Role of pressure on electronic, magnetic and structural properties at iron's Curie temperature: a DFT + DMFT study.

We use the combination of density functional theory and dynamical mean-field theory to compute the Curie temperature of the iron body-centered cubicαphase and probe its pressure dependence. Our calculations reveal thatTCshows a decrease which is very weak over a domain of pressures that is much larger than the stability domain of theαphase. This is consistent with the experimental results. We highlight the importance of the Hund's couplingJnot only on the electronic and magnetic properties but also on the structural properties. Lastly, we analyze the electronic and magnetic properties under pressure and discuss the evolution of magnetic moments in both phases in relation to the change of Curie temperature.

Association between genetic variants in the HNF4A gene and childhood-onset Crohn's disease.

Hepatocyte nuclear 4 alpha (HNF4α), involved in glucose and lipid metabolism, has been linked to intestinal inflammation and abnormal mucosal permeability. Moreover, in a genome-wide association study, the HNF4A locus has been associated with ulcerative colitis. The objective of our study was to evaluate the association between HNF4α genetic variants and Crohn's disease (CD) in two distinct Canadian pediatric cohorts. The sequencing of the HNF4A gene in 40 French Canadian patients led to the identification of 27 single nucleotide polymorphism (SNP)s with a minor allele frequency >5%. To assess the impact of these SNPs on disease susceptibility, we first conducted a case-control discovery study on 358 subjects with CD and 542 controls. We then carried out a replication study in a separate cohort of 416 cases and 1208 controls. In the discovery cohort, the genotyping of the identified SNPs revealed that six were significantly associated with CD. Among them, rs1884613 was replicated in the second CD cohort (odds ratio (OR): 1.33; P<0.012) and this association remained significant when both cohorts were combined and after correction for multiple testing (OR: 1.39; P<0.004). An 8-marker P2 promoter haplotype containing rs1884613 was also found associated with CD (P<2.09 × 10(-4) for combined cohorts). This is the first report showing that the HNF4A locus may be a common genetic determinant of childhood-onset CD. These findings highlight the importance of the intestinal epithelium and oxidative protection in the pathogenesis of CD.

Set-up and routine use of a database of 10,555 genotyped blood donors to facilitate the screening of compatible blood components for alloimmunized patients.

BACKGROUND AND OBJECTIVES: Large-scale genotyping of blood donors for red blood cell and platelet antigens has been predicted to replace phenotyping assays in the screening of compatible blood components for alloimmunized patients. Although several genotyping platforms have been described, novel procedures and processes are needed to perform genotyping efficiently and to maximize its benefits for blood banks. MATERIALS AND METHODS: Here we describe the processes and procedures developed to introduce large-scale genotyping in our routine operations. RESULTS: Preliminary cost-benefit analysis indicated that genotyping must target frequent blood donors (> 3 donations/year) to be efficiently used. A custom-designed computer application was developed to manage the whole project. It selects frequent donors among recent donations, prints coded labels to identify blood samples sent to the external genotyping laboratory, and stores genotyping results. It can search for donors compatible for any combination of the 22 genotyped antigens as well as consult the current inventory for the presence of the corresponding blood components. The phenotype of recovered components is confirmed by standard serology techniques prior to shipment to hospitals. CONCLUSION: Since October 2007, 10 555 blood donors have been genotyped. The database is used on a regular basis to find compatible blood components with a genotype-phenotype concordance of 99.6%.

FTIR features of lithium-iron phosphates as electrode materials for rechargeable lithium batteries.

The essential structural features of lithium-metal phosphates (LMP) have been studied using FTIR spectroscopy which is a sensitive tool to probe the local environment in the solid materials. Various LMP materials where M is iron have been investigated including phospho-olivine LiFePO(4), diphosphate LiFeP(2)O(7), Nasicon-type phosphate Li(3)Fe(2)(PO(4))(3) and dihydrate FePO(4).2H(2)O. Vitreous and amorphous materials are also considered. Analysis of internal and external modes of vibration allows to distinguish between the different phases and the type of cationic environment in the framework. Results corroborate the contribution of the main factors which are responsible for the complexity of the spectra, i.e. departure from ideal symmetry, interactions between polyhedra, bridging atoms and lattice distortion.

Characterization of the NTPDase activities in the mesentery pre- and post-capillary circuits of the guinea pig.

NTPDase is one of the principal enzymes involved in the sequential hydrolysis of ATP. In the present study, the presence and functionality of NTPDase in the mesenteric vein and artery were examined. Adenosine triphosphate (ATP) (0.01-1000 pmol) induces a dose-dependent vasodilation in the isolated arterial and venous mesenteric vasculatures of the guinea pig. Adenosine diphosphate (ADP) (0.01-1000 pmol) but not adenosine monophosphate (AMP) (0.01-1000 pmol) induces a similar response in the mesenteric vascular circuit. L-NAME, a nitric oxide synthase inhibitor (200 microM, 30 min), significantly reduces the arterial dilatory effect of ATP and abolishes the responses to ADP and AMP. Complete removal of the endothelium with 3-[(3-cholamidopropyl) dimethylammonio]-1-propansulfonate (CHAPS) (20 mM, 2 x 45 s) abolishes ATP-induced responses. Infusion of ATP in the vascular circuit generated detectable amounts of ADP and AMP, as measured by HPLC. CHAPS treatment significantly reduced the level of ATP and the production of AMP in the arterial mesenteric circuit. In contrast to the arterial mesenteric vasculature, endothelium removal in the venous circuit triggered a marked potentiation of ADP release and, interestingly, a marked reduction in the release of AMP. Moreover, a specific inhibitor of NTP diphosphohydrolase, 1-hydroxynaphthlene-3,6-disulfonic acid BGO 136 (10 mM for 20 min), significatively reduced AMP production in both vascular preparations. These results confirm that the endothelium contributes to the vasoactive properties of ATP, ADP, and AMP. Our data also demonstrated a significant role of endothelium in NTPDase activity on ADP and AMP production prior to exogenous administration of ATP. The activity of this particular enzyme appears to be different from the reaction products viewpoint (i.e., the production of ADP) in the pre- and post-mesenteric circuits, suggesting two different isoforms with different substrate specificities.

Purine signaling and potential new therapeutic approach: possible outcomes of NTPDase inhibition.

Interest for extracellular nucleotides has increased since the pioneer work of Burnstock in the early seventies. Research on cellular functions modulated by purines and pyrimidines has led to the identification and characterization of the different components of purine signaling, namely purinoceptors and ecto-nucleotidases. Receptors for tri- and diphosphonucleosides, known as P2 nucleotide receptors, are designated either P2Y receptors, for those coupled to G-proteins, or P2X for those which are ligand gated-ion channels. Ecto-nucleoside triphosphate diphosphohydrolase (NTPDase; EC 3.6.1.5), previously identified as ecto-ATPase, ecto-ATPDase or CD39, is now considered as the main ecto-nucleotidase responsible for the sequential hydrolysis of beta and gamma phosphates of tri- and diphosphonucleosides. More recently, research has been focused on the development of specific agonists and antagonists to P2 purinoceptors. The need to develop specific inhibitors for NTPDase to understand the role of this enzyme has clearly emerged. This paper covers the development of specific molecules targeting purinergic signaling, more specifically the inhibition of NTPDase and their impact on the different physiological systems.

Ca(2+)-channel blockers and nucleoside triphosphate diphosphohydrolase (NTPDase) influence of diltiazem, nifedipine, and verapamil.

The nucleoside triphosphate diphosphohydrolases (NTPDase; EC 3.6.1. 5) are a family of ectonucleotidases associated with vascular endothelial and smooth muscle cells. These ectonucleotidases are involved in the control of vascular tone by regulating the level of circulating ATP. Ca(2+)-channel blocking agents are currently used for the treatment of hypertension. Considering the external localization of the NTPDase catalytic site and its Ca(2+) requirement for enzyme activity, a possible interference of calcium antagonists (nifedipine, verapamil-HCl, and diltiazem-HCl and some of its metabolites) could be anticipated. To test that hypothesis, an NTPDase-enriched particulate fraction was used. Our results show that verapamil, diltiazem, and its metabolites all produced a concentration-dependent inhibition of NTPDase, at concentrations greater or equal to 0.1 mM with verapamil and to 0.5 mM with diltiazem and its metabolites, whereas no significant effect was observed with nifedipine. Kinetic studies, carried out to define the mode of action of these drugs, showed a mixed type of inhibition. Based on their respective K(i) values (in parentheses, in mM), inhibitory potencies of these molecules were in the following order: desacetyl-N-desmethyldiltiazem (M(2)-HCl; 0.6) > verapamil (0.76) > N-desmethyldiltiazem (M(A;) 0.9) > diltiazem (2.4) > desacetyl-O-desmethyldiltiazem (M(4)-HCl; 3.5) > desacetyl N, O-desmethyldiltiazem (M(6)-HCl; 3.9). Hence, these calcium antagonists can be considered as weak NTPDase inhibitors. Moreover, based on these K(i) values and the range of concentrations found in the blood, NTPDase would not be inhibited significantly in vivo.

Synthesis, mechanism and fluorescence properties of 8-(aryl)-3-beta-D-ribofuranosylimidazo[2,1-i]purine 5'-phosphate derivatives.

The synthesis of new fluorescent nucleotides is described. This synthesis comprises two parallel reactions, the Kornblum oxidation and imidazole formation, which lead to 8-(aryl)-3-beta-D-ribofuranosylimidazo[2,1-i]purine 5'-phosphates 2 from AMP or ATP. A detailed mechanism is proposed based on monitoring the reaction by 1H- and 13C-NMR spectroscopy, MS, FAB, HPLC, and pH meter. The spectral and fluorescent properties of the new derivatives at various pH values are described. Excitation and emission maxima for 3 were observed at 290 and 420 nm, respectively, in both basic and neutral media. In acidic media, the emission maximum shifted to 410 nm, however, the fluorescence intensity increased 1.5-fold. ATP analogues 2b and 3b exhibited relative stability regarding hydrolysis by type II ATPDase. Compound 3b is relatively chemically stable at pH 10.4 and 7.4.

2-Thioether-5'-O-(1-thiotriphosphate)-adenosine derivatives: new insulin secretagogues acting through P2Y-receptors.

P2-receptors (P2-Rs) represent significant targets for novel drug development. P2-Rs were identified also on pancreatic B cells and are involved in insulin secretion. The aim of our study was to synthesize and evaluate pharmacologically the novel P2Y-R ligands, 2-thioether-5'-O-phosphorothioate adenosine derivatives, as potential insulin secretagogues. An efficient synthesis of these nucleosides and a facile method for separation of the chiral products is described. The enzymatic stability of the compounds towards pig-pancreas NTPDase was evaluated. The rate of hydrolysis of 2-hexylthio-5'-O-(1-thiotriphosphate)-adenosine (2-hexylthio-ATP-alpha-S) isomers by NTPDase was 28% that of ATP. The apparent affinity of the compounds to P2Y1-R was determined by measurement of P2Y-receptor-promoted phospholipase C activity in turkey erythrocyte membranes. 2-RS-ATP-alpha-S derivatives were agonists, stimulating the production of inositol phosphates with K0.5 values in the nM range. 2-RS-AMP-S derivatives were full agonists although 2 orders of magnitude less potent. All the compounds were more potent than ATP. The effect on insulin secretion and pancreatic flow rate was evaluated on isolated and perfused rat pancreas. A high increase, up to 500%, in glucose-induced insulin secretion was due to addition of 2-hexylthio-ATP-alpha-S in the nM concentration range, which represents 100-fold enhancement of activity relative to ATP. 2-Hexylthio-AMP-S was 2.5 orders of magnitude less effective. A high chemical hydrolytic stability was observed for 2-hexylthio-ATP-alpha-S. Hydrolysis of the phosphoester bond, which was the only detectable degrading reaction under the investigation conditions (pH 7.4, 37 degrees C), was slow, with a half-life of 264 hours. Moreover, even at gastric juice conditions (pH 1.4, 37 degrees C), hydrolysis of the terminal phosphate was the only detectable reaction, with a half-life of 17.5 hours. 2-Hexylthio-ATP-alpha-S isomers are enzymatically and chemically stable. These isomers are highly potent and effective insulin secretagogues, increasing, however, pancreatic vascular resistance.

Identification, characterization, and immunolocalization of a nucleoside triphosphate diphosphohydrolase in pig liver.

Different isoforms of nucleoside triphosphate diphosphohydrolases (NTPDases; EC 3.6.1.5), also identified as ATP diphosphohydrolases, have been previously described in mammalian tissues. We report here the biochemical characterization of NTPDases in the pig liver. Optimum pH of catalysis is more acidic for this enzyme than for NTPDases (neutral or alkaline pH) found in other mammalian tissues. It is less sensitive to bile salts than the bovine spleen NTPDase. Calculated Km values for ATP and ADP (31 and 21 microM, respectively) are slightly higher than those reported for the latter enzyme. Electrophoretograms of these enzymes also show different migration patterns. Western blots with Ringo, an antibody that recognizes the different isoforms of mammalian NTPDases, show a small but reproducible difference in estimated molecular masses (75 kDa for liver vs 78 kDa for spleen NTPDase). A second antibody, generated against a different sequence of NTPDase I, does not recognize the liver enzyme, thereby indicating some differences in primary structure. Immunolocalization produced a strong signal on hepatocytes, epithelial cells of the bile duct system, and vascular cells. Immunoreactivity was variable among hepatocytes of different lobules and among hepatocytes within a given lobule. In general, those located in the perilobular zone were more reactive than those located in the central zone and in the periphery of the centrolobular vein.

Novel inhibitors of nucleoside triphosphate diphosphohydrolases: chemical synthesis and biochemical and pharmacological characterizations.

To elucidate the physiological role played by nucleoside triphosphate diphosphohydrolase (NTPDase; EC 3.6.1.5), adenine nucleotide analogues, modified on the purine ring, have been synthesized and tested as potential inhibitors. Resistance of ATP analogues to hydrolysis and their potency as NTPDase inhibitors were evaluated. For this purpose, a particulate fraction isolated from bovine spleen was used as the enzyme source. Among the synthesized analogues, 8-thiobutyladenosine 5'-triphosphate (8-BuS-ATP) was found to be the most effective nonhydrolyzable competitive inhibitor, with an estimated K(i) of 10 microM. This nonhydrolyzable analogue did not exert any P2X-receptor-mediated effect on endothelium-denuded blood vessels, from the guinea pig mesenteric bed. In agreement with this observation, infusion of the analogue did not cause any significant blood pressure variations of the precontracted vessel. Because in previous studies on isolated turkey erythrocytes and rat astrocytes 8-BuS-ATP was not able to trigger any P2Y(1)-receptor-mediated effect, it therefore appears that this NTPDase inhibitor does not interfere with purinergic receptors.

Identification and immunolocalization of two isoforms of ATP-diphosphohydrolase (ATPDase) in the pig immune system.

The occurrence of a variety of purine receptors in the immune system indicates that extracellular purines play important functional roles. Extracellular purine concentrations are, in great part, determined by ectonucleotidases, namely, the ATP diphosphohydrolase, also identified as CD39, a lymphocyte cell surface marker. The latter enzyme converts triphospho- and diphosphonucleosides to nucleoside monophosphates. In this study, high levels of ATPase and ADPase activities have been found in homogenates of the different pig lymphoid organs. Specific activities decreased in the following order: spleen > bone marrow > thymus > lymph glands. The parallel decrease in ATPase and ADPase activities, in the presence of sodium azide, indicated that an ATP diphosphohydrolase (ATPDase) was responsible for these activities. Particulate fractions, prepared from the different lymphoid organs by ultracentrifugation on a sucrose cushion, showed about a 10-fold enrichment of ATPDase activity. Identity of ATPDase was confirmed by electrophoretograms of the particulate fractions and Western immunoblots, with an antibody that recognizes ATPDases from different sources. Two isoforms of ATPDase were found (I and II), corresponding to molecular masses of 78,000 and 54,000, respectively, as estimated by SDS-PAGE. Immunohistochemical localization was carried out on these different organs: In spleen, reaction was found in both white and red pulps. A particularly intense reaction was put in evidence in nervous fibers of this organ. Immunolocalization also showed positive reactions with tonsilar lymphoid structures, diffuse lymphoid tissues, and nodules associated with stomach, duodenum, jejunum, and ileum. In addition, our observations establish the presence of ATPDase in lymphocytes and macrophages of the pig immune system.

2-thioether 5'-O-(1-thiotriphosphate)adenosine derivatives as new insulin secretagogues acting through P2Y-Receptors.

P2-Receptors (P2-Rs) represent significant targets for novel drug development. P2-Rs were identified also on pancreatic B cells and are involved in insulin secretion. Therefore, novel P2Y-R ligands, 2-thioether 5'-O-phosphorothioate adenosine derivatives (2-RS-ATP-alpha-S), were synthesized as potential insulin secretagogues. An efficient synthesis of these nucleotides and a facile method for separation of the chiral products are described. The enzymatic stability of the compounds toward pig pancreas type I ATPDase was evaluated. The rate of hydrolysis of 2-hexylthio-5'-O-(1-thiotriphosphate)adenosine (2-hexylthio-ATP-alpha-S) isomers by ATPDase was 28% of that of ATP. Some 2-thioether 5'-(monophosphorothioate)adenosine derivatives (2-RS-AMP-S) exerted an inhibitory effect on ATPDase. The apparent affinity of the compounds to P2Y(1)-R was determined by measurement of P2Y-R-promoted phospholipase C activity in turkey erythrocyte membranes. 2-RS-ATP-alpha-S derivatives were agonists, stimulating the production of inositol phosphates with K(0.5) values in the nanomolar range. 2-RS-AMP-S derivatives were full agonists, although 2 orders of magnitude less potent. All the compounds were more potent than ATP. The effect on insulin secretion and pancreatic flow rate was evaluated on isolated and perfused rat pancreas. A high increase, up to 500%, in glucose-induced insulin secretion was due to addition of 2-hexylthio-ATP-alpha-S in the nanomolar concentration range, which represents 100-fold enhancement of activity relative to ATP. 2-Hexylthio-AMP-S was 2.5 orders of magnitude less effective.

Demonstration and immunolocalization of ATP diphosphohydrolase in the pig digestive system.

Two isoforms of ATP diphosphohydrolase (ATPDase; EC 3.6.1.5) have been previously characterized, purified, and identified. This enzyme is an ectonucleotidase that catalyzes the sequential release of gamma- and beta-phosphate groups of triphospho- and diphosphonucleosides. One of its putative roles is to modulate the extracellular concentrations of purines in different physiological systems. The purpose of this study was to define, identify, and localize these two isoforms of ATPDase in the pig digestive system. ATPDase activity was measured in pig stomach, duodenum, pancreas, and parotid gland. Enzyme assays, electrophoretograms, and Western blots with a polyclonal antibody that recognizes both isoforms demonstrate the presence of ATPDase in these organs. Immunolocalization showed intense reactions with gastric glands (parietal and chief cells), intestine (columnar epithelial cells), parotid gland, and pancreas. Smooth muscle cells all along the digestive tract were also highly reactive. Considering the variety of purinoceptors associated with the digestive system, the ATPDase is strategically positioned to modulate purine-mediated actions such as electrolyte secretion, glandular secretion, smooth muscle contraction, and blood flow.

A five-year experience with second-trimester induced abortions: no increase in complication rate as compared to the first trimester.

OBJECTIVE: Our purpose was to compare the complication rate of first-trimester suction curettage with that of second-trimester dilation-and-evacuation abortions in the same clinical setting. STUDY DESIGN: Retrospective analysis (chart review) of the 3772 induced abortions performed between 1986 and 1990 at the Family Planning Clinic of the Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada. RESULTS: Among the 3355 cases with known follow-up (89%), the complication rate was 5.1% for the 2908 suction curettages at < 15 weeks' gestation compared with 2.9% for the 447 dilation-and-evacuation procedures at 15 to 20 weeks' gestation. Serious complications were few and not increased among patients undergoing dilation and evacuation. CONCLUSION: A careful approach to second-trimester dilation-and-evacuation procedures can make them comparatively as safe as suction curettages, contrary to common belief derived from large surveys done in the late 1970s.

PIP: Physicians reviewed 3355 charts of women who underwent an induced abortion between 1986 and 1990 at the family planning clinic of the Sherbrooke University Hospital in Quebec, Canada, to compare the complication rate of late second trimester abortions (15-20 weeks gestation) with that of first trimester abortions (15 weeks gestation). For all cases, physicians ordered preoperative cervical cultures for gonorrhea and chlamydia and used local anesthesia. They used laminaria tents for cases of at least 13 weeks gestation. They did an ultrasound for all cases of at least 15 weeks gestation. They disinfected the vagina, cervix, and perineum in all cases. They followed the no-touch sterile technique. Cases of at least 15 weeks gestation received iv oxytocin during the operation while the 10-14 week cases received injected oxytocin intracervically. The physicians applied Pratt cervical dilatation, ruptured the membranes, and let the amniotic fluid drain. They use Hern or Bierer forceps with adjunctive suction to empty the conceptus. They scraped the uterine cavity with sharp curettes in all cases to confirm that it was empty. 4.8% of all women had surgical complications which were more likely to occur in the 15-week group than in the or= 15-week group (5.1% vs. 2.9%; p = .056). Most common complications were infection (3.4% vs. 2%; p = .14) and incomplete abortions (0.9% vs. 0.4%, not significant, however). Just 11% of infection cases had to be hospitalized. 4 women experienced uterine perforations (3 in first trimester). Just 2 hospitalization cases were considered major surgical complications: postoperative moderate bleeding for 3 days in an incomplete abortion at 17 weeks, gestation, resulting in transfusion, and a first trimester postoperative infection case with a fever lasting more than 3 days. These findings showed that prudent second trimester dilatation and evacuation is essentially as safe as first trimester suction curettages.