Crop domestication as a step towards reproductive isolation

Speciation, Darwin's mystery of mysteries, is a continuous process that results in genomic divergence accompanied by the gradual increment of reproductive barriers between lineages. Since the beginning of research on the genetics of speciation, several questions have emerged such as: What are the genetic bases of incompatibilities? How many loci are necessary to prevent hybridization and how are they distributed along genomes? Can speciation occur despite gene flow and how common is ecological speciation? Early stages of divergence are key to understand the ecology and genetics of speciation, and semi-isolated species where hybrids can still be produced are particularly relevant This article is protected by copyright. All rights reserved.

Early physiological responses of Arabidopsis thaliana cells to fusaric acid: toxic and signalling effects

Fusaric acid (FA) is a toxin produced by Fusarium species. Most studies on FA have reported toxic effects (for example, alteration of cell growth, mitochondrial activity and membrane permeability) at concentrations greater than 10(-5) m. FA participates in fungal pathogenicity by decreasing plant cell viability. However, FA is also produced by nonpathogenic Fusarii, potential biocontrol agents of vascular wilt fusaria. The aim of this study was to determine whether FA, at nontoxic concentrations, could induce plant defence responses. Nontoxic concentrations of FA were determined from cell-growth and O2-uptake measurements on suspensions of Arabidopsis thaliana cells. Ion flux variations were analysed from electrophysiological and pH measurements. H2O2 and cytosolic calcium were quantified by luminescence techniques. FA at nontoxic concentrations (i.e. below 10(-6) m) was able to induce the synthesis of phytoalexin, a classic delayed plant response to pathogen. FA could also induce rapid responses putatively involved in signal transduction, such as the production of reactive oxygen species, and an increase in cytosolic calcium and ion channel current modulations. FA can thus act as an elicitor at nanomolar concentrations.

Population pharmacokinetics of ibuprofen enantiomers in very premature neonates

The objective of the present study was to evaluate the pharmacokinetic parameters for both S- and R-ibuprofen enantiomers in very premature neonates (gestational age strictly inferior to 28 weeks) and possible relationships between the pharmacokinetic parameters and various covariates. Newborns were randomized to receive ibuprofen or placebo for the prophylactic treatment of patent ductus arteriosus (PDA) at an initial dose of 10 mg/kg ibuprofen within 6 hours after birth, followed by two 5-mg/kg doses at 24-hour intervals (n = 52). If a PDA was still present afterwards, a curative course of ibuprofen using the same dosage regimen was administered (n = 10). A sparse sampling strategy was used because only 2 samples were collected after the third prophylactic injection and 1 after the third curative injection. A model including the chiral transformation of R- to S-ibuprofen was fitted to the concentration-time data using a population approach (NONMEM). R- and S-ibuprofen t(1/2) were about 10 hours and 25.5 hours, respectively. After prophylactic treatment, the mean clearance of R-ibuprofen (CLR = 12.7 mL/h) was about 2.5-fold higher than for S-ibuprofen (CLS = 5.0 mL/h). In addition, clearance of R- and S-ibuprofen increased significantly with gestational age. The mean estimation of R-ibuprofen clearance was found to be higher than for S-ibuprofen, and the clearance of both enantiomers increased with gestational age. This should be considered to assess pharmacokinetic-pharmacodynamic relationships of ibuprofen in premature neonates and subsequently to understand and refine the use of ibuprofen in managing PDA either as a prophylactic or curative treatment.

Bioequivalence Study of Two Ibuprofen Formulations Administered Intravenously in Healthy Male Volunteers

OBJECTIVE

To compare the systemic bioavailability of two ibuprofen formulations, Pedea((R)) (ibuprofen intravenous [IV] formulation) and Imbun((R)) (ibuprofen intramuscular [IM] formulation) in 18 healthy male volunteers.

METHODS

Each subject received a 5 mg/kg dose of ibuprofen base as a short 15-minute IV infusion as the Pedea((R)) ibuprofen IV formulation or as the reference Imbun((R)) IM formulation. Concentrations of R- and S-ibuprofen were measured by a validated HPLC method with a lower limit of quantification of 0.100 microg/mL.

RESULTS

A single 5 mg/kg injection of Pedea((R)) was well tolerated. The most frequent adverse event was a mild to moderate burning sensation along the injection vein probably related to the study treatments.The maximum serum concentration (C(max)) of R- and S-ibuprofen ranged from 20 to 35 microg/mL with both formulations. No statistical differences were observed for either C(max) or area under the plasma concentration-time curve (AUC). 90% CIs calculated for C(max) and AUC from time zero to infinity (AUC(infinity)) of R-ibuprofen and S-ibuprofen were included in the bioequivalence range 0.80-1.25. Based on AUC(infinity), the mean (SD) relative bioavailability of Pedea((R)) (ibuprofen IV formulation) versus the Imbun((R)) IM reference formulation was 1.06 (0.17) for R-ibuprofen and 1.05 (0.08) for S-ibuprofen.

CONCLUSION

This study showed that Pedea((R)) (test formulation) is bioequivalent to Imbun((R)) IM (reference formulation) for both R-ibuprofen and S-ibuprofen. The Imbun((R)) IM formulation (lyophilisate) could be replaced by the Pedea((R)) ready-to-use IV solution. Moreover, these results allow a comparison of safety and efficacy data previously generated with either formulation. Consequently, neonatologists, who previously used the IM formulation intravenously for the treatment of patent ductus arteriosus in preterm infants, will now be able to administer the new ready-to-use IV solution of ibuprofen directly.

The role of cocaine in fatal crashes: first results of the Québec drug study

As part of a major undertaking to establish the contribution of drugs in road crashes in Quebec, the present study focuses on the role of cocaine. Coroner, forensic laboratory and police accident records from April 1999 to December 2000 were matched for 265 fatally injured drivers of passenger vehicles. Cocaine was found in 7.9% of urine samples and 6.0% of blood samples. In order to set up a control group, two roadside surveys were conducted in August 1999 and 2000. The survey sample was distributed proportionately to the number of fatal accidents per time of day and day of the week. During both daytime and nighttime, a total of 11,952 drivers participated in the two surveys among which 11,574 provided a breath sample (96.8%), 8,177 a saliva sample (68.4%) and 5,931 a urine sample (49.6%). Cocaine was detected in 1.1% of urine samples and 1.0% of saliva samples of the driving population. In both fatally injured drivers and driving population, cocaine was found mostly (> 90%) in four main types of combination: cocaine alone, cocaine + cannabis, cocaine + alcohol, cocaine + cannabis + alcohol. The data collected allowed two different analyses: a case-control (urine/urine) and a responsibility analysis (case-case approach) that compares cocaine cases to drug-free cases. Despite some data limitations, all analyses for the four main types of combination clearly suggest that cocaine use plays a role in fatal crashes.

Evaluation of a cognitive-behavioural program for the management of chronic tic and habit disorders

The aim was to evaluate the efficacy of a manualized cognitive-behavioural program based on habit reversal for the management of chronic tic disorder (CTD) and habit disorder (HD). Forty-seven CTD and 43 HD received a 4-month treatment program. Thirty-eight (22 CTD, 16 HD) were placed on a waitlist control group, which subsequently received treatment. The treatment approach combined awareness training, relaxation (including modification of a tension-producing style of action), and habit-reversal training, with more general cognitive restructuring of anticipations linked to ticcing. Sixty-five percent of completers reported between 75 and 100% control over the tic. At 2-year follow-up, 52% rated 75-100% control. There were also significant changes post-treatment in measures of self-esteem, anxiety, depression and style of planning action. Successful tic/habit modification was associated in CTD and HD groups with successful change in style of planning action. There were no consistent differences in any outcome measures between CTD and HD groups.

Functional analysis of a tryptophan-less P-glycoprotein: a tool for tryptophan insertion and fluorescence spectroscopy

P-glycoprotein (Pgp) functions as an ATP-dependent drug efflux pump to confer multidrug resistance to tumor cells. In the absence of a high-resolution structure for this protein, several important and intriguing aspects of Pgp structure and function remain poorly understood. Fluorescence spectroscopy of endogenous or genetically engineered tryptophan residues represents a potentially powerful method to probe static and dynamic aspects of Pgp at high resolution. We have used site-directed mutagenesis to modify the wild-type (WT) mouse mdr3 Pgp for tryptophan fluorescence spectroscopy by replacement of all 11 tryptophan residues individually with phenylalanine. None of the 11 tryptophans were found to be absolutely essential for Pgp activity, because Chinese hamster ovary cells transfected and overexpressing this mutant Trp-less mdr3 cDNA (mdr3F(1-11)) become multidrug-resistant and can carry out active transport of vinblastine, colchicine, and Calcein-AM. The mdr3F(1-11) mutant has reduced activity compared with WT Mdr3, and shows a unique pattern of drug resistance clearly distinct from WT and, as opposed to the latter, can neither confer FK-506 resistance nor functionally complement ste6 in yeast. Studies with Pgp mutants containing either single or double tryptophan residues or with chimeric molecules constructed between wild-type Pgp and mdr3F(1-11) indicated that no single tryptophan residue was responsible for the reduced activity of the mdr3F(1-11) mutant. Likewise, all but one chimeric Pgp preserved the unique drug resistance profile of the mdr3F(1-11) mutant. Altogether, we show that a Trp-less Pgp is functionally active and can be used as a molecular backbone for insertion of tryptophans in strategic locations to probe various aspects of Pgp function.

Detection of membrane-bound cytokinin-binding proteins in Arabidopsis thaliana cells

In order to isolate cytokinin-binding proteins (CBPs), we have developed new affinity probes constituted of a cytokinin such as zeatin riboside ([9R]Z) conjugated to a carrier protein. These probes were used for detecting CBPs in an ELISA procedure. The efficiency of the cytokinin conjugate in detecting CBPs was controlled with protein model: proteins having an affinity for cytokinin such as the monoclonal anti-[9R]Z antibodies did bind the cytokinin conjugate whereas proteins unable to bind cytokinin such as bovine serum albumin did not. Using these new affinity probes, we showed that CBPs are present in the membrane fraction of in vitro cultured Arabidopsis thaliana cells. The nature of the protein at the detected binding sites was demonstrated by submitting the microsomal proteins to a proteolytic treatment, which was found to eradicate the binding. Free biologically active cytokinins or monoclonal anti-[9R]Z antibodies inhibited the binding, thus showing the specificity of the interaction. The detected CBPs were partially solubilized from the membranes with potassium chloride, indicating their peripheral membrane location. The separation by anion exchange chromatography of solubilized microsomal proteins revealed the existence of two different CBPs. They were present at higher levels in cells during the exponential growth phase.

Cognitive-behaviour therapy and medication in the treatment of obsessive-compulsive disorder: a controlled study

OBJECTIVE

To evaluate the effect of combining cognitive-behaviour therapy (CBT) and medication in the treatment of obsessive-compulsive disorder (OCD).

METHOD

Twenty-nine subjects diagnosed with OCD according to Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) criteria were recruited through the Anxiety Clinic of Louis-H Lafontaine Hospital. They were evaluated at baseline and after treatment on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) by a psychiatrist who was blind to treatment modality. Subjects rated their degree of resistance to their rituals and the strength of their obsessional beliefs. Subjects then received 1 of 4 treatments: medication and CBT simultaneously (n = 9), CBT only (n = 6), medication while on a wait-list for CBT (n = 6), or no treatment while on a wait-list for CBT (n = 5).

RESULTS

Multivariate analysis revealed that Y-BOCS scores and clinical ratings significantly improved posttreatment in all groups except the nontreatment wait-list control group. Subjects in the 2 active treatment groups receiving CBT showed reduced strength in their obsessional beliefs. The subsequent administration of CBT to those groups on the wait-list also decreased the strength of their primary obsessional beliefs and beliefs about the consequences of not performing the rituals.

CONCLUSIONS

Our results suggest that either CBT or medication alone is more effective than no treatment. The combination of CBT and medication seems to potentiate treatment efficacy, and we found it more clinically beneficial to introduce CBT after a period of medication rather than to start both therapies simultaneously.

Detection of abscisic-acid-binding proteins in the microsomal protein fraction of Arabidopsis thaliana with abscisic-acid-protein conjugates used as affinity probes

A family of affinity probes has been generated to detect and purify abscisic-acid (ABA)-binding proteins, by coupling ABA onto carrier proteins (ovalbumin or BSA) through the C1 carboxyl group or the C4' carbonyl group of ABA. ELISA detection showed that these ABA-protein conjugates bound efficiently to the solubilized microsomal protein fraction of Arabidopsis thaliana, but not to the soluble protein fraction. Heat or proteolytic treatments inhibited the binding of the conjugates, indicating the protein nature of these binding sites. After membrane purification of the microsomes, the binding sites were found to be preferentially located in the plasma membrane fraction. The binding of the conjugates was independent of the nature of the carrier protein or the ABA-carrier protein linker, but was competitively inhibited with an anti-ABA mAb. Furthermore, the competitive inhibition of the binding of the conjugates with ABA, but not with the inactive ABA methyl ester analog, demonstrated the specificity of the binding and the saturability of the binding sites. The binding of the conjugates was strictly correlated to the ABA/carrier protein molar coupling ratio, confirming that the affinity of the conjugates to the ABA-binding proteins was enhanced by the increase in the probability of binding events. The experimental approach permits a new insight into the nature of membrane-associated ABA-binding proteins.

Functional interactions between synthetic alkyl phospholipids and the ABC transporters P-glycoprotein, Ste-6, MRP, and Pgh 1

The ABC superfamily of transporters includes the mammalian P-glycoprotein family (Class I and Class II P-gps), the multidrug resistance-associated protein (MRP), the Pgh-1 product of Plasmodium falciparum gene pfmdr1, all of which are associated with cellular pleiotropic drug resistance phenomena. STE6, the yeast transporter for the farnesylated peptide pheromone a, is also a member of this family. Structural similarities in this family translate into functional homology as expression of mouse Mdr3S (P-gp), P. falciparum Pgh-1, and human MRP partially restore mating in a sterile yeast mutant lacking a functional STE6 gene. The demonstration that Class II P-gps function as phosphatidylcholine (PC) translocators raise the possibility that other ABC transporters may also interact with physiological lipids. We report the identification of the synthetic lipid and PC analog ET-18-OCH3 (edelfosine) as a substrate for not only Class II P-gp but also for Class I P-gps and surprisingly for the other ABC transporters MRP, Pgh-1, and STE6. Expression of these proteins in the yeast Saccharomyces cerevisiae JPY201 was found to confer cellular resistance to cytotoxic concentrations of this lipid by a factor of 4-20-fold in a growth inhibition assay. The noted activity of ABC transporters toward this synthetic lipid was specific as a mutant variant of Mdr3 (Mdr3F) with reduced activity could not convey cellular resistance to ET-18-OCH3. ET-18-OCH3 was also found capable of blocking a-peptide pheromone transport and STE6 complementation by these ABC proteins. The inhibitory effect of ET-18-OCH3 on cell growth and a-factor transport could be abrogated by incubation with the lipid acceptor protein BSA or by enzymatic cleavage by microsomal alkylglycerol mono-oxygenase (MAMO). MAMO and BSA reversal of the ether lipid effect was only seen in the presence of a functional transporter. These results suggest that the group of cytotoxic synthetic PC analogs studied reveal possible structural and functional aspects common to the ABC transporters tested. Furthermore, the studies with BSA and MAMO suggest that the mechanism of transport of ET-18-OCH3 by these ABC transporters may be related to the flippase mechanism of PC transport by Mdr2.

The pfmdr1 gene of Plasmodium falciparum confers cellular resistance to antimalarial drugs in yeast cells

The exact role of the pfmdr1 gene in the emergence of drug resistance in the malarial parasite Plasmodium falciparum remains controversial. pfmdr1 is a member of the ATP binding cassette (ABC) superfamily of transporters that includes the mammalian P-glycoprotein family. We have introduced wild-type and mutant variants of the pfmdr1 gene in the yeast Saccharomyces cerevisiae and have analyzed the effect of pfmdr1 expression on cellular resistance to quinoline-containing antimalarial drugs. Yeast transformants expressing either wild-type or a mutant variant of mouse P-glycoprotein were also analyzed. Dose-response studies showed that expression of wild-type pfmdr1 causes cellular resistance to quinine, quinacrine, mefloquine, and halofantrine in yeast cells. Using quinacrine as substrate, we observed that increased resistance to this drug in pfmdr1 transformants was associated with decreased cellular accumulation and a concomitant increase in drug release from preloaded cells. The introduction of amino acid polymorphisms in TM11 of Pgh-1 (pfmdr1 product) associated with drug resistance in certain field isolates of P. falciparum abolished the capacity of this protein to confer drug resistance. Thus, these findings suggest that Pgh-1 may act as a drug transporter in a manner similar to mammalian P-glycoprotein and that sequence variants associated with drug-resistance pfmdr1 alleles behave as loss of function mutations.

High-performance liquid chromatographic determination of baclofen in human plasma

A reversed-phase isocratic HPLC method is described for the determination of baclofen in human plasma. Solid-phase extraction using a SCX Bond Elut column is used followed by derivatization with o-phthalaldehyde-tert.-butanethiol and electrochemical detection. Both the within- and between-day R.S.D. and inaccuracy are less than 10% and 7%, respectively, even at the limit of quantification of the method, i.e., 10 ng/ml. The method was shown to give optimum performance in terms of sensitivity, precision and accuracy for the pharmacokinetic study of baclofen after a single oral administration to volunteers.

Mutagenesis of transmembrane domain 11 of P-glycoprotein by alanine scanning

The biochemical and genetic analyses of P-glycoprotein (P-gp) have indicated that the membrane-associated regions of P-gp play an important role in drug recognition and drug transport. Predicted transmembrane domain 11 (TM11) maps near a major drug binding site revealed by photoaffinity labeling, and mutations in this domain alter the substrate specificity of P-gp. To investigate further the role of TM11 in P-gp function in general, and substrate specificity in particular, each of the 21 residues of TM11 of the P-gp isoform encoded by the mouse mdr3 gene was independently mutated to alanine, or to glycine in the case of endogenous alanines. After transfection and overexpression in Chinese hamster ovary cells, pools of stable transfectants were analyzed for qualitative or quantitative deviations from the profile of resistance to vinblastine, adriamycin, colchicine, and actinomycin D displayed by the wild-type protein. While mutations at eight of the positions had no effect on P-gp function, 13 mutants showed a 2-10-fold reduction of activity against one of the four drugs tested. Although the phenotype of individual mutants was varied, replacements at most mutation-sensitive positions seemed to affect the drug resistance profiles rather than the overall activity of the mutant P-gp. When TM11 was projected in a alpha-helical configuration, the distribution of deleterious and neutral mutations was not random but segregated with a more hydrophobic (mutation-insensitive) face and a more hydrophilic (mutation-sensitive) face of a putative amphipathic helix. The alternate clustering pattern of deleterious vs neutral mutations in TM11 together with the altered drug resistance profile of deleterious mutants suggest that the more hydrophilic face of the TM11 helix may play an important structural or functional role in drug recognition and transport by P-gp. Finally, the conservation of the two residues most sensitive to mutations (Y949 and Y953) in TM11, and in the homologous TM5, of all mammalian P-gps and also in other ABC transporters, suggests that these residues and domains may play an important role in structural as well as mechanistic aspects common to this family of proteins.

Functional expression of the multidrug resistance-associated protein in the yeast Saccharomyces cerevisiae

The multidrug resistance-associated protein (MRP) is a member of the ATP binding cassette superfamily of transporters which includes the mammalian P-glycoproteins (P-gp) family. In order to facilitate the biochemical and genetic analyses of MRP, we have expressed human MRP in the yeast Saccharomyces cerevisiae and have compared its functional properties to those of the mouse Mdr3 P-gp isoform. Expression of both MRP and Mdr3 in the anthracycline hypersensitive mutant VASY2563 restored cellular resistance to Adriamycin in this mutant. MRP and Mdr3 expression produced pleiotropic effects on drug resistance in this mutant, as corresponding VASY2563 transformants also acquired resistance to the anti-fungal agent FK506 and to the K+/H+ ionophore valinomycin. The appearance of increased cellular resistance to the toxic effect of Adriamycin (ADM) in MRP and Mdr3 transformants was concomitant with a reduced intracellular accumulation of [14C]ADM in spheroplasts prepared from these cells. Moreover, MRP and Mdr3, but not control spheroplasts, could mediate a time-dependent reduction in the overall cell-associated [14C]ADM from preloaded cells, suggesting the presence of an active ADM transport mechanism in MRP and Mdr3 transformants. Finally, human MRP was found to complement the biological activity of the yeast peptide pheromone transporter Ste6 and partially restored mating in a sterile ste6 null mutant. These findings suggest that despite their relatively low level of structural homology, MRP and P-gp share similar functional aspects, since both proteins can mediate transport of chemotherapeutic drugs and the a mating peptide pheromone in yeast.