Pitcher geometry facilitates extrinsically powered ‘springboard trapping' in carnivorous Nepenthes gracilis pitcher plants

Carnivorous pitcher plants capture insects in cup-shaped leaves that function as motionless pitfall traps. Nepenthes gracilis evolved a unique ‘springboard'' trapping mechanism that exploits the impact energy of falling raindrops to actuate a fast pivoting motion of the canopy-like pitcher lid. We superimposed multiple computed micro-tomography images of the same pitcher to reveal distinct deformation patterns in lid-trapping N. gracilis and closely related pitfall-trapping N. rafflesiana. We found prominent differences between downward and upward lid displacement in N. gracilis only. Downward displacement was characterized by bending in two distinct deformation zones whist upward displacement was accomplished by evenly distributed straightening of the entire upper rear section of the pitcher. This suggests an anisotropic impact response, which may help to maximize initial jerk forces for prey capture, as well as the subsequent damping of the oscillation. Our results point to a key role of pitcher geometry for effective ‘springboard'' trapping in N. gracilis.     

Substitution of a proline for alanine 183 in the hinge region of phosphoglycerate kinase: Effects on catalysis, activation by sulfate, and thermal stability

A hinge-bending domain movement has been postulated as an important part of the catalytic mechanism of phosphoglycerate kinase (PGK) (Bankset al., 1979). In order to test the role of the flexibility of a putative interdomain hinge in the substrate- and sulfate-induced conformational transitions, alanine-183 was replaced by proline using site-directed mutagenesis. The maximal velocity of the Ala 183Pro mutant, measured at saturating concentrations of ATP and phosphoglycerate (5 mM and 10 mM, respectively) and in the absence of sulfate ions, is increased approximately 21% in comparison to the wild type PGK. TheK _m values for both substrates are essentially unchanged. The effect of sulfate on the specific activity of the Ala 183Pro mutant and the wild type PGK was measured in the presence of 1 mM ATP and 2 mM 3-phosphoglycerate (3-PG). A maximum activation of 70% was observed at 20 mM sulfate for the mutant enzyme, as compared to 130% activation at 30 mM sulfate for the wild type PGK. These results demonstrate that the increased rigidity of the putative hinge, introduced by the AlaPro mutation, does not impair catalytic efficiency of phosphoglycerate kinase, while it appears to decrease the sulfate-dependent activation. The differential scanning calorimetry (DSC) studies demonstrate an increased susceptibility of the Ala 183 Pro mutant to thermal denaturation. In contrast to one asymmetric transition observed in the DSC scan for the wild type PGK, withT _m near 54°C, two transitions are evident for the mutant enzyme withT _m values of about 45 and 54°C. Using a thermodynamic model for two interacting domains, a decrease in the free energy of domain-domain interactions of about 2 kcal was estimated from the DSC data.     

Ca2+参与水杨酸诱导蚕豆气孔运动时的信号转导

在一定条件下,外源水杨酸(SA)可以诱导蚕豆(Vicia faba L.)气孔关闭,阻止气孔张开。以Fluo-3—AM作为Ca^2 的荧光探针,利用激光共聚焦扫描显微技术,对水杨酸调控气孔运动中保卫细胞胞质Ca^2 的变化趋势及Ca^2 的来源进行了研究。结果表明,水杨酸可引起胞质Ca^2 增加,这种变化发生在气孔开度改变之前。Ca^2 螯合剂BAPTA（1,2-bis(2-amino phenox-y)ethane-N,N,N′,N′-tetraacetic acid,1mmol/L)几乎可以完全抑制水杨酸诱导气孔开度减小的作用;胞外Ca^2 螯合剂EGTA(2mmol/L)、质膜Ca^2 通道抑制剂尼群地平(nifedipine,NIF,1μmol/L)和LaCl3(1mmol／L)可不同程度地减弱水杨酸诱导气孔关闭的效应。BAPTA(1mmol／L)预处理后,水杨酸不再引起胞质Ca^2 含量改变;尼群地平能够降低水杨酸引起的胞质Ca^2 增加的幅度。说明Ca^2 可能参与水杨酸诱导气孔运动的信号转导。水杨酸引起胞内升高的Ca^2 可能既来自胞外又来自胞内,胞内Ca^2 库可能是其主要来源。     

Population genetic structure of the western cherry fruit fly Rhagoletis indifferens (Diptera: Tephritidae) in British Columbia,Canada

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Temperature-sensitive random insulin granule diffusion is a prerequisite for recruiting granules for release

Glucose-evoked insulin secretion exhibits a biphasic time course and is associated with accelerated intracellular granule movement. We combined live confocal imaging of EGFP-labelled insulin granules with capacitance measurements of exocytosis in clonal INS-1 cells to explore the relation between distinct random and directed modes of insulin granule movement, as well as exocytotic capacity. Reducing the temperature from 34 degrees C to 24 degrees C caused a dramatic 81% drop in the frequency of directed events, but reduced directed velocities by a mere 25%. The much stronger temperature sensitivity of the frequency of directed events (estimated energy of activation approximately 135 kJ/mol) than that of the granule velocities (approximately 22 kJ/mol) suggests that cooling-induced suppression of insulin granule movement is attributable to factors other than reduced motor protein adenosine 5'-triphosphatase activity. Indeed, cooling suppresses random granule diffusion by approximately 50%. In the single cell, the number of directed events depends on the extent of granule diffusion. Finally, single-cell exocytosis exhibits a biphasic pattern corresponding to that observed in vivo, and only the component reflecting 2nd phase insulin secretion is affected by cooling. We conclude that random diffusive movement is a prerequisite for directed insulin granule transport and for the recruitment of insulin granules released during 2nd phase insulin secretion.     

Ecological and demographic correlates of cooperation from individual to budding dispersal

Identifying the ecological and demographic factors that promote the evolution of cooperation is a major challenge for evolutionary biologists. Explanations for the adaptive evolution of cooperation seek to determine which factors make reproduction in cooperative groups more favourable than independent breeding or other selfish strategies. A vast majority of the hypotheses posit that cooperative groups emerge in the context of philopatry, high costs of dispersal, high population density and environmental stability. This route to cooperation, however, fails to explain a growing body of empirical evidence in which cooperation is not associated with one or more of these predictors. We propose an alternative evolutionary path towards the emergence of cooperation that accounts for the disparities observed in the current literature. We find that when dispersal is mediated by a group mode of dispersal, commonly termed budding dispersal, our mathematical model reveals an association between cooperation and immigration, lower costs of dispersal, low population density and environmental variability. Furthermore, by studying the continuum from the individual to the partial and full budding mode of dispersal, we can explicitly explain why the correlates of cooperation change under budding. This enables us to outline a general model for the evolution of cooperation that accounts for a substantial amount of empirical evidence. Our results suggest that natural selection may have favoured two major contrasting pathways for the evolution of cooperation depending on a set of key ecological and demographic factors.     

Paroxysmal and cognitive phenotypes in Prrt2 mutant mice

Mutations in proline‐rich transmembrane protein 2 (PRRT2) cause a range of episodic disorders that include paroxysmal kinesigenic dyskinesia and benign familial infantile epilepsy. Mutations are generally loss of function and include the c649dupC frameshifting mutation that is present in around 80% of affected individuals. To investigate how Prrt2 loss of function mutations causes disease, we performed a phenotypic investigation of a transgenic Prrt2 knockout (Prrt2 KO) mouse. We observed spontaneous paroxysmal episodes with behavioural features of both seizure and movement disorders, as well as unexplained deaths in KO and HET animals. KO mice showed spatial learning deficits in the Morris water maze, as well as gait abnormalities in the quantitative Digigait analysis; both of which may be representative of the more severe phenotypes experienced by homozygous patients. These findings extend the described phenotypes of Prrt2 mutant mice, further confirming their utility for in vivo investigation of the role of Prrt2 mutations in episodic diseases.     

Annual and seasonal patterns in wildlife road-kill and their relationship with traffic density

Hedgehogs (Erinaceous europaeus), rabbits (Oryctolagus cuniculus) and possums (Trichosurus vulpecula) were 93.4% of 1390 mammal carcasses counted during 92 trips along a 63.2?km route, 2009–2014, through peri-urban and farmland habitats. Pukeko (Porphyrio melanotus) and swamp harriers (Circus approximans) constituted 29% of the 466 bird road-kill. Comparisons indicate the recovery of hedgehog and rabbit populations from declines to 2005 and 2009, respectively, and the increased suppression of possum populations, consistent with disease and pest control trajectories. Road-kill density was spatially and temporally aggregated. Seasonal peaks reflected species-specific periodicity in breeding and dispersal. Carcass densities varied positively with traffic volume and did not asymptote with increasing traffic up to 25,000 vehicles per day. Kill rates per vehicle were maintained at the highest traffic volumes. Busier roads were not avoided by wildlife and could be substantial demographic sinks and barriers to their spread. We discuss the implications for wildlife management and conservation.     

快速眼动睡眠期行为障碍(RBD)的帕金森病临床特征分析

目的:探究合并不同发作形式的快速眼动睡眠期行为障碍(RBD)与帕金森病的临床特点及自主神经功能障碍变化。方法:采用快速眼动期睡眠行为障碍筛查量表及帕金森综合评分量表(Unified Parkinson's disease rating scale),对20例合并简单型(RBD)的帕金森病患者(RBD-简单组)与20例合并复杂型(RBD)的帕金森病患者(RBD-复杂组)进行研究。结果:两组帕金森病患者的一般情况、左旋多巴药物日剂量、疾病病程等无统计学差异(P>0.05)。合并复杂型(RBD)的帕金森病患者运动部分评分高于合并简单型(RBD)的帕金森病患者(P<0.05)。两组患者之间在非震颤、强直、运动减少症状均存在统计学差异(P<0.05),(RBD)复杂组评分均高于(RBD)简单组。多因素logistics回归显示,复杂型(RBD)的存在与UPDRS-Ш部分评分相关,而与年龄、病程、教育年限、左旋多巴药物日剂量等无显著相关,与运动减少症状最为相关,与震颤、非震颤、强直症状无相关性。两组患者运动障碍类型与(RBD)发作形式无明显相关性(P=0.108)。结论:合并复杂型(RBD)的帕金森病患者运动症状更重,并且累及运动障碍的诸多方面。帕金森病患者存在复杂型(RBD)症状主要与UPDRS-Ш评分相关,其中与运动减少方面显著相关。     

Estimating dispersal distributions at multiple scales: within‐colony and among‐colony dispersal rates,distances and directions in European Shags Phalacrocorax aristotelis

Knowledge of the rate, distance and direction of dispersal within and among breeding areas is required to understand and predict demographic and genetic connectivity and resulting population and evolutionary dynamics. However dispersal rates, and the full distributions of dispersal distances and directions, are rarely comprehensively estimated across all spatial scales relevant to wild populations. We used re‐sightings of European Shags Phalacrocorax aristotelis colour‐ringed as chicks on the Isle of May (IoM), UK, to quantify rates, distances and directions of dispersal from natal to subsequent breeding sites both within IoM (within‐colony dispersal) and across 27 other breeding colonies covering 1045 km of coastline (among‐colony dispersal). Additionally, we used non‐breeding season surveys covering 895 km of coastline to estimate breeding season detection probability and hence potential bias in estimated dispersal parameters. Within IoM, 99.6% of individuals dispersed between their natal and observed breeding nest‐site. The distribution of within‐colony dispersal distances was right‐skewed; mean distance was shorter than expected given random settlement within IoM, yet some individuals dispersed long distances within the colony. The distribution of within‐colony dispersal directions was non‐uniform but did not differ from expectation given the spatial arrangement of nest‐sites. However, 10% of all 460 colour‐ringed adults that were located breeding had dispersed to a different colony. The maximum observed dispersal distance (170 km) was much smaller than the maximum distance surveyed (690 km). The distribution of among‐colony dispersal distances was again right‐skewed. Among‐colony dispersal was directional, and differed from random expectation and from the distribution of within‐colony dispersal directions. Non‐breeding season surveys suggested that the probability of detecting a colour‐ringed adult at its breeding location was high in the northeastern UK (98%). Estimated dispersal rates and distributions were therefore robust to incomplete detection. Overall, these data demonstrate skewed and directionally divergent dispersal distributions across small (within‐colony) and large (among‐colony) scales, indicating that dispersal could create genetic and demographic connectivity within the study area.