共查询到20条相似文献,搜索用时 31 毫秒
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《Carbohydrate research》1990,203(1):C3-C8
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Downregulation or loss of α-catenin occurs in multiple human cancer types. The traditional view of α-catenin is that it is one of the core components of the E-cadherin-catenin complex and is required for maintaining the integrity of the intercellular adherens junction, a cell junction whose cytoplasmic face is linked to the actin cytoskeleton. Therefore, loss of α-catenin can result in loss of cell-cell adhesion, a common characteristic of cancer cells. There is an emerging recognition; however, that α-catenin also regulates multiple signaling pathways independent of adherens junctions. For instance, α-catenin functions as a tumor suppressor in E-cadherin-negative basal like breast cancer cells by inhibiting NF-κB signaling. In this perspective, we discuss the role and mechanisms of α-catenin in regulating several signaling pathways in cancer. 相似文献
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This review highlights the main properties of mammalian, plant, and microbial alpha-glucosidases. Special attention is given to the classification of these enzymes, possible catalytic mechanisms, their tertiary structure, and the structure of major inhibitors. Experimental data on the elucidation of amino acid residues essential for catalysis are also discussed. 相似文献
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Savchenko RG Urasaeva YR Galyautdinov IV Afonkina SR Khalilov LM Dolgushin FM Odinokov VN 《Steroids》2011,76(6):603-606
A Pd-C-catalyzed hydrogenation in methanol and in the presence of sodium methylate is a simple, convenient and high yielding reduction method to convert the 7,14-dien-6-one ecdysteroids to their corresponding 7,8α-dihydro-14α-deoxyecdysteroids. 相似文献
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S. Achamlal A. Elachgar Pr. A. El Hallaoui S. El Hajji M. L. Roumestant Ph. Viallefont 《Amino acids》1997,12(3-4):257-263
Summary We report the synthesis of-triazolyl-amino esters by 1,3 dipolar cycloaddition of acetylenic compounds and-azido-amino esters. 相似文献
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The accumulation of α-synuclein is critical for the development of Parkinson disease (PD), and unraveling the mechanisms that regulate α-synuclein levels is key to understanding the pathophysiology of the disease. We recently found that USP9X deubiquitinates α-synuclein, and that this process determines the partition of α-synuclein between the proteasomal and autophagy pathways. By manipulating USP9X levels, we observed that monoubiquitinated α-synuclein is degraded by the proteasome, whereas deubiquitination of α-synuclein favors its degradation by autophagy. As USP9X levels and activity are decreased in α-synucleinopathy brains, USP9X may now represent a novel target for PD. 相似文献
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《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):1143-1145
Abstract Two pyrimidine α-LNA nucleoside monomers have been synthesised and incorporated into α-configured oligonucleotides. A fully modified mixed α-LNA sequence displays unprecedented parallel stranded hybridisation with complementary RNA and a remarkable selectivity for RNA over DNA. Modelling shows α-LNA : RNA to form an extended duplex with a very broad major groove. 相似文献
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The neutral urinary excretion products of 17β-hydroxy-2α,3α-cyclopropano-5α-androstane from the rabbit, dosed orally, were investigated. Column chromatography yielded five crystalline metabolites which were identified by GLC and spectroscopic measurements. Three of these substances were hydroxylated in the 4α-position and one in the 6a-position with the cyclopropane ring intact. The fifth substance, 17β-hydroxy-3β-methyl-5α-androstan-2-one, can be derived from initial hydroxylation of the cyclopropane ring at C-2 followed by ring opening. The dosed substance and triol material was shown to be present by GLC and m.s. measurements. GLC determinations show that hydroxylation has occurred at C-4?C-6>C-2. 相似文献
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《Journal of steroid biochemistry》1982,16(1):85-88
From incubations of testosterone with rat testicular homogenates in the presence of a NADPH-generating system, the following 7α-hydroxylated metabolites could be isolated and identified: 7α,17β-dihydroxy-4-androsten-3-one (7α-hydroxy-testosterone), 7α-17β-dihydroxy-5α-androstan-3-one (7α-hydroxy-Dht), 5α-androstan-3α,7α,17β-triol (7α-hydroxy-3α-A'DIOL) and 5α-androstane-3β,7α,l7β-triol (7α-hydroxy-3β-A'DIOL). To our knowledge this is the first demonstration of the formation of 5α-reduced-7α-hydroxylated metabolites of testosterone in the male gonad. These 5α-reduced-7α-hydroxylated metabolites could also be isolated after incubations of 5α-androstane-3α,17β-diol (3α-A'D10L) with testicular homogenates in the presence of a NADPH-generating system.Measured as the sum of 7α-hydroxy-testosterone, 7α-hydroxy-Dht. 7α-hydroxy-3α-A'DIOL and 7α-hydroxy-3β-A'DIOL formed using testosterone as substrate, total 7α-hydroxylase activity was six times higher in testes of mature rats than in testes from animals 23 days old. With 3α-A'DIOL as substrate total 7α-hydroxylase in the mature testis was about three times greater than in the sexually immature testis. 相似文献
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《Journal of steroid biochemistry》1978,9(8):779-784
The 5β-pregnane-3α,6α,20α-iriol and 5β-pregnane-3α,6α,20β-triol obtained by reduction of 3α,6α-dihydroxy-5β-pregnan-20-one were converted to trimethylsilyl ether derivatives and analysed by gas-liquid chromatography (GLC) and gas chromatography-mass spectrometry (GC-MS).After extraction, solvolysis and enzymatic hydrolysis of urinary steroid conjugates (from 19 normal pregnant women), the liberated steroids were separated by liquid-gel chromatography and were analysed by GLC and GLC-MS. The 5β-pregnane-3α,6α,20α-triol isolated and identified in the Sephadex LH-20 fractions 8 and 9, was present in urine from 15 pregnant women after the 16th week of gestation. After this time, this metabolite was found in a quantity between 0.20 to 2.90 mg/24 h, with a significant increase between the 26th to 30th week of the gestation.With the present in vivo data, it is not possible to establish the exact enzymatic pathway involved in the biosynthesis of the 5β-pregnane-3α,6α,20α-triol. However, it is probable that the immediate precursor of this compound was the 3α,6α-dihydroxy-5β-pregnan-20-one, and that urinary excretion of 5β-pregnane-3α,6α,20α-triol reflected one part of hepatomaternal metabolism of 6-hydroxyprogesterone formed in the foeto-placental unit. 相似文献
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文[1]中,着重介绍了模糊集的基本概念及其在生态学中的简单应用。文中从隶属度这一概念出发,建立模糊集的运算及模糊关系等,并指出了这一理论在生态学研究中应用的基本思想方法。文[1]中也曾提到,由于生态学中某些问题与现象是具有模糊性的,模糊集合便是客观存在的。研究的结果必须要求是精确与清晰的,因此,模糊集合必须清晰化。本文介绍模糊集合清晰化的手段和方法。同时也介绍模糊集合向普通集合转化后在生态学中的应用。 相似文献
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17α-Methyl-5α-dihydrotestosterone and the reduced metabolites, 17α-methyl-5α-androstane-3α, 17β-diol and -3β, 17β-diol together with two hydroxylated metabolites, 17α-methyl-5α-androstane-3β, 15α, 17β-triol and 17α-methyl-5α-androstane-3α, 6α, 17β-triol were isolated and identified in the urine of rabbits orally dosed with 17α-methyl-5α-dihydrotestosterone. Formation of the C-6 hydroxylated derivative demonstrates that the 4,6-enolization of a 4-en-3-one is not a necessary requirement for hydroxylation at C-6 of the androstane nucleus in the rabbit. No evidence was obtained for the presence of 17α-methyl/17β-hydroxyl epimerization. 相似文献