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Biomedical subjects

R Ravid

Publications and source records attributed to R Ravid.

At least 109 records · Page 6Linked to original sources
PubMed1983

Changes in hypothalamic and extra-hypothalamic vasopressin content of water-deprived rats.

A correlative radioimmunoassay (RIA) and immunocytochemical (ICC) study was carried out on vasopressin (VP) distribution and content in brains of normal and 3-day water-deprived rats. By RIA there were statistically significant differences in brain VP per pg/mg between normal and osmotically stressed specimens in hypothalamus (338.4 versus 134.4), thalamus (4.8 versus 0.9), septum (18.0 versus 3.4), striatum (1.6 versus 0.7) and amygdala (17.3 versus 1.3), but not in other brain regions measured. Pituitary VP decreased from 71.1 to 8.7 ng/mg, and plasma VP rose from 3.6 to 19.3 pg/ml during water deprivation. Application of the peroxidase-anti-peroxidase ICC method of Sternberger to vibratome sections showed that VP-immunoreactivity in dehydrated specimens decreased in perikarya of paraventricular nucleus and suprachiasmatic nucleus, while intrahypothalamic immunoreactive magnocellular fibers appeared more conspicuous due to proliferation of large Herring bodies. In extrahypothalamic sites VP-immunoreactivity in water-deprived rats was visibly reduced in periventricular thalamus and septum. Thus it is apparent that both intra- and extrahypothalamic VP are affected by osmotic stress, and these results are discussed within the context of current ideas relating to co-activation of neurosecretory cells that project to different sites.

Animals↗
PubMed1982

Paradoxical hypersecretion of growth hormone in patients with endometrial atypical hyperplasia and carcinoma. Effect of hysterectomy.

Paradoxical hypersecretion of human growth hormone (HGH) followed a glucose load in patients with endometrial cancer and atypical hyperplasia of the endometrium. All patients had normal fasting plasma glucose and serum HGH concentration with a normal glucose tolerance curve. Their urinary estrogen concentrations were within the normal postmenopausal range. 6 months after abdominal total hysterectomy and bilateral oophorectomy, the glucose load was repeated. Following surgery all patients showed a normal suppression of HGH secretion during the hyperglycemic period. These findings suggest the existence of a HGH-releasing factor in the neoplastic and preneoplastic endometrial tissue. This factor might be related to the abnormal HGH responses observed.

Aged↗
PubMed1981

Dissociation of thyrotropin and prolactin responsiveness to thyrotropin releasing hormone stimulation in L-dopa treated parkinsonian patients.

The hPRL, hTSH and T3 response to thyrotropin releasing hormone (TRH) stimulation (200 microgram i.v.) were studied in 8 parkinsonian patients under chronic L-dopa-carbidopa therapy. In 6 out of the 8 patients studied, treatment was stopped for a period of 2 weeks and the TRH stimulation test was repeated under similar experimental conditions. In the L-dopa-carbidopa treated patients basal hTSH levels and the hTSH response to TRH were significantly suppressed. By contrast, in the 6 patients 2 weeks after cessation of treatment, although basal hTSH levels were still suppressed, a normal hTSH response to TRH was observed. Neither the basal T3 and T4 concentrations, nor the T3 response to TRH were affected by the L-dopa-carbidopa treatment. In addition, basal hPRL levels as well as the hPRL: response to TRH were within the normal range in the two groups of patients studied. Our study provides further support for a dopaminergic inhibitory action on the hypothalamo-hypophyseal-thyroidal axis (HHTA). The inhibition of basal hTSH secretion and th hTSH response to TRH by L-dopa, suggest that the blocking action of dopamine is exerted at the hypothalamic as well as at the pituitary level. In our hands, chronic administration of L-dopa did not affect either tonic hPRL secretion of the hPRL response to TRH. The dissociation or response to TRH under the same inhibitory action of dopaminergic stimulation can be interpreted as demonstrating a greater sensitivity of the pituitary thyrotrophs, than the prolactin secreting cells, to the blocking effect of dopamine.

Aged↗
PubMed1981

Effect of androstanediol sulfates on luteinizing hormone release in ovariectomized rats.

Androstanediols are the major products of the immature rat ovary and are present in peripheral circulation mainly as sulfate conjugates. In this paper we identified 5 alpha-androstane-3 beta, 17 beta-diol-3-monosulfate (3 beta-A-MS) as one of the forms found in blood and subsequently synthesized and administered it to ovariectomized rats at a dose of 100 microgram/100 g BW . day from 21-45 days of age. This dose effectively inhibits postcastrational LH elevation. Other androstanediols examined, like 5 alpha-A-3 alpha, 17 beta-diol-disulfate, 5 alpha-A-3 beta, 17 beta-diol-disulfate, and the free 5 alpha-A-3 beta, 17 beta-diol do not exert such an effect on LH release. The MCR of 3 beta-A-MS was 441 +/- 64 ml/h, independent of the infusion rate between 0.15-15.0 microgram/h, and its production rate was calculated to be 37 microgram/day at the age of 30 days. The quantitative relations of the steroid level in serum to its capacity to inhibit LH release was studied using Silastic capsules. A steady concentration of 1.1 ng 3 beta-A-MS/ml serum inhibits postcastrational LH release in the immature female rat. Since a similar or higher concentration of the steroid is present in the intact rat, it is assumed that 3 beta-A-MS controls pituitary LH release in the intact immature female rat. (Endocrinology 108: 500, 1981)

Androstane-3,17-diol↗
PubMed1980

Regulation of ovarian 17 beta-hydroxysteroid dehydrogenase activity by gonadotropin.

Serum testosterone levels are elevated prior to the lutropin surge, and decline abruptly following the release of endogenous lutropin. To investigate this phenomenon, the activity of 17 beta-hydroxysteroid dehydrogenase, the enzyme directly related to testosterone production from androstenedione, was measured. This was done in immature rats in which follicular maturation and ovulation were induced by pregnant mare serum gonadotropin administration. It appears that the effect of the gonadotropin on the enzyme activity is sharply divided into two phases that match with the follicular and the luteal phases. One day following gonadotropin administration, there was already a 7.67-fold increase in the original activity which further increased 48 h following hormone administration. At the peak of the lutropin surge, when follicular development is at its maximum, a 18.44-fold increase was measured. The activity fell abruptly 10 h following ovulation, at a time when fresh corpora lutea are already present in the ovary. It seems that the elevation of serum testosterone followed by its abrupt decline, is directly related to the increased and decreased ovarian 17 beta-hydroxy-steroid dehydrogenase activity. The possible importance of the observed changes to the mechanism of the onset of puberty are discussed.

17-Hydroxysteroid Dehydrogenases↗
PubMed1979

The diagnostic value of pharmacodynamic tests in the hyperprolactinaemic syndrome.

Patterns of prolactin (PRL) secretion were studied in a group of 18 hyperprolactinaemic patients with galactorrhoea and menstrual disorders and in a control group of thirty-two women in the early puerperium (24 h after a normal delivery) following provocative (TRH and Chlorpromazine) and suppressive (L-Dopa and bromocriptine) stimuli. Five out of the eighteen hyperprolactinaemic patients tested had radiological evidence of a pituitary tumour, and two were treated surgically. The early puerperium patients with elevated basal PRL levels (100--700 ng/ml) demonstrated a significant PRL response to the various treatments. On the other hand, in the hyperprolactinaemic group, an impaired PRL response to TRH, Chlorpromazine and L-Dopa was noted in patients with basal PRL levels higher than 30 ng/ml, whereas bromocriptine suppressed effectively PRL levels in all the hyperprolactinaemic patients tested irrespective of their basal PRL concentrations. The ratio between the fall in PRL concentrations (as percent of the baseline) after L-Dopa administration (delta%L) versus the PRL decrement after bromocriptine treatment (delta%B) was calculated. In the early puerperium group with normal pituitary prolactin secreting cells this ratio was equal to 0.8. In the hyperprolactinaemic group, the five patients with radiological evidence of a pituitary tumour had significantly lower ratios ranging from 0.2 to 0.57. These data suggest that in terms of prolactin release, prolactin producing tumour cells are intrinsically refractory to hypo thalamic dopaminergic signals. The calculation of individual delta%L/delta%B ratios may serve, therefore, as a valuable indicator for early detection of autonomous pituitary prolactin secreting cells and for evaluation of the extent of the pituitary lesion.

Adult↗
PubMed1977

Gonadotrophin release in ovariectomized patients. I. Suppression by clomiphene or low doses of ethinyl oestradiol.

Administration of clomiphene citrate (150 mg/day) for 5 days to twenty-four ovariectomized patients and seven normal female patients evoked a significant release of FSH and LH in the normal control group and suppressed the gonadotrophin secretion in the castrated patients. A similar suppressive effect on gonadotrophin secretion was noted in eight ovariectomized patients treated for 10 days with low doses (50 microgram/day) of ethinyl oestradiol. It is suggested that in the ovariectomized hypoestrogenic patients, clomiphene acted as an oestrogen, suppressing by a negative feedback action gonadotrophin release in a way similar to ethinyl oestradiol. In the normal control group with an adequate steroid environment, clomiphene acted (probably at the hypothalamic level) as an oestrogen antagonist and stimulated gonadotrophin secretion. In view of our findings, it seems as if the ability of anovulatory patients to respond to clomiphene treatment by increased gonadotrophin secretion depends upon the absolute concentration of the compound in the different organs and by the quantitative relation of clomiphene to the endogenous oestrogens.

Adult↗
PubMed1976

Androstanediol sulphates in peripheral blood of immature rats and some of their biological effects.

The conjugation of 5alpha-androstane-3alpha,17beta-diol (3alpha-A) and its 3beta epimer (3beta-A) was determined in the peripheral blood of immature female rats. About two thirds of these steroids were present in blood as sulphates and one third as glucuronides; no free steroids were detected. Administration of 3beta-A sulphate (25mug/100 g body weight/day) and of 3alpha-A sulphate (50 mug/100 g/day) from day 21 of life until the day of vaginal opening, advanced the day of the first ovulation. Administration of the 3beta-A sulphate did not induce precocious vaginal opening whereas the free alcohol was active in this respect. Implantation of 3beta-A sulphate, but not of the 3alpha epimer, into the basal medial hypothalamus resulted in the dealth of all animals within 24 h.

Androstane-3,17-diol↗