Biomedical subjects

S Paoletti

Publications and source records attributed to S Paoletti.

At least 19 recordsLinked to original sources

PubMed2006

Safety and effects on the lipid and C-reactive protein plasma concentration of the association of ezetimibe plus atorvastatin in renal transplant patients treated by cyclosporine-A: a pilot study.

Ezetimibe (E) is a new cholesterol adsorption inhibitor which prevents the adsorption of dietary and biliary cholesterol by binding to a recently described cholesterol transporter. This pilot study was performed to evaluate the safety and the low-density lipoprotein (LDL)-C and C-reactive protein lowering efficacy of atorvastatin (A) and of the association of A plus E in five renal transplant patients with hypercholesterolemia and mild renal functional impairment receiving cyclosporine-A (CsA). Patients received for three periods, each of 3 weeks, A at a dose of 20 mg/day; A at a dose of 10 mg/day and finally, A 10 mg plus E 10 mg daily. The medications were well-tolerated and no important clinical or laboratory (muscle enzyme, creatinine clearance and CsA concentration) abnormalities were observed throughout the study period. A alone lead to target LDL-C values only in two of five patients and did not significantly reduce the mean CRP values. The combination of E plus A produced the lowest lipid levels and significantly reduced CRP mean values and allowed all patients to attain target levels of LDL-C: total cholesterol decreased from 240 +/- 42 (mean +/- S.D.) to 171 +/- 34 mg/dl, LDL-C from 129 +/- 32 to 87 +/- 21 mg/dl, plasma triglycerides from 330 +/- 54 to 194 +/- 71 mg/dl and CRP from 6.2 +/- 1.9 to 3.9 +/- 2.4 mg/l (P < 0.05 for all). This pilot study suggests that the co-administration of E and A at 10 mg/day in renal transplant patients receiving CsA is well-tolerated and effective in reducing important cardiovascular risk factors.

Aged↗

PubMed2005

C-reactive protein in patients on chronic hemodialysis with different techniques and different membranes.

In hemodialysis patients, C-reactive protein (CRP), an acute-phase reactant, is a sensitive and independent marker of malnutrition, anemia, and cardiovascular mortality. The aim of the present study was to evaluate CRP levels in plasma samples from long-term hemodialysis patients on different extracorporeal modalities and dialyzed with different membranes, at baseline and after 6 months. Two hundred and forty-seven patients were recruited in eight hospital-based centers. All patients had been on their dialytic modality for at least 3 months and were prospectively followed in their initial dialytic modality for 6 months. Patients were treated with conventional bicarbonate dialysis (N = 127) or hemodiafiltration (N = 120). Patients treated with conventional bicarbonate dialysis were dialyzed with different membranes: Cuprophane (N = 51), low-flux cellulose modified membrane (N = 37) and synthetic membranes (N = 39). Hemodiafiltration was performed in post-dilution mode with polysulfone (N = 66) and polyacrylonitrile (N = 54) membranes. Analysis of baseline CRP values in the clinically stable patients showed that an unexpectedly high proportion (47%) of the patients had CRP values higher than 5 mg/l (upper limit in normal subjects). The mean +/- S.D. CRP values were significantly higher (P < 0.05) in hemodiafiltration with infusion volumes < 10 l per session (14.6+/-3.1 mg/l) than in standard hemodialysis (5.1 +/- 2.1 mg/l) and hemodiafiltration with infusion volumes > 20 l per session (4.9 +/- 2.1 mg/l). These values did not significantly change after 6 months of follow-up. Concerning the membranes, the highest levels of CRP were observed in patients dialyzed with Cuprophane with a significant increase from 15.1 +/- 3.6 to 21.2 +/- 3.1 mg/l after 6 months (P < 0.05); a significant reduction of CRP levels was observed in patients dialyzed with polysulfone in the same follow-up period (from 13.5 +/- 2.9 to 8.1 +/- 2.4 mg/l; P < 0.05). The CRP increase following low volume HDF can be related to back-filtration of bacterial derived contaminants.; moreover, an important effect on CRP of the hemodialysis membrane is observed and new synthetic membranes can be used to decrease these levels.

Acrylic Resins↗

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↗

PubMed2004

Non-equilibrium processes of interchain association induced by Cs+ ions in kappa-carrageenan aqueous solutions.

We present preliminary results of the investigation of interchain association processes induced by Cs+ ions in kappa-carrageenan aqueous solution. The solutions contained variable amounts of NaI and CsI, under the condition that the total concentration of 1:1 electrolyte was 0.1M. The associative processes were observed by static light scattering under isothermal conditions (at T = 25 degrees C), after cooling molecularly dispersed solutions obtained at high temperature (80 degrees C). It was found that, under all the investigated conditions of polymer concentration (from 0.2 to 2 g l(-1)) and ionic composition, the onset of time-dependent association fails to lead to an equilibrium, but proceeds up to physical gelation of the associating system. Depending on the experimental variables, however, the gelation threshold may take up to several days to be achieved.

Carrageenan↗

PubMed2003

Polyalkylphenyl-sulphonic acid with acid groups of variable strength from compost.

The insoluble organic fraction (humin-like material, HLM) from rice hull-dairy cattle compost is well converted into water soluble HLM-sulphonate by reaction in liquid SO3. Microanalytical, potentiometric, molecular weight, and NMR data are consistent with a highly homogeneous polymeric arylsulphonate having 4000 Da MW, 1.3 sulphonic groups per aromatic ring and significant content of carboxylic and phenolic groups. By comparison with structure-property relationships for commercial lignosulphonates derived from the pulp and paper industry, the above arylsulphonate is likely to be a candidate at a variety of applications in the chemical industry and in agriculture. Therefore, sulphonation is a means for upgrading composts HLM to the same uses as for commercial lignosulphonates.

Agriculture↗

PubMed2001

Human osteosarcoma cells release matrix degrading enzymes in response to chemokine activation.

Matrix degrading enzymes released upon autocrine and/or paracrine induction exert a key role in modulating tumor cell behavior. Osteosarcoma is a highly metastatic cancer, with a redundancy of autocrine loops. Here we report that human osteosarcoma cells express a wide array of chemokine receptors and respond to chemokine activation with the release of N-acetyl-beta-D-glucosaminidase and gelatinase/collagenase activity. Of the two cell lines studied, the osteoblast-like MG-63 showed a higher responsivity compared to the less differentiated HOS. This suggests that chemokine modulation of matrix degrading enzymes requires the maintaining of the osteoblastic phenotype and of signaling pathways which occur in normal tissue.

Acetylglucosaminidase↗

PubMed2000

Analysis of potentiometric titrations of heterogeneous natural polyelectrolytes in terms of counterion condensation theory: application to humic acid.

A model, developed within the framework of the counterion condensation theory of linear polyelectrolytes, is presented in this paper to describe the acid-base properties of linear polyelectrolytes, consisting of several types of functional ionizable groups. This formalism has been successfully applied to Fluka humic acid under salt-free conditions, as well as in the presence of supporting simple 1:1 salt (KNO3) at three different concentrations. As part of this approach, the charge density of the humic acid is obtained from the activity coefficient measurements of potassium counterions at different humic acid concentrations at a constant degree of dissociation of the polyelectrolyte. The humic acid average charge density was found to be 0.80 +/- 0.05. Using the present model, we are able to satisfactorily describe the experimental data obtained from acid-base potentiometric titrations. Four main functional groups making up the polymer are determined through their fractional abundances (Xi) and intrinsic pK (pK0i) values. The fractional abundances remained constant and independent of the ionic strength, indicating that the humic acid constitution does not depend on the concentration of excess salts. The pK0i values show a small change with ionic strength, which can be explained by the polyelectrolytic behavior of the solution.

Algorithms↗

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

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↗

PubMed1999

Metal complexes as allosteric effectors of human hemoglobin: an NMR study of the interaction of the gadolinium(III) bis(m-boroxyphenylamide)diethylenetriaminepentaacetic acid complex with human oxygenated and deoxygenated hemoglobin.

The boronic functionalities on the outer surface of the Gd(III) bis(m-boroxyphenylamide)DTPA complex (Gd(III)L) enable it to bind to fructosamine residues of oxygenated glycated human adult hemoglobin. The formation of the macromolecular adduct can be assessed by NMR spectroscopy via observation of the enhancement of the solvent water proton relaxation rate. Unexpectedly, a strong binding interaction was also observed for the oxygenated unglycated human adult hemoglobin, eventually displaying a much higher relaxation enhancement. From relaxation rate measurements it was found that two Gd(III)L complexes interact with one hemoglobin tetramer (KD = 1.0 x 10(-5) M and 4.6 x 10(-4) M, respectively), whereas no interaction has been observed with monomeric hemoproteins. A markedly higher affinity of the Gd(III)L complex has been observed for oxygenated and aquo-met human adult hemoglobin derivatives with respect to the corresponding deoxy derivative. Upon binding, a net change in the quaternary structure of hemoglobin has been assessed by monitoring the changes in the high-resolution 1H-NMR spectrum of the protein as well as in the Soret absorption band. On the basis of these observations and the 11B NMR results obtained with the diamagnetic La(III)L complex, we suggest that the interaction between the lanthanide complex and deoxygenated, oxygenated, and aquo-met derivatives of human adult hemoglobin takes place at the 2, 3-diphosphoglycerate (DPG) binding site, through the formation of N-->B coordinative bonds at His143beta and His2beta residues of different beta-chains. The stronger binding to the oxygenated form is then responsible for a shift of the allosteric equilibrium toward the high-affinity R-state. Accordingly, Gd(III)L affinity for oxygenated human fetal hemoglobin (lacking His143beta) is significantly lower than that observed for the unglycated human adult tetramer.

Adult↗

PubMed1999

NK binding capacity and lytic activity depend on the expression of ICAM-1 on target bone tumours.

Osteosarcoma cell lines are differently lysed by natural killer (NK) lymphocytes. A critical step in the lytic process is the recognition and attachment of effector to target cells. To determine binding capacity and lytic activity of NK cells, we investigated the distribution and role of ICAM-1, 2 and 3 on two osteosarcoma cell lines (HOS and Saos-2) in basal conditions and after TNFalpha treatment. Modulation of ICAM-1 after TNFalpha treatment modified the binding capacity of NK cells to osteosarcoma target cells. This modulation process appears to play a critical role in determining the susceptibility of these cells to NK-mediated lysis.

Antigens, CD↗

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

Structural investigation of the exopolysaccharide produced by Pseudomonas flavescens strain B62--degradation by a fungal cellulase and isolation of the oligosaccharide repeating unit.

Pseudomonas flavescens strain B62 (NCPPB 3063) is a recently described bacterium isolated from walnut blight cankers. This strain has been designated as the type strain of a Pseudomonas rRNA group-I species. Strain B62 produced a mixture of two exopolysaccharides, differing in weight average relative molecular mass and composition. Only the most abundant exopolysaccharide (90% by mass), corresponding to the one with the lower molecular mass, was investigated by use of methylation analysis, partial acid hydrolysis, and NMR spectroscopy. The polysaccharide was depolymerised by the action of the cellulase produced by Penicillum funiculosum and the oligosaccharide obtained, corresponding to the repeating unit, was characterised by NMR spectroscopy and ion-spray mass spectrometry. The repeating unit of the B62 exopolysaccharide is [structure in text] where X is glucose (75%) or mannose (25%), and Lac is lactate. The O-acetyl groups are present only on 75% of the repeating units, and they are linked to the C6 of the hexose residues in non-stoichiometric amounts.

Carbohydrate Conformation↗

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↗

PubMed1998

Stabilization of the T-state of ferrous human adult and fetal hemoglobin by Ln(III) complexes: a thermodynamic study.

The effect of the lanthanide(III) complexes [Gd(1,4,7,10-tetraazacyclododecane-N,N',N", N"'-tetrakis(methylenephosphonate))]5- (Gd-DOTP) and La-DOTP on the oxygen binding and spectroscopic properties of human adult and fetal hemoglobin (HbA and HbF, respectively) has been investigated. The affinity of Gd-DOTP and La-DOTP for oxygenated HbA (HbAO2; KHbAO2 = 2.6 x 10(-3) M) is closely similar to that observed for Ln(III) complexes association to nitrosylated HbA (HbANO KHbANO = 1.8 x 10(-3) M) and to aquo-met HbA (met-HbA; Kmet-HbA = 1.9 x 10(-3) M), being lower than that determined for Gd-DOTP and La-DOTP binding to the deoxygenated form of the tetramer (HbAd; KHbAd = 3.0 x 10(-4) M). The affinity of Gd-DOTP for deoxygenated HbF (HbFd; KHbFd = 9.5 x 10(-4) M) and oxygenated HbF (HbFO2; KHbFO2 = 3.7 x 10(-3) M) is lower than that observed for Ln(III) complexes association to HbAd and HbAO2, respectively. Gd-DOTP and La-DOTP bind to HbA and HbF with a 1:1 stoichiometry per tetramer. Increasing Gd-DOTP and La-DOTP concentration, oxygen affinity for HbA decreases (i.e. P50 increases), this effect being minor for HbF. Upon binding of Ln(III) complexes to HbANO, the X-band EPR spectrum and the absorption spectrum in the Soret region display the characteristics which have been attributed to the T-state of the ligated tetramer. These results represent a clear cut evidence for the specific binding of Gd-DOTP and La-DOTP to the 2,3-D-glycerate bisphosphate (BPG) pocket (i.e. at the dyad axis, in between the beta-chains) of HbA and HbF. The effect of Ln(III) complexes on the ligand binding and spectroscopic properties of HbA and HbF is reminiscent that of BPG, the physiological modulator of human Hb action.

Adult↗

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↗