Ex-situ conservation of Black poplar in Europe: genetic diversity in nine gene bank collections and their value for nature development.

Populus nigra L. is a pioneer tree species of riparian ecosystems that is threatened with extinction because of the loss of its natural habitat. To evaluate the existing genetic diversity of P. nigra within ex-situ collections, we analyzed 675 P. nigra L. accessions from nine European gene banks with three amplified fragment length polymorphism (AFLP) and five microsatellite [or simple sequence repeat (SSR)] primer combinations, and 11 isozyme systems. With isozyme analysis, hybrids could be detected, and only 3% were found in the gene bank collection. AFLP and SSR analyses revealed effectively that 26% of the accessions were duplicated and that the level of clonal duplication varied from 0% in the French gene bank collection up to 78% in the Belgian gene bank collection. SSR analysis was preferred because AFLP was technically more demanding and more prone to scoring errors. To assess the genetic diversity, we grouped material from the gene banks according to topography of the location from which the accessions were originally collected (river system or regions separated by mountains). Genetic diversity was expressed in terms of the following parameters: percentage of polymorphic loci, observed and effective number of alleles, and Nei's expected heterozygosity or gene diversity (for AFLP). Genetic diversity varied from region to region and depended, to some extent, on the marker system used. The most unique alleles were identified in the Danube region (Austria), the Rhône region (France), Italy, the Rijn region (The Netherlands), and the Ebro region (Spain). In general, the diversity was largest in the material collected from the regions in Southern Europe. Dendrograms and principal component analysis resulted in a clustering according to topography. Material from the same river systems, but from different countries, clustered together. The genetic differentiation among the regions (F(st)/G(st)) was moderate.

Molecular analysis of natural populations of Populus nigra L intermingled with cultivated hybrids.

In this study six simple sequence repeats (SSR or microsatellites) were selected for their ability to fingerprint a total of 60 commercial clones of Populus deltoides Marsh. and Populus x canadensis Moench (typically derived from crosses between Populus nigra L and P. deltoides) and to characterize a natural population of P. nigra growing along the Ticino river in the North of Italy. Out of six SSRs used, four microsatellite loci were found to have alleles which were species-specific to P. deltoides and could therefore be used as markers for introgression of P. deltoides into P. nigra. In the studied region hybrid poplars and P. deltoides commercial clones are cultivated as monoclonal stands close to the area where black poplar has its natural habitat. SSR analysis was performed to investigate whether there was evidence of introgression between the natural population and the monoclonal plantations of hybrids and P. deltoides clones cultivated in the surrounding area. Three stages of the natural population were analysed: a group of old trees about a hundred years old, a younger population (aged 2-30 years) and the seedlings of three females of this population. Alleles specific to P. deltoides were detected only in the old cohort of the natural population, while no introgression was observed in the younger individuals and their progenies. These results were also confirmed by isozyme analysis of loci PGI-B, PGM and LAP-A, which were previously identified as diagnostic for P. nigra, P. deltoides and P.xcanadensis.

Determination of plasma choline by high-performance liquid chromatography with a postcolumn enzyme reactor and electrochemical detection.

A method for the determination of choline in human plasma is described, involving rapid purification of plasma samples and analysis by high-performance liquid chromatography using an on-column enzyme reactor with electrochemical detection. The linearity of the method was tested at choline levels from 3.5 to 28.6 microM in plasma. The recovery was 86% and was independent of the analyte concentration. The inter-assay precision (as coefficient of variation) and accuracy (as the deviation of the concentration found from the theoretical value) were always below 12% in the whole concentration range. The method was applied to the determination of plasma choline levels in eight healthy volunteers after intramuscular administration of L-alpha-glycerophosphorylcholine (1 g) or a placebo. Mean plasma choline levels in the placebo group ranged from 10.6 to 12.0 microM. After drug administration, the plasma choline level reached 35.1 microM in 30 min, then decreased gradually. Plasma choline levels became comparable in the treated and placebo groups 6-8 h after administration.

Absorption, tissue distribution and excretion of radiolabelled compounds in rats after administration of [14C]-L-alpha-glycerylphosphorylcholine.

The kinetics and metabolism of L-alpha-glycerylphosphoryl-choline (alpha-GPC) were investigated in male and female rats after i.v. (10 mg/kg) and oral doses (100-300 mg/kg). alpha-GPC was labelled with [14C]-glycerol ([14G]-GPC) or [14C]-choline ([14C]-GPC). Different kinetic and metabolic profiles were observed after i.v. and oral administration. It is assumed that alpha-GPC is hydrolyzed by phosphodiesterases in the gut mucosa. The different labelled metabolites have different kinetic properties of absorption, distribution and clearance, leading to different blood concentration-time curves of total radioactivity. Both labelled compounds gave a wide distribution of radioactivity, particularly concentrated in the liver, kidney, lung and spleen compared to blood. Brain concentrations of [14C]-GPC were comparable to ([14G]-GPC) or lower than ([14C]-GPC) total blood radioactivity. The metabolite profile in the perfused brain showed a small amount of choline and two unknown metabolites, probably the same as in blood. In addition, choline was incorporated into brain phospholipids in increasing amounts within 24 h of dosing. In all cases renal and fecal excretion of radioactivity was low and comparable for [14G]-GPC and [14C]-GPC. Mostly the administered radioactivity was exhaled as 14CO2, this degradation being faster and more pronounced for the glycerol-labelled metabolites than for the choline-labelled metabolites for both routes of administration. In all cases the results were the same for male and female rats.

A comparative study of free plasma choline levels following intramuscular administration of L-alpha-glycerylphosphorylcholine and citicoline in normal volunteers.

L-alpha-glycerylphosphorylcholine (alpha-GPC) is a recently developed cognitive enhancer whose mode of action is considered to involve the release of free choline, which is then utilized for acetylcholine and phosphatidylcholine biosynthesis in the brain. The purpose of this study was to evaluate the profile of free plasma choline levels following a single i.m. dose of alpha-GPC in 12 normal volunteers. Citicoline (CTC), which also acts as a choline precursor, was included for comparison purposes. Each subject was studied on three randomized occasions, (i) in a control day in the absence of drug administration (to evaluate the plasma level profile of endogenous choline), (ii) after i.m. alpha-GPC (1,000 mg) and (iii) after i.m. CTC (1,000 mg) respectively, with a wash-out period of at least 1-week between sessions. Blood samples for plasma choline HPLC determinations were collected at regular intervals over a 6 h period. In the control session, plasma choline levels remained stable during the sampling period. The administration of alpha-GPC was associated with a rapid rise in plasma choline, peak levels being usually observed at the first (0.25 h) or second (0.5 h) sampling time after the injection. Thereafter, the concentration of choline declined gradually and returned to near baseline values at the end of the observation period. After the administration of CTC, plasma choline levels showed a similar time course but were considerably lower than those observed after the administration of alpha-GPC.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of picotamide in human plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the determination of picotamide in human plasma and urine is described. After addition of an internal standard (bamifylline), the plasma and urine samples were subjected to liquid-liquid extraction and clean-up procedures. The final extracts were evaporated to dryness and the resulting residues were reconstituted in 100 microliters of methanol-water (50:50, v/v) and chromatographed on a LiChrosorb RP-SELECT B reversed-phase column coupled to an ultraviolet detector monitored at 230 nm. Chromatographic analysis takes about 10 min per sample. The assay was linear over a wide range and has a limit of detection of 0.005 and 0.1 micrograms/ml in plasma and urine, respectively. It was selective for picotamide, accurate and robust and thus suitable for routine assays after therapeutic doses of picotamide.

High-performance liquid chromatographic assay of L-alpha-glycerophosphorylcholine using a two-step enzymic conversion.

A high-performance liquid chromatographic method using an enzymic reactor for determination of L-alpha-glycerophosphorylcholine in pharmaceutical forms is described. The procedure includes incubation of L-alpha-glycerophosphorylcholine with glycerophosphorylcholine phosphodiesterase (EC 3.1.4.2), giving choline and glycerophosphate, and subsequent chromatography of choline with a post-column enzymic reactor and electrochemical detection. The results obtained show a close linearity of the whole assay from 2 to 150 nmol/ml L-alpha-glycerophosphorylcholine, the sensitivity being 2 pmol per 20 microliters of injected sample. The precision of the method in the analysis of L-alpha-glycerophosphorylcholine in pharmaceutical forms, ampoules and capsules, was 1.34 and 1.21%, respectively.

Disposition and metabolism of minaprine in the rat.

After iv. injection (5 mg/kg) to rats, minaprine is cleared rapidly from plasma with an elimination t 1/2 of 34 min. After the same dose but given orally the drug is rapidly absorbed from the rat gastrointestinal tract. The ratio of the area under the curves (AUC) of the parent drug indicates low bioavailability (5%). Two metabolites of minaprine (M3 and M5) appeared rapidly in rat plasma and far exceed minaprine concentrations. Other known urinary metabolites of the drug were undetectable in rat plasma and brain within the limits of the sensitivity of the method. Minaprine rapidly enters the central nervous system and then distributes almost evenly in various regions beyond the blood/brain barrier. It concentrates in brain tissue reaching concentrations two-three times those in plasma. It metabolites enter the brain less rapidly and their brain AUC never reached 50% of the plasma AUC.