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71.
72.
Nras loss induces metastatic conversion of Rb1-deficient neuroendocrine thyroid tumor 总被引:2,自引:0,他引:2
Takahashi C Contreras B Iwanaga T Takegami Y Bakker A Bronson RT Noda M Loda M Hunt JL Ewen ME 《Nature genetics》2006,38(1):118-123
Mutations in the gene encoding the retinoblastoma tumor suppressor predispose humans and mice to tumor development. Here we have assessed the effect of Nras loss on tumor development in Rb1 heterozygous mice. Loss of one or two Nras alleles is shown to significantly reduce the severity of pituitary tumors arising in Rb1(+/-) animals by enhancing their differentiation. By contrast, C-cell thyroid adenomas occurring in Rb1(+/-) mice progress to metastatic medullary carcinomas after loss of Nras. In Rb1(+/-)Nras(+/-) animals, distant medullary thyroid carcinoma metastases are associated with loss of the remaining wild-type Nras allele. Loss of Nras in Rb1-deficient C cells results in elevated Ras homolog family A (RhoA) activity, and this is causally linked to the invasiveness and metastatic behavior of these cells. These findings suggest that the loss of the proto-oncogene Nras in certain cellular contexts can promote malignant tumor progression. 相似文献
73.
研究了2(5H)-呋喃酮、5-羟基-2(5H)-呋喃酮与环戊二烯发生Diels-Alder反应,产物用FT-IR、1HNMR、MS进行了表征。该反应在水相中进行时,反应时间为0.5 h,比在有机相反应的时间大大缩短。 相似文献
74.
The gas-liquid-liquid reactive extraction system for preparing hydrogen peroxide via anthraquinone was investigated. The oxidation reaction of hydrogenated working solution was combined with the extraction of hydrogen peroxide from working solution in a sieve plate column. The reaction of 2-ethylanthrahydroquionone with oxygen and the liquid-liquid extraction of hydrogen peroxide take place simultaneously. The oxygen was introduced with hydrogenated working solution through a nozzle in the bottom of the column, which worked as agitated air as well as oxidation reagent. The results showed the oxidation and extraction do not hamper each other, on the contrary, the presence of oxidation gas in the column can promote the transfer of hydrogen peroxide from organic phase to aqueous phase, thus the reaction efficiency and extraction efficiency increased with increasing gas superficial velocity. Furthermore, the oxidation efficiency is almost 100% and the extraction efficiency is higher than 90% in this process. 相似文献
75.
76.
卢武星 《北京师范大学学报(自然科学版)》1994,(4)
1.0MeV208Pb离子在非晶Si中的投影射程RP和射程偏差ΔRP作为注量和温度二者的函数用背散射法进行测定.注量的变化范围为5×1013~7×1014cm-2.注入是在室温和t=-120℃下完成的.由由实验所确定的投影射程,射程偏差与注量或温度无关,并且分别等于295和72.2nm.与TRIM86的计算结果相比较,发现RP的偏离为18%,而ΔRP的偏离为36%.RP和ΔRP二者与注量及温度的无关性,排除了所观察到的与TRIM的矛盾是由于注入期间辐射增强扩散或离子束混合效应而引起的解释。 相似文献
77.
78.
Aspirin-like drugs may block pain independently of prostaglandin synthesis inhibition 总被引:2,自引:0,他引:2
K. Brune W. S. Beck G. Geisslinger S. Menzel-Soglowek B. M. Peskar B. A. Peskar 《Cellular and molecular life sciences : CMLS》1991,47(3):257-261
Summary Using flurbiprofen, a chiral anti-inflammatory and analgesic 2-arylpropionic acid derivative, the enantiomers of which are not converted to each other (less than 5%) in rats or man, we obtained evidence that prostaglandin synthesis inhibition is primarily mediating the anti-inflammatory activity but prostaglandin synthesis independent mechanisms contribute to the analgesic effects. Thus, the S-form inhibited prostaglandin synthesis, inflammation and nociception in rats. The R-form had much less effect on prostaglandin synthesis and did not affect inflammation. It did, however, block nociception in rats almost as potently as the S-form. S-flurbiprofen, in contrast to the R-form, was clearly ulcerogenic in the gastrointestinal mucosa. These results indicate additional molecular mechanisms of analgesia and suggest the use of R-arylpropionic acids as analgesics. 相似文献
79.
We develop in this paper an efficient way to select the best subset threshold autoregressive model. The proposed method uses a stochastic search idea. Differing from most conventional approaches, our method does not require us to fix the delay or the threshold parameters in advance. By adopting the Markov chain Monte Carlo techniques, we can identify the best subset model from a very large of number of possible models, and at the same time estimate the unknown parameters. A simulation experiment shows that the method is very effective. In its application to the US unemployment rate, the stochastic search method successfully selects lag one as the time delay and five best models from more than 4000 choices. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
80.
应用生物信息学数据库查询的方法,对B ioS tarM-140s小鼠基因表达芯片上的14 112个基因进行相应注释信息的查询和所对应蛋白质功能的分类.首先参照人类综合型芯片上基因的功能分类,设定了14个蛋白质类别,然后采用V isual C 编程语言,构建了基因信息查询系统.应用该查询系统,进行了网络生物学数据库信息资源的自动直接查询,共搜索到有注释信息的基因12 070个;进一步按照所设定的14个蛋白质类别对12 070个基因进行分类查询,搜索到了与这14个分类相符合的、具有详细蛋白质功能注释信息的基因共1 606个. 相似文献