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Biomedical subjects

M Bosco

Publications and source records attributed to M Bosco.

At least 37 records · Page 2Linked to original sources
PubMed2001

Isolation and characterization of the exopolysaccharide produced by Streptococcus thermophilus SFi20.

This paper reports isolation, structural characterization and some physico-chemical properties in aqueous solution of the exopolysaccharide (EPS) produced by Streptococcus thermophilus strain SFi20. The yield of the purified EPS was found to be reproducible and close to the average value of 143 mg/l. The chemical structure, previously suggested, has been confirmed on the basis of NMR data. Viscometric, chiro-optical and rheological measurements have been carried out with the aim of characterizing the conformational state of the polysaccharide in aqueous solution. All the data reported indicate that the EPS does not undergo a cooperative conformational transition under the investigated experimental conditions. Furthermore, the viscosity data and the viscoelastic behaviour suggest that the polymer is rather flexible and adopts a random coil conformation in aqueous solution.

Carbohydrate Conformation↗
PubMed2001

Increased airway responsiveness and decreased alveolar attachment points following in utero smoke exposure in the guinea pig.

Maternal smoking during pregnancy has been shown to result in abnormalities in lung function in newborn infants, including reduced expiratory flow and increased airway responsiveness to inhaled agonists. The mechanisms by which this occurs remain unclear. Using a guinea pig model of in utero smoke exposure, we measured airway responsiveness and lung morphology in a group of neonatal guinea pigs 21 d after delivery. Pregnant guinea pigs were exposed to cigarette smoke from Day 28 to term (Day 68 of gestation). After delivery newborn animals did not receive any smoke exposure. Airway wall thickness, smooth muscle area, and the number of points where the alveoli attached to the airway adventitia were measured. Airway responsiveness was increased (p < 0.05) and the mean distance between alveolar attachment points was increased (mean 0.052 +/- SE 0.001 mm versus 0.046 +/- 0.001, p = 0.001) in animals exposed to cigarette smoke in utero compared with nonexposed animals. Although not statistically significant, both the inner and outer airway wall and the smooth muscle area were greater in exposed animals compared with nonexposed animals. The increased mean distance between alveolar attachments in the smoke-exposed group was the result of a reduction in the number of attachments and an increase in the outer airway wall perimeter. These findings suggest that the increased airway responsiveness observed in postnatal animals, subsequent to in utero cigarette smoke exposure, may be the result of decreased alveolar attachment points to the airways and changes in airway dimensions.

Animals↗
PubMed2000

A novel route to the vinyl sulfide nine-membered macrocycle moiety of Griseoviridin.

The synthetic potentialities of cerium(III) chloride are demonstrated by the synthesis of a nine-membered ring heterocycle component of Griseoviridin (3) in optically active form. The key step involves the stereospecific formation of the alpha-carbalkoxy alkenyl sulfide moiety using a combination system of cerium(III) chloride heptahydrate and sodium iodide.

Anti-Bacterial Agents↗
PubMed2000

The role of the alpha-stereogenic center in the control of stereoselection in the reduction of alpha-alkyl-beta-hydroxy ketones: a highly diastereoselective protocol for the synthesis of 1,2-syn-2-alkyl-1,3-diols

Accurate investigations on the role played by an alpha-stereogenic center in controlling the reduction of various classes of beta-hydroxy ketones allowed us to set up a general and highly diastereoselective protocol for the synthesis of 2-alkyl-1,3-diols with 1,2-syn relationship. This methodology is based on the conversion of a beta-hydroxy ketone into the corresponding titanium alcoholate that permits us to organize the substrate in a stable and rigid structure, which stereofacially favors attacking hydride ions. The use of THF as solvent makes available a variety of hydride donors that cover a large spectrum of steric demand: the choice of the more appropriate one depends on the conformational stability of the cyclic intermediate. Excellent results are obtained also in the presence of an additional stereogenic center in the beta-position, even if it exerts a concordant or an opposite steric effect with respect to the alpha-substituent.

Journal Article↗
PubMed2000

Structural study of the exopolysaccharide produced by a clinical isolate of Burkholderia cepacia.

The primary structure of the exopolysaccharide produced by a clinical isolate of the bacterium Burkholderia cepacia was studied by means of methylation analysis, selective degradation, NMR spectroscopy, and electrospray mass spectrometry. The resulting data showed that the parent repeating unit of the exopolysaccharide is a highly branched heptasaccharide with the following structure: Two acetyl groups are present per repeating unit, as noncarbohydrate substituents.

Burkholderia cepacia↗
PubMed2000

Hydroxyl group interactions in polysaccharides: a deuterium-induced differential isotope shift 13C-NMR investigation.

The secondary isotope shift in (13)C-nmr spectra in water was used to obtain information on the interactions of hydroxyl groups with their environment in polysaccharides. Specifically, the possibility of detecting the preference of intramolecular hydrogen bonding with respect to solvation was investigated. Different aliphatic alcohols were studied in both protic and aprotic solvents in order to obtain reference systems. The polysaccharides investigated were selected so as to include both different types of glycosidic linkages and different conformational properties of the polymeric chain. In addition to polysaccharides, beta-cyclodextrin and inulin were also investigated. The experiments demonstrated that isotope shift data can advantageously contribute to the understanding of the conformational properties of polysaccharides and in particular, in setting up of constraints in molecular modeling calculations.

Alcohols↗
PubMed2000

The structure of gellan in dilute aqueous solution.

A full assignment of high-field nmr spectra of gellan was obtained in dilute aqueous solution by performing a series of selective one-dimensional nmr experiments. The observed nuclear Overhauser effects (NOEs) cannot be interpreted assuming that each sugar residue is intrinsically rigid and in a chair conformation. In fact, the rhamnose residue gives strong NOE contacts coherent only with an equilibrium involving both a chair as well as a boat (or a hemiboat) conformation. Molecular dynamic calculations performed on a heptamer with a central rhamnose support the above finding, and show a structure based on a very stiff single chain in which it is present a flipping of the rhamnose residue. At low temperatures (5-20 degrees C) in very dilute solutions (0.018 mg/mL) nmr spectra show a splitting of the resonance due to the methyl group of rhamnose residue, thus confirming the presence of a slow equilibrium among different conformers.

Carbohydrate Conformation↗
PubMed2000

TiCl4-mediated reduction of 1,3-diketones with BH3-pyridine complex: a highly diastereoselective method for the synthesis of syn-1,3-Diols

[reaction: see text] 1,3-Diketones can be reduced in high yields and with excellent diastereoselectivity to the corresponding syn-1,3-diols by carrying out the reaction with BH3-pyridine complex in CH2Cl2 at -78 degrees C in the presence of an equivalent of TiCl4 and 0.1 equiv of pyridine. This protocol shows a general character: excellent results are obtained when the groups bound to the carbonylic functions are linear or branched carbon chains and aromatic or benzylic frameworks as well.

Journal Article↗
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↗
PubMed2000

Nephrotic syndrome and plasmapheresis.

We studied 15 patients suffering from nephrotic syndrome (NS) in bioptically-accertained primary and secondary glomerulopathies responding poorly to the common pharmacological treatment. They were monitored for one year by assessing their immunological and kidney functionality parameters, especially proteinuria. The patients underwent 3 apheretic sittings using the cascade double-filtration technique. After the third apheretic sitting the patients received metilprednisolone 300 mg/m2. This therapy was repeated every month for 6 months. At the end of the apheretic cycle it was shown that all patients had responded well to the therapy with a dramatic decrease in proteinuria, maintenance and/or recuperation of kidney functionality and improvement of lipidic asset; these data remained unchanged over time. Considering our preliminary results, we believe that therapeutic apheresis has a precise function in refractory nephrotic syndrome and, in particular, we propose the use of the cascade double-filtration technique.

Adult↗
PubMed1999

Influence of substituents on the solution conformation of the exopolysaccharide produced by Pseudomonas 'gingeri' strain Pf9.

The influence of pyruvate ketals and acetyl groups on the conformational behaviour of the exopolysaccharide produced by Pseudomonas 'gingeri' strain Pf9 has been investigated experimentally through studies of intrinsic viscosity and circular dichroism experiments. A conformational variation was detected as a function of the ionic strength. Measurements carried out on the native polymer, as well as on both de-pyruvated and de-acetylated samples, suggested a critical role for the acetyl group on the solution conformation of the polysaccharide. Molecular mechanics calculations indicated the possibility of intramolecular hydrogen bonding between acetyl substituents on the mannose and the C(2)OH group of the preceding saccharidic unit. NMR linewidth measurements, carried out as a function of temperature, on the low molecular weight de-pyruvated sample indicated different polymeric backbone dynamics in aqueous solutions with respect to that observed in 0.3 M NaCl solutions.

Carbohydrate Sequence↗
PubMed1999

Exopolysaccharide-producing lactic acid bacteria strains from traditional Thai fermented foods: isolation, identification and exopolysaccharide characterization.

Lactic Acid Bacteria (LAB) isolated from various traditional Thai fermented foods were screened for exopolysaccharides (EPS) production. From 104 isolates, two rod-shaped and five coccal-shaped LAB were able to produce EPS from sucrose on solid media. However, only the cocci were capable of producing EPS in liquid media and these were identified as Pediococcus pentosaceus. Pediococcus pentosaceus strains AP-1 and AP-3 produced EPS in high yield. In liquid media containing sucrose as carbon source, the amount of EPS produced by AP-1 and AP-3 strains was 6.0 and 2.5 g/L, respectively. The isolated and purified EPSs were chemically characterized. On the basis of sugar composition, methylation analysis and nuclear magnetic resonance spectroscopy, both the EPSs were shown to belong to the same dextran class. In particular, both EPSs differed from linear dextran by branching through 3,6-di-Osubstituted alpha-D-glucopyranosyl residues. The EPS from P. pentosaceus AP-3 was characterized by a relatively higher degree of branching and by a higher molecular weight than that from P. pentosaceus AP-1.

Animals↗