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71.
72.
Adams M 《Science (New York, N.Y.)》1973,180(4088):840-842
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Smither-Kopperl ML 《Science (New York, N.Y.)》2002,298(5600):1891-1892
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Chen J de Felipe KS Clarke M Lu H Anderson OR Segal G Shuman HA 《Science (New York, N.Y.)》2004,303(5662):1358-1361
Legionella pneumophila, the bacterial agent of legionnaires' disease, replicates intracellularly within a specialized vacuole of mammalian and protozoan host cells. Little is known about the specialized vacuole except that the Icm/Dot type IV secretion system is essential for its formation and maintenance. The Legionella genome database contains two open reading frames encoding polypeptides (LepA and LepB) with predicted coiled-coil regions and weak homology to SNAREs; these are delivered to host cells by an Icm/Dot-dependent mechanism. Analysis of mutant strains suggests that the Lep proteins may enable the Legionella to commandeer a protozoan exocytic pathway for dissemination of the pathogen. 相似文献
77.
Nancy Grudens-Schuck Will Allen Tasha M. Hargrove Margaret Kilvington 《Agriculture and Human Values》2003,20(1):53-64
Dependency stands for manygrievances and is generally considered asymptom of oppression. An opposing concept,offered as the preferred state, isself-reliance. Dependency and self-reliance arekey concepts in sustainable developmentprograms that feature participatory approaches.Some of the ways in which development projectsemploy the concepts of dependency andself-reliance, however, are troubling.Dependency and self-reliance in two programsfor participatory sustainable development areexamined, one in Canada and the other in NewZealand. Frameworks for dependency and self-reliance aredrawn from social psychology and philosophy toexamine problematic aspects associated with theconcepts. Analysis produced a proposal foruse of the term situatedinterdependence as a way to cast the outcomesof participatory sustainable development moreprecisely. The location of the cases (Canadaand New Zealand) centers the discussion withina context of industrialized agriculture, butalso points to issues pertinent to developingcountries. 相似文献
78.
Shimojima M Miyazawa T Ikeda Y McMonagle EL Haining H Akashi H Takeuchi Y Hosie MJ Willett BJ 《Science (New York, N.Y.)》2004,303(5661):1192-1195
Feline immunodeficiency virus (FIV) induces a disease similar to acquired immunodeficiency syndrome (AIDS) in cats, yet in contrast to human immunodeficiency virus (HIV), CD4 is not the viral receptor. We identified a primary receptor for FIV as CD134 (OX40), a T cell activation antigen and costimulatory molecule. CD134 expression promotes viral binding and renders cells permissive for viral entry, productive infection, and syncytium formation. Infection is CXCR4-dependent, analogous to infection with X4 strains of HIV. Thus, despite the evolutionary divergence of the feline and human lentiviruses, both viruses use receptors that target the virus to a subset of cells that are pivotal to the acquired immune response. 相似文献
79.
A transient rise in tropical sea surface temperature during the Paleocene-Eocene thermal maximum 总被引:1,自引:0,他引:1
Zachos JC Wara MW Bohaty S Delaney ML Petrizzo MR Brill A Bralower TJ Premoli-Silva I 《Science (New York, N.Y.)》2003,302(5650):1551-1554
The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8 degrees to 10 degrees C) and in bottom water temperatures (4 degrees to 5 degrees C). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4 degrees to 5 degrees C rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO2 to levels three to four times as high as those estimated for the late Paleocene. 相似文献
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