Development and application of environmental DNA surveillance for the threatened crucian carp (Carassius carassius)

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Coexistence of bombesin and 5-hydroxytryptamine in the cutaneous gland of the frog,Bombina orientalis

Summary Impulse generation and propagation was previously shown to occur in skin epithelium of newt (Cynops orientalis) embryos during certain stages of development and to be correlated with morphological changes of gap junctions. These properties are not detected in embryonic epithelia explanted and grown in culture. However, early explants when transplanted to a host embryo develop conductivity, and relatively large gap junctions with loose arrangement of connexons occur as soon as the host embryo reaches the stage when conductivity is at its maximum. In contrast, morphological and physiological characteristics of impulse propagation are lost when the transplanted epithelium is extirpated from the host embryo and returned to in-vitro conditions. Therefore, it appears that impulse propagation is dependent not solely on the differentiation of epithelial cells but upon signals from non-epithelial (possibly mesodermal) tissue as well.     

Spatial genetic structure in wild cherry (Prunus avium L.): II. Effect of density and clonal propagation on spatial genetic structure based on simulation studies

We conducted simulations to disentangle the effect of density and clonal propagation on spatial genetic structure and genetic diversity parameters in Prunus avium. In a previous paper, we observed stronger family structure in populations exhibiting high density and high clonal propagation, whereas one low-density and low clonal propagation population showed negative spatial autocorrelation. We tried to understand these results by simulating 200 years of growth, mating and dispersal with the model Eco-Gene, using two levels of density and three levels of clonal propagation in one high-density population (Spargründe) and one low-density population (Chorin). We used allele frequencies from eight microsatellite loci to generate the populations used for simulations. In order to detect effects of the initial structure on the results, we also ran the simulations starting from the real data. We observed positive effect of clonal propagation on the strength of SGS, while high densities exhibited a negative impact. Genetic diversity was maintained at high densities, while pollen dispersal was shorter. Heterozygosity increased at higher clonal propagation rates, although genetic diversity (accumulated number of genotypes) was lower. We discuss the results according to mating processes and potential management scenario.     

Quantifying the Trade‐Off between Absolute Capacity and Rate Performance in Battery Electrodes

Among other things, battery electrodes need to display large absolute capacities coupled with high rate performance. However, enhancing areal capacity, for example via increased electrode thickness, results in reductions in rate performance. The basis for this negative correlation has not been studied in a quantitative fashion. Here, a semiempirical model is used to analyze capacity versus rate data for electrodes fabricated from a number of materials, each measured at various thicknesses. Fitting the model to the data outputs the low‐rate areal capacity, Q_A, and the characteristic time associated with charge/discharge, τ, fit parameters which quantify absolute capacity and rate performance respectively. A clear correlation is found between Q_A and τ, with all data siting close to a mastercurve approximately defined by constant τ/Q_A. This data is consistent with a simple model based on the timescales associated with rate‐limiting processes. This model implies that the capacity‐rate trade‐off can be improved for high areal capacity electrodes by increasing the volumetric capacity, electrical conductivity, and porosity of the electrode. Conversely, solid‐state diffusion and reaction kinetics are only important for low areal capacity electrodes.     

<Emphasis Type="Italic">In vitro</Emphasis> culture of the resurrection plant <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis>

The small group of resurrection plants is a unique model which could help us in further understanding of abiotic stress tolerance. The most frequently used approach for investigations on gene functions in plant systems is genetic transformation. In this respect, the establishment of in vitro systems for regeneration and micro propagation is necessary. On the other hand, in vitro cultures of such rare plants could preserve their natural populations. Here, we present our procedure for in vitro regeneration and propagation of Haberlea rhodopensis – a resurrection plant species, endemic for the Balkan region.     

连栽桉树人工林土壤大孔隙特征及其对饱和导水率的影响

速生人工林多代连栽容易导致土地水源涵养能力下降。土壤大孔隙以优先流的形式补充地下水,是定量研究土壤水分运动的重要指标。以连栽1-4代桉树人工纯林为研究对象（记录为Ⅰ、Ⅱ、Ⅲ、Ⅳ）,采用水分穿透曲线法,绘制水分穿透曲线,结合Poiseulle方程计算出大孔隙数量、半径及饱和导水率等指标,对土壤大孔隙特征及其对饱和导水率的影响进行研究。结果表明：（1）桉树人工林土壤的出流速率总体表现先匀速增加后趋于稳定,稳定出流速率总体表现为I > II > III > IV。（2）大孔隙半径范围在0.3-1.5 mm,主要集中于0.4-0.6 mm,随土层深度增加显著减小（P<0.05）。大孔隙数量范围在3.56×10⁴-4.81×10⁵个/m²。随着连栽代次的增加,大孔隙孔径范围变小,同一孔径范围的大孔隙数量减少。土壤容重与大孔隙特征呈极显著负相关关系;有机质含量与大孔隙特征呈极显著正相关关系。（3）各样地土壤饱和导水率范围在0.41-4.50 mm/min,并随着连栽代次增加而降低。将大孔隙的总数量、平均体积与土壤饱和导水率进行线性拟合,拟合方程为：y=ax+b=,（R²>0.66）。综上,随着桉树人工林连栽代次的增加,土壤大孔隙孔径范围缩小、同等半径的大孔隙数量减少,饱和导水率降低,土壤入渗及导水性能减弱,容易造成水土流失。     

The effect of ion pumps on the speed of travelling waves in the fire-diffuse-fire model of Ca2+ release

The fire-diffuse-fire model provides an idealized model of Ca²⁺ release within living cells. The effect of calcium pumps, which drive Ca²⁺ back into internal stores, is often neglected for mathematical simplicity. Here we show how to explicitly analyse such effects by extending the work of Keizer et al. [Keizer, J. E., G. D. Smith, S. Ponce Dawson and J. Pearson (1998). Saltatory propagation of Ca²⁺ waves by Ca²⁺ sparks. Biophys. J. 75, 595–600.]. For travelling waves, in which release events occur sequentially, we construct the speed of waves in terms of the time-scale at which pumps operate. An immediate consequence of this analysis is that the inclusion of calcium pumps leads to multiple solutions. A linear stability analysis determines those solution branches in parameter space which are stable. Numerical continuation is used to provide explicit examples of the bifurcation diagrams of the speed of waves as a function of physiologically significant system parameters.     

Mechanisms of very fast oscillations in networks of axons coupled by gap junctions

Because electrical coupling among the neurons of the brain is much faster than chemical synaptic coupling, it is natural to hypothesize that gap junctions may play a crucial role in mechanisms underlying very fast oscillations (VFOs), i.e., oscillations at more than 80 Hz. There is now a substantial body of experimental and modeling literature supporting this hypothesis. A series of modeling papers, starting with work by Roger Traub and collaborators, have suggested that VFOs may arise from expanding waves propagating through an “axonal plexus”, a large random network of electrically coupled axons. Traub et al. also proposed a cellular automaton (CA) model to study the mechanisms of VFOs in the axonal plexus. In this model, the expanding waves take the appearance of topologically circular “target patterns”. Random external stimuli initiate each wave. We therefore call this kind of VFO “externally driven”. Using a computational model, we show that an axonal plexus can also exhibit a second, distinctly different kind of VFO in a wide parameter range. These VFOs arise from activity propagating around cycles in the network. Once triggered, they persist without any source of excitation. With idealized, regular connectivity, they take the appearance of spiral waves. We call these VFOs “re-entrant”. The behavior of the axonal plexus depends on the reliability with which action potentials propagate from one axon to the next, which, in turn, depends on the somatic membrane potential V _s and the gap junction conductance g _gj . To study these dependencies, we impose a fixed value of V _s , then study the effects of varying V _s and g _gj . Not surprisingly, propagation becomes more reliable with rising V _s and g _gj . Externally driven VFOs occur when V _s and g _gj are so high that propagation never fails. For lower V _s or g _gj , propagation is nearly reliable, but fails in rare circumstances. Surprisingly, the parameter regime where this occurs is fairly large. Even a single propagation failure can trigger re-entrant VFOs in this regime. Lowering V _s and g _gj further, one finds a third parameter regime in which propagation is unreliable, and no VFOs arise. We analyze these three parameter regimes by means of computations using model networks adapted from Traub et al., as well as much smaller model networks.     

Seeing is believing: novel imaging techniques help clarify microbial nanowire structure and function

Novel imaging approaches have recently helped to clarify the properties of ‘microbial nanowires’. Geobacter sulfurreducens pili are actual wires. They possess metallic‐like conductivity, which can be attributed to overlapping pi‐pi orbitals of key aromatic amino acids. Electrostatic force microscopy recently confirmed charge propagation along the pili, in a manner similar to carbon nanotubes. The pili are essential for long‐range electron transport to insoluble electron acceptors and interspecies electron transfer. Previous claims that Shewanella oneidensis also produce conductive pili have recently been recanted, based on novel live‐imaging studies. The putative pili are, in fact, long extensions of the cytochrome‐rich outer membrane and periplasm that, when dried, collapse to form filaments with dimensions similar to pili. It has yet to be demonstrated whether the cytochrome‐to‐cytochrome electron hopping documented in the dried membrane extensions takes place in intact hydrated membrane extensions or whether the membrane extensions enhance electron transport to insoluble electron acceptors such as Fe(III) oxides or electrodes. These findings demonstrate that G. sulfurreducens conductive pili and the outer membrane extensions of S. oneidensis are fundamentally different in composition, mechanism of electron transport and physiological role. New methods for evaluating filament conductivity will facilitate screening the microbial world for nanowires and elucidating their function.     

Behavioural adaptations of ground living bushcrickets to the properties of sound propagation in low grassland

Summary The acoustic behaviour of the closely related tetigoniid species Psorodonotus illyricus and Decticus verrucivorus have been invectigated by bioacoustical and behavioural methods. Both species show adaptations concerning the acoustic behaviour with respect to the biotope and the properties of sound propagation. These insects inhabit low grassland with an average vegetation height of about 20 cm which is also the general height for the song perches. Difficulties arise for efficient acoustic communication in such habitats. Sound propagation is influenced and limited by the strong ground attenuation and the excess damping by grass vegetation. Other limiting factors are the microclimatic conditions in the biotope. The two species counteract these difficulties by moving around in the biotope during stridulation. Both species mainly stridulate in the morning, avoiding problems of reduced sound transmission which often appear in the afternoon due to negative temperature gradients and resulting shadow zones. From the high mobility of these insects, it follows that individuals have no fixed territory and consequently no rivalry against conspecifics, which is very common among Orthopterans with a high degree of territoriality. It can be concluded that the preferred biotope influences and creates behavioural patterns in Orthopterans, especially here in the two investigated species of bushcrickets Psorodonotus illyricus and Decticus verrucivorus.     

Existence of excitation waves for a collection of cardiomyocytes electrically coupled to fibroblasts

We consider mathematical models of a collection of cardiomyocytes (myocardial tissue) coupled to a varying number of fibroblasts. Our aim is to understand how conductivity (δ) and fibroblast density (η) affect the stability of the collection. We provide mathematical and computational arguments indicating that there is a region of instability in the η-δ space. Mathematical arguments, based on a simplified model of the coupled myocyte-fibroblast system, show that for certain parameter choices, a stationary solution cannot exist. Numerical experiments (1D, 2D) are based on a recently developed model of electro-chemical coupling between a human atrial myocyte and a number of associated atrial fibroblasts. The numerical experiments demonstrate that there is a region of instability of the form observed in the simplified model analysis.     

Modeling of intraorgan arterial vasculatures. II. Propagation of pressure waves

The dependences of the wave conductivity of self-similar dichotomous branching models of intraorgan arterial vasculatures on the model parameters have been calculated. It was found that, with different sets of parameters, it is possible to model the sucking effect connected with negative wave reflection at the arterial branching as well as the resonant properties of arterial beds. It was shown that the selection of an adequate model for a given intraorgan vasculature should be based on the agreement between the biophysical characteristics of the model and the vasculature that reflect the propagation and reflection of pulse waves.     

敦煌西湖荒漠-湿地生态系统优势物种生态位研究

水文情势改变会引起土壤盐分变化,直接影响到荒漠-湿地生态系统植被的分布与演替。基于对57个样地、171个样方植物物种分布影响较大的土壤pH值和土壤电导率两个环境因子,将其划分为6个梯度等级,测度分析了敦煌西湖植被群落中15个主要优势种的生态位特征,了解不同物种利用资源和占据生态空间的能力,对维持和科学保育植物群落的多样性具有重要意义。结果表明：（1）在土壤pH值和电导率梯度两个资源维上,多枝柽柳和芦苇的重要值和生态位宽度均较大,说明这两个物种适应能力强能够较好地利用环境资源,分布范围大且均匀。它们作为敦煌西湖植被群落中的广域种,具有重要的生态地位和作用。其次生态位较宽的疏叶骆驼刺、胡杨和苏枸杞对环境因子也具有较强的适应能力。（2）两个土壤因子梯度下植物种群生态位宽度相似,但也存在差异。如泡泡刺、蒙古沙枣在土壤pH值梯度资源维上的生态位宽度值远大于在土壤电导率梯度资源维上,但尖叶盐爪爪和甘蒙柽柳在土壤电导率梯度资源维上生态位宽度较大,表现出较强的耐盐能力,从而说明这些物种对不同土壤因子的利用能力和适应性不完全相同。（3）在两个资源维上优势物种间的生态位重叠值小于0.5的种对均为61对,占总种对的58.10%,因此生态位重叠值整体保持在较低水平,说明物种在土壤pH值和土壤电导率两个环境梯度上生态位分化明显。（4）敦煌西湖优势物种间总体表现为不显著的负关联,表明物种之间处于竞争关系,但竞争强度不大且群落结构稳定性较弱。     

Independence of stem and leaf hydraulic traits in six Euphorbiaceae tree species with contrasting leaf phenology

Hydraulic traits and hydraulic-related structural properties were examined in three deciduous (Hevea brasiliensis, Macaranga denticulate, and Bischofia javanica) and three evergreen (Drypetes indica, Aleurites moluccana, and Codiaeum variegatum) Euphorbiaceae tree species from a seasonally tropical forest in south-western China. Xylem water potential at 50% loss of stem hydraulic conductivity (P50_stem) was more negative in the evergreen tree, but leaf water potential at 50% loss of leaf hydraulic conductivity (P50_leaf) did not function as P50_stem did. Furthermore, P50_stem was more negative than P50_leaf in the evergreen tree; contrarily, this pattern was not observed in the deciduous tree. Leaf hydraulic conductivity overlapped considerably, but stem hydraulic conductivity diverged between the evergreen and deciduous tree. Correspondingly, structural properties of leaves overlapped substantially; however, structural properties of stem diverged markedly. Consequently, leaf and stem hydraulic traits were closely correlated with leaf and stem structural properties, respectively. Additionally, stem hydraulic efficiency was significantly correlated with stem hydraulic resistance to embolism; nevertheless, such a hydraulic pattern was not found in leaf hydraulics. Thus, these results suggest: (1) that the evergreen and deciduous tree mainly diverge in stem hydraulics, but not in leaf hydraulics, (2) that regardless of leaf or stem, their hydraulic traits result primarily from structural properties, and not from leaf phenology, (3) that leaves are more vulnerable to drought-induced embolism than stem in the evergreen tree, but not always in the deciduous tree and (4) that there exists a trade-off between hydraulic efficiency and safety for stem hydraulics, but not for leaf hydraulics.     

Epistasis in the multiple locus symmetric viability model

The n-locus two-allele symmetric viability model is considered in terms of the parameters measuring the additive epistasis in fitness. The dynamics is analysed using a simple linear transformation of the gametic frequencies, and then the recurrence equations depend on the epistatic parameters and Geiringer's recombination distribution only. The model exhibits an equilibrium, the central equilibrium, where the 2 ⁿ gametes are equally frequent. The transformation simplifies the stability analysis of the central point, and provides the stability conditions in terms of the existence conditions of other equilibria. For total negative epistasis (all epistatic parameters are negative) the central point is stable for all recombination distributions. For free recombination either a central point (segregating one, two, ... or n loci) or the n-locus fixation states are stable. For no recombination and some epistatic parameters positive the central point is unstable and several boundary equilibria may be locally stable. The sign structure of the additive epistasis is therefore an important determinant of the dynamics of the n-locus symmetric viability model. The non-symmetric multiple locus models previously analysed are dynamically related, and they all have an epistatic sign structure that resembles that of the multiplicative viability model. A non-symmetric model with total negative epistasis which share dynamical properties with the similar symmetric model is suggested.Supported in part by NIH grant GM 28016, and by grant 81-5458 from the Danish Natural Science Research Council     

Targeted deletion of the <Emphasis Type="Italic">uvrBA</Emphasis> operon and biological containment in the industrially important <Emphasis Type="Italic">Bacillus licheniformis</Emphasis>

From a Bacillus licheniformis wild type as well as a defined asporogenous derivative, stable UV hypersensitive mutants were generated by targeted deletion of the uvrBA operon, encoding highly conserved key components of the nucleotide excision repair. Comparative studies, which included the respective parental strains, revealed no negative side effects of the deletion, neither on enzyme secretion nor on vegetative propagation. Thus, the uvrBA locus proved to be a useful deletion target for achieving biological containment in this industrially exploited bacterium. In contrast to recA mutants, which also display UV hypersensitivity, further strain development via homologous recombination techniques will be still possible in such uvr mutants.     

The effects of excessive drilling diagnosis on decay propagation in trees

The effects of excessive drilling into the trunk with an increment borer and drilling resistance measurement device were determined for four trees of three different species (Populus nigra L., Acer pseudoplatanus L., Quercus robur L.). At the test trees with an internal decay it was found that there are two counteracting effects: First, the internal decay slightly enters into the drilling channel, which is locally a negative effect. But, on the other hand, there is the creation of a reaction zone beside the drilling hole enclosing the drilling channel in order to delay efficiently further decay propagation. Furthermore, there is the formation of a barrier zone spacious covering the location of drilling with multiple layers of fungicide tissue. These are two positive effects stopping or delaying the local outgrowth of the internal decay. Far away from the drilling hole the internal decay is not only locally coming out into the sound wall thickness but is also not specially delayed in propagation. So after some years the decay front is everywhere homogenous again, respectively, the spreading central inner decay has caught up with the migrated decay in the drilling channel. For the tree the negative effect of drilling was compensated nearly completely. In addition, it was found that in no case a decay had entered the drilling channels from outside and survived in the outer area of the drill hole.     

An artificial osmotic cell: a model system for simulating osmotic processes and for studying phenomena of negative pressure in plants

Abstract An artificial osmotic cell has been constructed using reverse osmosis membranes. The cell consisted of a thin film of an osmotic solution (thickness: 100 to 200 μm) containing a non-permeating solute and was bounded between the membrane and the front plate of a pressure transducer which continuously recorded cell turgor. The membrane was supported by metal grids to withstand positive and negative pressures (P). At maximum, negative pressures of up to –0.7 MPa (absolute) could be created within the film on short-term and pressures of up to –0.3 MPa could be maintained without cavitation for several hours. As with living plant cells, the application of osmotic solutions of a non-permeating solute resulted in monophasic relaxations of turgor pressure from which the hydraulic conductivity of the membrane (Lp) and the elastic modulus of the cell (?) could be estimated. The application of solutions with permeating solutes resulted in biphasic pressure relaxation curves (as for living cells) from which the permeability (P_s) and reflection (σ_s) coefficients could be evaluated for the given membrane. Lp, P_s, and σ_s were independent of P and did not change upon transition from the positive to the negative range of pressure. It is concluded that the artificial cell could be used to simulate certain transport properties of living cells and to study phenomena of negative pressure as they occur in the xylem and, perhaps, also in living cells of higher plants.