Biomedical subjects
Publications and source records attributed to B Conte-Devolx.
alpha-MSH secretion was significantly lowered in Rats after lesion of the mediobasal hypothalamus with microinjections of kainic acid. beta-Endorphin release after ether-stress was also reduced. In opposition, no significant change in basal and ether-stress ACTH secretion was observed.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Plasma alpha-MSH, beta-endorphin and ACTH were measured at 60 days of age in rats which had been injected during the neonatal period with monosodium glutamate (MSG). Although the arcuate nucleus tuberoinfundibular dopaminergic and cholinergic system was lesioned by the MSG, no change in circulating alpha-MSH, ACTH and corticosterone levels was observed under basal conditions, after ether stress of adrenalectomy. In contrast, a moderate, but significant decrease in plasma beta-endorphin was noticed after MSG treatment.
The injection of haloperidol, a dopamine receptor blocker, was followed by a large increase of plasma ACTH and beta-endorphin-like immunoreactivity (beta-EI) in the rat. This effect was prevented when the rats were previously treated with corticosteroids. These results suggest that catecholamines inhibit ACTH and beta-endorphin secretion in the rat.
beta-Endorphin-like immunoreactivity (beta-ELI) was measured in hypophysial portal and arterial blood of intact, adrenalectomized and hypophysectomized rats. beta-ELI levels were 61 times higher in the long portal vessels than in the general circulation. Circulating, and especially portal, levels of beta-ELI were significantly increased after adrenalectomy. After removal of the pituitary gland, the mean level of beta-ELI in portal blood was significantly lower than in intact rats. beta-ELI in portal blood displayed the same chromatographic properties as synthetic beta-endorphin.
The hypothalamic regulation of ACTH secretion has been reviewed. Recent biochemical investigations on corticotropin-releasing factor (CRF) suggest that CRF is present in the hypothalamus under two or more different molecular weight forms, their structure being not elucidated yet. Vasopressin has a CRF-like activity. However, contradictory results have been reported on the role of AVP as a physiological CRF. The synthesis of CRF appears to occur in a large hypothalamic area outside the median eminence. CRF-carrying fibers are thought to pass through the lateral retrochiasmatic area and project on the hypophysial portal vessels at the junction between the pituitary stalk and the median eminence. Conflicting data have been published on the influence of monoamines on ACTH secretion. In the dog, ACTH release is inhibited by the alpha-adrenergic receptors, this effect being not as clearly demonstrated in other species. The stimulation of nicotinic and muscarinic receptors followed by increased ACTH secretion. Glucocorticoids appear to lower ACTH secretion through an action at both the hypothalamic and pituitary levels.
The effect of neonatal hypothyroidism and neonatal caloric deprivation on brain TRH levels and serum and pituitary TSH levels has been determined in rats on the following postnatal days: 1, 5, 10, 15, 25, 40 and 60. After neonatal hypothyroidism, there was a slight reduction in brain TRH content although TRH concentration in the brain increased. Serum TSH was elevated at birth, suggesting that the feedback of thyroid hormones on the pituitary gland acts in rat fetuses. After neonatal caloric deprivation, a decrease in brain TRH content was observed along with a decrease in circulating TSH levels, however, there was no change in brain TRH concentration.
A syndrome of chronic hypernatremia (range 148 to 161 mmoles/l) and partial hypopituitarism (growth hormone and gonadotropin deficiencies) is reported in a 27 year-old man with sarcoid hypothalamic involvement. The patient did not complain of thirst and spontaneous fluid intake was not sufficient to restore the serum sodium to normal. However, when larger amounts of water were given (50 ml/kg for 180 min), the plasma osmolality returned to normal values in 3 hours. Blood volume values were found subnormal on two occasions on free diet (63 and 74% of the theorical normal values) and plasma renin activity was elevated (22 ng/ml/hour). Plasma vasopressin (AVP) concentrations (range < 1 to 1.9 pg/ml) were inappropriately low for the degree of plasma osmolality and remained markedly subnormal when hypertonic saline was infused (NaCl 5%, 10 ml/min for 60 min). However, the secretory stores and hemodynamic control of AVP release were intact since a rise in plasma AVP to 10.8 pg/ml was observed after induction of arterial hypotension with sodium nitroprusside infusion. These results provide further direct evidence fo the dysfunction of the thirst mechanism and the osmotic contol of AVP release. They support the concept that osmoreceptor areas are anatomically distinct from the neurohypophyseal AVP secretory system and that neural inputs from baroreceptor and osmoreceptor cells are completely separated.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
High concentrations of Thyrotrophin-Releasing Hormone (TRH) have been found in the dorsal skin of the Frog Rana esculenta, lower levels being measured in the ventral skin. alpha-MSH and somatostatin were undetectable in these tissues. Nor was TRH detected in the blood of these animals. The concentration of somatostatin in the pancreas was similar to that of the hypothalamus and twice or one hundred times higher than in the intestine or stomach respectively.
Somatostatin levels have been determined by RIA in hypophysial portal blood of pentobarbital-anesthetized male rats. In most animals, immunoreactive somatostatin (SRIF) levels were higher in hypophysial portal blood than in systemic blood. In euthyroid rats, the mean level was 158 +/- 27 pg/ml (n = 8); SRIF was undetectable (less than 30 pg/ml) in systemic blood of these rats. It is suggested that endogenous SRIF was not degraded during the collection of stalk blood, since synthetic SRIF is stable when incubated in rat serum during 4 min at 37 c and 2 h at 0 C, i.e. under the conditions the blood was kept during the collection. SRIF in hypophysial portal plasma had the same immunoreactivity with a specific antiserum against SRIF as did synthetic SRIF. Gel filtration of hypophysial portal plasma revealed two immunoreactive peaks, the major one corresponding to synthetic SRIF, the smaller one representing a larger molecular form. Thyroidectomy and excess of T4 did not modify the levels of SRIF in hypophysial portal blood, suggestinc SRIF is stable when incubated in rat serum during 4 min at 37 C and 2 h at 0 C, i.e. under the conditions the blood was kept during the collection. SRIF in hypophysial portal plasma had the same immunoreactivity with a specific antiserum against SRIF as did synthetic SRIF. Gel filtration of hypophysial portal plasma revealed two immunoreactive peaks, the major one corresponding to synthetic SRIF, the smaller one representing a large molecular form. Thyroidectomy and excess of T4 did not modify the levels of SRIF in hypophysial portal blood, suggesting that the feedback of thyroid hormones on TSH secretion does not involve changes in the secretion of SRIF by the hypothalamus.
Plasma AVP level, neurophysins and osmolality have been measured in 10 patients with oat cell carcinoma of the lung but without any biological signs of syndrome of inappropriate secretion of ADH (SIADH), before and 15 mn after an intravenous injection of Ethanol. No statistically significant difference was noted in the AVP, neurophysins and osmolality values between 10 patients with asymptomatic oat cell carcinoma and control population (10 normal volunteers, 12 patients with non neoplasic lung pathology and 10 patients with different lung carcinoma). We concluded that AVP and neurophysins cannot be considered as a good tumoral marker in the detection of oat cell carcinoma of the lung.
Serum vasopressin level has been measured by radioimmunoassay in 5 healthy subjects during water loading, before and during treatment by carbamazepine. Serum vasopressin drops significantly during carbamazepine in spite of antidiuresis. This drop may be explained by an effect of carbamazepine on renal tubular cell.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.