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Biomedical subjects

P Lefebvre

Publications and source records attributed to P Lefebvre.

At least 127 records · Page 7Linked to original sources
PubMed1993

Role of actin in platelet function.

Cytochalasin E (CE) was used in this study to evaluate relationships between platelet shape change, pseudopod extension, internal transformation, actin filament assembly, fibrinogen receptor expression, aggregation, clot tension and secretion. Various ratios of G- to F-actin, measured by the DNase inhibition assay, were achieved by using several concentrations of CE in stirred and unstirred thrombin-stimulated platelets. An increased rate of actin polymerization was found in "aggregating" conditions as compared to "activating" conditions, the latter achieved by either absence of stirring or stirring in the presence of the tetrapeptide Arg-Gly-Asp-Ser (RGDS). Larger concentrations of CE were required in aggregated than in activated platelets to obtain G-actin levels analogous to those in resting platelets. Concentrations of polymerizing actin above 20% and 55% for activated and aggregated platelets, respectively, trigger platelet shape change and the extension of pseudopods. Prevention of de novo actin polymerization by CE, added either before or after thrombin stimulation, inhibits fibrinogen binding to platelets. This suggests an involvement of the new actin polymers in fibrinogen receptor exposure. As expected, platelet aggregation and clot tension, which are dependent on fibrinogen receptor exposure, were inhibited by CE. Granular secretion was not dependent on polymerizing actin.

Actins↗
PubMed1993

[The use of growth hormone (hGH) in ovulation induction in women].

Number of in vitro experiments have shown increasing evidence for local ovarian actions of GH by demonstrating: the presence of receptors for GH in human granulosa cells; the ability of GH to enhance estradiol (E2) production by human granulosa cells withdrawn in late follicular phase; the increasing effect of GH on progesterone (P) biosynthesis by human luteal cells. Moreover, GH being the main regulator of IGF-I plasma levels, its indirect effect by means of hepatic and/or ovarian IGF-I production remains possible. Few patients have been included in randomized studies using hGH with gonadotropins for induction of ovulation and their selection criteria were heterogeneous so that no definitive conclusion can be drawn about the beneficial effect of GH in facilitating ovulation. The reduction both in duration of stimulation and in the requirement for menopausal gonadotropins found in some studies have been challenged by others. The recombinant human growth hormone (hGH) is able to modify the game of intraovarian regulators and may affects ovocyte and embryo. Such a potential impact cannot be occulted, justifying to develop larger in vivo animal experimentation before new further clinical studies.

Clinical Trials as Topic↗
PubMed1993

[Neonatal abstinence syndrome: current and future aspects].

Pregnant heroin-addicted women constitute a major social problem that should not be ignored. Newborns may develop a neonatal abstinence syndrome (NAS). They present with behavioural troubles running a typical clinical course. The level of severity of NAS will be accurately determined, leading to definition of the most appropriate therapy. The best therapeutic formula appears to be paregoric elixir, mixed with phenobarbital if necessary. Least severe cases can be easily controlled by appropriate surrounding conditions. Pharmacological as well as physiopathological effects of opiates are described. Little is known about the long-term effects of opiate exposure; they apparently include frequent instrumental troubles. At the present time, the rapid intervention of a multidisciplinary team is recommended, taking charge of the mothers who should receive methadone in progressively tapering doses.

Female↗
PubMed1992

Transcription factor loading on the MMTV promoter: a bimodal mechanism for promoter activation.

The mouse mammary tumor virus (MMTV) promoter attains a phased array of six nucleosomes when introduced into rodent cells. This architecture excludes nuclear factor 1/CCAAT transcription factor (NF1/CTF) from the promoter before glucocorticoid treatment and hormone-dependent access of nucleolytic agents to promoter DNA. In contrast, when the promoter was transiently introduced into cells, NF1/CTF was bound constitutively and nucleolytic attack was hormone-independent. Thus, induction at this promoter was a bimodal process involving receptor-dependent remodeling of chromatin that allows NF1/CTF loading and direct receptor-mediated recruitment of additional transcription factors.

Animals↗
PubMed1992

Effects of platelets and plasma on fibrinolysis.

The effects of various concentrations of platelets and plasma on in vitro t-PA-induced fibrinolysis were investigated. At t-PA levels between 30 and 70 ng/ml, fibrinolysis proceeded faster in platelet-rich plasma (PRP) than in platelet-poor plasma (PPP). When PRP was serially diluted with PPP and the rate of fibrinolysis compared to PPP, higher platelet counts (up to 300 x 10(9)/l) were associated with increased enhancement of lysis. However, lysis was inhibited when platelets were added to plasma diluted with buffer. Thus, platelets enhance fibrinolysis in undiluted plasma but inhibit lysis in diluted plasma. This is probably because platelets provide a catalytic surface for fibrinolysis but also release inhibitors of fibrinolysis. In undiluted plasma, there would be sufficient fibrinogen and plasminogen to overcome the effect of the platelet inhibitors, but in diluted systems, the inhibitors would predominate, retarding fibrinolysis.

Blood Platelets↗
PubMed1992

[Lambert-Eaton syndrome. Apropos of 2 cases].

Lambert-Eaton syndrome is a myasthenia-like syndrome of paraneoplastic origin which is often associated with anaplastic small-cell lung cancer. It seems to be an autoimmune disease responsible for a deficit of acetylcholine ejection in the motor end plate. On the occasion of two recent cases, we review the clinical, physiopathological and diagnostic aspects of this paraneoplastic syndrome.

Aged↗
PubMed1992

[A comparative study of the cost of open-circuit as opposed to closed-circuit ventilation].

The authors compared two open randomized groups of patients undergoing surgery through general anaesthesia. Group 1 consisted of 54 patients ventilated by a Siemens 900 B ventilator in open circuit, and group 2, 56 patients ventilated by an ELSA de Gambro ventilator in a closed circuit. Comparative hour cost for nitrous oxide (N2O), oxygen (O2) and halogen gas, Enflurane, Isoflurane, was noted. All patients received the same regimen of anaesthesia and the two groups were identical in age, weight, surgery, respiratory volume and ventilation time. The evaluation of comparative hour cost included specific materials of close circuit ventilator: CO2 filter (Aridus), Lime. Were excluded maintenance and gas consumption expenditures before patient connected to the ventilator. The total hour cost (O2, N2O, specific materials for close circuit, without halogen gas) was 8.23 FF in closed circuit against 13.28 FF in open circuit, an economy of 38.27%. Hence, for oxygen, the hour cost was 0.70 FF in open circuit against 0.27 FF in closed circuit (gain of 65.3%). For nitrous oxide, the hour cost in open circuit was 12.50 FF against 2.44 FF in closed circuit (80.5%). For Isoflurane, the open circuit hour cost was 41.38 FF against 22.44 FF in closed circuit (47%). For Enflurane, the open circuit hour cost was 14.17 FF against 5.94 FF in closed circuit (58.1%). And, lastly for Enflurane, open circuit hour cost was 14.17 FF against 5.94 FF in close circuit, gain of 58.1%. These "modest" economy against those found in previous studies can be explained by the long-time duration of ventilation, saturating time in open circuit more or less long, depending on the physician, specific materials for closed circuit ventilation--lime, CO2 filter--in not taken into account, the hour cost of O2 + NO2 goes from 8.23 FF to 2.71 FF, and the gain against the close circuit becomes 79.6%: reducing hour cost by 5 times. In order to improve the effective cost of close circuit, the authors proposed: the use of closed circuit ventilation for more than 3 hours surgery, gas saturation in closed circuit after denitrogenation--which demands the use of halogen infjectors, and lime in containers cheaper than disposable cartridges. Respecting the above criteria, the total hour cost in close circuit fell to 4.90 FF, gain of 63% against open circuit. For O2 et N2O, the hour cost goes from 1.34 FF in close circuit to 13.28 FF in open circuit, 90% economy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Interpreting hypereosinophilia].

The diagnosis of a blood hypereosinophilia requires a review of various disease processes such as blood dyscrasias, skin diseases, auto-immune diseases, asthma, parasitic infections, enteropathies, etc. A complete check-up including clinical, laboratory and radiological data allows the identification of an etiology in a majority of cases. Nevertheless, the etiology of hypereosinophilia remains obscure in some cases. Among these unexplained situations, the rare idiopathic hypereosinophilic syndrome requires special attention because of its fatal course due to cardiac involvement which can remain clinically silent for a long period of time. Therefore, the follow-up should include repeated echocardiograms. At the present time, the usual therapy for the most severe cases includes corticosteroids and hydroxyurea.

Adrenal Cortex Hormones↗
PubMed1992

[Hiatal hernia with intrathoracic gastric volvulus as a rare cause of biliary obstruction].

Gastric volvulus can complicate paraesophageal hiatal hernia. Acquired gastric torsion results in acute or chronic gastrointestinal symptoms. Biliary complications are possible but exceptional. A case of asymptomatic diaphragmatic hiatal hernia with intrathoracic gastric volvulus presenting as a cholestatic syndrome secondary to stretching and tension of the common bile duct in the diaphragmatic hiatus is reported. This observation emphasizes the possibility of direct relationship between two otherwise frequent diagnostics: hiatal hernia and biliary obstruction. Only one similar case has been reported to date.

Cholangiography↗