Biomedical subjects
Publications and source records attributed to R Verbeke.
A simple, cheap and rapid method for the quantitative determination of the boar taint substance, 5 alpha-androst-16-en-3-one, in pig adipose tissue is described. After saponification of the fat the androstenone is extracted, derivatised with o-(pentafluorobenzyl)hydroxylamine hydrochloride in pyridine and analysed by fused-silica open-tubular capillary gas chromatography with electron-capture detection.
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.
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.
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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.
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A method for the quantitative extraction of thiocyanate from biological material has been developed. Levels of 0.2-5 ppm of thiocyanate, in the presence of cyanide, were determined by gas-solid chromatography using 2-bromopropane as internal standard. Reliable results can be obtained only after careful deproteinization of the extracts with hot methanol. Cyanide can be eliminated by reaction with alkaline formaldehyde. The reproducibility of the determination of thiocyanate in biological extracts was +/-5%; the recoveries were over 90%. In vivo experiments with KS14CN-treated rats gave good agreement between the analytical results and the amount of thiocyanate determined by isotope dilution.
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Small amounts of kallikrein were isolated from bovine mammary tissue. Immediately after slaughter, the udder was removed, perfused with ice-cold xylocaine-Rheomacrodex solution, and homogenized in ice-cold acetic acid solution. Kallikrein-like substances were adsorbed on DEAE-cellulose, eluted with ammonium formate and fractionated by acetone precipitation. The 40-70% acetone fraction was separated on a Shephadex-G 75 column and aliquots of each fraction were incubated for 1 or 2 hr with kininogen. After incubation, extracts were tested for kinin activity on the isolated rat uterus, the rat duodenum, blood flow through the femoral artery of dogs and by intramammary pressure assay in sheep. Release of kinins was demonstrated by all these techniques, highest kallikrein activity being detected in the molecular weight range 50,000 to 60,000. Direct injection of the enzyme into the udder artery of sheep, without prior incubation with kinninogen, resulted in vasodilation and a rise in intramammary pressure. The kallikrein activity was strongly inhibited by aprotinin, but not by soybean trypsin inhibitor or ovomucoid. Kallikrein activity was always associated with esterase activity.
Experiments were carried out to test the effect of implantation of Implix¿ (20 mg estradiol + 200 mg testosterone) or Revalor¿ (140 mg trienbolone acetate + 20 mg estradiol) on growth, feed conversion, slaughter quality, and residue levels in black Friesian bull calves at 4, 8, or 4 and 8 weeks before slaughtering. Weighings and calculations of feed conversion were carried out weekly. The control group of weight gain and feed conversion consisted of 22 calves; the chemical analyses of the control group was restricted to 8 animals. Implantation of the hormones at 4 or 8 weeks before slaughtering resulted in a significant beneficial effect on weight gain, feed conversion and carcass index over the control. This effect was improved (up to 15%) by implanting the hormones at 8 and 4 weeks before slaughter. The effects obtained with Revalor seemed to be superior to those obtained with Implix. In 75% of the treated animals, some remainder of implants was found. No effect was found on water binding capacity and colour of raw meat. Carcass quality was not significantly improved as judged from water, fat, ash, and protein content of the M. Longissimus Dorsi. The collagen content of the animals treated with Revalor was slightly, though not significantly, increased. There is a slight decrease in the relative bone content of the treated animals over the control resulting in higher meat percentages. Residues were determined in meat obtained from rib and neck by biological and chemical methods. Oestrogenic activity was found in only 7 samples from the neck; all samples from the rib were negative. Chemical examination indicates the presence of oestradiol in these samples. No residues of trienbolone could be detected in the meat samples. The Pars Dissiminata of the prostate was examined histologically on frozen and paraffin sections. Although the latter permitted a sharper interpretation, both methods indicated an increased activity of the prostates induced by hormone treatment. Compared to Implix, Revalor treatment provoked a more pronounced mucous activity. In recent years, the administration of estrogens in combination with testosterone or with trenbolone acetate (androst-4,9[10]-11-trien-3-one 17-acetate)2,3,4,17 has been shown to improve the growth rate and feed conversion5,14,17 in farm animals. However, there is a lack of information on carcass quality, which is of interest to the producer as well as to the consumer. Moreover, there are sample data14 about the residue levels remaining in the carcass following hormone implantation. These experiments were carried out to test the effect of the implantation of Implix¿ (20 mg estradiol + 200 mg testosterone) or Revalor¿ (140 mg trienbolone acetate + 20 mg estradiol) on growth, feed conversion, slaughter quality, and residue levels in black Friesian bull calves.
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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.
1. A lactating-sheep mammary gland was perfused for 12h in the presence of l-[2-(14)C]-citrulline and received adequate quantities of glucose, acetate and amino acids. Two lactating-goat udders were similarly perfused in the presence of either l-[carbamoyl-(14)C,-2-(14)C]citrulline or l-[carbamoyl-(14)C,1-(14)C]citrulline and l-[4-(3)H]arginine. 2. In these experiments, [(14)C]citrulline was substantially oxidized to CO(2) and converted into arginine and proline of casein. 3. The specific radioactivities of arginine, ornithine and proline of the plasma increased after passage through the udders, demonstrating that [(14)C]citrulline is metabolized by the mammary gland. 4. The presence of two unknown radioactive metabolites of [(14)C]citrulline was detected in the perfusate. These substances were not found after incubation in vitro of oxygenated blood in the presence of the radioactive precursor. 5. From these experiments, it is concluded that citrulline is metabolized in mammary tissue by way of arginine to urea, ornithine and proline.
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