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Biomedical subjects

M Fontana

Publications and source records attributed to M Fontana.

At least 55 records · Page 3Linked to original sources
PubMed1997

Simultaneous determination of urinary cystathionine, lanthionine, S-(2-aminoethyl)-L-cysteine and their cyclic compounds using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization.

A measurement system for cystathionine (Cysta) lanthionine (LT), and S-(2-aminoethyl)-L-cysteine (AEC), and reduced products of their ketimines, perhydro-1,4-thiazepine-3,5-dicarboxylic acid (PHTZDC), 1,4-thiomorpholine-3,5-dicarboxylic acid (TMDA) and 1,4-thiomorpholine-3-carboxylic acid (TMA) in the urine samples of a patient with cystathioninuria and normal human subjects has been developed, using column liquid chromatography-mass spectrometry. The recoveries were about 90-105% for Cysta, LT and AEC, and about 77-87% for PHTZDC, TMDA and TMA after ion-exchange treatment. The concentrations of Cysta and PHTZDC in the urine of a patient with cystathioninuria were much higher compared with those in the urine of normal human subjects. The concentrations of AEC and TMDA were almost the same. LT and TMA could not be detected in the urine samples by this method. This method proved useful for the determination of sulfur-containing amino acids and their cyclic compounds in biological samples.

Alanine↗
PubMed1997

Detection of cystathionine ketimine and lanthionine ketimine in human brain.

The sulfur containing imino acids cystathionine ketimine (CK) and lanthionine ketimine (LK) have been detected in the human brain by an HPLC procedure. The HPLC procedure takes advantage of the selective absorbance at 380 nm of the phenylisothiocyanate-ketimine adduct. Quantitation of cystathionine ketimine and lanthionine ketimine indicates a mean concentration (mean +/- SD, n = 4) of 2.3 +/- 0.8 nmol/g for CK and of 1.1 +/- 0.3 nmol/g for LK in four human cerebral cortex samples of neurosurgical source. The identification of these cyclic ketimine derivatives of L-cystathionine and L-lanthionine as normal human metabolites in human nervous tissue may have interesting metabolic and physiological implications.

Amino Acids, Sulfur↗
PubMed1997

A specific assay for discriminating between peroxidase and lipoxygenase activities.

Peroxidases are widespread heme-containing enzymes able to catalyze the oxidation of a large array of organic substrates. There is growing interest in the measurements of peroxidase activity. We noticed that many substrates used in the routine assays for the biological and cytological determinations of peroxidase could be oxidized by lipoxygenase. We found interesting to set up a procedure to detect selectively peroxidase. In the present note, we report a fluorometric test for peroxidase detection using phenolic compounds or hydroxycoumarins.

Amino Acid Sequence↗
PubMed1997

Antigenic characterization of fimbria preparations from Streptococcus mutans isolates from caries-free and caries-susceptible subjects.

The adhesion of pathogenic bacteria to the host surface is an essential step in the development of numerous infections, including dental caries. Attachment of Streptococcus mutans, the main etiological agent of human dental caries, to the tooth surface may be mediated by glucan synthesized by glucosyltransferase (GTF) and by cell surface proteins, such as P1, which bind to salivary receptors. Fimbriae on the surfaces of many microorganisms are known to function in bacterial adhesion. Previous studies in this laboratory have initially characterized the fibrillar surface of S. mutans. The purpose of this investigation was the comparison of the antigenic properties of fimbria preparations of S. mutans isolates from five caries-resistant (CR) and six caries-susceptible (CS) subjects. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of S. mutans fimbrial preparations revealed five major protein bands at 200, 175, 157, 86, and 66 kDa in preparations from CR and CS subjects. Immunoblot analysis indicated the presence of the same major bands recognized by anti-S. mutans fimbria antisera. Furthermore, the 175- and 157-kDa bands were recognized by antibodies to P1 and GTF, respectively. Immunoblot analysis with antisera to the fimbria preparation, to P1, or to GTF indicated that the levels of fimbria-reactive components and P1 and GTF antigens were higher in S. mutans fimbria preparations from CS subjects than in those from CR individuals. For example, four of six fimbria preparations from CS patients had demonstrable P1, and all had GTF. In contrast, only two of five CR fimbrial preparations exhibited P1 and GTF. Enzyme-linked immunosorbent assay demonstrated similar results for levels of GTF antigen in the fimbrial preparations from CR and CS subjects. The results suggest that differences between the compositions of S. mutans fimbriae in CR and CS individuals may play an important role in the virulence of this microorganism in dental caries.

Adolescent↗
PubMed1997

Intranasal immunogenicity and adjuvanticity of site-directed mutant derivatives of cholera toxin.

Genetically modified derivatives of cholera toxin (CT), harboring a single amino acid substitution in and around the NAD binding cleft of the A subunit, were isolated following site-directed mutagenesis of the ctxA gene. Two mutants of CT, designated CTS106 (with a proline-to-serine change at position 106) and CTK63 (with a serine-to-lysine change at position 63), were found to have substantially reduced ADP-ribosyltransferase activity and toxicity; CTK63 was completely nontoxic in all assays, whereas CTS106 was 10(4) times less toxic than wild-type CT. The mucosal adjuvanticity and immunogenicity of derivatives of CT were assessed by intranasal immunization of mice, with either ovalbumin or fragment C of tetanus toxin as a bystander antigen. Mice immunized with wild-type CT produced both local (immunoglobulin A in mucosal washes) and systemic immune responses to both CT and bystander antigens. CTS106 showed good local and systemic responses to bystander proteins and to itself. Interestingly, mice immunized with the nontoxic derivative of CT, CTK63, generated weak immune responses to the bystander antigens which were similar to those achieved when CT B subunit was used as an adjuvant. In parallel experiments, an equivalent nontoxic mutant of the Escherichia coli heat-labile enterotoxin, LTK63 (with a serine-to-lysine change at position 63), was tested (9). In contrast to CTK63, LTK63 was found to be more immunogenic and a better intranasal adjuvant than recombinant heat-labile enterotoxin B subunit or CTK63. This information, together with data on immunoglobulin subclass responses, suggests that although highly homologous, CT and heat-labile enterotoxin should not be considered biologically identical in terms of their ability to act as intranasal adjuvants.

Adjuvants, Immunologic↗
PubMed1997

Antibiotic and cholestyramine treatment of chronic diarrhea in HIV-infected children.

BACKGROUND: Chronic diarrhea is a common feature in children infected with human immunodeficiency virus (HIV), and is associated with an increased risk of death in these patients. To describe the effects of an empiric treatment on diarrhea and body weight on HIV-infected pediatric patients. PATIENTS: Eleven vertically HIV-infected children with chronic diarrhea were treated with oral gentamicin, metronidazole and cholestyramine for 3 to 5 days. RESULTS: In children not infected by Cryptosporidium the treatment resulted in a 50% reduction of stool frequency and a 9% increase in body weight. No statistically significant effect was found in children harbouring this parasite. Diarrhea relapsed within 1-2 months in 3/3 children with Cryptosporidium and in 1/8 children without Cryptosporidium (p < 0.05). No untoward side effects from the treatment were observed. CONCLUSIONS: These results suggest that an empiric treatment of this type should be attempted early in HIV-infected children with chronic diarrhea, particularly in those not infected by Cryptosporidium.

Anti-Bacterial Agents↗
PubMed1997

[The treatment of chronic viral hepatitis with recombinant alpha-2 interferon: meta analysis and clinical contribution].

The Authors have developed a work of meta-analysis on the employment of IFN in the virus-correlated chronic hepatitis. They have examined World literature on: virus causing chronic hepatitis, type and duration of the treatment, criteria in the choice of the observed patients, clinical effects, effects on the virus, effects on the isto-pathologic situation. Have been considered the useful actions at the end of the treatment and in the follow-ups, so to evaluate the permanence of favourable effects. Have been also reminded the main collateral effects, even about frequency and intensity, as the various Authors relate. There are quite clear data indicating: efficacy in B-correlated chronic hepatitis greater than in C-correlated ones, greater efficacy in the treatments with Interferon with duration of more then 6 months in chronic hepatitis C. Doses greater than those generally employed appear not to give better results. The Authors moreover show the results of a clinical survey they made on patients with chronic hepatitis HBsAg+/HBeAg+ (treated with IFN-alpha 2r 5 MU t.i.w. for six months) and chronic hepatitis anti-HCV+ (treated with IFN-alpha 2r 3 MU t.i.w. for six months). The results confirm the efficacy of IFN in B-correlated chronic hepatitis (50% of sustained response) and its scarce efficacy in C-correlated chronic hepatitis for treatment shorter than 12 months (9.1% of sustained response).

Adult↗
PubMed1997

Lanthionine ketimine and S-(2-aminoethyl)-L-cysteine ketimine induce the tyrosyl phosphorylation of 45 kDa protein in parallel with its stimulation of superoxide generation in human neutrophils.

Human peripheral blood polymorphonuclear leukocytes were preincubated with lanthionine, S-(2-aminoethyl)-L-cysteine, and some of their derivatives found in normal human urine and bovine brain. Among these compounds, lanthionine ketimine and to a lesser extent S-(2-aminoethyl)- L-cysteine ketimine enhanced the N-formyl-methionyl-leucyl-phenylalanine-induced superoxide generation. These ketimines induced tyrosyl phosphorylation of 45 kDa protein of cells. The tyrosyl phosphorylation was markedly increased with time, and the phosphorylation process was dependent on the concentration of both ketimines. However, lanthionine, 1,4-thiomorpholine-3,5-dicarboxylic acid, S-(2-aminoethyl)-L-cysteine and 1,4-thiomorpholine-3-carboxylic acid were without effect both on superoxide generation and on tyrosyl phosphorylation of 45 kDa protein. Lanthionine ketimine and S-(2-aminoethyl)-L-cysteine ketimine also enhanced superoxide generation induced by opsonized zymosan but not the one induced by arachidonic acid and phorbol 12-myristate 13-acetate. Ketimine-primed superoxide generation and tyrosyl phoshorylation of 45 kDa protein were inhibited by genistein, an inhibitor of protein tyrosine kinase, but not by 1-(5-isoquinoline sulfonyl)-2- methylpiperazine, an inhibitor of protein kinase C.

Amino Acids, Sulfur↗
PubMed1996

Determination of PAH in airborne particulate: comparison between off-line sampling techniques and an automatic analyser based on a photoelectric aerosol sensor.

The automatic analyser is based on a photoelectric aerosol sensor, with continuous sampling and an on-line detection system. Traditional sampling monitoring systems consist of collecting airborne particulate on filters; the sample is then extracted, purified and analysed. It is possible to identify each compound and to determine its relative abundance in the total particulate matter, on the other hand, this method requires great complexity of analysis. Continuous monitoring systems allow getting quicker results to compare with threshold levels. It is also possible to obtain an easier correlation with factors such as traffic flows or meteorological conditions. However, such systems cannot quantify single compounds, and data are expressed as total PAH. The comparison between the results shows a satisfactory linearity between the data obtained with the two methods. The difference of about one order of magnitude between the data obtained with photoelectric aerosol sensor (PAS) system and the sum of the concentrations of selected PAHs determined with off-line methods can be explained with the different selectivity of the two methods employed. This work has been developed in Aosta, the administrative centre of the Aosta Valley district.

Aerosols↗
PubMed1996

Effect of cystathionine and cystathionine metabolites on the phosphorylation of tyrosine residues in human neutrophils.

The effect of cystathionine and cystathionine metabolites found in the urine of patients with cystathioninuria on the phosphorylation of tyrosine residues was studied with human peripheral blood polymorphonuclear leukocytes. Among the cystathionine metabolites, cystathionine ketimine markedly increased phosphorylation of a 45 kDa protein with time and the phosphorylation depended on the concentration of cystathionine ketimine, while cystathionine and the reduced form of cystathionine ketimine (cyclothionine) did not increase the phosphorylation of the 45 kDa protein. The phosphorylation of the 45 kDa protein induced by cystathionine ketimine was inhibited by genistein and herbimycin A, inhibitors of tyrosine kinase, but was not inhibited by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine and staurosporine, inhibitors of protein kinase C.

Benzoquinones↗
PubMed1996

Effect of cystathionine ketimine on the stimulus coupled responses of neutrophils and their modulation by various protein kinase inhibitors.

Human peripheral blood polymorphonuclear leukocytes were perincubated with cystathionine and cystathionine metabolites found in the urine of the patients with cystathioninuria. Among the cystathionine metabolites, cystathionine ketimine significantly enhanced the N-formyl-methionyl-leucyl-phenylalanine-induced superoxide generation, but cystathionine and cyclothionine did not enhance the superoxide generation. Cystathionine ketimine also enhanced superoxide generation induced by opsonized zymosan but not those induced by arachidonic acid and phorbol myristate acetate. Superoxide generation induced by cystathionine ketimine was inhibited by genistein, an inhibitor of tyrosine kinase, and was enhanced by 1-(5-isoquinoline-sulfonyl)-2-methyl-piperazine, an inhibitor of protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Solubilization of [35S]lanthionine ketimine binding sites from bovine brain.

Lanthionine ketimine (LK) binding sites were solubilized from bovine brain membranes using 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and Triton X-100. 10 mM CHAPS in 0.5 M potassium phosphate, pH 7.0, containing 20% glycerol was selected to solubilize LK binding entities. Some properties of CHAPS-solubilized LK binding sites have been studied. The CHAPS-solubilized preparation appeared to contain a homogenous population of binding sites for [35S]LK. Binding properties indicated that the solubilized binding sites were similar to the membrane-bound sites. [35S]LK specific binding was inhibited by other structurally related ketimines obtaining a similar rank order of inhibition for the soluble and the membrane-bound preparations. The successful solubilization of [35S]LK binding sites is a useful starting point for the purification of this binding protein.

Amino Acids, Sulfur↗
PubMed1996

An in vitro microbial model for studying secondary caries formation.

Secondary caries is a major reason for the replacement of restorations. Because it is hypothesized that the development of secondary caries is closely associated with pathogenic oral bacteria, an in vitro microbial model has been developed to produce secondary carious lesions. A mixture of overnight cultures of Streptococcus mutans and Lactobacillus casei in dextrose-free trypticase soy broth, supplemented with 5% sucrose (TSBS), at 37 degrees C was used in this model as the inoculum for the experimental groups. Uninoculated control groups were incubated with medium only. Groups of human tooth specimens restored using composite, together with their respective controls, were exposed for 7 or 12 days to circulating cycles of TSBS (30 min each, 3 times per day) and a mineral wash solution (for a total of 22.5 h per day), at 37 degrees C. The pH of the experimental groups dropped to 4.l-4.5 during the test periods. The pH of the control groups remained at 6.8-7.0. The inoculated bacteria remained viable throughout the study. No contamination of experimental or control samples occurred. Laser scanning confocal microscopy demonstrated the development of incipient surface and wall lesions in all the specimens of experimental groups in as few as 7 days. Reproducibility of the model was confirmed in a second investigation. Therefore, it was concluded that this model can be used for studying the microbial etiology and prevention of secondary caries.

Composite Resins↗
PubMed1996

Measurement of enamel demineralization using microradiography and confocal microscopy. A correlation study.

Substantial amounts of tooth minerals are lost during dental caries formation. Transversal microradiography, a well-accepted method used to quantify mineral loss, is a time-consuming technique which requires a thin enamel section (100 microns) and involves the use of x-rays. In an attempt to solve these difficulties, a procedure has been developed in which a human tooth specimen with demineralized enamel is cut in half (HT), stained with a fluorescent dye (rhodamine B) and analyzed using a laser scanning confocal microscope. A series of three studies was conducted to correlate measurements of enamel demineralization obtained from enamel thin (100 microns) sections (TS) using transversal microradiography with three parameters (area of the lesion; total and average dye fluorescence intensities) measured on the same TS or on a thicker section (HT) of the same specimen by laser scanning confocal microscopy. Results showed that a 0.1 mM rhodamine B solution provided the most adequate imaging conditions for confocal microscopy. Pearson's correlation coefficients, calculated between microradiography and confocal microscopy data obtained using a 0.1 mM rhodamine B solution, were: delta Z vs. HT lesion area = 0.95; delta Z vs. HT total fluorescence = 0.80; delta Z vs. HT average fluorescence = 0.74; delta Z vs. TS lesion area = 0.95; delta Z vs. TS total fluorescence = 0.74; delta Z vs. TS average fluorescence = 0.55. All these correlations coefficients were statistically significant (p < 0.01). It is concluded that in enamel demineralization studies statistically significant correlations exist between parameters measured using transversal microradiography and parameters quantified using confocal microscopy.

Analysis of Variance↗