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排序方式: 共有547条查询结果,搜索用时 15 毫秒
541.
542.
Sylvain Antoniazza Reto Burri Luca Fumagalli Jérôme Goudet Alexandre Roulin 《Evolution; international journal of organic evolution》2010,64(7):1944-1954
Ecological parameters vary in space, and the resulting heterogeneity of selective forces can drive adaptive population divergence. Clinal variation represents a classical model to study the interplay of gene flow and selection in the dynamics of this local adaptation process. Although geographic variation in phenotypic traits in discrete populations could be remainders of past adaptation, maintenance of adaptive clinal variation requires recurrent selection. Clinal variation in genetically determined traits is generally attributed to adaptation of different genotypes to local conditions along an environmental gradient, although it can as well arise from neutral processes. Here, we investigated whether selection accounts for the strong clinal variation observed in a highly heritable pheomelanin‐based color trait in the European barn owl by comparing spatial differentiation of color and of neutral genes among populations. Barn owl's coloration varies continuously from white in southwestern Europe to reddish‐brown in northeastern Europe. A very low differentiation at neutral genetic markers suggests that substantial gene flow occurs among populations. The persistence of pronounced color differentiation despite this strong gene flow is consistent with the hypothesis that selection is the primary force maintaining color variation among European populations. Therefore, the color cline is most likely the result of local adaptation. 相似文献
543.
Johanna Faist Werner Seebacher Marcel Kaiser Reto Brun Robert Saf Robert Weis 《Bioorganic & medicinal chemistry》2013,21(17):4988-4996
ω-Aminoacyl and -alkyl derivatives of 4-(4-methylpiperazin-1-yl)bicyclo[2.2.2]octan-2-amines and of 5-(4-methylpiperazin-1-yl)-2-azabicyclo[3.2.2]nonanes were prepared and their activities were examined in vitro against the multiresistant K1 strain of Plasmodium falciparum and against Trypanosoma brucei rhodesiense (STIB 900). Some of the newly synthesized compounds showed very promising antiprotozoal activity and selectivity. A few of the alkylamino-2-azabicyclo[3.2.2]nonanes exhibited high antiplasmodial activity, whereas a single bicyclo[2.2.2]octane derivative was the most potent antitrypanosomal compound. The results of the newly synthesized compounds were compared with the activities of already synthesized compounds and of drugs in use. Structure–activity relationships were discussed. 相似文献
544.
545.
Although juvenile dispersal is an important life history component, it remains one of the less understood ecological processes
regulating the dynamics of animal populations. Lack of information about patterns of dispersal hampers the estimation of the
actual status and demographic trajectory of populations, and can preclude the development of sound conservation strategies.
The Eagle Owl Bubo bubo is an endangered bird species in the European Alps. Many breeding sites have been abandoned in the twentieth century, although
some recovery has been reported lately. Moreover, the occupancy of traditional breeding sites across years in well-monitored
Alpine populations varies a lot, this despite a relatively high breeding success at the population level. This raises concern
about the long-term persistence of Alpine populations. Using conventional and satellite radiotracking, we investigated the
spatio-temporal dispersal of 41 juvenile Eagle Owls originating from a population in the southwestern Swiss Alps. Our main
goal was to determine dispersal distances, places and times of post-dispersal settlement. Juveniles left their parents between
mid-August and mid-November. They covered, on average, 12.7 km per night (linear distance between two consecutive day roosts),
often crossing high mountain ranges (up to 3,000 m altitude). The mean total distance covered by an individual during dispersal
was 102 km (sum of night movements), with a maximum of 230 km. Settlement places were, on average, 46 km distant from the
birth place. Our study establishes long-distance dispersal in juvenile Eagle Owls, even in a complex topography, suggesting
the existence of a wide-scale metapopulation system across the northwestern Alps. This metapopulation dimension should be
accounted for in conservation plans. 相似文献
546.
Kevin?M. Dean Philippe Roudot Carlos?R. Reis Erik?S. Welf Marcel Mettlen Reto Fiolka 《Biophysical journal》2016,110(6):1456-1465
In subcellular light-sheet fluorescence microscopy (LSFM) of adherent cells, glass substrates are advantageously rotated relative to the excitation and emission light paths to avoid glass-induced optical aberrations. Because cells are spread across the sample volume, three-dimensional imaging requires a light-sheet with a long propagation length, or rapid sample scanning. However, the former degrades axial resolution and/or optical sectioning, while the latter mechanically perturbs sensitive biological specimens on pliant biomimetic substrates (e.g., collagen and basement membrane). Here, we use aberration-free remote focusing to diagonally sweep a narrow light-sheet along the sample surface, enabling multicolor imaging with high spatiotemporal resolution. Further, we implement a dithered Gaussian lattice to minimize sample-induced illumination heterogeneities, significantly improving signal uniformity. Compared with mechanical sample scanning, we drastically reduce sample oscillations, allowing us to achieve volumetric imaging at speeds of up to 3.5 Hz for thousands of Z-stacks. We demonstrate the optical performance with live-cell imaging of microtubule and actin cytoskeletal dynamics, phosphoinositide signaling, clathrin-mediated endocytosis, polarized blebbing, and endocytic vesicle sorting. We achieve three-dimensional particle tracking of clathrin-associated structures with velocities up to 4.5 μm/s in a dense intracellular environment, and show that such dynamics cannot be recovered reliably at lower volumetric image acquisition rates using experimental data, numerical simulations, and theoretical modeling. 相似文献
547.
Oumaïma Ibrahim-Granet Grégory Jouvion Tobias M Hohl Sabrina Droin-Bergère François Philippart Oh Yoen Kim Minou Adib-Conquy Reto Schwendener Jean-Marc Cavaillon Matthias Brock 《BMC microbiology》2010,10(1):105