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Biomedical subjects

F Pierre

Publications and source records attributed to F Pierre.

At least 19 recordsLinked to original sources
PubMed2006

Apc mutation induces resistance of colonic cells to lipoperoxide-triggered apoptosis induced by faecal water from haem-fed rats.

Recent epidemiological studies suggest that high meat intake is associated with promotion of colon cancer linked with haem-iron intake. We previously reported that dietary haem, in the form of either haemoglobin or meat, promotes precancerous lesions in the colon of rats given a low-calcium diet. The mechanism of promotion by haem is not known, but is associated with increased lipid peroxidation in faecal water and strong cytotoxic activity of faecal water on a cancerous mouse colonic epithelial cell line. To better understand the involvement of faecal water components of haem-fed rats in colon-cancer promotion, we explored the effect of faecal water on normal [adenomatous polyposis coli (Apc)+/+] or premalignant cells (Apc-/+). Further, we tested if this effect was correlated to lipoperoxidation and 4-hydroxynonenal (HNE). We show here for the first time that heterozygote Apc mutation represents a strong selective advantage, via resistance to apoptosis induction (caspase 3 pathway), for colonic cells exposed to a haem-iron-induced lipoperoxidation. The fact that HNE treatment of the cells provoked the same effects as the faecal water of rats fed the haem-rich diet suggests that this compound triggers apoptosis in those cells. We propose that this mechanism could be involved in the promotion of colon carcinogenesis by haem in vivo.

Animals↗
PubMed2006

Emission and absorption asymmetry in the quantum noise of a Josephson junction.

We measure current fluctuations of mesoscopic devices in the quantum regime, when the frequency is of the order of or higher than the applied voltage or temperature. Detection is designed to probe separately the absorption and emission contributions of current fluctuations, i.e. the positive and negative frequencies of the Fourier transformed nonsymmetrized noise correlator. It relies on measuring the quasiparticles photon assisted tunneling current across a superconductor-insulator-superconductor junction (the detector junction) caused by the excess current fluctuations generated by quasiparticles tunneling across a Josephson junction (the source junction). We demonstrate unambiguously that the negative and positive frequency parts of the nonsymmetrized noise correlator are separately detected and that the excess current fluctuations of a voltage biased Josephson junction present a strong asymmetry between emission and absorption.

Journal Article↗
PubMed2006

[Obstructive Sleep Apnea Syndrom during pregnancy: prevalence of main symptoms and relationship with Pregnancy Induced-Hypertension and Intra-Uterine Growth Retardation].

OBJECTIVE: To investigate the frequency of main symptoms of Obstructive Sleep Apnea Syndrom (OSAS) and their relationship with Pregnancy Induced-Hypertension (PIH) as well as Intrauterine Growth Retardation (IGR) as suggested by recent studies. METHODOLOGY: Four hundred (and) thirty-eight enquiry forms completed during post-partum period were analysed, after exclusion of multiple pregnancies. Collected data were demographic characteristics, obstetrical events, sleep disorders during last trimester, screening of snoring and vigilance troubles with an Epworth score. RESULTS: Forty-five percentages of the patients reported to have habitual snoring during pregnancy. Among these, 85% were non-snorers before pregnancy. Daytime somnolence concerned 84,5% of the population with an Epworth score significatively increased (P<0,0001). The prevalence of PIH was found to be 4,5%, with two apparently independent risk factors: the body mass index (OR=1,1) and an association between snoring and increased vigilance trouble (OR=2,6). No statistical difference was found concerning IGR. CONCLUSIONS: SAS symptoms are frequent during pregnancy and snoring appears to be linked with PIH. However, polysomnographic data are not yet sufficient to explain pathophysiological mechanisms and find relevant diagnostic markers during pregnancy.

Adolescent↗
PubMed2005

Direct observation of dynamical bifurcation between two driven oscillation states of a Josephson junction.

We performed a novel phase-sensitive microwave reflection experiment which directly probes the dynamics of the Josephson plasma resonance in both the linear and the nonlinear regime. When the junction was driven below the plasma frequency into the nonlinear regime, we observed for the first time the transition between two different dynamical states predicted for nonlinear systems. In our experiment, this transition appears as an abrupt change in the reflected signal phase at a critical excitation power. This controlled dynamical switching can form the basis of a sensitive amplifier, in particular, for the readout of superconducting qubits.

Journal Article↗
PubMed2005

[Maternal diaphragmatic hernia during pregnancy: report of two cases].

We report two cases of maternal diaphragmatic hernia during pregnancy. Diaphragmatic hernia is an unusual and severe disease. Maternal and fetal prognosis are threatened. Diagnosis is uncertain when confronted to respiratory and digestive symptoms without any specificity. The chest X ray is the first exam to perform. The objective of this work is to discuss the management of such a pathology in terms of ways of delivery and surgical cure of hernia.

Adult↗
PubMed2004

RF-driven Josephson bifurcation amplifier for quantum measurement.

We have constructed a new type of amplifier whose primary purpose is the readout of superconducting quantum bits. It is based on the transition of a rf-driven Josephson junction between two distinct oscillation states near a dynamical bifurcation point. The main advantages of this new amplifier are speed, high sensitivity, low backaction, and the absence of on-chip dissipation. Pulsed microwave reflection measurements on nanofabricated Al junctions show that actual devices attain the performance predicted by theory.

Journal Article↗
PubMed2004

[Risk factors of postpartum hemorrhage during labor and clinical and pharmacological prevention].

Prevention of postpartum hemorrhage (PPH) is a major concern in regards to its impact on maternal morbidity and mortality. While established risk factors can be identified among risk factors of PPH during labor after multivariate analysis: prolonged labor, oxytocin stimulation of labor, cesarean section, instrumental delivery, genital lacerations and episiotomy, prolonged third stage of labor, retained placenta; other risk factors are still uncertain: induction of labor, hyperthermia or chorioamniotitis, analgesia or anesthesia, macrosomia, various cesarean section techniques. Isolated identified risk factors have a moderate incidence on PPH, but their cumulation in one patient is a potential high risk. Among active management schemes of third stage of labor for PPH prevention, the most efficient technique seems to be direct injection of oxytocin when the baby's shoulders are delivered, associated with controlled cord traction. If this technique is a must for high-risk patients for PPH, and seems efficient for every patient, a correctly performed procedure requires the presence of a competent professional in addition to the midwife or obstetrician in charge of delivery, and a permanent attention so the length of third stage of labor is shortened. The alternative use of prophylactic misoprostol in the third stage of labor is less effective than injectable uterotonics in reducing PPH, and is associated with more side effects (severe shivering, pyrexia, diarrhea). None of other described prophylactic methods have proved efficiency: early suckling, umbilical blood drainage, oxytocin umbilical vein injection, among others. A decrease in PPH prevalence should be obtained by particular attention on data from the early postpartum period, active diffusion of effective prophylactic techniques, and an appropriate choice in regards to each delivery unit organization.

Delivery, Obstetric↗
PubMed2003

Magnetic-field-dependent quasiparticle energy relaxation in mesoscopic wires.

In order to find out if magnetic impurities can mediate interactions between quasiparticles in metals, we have measured the effect of a magnetic field B on the energy distribution function f(E) of quasiparticles in two silver wires driven out of equilibrium by a bias voltage U. In a sample showing sharp distributions at B=0, no magnetic field effect is found, whereas, in the other sample, rounded distributions at low magnetic field get sharper as B is increased, with a characteristic field proportional to U. Comparison is made with recent calculations of the effect of magnetic-impurities-mediated interactions taking into account Kondo physics.

Journal Article↗
PubMed2003

[Medical-legal aspects: the obstetrician as a defendant or as an expert].

Most claims ab out term intrapartum fetal asphyxia (or cerebral palsy presumed to be in relation with it) are based on abnormal intrapartum fetal heart rate patterns, and presumed excessive delay from decision-to-delivery and/or inadequate care. For the obstetrician, whether as a defendant or a judicial expert, the difficulty lies in data interpretation which should not be reduced to an analysis of fetal monitoring, but should consider the context, the explorations used to be sure of abnormal fetal heart rate interpretation, and appropriate delay for delivery in light of the findings.

Asphyxia Neonatorum↗