the child's sleep patterns. However, recent research has indicated that a child's temperamental style may be a possible causal factor as to whether the child will present its parents with a sleep problem. This study, therefore, sets out to investigate the importance of temperament as a predictor of whether children may or may not have sleep problems. Environmental factors are controlled as far as possible by selecting toddlers with and without sleep problems from very similar environments. Case studies are also introduced to further illuminate other possible associated factors such as parental handling. The results from this study found significant differences in the temperament profiles of children with and without sleep problems. Children with reported sleep problems were more likely to obtain a 'intermediate high to difficult' profile. Various findings from a group of toddlers with and without sleep problems are discussed in this paper together with implications of the findings and recommendations for further research.

Behavior Therapy↗
PubMed1994

Properties of the flavoenzyme D-aspartate oxidase from Octopus vulgaris.

The properties of D-aspartate oxidase from Octopus vulgaris (EC 1.4.3.1) have been investigated. The protein is a monomer of M(r) 37,000 containing one mol flavin/mol protein. The enzyme as isolated exists at least in two forms, one containing FAD and the other, which is catalytically inactive, probably containing 6-OH-FAD, as inferred from the absorption spectrum of the enzyme. An additional form of the enzyme, as far as the nature of the coenzyme is concerned, has been detected in the purified enzyme and shown to derive from the form originally containing FAD. The modulation of the coenzyme reactivity exerted by Octopus D-aspartate oxidase, as studied by spectrophotometric techniques, conforms to the one expected for an enzyme belonging to the oxidase class of flavoproteins. Structural investigations show similarities in both the amino-acid composition and the N-terminal amino-acid sequence to bovine D-aspartate oxidase and porcine D-amino-acid oxidase. In summary, the general properties of the enzyme from Octopus vulgaris closely resemble those of the enzyme from beef kidney. Moreover, kinetic analyses suggest that two active-site residues with pKa of 7.1 and 9.1 are critical for catalysis, and that the ionization of such residues has different effects on the catalytic activity depending whether mono- or dicarboxylic D-amino acids are used as substrate.

Amino Acid Oxidoreductases↗
PubMed1993

Biological role of D-amino acid oxidase and D-aspartate oxidase. Effects of D-amino acids.

D-Amino acids administered to animals are absorbed by the intestine and transported through the blood-stream to solid tissues where they are oxidized in vivo by D-amino acid oxidase and D-aspartate oxidase to produce the same compounds they do in vitro; i.e. NH3, H2O2, and the keto acid corresponding to the amino acid ingested. In the liver and kidneys of the animals, an inverse relationship exists between the occurrence of D-amino acids and these oxidative enzymes. For example, younger animals have lower amounts of these oxidases and consequently higher concentrations of free D-amino acids compared to adult animals. If the ingested D-amino acids are not metabolized by these enzymes, they will accumulate in the tissues and may provoke serious damage, e.g. suppression of the synthesis of other essential enzymes and inhibition of the growth rate of the animals. A specific enzyme induction for these D-amino acid oxidases exists in young rats following ingestion of free D-amino acids by the mother. Specifically, when a mother rat ingests D-Ala or D-Asp during pregnancy and suckling, an increase in D-amino acid oxidase or D-aspartate oxidase is observed in the liver and kidneys of the baby rats. These results suggest that the in vivo biological role of these oxidases in animals is to act as detoxifying agents to metabolize D-amino acids which may have accumulated during aging.

Amino Acid Oxidoreductases↗
PubMed1993

Occurrence of free D-aspartic acid in the circumsoesophageal ganglia of Aplysia fasciata.

This study reports the presence of high concentrations of free D-aspartic acid (D-Asp) in the circumoesophageal ganglia of the opisthobranch mollusc Aplysia fasciata. D-Asp was discovered using specific methods that employ Octopus D-aspartate oxidase and hog kidney D-amino acid oxidase to measure D-Asp levels. The concentration of D-Asp was 0.281 mumol/g wet tissue weight, which was 8.3% of the total free aspartic acid (D and L forms) present. No other free D-amino acids that were oxidised by D-amino acid oxidase were detected. To our knowledge the only molluscs that have previously been shown to have D-Asp within their nervous tissue are the cephalopods Octopus vulgaris, Loligo vulgaris and Sepia officinalis. In these, as in A. fasciata, no other D-amino acids were detected within the nervous tissue. The fact that free D-Asp occurs specifically in the nervous tissue of the above molluscs suggests that it may have a neurological function that is yet to be described.

Animals↗
PubMed1992

Presence of D-alanine in proteins of normal and Alzheimer human brain.

This report constitutes the first demonstration of the presence of D-alanine in the proteins of the human nervous system. Proteins of the frontal lobe white and gray matter of human brains, both normal and Alzheimer subjects, contain D-alanine at concentrations between 0.50 and 1.28 mumol/g of wet tissue, 50-70-times lower than the concentration of L-alanine. Both white and gray matter of Alzheimer brains contain D-alanine 1.4-times higher than the respective regions of normal brains. The gray matter proteins of Alzheimer brains show a highly significant 8% decrease in total alanine content, when compared with normal brain gray matter proteins. Since Alzheimer's disease is exhibited by deterioration of the gray matter, the occurrence of elevated D-alanine levels in the gray matter of Alzheimer brains is a significant discovery and raises the question whether this enantiomer causes the degeneration of the gray matter proteins in Alzheimer's disease, or whether it is an effect of the disease.

Aged↗