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Biomedical subjects

P Arnaud

Publications and source records attributed to P Arnaud.

At least 37 records · Page 2Linked to original sources
PubMed2001

A single dose of methadone inhibits cytochrome P-4503A activity in healthy volunteers as assessed by the urinary cortisol ratio.

AIMS: To examine the effect of a single oral dose of methadone on cytochrome P450 (CYP) 3A activity using the urinary 6beta-hydroxycortisol to cortisol ratio (UCR) as a marker of CYP3A activity. METHODS: A single oral dose (0.2 mg kg-1) of rac-methadone was administered to eight healthy female volunteers. Frequent blood samples and all urine over seven time periods was collected for 96 h following dosing. The UCR and the concentration of the major CYP3A metabolite of methadone, EDDP, were measured in urine. Methadone enantiomer concentrations were determined in plasma and urine. All quantifications were performed by validated high performance liquid chromatography assays. RESULTS: In all volunteers a significant decline of the UCR from immediately predose values was observed at the 4-8 and 8-12 h collection periods (P < 0.05, 95% CI for the differences: 0.4,16 and 0.6,16, respectively) with a return to immediately predose values after 2-3 days, suggesting methadone was an inhibitor of CYP3A. The UCR was found to be significantly correlated with the amount of EDDP excreted in the urine and with the area under the plasma concentration vs time profile for total (R + S) methadone, supporting in vitro data that CYP3A is primarily responsible for EDDP formation and has a significant influence on methadone disposition. CONCLUSIONS: Methadone appears to be a CYP3A inhibitor in vivo following a single oral dose and measurements of the urinary cortisol ratio appear to be a useful index to follow this inhibition.

Analysis of Variance↗
PubMed2001

Analysis of the SINE S1 Pol III promoter from Brassica; impact of methylation and influence of external sequences.

Transcription is an important control point in the transposable element mobilization process. To better understand the regulation of the plant SINE (Short Interspersed Elements) S1, its promoter sequence was studied using an in vitro pol III transcription system derived from tobacco cells. We show that the internal S1 promoter can be functional although upstream external sequences were found to enhance this basal level of transcription. For one putative 'master' locus (na7), three CAA triplets (in positions -12, -7 and -2) and two overlapping TATA motifs (in positions -54 to -43) were important to stimulate transcription. For this locus, two transcription initiation regions were characterized, one centered on position + 1 (first nucleotide of the S1 element) and one centered on position - 19 independently of the internal motifs. The CAA triplets only influence transcription in + 1 and work in association with the internal motifs. We show that methylation can inhibit transcription at the na7 locus. We also observe that S1 RNA is cleaved in a smaller Poly (A) minus product by a process analogous to the maturation of mammalian SINEs.

Base Sequence↗
PubMed2001

Pharmacokinetics and pharmacodynamics of methadone enantiomers after a single oral dose of racemate.

BACKGROUND: The pharmacokinetics and dynamics of methadone are characterized by high interindividual variability. This study aimed to examine a number of factors that may contribute to this variability. METHODS: Eight healthy drug-free women were administered 0.2 mg/kg of R,S-methadone orally. The concentrations of methadone's enantiomers in plasma and urine were monitored for 96 hours. Vital signs, blood biochemical parameters, and pupillary diameter were monitored frequently during this period. Cytochrome P450 3A (CYP3A) activity and alpha1-acid glycoprotein (alpha1-AGP) concentrations and phenotypes were determined. Pharmacokinetic and pharmacodynamic modeling was used to assess the influence of the above-mentioned covariables on methadone enantiomer disposition and actions. RESULTS: The pharmacokinetic profile of the active enantiomer of methadone, R -methadone, showed a relatively normal distribution with 38% to 90% of the interindividual variability in modeled pharmacokinetic parameters being explained by their individual variability in CYP3A activity, the cumulative amount of the main CYP3A4 metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrolidine, excreted in the urine, the fraction unbound in plasma, and the alpha1-AGP orosomucoid 2 (ORM2) variant plasma concentration. S-Methadone showed an idiosyncratic distribution with largely unpredictable pharmacokinetics. Pupillary constriction response was highly variable between individuals. CONCLUSIONS: The disposition of the active enantiomer, R -methadone, can be predicted in part by CYP3A activity and protein binding to alpha1-AGP (ORM2), whereas S-methadone disposition is not well explained by the factors examined in this study. Central nervous system effects were difficult to interpret on the basis of plasma R-methadone pharmacokinetics.

Administration, Oral↗
PubMed2000

Stability assessment of ketoconazole in aqueous formulations.

Ketoconazole is an imidazole antifungal agent. It has a wide antifungal spectrum and possesses some antibacterial activity. In inappropriate formulations, especially in aqueous media, ketoconazole molecules may be unsteady. The stability of ketoconazole in aqueous media was assessed as a function of pH, antioxidant and ketoconazole concentrations. It was found that ketoconazole was least stable at pH 1 among the pH values studied (pH 1-9). Since the major degradation pathway was specific acid catalysis, based upon the transition-state theory, the entropy (DeltaS) of the activation was calculated and found to be negative indicating that the activated complex was more constrained than the individual species. The free energy of activation (DeltaG) was estimated to be 30 kcal mol(-1). The viscosity of the formulation was found to be more stable at high pH because carbopol is stable at basic pH and protected ketoconazole. It appears that the amount of ketoconazole in the formulation has a low influence on the degradation mechanisms. The increase of the butylated hydroxytoluene antioxidant levels from 0.05 to 0.4%, adversely affected the stability of ketoconazole. In conclusion, the expected shelf life of the final ketoconazole formulation (pH 7, 0.1% butylated hydroxytoluene) was 15 months.

Antifungal Agents↗
PubMed2000

Stereospecific versus nonstereospecific assessments for the bioequivalence of two formulations of racemic chlorpheniramine.

Chlorpheniramine (chlorphenamine, CPAM) is a racemic antihistaminic H1 drug containing two enantiomers. The aim of this study was to assess the bioequivalence of two formulations (reference and Vietnamese-tested formulation) of racemic chlorpheniramine combined with phenylpropanolamine in an open-labeled, randomized, crossover two-period study, after administration of 8 mg of racemic chlorpheniramine in 12 healthy Vietnamese subjects. First, dissolution of both formulations was tested in vitro according to USP requirements. Then the 12 subjects received both formulations after an overnight fast and a 7-day wash-out period. Plasma samples were collected up to 168 h. Plasma concentrations of total chlorpheniramine and its individual enantiomers were determined with a validated chiral HPLC method and pharmacokinetic parameters were estimated using model-independent analysis. For the reference formulation, Cmax and AUC values were higher for (+)S-chlorpheniramine ((+)S-CPAM) compared to (-)R-chlorpheniramine ((-)R-CPAM) (13.3 vs. 6.8 ng/ml and 409 vs. 222 ng/ml/h, respectively) while Clt/F and Vd/F were lower (9.8 vs. 17.6 l/h and 321 vs. 627 l, respectively). No difference was observed for Tmax, t(1/2), and MRT. Pharmacokinetic parameters were similar for the reference and the Vietnamese-tested formulation. Bioequivalence was assessed by Schuirmann test, as recommended by the current FDA and European Community criteria. Dissolution tests showed that both formulations were equivalent. A nonstereospecific, but not a stereospecific, approach indicated bioequivalence between the formulations.

Adult↗
PubMed2000

SINE retroposons can be used in vivo as nucleation centers for de novo methylation.

SINEs (short interspersed elements) are an abundant class of transposable elements found in a wide variety of eukaryotes. Using the genomic sequencing technique, we observed that plant S1 SINE retroposons mainly integrate in hypomethylated DNA regions and are targeted by methylases. Methylation can then spread from the SINE into flanking genomic sequences, creating distal epigenetic modifications. This methylation spreading is vectorially directed upstream or downstream of the S1 element, suggesting that it could be facilitated when a potentially good methylatable sequence is single stranded during DNA replication, particularly when located on the lagging strand. Replication of a short methylated DNA region could thus lead to the de novo methylation of upstream or downstream adjacent sequences.

5-Methylcytosine↗
PubMed2000

[Efficacity of antiseptic products].

Chemical antiseptics are used in specified conditions. This work studied the actual standards to evaluate the activity of antiseptics. Afterward, the main indications of antiseptics are summarized.

Anti-Bacterial Agents↗
PubMed1999

Stability and compatibility of an aerosol mixture including N-acetylcysteine, netilmicin and betamethasone.

The physicochemical stability and the compatibility between N-acetylcysteine (1 g/5 ml), betamethasone (4 mg/1 ml) and netilmicin (100 mg/1 ml) were studied at room temperature (25+/-2 degrees C) over 1 h. During this study, drug concentrations were measured using three separate HPLC methods with UV detection at t=0, 5, 10, 20, 30, and 60 min. The pH of the mixture was determined. Degradation products of the drugs were assayed using HPLC. This study demonstrates the stability and compatibility of the mixture over 1 h at room temperature. The pinkish non-remnant coloration observed when pouring N-acetylcysteine into a recipient has no effect on the stability of the drug.

Acetylcysteine↗
PubMed1999

Microencapsulation of lipophilic drugs in chitosan-coated alginate microspheres.

Chitosan-coated alginate microspheres containing a lipophilic marker dissolved in an edible oil, were prepared by emulsification/internal gelation and the potential use as an oral controlled release system investigated. Microsphere formation involved dispersing a lipophilic marker dissolved in soybean oil into an alginate solution containing insoluble calcium carbonate microcrystals. The dispersion was then emulsified in silicone oil to form an O/W/O multiple phase emulsion. Addition of an oil soluble acid released calcium from carbonate complex for gelation of the alginate. Chitosan was then applied as a membrane coat to increase the mechanical strength and stabilize the microspheres in simulated intestinal media. Parameters studied included encapsulation yield, alginate concentration, chitosan molecular weight and membrane formation time. Mean diameters ranging from 500 to 800 micron and encapsulation yields ranging from 60 to 80% were obtained. Minimal marker release was observed under simulated gastric conditions, and rapid release was triggered by transfer into simulated intestinal fluid. Higher overall levels of release were obtained with uncoated microspheres, possibly due to binding of marker to the chitosan membrane coat. However the slower rate of release from coated microspheres was felt better suited as a delivery vehicle for oil soluble drugs.

Alginates↗
PubMed1999

S1 SINE retroposons are methylated at symmetrical and non-symmetrical positions in Brassica napus: identification of a preferred target site for asymmetrical methylation.

DNA methylation has been often proposed to operate as a genome defence system against parasitic mobile elements. To test this possibility, the methylation status of a class of plant mobile elements, the S1Bn SINEs, was analysed in detail using the bisulfite modification method. We observed that S1Bn SINE retroposons are methylated at symmetrical and asymmetrical positions. Methylated cytosines are not limited to transcriptionally important regions but are well distributed along the sequence. S1Bn SINE retroposons are two-fold more methylated than the average methylation level of the Brassica napus nuclear DNA. By in situ hybridization, we showed that this high level of methylation does not result from the association of S1Bn elements to genomic regions known to be highly methylated suggesting that S1Bn elements were specifically methylated. A detailed analysis of the methylation context showed that S1Bn cytosines in symmetrical CpG and CpNpG sites are methylated at a level of 87% and 44% respectively. We observed that 5.3% of S1Bn cytosines in non-symmetrical positions were also methylated. Of this asymmetrical methylation, 57% occurred at a precise motif (Cp(A/T)pA) that only represented 12% of the asymmetrical sites in S1Bn sequences suggesting that it represents a preferred asymmetrical methylation site. This motif is methylated in S1Bn elements at only half the level observed for the Cp(A/T)pG sites. We show that non-S1Bn CpTpA sites can also be methylated in DNA from B. napus and from other plant species.

5-Methylcytosine↗
PubMed1999

Levels of transferrin and alpha 2-HS glycoprotein in women with and without endometriosis.

The study objective was to test the hypothesis that elevated levels of transferrin and alpha 2-HS glycoprotein occur in the peritoneal environment of patients with endometriosis that may lead to the observed autoimmunity to these proteins. We set up a double sandwich enzyme-linked immunosorbent assay (ELISA) for measuring levels of transferrin and alpha 2-HS glycoprotein in the serum and peritoneal fluid samples from women with (n = 24-60) and without endometriosis (n = 35-49). Serum and peritoneal fluid levels of alpha 2-HS glycoprotein and peritoneal fluid levels of transferrin were significantly elevated in patients with endometriosis, in contrast to the controls. Serum levels of transferrin in patients, however, were significantly less in the patients than in controls. We conclude that transferrin and alpha 2-HS glycoprotein are present at high concentrations in the peritoneal fluids of patients with endometriosis. This may play a significant role in the autoimmune pathophysiology of endometriosis.

Ascitic Fluid↗
PubMed1998

Evaluation of a filling system for binary pediatric solutions.

The aim of this study was to assess the use of an automatic filling system (Siframix M31 and M32 system) to prepare pediatric parenteral nutrition. Volumetric accuracy was measured for each siframix system loads cells (< 5% for 5 ml with the Siframix M32 and < 5% for 9 ml with the Siframix M31) with sterile water for injection. The minimal 20 ml of flushing sterile water of the common tubulure of the Siframix M32 (p = 0.211 for 20 ml and p = 0.75 for 500 ml), the use of viscous solutions (70% dextrose) on the Siframix M31 (p = 0.28 for 20 ml and p = 0.12 for 500 ml) and the use of a special tubulure for using E.V.A. Luer-lock bags (p = 0.89 for 20 ml and p = 0.103 for 500 ml) do not modify the accuracy. Changing bags or bottles during the filling operation modify the accuracy (p = 0.004 for 20 ml and p = 0.009 for 500 ml). A flushing operation is necessary to lower the risk of electrolytic pollution for the filling of little bags. The filling speed for each module was also measured (the maximal filling speed was five liters per minute). The Siframix system allows one to prepare pediatric parenteral nutrition bags when volumes are above 4 ml and with adapted source solutions in terms of concentration and conditioning volumes.

Child↗
PubMed1998

Human recombinant alpha 2-HS glycoprotein is produced in insect cells as a full length inhibitor of the insulin receptor tyrosine kinase.

Human Alpha 2-HS glycoprotein (AHSG), a glycoprotein synthesized by hepatocytes, was expressed in insect cells using the recombinant baculovirus system. The protein was purified from the cell supernatant, and appeared as a single band at about 52 kDa. Western blot using a specific antibody to the B-chain of AHSG indicated that the connecting peptide was present in the protein. When incubated with solubilized insulin receptors, recombinant AHSG inhibited the tyrosine kinase activity of the receptors in a dose-dependent fashion at concentrations in the range of those of the circulating protein. AHSG did not interfere with the binding of insulin to its receptor. These results indicate that human AHSG represents a natural inhibitor of the insulin receptor tyrosine kinase, is active as a single-chain protein and possesses a biological role similar to that of its homologue in rats, pp63, described by Auberger et al. (1).

Baculoviridae↗
PubMed1998

Effect of the granulation process on nitrofurantoin granule characteristics.

We studied four granulation methods on the same quantitative and qualitative formula: wet massing by forced agglomeration (Lödige) and free agglomeration (Glatt); and dry massing by slugging and roller compaction technique. Three different particle sizes of nitrofurantoin (bioinequivalent drug) were used. The nitrofurantoin particle size has a very low influence on the physical characteristics of the granules. The granulating process influenced the binding of the particles. Granules processed using the wet granulating method were harder than those made by dry process. Lödige granules were more bonded than Glatt granules. Granules prepared by dry massing presented broken particles. The surface area and the porosity of Glatt granules were the most important parameters. Dissolution studies must be effected to make a correlation between the physical results and the dissolution rates. It is necessary to effect a new validation and a comparison of the results when a new granulating apparatus is used.

Anti-Infective Agents, Urinary↗
PubMed1998

Isolation of human alpha 2HS-glycoprotein synthesized by Sf9 cells.

The human alpha 2HS-glycoprotein is a negative acute phase protein synthesized by hepatocytes. Because of its fragility and the difficulty of its purification, we used recombinant DNA techniques to produce the protein in order to investigate its biological effects. The cDNA coding for the whole alpha 2HS-glycoprotein from human liver library had been cloned into the baculovirus expression vector system using the pVL 1392 transfer vector and Sf9 cells. The recombinant protein was synthesized in the Sf9 cells and was isolated on a hydroxiapatite column from the culture medium. Western blot analysis indicated that the cells synthesized large quantities of the recombinant human protein. The molecular mass of the recombinant AHSG was the same as that of the protein in human plasma but was slightly lower than that of AHSG in the cell culture supernatants of HepG2 and higher than that of AHSG from Hep3B cell cultures, respectively.

Acute-Phase Proteins↗
PubMed1997

Stability of nystatin in mouthrinses; effect of pH temperature, concentration and colloidal silver addition, studied using an in vitro antifungal activity.

Alkaline low concentration nystatin mouthrinses extemporanely prepared can be used to treat oropharyngeal candidiasis in immunodeficient patients. However, their expiration dates are not distinctly determined. The stability of nystatin, added (as Mycostatine) at a concentration of 14,400 U/ml in 10-4N hydrochloric acid, purified water and 1.4% injectable sodium hydrogen carbonate with or without 0.002% colloidal silver (an antiseptic agent added because of its known antifungal potency) was studied after storage in tinted glass bottles at 5 degrees C and 22 degrees C over 11 days, and compared with reconstituted 100,000 U/ml aqueous Mycostatine oral suspension. At 2, 4, 7, 9, and 11 days after preparation. Samples were tested for pH, microbial contamination, and assayed by an in vitro microbiological test. Neither significant variation of pH nor microbial contamination were in evidence. Nystatin 14400 U/ml maintained at least 90% of its initial concentration for 4 days in acid at both temperatures, for 7 days (5 degrees C) and 4 days (22 degrees C) in aqueous and alkaline environments, for 9 days (5 degrees C) and 7 days (22 degrees C) in 1.4% injectable sodium hydrogen carbonate containing colloidal silver which showed an antifungal potency. The 100,000 U/ml aqueous Mycostatine oral suspension was stable for 9 days and 4 days at 5 degrees C and 22 degrees C respectively. An ambulant patient can keep a low concentration alkaline antifungal mouthrinse at home for a week at 5 degrees C.

Antifungal Agents↗