Polymorphisms of MTHFD,plasma homocysteine levels, and risk of gastric cancer in ahigh-risk Chinese population

Purpose:Accumulative evidence suggests that folate has a protective effect on gastric cancer. The methylenetetrahyd-rofolate dlehydrogenase(MTHFD) plays an important role in folate and homocysteine metabolisms, and polymorphisms of MTHFD may result in disturbance of the folate-mediated homocysteine pathway. The aim of this study is to test the hypothesis that genetic variants of MTHFD and plasma homocysteine levels are associated with risk of gastric cancer and modulated by genotypes of methylenetetrahydrofolate reductase(MTHFR). Experimental Design: We genotyped G1958A and T401C in MTHFD and C677T in MTHFR and detected total plasma homocysteine(tHcy) levels in a case-control study of 589 gastric cancer cases and 635 cancer-free controls in a high-risk Chinese population. Results:The variant genotypes of MTHFD 1958AA and 401CC were associated with a significantly increased risk of gastric canceradjusted odds ratio(OR), 2.05; 95% confidence interval(95% CI),1.34-3.13 for 1958AA; adjusted OR,1.43; 95% CI,1.14-1.80 for 401CC compared with 1958GG/GA and 401TT/TC genotypes, respectively. Both of the effects were more evident in the subjects carrying MTHFR 677CT/TT genotypes. The average tHcy level was significantly higher in gastric cancer cases than in controls(P < 0.01), and the upper quartile of tHcy (> 13.6 mu mol/L) was associated with an 82% significantly increased risk of gastric cancer, compared with the lowest quartile of tHcy(<= 8.0 pmol/L;adjusted OR,1.82; 95% CI,1.20-2.75). Conclusions:The strong associations between MTHFD variants and the plasma tHcy levels and gastric cancer risk suggest, for the first time, a possible gene-environment interaction between genetic variants of folate-metabolizing genes and high tHcy levels in gastric carcinogenesis.

MATRIX ANALYSIS TO ADDITIVE SCHWARZ METHODS

Matrix analysis on additive Schwarz methods as preconditioners is given in this paper. Both cases of with and without coarse mesh are considered. It is pointed out that an advantage of matrix analysis is to obtain more exact upper hound. Our numerical tests access the estimations.

Engineering Design of High Quality GaN Epitaxy on Silicon Substrate Using Varying GaN/AlGaN Composite Buffer Structures

High quality GaN epitaxy thin films have been desired for the energy-efficient,solid-state semiconductor illuminating devices.Silicon substrates offer high crystal quality,low wafer cost,large wafer size,and potential integration with the well-established silicon processing technologies.However,due to the large mismatch in lattice constants and thermal expansion coefficients,it is still challenging to grow high quality GaN on silicon substrates.In this study,high quality GaN epitaxy has been engineering designed to grow on Si(111)substrate using varying GaN/AlGaN composite buffer structures by an Axitron 200 metal-organic vapor phase epitaxy deposition system.A thin AlN seed layer of 25 nm was firstly grown at 720℃.AlGaN layer of different thickness was then grown at 1050℃with subsequent GaN thin film until the total thickness reached 500 nm.The thickness of the subsequent GaN thin film could be increased by reducing the AlGaN thickness in the composite buffer structures.The results have shown that the lower GaN/AlGaN thickness ratio would decrease the dislocation density and provide crack-free,mirror-like upper GaN crystal thin film.On the other hand,the GaN/AlGaN thickness ratio could be designed to be 2-6 to balance the processing cost and the thin film quality for engineering applications.The dislocation density has been about 2×10 9 cm-2.In addition,dislocation close loop was observed near the GaN/AlGaN interface.The annihilation mechanism could be depicted by the reduction in dislocation strain energy.

CONVERGENCE OF LEGENDRE METHODS FOR NAVIER-STOKES EQUATIONS

This paper is concerned with spectral type of methods using Legendre polynomials. Both Galerkin and collocation approximations for the Navier-Stokes equations are considered and their rates of convergence are obtained. As a consequence, it is shown that these methods achieve spectral accuracy if the solutions to the Navier-Stokes equations are smooth.

Differentiation of human bone marrow precursor cells into neuronal-like cells after transplantation into canine spinal cord organotypic slice cultures

Background Treatments to regenerate different tissue involving the transplantation of bone marrow derived mesenchymal precursor cells are anticipated. Using an alternative methods, in vitro organotypic slice culture method, would be useful to transplant cells and assessing the effects. This study was to determine the possibility of differentiating human bone marrow precursor cells into cells of the neuronal lineage by transplanting into canine spinal cord organotypic slice cultures. Methods Bone marrow aspirates were obtained from posterior superior iliac spine （PSIS） of patients that had undergone spinal fusion due to a degenerative spinal disorder. For cell imaging, mesenchymal precursor cells （MPCs） were pre-stained with PKH-26 just before transplantation to canine spinal cord slices. Canine spinal cord tissues were obtained from three adult beagle dogs. Spinal cords were cut into transverse slices of 1 mm using tissue chopper. Two slices were transferred into 6-well plate containing 3 ml DMEM with antibiotics. Prepared MPCs （lx104） were transplanted into spinal cord slices. On days 0, 3, 7, 14, MPCs were observed for morphological changes and expression of neuronal markers through immunofluorescence and reverse transcription-polymerase chain reaction （RT-PCR）. Results The morphological study showed： spherical cells in the control and experiment groups on day 0; and on day 3, cells in the control group had one or two thick, short processes and ones in the experiment group had three or four thin, long processes. On day 7, these variously-sized processes contacted each other in the experiment group, but showed typical spindle-shaped cells in the control group. Immunofluorescence showed that PKH-26（＋） MPCs stained positive for NeuN （＋） and GFAP（＋） in experimental group only. Also RT-PCR showed weak expression of β-tubulin III and GFAP. Conclusions Human bone marrow mesenchymal precursor cells （hMPCs） have the potential to differentiate into the neuronal like cells in this canine spinal cord organotypic slice culture model. Furthermore, these findings suggested the possibility that these cells can be utilized to treat patients with spinal cord injuries.

Nat Genet:科学家发现相同肿瘤中存在不同遗传复杂性的癌细胞

近日，一项刊登于国际杂志Namre Genetics上的研究报告中。来自美国洛杉矶希达-西奈（Cedars-Sinai）医学院的研究人员通过研究在食管肿瘤的组织样本中鉴别出了2000多个基因突变，从而详细阐述了癌症的复杂性。本文研究表明。单一肿瘤的不同区域或许具有多种遗传模式。