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861.
862.
Straight AF Cheung A Limouze J Chen I Westwood NJ Sellers JR Mitchison TJ 《Science (New York, N.Y.)》2003,299(5613):1743-1747
Completion of cell division during cytokinesis requires temporally and spatially regulated communication from the microtubule cytoskeleton to the actin cytoskeleton and the cell membrane. We identified a specific inhibitor of nonmuscle myosin II, blebbistatin, that inhibited contraction of the cleavage furrow without disrupting mitosis or contractile ring assembly. Using blebbistatin and other drugs, we showed that exit from the cytokinetic phase of the cell cycle depends on ubiquitin-mediated proteolysis. Continuous signals from microtubules are required to maintain the position of the cleavage furrow, and these signals control the localization of myosin II independently of other furrow components. 相似文献
863.
Amy L. Bentley 《Agriculture and Human Values》1994,11(4):4-18
The United States, which committed itself to alleviating the severe post-World War II global famine, failed to meet its relief commitments. Relief efforts failed largely because voluntary attempts at reducing consumption proved too difficult, and the U. S. government refused to return to mandatory rationing of food despite evidence indicating the majority of Americans, especially American women, would have welcomed such a move. Contributing to officials' opposition to mandatory post-war rationing were the revived ideology of government non-interference; a strong government/agriculture alliance; the focus on private, as opposed to public, interests and obligations; and increasing Cold War tensions precluding any worldwide efforts at famine relief. It seemed only the fear of Communist takeover could provoke Congress in partnership with business interests into sufficiently alleviating famine conditions, but only for those countries willing to abide by U. S. terms. 相似文献
864.
Toth AL Varala K Newman TC Miguez FE Hutchison SK Willoughby DA Simons JF Egholm M Hunt JH Hudson ME Robinson GE 《Science (New York, N.Y.)》2007,318(5849):441-444
The presence of workers that forgo reproduction and care for their siblings is a defining feature of eusociality and a major challenge for evolutionary theory. It has been proposed that worker behavior evolved from maternal care behavior. We explored this idea by studying gene expression in the primitively eusocial wasp Polistes metricus. Because little genomic information existed for this species, we used 454 sequencing to generate 391,157 brain complementary DNA reads, resulting in robust hits to 3017 genes from the honey bee genome, from which we identified and assayed orthologs of 32 honey bee behaviorally related genes. Wasp brain gene expression in workers was more similar to that in foundresses, which show maternal care, than to that in queens and gynes, which do not. Insulin-related genes were among the differentially regulated genes, suggesting that the evolution of eusociality involved major nutritional and reproductive pathways. 相似文献
865.
Dyudina UA Ingersoll AP Ewald SP Vasavada AR West RA Del Genio AD Barbara JM Porco CC Achterberg RK Flasar FM Simon-Miller AA Fletcher LN 《Science (New York, N.Y.)》2008,319(5871):1801
The camera onboard the Cassini spacecraft has allowed us to observe many of Saturn's cloud features. We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also shares properties with the polar vortices on Venus, such as polar location, cyclonic circulation, warm center, and long lifetime, but the Venus vortices have cold collars and are not associated with convective clouds. The SPV's combination of properties is unique among vortices in the solar system. 相似文献
866.
867.
Urizar NL Liverman AB Dodds DT Silva FV Ordentlich P Yan Y Gonzalez FJ Heyman RA Mangelsdorf DJ Moore DD 《Science (New York, N.Y.)》2002,296(5573):1703-1706
Extracts of the resin of the guggul tree (Commiphora mukul) lower LDL (low-density lipoprotein) cholesterol levels in humans. The plant sterol guggulsterone [4,17(20)-pregnadiene-3,16-dione] is the active agent in this extract. We show that guggulsterone is a highly efficacious antagonist of the farnesoid X receptor (FXR), a nuclear hormone receptor that is activated by bile acids. Guggulsterone treatment decreases hepatic cholesterol in wild-type mice fed a high-cholesterol diet but is not effective in FXR-null mice. Thus, we propose that inhibition of FXR activation is the basis for the cholesterol-lowering activity of guggulsterone. Other natural products with specific biologic effects may modulate the activity of FXR or other relatively promiscuous nuclear hormone receptors. 相似文献
868.
869.
Boutros M Kiger AA Armknecht S Kerr K Hild M Koch B Haas SA Paro R Perrimon N;Heidelberg Fly Array Consortium 《Science (New York, N.Y.)》2004,303(5659):832-835
A crucial aim upon completion of whole genome sequences is the functional analysis of all predicted genes. We have applied a high-throughput RNA-interference (RNAi) screen of 19,470 double-stranded (ds) RNAs in cultured cells to characterize the function of nearly all (91%) predicted Drosophila genes in cell growth and viability. We found 438 dsRNAs that identified essential genes, among which 80% lacked mutant alleles. A quantitative assay of cell number was applied to identify genes of known and uncharacterized functions. In particular, we demonstrate a role for the homolog of a mammalian acute myeloid leukemia gene (AML1) in cell survival. Such a systematic screen for cell phenotypes, such as cell viability, can thus be effective in characterizing functionally related genes on a genome-wide scale. 相似文献
870.
Daniel L. Evans Victoria Janes-Bassett Pasquale Borrelli Claire Chenu Carla S. S. Ferreira Robert I. Griffiths Zahra Kalantari Saskia Keesstra Rattan Lal Panos Panagos David A. Robinson Samaneh Seifollahi-Aghmiuni Pete Smith Tammo S. Steenhuis Amy Thomas Saskia M. Visser 《European Journal of Soil Science》2022,73(1):e13145