Tuning the magnetic exchange via a control of orbital hybridization in Cr(2)(Te(1-x)W(x))O(6)

We report the complex magnetic phase diagram and electronic structure of Cr_{2}(Te_{1-x}W_{x})O_{6} systems. While compounds with different x values possess the same crystal structure, they display different magnetic structures below and above x_{c}=0.7, where both the transition temperature T_{N} and sublattice magnetization (M_{s}) reach a minimum. Unlike many known cases where magnetic interactions are controlled either by injection of charge carriers or by structural distortion induced via chemical doping, in the present case it is achieved by tuning the orbital hybridization between Cr 3d and O 2p orbitals through W 5d states. The result is supported by ab initio electronic structure calculations. Through this concept, we introduce a new approach to tune magnetic and electronic properties via chemical doping.

Competition between antiferromagnetism and ferromagnetism in Sr2RuO4 probed by Mn and Co doping

Spin-triplet superconductivity in Sr₂RuO₄ has attracted enormous interest. Like other unconventional superconductors, superconductivity in Sr₂RuO₄ is in close proximity to magnetic instability. Undoped Sr₂RuO₄ exhibits incommensurate antiferromagnetic (AFM) fluctuations, which can evolve into static, short-range AFM order via Ti doping. Moreover, weak ferromagnetic (FM) coupling in Sr₂RuO₄ has also been suggested by NMR/neutron scattering experiments and studies on Ca_2−xSr_xRuO₄ and Sr_2−yLa_yRuO₄, implying orbital dependent magnetism. We report bulk static, short-range FM order in Sr₂RuO₄ triggered by <2% Co doping, showing superconductivity in Sr₂RuO₄ is much closer to FM instability than previously reported in Ca_2−xSr_xRuO₄. We also find Mn doping can effectively establish incommensurate AFM order, with T_N ~ 50 K for 3% Mn doping. These new results place Sr₂RuO₄ in a unique situation where superconductivity lies directly on the borderline of two distinct magnetic states, highlighting the important role of competing magnetic fluctuations in determining superconducting properties of Sr₂RuO₄.

Spin structure in an interfacially coupled epitaxial ferromagnetic oxide heterostructure

We report the spin structure of an exchange-biased ferromagnetic oxide heterostructure, La(0.67)Sr(0.33)MnO(3)/SrRuO(3), through magnetization and polarized neutron reflectometry measurements. We reveal that the magnetization reversal process of the La(0.67)Sr(0.33)MnO(3) biased layer critically depends on the frozen-in spin structure of the SrRuO(3) biasing layer during the cooling process. Furthermore, we observe unexpected double-shifted hysteresis loops of the biased layer that originates from the formation of lateral 180° magnetic domains within the biasing layer, a new mechanism not found in conventional exchange-bias systems.

KH902 suppresses high glucose-induced migration and sprouting of human retinal endothelial cells by blocking VEGF and PIGF

AIMS

Vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are upregulated in many ocular neovascular diseases such as diabetic retinopathy (DR). KH902 is a recombinant fusion protein with its binding ligand taken from the domains of VEGF receptor-1 (VEGFR-1) and VEGF receptor-2 (VEGFR-2) and can bind all VEGF-A isoforms and PlGF. The aim of this study was to investigate the underlying mechanisms of anti-angiogenic effects of KH902.

METHODS

The toxic effect of KH902 on cultured human retinal endothelial cells (HRECs) was measured by Annexin V/PI staining and MTT assay. The concentrations of secreted VEGF and PlGF were measured by ELISA. The migration of HRECs was assessed by scratch wound and transwell assay. The sprouting of HRECs was determined by tube formation assay. The protein levels of Src, p-Src, PI3K, Akt1, p-Akt1, Erk1/2 and p-Erk1/2 were measured by Western blot.

RESULTS

KH902 at the concentrations from 100 ng/ml to 100 µg/ml had no cytotoxicity to cultured HRECs. KH902 bound not only VEGF165, but also PlGF that were secreted by HRECs under high glucose condition. A 500 ng/ml of KH902 significantly suppressed high glucose-induced migration and sprouting of HRECs through downregulating the expression of PI3K and inhibiting the activation of Src, Akt1 and Erk1/2.

CONCLUSION

Our study indicates that KH902 suppresses high glucose-induced migration and sprouting of HRECs through not only binding VEGF, but also PlGF to inhibit the activation of Src-Akt1-Erk1/2 pathway. KH902 is a drug that potentially inhibits angiogenic pathways involving in DR or other ocular neovascular diseases.

Electrical tomography using atomic force microscopy and its application towards carbon nanotube-based interconnects

The fabrication and integration of low-resistance carbon nanotubes (CNTs) for interconnects in future integrated circuits requires characterization techniques providing structural and electrical information at the nanometer scale. In this paper we present a slice-and-view approach based on electrical atomic force microscopy. Material removal achieved by successive scanning using doped ultra-sharp full-diamond probes, manufactured in-house, enables us to acquire two-dimensional (2D) resistance maps originating from different depths (equivalently different CNT lengths) on CNT-based interconnects. Stacking and interpolating these 2D resistance maps results in a three-dimensional (3D) representation (tomogram). This allows insight from a structural (e.g. size, density, distribution, straightness) and electrical point of view simultaneously. By extracting the resistance evolution over the length of an individual CNT we derive quantitative information about the resistivity and the contact resistance between the CNT and bottom electrode.

Optimized self-microemulsifying drug delivery systems (SMEDDS) for enhanced oral bioavailability of astilbin

The main purpose of this research work was to design an optimized self micro-emulsifying drug delivery system (SMEDDS) to enhance the bioavailability of the poor water soluble drug, astilbin. The solubility of astilbin was evaluated in various vehicles. Pseudoternary phase diagrams were used to select the components and their ranges by evaluating the micro-emulsification area. Central composite design was applied to optimize the properties of the formulation, including particle size, polydispersity index, drug loading capacity and effective intestinal permeability. The optimized SMEDDS characteristics were investigated including the study of factors influencing particle size and showed the stability of microemulsion when varying the pH and volume of diluents. In vitro drug release profile study was performed using the reverse dialysis method where 95% of the drug was released after 4 h. The developed astilbin SMEDDS was subjected to bioavailability studies in beagle dogs by LC-MS and showed a significant enhancement of bioavailability, indicating the possibility of using SMEDDS as possible drug carrier for astilbin.

Examining the overlap between genome-wide rare variant association signals and linkage peaks in rheumatoid arthritis

OBJECTIVE

With the exception of the major histocompatibility complex (MHC) and STAT4, no other rheumatoid arthritis (RA) linkage peak has been successfully fine-mapped to date. This apparent failure to identify association under peaks of linkage could be ascribed to the examination of common variation, when linkage is likely to be driven by rare variants. The purpose of this study was to investigate the overlap between genome-wide rare variant RA association signals observed in the Wellcome Trust Case Control Consortium (WTCCC) study and 11 replicating RA linkage peaks, defined as regions with evidence for linkage in >1 study.

METHODS

The WTCCC data set contained 40,482 variants with minor allele frequency of ≤0.05 in 1,860 RA patients and 2,938 controls. Genotypes of all rare variants within a given gene region were collapsed into a single locus and a global P value was calculated per gene.

RESULTS

The distribution of rare variant signals (association P≤10(-5)) was found to differ significantly between regions with and without linkage evidence (P=2×10(-17) by Fisher's exact test). No significant difference was observed after data from the MHC region were removed or when the effect of the HLA-DRB1 locus was accounted for.

CONCLUSION

The results suggest that rare variant association signals are significantly overrepresented under linkage peaks in RA, but the effect is driven by the MHC. This is the first study to examine the overlap between linkage peaks and rare variant association signals genome-wide in a complex disease.

Melittin liposomes surface modified with poloxamer 188: in vitro characterization and in vivo evaluation

Melittin liposomes surface modified with poloxamer 188 were developed, and the effect of poloxamer 188 was investigated with regard to anti-cancer effect and vascular stimulation. Melittin liposomes surface modified with poloxamer 188 at different concentrations (0%, 2%, and 5%) were prepared using the adsorption method, followed by in vitro characterization, including entrapment efficiency, zeta potential, particle size, and morphology. Subsequently, the influence of repeated freeze-thawing on the liposomes was investigated, and the effect of poloxamer 188 on the repeated freeze-thawing process was explored. Vascular stimulation effects of MLT, and MLT liposome that surface coated with or without poloxamer were all studied. Pharmacokinetics of the different MLT preparations were determined and the anticancer activity of the MLT formulations was investigated. The particle size of the liposomes gradually increased with increasing poloxamer 188 content, while the entrapment efficiency did not change significantly. After the first freeze-thaw cycle, size and PDI were both markedly reduced, entrapment efficiency rose, and there was no significant change of zeta potential. The vascular irritation caused by MLT could be reduced to an extent by encapsulation in liposome, but not completely eliminated, while liposomes coated with poloxamer 188 can effectively abolish the phenomenon. Melittin liposomes with surface modified by poloxamer exhibit enhanced bioavailability, effective anticancer activity, and reduced side effects compared with melittin solution. Poloxamer plays an important role in melittin liposomes.

In vitro and in vivo evaluation of sanguinarine liposomes prepared by a remote loading method with three different ammonium salts

Sanguinarine liposomes were prepared by a remote loading method using three different ammonium salts. A series of studies, including in vitro release, in vitro and in vivo anti-tumor effects and pharmacokinetics in rats, were conducted. The three liposomes showed pH-sensitive release characteristics in vitro, but there were obvious variations in their release profiles. Among the three liposomes, the liposomes made using ammonium citrate and phosphate possessed better anti-tumor activity in vitro and in vivo, compared with the liposome using ammonium sulfate. Pharmacokinetics test results in rats indicated that sanguinarine liposomes have notably elevated AUC (P<0.05) and markedly lower CL (P<0.05) compared with the solution, but there were no obvious differences between the three liposomes. The present study may be useful for better understanding and better choice of a suitable ammonium salt for the remote loading method.

HLA-DPB1-COL11A2 and three additional xMHC loci are independently associated with RA in a UK cohort

The aim of this study was to investigate the complex association pattern of the extended major histocompatibility complex (xMHC) region with rheumatoid arthritis (RA) susceptibility to identify effects independent of HLA-DRB1. A total of 1804 RA cases and 1474 controls were included. High-resolution HLA-DRB1 typing was performed. Subjects were genotyped for 1546 single-nucleotide polymorphisms (SNPs) using Affymetrix GeneChip 500 K (Santa Clara, CA, USA) as part of the Wellcome Trust Case Control Consortium Study. Statistical analysis was carried out using PLINK. To avoid confounding by RA-associated HLA-DRB1 alleles, we analyzed xMHC SNPs using a data set with pairwise matching of cases and controls on DRB1 genotypes. A total of 594 case-control pairs with identical DRB1 genotypes were identified. After this adjustment, 104 SNPs remained significantly associated with RA (P<0.05), suggesting that additional RA loci independent of HLA-DRB1 can be found in the xMHC region. Of these, four loci showed the strongest associations with RA (P<0.005): ZNF391, the olfactory receptor (OR) gene cluster, C6orf26-RDBP and HLA-DPB1-COL11A2. An additional locus mapping to the BTN (butyrophilin) cluster showed independent association with RA in anti-cyclic citrullinated peptide-positive patients exclusively. We have validated the previously described independent association of the HLA-DPB1-COL11A2 locus with RA. In addition, association with three novel independent RA loci in the xMHC region (ZNF391, OR2H1 and C6orf26-RDBP) has been detected.