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121.
122.
Many factors affect the distribution of species richness. This study examines the relative influence of habitat heterogeneity,
climate, human disturbance, and spatial structure on the species-richness distribution of terrestrial vertebrates (amphibians,
reptiles, birds and mammals) in mainland Spain. The results indicate that spatial structure and environment exert similar
influences on species richness. For all four taxa, species richness increases southward and northward, being lower in the
center of the country, when controlled for other variables. This may be the result of a peninsular effect, as found in other
studies, and reflect the importance of historical events on species richness in the Iberian Peninsula. Climate is more important
than habitat heterogeneity in determining species richness. Temperature is positively correlated with amphibian, reptile,
and bird species richness, while mammalian species richness is highest at intermediate temperatures. This effect is stronger
in ectotherms than among endotherms, perhaps reflecting physiological differences. Precipitation positively correlates with
bird and mammalian species richness, but has no effect on ectotherm species richness. Amphibian species richness increases
with altitudinal range, and bird species richness with habitat diversity. Human population density is positively correlated
with bird and mammalian species richness, but does not affect ectotherm species richness, while amphibian and bird species
richness is highest at moderate levels of human land alteration (farmland). However, unexplained variance remains, and we
discuss that the effects of environmental variables on species richness may vary geographically, causing different effects
to be obscured on a national scale, diminishing the explanatory power of environmental variables. 相似文献
123.
Barrero C Royo J Grijota-Martinez C Faye C Paul W Sanz S Steinbiss HH Hueros G 《Planta》2009,229(2):235-247
124.
Belinchón R Martínez I Otálora MA Aragón G Dimas J Escudero A 《American journal of botany》2009,96(11):1974-1982
Destruction and fragmentation of habitats represent one of the most important threats for biodiversity. Here, we examined the effects of fragmentation in Mediterranean forests on the epiphytic lichen Lobaria pulmonaria (Lobariaceae). We tested the hypothesis that not only the level of fragmentation affects L. pulmonaria populations, but also the quality of the habitat and the nature of the surrounding matrix affect them. The presence and abundance of the lichen was recorded on 2039 trees in a total of 31 stands. We recorded habitat quality and landscape variables at three hierarchical levels: tree, plot, and patch. We found that L. pulmonaria tends to occur in trees with larger diameters in two types of surveyed forests. In Quercus pyrenaica patches, the mean diameter of colonized trees was smaller, suggesting the importance of bark roughness. Factors affecting the presence and cover of the lichen in each type of forest were different. There was a strong positive influence of distance from a river in beech forests, whereas proximity to forest edge positively affected in oak forests. The influence of the surrounding matrix was also an important factor explaining the epiphytic lichen abundance. 相似文献
125.
Anna Corcione Elisa Ferretti Maria Bertolotto Franco Fais Lizzia Raffaghello Andrea Gregorio Claudya Tenca Luciano Ottonello Claudio Gambini Glaucia Furtado Sergio Lira Vito Pistoia 《PloS one》2009,4(12)
Background
Fractalkine/CX3CL1, a surface chemokine, binds to CX3CR1 expressed by different lymphocyte subsets. Since CX3CL1 has been detected in the germinal centres of secondary lymphoid tissue, in this study we have investigated CX3CR1 expression and function in human naïve, germinal centre and memory B cells isolated from tonsil or peripheral blood.Methodology/Principal Findings
We demonstrate unambiguously that highly purified human B cells from tonsil and peripheral blood expressed CX3CR1 at mRNA and protein levels as assessed by quantitative PCR, flow cytometry and competition binding assays. In particular, naïve, germinal centre and memory B cells expressed CX3CR1 but only germinal centre B cells were attracted by soluble CX3CL1 in a transwell assay. CX3CL1 signalling in germinal centre B cells involved PI3K, Erk1/2, p38, and Src phosphorylation, as assessed by Western blot experiments. CX3CR1+ germinal centre B cells were devoid of centroblasts and enriched for centrocytes that migrated to soluble CX3CL1. ELISA assay showed that soluble CX3CL1 was secreted constitutively by follicular dendritic cells and T follicular helper cells, two cell populations homing in the germinal centre light zone as centrocytes. At variance with that observed in humans, soluble CX3CL1 did not attract spleen B cells from wild type mice. OVA immunized CX3CR1−/− or CX3CL1−/− mice showed significantly decreased specific IgG production compared to wild type mice.Conclusion/Significance
We propose a model whereby human follicular dendritic cells and T follicular helper cells release in the light zone of germinal centre soluble CX3CL1 that attracts centrocytes. The functional implications of these results warrant further investigation. 相似文献126.
Musi V Birdsall B Fernandez-Ballester G Guerrini R Salvatori S Serrano L Pastore A 《Protein science : a publication of the Protein Society》2006,15(4):795-807
SH3 domains are small protein modules that are involved in protein-protein interactions in several essential metabolic pathways. The availability of the complete genome and the limited number of clearly identifiable SH3 domains make the yeast Saccharomyces cerevisae an ideal proteomic-based model system to investigate the structural rules dictating the SH3-mediated protein interactions and to develop new tools to assist these studies. In the present work, we have determined the solution structure of the SH3 domain from Myo3 and modeled by homology that of the highly homologous Myo5, two myosins implicated in actin polymerization. We have then implemented an integrated approach that makes use of experimental and computational methods to characterize their binding properties. While accommodating their targets in the classical groove, the two domains have selectivity in both orientation and sequence specificity of the target peptides. From our study, we propose a consensus sequence that may provide a useful guideline to identify new natural partners and suggest a strategy of more general applicability that may be of use in other structural proteomic studies. 相似文献
127.
Giménez D Andreu C del Olmo Ml Varea T Diaz D Asensio G 《Bioorganic & medicinal chemistry》2006,14(20):6971-6978
The effect of introducing fluorine atoms or trifluoromethyl groups in either the peptidic chain or the C-terminal end of cationic pentapeptides is reported. Three series of amide and ester peptides were synthesised and their antimicrobial properties evaluated. An enhanced activity was found in those derivatives whose structure contained fluorine, suggesting an increase in their hydrophobicity. 相似文献
128.
129.
Polyglutamine toxicity in yeast uncovers phenotypic variations between different fluorescent protein fusions
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Yuwei Jiang Sonja E. Di Gregorio Martin L. Duennwald Patrick Lajoie 《Traffic (Copenhagen, Denmark)》2017,18(1):58-70
The palette of fluorescent proteins (FPs) available for live‐cell imaging contains proteins that strongly differ in their biophysical properties. FPs cannot be assumed to be equivalent and in certain cases could significantly perturb the behavior of fluorescent reporters. We employed Saccharomyces cerevisiae to comprehensively study the impact of FPs on the toxicity of polyglutamine (polyQ) expansion proteins associated with Huntington's disease. The toxicity of polyQ fusion constructs is highly dependent on the sequences flanking the polyQ repeats. Thus, they represent a powerful tool to study the impact of fluorescent fusion partners. We observed significant differences on polyQ aggregation and toxicity between commonly used FPs. We generated a novel series of vectors with latest yeast‐optimized FPs for investigation of Htt toxicity, including a newly optimized blue FP for expression in yeast. Our study highlights the importance of carefully choosing the optimal FPs when designing tagging strategies. 相似文献
130.
Francisco J. Zamora-Camacho Senda Reguera M. Virtudes Rubiño-Hispán Gregorio Moreno-Rueda 《Evolutionary biology》2014,41(4):509-517
Most animals rely on their escape speed to flee from predators. Here, we test several hypotheses on the evolution of escape speed in the lizard Psammodromus algirus. We test that: (1) Longer limbs should improve speed sprint. (2) Heavier lizards should be impaired regarding their sprint speed ability, suggesting a trade-off between fat storage and escape capability. (3) Males should achieve faster speeds due to their higher exposure to predators. (4) Gravid females, with increased body mass, should perform lower speed than non-gravid females. And (5) there are inter-population differences in sprint speed across an elevational gradient. We measured lizards sprint speed in a lineal raceway in the laboratory, filming races in standardized conditions and then calculating their maximal speed. We found that hind limb length greatly determined maximal sprint speed, lizards with longer limbs being faster. In parallel, higher body masses reduced maximal speed, which points to a trade-off between fat storage and escaping capability. Sexual differences also arose, as males were faster than females, as a consequence of males having longer limbs. Regarding females, gravidity did not impair maximal sprint speed, suggesting adaptations which compensate for the increased body mass. Finally, we found no elevational trend in both limbs length and sprint speed. In any case, this study suggests that selection on escape capacity may cast morphological evolution, and affect other life-history traits, such as fat storage and reproduction. 相似文献