共查询到20条相似文献,搜索用时 15 毫秒
1.
Lamming DW Latorre-Esteves M Medvedik O Wong SN Tsang FA Wang C Lin SJ Sinclair DA 《Science (New York, N.Y.)》2005,309(5742):1861-1864
Calorie restriction (CR) extends the life span of numerous species, from yeast to rodents. Yeast Sir2 is a nicotinamide adenine dinucleotide (NAD+-dependent histone deacetylase that has been proposed to mediate the effects of CR. However, this hypothesis has been challenged by the observation that CR can extend yeast life span in the absence of Sir2. Here, we show that Sir2-independent life-span extension is mediated by Hst2, a Sir2 homolog that promotes the stability of repetitive ribosomal DNA, the same mechanism by which Sir2 extends life span. These findings demonstrate that the maintenance of DNA stability is critical for yeast life-span extension by CR and suggest that, in higher organisms, multiple members of the Sir2 family may regulate life span in response to diet. 相似文献
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Requirement of NAD and SIR2 for life-span extension by calorie restriction in Saccharomyces cerevisiae 总被引:1,自引:0,他引:1
Calorie restriction extends life-span in a wide variety of organisms. Although it has been suggested that calorie restriction may work by reducing the levels of reactive oxygen species produced during respiration, the mechanism by which this regimen slows aging is uncertain. Here, we mimicked calorie restriction in yeast by physiological or genetic means and showed a substantial extension in life-span. This extension was not observed in strains mutant for SIR2 (which encodes the silencing protein Sir2p) or NPT1 (a gene in a pathway in the synthesis of NAD, the oxidized form of nicotinamide adenine dinucleotide). These findings suggest that the increased longevity induced by calorie restriction requires the activation of Sir2p by NAD. 相似文献
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Anderson RM Latorre-Esteves M Neves AR Lavu S Medvedik O Taylor C Howitz KT Santos H Sinclair DA 《Science (New York, N.Y.)》2003,302(5653):2124-2126
Calorie restriction (CR) slows aging in numerous species. In the yeast Saccharomyces cerevisiae, this effect requires Sir2, a conserved NAD+-dependent deacetylase. We report that CR reduces nuclear NAD+ levels in vivo. Moreover, the activity of Sir2 and its human homologue SIRT1 are not affected by physiological alterations in the NAD+:NADH ratio. These data implicate alternate mechanisms of Sir2 regulation by CR. 相似文献
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Sanai N Berger MS Garcia-Verdugo JM Alvarez-Buylla A 《Science (New York, N.Y.)》2007,318(5849):393; author reply 393
Curtis et al. (Research Articles, 2 March 2007, p. 1243) claimed discovery of a human neuronal migratory stream to the olfactory bulb along a putative lateral ventricular extension. However, high levels of proliferation reported with proliferating cell nuclear antigen were not confirmed using different markers, neuronal chain migration was not demonstrated, and no serial reconstruction shows a true ventricular extension. 相似文献
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Keeling RF 《Science (New York, N.Y.)》2005,308(5729):1743; author reply 1743
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Sandford et al. (Reports, 15 December 2006, p. 1720) reported on organic compounds captured from Comet 81P/Wild 2 by the Stardust spacecraft. We emphasize the difficulty in assigning the origin of compounds detected diffusely along particle impact tracks and show that rapid heating of aerogel that has never been exposed to cometary particle capture can generate complex aromatic molecules from low-mass carbon impurities present in the aerogel. 相似文献
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Fujishima A 《Science (New York, N.Y.)》2003,301(5640):1673; discussion 1673
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Lackner KS 《Science (New York, N.Y.)》2003,301(5640):1673; discussion 1673
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Frey and Dueck (Reports, 16 February 2007, p. 972) described an algorithm termed "affinity propagation" (AP) as a promising alternative to traditional data clustering procedures. We demonstrate that a well-established heuristic for the p-median problem often obtains clustering solutions with lower error than AP and produces these solutions in comparable computation time. 相似文献
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Selman C Lingard S Gems D Partridge L Withers DJ 《Science (New York, N.Y.)》2008,320(5879):1012; author reply 1012
Taguchi et al. (Reports, 20 July 2007, p. 369) reported that mice heterozygous for a null mutation in insulin receptor substrate-2 (Irs2) display a 17% increase in median life span. However, using the same mouse model, we find no evidence for life-span extension and suggest that the findings of Taguchi et al. were due to atypical life-span profiles in their study animals. 相似文献
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Chisholm MF Wang Y Lupini AR Eres G Puretzky AA Brinson B Melechko AV Geohegan DB Cui H Johnson MP Pennycook SJ Lowndes DH Arepalli S Kittrell C Sivaram S Kim M Lavin G Kono J Hauge R Smalley RE 《Science (New York, N.Y.)》2003,300(5623):1236; author reply 1236
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Nauenberg M 《Science (New York, N.Y.)》2011,334(6054):311; author reply 311
Reis et al. (Reports, 26 November 2010, p. 1231) reported on the mechanism by which cats lap and gave a theoretical and experimental analysis of their observations. Their explanation for the cat's lapping frequency, however, is based on an incorrect application of the principles of fluid dynamics. The revised analysis given here agrees with their observations and predicts a similar lapping frequency for cats and dogs. 相似文献
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Verlet JR Bragg AE Kammrath A Cheshnovsky O Neumark DM 《Science (New York, N.Y.)》2005,310(5755):1769; author reply 1769
The conclusion by Turi et al. (Reports, 5 August 2005, p. 914) that all experimental spectral and energetic data on water-cluster anions point toward surface-bound electrons is overstated. Comparison of experimental vertical detachment energies with their calculated values for (H2O)n- clusters with surface-bound and internalized electrons supports previous arguments that both types of clusters exist. 相似文献
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Rösler C Köck J Malim MH Blum HE von Weizsäcker F 《Science (New York, N.Y.)》2004,305(5689):1403; author reply 1403
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Waller RF Keeling PJ van Dooren GG McFadden GI 《Science (New York, N.Y.)》2003,301(5629):49; author reply 49