Biomedical subjects
Publications and source records attributed to B Hoffmann.
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With the view to complementing the feedstuff data store and, consequently, to further improving the GDR Feed Evaluation System, some newly bred high-protein and/or high-lysine cereal varieties and strains (spring barley, winter wheat, maize) were studied for their nutrient composition and digestibility. Apart from from WEENDER's feed analysis technique, more recent methods were applied to determine total fat (after HCl treatment), carbohydrates (enzymatic method), lignin and amino acids. The digestibility of the nutrients was determined using growing pigs of different live weight, the test rations being made up of the cereals under and supplementations of limiting amino acids as well as vitamins and minerals. In comparison with the values from currently applied tables, the newly bred strains and varieties proved to have markedly higher contents of crude protein, digestible crude protein, lysine and energetic feed equivalents. Compared to crude fat, the total fat values proved markedly higher in the barley and wheat samples. The readily soluble and easily hydrolizable carbohydrates found with the new analysis procedure suggested, were 100% digestible in all cereal samples used. Lignin proved the constituent most difficult to digest and must be regarded as virtually undigestible in the case of pigs.
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Radioimmunoassay (RIA) is valuable for sensitive and specific routine measurements of hormones in body fluids. The method is also applicable to determine tissue levels of hormones which, according to tracer studies and depending on the compound, are scattered in the lower ng and pg/g range. For practical assay application it must be decided whether the parent compound or a major metabolite should be measured. Both toxicological and practical regulatory aspects have to be considered, but in any case knowledge of the metabolic profile of the compounds is necessary, especially since the specificity of the RIA group analysis is limited. When applying extraction and purification steps, differences between compounds and between tissues have to be considered; generally more difficulties are encountered than with plasma. Validation of the method should first demonstrate no unspecific interference with the antigen-antibody reaction; then the other reliability criteria have to be established. So far RIAs for the quantitation of estrogens, testosterone, progesterone, and trienbolone--a synthetic androgen--in various bovine tissue samples have been developed. The lower limit of sensitivity ranges between 10 and 70 pg/g. Quantitation of physiological levels of testosterone and progesterone is possible, but there are still some problems with estrogens.
Two heifers were implanted with 300 mg of the radiolabeled anabolic steroid, trenbolone acetate (TBA). After a 60 day slaughter and a 60 day removal followed by 76 day slaughter, total 3H-content in various tissues was 0.5--25 ng/g equivalents of TBA. Radioimmunoassay of the tissues showed that only 1--5% of the total residue present was TBA, its main metabolite trenbolone (TBOH), and TBOH glucuronide, plus up to 5% of other organic-soluble material. Of the radioactivity remaining about half was directly water-soluble, and the insoluble residue could be made water-soluble by treatment with the proteolytic enzymes pepsin and trypsin. These 2 portions were purified with Sephadex G-25 to give a low and high molecular weight fraction. Raney nickel reduction of sulfur bonds in either fraction released up to 50% of radioactivity into the organic phase. TLC showed that the latter contained 2 components which had characteristics similar to TBOH and its metabolites, and thus were at least partly drug-related metabolites. In vitro experiments with bovine liver also showed a small but definite protein binding. It is proposed that in dealing with these covalently bound residues, priority be given to the reactive drug intermediate and the type of binding to macromolecules rather than to the presence of the bound residue itself.
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The study has been made to analyse changes in heart rate, in mechanical and bioelectrical muscle activity during thythmical handgrip contractions. Loads of 20% to 100% of the maximal voluntary contraction (MVC) were applied. The working frequency was 30 cpm. With loads of 40%--100% of the maximal voluntary contraction (MVC) the following characteristic changes were obtained: Both the plane of the mechanogram and the duration of the mechanogram increased permanently. The heart rate rose to the end of the experiment and so did the EMGs of the flexor, the extensor, the brachioradial muscle and the muscle of the thenar. The rate of the rise (%/s) of all physiological functions was greatest during maximal load test and decreased with decreasing contraction strength. The endurance as a function of the force showed a parabolic curve. The physical endurance capacity of this rhythmical hand work is between 20% and 40% MVC.
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The experiments were carried out on 11 subjects ranging in the age from 23 to 37 years. Heart rate, integrated electrical activity from 4 muscles of the forearm and the hand and mechanical activity were measured simultaneously during rhythmical work using a hand-ergometer. The strength of the dynamic contractions was 20, 40, 60, 80 and 100% of a maximal voluntary contraction. The mean values of the maximal voluntary contraction obtained on male subjects were 57.3 kp and on female subjects 33.2 kp. The results showed that during dynamic contractions mechanical activity was related to the integrated electrical activity and both integrated electrial activity of 3 muscles and heart rate were linearly related to the load. The correlation coefficients for the EMG/EMG relationships of different muscles and for the EMG/heart rate varied between 0.83 and 0.98.
A specific, sensitive, precise and accurate radioimmunoassay has been developed for the quantitation of the synthetic anabolic steroid trienbolone acetate (TBA) and its major metabolites, free and conjugated trienbolone (TBOH) in bovine tissues and plasma. With the extraction procedure described unspecific interference with the antigen-antibody reaction could be ruled out. The assay can significantly detect amounts of more than 40 pg TBOH and 70 pg TBA. 0.1 - 2.0 g tissue and 0.1 - 1 ml plasma are sufficient for 1 determination. Residues (range 0.1 -2.0 ng/g) were still present in calves 69 days after implantation of "Revalor" (20 mg estradiol-17beta and 140 mg TBA) with the highest concentrations found in liver and TBA could only be quantitated in fat.
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