Isolation of Acanthamoeba isolates belonging to T2, T3, T4 and T7 genotypes from environmental samples in Ankara, Turkey

Acanthamoeba keratitis is a blinding infection that is becoming increasingly important in human health. Early diagnosis is a prerequisite for successful treatment and requires identification of Acanthamoeba at the genotypic level. The genus Acanthamoeba consists of both pathogenic and non-pathogenic species and has been recently classified into 13 different genotypes, T1-T12 and T14. More importantly, 95% of Acanthamoeba isolates that produce keratitis belong to T4 genotypes. In this study, we attempted to determine whether predominance of T4 isolates in Acanthamoeba keratitis is due to greater virulence or greater prevalence. We isolated 18 Acanthamoeba isolates from environmental samples in Ankara, Turkey and determined their pathogenic potential by means osmotolerance, temperature tolerance and in vitro cytotoxicity assays using corneal epithelial cells. Ribosomal DNA sequencing revealed that 10 isolates belong to T2, 5 belong to T3, 2 belong to T4 and one belongs to T7 genotype. As expected, T3 and T4 isolates exhibited the most pathogenic traits and were osmotolerant, temperature tolerant and exhibited severe corneal epithelial cell cytotoxicity indicating their pathogenic potential. Overall these data indicate that high frequency of T4 isolates in keratitis cases may well be due to their greater virulence. This is the first report presenting environmental distribution of Acanthamoeba in Ankara, Turkey

Acanthamoeba castellanii induces host cell death via a phosphatidylinositol 3-kinase-dependent mechanism

Granulomatous amoebic encephalitis due to Acanthamoeba castellanii is a serious human infection with fatal consequences, but it is not clear how the circulating amoebae interact with the blood-brain barrier and transmigrate into the central nervous system. We studied the effects of an Acanthamoeba encephalitis isolate belonging to the T1 genotype on human brain microvascular endothelial cells, which constitute the blood-brain barrier. Using an apoptosis-specific enzyme-linked immunosorbent assay, we showed that Acanthamoeba induces programmed cell death in brain microvascular endothelial cells. Next, we observed that Acanthamoeba specifically activates phosphatidylinositol 3-kinase. Acanthamoeba-mediated brain endothelial cell death was abolished using LY294002, a phosphatidylinositol 3-kinase inhibitor. These results were further confirmed using brain microvascular endothelial cells expressing dominant negative forms of phosphatidylinositol 3-kinase. This is the first demonstration that Acanthamoeba-mediated brain microvascular endothelial cell death is dependent on phosphatidylinositol 3-kinase

First-Principles Calculation of Thermal Transport in the Metal/Graphene System

Thermal properties in the metal/graphene (Gr) systems are analyzed by using an atomistic phonon transport model based on Landauer formalism and first-principles calculations. The specific structures under investigation include chemisorbed Ni(111)/Gr, physisorbed Cu(111)/Gr and Au(111)/Gr, as well as Pd(111)/Gr with intermediate characteristics. Calculated results illustrate a strong dependence of thermal transfer on the details of interfacial microstructures. In particular, it is shown that the chemisorbed case provides a generally smaller interfacial thermal resistance than the physisorbed due to the stronger bonding. However, our calculation also indicates that the weakly chemisorbed interface of Pd/Gr may be an exception, with the largest thermal resistance among the considered. Further examination of the electrostatic potential and interatomic force constants reveal that the mixed bonding force between the Pd and C atoms results in incomplete hybridization of Pd and graphene orbital states at the junction, leading effectively to two phonon interfaces and a larger than expected thermal resistance. Comparison with available experimental data shows good agreement. The result clearly suggests the feasibility of phonon engineering for thermal property optimization at the interface

Market Impact on financial market integration: Cross-quantilogram analysis of the global impact of the euro

[eng] We contribute to the literature by providing a more comprehensive understanding of the impact the euro has had on financial market integration with economies of different characteristics outside and within the European market via inclusion of market conditions influence on the level of financial integration. Our paper employs the recently developed cross-quantilogram (Han et al., 2016) approach to examine quantile dependence between the conditional stock return distributions of Germany and the UK with that of three common currency groups within EMU (Finland, France, and Italy), two global leading markets (the US and Japan), and two of the most promising emerging markets (China and India). We find three key results. First, both the EU membership and the common currency union affect the degree of financial market integration. Nevertheless, disentangling the effects of EU membership from the common currency shows that the common currency group has an additional impact on financial integration, as the degree of dependence is stronger in the common currency group than in the sovereign currency group and other groups. Second, there is a heterogeneous dependence structure, which is strongly observed for the UK and German stock returns with that of developed (the US and Japan) and emerging markets (India and China). Third, cross-quantile correlations change over time, especially in low and high quantiles, indicating that they are prone to jumps and discontinuities in the dependence structure. As far as we are aware, this is the first study in this field employing a cross-quantilogram method to examine the impact of different market conditions on the correlations, making our study a pioneer in the field of stock market integration

Study of avidity of antigen-specific antibody as a means of understanding development of long-term immunological memory after Vibrio cholerae O1 infection

The avidity of antibodies to specific antigens and the relationship of avidity to memory B cell responses to these antigens have not been studied in patients with cholera or those receiving oral cholera vaccines. We measured the avidity of antibodies to cholera toxin B subunit (CTB) and Vibrio cholerae O1 lipopolysaccharide (LPS) in Bangladeshi adult cholera patients (n = 30), as well as vaccinees (n = 30) after administration of two doses of a killed oral cholera vaccine. We assessed antibody and memory B cell responses at the acute stage in patients or prior to vaccination in vaccinees and then in follow-up over a year. Both patients and vaccinees mounted CTB-specific IgG and IgA antibodies of high avidity. Patients showed longer persistence of these antibodies than vaccinees, with persistence lasting in patients up to day 270 to 360. The avidity of LPS-specific IgG and IgA antibodies in patients remained elevated up to 180 days of follow-up. Vaccinees mounted highly avid LPS-specific antibodies at day 17 (3 days after the second dose of vaccine), but the avidity waned rapidly to baseline by 30 days. We examined the correlation between antigen-specific memory B cell responses and avidity indices for both antigens. We found that numbers of CTB- and LPS-specific memory B cells significantly correlated with the avidity indices of the corresponding antibodies (P < 0.05; Spearman's ρ = 0.28 to 0.45). These findings suggest that antibody avidity after infection and immunization is a good correlate of the development and maintenance of memory B cell responses to Vibrio cholerae O1 antigens