Rapid confirmatory method for the determination of sixteen synthetic growth promoters and bisphenol A in bovine milk using dispersive solid-phase extraction and liquid chromatography-tandem mass spectrometry

A rapid liquid chromatographic-tandem mass spectrometric (LC-MS/MS) multi-residue method for the simultaneous quantitation and identification of sixteen synthetic growth promoters and bisphenol A in bovine milk has been developed and validated. Sample preparation was straightforward, efficient and economically advantageous. Milk was extracted with acetonitrile followed by phase separation with NaCl. After centrifugation, the extract was purified by dispersive solid-phase extraction with C18 sorbent material. The compounds were analysed by reversed-phase LC-MS/MS using both positive and negative ionization and operated in multiple reaction monitoring (MRM) mode, acquiring two diagnostic product ions from each of the chosen precursor ions for unambiguous confirmation. Total chromatographic run time was less than 10 min for each sample. The method was validated at a level of 1 mu g L-1. A wide variety of deuterated internal standards were used to improve method performance. The accuracy and precision of the method were satisfactory for all analytes. The confirmative quantitative liquid chromatographic tandem mass spectrometric (LC-MS/MS) method was validated according to Commission Decision 2002/657/EC. The decision limit (CC alpha) and the detection capability (CC beta) were found to be below the chosen validation level of 1 mu g L-1 for all compounds. (C) 2010 Elsevier B.V. All rights reserved.

Studies on the persistence of estradiol benzoate and nortestosterone decanoate in hair of cattle following treatment with growth promoters, determined by ultra-high-performance liquid chromatography-tandem mass spectrometry

Measurement of steroid esters in bovine hair samples, using sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS), provides a powerful tool for identifying animals treated illicitly with growth promoters. The successful application of such testing requires appropriate sampling of hair from treated animals. This paper describes the results of hair analysis by LC-MS/MS for two animal studies in which animals were treated with estradiol-3-benzoate and nortestosterone decanoate. The results from the first animal study indicate that animals treated with these anabolic steroids may not always be identified from analysis of hair samples; positive test results occur sporadically and only for some of the treated animals. The results from the second animal study identify conditions attaching to positive hair samples, such as, that concentrations of steroid esters in hair are related to distance of sampling from point of injection and to time post-treatment, that concentrations of steroid esters in hair are related to dose given to the animal but that this relationship may vary over time post-treatment, and that steroid esters may be measured in regrowth hair taken some weeks after treatment. Steroid esters are determined along the length of the hair, confirming that accumulation of steroid esters into hair occurs from various sources, including blood, sweat and sebum. The reported research provides some useful insights into the mechanisms governing the persistence of steroid esters in bovine hair following illicit treatment with growth promoters. (C) 2009 Elsevier B.V. All rights reserved.

Surveillance study of a number of synthetic and natural growth promoters in bovine muscle samples using liquid chromatography-tandem mass spectrometry

A simple, new method permitting the simultaneous determination and confirmation of trace residues of 24 different growth promoters and metabolites using liquid chromatography-mass spectrometry was developed and validated. The compounds were extracted from bovine tissue using acetonitrile; sodium sulphate was also added at this stage to aid with purification. The resulting mixture was then evaporated to approximately 1 ml and subsequently centrifuged at high speed and an aliquot injected onto the LC-MS/MS system. The calculated CC values ranged between 0.11 and 0.46 mu g kg-1; calculated CC were in the range 0.19-0.79 mu g kg-1. Accuracy, measurement of uncertainty, repeatability and linearity were also determined for each analyte. The analytical method was applied to a number of bovine tissue samples imported into Ireland from third countries. Levels of progesterone were found in a number of samples at concentrations ranging between 0.28 and 30.30 mu g kg-1. Levels of alpha- and beta-testosterone were also found in a number of samples at concentrations ranging between 0.22 and 8.63 mu g kg-1 and between 0.16 and 2.08 mu g kg-1 respectively.

Identification and isolation of plant promoters induced by thiocyanate

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Alternative promoters in the pst operon of Escherichia coli

The pst operon of Escherichia coli is composed of five genes pstS, pstC, pstA, pstB and phoU, that encode a high-affinity phosphate transport system and a negative regulator of the PHO regulon. Transcription of pst is induced under phosphate shortage and is initiated at the promoter located upstream of the first gene of the operon, pstS. Here, we show by four different technical approaches the existence of additional internal promoters upstream of pstC, pstB and phoU. These promoters are not induced by Pi-limitation and do not possess PHO-box sequences. Plasmids carrying the pst internal genes partially complement chromosomal mutations in their corresponding genes, indicating that they are translated into functional proteins.

Intestinal mucosa development in broiler chickens fed natural growth promoters

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Productive traits of broiler chickens fed diets containing different growth promoters

This study evaluated the effect of different probiotics and prebiotics on the performance of broilers. One-day-old male broiler chicks from the Cobb strain (n=1,260) were randomly distributed in a 3 x 3 factorial arrangement, considering 3 probiotics and 3 prebiotics sources. Nine treatments with 4 repetitions and 35 birds per parcel were used. The results showed that there was no influence of treatment on feed intake at the different rearing phases. Better weight gain (p<0.05) was seen when diet was supplemented with the phosphorylated mannanoligosaccharide-based prebiotic (MOS) compared to diets without prebiotics. Feed conversion of birds fed diets with probiotics and prebiotics was better than feed conversion of birds not receiving such additives. Such better results were seen in the initial period (1 to 21 days), but not in the following period (1 to 35 days) or in the total period (1 to 42 days). Better rearing viability was seen when MOS was used together with organic acidifier when compared to the diets without prebiotic. Viability was worst when no prebiotics or probiotics were used. It was concluded that beneficial effects were seen in performance of birds at 21 days when the growth promoters were used, but not at 42 days of age. Nevertheless, there was better growth viability at 42 days of age when growth promoters were added.

Performance of broilers fed diets containing natural growth promoters

The present study evaluated the effect of different probiotics on the performance of broiler chickens. A thousand and fifty one-day-old male Cobb chicks were distributed in a completely randomized design in a 3 x 2 + 1 factorial arrangement (3 probiotics sources in the diet, 2 probiotics concentrations in drinking water and 1 control group), with 5 repetitions of 30 birds per parcel. The results showed better feed conversion (p<0.01) (1-21, 22-35 and 1-45 days) and weight gain (p<0.05) (22-35 and 1-45 days) in the control group in relation to the groups receiving probiotics. The use of Bacillus subtilis in the diet improved (p<0.05) feed conversion during the growing phase, but this was not seen in the following period. Thus, it was concluded that probiotics supplementation had no beneficial effects on the performance.