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Biomedical subjects

H Karg

Publications and source records attributed to H Karg.

At least 37 records · Page 2Linked to original sources
PubMed1978

Control of hormone treatment in animals and residues in meat--regulatory aspects and approaches in methodology.

Although the benefit of using anabolic hormones for fattening purposes under specific situations in animal husbandry (for instance, veal production) has been acknowledged in European countries, the regulatory consequences were quite different from those in the United States. With the exception of the United Kingdom, there were no approvals to use estrogens for other than distinct veterinary purposes. Hence the methodological approaches were rather to control the illegal treatments and imports. One measure is the uterus weight bioassay. Furthermore morphological parameters (prostate test) and estrogen determinations by thin layer chromatography in urine (also from the bladder) were proposed for detection of treated animals. Radioimmunoassays are in development and considered sensitive enough for residue studies in carcasses, perhaps applicable in combination with high pressure liquid chromatography. The re-evaluation of the regulatory situation is in progress in France and Germany and under consideration in the United Kingdom. Guidelines may be the recommendations of the FAO/WHO Symposium 1975 in Rome on anabolic agents in animal production indicating the variety of risks due to different compounds in question and preference to those with low oral activity and defined bio-degradation.

Biological Assay↗
PubMed1976

Metabolic fate of anabolic agents in treated animals and residue levels in their meat.

Anabolic agents applied in animal production can be classified as sex hormones, as far as one aspect of their biological activity is concerned. In respect to their chemical nature the agents can be divided into three sub-groups: (a) steroids natural to the body (endogenous steroids); (b) steroids foreign to the body; (c) other compounds foreign to the body. After exogenous application (oral or parenteral) metabolism of compounds in group (a), e.g. 17beta-estradiol or testosterone, follows the pathways for the identical endogenous hormones; i.e. enzymatic transformation of the biologically active molecule into less active compounds. Excretion seems to occur predominantly via the feces, followed by the excretion via the urine. Steroids foreign to the body (group [b]) may be simple esters of endogenous steroids (estradiol benzoate, testosterone propionate) or compounds with basically modified steroidal structures, like trenbolone acetate (estra-4, 9, 11-trien-17beta-OH-3one-Ac). After enzymatic cleavage of an ester in the animal, metabolism of natural steroids again follows the endogenous pathways. Other steroids are mainly excreted without changes of the original steroid structure. It has been demonstrated, that compounds applied as esters have a delayed elimination. Anabolic agents of nonsteroidal structure, (group [c]) like stilbene derivatives and zeranol (6-[6, 10-dihydroxy-undecyl] beta-resorcylicacid-mu-lactone) are not, or only to a minor percentage, catabolized in the body. It can be generalized so far, that the fraction of the hormone eliminated in the urine, is in the conjugated from, while the fraction appearing in the feces is in the free form. This is due to enterohepatic circulation, which occurs with both, the intact or catabolized compound. The elimination rate of anabolic agents not only depends on the absorption after oral or parenteral application, which is strongly related to the type of formula---or cleavage of possible esters, but also on the metabolic clearance rate, which is a function of several factors, for example binding to plasma proteins or tissue structures. Differences in the elimination rate between compounds could be attributed to these phenomena. Tissue residue formation not only depends on the elimination rate, but also on other factors like mode of application, formula and withdrawal time. The possibility for their detection is related to the method applied. In cases of adequate treatments of the animals, and with the exception of the implantation site (see below), positive hormone values in tissues (qualitative and quantitative) could only be obtained, when radioimmunoassay techniques with a sensitivity in the low nanogram range were applied...

Anabolic Agents↗
PubMed1975

[Natural occurrence of progesterone in commercial milk products (author's transl)].

By means of radioimmunoassay the concentrations of progesterone in commercial milk products were determined. The values range from 1.4 ng/ml (skin milk) to 300 ng/g (butter). The results show a close correlation between progesterone and fat contents in milk products. It is discussed that - due to recent progress in analytical methods - hormones in their natural occurrence in food are now measurable in micro-quantities which were not yet considered to be of biological importance; these findings should provoke a revision of terms like "free of hormones" in the sense of "zero tolerances".

Animals↗