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711.
Macpherson AJ Gatto D Sainsbury E Harriman GR Hengartner H Zinkernagel RM 《Science (New York, N.Y.)》2000,288(5474):2222-2226
The immunoglobulin A (IgA) is produced to defend mucosal surfaces from environmental organisms, but host defenses against the very heavy load of intestinal commensal microorganisms are poorly understood. The IgA against intestinal commensal bacterial antigens was analyzed; it was not simply "natural antibody" but was specifically induced and responded to antigenic changes within an established gut flora. In contrast to IgA responses against exotoxins, a significant proportion of this specific anti-commensal IgA induction was through a pathway that was independent of T cell help and of follicular lymphoid tissue organization, which may reflect an evolutionarily primitive form of specific immune defense. 相似文献
712.
Roberts CM McClean CJ Veron JE Hawkins JP Allen GR McAllister DE Mittermeier CG Schueler FW Spalding M Wells F Vynne C Werner TB 《Science (New York, N.Y.)》2002,295(5558):1280-1284
Coral reefs are the most biologically diverse of shallow water marine ecosystems but are being degraded worldwide by human activities and climate warming. Analyses of the geographic ranges of 3235 species of reef fish, corals, snails, and lobsters revealed that between 7.2% and 53.6% of each taxon have highly restricted ranges, rendering them vulnerable to extinction. Restricted-range species are clustered into centers of endemism, like those described for terrestrial taxa. The 10 richest centers of endemism cover 15.8% of the world's coral reefs (0.012% of the oceans) but include between 44.8 and 54.2% of the restricted-range species. Many occur in regions where reefs are being severely affected by people, potentially leading to numerous extinctions. Threatened centers of endemism are major biodiversity hotspots, and conservation efforts targeted toward them could help avert the loss of tropical reef biodiversity. 相似文献
713.
Hammond GR Fischer MJ Anderson KE Holdich J Koteci A Balla T Irvine RF 《Science (New York, N.Y.)》2012,337(6095):727-730
The quantitatively minor phospholipid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P(2)] fulfills many cellular functions in the plasma membrane (PM), whereas its synthetic precursor, phosphatidylinositol 4-phosphate (PI4P), has no assigned PM roles apart from PI(4,5)P(2) synthesis. We used a combination of pharmacological and chemical genetic approaches to probe the function of PM PI4P, most of which was not required for the synthesis or functions of PI(4,5)P(2). However, depletion of both lipids was required to prevent PM targeting of proteins that interact with acidic lipids or activation of the transient receptor potential vanilloid 1 cation channel. Therefore, PI4P contributes to the pool of polyanionic lipids that define plasma membrane identity and to some functions previously attributed specifically to PI(4,5)P(2), which may be fulfilled by a more general polyanionic lipid requirement. 相似文献
714.
Foulger GR 《Science (New York, N.Y.)》2006,313(5788):768-769
715.
Wei MC Zong WX Cheng EH Lindsten T Panoutsakopoulou V Ross AJ Roth KA MacGregor GR Thompson CB Korsmeyer SJ 《Science (New York, N.Y.)》2001,292(5517):727-730
Multiple death signals influence mitochondria during apoptosis, yet the critical initiating event for mitochondrial dysfunction in vivo has been unclear. tBID, the caspase-activated form of a "BH3-domain-only" BCL-2 family member, triggers the homooligomerization of "multidomain" conserved proapoptotic family members BAK or BAX, resulting in the release of cytochrome c from mitochondria. We find that cells lacking both Bax and Bak, but not cells lacking only one of these components, are completely resistant to tBID-induced cytochrome c release and apoptosis. Moreover, doubly deficient cells are resistant to multiple apoptotic stimuli that act through disruption of mitochondrial function: staurosporine, ultraviolet radiation, growth factor deprivation, etoposide, and the endoplasmic reticulum stress stimuli thapsigargin and tunicamycin. Thus, activation of a "multidomain" proapoptotic member, BAX or BAK, appears to be an essential gateway to mitochondrial dysfunction required for cell death in response to diverse stimuli. 相似文献
716.
于6月底给澳洲坚果树(Ikaika 种)喷洒浓度为500或1000ppm 的乙烯溶液,在12天内分别使40%和60%的果实脱落。在开花高蜂后38周,用800或400ppm 的乙烯处理,分别在1周和3周内的带壳果产量与对照树(未用乙烯处理)5周后的产量(14.4公斤/树)接近。 相似文献
717.
718.
Emissions of atomic oxygen (1304 angstroms), atomic carbon (1657 angstroms), and atomic hydrogen (1216 angstroms) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on 8 January 1974. Analysis of the Lyman alpha halo at 1216 angstroms gave an atomic hydrogen production rate of 4.5 x 10(29) atoms per second. 相似文献
719.
Heath GR 《Science (New York, N.Y.)》1979,205(4409):903-904
The size distributions of deep-sea manganese nodules are consistent with a simple model of uniform growth at a few millimeters per million years and with the same probability of burial for all nodules, regardless of size. The model suggests that most nodules spend 1 million years or less on the sea floor. 相似文献
720.