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排序方式: 共有203条查询结果,搜索用时 31 毫秒
21.
Perforin. A family of killer proteins 总被引:3,自引:0,他引:3
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The most important effect of dihydroergotamine is venoconstriction, but certain metabolic effects and changes in vessel prostanoid activity have also been suggested. In this study endothelial cell production of 6-keto PGF1 alpha and TxB2 was quantitated in vitro. No evidence of altered prostanoid production was noted after incubation with dihydroergotamine (exposure ranging from 5 x 10(-3) to 5 x 10(-7) g/l). Similarly, no effect of dihydroergotamine on the growth rates of endothelial cells or smooth muscle cells in vitro was documented. 相似文献
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A new diagram for discriminating a forecasting technique's history with respect to the two types of turning-point errors, missed turns and false signals is presented. This diagram extends Theil's original prediction-realization (P-R) presentation so that each of the four quadrants and the axes locates a distinct type of forecasting error or correct forecast, thus reducing much of the former ambiguity. This improvement is accomplished without the loss of any information. 相似文献
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Résumé La réponse pressive systémique à des injections intra-artérielles d'angiotensine I et II a été étudiée chez deux chiens avant et après avoir totalement exclu les poumons de la circulation. La réactivité à l'angiotensine I diminua presque 3 fois plus que celle à l'angiotensine II durant le shunt cardio-pulmonaire. Il apparaÎt donc que la circulation pulmonaire est un site important mais non exclusif de conversion de l'angiotensine I. 相似文献
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Pressor response to angiotensin I during cardio-pulmonary bypass 总被引:1,自引:0,他引:1
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Kwok TC Ricker N Fraser R Chan AW Burns A Stanley EF McCourt P Cutler SR Roy PJ 《Nature》2006,441(7089):91-95
Small-molecule inhibitors of protein function are powerful tools for biological analysis and can lead to the development of new drugs. However, a major bottleneck in generating useful small-molecule tools is target identification. Here we show that Caenorhabditis elegans can provide a platform for both the discovery of new bioactive compounds and target identification. We screened 14,100 small molecules for bioactivity in wild-type worms and identified 308 compounds that induce a variety of phenotypes. One compound that we named nemadipine-A induces marked defects in morphology and egg-laying. Nemadipine-A resembles a class of widely prescribed anti-hypertension drugs called the 1,4-dihydropyridines (DHPs) that antagonize the alpha1-subunit of L-type calcium channels. Through a genetic suppressor screen, we identified egl-19 as the sole candidate target of nemadipine-A, a conclusion that is supported by several additional lines of evidence. egl-19 encodes the only L-type calcium channel alpha1-subunit in the C. elegans genome. We show that nemadipine-A can also antagonize vertebrate L-type calcium channels, demonstrating that worms and vertebrates share the orthologous protein target. Conversely, FDA-approved DHPs fail to elicit robust phenotypes, making nemadipine-A a unique tool to screen for genetic interactions with this important class of drugs. Finally, we demonstrate the utility of nemadipine-A by using it to reveal redundancy among three calcium channels in the egg-laying circuit. Our study demonstrates that C. elegans enables rapid identification of new small-molecule tools and their targets. 相似文献
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Multifractality in human heartbeat dynamics. 总被引:35,自引:0,他引:35
P C Ivanov L A Amaral A L Goldberger S Havlin M G Rosenblum Z R Struzik H E Stanley 《Nature》1999,399(6735):461-465
There is evidence that physiological signals under healthy conditions may have a fractal temporal structure. Here we investigate the possibility that time series generated by certain physiological control systems may be members of a special class of complex processes, termed multifractal, which require a large number of exponents to characterize their scaling properties. We report on evidence for multifractality in a biological dynamical system, the healthy human heartbeat, and show that the multifractal character and nonlinear properties of the healthy heart rate are encoded in the Fourier phases. We uncover a loss of multifractality for a life-threatening condition, congestive heart failure. 相似文献