Eutrophication and fragmentation are related to species’ rate of decline but not to species rarity: results from a functional approach

Due to ubiquitous eutrophication and fragmentation, many plant species are actually threatened in Europe. Most ecosystems face an overall nutrient input leading to changes in species composition. Fragmentation is effectively influencing species survival. We investigate if two different measures of species performance of 91 calcareous grassland species–rate of decline and rarity—are related to comparable traits and hence processes. On the one hand we expected that species rate of decline is mainly determined by the processes of eutrophication and fragmentation. On the other hand we hypothesized that the importance of site characteristics may overwhelm the effect of eutrophication and fragmentation for species rarity. Hence, we compared persistence traits responding to eutrophication, dispersal traits being related to fragmentation and ecological site factors for decreasing and increasing species and for rare and common species. The results suggest that increasing species had better means of long-distance dispersal and were more competitive than decreasing species. In contrast, there were hardly any differences in traits between rare and common species, but site characteristics were related to species rarity. Rare species were in the main those with ecological preferences for warm, dry, light and nutrient poor conditions. This study may represent a basis for the assessment of plant species threat. Applying the deduced knowledge about the life history of decreasing versus increasing species to habitat-scale approaches it is possible to predict which species may become threatened in the future simply from the combination of their trait values. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

NeuroXidence: reliable and efficient analysis of an excess or deficiency of joint-spike events

We present a non-parametric and computationally efficient method named NeuroXidence that detects coordinated firing of two or more neurons and tests whether the observed level of coordinated firing is significantly different from that expected by chance. The method considers the full auto-structure of the data, including the changes in the rate responses and the history dependencies in the spiking activity. Also, the method accounts for trial-by-trial variability in the dataset, such as the variability of the rate responses and their latencies. NeuroXidence can be applied to short data windows lasting only tens of milliseconds, which enables the tracking of transient neuronal states correlated to information processing. We demonstrate, on both simulated data and single-unit activity recorded in cat visual cortex, that NeuroXidence discriminates reliably between significant and spurious events that occur by chance.     

Comparison of heat strain recovery in different anti-heat stress clothing ensembles after work to exhaustion

A hot environment combined with physically demanding tasks can subject workers to a higher risk of heat stress. A series of regulations and guidelines have been proposed to design appropriate anti-heat stress work uniform to reduce body heat strain. The present study aimed to examine heat strain recovery in different anti-heat stress clothing ensembles after work to exhaustion in the heat. 10 healthy males performed intermittent treadmill running/walking to exhaustion, followed by 30 min passive recovery sitting in a climatic chamber, which simulated the hot and humid outdoor environment (34 °C temperature, 60% relative humidity, 0.3 m/s air velocity, and 450 W/m² solar radiation). The participants took part in five wear trials in counter-balanced order, including Sportswear, CIC Uniform, NEW Uniform, ICEBANK Cooling Vest, and NEW Cooling Vest, which have different levels of cooling capacity. Core temperature, skin temperature, heart rate, sweat loss, ratings of perceived exertion, and thermal sensations were measured throughout the entire heat exposure period. Physiological heat strain indices, including the physiological strain index (PhSI) and the perceptual strain index (PeSI), were used as a yardstick to quantify and compare the rate of recovery. Significantly lower physiological strain was observed in the newly developed NEW Uniform and NEW Cooling Vest groups compared with the commonly worn CIC Uniform group during recovery. At the end of the recovery period, participants in NEW Cooling Vest achieved the highest recovery (42.18% in PhSI and 81.08% in PeSI), followed by ICEBANK Cooling Vest, Sportswear, NEW Uniform, and CIC Uniform. The cooling capacity of anti-heat stress clothing ensembles and the recovery time significantly affect the rate of recovery in PhSI and PeSI, which may benefit the industry by formulating the appropriate work–rest schedule by considering the clothing effect.     

Indirect sinusoidal vibrations induces an acute increase in explosive strength

The purpose of this study was to examine the acute effect of indirect vibration on neuromuscular responses and fatigue resistance (electromyographic activity - EMG and force) during isometric exercise. Nineteen healthy men (age = 22.4 ± 2.7 years; body mass = 76.4 ± 12.9 kg, height = 175 ± 6.7 cm) performed isometric elbow flexion exercises in three experimental treatments: only isometric exercise (control - CON); isometric exercise with the addition of sinusoidal vibrations (SVE₁; frequency = 20 Hz, displacement = 3.55 ± 0.54 mm); and isometric exercise with the addition of sinusoidal vibrations with frequency variation (SVE₂; frequency = 20 ± 3 Hz, displacement = 3.6 ± 0.8 mm). The peak of the rate of EMG rise (RER) and the root mean square of biceps brachii during the first 200 ms (RMS200bic) were significantly higher in SVE₁ (RMS200bic, 25.57 ± 11.70%MVC; RER, 266.91 ± 130.16%MVC s⁻¹) than CON (RMS200bic, 19.31 ± 8.19%MVC; RER, 169.15 ± 65.98%MVC s⁻¹). Regarding force, in SVE₁, compared to CON, significant increases were observed in peak of rate of force development (CON, 643.96 ± 192.57 N/s; SVE₁, 845.54 ± 292.84 N/s), rate of force development in the first 200 ms (CON, 382.92 ± 138,63 N/s; SVE₁, 501.09 ± 147.46 N/s), and impulse in 200 ms (CON, 8.56 ± 3.56 N s; SVE₁, 11.67 ± 4.45 N s). The addition of indirect sinusoidal vibrations during exercise induced increases in the rate of force development (explosive strength), without affecting the peak force (maximal strength) and the ability to sustain strength production.     

不同品系小鼠胚胎玻璃化冷冻保存的比较研究

目的　研究甘油作为冷冻保护剂、不同基因型小鼠对胚胎玻璃化冷冻的影响。方法　采用 6 5mol L的甘油作为冷冻保护剂 ,采用二步法对CBA、NOD、C57BL 6J、ICR及CD1小鼠 3 5d的胚胎进行玻璃化冷冻 ,并比较了不同品系小鼠胚胎的复苏率及移植受孕率。结果和结论　CBA、NOD、C57BL 6J,ICR及CD1的复苏率分别为 5 7 6 %、4 8%、31 3%、86 5 %及 88% ,移植受孕率为 2 1%、2 3 5 %、11%、38%和 35 5 % ,封闭群小鼠的胚胎复苏率、移植受孕率均显著高于近交系小鼠。这提示胚胎的复苏率及移植受孕率可能与小鼠的不同基因型有关。五个品系中 ,桑椹胚及早期囊胚的体外复苏率均显著高于扩张囊胚。这说明不同基因型及胚胎的不同发育阶段对胚胎玻璃化冷冻效果有影响     

三氧化二砷(As2O3)对雄性小鼠的遗传毒性的研究

本以清洁级ICR雄性小鼠为实验动物,研究As2O3对小鼠的遗传毒性。采用小鼠精子畸形实验法以及小鼠骨髓PCE微核实验法,对成年的小鼠腹腔注射0．25—6．0mg/kg/dAs2O3,染毒7d。结果表明,AsO3对小鼠的体重增长及睾丸的重量存在抑制作用,其中1．00mg/kg／d剂量AS2O3对小鼠体重增长及睾丸重量的抑制是最显的(P＜0.001);AS2O3使小鼠精子的畸形率明显增加(P＜0.001),且呈明显的剂量-效应关系;此外As2O3还使小鼠PCE微核率增加,且As2O3与PCE微核率之间也具有明显的剂量效应。结论是As2O3对雄性小鼠具有明显的遗传毒性。     

微型生态系统中正磷酸盐的周转时间的估算

在考查罗非鱼或鲢、鳙下行影响的微型生态系统实验后期,以水柱正磷酸盐(PO4-P)完全被浮游植物摄取所需要的时间为指标,估算了系统中PO4-P的周转时间,其中浮游植物的PO4-P摄取率是采用挂瓶法来测定和估算的。结果表明,两组实验中大多数有鱼系统的浮游植物PO4-P摄取率都显着地比无鱼系统高,而PO4-P周转时间的估算值均最着地小于无鱼系统。经相关分析测定,两组实验中浮游植物的PO4-P摄取率皆显着地正相关于浮游植物密度和初级生产力,同水柱PO4-P浓度之间的负相关关系则不显着。根据估算结果看来,罗非鱼对系统中磷循环速率的影响比鲢、鳙大得多,而鳙的影响又明显地大于鲢。这些鱼类使微型生态系统中PO4-P的周转时间缩短,可能主要是它们加速了系统中PO4-P再生的结果。       

Detection of Seven Major Evolutionary Lineages in Cyanobacteria Based on the 16S rRNA Gene Sequence Analysis with New Sequences of Five Marine Synechococcus Strains

Although molecular phylogenetic studies of cyanobacteria on the basis of the 16S rRNA gene sequence have been reported, the topologies were unstable, especially in the inner branchings. Our analysis of 16S rRNA gene phylogeny by the maximum-likelihood and neighbor-joining methods combined with rate homogeneous and heterogeneous models revealed seven major evolutionary lineages of the cyanobacteria, including prochlorophycean organisms. These seven lineages are always stable on any combination of these methods and models, fundamentally corresponding to phylogenetic relationships based on other genes, e.g., psbA, rbcL, rnpB, rpoC, and tufA. Moreover, although known genotypic and phenotypic characters sometimes appear paralleled in independent lineages, many characters are not contradictory within each group. Therefore we propose seven evolutionary groups as a working hypothesis for successive taxonomic reconstruction. New 16S rRNA sequences of five unicellular cyanobacterial strains, PCC 7001, PCC 7003, PCC 73109, PCC 7117, and PCC 7335 of Synechococcus sp., were determined in this study. Although all these strains have been assigned to ``marine clusters B and C,' they were separated into three lineages. This suggests that the organisms classified in the genus Synechococcus evolved diversely and should be reclassified in several independent taxonomic units. Moreover, Synechococcus strains and filamentous cyanobacteria make a monophyletic group supported by a comparatively high statistical confidence value (80 to 100%) in each of the two independent lineages; therefore, these monophylies probably reflect the convergent evolution of a multicellular organization. Received: 3 September 1998 / Accepted: 30 November 1998     

Temperature-dependent subunit exchange and chaperone-like activities of Hsp16.3, a small heat shock protein from Mycobacterium tuberculosis

Small heat shock proteins (sHsps) usually exist as oligomers that undergo dynamic oligomeric dissociation/re-association, with the dissociated oligomers as active forms to bind substrate proteins under heat shock conditions. In this study, however, we found that Hsp16.3, one sHsp from Mycobacterium tuberculosis, is able to sensitively modulate its chaperone-like activity in a range of physiological temperatures (from 25 to 37.5 degrees C) while its native oligomeric size is still maintained. Further analysis demonstrated that Hsp16.3 exposes higher hydrophobic surfaces upon temperatures increasing and that a large soluble complex between Hsp16.3 and substrate is formed only in the condition of heating temperature up to 35 and 37.5 degrees C. Structural analysis by fluorescence anisotropy showed that Hsp16.3 nonameric structure becomes more dynamic and variable at elevated temperatures. Moreover, subunit exchange between Hsp16.3 oligomers was found to occur faster upon temperatures increasing as revealed by fluorescence energy resonance transfer. These observations indicate that Hsp16.3 is able to modulate its chaperone activity by adjusting the dynamics of oligomeric dissociation/re-association process while maintaining its static oligomeric size unchangeable. A kinetic model is therefore proposed to explain the mechanism of sHsps-binding substrate proteins through oligomeric dissociation. The present study also implied that Hsp16.3 is at least capable of binding non-native proteins in vivo while expressing in the host organism that survives at 37 degrees C.