The application of a potential-sensitive cyanine dye to rat small intestinal brush border membrane vesicles

The sensitivity of the fluorescent dye, 3,3′-diethylthiadicarbocyanine (DiS-C₂(5)), was too low for the detection of membrane potential changes in rat small intestinal membrane vesicles. Only after adding LaCl₃ or after fractionation of the intestinal membranes by free-flow electrophoresis could the dye be used to monitor electrogenic Na⁺-dependent transport systems. It is concluded that the response of this potential-sensitive dye is influenced by the negative surface charge density of the vesicles.     

Blue light controls solar tracking by flowers of an alpine plant

In at least 18 plant families, leaves or flowers can maintain a specific orientation with respect to diurnal movements of the sun. Previous work on heliotropic leaves has demonstrated that blue light (400–500nm) provides the cue for their tracking response. Floral heliotropism occurs in several families of arctic and alpine plants, but the spectral sensitivity of the response has not been studied previously. Moreover, no studies on the spectral sensitivity of any heliotropism have been conducted on wild plants growing in their natural habitat. Working under field conditions, we used coloured acrylic filters to determine whether heliotropism by flowers of the snow buttercup (Ranunculus adoneus) is responsive to broad-band blue or red light. Flowers were able to orient towards the sun under boxes made entirely of blue-transmitting filters and in red-transmitting boxes having a single blue side that faced the sun. In these treatments, solar tracking ability was not significantly different from that observed in adjacent control flowers. In contrast, the precision of solar orientation was significantly reduced in red-transmitting boxes and red boxes with a single blue side oriented away from the sun. In the early morning, flowers covered by red-transmitting boxes failed to orient in the direction of sunrise, suggesting that this floral response, unlike that seen in some heliotropic leaves, lacks a residual‘memory’ for previous solar movements.     

Dye-flow apparatus to measure the variation in axial xylem permeability over a stem cross-section

Abstract Equipment and methodology are described that allows the radial variation in axial xylem permeability (hydraulic conductivity) over a tree cross-section to be measured and the flow paths to be identified by the strictly controlled flow of dye through a specimen. The apparatus can be calibrated so that the point-to-point variation of absolute permeability over a xylem cross-section can be calculated from the dye-flow patterns, which otherwise show only relative variations in permeability. The effect of using different dyes and dye concentrations on the penetration time and the shape of the dye patterns was investigated. The penetration time through the wood of identical end-matched specimens is appreciably longer for fixing dyes than for non-fixing dyes, and for the fixing dyes it depends strongly on the dye concentration. However, the dye patterns of the end-matched specimens were indistinguishable with fixing and non-fixing dyes, and independent of dye concentration. The fixing dye toluidine blue at 0.25% to 0.5% (w/w) was found most suitable as it yields a clear permanent pattern.     

Clostridium thermoaceticum forms methanol from carbon monoxide in the presence of viologen dyes

Whole cells of Clostridium thermoaceticum, crude extracts of such cells as well as the supernatant of 100 000 × g centrifugations catalyse the reduction of carbon monoxide to methanol in the presence of viologens or cobalt sepulchrate. Without such a mediator methanol could not be detected. The reaction shows a marked optimum at pH 5. The incubation of [5-¹⁴C]methyltetrahydrofolate led only to the formation of ¹⁴C-labeled ethanol; the radioactivity in methanol was negligible. The reaction seems to be catalysed by carbon monoxide dehydrogenase.     

北京地区红隼的迁徙路线和活动区域

红隼(Falco tinnunculus)被列为国家二级重点保护野生动物,是能同时适应农村和城市环境的小型猛禽,对维持城市生态系统稳定具有重要意义。2022年4月至7月,为在北京救助的7只红隼佩戴了卫星追踪器,追踪其活动轨迹,依据追踪的动物活动位点数据,采用净平方位移-时间曲线依次对各红隼的迁徙模式进行了判别,深入分析了迁徙红隼的迁徙时间、距离和路线等,并采用核心密度法分别计算了迁徙及留居型红隼95%及50%活动区面积。研究结果表明,在北京地区红隼的迁徙模式为部分迁徙,追踪的7只红隼个体(N01 ~ N07)中,4只为留鸟,1只为迁徙鸟,2只居留类型无法准确判断。N01为迁徙红隼,其度夏地和越冬地分别在内蒙古锡林郭勒盟和河北廊坊,此红隼秋季迁徙速度明显高于春季,其春季迁徙距离551 km,历时25 d,平均迁徙速度为22 km/d,而秋季迁徙距离412 km,历时2 d,平均迁徙速度为203 km/d,河北承德滦平县是其春季迁徙的重要中途停歇地。不同红隼个体间95%及50%活动区面积均存在较大差异,迁徙红隼N01 95%、50%活动区面积在度夏区分别为93.10 km²、17.50 km²,在越冬区分别为7.03 km²、0.99 km²;留居型红隼95%、50%活动区面积均值分别为1 165.34 km²、178.71 km²(n = 4),其中最大95%、50%活动区面积分别为4 320.26 km²(N02)、648.22 km²(N02),最小95%、50%活动区面积分别为2.80 km²(N03)、0.29 km²(N03)。本研究揭示了北京地区红隼的迁徙模式、迁徙路线、重要停歇地及活动区状况,为红隼的针对性保护和管理提供了科学依据。     

Efficacy of releasing captive reared broodstock into an imperilled wild Atlantic salmon population as a recovery strategy

The strategy of releasing captive reared adult Atlantic salmon Salmo salar into the Magaguadavic River, New Brunswick, Canada, to spawn, was not an effective tool for rebuilding a seriously depressed wild population. The fish were first generation progeny from wild parents, and had spent their entire lives in captivity in either sea or fresh water. No differences in movement or behaviour patterns were observed between freshwater and seawater reared groups. Fish released in the lower river early (35 to 80 days prior to the natural spawning period) moved into a lake low in the system, and most stayed there near the commercial hatchery where they had been reared from egg to smolt. During the spawning season, none moved to the upper river reaches where most spawning habitat exists. Most broodstock released in the upper river reaches near the time of spawning stayed there during the spawning period. The following year few to no Atlantic salmon fry were found, and most appeared not to be offspring of released adults.     

Stochastic exits from dormancy give rise to heavy‐tailed distributions of descendants in bacterial populations

Variance in reproductive success is a major determinant of the degree of genetic drift in a population. While many plants and animals exhibit high variance in their number of progeny, far less is known about these distributions for microorganisms. Here, we used a strain barcoding approach to quantify variability in offspring number among replicate bacterial populations and developed a Bayesian method to infer the distribution of descendants from this variability. We applied our approach to measure the offspring distributions for five strains of bacteria from the genus Streptomyces after germination and growth in a homogenous laboratory environment. The distributions of descendants were heavy‐tailed, with a few cells effectively ‘winning the jackpot’ to become a disproportionately large fraction of the population. This extreme variability in reproductive success largely traced back to initial populations of spores stochastically exiting dormancy, which provided early‐germinating spores with an exponential advantage. In simulations with multiple dormancy cycles, heavy‐tailed distributions of descendants decreased the effective population size by many orders of magnitude and led to allele dynamics differing substantially from classical population genetics models with matching effective population size. Collectively, these results demonstrate that extreme variability in reproductive success can occur even in growth conditions that are far more homogeneous than the natural environment. Thus, extreme variability in reproductive success might be an important factor shaping microbial population dynamics with implications for predicting the fate of beneficial mutations, interpreting sequence variability within populations and explaining variability in infection outcomes across patients.     

二维斑点追踪技术评价犬心梗后自体骨髓CD34＋干细胞移植对心肌功能的影响

目的应用二维斑点追踪成像超声心动图（2D-STE）,评价犬心梗后自体骨髓CD34＋干细胞移植对心肌功能的影响。方法 12只杂种犬行冠脉左前降支结扎术,导致前壁心肌梗死,随机分为两组,A组为对照组,结扎术后两周二次开胸手术,经心肌注射磷酸盐缓冲液（PBS）1 mL;B组为治疗组,结扎术后两周二次开胸手术,经心肌注射含自体骨髓CD34＋干细胞的磷酸盐缓冲液1 mL。应用STE对12只犬结扎术前、术后左室短轴基底段及心尖段心室节段径向应变（RS）、圆周方向应变（CS）以及局部心肌旋转（Rot）进行分析,并对对照组和治疗组治疗后的RS、CS及Rot变化进行比较。结果心肌梗死后梗死节段的RS、CS以及Rot均下降,治疗后治疗组梗死段RS及Rot较对照组好转。结论 STE能够评价左室短轴局部心肌的收缩功能,心肌梗死后梗死段短轴各方向应变减低,自体骨髓CD34＋干细胞移植能够提高局部心肌的收缩功能。     

Morphology of the first-instar nymph and adult female of Kermes echinatus Balachowsky,with a comparison to K. vermilio Planchon (Hemiptera,?Coccoidea,?Kermesidae)

Thefirst-instar nymph and the adult female of Kermes echinatus Balachowsky (Hemiptera, Coccoidea, Kermesidae) are described and illustrated. This species is compared with Kermes vermilio Planchon, a morphologically similar species known in the Palaeractic region.     

Individualistic species limitations of climate‐induced range expansions generated by meso‐scale dispersal barriers

Aim Evidence indicates that species are responding to climate change through distributional range shifts that track suitable climatic conditions. We aim to elucidate the role of meso‐scale dispersal barriers in climate‐tracking responses. Location South coast of England (the English Channel). Methods Historical distributional data of four intertidal invertebrate species were logistically regressed against sea surface temperature (SST) to determine a climate envelope. This envelope was used to estimate the expected climate‐tracking response since 1990 along the coast, which was compared with observed range expansions. A hydrodynamic modelling approach was used to identify dispersal barriers and explore disparities between expected and observed climate tracking. Results Range shifts detected by field survey over the past 20 years were less than those predicted by the changes that have occurred in SST. Hydrodynamic model simulations indicated that physical barriers produced by complex tidal currents have variably restricted dispersal of pelagic larvae amongst the four species. Main conclusions We provide the first evidence that meso‐scale hydrodynamic barriers have limited climate‐induced range shifts and demonstrate that life history traits affect the ability of species to overcome such barriers. This suggests that current forecasts may be flawed, both by overestimating range shifts and by underestimating climatic tolerances of species. This has implications for our understanding of climate change impacts on global biodiversity.