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Biomedical subjects

A Villeneuve

Publications and source records attributed to A Villeneuve.

At least 55 records · Page 3Linked to original sources
PubMed1985

Characterization of dog platelet alpha-adrenergic receptor: lack of in vivo down regulation by adrenergic agonist treatments.

The dog platelet alpha-adrenergic receptor was characterized using [3H]clonidine and [3H]yohimbine. The binding of both radioligands was rapid and reversible at 25 degrees C; saturation and kinetic experiments revealed a single population of binding sites. The number of [3H]yohimbine sites was 2-3-fold higher than the number of [3H]clonidine sites as reported in other tissues containing alpha2-adrenoceptors. The various alpha-agonists and antagonists displaced [3H]clonidine and [3H]yohimbine with an order of potency indicating alpha2-adrenoceptor specificity. Neither (-)adrenaline nor clonidine infusions (0.5 micrograms/min/kg during 3 hr) modified the number of [3H]yohimbine and [3H]clonidine sites or the affinity of the ligands for the alpha2-sites of the dog platelet. Oral administration of clonidine (3 X 150 micrograms/day) did not alter the binding parameters of either ligand.

Adenosine Diphosphate↗
PubMed1985

Platelet alpha 2 adrenoceptors in Parkinson's disease: decreased number in untreated patients and recovery after treatment.

[3H]-yohimbine binding sites were quantified in platelets from Parkinsonians with no clinical signs of dysautonomia. Never-treated Parkinsonians had a lower specific binding than control subjects. This alteration was associated with decreased epinephrine-induced platelet aggregation. Treatment with dopaminergic agents induced a significant increment of [3H]-yohimbine binding sites. These results show that Parkinson's disease is associated with a reduced number of peripheral alpha 2 adrenoceptors and that dopaminergic agents induce partial recovery.

Aged↗
PubMed1985

Lack of desensitization of alpha-2-mediated inhibition of lipolysis in fat cells after acute and chronic treatment with clonidine.

The regulation of alpha-2 adrenoceptors and alpha-2 adrenergic responses by alpha-2 agonist treatment was investigated in in vitro and in vivo conditions. The alpha-2 adrenergic responsiveness of the adipocytes was tested with an alpha-2 agonist, clonidine, which inhibits, in a concentration-dependent manner, the lipolytic activity of the isolated fat cells incubated in the presence of adenosine deaminase (1-2 micrograms/ml). The effect of in vitro treatment of human s.c. fat cells and hamster adipocytes with clonidine as well as the incidence of chronic clonidine treatment (10 days) of golden hamsters were studied by testing lipolytic and antilipolytic responses of the isolated fat cells. Moreover, binding parameters were determined on the corresponding fat cell ghosts using [3H]clonidine and [3H]yohimbine. The preincubation of hamster (90 min) and human (3 hr) fat cells with clonidine did not modify the biological responses promoted by isoproterenol or clonidine. Binding analysis showed that the number of [3H]clonidine sites was reduced by 30 to 40% in human fat cell ghosts whereas [3H]yohimbine sites were unaffected by clonidine treatment. The chronic treatment of hamsters with clonidine (10 days, 200 micrograms/day) did not influence the lipolytic and antilipolytic responses of the fat cells. However, the number of alpha-2 adrenoceptor sites, identified by [3H]clonidine was reduced (40-50%). To conclude, short-term incubations of adipocytes with clonidine or long-term in vivo treatments with this drug are without any noticeable influence on the lipolytic and antilipolytic responses of human and hamster isolated fat cells. The reduction of [3H]clonidine binding sites described in both experiments must be questioned concerning its biological relevance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Deaminase↗
PubMed1983

[Clinical choice of a benzodiazepine].

If the differential specific anxiolytic activity between various benzodiazepines remains controverted , the clinician nevertheless now possesses scientific data allowing him to make a more rational selection, in order to obtain a better overall efficacy, either for an anxiolytic or hypnotic action. In other respects, the concept of anxiety has evolved and given rise to distinctions that will need to be taken into account in the choice of the adequate psychotropic medication, either a benzodiazepine or another psychotropic drug. When a benzodiazepine must be prescribed, the main criteria involved in its choice need to be considered. As anxiolytic medication, besides a selective action on anxiety, the absence of cumbersome effect on psychomotor activity and vigilance, pharmacokinetics constitute an important factor that must be looked at. Although the classification of benzodiazepines according to their half-life is only an approximation, some overlapping being possible between the various groups, it proves nevertheless extremely useful with respect to the therapeutic goal considered and the various clinical parameters involved. Some other aspects must also be considered, for example the rebound phenomenon. Finally, the variability of individual responses to drug treatment must be remembered.

Administration, Oral↗
PubMed1983

Preponderance of alpha 2- over beta 1-adrenergic receptor sites in human fat cells is not predictive of the lipolytic effect of physiological catecholamines.

Adrenergic control of human fat cell lipolysis is mediated by two kinds of receptor sites that are simultaneously stimulated by physiological amines. To establish a correlation between the binding characteristics of the receptor and biological functions, the ability of physiological amines to stimulate or inhibit isolated fat cell lipolysis in vitro was compared to the beta- and alpha 2-adrenoceptor properties of the same fat cell batch. The beta-selective antagonist (-)[3H]dihydroalprenolol ([3H]DHA) and the alpha 2-selective antagonists [3H]yohimbine ([3H]YOH) and [3H]rauwolscine ([3H]RAU) were used to identify and characterize the two receptor sites. Binding of each ligand was rapid, saturable, and specific. The results demonstrate 1) the weaker lipolytic effect of epinephrine compared with norepinephrine. This can be explained by the equipotency of the amines at the beta 1-sites and the higher affinity of epinephrine for alpha 2-adrenergic receptors. 2) The preponderance of alpha 2-adrenergic receptor sites labeled by [3H]YOH (Bmax, 586 +/- 95 fmol/mg protein; KD, 2.7 +/- 0.2 nM) or [3H]RAU (Bmax, 580 +/- 100 fmol/mg protein; KD, 3.7 +/- 0.1 nM). These two ligands can be successfully used to label alpha 2-adrenergic receptor sites. 3) The beta 1-adrenergic receptor population labeled by [3H]DHA(Bmax, 234 +/- 37 fmol/mg protein; KD, 1.8 +/- 0.4 nM), although a third as numerous as the alpha 2-adrenergic population, is responsible for the lipolytic effect of physiological amines and is weakly counteracted by simultaneous alpha 2-adrenergic receptor stimulation under our experimental conditions. It is concluded that, in human fat cells, the characterization of beta 1- and alpha 2-adrenergic receptors by saturation studies or kinetic analysis to determine affinity (KD) and maximal number of binding sites (Bmax) is not sufficient for an accurate characterization of the functional adrenergic receptors involved in the observed biological effect.

Adipose Tissue↗
PubMed1980

[Lithium and renal function (author's transl)].

Reviewing the literature on the effect of lithium on renal function, the authors summarize the mechanisms involved in the concentration and elimination of lithium by this organ, as well as the urinary modifications in ionic exchanges and concentration capacity induced by this metal. After having mentioned the different factors influencing lithium clearance, the authors emphasize that diuretics should be used with caution with lithium and examine critically the various publications on the eventual nephrotoxicity of this agent. Although they conclude that there is no absolute proof of renal toxicity, they suggest for the time being to consider lithium intoxications and lithium-induced insipid diabetes, without ruling out lithium treatment itself, as risk factors of renal insufficiency. Their importance still needs further evaluation and requires, before and during treatment with this drug, a monitoring of the renal function, some essential element of this surveillance being proposed.

Animals↗
PubMed1979

The utilization of hypnotics in chronic schizophrenics: some critical remarks.

Of 23 hospitalized chronic schizophrenic patients, all under neuroleptic medication, hypnotics taken previously for a long time could be totally withdrawn in 16 cases, and in 7 cases, the dosage was diminished by 30%, without any sleep impairment. The gradual reduction of hypnotics was accompanied by a shift of neuroleptic dosage to the evening and bedtime, with reduction of the morning and midday dose, without change of the total daily dose. A significant improvement in the psychic state was observed in 16 patients after withdrawal of the hypnotic; 7 patients showed a slight improvement after reduction of the hypnotic. Monthly or bimonthly reassessment of insomnia in the hospitalized population of chronic schizophrenics is indispensable to avoid the deleterious effects and abuse of hypnotic drugs.

Adult↗
PubMed1979

[Modern aspects of mood disorders].

Mood disorders, particularly depression, now represent a major world health problem which will most likely continue increasing. From a clinical standpoint, the synthesis of new antidepressant agents of various chemical structures and the advent of the thymoregulators (lithium salts) has allowed a more flexible, better individualized, therapeutic approach to the affective disorders. However, the widespread use by general practitioners of the antidepressants, alone or in combination with other psychotropic drugs, often with mitigated success, brings to psychiatric consultation patients whose symptomatology has become less characteristics, is more difficult to identify rapidly, requiring thus greater diagnositc refinement. Moreover, greater attention is currently given to depressive affects that can occur during organic illnesses or at various periods of life, particularly at senescence. Besides sustained concerns concerning suicide, the attitude of man confronted with his death arouses great interest and a depressive phase constitutes one of the steps towards this ending. Finally, during the last two decades, some psychoanalysts have reexamined the psychodynamic concepts of mood disorders, whereas from behavioral and cognitive theories new techniques of treatment of depression have emerged. In brief, if no revolution has occurred, there has been evolution. Mood disorders and their approach have known modifications and some concepts pertinent to this are considered here from various angles, particularly from the clinical (association with organic illnesses, with respect to death), therapeutic (psychopharmacological, behavioral and cognitive therapies), sociological (including suicide) and psychoanalytic viewpoints.

Antidepressive Agents, Tricyclic↗
PubMed1978

Deanol, lithium and placebo in the treatment of tardive dyskinesia. A double-blind crossover study.

A double-blind crossover study on the effects of deanol and lithium carbonate was conducted on a sample of 29 chronic schizophrenic patients with tardive dyskinesia. In addition to his usual treatment with different neuroleptics, each patient received during an 8-week period either deanol, lithium carbonate or placebo. A 4-week wash-out period was inserted between each of the 8-week periods of experimental treatment of the tardive dyskinesia. The administration of either deanol, lithium carbonate or placebo added to the neuroleptic treatment did not produce a statistically significant improvement of tardive dyskinesia in our patient population as a whole. Favorable and unfavorable responses are discussed.

Adult↗
PubMed1978

Pharmacokinetic interaction between amitriptyline and neuroleptics.

The influence of amitriptyline on the plasma level of various neuroleptics was studied in 25 chronic schizophrenic patients. The study lasted 20 weeks. Patients were kept first 4 weeks on their former neuroleptic medication, with amitriptyline added for 12 subsequent weeks, and withdrawn during the last 4 weeks when only the neuroleptic medication was continued unchanged. The plasma level of neuroleptics was assayed by gas-liquid chromatography, once weekly throughout the study. The amitriptyline plasma level was also evaluated once weekly during the 12 weeks of its administration. The mean neuroleptic plasma values for each 4-week period were pooled together in three groups: aliphatic, piperdine and piperazine phenothiazine derivatives. Amitriptyline provoked some increase of the plasma level of all phenothiazine derivatives. This augmentation was significant only transitorily, however. The putative mechanisms of this neuroleptic tricyclic antidepressant interaction are discussed.

Adult↗