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31.
Cunningham B 《Science (New York, N.Y.)》1924,59(1537):536-537
32.
A critical step in the infectious cycle of Leishmania is the differentiation of parasites within the sand fly vector to the highly infective metacyclic promastigote stage. Here, we establish tetrahydrobiopterin (H4B) levels as an important factor controlling the extent of metacyclogenesis. H4B levels decline substantially during normal development, and genetic or nutritional manipulations showed that low H4B caused elevated metacyclogenesis. Mutants lacking pteridine reductase 1 (PTR1) had low levels of H4B, remained infectious to mice, and induced larger cutaneous lesions (hypervirulence). Thus, the control of pteridine metabolism has relevance to the mechanism of Leishmania differentiation and the limitation of virulence during evolution. 相似文献
33.
Myosin: a link between streptococci and heart 总被引:32,自引:0,他引:32
Murine monoclonal antibodies to Streptococcus pyogenes reacted with skeletal muscle myosin. High molecular weight proteins in extracts of human heart tissue that reacted with an antibody to S. pyogenes also reacted with a monoclonal antibody to ventricular myosin. Adsorption of the antibody to streptococci with S. pyogenes simultaneously removed reactivity of the antibody for either S. pyogenes or myosin. These results indicate that myosin shares immunodeterminants with a component of S. pyogenes. 相似文献
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36.
Temporal variability of the Atlantic meridional overturning circulation at 26.5 degrees N 总被引:4,自引:0,他引:4
Cunningham SA Kanzow T Rayner D Baringer MO Johns WE Marotzke J Longworth HR Grant EM Hirschi JJ Beal LM Meinen CS Bryden HL 《Science (New York, N.Y.)》2007,317(5840):935-938
The vigor of Atlantic meridional overturning circulation (MOC) is thought to be vulnerable to global warming, but its short-term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain. We combine continuous measurements of the MOC (beginning in 2004) using the purposefully designed transatlantic Rapid Climate Change array of moored instruments deployed along 26.5 degrees N, with time series of Gulf Stream transport and surface-layer Ekman transport to quantify its intra-annual variability. The year-long average overturning is 18.7 +/- 5.6 sverdrups (Sv) (range: 4.0 to 34.9 Sv, where 1 Sv = a flow of ocean water of 10(6) cubic meters per second). Interannual changes in the overturning can be monitored with a resolution of 1.5 Sv. 相似文献
37.
Fossilized nuclei and germination structures identify Ediacaran "animal embryos" as encysting protists 总被引:1,自引:0,他引:1
Huldtgren T Cunningham JA Yin C Stampanoni M Marone F Donoghue PC Bengtson S 《Science (New York, N.Y.)》2011,334(6063):1696-1699
Globular fossils showing palintomic cell cleavage in the Ediacaran Doushantuo Formation, China, are widely regarded as embryos of early metazoans, although metazoan synapomorphies, tissue differentiation, and associated juveniles or adults are lacking. We demonstrate using synchrotron-based x-ray tomographic microscopy that the fossils have features incompatible with multicellular metazoan embryos. The developmental pattern is comparable with nonmetazoan holozoans, including germination stages that preclude postcleavage embryology characteristic of metazoans. We conclude that these fossils are neither animals nor embryos. They belong outside crown-group Metazoa, within total-group Holozoa (the sister clade to Fungi that includes Metazoa, Choanoflagellata, and Mesomycetozoea) or perhaps on even more distant branches in the eukaryote tree. They represent an evolutionary grade in which palintomic cleavage served the function of producing propagules for dispersion. 相似文献
38.
Epstein E Norlyn JD Rush DW Kingsbury RW Kelley DB Cunningham GA Wrona AF 《Science (New York, N.Y.)》1980,210(4468):399-404
Increasing salinity of soil and water threatens agriculture in arid and semiarid regions. By itself, the traditional engineering approach to the problem is no longer adequate. Genetic science offers the possibility of developing salt-tolerant crops, which, in conjunction with environmental manipulation, could improve agricultural production in saline regions and extend agriculture to previously unsuited regions. 相似文献
39.
Dimerization of the extracellular domain of the human growth hormone receptor by a single hormone molecule 总被引:51,自引:0,他引:51
B C Cunningham M Ultsch A M De Vos M G Mulkerrin K R Clauser J A Wells 《Science (New York, N.Y.)》1991,254(5033):821-825
Human growth hormone (hGH) forms a 1:2 complex with the extracellular domain of its receptor-binding protein (hGHbp) as studied by crystallization, size exclusion chromatography, calorimetry, and a previously undescribed fluorescence quenching assay. These and other experiments with protein engineered variants of hGH have led to the identification of the binding determinants for two distinct but adjacent sites on hGH for the hGHbp, and the data indicated that there are two overlapping binding sites on the hGHbp for hGH. Furthermore, the binding of hGH to the hGHbp occurred sequentially; a first hGHbp molecule bound to site 1 on hGH and then a second hGHbp bound to site 2. Hormone-induced receptor dimerization is proposed to be relevant to the signal transduction mechanism for the hGH receptor and other related cytokine receptors. 相似文献
40.
Ferguson AD McKeever BM Xu S Wisniewski D Miller DK Yamin TT Spencer RH Chu L Ujjainwalla F Cunningham BR Evans JF Becker JW 《Science (New York, N.Y.)》2007,317(5837):510-512
Leukotrienes are proinflammatory products of arachidonic acid oxidation by 5-lipoxygenase that have been shown to be involved in respiratory and cardiovascular diseases. The integral membrane protein FLAP is essential for leukotriene biosynthesis. We describe the x-ray crystal structures of human FLAP in complex with two leukotriene biosynthesis inhibitors at 4.0 and 4.2 angstrom resolution, respectively. The structures show that inhibitors bind in membrane-embedded pockets of FLAP, which suggests how these inhibitors prevent arachidonic acid from binding to FLAP and subsequently being transferred to 5-lipoxygenase, thereby preventing leukotriene biosynthesis. This structural information provides a platform for the development of therapeutics for respiratory and cardiovascular diseases. 相似文献