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C Le Guellec

Publications and source records attributed to C Le Guellec.

26 records · Page 2Linked to original sources
PubMed1988

Vitellogenin gene expression in primary culture of male rainbow trout hepatocytes.

Using a primary culture of trout hepatocytes we compare the kinetics of accumulation of vitellogenin and its messenger RNA after estrogen administration. We found that the cells were more sensitive to estradiol than to other estrogens. The lowest effective concentration of estradiol was 10(-9) M. At 10(-6) M the androgens have no effect. Comparison of the primary and secondary stimulation with E2 shows that the initial rate of accumulation of vitellogenin is very much higher in the secondary stimulation. Over a time course of primary stimulation we show that after estradiol withdrawal the rate of accumulation of vitellogenin mRNA in the secondary is a function of time of the first stimulation.

Androgens↗
PubMed1984

The preparation and characterization of vitellogenin messenger RNA from rainbow trout (Salmo gairdneri).

Agarose-gel electrophoresis of polyadenylated RNA from livers of oestrogen-treated male rainbow trout revealed a major high-Mr species (7200 nucleotides), which is absent from the polyadenylated RNA isolated from hormonally unstimulated male trout liver. Translation in vitro of the RNA from oestrogen-treated males in a mRNA-dependent rabbit reticulocyte lysate produced a protein (Mr 200 000) that could be immunoprecipitated with antibodies against trout serum vitellogenin, but no immunoprecipitable protein was synthesized with RNA from control animals. DNA complementary to the RNA from oestrogen-stimulated and control male trout liver was synthesized and back-hybridized, with R0t1/2 of 3.8 X 10(-2) and 1 X 10(-1) mol X litre-1 X s for RNA from hormone-treated and control animals respectively. The 9% increase in the abundant mRNA after oestrogen stimulation is due to the induction of vitellogenin mRNA.

Animals↗
PubMedDate not supplied

Determination of nifedipine in plasma by a rapid capillary gas chromatographic method.

A rapid, specific and reliable gas chromatographic assay procedure for Nifedipine in plasma has been developed. With a single-step solvent extraction, and electron capture detection, the method is sensitive to 0.5 ng/mL of plasma and the standard curve is linear from 0.5 to 500 ng/mL. Samples are protected from light to prevent formation of photodecomposition products. The method has been used to monitor drug concentrations in patients receiving therapeutic doses.

Chromatography, Gas↗
PubMedDate not supplied

[Issues in therapeutic drug monitoring evaluation].

A reassessment of the interest of therapeutic drug monitoring (TDM) is needed for a better definition of its applications. It rests on the hypothesis of the existence of an interindividual variability of the dose-effect relationship, this variability being influenced by pharmacokinetic variability. Different types of endpoints were used in validation studies (pharmacokinetic, indirect, economic) and few studies have used clinical endpoints. The question should be: does TDM allow for a better dose adjustment than one based only on criteria other than drug concentration? Retrospective studies have a 'diagnostic test' approach and only prospective clinical trials will provide a real validation. Factors which limit the setting up of such studies are: the number of subjects to include, the often imprecise measurement of drug exposure and poor knowledge of the pharmacokinetic-pharmacodynamic relationship and its variability.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

Ciprofloxacin pharmacokinetics in young cystic fibrosis patients after repeated oral doses.

Until recently, only compassionate use of ciprofloxacin in children with cystic fibrosis was possible despite limited pharmacokinetic data. We studied five subjects with cystic fibrosis and exacerbation of pulmonary infection. A 15 mg/kg b.i.d. regimen of oral ciprofloxacin was administered. On the 15th day, eight blood samples were collected and plasma concentrations were measured by HPLC. The actual dose administered ranged from 10 to 14 mg/kg b.i.d., due to the fixed-dosage formulation. Corresponding AUC0-12 ranged from 8.2 to 11.9 mg.h/L. Plasma concentrations were maintained above individual MICs for a median time of 12.7 h over 24 h. The median area under the inhibitory curve was 52.8, which is about half the proposed target value for ciprofloxacin in pulmonary infections with Gram-negative bacteria such as Pseudomonas aeruginosa. A higher dose, administered from a specific formulation to ensure precise dosing, must be given in order to obtain adequate concentrations in cystic fibrosis children.

Administration, Oral↗
PubMedDate not supplied

[Pharmacokinetic studies in neonatology: regulatory and methodologic problems].

Pharmacokinetic studies in neonates are essential because of maturational changes in physiological functions during this period. International harmonization conferences have established guidelines for such studies, including recommendations on age ranges to be studied and description of methods and study design. Multiple blood sampling to obtain a full pharmacokinetic profile cannot be proposed in neonates. Population pharmacokinetic analysis, with minimal sampling schemes, is more appropriate but involves more subjects than the traditional approach. Population pharmacokinetic analysis also focuses on the influence of individual factors on pharmacokinetic parameters. Most studies performed with neonates have involved drugs with a narrow safety margin and cleared by renal or metabolic routes to study the impact of immaturity on drug concentrations and on clinical effects.

Humans↗
PubMedDate not supplied

[Clinical relevance of N-acetyltransferase type 2 (NAT2) genetic polymorphism].

Polymorphic N-acetyltransferase (NAT2) is involved in the metabolism of several compounds relevant in pharmacology or toxicology, with diverse clinical consequences. Inter-ethnic variations in distribution of the acetylation phenotype are significant. The caffeine test is most often used to assess the acetylation phenotype and to identify rapid and slow acetylators. The NAT2 phenotype could account for the increased risk of certain side effects in slow acetylators treated with isoniazid (particularly peripheral neuropathies and lupus erythematosus), although therapeutic efficacy seems to be independent of the acetylation status. Hypersensibility reactions with sulfonamides (including Lyell and Stevens-Johnson syndromes) are more frequent in slow acetylators, who also show poor tolerance to sulfasalazine and dapsone. In contrast, myelotoxicity induced by amonafide is more frequent in rapid acetylators, probably because of increased production of a toxic metabolite of the drug. In carcinogenesis, NAT2 may play a protective role against bladder cancer, although studies have shown contradictory results. Slow acetylators may have a risk of developing primitive liver cancer. For lung cancer, data are not conclusive, but slow acetylation status may predispose to mesothelioma in subjects exposed to asbestos. No relation has been found between acetylation phenotype and breast cancer. Contradictory results were reported on its role in colorectal cancer. Non-smoking type 1 diabetics may be at increased risk of nephropathy if they are rapid acetylators. Parkinson's disease may be more frequent among slow acetylators, but again, data have shown contradictory results. Finally, a poor acetylator phenotype may predispose to atopic diseases.

Acetylation↗