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271.
Sheng-An Tang Qianxiang Zhou Wen-Zhi Guo Yuling Qiu Ran Wang Meihua Jin Wenjing Zhang Ke Li Takao Yamori Shingo Dan Dexin Kong 《Marine drugs》2014,12(7):4200-4213
Stellettin B was isolated from marine sponge Jaspis stellifera. In vitro antitumor activities were investigated on 39 human cancer cell lines. Stellettin B exhibited highly potent inhibition against the growth of a human glioblastoma cell line SF295, with a GI50 of 0.01 μM. In contrast, stellettin B showed very weak inhibitory activity on normal cell lines including HMEC, RPTEC, NHBE and PrEC, with GI50s higher than 10 μM, suggesting its relatively selective cytotoxicity against human cancer cells compared to normal human cell lines. We then focused on the antitumor activity of this compound on SF295 cells. Flow cytometric analysis indicated that stellettin B induced apoptosis in SF295 cells in a concentration-dependent manner. Further study indicated that stellettin B increased the production of ROS, the activity of caspase 3/7, as well as the cleavage of PARP, each of which is known to be involved in apoptosis. To investigate the molecular mechanism for cell proliferation inhibition and apoptosis induction, effect on the phosphorylation of several signal proteins of PI3K/Akt and RAS/MAPK pathways was examined. Stellettin B inhibited the phosphorylation of Akt potently, with no activity on p-ERK and p-p38, suggesting that inhibition of PI3K/Akt pathway might be involved in the antiproliferative and apoptosis-inducing effect. However, homogenous time-resolved fluorescence (HTRF) assay indicated that stellettin B did not inhibit PI3K activity, suggesting that the direct target might be signal protein upstream of Akt pathway other than PI3K. 相似文献
272.
Abstract Microbial metabolism in reduction process of waterlogged paddy soils has been studied by Takai, Koyama, and Kamura (1, 2, 3, 4, 5, 6), Koyama (7, 8, 9, 10, 11, 12), and others. The results indicated that microbial metabolism in waterlogged soils takes place according to the following steps: (1) In the early stage of the incubation period, dissolved O2, is consumed and the redox potential drops rapidly. (2) NO2? and NO2? are reduced to N2. (3) Mn4+ is reduced to Mn2+. (4) Fe3+ is reduced to Fe2+. (5) SO4 2? is reduced to S2?. (6) H2 and CH4 are produced. Takai and Chiang (13) reported that NH4+ and PO4 3+ in waterlogged paddy soils increase with the incubation period. Chiang and Takai (14) indicated that carbohydrates in the soil solutions almost remain constant throughout the incubation period, however, organic acids change similarly to those reported previously (5, 6). 相似文献