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121.
Developmental integration results from coordination among components of different embryonic fields to realize the later anatomical and functional relationships. We demonstrate that in the chick head, integration between the epibranchial placodes and the hindbrain is achieved as the neuroglial hindbrain crest cells guide the epibranchial neuronal cells inward to establish their central connections. This work defines a role for the neuroglial hindbrain crest in organizing the afferent innervation of the hindbrain. 相似文献
122.
Soon FF Ng LM Zhou XE West GM Kovach A Tan MH Suino-Powell KM He Y Xu Y Chalmers MJ Brunzelle JS Zhang H Yang H Jiang H Li J Yong EL Cutler S Zhu JK Griffin PR Melcher K Xu HE 《Science (New York, N.Y.)》2012,335(6064):85-88
Abscisic acid (ABA) is an essential hormone for plants to survive environmental stresses. At the center of the ABA signaling network is a subfamily of type 2C protein phosphatases (PP2Cs), which form exclusive interactions with ABA receptors and subfamily 2 Snfl-related kinase (SnRK2s). Here, we report a SnRK2-PP2C complex structure, which reveals marked similarity in PP2C recognition by SnRK2 and ABA receptors. In the complex, the kinase activation loop docks into the active site of PP2C, while the conserved ABA-sensing tryptophan of PP2C inserts into the kinase catalytic cleft, thus mimicking receptor-PP2C interactions. These structural results provide a simple mechanism that directly couples ABA binding to SnRK2 kinase activation and highlight a new paradigm of kinase-phosphatase regulation through mutual packing of their catalytic sites. 相似文献
123.
124.
Lopez N Graham DJ McGuire R Alliger GE Shao-Horn Y Cummins CC Nocera DG 《Science (New York, N.Y.)》2012,335(6067):450-453
Generation of soluble sources of peroxide dianion (O(2)(2-)) is a challenge in dioxygen chemistry. The oxidizing nature of this anion renders its stabilization in organic media difficult. This Report describes the chemically reversible reduction of oxygen (O(2)) to cryptand-encapsulated O(2)(2-). The dianion is stabilized by strong hydrogen bonds to N-H groups from the hexacarboxamide cryptand. Analogous stabilization of peroxide by hydrogen bonding has been invoked recently in crystalline saccharide and protein systems. The present peroxide adducts are stable at room temperature in dimethyl sulfoxide (DMSO) and N,N'-dimethylformamide (DMF). These adducts can be obtained in gram quantities from the cryptand-driven disproportionation reaction of potassium superoxide (KO(2)) at room temperature. 相似文献
125.
Mnierpes macrocephalus, a clinid fish of rocky shores of the eastern tropical Pacific, makes frequent terrestrial sojourns. The normal fish eye is myopic in air because of curvature of the cornea. This is overcome in Mnierpes by the presence of two flattened corneal surfaces. 相似文献
126.
Hörz F Bastien R Borg J Bradley JP Bridges JC Brownlee DE Burchell MJ Chi M Cintala MJ Dai ZR Djouadi Z Dominguez G Economou TE Fairey SA Floss C Franchi IA Graham GA Green SF Heck P Hoppe P Huth J Ishii H Kearsley AT Kissel J Leitner J Leroux H Marhas K Messenger K Schwandt CS See TH Snead C Stadermann FJ Stephan T Stroud R Teslich N Trigo-Rodríguez JM Tuzzolino AJ Troadec D Tsou P Warren J Westphal A Wozniakiewicz P Wright I Zinner E 《Science (New York, N.Y.)》2006,314(5806):1716-1719
Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup. 相似文献
127.
Visitors' reactions to six types of path barrier were recorded both by observation and by means of a questionnaire survey. ‘Natural’ barriers such as logs or branches were not very effective. A plank with notice was the most efficient barrier, and also the type most preferred by visitors. Barbed wire was effective but disliked by visitors. Few people objected to the closure of paths. Children and bird watchers took less notice of barriers than did other categories of visitors. 相似文献
128.
129.
Steffen S. Madsen Stephen D. McCormick Graham Young Jeanette S. Endersen Richard S. Nishioka Howard A. Bern 《Fish physiology and biochemistry》1994,13(1):1-11
Several experiments were performed to investigate the physiology of seawater acclimation in the striped bass, Morone saxatilis. Transfer of fish from fresh water (FW) to seawater (SW; 31–32 ppt) induced only a minimal disturbance of osmotic homeostasis.
Ambient salinity did not affect plasma thyroxine, but plasma cortisol remained elevated for 24h after SW transfer. Gill and
opercular membrane chloride cell density and Na+,K+-ATPase activity were relatively high and unaffected by salinity. Average chloride cell size, however, was slightly increased
(16%) in SW-acclimated fish. Gill succinate dehydrogenase activity was higher in SW-acclimated fish than in FW fish. Kidney
Na+, K+-ATPase activity was slightly lower (16%) in SW fish than in FW fish. Posterior intestinal Na+,K+-ATPase activity and water transport capacity (Jv) did not change upon SW transfer, whereas middle intestinal Na+,K+-ATPase activity increased 35% after transfer and was correlated with an increase in Jv (110%). As salinity induced only minor changes in the osmoregulatory organs examined, it is proposed that the intrinsic euryhalinity
of the striped bass may be related to a high degree of “preparedness” for hypoosmoregulation that is uncommon among teleosts
studied to data. 相似文献
130.