Papers by Clara Montesissa
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Veterinary Journal, 2010
This study reports fluorescence high performance liquid chromatography (HPLC) and UV-Vis HPLC met... more This study reports fluorescence high performance liquid chromatography (HPLC) and UV-Vis HPLC methods for the determination of 7-ethoxyresorufin O-deethylase (EROD) and tolbutamide methylhydroxylase (TMH) activities, respectively, using bovine liver microsomes. The detection limits were 0.022 and 5.5 pmol on the column, respectively; intra-day and inter-day precisions (expressed as relative standard deviation) were <10%. Both methods showed enough sensitivity to allow for an accurate determination of enzyme kinetic parameters according to Michaelis-Menten plots and the results were: K(m)=0.23+/-0.051 microM, V(max)=0.488+/-0.035 nmol/min/mg protein for EROD activity, and K(m)=1010+/-155.7 microM, V(max)=0.089+/-0.006 nmol/min/mg protein for TMH activity. An Eadie-Hofstee plot analysis showed that in bovine liver microsomes, EROD and TMH activities followed a monophasic kinetic pattern. alpha-Naphthoflavone, a cytochrome P450 1A1/2 (CYP1A1/2) inhibitor, and sulfaphenazole, a cytochrome P450 2C9 (CYP2C9) inhibitor, decreased EROD and TMH activities, respectively. The sensitivity of the methods allowed the use of microsomes with low enzyme activity, such as those from veal calf liver. Thus, EROD and TMH activities may be adopted as markers for the evaluation of CYP1A and CYP2C9-like activities in liver microsomes from veal and beef cattle.
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Food Analytical Methods, Nov 20, 2015
Pyrrolizidine alkaloids (PAs) are natural toxins, supposed to be converted to hepatotoxic metabol... more Pyrrolizidine alkaloids (PAs) are natural toxins, supposed to be converted to hepatotoxic metabolites in the liver of mammalians, and preventing the uptake of PAs is the only way to reduce the attendant health risks. A liquid chromatography coupled to mass spectrometry (LC-MS/MS) method was developed according to the Decision 2002/657/EC, to evaluate the contamination of Veneto honey by the following pyrrolizidine alkaloids: echimidine, heliotrine, lycopsamine, retrorsine, senecionine, and seneciphylline, as well as their N-oxides (pyrrolizidine alkaloid N-oxides (PANOs)). Before the solid-phase extraction, a reduction step with zinc dust in the presence of sulfuric acid was carried out for the reduction of PANOs to PAs in honey samples. For all of the analytes, the mean recovery ranged between 82.70 and 104.16 % and the limit of quantification (LOQ) was 0.25 μg kg−1, fully satisfying the LOQ of 1 μg kg−1 as requested by EFSA (2012). The validated method was applied for the analysis of 60 Veneto samples produced from local beekeepers. Among the samples, 17 % were positive for the PAs monitored, and their total PA contents ranged from 0.6 to 17.6 μg kg−1. In all of the samples, the contribution from the PANOs appeared to be negligible. The total PA contents found in the Veneto honey samples never exceeded the limit of 0.42 μg per day for an individual weighing 60 kg, established by the German Federal Institute of Risk Assessment (BfR) in 2011. These preliminary results provide useful advice to beekeepers for finding the most suitable location for beehives to achieve a substantial reduction of the PAs in honey.
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Journal of Veterinary Pharmacology and Therapeutics, 2006
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Journal of Veterinary Pharmacology and Therapeutics, 2006
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Food Additives & Contaminants: Part A, Oct 21, 2015
For the treatment of rabbit dysentery and bacterial enteritis, veterinary practitioners often ado... more For the treatment of rabbit dysentery and bacterial enteritis, veterinary practitioners often adopt veterinary medicinal products authorised for other food-producing species, but in some cases non-authorised drugs frequently used in the past, such as carbadox and olaquindox, might be illegally adopted. To verify the carbadox and olaquindox distribution and persistence in rabbit tissues, two independent in vivo studies were carried out. In the first study, 24 healthy rabbits received water medicated with carbadox at 100 mg l(-1) over a period 28 days, whereas in the second one, 24 healthy rabbits were administered water containing olaquindox at 100 mg l(-1). In each study rabbits were randomly assigned to four groups to be sacrificed respectively at 0, 5, 10 and 20 days from treatment withdrawal, for depletion studies. A control group of six animals was adopted for control and as a reservoir of blank tissues. Muscle and liver samples collected from each treated animal were stored at -20°C pending the analysis. Sensitive and robust liquid chromatography-tandem mass spectrometry analytical methods were set up for the parent compounds and their main metabolites quinoxaline-2-carboxylic acid, desoxycarbadox and 3-methylquinoxaline-2-carboxylic acid to verify their residual. Data collected demonstrate that the combination of liver as target matrix, quinoxaline-2-carboxylic acid and 3-methylquinoxaline-2-carboxylic acid as marker residue and enzymatic digestion is strategic to evidence carbadox and/or olaquindox illegal treatments in rabbits, even 20 days after treatment withdrawal at concentration levels higher than 0.5 µg kg(-1). This findings suggests that liver should be proposed as target matrix for official control in national monitoring plan.
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10th EAVPT Congress, 2006
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Journal of AOAC INTERNATIONAL, 2002
Residues of oxytetracycline (OTC) in edible tissues (muscle, liver, and kidney) of 18 turkeys wer... more Residues of oxytetracycline (OTC) in edible tissues (muscle, liver, and kidney) of 18 turkeys were determined after continuous administration of the drug for 3 days in drinking water at the maximum recommended concentration of 400 mg/L. The European Union (EU) maximum residue limits (MRLs) set for OTC are 100 μg/kg in muscle tissues, 300 μg/kg in liver, and 600 μg/kg in kidney, as the sum of the parent compound and its derivative 4′-epi-oxytetracycline (4-epi-OTC). Cleanup of tissue samples was performed by metal chelate affinity chromatography (MCAC), but the original technique was miniaturized by the adoption of a mini solid-phase extraction column, allowing reduction of solvents, time, and hazardous waste. OTC and its 4′-epimer were quantitated by an isocratic liquid chromatography elution with UV detection. After 1 day of withdrawal, OTC plus 4-epi-OTC residues were greater than MRL values in muscle and liver; 3 days after the end of treatment, all tissue residues were far lower...
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Analytical and Bioanalytical Chemistry, 2016
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Food Control, 2016
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Papers by Clara Montesissa