DNA/RNA analysis of phytoplankton by flow cytometry

The past 10 years or so have seen the combination of molecular and biochemical techniques within the confines of cytometry. The use of flow cytometry in microbiology is finally coming of age. This unit carefully defines the criteria for evaluation of DNA and RNA in phytoplankton. Of course not everyone works with phytoplankton, but the methods outlined are very appropriately representative for other organisms. In addition, the unit discusses the methods for evaluating cell cycle and discriminating specific taxa using fluorescent oligonucleotide probes targeted to 18S rRNA.

Isolated Endocarditis of the Pulmonary Valve Caused by Pasteurella multocida

We describe the rare case of a patient with an isolated endocarditis of the pulmonary valve caused by Pasteurella multocida. The bacterium was cultured from blood as well as from the excised valve after pulmonary valve replacement. Risk factors were contact with animals and concurrent intravenous drug use.

A single species, Micromonas pusilla (Prasinophyceae), dominates the eukaryotic picoplankton in the Western English Channel

The class Prasinophyceae (Chlorophyta) contains several photosynthetic picoeukaryotic species described from cultured isolates. The ecology of these organisms and their contributions to the picoeukaryotic community in aquatic ecosystems have received little consideration. We have designed and tested eight new 18S ribosomal DNA oligonucleotide probes specific for different Prasinophyceae clades, genera, and species. Using fluorescent in situ hybridization associated with tyramide signal amplification, these probes, along with more general probes, have been applied to samples from a marine coastal site off Roscoff (France) collected every 2 weeks between July 2000 and September 2001. The abundance of eukaryotic picoplankton remained high (>10(3) cells ml(-1)) during the sampling period, with maxima in summer (up to 2 x 10(4) cells ml(-1)), and a single green algal species, Micromonas pusilla (Prasinophyceae), dominated the community all year round. Members of the order Prasinococcales and the species Bathycoccus prasinos (Mamiellales) displayed sporadic occurrences, while the abundances of all other Prasinophyceae groups targeted remained negligible.

Population pharmacokinetics of pyrimethamine and sulfadoxine in children with congenital toxoplasmosis

AIMS

To develop a population pharmacokinetic model for pyrimethamine (PYR) and sulfadoxine (SDX) in children with congenital toxoplasmosis.

METHODS

Children were treated with PYR (1.25 mg kg(-1)) and SDX (25 mg kg(-1)) (Fansidar) plus folinic acid (Lederfoline) 5 mg). Plasma concentrations, available from a therapeutic drug monitoring database, were determined by high-performance liquid chromatography. Population pharmacokinetic analysis was performed using a nonlinear mixed effects model.

RESULTS

Eighty-nine children, aged 1 week to 14 years and weighing 2.9-59 kg, were available for evaluation. Both PYR and SDX concentration-time profiles were best described by a one-compartment open model. Volume of plasma distribution (V) and clearance (CL) were significantly related to body weight (BW) using an allometric function. Typical CL and V estimates (95% confidence interval), for a child weighing 11 kg were 5.50 (5.28, 5.73) l day(-1) and 36 (33, 39) l for PYR and 0.26 (0.25, 0.27) l day(-1) and 2.1 (1.9, 2.3) l for SDX. For BW between 3.5 and 60 kg, plasma half-lives were predicted to vary from 4.0 to 5.2 days for PYR, and from 5.0 to 7.5 days for SDX.

CONCLUSION

This study indicated that body weight influences PYR and SDX pharmacokinetics in children. To optimize PYR/SDX combination treatment in congenital toxoplasmosis, short dosing intervals in very young low-wight children are probably appropriate.

High plasma ropivacaine concentrations after fascia iliaca compartment block in children

BACKGROUND

The pharmacokinetic profile of local anaesthetics is influenced by the mode of administration. We sought to compare the pharmacokinetics of two doses of ropivacaine after fascia iliaca compartment (FIC) block in children.

METHODS

In this prospective, double-blind study, children received an FIC block as a part of their anaesthetic management during elective orthopaedic surgery on the thigh. They were randomized to receive ropivacaine 0.7 ml x kg(-1) using either a 0.375% or 0.5% solution. Venous blood samples were drawn up to 6 h after injection. Plasma concentrations of ropivacaine were measured by gas-liquid chromatography.

RESULTS

Six children (10.2 (range 5-15) yr, 35.6 (sd 10) kg were included. FIC block provided satisfactory peroperative pain relief. No signs of toxicity were observed, but high maximal plasma concentrations (C(max) 4.33-5.6 microg ml(-1)), were observed for three of four patients in the ropivacaine 0.5% group. The two patients in the 0.375% group showed values within the safe range (C(max) 0.66 and 0.98 microg ml(-1) respectively). Even though no toxic effects were observed, these results led us to discontinue the study.

CONCLUSIONS

The administration of ropivacaine 3.5 mg x kg(-1) can be associated with sustained high plasma concentrations of ropivacaine, outside the tolerable range. In view of these results, we recommend the use of lower ropivacaine dosage during FIC block in children.

Population pharmacokinetics of short intravenous vinorelbine infusions in patients with metastatic breast cancer

PURPOSE

To develop a population pharmacokinetic model of vinorelbine administered by short intravenous infusion in metastatic breast cancer patients.

METHODS

Vinorelbine was administered as infusions of 5-10 min at 15, 20 or 25 mg/m(2) to 30 patients. Blood samples were collected over 18 h. Plasma concentrations of vinorelbine were determined by HPLC. Population pharmacokinetic analysis was performed using a nonlinear mixed effects modeling method.

RESULTS

Vinorelbine concentration-time profiles were best described by a three-compartment open model. Plasma clearance (CL) was high and positively related to lean body weight (LBW) and body surface area (BSA) or to a combination of height and body weight (BW). Elevated serum alkaline phosphatases had a negative effect on CL. Typical population estimates of CL and central distribution volume (V(1)) were 74.2 l/h and 7.8 l, respectively. The interindividual population coefficients of variation for CL and V(1) were 17.0% and 32.0%, respectively. The stability and predictive performance of the final population pharmacokinetic model were assessed using 200 bootstrap samples of the original data.

CONCLUSION

This study identified combined effects of BSA and serum alkaline phosphatases on clearance. These results partly support the conventional dose adjustment of vinorelbine based on BSA, but suggest dose modification in cases of extreme values of serum alkaline phosphatases.

Chromatographic determination of the association constant between 8-methoxypsoralen and modified β-cyclodextrin: protective effect of hydroxypropyl-β-cyclodextrin on 8-methoxypsoralen toxicity in human keratinocytes

The retention of 8-methoxypsoralen (8-MOP) on an immobilised hydroxypropyl-beta-cyclodextrin (HP-beta-CD) column was analysed in HPLC by the determination of its Langmuir distribution isotherm. A such method was used to confirm the potential drug complexing role of this cyclodextrin. The 8-MOP/HP-beta-CD association constant (K) was equal to 29.5 and 18.7 M-1, respectively, at a temperature equal to 5 and 25 degrees C, respectively. These association constant values were used to determine the cytotoxicity profile of human keratinocyte cell line (HaCaT) in relation to the complex concentration. It was showed through these data that HP-beta-CD had a cytoprotective since a reverse effect of HP-beta-CD on 8-MOP cytotoxicity was observed.

Quantitative assessment of picoeukaryotes in the natural environment by using taxon-specific oligonucleotide probes in association with tyramide signal amplification-fluorescence in situ hybridization and flow cytometry

Picoeukaryotes (cells of <3 micro m in diameter) contribute significantly to marine plankton biomass and productivity, and recently molecular studies have brought to light their wide diversity. Among the methods that have been used so far to quantify aquatic microorganisms, fluorescence in situ hybridization of oligonucleotide probes combined with flow cytometry offers the advantages of both high resolution for taxonomic identification and automated cell counting. However, cell losses, cell clumps, and low signal-to-background ratio have often been mentioned as major problems for routine application of this combination of techniques. We developed a new protocol associating tyramide signal amplification-fluorescence in situ hybridization and flow cytometry, which allows the detection of picoeukaryotes in cultures during both the exponential and stationary phases. The use of surfactant and sonication proved to be essential for the detection and quantification of picoeukaryotes from the natural environment, with as little as a few tenths of a milliliter of 3- micro m-pore-size prefiltered sea water. The routine application of the technique was tested along a coastal transect off Brittany (France), where the different groups of picoeukaryotes were investigated using already published specific probes and a newly designed probe that targets the order Mamiellales (Prasinophyceae, Chlorophyta). Among the picoeukaryotes, Mamiellales outnumbered by 1 order of magnitude both the cyanobacteria and the non-Chlorophyta, which were represented mainly by the Pelagophyceae class. Picoeukaryote abundance increased from open toward more estuarine water, probably following changes in water temperature and stability.

Dehydroepiandrosterone and alpha-estradiol limit the functional alterations of rat brain mitochondria submitted to different experimental stresses

The effects of dehydroepiandrosterone (DHEA), dehydroepiandrosterone-sulfate (DHEA-S), alpha-estradiol and beta-estradiol on the main functions of purified rat brain mitochondria were investigated in basal conditions and after being submitted to various stresses including anoxia-reoxygenation, uncoupling and apoptosis. In basal conditions, DHEA (1 microM) and alpha-estradiol (1 microM) inhibited the respiratory control ratio (RCR) from 3.1 to 2.3 (25%). After anoxia-reoxygenation, DHEA (1 microM) and alpha-estradiol (1 microM) reversed significantly (P<0.01) the RCR decrease from 1.4 to 2.0 (21.5%) by restoring the state 4. This effect was observed when DHEA was added either before anoxia or before reoxygenation and when alpha-estradiol was added before anoxia. The mitochondrial membranes damaged after the anoxia-reoxygenation were 70 and 50%, respectively, protected by DHEA and alpha-estradiol at 1 microM. They also limited by about 50%, the cytochrome c release induced by the anoxia-reoxygenation. The oxygen consumption of mitochondria in presence of NADH (130 microM) and cytochrome c (5 microM) was significantly inhibited by DHEA and alpha-estradiol with high EC(50) of 30 and 22 pM, respectively. At 1 microM, they also inhibited the 10 microM carbonyl cyanide m-chlorophenylhydrazone-induced uncoupling to about 35% whereas beta-estradiol only decreased it to 9%. Our results indicated that DHEA and alpha-estradiol partly preserved the mitochondrial functions altered by an anoxia-reoxygenation with a concentration-dependent effect. The mechanism involved was independent of the classical genomic effect of steroids, the antioxidant properties but implicated a direct action on the mitochondrial membranes.

Lack of daily rhythms major modifications despite continuous infusion of melatonin in the rat

The present study was conducted to evaluate the effect of melatonin on the daily rhythms of temperature, heart rate and locomotor activity in rats that received subcutaneously a continuous infusion of two different doses e.g. 1 and 5 mg/kg per day for seven days. Our results indicate that melatonin does not induce a loss of the daily rhythmicity of temperature, heart rate and locomotor activity. Whatever the dose, melatonin slightly modifies the main parameters of these rhythms e.g. a decrease of the amplitude of the daily rhythms of temperature and heart rate and an increase of the mesor of temperature. Taking into account these results obtained after constant rate delivery in normal rats, we plan now to investigate the effects of melatonin on our experimental model of Parkinson's disease (double bilateral intrastriatal 6-hydroxydopamine injection).