Biomedical subjects

L Humbert

Publications and source records attributed to L Humbert.

At least 19 recordsLinked to original sources

PubMed2006

Ultracold heteronuclear molecules in a 3D optical lattice.

We report on the creation of ultracold heteronuclear molecules assembled from fermionic 40K and bosonic 87Rb atoms in a 3D optical lattice. Molecules are produced at a heteronuclear Feshbach resonance on both the attractive and the repulsive sides of the resonance. We precisely determine the binding energy of the heteronuclear molecules from rf spectroscopy across the Feshbach resonance. We characterize the lifetime of the molecular sample as a function of magnetic field and measure lifetimes between 20 and 120 ms. The efficiency of molecule creation via rf association is measured and is found to decrease as expected for more deeply bound molecules.

Journal Article↗

PubMed2006

Tuning of heteronuclear interactions in a degenerate Fermi-Bose mixture.

We demonstrate tuning of interactions between fermionic 40K and bosonic 87Rb atoms by Feshbach resonances and access the complete phase diagram of the harmonically trapped mixture from phase separation to collapse. On the attractive side of the resonance, we observe a strongly enhanced mean-field energy of the condensate due to the mutual mean-field confinement, predicted by a Thomas-Fermi model. As we increase heteronuclear interactions beyond a threshold, we observe an induced collapse of the mixture. On the repulsive side of the resonance, we observe vertical phase separation of the mixture in the presence of the gravitational force, thus entering a completely unexplored part of the phase diagram of the mixture. In addition, we identify the 515 G resonance as p wave by its characteristic doublet structure.

Journal Article↗

PubMed2006

[Assessment of occupational exposure to ortho-toluidine using gas chromatography-mass spectrometry].

Ortho-toluidine is a carcinogen aromatic amine. It is in part eliminated as unchanged form and its urine determination allows biologic monitoriing of occupational exposure. We propose a new method simple and fast in gas chromatography mass spectrometry. In the Nord-Pas-de-Calais region, a company initiated destruction and depollution of an old industrialsite.The GS-MS method permits exposition evaluation of workers employed in demolition of a liquid SO2 plant polluted with ortho-toluidine. This plant has been stopped twenty years ago. These results are compared with results of workers without any exposure in the same company. A 5 mL urine sample spiked with internal standard (ortho-toluidine D9) is extracted with hexane. Derivatisation is achieved with anhydrous pentafluoropropionic acid during 30 min at 60 degrees C. Chromatographic separation is performed on a BPX5MS column (25 m x 0.25 mm, 0.25 microm; SGE). Initial column temperature (60 degrees C) is hold 3 min then is raised to 300 degrees C at 25 degrees C/min. Detection is performed with mass spectrometry with negative chemical ionisation with methane. Acquisition is performed in single ion monitoring. Identification ions are 233 ion (m/z) and 213 ion (m/z) with 233 (m/z) used for quantification. Linearity of the method is verified between 0.1 and 100 microg/L. The limit of detection is 0.02 micro/L. Repeatability and intermediate fidelity are satisfactory (CV < 9%). For unexposed workers, urinary concentrations of ortho-toluidine ranged between 0.17 microg/L and 2.46 microg/g creatinine. Urinary concentrations for exposed workers ranged between 26.14 and 462.00 microg/g creatinine and after new action of protection between 2.35 et 20.11 microg/g creatinine. This new GC-MS method is specific and sensitive and allows for urinary determination of ortho-toluidine. Results showed that this method is adapted for biomonitoring as much for unexposed workers to this aromatic amine as for exposed workers.

Gas Chromatography-Mass Spectrometry↗

PubMed2005

Sterol profiling of amniotic fluid: a routine method for the detection of distal cholesterol synthesis deficit.

OBJECTIVES: Smith Lemli Opitz syndrome (SLOS) caused by a deficit of 3beta-hydroxysterol-Delta7 reductase was the first sterol deficit described with multiple malformations. The lack of specificity of many morphological abnormalities detected by ultrasound and their frequency have justified routine screening of amniotic fluid (AF) for sterols by GC-MS. The examination contributes to an improved knowledge of the sterol status in the fluid. METHODS: A series of sterol profiles is collated here. Accumulation of 7- and 8-dehydrocholesterol are diagnostic for SLOS. However, a number of other sterols have also been detected by GC-MS in control AF and their presence may be confusing. RESULTS AND CONCLUSIONS: In addition to cholesterol, the level of which varies as function of the gestational age, lathosterol is present together with trace amounts of 7- and 8-dehydrocholesterol and other precursors such as desmosterol, lanosterol, and dimethylsterol. Phytosterols are also present in 70% of AF samples that have been tested. Besides SLOS, GC-MS examination of amniotic fluid can detect various sterol deficits associated with malformations (lathosterolosis, desmosterolosis, X-linked chondrodysplasia, and particular Antley-Bixler syndrome). Practical conclusions support GC-MS as a routine method to investigate skeletal and central nervous system malformations.

Amniotic Fluid↗

PubMed2005

Influence of acetaminophen consumption on perceived exertion at the lactate concentration threshold.

The purpose of this investigation was to study effects of acetaminophen consumption on ratings of perceived exertion and estimated time limit responses at the lactate threshold. 98 young regional to national level athletes performed a graded exhausting exercise on an outdoor running track to estimate their maximal aerobic velocity and the velocity associated with their lactate concentration threshold. Urine (30 mL) was collected during this test and analysed for numerous substances. During urinary screening for doping substances, 9 acetaminophen consumers (9.2%) among the 98 included athletes were detected. These acetaminophen consumers have significantly lower perceived exertion at velocity corresponding to the lactate concentration threshold than nonconsumers (11.9 +/- 2.1 vs 13.6 +/- 2.1, respectively) although they were at the same relative exercise intensity. This result shows that acetaminophen consumption may have mediated the perceived exertion response at the lactate concentration threshold. This may then suggest that the pain induced by training load could be a factor in use of self-prescribed pain relievers. Such consumption must be taken into account by medical staff, trainers, or educators who have to give information on the use and adverse effects of this substance and to propose palliative methods to their athletes.

Acetaminophen↗

PubMed2005

Use of acetaminophen in young subelite athletes.

AIM: The purpose of the present investigation was to look for other drugs besides doping substances in the urine of subelite athletes submitted to heavy training. METHODS: One hundred and forty-one young subelite athletes (in sprint, cycling, middle distance running and handball) were included in the study, with a control group of 89 high school pupils. Drugs were researched by high performance liquid chromatography using a diode array detector. RESULTS: Among the 212 subjects who agreed to give a urine sample, acetaminophen was detected: 9.5% for the subelite athletes versus 1.3% for the control group with a greater difference for sprint and cycling training (26.7% and 20%, respectively). Acetaminophen is used to treat both acute and chronic pains. It relieves pain by elevating the pain threshold. CONCLUSIONS: The use of acetaminophen has to be taken into account by medical staff, trainers and educators.

Acetaminophen↗

PubMed2002

[Serial determination of crimidine by HPLC/SE/SM in a patient ingesting a "mouse trap"].

Crimidine (2 chloro, 4 methyl, 6 dimethyl amidopyrine) is a synthetic rodenticide which causes acute poisonings after oral ingestion in human. Major toxic effects are consciousness disorders, hypertonic coma and convulsions. Toxic level in human is about 5 mg/Kg. An intoxication case is reported. Five serums collected at different times were analyzed with HPLC/ES/MS. Crimidine was extracted with ethylacetate with recovery over 80%. Linearity was up to 800 micrograms/L. LOQ and LOD were 0.5 and 0.3 microgram/L respectively. The coefficients of variation were less than 10% for repeatability and reproductibility. Serum levels varied from 368 micrograms/L for H0 to 64 micrograms/L for H10 and elimination of crimidine was linear in time.

Chromatography, High Pressure Liquid↗

PubMed2001

Separation and quantification of paraquat and diquat in serum and urine by capillary electrophoresis.

The use of capillary electrophoresis (CE) for simultaneous qualitative and quantitative detection of paraquat (PQ) and diquat (DQ) in both serum and urine was investigated. The two herbicides were extracted from biological fluids with liquefied phenol. Serum required a deproteinization with chloroform and ammonium sulfate as pretreatment. The extracts were hydrodynamically injected and the complete separation was carried out in 10 min, using a capillary tube (75 microm i.d., 500 mm) of fused silica containing 50 mM phosphate buffer (pH 2.50) as the carrier. UV absorbance detection at 200 nm was performed by an on-column detector. The analytes were characterized by their respective migration times. Analytical recoveries were 52.6% for PQ and 62.6% for DQ in serum, and 71.4% and 59.3%, respectively, in urine. The linearity was studied up to 4 mg/L and the limits of detection (LODs) were better than 5 pg/mL in serum or urine. The CE method described was applied to the characterization of two lethal poisonings and results were related.

Adult↗

PubMed2000

Dramatic inhibition of amiodarone metabolism induced by grapefruit juice.

AIMS: Grapefruit juice increases blood concentrations of many drugs metabolized by CYP3A. Amiodarone is metabolized by CYP3A to N-desethylamiodarone (N-DEA). The aim of this study was to determine amiodarone kinetics when administrated with and without grapefruit juice. METHODS: Eleven healthy adult volunteers took part in a single sequence, repeated-measures design study. Each subject, who had been evaluated 6 months previously for amiodarone pharmacokinetics, was given a single oral dose of amiodarone (17 mg kg-1) with three glasses of 300 ml of grapefruit juice on the same day. RESULTS: Grapefruit juice completely inhibited the production of N-DEA, the major metabolite of amiodarone, in all subjects and increased the area-under-the-curve (AUC) and maximum concentration of amiodarone (Cmax) by 50% and 84%, respectively, as compared with the control period during which water had been administrated instead of grapefruit juice (AUC: 35.9 +/- 14.3 vs 23.9 +/- 11.2 microg ml-1 h, P < 0.005 and Cmax: 3.45 +/- 1.7 vs 1.87 +/- 0.6 microg ml-1, P < 0. 02, respectively) (means +/- s.d.). This inhibition of N-DEA production led to a decrease in the alterations caused by amiodarone on PR and QTc intervals. CONCLUSIONS: Grapefruit juice dramatically alters the metabolism of amiodarone with complete inhibition of N-DEA production. These results are in agreement with in vitro data pointing to the involvement of CYP3 A in the metabolism of amiodarone and suggests that this interaction should be taken into account when prescribing this antiarrhythmic drug.

Adult↗

PubMed2000

Critical role of C/EBPdelta and C/EBPbeta factors in the stimulation of the cyclooxygenase-2 gene transcription by interleukin-1beta in articular chondrocytes.

The activity of the [-831; +103] promoter of the human cyclooxygenase-2 gene in cultured rabbit chondrocytes is stimulated 2.9 +/- 0.3-fold by interleukin-1beta and this stimulation depends on [-132; -124] C/EBP binding-and [-223; -214] NF-kappaB binding-sites. The C/EBPbeta and C/EBPdelta factors bind to the [-132; -124] sequence. The [-61; -53] sequence is also recognized by C/EBPbeta and C/EBPdelta as well as USF. Mutation of the whole [-61; -53] sequence abolished the stimulation of transcription but single mutations of the C/EBP or USF site did not alter the activity of the promoter, suggesting that the factors bound to the proximal [-61; -53] sequence interact with different members of the general transcription machinery. The [-223; -214] site binds only the p50/p50 homodimer and a non-rel-related protein, but not the transcriptionally active heterodimer p50/p65. The p50/p50 homodimer could interact with the C/EBP family members bound to the [-132; -124] sequence for full stimulation of the COX-2 transcription by interleukin-1beta in chondrocytes. By contrast, the [-448; -449] sequence binds with a low affinity both the p50/p50 homodimeric and p50/p65 heterodimeric forms of NF-kappaB but has no role in the regulation of the human COX-2 promoter in chondrocytes.

Animals↗

PubMed1999

[Hepatonephritis and massive ingestion of buprenorphine].

We present a case of a severe hepatitis associated with acute renal failure and anuria consequently to the ingestion of 112 mg of buprenorphine, 48 hours before. The normalisation of hepatic and renal functions is associated with discontinuation of buprenorphine administration and hemodialysis treatment. Buprenorphine seems to be directly responsible for this hepatonephritis as indicated by the high plasmatic levels of buprenorphine (224 ng/ml) and norbuprenorphine (30 ng/ml) never described until now. Buprenorphine toxicity could be due to the inappropriate ingestion mode (oral instead of sublingual) and could be increased by previous acetaminophen intake.

Acute Kidney Injury↗

PubMed1999

[Identification and quantitative determination of chlorinated++ solvents after solid phase microextraction. Applications in hospital toxicology].

A simple method for the research and the identification of chlorinated solvents in biological fluids and tissues is described. The solvents are extracted using headspace solidphase microextraction and detected or measured by gas chromatography with electron capture detector. Three accidental poisonings are reported: one with carbon tetrachloride, one with trichlorethylene and the last one is a double intoxication with tetrachloroethylene and trichlorethylene.

Chromatography, Gas↗

PubMed1999

Cyclooxygenase activity in chondrocytes from osteoarthritic and healthy cartilage.

OBJECTIVES: To compare prostaglandin production and cyclooxygenase activity in high-density primary cultures of chondrocytes from patients with osteoarthritis and from healthy controls. METHODS: Chondrocytes harvested from operative specimens obtained during hip or knee arthroplasty were cultured at a very high density for 48 h. Cyclooxygenase activity was evaluated based on prostaglandin E2 levels (radioimmunological assay) after addition of arachidonic acid. The chondrocytes were cultured with and without IL-1 beta and TNF alpha. RESULTS: Prostaglandin E2 production and cyclooxygenase activity were significantly higher in cultures of chondrocytes from osteoarthritic than from healthy joints. Adding IL-1 beta to the osteoarthritic chondrocyte cultures further increased the high cyclooxygenase activity, whereas adding TNF alpha alone had no effect. CONCLUSION: Cultured chondrocytes from osteoarthritic joints showed increased prostaglandin E2 production and cyclooxygenase activity.

Cartilage↗

PubMed1997

Posttranscriptional effect of insulin-like growth factor-I on interleukin-1beta-induced type II-secreted phospholipase A2 gene expression in rabbit articular chondrocytes.

Large amounts of type II-secreted phospholipase A2 (type II sPLA2) are secreted into inflammatory synovial fluid and they are believed to induce the synthesis of lipid mediators by articular chondrocytes. Preliminary experiments showed that insulin-like growth factor-I, which counteracts cartilage degradation in arthritis, inhibits interleukin-1beta-induced type II sPLA2 gene expression in rabbit articular chondrocytes (Berenbaum, F., G. Thomas, S. Poiraudeau, G. Bereziat, M.T. Corvol, and J. Masliah. 1994. FEBS Lett. 340: 51-55). The present study showed that IL-1beta induced the sustained synthesis of prostaglandin E2 and a parallel increase in type II sPLA2 gene expression (assessed by enzymatic activity and Northern blot analysis), but no increase in cytosolic PLA2 gene expression (assessed by Northern and Western blot analysis) or cytosolic PLA2 activity in rabbit articular chondrocytes. IGF-I inhibited both IL-1beta-stimulated PGE2 synthesis and type II sPLA2 gene expression, but had no effect on cytosolic PLA2 gene expression. Nuclear run-on experiments revealed that IL-1beta stimulated the transcription rate of type II sPLA2 gene, giving rise to long-lived mRNA in cells treated with actinomycin D. IGF-I did not affect transcription rate, suggesting that it acts as a post-transcriptional step. Sucrose density gradient analysis of the translation step showed no effect of IGF-I on the entry of type II sPLA2 mRNA into the polysomal pool or on its distribution into the various polysomal complexes, suggesting that IGF-I does not act on the translation of the mRNA. Lastly, IGF-I strongly decreased the half-life of IL-1beta-induced type II sPLA2 mRNA (from 92 to 12 h), suggesting that IGF-I destabilizes mRNA. These data demonstrate that IL-1beta stimulates the transcription rate of the type II sPLA2 gene and gives rise to a very stable mRNA. In contrast, IGF-I decreases the half-life of the type II sPLA2 message.

Amino Acid Sequence↗

PubMed1997

Differential stimulation of cytosolic phospholipase A2 by bradykinin in human cystic fibrosis cell lines.

Tracheal epithelial cells and skin fibroblasts from different cystic fibrosis (CF) patients bearing the deltaF508 mutation of cystic fibrosis transmembrane conductance regulator (CFTR) released more arachidonic acid in response to bradykinin than do other CF and normal cells. Immortalized tracheal epithelial cell lines were used as models to study the mechanisms of this dysregulation. An 85 kD cytosolic phospholipase A2 (cPLA2) was found in these cells and bradykinin increased its binding to membranes of deltaF508 cells (CFT-2) but not to those of a double heterozygous CF cells (CFT-1), or of control cells (NT-1). The expression of G alpha(q)/11 protein was also increased in deltaF508 cells, with increased stimulation of phosphatidylinositol diphosphate-specific phospholipase C (PLC) by bradykinin, and an early, transient activation of mitogen-activated protein (MAP) kinase. As the binding of cPLA2 to membranes is Ca2+-dependent, the increased coupling to PLC could cause the hypersensitivity to bradykinin. Comparison of the effects of bradykinin to those observed with thapsigargin, an inhibitor of calcium reuptake, suggests that the increase of intracellular calcium is not the only mechanism involved in arachidonic acid release by bradykinin in deltaF508 cells. The lack of effect of calcium ionophore A23187 or TPA on arachidonic acid release from any of the cell lines suggested that activation needs a PKC-independent cPLA2 phosphorylation step, perhaps via MAP kinase activation. The binding of cPLA2 to membranes after bradykinin stimulation still occurred in CFT2 cells (deltaF508) homogenized in EDTA, suggesting that a membrane component plus increased intracellular calcium influenced cPLA2 anchoring to membranes. The defective processing of deltaF508 CFTR seems to increase cPLA2 stimulation by bradykinin, since the bradykinin-stimulated release of arachidonic acid is reversed by growing cells at 28 degrees C for 48 h. The deltaF508 mutation of CFTR appears to increase the stimulation of cPLA2 by Gq-mediated receptors in a PKC-independent and MAP kinase-dependent manner. Hence normal CFTR, or normally processed deltaF508 CFTR, inhibit cPLA2 stimulation. The greater reactivity of deltaF508 CFTR cells to inflammatory mediators might be part of the increased sensitivity of CF patients to lung inflammation.

Bradykinin↗

PubMed1996

Dual diagnosis: a treatment model for substance abuse and major mental illness.

The treatment of "dual diagnosis", co-occurring substance abuse and mental illness, calls for addressing two serious and often confounding problems. The authors introduce an expanded version of the transtheoretical model of change as formulated by J.O. Prochaska and C.C. DiClemente, and suggest that this new version offers a pragmatic approach to the conceptualization and treatment of dual diagnosis. The potential utility of the treatment model is presented through the authors' experiences in working with inner-city, chronic mentally ill individuals with substance abuse problems. Practical guidelines for dual diagnosis group therapy are discussed.

Chronic Disease↗

PubMed1990

[The prevention of bacterial endocarditis].

The paper examines the prevention of bacterial endocarditis in risk patients undergoing outpatient treatment. The hypothesis of possible bacteremia provoked by either diagnostic or therapeutic surgery should be carefully assessed. For this purpose antibiotic prophylaxis should be commenced, using different methods and doses according to the type of patient, in association with hygienic and behavioural norms which the specialist will recommend and monitor.

Anti-Bacterial Agents↗

PubMedDate not supplied

Determination of chloral hydrate and its metabolites (trichloroethanol and trichloracetic acid) in human plasma and urine using electron capture gas chromatography.

Capillary gas chromatography with electron capture detection is described for the quantification of chloral hydrate (CH) and is metabolites trichloroethanol (TCE) and trichloroacetic acid (TCA) in 0.1-1 mL of plasma samples. The method, with 2,2'-dichloroethanol (DCE) as internal standard, involved extraction of chloral hydrate and trichloroethanol with diethyl ether and methylation of trichloroacetic acid with 3-methyl-1-tolyltriazene (MTT), followed by diethyl ether extraction. The method has a detection limit of 5 ng/mL for CH and TCE and 10 ng/mL for TCA and also allows the determination of TCE-glucuronide in 0.1-1 mL of plasma samples. It exhibits good linearity and precision. The method was applied to samples of plasma from a neonate after a single dose of 40 mg/kg of chloral hydrate and from an adult after a single dose of 6.25 mg/kg.

Chloral Hydrate↗