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A growing body of literature suggests that infanticide is common in a variety of animals. However, most reports are concerned
with infanticide by males and these evidences are often indirect or questionable. Here we describe the first videotaped non-parental
infanticide by a female common pochard (Aythya ferina) which killed one conspecific duckling. Our observation does not suggest that this attack was caused by a high density of
breeding pairs as was found for other ducks (resource competition hypothesis). We speculate that infanticide in this particular
case might be adaptive because a reduced number of ducklings in the pond decreased the vulnerability to predation by raptors. 相似文献
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Drosophila growth cones: A genetically tractable platform for the analysis of axonal growth dynamics
Natalia Sánchez‐Soriano Catarina Gonçalves‐Pimentel Robin Beaven Ulrike Haessler Lisa Ofner‐Ziegenfuss Christoph Ballestrem Andreas Prokop 《Developmental neurobiology》2010,70(1):58-71
The formation of neuronal networks, during development and regeneration, requires outgrowth of axons along reproducible paths toward their appropriate postsynaptic target cells. Axonal extension occurs at growth cones (GCs) at the tips of axons. GC advance and navigation requires the activity of their cytoskeletal networks, comprising filamentous actin (F‐actin) in lamellipodia and filopodia as well as dynamic microtubules (MTs) emanating from bundles of the axonal core. The molecular mechanisms governing these two cytoskeletal networks, their cross‐talk, and their response to extracellular signaling cues are only partially understood, hindering our conceptual understanding of how regulated changes in GC behavior are controlled. Here, we introduce Drosophila GCs as a suitable model to address these mechanisms. Morphological and cytoskeletal readouts of Drosophila GCs are similar to those of other models, including mammals, as demonstrated here for MT and F‐actin dynamics, axonal growth rates, filopodial structure and motility, organizational principles of MT networks, and subcellular marker localization. Therefore, we expect fundamental insights gained in Drosophila to be translatable into vertebrate biology. The advantage of the Drosophila model over others is its enormous amenability to combinatorial genetics as a powerful strategy to address the complexity of regulatory networks governing axonal growth. Thus, using pharmacological and genetic manipulations, we demonstrate a role of the actin cytoskeleton in a specific form of MT organization (loop formation), known to regulate GC pausing behavior. We demonstrate these events to be mediated by the actin‐MT linking factor Short stop, thus identifying an essential molecular player in this context. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2010 相似文献
316.
A droplet fractionation method was previously developed to concentrate a dilute nonfoaming protein solution. In that earlier
study with invertase, it was demonstrated that droplets created by ultrasonic energy waves could be enriched up to 8 times
that of the initial dilute invertase solution. In this study, a mixture of bromelain (a foaming protein) and invertase (a
nonfoaming protein) is investigated as a preliminary step to determine if droplet fractionation can also be used to separate
a non-foaming protein from foaming proteins. The foaming mixture containing bromelain is first removed by bubbling the binary
mixture with air. After the foam is removed, the protein rich air-water interfacial layer is skimmed off (prior to droplet
fractionation) so as not to interfere with the subsequent droplet production from the remaining bulk liquid, rich in non-foaming
protein. Finally, sonic energy waves are then applied to this residual bulk liquid to recover droplets containing the non-foaming
protein, presumed to be invertase. The primary control variable used in this droplet fractionation process is the pH, which
ranged for separate experiments between 2 and 9. It was observed that the maximum overall protein partition coefficients of
5 and 4 were achieved at pH 2 and 4, respectively, for the initial foaming experiment followed by the post foaming droplet
fractionation experiment. 相似文献