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211.
212.
Charlotte Récapet Lise Dauphin Lisa Jacquin Julien Gasparini Anne‐Caroline Prévot‐Julliard 《Journal of avian biology》2013,44(6):583-590
Urbanisation introduces deep changes in habitats, eventually creating new urban ecosystems where ecological functions are driven by human activities. The higher frequency of some phenotypes in urban vs rural/wild areas has led to the assumption that directional selection in urban habitats occurs, which may thereby favour some behavioural and physiological traits in urban animal populations compared to rural ones. However, empirical evidence of directional selection on phenotypic traits in urban areas remains scarce. In this study we tested whether eumelanin‐based colouration could be linked to survival in two urban populations of the feral pigeon Columba livia. A number of studies in different cities pointed out a higher frequency of darker individuals in more urbanised areas compared to rural ones. To investigate whether directional selection through survival on this highly heritable trait could explain such patterns, we conducted mark–recapture studies on two populations of feral pigeons in highly urbanized areas. We predicted that darker coloured individuals would exhibit higher survival and/or philopatry (integrated into ‘local survival’) than paler coloured ones. No difference in local survival was found between adults of different colouration intensities. However, on one site, we found that darker juveniles had a higher local survival probability than light ones. Juvenile local survival on that site was also negatively correlated with the number of chicks born. This suggests the existence of colour‐ and/or density‐dependent selection processes acting on juvenile feral pigeons in urban environments, acting through differential mortality and/or dispersal. 相似文献
213.
Recently developed methods to measure distances in proteins with high accuracy by “exact” nuclear Overhauser effects (eNOEs) make it possible to determine stereospecific assignments, which are particularly important to fully exploit the accuracy of the eNOE distance measurements. Stereospecific assignments are determined by comparing the eNOE-derived distances to protein structure bundles calculated without stereospecific assignments, or an independently determined crystal structure. The absolute and relative CYANA target function difference upon swapping the stereospecific assignment of a diastereotopic group yields the respective stereospecific assignment. We applied the method to the eNOE data set that has recently been obtained for the third immunoglobulin-binding domain of protein G (GB3). The 884 eNOEs provide relevant data for 47 of the total of 75 diastereotopic groups. Stereospecific assignments could be established for 45 diastereotopic groups (96 %) using the X-ray structure, or for 27 diastereotopic groups (57 %) using structures calculated with the eNOE data set without stereospecific assignments, all of which are in agreement with those determined previously. The latter case is relevant for structure determinations based on eNOEs. The accuracy of the eNOE distance measurements is crucial for making stereospecific assignments because applying the same method to the traditional NOE data set for GB3 with imprecise upper distance bounds yields only 13 correct stereospecific assignments using the X-ray structure or 2 correct stereospecific assignments using NMR structures calculated without stereospecific assignments. 相似文献
214.
Caroline Michot Asmaa Mamoune Joseph Vamecq Mai Thao Viou Lu-Sheng Hsieh Eric Testet Jeanne Lainé Laurence Hubert Anne-Frédérique Dessein Monique Fontaine Chris Ottolenghi Laetitia Fouillen Karim Nadra Etienne Blanc Jean Bastin Sophie Candon Mario Pende Arnold Munnich Pascale de Lonlay 《生物化学与生物物理学报:疾病的分子基础》2013,1832(12):2103-2114
215.
The effects of constant light on the expression of the circadian rhythm of feeding activity in Japanese quail, and in particular on the clarity of the rhythm were investigated. We used 46 4-week-old birds (35 females and 11 males) issued from two lines selected for a more (line R: 25 females and 10 males) or less (line A: 10 females and 1 male) clear circadian rhythm of feeding activity. The birds, were placed successively under three light schedules: constant darkness (DD), constant dim green light (LLdim) and constant bright light (LLbright). Schedules were changed every 2 weeks. Feeding activity was recorded continuously, analysed by autocorrelation and spectral analysis, and the ratio of the correlation coefficients and the area of the spectrum peak were used as indexes to quantify the clarity of the circadian rhythm. During the experiment, some birds showed gonadal development. Therefore, we analysed separately birds showing either a high or low degree of sexual development at the end of the experiment. In DD, 35 birds showed a circadian feeding rhythm with a mean period of 22.5 ± 0.1 h, whereas 11 birds showed an arrhythmic activity. In LLdim, 27 birds were rhythmic (22 birds R and 5 birds A), and in LLbright, only 3 birds showed a rhythmic circadian activity. For the R-line birds (for females and males), the rhythm clarity decreased in LLdim compared to DD, except for the not developed females. For the A-line birds (for females), the rhythm clarity of the immature birds increased in LLdim and that of the developed birds remained stable. In LLbright, circadian activity became arrhythmic. In LLdim, the active phases of 12 birds showed two main peaks, with mean periods of 22.7 h and 25.1 h, respectively. Therefore, constant light appeared to have an inhibitory effect on the expression of the circadian rhythm. We postulate that two hierarchically coupled oscillators could control circadian feeding activity, and arrhythmia in LLbright could be the results of internal desynchronization of the pacemakers. 相似文献
216.
Charlotte Ndiribe Loïc Pellissier Silvia Antonelli Anne Dubuis Julien Pottier Pascal Vittoz Nicolas Salamin 《Ecology and evolution》2013,3(15):4925-4939
The trend of closely related taxa to retain similar environmental preferences mediated by inherited traits suggests that several patterns observed at the community scale originate from longer evolutionary processes. While the effects of phylogenetic relatedness have been previously studied within a single genus or family, lineage‐specific effects on the ecological processes governing community assembly have rarely been studied for entire communities or flora. Here, we measured how community phylogenetic structure varies across a wide elevation gradient for plant lineages represented by 35 families, using a co‐occurrence index and net relatedness index (NRI). We propose a framework that analyses each lineage separately and reveals the trend of ecological assembly at tree nodes. We found prevailing phylogenetic clustering for more ancient nodes and overdispersion in more recent tree nodes. Closely related species may thus rapidly evolve new environmental tolerances to radiate into distinct communities, while older lineages likely retain inherent environmental tolerances to occupy communities in similar environments, either through efficient dispersal mechanisms or the exclusion of older lineages with more divergent environmental tolerances. Our study illustrates the importance of disentangling the patterns of community assembly among lineages to better interpret the ecological role of traits. It also sheds light on studies reporting absence of phylogenetic signal, and opens new perspectives on the analysis of niche and trait conservatism across lineages. 相似文献
217.
Sophie Martin Stéphanie Cohu Céline Vignot Guillaume Zimmerman Jean‐Pierre Gattuso 《Ecology and evolution》2013,3(3):676-693
The response of respiration, photosynthesis, and calcification to elevated pCO2 and temperature was investigated in isolation and in combination in the Mediterranean crustose coralline alga Lithophyllum cabiochae. Algae were maintained in aquaria during 1 year at near‐ambient conditions of irradiance, at ambient or elevated temperature (+3°C), and at ambient (ca. 400 μatm) or elevated pCO2 (ca. 700 μatm). Respiration, photosynthesis, and net calcification showed a strong seasonal pattern following the seasonal variations of temperature and irradiance, with higher rates in summer than in winter. Respiration was unaffected by pCO2 but showed a general trend of increase at elevated temperature at all seasons, except in summer under elevated pCO2. Conversely, photosynthesis was strongly affected by pCO2 with a decline under elevated pCO2 in summer, autumn, and winter. In particular, photosynthetic efficiency was reduced under elevated pCO2. Net calcification showed different responses depending on the season. In summer, net calcification increased with rising temperature under ambient pCO2 but decreased with rising temperature under elevated pCO2. Surprisingly, the highest rates in summer were found under elevated pCO2 and ambient temperature. In autumn, winter, and spring, net calcification exhibited a positive or no response at elevated temperature but was unaffected by pCO2. The rate of calcification of L. cabiochae was thus maintained or even enhanced under increased pCO2. However, there is likely a trade‐off with other physiological processes. For example, photosynthesis declines in response to increased pCO2 under ambient irradiance. The present study reports only on the physiological response of healthy specimens to ocean warming and acidification, however, these environmental changes may affect the vulnerability of coralline algae to other stresses such as pathogens and necroses that can cause major dissolution, which would have critical consequence for the sustainability of coralligenous habitats and the budgets of carbon and calcium carbonate in coastal Mediterranean ecosystems. 相似文献
218.
Despite increased image quality including medical imaging, image segmentation continues to represent a major bottleneck in practical applications due to noise and lack of contrast. In this paper, we present a new methodology to segment noisy, low contrast medical images, with a view to developing practical applications. Firstly, the contrast of the image is enhanced and then a modified graph-based method is followed. This paper has mainly two contributions: (1) a contrast enhancement stage performed by suitably utilizing the noise present in the medical data. This step is achieved through stochastic resonance theory applied in the wavelet domain and (2) a new weighting function is proposed for traditional graph-based approaches. Both qualitative (by our clinicians/radiologists) and quantitative evaluation performed on publicly available computed tomography (CT) (MICCAI 2007 Grand Challenge workshop database) and cardiac magnetic resonance (CMR) databases reflect the potential of the proposed method even in the presence of tumors/papillary muscles. 相似文献
219.
Yoan Arribat Nathalie Bonneaud Yasmina Talmat-Amar Sophie Layalle Marie-Laure Parmentier Florence Maschat 《PloS one》2013,8(7)
Background
Huntington’s disease (HD) is caused by the abnormal expansion of the polyglutamine tract in the human Huntingtin protein (polyQ-hHtt). Although this mutation behaves dominantly, huntingtin loss of function also contributes to HD pathogenesis. Indeed, wild-type Huntingtin plays a protective role with respect to polyQ-hHtt induced defects.Methodology/Principal Findings
The question that we addressed here is what part of the wild-type Huntingtin is responsible for these protective properties. We first screened peptides from the Huntingtin protein in HeLa cells and identified a 23 aa peptide (P42) that inhibits polyQ-hHtt aggregation. P42 is part of the endogenous Huntingtin protein and lies within a region rich in proteolytic sites that plays a critical role in the pathogenesis process. Using a Drosophila model of HD, we tested the protective properties of this peptide on aggregation, as well as on different polyQ-hHtt induced neuronal phenotypes: eye degeneration (an indicator of cell death), impairment of vesicular axonal trafficking, and physiological behaviors such as larval locomotion and adult survival. Together, our results demonstrate high protective properties for P42 in vivo, in whole animals. These data also demonstrate a specific role of P42 on Huntington’s disease model, since it has no effect on other models of polyQ-induced diseases, such as spinocerebellar ataxias.Conclusions/Significance
Altogether our data show that P42, a 23 aa-long hHtt peptide, plays a protective role with respect to polyQ-hHtt aggregation as well as cellular and behavioral dysfunctions induced by polyQ-hHtt in vivo. Our study also confirms the correlation between polyQ-hHtt aggregation and neuronal defects. Finally, these results strongly suggest a therapeutic potential for P42, specific of Huntington’s disease. 相似文献220.
Oana I. Stanisor Sophie A. van Diest Zhumei Yu Olaf Welting Noor Bekkali Jing Shi Wouter J. de Jonge Guy E. Boeckxstaens Rene M. van den Wijngaard 《PloS one》2013,8(6)