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Biomedical subjects

J Barré

Publications and source records attributed to J Barré.

At least 19 recordsLinked to original sources
PubMed2003

Pharmacokinetic profile of a modified release formulation of trimetazidine (TMZ MR 35 mg) in the elderly and patients with renal failure.

Objectives - To study the effect of age and renal function on the pharmacokinetic profile of a modified release tablet of trimetazidine (TMZ MR 35 mg) administered twice daily.Methods- Study 1: Twelve healthy elderly subjects (CL(creat) 72+/-8 ml/min, 72+/-4 years mean+/-SD) and eight young volunteers (CL(creat) 134+/-18 ml/min, 25+/-8 years) received TMZ MR 35 mg b.i.d. (eight doses). Study 2: eight patients with severe renal failure (CL(creat.) 17+/-5 ml/min, 54+/-10 years), five patients with moderate renal failure (CL(creat.) 39+/-6 ml/min, 54+/-15 years) and eight volunteers (CL(creat.) 104+/-17 ml/min, 53+/-9 years) received TMZ MR 35 mg b.i.d. (patients: ten doses, volunteers: eight doses). Serial blood and urine samples were obtained following administration of the last dose in each study. TMZ plasma and urine concentrations were determined by gas chromatography (NPD-detector). The resulting data were analysed using standard non-compartmental pharmacokinetic methods.Results- Study 1: Elimination half-life of TMZ was significantly longer and renal clearance significantly lower in the elderly subjects. Study 2: In patients with either moderate or severe renal failure, exposure (AUC(0-24)) was significantly increased and renal clearance (CL(R)) was significantly decreased. Significant correlations were observed between CL(creat) and CL(R) (r=0.94) and between CL(creat) and AUC(0-24) (r=-0.94). Conclusion - With repeated administration of TMZ MR 35 mg b.i.d., a decrease in CL(creat) is directly related to a decrease in CL(R) and results in an increase in exposure to TMZ.

Adolescent↗
PubMed2001

Inequivalence of ensembles in a system with long-range interactions.

We study the global phase diagram of the infinite-range Blume-Emery-Griffiths model both in the canonical and in the microcanonical ensembles. The canonical phase diagram shows first-order and continuous transition lines separated by a tricritical point. We find that below the tricritical point, when the canonical transition is first order, the phase diagrams of the two ensembles disagree. In this region the microcanonical ensemble exhibits energy ranges with negative specific heat and temperature jumps at transition energies. These results can be extended to weakly decaying nonintegrable interactions.

Journal Article↗
PubMed2000

Expression of the genetic variants of human alpha-1-acid glycoprotein in cancer.

OBJECTIVES: We have investigated the AAG and its genetic variants concentrations in plasma samples of 61 patients suffering from different types of cancers. DESIGN AND METHODS: The patients were shared out in three groups, breast, lung, and ovary cancers groups. AAG concentration was measured by an immunonephelometric method and the phenotype was determined, after desialylation of plasma by analytical isoelectric focusing. Detection of AAG variants was made by immunoblotting and their proportions were determined by laser densitometry analysis. A population of 74 healthy individuals served as controls. RESULTS: The plasma concentrations of AAG in the breast and lung cancer groups were 2.5 times increased, while in the ovary cancer group, the concentrations were 1.6 times increased. AAG concentrations in the cancer population ranged between 0.45 and 2.85 g/L (mean value 1.12 +/- 0.51 g/L). The proportions of the ORM1 and ORM2 variants were similar to those in the healthy population. In breast and lung cancer groups, the relative concentrations of genetic variants were increased more than 2.5 fold, whereas a 1. 6-fold increase was observed in the ovary cancer group. CONCLUSIONS: These results show that AAG plasma concentrations are increased in these types of cancers and that changes in the expression of the genetic variants of AAG could also occur according to the type of cancer.

Adult↗
PubMed2000

In vitro binding and partitioning of irinotecan (CPT-11) and its metabolite, SN-38, in human blood.

The binding of CPT-11 and SN-38 to human plasma proteins was studied by ultrafiltration at 37 degrees C and pH 7.4. In plasma, CPT-11 was 66-60% bound in the range 100-4000 ng/ml and SN-38 was 94-96% bound in the range 50-200 ng/ml. At these concentrations the plasma binding of CPT-11 was slightly saturable, but the plasma binding of SN-38 was concentration-independent. Albumin was the main carrier of CPT-11 and SN-38 in plasma. In blood, the binding of CPT-11 was moderate (80%), mainly to plasma proteins (47%) and erythrocytes (33%). The binding of SN-38 was high (99%) and most of SN-38 in blood was located in blood cells (approximately 66%) The simulation of a grade 3 hematotoxicity (according to National Cancer Institute's Common Toxicity Criteria grading) on the SN-38 blood distribution yielded an increase in fu (free fraction of drug in plasma) from 1.05 to 2.08 and a decrease in C(Bl)/C(P) from 1.66 to 1.14 (both resulting from a decreased cell binding).

Antineoplastic Agents, Phytogenic↗
PubMed1998

Role of bilirubin in the regulation of the total peroxyl radical trapping antioxidant activity of plasma in sickle cell disease.

Alpha-tocopherol and bilirubin antioxidant properties were evaluated in sickle cell disease. The total peroxyl radical trapping antioxidant activity of plasma (TRAP) was measured with a polarographic method using hemin as oxidative stress initiator. The TRAP was not correlated with plasma alpha-tocopherol concentration. The TRAP was correlated with plasma total bilirubin concentration [TRAP = 8.1 (total bilirubin) +363.7 (r = 0.67)] and the correlation was even better with the sum (alpha-tocopherol + total bilirubin) plasma concentration [TRAP = 9.1(alpha-tocopherol + total bilirubin)+ 170.5(r = 0.77)]. The alpha-tocopherol contribution in the antioxidant capacity of plasma was significant but bilirubin level acted as the limiting factor of plasma antioxidant capacity in sickle cell anemia. This result can be explained by the antioxidant property of bilirubin but also by coantioxidant activity towards oxidized alpha-tocopherol.

Anemia, Sickle Cell↗
PubMed1998

Plasma coenzyme Q10 concentrations in breast cancer: prognosis and therapeutic consequences.

BACKGROUND: Coenzyme Q10 or ubiquinone is a redox component of the respiratory chain, which may be involved in the pathogenesis of cancer. METHODS: In order to better understand the role of this vitamin in the pathogenesis of breast cancer, a clinical trial including 200 women hospitalized for the biopsy and/or the ablation of a breast tumor was conducted. Ubiquinone plasma concentrations were determined simultaneously with vitamin E plasma concentrations (as antioxidant reference) by HPLC. RESULTS: A coenzyme Q10 deficiency was noted both in carcinomas (80 patients) and non-malignant lesions (120 patients), while vitamin E concentrations were within the normal range. A correlation was shown between the intensity of the deficiency and the bad prognosis of the breast disease based on high TNM and SBR values or the lack of estrogen receptors. However, neither cathepsin D level nor adenopathy invasion was related to ubiquinone levels. CONCLUSIONS: Since prooxidants may promote tumorigenesis, ubiquinone supplementation in breast cancer could be relevant.

Adult↗
PubMed1997

Food increases the bioavailability of mefloquine.

OBJECTIVES: To assess the effect of food on the pharmacokinetics of the antimalarial mefloquine and its major plasma metabolite in healthy volunteers. METHODS: In an open, two-way cross-over study, 20 healthy male volunteers who had fasted overnight were randomised to receive a single oral dose of 750 mg mefloquine in the absence or presence of a standardised, high-fat breakfast, administered 30 min before drug administration. Blood samples were taken at specific times over an 8-week period. Plasma concentrations of mefloquine and its carboxylic acid metabolite were determined by high-performance liquid chromatography for pharmacokinetic evaluation. RESULTS: The parameters Cmax and AUC of both mefloquine and its metabolite were significantly (P < 0.05) higher under post-prandial conditions than under fasting conditions (mefloquine: mean Cmax 1500 vs 868 micrograms.l-1, mean AUC 645 vs 461 mg l-1.h; metabolite: Cmax 1662 vs 1231 micrograms.l-1, AUC 1740 vs 1310 mg l-1.h). The intersubject variability in Cmax and AUC of mefloquine was less than 30% (coefficient of variation). The time to peak plasma concentration of mefloquine was significantly shorter after food intake (17 vs 36 h). Compared with absorption in volunteers who had fasted, food did not alter t1/2 (mefloquine and its metabolite) and tmax (metabolite). CONCLUSION: Under the conditions of this study, food increases the rate and the extent of mefloquine absorption. It is reasonable to recommend that mefloquine be administered with food in travellers receiving chemoprophylaxis and in patients on recovery receiving curative treatment. In acutely ill patients, mefloquine should be taken as soon as possible and administration with or shortly after meals should be attempted as soon as feasible.

Administration, Oral↗
PubMed1996

Docetaxel serum protein binding with high affinity to alpha 1-acid glycoprotein.

The binding of docetaxel to human plasma proteins was studied by ultrafiltration at 37 degrees C and pH 7.4. Docetaxel was extensively (> 98%) plasma protein bound. At clinically relevant concentrations (1-5 micrograms/ml), the plasma binding was concentration-independent. Lipoproteins, alpha1-acid glycoprotein and albumin were the main carriers of docetaxel in plasma, and owing to the high interindividual variability of alpha1-acid glycoprotein plasma concentration, particularly in cancer, it was concluded that alpha1-acid glycoprotein should be the main determinant of docetaxel plasma binding variability. Drugs potentially coadministered with docetaxel (cisplatin, dexamethasone, doxorubicin, etoposide, vinblastine) did not modify the plasma binding of docetaxel. In blood, docetaxel was found to be mainly located in the plasma compartment (less than 15% associated to erythrocytes).

Antineoplastic Agents, Phytogenic↗
PubMed1996

Binding of disopyramide, methadone, dipyridamole, chlorpromazine, lignocaine and progesterone to the two main genetic variants of human alpha 1-acid glycoprotein: evidence for drug-binding differences between the variants and for the presence of two separate drug-binding sites on alpha 1-acid glycoprotein.

Human alpha 1-acid glycoprotein (AAG), a plasma drug transport protein, has three main genetic variants, the A variant and the F1 and S variants, which are encoded by two different genes. The binding of disopyramide, methadone, dipyridamole, chlorpromazine, lignocaine and progesterone to the two main gene products of AAG-the A variant and a mixture of the F1 and S variants (60% F1 and 40% S)-separated by chromatography from native commercial AAG, a mixture of almost equal proportions of the F1, S and A variants, was studied by equilibrium dialysis. A selective binding of disopyramide and methadone to the A variant and a preferential binding of dipyridamole to the F1S variant mixture were found. Lignocaine and chlorpromazine had a slight preference for binding to the A variant and to the F1S mixture, respectively, but progesterone showed no selectivity with regard to any of the variants of AAG. The differences in drug-binding demonstrated between the A variant and the F1S mixture confirmed those of a previous study, in which a selective binding of imipramine to the A variant and of warfarin and mifepristone to the F1S mixture have been found. These results indicate specific drug transport roles for each AAG variant, according to its separate genetic origin. The results of control binding experiments performed with (unfractionated) commercial AAG and the series of tested ligands concurred with that for the separate AAG variants, with respect to the proportion of the A variant (27%) and that of the F1 and S variants (73%) in the commercial protein. In addition, disopyramide, methadone, dipyridamole, chlorpromazine, lignocaine and progesterone were used in equilibrium dialysis displacement experiments to study interactions on binding sites labelled with imipramine for the A variant and with warfarin for the F1S variant mixture. The four latter ligands were found to competitively inhibit the binding of warfarin to the F1S variant mixture and all of them that of imipramine to the A variant. The ligands association constants to each AAG variant obtained from such inhibitory experiments were comparable to those determined in the direct binding studies. As the stochlometry of the interactions of the A variant and the F1S variants, respectively, with their specific ligands was approximately one (1), it was concluded that these ligands bind to each of these variants via a single common binding site. These results indicate that the AAG molecule would have for its ligands at least two separate binding sites, showing different specificity and localization, and not one site, as it is generally assumed. The possible pharmacological and clinical consequences of the binding results with the separate AAG variants are discussed.

Binding, Competitive↗
PubMed1996

[Locoregional anesthesia for injuries of the lower limbs].

Isolated lower limb injuries are very common; difficulties for emergency anaesthesia may come from full stomach and drug interferences. The outcome of geriatric-fractured hip is influenced neither by a preoperative delay shorter than 48 hours, nor by the choice of anaesthetic technique; Nevertheless the use of acrylic cement is associated with an increased early mortality rate in hemiarthroplasties. Regional anaesthesia is the best choice for stable patients with a limited peripheral injury; The technique must be adapted to the pain induced by fracture; sitting position is useful for puncture. Spinal anaesthesia using 0.5% plain bupivacaine produces a block quickly achieved, not influenced by posture, allowing surgical installation and procedures. Postoperative analgesia using local anaesthetics may obscure symptoms of compartment syndrome which occasionally complicate tibial and femoral nailing.

Age Factors↗
PubMed1995

Methylprednisolone infusion during acute exacerbation of MS: plasma and CSF concentrations.

Plasma and CSF concentrations of methylprednisolone (MP), after a high-dose intravenous administration (1,500 mg) prescribed to patients presenting acute exacerbation of multiple sclerosis, were measured. A plasma pharmacokinetic study with 1 CSF sample was performed in 9 patients and 4 other patients had a single plasma sample at the time of lumbar puncture. MP plasma kinetics were similar between patients. Pharmacokinetic parameters were very close to previous published values obtained in normal volunteers or patients with rheumatoid disease. Passage of MP into the CSF was delayed since mean plasma/CSF ratio dropped dramatically from 150 at the 2nd h to 25 at the 3rd h after starting infusion. CSF concentrations of MP were high with a mean reaching 522 micrograms/l at the 6th h. The high levels of CSF concentrations suggest that MP may have powerful pharmacological effects within the CNS. No correlation was found between CSF concentration and the clinical response to steroid therapy. The issues related to previous data on clinical, biological and radiological effects of high-dose intravenous MP are discussed in the light of our results.

Adult↗
PubMed1993

[Intraoperative posture in the surgery of lumbar disk hernia].

For surgery of the lumbar disc, with a posterior route, the patient is placed either in a prone, or a knee-chest, or a lateral position. They aim at facilitating the surgical access in decreasing local bleeding and collapsing the dural sheath. This benefit, as a result of the maintenance of the pressure in the epidural venous system at a low level, is obtained through the absence of any abdominal compression as well as the posture. In the prone position, the abdominal compression and the increase of the physiologic lordosis impair the systemic venous return and carry the risk of cardiac arrest. In addition to these adverse effects, the conventional knee-chest position increases the haemodynamic repercussions in modifying the distribution of blood volume and increasing the potential risk of mediastinal compression and air embolism. The lateral position generates only minor haemodynamic modifications, except in the obese. However it is difficult to stabilize the patients' position and to maintain the alignment of the spine. Therefore it is used the less one. The postural risks of all three positions are numerous and include mainly the compression of nerves, vessels and skin. Finally the selection of the position depends basically on morphological criteria and the adaptative capacities of the patient. The optimal position is the one offering a low pressure level in the spinal venous system, while maintaining the venous return.

Anesthesia, General↗
PubMed1993

Effects of plasma lipid levels on blood distribution and pharmacokinetics of cyclosporin A.

The present study attempted to characterize the distribution of cyclosporin A (CsA) among the lipoprotein fractions, very-low-, intermediate-, low-, and high-density (VLDL, IDL, LDL, and HDL, respectively) in the plasma of patients awaiting heart transplantation and the influence of plasma lipid constituents on the pharmacokinetics of CsA. Major fractions of a therapeutic concentration of CsA were found in HDL and in LDL. In addition, plasma lipid concentrations (total cholesterol, triglycerides, phospholipids, VLDL-cholesterol--TC, TG, PL, VLDLc, respectively) are positively correlated with the CsA distribution within the LDL fraction, and negatively correlated with the CsA distribution within the HDL fraction. Thus, the percentage of CsA in each type of lipoproteins was shown to vary with the lipid levels among individuals. A significant negative correlation was found between apparent distribution volume at steady state (Vss) in plasma and TC, PL, and LDLc and between the area under the curve measured in blood (AUCB) for whole blood and PL.

Adult↗
PubMed1993

Dextromethorphan O-demethylation and dextrorphan glucuronidation in a French population.

The dextromethorphan (DMP) O-demethylation and the dextrorphan (DRP) glucuronidation distributions were studied in 120 French Caucasian subjects. After a single 25 mg DMP oral administration, DMP, free and total DRP concentrations were measured in 8h-urine collection, using an HPLC technique with fluorescent detection. The DMP and free DRP concentrations ratio, in log form, was used to estimate the oxidative demethylation phenotype of the subjects. Two different populations were found. The first one consisted of the extensive metabolizers (90.8%, 95% confidence interval from 85.6 to 95.9%) and the second one consisted of poor metabolizers (9.2%, 95% confidence interval from 4.0 to 14.4%). The antimode value of the distribution was estimated at approximately 0.7 corresponding to a ratio of 5. Moreover, this ratio was compared to the DMP and total DRP concentrations ratio, usually defined to DMP O-demethylation phenotyping. On the other hand, the glucuronide DRP concentration was calculated by subtracting the free DRP concentration from the total DRP concentration. Consequently, the free DRP and glucuronide DRP concentrations ratio was also used to estimate the DRP glucuronidation in the present population. This ratio in log form reflected the UDP-glucuronyltransferase(s) capacity(ies). This log ratio appeared to be normally distributed in the population studied. These results show that log DMP/free DRP ratio can be used, as well as log DMP/total DRP ratio, to determine the oxidative phenotype of subjects and that the DRP conjugation does not exhibit any apparent genetic polymorphism.

Administration, Oral↗
PubMed1992

pH titration curves of the desialylated human alpha 1-acid glycoprotein variants by combined isoelectrofocusing-electrophoresis: utilization in the development of a fractionation method for the protein variants by chromatography on immobilized metal affinity adsorbent.

Using a two-dimensional isoelectrofocusing (IEF)-electrophoresis technique, the pH titration curves of the three main desialylated variants (F1, S and A) of human alpha 1-acid glycoprotein (AAG) were studied to assist in the development of a fractionation method for the AAG variants. For this purpose, different AAG samples, each corresponding to one of the three main phenotypes of the protein (F1S/A, F1/A and S/A), were first purified by chromatographic separation of individual human plasma samples on immobilized Cibacron Blue F3G-A. The purified AAG samples were then disialylated and their heterogeneity was checked by analytical IEF. The pH-mobility curves of the desialylated AAG samples were displayed in polyacrylamide gel slabs, under a constant set of experimental conditions, by carrying out electrophoresis of the protein samples perpendicularly to two stationary pH gradients: a large gradient (pH 3.5-9.5) and a narrow gradient (pH 5-8). The curves showed that all the desialylated variants of AAG exhibited small charge differences and moved closely together between about pH 3.5-5.5 and pH 7.5-9.5. However, the variants were found to show microheterogeneity in their total charge between about pH 5.5 and 7.5 due to the titrated ionizable groups involved along this pH zone. This microheterogeneity was assumed to be accounted for by the existence of differences between the titratable histidyl residues of the AAG variants. Consequently, the interactions of the variants with immobilized transition metal ions were studied at pH 7, using affinity chromatography on an iminodiacetate Sepharose-Cu(II) gel. It was found that the A variant was strongly bound by immobilized Cu(II) ions, whereas the F1 and S variants interacted non-specifically with the immobilized ligand. This finding allowed the development of a rapid and effective fractionation method for desialylated AAG into its A and F1 or S variants, depending on the AAG phenotype, by chromatography on an immobilized affinity Cu(II) adsorbent. The quantitative relationships between immobilized Cu(II) ions and desialylated AAG (the apparent association constant and gel protein-binding capacity) were also determined using a non-chromatographic equilibrium binding technique.

Chromatography, Affinity↗