The La-Mg-Ni-based A2B7-type La0.8-xNdxMg0.2Ni3.35 Al0.1Si0.05(x=0,0.1,0.2,0.3,and0.4) electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the structure and electrochemical performances of the alloys was investigated. The structural analysis of X-ray diffraction and scanning electron microscopy reveals that the experimental alloys consist of two major phases: (La,Mg)2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCu 5-type structure as well as some residual phases of LaNi3 and NdNi5 . The electrochemical measurements indicate that an evident change of the electrochemical performance of the alloys is associated with the substitution of Nd for La. The discharge capacity of the alloy first increases then decreases with the growing Nd content, whereas their cycle stability clearly grows all the time. Furthermore, the measurements of the high rate discharge ability, the limiting current density, and hydrogen diffusion coefficient all demonstrate that the electrochemical kinetic properties of the alloy electrodes first augment then decline with the rising amount of Nd substitution.
AIM: To explore the alteration of DNA methyltransferase expression in gastric cancer and to assess its prognostic value.METHODS: From April 2000 to December 2010, 227men and 73 women with gastric cancer were enrolled in the study. The expression of DNA methyltransferases(DNMTs), including DNMT1, DNMT3a and DNMT3b,in the 300 cases of gastric carcinoma, of which 85 hadpaired adjacent normal gastric mucus samples, was evaluated by immunohistochemistry using a tissue microarray. Serum anti-Helicobacter pylori(H. pylori) IgG was detected by enzyme-linked immunosorbent assay(ELISA). The relationships between the above results and the clinicopathological characteristics were analyzed. Their prognostic value was evaluated using the Cox proportional hazards model.RESULTS: In gastric cancer, expression of DNMTs was mainly seen in the nucleus. Weak staining was also observed in the cytoplasm. Expression of DNMT1, DNMT3a and DNMT3b in gastric cancer was significantly higher compared to that in the paired control samples(60.0% vs 37.6%, 61.2% vs 4.7%, and 94.1% vs 71.8%, P < 0.01). The overall survival rate was significantly higher in the DNMT3a negative group than in the DNMT3a positive group in gastric cancer patients(Log-rank test, P = 0.032). No significant correlation was observed between DNMT1 and DNMT3b expression and the overall survival time(Log-rank test, P = 0.289, P = 0.347). Multivariate regression analysis indicated that DNMT3a expression(P = 0.025) and TNM stage(P < 0.001), but not DNMT1(P = 0.54) or DNMT3b(P = 0.62), were independent prognostic factors in gastric cancer. H. pylori infection did not induce protein expression of DNMTs.CONCLUSION: The results suggest that expression of DNMT3a is an independent poor prognostic indicator in gastric cancer. DNMT3a might play an important role in gastric carcinogenesis.
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