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Biomedical subjects

B Mess

Publications and source records attributed to B Mess.

At least 55 records · Page 3Linked to original sources
PubMed1977

The role of the pineal gland in the regulation of LH-release in rats with different types of the anovulatory syndrome.

The effect of different doses of testosterone propionate was investigated in provoking the development of the constant estrous anovulatory (CEA) syndrome in the rat. A direct relationship was observed between the dose of neonatally administered androgen (NA) and the percentage occurrence of this syndrome. Pinealectomy and superior cervical sympathetic ganglionectomy elicited the development of marked thecal luteinization in the NA-CEA rat, but the formation of corpora lutea was limited after these operations. The efficacy of pinealectomy and ganglionectomy in provoking luteinization was inversely related to the dose of testosterone used for neonatal androgenization. The LH-RH sensitivity of the adenohypophysis to release LH was decreased in the NA animals, as well as in the light-induced CEA syndrome (LCE), whereas it was increased in those CEA rats in which this syndrome was provoked by frontal hypothalamic deafferentation (FHD). Pinealectomy and ganglionectomy were able to elicit ovulation and luteinization in the FHD animals, but were ineffective in the LCE and high dose NA rats. The results are discussed in relation to those reported by others, in an attempt to explain the multitude of dissociated effects.

Animals↗
PubMed1976

Brain serotonin and estradiol retention in the hypothalamus and pituitary of the rat.

In order to investigate whether the capacity of hypothalamic and anterior pituitary tissue to concentrate and retain estradiol is affected by serotonin (5-HT), 3H-estradiol (3HE2) retention in these structures was measured after 5-HT synthesis inhibition by either parachlorophenylalanine (PCPA) or 6-fluoro-tryptophane (6 FTrp), or after destruction of midbrain raphe nuclei containing 5-HT cell bodies, as well as after administration of the 5-HT precursor 5-hydroxytryptophane (5-HTP). No modification in 3HE2 retention was observed after tryptophane hydroxylase inhibitors of raphe lesions; administration of the precursor only increased the steroid retention at very high, nonphysiological dose levels. It is concluded that the interaction of 5-HT with gonadotropic release cannot be accounted for by a direct effect on specific estrogenic receptors, but occurs at a different level of gonadotropic release regulating structures or directly on LH-RH neurons.

5-Hydroxytryptophan↗
PubMed1976

Changes in hypothalamic serotonin concentration following manipulations on the gonadotrophic gonadal axis of the constant estrous anovulatory (CEA) rat.

The effect of pinealectomy or of injection of luteinizing hormone (LH) containing pituitary extract on the serotonin concentration of the hypothalamus was comparatively investigated in female rats with three different types of constant estrous anovulatory (CEA) syndrome. CEA syndrome was provoked by frontal hypothalamic deafferentation (FHD), by neonatal androgen treatment (NA) and by exposure of continuous illumination (light induced constant estrous; LCE syndrome). Pinealectomy caused an increase in hypothalamic serotonin concentration in the FHD rat, but failed to increase it in the NA and LCE group. The injection of crude anterior pituitary extract, however, provoked significant elevation of the hypothalamic serotonin concentration equally in all three types of CEA syndrome. Ovariectomy in itself failed to cause any significant change in the serotonin level of the brain. However, pinealectomy or the injection of LH containing pituitary extract proved to be effective also in the ovariectomized CEA animals. It is concluded that the increase in the brain-serotonin concentration of CEA rats, observed after pinealectomy or after injection of LH containing crude pituitary estract, is running through a hypothalamo-pituitary mechanism rather than through the hormone secreting activity of the ovaries.

Animals↗
PubMed1976

Investigation of luteinizing-inducing effect of pinealectomy or thyroidectomy in different types of anovulatory syndromes in rats.

The luteinizing-inducing effect of pinealectomy and of thyroidectomy was investigated in the constant estrous anovulatory (CEA) syndrome caused either by frontal hypothalamic deafferentation (FHD) or by neonatal androgen treatment (NA). Thyroidectomy failed to induce luteinization in both types of CEA syndrome. However, pinealectomy provoked the formation of corpora lutea in FHD, but not in NA induced CEA syndrome. It was concluded that the luteinizing-inducing effect of pinealectomy is a specific consequence of the removal of the pineal hormone-like principles. The differences in the mechanism of development of the CEA syndrome following FHD or NA might account for the failure of pinealectomy to elicite luteinization in the NA induced CEA rat.

Animals↗
PubMed1976

Altered response of blood thyroxine level after its acute depletion by isovolemic exchange transfusion in rats with lesions in hypothalamus and thalamus.

Bilateral electrolytic lesions were made in various areas of hypothalamus or thalamus on the 6th day of a period of daily radioiodide injections (1 or 5 muCi125I-daily per animal) in male rats weighing about 350 g. Such injections were continued for another 4 days and after 2 days of intermission the blood thyroid hormone was acutely depleted by isovolemic exchange transfusion of thyroid hormone free blood cell suspension. Relative changes of plasma thyroxine level were measured with the aid of paper chromatography in small aliquots of plasma frequently taken from the animals under maintaining isovolemia by replacing the removed plasma. It was found that in animals with various bilateral electrolytic lesions in hypothalamus (suprachiasmatic and paraventricular areas) the response of blood thyroxine level after the transfusion is similar as in sham-operated controls bearing unilateral subcortical lesion or in normal animals observed previously. On the other hand, the response in animals with thalamic lesions was repeatedly found to resemble that observed previously in thyroidectomized animals. Since the response of blood thyroxine level presumably results from changes of pituitary thyrotropic activity, it is concluded that in rats with thalamic lesions the normal response of hypothalamo-pituitary-thyroid axis was prevented. The mechanism of this action, however, remains to be elucidated.

Animals↗
PubMed1975

Melatonin content of cat cerebrospinal fluid and blood following intravenous injection of melatonin as measured by Xenopus laevis skin melanophore test.

Melatonin content of the cerebrospinal fluid (CSF), serum and choroid plexus was measured in untreated and melatonin-injected cats using the Xenopus laevis melanophore-contracting bioassay. CSF and choroid plexus had a considerable melanophore contracting activity in the untreated animals. Intravenously injected melatonin considerably enhanced the melanophore-contracting activity of the CSF and choroid plexus. Two hours later, melatonin was still present at high concentrations in these tissues, whereas it had considerably diminished in the blood. It is concluded that the choroid plexus concentrates and secretes melatonin into the CSF in a bioactive form.

Animals↗
PubMed1975

Effect of intracerebral serotonin administration on pituitary-thyroid function.

Thyroid function was investigated following intrahypothalamic implantation of cannulae containing 80 mug serotonin-creatine sulphate or after intraventricular injection of 100 mug of the same substance. Control animals received either needle implantations or intraventricular injections of creatine-sulphate. Thyroid/serum 131-I ratio, activity of the thyroid gland as evaluated histologically and thyrotrophic hormone (THS) content in the pituitary were significantly decreased in serotonin-treated animals. Thyrotrophic hormone releasing hormone (TRH) concentration of the hypothalamus was also significantly lowered in serotonin-treated animals when compared to intact controls. Creatine-sulphate injected rats showed a slight decrease of TSH content of the pituitary and of TRH concentration of the hypothalamus which is probably due to a stress effect caused by the intracranial intervention and/or by the intraventricular administration of a relatively large molecule, such as creatine sulphate. It is concluded that serotonin decreases the functional activity of the hypothalamo-pituitary-thyroid system by inhibiting the TRH-secretion of the hypothalamus.

Animals↗