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ABSTRACT: In 1992, the European Union set up a network of National Reference Laboratories and charged the Community Reference Laboratory with the responsibility to design a proficiency testing scheme for assessing the analytical ability of laboratories involved in the official control of aflatoxin M1 in milk. Since 1996, two exercises of proficiency testing have been performed on samples of milk powder and liquid milk at various levels of aflatoxin M1 contents. The trials were conducted according to ISO Guide 43, in particular for the homogeneity testing of sample batches and for the calculation of laboratory z-scores. The National Reference Laboratories officially designated by their governments participated in this programme. Samples were naturally-contaminated milk obtained by feeding cows with aflatoxin B1-contaminated feed. The levels of aflatoxin M1 in the samples ranged from 0.2 to 0.7 microg/kg in milk powder and from 0.05 to 0.07 microg/l in liquid milk. These levels were chosen as being close to the European Union-regulated limit of 0.05 microg of aflatoxin M1 per litre. The results produced by laboratories were compiled and statistically analysed to detect any outlying results and to calculate the individual z-scores. Except for one laboratory in each exercise, all laboratories exhibited acceptable or questionable z-scores. The interlaboratory relative standard deviation for reproducibility (RSDR) obtained for both 1996 and 1998 exercises were in the range 15.7-30.3%. Compared with other published studies, this indicates a very good precision for the performance of this laboratory network in the analysis of traces of aflatoxin M1 in milk.
Food Additives and Contaminants 06/2001; 18(5):405-15. · 2.13 Impact Factor
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ABSTRACT: The investigations on the activity of respiratory ciliae in vivo are of considerable interest for the study of physiopathological disorders resulting from chronic infection or inhaled pollutants. We present an image analysis method for the measurement of ciliary beat frequency on mammal or human in vivo samples. Videofilm sequences of samples placed under the microscope were analyzed frame by frame by image analysis. The operator defines on the screen several areas of interest on the cell apex. The variation of grey levels in each areas allows the calculation of ciliary beat parameters. This method permits one to investigate the effects of pharmacological agents or noxious pollutants on ciliae beating and the physiological causes underlying them. Our results on rabbits were in agreement with the data published in literature, showing no significant difference between intratracheal frequencies obtained at medium and lower levels. The upper level near the cracoid cartilage has shown a greater variability than the other two levels with higher beating frequencies, a difference of likely physiological importance.
Analytical cellular pathology: the journal of the European Society for Analytical Cellular Pathology 11/1995; 9(3):165-77.
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ABSTRACT: The marine toxin maitotoxin (MTX) induces stimulation of ciliary beating in primary cultures of rabbit tracheal epithelial cells. The response is time- and concentration-dependent. External calcium is an absolute requirement, although at a very low concentration (50 microM for maximal effect). Pretreatment of the cells with MTX induces an early (5 min) and sustained ( > or = 24 h) homologous desensitization. The response to MTX is strongly inhibited by trifluoperazin (an inhibitor of Ca-calmodulin-dependent enzymes) and by chelation of [Ca]i with BAPTA. However, the magnitude and kinetics of [Ca]i rise elicited by MTX do not correlate with those of the ciliary beat frequency (CBF) increase: the CBF increase is transient (with a peak at 5-10 min) while the [Ca]i rise is sustained; the CBF increase occurs at concentrations of MTX which are without an effect on [Ca]i; the CBF increase is not inhibited by 200 microM verapamil, genistein or okadaic acid, which inhibit the MTX-induced [Ca]i rise. The CBF increase is strongly inhibited by antagonists of arachidonic acid metabolism, mepacrine and nordiguaiaretic acid. However, MTX does not stimulate cAMP synthesis. These results suggest that calcium is not the only factor involved in the biological effects of MTX and even suggest that MTX may primarily stimulate phospholipid breakdown in the cell membrane.
Biology of the Cell 01/1995; 85(2-3):197-205. · 3.60 Impact Factor
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ABSTRACT: Maitotoxin induces a concentration-dependent 45Ca uptake in primary cultures of rabbit tracheal epithelial cells. This response is insensitive to the calcium channel antagonists nifedipine, diltiazem and verapamil up to 20 microM. However, verapamil at 200 microM completely prevents 45Ca uptake. Measurements of indo-1 fluorescence show that MTX induces a very sustained (> or = 2 h) [Ca]i rise, which is completely inhibited by 200 microM of verapamil. Genistein (110 microM) (an inhibitor of tyrosine kinases) also strongly inhibits it. The inhibitory effect of 50 microM miconazole (an inhibitor of cytochrome P450) is only partial. Okadaic acid (inhibitor of protein-phosphatases) primarily delays the response to the toxin without decreasing its magnitude. MTX induces the formation of (1,4,5) inositol trisphosphate (IP3). The MTX response curve is biphasic. Stimulation is transient (< or = 10 min) and is not inhibited by chelation of intracellular Cai with BAPTA, nor by verapamil (200 microM) or U73122 (10 microM) (an inhibitor of activation of PLC beta 1 through a trimeric G protein). Results suggest that MTX independently activates a calcium transport process (which might imply phosphorylation on tyrosine residues) and a PLC not linked to a trimeric G protein.
Biology of the Cell 02/1994; 82(2-3):195-202. · 3.60 Impact Factor
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Bulletin of Environmental Contamination and Toxicology 04/1993; 50(3):425-32. · 1.02 Impact Factor
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Bulletin of Environmental Contamination and Toxicology 06/1991; 46(5):756-60. · 1.02 Impact Factor
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ABSTRACT: An OECD study of contaminants in animals sampled from the wild is reviewed briefly. Results are presented of analysis of residues of organochlorines of agricultural origin, and of PCBs, in samples of fish taken from the French zone of Lac Léman at Thonon-les-Bains. Trends in organochlorine contamination in muscle of Perca fluviatilis and Rutilus rutilus are presented, for the years 1973 to 1981, and show low levels of the chemicals. All values found are lower than the maximum acceptable residue limits set by several countries for fish for human consumption; many were below the limit of detection of the analytical methods. Results are consistent with published studies by other authors.
Environmental Pollution 02/1987; 43(3):163-73. · 3.75 Impact Factor
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ABSTRACT: A method is described for the determination of deltamethrin, particularly in mild and dairy products. Residues and fat were co-extracted with acetone and light petroleum, partitioned with acetonitrile-methylene chloride and centrifuged (-10 degrees C). The extract was purified by gel permeation chromatography. A Florisil clean-up method was tested but did not seem effective enough. Analysis was performed by gas-liquid chromatography with a 63Ni electron-capture detector on 3% SE-30 using a short column (40 cm). Confirmation was effected by gas chromatography-mass spectrometry with an SE-30 capillary column (10 m). Recoveries from fortified samples ranged from 72 to 88% for milk spiked with 0.06 ppm and butter spiked with 2 ppm and was 94% for milk spiked with 0.016 ppm of deltamethrin.
Food Additives and Contaminants 7(1):117-23. · 2.13 Impact Factor
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ABSTRACT: A study was conducted to determine the metabolic fate of deltamethrin in lactating cows after a 'pour-on' application. Two cows were treated with 0.1 g deltamethrin and two with 1 g of the compound. Urine, faeces, milk and blood were collected over an 8-day period and analyzed for deltamethrin. This preliminary experiment has shown that it is necessary to undertake further experiment of longer duration (1 month). Deltamethrin was rapidly absorbed and slowly excreted. In milk, residues levels were very low: less than 1% of the treatment dose, and maximum levels were reached after 2 days (0.009 micrograms/ml for 0.1 g deltamethrin and 0.053 micrograms/ml for 1 g deltamethrin). For cows 1 and 2 (0.1 g deltamethrin), no residue level was detected at the detection limit (0.001 micrograms/ml) after 8 days. A total of 0.3-0.6% of excreted deltamethrin was present in urine, and no residue was found after 8 days. The major route for elimination was via faeces (about 95% of the total eliminated compound). Maxima were reached after 2 days and were still present after 8 days. Results shown in this study substantiate previously published work.
Food Additives and Contaminants 7(4):535-43. · 2.13 Impact Factor
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ABSTRACT: An OECD study of contaminants in animals sampled from the wild is reviewed briefly. Results are presented of analysis of residues of organochlorines of agricultural origin, and of PCBs, in samples of fish taken from the French zone of Lac Léman at Thonon-les-Bains. Trends in organochlorine contamination in muscle of Perca fluviatilis and Rutilus rutilus are presented, for the years 1973 to 1981, and show low levels of the chemicals. All values found are lower than the maximum acceptable residue limits set by several countries for fish for human consumption; many were below the limit of detection of the analytical methods. Results are consistent with published studies by other authors.
Environmental Pollution.
