排序方式: 共有124条查询结果,搜索用时 31 毫秒
101.
The worldwide leaf economics spectrum 总被引:48,自引:0,他引:48
Wright IJ Reich PB Westoby M Ackerly DD Baruch Z Bongers F Cavender-Bares J Chapin T Cornelissen JH Diemer M Flexas J Garnier E Groom PK Gulias J Hikosaka K Lamont BB Lee T Lee W Lusk C Midgley JJ Navas ML Niinemets U Oleksyn J Osada N Poorter H Poot P Prior L Pyankov VI Roumet C Thomas SC Tjoelker MG Veneklaas EJ Villar R 《Nature》2004,428(6985):821-827
Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate. 相似文献
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Römer W Berland L Chambon V Gaus K Windschiegl B Tenza D Aly MR Fraisier V Florent JC Perrais D Lamaze C Raposo G Steinem C Sens P Bassereau P Johannes L 《Nature》2007,450(7170):670-675
Clathrin seems to be dispensable for some endocytic processes and, in several instances, no cytosolic coat protein complexes could be detected at sites of membrane invagination. Hence, new principles must in these cases be invoked to account for the mechanical force driving membrane shape changes. Here we show that the Gb3 (glycolipid)-binding B-subunit of bacterial Shiga toxin induces narrow tubular membrane invaginations in human and mouse cells and model membranes. In cells, tubule occurrence increases on energy depletion and inhibition of dynamin or actin functions. Our data thus demonstrate that active cellular processes are needed for tubule scission rather than tubule formation. We conclude that the B-subunit induces lipid reorganization that favours negative membrane curvature, which drives the formation of inward membrane tubules. Our findings support a model in which the lateral growth of B-subunit-Gb3 microdomains is limited by the invagination process, which itself is regulated by membrane tension. The physical principles underlying this basic cargo-induced membrane uptake may also be relevant to other internalization processes, creating a rationale for conceptualizing the perplexing diversity of endocytic routes. 相似文献
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Johannes Lenhard Eric Winsberg 《Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics》2010,41(3):253-262
In this paper, we explore the extent to which issues of simulation model validation take on novel characteristics when the models in question become particularly complex. Our central claim is that complex simulation models in general, and global models of climate in particular, face a form of confirmation holism. This holism, moreover, makes analytic understanding of complex models of climate either extremely difficult or even impossible. We argue that this supports a position we call convergence skepticism: the belief that the existence of a plurality of different models making a plurality of different forecasts of future climate is likely to be a persistent feature of global climate science. 相似文献
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Nicola Alessio Wolfgang Bohn Verena Rauchberger Flavio Rizzolio Marilena Cipollaro Michael Rosemann Martin Irmler Johannes Beckers Antonio Giordano Umberto Galderisi 《Cellular and molecular life sciences : CMLS》2013,70(9):1637-1651
Stem cell senescence is considered deleterious because it may impair tissue renewal and function. On the other hand, senescence may arrest the uncontrolled growth of transformed stem cells and protect organisms from cancer. This double function of senescence is strictly linked to the activity of genes that the control cell cycle such as the retinoblastoma proteins RB1, RB2/P130, and P107. We took advantage of the RNA interference technique to analyze the role of these proteins in the biology of mesenchymal stem cells (MSC). Cells lacking RB1 were prone to DNA damage. They showed elevated levels of p53 and p21cip1 and increased regulation of RB2/P130 and P107 expression. These cells gradually adopted a senescent phenotype with impairment of self-renewal properties. No significant modification of cell growth was observed as it occurs in other cell types or systems. In cells with silenced RB2/P130, we detected a reduction of DNA damage along with a higher proliferation rate, an increase in clonogenic ability, and the diminution of apoptosis and senescence. Cells with silenced RB2/P130 were cultivated for extended periods of time without adopting a transformed phenotype. Of note, acute lowering of P107 did not induce relevant changes in the in vitro behavior of MSC. We also analyzed cell commitment and the osteo-chondro-adipogenic differentiation process of clones derived by MSC cultures. In all clones obtained from cells with silenced retinoblastoma genes, we observed a reduction in the ability to differentiate compared with the control clones. In summary, our data show evidence that the silencing of the expression of RB1 or RB2/P130 is not compensated by other gene family members, and this profoundly affects MSC functions. 相似文献
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Wortmann SB Vaz FM Gardeitchik T Vissers LE Renkema GH Schuurs-Hoeijmakers JH Kulik W Lammens M Christin C Kluijtmans LA Rodenburg RJ Nijtmans LG Grünewald A Klein C Gerhold JM Kozicz T van Hasselt PM Harakalova M Kloosterman W Barić I Pronicka E Ucar SK Naess K Singhal KK Krumina Z Gilissen C van Bokhoven H Veltman JA Smeitink JA Lefeber DJ Spelbrink JN Wevers RA Morava E de Brouwer AP 《Nature genetics》2012,44(7):797-802
Using exome sequencing, we identify SERAC1 mutations as the cause of MEGDEL syndrome, a recessive disorder of dystonia and deafness with Leigh-like syndrome, impaired oxidative phosphorylation and 3-methylglutaconic aciduria. We localized SERAC1 at the interface between the mitochondria and the endoplasmic reticulum in the mitochondria-associated membrane fraction that is essential for phospholipid exchange. A phospholipid analysis in patient fibroblasts showed elevated concentrations of phosphatidylglycerol-34:1 (where the species nomenclature denotes the number of carbon atoms in the two acyl chains:number of double bonds in the two acyl groups) and decreased concentrations of phosphatidylglycerol-36:1 species, resulting in an altered cardiolipin subspecies composition. We also detected low concentrations of bis(monoacyl-glycerol)-phosphate, leading to the accumulation of free cholesterol, as shown by abnormal filipin staining. Complementation of patient fibroblasts with wild-type human SERAC1 by lentiviral infection led to a decrease and partial normalization of the mean ratio of phosphatidylglycerol-34:1 to phosphatidylglycerol-36:1. Our data identify SERAC1 as a key player in the phosphatidylglycerol remodeling that is essential for both mitochondrial function and intracellular cholesterol trafficking. 相似文献
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Hennies HC Kornak U Zhang H Egerer J Zhang X Seifert W Kühnisch J Budde B Nätebus M Brancati F Wilcox WR Müller D Kaplan PB Rajab A Zampino G Fodale V Dallapiccola B Newman W Metcalfe K Clayton-Smith J Tassabehji M Steinmann B Barr FA Nürnberg P Wieacker P Mundlos S 《Nature genetics》2008,40(12):1410-1412
Gerodermia osteodysplastica is an autosomal recessive disorder characterized by wrinkly skin and osteoporosis. Here we demonstrate that gerodermia osteodysplastica is caused by loss-of-function mutations in SCYL1BP1, which is highly expressed in skin and osteoblasts. The protein localizes to the Golgi apparatus and interacts with Rab6, identifying SCYL1BP1 as a golgin. These results associate abnormalities of the secretory pathway with age-related changes in connective tissues. 相似文献