排序方式: 共有47条查询结果,搜索用时 15 毫秒
41.
Marianne Fillenz 《Cellular and molecular life sciences : CMLS》1969,25(8):842-842
Zusammenfassung Nachweis einer doppelt motorischen Innervation eines Teiles der Kapillaren in der Hundelunge: Bündel markloser Nervenfasern mit elektronenmikroskopischer Charakteristik cholinerger und noradrenerger Nervenendigungen bis 1000 å Entfernung von der Kapillarwand. 相似文献
42.
Boes M Cerny J Massol R Op den Brouw M Kirchhausen T Chen J Ploegh HL 《Nature》2002,418(6901):983-988
Assembly of major histocompatibility complex (MHC) molecules, which present antigen in the form of short peptides to T lymphocytes, occurs in the endoplasmic reticulum; once assembled, these molecules travel from the endoplasmic reticulum to their final destination. MHC class II molecules follow a route that takes them by means of the endocytic pathway, where they acquire peptide, to the cell surface. The transport of MHC class II molecules in 'professional' antigen-presenting cells (APCs) is subject to tight control and responds to inflammatory stimuli such as lipopolysaccharide. To study class II transport in live APCs, we replaced the mouse MHC class II gene with a version that codes for a class II molecule tagged with enhanced green fluorescent protein (EGFP). The resulting mice are immunologically indistinguishable from wild type. In bone-marrow-derived dendritic cells, we observed class II molecules in late endocytic structures with transport patterns similar to those in Langerhans cells observed in situ. We show that tubular endosomes extend intracellularly and polarize towards the interacting T cell, but only when antigen-laden dendritic cells encounter T cells of the appropriate specificity. We propose that such tubulation serves to facilitate the ensuing T-cell response. 相似文献
43.
Mutations in PCSK9 cause autosomal dominant hypercholesterolemia 总被引:22,自引:0,他引:22
Abifadel M Varret M Rabès JP Allard D Ouguerram K Devillers M Cruaud C Benjannet S Wickham L Erlich D Derré A Villéger L Farnier M Beucler I Bruckert E Chambaz J Chanu B Lecerf JM Luc G Moulin P Weissenbach J Prat A Krempf M Junien C Seidah NG Boileau C 《Nature genetics》2003,34(2):154-156
Autosomal dominant hypercholesterolemia (ADH; OMIM144400), a risk factor for coronary heart disease, is characterized by an increase in low-density lipoprotein cholesterol levels that is associated with mutations in the genes LDLR (encoding low-density lipoprotein receptor) or APOB (encoding apolipoprotein B). We mapped a third locus associated with ADH, HCHOLA3 at 1p32, and now report two mutations in the gene PCSK9 (encoding proprotein convertase subtilisin/kexin type 9) that cause ADH. PCSK9 encodes NARC-1 (neural apoptosis regulated convertase), a newly identified human subtilase that is highly expressed in the liver and contributes to cholesterol homeostasis. 相似文献
44.
Structure and thermal history of the H-chondrite parent asteroid revealed by thermochronometry 总被引:1,自引:0,他引:1
Trieloff M Jessberger EK Herrwerth I Hopp J Fiéni C Ghélis M Bourot-Denise M Pellas P 《Nature》2003,422(6931):502-506
Our Solar System formed approximately 4.6 billion years ago from the collapse of a dense core inside an interstellar molecular cloud. The subsequent formation of solid bodies took place rapidly. The period of &<10 million years over which planetesimals were assembled can be investigated through the study of meteorites. Although some planetesimals differentiated and formed metallic cores like the larger terrestrial planets, the parent bodies of undifferentiated chondritic meteorites experienced comparatively mild thermal metamorphism that was insufficient to separate metal from silicate. There is debate about the nature of the heat source as well as the structure and cooling history of the parent bodies. Here we report a study of 244Pu fission-track and 40Ar-39Ar thermochronologies of unshocked H chondrites, which are presumed to have a common, single, parent body. We show that, after fast accretion, an internal heating source (most probably 26Al decay) resulted in a layered parent body that cooled relatively undisturbed: rocks in the outer shells reached lower maximum metamorphic temperatures and cooled faster than the more recrystallized and chemically equilibrated rocks from the centre, which needed approximately 160 Myr to reach 390K. 相似文献
45.
De Joussineau C Soulé J Martin M Anguille C Montcourrier P Alexandre D 《Nature》2003,426(6966):555-559
Drosophila thoracic mechanosensory bristles originate from cells that are singled out from 'proneural' groups of competent epithelial cells. Neural competence is restricted to individual sensory organ precursors (SOPs) by Delta/Notch-mediated 'lateral inhibition', whereas other cells in the proneural field adopt an epidermal fate. The precursors of the large macrochaetes differentiate separately from individual proneural clusters that comprise about 20-30 cells or as heterochronic pairs from groups of more than 100 cells, whereas the precursors of the small regularly spaced microchaetes emerge from even larger proneural fields. This indicates that lateral inhibition might act over several cell diameters; it was difficult to reconcile with the fact that the inhibitory ligand Delta is membrane-bound until the observation that SOPs frequently extend thin processes offered an attractive hypothesis. Here we show that the extension of these planar filopodia--a common attribute of wing imaginal disc cells--is promoted by Delta and that their experimental suppression reduces Notch signalling in distant cells and increases bristle density in large proneural groups, showing that these membrane specializations mediate long-range lateral inhibition. 相似文献
46.
Williams K Christensen J Pedersen MT Johansen JV Cloos PA Rappsilber J Helin K 《Nature》2011,473(7347):343-348
47.
This paper examines the information available through leading indicators for modelling and forecasting the UK quarterly index of production. Both linear and non‐linear specifications are examined, with the latter being of the Markov‐switching type as used in many recent business cycle applications. The Markov‐switching models perform relatively poorly in forecasting the 1990s production recession, but a three‐indicator linear specification does well. The leading indicator variables in this latter model include a short‐term interest rate, the stock market dividend yield and the optimism balance from the quarterly CBI survey. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献