Biomedical subjects

A Visconti

Publications and source records attributed to A Visconti.

At least 37 records · Page 2Linked to original sources

PubMed2001

Determination of fumonisins B1 and B2 in cornflakes by high performance liquid chromatography and immunoaffinity clean-up.

The determination of fumonisins in cornflakes is a challenging matter as the actually available methods for the analysis of corn do not perform well when applied to this more complex matrix. After testing several factors that may affect the analytical performance, an accurate method for the determination of fumonisin B1 (FB1) and B2 (FB2) in cornflakes has been developed. The method uses immunoaffinity chromatography for clean-up and high performance liquid chromatography (HPLC) for quantification of the toxins. Samples were extracted twice with acetonitrile-methanol-water (25:25:50) and the combined extracts were diluted with phosphate buffered saline (PBS) and applied to a FumoniTest immunoaffinity column. After washing with PBS, fumonisins were eluted from the column with methanol and reacted with o-phthaldialdehyde/2-mercaptoethanol to form fluorescent derivatives. Fumonisin derivatives were analysed by reversed phase HPLC with fluorometric detection using methanol-0.1 M phosphate buffer (77:23; pH adjusted at 3.35) as mobile phase. The average recoveries for FB1 and FB2 spiked in the ranges of 0.33 2.80 microg/g and 0.17-1.40 microg/g were 102.6% and 95.1%, respectively, with average relative standard deviations of 9% and 8%. The limit of quantification for FB1 and FB2 was 0.005 microg/g based on a signal-to-noise ratio of 6.1 by using a sensitive fluorescence detector. The method was used to analyse 18 cornflakes and cornflake cereals samples/for FB1 and FB2 contamination. All but one sample were found to be contaminated, with maximum FB1 and FB2 concentrations of 1.092 microg/g and 0.235 microg/g, respectively. Mean FB1 and FB2 concentrations were 0.157 microg/(g and 0.036 microg/g, respectively.

Carboxylic Acids↗

PubMed2001

Effect of processing on fumonisin concentration in corn flakes.

The stability of fumonisin B1 and fumonisin B2 during processing of corn flakes was investigated with three different methods for analysis of the naturally contaminated raw material (corn flour), intermediate product (extruded, but not roasted corn flakes), and final product (roasted corn flakes). Only one method, using immunoaffinity column clean-up, provided reliable results in the determination of fumonisins in corn flake samples at the intermediate and final steps of processing. About 60 to 70% of the initial amount of fumonisins were lost during the entire cycle of corn flake processing, with less than 30% losses occurring during the intermediate extrusion step (70 to 170 degrees C for 2 to 5 min). The effect of different additives commonly present in commercial products (sodium chloride, sucrose, and ferrous sulfate heptahydrate) on the reliability of fumonisin analysis has also been investigated. The presence of sodium chloride strongly reduced fumonisin recovery when strong anion-exchange (SAX) columns were used for the clean-up step, whereas the other additives appeared to have little or no effect on the accuracy of fumonisin analysis. The use of reliable analytical methods that are effective for both raw materials and processed products is of paramount relevance for studying the effect of food processing on mycotoxin-contaminated commodities. Despite the fact that some effective fumonisin decontamination occurring during corn flake processing has been shown, more work is needed to identify the thermal breakdown products of fumonisins and their relevant toxicity.

Carboxylic Acids↗

PubMed2000

Determination of ochratoxin A in domestic and imported beers in italy by immunoaffinity clean-up and liquid chromatography.

A method first developed to quantify ochratoxin A in wine has been applied to the analysis of domestic and imported beers in Italy. The method uses commercial immunoaffinity columns for clean-up and high-performance liquid chromatography for quantification of the toxin. Beer was degassed, then diluted with a polyethylene glycol-sodium hydrogencarbonate solution and applied to an OchraTest immunoaffinity column. Ochratoxin A was eluted from the immunoaffinity column with methanol and quantified by reversed-phase HPLC with fluorometric detector. Average recoveries of ochratoxin A from blank beer spiked at levels from 0.04 to 1.0 ng/ml ranged from 93.8% to 100.4%, with relative standard deviations between 3.3% and 5.7%. The detection limit was 0.01 ng/ml based on a signal-to-noise ratio of 3:1. The analysis of 61 samples of domestic (10) and imported (51) beers showed ochratoxin A levels ranging from <0.01 to 0.135 ng/ml with an incidence of contamination of 50% and no substantial difference between strong and pale beers.

Beer↗

PubMed2000

Spontaneous gastroesophageal reflux and airway patency during the night in adult asthmatics.

Controversies still exist on the role of nighttime gastroesophageal reflux (GER) in precipitating nocturnal asthma. We tested the relationship between GER and nocturnal bronchoconstriction by continuously and simultaneously monitoring both respiratory resistances and esophageal pH in seven asthmatics with moderate to severe GER disease. Twenty-nine GER episodes were found during the study night lasting more than 5 min (LGER) and 72 not longer than 5 min (SGER). Both long (LGER) and short (SGER) gastroesophageal refluxes were able to maintain significantly higher lower respiratory resistances (RLR) at the resolution of each GER episode (RLR(e)) with respect to baseline values. RLR, expressed as the area under the RLR curve along each GER episode (AUCR(LR)) and as RLR(e), showed significant correlations with GER duration. Moreover, a significant correlation was found between RLR measured 10 min after GER resolution and GER duration during each episode. We conclude that GER itself is able to elicit nocturnal bronchoconstriction in asthmatics with moderate to severe GER disease and that bronchoconstriction severity and duration are related to GER duration.

Adult↗

PubMed1999

Determination of ochratoxin A in wine by means of immunoaffinity column clean-up and high-performance liquid chromatography.

A new and accurate method to quantify ochratoxin A (OA) in table wine has been developed. The method uses commercial immunoaffinity columns for clean-up and high-performance liquid chromatography (HPLC) with fluorescence detection for quantification of the toxin. Wine was diluted with a solution containing 1% polyethylene glycol (PEG 8000) and 5% sodium hydrogencarbonate, filtered and applied to an OchraTest immunoaffinity column. The column was washed with a solution containing sodium chloride (2.5%) and sodium hydrogencarbonate (0.5%) followed by water. OA was eluted with methanol and quantified by reversed-phase HPLC with fluorometric detection (excitation wavelength 333 nm, emission wavelength 460 nm) using acetonitrile-water-acetic acid (99:99:2) as mobile phase. Average recoveries of OA from white, rosé and red wine samples spiked at levels from 0.04 to 10 ng/ml ranged from 88% to 103%, with relative standard deviations (RSDs) between 0.2 and 9.7%. Detection limit was 0.01 ng/ml based on a signal-to-noise ratio of 3:1. The method was applied successfully to 56 samples of red (38), rosé (8), white (9) and dessert (1) wine. The levels of OA ranged from <0.01 to 7.6 ng/ml with red wines more contaminated than rosé and white wines. A good correlation (r=0.987) was found by comparative analysis of 20 naturally contaminated samples using this method and the method of Zimmerli and Dick with better recoveries of OA and better performances for the new method. Several advantages of this method with respect to the actually available methods have been pointed out, with particular reference to red wine which appears to be the most difficult to analyze.

Acetic Acid↗

PubMed1999

Isolation and characterization of phytotoxic compounds produced by Phomopsis helianthi.

The isolation, chemical characterization and biological activity of two phytotoxic metabolites of Phomopsis helianthi Munt-Cvet et al. is reported. These compounds were identified by spectroscopic methods (UV, IR, 1H and 13C NMR, and MS) as trans-4,6-dihydroxymellein (trans-3-methyl-4,6,8-trihydroxy-3,4-dihyroisocoumarin) and cis-4,6-dihydroxymellein (cis-3-methyl-4,6,8-trihydroxy-3,4-dihydroisocoumarin). This is the first report of the isolation of trans-4,6-dihydroxymellein from fungal cultures and of the production of cis- and trans-4,6-dihydroxymelleins by P. helianthi. Rice was found to be a good substrate for the production of the dihydroxymelleins. Culture extracts of some Italian and French strains of P. helianthi showed different degrees of phytotoxicity towards sunflower leaves and seedlings. The minimum effective doses of trans- and cis-4,6-dihydroxymelleins with different bioassays were 76 and 135 microg per spot (leaf puncture bioassay), 3 and 5 micromol g(-1) fresh tissue (absorption by leaf cutting) and 5 and 2 micromol g(-1) fresh tissue (absorption by cut seedlings), respectively. These compounds may contribute to the severity of the sunflower disease caused by P. helianthi.

Helianthus↗

PubMed1998

Identification of a beta-lactoglobulin lactosylation site.

Thermal treatment of milk leads to non-enzymatic glycosylation of proteins through Maillard reaction. Free NH2 groups of basic amino acids react with the reducing carbonyl group of lactose forming the so-called Amadori products. Electrospray mass spectrometry analysis shows that beta-lactoglobulin (beta-LG), the major whey protein, undergoes lactosylation under industrial thermal treatment. In order to investigate the specificity of reactive sites for lactose binding the analysis of trypsin hydrolysates of beta-LG isolated from different industrial milks was performed. Results demonstrate that Lys-100 is a preferential lactosylation site of beta-LG during industrial milk treatment. These results were confirmed by an analysis of the three-dimensional model of the protein which showed that Lys-100 had the highest solvent accessibility and proximity to another amino group making Lys-100 the best candidate to lactosylation. Lys-47, previously identified by other authors, showed a good proximity to another Lys residue, but an intermediate level of exposition to solvent.

Amino Acid Sequence↗

PubMed1998

Use of various clean-up procedures for the analysis of ochratoxin A in cereals.

A rapid and reliable procedure has been developed for the determination of ochratoxin A in wheat and oats. The method consists of extraction of the sample with acidic chloroform, followed by defatting with n-hexane and finally, HPLC determination with fluorometric detection. Mean recoveries for wheat and oats spiked at levels between 1 and 100 micrograms/kg ranged from 80 to 104%. The limit of determination (field blank +6 sigma) was 0.8 micrograms/kg and the precision (within-laboratory relative standard deviation) ranged from 3 to 7%. The method was tested on 34 wheat and 34 oats samples. Ochratoxin A was confirmed in some positive samples by methyl ester formation and/or by clean-up of the extracts with immunoaffinity columns. The method was not appropriate for the analysis of barley (45 tested samples), rye (69 samples) or trout feed (13 samples). A false positive was recorded within the four positive barley samples and 18 false positives were recorded within the 21 positive rye samples whereas trout feed samples could not be analysed due to insufficient clean-up. The use of immunoaffinity columns made the analysis of trout feed and rye samples possible, providing excellent clean-up of the extracts with no false positive results and a good limit of determination (0.2 micrograms/kg).

Animal Feed↗

PubMed1998

Determination of zearalenone in corn by means of immunoaffinity clean-up and high-performance liquid chromatography with fluorescence detection.

A rapid and accurate method to quantify zearalenone in corn is described. The method uses immunoaffinity chromatography for purification and high-performance liquid chromatography (HPLC) for detection and quantification of the toxin. Corn samples were extracted with acetonitrile-water (90:10, v/v) and the extract was diluted with water (1:10, v/v) and applied to a Vicam ZearalaTest immunoaffinity column. The column was washed with water and zearalenone was eluted with methanol and quantified by reversed-phase HPLC with fluorometric detection (lambda ex = 274 nm, lambda em = 440 nm) using acetonitrile-water-methanol (46:46:8, v/v) as mobile phase. Zearalenone recoveries from the ZearalaTest column were higher than 95%, and the column can hold a maximum of 4.0 micrograms of toxin. Average recoveries of zearalenone from corn spiked at levels of 0.1-10 micrograms/g ranged from 9 to 99.5%, with relative standard deviations of < 6%. The detection limit was 3 ng/g based on a signal-to-noise ratio of 3:1. Comparative analysis of 14 naturally contaminated samples using this method and the AOAC official method 985.18 showed a reasonable correlation (r = 0.87). Advantages of the immunoaffinity method as compared to the AOAC method are discussed.

Chromatography, Affinity↗

PubMed1997

Rapid method to determine sphinganine/sphingosine in human and animal urine as a biomarker for fumonisin exposure.

The widespread occurrence of fumonisins in maize and maize-based foods and feeds demands the development of rapid and reliable methods for the analysis of suitable biomarkers in biological fluids in order to assess human and animal exposure to these important mycotoxins. The increase in the ratio of free sphinganine/sphingosine (SA/SO) in urine has been recently proposed as a biomarker to evaluate exposure to fumonisins. The presently available method for the determination of SA and SO in biological samples is labor intensive, time consuming and insufficiently accurate. A new method has been proposed for the determination of SA and SO in human and animal urine which is more precise and accurate, and drastically reduces the number of steps during extraction and clean-up. The method is essentially based on the use of silica minicolumn clean-up of the chloroform extract from alkalinized urine. The final extract is derivatized with o-phthaldialdehyde reagent and SO and SA are determined by reversed-phase HPLC with fluorimetric detector. Urine samples spiked with SO, SA standards at concentrations ranging from 1.5 to 15 ng/ml have given mean recoveries higher than 80% and precision (coefficient of variation) lower than 10%. Detection limit for SO and SA was 0.1 ng/ml.

Adult↗

PubMed1997

Relationship of microbiologic diagnostic criteria to morbidity and mortality in patients with ventilator-associated pneumonia.

OBJECTIVE: To evaluate whether the mortality and the morbidity of ventilator-associated pneumonia, defined by positive result of protected specimen brush culture, was different from that defined by other methods. DESIGN: Matched-cohort study. All patients with clinical suspicion of pneumonia were investigated with protected specimen brush, bronchoalveolar lavage, and blind bronchial samplings. Two groups were defined: brush-positive patients (positive culture of the protected specimen brush) and brush-negative patients (negative culture of the protected specimen brush, but positive culture with another method). SETTING: A 14-bed medicosurgical intensive care unit (ICU) in an 850-bed teaching hospital. PATIENTS: All patients with documented ventilator-associated pneumonia over 4 years 9 months. A total of 102 cases documented by protected specimen brush culture and 223 documented by another sampling procedure. Patients were matched according to diagnosis on admission, age, sex, date of admission, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, and date of onset of pneumonia. MAIN OUTCOME MEASURES: Mortality rate, duration of mechanical ventilation, duration of ICU stay, duration of hospital stay, sampling methods, and microbiologic cultures. RESULTS: A total of 76 pairs were submitted for analysis. The effectiveness of matching was 81.85%. There was no difference in mortality between brush-positive patients and brush-negative patients. The ICU fatality rate was 38% in the brush-positive group and 39.4% in the brush-negative group (odds ratio [OR], 0.95; 95% confidence interval [CI], 0.46-1.93). The hospital fatality rate was 41% (OR, 1; 95% CI, 0.5-2.01). The mean (SD) duration of ventilation was 26 (23) days in the 2 groups (range, 3-132 days). The duration of ICU stay was 33 (27.4) days in the 2 groups (range, 3-152 days). CONCLUSIONS: When confounding factors are controlled, patient outcome is the same if ventilator-associated pneumonia has been diagnosed by protected specimen brush or by another sampling method.

APACHE↗

PubMed1996

Simultaneous high-performance liquid chromatographic determination of visoltricin, acuminatopyrone and chlamydosporols in Fusarium cultures on maize.

Visoltricin (VIS), acuminatopyrone (ACP), clamydosporol (CL), isochlamydosporol (ICL) and chlamydospordiol (DIOL), recently characterized Fusarium metabolites, were separated on a polymeric RP-18 column eluted with acetonitrile-0.01% ammonia solution (35:65) at 1 ml/min and detected with a diode-array UV detector. The presence of ammonia in the mobile phase improved the shape of the CL and VIS peaks. The use of a polymeric column was required owing to the basic pH of the mobile phase. Maize cultures of several strains of F.tricinctum and F. chlamydosporum were analysed with this procedure after extraction with aqueous methanol, partitioning with methylene chloride and clean-up with a C18 minicolumn. VIS was produced only by F. tricinctum, whereas ACP and chlamydosporols were produced by both Fusarium species.

Cholinesterase Inhibitors↗

PubMed1996

Fumonisins in maize genotypes grown in various geographic areas.

Data on the occurrence of fumonisins B1 and B2 in maize genotypes (inbred lines and hybrids) cultivated in several countries from three continents will be presented. Samples originated at different times (from 1990 to 1994) from experimental stations in Argentina, Benin, Croatia, Poland, Portugal, Italy, Romania and Zambia. Fumonisin contamination was negligible in samples from eastern Europe (Croatia, Romania and Poland), whereas it was quite relevant and widespread in samples from Argentina, western Europe and Africa. A general trend of higher fumonisin levels was observed in Argentina, Zambia (limited to 1993 crop), Portugal, and Italy (mainly 1990 and 1991 crop years), with a significant percentage of samples showing more than 1000 ng/g, a level of concern. The data from the present study suggest that the environmental conditions in the specific area of cultivation play an important role in the accumulation of fumonisins in maize.

Africa↗

PubMed1996

Evaluation of nocturnal bronchoconstriction by all night tracheal sound monitoring.

BACKGROUND: A study was undertaken to evaluate the reliability of a digital tracheal sound analyser (ELENS-DSA) in predicting nocturnal changes in airways resistance in asthmatic patients. This device allows continuous measurement of the proportion of the time occupied by wheezing (Wh%). METHODS: Nocturnal polygraphic studies with simultaneous continuous monitoring of tracheal sounds and airways resistance were performed in seven patients with nocturnal asthma. In order to evaluate the possible bias in wheezing estimation, each tracheal sound recording was passed through the automatic analyser and simultaneously monitored with earphones by an experienced observer. RESULTS: The device detected audible wheezing with an optimal sensitivity and specificity of 70%. Snoring was a minor cause of the relatively poor characteristics of the system. A close correlation (p < 0.001) between Wh% and airways resistance was observed only in those patients with the highest increase in resistance; when the results of all the subjects were pooled the correlation observed was poor. The predictive value of Wh% in detecting changes in airways resistance during 10 minute intervals was lower than 70%. The positive and negative predictive values of Wh% were raised to 79% and 83%, respectively, for 30 minute intervals. CONCLUSIONS: The ELENS-DSA system is a relatively crude means of detecting wheezing and assessing bronchoconstriction quantitatively. However, it is able to detect accurately nocturnal bronchoconstriction for 30 minute intervals. This finding, along with the fact that the monitoring is non-invasive, suggests that it may be a promising tool, especially for patients during sleep.

Adult↗

PubMed1995

Occurrence of fumonisins in Europe and the BCR--measurements and testing projects.

Fumonisins are mycotoxins mainly produced by Fusarium moniliforme, one of the most prevalent seed-borne fungi of maize. Strains of Fusarium moniliforme isolated from cereals in Europe produced in cultures high levels (up to 4 mg/g) of fumonisins B1 and B2 (FB1 and FB2). FB1 and FB2 have been found in maize and maize-based foods and feeds in most European countries. In Italy these mycotoxins have been directly involved in a fatal outbreak of equine leukoencephalomalacia, and have been found at different levels in most maize-based food products, including polenta--a staple food in a region with high incidence of esophageal cancer. The European Commission, Community Bureau of Reference (BCR) and Measurements and Testing Programme (M&T), has undertaken two consecutive intercomparison studies, involving over 20 laboratories from 12 European countries, to improve the quality of fumonisins analysis at European level. The first study consisted in the evaluation of the determination of fumonisins in an unknown solution, while the second one involved the analytical methodology for fumonisins in contaminated and blank maize samples. A definite improvement in the performance of the different laboratories has been observed in the second study. In view of the production of reference materials certified for their fumonisins contents, new analytical procedures need to be developed.

Food Microbiology↗

PubMed1995

Modifications in uterine and intraovarian artery impedance in cycles of treatment with exogenous gonadotropins: effects of luteal phase support.

OBJECTIVE: To determine the effects of induction of multiple ovulation and of luteal P supplementation on the impedance to blood flow in the uterine and intraovarian arteries during the luteal phase. DESIGN: A prospective study using transvaginal color flow Doppler imaging. SETTING: A university-based infertility center. PATIENTS: Fifty-six women with unexplained or male factor-related infertility undergoing IUI. INTERVENTIONS: The patients were studied either during spontaneous cycles (n = 16) or in cycles of induction of multiple follicular development with purified FSH (n = 40). In 18 treated cycles, the luteal phase was supplemented with natural P. MAIN OUTCOME MEASURES: The pulsatility index was recorded from uterine and intraovarian arteries on the day of E2 peak and 5 and 10 days thereafter. On the same days, E2 and P plasma levels were measured by RIA. RESULTS: The intraovarian pulsatility index was significantly lower in FSH-treated than in spontaneous cycles on the day of E2 peak. Also, the uterine pulsatility index was significantly lower in treated cycles than in spontaneous cycles on the day of E2 peak and 5 days thereafter. In the late luteal phase, P supplementation was correlated with a significant decrease in uterine pulsatility index as compared with both spontaneous cycles and FSH-treated cycles without luteal support. CONCLUSIONS: Multiple follicular development is associated with a significant reduction in the impedance to perifollicular blood flow. Progesterone, as well as E2, seems able to decrease the impedance to blood flow in uterine arteries in women.

Adult↗

PubMed1994

Production of a toxin stemphol by Stemphylium species.

Five of 11 isolates of Stemphylium botryosum Wallr. from oilseed rape produced the phytotoxin stemphol when cultured on rice, with yields varying from 15.0 to 98.4 mg/kg, and three of them also produced the toxin on Czapek Dox (CD) liquid medium supplemented with cations (0.12-0.31 mg/L) and potato-dextrose (PD) broth (0.37-1.47 mg/L). In liquid cultures about 95% of stemphol was found in the mycelium, and toxin production was slightly increased when cultures were exposed to near UV light rather than being grown in the dark. The LD50 concentrations for stemphol against isolated cells of oilseed rape and chickpea were 8.4 and 7.0 microM, respectively. One isolate of S. majusculum (strain no. 135459) produced much greater amounts of stemphol, i.e., 22.8 mg/L, 535.3 mg/L, and 548 mg/kg when grown on CD, PD, and rice, respectively. Leaves of oilseed rape, artificially infected with S. majusculum and bearing lesions that occupied an average of 70% of the lamina contained 0.9 microgram stemphol per gram dry weight of leaf tissue.

Biological Assay↗

PubMed1994

In vitro neutralization of T-2 toxin toxicity by a monoclonal antibody.

A T-2 toxin specific monoclonal antibody, IgG1 K, with a low level of ELISA cross-reactivity to Acetyl T-2, HT-2, and iso T-2 toxins has been produced. The ability of this monoclonal antibody to neutralize the cytotoxicity of T-2 toxin in PHA stimulated cultures of human lymphocytes was determined by the MTT method. The complete neutralization of the toxic effect of 0.02 microM T-2 toxin was obtained with 0.03 microM of MoAb, whereas the 50% neutralizing dose (ND50) was observed at 0.009 microM of MoAb. Partial neutralization was observed with Acetyl T-2 toxin (ND50 = 0.038 microM) and HT-2 (ND50 = 0.94 microM). These results could represent a rational for clinical use of T-2 toxin specific monoclonal antibody in prophylaxis and therapy of T-2 toxemia.

Animals↗