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Hummingbirds have developed a wealth of intriguing features, such as backwards flight, ultraviolet vision, extremely high metabolic rates, nocturnal hibernation, high brain-to-body size ratio and a remarkable species-specific diversity of vocalizations. Like humans, they have also developed the rare trait of vocal learning, this being the ability to acquire vocalizations through imitation rather than instinct. Here we show, using behaviourally driven gene expression in freely ranging tropical animals, that the forebrain of hummingbirds contains seven discrete structures that are active during singing, providing the first anatomical and functional demonstration of vocal nuclei in hummingbirds. These structures are strikingly similar to seven forebrain regions that are involved in vocal learning and production in songbirds and parrots--the only other avian orders known to be vocal learners. This similarity is surprising, as songbirds, parrots and hummingbirds are thought to have evolved vocal learning and associated brain structures independently, and it indicates that strong constraints may influence the evolution of forebrain vocal nuclei. 相似文献
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One important aspect concerning the analysis and forecasting of time series that is sometimes neglected is the relationship between a model and the sampling interval, in particular, when the observation is cumulative over the sampling period. This paper intends to study the temporal aggregation in Bayesian dynamic linear models (DLM). Suppose that a time series Yt is observed at time units t and the observations of the process are aggregated over r units of time, defining a new time series Zk=Σri=1Yrk+i. The relevant factors explaining the variation of Zk can, and in general will, be different, depending on how the sampling interval r is chosen. It is shown that if Yt follows certain dynamic linear models, then the aggregated series can also be described by possibly different DLM. In the examples, the industrial production of Brazil is analysed under various aggregation periods and the results are compared. © 1997 John Wiley & Sons, Ltd. 相似文献
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W. C. De Mello 《Cellular and molecular life sciences : CMLS》1972,28(10):832-833
Résumé L'influence de la température dans le phénoméne de suppression des potentiels de lésion «healingover» du muscle cardiaque deBufo marinus est édudiée avec des électrodes extracellulaires. A la température de 15°C ou 5°C, une réduction marquée de la vélocité de suppression est observée. 相似文献
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W. R. Terra A. G. de Bianchi M. Paes de Mello R. Basile 《Cellular and molecular life sciences : CMLS》1976,32(4):432-434
Summary Disorders in the carotenoid metabolism are proposed to explain the absence of the yellow and violet or only the violet carotenoid-linked proteins from the haemolymph of someR. americana larvae. The lack of only the yellow chromoprotein is considered to be due to a failure in the biosynthesis of its apoprotein.Supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Pesquisas (CNPq). W.R.T. and A.G. de B. are indebted to Prof.F. J. S. Lara for advice, encouragement and for laboratory facilities. We thank Mr.A. Malavasi for collecting larvae in nature, Mrs.R. M. Zanelato for larvae culture and MissI. L. Jorge for typing. 相似文献
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Résumé Le système neuromusculaire dansElectrophorus electricus est étudié avec des électrodes intracellulaires. La transmission neuromusculaire est supprimée avec D-tubocurarine (5 · 10–7
p/v) ou avec un excès des ions Mg++ (12 mM) dans la solution. 相似文献
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Influence of temperature on myocardial healing-over 总被引:1,自引:0,他引:1
W C De Mello 《Experientia》1972,28(7):832-833
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Revealing the world of RNA interference 总被引:3,自引:0,他引:3
The recent discoveries of RNA interference and related RNA silencing pathways have revolutionized our understanding of gene regulation. RNA interference has been used as a research tool to control the expression of specific genes in numerous experimental organisms and has potential as a therapeutic strategy to reduce the expression of problem genes. At the heart of RNA interference lies a remarkable RNA processing mechanism that is now known to underlie many distinct biological phenomena. 相似文献