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Biomedical subjects

F Neumann

Publications and source records attributed to F Neumann.

At least 127 records · Page 7Linked to original sources
PubMed1977

Comparison of the biological effectiveness of injected testosterone propionate and testosterone released from silastic capsules.

The in vitro release and biological effectiveness of silicone rubber implants containing testosterone in orchidectomized male rats was investigated over a period of 20 weeks. A marked reduction in release in 0.9% saline solution could be observed in vitro relative to the incubation time in the medium. The reduction in release was greatest during the first few weeks of the experiment. Rat seminal vesicles and prostates, which were greatly stimulated at the start of the experiment, lost weight corresponding to the release rate in vitro. The implants containing testosterone used here were 4 to 26 times more effective than testosterone propionate injected s.c.

Animals↗
PubMed1977

[The effect of glucocorticosteroids on sex differentiation in rats].

The influence of two glucocorticoids (hydrocortisone and dexamethasone) on the somatic sex differentiation of female rats was investigated. During the time of sexual differentiation of their foetuses, pregnant rats were given dexamethasone (0.1-0.3 mg/day) or hydrocortisone (20-200 mg). Both compounds interfere with foetal development by virtue of their strong growth-inhibitory activity which manifests itself in reduction of the body weight, the crown-rump length, the length of the genital folds and the genital cord. The inhibition of growth seems to be reversible. Only hydrocortisone acts teratogenically as it causes a shift of the differentiation of the female genital tract into male direction. This virilisation consists of partial stabilisation of the Wolffian ducts, the suppression of mammary nipple development and a male-type differentiation of the urogenital sinus. The relevance of these findings for human beings is briefly discussed.

Animals↗
PubMed1976

Is feminine differentiation of the brain hormonally determined?

The androgen insensitive, genetically male rat pseudohermaphrodite displays neither masculine or feminine sexual behavior when primed with the appropriate sex hormones. Although in the absence of androgen imprinting the animal develops anatomically as female, our results suggest that feminine differentiation of the brain requires active imprinting by perinatal hormone(s), possibly adrenal progesterone.

Animals↗
PubMed1976

Comparative evaluation of the dissociation rate between the vaginotrophic and uterotrphic activities of 1-hydroxy-1, 3, 5 (10)-estratriene derivatives with natural and unnatural configuration at C8 using ovariectomized mice.

Influences on estrogenic.activities of 1-hydroxylation and C8-isomerization in the molecules of naturally occurring estrogens have been studied. All compounds tested behaved qualitatively in the same manner as estradiol, as far as the decrease in the vaginal and uterine sialic acid levels and the increase in the organ weights of the vagina and uterus of castrated mice are concerned. They were, however, different not only in the relative ptoencies of the estrogenic effects, but also in the dissociation rate between the vaginotrphic and uterotrophic activities. Of the compounds tested, 1-hydroxy-8alpha-estrone, 1-hydroxy-8alpha-estradiol and their acetates had a higher value of the dissociation index than that of estriol. These compounds seemed to exert a predominant effect on the vagina rather than on the uterus. Following structural factors seem to be of significance for the dissociation of estrogenic effects: the 1- or 16alpha- hydroxy group and 8alpha-configuration decrease the uterotrophic activity more intensely than the vaginotrophic activity, and the 17alpha-ethinyl group selectively increases the uterotrophic activity.

Animals↗
PubMed1976

The influence of pharmaceutical compounds on male fertility.

1. Steroid hormones can affect spermatogenesis and thereby fertility directly and/or indirectly. All antigonadotropically active steroids inhibit spermatogenesis via inhibition of gonadotropin secretion, mainly that of H. Androgens and steroids occurring in the biosynthetic chain of testosterone synthesis have a direct promoting effect on spermatogenesis if applied in high doses. It has not been possible as yet to make clinical use of this positive effect since it is obviously not possible to achieve the necessary intratesticular androgen concentrations. 2. As concerns the different androgens and the steroids in the androgen biosynthetic chain, and also all synthetic anabolics, there is no parallelism between the direct spermatogenic activity, the androgenic activity and the antigonadotropic activity. 3. Estrogens and synthetic gestagens do not inhibit spermatogenesis directly at the testicular level. All effects of estrogens can be abolished experimentally by adequate substitution with gonadotropins or androgens, or a combination of androgens and gonadotropins. 4. Only those antiandrogens inhibit spermatogenesis with additional antigonadotropic properties (e.g. cyproterone acetate). Pure antiandrogens, like flutamide or cyproterone, have a slight and transient influence on spermatogenesis at the most. If at all, they merely cause transient subfertility. 5. Beside steroids and several centrally active pharmaceutics (e.g. psychotropic drugs and several antihypertensive compounds), only siloxanes and methallibur seem to affect spermatogenesis via inhibition of gonadotropin secretion. Other antispermatogenic agents act by inhibition of mitosis (Colchicine, alkylating agents) or presumably via damage of the Sertoli cells. 6. Based on present knowledge, contraception in men could be principally managed by administration of a) androgens alone, b) gestagen/androgen combinations, c) estrogen/androgen combinations, d) certain antiandrogens. 7. The difficulties of contraception in men by steroid hormones or steroid hormone combinations have been pointed out. As regards the usefulness of antiandrogens for contraception, no definite conclusions can be drawn at the moment. All non-steroidal inhibitors of spermatogenesis which have been found up to the present are not suitable because of toxic effects.

Androgen Antagonists↗
PubMed1976

Effect of the ergot derivative lisuride hydrogen maleate on serum prolactin concentrations in female rats.

The influence of a new synthetic ergot derivative, lisuride hydrogen maleate (LHM) on serum prolactin (PRL) concentrations was investigated in female rats using different test models: 1. in reserpine (R)-pretreated intact females, and 2. in ovariectomized (OVX) estradiol benzoate (E2)-primed animals with or without an additional pretreatment with R. In all the models used LHM was strongly effective in lowering serum PRL. Doses from 0.025 to 0.5 mg/kg LHM, given orally as well as subcutaneously, suppressed serum PRL. Depending on the dose used, the serum PRL was lowered to a different extent for up to 12 h. LHM was at least as effective as the well-known potent inhibitor of PRL secretion CB-154 in lowering serum PRL in OVX rats primed with E2. The effects of R, E2, and LHM are described in relation to their mode of action within the hypothalamic-hypophyseal system which regulates PRL secretion. While the increase in serum PRL induced by R seems to be directly relatable to its known catecholamine depletion, the circadian rhythm of PRL secretion induced by E2 seems to be influenced or mediated by central neural mechanisms. The effects of LHM on serum PRL in these test models can be related to its dopaminergic action and constitute further evidence for the central functions of dopaminergic mechanisms in the regulation of PRL secretion.

Animals↗
PubMed1976

Role of testosterone and its metabolites in the differentiation of the mammary gland in rats.

The capacity of various androgens to virilize the differentiating mammary gland in the female rat fetus has been determined. Testosterone, 5alpha-androstane-3alpha, 17beta-diol (3alpha-diol), and dihydrotestosterone (DHT) virilize the anlagen of the mammary gland by suppressing nipple formation but 5alpha-androstane-3beta, 17beta-diol, androsterone, and dehydroepiandrosterone sulfate do not affect female mammary differentiation. However, unlike the genitalia and wolffian ducts of the female rat fetus in which the masculinizing potency of DHT and 3alpha-diol is greater than that of testosterone, testosterone is more potent than its metabolites DHT and 3alpha-diol, in virilizing the mammary gland. The results suggest that testosterone is the fetal androgen mediating masculine development of the mammary gland.

Androgens↗
PubMed1976

Pharmacological and endocrinological studies on anabolic agents.

When used in connection with animal production the term "anabolic agents" covers a wide range. Ther steroidal male and female sex hormones are included in this list, as are the nonsteroidal estrogens. For the clinician and for the endocrinologist, anabolics are only steroids chemically related to testosterone and 19-nortestosterone. Estrogens, though possessing anabolic properties, too, do not belong to this class. This paper will deal with anabolic agents in in the stricter sense of which mainly trenbolone acetate combined with hexestrol has been recommended for bull and heifer fattening. To consider possible consumer injury from ingestion of meat from anabolic agent treated animals, it is necessary to know the pharmacological properties of the agents, the doses producing certain effects or might produce, and the levels of residues in the meat. Trenbolone acetate will be compared with the following anabolic agents: methenolone acetate, methandrostenolone, nandrone, androstanazole, and 19-nortestosterone. The activity spectrum of trenbolone acetate is similar to that of 19-nortestosterone or those anabolics that are derived from 19-nortestosterone. The compound has about three times stronger androgenic effect than testosterone propionate. Its index of dissociation between anabolic/androgenic activity is 2--3. This index is 3--10 for the other anabolic agents. As regards the virilizing potency, trenbolone acetate is also on the top of the list. It seems that androgenicity and degree of virilization run paralle. The antigonadotropic activity (inhibition of ovulation and testicular growth) of trenbolone acetate exceeds that of testosterone propionate by the factor 3. The compound is not estrogenic and seemingly not or only weakly progestationally active. In principle, the androgenic activity (symptoms of virilization) as well as the antigonadotropic effect (disturbances of the menstrual cycle in women, inhibition of spermiogenesis in men) of trenbolone acetate might be noted. This risk, however, can be excluded by mere calculation. In rats, 0.1 mg/kg trenbolone acetate have an antigonadotropic effect. This corresponds to a daily dose of 5--7 mg in humans. By the same extrapolation, a daily human dose of 100 mg can be calculated for androgenic activity. Such factors of conversion are, of course, not precise because rats are much less sensitive to androgens and anabolics than humans. Thus, testosterone propionate is active only in daily doses of 10--20 mg. If in humans trenbolone acetate also has three times the activity of testosterone propionate, effects in man had to be counted with not less than a daily intake of 3--5 mg trenbolone acetate. The dose which is recommended for livestock fattening is 300 mg. IT can, therefore, be excluded almost with certainty that the meat would contain such large amounts of hormone residues.

Anabolic Agents↗
PubMed1975

Partial feminization of hepatic steroid metabolism in male rats after neonatal administration of cyproterone acetate.

The metabolism of (4-14C)4-androstene-3,17-dione, (4-14C)5alpha-androstane-3alpha, 17beta-diol and (1,2-3H)5alpha-androstane-3alpha, 17beta-diol 3,17-disulphate was studied using the microsomal fraction and the metabolism of (4-14C)4-androstene-3,17-dione was studied using the 105 000 g supernatant fraction of liver from male and female rats aged 5 months that had been treated with cyproterone acetate before (from day 13 of pregnancy) and after birth (until 3 weeks of age). Nearly all sex-dependent enzyme activities in the treated male rats were changes in a direction characteristic of female rats: 5alpha-reductase active on 4-androstene-3,17-dione increased in activity whereas 3beta- and 17alpha-hydroxysteroid reductases and 6beta- and 16alpha-hydroxylases active on 4-androstene-3,17-dione and 2alpha-, 2beta- and 18-hydroxylases active on 5alpha-androstane-3alpha,17beta-diol decreased in activity. Enzyme activities not under gonadal control, i.e. 3alpha- and 17beta-hydroxysteroid reductases active on 4-androstene-3,17-dione and 7alpha-hydroxylase active on both 4-androstene-3,17-dione and 5alpha-androstane-3alpha, 17beta-diol, were not affected by cyproterone acetate. The liver enzyme activities in treated female rate were generally not affected although significant effects were noted in two cases; in one of these (17alpha-hydroxysteroid reductase) a testosterone-like effect was observed. The results obtained are probably best explained in the following way: treatment with theanti-androgen during the neonatal period results in less efficient imprinting of the hypothalamo-hypophysial system leading to less pronounced masculine setting of sex-dependent enzyme levels and also to a relative androgen unresponsiveness. It is suggested that the biochemical methods used in the degree of neonatal sexual differentiation of the hypothalamo-hypophysial system than biological and psychological methods previously available.

Androstanes↗