In vitro inhibition of porcine cytochrome P450 by 17β -estradiol and 17α-estradiol

Sexually mature pigs are known to possess high concentrations of testicular steroids, which have been shown to change the activities of cytochrome P450 in vitro. The aim of the present study was to evaluate the regulation of CYP1A and CYP2E1 activity by the steroids dihydrotestosterone (DHT), 3β-androstenol, 17β-estradiol and 17α-estradiol. Catalytic activities of 7-ethoxyresorufin O-deethylase (EROD) and 7-methoxyresorufin O-demethylase (MROD) were used as markers of CYP1A activities, while p-nitrophenol hydroxylase (PNPH) was used as a marker of CYP2E1 activities. Of the steroids tested, only 17β-estradiol and 17α-estradiol inhibited EROD and MROD activities. This inhibition was observed when a steroid concentration of 100 µM was used, while lower concentrations showed no inhibitory effect. PNPH activities were inhibited only by 100 µM of 17β-estradiol. The significance of these results in vivo is unknown because inhibition was only found when concentrations of estrogens higher than physiological levels were used. Nevertheless, the results provided further evidence on the important role of estrogens in regulation of porcine cytochrome P450 activities

Des mathématiciens découvrent les volumes finis

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Des mathématiciens découvrent les volumes finis

National audienc

Development of a reference material for Staphylococcus aureus enterotoxin A in cheese: Feasibility study, processing, homogeneity and stability assessment

Staphylococcal food poisoning is caused by ingestion of enterotoxins which are excreted into foods by some strains of coagulase positive staphylococci, mainly Staphylococcus aureus. To protect consumers, Commission Regulation 1441/2007 specifies thresholds for the presence of these toxins in foods such as cheeses. In addition, the reference method to be applied for detection is defined (extraction, dialysis concentration, immunochemical toxin detection). In order to enforce legislation, it is indispensable to have suitable quality assurance tools such as reference materials (RMs) available to implement and safeguard reliable measurements. Anses and IRMM collaborate to develop a RM for Staphylococcal enterotoxin A (SEA) in cheese. First a feasibility study was conducted to establish a suitable processing procedure for producing large quantities of homogeneous and stable cheese powders. Three types of materials were made, and the following one proved to be most suitable: the blank material was prepared by cutting, grinding, freeze-drying, milling and mixing. For the spiked material, the cheese was converted into a slurry, spiked with a solution of SEA, freeze-dried, mixed, and diluted with blank material to the target SEA concentration level. Thereafter, large batches of three materials (blank, very low contaminated, low contaminated) were processed, and the materials' homogeneity and short-term stability were assessed using the reference method. The materials showed to be sufficiently homogeneous for the intended used, and storage at +18 ºC for 4 weeks did not indicate any detectable material degradation. These results provide the basis for the development of a RM for SEA in cheese.JRC.D.2-Standards for Innovation and sustainable Developmen

M'as-tu vu ?: Être et paraître à la romaine dans le Nord de la Gaule entre le Ier et le Ve s. apr. J.-C. Catalogue de l'exposition organisée par le Forum antique de Bavay [14 mai - 8 novembre 2022]

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