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Biomedical subjects

A Mercier

Publications and source records attributed to A Mercier.

At least 19 recordsLinked to original sources
PubMed2005

Anomalous roughening of viscous fluid fronts in spontaneous imbibition.

We report experiments on spontaneous imbibition of a viscous fluid by a model porous medium in the absence of gravity. The average position of the interface satisfies Washburn's law. Scaling of the interface fluctuations suggests a dynamic exponent z approximately 3, indicative of global dynamics driven by capillary forces. The complete set of exponents clearly shows that interfaces are not self-affine, exhibiting distinct local and global scaling, both for time (beta = 0.64 +/- 0.02, beta(*) = 0.33 +/- 0.03) and space (alpha = 1.94 +/- 0.20, alpha(loc) = 0.94 +/- 0.10). These values are compatible with an intrinsic anomalous scaling scenario.

Journal Article↗
PubMed2005

[Management of phenylketonuria and hyperphenylalaninemia: the French guidelines].

Phenylketonuria (PKU) is an inherited metabolic disease affecting about one birth out of 15 000. From 1978, a national systematic neonatal screening was set up in France with a regional organisation. French rational and guidelines have been established by the national PKU group with the collaboration of all the physicians responsible for the regional centres. These guidelines specify the minimal diagnosis procedures leading to an optimal treatment of all patients. A low-phenylalanine diet must be started as soon as possible in the neonatal period for all newborns whose phenylalanine levels are above 10 mg/dl. The dietary control must keep the phenylalanine plasma levels between 2 and 5 mg/dl until 10 years of age. After this age, several data argue for a progressive and controlled relaxation of the diet, keeping the phenylalanine level below 15 mg/dl until the end of the adolescence and below 20 to 25 mg/dl in adulthood. All PKU patients must be followed up for life, in order to screen those who may not bear the diet relaxation and in order to strictly prevent maternal PKU deleterious consequences.

Child↗
PubMed2003

Effect of enteral supplementation with glutamine on mesenteric blood flow in premature neonates.

BACKGROUND AND AIMS: This study investigated the effects of enterally supplied glutamine on mesenteric blood flow in premature neonate. METHODS: Twenty-five neonates, aged at least 14 days and free of acute illness participated in a prospective, randomised, double-blind study. All were fed with total enteral nutrition enriched with glutamine (0.7 g kg(-1)day(-1), group 1) or isonitrogenous control (group 2). Blood flow velocities in the superior mesenteric artery were analysed by pulsed Doppler US before and after 21 days of supplemented feeding. Peak systolic velocity (PSV), end-diastolic velocity (EDV) and time-averaged mean velocity (TAV) were measured and resistance index (RI) and flow (Q) were calculated. RESULTS: Both groups were well matched clinically at inclusion. At inclusion, the velocimetry parameters were (mean +/- SD) : PSV:114.9 +/- -38 cms(-1), EDV:17.5 +/- 7.5 cm x s(-1), TAV:44.8 +/- 18.2 cms(-1), RI : 0.8 +/- 0.1, Q : 2.4 +/- 1.2 mls(-1). Mesenteric blood flow parameters remained stable between day 0 and day 21 with same values in both groups. CONCLUSIONS: Superior mesenteric blood flow remained stable in neonates after 14 days of life and did not appear to be influenced by enteral glutamine at that stage.

Blood Flow Velocity↗
PubMed2001

Isolated mild fetal cerebral ventriculomegaly: a retrospective analysis of 26 cases.

We retrospectively studied 26 fetuses with isolated mild cerebral ventriculomegaly diagnosed between 1992 and 1998 and defined by a lateral ventricular atrial diameter of 10-15 mm without any other cerebral anomaly. Our objectives were to determine maternal risk factors, to evaluate complementary investigations, to assess developmental prognosis and to propose possible management. During pregnancy 10/26 patients had regressive ventriculomegalies, ten remained borderline at birth and six were confirmed postnatally. No maternal risk factors were identified. Prenatal investigations were carried out in 69% of cases but in only a few cases supplied any information. Postnatal examinations revealed one case of Down syndrome and one of porencephaly. Four children were lost to follow-up. In the 22 other cases, four had developmental delay. Early and unexplained mild ventriculomegaly appears to have a good prognosis. If ventriculomegaly is persistent, prenatal management should be carried out to investigate chromosomal abnormalities, viral infection, and fetal cerebral parenchymal damage. A long postnatal clinical follow-up is required.

Adult↗
PubMed2001

Neonatal screening and long-term follow-up of phenylketonuria: the French database.

BACKGROUND: In France, neonatal screening of phenylketonuria (PKU) started in 1966. A national association was created in 1978 in order to organise the neonatal screening program and to control the efficacy of the screening and patients' follow-up. AIMS: To evaluate the results of the French PKU screening program in terms of hyperphenylalaninaemia epidemiology, efficacy of the screening procedure, management and outcome of the patients. STUDY DESIGN: The national database has been filled-up first with the answers to questionnaires that were sent each year by the PKU patients' physicians, and second with the results of an additional inquiry, which was set up in 1994 in order to investigate diagnosis, treatment, and school outcome of all French PKU patients. RESULTS: PKU was diagnosed in 81.6% of patients with hyperphenylalaninaemia (HPA), non-PKU HPA in 17.2% and cofactor deficiency in 1.1%. From 1980, incidence of PKU has been stable: 1 per 17,124 live births. Sensitivity of the screening procedure was 99.3%. Age at diet initiation regularly decreased to reach 14 days as a median in 1996. Until 1990, median age at diet discontinuation was 6 years of age. Later, strict diet was continued longer (at least, up to 8-10 years). PKU patients who entered to secondary school at normal age were characterised by an earlier age at diagnosis and at diet initiation and a later age at diet discontinuation, compared to those who entered 1 year or more behind normal age. CONCLUSION: These data confirm the benefit of a nationwide organised screening program. They emphasise the importance of an early neonatal diagnosis and diet initiation in PKU patients and are consistent with the benefit of a longer period of strict diet in childhood.

Child↗
PubMed2001

Fetal and neonatal cerebral infarcts.

Focal arterial infarction in the full-term newborn is an important cause of acquired cerebral lesions in the perinatal period. Clinical motor seizures, most often unifocal, are the nearly constant disclosing symptom confirmed by focal EEG abnormalities. A multifactorial physiopathology is usual, including genetic and perinatal environmental factors. In the past decade, various acquired or genetic thrombophilias have been discussed as risk factors. For several of the involved mechanisms, the excitotoxic cascade could represent a common final pathway leading to neuronal cell death. Early magnetic resonance imaging studies and EEG help to identify the newborns with strokes who are likely to develop hemiplegia and disabilities at school. Protection of the human fetal brain remains difficult, since the triggering factor initiating the excitotoxic cascade is rarely observed. Treatment of seizures is nevertheless necessary, because it seems that they accelerate anoxia-induced neuronal death in animal models of focal hypoxic ischemia.

Animals↗
PubMed2000

Settlement preferences and early migration of the tropical sea cucumber Holothuria scabra.

Settlement and post-settlement processes of the sea cucumber Holothuria scabra Jaeger were studied in the laboratory. Independent and paired choice experiments revealed that several substrates could induce metamorphosis into pentactulae, but that specific substrates favoured settlement. Leaves of seagrass Thalassia hemprichii, with or without their natural bio-film, yielded the highest settlement rates (4.8-10.5%). T. hemprichii was preferred as a settlement substrate over sand, crushed coral, several other plant species and artificial seagrass leaves with or without a bio-film. Only settlement on the seagrass, Enhalus acoroides, was similar to that recorded for T. hemprichii. In the absence of a substrate, the larvae delayed settlement for nearly 96 h and survival was less than 0.5%. Sand and crushed coral, either alone or together, induced settlement from <1.5% of the available larvae. The pentactulae found on sand, coral and in bare containers were 10-35% smaller than those on T. hemprichii leaves. Soluble extracts from T. hemprichii and E. acoroides successfully induced metamorphosis and settlement on clean plastic surfaces. Newly settled juveniles remained on the seagrass leaves for 4-5 weeks before migrating to sand at around 6 mm in length. Prior to this, the juveniles spent 4-5 days moving on and off the leaves. Once on the sand, the juveniles became deposit-feeders, but did not show the typical burrowing behaviour of older specimens until they reached around 11 mm in length. The larvae of H. scabra appear to actively select seagrass leaves, possibly through chemical detection. We hypothesise that larvae settling on seagrass have an increased chance of growth and survival because they are provided with a suitable substrate on which to grow, and a bridge to sand substrates as they become deposit-feeders.

Journal Article↗
PubMed2000

2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide: evaluation of the spin trapping properties.

The 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-l-oxide (EMPO), an easily prepared pyrroline-N-oxide has been tested as a free radical scavenger. Spin adducts of superoxide, hydroxyl radical, and other free radicals were characterized in phosphate buffer at pH 7.0 and 5.6. At pH 7 in phosphate buffer, the EMPO/O(2)(-*) spin adduct was estimated to be about five times more persistent than its DMPO analogue. Furthermore, its decay does not produce the EMPO/HO&z.rad; adduct.

Animals↗
PubMed1997

beta-phosphorylated nitroxides in the pyrrolidine series: reduction by ascorbate.

Reduction-resistant nitroxides are particularly interesting for biomedical applications. beta-Phosphorylated pyrrolidinyl nitroxides, a new series of stable pyrrolidinoxyl radicals prepared in our laboratory, were tested toward ascorbate reduction in phosphate buffer at pH 7.4. The kinetics of decay were monitored by ESR and compared to those of two reference nitroxides, PCA and Proxyl. The introduction of a beta-phosphoryl group on a pyrrolidinoxyl structure resulted in a moderate increase of the reduction rate constant. However, inside the phosphorylated series, slight structural modifications can induce significant changes in the rate constants.

Ascorbic Acid↗
PubMed1995

Physiological effects of two FMRFamide-related peptides from the crayfish Procambarus clarkii

The present study examined the effects of two recently identified neuropeptides on crayfish hearts and on neuromuscular junctions of the crayfish deep abdominal extensor muscles. The two peptides, referred to as NF1 (Asn-Arg-Asn-Phe-Leu-Arg-Phe-NH2) and DF2 (Asp-Arg-Asn-Phe-Leu-Arg-Phe-NH2), increased the rate and amplitude of spontaneous cardiac contractions and increased the amplitude of excitatory junctional potentials (EJPs) in the deep extensors. Both effects were dose-dependent, but threshold and EC50 values for the cardiac effects were at least 10 times lower than for the deep extensor effects. The heart responded equally well to three sequential applications of peptide in any given preparation, but the responses of the deep extensors appeared to decline with successive peptide applications. The results support the hypothesis that these two neuropeptides act as neurohormones to modulate the cardiac and neuromuscular systems in crayfish. Quantal synaptic current recordings from the deep extensor muscles indicate that both peptides increase the number of quanta of transmitter released from synaptic terminals. Neither peptide elicited a measurable change in the size of quantal synaptic currents. NF1 caused a small increase in muscle cell input resistance, while DF2 did not alter input resistance. These data suggest that DF2 increases EJP amplitudes primarily by increasing transmitter release, while the increase elicited by NF1 appears to involve presynaptic and postsynaptic mechanisms.

Journal Article↗
PubMed1978

[Pyrithioxine a new basic treatment of rheumatoid polyarthritis: initial study of 72 cases with a 6-month follow-up].

Pyrithioxine has certain chemical resemblances to penicillamine and is used as original treatment in a series of 72 cases of rheumatoid arthritis over a period of six months in a dose of 600 mgs daily. Results were favourable in 63% of cases with important lowering of the articular index, return to normal of the sedimentation rate and less frequently a reversal of the Waaler-Rose reaction. Secondary complications were essentially muco-cutaneous, sometimes gastric and necessitated stopping treatment in 15% of cases. No other serious side effect has been observed. When compared with penicillamine pyrithioxine would appear less efficacious but better tolerated. The usefulness of this new medicament in the treatment of rheumatoid arthritis needs to be further explored.

Adult↗