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Biomedical subjects

A Enjalbert

Publications and source records attributed to A Enjalbert.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Interference of endogenous B endorphin with opiate binding in the anterior pituitary.

Opiates have been shown to affect prolactin secretion directly at the pituitary level. However, opiate binding sites have not been characterized on anterior pituitary tissue. In the present work we show that a soluble factor present in anterior pituitary membrane preparation inhibit opiate binding on striatal membranes. The high concentrations of B-endorphin like immunoreactivity recovered from the supernatant of pituitary membrane preparations seem to account for this effect on striatal binding and to be responsible for a partial masking of pituitary opiate receptors. We thus attempted to improve membrane fractionation procedure in order to decrease B-endorphin contamination and thus to increase binding of opiate ligands on pituitary membranes. 3-H Etorphine binds to pituitary membranes with a constant of association (kon) of 20.8 10(6) M-1 min-1 and a constant of dissociation (hoff) of 33 min-1. Saturation experiments with 3-H Etorphine and 3-H ethylketocyclazocine indicate the presence of a single population of specific binding sites (KD) value of 12.2 +/- 3.9 nM a maximal binding capacity of 55.9 +/- 10.7 fm/mg protein for 3-H Etorphine binding). These results demonstrate the presence of opiate binding sites in the anterior pituitary. However the difficulty of the membrane preparation and the low density of binding sites did not allow a complete pharmacological characterization of these sites.

Animals↗
PubMedDate not supplied

Autoradiographic localization of a non-reducible somatostatin analog (125I-CGP 23996) binding sites in the rat brain: comparison with membrane binding.

The regional distribution of somatostatin binding sites in the rat brain was determined by quantitative autoradiography, using 125I-CGP 23996, a non-reducible somatostatin analog. In preliminary experiments, kinetic properties of 125I-CGP 23996 binding to rat brain membranes and slide mounted frozen brain sections were compared and found similar. In addition, distribution of 125I-CGP 23996 and 125I-N-Tyr-SRIF14 binding sites on membrane prepared from 10 different rat brain structures were closely correlated (r = 0.91, 2 p less than 0.01), indicating that the non-reducible analog recognizes the same binding site as the Tyr-extended native peptide. Highest levels of 125I-CGP 23996 binding sites were found in anterior temporal, frontal and cingular cortex as well as hippocampus. Moderate levels were found in the remaining part of the limbic system including amygdala, olfactory tubercles and bed nucleus of the stria terminalis. In the brain stem, nuclei involved in the auditory system such as the ventral cochlear nucleus and the superior olive nucleus, contained high levels of 125I-CGP 23996 binding sites. The distribution of 125I-CGP 23996 binding sites roughly correlated with that of the endogenous peptide in most structures, except in the mediobasal hypothalamus.

Amygdala↗
PubMedDate not supplied

ADP-ribosylation of G alpha i and G alpha o in pituitary cells enhances their recognition by antibodies directed against their carboxyl termini.

Using antibodies raised against synthetic peptides of heterotrimeric GTP binding proteins, we demonstrate the presence of G alpha s, G alpha i1,2, G alpha i3, G alpha o2, and G beta subunits in pituitary cells. Pretreatment of pituitary cells with cholera toxin diminished the immunoreactivity of G alpha s and this decrease was kinetically coupled to the rate of G alpha s ADP-ribosylation. ADP-ribosylation by islet activating protein (IAP or Bordetella pertussis toxin) of G alpha i and G alpha o enhanced their immunoreactivities to antibodies raised against synthetic decapeptides that correspond to the G alpha carboxyl termini. Such enhancement was not observed when antibodies directed against the NH2-termini were used. These findings are consistent with the fact that ADP-ribosylation by IAP occurs on the cysteine located in the carboxyl terminal part of G alpha i and G alpha o. These observations mean that the kinetics and extent of Gi and Go ADP-ribosylation by IAP in whole pituitary cells and membrane preparations can be followed. It could be that ADP-ribosylation causes conformational changes in G alpha i and G alpha o. Indeed, we observed that ADP-ribosylated G alpha i was more sensitive to trypsin proteolysis and that the ADP-ribosylation rates of G alpha i and G alpha o in whole cells were comparable to the rate of loss of coupling between inhibitory neurohormone receptors and adenylyl cyclase.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

Effect of lumbar sympathectomy on the muscles.

With the physiological data concerning microcirculation and sympathetic control, the author foresees the effects that one must obtain with lumbar sympathectomy. The improvements of cutaneous circulation are usually well known while those of muscular circulation are more debated. To prove it, the author has studied the muscular flow after sympathectomy using Xenon radioactive method and the non invasive electromagnetic flowmetry method. Despite the background of a short experience in this matter, the results seems to point out a beneficial effect of lumbar sympathectomy in muscular circulation at rest and exercise, in patients having obstructive arteriopathies of the lower extremities.

Adrenergic Fibers↗