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This study aimed to explore the mediation effects of one-carbon metabolism (OCM) related nutrients on the association between MTHFR rs1801133 polymorphism and gestational diabetes mellitus (GDM). Folate, vitamin B12 and homocysteine (Hcy) were measured in the serum of 1254 pregnant women. Linear and logistic regressions were used to estimate the associations of OCM nutrients and MTHFR rs1801133 polymorphism with blood glucose levels and GDM risk. Mediation analysis was applied to test the mediation effects of folate, vitamin B12 and Hcy on the association of MTHFR rs1801133 polymorphism with blood glucose concentrations and GDM. Pregnant women with MTHFR rs1801133 CC genotype had higher serum folate (10·75 v. 8·90 and 9·40 ng/ml) and lower serum Hcy (4·84 v. 4·93 and 5·20 μmol/l) than those with CT and TT genotypes. Folate concentrations were positively associated with fasting plasma glucose (FPG), 1-h plasma glucose (1-h PG), 2-h plasma glucose (2-h PG) and GDM risk. Vitamin B12 levels were negatively correlated with FPG and GDM. Although no direct association was found between MTHFR rs1801133 genotypes and GDM, there were significant indirect effects of MTHFR rs1801133 CC genotype on FPG (β: 0·005; 95 % CI: 0·001, 0·013), 1-h PG (β: 0·006; 95 % CI: 0·001, 0·014), 2-h PG (β: 0·007; 95 % CI: 0·001, 0·015) and GDM (β: 0·006; 95 % CI: 0·001, 0·014) via folate. In conclusion, serum folate mediates the effect of MTHFR rs1801133 on blood glucose levels and GDM. Our findings potentially provide a feasible GDM prevention strategy via individualised folate supplementation according to the MTHFR genotypes.
An integrated optical method for measuring deformation of micro-mechanical systems with better than sub-micron resolutions is detailed. Both a confocal laser scanning microscope and a photon tunneling microscope were integrated into a single microscopy system due to their complimentary capabilities for examining sub-micrometer deformations. A halogen lamp and laser were adopted as the two light sources for the measurements. Since topographic information of samples up to a 15μm by 15μm area can be measured, a three-dimensional displacement field of the sample was extracted by comparing topographies of the same specimen area before and after deformation. The bending and twisting deformation of a micro-mirror driven by the electrostatic force was measured to demonstrate the capability of this newly developed instrument. The experimental data obtained agrees reasonably well with the theoretical results calculated by adopting an analytical solution and a finite element method. The small discrepancy in the result can be traced to the surface roughness effect, which is often non-negligible in micro-systems.
Introduction
In China, nonmarine Permian and Triassic strata are distributed mainly in the vast area north of a line formed by the Kunlun, Qinling, and Dabie mountains. They are particularly well developed in the Junggar, Turpan, and Shaanxi-Gansu-Ningxia basins. South of the line, nonmarine Permo-Triassic sediments occur mostly in eastern Yunnan and western Guizhou. In addition, alternating marine and continental Permian and Triassic rocks are also developed in a few areas in both South and North China. In the past decade or so great progress has been made in studies of both the biological and nonbiological features of the nonmarine Permo-Triassic boundary. Existing data reveal distinct changes across the boundary in biologic groups such as vertebrates, bivalves, ostracodes, spores, pollen, and other flora, and in nonbiologic features such as grain size and color of sediments, sedimentary environments and climate. These changes suggest an event between the Permian and Triassic and can be applied to correlation of the nonmarine Permo-Triassic boundary.
Biotic changes
Determination of the Permo-Triassic boundary in nonmarine sequences is made at present mainly on the basis of vertebrates and spore-pollen assemblages, and to a lesser extent, on the basis of ostracodes, bivalves, and other elements of the flora.
Vertebrate fauna
The vertebrate fauna changes markedly from Permian to Triassic. Dicynodonts such as Kunpania scopulusa, Striodon magnus, Jimusaria sinkiangensis, Dicynodon tienshanensis, Jimusaria taoshuyanensis, Turfandon bogdaensis and Kansuodon sp. are represented in Upper Permian strata in the Junggar and Turpan basins of Xinjiang and Gansu provinces, northwest China (Zhao, 1980; Yang et al., 1986). A Pareiasaurus fauna, represented by Tapinocephalidae and Shihtienfenia permica, and Shansisaurus xuecunensis, has been reported from equivalent strata in Shanxi and Shaanxi provinces, North China.
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