Esterification of acrylic acid with but-1-ene over sulfated Fe- and Mn-promoted zirconia

International audienceThe role of Mn and Fe as promoters of sulfated zirconia (ZS) has been studied in the reaction of acrylic acid (AA) esterification by but-1-ene to sec-butyl acrylate (SBA) at 343 K. The main result is that Mn and Fe did not improve the catalytic properties of sulfated zirconia as far as activity and selectivity to sec-butyl acrylate (90–95%) are concerned but strongly improved its resistance to deactivation, which makes this system attractive for substituting Amberlyst resins or sulfuric acid. The deactivation was shown not to be due to sulfated species and/or promoters leaching or to zirconia tetragonal phase transformation. It is proposed that in all cases acid sites are poisoned by the accumulation of unsaturated species primarily issue from the acrylic acid. Pyridine adsorption and n-butane isomerisation reaction at 473 K showed that the acidity of sulfated promoted zirconia was not increased by the addition of the promoters. Mn was observed by XPS to be slightly reduced during reaction while the oxidation state of the Fe was not changed. But this was shown not to be related to the deactivation process

Influence of acute administration of human growth hormone and alpha-MSH on plasma concentrations of aldosterone, cortisol, corticosterone and growth hormone in man

The effect of acute administration of human growth hormone (HGH) and of alpha-melanocyte stimulating hormone (alpha-MSH) on plasma aldosterone, cortisol, corticosterone and growth hormone has been studied in normal man and in patients with panhypopituitarism. There is no acute effect of exogenous HGH on plasma levels of aldosterone, cortisol and corticosterone in normal man and in patients with panhypopituitarism. The plasma level of immunoreactive HGH measured during acute HGH infusion in man does not seem to be proportional to the dose administred in our study. Alpha-MSH raises the concentartion of plasma HGH, BYT THIS STIMULATION IS NOT DOSE-DEPENDENT. Aldosterone, cortisol and corticosterone concentrations are not influenced by the elevation of HGH mediated by alpha-MSH in normal man. Although in some patients with panhypopituitarism an elevation of plasma aldosterone concenntration following alpha-MSH infusion is observed, it is unlikely that MSH is directly involved in the acute regulation of aldosterone secretion in healthy subjects

Corticotropin releasing factor activity of CRF 41 in normal man is potentiated by angiotensin II and vasopressin but not by desmopressin

Multiple hypothalamic factors seem to influence ACTH release. In vitro and/or in vivo animal models have shown that angiotensin II, vasopressin and some of its analogs are ACTH secretagogues capable of potentiating the corticotropin releasing activity of CRF41. Since these effects are controversial in man, we investigated in 3 groups of volunteers the corticotropin releasing activity of a 2h-infusion of angiotensin II (7 ng/kg/min), vasopressin (1 ng/kg/min) and desmopressin (1 ng/kg/min) given alone or in combination with a bolus injection of 100 micrograms CRF41 by measuring plasma concentrations of ACTH, cortisol, dehydroepiandrosterone and delta 4-androstenedione. Given alone angiotensin II and desmopressin had no significant effect in contrast to vasopressin which increased significantly the ACTH and steroid levels. Angiotensin II and vasopressin were both able to potentiate the corticotropin releasing activity of CRF41, whereas desmopressin was unable to produce such a potentiation. These results suggest that in man vasopressin and angiotensin II may well regulate the responsiveness of the pituitary-adrenal axis in various physiological or pathophysiological situations

RU 486 inhibits peripheral effects of glucocorticoids in humans

RU 486 [17 beta-hydroxy-11 beta-(4-dimethylaminophenyl)17 alpha-(prop-1-ynyl)estra-4,9-dien-3-one] is a synthetic steroid receptor antagonist. To evaluate the peripheral antiglucocorticoid action of this compound, we investigated its ability to antagonize cutaneous steroid-induced vasoconstriction. This phenomenon, produced by three different topical steroids in six normal men, was consistently and significantly attenuated or abolished by oral administration of 6 mg/kg RU 486. This demonstration of a peripheral action of RU 486 is important in relation to the potential therapeutic use of this well tolerated drug in states of hypercortisolism. It also indicates that the cutaneous vasoconstrictor effects of topical steroids are mediated by occupancy of glucocorticoid receptors