Hypoxic dilation of coronary arteries is mediated by ATP-sensitive potassium channels   总被引：44，自引：0，他引：44  

J Daut  W Maier-Rudolph  N von Beckerath  G Mehrke  K Günther  L Goedel-Meinen 《Science (New York, N.Y.)》1990,247(4948):1341-1344

The function of the heart depends critically on an adequate oxygen supply through the coronary arteries. Coronary arteries dilate when the intravascular oxygen tension decreases. Hypoxic vasodilation in isolated, perfused guinea pig hearts can be prevented by glibenclamide, a blocker of adenosine triphosphate (ATP)-sensitive potassium channels, and can be mimicked by cromakalim, which opens ATP-sensitive potassium channels. Opening of potassium channels in coronary smooth muscle cells and the subsequent drop in intracellular calcium is probably the major cause of hypoxic and ischemic vasodilation in the mammalian heart.  相似文献   

Guided growth of millimeter-long horizontal nanowires with controlled orientations     

Tsivion D  Schvartzman M  Popovitz-Biro R  von Huth P  Joselevich E 《Science (New York, N.Y.)》2011,333(6045):1003-1007

The large-scale assembly of nanowires with controlled orientation on surfaces remains one challenge preventing their integration into practical devices. We report the vapor-liquid-solid growth of aligned, millimeter-long, horizontal GaN nanowires with controlled crystallographic orientations on different planes of sapphire. The growth directions, crystallographic orientation, and faceting of the nanowires vary with each surface orientation, as determined by their epitaxial relationship with the substrate, as well as by a graphoepitaxial effect that guides their growth along surface steps and grooves. Despite their interaction with the surface, these horizontally grown nanowires display few structural defects, exhibiting optical and electronic properties comparable to those of vertically grown nanowires. This paves the way to highly controlled nanowire structures with potential applications not available by other means.  相似文献   

CD8alphaalpha-mediated survival and differentiation of CD8 memory T cell precursors   总被引：1，自引：0，他引：1  

Madakamutil LT  Christen U  Lena CJ  Wang-Zhu Y  Attinger A  Sundarrajan M  Ellmeier W  von Herrath MG  Jensen P  Littman DR  Cheroutre H 《Science (New York, N.Y.)》2004,304(5670):590-593

Memory T cells are long-lived antigen-experienced T cells that are generally accepted to be direct descendants of proliferating primary effector cells. However, the factors that permit selective survival of these T cells are not well established. We show that homodimeric alpha chains of the CD8 molecule (CD8alphaalpha) are transiently induced on a selected subset of CD8alphabeta+ T cells upon antigenic stimulation. These CD8alphaalpha molecules promote the survival and differentiation of activated lymphocytes into memory CD8 T cells. Thus, memory precursors can be identified among primary effector cells and are selected for survival and differentiation by CD8alphaalpha.  相似文献   

Immunology. Memory T cells--local heroes in the struggle for immunity     

Mackay CR  von Andrian UH 《Science (New York, N.Y.)》2001,291(5512):2323-2324

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CD95/CD95 ligand interactions on epithelial cells in host defense to Pseudomonas aeruginosa     

Grassmé H  Kirschnek S  Riethmueller J  Riehle A  von Kürthy G  Lang F  Weller M  Gulbins E 《Science (New York, N.Y.)》2000,290(5491):527-530

Pseudomonas aeruginosa causes severe infections, particularly of the lung, that are life threatening. Here, we show that P. aeruginosa infection induces apoptosis of lung epithelial cells by activation of the endogenous CD95/CD95 ligand system. Deficiency of CD95 or CD95 ligand on epithelial cells prevented apoptosis of lung epithelial cells in vivo as well as in vitro. The importance of CD95/CD95 ligand-mediated lung epithelial cell apoptosis was demonstrated by the rapid development of sepsis in CD95- or CD95 ligand-deficient mice, but not in normal mice, after P. aeruginosa infection.  相似文献   

PKA type IIalpha holoenzyme reveals a combinatorial strategy for isoform diversity     

Wu J  Brown SH  von Daake S  Taylor SS 《Science (New York, N.Y.)》2007,318(5848):274-279

The catalytic (C) subunit of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is inhibited by two classes of regulatory subunits, RI and RII. The RII subunits are substrates as well as inhibitors and do not require adenosine triphosphate (ATP) to form holoenzyme, which distinguishes them from RI subunits. To understand the molecular basis for isoform diversity, we solved the crystal structure of an RIIalpha holoenzyme and compared it to the RIalpha holoenzyme. Unphosphorylated RIIalpha(90-400), a deletion mutant, undergoes major conformational changes as both of the cAMP-binding domains wrap around the C subunit's large lobe. The hallmark of this conformational reorganization is the helix switch in domain A. The C subunit is in an open conformation, and its carboxyl-terminal tail is disordered. This structure demonstrates the conserved and isoform-specific features of RI and RII and the importance of ATP, and also provides a new paradigm for designing isoform-specific activators or antagonists for PKA.  相似文献   

Peripheral selection of the T cell repertoire   总被引：63，自引：0，他引：63  

B Rocha  H von Boehmer 《Science (New York, N.Y.)》1991,251(4998):1225-1228

T lymphocytes undergo selection events not only in the thymus, but also after they leave the thymus and reside in the periphery. Peripheral selection was found to be dependent on T cell receptor (TCR)-ligand interactions but to differ from thymic selection with regard to specificity and mechanism. Unlike thymic selection, peripheral selection required binding of antigen to the TCR, and it induced expansion of T cell clones. Tolerance to self antigens that are restricted to the periphery occurred through the elimination of self-reactive T cells and by the clonal anergy, which was associated with down-regulation of the alpha beta TCR and CD8.  相似文献   

Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays     

Fritz DM  Reis DA  Adams B  Akre RA  Arthur J  Blome C  Bucksbaum PH  Cavalieri AL  Engemann S  Fahy S  Falcone RW  Fuoss PH  Gaffney KJ  George MJ  Hajdu J  Hertlein MP  Hillyard PB  Horn-von Hoegen M  Kammler M  Kaspar J  Kienberger R  Krejcik P  Lee SH  Lindenberg AM  McFarland B  Meyer D  Montagne T  Murray ED  Nelson AJ  Nicoul M  Pahl R  Rudati J  Schlarb H  Siddons DP  Sokolowski-Tinten K  Tschentscher T  von der Linde D  Hastings JB 《Science (New York, N.Y.)》2007,315(5812):633-636

Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.  相似文献   

Submarine thermal sprirngs on the galapagos rift   总被引：2，自引：0，他引：2  

Corliss JB  Dymond J  Gordon LI  Edmond JM  von Herzen RP  Ballard RD  Green K  Williams D  Bainbridge A  Crane K  van Andel TH 《Science (New York, N.Y.)》1979,203(4385):1073-1083

The submarine hydrothermal activity on and near the Galápagos Rift has been explored with the aid of the deep submersible Alvin. Analyses of water samples from hydrothermal vents reveal that hydrothermal activity provides significant or dominant sources and sinks for several components of seawater; studies of conductive and convective heat transfer suggest that two-thirds of the heat lost from new oceanic lithosphere at the Galápagos Rift in the first million years may be vented from thermal springs, predominantly along the axial ridge within the rift valley. The vent areas are populated by animal communities. They appear to utilize chemosynthesis by sulfur-oxidizing bacteria to derive their entire energy supply from reactions between the seawater and the rocks at high temperatures, rather than photosynthesis.  相似文献   

Controlling chemical turbulence by global delayed feedback: pattern formation in catalytic CO oxidation on Pt(110)     

Kim M  Bertram M  Pollmann M  von Oertzen A  Mikhailov AS  Rotermund HH  Ertl G 《Science (New York, N.Y.)》2001,292(5520):1357-1360

Control of spatiotemporal chaos is one of the central problems of nonlinear dynamics. We report on suppression of chemical turbulence by global delayed feedback using, as an example, catalytic carbon monoxide oxidation on a platinum (110) single-crystal surface and carbon monoxide partial pressure as the controlled feedback variable. When feedback intensity was increased, spiral-wave turbulence was transformed into new intermittent chaotic regimes with cascades of reproducing and annihilating local structures on the background of uniform oscillations. The global feedback further led to the development of cluster patterns and standing waves and to the stabilization of uniform oscillations. These findings are reproduced by theoretical simulations.  相似文献