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Biomedical subjects

M Legrand

Publications and source records attributed to M Legrand.

At least 19 recordsLinked to original sources
PubMed2006

[Colonic necrosis following a pancreatic pseudocyst embolization].

A 43-year-old man with chronic alcohol pancreatitis was admitted in our intensive care unit for an haemorrhagic shock. An abdominal CT-scan performed on admission showed bleeding from a vessel in a pancreatic pseudocyst. Initial treatment included intravenous fluids, transfusion, mechanical ventilation and vasopressive support. Percutaneous arterial embolization (PAE) of a bleeding right superior colon artery was performed with an initial good result. Nevertheless after initial clinical improvement, hypotension refractory to fluid management occurred. An abdominal CT-scan disclosed pneumatosis in right colon. A right hemicolectomy was performed. Histologic analysis confirmed ischemic colitis. The patient recovered and was discharged from the intensive care unit. Colitis necrosis after PAE for pancreatic pseudoaneurysm had never been described before. It should be suspected when haemodynamic instability occurs following PAE.

Adult↗
PubMed2005

Population pharmacokinetic analysis for nelfinavir and its metabolite M8 in virologically controlled HIV-infected patients on HAART.

AIMS: To describe the pharmacokinetics of nelfinavir and its main metabolite M8 in HIV-infected patients with a sustained virological response, to characterize the effect of covariates and to estimate inter- and intra-individual variability in the pharmacokinetics. METHODS: Three hundred and twenty concentrations of both nelfinavir and M8 were measured in 46 patients enrolled in the COPHAR 1-ANRS 102 study. Blood samples were taken at a first visit (one sample before drug administration and four samples at fixed times after) and at a second visit 1 to 3 months later (one before and one 3 h after drug administration). The data from both visits on nelfinavir and M8 were modelled jointly in all patients using a population approach. RESULTS: A one-compartment model with first-order absorption and elimination best described nelfinavir data, with an additional compartment incorporating a first order rate-constant describing the metabolism of the drug to M8. For nelfinavir, the apparent volume of distribution (V/F ) (95% confidence interval for the mean), was 309 l (185, 516), the absorption rate constant (k(a)) was 0.4 h(-1) (0.2, 0.8), and the apparent clearance (CL/F ) was 37.3 l h(-1) (32, 44). For M8, V(m) /(Fk(m)) and CL(m)/(Fk(m)) were 866 l h(-1) (351, 2161) and 1670 l (965, 2894), respectively. The interindividual variabilities were 34.9%, 34.3% and 62.2% for V/F, CL/F and CL(m)/(Fk(m)), respectively. The interoccasion variability was 27.8% for CL/F. The mean half-lives were 05.38 h and 00.44 h for nelfinavir and M8, respectively. Significant but opposite effects of comedication with zidovudine were found on nelfinavir CL/F and M8 CL(m)/(Fk(m)), but they were not considered to be clinically relevant. CONCLUSIONS: A joint model was found to describe adequately nelfinavir and M8 concentrations and was used to estimate pharmacokinetic parameters for M8. The model can be used to build reference pharmacokinetic profiles for therapeutic drug monitoring of the drug.

Adult↗
PubMed2003

P-glycoprotein in blood CD4 cells of HIV-1-infected patients treated with protease inhibitors.

OBJECTIVE: Many factors are involved in the virological failure of antiretroviral treatments such as low pharmacological plasma levels of drugs, poor adherence to therapy and emergence of viral resistance. P-glycoprotein (P-gp) has been demonstrated to play a role in multidrug resistance in the therapy of solid tumours, haematological malignancies and Plasmodium falciparum infection. HIV-1 protease inhibitors (PIs) have been described to be substrates of P-gp. In vitro and in vivo studies performed in mice have demonstrated that P-gp may affect the oral bioavailability and intracellular accumulation of PIs. P-gps have been detected on peripheral CD4 blood cells in HIV-1-infected, but antiretroviral-naive patients. METHOD: We quantified P-gp expression and performed functional tests of P-gp activity in the CD4 cells in HIV-1-infected patients, with and without virological failure, treated with PIs, and in healthy patients (control group). RESULT: Out of the 18 HIV-infected patients studied, P-gp expression and function were found in the CD4 cells of six patients (four of 10 without, and two of eight with virological failure). Out of the 43 healthy patients studied, P-gp expression and function were found in the CD4 cells of 11 patients (26%). We found P-gp in peripheral CD4 cells of patients treated with PIs, with and without virological failure, within the same frequency than in antiretroviral naive patients or than in non HIV-infected patients. CONCLUSIONS: P-gp expression in peripheral CD4 blood cells does not seem to be enhanced by PI treatment and does not seem to be linked particularly to virological failures. These facts do not preclude of the role of P-gp on PI absorption or efficacy in other compartments of the body such as gut, lymph nodes or brain in HIV-1 PI-treated patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Laparoscopic liver resection of benign liver tumors.

OBJECTIVE: The objective of this study was to assess the feasibility, safety, and outcome of laparoscopic liver resection for benign liver tumors in a multicenter setting. BACKGROUND: Despite restrictive, tailored indications for resection in benign liver tumors, an increasing number of articles have been published concerning laparoscopic liver resection of these tumors. METHODS: A retrospective study was performed in 18 surgical centres in Europe regarding their experience with laparoscopic resection of benign liver tumors. Detailed standardized questionnaires were used that focused on patient's characteristics, clinical data, type and characteristics of the tumor, technical details of the operation, and early and late clinical outcome. RESULTS: From March 1992 to September 2000, 87 patients suffering from benign liver tumor were included in this study: 48 patients with focal nodular hyperplasia (55%), 17 patients with liver cell adenoma (21%), 13 patients with hemangioma (15%), 3 patients with hamartoma (3%), 3 patients with hydatid liver cysts (3%), 2 patients with adult polycystic liver disease (APLD) (2%), and 1 patient with liver cystadenoma (1%). The mean size of the tumor was 6 cm, and 95% of the tumors were located in the left liver lobe or in the anterior segments of the right liver. Liver procedures included 38 wedge resections, 25 segmentectomies, 21 bisegmentectomies (including 20 left lateral segmentectomies), and 3 major hepatectomies. There were 9 conversions to an open approach (10%) due to bleeding in 45% of the patients. Five patients (6%) received autologous blood transfusion. There was no postoperative mortality, and the postoperative complication rate was low (5%). The mean postoperative hospital stay was 5 days (range, 2-13 days). At a mean follow-up of 13 months (median, 10 months; range, 2-58 months), all patients are alive without disease recurrence, except for the 2 patients with APLD. CONCLUSIONS: Laparoscopic resection of benign liver tumors is feasible and safe for selected patients with small tumors located in the left lateral segments or in the anterior segments of the right liver. Despite the use of a laparoscopic approach, selective indications for resection of benign liver tumors should remain unchanged. When performed by expert liver and laparoscopic surgeons in selected patients and tumors, laparoscopic resection of benign liver tumor is a promising technique.

Adolescent↗
PubMed2001

Identification of the enzymatic active site of tobacco caffeoyl-coenzyme A O-methyltransferase by site-directed mutagenesis.

Animal catechol O-methyltransferases and plant caffeoyl-coenzyme A O-methyltransferases share about 20% sequence identity and display common structural features. The crystallographic structure of rat liver catechol O-methyltransferase was used as a template to construct a homology model for tobacco caffeoyl-coenzyme A O-methyltransferase. Integrating substrate specificity data, the three-dimensional model identified several amino acid residues putatively involved in substrate binding. These residues were mutated by a polymerase chain reaction method and wild-type and mutant enzymes were each expressed in Escherichia coli and purified. Substitution of Arg-220 with Thr resulted in the total loss of enzyme activity, thus indicating that Arg-220 is involved in the electrostatic interaction with the coenzyme A moiety of the substrate. Changes of Asp-58 to Ala and Gln-61 to Ser were shown to increase K(m) values for caffeoyl coenzyme A and to decrease catalytic activity. Deletions of two amino acid sequences specific for plant enzymes abolished activity. The secondary structures of the mutants, as measured by circular dichroism, were essentially unperturbed as compared with the wild type. Similar changes in circular dichroism spectra were observed after addition of caffeoyl coenzyme A to the wild-type enzyme and the substitution mutants but not in the case of deletion mutants, thus revealing the importance of these sequences in substrate-enzyme interactions.

Adenine↗
PubMed2001

Pharmacodynamics and pharmacokinetics of single nasal (5 mg and 10 mg) and oral (50 mg) doses of ephedrine in healthy subjects.

OBJECTIVE: To determine the cardiovascular, subjective effects and potential of abuse liability of single dose (-) ephedrine (E) administered orally (50 mg) or intranasally (10 mg and 5 mg). METHODS: Sixteen healthy Caucasian men with no history of drug/alcohol/nicotine abuse or dependence received intranasal single doses of E 5 mg, 10 mg and oral doses of 50 mg and placebo in a double-blind, double-dummy, crossover study. Dependent measures included assessment of subjective feelings by Addiction Research Centre Inventory (ARCI). Profile of Mood States (POMS). visual analogue scales (VAS); "drug liking", "any drug effect", subjective quality of sleep and blood pressure and heart rate. Plasma E concentrations were also determined. RESULTS: (-) E increased supine systolic, diastolic blood pressure (P < 0.01). Changes in supine systolic blood pressure (areas under the 8 h of the experimental sessions) were -59 +/- 47 mmHgh with placebo, -59 +/- 57 mmHg-h with E5 mg by the nasal route, -18 +/- 48 mmHg x h with E 10 mg by the nasal route and 13 +/- 58 mmHgh with E 50 mg by the oral route (P<0.001). (-) E-induced orthostatic hypotension (P < 0.01) (maximal systolic blood pressure drop: E 50 mg 14 +/- 10 mmHg, P < 0.03; E 10 mg 11 +/- 6 mmHg, P = 0.08 compared with placebo) and resulted in decreased tiredness (placebo -2 +/- 39 mm x h, E 5 mg -17 +/- 39 mm x h, E 10 mg -30 +/- 42 mm x h, E 50 mg -24 +/- 35 mm x h; P < 0.03). E did not modify ARCI subscales--in particular the "amphetamine" subscale--but showed a tendency for drug liking (P= 0.09). On the "any drug effect" questionnaire, subjects could identify drug effect (P=0.007). Maximal plasma E concentration (Cmax) and areas under the curves for up to 8 h were proportional to the doses. Elimination half-life was approximately 6 h. A clockwise hysteresis was observed for systolic blood pressure in all but one subject with E 50 mg by the oral route. CONCLUSION: E even at low doses and by the nasal route can decrease tiredness in healthy persons; this is accompanied by a substantial increase in blood pressure and orthostatic hypotension exposing individuals in case of intensive physical exercise to cardiovascular risks. No clear evidence of abuse liability in healthy drug naive subjects was observed.

Administration, Intranasal↗
PubMed2001

Repression of O-methyltransferase genes in transgenic tobacco affects lignin synthesis and plant growth.

Among the different enzymatic steps leading to lignin biosynthesis, two methylation reactions introduce the methyl groups borne by guaiacyl (G) and syringyl (S) units. Tobacco possesses a complex system of methylation comprising three classes of CCoAOMTs (caffeoyl-CoA-O-methyltransferases) and two classes of COMTs (caffeic acid OMTs). Antisense plants transformed with the CCoAOMT sequence alone or fused to COMT I sequence have been produced and compared to ASCOMT I plants in order to study the specific role of each OMT isoform in lignin biosynthesis, plant development and resistance to pathogens. Tobacco plants strongly inhibited in OMT activities have been selected and analyzed. Whereas antisense COMT I plants exhibited no visual phenotype, CCoAOMT repression was shown to strongly affect the development of both single and double transformants: a reduction of plant growth and the alteration of flower development were observed in the most inhibited plants. Lignin analysis performed by Klason and thioacidolysis methods, showed a decrease in the lignin quantity and changes in the lignin structure of ASCCoAOMT and ASCCoAOMT/ASCOMT I transgenics but not in ASCOMT I plants. Inhibition of COMT I in single as well as in double transformed tobacco was demonstrated to decrease S unit synthesis and to provoke the accumulation of 5-hydroxyguaiacyl lignin units. ASCCoAOMT/ASCOMT I tobacco was affected in lignin amount and composition, thus demonstrating additive effects of inhibition of both enzymes. The changes of lignin profiles and the phenotypical and molecular alterations observed in the different transgenic lines were particularly prominent at the later stages of plant development.

Lignin↗
PubMed2001

Reassessment of qualitative changes in lignification of transgenic tobacco plants and their impact on cell wall assembly.

In tobacco plants the effect of antisense down-regulation of various genes encoding enzymes of the monolignol biosynthetic pathway resulted in quantitative and qualitative changes in lignin distribution and in diverse alterations of the secondary wall assembly of modified tobacco plants. Total lignin content, composition in syringyl and guaiacyl units, and absolute proportions of condensed and non-condensed substructures occurring in the cell walls, were differentially modified according to the repressed gene. Immunocytochemical characterisation and visualisation of the distribution of condensed and non-condensed lignin substructure epitopes in transmission electron microscopy (TEM) revealed that some transformations entailed profound and specific alterations in the secondary wall biogenesis. Correlation between micro-morphological cell wall alterations and semi-quantitative immuno-analysis of the topochemical distribution of lignin sub-units suggests that the mode of polymerisation of monolignols into non-condensed units, favoured by the microfibril matrix of the secondary wall, plays an important part in the lignified cell wall assembly.

Cell Wall↗
PubMed2001

Simultaneous down-regulation of caffeic/5-hydroxy ferulic acid-O-methyltransferase I and cinnamoyl-coenzyme A reductase in the progeny from a cross between tobacco lines homozygous for each transgene. Consequences for plant development and lignin synthesis.

Inhibition of specific lignin biosynthetic steps by antisense strategy has previously been shown to alter lignin content and/or structure. In this work, homozygous tobacco (Nicotiana tabacum) lines transformed with cinnamoyl-coenzyme A reductase (CCR) or caffeic acid/5-hydroxy ferulic acid-O-methyltransferase I (COMT I) antisense sequences have been crossed and enzyme activities, lignin synthesis, and cell wall structure of the progeny have been analyzed. In single transformed parents, CCR inhibition did not affect COMT I expression, whereas marked increases in CCR activity were observed in COMT I antisense plants, suggesting potential cross talk between some genes of the pathway. In the progeny, both CCR and COMT I activities were shown to be markedly decreased due to the simultaneous repression of the two genes. In these double transformants, the lignin profiles were dependent on the relative extent of down-regulation of each individual enzyme. For the siblings issued from a strongly repressed antisense CCR parent, the lignin patterns mimicked the patterns obtained in single transformants with a reduced CCR activity. In contrast, the specific lignin profile of COMT I repression could not be detected in double transformed siblings. By transmission electron microscopy some cell wall loosening was detected in the antisense CCR parent but not in the antisense COMT I parent. In double transformants, immunolabeling of non-condensed guaiacyl-syringyl units was weaker and revealed changes in epitope distribution that specifically affected vessels. Our results more widely highlight the impact of culture conditions on phenotypes and gene expression of transformed plants.

Aldehyde Oxidoreductases↗
PubMed2001

Norepinephrine kinetics in freely moving rats.

Norepinephrine (NE) kinetics were investigated in freely moving (FM) and minimally stressed (MS) rats with the isotope dilution technique. 1) The mean NE spillover rate (NE-SOR) was 79 +/- 6 ng. kg(-1). min(-1), and the mean NE metabolic clearance rate (NE-MCR) 179 +/- 9 ml. kg(-1). min(-1) (n = 31). Thus the NE kinetics in FM and MS rats are much faster than in human beings, probably related to a higher sympathetic drive. 2) Whether the magnitude of NE-MCR is related to the level of plasma NE concentration was investigated. No significant correlation was calculated between plasma NE concentration and NE-MCR in 31 control rats. When plasma NE concentration was varied during either acute or chronic infusion of exogenous NE, NE-MCR remained unchanged as long as animal hemodynamics were not altered. When plasma NE concentration was high enough to increase mean arterial pressure (MAP), NE-MCR was decreased. However, when MAP was increased within comparable magnitude, NE-MCR was decreased during NE and increased during epinephrine (Epi) infusion. Thus the existence of an alpha-/beta-adrenergic mechanism involved in the regulation of NE-MCR independent of known hemodynamic mechanisms is suggested. 3) The "epinephrine hypothesis" was revisited in FM and MS rats. At variance with humans, very high plasma Epi concentrations have to be induced to increase NE-SOR in resting rats. Furthermore, NE-MCR was also increased, accounting for the nonsignificant increase of plasma NE concentration. Within the range of Epi concentrations with no effect on NE-SOR, an increase of NE release was revealed when the presynaptic alpha(2)-adrenoreceptors were partially inhibited by yohimbine. This suggests the existence of a second epinephrine hypothesis.

Animals↗
PubMed2001

Pharmacokinetics of abacavir in HIV-1-infected patients with impaired renal function.

BACKGROUND: Abacavir is a potent, novel 2'-deoxyguanosine analogue reverse transcriptase inhibitor (NRTI) which effectively suppresses HIV-1 replication. To date, there is no pharmacokinetic study in patients with renal impairment. METHODS: Five HIV-1-infected patients with various degrees of renal dysfunction (creatinine clearance 60, 40, 25, 20 and 1 haemodialyzed patient) were evaluated after being treated for at least 2 months with multi-antiretroviral therapy including abacavir. After an overnight fast, the subjects received their abacavir dosage (600 or 300 mg). Blood samples were withdrawn and plasma concentrations determined. A nonparametric pharmacokinetic analysis was then performed. The dialysability of abacavir was also evaluated. RESULTS: Time of maximum plasma concentration (T(max)) was constant among the subjects with a mean value of 0.7 +/- 0.27 h (range 0.33-1). Maximum plasma concentration (C(max)) ranged from 2.76 to 4.15 mg/l (mean 3.44 +/- 0.59). The elimination half-life ranged from 1.31 to 2.67 h (mean 2.08 +/- 0.51). Normalized C(max)/dose ranged from 0.007 to 0.014 mg/l and normalized AUC(0-inf)/dose ranged from 0.014 to 0.035 mg.h/l. In haemodialysis the dialysance was 60-80 ml/min with a fractional drug removal of 24% during a 4-hour haemodialysis session with a high permeability membrane. DISCUSSION: In our patients, absorption, elimination and distribution phases were not altered by renal insufficiency. Furthermore, our pharmacokinetic data are similar to those obtained in patients with normal renal function. Therefore, dosage adjustment is not necessary in patients with renal insufficiency. In haemodialyzed patients, treatment can be administered independently to the dialysis session because of the negligible elimination of abacavir in the dialysate.

Administration, Oral↗
PubMed2000

Determination of twelve antiretroviral agents in human plasma sample using reversed-phase high-performance liquid chromatography.

A new high-performance liquid chromatography (HPLC) with UV detection assay was developed for the simultaneous determination of protease inhibitors (PIs), nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs, NNRTIs) using a single 1-ml plasma samples. A solid-liquid extraction procedure without internal standard was coupled with two separate reversed-phase HPLC systems; one for the determination of amprenavir, efavirenz, indinavir, nelfinavir, ritonavir, saquinavir (run time=32 min) and one for the determination of abacavir, didanosine, lamivudine, stavudine, nevirapine, zidovudine (run time=40 min). The first requires a mobile phase containing sodium phosphate buffer+ion pair-acetonitrile (50:50, v/v) through a C18 Symmetry column (250x4.6 mm I.D., 5 microm particle size), using variable wavelengths (241, 254 and 261 nm). The second system requires three mobile phases (potassium phosphate buffer+ion pair-acetonitrile) for different elution through a C18 Symmetry Shield column (250x4.6 mm I.D., 5 microm), using a single wavelength (260 nm). Peak-areas are linear; correlation coefficients are better than 0.998 for all compounds, with both inter- and intra-day relative standard deviations lower than 12%. Extraction recoveries are higher than 93% for PIs and NNRTIs and higher than 70% for NRTIs. The method is specific and sensitive and was used to determine trough and peak levels of antiretroviral drugs in HIV infected patients under various combinations of RTIs and PIs.

Anti-HIV Agents↗