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A Pascaud

Publications and source records attributed to A Pascaud.

11 recordsLinked to original sources
PubMed1988

5'-Guanylylimidodiphosphate decreases affinity for agonists and apparent molecular size of a frog brain opioid receptor in digitonin solution.

When assayed for specific opiate binding in the presence of 120 mM NaCl, digitonin extracts from frog (Rana ridibunda) brain membranes were found to contain about the same quantity (0.5 pmol/mg of protein) of high (Kdh = 0.4 nM) and of lower (Kdl = 15-20 nM) affinity sites for the opiate agonist [3H]etorphine. The two classes of [3H]etorphine binding sites displayed equally high (Kd = 0.3 nM) affinity for the opiate antagonist [3H]diprenorphine. 5'-Guanylylimidodiphosphate (GppNHp) selectively and potently (IC50 = 0.1 microM) inhibited high affinity binding of the tritiated agonist, and this inhibition resulted from the GppNHp-induced conversion of the high into the lower affinity sites for [3H]etorphine. Following centrifugation of the digitonin extract in sucrose gradients, opioid binding activity was found to be associated with two clearly separated macromolecular components of apparent sedimentation coefficients 11.5 and 9.7 S, respectively. The two components bound [3H]diprenorphine equally well, whereas the fast sedimented component bound [3H]etorphine better than did the slower sedimented one. In addition, labeling of the component of bigger apparent size with [3H]etorphine was considerably reduced in the presence of 50 microM GppNHp. Finally, in soluble extracts which had been (i) preincubated with and (ii) centrifuged in the presence of GppNHp, the fast sedimented component was no longer observed while there was about twice as much of the component of smaller apparent size as in control (no GppNHp) extracts. Together, these results demonstrated the existence of an opioid receptor-G protein complex which, in digitonin solution, was still amenable to regulation (dissociation) by guanine nucleotides.

Animals↗
PubMed1988

Evidence for a new type of opioid binding site in the brain of the frog Rana ridibunda.

The crude membrane fraction from the brain of the frog Rana ridibunda was shown to contain 0.7-0.8 pmol/mg protein for a site with high (KD = 0.1 nM) and about 3.2 pmol/mg protein for a site with lower (KD = 10-15 nM) affinity for the opiate agonist [3H]etorphine and for the opiate antagonist [3H]diprenorphine. In addition to its very high affinity for the two tritiated oripavine derivatives, the high affinity site displayed (i) a considerably reduced ability to bind the agonist but not the antagonist in the presence of Na+ ions and (ii) pronounced stereospecificity. These properties are all typical of an opioid receptor site. The lower affinity site, which was about four times as abundant as the other exhibited none of the aforementioned characteristics and is therefore probably not opioid in nature. Detailed testing of the potency of various unlabelled opioid ligands to inhibit the binding of [3H]etorphine at the high affinity site showed that the latter consists of a mixture of several types of opioid sites, including a major type with an apparent binding profile clearly different from those of mammalian brain mu, delta- and kappa-opioid sites. In particular, this major type of site, which accounted for about 70% of the opioid binding in frog brain membranes, bound mu ([D-Ala2,MePhe4,Glyol5]enkephalin), delta ([D-Thr2,Leu5]enkephalyl-Thr) and kappa (U50,488) selective ligands with much lower affinity than did mu-, delta- and kappa-opioid receptor sites, respectively.

Animals↗
PubMed1987

Hydrochloric acid hydrolysis of proteins and determination of tryptophan by reversed-phase high-performance liquid chromatography.

A simple method was developed for determination of tryptophan in proteins. Hydrolysis is achieved under reducing conditions, in 6 N hydrochloric acid containing 0.4% beta-mercaptoethanol, at 110 degrees C for 24 h. The phenylthiocarbamyl derivatives of the amino acids are separated by reversed-phase high-performance liquid chromatography, without any by-product interference. The recovery of tryptophan is complete. However, the method does not allow the determination of tryptophan in carbohydrate-rich biological samples.

Amino Acids↗
PubMed1986

Characterization, solubilization and purification of an opioid receptor from the brain of the frog Rana ridibunda.

The brain of the frog R. ridibunda contains a major opioid binding site which in vitro pharmacological profile is different from those of mammalian mu, delta- and kappa-opioid sites. In digitonin extracts, this major opioid site exists as two molecular forms -10S and 12S- which are clearly resolved by sedimentation in sucrose gradients and which are thought to represent the opioid receptor alone (10S) or associated (12S) with a guanine nucleotide regulatory protein. Purification of the digitonin extracts by affinity chromatography on immobilized dynorphin, results in a single major protein component of apparent Mr approximately 64,000.

Animals↗
PubMedDate not supplied

[An intensive survey of drug surveillance in a medical admissions department].

An intensive survey of pharmacovigilance was carried out in a medical admission department over a 4-month period. Out of 2,017 admissions to hospital, 23 (1,1 p. 100) were motivated by adverse reactions to drugs. Questioning brought out allergy and multiple drug therapy as important factors. Lesions of the skin and mucosae predominated, notably after treatment with antibacterial and non-steroidal anti-inflammatory agents. The categories of drugs involved were, in decreasing order of frequency: cardiovascular (6/23), anti-bacterial (5/23), neuropsychiatric (4/23) and non-steroidal anti-inflammatory drugs (4/23). The fact that the patients had taken several products rendered evaluation difficult. Using imputability scales made it possible to reduce the cause-effect relationship in 26 p. 100 of the cases.

Admitting Department, Hospital↗