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排序方式: 共有173条查询结果,搜索用时 15 毫秒
51.
Mikkelsen TS Wakefield MJ Aken B Amemiya CT Chang JL Duke S Garber M Gentles AJ Goodstadt L Heger A Jurka J Kamal M Mauceli E Searle SM Sharpe T Baker ML Batzer MA Benos PV Belov K Clamp M Cook A Cuff J Das R Davidow L Deakin JE Fazzari MJ Glass JL Grabherr M Greally JM Gu W Hore TA Huttley GA Kleber M Jirtle RL Koina E Lee JT Mahony S Marra MA Miller RD Nicholls RD Oda M Papenfuss AT Parra ZE Pollock DD Ray DA Schein JE Speed TP Thompson K VandeBerg JL Wade CM Walker JA Waters PD Webber C 《Nature》2007,447(7141):167-177
We report a high-quality draft of the genome sequence of the grey, short-tailed opossum (Monodelphis domestica). As the first metatherian ('marsupial') species to be sequenced, the opossum provides a unique perspective on the organization and evolution of mammalian genomes. Distinctive features of the opossum chromosomes provide support for recent theories about genome evolution and function, including a strong influence of biased gene conversion on nucleotide sequence composition, and a relationship between chromosomal characteristics and X chromosome inactivation. Comparison of opossum and eutherian genomes also reveals a sharp difference in evolutionary innovation between protein-coding and non-coding functional elements. True innovation in protein-coding genes seems to be relatively rare, with lineage-specific differences being largely due to diversification and rapid turnover in gene families involved in environmental interactions. In contrast, about 20% of eutherian conserved non-coding elements (CNEs) are recent inventions that postdate the divergence of Eutheria and Metatheria. A substantial proportion of these eutherian-specific CNEs arose from sequence inserted by transposable elements, pointing to transposons as a major creative force in the evolution of mammalian gene regulation. 相似文献
52.
A human natural killer cell subset provides an innate source of IL-22 for mucosal immunity 总被引:2,自引:0,他引:2
Cella M Fuchs A Vermi W Facchetti F Otero K Lennerz JK Doherty JM Mills JC Colonna M 《Nature》2009,457(7230):722-725
Natural killer (NK) cells are classically viewed as lymphocytes that provide innate surveillance against virally infected cells and tumour cells through the release of cytolytic mediators and interferon (IFN)-gamma. In humans, blood CD56(dim) NK cells specialize in the lysis of cell targets. In the lymph nodes, CD56(bright) NK cells secrete IFN-gamma cooperating with dendritic cells and T cells in the generation of adaptive responses. Here we report the characterization of a human NK cell subset located in mucosa-associated lymphoid tissues, such as tonsils and Peyer's patches, which is hard-wired to secrete interleukin (IL)-22, IL-26 and leukaemia inhibitory factor. These NK cells, which we refer to as NK-22 cells, are triggered by acute exposure to IL-23. In vitro, NK-22-secreted cytokines stimulate epithelial cells to secrete IL-10, proliferate and express a variety of mitogenic and anti-apoptotic molecules. NK-22 cells are also found in mouse mucosa-associated lymphoid tissues and appear in the small intestine lamina propria during bacterial infection, suggesting that NK-22 cells provide an innate source of IL-22 that may help constrain inflammation and protect mucosal sites. 相似文献
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The dynamics of a single impurity in an environment is a fundamental problem in many-body physics. In the solid state, a well known case is an impurity coupled to a bosonic bath (such as lattice vibrations); the impurity and its accompanying lattice distortion form a new entity, a polaron. This quasiparticle plays an important role in the spectral function of high-transition-temperature superconductors, as well as in colossal magnetoresistance in manganites. For impurities in a fermionic bath, studies have considered heavy or immobile impurities which exhibit Anderson's orthogonality catastrophe and the Kondo effect. More recently, mobile impurities have moved into the focus of research, and they have been found to form new quasiparticles known as Fermi polarons. The Fermi polaron problem constitutes the extreme, but conceptually simple, limit of two important quantum many-body problems: the crossover between a molecular Bose-Einstein condensate and a superfluid with BCS (Bardeen-Cooper-Schrieffer) pairing with spin-imbalance for attractive interactions, and Stoner's itinerant ferromagnetism for repulsive interactions. It has been proposed that such quantum phases (and other elusive exotic states) might become realizable in Fermi gases confined to two dimensions. Their stability and observability are intimately related to the theoretically debated properties of the Fermi polaron in a two-dimensional Fermi gas. Here we create and investigate Fermi polarons in a two-dimensional, spin-imbalanced Fermi gas, measuring their spectral function using momentum-resolved photoemission spectroscopy. For attractive interactions, we find evidence for a disputed pairing transition between polarons and tightly bound dimers, which provides insight into the elementary pairing mechanism of imbalanced, strongly coupled two-dimensional Fermi gases. Additionally, for repulsive interactions, we study novel quasiparticles--repulsive polarons--the lifetime of which determines the possibility of stabilizing repulsively interacting Fermi systems. 相似文献
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Monica Bari Tiziana Bonifacino Marco Milanese Paola Spagnuolo Simona Zappettini Natalia Battista Francesco Giribaldi Cesare Usai Giambattista Bonanno Mauro Maccarrone 《Cellular and molecular life sciences : CMLS》2011,68(5):833-845
The endocannabinoid system and endocannabinoid receptor-driven modulation of glutamate release were studied in rat brain cortex
astroglial gliosomes. These preparations contained the endocannabinoids N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol, as well their major biosynthetic (N-acyl-phosphatidylethanolamines-hydrolyzing-phospholipase D and diacylglycerol-lipase) and catabolic (fatty acid amide-hydrolase
and monoacylglycerol-lipase) enzymes. Gliosomes expressed type-1 (CB1R), type-2 (CB2R) cannabinoid, and type-1 vanilloid (TRPV1)
receptors, as ascertained by Western blotting and confocal microscopy. Methanandamide, a stable analogue of anandamide acting
as CB1R, CB2R, and TRPV1 agonist, stimulated or inhibited the depolarization-evoked gliosomal [3H]d-aspartate release, at lower and higher concentrations, respectively. Experiments with ACEA (arachidonyl-2′-chloroethylamide),
JWH133 ((6aR,10aR)-3-(1,1-dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]-pyran) and capsaicin, selective
agonists at CB1R, CB2R and TRPV1, respectively, demonstrated that potentiation of [3H]d-aspartate release was due to CB1R while inhibition to CB2R and TRPV1 engagement. These findings were confirmed by using selective
receptor antagonists. Furthermore, CB1R activation caused increase of intracellular IP3 and Ca2+ concentration, suggesting an involvement of phospholipase C. 相似文献
57.
This paper offers an introduction to Hermann Cohen's Das Princip der Infinitesimal-Methode (1883), and recounts the history of its controversial reception by Cohen's early sympathizers, who would become the so-called ‘Marburg school’ of Neo-Kantianism, as well as the reactions it provoked outside this group. By dissecting the ambiguous attitudes of the best-known representatives of the school (Paul Natorp and Ernst Cassirer), as well as those of several minor figures (August Stadler, Kurd Lasswitz, Dimitry Gawronsky, etc.), this paper shows that Das Princip der Infinitesimal-Methode is a unicum in the history of philosophy: it represents a strange case of an unsuccessful book's enduring influence. The “puzzle of Cohen's Infinitesimalmethode,” as we will call it, can be solved by looking beyond the scholarly results of the book, and instead focusing on the style of philosophy it exemplified. Moreover, the paper shows that Cohen never supported, but instead explicitly opposed, the doctrine of the centrality of the ‘concept of function’, with which Marburg Neo-Kantianism is usually associated. 相似文献
58.
Marco Beretta 《Annals of science》2013,70(4):327-356
On the basis of a significant number of unpublished documents, here published for the first time, the article reconstructs the historical and scientific origins of Lavoisier's Mémoires de physique et de chimie. Because of the paucity of primary sources available so far, this work has previously received little attention and its 'publication' is commonly attributed to Madame Lavoisier's effort to revive the memory of her husband. In contrast with this image, this article suggests that Madame Lavoisier had only a subsidiary role and that Armand Séguin's contribution to both the editing and the scientific organization of the Mémoires needs a historical reassessment. Lavoisier's collaboration with Séguin, dating from 1792, resulted in a work the aim of which was far more ambitious than that of collecting already published memoirs. Furthermore, it is argued that the contents of the first volume of the Mémoires indicate an important evolution in Lavoisier's chemical theory. 相似文献
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