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Biomedical subjects

R Massa

Publications and source records attributed to R Massa.

At least 91 records · Page 5Linked to original sources
PubMed1985

Effect of progesterone on the sexual behavior of the male Japanese quail.

The reduced metabolites of testosterone produced in the central nervous system of birds are known to be involved in the regulation of male sexual behavior. Since progesterone may compete with testosterone for 5 alpha- and 5 beta-reduction, it may also interfere with the sexual behavior of birds. In order to test this hypothesis, progesterone was administered to male quail either transferred from short days to long days or kept in short days and treated with testosterone. Sexual behavior and crowing were scored at intervals for 21 days and the size of the cloacal gland was measured at the same times. On Day 21, the birds were killed and their testes were weighed. The administration of a large dose (1 mg/day) of progesterone depressed the sexual behavior of the birds stimulated either by long days or by the administration of testosterone. It is suggested that progesterone may compete with testosterone for the active sites of 5 alpha- and 5 beta-reductase; alternatively, its effect may be due to an antiandrogenic activity.

Animals↗
PubMed1985

Isolated symptomatic lesions of the vertebral artery: cure after surgical repair.

Nine patients with uni-or bilateral stenosis of vertebral arteries, not associated with other lesions of supraaortic trunks are reported. They showed a vertebrobasilar insufficiency syndrome not due to other assessable causes. Seven of them underwent surgical treatment always as reimplantation of the vertebral into the subclavian artery. The procedure was unilateral also in cases with bilateral lesions. In all 7 patients a favourable result was obtained: 5 patients recovered completely and 2 showed a marked improvement. The study demonstrates that the surgical repair of symptomatic unilateral lesions of vertebral arteries is able to cure the vertebrobasilar insufficiency syndrome.

Adult↗
PubMed1984

Prognostic evaluation of brainstem hematomas: the role of CT scan and brainstem auditory evoked potentials.

6 cases of brainstem hematoma were studied utilizing CT scan and brainstem auditory evoked potential (BAEP) recordings. CT scan did not contribute to an early discrimination between primary and secondary hematomas. Size of the hematoma and the presence of blood in the CSF did not represent evident signs in differentiating benign from unfavourable brainstem hematomas or hemorrhages. BAEP recordings showed the presence of electrophysiological anomalies at the level of the lesion, demonstrating that bleeding as well as tumor in the brainstem can provoke a focal damage.

Adult↗
PubMed1983

Effect of photoperiod and gonadectomy on testosterone metabolism in vitro by the prostate of the golden hamster.

Testosterone metabolism was studied in vitro in the prostate of intact and castrated golden hamsters maintained either in short days (8 h light: 16 h darkness, 8L: 16D) or in long days (14L: 10D). Testosterone was found to be converted into 17 beta-hydroxy-5 alpha-androstan-3-one (5 alpha-DHT), 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3, 17-dione and androstenedione. The mean conversion of testosterone to 5 alpha-DHT was higher in prostates from animals maintained in long days than in short days (P less than 0.0025) while that to androstenedione was higher in short days (P less than 0.0005); no significant changes in the formation of the other three metabolites were noted. Castration of animals maintained in short days resulted in a significant (P less than 0.05) decrease in the mean conversion to all four metabolites. In contrast, castration of animals kept in a long-day regime caused a significant (P less than 0.01) decrease in the mean formation of 5 alpha-DHT but a significant (P less than 0.05) increase in the mean formation of 5 alpha-androstane-3 alpha, 17 beta-diol.

Androstane-3,17-diol↗
PubMed1981

Conversion of testosterone to 5 beta-reduced metabolites in the neuroendocrine tissues of the maturing cockerel.

The metabolism in vitro of [4-14C]testosterone to reduced derivatives was studied in the pituitary gland, hypothalamus and hyperstriatum dorsale of cockerels from hatch to sexual maturity. The most important metabolites were 5 beta-dihydrotestosterone (5 beta-DHT), 5 beta-androstane-3 alpha, 17 beta-diol (5 beta-3 alpha-diol) and 5 beta-androstane-3 beta, 17 beta-diol. Trace amounts of androstenedione and, in the hypothalamus only, of 5 alpha-DHT were also detected. The amounts of 5 beta-reduced metabolites produced by all neuroendocrine tissues declined progressively during maturation with the steepest fall occurring during the first 2 weeks after hatch. At all ages studied, 5 beta-DHT was formed to the greatest extent by the hyperstriatum dorsale, to a lesser extent by the hypothalamus and in the smallest quantities by the pituitary gland. In the three tissues studied, 5 beta-3 alpha-diol tended to be formed to the greatest extent by the pituitary gland. No significant change was observed in the metabolism of testosterone to reduced derivatives in any of the neuroendocrine tissues after castration. It was concluded that in the cockerel, unlike the rat, a change in 5 alpha-reductase activity of the neuroendocrine tissues is unlikely to be involved in the initiation of puberty. The physiological significance of 5 beta-reductase activity in the neuroendocrine tissues remains to be established.

Animals↗
PubMed1980

Role of testosterone and of its metabolites in regulating gonadotrophin secretion in the Japanese quail.

In the Japanese quail gonadal steroids can depress plasma levels of LH and FSH. Since it is now accepted that testosterone metabolites may be metabolized to the tissue-active forms of the hormone, the in-vitro tissue incubation has been combined with steroid replaement therapy in vivo to investigate the physiological roles of various testosterone metabolites as inhibitory feedback agents on gonadtorophin secretion in quail. After the incubation of quail pituitary glands for 3 h with labelled testosterone four metabolites could be identified; androst-4-ene-3,17-dione, 5 beta-dihydrotestosterone (5 beta-DHT), 5 beta-androstane-3 alpha, 17 beta-diol and 5 alpha-DHT. No 5 alpha-androstane-3 alpha, 17 beta-diol was found. Quantitatively, androstenedione was the major metabolite and converison of testosterone to 5 beta-metabolites was significantly greater than to 5 alpha-androgens. Hypothalamic and hyperstriatal tissues converted testosterone than to 5 alpha-androgens. Hypothalamic and hyperstriatal tissues converted testosterone to androstendione, 5 beta-DHT and 5 beta-androstane-3 alpha, 17 beta-diol but not to 5 alpha-DHT or 5 alpha-androstane-3 alpha, 17 beta-diol. Gonadotrophin secretion was studied in castrated quail after chronic s.c. implantation of steroid-containing silicone elastomer capsules or acute injection i.m. of steroid in ethanol: saline. Irrespecive of the route of administration seven androgens, listed in descending order of potency, reduced the increased levels of plasma LH: testosterone: 5 alpha-DHT; androstenedione; 5 alpha-androstane-3, 17-dione; 5 alpha-androstane-3 alpha, 17 beta-diol; 5 alpha-androstan-3 alpha-ol-17-one; 5 alpha-androstan-3 beta-ol-17-one. No changes in levels of plasma LH were observed after the administration of 5 beta-DHT, 5 alpha-androstane-3 beta,17 beta-diol, 5 beta-androstante-3 alpha, 17 beta-diol, 5 beta-androstane-3, 17-dione, androst-5-ene-3 beta, 17 beta-diol or androst-5-en-3 beta-ol-17-one. Testosterone and oestradiol-17 beta were effective in inhibiting secretion of both LH and FSH in young photostimulated quail and completely blocked testicular growth: 5 alpha-DHT inhibited only the release of LH and testicular growth was unaffected.

Androgens↗
PubMed1980

Cloacal gland of the Japanese quail: androgen dependence and metabolism of testosterone.

A cloacal gland complex whose growth and development is androgen-dependent exists in the Japanese quail. In-vitro incubation studies of the cloacal gland using 4-14C-labelled testosterone as substrate allowed the positive identification of five metabolites: androstenedione, 5 beta-dihydrotestosterone (5 beta-DHT), 5 beta-androstane-3 alpha, 17 beta-diol, 5 alpha-DHT and 5 alpha -androstane-3 alpha, 17 beta-diol. More polar metabolites, not yet chemically identified, were detected in trace amounts. Androstenedione appeared to be the main testosterone metabolite in immature birds while in mature birds on long daylengths testosterone was preferentially metabolized to 5 alpha-DHT. This change may have been in response to the higher levels of plasma steroids found in mature birds. When various testosterone metabolites, contained in silicone elastomer capsules, were implanted s.c. into castrated birds maintained on a photostimulatory light regime, 5 alpha-DHT, 5 alpha-androstane-3,17-dione, androstenedione and 5 alpha-androstan-3 alpha-ol-17-one were shown to be equipotent with testosterone in stimulating the development of the cloacal gland. 5 alpha-Androstane-3 alpha, 17 beta-diol and 5 alpha-androstan-3 beta-ol-17-one stimulated some growth while 5 beta-DHT, 5 alpha-androstane-3 beta, 17 beta-diol, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 beta-androstane-3,17-dione, androst-5-en-3 beta-ol-17-one and androst-5-ene-3 beta, 17 beta-diol were completely ineffective.

Androgens↗
PubMed1980

Conversion of progesterone to 5 alpha- and 5 beta-reduced metabolites in the hen and its potential role in the induction of the preovulatory release of luteinizing hormone.

In the laying hen, progesterone was shown to be converted in vitro in the pituitary gland and the hypothalamus to 5 beta-pregnane-3,20-dione (5 beta-pregnane-3 alpha-ol-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP) and in the hyperstriatum dorsale to 5 beta-DHP and 5 beta,3 alpha-ol. The conversion of progesterone to 5 beta-reduced metabolites was greater in the hyperstriatum dorsale than in the hypothalamus (P < 0.001) and greater in the hypothalamus than in the pituitary gland (P < 0.01). The conversion of progesterone to 5 beta-reduced metabolites was greater than its conversion to 5 alpha-DHP in the pituitary gland (P < 0.01) and the hypothalamus (P < 0.001). The possibility was investigated that 5 alpha-DHP and 5 beta-DHP may act as metabolic intermediaries in the mechanism by which progesterone exerts a positive feedback effect on LH release. Progesterone, 5 alpha-DHP and 5 beta-DHP were injected into laying hens at doses of 0.05, 0.25 and 1.25 mg/kg and the changes in the concentration of plasma LH were followed for 4 h thereafter. Secretion of LH was stimulated after treatment with progesterone or 5 alpha-DHP but not 5 beta-DHP. Progesterone stimulated Lh release more effectively than did 5 alpha-DHP, since an increase in the concentration of plasma LH was observed after 0.25 mg progesterone/kg but not after the same dose of 5 alpha-DHP. It was concluded that in the hen 5 alpa-DHP is unlikely to play a role in the induction of the preovulatory release of LH.

Animals↗