Search PubMed⌕ Search

Biomedical subjects

R Ferretti

Publications and source records attributed to R Ferretti.

At least 19 recordsLinked to original sources
PubMed2005

Analytical and semipreparative high performance liquid chromatography enantioseparation of new substituted 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-(1H)-pyrazoles on polysaccharide-based chiral stationary phases in normal-phase, polar organic and reversed-phase conditions.

The direct HPLC enantioseparation of five pairs of new chiral pyrazole derivatives on coated cellulose- and amylose-based chiral stationary phases (Chiralpak AD, Chiralcel OJ and Chiralcel OJ-RH) and new immobilised amylose-based Chiralpak IA CSP was performed. Very high enantioselectivity factor (alpha) values were achieved in polar organic and reversed-phase conditions by using OJ-RH as CSP. Chiralpak IA exhibited an excellent chiral resolving ability in normal-phase mode and it allowed the enantioseparation of analytes investigated with resolution factors (Rs) >20. Due to its bonded nature, it was successfully employed at analytical and semipreparative scale in combination with normal-phase eluents containing "non-standards" solvents such as acetone.

Amylose↗
PubMed2005

Interactions between Saccharomyces cerevisiae and malolactic bacteria: preliminary characterization of a yeast proteinaceous compound(s) active against Oenococcus oeni.

AIMS: To investigate the occurrence and extent of Saccharomyces cerevisiae and Oenococcus oeni interactions. METHODS AND RESULTS: Interactions between S. cerevisiae and O. oeni were investigated by double-layer and well-plate assays showing the occurrence of specific interactions for each yeast-malolactic bacteria (MLB) coupling. Heat and protease treatments of synthetic grape juice fermented by the S. cerevisiae strain F63 indicated that the inhibitory activity exerted by this yeast on O. oeni is due to a proteinaceous factor(s) which exerts either bacteriostatic or bactericidal effect depending on concentration and affects malolactic fermentation in natural grape juice and wine. CONCLUSIONS: A proteinaceous factor(s) produced by a S. cerevisiae wine strain able to inhibit O. oeni growth and malic acid fermentation was characterized. SIGNIFICANCE AND IMPACT OF THE STUDY: The individuation, characterization and exploitation of yeast proteinaceous factor(s) exerting inhibitory activity on MLB may offer new opportunities for the management of malolactic fermentation.

Anti-Bacterial Agents↗
PubMed2004

A new application of stopped-flow chiral HPLC: inversion of enantiomer elution order.

A newly developed procedure to reverse the enantiomer elution order of compounds resolved on chiral stationary phases (CSPs) for HPLC is presented. The optimized analytical protocol is based on the effect of temperature on enantioselectivity and does not involve any changing in mobile phase composition or type of CSP. In essence, the approach entails variable temperature chromatography at two temperatures. The enantiomer separation is performed at a low column temperature, with stopping the flow prior to elution of the less retained enantiomer. Then, the column temperature is changed with the peaks trapped inside the column, followed by elution with the same mobile phase in reverse direction. Under these conditions, the more pronounced loss in free energy of binding for the more strongly bound enantiomer results in an inversion of the elution order. This procedure may be applied to each enantiomer pair that is separated by chiral HPLC under an appreciable enthalpy-control.

Chromatography, High Pressure Liquid↗
PubMed2003

Conversion of a racemic mixture of 8-chloro-2-(2,6-difluorophenylmethyl)-2,3-dihydro-3-methyl-1,2,5-benzothiadiazepin-4(5h)-one 1,1-dioxide into a single enantiomer via a chromatographic resolution/racemization method.

A simple and efficient strategy to convert the racemic mixture of 8-chloro-2-(2,6-difluorophenylmethyl)-2,3-dihydro-3-methyl-1,2,5-benzothiadiazepin-4(5H)-one 1,1-dioxide, a new anti-HIV-1 agent targeted to reverse transcriptase, into the more active (S)-enantiomer is described. The method utilizes repetition of the following two steps: 1) semipreparative enantioseparation by HPLC on chiral stationary phase; 2) base-induced racemization of the less active (R)-enantiomer.

Journal Article↗
PubMed2002

Analytical and semipreparative enantiomeric separation of azole antifungal agents by high-performance liquid chromatography on polysaccharide-based chiral stationary phases. Application to in vitro biological studies.

High-performance liquid chromatography (HPLC) was used for the enantiomeric separation of chiral imidazole derivatives endowed with antimycotic activity. Enantioselective columns, containing carbamates of cellulose and amylose, were used. The influence of the nature and content of an alcoholic modifier in the mobile phase was studied. The isolated enantiomers, separated on semipreparative columns, were submitted to in vitro biological investigations.

Antifungal Agents↗
PubMed2001

Conformational and temperature effects on separation of stereoisomers of a C3,C4-substituted beta-lactamic cholesterol absorption inhibitor on amylose-based chiral stationary phases.

A direct liquid chromatography method was developed for the diastereo- and enantioselective analysis of a C3,C4-substituted beta-lactamic hypolipodemic agent (SCH 48461) and its stereoisomers on two commercially available amylose-based chiral stationary phases (CSPs), namely, Chiralpak AS and Chiralpak AD. The mobile phase composition (type and content of alcoholic modifier) was considered to achieve baseline resolutions in a single chromatographic run. In order to investigate the influence of molecular flexibility on chiral recognition process, beta-lactams were ring-opened and converted into beta-amino esters derivatives. Thermodynamic parameters associated with adsorption equilibria between acyclic and cyclic stereoisomers and CSPs were calculated from chromatographic runs at various temperatures.

Amylose↗
PubMed2001

Twelve-hour PCR-based method for detection of Salmonella spp. in food.

A PCR-based method for the detection of Salmonella spp. in food was developed. The method, set up on typical salami from the Italian region of Marche, is sensitive and specific and shows excellent correlation with the conventional method of reference when naturally contaminated foods are analyzed. Moreover, it can be easily performed within a maximum of 12 h from food sampling, thus allowing prompt detection of Salmonella spp. in the food stocks analyzed.

Animals↗
PubMed2000

Vanadate and copper induce overlapping oxidative stress responses in the vanadate-tolerant yeast Hansenula polymorpha.

The mechanisms by which vanadate exerts a toxic effect on living organisms are not completely understood. This is principally due to the variety of intracellular targets of the metal and to the changes in the chemical form and oxidation states that vanadate can undergo, both in the external environment and intracellularly. In order to further elucidate the reasons for vanadate toxicity, and assuming that common detoxification mechanisms can be evoked by a general heavy metal response, we have compared some aspects of the cellular responses to vanadate and copper in the yeast Hansenula polymorpha. By means of 2D electrophoresis we show the existence of common determinants in the responses to vanadate- and copper-induced stresses. Moreover, we demonstrate that both metals induce significant increases in antioxidant enzyme levels, and that there are significant overlaps in the heavy metal and oxidative stress responses. Interestingly, vanadate induces an increase in catalase activity that is much higher than that seen with copper and, unlike copper, does not cause lipid peroxidation of cellular membranes. This suggests that H. polymorpha cells activate a further specific detoxification pathway against vanadate-induced oxidative insults.

Catalase↗
PubMed1998

Flocculation of Hematite with Polyacrylic Acid: Fractal Structures in the Reaction- and Diffusion-Limited Aggregation Regimes.

The structure of hematite aggregates in the presence of fairly monodisperse polyacrylic acid (PAA) with two different molecular weights (Mw = 1.36 x 10(6), Mw/Mn = 1.53; Mw = 3.69 x 10(4), Mw/Mn = 1.60) was studied using static light scattering (SLS). The fractal dimensions were calculated from the scattering exponents, after taking into account the finite size of aggregates, using exponential and Gaussian cutoff functions. Three flocculation regimes, namely, pre-DLA, DLA (diffusion-limited aggregation), and post-DLA, were defined based on the polymer concentration. In the DLA regime, fractal dimension values, Df = 1.84 +/- 0.02 and 1.73 +/- 0.02, were obtained using exponential and Gaussian cutoff functions, respectively. A fractal dimension of approximately 2.0 was found, as expected, in the pre-DLA regime (at PAA concentrations lower than the optimal dosage for a DLA regime) where the flocculation rate was reaction limited. In contrast, in the post-DLA regime, the flocculation was slow but the structure of aggregates was as tenuous as in the DLA regime with a fractal dimension Df approximately 1.8. Moreover, for all three regimes, the Df values were independent of the molecular weights of PAA. The lower fractal dimension in post-DLA was probably due to the increased concentration of polymer chains between adjacent particles in aggregates. The steric hindrance favored tip-to-tip aggregation, leading to a more tenuous structure. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Validated chiral high-performance liquid chromatographic method for the determination of trans-(-)-paroxetine and its enantiomer in bulk and pharmaceutical formulations.

A stereospecific high-performance liquid chromatography method for the determination of trans-(-)-paroxetine and its enantiomer in bulk raw material and pharmaceutical formulations was developed and validated. The enantiomeric separation was achieved, without any derivatization, on a carbamate derivative-based column (Chiralpak AD). The effect of the organic modifiers, 2-propanol and ethanol, in the mobile phases was optimised to obtain enantiomeric separation. Limits of detection and quantitation of 2 and 6 ng, respectively, were obtained for both of the enantiomers. The linearity was established in the range of 5-41 microg for trans-(-)-paroxetine and in the range of 10-160 ng for trans-(+)-paroxetine. The accuracy of the method was 102.3% (mean value) for trans-(-)-paroxetine and 99.9% (mean value) for trans-(+)-paroxetine. For the precision (repeatability), a relative standard deviation value of 1.5% (mean value) for trans-(-)-paroxetine and of 2.1% (mean value) for trans-(+)-paroxetine was found. The method is capable of determining a minimum limit of 0.2% of trans-(+)-isomer in commercial samples.

Chromatography, High Pressure Liquid↗
PubMed1995

[Non-invasive intermittent mechanical ventilation: usefulness in treatment of chronic severe heart failure].

BACKGROUND: The higher respiratory work and less inspiratory muscle strength of patients with cardiac failure may contribute to decrease their functional capacity. AIM: To assess the effects of non invasive intermittent mechanical ventilation on clinical parameters, peripheral perfusion, cardiac and inspiratory muscle function. PATIENTS AND METHODS: Patients with chronic cardiac failure, functional capacity III-IV were subjected to 6 sessions of nasal non invasive intermittent ventilation during 4 hours or to simulated ventilation (controls). RESULTS: Fifteen ventilated patients and six controls completed the protocol. Ventilated patients improved the Mahler transition score for dyspnea by 4 +/- 1.6 points. They also improved their aerobic capacity, increasing the exercise duration from 10.9 +/- 4 to 12.7 +/- 5 min and their maximal oxygen consumption from 14.6 +/- 4 to 16.4 +/- 5.7 ml/kg/min. These patients also decreased their O2 and CO2 ventilatory equivalents. Maximal inspiratory pressure increased from 67.9 +/- 23.6 to 80.19 +/- 21.4 cm H2O, sustained maximal inspiratory pressure increased from 101.4 +/- 48 to 133 +/- 53 cm H2O and maximal endurance increased from 132 +/- 52 to 162 +/- 58 g in ventilated patients. None of these variables was modified in control patients. No changes were observed in renal function, blood volume, arterial gases, spirometry or plasma catecholamine levels in any group. CONCLUSIONS: Intermittent nasal ventilation or other measures to improve inspiratory muscle function may be beneficial for patients with severe cardiac failure.

Adult↗
PubMed1991

Application of a high-performance liquid chromatography coulometric method for the estimation of mebendazole and its metabolites in human sera.

A novel, sensitive high-performance liquid chromatographic method, making use of coulometric detection, for the estimation of mebendazole and its metabolites in the sera of eight hydatidosis patients was devised. Recovery rates, precision, accuracy and sensitivity for each compound are reported and compared with those of the previously published methods.

Biotransformation↗
PubMed1985

Inspiratory muscle function in patients with severe kyphoscoliosis.

In 9 patients with severe kyphoscoliosis we studied inspiratory muscle function by measuring transdiaphragmatic pressure (Pdi) and its components: gastric (Pga) and esophageal (Pes) pressures during quiet breathing. Maximal Pdi and maximal inspiratory mouth pressure (Pimax) were also measured. The results showed that Pimax and Pdimax were significantly lower in patients than in normal subjects. During quiet breathing, all patients had positive swings in Pga, indicating an active contraction of the diaphragm, but Pes was significantly more negative, suggesting the recruitment of intercostal and accessory inspiratory muscles. We did not find significant correlations between Pimax, Pdimax, delta Pga/delta Pes, FVC, PaO2, or PaCO2 and the degree of spinal deformity. The FVC tended to correlate with Pimax (r = 0.63) and with Pdimax (r = 0.53). The Pdi correlated with PaO2 (r = 0.66) and with PaCO2 (r = -0.76; p less than 0.05). A significant correlation was also observed between Pimax and PaO2 (r = 0.785; p less than 0.05) and between Pimax and PaCO2 (r = -0.86; p less than 0.01). We conclude that impairment of inspiratory muscle function is related to the development of ventilatory failure in kyphoscoliosis.

Adult↗
PubMed1985

Acute effect of ketotifen on the dose-response curve of histamine and methacholine in asthma.

This study was designed to assess the acute effect of 1 mg of orally administered ketotifen on the dose-response curve to both histamine and methacholine, in 15 patients with bronchial asthma. From this curve we measured the concentration that produced a 20% fall in FEV1 (PC20) and reactivity, defined as the slope of the curve beyond the threshold dose. Results were analysed comparing the change in log PC20 and in reactivity before and after a double-blind administration of ketotifen and placebo. Ketotifen, compared to placebo, significantly increased the histamine PC20 (P less than 0.001) and reduced reactivity (P less than 0.001). After adjusting for starting FEV1 the difference of effect between ketotifen and placebo was still significant, although to a lesser degree (P less than 0.01). In contrast, ketotifen did not modify the methacholine dose-response curve. No significant changes were observed in FEV1 after ketotifen. The results suggest that acute administration of ketotifen has a selective action on histamine-activated pathways of bronchoconstriction.

Adolescent↗