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41.
Norepinephrine: release from brain by d-amphetamine in vivo 总被引:1,自引:0,他引:1
After injection of H(3)-norepinephrine into the left lateral cerebral ventricle of cats, the lateral and third cerebral ventricles were perfused with an artificial cerebrospinal fluid. Addition of d-amphetamine to the perfusion fluid caused a significant increase in the concentration of H(3)-norepinephrine in the effluent. 相似文献
42.
Endotoxin-stimulated opioid peptide secretion: two secretory pools and feedback control in vivo 总被引:3,自引:0,他引:3
D B Carr R Bergland A Hamilton H Blume N Kasting M Arnold J B Martin M Rosenblatt 《Science (New York, N.Y.)》1982,217(4562):845-848
Small doses of endotoxin evoked a dramatic biphasic response of opioid peptide secretion into blood in sheep. The first phase began within minutes and coincided with a brief hypertensive response to endotoxin well before the appearance of fever or hypotension. The ratio of beta-endorphin to beta-lipotropin fell abruptly at the onset of the second phase of release, suggesting early depletion of a pool rich in beta-endorphin and subsequent emergence of a pool rich in unprocessed precursor. The concentration of cerebrospinal fluid opioids increased tenfold during the second phase. Naloxone administration augmented endotoxin-induced opioid secretion in both early and late phases, suggesting a short-loop feedback regulation of stress-induced endorphin secretion. 相似文献
43.
Grant JA Arvidson R Bell JF Cabrol NA Carr MH Christensen P Crumpler L Des Marais DJ Ehlmann BL Farmer J Golombek M Grant FD Greeley R Herkenhoff K Li R McSween HY Ming DW Moersch J Rice JW Ruff S Richter L Squyres S Sullivan R Weitz C 《Science (New York, N.Y.)》2004,305(5685):807-810
The Mars Exploration Rover Spirit has traversed a fairly flat, rock-strewn terrain whose surface is shaped primarily by impact events, although some of the landscape has been altered by eolian processes. Impacts ejected basaltic rocks that probably were part of locally formed lava flows from at least 10 meters depth. Some rocks have been textured and/or partially buried by windblown sediments less than 2 millimeters in diameter that concentrate within shallow, partially filled, circular impact depressions referred to as hollows. The terrain traversed during the 90-sol (martian solar day) nominal mission shows no evidence for an ancient lake in Gusev crater. 相似文献
44.
Salières P Carré B Le Déroff L Grasbon F Paulus GG Walther H Kopold R Becker W Milosević DB Sanpera A Lewenstein M 《Science (New York, N.Y.)》2001,292(5518):902-905
Atoms interacting with intense laser fields can emit electrons and photons of very high energies. An intuitive and quantitative explanation of these highly nonlinear processes can be found in terms of a generalization of classical Newtonian particle trajectories, the so-called quantum orbits. Very few quantum orbits are necessary to reproduce the experimental results. These orbits are clearly identified, thus opening the way for an efficient control as well as previously unknown applications of these processes. 相似文献
45.
Roosevelt AC Housley RA DA Silveira MI Maranca S Johnson R 《Science (New York, N.Y.)》1991,254(5038):1621-1624
The earliest pottery yet found in the Western Hemisphere has been excavated from a prehistoric shell midden near Santarém in the lower Amazon, Brazil. Calibrated accelerator radiocarbon dates on charcoal, shell, and pottery and a thermoluminescence date on pottery from the site fall from about 8000 to 7000 years before the present. The early fishing village is part of a long prehistoric trajectory that contradicts theories that resource poverty limited cultural evolution in the tropics. 相似文献
46.
47.
The phage typing patterns of 194 typable strains of Staphylococcus aureus isolated in the years 1927 through 1947 and preserved as stock cultures revealed that 43 strains were of phage type 80/81. The occurrence of other typable strains in the broad phage groups I, II, and III corresponded closely to the frequency distribution of staphylococci reported in 1945 by Wilson and Atkinson. 相似文献
48.
49.
Cutts JA Blasius KR Briggs GA Carr MH Greeley R Masursky H 《Science (New York, N.Y.)》1976,194(4271):1329-1337
During October 1976, the Viking 2 orbiter acquired approximately 700 high-resolution images of the north polar region of Mars. These images confirm the existence at the north pole of extensive layered deposits largely covered over with deposits of perennial ice. An unconformity within the layered deposits suggests a complex history of climate change during their time of deposition. A pole-girdling accumulation of dunes composed of very dark materials is revealed for the first time by the Viking cameras. The entire region is devoid of fresh impact craters. Rapid rates of erosion or deposition are implied. A scenario for polar geological evolution, involving two types of climate change, is proposed. 相似文献
50.