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111.
112.
Aim
To assess how environmental, biotic and anthropogenic factors shape native–alien plant species richness relationships across a heterogeneous landscape.Location
Banks Peninsula, New Zealand.Methods
We integrated a comprehensive floristic survey of over 1200 systematically located 6 × 6 m plots, with corresponding climate, environmental and anthropogenic data. General linear models examined variation in native and alien plant species richness across the entire landscape, between native‐ and alien‐dominated plots, and within separate elevational bands.Results
Across all plots, there was a significant negative correlation between native and alien species richness, but this relationship differed within subsets of the data: the correlation was positive in alien‐dominated plots but negative in native‐dominated plots. Within separate elevational bands, native and alien species richness were positively correlated at lower elevations, but negatively correlated at higher elevations. Alien species richness tended to be high across the elevation gradient but peaked in warmer, mid‐ to low‐elevation sites, while native species richness increased linearly with elevation. The negative relationship between native and alien species richness in native‐dominated communities reflected a land‐use gradient with low native and high alien richness in more heavily modified native‐dominated vegetation. In contrast, native and alien richness were positively correlated in very heavily modified alien‐dominated plots, most likely due to covariation along a gradient of management intensity.Main conclusions
Both positive and negative native–alien richness relationships can occur across the same landscape, depending on the plant community and the underlying human and environmental gradients examined. Human habitat modification, which is often confounded with environmental variation, can result in high alien and low native species richness in areas still dominated by native species. In the most heavily human modified areas, dominated by alien species, both native and alien species may be responding to similar underlying gradients.113.
114.
N. Fernàndez‐Castillo C. Roncero L. Grau‐Lopez C. Barral G. Prat L. Rodriguez‐Cintas C. Sánchez‐Mora M. Gratacòs J.A. Ramos‐Quiroga M. Casas M. Ribasés B. Cormand 《Genes, Brain & Behavior》2013,12(1):39-46
Cocaine dependence is a neuropsychiatric disorder in which both environmental and genetic factors are involved. Several processes, that include reward and neuroadaptations, mediate the transition from use to dependence. In this regard, dopamine and serotonin neurotransmission systems are clearly involved in reward and other cocaine‐related effects, whereas neurotrophic factors may be responsible for neuroadaptations associated with cocaine dependence. We examined the contribution to cocaine dependence of 37 genes related to the dopaminergic and serotoninergic systems, neurotrophic factors and their receptors through a case–control association study with 319 single nucleotide polymorphisms selected according to genetic coverage criteria in 432 cocaine‐dependent patients and 482 sex‐matched unrelated controls. Single marker analyses provided evidence for association of the serotonin receptor HTR2A with cocaine dependence [rs6561333; nominal P‐value adjusted for age = 1.9e?04, odds ratio = 1.72 (1.29–2.30)]. When patients were subdivided according to the presence or absence of psychotic symptoms, we confirmed the association between cocaine dependence and HTR2A in both subgroups of patients. Our data show additional evidence for the involvement of the serotoninergic system in the genetic susceptibility to cocaine dependence. 相似文献
115.
Cephas E. Small Sai‐Wing Tsang Song Chen Sujin Baek Chad M. Amb Jegadesan Subbiah John R. Reynolds Franky So 《Liver Transplantation》2013,3(7):909-916
Polymer bulk heterojunction solar cells based on low bandgap polymer:fullerene blends are promising for next generation low‐cost photovoltaics. While these solution‐processed solar cells are compatible with large‐scale roll‐to‐roll processing, active layers used for typical laboratory‐scale devices are too thin to ensure high manufacturing yields. Furthermore, due to the limited light absorption and optical interference within the thin active layer, the external quantum efficiencies (EQEs) of bulk heterojunction polymer solar cells are severely limited. In order to produce polymer solar cells with high yields, efficient solar cells with a thick active layer must be demonstrated. In this work, the performance of thick‐film solar cells employing the low‐bandgap polymer poly(dithienogermole‐thienopyrrolodione) (PDTG‐TPD) was demonstrated. Power conversion efficiencies over 8.0% were obtained for devices with an active layer thickness of 200 nm, illustrating the potential of this polymer for large‐scale manufacturing. Although an average EQE > 65% was obtained for devices with active layer thicknesses > 200 nm, the cell performance could not be maintained due to a reduction in fill factor. By comparing our results for PDTG‐TPD solar cells with similar P3HT‐based devices, we investigated the loss mechanisms associated with the limited device performance observed for thick‐film low‐bandgap polymer solar cells. 相似文献
116.
目的:5-HT(5-hydroxytryptamine,5-HT)参与了多种中枢神经活动的生理过程,其功能异常可以影响很多行为障碍,已有研究显示,5-HT水平与多种精神疾病密切相关。5-HT受体及其转运体基因在海洛因依赖发生发展中起到了重要的作用,是海洛因依赖的主要候选基因。探讨5羟色胺2A受体(Serotonin 2A receptor,HTR2A)基因启动子区-1438A/G(rs6311)、外显子区102T/C(rs6313)与5羟色胺1B受体(Serotonin 1B receptor,HTR1B)基因外显子区861G/C(rs6296)3个单核苷酸多态性和海洛因依赖的关联性分析。方法:严格按照诊断标准,选取无亲缘关系的海洛因依赖个体616例及健康个体600例提取基因组DNA,采用PCR-RFLP方法检测rs6311、rs6313和rs6296 3个SNPs位点的基因型频率,采用SPSS16.0软件分析各位点等位基因、基因型频率在病例-对照组间差异。结果:HTR2A基因rs6311和HTR1B基因rs6296位点的等位基因及基因型频率分布在2组间存在统计学差异(P〈0.05),病例组rs6311位点的等位基因A频率显著高于对照组(X2=5.436,P=0.020,OR=1.208,CI=1.031~1.417),rs6296位点的等位基因C频率显著高于对照组(X2=12.116,P=0.000,OR=1.329,CI=1.132~1.560)。连锁不平衡检验结果显示,HTR2A基因rs6311、rs6313位点处于不连锁状态,D'〈0.5。结论:HTR2A基因rs6311和HTR1B基因rs6296多态性可能与海洛因成瘾有关,携带有rs6311 A等位基因与rs6296 C等位基因的人可能更容易对海洛因产生依赖。我们的研究为海洛因依赖易感人群筛选及药物靶向治疗提供了理论依据。 相似文献
117.
Ana Damjanovic Ada Y. Chen Robert L. Rosenberg Daniel R. Roe Xiongwu Wu Bernard R. Brooks 《Proteins》2020,88(3):527-539
The selectivity filter (SF) of bacterial voltage-gated sodium channels consists of four glutamate residues arranged in a C4 symmetry. The protonation state population of this tetrad is unclear. To address this question, we simulate the pore domain of bacterial voltage-gated sodium channel of Magnetococcus sp. (NavMs) through constant pH methodology in explicit solvent and free energy perturbation calculations. We find that at physiological pH the fully deprotonated as well as singly and doubly protonated states of the SF appear feasible, and that the calculated pKa decreases with each additional bound ion, suggesting that a decrease in the number of ions in the pore can lead to protonation of the SF. Previous molecular dynamics simulations have suggested that protonation can lead to a decrease in the conductance, but no pKa calculations were performed. We confirm a decreased ionic population of the pore with protonation, and also observe structural symmetry breaking triggered by protonation; the SF of the deprotonated channel is closest to the C4 symmetry observed in crystal structures of the open state, while the SF of protonated states display greater levels of asymmetry which could lead to transition to the inactivated state which possesses a C2 symmetry in the crystal structure. We speculate that the decrease in the number of ions near the mouth of the channel, due to either random fluctuations or ion depletion due to conduction, could be a self-regulatory mechanism resulting in a nonconducting state that functionally resembles inactivated states. 相似文献
118.
Trade-offs in resource selection by central-place foragers are driven by the need to balance the benefits of selecting resources against the costs of travel from the central place. For group-territorial central-place foraging birds, trade-offs in resource selection are likely to be complicated by a competitive advantage for larger groups at high group density that may limit accessibility of high-quality distant resources to small groups. We used the group-territorial, central-place foraging Red-cockaded Woodpecker Leuconotopicus borealis (RCW) as a case study to test predictions that increases in group density lead to differences in foraging distances and resource selection for groups of different sizes. We used GPS tracking and LiDAR-derived habitat data to model effects of group size on foraging distances and selection for high-quality pines (≥ 35.6 cm diameter at breast height (dbh)) and lower quality pines (25.4–35.6 cm dbh) by RCW groups across low (n = 14), moderate (n = 10) and high group density (n = 10) conditions. At low and moderate group density, all RCW groups selected distant high-quality pines in addition to those near the central place because competition for resources was low. In contrast, at high group density, larger groups travelled further to select high-quality pines, whereas smaller groups selected high-quality pines only when they were close to the central place and, conversely, were more likely to select lower quality pines at greater distances from the central place. Selection for high-quality pines only when close to the cavity tree cluster at high group density is important to long-term fitness of small RCW groups because it allows them to maximize benefits from both territorial defence and selecting high-quality resources while minimizing costs of competition. These relationships suggest that intraspecific competition at high group density entails substantive costs to smaller groups of territorial central-place foragers by limiting accessibility of distant high-quality foraging resources. 相似文献
119.
Ying Ma Shun-Xian Wang Yun Liu Guo-Guang Peng Xiao-Ming Wang Bo Zhang Bi-Hua Wu Ju-Ming Yu 《Gene》2013
Objectives
Ischemic stroke is influenced by both environmental and genetic factors. The CD40/CD40L system is related to proinflammatory and prothrombogenic responses, which are involved in the pathophysiology of ischemic stroke. The aim of this study was to evaluate association between the CD40 -1C/T single nucleotide polymorphism (SNP) and ischemic stroke in a Chinese population.Methods
We conducted a case–control study including 286 ischemic stroke patients and 336 controls. CD40 -1C/T SNP was genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing methods, and evaluated its relevance to ischemic stroke susceptibility.Results
Significantly increased ischemic stroke risk was found to be associated with the T allele of CD40 -1C/T (OR = 1.273, 95% CI = 1.016–1.594). The frequencies of CT and TT/CT genotypes of CD40 -1C/T in ischemic stroke patients were significantly higher than those of controls, respectively (for CT: OR = 2.350, 95% CI = 1.601–3.449; for TT/CT: OR = 2.148, 95% CI = 1.479–3.119). And, similar results were obtained after adjusting non-matched variables. We found that the frequency of carried T genotypes (TT and TT/CT) was significantly increased in patients with history of stroke compared with patients without (for TT: OR = 6.538, 95%CI = 1.655–25.833; for TT/CT: OR = 3.469, 95%CI = 1.031–11.670), respectively.Conclusions
The findings suggested that the CD40 -1C/T polymorphism might contribute to the susceptibility to ischemic stroke in the Chinese population, and might be associated with history of previous stroke. 相似文献120.
The association between angiotensin-converting enzyme insertion/deletion (ACE I/D) polymorphism and risk of myocardial infarction (MI) has been extensively studied. However, the results were in controversy. This study aimed to explore the association between ACE I/D polymorphism and risk of MI by using a meta-analysis. We retrieved the following databases to indentify eligible studies: Medline, Embase, ISI, VIP, CBM and Wan Fang database. The latest update was 10th May, 2012. Odds ratio and 95% confidence interval (95% CI) were used to present the strength of the association. A total of 40 case–control studies with 34 993 participants were included. Overall, D allele of ACE I/D polymorphism was significantly associated with an increased risk of MI in genetic comparison models (OR (95% CI): 1.41 (1.22–1.64) for DD vs. II; 1.11 (1.01–1.21) for ID vs. II; 1.23 (1.10–1.37) for D carriers vs. II; 1.28 (1.15–1.43) for DD vs. I carriers and 1.06 (1.02–1.10) for D carriers vs. I carriers). Subgroup analyses, according to ethnicities and countries of participants also indicated that D allele was significantly associated with an increased risk of MI in Asians (especially for Chinese) and Caucasians (especially for English, French, Germans and Italians) (OR (95% CI) of DD vs. ID + II: 2.11 (1.65–2.70) for Asians and 1.15 (1.05–1.27) for Caucasians). In conclusion, this meta-analysis indicated that D allele of ACE I/D polymorphism was a possible risk factor for MI incidence for both Asians and Caucasians. 相似文献