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R Verbeke

Publications and source records attributed to R Verbeke.

9 recordsLinked to original sources
PubMed1979

Sensitive multi-residue method for detection of anabolics in urine and in tisssues of slaughtered animals.

A routine procedure is described for the dependable detection of various anabolic residues in tissues or urine contaminated at levels as low as 0.5-10 ppb (10 parts per 10(9)). A suitable extraction and clean-up procedure was developed, permitting adequate recovery (60-80%) of various anabolics from tissue samples (50 g) or urine (50 ml). Following two-dimensional thin-layer chromatography, the presence of the anabolic residues are detected by sulphuric acid-induced fluorescence. The detection limit of most anabolics is of the order of 1-10 ng.

Androgens↗
PubMed1979

Metabolism of [U-14C; 2,3-3H]-L-valine by the isolated perfused goat udder.

Two lactating mammary glands excised from 2 goats were perfused for several hours in the presence of [U-14C; 2,3-3H]-L-valine and received adequate quantities of glucose, acetate and amino acids. In the synthesized milk 96 and 89% respectively of the casein valine was derived from free plasma valine. Valine was extensively catabolized by mammary tissue, resulting in a considerable 14CO2 production and in the incorporation of 14C into milk citric acid and to a lesser extent into casein aspartic acid and glutamic acid. About 30% of the valine molecules which were taken up by the mammary gland were oxidized to CO2 and 70% were incorporated in casein as valine residues. About 10% of the plasma valine molecules were reversibly transaminated during one passage through the udder. An important amount of radioactivity of plasma was present in unknown metabolites. Only 7% of this activity was localized in isobutyrate. The radioactivity of total milk fat was very low. Mainly iso-14:0, iso-16:0 and 15:0 were labelled.

Animals↗
PubMed1979

Metabolism of ornithine in perfused goat udder.

Four lactating goat mammary glands were perfused for several hours in the presence of ornithine labeled with 1-carbon-14 and delta-nitrogen-15 or 5-hydrogen-3 and received adequate quantities of glucose, acetate, and amino acids. For the first label carbon and nitrogen were incorporated in casein of milk. After isolation of the casein amino acids the carbon-14 was incorporated into proline only while nitrogen-15 was localized in aspartic acid, glutamic acid, alanine, serine, glycine, and the branched-chain amino acids. In the experiments with hydrogen-3 labeled ornithine, no reversible transamination of ornithine could be measured during passage through the udder. After incubation in vitro of goat blood in the presence of the labeled ornithine, no nitrogen-15 could be detected in other free amino acids of plasma. Ornithine is transaminated by the udder itself. The delta-amino group of ornithine contributed nitrogen for the synthesis of several nonessential amino acids in the mammary gland.

Amination↗
PubMed1975

Detection of antithyroid residues in meat and some organs of slaughtered animals.

A simple method is described for the routine detection of antithyroid residues in thyroid, liver, kidney and meat contaminated at levels as low as 10 ppb (10 parts per 10(9)). Tissue samples (2 g) are homogenized in methanol, contaminating lipids and amino acids are removed and the antithyroid residues are subjected to reaction with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in buffer. The NBD derivatives are extracted with diethyl ether and separated by thin-layer chromatography. After spraying with cysteine or mercaptoethylamine, the antithyroid residues appear as fluorescent spots. The detection limit of these compounds is of the order of 200 pg.

Animals↗