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Biomedical subjects

P Lefebvre

Publications and source records attributed to P Lefebvre.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Pulmonary embolism and anterior septal ischemia on the electrocardiogram: diagnostic trap. Two case reports].

The authors reports two cases of pulmonary embolism which have, on ECG, an anteroseptal subepicardial ischemia which could indicate a coronary origin. The value and role of electrocardiographic findings in the diagnosis of pulmonary embolism are analysed. Once the diagnosis of pulmonary embolism has been established, the rest-ECG could allow the massive forms to be distinguished from the non-massive ones. The anteroseptal subepicardial ischemia pattern in the precordial leads is the most frequent sign of pulmonary embolism. This parameter is easy to obtain and reflects the severity of pulmonary embolism.

Aged↗
PubMed1999

[Anticoagulation in cardiac pathologies (except atrial fibrillation)].

Anticoagulants, including heparins and antivitamins K are medicines which are largely prescribed in cardiology. Even though the outlines of the treatment have been clearly established for a few decades, new cardiological indications have recently appeared. The long-term treatment of cardiac valvular prosthesis by oral anticoagulants significantly reduces the risk of thrombo-embolic incident among people carrying a cardiac valvular prosthesis. In case of non-operated valvulopathy, treatment indication must be evaluated for each patient; in so doing, the connection benefit/risk must always be taken into account. In case of dilated cardiomyopathy, the treatment prescription must be limited to the patients with a high embolic risk. Other cardiological indications (apart from atrial fibrillation) must be carefully weighed up.

Anticoagulants↗
PubMed1999

U wave alternans in severe ischaemia.

A patient with unstable angina and known heart failure, and marked U wave alternans on the electrocardiogram is reported. Alternans of the U wave with no change in the QRS complex is extremely rare. The relevant literature is reviewed.

Aged↗
PubMed1999

[Intermittent claudication in a young patient. A case of isolated fibromuscular dysplasia of the external iliac artery].

Effort-linked intermittent claudication of arterial origin in sportsmen is often attributed to endofibrosis of the external iliac artery. Some knowledge of possible differential diagnoses, in particular the fibrodysplasia, is of importance regarding the therapy involved. Angioplasty treatment of external iliac endofibrosis may be controversial. However, the same does not apply to fibrodysplasia angioplasty, particularly if the latter is accomplished by inserting an endoprothesis. A case of fibromuscular dysplasia of external iliac artery in a 37 year old woman, treated with endoluminal angioplasty and stent, is reported.

Adult↗
PubMed1998

Caspase inhibitors prevent cisplatin-induced apoptosis of auditory sensory cells.

In vitro studies tested the efficacy of three caspase inhibitors, Ac-VAD-cmk (caspase-1 inhibitor), z-DEVD-fmk (caspase-3 inhibitor) and B-D-fmk (BOCDFK, a general inhibitor), for protecting auditory sensory cells from cisplatin-damage induced loss. Treatment of 3-day-old rat organ of Corti explants with these caspase inhibitors protected > 80% of the auditory hair cells from cisplatin-damage initiated apoptosis. Dissociated cell cultures of 3-day-old rat spinal ganglia treated with any of these three caspase inhibitors in addition to exogenous neurotrophin have highly significant increases in neuronal survival following cisplatin exposure. These results indicate that loss of auditory sensory cells as a result of cisplatin-induced damage involves apoptosis and that blocking of this cell death pathway at the caspase level effectively rescues both hair cells and neurons.

Animals↗
PubMed1998

H11-H12 loop retinoic acid receptor mutants exhibit distinct trans-activating and trans-repressing activities in the presence of natural or synthetic retinoids.

Retinoids, such as the naturally occurring all-trans-retinoic acid (atRA) and synthetic ligand CD367 modulate ligand-dependent transcription through retinoic acid receptors (RARs). Retinoid binding to RAR is believed to trigger structural transitions in the ligand-binding domain (LBD), leading to helix H1 and helix H12 repositioning and coactivator recruitment and corepressor release. Here, we carried out a detailed mutagenesis analysis of the H11-H12 loop (designated the L box) to study its contribution to hRARalpha activation process. Point mutations that reduced transactivation by atRA also reduced atRA-induced transrepression of AP1 transcription, correlating ligand-induced activation and repression. However, a correlation was not observed with these mutations when tested with another ligand CD367, a synthetic agonist with binding properties identical to those of atRA. Transcription was strongly inhibited in the presence of CD367 for some mutants, thus leading to an inverse agonist activity of this ligand. None of these mutations significantly altered binding affinity for either ligand, indicating that altered transcription was not caused by altered ligand binding by these mutations. Although simple correlations with transcriptional activities were not found, these mutations were also characterized by altered ligand-induced structural transitions, which were distinct for the atRA-hRARalpha or CD367-hRARalpha complexes. These results indicate that amino acids in the L box are involved in specifying trans-repressive and trans-activating properties of the hRARalpha, and support the notion that different agonists induce distinct conformations in the LBD of the receptor.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Binding of retinoic acid receptor heterodimers to DNA. A role for histones NH2 termini.

The retinoic acid signaling pathway is controlled essentially through two types of nuclear receptors, RARs and RXRs. Ligand dependent activation or repression of retinoid-regulated genes is dependent on the binding of retinoic acid receptor (RAR)/9-cis-retinoic acid receptor (RXR) heterodimers to retinoic acid response element (RARE). Although unliganded RXR/RAR heterodimers bind constitutively to DNA in vitro, a clear in vivo ligand-dependent occupancy of the RARE present in the RARbeta2 gene promoter has been reported (Dey, A., Minucci, S., and Ozato, K. (1994) Mol. Cell. Biol. 14, 8191-8201). Nucleosomes are viewed as general repressors of the transcriptional machinery, in part by preventing the access of transcription factors to DNA. The ability of hRXRalpha/hRARalpha heterodimers to bind to a nucleosomal template in vitro has therefore been examined. The assembly of a fragment from the RARbeta2 gene promoter, which contains a canonical DR5 RARE, into a nucleosome core prevented hRXRalpha/hRARalpha binding to this DNA, in conditions where a strong interaction is observed with a linear DNA template. However, histone tails removal by limited proteolysis and histone hyperacetylation yielded nucleosomal RAREs able to bind to hRXRalpha/hRARalpha heterodimers. These data establish therefore the role of histones NH2 termini as a major impediment to retinoid receptors access to DNA, and identify histone hyperacetylation as a potential physiological regulator of retinoid-induced transcription.

Base Sequence↗
PubMed1998

Distinct modes of interaction of the retinoic acid receptor alpha with natural and synthetic retinoids.

Retinoids regulate key cellular processes through their binding to their cognate nuclear receptors, RARs and RXRs. Synthetic ligands mimic most of their biological effects and alteration of their chemical structure confers selectivity for RAR isotypes alpha, beta or gamma. In this study, we have examined the contribution of a domain (L box) of hRARalpha located at the C-terminus of the ligand binding domain (LBD), between helices H11 and H12, to the ligand binding activity of this receptor. By site-directed mutagenesis, we demonstrate that, in the absence of the ligand-dependent activation domain 2 (AF2-AD), the receptor discriminates between classes of structurally distinct retinoids. This property was lost in the presence of the AF2-AD domain, evidencing major structural transitions in this part of the receptor. We propose that ligand binding occurs in two steps: first, the ligand interacts with the LBD in its opened, holo-receptor conformation in which the L box plays a crucial role in defining the ligand binding repertoire of hRARalpha; secondly, the LBD adopts its closed conformation in which the ligand interacts with the receptor mostly through its carboxylic moiety.

Amino Acid Sequence↗
PubMed1998

Cerebral venous thrombosis and procoagulant factors--a case study.

Cerebral venous thrombosis is a polymorphic clinical entity for which diagnosis has become more frequent with the advent of neuroradiology. The superior sagittal and transverse sinuses are frequently involved, whereas cavernous sinus thrombosis is much less frequent. Inherited resistance to the anticoagulant action of activated protein C (APC resistance), antithrombin deficiency, protein C and S deficiencies, and hyperhomocysteinemia seem to represent major causes of thrombophilia when unusual thromboembolic events (ie, before the age of 45 years) are observed. The authors present the combined occurrence of protein C and protein S deficiencies in a 32-year-old woman, manifested by extensive cerebral venous thrombosis.

Adult↗
PubMed1998

[Voluntary abortion: new perspectives in local anesthesia].

New perspectives have been envisioned for the TOP instrumental technique, through the utilization of pharmacologic products, whose property is to dilatate the cervix. Misoprostol or mifepristone, when administrated to a patient a few hours before a TOP by uterine suction curettage, enables a dilatation of the cervix in such a way that it allows the surgically induced abortion to be carried out with local anesthesia, under optimal comfort conditions for the patients as well as for the operator.

Abortifacient Agents, Nonsteroidal↗
PubMed1998

Effects of regular insulin or insulin LISPRO on glucose metabolism after an oral glucose load in patients with type 2 diabetes mellitus.

Seven obese Type 2 diabetic patients were studied for two 4-h periods after ingestion of a glucose load to determine the effects of preprandial subcutaneous injection of Insulin Lispro (5 min before the meal) or regular insulin (20 min before the meal) on glucose metabolism. Glucose production and utilisation were measured using a dual isotope method. After Lispro, the mean postprandial increase in plasma glucose was 29% lower and the increase in insulin concentration 25% higher than after regular insulin (p < 0.05). Suppression of endogenous glucose production was similar with both types of insulin. Thus, preprandial injection of Lispro reduced postprandial glucose increments in Type 2 diabetic patients as compared to regular insulin. This effect is best explained by the increased postprandial bioavailability of Lispro.

Administration, Oral↗
PubMed1997

Identification of two novel insulin receptor mutations, Asp59Gly and Leu62Pro, in type A syndrome of extreme insulin resistance.

To elucidate genetic determinants of insulin resistance, we investigated insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) genes, in vitro IR function and in vivo insulin sensitivity in a family with Type A syndrome. Two missense IR mutations (Asp59Gly and Leu62Pro) found in the proband, resulted in reduction by 90% of insulin binding to erythrocytes, decreased receptor autophosphorylation and a dramatic reduction of insulin sensitivity. The proband and mother were heterozygote for Gly972Arg IRS-1 variant. Asp59Gly mutation, also carried by proband's brother with no consequence on insulin sensitivity, was inherited from the mother who is diabetic and insulin resistant and Leu62Pro was from the father. We conclude that severity of insulin resistance in the proband may be explained by the genetic condition of compound heterozygote for IR mutations while severe insulin resistance in the mother raises the possibility that other genetic factors, like IRS-1 polymorphisms, may contribute to the phenotypic expression of IR mutations.

Amino Acid Sequence↗
PubMed1997

Single- and multiple-dose pharmacokinetics of riluzole in white subjects.

Riluzole is a novel neuroprotective agent that has been developed for the treatment of amyotrophic lateral sclerosis. A series of studies was undertaken to establish its pharmacokinetics on single- and multiple-dose administration in young white male volunteers. The mean absolute oral bioavailability of riluzole (50-mg tablet) was approximately 60%. Maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) values were linearly related to dose for the range studied. Cmax occurred at 1.0 hour to 1.5 hours after administration. Plasma elimination half-life appeared to be independent of dose. After repeated administration of 100 mg riluzole for 10 days, some intraindividual variability in bioavailability was seen. A high-fat meal significantly reduced the rate (tmax = 2 hours compared with 0.8 hours; Cmax = 216 ng.mL-1 compared to 387 ng.mL-1) and extent of absorption (AUC = 1,047 ng.hr.mL-1 versus 1,269 ng.hr.mL-1). With multiple-dose administration, riluzole showed dose-related absorption, although the terminal plasma half-life was prolonged slightly. Steady-state plasma concentrations were achieved within 5 days. Steady-state trough plasma concentrations were significantly higher with a 75-mg dose twice daily than with a 50-mg dose three times daily, although AUC values did not differ.

Adolescent↗
PubMed1997

In vitro production of megakaryocytes from PIXY321 versus GM-CSF-mobilized peripheral blood progenitor cells.

The generation of megakaryocytes (MK) from cultured peripheral blood progenitor cells (PBSC), harvested via apheresis, from 18 female breast cancer patients treated with either PIXY321 or GM-CSF was compared. Nonadherent mononuclear cells (MNC) were cultured in liquid suspension with 50 U/ml thrombopoietin (TPO) and 2.5% autologous heparinized plasma for 12 days. Flow cytometric analysis was used to measure the percentage of CD34+ on day 1 and CD41+ cells on day 12. The frequency of CD34+ cells was greater in GM-CSF-mobilized samples than in PIXY321-mobilized samples, and MK/MNC yields correlated directly with the number of CD34+ cells seeded, PIXY321-mobilized samples produced more MKs per CD34+ cell than GM-CSF-mobilized samples. Overall, there was no significant difference in the MK/MNC yield between PIXY321- and GM-CSF-mobilized samples. Cyclophosphamide (CY) increased the frequency of CD34+ cells and the corresponding MK/MNC yield for both cytokines, but had no effect on the MK/CD34+ yield. Compared to GM-CSF, PIXY321 mobilization resulted in increased CD34+ cell commitment to the MK lineage.

Adult↗
PubMed1997

[The advent of a new class of antihypertensive agents: angiotensin II receptor antagonists].

The objective of this article is to give more information about the pharmacology of and recent clinical data on the angiotensin II receptors antagonists. The angiotensin II receptors antagonists, of which Losartan will be the first representative on the Belgian market, constitute a new therapeutic class in the treatment of hypertension and even heart failure. They are non peptic and orally active and their long mechanism of action allows one daily administration to improve therapeutic compliance. These agents block all known effects of the angiotensin II through binding to the AT1 receptors. Thanks to this unique mechanism of action they reduce blood pressure with a lower incidence of the adverse effects commonly associated with other antihypertensives. In controlled clinical trials, overall incidence of adverse experiences was comparable to placebo. Addition of thiazide-type diuretics provides additive efficacy.

Administration, Oral↗