Effect of genetic variation in the human S-adenosylhomocysteine hydrolase gene on total homocysteine concentrations and risk of recurrent venous thrombosis.

Contains fulltext : 57226.pdf (publisher's version ) (Closed access)Hyperhomocysteinemia is an independent and graded risk factor for arterial vascular disease and venous thrombosis. It is still debated via which mechanism homocysteine (Hcy) causes vascular disease. S-adenosylhomocysteine hydrolase (AHCY) catalyses the reversible hydrolysis of S-adenosylhomocysteine (AdoHcy) to Hcy. As an increase in AdoHcy, a strong inhibitor of many methyltransferases, is observed in hyperhomocysteinemic individuals, AdoHcy may play a role in the development of cardiovascular diseases by inhibiting transmethylation reactions. We sequenced the entire coding region and parts of the untranslated regions (UTRs) of the AHCY gene of 20 patients with recurrent venous thrombosis in order to identify genetic variation within this gene. We identified three sequence variants in the AHCY gene: a C > T transition in the 5' UTR (-34 bp C > T), a missense mutation in exon 2, which mandates an amino-acid conversion at codon 38 (112 C > T; Arg38Trp) and a silent mutation in exon 4 (390 C > T; Asp130Asp). We studied the effect of the first two variants on total plasma Hcy and venous thrombosis risk in a case-control study on recurrent venous thrombosis. The two polymorphisms under study seem to have no evident effect on tHcy. The adjusted relative risk of venous thrombosis associated with the 112CT genotype compared with 112CC individuals was 1.27 (95% CI 0.55-2.94), whereas the -34CT genotype confers a risk of 1.25 (95% CI 0.44-3.52) compared with the wild-type genotype at this locus. However, the wide confidence intervals do not allow firm conclusions to be drawn

Triblock copolymer based thermoreversible gels. 4. Effect of the midblock and characterization of the sol-gel transition

Thermoreversible gelation has been studied in o-xylene for poly(methyl methacrylate) containing 80% syndiotactic triads (sPMMA) and block copolymers of the MXM type, where M is sPMMA and X is either polybutadiene (PBD), hydrogenated PBD (PEB), poly(styrene-b-butadiene-b-styrene) (SBS) triblock, or the hydrogenated version of this triblock (SEBS). In o-xylene, which is a selective solvent for the central X block, sPMMA forms thermoreversible gels provided that the molecular weight is high enough. When sPMMA is the outer block of MXM triblock copolymers, the midblock X appears to favor the gelation and it considerably improves the thermal stability of the matured gels. This thermal stability is, however, largely independent of the actual nature of the midblock. The dynamic properties of solutions and gels have been analyzed and discussed on the basis of scaling assumptions. At the gel point, where the loss angle tan δc = G‘‘/G‘ is independent of the probing frequency, the sample obeys the typical power law G‘(ω) G‘‘(ω) ωΔ. The scaling exponent Δ is found in the 0.65−0.75 range for both sPMMA and MXM block copolymers, independent of the nature of the midblock. Modulus−frequency master curves have been built by using appropriate reaction time dependent renormalization factors for the individual frequency and modulus data. The scaling of these factors with reaction time has allowed us to calculate the static scaling exponents for the increase observed in both modulus and viscosity. The accordingly calculated values agree with the scalar elasticity percolation model

Photoelectron energy loss spectroscopy: a versatile tool for material science

International audienceX-ray Photoelectron Spectroscopy (XPS) used in quantitative chemical analysis of solid surfaces requires subtraction of a broad background, arising from various energy loss mechanisms, to obtain reliable core level peak intensities. Besides single electron excitation, collective electron oscillations (plasmons) can be excited in the bulk and at the surface. Photoelectron energy loss spectroscopy (XPS-PEELS) is a non-destructive tool useful for both process control and thin film metrology. This review emphasizes its versatility to elucidate material research issues. The energy loss function (ELF) is useful for thin film growth optimization since it gives insight in valence electron density, hardness, optical band gap and interface properties such as adhesion and wetting. XPS-PEELS also provides depth and width of implanted atom profiles in solid targets, e.g. Ar nanobubbles in Al. Special emphasis is given to the retrieval of electronic properties from XPS-PEELS data. Since the ELF, q, is related to the q-averaged dielectric function, q, the latter can be obtained by taking into account multiple bulk and surface plasmon excitations. This task is rather simple in wide band gap materials where the ELF and the no-loss peak are clearly separated, as illustrated by amorphous silicon, amorphous carbon or Al oxide data. In contrast, in metals or small band gap materials, the broad asymmetric photoemission peak overlaps the ELF and low energy features in the ELF may be lost. A Fourier Transform (FT) method is proposed to analyze PEELS data, with the objective of retrieving such low energy excitations, e.g. inter band transitions. This FT method is compared with an empirical method based on a smooth cutoff of the zero-loss peak, using PEELS data obtained from Al2O3. Current developments of a quantum mechanical theory are crucial to obtain the respective contributions of intrinsic and extrinsic plasmon excitation (along with their interference) and to assess some approximations performed in classical treatments